Long alkyl chain substituted multidentate chelate ligands and methods for their preparation

Abstract

This invention provides a long alkyl chain-substituted polydentate chelating phosphooxy neutral ligand, with the structural formula shown in Formula I or Formula II. This invention also provides a method for preparing the long alkyl chain-substituted polydentate chelating phosphooxy ligand, comprising reacting aminotrimethylene phosphate or ethylenediaminetetramethylene phosphate with orthocyanin triester (R... 1 C(OR 2 3) The reaction produces aminotrimethylene phosphate or ethylenediaminetetramethylene phosphate; aminotrimethylene phosphate or ethylenediaminetetramethylene phosphate reacts with an alkyl Grignard reagent (R 3 The target product is generated by a reaction involving -Mg-X, producing a long alkyl-chain-substituted aminotrimethylenephosphono-oxygen ligand or an ethylenediaminetetramethylenephosphono-oxygen ligand. The multidentate chelating phosphono-oxygen neutral ligand of this invention possesses advantages such as strong chelating and coordination ability, good solubility and dispersion performance, and exhibits excellent extraction effect on metal ions as an extractant. The synthetic route is simpler, and the raw materials are readily available, facilitating low-cost preparation.

Description

Technical Field

[0001] This invention relates to the field of organic chelating ligand technology, specifically to a long alkyl chain-substituted polydentate chelating neutral ligand and its preparation method. Background Technology

[0002] Phosphine oxide ligands (RP=O:) have prominent lone pairs of electrons, which can form stable coordination bonds with many metal ions. Therefore, they can bind firmly to many metal ions and are widely used in heavy metal extraction and separation, metal complex preparation, metal catalyst preparation, and nanoparticle preparation.

[0003] Trioctylphosphine oxide (TOPO) can be used for the extraction and separation of heavy metals uranium and thorium (fluorescence determination of trace thorium in uranium solution, *Nuclear Chemistry and Radiochemistry*, 2010, 32, 04). AlphaTao Medical Co., Ltd. reported the application of trioctylphosphine oxide (TOPO) in the extraction of radioactive thorium and radium to prepare radiation sources for tumor therapy (CN114502238A). Chinese patent CN115821040A describes the use of alkylphosphine oxide (R3-P=O:) and phosphate ester ((RO)3-P=O:) for the extraction of metallic lithium from salt lake lithium mines and the extraction of lithium from lithium-containing wastewater. TCL Corporation reported the application of trialkylphosphine oxide in the preparation of quantum dot luminescent materials (CN108977191A).

[0004] The aforementioned common phosphonooxy ligands are all monodentate coordination ligands, which are prone to dissociation under extreme conditions such as strong acidity, high temperature, and dilute solutions. The extraction of certain low-concentration metal elements requires strongly chelating polydentate ligands, which monodentate phosphonooxy ligands cannot satisfy.

[0005] Currently, there are some reports on bidentate phosphooxy ligands in the literature, such as Japanese Patent JP2022-70321A and the literature (Solvent Extraction and Ion Exchange, 2005, 23, 1) which describe the methylene-linked bidentate phosphooxy ligand R2-P(O)-(CH2). n -P(O)-R2 is used for the preparation of rare earth europium complexes and the extraction and separation of americium.

[0006] Multidentate chelating ligands composed of three or more phosphoxy groups (RP=O:) have strong chelating ability. Tridentate phosphoxy ligands can be constructed by combining phosphoxy groups using various functional groups, such as the phenyl-linked tridentate phosphoxy ligand [Ph2P(O)]-Ph-[PhP(O)]-Ph-[P(O)Ph2] (Eur.J.Inorg.Chem.2009,4777), the tertiary carbon atom directly linked tridentate phosphoxy ligand HC-[P(O)Ph2]3 (Dalt.Trans.2012,41,6634), the tertiary carbon atom linked to three methylene groups of the tridentate phosphoxy ligand RC-[CH2P(O)Ph2]3 (Polyhedron.2005,24,427), and the amino group linked to three methylene groups of the tridentate phosphoxy ligand N[CH2P(O)Ph2]3 (Inorganica ChimicaActa 2020,512,119870). However, in the tridentate phosphooxy ligands reported above, the substituents on the phosphine atom are all phenyl groups (because only phenyl-substituted phosphine-containing raw materials are relatively easy to obtain). But phenyl groups have a strong tendency for π-π stacking, which determines that these chelating ligands have poor dispersibility in many solvents, especially non-polar solvents (such as cyclohexane), and are prone to precipitation, limiting their application as chelating extractants. On the other hand, the synthetic routes for tridentate phosphooxy ligands reported in the above literature are relatively complex, and the raw materials (phenylphosphine derivatives) are expensive, making low-cost preparation difficult. Summary of the Invention

[0007] The purpose of this invention is to provide a long alkyl chain-substituted polydentate chelating phosphooxy neutral ligand, which can be used as an extractant or metal ion chelating agent, and has advantages such as strong coordination ability and good solubility and dispersion performance. This invention also provides a novel preparation method for the long alkyl chain-substituted polydentate chelating phosphooxy ligand, which has a simpler synthetic route, uses readily available raw materials, and is conducive to low-cost preparation.

[0008] Specifically, the technical solution of the present invention is as follows:

[0009] A long alkyl chain substituted polydentate chelate phosphonooxy ligand, the structural formula of which is shown in Formula I or Formula II:

[0010]

[0011] Wherein, the R substituent is selected from C4 to C18 straight-chain or branched alkyl groups; the R substituents can be the same or different.

[0012] Preferably, the R substituent is a C6-C18 straight-chain or branched alkyl group. More preferably, the R substituent is a C8-C18 straight-chain or branched alkyl group.

[0013] The compound shown in Formula I is a tridentate phosphooxy ligand, which consists of a nitrogen atom directly connected to three methylene-phosphooxy groups, and the three phosphooxy groups are connected to 6 alkyl substituents.

[0014] The compound shown in Formula II is a tetradentate phosphooxy ligand, which consists of four methylene-phosphooxy groups linked by ethylenediamine, and eight alkyl substituents are attached to the four phosphooxy groups.

[0015] The C4-C18 straight-chain or branched alkyl group in the R substituent is preferably n-butyl, isobutyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-dodecyl, n-hexadecyl, or n-octadecyl. The C8-C18 straight-chain or branched alkyl group in the R substituent is preferably n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-dodecyl, n-hexadecyl, or n-octadecyl.

[0016] In Formulas I and II, the R substituents may be the same or different. Preferably, the R substituents are two alkyl groups with different structures, and more preferably, the R substituents are one alkyl group with the same structure.

[0017] The alkyl group is particularly preferred to be an alkyl group with 8 or more carbon atoms, because a long alkyl chain will greatly reduce the polarity of the compound and bring better dispersibility, which is beneficial to the dispersion of the multidentate chelated phosphooxy ligand in a variety of low-polarity solvents, and can also be separated from the aqueous phase by two-phase extraction.

[0018] The present invention also provides a method for synthesizing a long alkyl chain substituted polydentate chelate phospho-oxygen ligand, the steps of which are: (1) reacting aminotrimethylene phosphate or ethylenediaminetetramethylene phosphate with orthocyanin triester (R 1 C(OR 2 )3) The reaction produces aminotrimethylene phosphate or ethylenediaminetetramethylene phosphate; (2) aminotrimethylene phosphate or ethylenediaminetetramethylene phosphate reacts with an alkyl Grignard reagent (R 3 -Mg-X) further reacts to generate the target product, a long alkyl-substituted aminotrimethylenephosphonoligand or an ethylenediaminetetramethylenephosphonoligand; the reaction equations are shown in Formula III a / b and Formula IV a / b:

[0019]

[0020]

[0021] In equations III a / b and IV a / b, R 1 Selected from hydrogen atom, methyl, ethyl, propyl, butyl, R 2 Selected from methyl, ethyl, R 3 X is selected from straight-chain or branched alkyl groups of C4 to C18, and X is selected from chlorine or bromine.

[0022] The reaction described in Formula III a / b is an esterification reaction. The reactant, aminotrimethylene phosphoric acid or ethylenediaminetetramethylene phosphoric acid, is a white solid, and the other reactant, orthoic acid triester (R... 1 C(OR 2 3) is a colorless and transparent liquid. During the reaction, the two are directly mixed without the need for an additional solvent. The reaction temperature is 100–150℃, preferably 110–140℃. The reaction time is 2–20 hours.

[0023] In the esterification reaction described in Formula III a / b, under heating conditions, the starting material aminotrimethylene phosphoric acid or ethylenediaminetetramethylene phosphoric acid dissolves in the orthocyanin triester (R 1 C(OR 2 In step 3), a homogeneous reaction occurs. The reaction mechanism is shown in equation V. First, the electron-rich hydroxyl group (P(O)-OH) in phosphoric acid attacks the orthocyanin triester (R). 1 C(OR 2 )3) Electron-deficient tertiary or quaternary carbon atoms in the middle lose one molecule of alcohol (R 2 OH) and form an intermediate; the intermediate is unstable and further undergoes an alkyl transfer reaction (R 2 (Group transfer), and then decomposes to produce phosphonate (P(O)OR) 2 ) and carboxylic acid esters (R 1 C(O)OR 2 When all the phosphonic acid hydroxyl groups in the raw material aminotrimethylene phosphoric acid or ethylenediaminetetramethylene phosphoric acid react with orthocyanin triester (R... 1 C(OR 2 3) After the reaction and esterification, the target product aminotrimethylene phosphate or ethylenediaminetetramethylene phosphate is generated.

[0024]

[0025]

[0026] The esterification reaction described in Formula III a / b, orthoanoic acid triester (R 1 C(OR 2 3) The molar ratio of aminotrimethylene phosphoric acid or ethylenediaminetetramethylene phosphoric acid is 6:1 to 20:1, with a preferred ratio of 8:1 to 12:1. Theoretically, the complete esterification of each molecule of aminotrimethylene phosphoric acid consumes 6 molecules of orthocyanin triester (R). 1 C(OR 2 )3); Theoretically, the complete esterification of each molecule of ethylenediaminetetramethylene phosphoric acid consumes 8 molecules of orthocyanin triester (R 1 C(OR 2 )3). In the actual reaction, orthoic acid triester (R 1 C(OR 23) The amount should be appropriately excessive to ensure that all the hydroxyl groups in the phosphonic acid are esterified. This is because the raw materials and solvents may contain a certain amount of water, and water molecules will consume the orthoic acid triester (water reacts with the orthoic acid triester to produce carboxylic acid esters and alcohols).

[0027] The esterification reaction described in Formula III a / b, orthoanoic acid triester (R 1 C(OR 2 R in )3) 2 The radical group is selected from methyl and ethyl groups. The byproducts produced during the reaction are methanol and ethanol. Methanol has a boiling point of 64℃, and ethanol has a boiling point of 78℃; both are low-boiling-point alcohols and are easily distilled off the reaction system, thus promoting the reaction equilibrium towards the product side. Additionally, R... 2 orthoesters with methyl or ethyl groups (R 1 C(OR 2 3) Low cost, suitable for large-scale production.

[0028] The esterification reaction described in Formula III a / b, orthoanoic acid triester (R 1 C(OR 2 R in )3) 1 The radical group is selected from hydrogen atom, methyl, ethyl, propyl, and butyl, and the corresponding orthoesters are orthoformate, orthoacetate, orthopropionate, orthobutyrate, and orthovalerate. The byproducts of orthoester decomposition are carboxylic acid esters, such as formate, acetate, propionate, butyrate, and valerate. These byproduct carboxylic acid esters can be removed by vacuum distillation after the reaction. R 1 It is not advisable to use carbon chains with too large a molecular weight, because high molecular weight carboxylic esters have too high a boiling point and are not easy to remove from the reaction system.

[0029] The reaction described in Formula IV a / b is a nucleophilic substitution reaction between a Grignard reagent and a phosphate ester. R 3 -Mg-X represents a Grignard reagent, which can nucleophilically attack phosphate esters, followed by -OR 2 The group leaves, generating R. 3 Alkyl-substituted polydentate phosphooxy ligands. The reaction mechanism is shown in Formula VI.

[0030]

[0031] The Grignard reagent nucleophilic substitution reaction described in Formula IV a / b, R 3 -Mg-X represents a Grignard reagent, prepared by a haloalkane (R 3 The haloalkane is obtained by reacting (-X) with metallic magnesium in solvents such as diethyl ether and tetrahydrofuran. The haloalkane is preferably a chloroalkane or a bromoalkane, and more preferably a bromoalkane.

[0032] The Grignard reagent nucleophilic substitution reaction described in Formula IV a / b uses a solvent selected from one or more of anhydrous diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and dioxane, preferably one of these, and particularly preferably tetrahydrofuran. The reaction temperature is 20–100°C, preferably 20–60°C. The reaction time is 2–20 hours.

[0033] In equation IV a / b, R 3 It is selected from straight-chain or branched alkyl groups of C4 to C18, preferably straight-chain or branched alkyl groups of C6 to C18, and particularly preferably n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-dodecyl, n-hexadecyl, and n-octadecyl.

[0034] The long alkyl chain-substituted polydentate chelating phosphooxy ligands of this invention have the advantages of strong chelating and coordination ability, the ability to form stable complexes with metal ions, and good dispersibility. They are miscible with a variety of organic solvents, especially with solvents of low polarity (such as petroleum ether and cyclohexane), facilitating extraction with aqueous solutions. The nitrogen atoms and phosphooxy functional groups in the molecular structure of the long alkyl chain-substituted polydentate chelating phosphooxy ligands of this invention have a certain degree of hydrophilicity, similar to the hydrophilic end of a surfactant. This facilitates the entry of these ligands into the aqueous phase to a certain extent during extraction, enabling efficient extraction of low concentrations of metal ions from water. Attached Figure Description

[0035] Figure 1 It is the intermediate aminotrimethylene phosphate ethyl ester described in Example 1. 1 H NMR spectrum.

[0036] Figure 2 It is the product aminotrimethylenetris(di-n-hexylphosphine oxide) described in Example 1. 1 H NMR spectrum. Detailed Implementation

[0037] The following specific embodiments further illustrate the products, preparation methods, and applications of the present invention, but these specific embodiments do not limit the scope of protection of the present invention in any way.

[0038] Example 1. The synthetic route involved in this example is as follows:

[0039] (I) Synthesis of intermediate aminotrimethylene phosphate ethyl ester

[0040]

[0041] In a 250ml three-necked flask, 20.0g of aminotrimethylenephosphonic acid (0.0669mol) and 100.0g of triethyl orthoformate (0.675mol) were weighed out and the reaction was carried out under nitrogen protection. The external temperature was set at 145℃ and gradually increased. During the reaction, the solution gradually turned yellow, and ethanol (boiling point 78℃) and ethyl formate (boiling point 54℃) evaporated. After 2.5 hours of reaction, the liquid in the flask was a clear yellow liquid, and the internal temperature gradually reached 136℃. The total reaction time was about 4 hours.

[0042] Vacuum distillation was performed, with the pressure slowly reduced to -0.09 MPa and the temperature set at 120°C until no more distillate was distilled off, yielding crude aminotrimethylene phosphate, which was a yellow oily substance.

[0043] After cooling to room temperature, the product was poured into a separatory funnel, 150 ml of dichloromethane was added, and the mixture was washed three times with 150 ml of sodium bicarbonate aqueous solution (to remove the unesterified phosphonic acid fraction), followed by washing with 50 ml of water. The lower dichloromethane phase was collected, dried over anhydrous sodium sulfate, and concentrated by rotary evaporation. Further purification by silica gel column chromatography (eluting with dichloromethane) was performed to remove dark impurities, yielding the product. A final yield of 21.3 g of a pale yellow liquid was obtained, with a yield of 68%. 1 HNMR (400MHz, CDCl3): δ 4.12 (m, J = 7.1Hz, 12H), 3.33 (d, J = 10.72Hz, P-CH2 coupling, 6H), 1.28 (t, J = 7.1, 18H).

[0044] (II) Synthesis of the product aminotrimethylenetris(di-n-hexylphosphine oxide) (NTDHPO)

[0045]

[0046] In a 1L three-necked flask, add 9.8g (0.404mol) of magnesium shavings, 200mL of redistilled anhydrous tetrahydrofuran, 5g of bromohexane, and 4 grains of iodine. Heat to 60°C to initiate the reaction; the solution turns dark gray. Dilute 62g of bromohexane with 500mL of anhydrous tetrahydrofuran and slowly add it dropwise using a constant-pressure low-pressure funnel, maintaining the temperature at approximately 60°C, for about 2 hours until the addition is complete. Continue the reaction at 60°C for 1 hour to obtain n-hexylmagnesium bromide Grignard reagent.

[0047] After cooling the Grignard reagent to room temperature, dilute 10.0 g (0.021 mol) of aminotrimethylene phosphate with 50 mL of anhydrous tetrahydrofuran in an ice-water bath, and slowly add it dropwise using a constant pressure low-pressure funnel. Let it sit overnight at room temperature.

[0048] After the reaction was complete, the reaction was quenched with approximately 35 mL of 12M concentrated hydrochloric acid, dissolving unreacted magnesium filings. The aqueous phase was extracted with dichloromethane (100 mL * 3, the first dichloromethane phase was in the upper layer, the subsequent two in the lower layer). The THF phase was evaporated to dryness, 100 mL of water was added, and then extracted with dichloromethane (100 mL * 2). The organic phases were combined and washed with saturated NaHCO3 aqueous solution (100 mL * 2), and dried over anhydrous sodium sulfate. The solvent was evaporated to dryness, and low-boiling substances were removed by vacuum distillation (-0.09 MPa, 120 °C). Further purification was performed by silica gel column chromatography (elution with dichloromethane / petroleum ether 1:1) to remove dark impurities, yielding the product. A final yield of 11.4 g of a pale yellow viscous liquid was obtained, with a yield of 75%. 1 ¹H NMR (400 MHz, CDCl₃): δ 3.25 (d, J = 5.6, P-CH₂ coupling, 1.6H, other hydrogens are deuterated due to acidity, theoretical 6H), 1.82–1.58 (m, 12H), 1.58–1.17 (m, 48H), 0.85 (m, 18H). Mass spectrometry (m / z, ESI): Calculated value 707.6, experimental value 708.6 (M+H).

[0049] In the embodiments 1 The 1H NMR spectrum was obtained using a JEOL 400YH nuclear magnetic resonance spectrometer. The mass spectrometry was obtained using an ultra-high performance liquid chromatography-tandem time-of-flight mass spectrometer.

[0050] Example 2. Extraction experiment of long alkyl chain substituted polydentate chelate phosphooxy ligands

[0051] To prepare a lead nitrate (Pb(NO3)2) aqueous solution using deionized water, first prepare the Pb... 2+ A concentrated solution with an ion concentration of 1 mg / mL was further diluted to Pb. 2+ A dilute solution with an ion content of 1 μg / mL was used as the extraction standard solution.

[0052] Take 10 mL of Pb(II) standard solution and place it in a 100 mL separatory funnel. Add 10 mL of HOAc-NaOAc buffer solution (pH = 5), then add 20 mL of petroleum ether dissolved extractant (1 mg / mL). The extractant can be either trimethylenetris(di-n-hexylphosphine oxide) (NTDHPO) or the control reagent tri-n-octylphosphine oxide (TOPO). After shaking and mixing for 2 minutes, allow the mixture to stand to separate into layers.

[0053] The aqueous layer was removed, concentrated by evaporation, and then acidified with 0.5 mL of nitric acid (1 mol / L). A 10 mL solution was then prepared. The Pb content in the solution was measured using inductively coupled plasma atomic emission spectrometry (ICP-AES). 2+ Ion content.

[0054] The test results are shown in Table 1 below.

[0055] Table 1

[0056]

[0057] As shown in Table 1, after extraction with the long-alkyl-chain-substituted polydentate chelate phosphine oxide trimethylenetris(di-n-hexylphosphine oxide) (NTDHPO), the Pb content in the solution was significantly reduced. 2+ The ion concentration decreased from 1 μg / mL to less than 0.01 μg / mL. In contrast, when monodentate tri-n-octylphosphine oxide (TOPO) was used as the extractant, the Pb concentration decreased after extraction. 2+ The ion concentration remained high (0.12 μg / mL). This indicates that the long alkyl chain-substituted polydentate chelate phosphooxy ligand has a good extraction effect on metal ions as an extractant.

[0058] The long alkyl chain substituted polydentate chelating phosphine oxide neutral ligands of the present invention are used as extractants or metal ion chelating agents. They can form stable complexes with metal ions and have the advantages of strong chelating coordination ability and good solubility and dispersion performance. As an extractant, they have a very good extraction effect on metal ions.

[0059] The preparation method of the present invention has a simple synthesis route, uses inexpensive and readily available raw materials, which is conducive to achieving low-cost preparation and is suitable for large-scale production.

[0060] The embodiments described above are merely some preferred embodiments of the present invention, and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A long alkyl chain-substituted polydentate chelate phosphonooxy ligand, characterized in that, The structural formula of the multidentate chelating phosphooxy ligand is shown in Formula I: ； Wherein, the R substituent is selected from C4~C18 straight-chain or branched alkyl groups; the R substituents can be the same or different; The C4-C18 straight-chain or branched alkyl groups are selected from n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, and n-dodecyl.

2. The long alkyl chain-substituted polydentate chelating phosphoxy ligand as described in claim 1, characterized in that, The R substituent is an alkyl group with two different structures.

3. The long alkyl chain-substituted polydentate chelate phosphonooxy ligand as described in claim 1, characterized in that, The R substituent is an alkyl group with the same structure.

4. A method for preparing a long alkyl chain-substituted polydentate chelate phosphonooxy ligand, characterized in that, The preparation method comprises the following steps: (1) The aminotrimethylene phosphate and orthocyanin triester (R 1 C(OR 2 3) The reaction produces aminotrimethylene phosphate; (2) Aminotrimethylene phosphate and alkyl Grignard reagent (R 3 -Mg-X) further reacts to generate the target product, a long alkyl-chain-substituted aminotrimethylenephosphonic ligand; The reaction equations are shown in equations IIIa and IVa: ； ； In equations IIIa and IVa, R 1 Selected from hydrogen atom, methyl, ethyl, propyl, butyl, R 2 Selected from methyl, ethyl, R 3 The alkyl group is selected from C4 to C18 straight-chain or branched alkyl groups, and X is selected from chlorine or bromine. The C4 to C18 straight-chain or branched alkyl groups are selected from n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, and n-dodecyl.

5. The method for preparing long alkyl chain-substituted polydentate chelate phosphooxy ligands as described in claim 4, characterized in that, The esterification reaction described in Formula III a is carried out at a temperature of 100-150°C for 2-20 hours.

6. The method for preparing long alkyl chain-substituted polydentate chelate phosphooxy ligands as described in claim 4, characterized in that, The esterification reaction described in Formula III a yields orthocyanin triester (R 1 C(OR 2 )3) The molar ratio of aminotrimethylene phosphoric acid is 6:1 to 20:

1.

7. The method for preparing long alkyl chain-substituted polydentate chelate phosphooxy ligands as described in claim 4, characterized in that, The Grignard reagent nucleophilic substitution reaction described in Formula IV a is carried out at a temperature of 20-100°C for 2-20 hours.

8. The method for preparing long alkyl chain-substituted polydentate chelate phosphooxy ligands as described in claim 4, characterized in that, In the Grignard reagent nucleophilic substitution reaction described in Formula IV a, R 3 -Mg-X represents a Grignard reagent, prepared by alkyl halogens (R... 3 -X) is obtained by reacting metallic magnesium in a solvent; the haloalkane is a chloroalkane or a bromoalkane; the solvent is one or more of diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and dioxane.

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