Organopolysiloxanes and use thereof

Abstract

The invention relates to new compounds of Formula I: [A]a [B]b [C]c [D]d in which: A is selected from: O3 / 2)Si–[X][- S–[Y]f H; (O3 / 2)Si–[X]- S– (CH2)0-5 [CHR']f-[Y]-H (O3 / 2)Si–[X] S [Y][C(O)]e- [NR'– [Y]]fH (O3 / 2)Si–[X] -NR'– [Y]fH B is selected from: (O3 / 2)Si–[X]- S–[Y]–[X]-Si(O)3 / 2 C is Si(O)4 / 2; and D is Si(O)3 / 2V. X is a hydrocarbyl group having 2 to 12 carbon atoms; Y is a divalent group selected from (CHR')0-8 -N- [((CHR')2-8-S)f R' ]; [(CHR')g-[C(O)]e S]f; and {(CHR')2-8 [C(O)]e N [((CHR')2-8-S)f R' ] }f [(CHR')2-8-S]f; R' is monovalent and selected from R, [S(CH2)2-8]fSH] and [(CH2)0-8- S]fH]; R is selected from H and a C1-22-alkyl, C2-22-alkenyl or C2-22-alkynyl group, an aryl and a C1-22-alkylaryl group; e is 0 or 1; f is an integer from 1 to 10 and g is 0 to 10. The compounds are useful for removing metal species, particularly precious metal species from a medium, particularly water in process streams, chemical synthesis processes, manufacturing and assembly processes in which specifications have stringent limits on the maximum amount of metals.

Description

[0001] ORGANOPOLYSILOXANES AND USE THEREOF The invention relates to new organopolysiloxanes, particularly to thiol-substituted organopolysiloxanes and especially to thiol-substituted organopolysiloxanes in which the organopolysiloxanes is substituted at any given substitution site with predominantly a thiol and their use in binding metal species, especially precious metal species in a medium and processes for making thiol-substituted organopolysiloxanes. Functionalised organopolysiloxanes are known for use in removing a metal species for example a catalyst or component thereof, from a medium, for example a process stream or a reaction medium. As a consequence of stricter environmental regulations there is a growing requirement for more effective removal and recovery of toxic and hazardous materials, for example metal species, from many sources including a wide spectrum of contaminated products, active pharmaceutical ingredients (API), solvents, potable water and aqueous based wastes and from contaminated waters. For example, the electronics industry has a particular need for ultra pure water with very low levels of cations. Other industries such as the nuclear industry and the electroplating industry generate substantial quantities of water-based effluent that are heavily contaminated with undesirable metal ions. In the pharmaceutical industry metal catalysts are increasing being used in the manufacture of APIs or their intermediates. Metal species often form complexes to the desired API or precursor compounds and residual metal contents in the range of 600–1000 ppm are not uncommon. The ICH HARMONISED GUIDELINE FOR ELEMENTAL IMPURITIES requires the careful control of metal impurities in pharmaceutical products to low levels depending on the classification of the metal based on toxicity, the maximum amount of metal allowed depending on the metal contaminate in and the amount of active to be treated per day and the route of treatment. This can require removal of particularly class 1 and class 2 metals, which includes many common catalytic metals, to less than 5 ppm in the product. The presence of elemental impurities in other fields, including electronics, can affect product performance and the removal of these impurities can give a higher quality, better performing and longer lasting products, particularly in silicon seals where trace metals may cause discolouration. Very low residual levels of metals in process streams waste are also desirable to avoid or reduce the risk of environmental toxicity and harm. Furthermore, Recovery of precious metals is desirable due to their cost and scarcity of supply and natural abundance ensuring their sustainable and cost effective use. Various methods have been tried to reduce the residual `metal content. Selective re- crystallisation often leads to only lowering of metal content. Reduction of metal levels to desirable levels using a metal exchanger such as a functionalised polystyrene resin have also had mixed results. Alternative processes such as washing with an aqueous solution of a suitable metal chelator also have drawbacks. Inorganic polymer systems such as silica, aluminium oxide and titanium oxide have also been disclosed for use in removing toxic materials, particularly metal species. Polymers having an organic, partly cross-linked polystyrene backbone with sulfonate groups attached to some of the phenyl rings are known for use as cation exchangers for removing metal ions from solution. The physical and chemical stability and other properties of these materials for example due to the organic nature of the polymeric backbone, may adversely affect their use in cation exchange applications. Organophosphonic acid cation exchangers have also been reported in US 5,281,631 and US 5,449,462. The feedstock in the manufacture of these materials may be costly and they have limited applicability due to their physical and chemical properties. WO2006 / 013060 describes a class of substituted organopolysiloxanes which are derivatised with substituents having a thioether link. Compounds of Formula I are described in which the organopolysiloxane is derivatised with a bisthiol HS(CR1R2)fSH and contains components in which one or both of the thiol groups are reacted with an organopolysiloxane to provide a compound containing a combination of a “mono” derivatised organopolysiloxane and a bis derivatised organopolysiloxane. A compound containing a combination of a “mono” derivatised organopolysiloxane and a bis derivatised organopolysiloxane in a ratio of mole ratio of approximately 55 “mono” to 45 “bis” is commercially available from PhosphonicS under the trade names Phos-04, Phos-05 and SPM32. Compounds with higher ratios of bis to mono are also available. However, there remains a need to improve further the efficiency of removal of metals, especially precious metals, from a medium and to very low levels and desirably to lower levels than hitherto achieved. We have now found that thiol-derivatised organopolysiloxanes having one or more free thiol groups and a high level of mono-substituted organopolysiloxanes relative to bis-substituted organopolysiloxanes and other organopolysiloxanes derivatives having thioether link, amine link or having a high loading of thiol mono-substituted derivative on the organopolysiloxane are particularly effective at removing metals, especially precious metals from a medium to very low levels. In a first aspect of the present invention, there is provided a compound of General Formula I: [A]a[B]b[C]c[D]d(Formula I) in which: A is selected from: (O3 / 2)Si–[X][- S–[Y]fH; (O3 / 2)Si–[X]- S– (CH2)0-5[CHR’]f-[Y]-H (O3 / 2)Si–[X] S [Y][C(O)]e- [NR’– [Y]]fH (O3 / 2)Si–[X] -NR’– [Y]fH B is selected from: (O3 / 2)Si–[X]- S–[Y]–[X]-Si(O)3 / 2; C is Si(O)4 / 2; and D is Si(O)3 / 2V wherein: X is, independently in each occurrence, a linear or branched, optionally substituted hydrocarbyl group comprising from 2 to 12 carbon atoms; Y is, independently in each occurrence selected from (CHR’)0-8 -N- [((CHR’)2-8-S)fR’ ] ; [(CHR’)g-[C(O)]eS]f; and {(CHR’)0-8[C(O)]eN [((CHR’)2-8-S)fR’ ] }f[(CHR’)2-8-S]f; R’ is monovalent and independently selected from R, [S(CH2)2-8]fSH] and [(CH2)0-8-S]fH]; R is independently selected from H and an optionally substituted linear or branched C1-22-alkyl, C2-22-alkenyl or C2-22-alkynyl group, an aryl and a C1-22-alkylaryl group; e is, independently in each occurrence, 0 or 1; f is, independently in each occurrence, an integer from 1 to 10; g is an integer from 0 to 10; V is an optionally substituted C1-22-alkyl, C2-22-alkenyl or C2-22-alkynyl group or an aryl group or C1-22-alkylaryl sulfide, amine or a polyalkyl amine or phosphine or other phosphorous containing group; the free valences of the silicate oxygen atoms are saturated by one or more of: silicon atoms of other groups of Formula 1; hydrogen; a linear or branched C1-12-alkyl group; ; and the integers a, b and c are positive integers and d is 0 or a positive integer such that: i) the molar ratio of a:b is at least 4:1, especially at least 8:1, more preferably at least 12:1, even, at least 20:1; ii) a:c+d is from 0.005 to 1:1, preferably 0.01 to 1:1 and especially 0.05 to 0.5:1. Where a group is optionally substituted, the substitution is preferably a monovalent sulfur containing group, for example a thiol and alkylene thiol, or a monovalent amine group. In a second aspect of the present invention, there is provided a compound of General Formula I: [A]a[B]b[C]c[D]d(Formula I) in which: A is selected from: (O3 / 2)Si–[X][- S–[Y]-]fH; (O3 / 2)Si–[X]- S– (CH2)0-5[CHR’]f-[Y]-H (O3 / 2)Si–[X] S [Y][C(O)]e- [NR’– [Y]]fH (O3 / 2)Si–[X] -NR’– [Y]fH B is selected from: (O3 / 2)Si–[X]- S–[Y]––[X]-Si(O)3 / 2; C is Si(O)4 / 2; and D is Si(O)3 / 2V wherein: X is, independently in each occurrence, a linear or branched, optionally substituted hydrocarbyl group comprising from 2 to 12 carbon atoms; Y is, independently in each occurrence, selected from (CHR’)0-8 -N- [((CHR’)2-8-S)fR’ ] ; [(CHR’)g-[C(O)]eS]f; and {(CHR’)0-8[C(O)]eN [((CHR’)2-8-S)fR’ ] }f[(CHR’)2-8-S]f; R’ is monovalent and independently selected from R and [(CH2)0-8-S]fH; R is independently selected from H and an optionally substituted linear or branched C1-22-alkyl, C2-22-alkenyl or C2-22-alkynyl group, an aryl and a C1-22-alkylaryl group and is more preferably selected from H and C1-12alkyl and especially H and C1-6alkyl; e is an integer from 0 to 1; f is an integer from 1 to 10, preferably from 1 to 6, especially 1 or 2, optimally 1; g is an integer from 0 to 10; V is an optionally substituted C1-22-alkyl, C2-22-alkenyl or C2-22-alkynyl group or an aryl group or C1-22-alkylaryl sulfide, sulfoxide, sulfone, amine or a polyalkyl amine or phosphine or other phosphorous containing group; the free valences of the silicate oxygen atoms are saturated by one or more of: silicon atoms of other groups of Formula 1; hydrogen; a linear or branched C1-12-alkyl group; or other known oxo metal bridging systems; and the integers a, b, c and d are such that: i) a:c+d is from 0.005 to 1:1, preferably 0.05 to 0.5 :1; and ii) a:b is from 4 to 100,000:1, preferably from 8 to 100,000:1; and component A is present at a functional group loading (FGL) of at least 0.5 and preferably 0.8 mmol / g of the compound I and especially more than 0.9 mmol / g of the compound. Examples of suitable ranges for the FGL for component A in compounds of the invention include 0.8 to 2, especially 0.8 to 1.7 and optimally 0.8 to 1.5 mmol / g of the compound I and greater than 0.9 to 2, especially greater than 0.9 to 1.7 and optimally greater than 0.9 to 1.5 mmol / g of the compound I, for example 1mmol / g, 1.1 mmol / g, 1.2 mmol / g, 1.3 mmol / g, 1.4mmol / g and 1.5 mmol / g. Where groups Y, R and R’, or integers e and f or other groups, for example -(CH2)2-8-, appear more than once in Compound I, they may be the same or different in each occurrence. g may be from 0 to 8 or selected from 1 and 3 to 10, for example 3, 4, 5, 6, 7, 8, 9 and 10. The invention also provides in a further aspect, use of a compound according to the invention in reducing the level of a metal species, preferably a precious metal species in an organic medium, aqueous medium or a mixed aqueous and organic medium. Suitably, the medium has been employed in a chemical production process or an industrial process for example ore extraction, mining and the like, the medium including aqueous medium and an organic medium for example acetonitrile, methanol, isopropanol, ethyl acetate, toluene, organic medium from production of aldehydes for example butyraldehyde, and other organic processes such as the manufacture of pharmaceutical intermediates. Advantageously, compounds of the invention provide a higher loading capacity for the metal species on the derivatised organopolysiloxane whilst retaining porosity in the siloxane enabling removal of a higher level of metal species from a medium for a given quantity of compound I. This provides improved efficiency or, to remove a given level of metal species or to meet a specification at a defined level for a metal species, allows a smaller quantity of the compound I to be used than with known metal removing compounds. Use of a lower level of compound I to achieve a given effect provides environmental benefits in reducing the level of the compound required yet still achieving a desired effect at a given level. Compounds according to the invention have a high level of intrinsic activity and the level of functional groups may be tuned to have either a high or low level of loading according to the requirements of the user. Other advantages include high thermal stability, fixed and rigid structures, good stability to a wide range of chemical conditions, insolubility in organic solvents, high resistance to ageing. The compounds also provide an excellent combination of physical and chemical stability, relative ease of manufacture and cost effectiveness. Moiety X preferably comprises 2 to 6, more preferably 2 to 4 carbon atoms. X may be linear or branched and is, preferably linear. X may be saturated or unsaturated and is preferably saturated. X is preferably aliphatic and more preferably comprises a C2to C4alkylene group, especially a linear alkylene group having 2 to 4 carbon atoms, for example ethylene ie -CH2CH2-, propylene ie -CH2CH2CH2-, methyl propylene ie -CH(CH3)CH2CH2- and butylene ie -CH2CH2CH2CH2-. X is divalent and may contain a heteroatom, suitably selected from O, NR and S. X may contain one or more substituents including substituents selected from halogen, OR, NRR and SR where R is independently selected from H and an optionally substituted linear or branched C1-22-alkyl, C2-22-alkenyl or C2-22-alkynyl group, an aryl and a C1-22-alkylaryl group and is more preferably selected from H and C1-12alkyl and especially H and C1-6alkyl. In a preferred embodiment, X does not contain a heteratom nor substituents. Y is divalent and is suitably selected from a hydrocarbyl group and preferably a hydrocarbyl group containing a sulfur atom, a hydrocarbyl group containing a nitrogen atom and a hydrocarbyl group containing a sulfur atom and a nitrogen atom. Where Y contains a hydrocarbyl group, it preferably comprises one or more hydrocarbyl chains of 2 to 8, more preferably 2 to 6, especially 2 to 4 and optimally 2 to 3 carbon atoms. Y may be linear or branched, preferably linear. Y may be saturated or unsaturated and is preferably saturated. The hydrocarbyl component of Y is suitably an aliphatic group and more preferably is a C2 to C6,especially C2to C4alkylene group, particularly a linear alkylene group having 2 to 4 carbon atoms, for example ethylene, propylene and butylene. In some embodiments, Y may be selected from a divalent group selected from N- [((CHR’)2-8-S)fR’H ]; [(CHR’)2-8-[C(O)]eS]f; and {(CHR’)2-8[C(O)]eN [((CHR’)2-8-S)fR’ ] }f[(CHR’)2-8-S]f. Preferably groups (CHR’)2-8have 2 to 4 carbon atoms. R’ is preferably selected from H, methyl and [(CHR’)2-4-S]f. (CHR’)2-8groups are preferably (CH2)2-8groups. ((CHR’)2-8-S)fR’ groups are preferably ((CH2)2-8-S)fH groups. e is preferably 0. f is preferably from 1 to 5. In a preferred embodiment, Y is a thioalkylene group having 1 to 4, preferably 1 or 2 sulphur atoms in the hydrocarbyl chain. Y may contain one or more substituents including substituents selected from halogen, OR, NRR and SR where R is independently selected from H and an optionally substituted linear or branched C1-8-alkyl, C2-8-alkenyl or C2-8-alkynyl group, an aryl and a C1-8-alkylaryl group and is more preferably selected from H and C1-6alkyl and especially H and C1-4alkyl. In a preferred embodiment, Y is selected from a C2to C6,alkylene group and preferably a C2to C4,alkylene group which is unsubstituted or which is substituted with 1 to 4 for example 1, 2, 3 and 4 -SR groups, preferably -SH. Y may include divalent glycol residues, that is a hydrocarbyl group comprising one or more - SH substituents and thioethers in which the group Y contains one or more S atoms in the hydrocarbyl chain and which desirable has a molecular weight not exceeding 400, preferably up to 300. Examples of preferred groups Y include: -CH2CH2-S- -CH2CH2CH2- S- -CH2CH2CH2CH2- S- -CH2CH(SH) CH2- S- -CH2CH(SH) CH(SH) CH2- S- -CH2CH(SH) CH(SH) CH(SH) CH2- S- -CH2CH(SH) CH(SH) CH(SH) CH(SH) CH2- S- -CH2CH2-S-CH2CH2- S- -CH2 CH2-S-CH2 CH2-S-CH2 CH2- S- -CH2 CH2N(-CH2 CH2SH)CH2 CH2- S- -CH2CH2N(-CH2CH2CH2SH)CH2CH2CH2- S- -CH2CH2N(-CH2CH2CH2CH2SH)CH2CH2CH2CH2- S- -CH2CH2[N(-CH2CH2SH)CH2CH2]3- S- -CH2CH2[N(-CH2CH2SH)CH2CH2]5- S- -CH2C(O)[N(CH2CH2SH)CH2CH2]4N(CH2CH2SH) CH2CH2S-. In an especially preferred embodiment, in component A and component B: X is independently in each occurrence, a saturated alkylene group having 2 to 4 carbon atoms, for example ethylene, propylene, butylene and methyl propylene; Y is independently in each occurrence, a linear alkylene group, having 2 to 4 carbon atoms, for example thioethylene, thiopropylene and thiobutylene moiety and optionally comprising 1 or 2 -SH substituents; X and Y are linked by S or -NR’- e is independently in each occurrence,0 and f is independently in each occurrence, 1; the ratio of a:b is at least 4:1, preferably at least 8:1 and suitably at least 10:1; and the functional group loading of component A is from 0.5 to 2, preferably 0.8 to 1.7 and especially 0.8 to 1.5 mmol / g of the Compound I. As regards components C and D, where an end group and / or cross linker and / or polymer chain is used, it is preferred that the ratio of end group, cross linker or polymer chains to a+b+c+d is selected to provide a functional group loading of a+b of 0.5 to 2 mmol / g of compound I. R may be, independently in each occurrence an optionally substituted linear or branched group selected from C1-22-alkyl, C2-22-alkenyl, C2-22-alkynyl group, an aryl and C1-22-alkylaryl group and / or may be substituted with one or more substituents but preferably contain only hydrogen and carbon atoms. If a substituent is present, it may be selected from nitro, chloro, fluoro, bromo, nitrile, hydroxyl, carboxylic acid carboxylic esters, sulfides, sulfoxides, sulfones, C1-6- alkoxy, a C1-22-alkyl or aryl di substituted phosphine, amino, amino C1-22-alkyl or amino di (C1-22- alkyl) or C1-22-alkyl phosphinic or phosphonic group. Preferably, R is selected from hydrogen, linear and branched C1-22and desirably C1-12-alkyl, C2-22- and desirably C2-12-alkenyl, aryl and a C1-22-alkylaryl group. It is especially preferred that these groups are independently selected from a linear or branched C1-8-alkyl, C2-8-alkenyl, aryl and a C1-8-alkylaryl group. Optimally R is independently selected from hydrogen and a C1-6– alkyl group for example methyl or ethyl, or a phenyl group. Examples of suitable alkyl groups include methyl, ethyl, isopropyl, n-propyl, butyl, tert-butyl, n- hexyl, n-decyl, n-dodecyl, cyclohexyl, octyl, iso-octyl, hexadecyl, octadecyl, iso-octadecyl and docosyl. Examples of suitable alkenyl groups include ethenyl, 2-propenyl, cyclohexenyl, octenyl, iso-octenyl, hexadecenyl, octadecenyl, iso-octadecenyl and docosenyl. C1-6-alkoxy refers to a straight or branched hydrocarbon chain having from one to six carbon atoms and attached to an oxygen atom. Examples include methoxy, ethoxy, propoxy, tert- butoxy and n-butoxy. The term aryl refers to a five or six membered cyclic, 8-10 membered bicyclic or 10-13 membered tricyclic group with aromatic character and includes systems which contain one or more heteroatoms, for example, N, O or S. Examples of suitable aryl groups include phenyl, pyridinyl and furanyl. Where the term “alkylaryl” is employed herein, the immediately preceding carbon atom range refers to the alkyl substituent only and does not include any aryl carbon atoms. Examples of suitable alkaryl groups include benzyl, phenylethyl and pyridylmethyl. Sulfides may can be prepared through the free radical addition of thiols to double bonds. This is described in Org. Reactions. Vol.13, 164 - 196. The majority of this work concerns the addition of thiols to simple alkyl substituted olefins. For silicon containing olefins there are a small number of examples that include the J. Gen. Chem., 1976, 46, 1013 describes the photochemical catalysed reaction of methyl thioglycolate with trimethoxy vinylsilane to give (RO)3Si(CH2)2SCH2CO2R. ACS Omega 2018, 3, 14327−14332 shows the reaction proceeds using vinyl trimethoxy silane with both methyl thioglycolate and cysteamine hydrochloride. Also it has been reported in the Russ. J. Appl. Chem, 1999, 72, 610-612 that the radical catalysed reaction of thioglycolic acid, HSCH2CO2H, to trimethoxy vinylsilane gives a complex mixture which on either acid or neutral treatment does not lead to a polymeric material. Strong base treatment followed by acidification was reported to give a polymeric material described as [O1.5Si(CH2)2SCH2CO2H]n. The sodium salts of this polymer are capable of removing both silver and gold ions but are ineffective for other metal ions. Known sol-gel technology may be used to produce the compounds of Formula 1. Known sol- gel technology and the hydrolysis of silicon esters are described by M.A.Brook in Silicon in Organic, Organometallic and Polymer Chemistry Chapter 10, page 318, John Wiley & Sons, Inc., 2000, G.A. Scherer in Sol-gel science: the physics and chemistry of sol-gel processing, Boston: Academic Press, 1990, and J.D. Wright in Sol-gel materials: chemistry and applications, Amsterdam: Gordon & Breach Science Publishers, 2001 and the references contained within. Water may be used to catalyse hydrolysis of silicon ester precursors of component A and component B in which the silicon containing part of the component is of formula (RO)3Si- and optionally with silicon ester precursors of component C and / or component D. Acids and bases may also be used. Compounds of the invention may be synthesised via a free radical promoted addition of a thiol HS–[Y-]fH to vinyl trialkoxy silane and analogies thereof for example a C3to C12hydrocarbyl group having an alkene bond and wherein, upon reaction, the hydrocarbyl group falls within the definition of X. Where the thiol adds across the double bond at the carbon atom nearest to the silicon atom, group X will be branched and a regioisomer is produced. The ratio of the mono product to the bis and other non-mono products may be altered by changing the molar ratio of the thiol HS–[Y-]fH to vinyl trialkoxy silane or analogue alkene. The functional group loading FGL may also be controlled by altering this ratio. A higher ratio of the thiol to the silane provides a higher proportion of mono product. Preferably, the mono product is produced at a ratio of at least 4:1 relative to the bis product, suitably at least 6:1, preferably at least 8:1, more preferably at least 12:1, even, at least 15:1 such that the molar ratio of a:b in Compound I is at least 4:1. We have found that a molar ratio of at least 4:1 of the thiol HS–[Y]fH to vinyl trialkoxy silane or analogue alkene, preferably 4 to 6:1 and more preferably 4 to 4,5:1 provides a molar ratio of mono to bis of at least 4:1. The ratio of thiol to VTMS determines the ratio of mono to bis in this liquid silane intermediate. We have found that the ratio of VTMS to the SiO2 determines the functional group loading. A ratio of at least 2:1 by weight of the silica to vinyl trialkoxy silane or analogue alkene, preferably at least 3:1, especially at least 4:1 and more preferably at least 5:1 provides an FGL of at least 0.5 mmol / g. Suitably, the FGL is greater than 0.9 mmol / g. The invention provides in a further aspect, a process for the production of a component formula A as defined above comprising reacting a thiol HS–[Y-]fH with a compound of formula (RO)3Si- X’ wherein X’ is a linear or branched, optionally substituted hydrocarbyl group comprising from 2 to 12 carbon atoms which contains at least one alkene bond, in a solvent, at elevated temperature wherein the molar ratio of the thiol to the silane is at least 2:1 and preferably at least 4:1. The reaction may be carried out neat, that is in the absence of a solvent or in the presence of a solvent. The solvent suitable acts to provide a heat sink to facilitate control of the exotherm. Suitable solvents include toluene, dimethylacetamide, pyridine, acetonitrile, butanol, tetrahydrofuran (THF) and 2-methyl THF. The invention provides in a further aspect, a process for the production of a Compound of formula I as defined above comprising reacting a thiol HS–[Y-]fH with a compound of formula (RO)3Si-X’ wherein X’ is a linear or branched, optionally substituted hydrocarbyl group comprising from 2 to 12 carbon atoms which contains at least one alkene bond at elevated temperature to produce a reaction product, reacting the reaction product with silica to form a silica lattice by hydrolysing the RO- groups in the silane and, removing evolved alcohol wherein the mass ratio of the silica to the reaction product is suitably at least 3:1, preferably at least 4:1. In one example, a weight ratio of 4.8 parts silica to 1 part (RO)3Si-X’ where R is methyl and X’ is a C2alkene ie VTMS combined with 4 to 6 parts of a C2-4dithiol, for example propane dithiol, provides a FGL of approximately 1. Preferably the silane is a methoxy silane and the evolved alcohol is methanol. In a preferred method, component A is produced by a process comprising mixing the thiol HS– [Y-]fH in toluene, for example at least 2 mole equivalents and preferably at least 4 mole equivalents of toluene, and heating to 110-120°C. The vinyl trialkoxy silane or analogue alkene is mixed with toluene and, as required, an initiator, for example di-tert butyl peroxide and this mixture is added to the thiol mixture at elevated temperature, for example at least 60°C, according to the initiator used. For example a temperature of 110-120°C may be suitable when employing di-tert butyl peroxide as initiator, and heated at that temperature for a further 2 hours until at least 95% and preferably at least 98% of the vinyl trialkoxy silane or analogue alkene is consumed. The reaction mixture is cooled. An initiator is suitably employed where the thiol is ethane dithiol and, for propane dithiol, an initiator is optional but provides high levels of conversion of the silane. In an illustrative example, propane dithiol reacts with vinyl trimethoxysilane to produce a mixture of products according to the following scheme: Scheme 1 The synthesis shown in Scheme 1 is suitably followed by a step in which the products of Scheme 1 are reacted with silica to produce a Compound I according to the invention, as shown in Scheme 2. Examples of suitable combinations of the equivalent level of alkylene dithiol, initiator, for example peroxide, rate of addition of the vinyl trimethoxysilane which provide Component A include: PDT (eq) Peroxide (eq) Addition rate VTMS Area % bis (h) 4 0 1 9 4 0.02 1 9.1 4 0 3 7 6 0.02 1 6.3 6 0 3 5.1 The Area% bis figures provide an indication of the relative amount of bis compound with the mono compound being the major component. A product of formula 1 can contain amounts of a monodisulfide of formula (O3 / 2)Si–[X]- S–[Y]-S [-S–[Y]-]fSH. This can be formed as a result of the presence of the disulfide as a contaminant in the starting dithiol or can be formed during the first step of the reaction. The mono disulfide can have more than one disulfide bond depending on the degree of disulfide formation. For example where the degree of disulfide formation is low f will be one but if more disulfide is formed there may be components where f is 1, 2 and 3 simultaneously. The reaction may also contain the a bis disulfide of formula (O3 / 2)Si–[X]- S–[Y]–S–S–[Y]–S– [X]-Si(O)3 / 2.The bis disulfide can be formed in the reaction shown in scheme 1 but can also be formed in the process of preparing the samples for Q-NMR. The disulfide formation is facilitated by the presence of base. Scheme 2 a. Propane dithiol, di-tert-butylperoxide, toluene; b. Silica, toluene water, methanol The liquid intermediate (the product of step a in Scheme 2) has a single primary thiol and this may react with a second molecule of the alkene to give the bis product (component B) and / or, a further molecule of the propane dithiol to provide other components shown in Scheme 1. Proton NMR spectroscopy, for example standard laboratory / bench-top scale NMR instruments, may be employed to monitor the progress of the reaction in Scheme 1 and Scheme 2. The presence of peaks due to the SH group of the mono isomer may be used to calculate the mono content and the bis content may be determined by taking into account the content of the mono product and unreacted propane dithiol, for example due to SH peaks for the thiol, and CH2-S and C-CH2-C peaks of the thiol, as appropriate. Preferably, excess thiol reactant is reduced or removed from the product after step b by washing prior to NMR or Q-NMR analysis. Gas chromatography or HPLC may be employed to monitor the ratio of mono to bis products and other components of the reaction in Scheme 1, step a, as required. Suitably, the HPLC method referred to herein is carried out using a ThermoScientific ™ Hypersil ™ BDSC18, 4.6x150mm, 5µm column. Preferably the process is operated at a temperature of 25°C and a flow rate of 1mL / minute with an injection volume of 15µL. Suitably, the mobile phases employed are A: water; B: methanol; D: 1%v / v trifluoroacetic acid (TFA) in water with a timetable of : The stop time is suitably 18minutes. Different detectors may be used, for example a UV detector (220nm) may be employed for monitoring and detecting thiol or thiol-type reactions and an evaporative light scattering detector may be employed for amine and alkylene sulfide reactions, for example with the evaporator at 30°C, nebuliser at °C, gas flow of 1.60 standard litre per minute (SLM). Suitably the sample is prepared by diluting 0.25mL of the reaction mixture to 10ml with methanol and analysed the same day. Suitably, NMR is suitable for providing an indication of the conversion or consumption of the silane during step a and HPLC provides an indication of the distribution of different products and their relative quantities from the reaction. To form the Compound I from the components of the addition reaction between the thiol and the silane, silica is added to the cooled reaction mixture, for example in a quantity of 5 times the mass of the vinyl trialkoxy silane or analogue alkene, and water is added and the mixture refluxed at a temperature of 80 to 85°C and the solvent remove, for example using Dean and Stark apparatus. Alcohol, from hydrolysis of the silane ester suitably evolves and the reaction is heated to remove solvent. The reaction product is then suitably washed a plurality of times, for example 5, and the product then dried. Aminothiols prepared by a one step reaction of an alkylene sulfide on aminopropyltriethoxysilaneare known, for example as described in the paper N,S Ligands for Preconcentration or Elimination of Heavy Metals. Synthesis and Characterisation of Aminoethanethiols and Aminoethanethiol-modified Silica Gel by Bresson et al, published as J. Chem. Research (S), 1998, 490. J. Chem. Research (M), 1998, 1919±1932. This paper reports a mix of reaction products. Where component A is of formula, (O3 / 2)Si–[X] -NR’– [Y]fH] or of formula: (O3 / 2)Si–[X][- S–[Y]-]fH where Y includes a divalent hetero group of formula: {(CHR’)2-8[C(O)]eN [((CHR’)2-8-S)fH ] }f[(CHR’)2-8-S]fcomponent A is suitably produced by reacting a trialkoxy silane having a primary amine group with a sulphur-containing hydrocarbyl compound to produce a compound A having a secondary and preferably tertiary amine with one or two hydrocarbyl thiol groups. The amine may be reacted under suitable conditions, for example at elevated temperature, with a substituted thiol, preferably a chloro alkyene thiol, for example chloroethane thiol and chloropropane thiol, or a cyclic sulfide. The cyclic sulfide may be thiirane (ethylene sulfide), a 5 to 6 membered ring containing a sulfur atom in the ring and optionally being substituted. One example of a reaction scheme to produce a Compound A includes: In other preferred embodiments, the Compound A is produced from a silane having a thio amine group, preferably a group comprising a thioether and a terminal amine group, for example as shown in the following reaction Scheme 4:: Scheme 4 The compounds A in the above schemes are predominantly mono, preferably at least 60% or at least 70% and suitably at least 80% or at least 90%. Preferably the Compound A comprises at least 95% mono and preferably exclusively, mono. Components A and B, if present, are suitably analysed and characterised using a 40 to 60MHz NMR instrument or a high field, for example over 200MHz, NMR instrument. Suitably, the functionality of the silica particles are dissolved in deuterium oxide (D2O) using NaOH or NaOD to release the material off the solid silica by cleaving all the Si-O-Si bonds holding the functional components onto the silica particle. The samples are prepared with a reference standard of potassium phthalate monobasic or maleic acid (see Anal. Chem. 2018, 90, 13322−13330) added to the solution of sample. Standard NMR instruments, for example 40 to 60MHz field may be employed for quantitative NMR analysis (Q-NMR) as well as high filed instruments such as 200 or 300 MHz. The Q-NMT procedure suitably adheres materially to the following procedure: A reference sample standard, for example potassium phthalate monobasic is prepared gravimetrically in D2O. A sample of the compound I (37.5 mg ±5 mg) is accurately weighed (4 decimal place) into a vial and the weight recorded. Sodium deuteroxide (4 drops) and deuterium oxide (0.7 mL ±0.1 mL) is added to the sample, the lid replaced and the sample warmed in an oven for 30 minutes, or until the sample is fully dissolved optionally with swirling to incorporate silica at the meniscus into the solution. The sample is allowed to cool. 0.7 mL ±0.1 mL of reference solution is weighed accurately (4 decimal place) into the vial (c) containing the dissolved Compound I to produce a homogeneous solution and the weight is accurately measured. 0.7 mL ±0.1 mL of the solution is transferred from (c) to a clean, dry NMR tube and the tube labelled. A suitable volume of the reference standard is added to the sample and the accurate mass recorded. The calibrant concentration should be with the range of 0.2 to 5 times the concentration of the analyte. The final mass of the solution (including reference standard) is recorded. It is important that the spin lattice relaxation (T1) is assessed for each new material. This is to ensure the molecule has fully relaxed to give the most accurate quantification of the components in the NMR sample. This can be determined by following the procedure in Anal. Chem.2018, 90, 13322−13330 on page 13328. The acquired spectrum requires phase and baseline correction. A 5th order polynomial baseline correction is suggested by the reference. For a compound as seen in Scheme 1 analysed by the above Q-NMR method the SiCH2 comes between 0.5 and 1 ppm in the 1H NMR spectrum. The CH2 ‘s next to S come between 2.4 and 3 ppm and the middle CH2 of the propyl group comes between 1.6 and 2.2 ppm. The middle CH2 of the propyl group is useful to determine the ratios of the mono, bis and disulfide components of the product. The calculation of the individual components is shown in Equations 1 to 7 below. Equation 1: mmol reference standard (Std) ^^^^ reference standard = 1000 × Std ^^^^ × (Std ^^^^^^ ^^^n ^^^^ / Std ^^^^^^^^^^ ^^^^ mass) ^^ Std Equation 2: mmol mono per gram ^^^^ ^^^^ / ^^^^ = ^^^^ Std × ∫^^ / 2 ∫Std / z sample mass Equation 3: mmol bis ^^^^ ^^^ / ^^^^ = ^^^^ Std × ∫^^ / 2 ∫Std / z ^^^^^^ ^^^^ Equation 4: mmol disulfide ^^^^ mono / ^^^^ = ^^^^ Std x ∫^G / 4 ∫Std / z sample mass Equation 5: mmol Regioisomer ^^^^ mono / ^^^^ = ^^^^ Std x ∫^A / 3 ∫Std / z sample mass Equation 6: FGL FGL (mmol per gram) = ^^^^ Std x ∫(1.7 to 2.1) / 2 ∫Std / z sample mass Equation 7: mmol Dipodal Content Dipodal Content = bis content x 100 FGL For a compound in Scheme 1 the assignment of the protons to differentiate the reaction components are shown in Scheme 3 below. Scheme 3: NMR assignment of components in Scheme 1 for Q-NMR method Figure 1A shows the NMR spectra of a material made according to Example 3 and Comparative Example A below. Figure 1B shows the HPLC comparison of step a of Scheme 2, with a markedly higher proportion of the mono product (at 8.2 min) than the bis product (at 7 min). In Figure 1A, the SH signal will not be observed due to the sample being in D2O. The protons on carbon next to sulfur are HFand are not explicitly labelled in Scheme 3. The approximate ppm shifts for a comparison NMR as shown in Figure 1 is provided in Table 1. Table 1: NMR assignment of components in Scheme 1 for Q-NMR method ppm Multiplicity Assignment 0.5-0.9 N / A Si-CH2 1.2 D HA1.65 Q HB1.75 Q HC 1.85 q / m HD2.35 T HE 2.55 M H 2.7 T HGNMR spectra showing material of Scheme 1 made by the new method and by Comparative Example A are shown in Figure 1. The results are used in the calculation to determine the FGL and the dipodal content according to the following equations where z is the number of protons integrated for the chosen internal standard: A wide range of free radical initiators may be used for this reaction including peroxides, especially for example alkyl peroxides for example di-tert-butyl peroxide. Other examples include AIBN (2,2'-Azobisisobutyronitrile). Addition of a very small amount of the initiator every few hours improves the overall yield. The amount of initiator required depends on the thiol used and additional quantities of initiator may be added to increase the consumption of the alkene. Reaction temperatures are dependent on the radical initiator, between 40 to 170°C, suitably 60-170oC may be used depending on whether a solvent is employed and, if so, the type of solvent. For example, a reaction temperature of between 70-120oC may be suitable where toluene is used as a solvent. Reaction times of between 5 minutes to 48 hours have been used with 1 / 2 to 6 hours preferred. For reactions showing incomplete consumption of the alkene, an additional portion of the radical initiator can be added and the reaction maintained at the original or higher temperature for periods of ½ to 2 hrs before reanalysing the reaction for reaction progress. The product may be modified by reaction to add further functional groups to the compound. A range of solvents may be used in the preparation of the mono compound, formation of the compound I and in washing, for example toluene, ethanol, tetrahydrofuran and butanol. Ratios, by weight, of the solvent to the combined weight of the reagents from 100 to 0.01 can be used, with ranges from 2-10 being preferred. Within this range the exotherm of the thiol radical reaction can be controlled. Hydrolysis is suitably carried out in the presence of water, acid or alkali, preferably water. Compounds of Formula 1 can also be prepared by treating a preformed material such as silica or aluminium oxide or carbon with precursor compounds of components A to D. At the end of the reaction the solid is filtered off and washed extensively with a solvent, for example water, toluene and alcohols, to remove any remaining starting materials. Templates to aid the preparation of pores with particular sizes and distributions in compounds of Formula 1 can be added at the sol gel stage. On preparation of the solid organopolysiloxane of Formula 1 these templates can be washed out using known methods. Compounds of Formula 1 have a wide range of uses. Compounds according to the invention have a desirable combination of characteristics rendering them suitable for use in reducing the levels of metal species in a medium, for example a process stream in a chemical process, mining process, or other industrial process or assembly process or a chemical or pharmaceutical synthesis and also in a range of other applications including acting as scavengers for inorganic and organic compounds, solid phase purification or extraction materials, solid phase synthesis materials and chromatography materials, or which are precursors for these. The present invention provides a process for treating a feed material comprising contacting a compound of Formula 1 with a feed material: i) to remove a component of the feed material so as to produce a material depleted in the removed component; or ii) to remove an ionic species in the feed material in an ion exchange process. The feed material may be a continuous stream for example a continuous process reaction feedstock, or may be in the form of a batch of material for discrete treatment. The feed material, for example a waste water or waste process stream, may be treated to selectively remove one or more components of the feed. The removed component may be an undesirable material in the feed and the process acts to provide a desired composition for the feed material that has been depleted in the selectively removed component after contact with compounds of Formula 1. This process may be used for example in removing unwanted species from a feed material in a pharmaceutical manufacturing or formulation process to improve the purity level of the pharmaceutical product as regards the removed material, for example metal species. Compounds of Formula 1 are suitable for removing precious metals such as palladium, platinum and rhodium species from a solution, for example a batch quantity or a process stream, thereby to reduce and suitably to minimise, the level of the precious metal. The level of other metals, for example catalytic metals may be reduced in a solution as desired. The metal may be free, have ligands or bound to functional groups. Such functional groups may be found in a wide range of applications, for example in active pharmaceutical ingredients such as amides, amines and carboxylic acids. Compounds of Formula 1 may be used, as scavengers, to remove excess inorganic or organic reagents and side products from reactions mixtures or from impure chemical products. Unlike the polystyrene based scavengers, organopolysiloxane compounds of Formula 1 can work in all solvents and are not limited in their application to reaction temperatures below 80oC. In addition compounds of Formula 1 are less prone to swelling and possess the significant advantage of very fast kinetics compared to organic polymers. These organopolysiloxane compounds of Formula 1 have many advantages for example they possess good thermal and chemical stability and broad solvent compatibility. Compounds of Formula 1 can be applied as thin films onto a variety of surfaces. The invention will now be described in detail with reference to illustrative examples of the invention. Examples 1 to 4 Products of Compound I according to the invention were produced by a process according to Scheme 1 as set out herein by reacting vinyl trimethyl silane (VTMS) with propane dithiol (PDT) in the ratios set out in Table 2 in accordance with the method set out below. Table 2 Example PDT VTMS Mono Bis 1 2.8 1 85 15 2 3 1 86 13 3 4 1 91 9 4 6 1 93 7 The ratio of mono to bis may be modified slightly, for example by + / - 1% and + / -2%, by varying the excess of PDT, rate of addition of VTMS / PDT, the amount of initiator, temperature and solvent. Step a: 1,3-propane dithiol (mole equivalents as per Table 2) and toluene (1ml per g of VTMS) were mixed in a flask and heated to 110 to 120 °C. VTMS, toluene (1ml per g of VTMS) and di-t- butylperoxide (0.03 wt % relative to VTMS) were mixed together in a dropping funnel and added to the PDT mixture over 1 hour and heated at 110-120 °C for 4 hours. The reaction was analysed by proton NMR during the reaction to monitor the consumption of VTMS. The reaction mixture was then cooled to ambient temperature. The progress of the reaction may also be monitored by HPLC Step b: Silica gel (5 g per g of VTMS) and toluene (12ml per g of VTMS) was mixed and the cooled reaction mixture from Step a was added and heated. Evolved methanol was removed and upon the reaction temperature exceeding 85 °C, the reaction mixture was cooled and water (0.7 weight equivalent of VTMS) was added. The reaction mixture was refluxed for 1 hr and solvent removed using Dean and Stark conditions. The Dean and Stark extraction of water was continued until a batch temperature of 108 to 110 °C was obtained. The reaction mixture was then cooled to ambient temperature, filtered, slurry washed 5 times with methanol and dried. The product had a mono to bis ratio as shown in Table 2 and an FGL of 0.8 to 1.1 mol / gram. Comparative Example A A product produced by reacting VTMS and PDT in a molar ratio of 1.2:1 was produced using the same procedure as set out for Examples 1 to 4. The reaction was monitored by Q-NMR and the final product from Step a had a molar ratio of mono to bis of 55:45. . The product of Step a) was reacted with silica according to the process for Step b), set out above in Examples 1 to 4. The FGL of the product was 0.75 to 0.9 mmol / gram. Example 5 A product of Compound I according to the invention as shown in Scheme 4 was produced by a process as follows: Step a: Cysteamine hydrochloride (3.75 g, 1.1 molar equivalents per mol of VTMS) was heated to 75°C to form a melt, to which a solution of VTMS (4.52 g) and di-tert-butyl peroxide (0.2 mL, 0.05 mL per g of VTMS) were added dropwise. Once addition of the VTMS solution was complete, a second charge of di-tert-butyl peroxide (0.05 mL per g of VTMS) was added to the reaction mixture. The mixture was stirred for three hours, maintaining the temperature, then a third charge of di-tert-butyl peroxide (0.2 mL, 0.05 mL per g of VTMS) was added to the reaction mixture. At this point, the flask contents were a homogeneous single-phase mixture. The reaction was analysed by proton NMR to monitor the consumption of VTMS. The reaction mixture was heated for a further two hours, then cooled to ambient temperature. Triethylamine (3.85 g, 1.3 molar equivalents per mol of VTMS) was added dropwise to the stirred reaction mixture causing formation of a precipitate. Toluene (10 mL, 2.2 mL per g of VTMS) was added, then the reaction mixture was filtered to remove the precipitate. Water was removed from the reaction intermediate on a rotary evaporator, then inert and dry conditions were maintained by use of a Schlenk line. Step b: The reaction product from Step a was heated to 50°C, then ethylene sulfide (3.8 mL, 2.3 molar equivalents per mol of VTMS) was added dropwise to flask under dry and inert conditions. The reaction mixture was stirred for a further 4 hours at 50°C, then cooled to ambient temperature. The reaction was analysed by proton NMR to assess reaction of the ethylene sulfide. Step c: Silica (13.6 g dry mass, 3 g per g of VTMS) and toluene (20 mL, 1.7 mL per g of VTMS) was added to the reaction product of Step b and heated to reflux, at which point evolved methanol was removed using Dean Stark conditions. This was maintained for two hours, then the reaction mixture was cooled to 60°C and water (0.45 mL, 0.1 mL per g of VTMS) was added to the reaction mixture. The mixture was returned to reflux with Dean Stark conditions for a further two hours until a batch temperature of 108 to 110 °C was obtained. The reaction mixture was then filtered to isolate the silica reaction product which was slurry washed five times with methanol (100 mL, 22 mL per g of VTMS) then dried. The final silica product was analysed by quantitative proton NMR. The products of Example 5 and Comparative Example A were tested in accordance with the General Procedure for Examples 6 to 12 set out immediately below to determine their relative effectiveness in removing platinum and palladium from a process stream containing those metals. The results showing the loading of the metal on the compound are set out below: Pt (g / kg) Pd (g / kg) Total (g / kg) Comparative Example A 9.5 35.2 45 Example 5 13.6 84.9 99 The compound of Example 5 has a far higher loading of platinum (43% greater) and a far higher loading of palladium (140%) and over double the total loading of platinum and palladium as compared to the loading of the compound of Comparative Example A. Examples 6 to 12 and Comparative Examples B to H General Procedure The Compound I of Example 3 and the comparative compound of Comparative Example A were tested to determine their effectiveness in reducing the level of residual metal species in different process streams and to calculate the loading of the metal species on the compound following treatment. Tests were carried out in which a chosen process stream containing a metal species was agitated with a defined number of molar equivalents of Compound I or the Comparative Example A relative to the metal content of the stream. The mass of Compound I or Comparative Example A to use per test was calculated from the number of molar equivalents defined in the test, the functional group loading of the material (mol of surface ligand per g of material), and the concentration of the target residual metal(s) in the stream. Compound I and Comparative Example A both have an estimated functional group loading of 0.8 mmol / g. Mass of scavenger = ) The metal content of the process stream following treatment with Compound I, Comparative Example A or Comparative Example J was measured via ICP-OES. For all process streams, a low molar equivalent (0.5-2) amount and a high molar equivalent (10-20) amount of Compound I and Comparative Example A were tested. For the low molar equivalent tests, the residual concentration of metal in the process stream was measured and the subsequent amount of metal bound to the Compound was either calculated (see equation) or measured directly, then the % Loading Improvement of Compound I relative to Comparative Example A was calculated. These results are shown in Table 3. A higher loading capacity of Compound I relative to Comparative Example A is a demonstration of the improved performance of the new compounds. Calculated^loading^ For the high molar equivalent tests, the minimum amount of residual metal in the process stream following treatment may be determined, and the % metal removal was calculated. These results are shown in Table 3. Example 6: To a 100ml multineck flask was added 31 g of an organic stream of acetonitrile containing 185ppm of Pd.0.5 molar equivalents of Compound I of Example 3 was calculated at 34 mg (185mg / kg, 0.8 mmol per g) from the equation above for mass of scavenger and added to the flask. The stream was stirred for 72hrs at room temperature. The liquid was filtered, a portion microwave digested with aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 102 mg / kg (Table 3). Based on the Pd removed from solution the calculated metal loading on compound 1 of Pd was 63 g / kg (Table 3). A treatment at 12 equivalents of the acetonitrile stream showed 93% removal of Pd to a residual of 13 mg / kg remaining in the stream. Comparative Example B: To a 100ml multineck flask was added 30 g an organic stream of acetonitrile containing 185ppm of Pd. 0.5 molar equivalents of Comparative Example A was calculated at 33 mg (185mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 72hrs at room temperature. The liquid was filtered, a portion microwave digested with aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 127 mg / kg. Based on the Pd removed from solution the calculated loading of Pd was 38.6 g / kg. A treatment at 10 equivalents showed 91% removal of Pd to a residual of 17 mg / kg remaining in the stream. Example 7: To a 500ml multineck flask was added 320 g of an organic waste stream of methanol containing 161ppm of Pd. 0.5 molar equivalents of Compound I was calculated at 304 mg (161mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 72hrs at room temperature. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 88 mg / kg. The filtered solid was washed with MeOH, oven dried under vacuum for 18 hrs, microwave digested with reverse aqua regia and analysed by ICP-OES to determine the loading of metal on the scavenger as 49.7 g / kg. A treatment at 10 equivalents showed 99% removal of Pd to a residual of 1 mg / kg. remaining in the stream. Comparative Example C: To a 500ml multineck flask was added 320 g of an organic waste stream of methanol containing 161ppm of Pd.0.5 molar equivalents of Comparative Example A was calculated at 300 mg (161mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 72hrs at room temperature. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 113 mg / kg. The filtered solid was washed with MeOH, oven dried, microwave digested with reverse aqua regia and analysed by ICP-OES to determine the loading of metal on the scavenger as 33.9 g / kg. A treatment at 10 equivalents showed 98% removal of Pd to a residual of 3.6 mg / mg. remaining in the stream. Example 8: To a 40ml tube with screw top lid was added 21 g of an organic waste stream of isopropanol containing 321ppm of Pd. 0.41 molar equivalents of Compound I was calculated at 32 mg (321mg / kg, 0.8 mmol per g) and added to the flask. The stream was shaken at 250 rpm for 24hrs at room temperature. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 234 mg / kg. Based on the Pd removed from solution the calculated loading of Pd on the scavenger was 51.5 g / kg. A treatment at 10 equivalents showed 99.7% removal of Pd to a residual of 0.9 mg / kg remaining in the stream. Comparative Example D: To a 40 ml tube with screw top lid was added 20.3 g of an organic waste stream of isopropanol containing 321ppm of Pd. 0.41 molar equivalents of Comparative Example A was calculated at 31 mg (321mg / kg, 0.8 mmol per g) and added to the flask. The stream was shaken at 250 rpm for 24hrs at room temperature. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 258 mg / kg. Based on the Pd removed from solution the calculated loading of Pd on the scavenger was 36 g / kg. A treatment at 10 equivalents showed 99% removal of Pd to a residual of 4 mg / mg remaining in the stream. Example 9 To a 40 ml tube with screw top lid was added 10 g of an organic waste stream of ethyl acetate containing 55ppm of Pd. 2 molar equivalents of Compound 1 was calculated at 12 mg (55mg / kg, 0.8 mmol per g) and added to the flask. The stream was shaken at 250 rpm for 24hrs at room temperature. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 5.8 mg / kg. Based on the Pd removed from solution the calculated loading of Pd on the scavenger was 41.3 g / kg. A treatment at 10 equivalents showed 99.5% removal of Pd to a residual of 0.3 mg / kg remaining in the stream. Comparative Example E To a 40 ml tube with screw top lid was added 10 g of an organic waste stream of ethyl acetate containing 55ppm of Pd. 2.1 molar equivalents of Comparative Example A was calculated at 12 mg (55mg / kg, 0.8 mmol per g) and added to the flask. The stream was shaken at 250 rpm for 24hrs at room temperature. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 17 mg / kg. Based on the Pd removed from solution the calculated loading of Pd on the scavenger was 30.4 g / kg. A treatment at 10 equivalents showed 99.1% removal of Pd to a residual of 0.5 mg / kg remaining in the stream. Example 10 To a 40 ml tube with screw top lid was added 25.7 g of an organic stream of methanol containing 550ppm of Pd.1.1 molar equivalents of Compound 1 was calculated at 182 mg (550mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 24hrs at ambient temperature. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 237 mg / kg. Based on the Pd removed from solution the calculated loading of Pd on the scavenger as 44.7 g / kg. A treatment at 10 equivalents showed 95% removal of Pd to a residual of 30 mg / kg remaining in the stream. Comparative Example F To a 40 ml tube with screw top lid was added 25.5 g of an organic stream of methanol containing 550ppm of Pd.1.1 molar equivalents of Comparative Example A was calculated at 181 mg (550mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 24hrs at ambient temperature. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 348 mg / kg. Based on the Pd removed from solution the calculated loading of Pd on the scavenger as 28.7 g / kg. A treatment at 10 equivalents showed 91% removal of Pd to a residual of 53 mg / kg remaining in in the stream. Example 11 To a 250ml multineck flask was added 112 g of an organic stream from butyraldehyde production containing 220ppm of Rh.0.5 molar equivalents of Compound I was calculated at 146 mg (550mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 72hrs at 72 degC. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 175 mg / kg. The filtered solid was washed with MeOH, oven dried, microwave digested and analysed by ICP- OES to determine the loading of Rh on the scavenger as 43.5 g / kg. A treatment at 10 equivalents showed 98% removal of Rh to a residual of 4.0 mg / kg remaining in the stream. Comparative Example G To a 250ml multineck flask was added 112 g of an organic stream from butyraldehyde production containing 220ppm of Rh.0.5 molar equivalents of Comparative Example A was calculated at 153 mg (550mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 72hrs at 72 degC. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 216 mg / kg. The filtered solid was washed with MeOH, oven dried, microwave digested and analysed by ICP-OES to determine the loading of Rh on the scavenger as 32.7 g / kg. A treatment at 10 equivalents (1.4 g for 50 g of stream) showed 98% removal of Rh to a residual of 4.0 mg / kg remaining in the stream. Example 12 To a 40 ml tube with screw top lid was added 20 g of an aqueous mining stream containing 23 ppm of Pd, 14 ppm of Rh and 773 ppm of Ir.1.0 molar equivalents of Compound I was calculated at 109 mg (550mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 24hrs at ambient temperature. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal remaining in the stream at 0.1 mg / kg Pd, 1.6 mg / kg Rh and 409 mg / kg Ir, . Based on the metal removed from solution the calculated loading of metal on the scavenger as 3.8 g / kg Pd, 2.2 g / kg Rh and 73.4 g / kg Ir (79.4 g / kg of combined PGM’s). A treatment at 10 equivalents showed 99% removal of Rh and Pd and 91 % removal of Ir to a residual of 67 mg / kg remaining in the stream. Comparative Example H To a 40 ml tube with screw top lid was added 20 g of an aqueous mining stream containing 23 ppm of Pd, 14 ppm of Rh and 773 ppm of Ir. 1.0 molar equivalents of Comparative Example A was calculated at 109 mg (550mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 24hrs at ambient temperature. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 0.9 mg / kg Pd, 2.2 mg / kg Rh and 426 mg / kg Ir, . Based on the metal removed from solution the calculated loading of metal of the scavenger as 3.6 g / kg Pd, 2.1 g / kg Rh and 69.6 g / kg Ir (75.3 g / kg of combined PGM’s). A treatment at 10 equivalents showed 99% removal of Rh and Pd and 89 % removal of Ir to a residual of 80 mg / kg remaining in the stream. Comparative Example J [for component A with molecular formula Si(O3 / 2)CH2CH2CH2SH and no component B] 3-Mercaptopropyl trimethoxysilane (13.75 ml, 1.0 vol, 3-MPTS) was added to a flask followed by Silica gel (44g, 3 g per g of 3-MPTS) and toluene (103 ml, 7.5 ml per g of 3- MPTS). The mixture was stirred with overhead stirring and heated. Evolved methanol was removed and upon the reaction temperature exceeding 85 °C, the reaction mixture was cooled and water (4.6ml, 0.33 ml per g of 3-MPTS) was added. The reaction mixture was refluxed for 1 hr and solvent removed using Dean and Stark conditions. The Dean and Stark extraction of water was continued until a batch temperature of 108 to 110 °C was obtained. The reaction mixture was then cooled to ambient temperature, filtered, slurry washed 5 times with methanol and dried. The FGL of the product as 1.2 to 1.5 mmol / gram. Comparative Example K To a 40 ml tube with screw top lid was added 20 g of an aqueous mining stream containing 23 ppm of Pd, 14 ppm of Rh and 773 ppm of Ir. 1.0 molar equivalents of Comparison Example J was calculated at 109 mg (550mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 24hrs at ambient temperature. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 3.6 mg / kg Pd, 8.2 mg / kg Rh and 485 mg / kg Ir, Based on the metal removed from solution the calculated loading of metal of the scavenger as 3.1 g / kg Pd, 1.0 g / kg Rh and 59.1 g / kg Ir (63.2 g / kg of combined PGM’s). A treatment at 10 equivalents showed 99% removal of Rh and Pd and 80 % removal of Ir to a residual of 151 mg / mg remaining in the stream. The results shown in Table 3 demonstrate that compounds according to the invention provide improved removal of metal species from a range of different mediums relative to a comparative compound having a lower proportion of “mono" component A. The metal loading on the compound of the invention increases markedly relative to the comparative compound and the metal may be recovered from the compound to a higher degree than for comparative compounds, thereby enabling recovery and reuse of a metal species to a far higher degree than a comparative compound which has a lower proportion of the mono component A. Example 13 To a 40 ml tube with screw top lid was added 15 g of an organic stream of ethanol and acetic acid from Rh hydrogenation of an alkene containing 11.5 ppm of Rh. 20 molar equivalents of Compound 1 was calculated at 44 mg (11.5 mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 64hrs at 70 degC. The liquid was filtered, a portion microwave digested with aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 3.9 mg / kg showing 66% Rh removal. Comparative Example L To a 40 ml tube with screw top lid was added 15.1 g of an organic stream of ethanol and acetic acid from Rh hydrogenation of an alkene containing 11.5 ppm of Rh. 20 molar equivalents of Comparative Example A was calculated at 45 mg (11.5 mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 64hrs at 70 degC. The liquid was filtered, a portion microwave digested with aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 5.0 mg / kg showing 56% Rh removal. Example 14 To a 40 ml tube with screw top lid was added 29.4 g of an organic stream from butyraldehyde production containing 20.7 ppm of Rh.10.3 molar equivalents of Compound 1 was calculated at 63 mg (20.7 mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 24hrs at 65 degC. The liquid was filtered, a portion microwave digested with aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 4.3 mg / kg showing 79% Rh removal. Comparative Example M To a 40 ml tube with screw top lid was added 30.5 g of an organic stream from butyraldehyde production containing 20.7 ppm of Rh.9.7 molar equivalents of Comparative Example A was calculated at 61 mg (20.7 mg / kg, 0.8 mmol per g) and added to the flask. The stream was stirred for 24hrs at 65 degC. The liquid was filtered, a portion microwave digested with aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 7.2 mg / kg showing 65% Rh removal. Example 15 To a 40 ml tube with screw top lid was added 10 g of an organic stream from butyraldehyde production diluted with toluene containing 762 ppm of Rh.1 molar equivalents of Compound I was calculated at 88 mg (762mg / kg, 0.8 mmol per g) and added to the flask. The stream was shaken for 24hrs at 100 degC. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 221mg / kg. The filtered solid was washed with MeOH, oven dried, microwave digested and analysed by ICP-OES to determine the loading of Rh on the scavenger as 63.8 g / kg. A treatment at 10 equivalents showed 96% removal of Rh to a residual of 27.6 mg / kg remaining in the stream. Comparative Example N To a 40 ml tube with screw top lid was added 10 g of an organic stream from butyraldehyde production diluted with toluene containing 762 ppm of Rh. 1 molar equivalents of Comparative Example A was calculated at 88 mg (762mg / kg, 0.8 mmol per g) and added to the flask. The stream was shaken for 24hrs at 100 degC. The liquid was filtered, a portion microwave digested with reverse aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 483 mg / kg. The filtered solid was washed with MeOH, oven dried, microwave digested and analysed by ICP-OES to determine the loading of Rh on the scavenger as 36.5 g / kg. A treatment at 10 equivalents showed 91% removal of Rh to a residual of 71 mg / kg remaining in the stream. Example 16 To a 40 ml tube with screw top lid was added 10 g of a 2-MeTHF solution of an API containing 250 mg / kg of Pd (pharmaceutical intermediate synthesis by a Negishi coupling). 10 molar equivalents of Compound I was calculated at 294 mg (250 mg / kg, 0.8 mmol per g) and added to the flask. The stream was shaken for 24hrs at 50 degC. The liquid was filtered, a portion microwave digested with aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 6.8 mg / kg giving 97% removal of Pd. To further examine the performance of Compound I, a jacketed glass column was packed with 5 g of Example 3 Compound I. The jacket was heated to 60 degC and the stream pumped through at a rate of 1.5 g / hr. The effluent of the column was collected in fractions of 2 to 10 grams. A portion of every third sample was a taken for microwave digested with aqua regia and analysed by ICP-OES to determine the residual metal in the stream. In Figure 2, the column progress shows that the 5 gram column treated 80g of stream before the column starts to reach saturation, treating approximately 60% more stream than the comparative compound in Comparative Example O. Comparative Example O To a 40 ml tube with screw top lid was added 10 g of a 2-MeTHF solution of an API containing 250 mg / kg of Pd. 10.3 molar equivalents of Comparative Example A was calculated at 304 mg (250 mg / kg, 0.8 mmol per g) and added to the flask. The stream was shaken for 24hrs at 50 degC. The liquid was filtered, a portion microwave digested with aqua regia and analysed by ICP-OES to determine the residual metal in the stream at 6.2 mg / kg giving 98% removal of Pd. A jacketed glass column was packed with 5 g of Comparative Example A. The jacket was heated to 60 degC with circulating fluid and the stream pumped through at a rate of 1.5 g / hr. The effluent of the column was collected in fractions of 2 to 10 grams. A portion of every third sample was a taken for microwave digested with aqua regia and analysed by ICP-OES to determine the residual metal in the stream. In Figure 3, the column progress shows that the 5 gram column treated 50g of stream before the column starts to reach saturation. The process stream for removal of Pd from a pharmaceutical intermediate synthesised by a Negishi coupling was treated with the comparative compound and the compound of Example 3 by contacting the stream with the relevant compound in a column. In the process, the mass of stream treated was recorded and the level of residual Pd in the stream at that mass was recorded. The results are shown in the graphs of Figure 2 and 3. The performance at 10 equivalents of scavenger showed little difference but the increased loading capacity of Compound I of Example 3 compared to Comparison Example A highlights the improved performance of the compounds of the invention. The summary of the results from the examples comparing Compound I to Comparative Example A are shown in Table 3 and demonstrate that a higher loading of the mono species in the compound of the invention as compared to the comparative compound provides a higher level of removal of the metal species. Where the level of metal removal is similar the loading capacity has increased by as much as 75%. The increased loading capacity means that the compound is more efficient and can treat more process stream before needing replacement, exhibiting improved efficiency compared to the comparative compound.

[0002] Table 3 Example Metal in Stream Residual Metal Loading % Loading Removal of metal Residual metal stream Metal in on compound Improvement from process mg / kg stream mg / kg g / kg stream % 6 185ppm Pd Acetonitrile 102 63 63 93 13 B 185ppm Pd Acetonitrile 127 38.6 - 91 17 7 161ppm Pd Methanol 88 49.7 47 >98.9 <1.8 C 161ppm Pd Methanol 113 33.9 - 98 3.6 8 321ppm Pd Isopropanol 234 51.5 43 >99.6 <1.2 D 321ppm Pd Isopropanol 258 36 - 99 4 9 55pm Pd Ethyl acetate 5.8 41.3 36 99.5 0.3 E 55ppm Pd Ethyl acetate 17 30.4 - 99.1 0.5 10 550ppm Pd Methanol 237 44.7 56 92 43 F 550ppm Pd Methanol 348 28.7 - 91 53 11 220ppm Rh Butyraldehyde 175 43.5 33 98 4 production G 220ppm Rh Butyraldehyde 216 32.7 - 98 4 production 12 23ppm Pd Aqueous 0.1 Pd 3.8 Pd 5 99 Pd 67 14ppm Rh acidic mining 1.6 Rh 2.2 Rh 11 99 Rh 773ppm Ir stream 409 Ir 73.4 Ir 5 91 Ir

[0003] H 23ppm Pd Aqueous 0.9 Pd 3.6 Pd - 99 Pd 80 14ppm Rh acidic mining 2.2 Rh 2.1 Rh - 99 Rh 773ppm Ir stream 426 Ir 69.6 Ir - 89 Ir 13 11.5ppm Rh ethanol / acetic 66% 3.9 acid L 11.5ppm Rh ethanol / acetic 56% 5 acid 14 20.7ppm Rh Oxo 79% 4.3 hydroformylati on process stream M 20.7ppm Rh Oxo 65% 7.2 hydroformylati on process stream 15 762ppm Rh concentrated 221 63.8 75 96% 27.6 OXO hydroformylatio n stream diluted with toluene (4:1) N 762ppm Rh concentrated 483 36.5 90% 71 OXO 34 | P a g e

[0004] hydroformylatio n stream diluted with toluene (4:1) 250ppm Pd from Negishi 27 30 97 % 6.8 cross coupling in THF250ppm Pdfrom Negishi20.8 97% 6.2 cross coupling in THF 35 | P a g e

Claims

CLAIMS 1. A compound of General Formula I: [A]a[B]b[C]c[D]d(Formula I) in which: A is selected from: (O3 / 2)Si–[X][- S–[Y]fH; (O3 / 2)Si–[X]- S– (CH2)0-5[CHR’]f-[Y]-H (O3 / 2)Si–[X] S [Y][C(O)]e- [NR’– [Y]]fH (O3 / 2)Si–[X] -NR’– [Y]fH B is selected from: (O3 / 2)Si–[X]- S–[Y]–[X]-Si(O)3 / 2; C is Si(O)4 / 2; and D is Si(O)3 / 2V wherein: X is, independently in each occurrence, a linear or branched, optionally substituted hydrocarbyl group comprising from 2 to 12 carbon atoms; Y is, independently in each occurrence, a linear or branched, optionally substituted divalent hydrocarbyl group comprising from 2 to 8 carbon atoms and optionally containing a divalent hetero group selected from (CHR’)0-8 -N- [((CHR’)2-8-S)fR’ ] ; [(CHR’)g-[C(O)]eS]f; and {(CHR’)0-8[C(O)]eN [((CHR’)2-8-S)fR’ ] }f[(CHR’)2-8-S]f; R’ is monovalent and independently selected from R, [S(CH2)2-8]fSH] and [(CH2)0-8-S]fH]; R is independently selected from H and an optionally substituted linear or branched C1- 22-alkyl, C2-22-alkenyl or C2-22-alkynyl group, an aryl and a C1-22-alkylaryl group; e is, independently in each occurrence, 0 or 1; f is, independently in each occurrence, an integer from 1 to 10; g is 0 to 10; V is an optionally substituted C1-22-alkyl, C2-22-alkenyl or C2-22-alkynyl group or an aryl group or C1-22-alkylaryl sulfide, amine or a polyalkyl amine or phosphine or other phosphorous containing group; the free valences of the silicate oxygen atoms are saturated by one or more of: silicon atoms of other groups of Formula 1; hydrogen; 36 | P a g ea linear or branched C1-12-alkyl group; and the integers a, b and c are positive integers and d is 0 or a positive integer such that: i) the molar ratio of a:b is at least 4:1; ii) a:c+d is from 0.005 to 1:

1.

2. A compound of General Formula I: [A]a[B]b[C]c[D]d(Formula I) in which: A is selected from: (O3 / 2)Si–[X][- S–[Y]-]fH; (O3 / 2)Si–[X]- S– (CH2)0-5[CHR’]f-[Y]-H (O3 / 2)Si–[X] S [Y][C(O)]e- [NR’– [Y]]fH (O3 / 2)Si–[X] -NR’– [Y]fH B is selected from: (O3 / 2)Si–[X]- S–[Y]––[X]-Si(O)3 / 2; C is Si(O)4 / 2; and D is Si(O)3 / 2V wherein: X is, independently in each occurrence, a linear or branched, optionally substituted hydrocarbyl group comprising from 2 to 12 carbon atoms; Y is, independently in each occurrence, a linear or branched, optionally substituted hydrocarbyl group comprising from 2 to 8 carbon atoms and optionally containing a divalent hetero group selected from N- [((CHR’)2-8-S)fR’ ] ; [(CHR’)g-[C(O)]eS]f; and {(CHR’)0-8[C(O)]eN [((CHR’)2-8-S)fR’ ] }f[(CHR’)2-8-S]f; R’ is monovalent and independently selected from R and [(CH2)0-8-S]fH; R is independently selected from H and an optionally substituted linear or branched C1-22-alkyl, C2-22-alkenyl or C2-22-alkynyl group, an aryl and a C1-22-alkylaryl group and is more preferably selected from H and C1-12alkyl and especially H and C1-6alkyl; e is an integer from 0 to 1; f is an integer from 1 to 10; g is an integer from 0 to 10; V is an optionally substituted C1-22-alkyl, C2-22-alkenyl or C2-22-alkynyl group or an aryl group or C1-22-alkylaryl sulfide, sulfoxide, sulfone, amine or a polyalkyl amine or phosphine or other phosphorous containing group; the free valences of the silicate oxygen atoms are saturated by one or more of: 37 | P a g esilicon atoms of other groups of Formula 1; hydrogen; a linear or branched C1-12-alkyl group; or other known oxo metal bridging systems; and the integers a, b, c and d are such that: i) a:c+d is from 0.005 to 1 :1; and ii) a:b is from 4 to 100,000:1; and component A is present at a functional group loading (FGL) of at least 0.5 mmol / g of the compound I. .

3. A compound according to any one of claims 1 and 2 in which: A is selected from: (O3 / 2)Si–[X][- S–[Y]-]fH; (O3 / 2)Si–[X]- S– (CH2)0-5[CHR’]f-[Y]-H ; and (O3 / 2)Si–[X] S [Y][C(O)]e- [NR’– [Y]]fH.

4. A compound according to any one of the preceding claims wherein g is 0 to 8.

5. A compound according to any one of claims 1 to 3 in which g is selected from 1 and 3 to 10.

6. A compound according to any one of the preceding claims wherein component A is present at a functional group loading of at least 0.8 mmol / g of the compound I and the molar ratio of a:b is at least 4:

1.

7. A compound according to any one of the preceding claims in which component A is present at a functional group loading (FGL) of at least 0.8 mmol / g of the compound I, preferably greater than 0.9 mmol / g.

8. A compound according to any one of the preceding claims in which X comprises from 2 to 6 carbon atoms.

9. A compound according to any one of the preceding claims in which X is selected from - CH2CH2-, -CH2CH2CH2-, -CH(CH3)CH2CH2- and -CH2CH2CH2CH2-.

10. A compound according to any one of the preceding claims in which Y is selected from (CHR’)0-8N-[((CHR’)2-4-S)1-4H ]; [(CHR’)2-4- S]1-4; and {(CHR’)2-4[C(O)]eN [((CHR’)2-4- S)1-4H ] }1-4[(CHR’)2-4-S]1-4; 38 | P a g e11. A compound according to any one of the preceding claims in which R’ is selected from H, methyl and [(CHR’)2-4-S]fH.

12. A compound according to any one of the preceding claims in which Y comprises a hydrocarbyl group comprising one or more -SH substituents and thioether sulfur atoms and which has a molecular weight not exceeding 400.

13. A compound according to any one of the preceding claims in which Y is selected from: -CH2CH2-S- -CH2CH2CH2- S- -CH2CH2CH2CH2- S- -CH2CH(SH) CH2- S- -CH2CH(SH) CH(SH) CH2- S- -CH2CH(SH) CH(SH) CH(SH) CH2- S- -CH2CH(SH) CH(SH) CH(SH) CH(SH) CH2- S- -CH2CH2-S-CH2CH2- S- -CH2CH2-S-CH2CH2-S-CH2CH2- S- -CH2CH2N(-CH2CH2SH)CH2CH2- S- -CH2CH2N(-CH2CH2CH2SH)CH2CH2CH2- S- -CH2CH2N(-CH2CH2CH2CH2SH)CH2CH2CH2CH2- S- -CH2CH2[N(-CH2CH2SH)CH2CH2]3- S- -CH2CH2[N(-CH2CH2SH)CH2CH2]5- S- -CH2C(O)[N(CH2CH2SH)CH2CH2]4N(CH2CH2SH) CH2CH2S-.

14. A compound according to any one of the preceding claims in which f is selected from 1 and 2.

15. A compound according to any one of the preceding claims in which: X is a saturated alkylene group having 2 to 4 carbon atoms Y is independently in each occurrence, thioethylene, thiopropylene and thiobutylene moiety and optionally comprising 1 or 2 -SH substituents; X and Y are linked by S or -NR’- e is independently in each occurrence,0 and f is independently in each occurrence, 1; the ratio of a:b is at least 8:1; and the functional group loading of component A is from 0.8 to 1.

7. mmol / g of the Compound I. 39 | P a g e16. Use of a compound according to any one of the preceding claims in reducing the level of a metal species in an organic medium, aqueous medium or a mixed aqueous and organic medium.

17. Use according to claim 16 in reducing the level of a precious metal species.

18. A process for the production of a component formula A as defined in any one of claims 1 to 15 comprising reacting a thiol HS–[Y-]fH with a compound of formula (RO)3Si-X’ wherein X’ is a linear or branched, optionally substituted hydrocarbyl group comprising from 2 to 12 carbon atoms which contains at least one alkene bond, in a solvent, at elevated temperature wherein the molar ratio of the thiol to the silane is at least 4:

1.

19. A process for the production of a component formula A as defined in any one of claims 1 to 15 comprising reacting a thiol HS–[Y-]fH with a compound of formula (RO)3Si-X’ wherein X’ is a linear or branched, optionally substituted hydrocarbyl group comprising from 2 to 12 carbon atoms which contains at least one alkene bond, in a solvent, at elevated temperature wherein the molar ratio of the thiol to the silane is at least 4:

1.

20. A process for the production of a Compound of formula I as defined in any one of claims 1 to 11 comprising reacting a thiol HS–[Y-]fH with a compound of formula (RO)3Si-X’ wherein X’ is a linear or branched, optionally substituted hydrocarbyl group comprising from 2 to 12 carbon atoms which contains at least one alkene bond at elevated temperature to produce a reaction product, reacting the reaction product with silica to form a silica lattice by hydrolysing the RO- groups in the silane and, removing evolved alcohol wherein the mass ratio of the silica to the reaction product is at least 4:

1. 40 | P a g e

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