Process for the production of substituted ferrocene

Abstract

Process for the preparation of substituted ferrocene and ferrocene-containing polymers, comprising a step (a) in which ferrocene (bis(5-cyclopentadienyl)iron) is reacted with an organometallic base of lithium neopentyl (LiNp, LiCH2C(CH3)3) and an alkali alkoxide to give 1,1',3,3'-metallated ferrocene of the structure wherein M is an alkali metal, wherein the organometallic base has the structural formula K4Np(OtAm)3 or Na4Np(OtAm)3, wherein Np is a neopentyl group with structural formula CH2C(CH3)3 and OtAm is a tert-amyl oxide group with structural formula OC(CH3)2(CH2CH3).

Description

The present invention relates to a process for the production of substituted ferrocene. Polymers containing substituted ferrocenes and ferrocene units (Fe(C5H(5-n)Xn)(C5H(5-m)Xm) with 0 ≤ n, m ≤ 4) exhibit unique properties. This applies particularly to their redox-chemical, optical, and catalytic properties, enabling applications in supramolecules, nanoparticles, battery materials, liquid crystals, nonlinear optical materials, and sensors (D. Astruc, Eur. J. Inorg. Chem. 2017, 6-29). The present invention enables the functionalization of ferrocene in a simple reaction. This is made possible by the quadruple metallation of commercially available ferrocene and the subsequent reaction with electrophiles. Previously, multiply (> double) substituted ferrocenes had to be generated by prior synthesis of the underlying substituted cyclopentadiene units and reaction with iron(II) halides (AK Diallo, J. Ruiz, D. Astruc, Inorg. Chem. 2010, 49, 1913-1920). A direct route to quadruply substituted ferrocenes has already been described by Holthausen, Wagner and coworkers (M. Scheibitz, M. Boite, JW Bats, H.-W. Lerner, I. Nowik, RH Herber, A. Krapp, M. Lein, MC Holthausen, M. Wagner, Chem. Eur. J. 2005, 11, 584-603), however, the syntheses are limited to the corresponding boron compounds.However, further examples in the literature are limited to the substitution of boron atoms by other groups; the substitution of the boron atoms themselves by, for example, organic residues is not described. A common and elegant method involves the direct metallation of ferrocene, in which one or more hydrogens of the cyclopentadienide rings are directly replaced by metal atoms (mostly alkali metals) using organometallic bases (Scheme 1). These metals, in turn, can be easily replaced by functional groups using suitable reagents. This allows ferrocene molecules to be specifically functionalized, thereby acquiring desired properties required in the applications mentioned above. Previous methods used for the functionalization of ferrocene by metallation replace only one (R. Sanders, UT Mueller-Westerhoff, J. Organomet Chem. 1996, 512, 219-224; F. Rebiere, O. Samuel, HB Kagan, Tetrahedron Lett. 1990, 31, 3121-3124; D. Guillaneux, HB Kagan, J. Org. Chem. 1995, 60, 2502-2505) or two (IR Butler, WR Cullen, J. Ni, SJ Rettig, Organometallics 1985, 4, 2196-2201; M. Walczak, K. Walczak, R. Mink, MD Rausch, G. Stucky, J. Am. Chem. Soc. 1978, 100, 6382-6388) Hydrogen atoms on the rings are bonded to the corresponding number of metal atoms. Multiple metallations have already been described; however, their disadvantage lies in the generation of mixtures with varying degrees of metallation, ranging from single to eightfold metallations (RA Benkeser, Y. Nagai, J. Hooz, J. Am. Chem. Soc. 1964, 86, 3742-3746; AF Halasa, DP Täte, J. Organometal. Chem.1970, 24, 769-773) or due to the insufficient reactivity of the quadruple-metallated compound (W. Clegg, KW Henderson, AR Kennedy, RE Mulvey, CT O'Hara, RB Rowlings, DM Tooke, Angew. Chem. Int. Ed. 2001, 40, 3902-3905), which makes its further use impossible. Halasa and Tate (Polylithiation of ferrocene. In: Journal of Organometallic Chemistry. 1970, Vol. 24, No. 3, pp. 769-773. ISSN 1872-8561 (E); 0022-328X (P). DOI: 10.1016 / S0022-328X(00) 84509-X) describe the reaction of ferrocene with n-butyllithium in hexane or benzene to give FeC10H10-xLix with x = 1 to 8. After deuteration of the reaction product, the yield of deuterated FeC10H10-xLix is ​​58%. The reaction product consists of a mixture of lithiated ferrocene (FeC10H10-xLix) which is reacted with TMEDA (N,N,N',N'-tetramethylethane-1,2-diamine) to form trimethylsilylated ferrocene with a proportion of 45% of quadruple, partially 1,1',3,3'-substituted ferrocene. Okuda and Herdtweck (Complexes with sterically demanding ligands VII. Crystal structure and dynamic solution behavior of 1,1',3,3'-tetrakis(trimethylsilyl)ferrocene. Journal of Organometallic Chemistry 1989, Vol. 373, pp. 99-105) report the reaction of FeCl2·1,5 THF (470 mg, 2 mmol) in THF (50 ml) with a solution of bis(trimethylsilyl) cyclopentadienyllithium to give 1,1',3,3'-tetrakis(trimethylsilyl)ferrocene in a yield of 58%. Osborne and Whiteley (Metallation of Ferrocene with n-Butylpotassium. Journal of Organometallic Chemistry 1978, Vol. 162, pp. 79-81) concerns the metallation of ferrocene with n-butylpotassium, which is synthesized in situ from potassium(-)-(1R)-menthoxide (potassium-(1R,2S,5R)-2-isopropyl-5-methylcyclohexanolate) and n-butyllithium. Hanack (Polymetallic-organic compounds of sodium, potassium, rubidium and cesium. In: Carbanions. Vol. E19d. Stuttgart : Thieme, 1993. pp. 515-516. ISBN 3-13-220104-9) describes the metallation of ferrocene with pentyl sodium in octane in the presence of 1,2-bis[dimethylamino]ethane to obtain 1,1'-dinatrioferrocene with a yield of 90%. Benrath et al. (Combining Neopentyllithium with Potassium tert-Butoxide: Formation of an Alkane-Soluble Lochmann-Schlosser Superbase. In: Angewandte Chemie Int. Ed. 2016, Vol. 55, pp. 10886–10889) report on mixtures of alkali metal alkyl and alkali metal alkoxide compounds produced by reacting neopentyllithium with potassium tert-butoxide. Huber (1,1'-Ferrocenedicarboxylic acid. http: / / n.ethz.ch / -nielssi / download / 5.%20Semester / Praktikum%20Organische%20Chemie%201%20f%FCr%20Biol.%20Pharm.Wiss. / Reports / 01d%20Reports / Praktikum-OCI-Teil-21 / Praktikum %200C1%20(Teil%202) / FecpCOOH2.pdf ) concerns the production of 1,1'-ferrocenedicarboxylic acid by reacting iron(II) chloride tetrahydrate with potassium hydroxide and cyclopentadiene. Petrov (Large-Scale Preparation of 1,1'-Ferrocenedicarboxylic Acid, a Key Compound for the Synthesis of 1,1'-Disubstituted Ferrocene Derivatives. Organometallics. 2013, Vol. 32, No. 20, pp. 5946-5954. ISSN 1520-6041 (E); 0276-7333 (P). DOI: 10.1021 / om4004972) discloses a process for the quantitative preparation of 1,1'-ferrocenedicarboxylic acid using sodium salts of cyclopentadienecarboxylic methyl ester and ethyl ester. The present invention utilizes an organometallic, alkane-soluble potassium base, prepared by combining neopentyllithium (RR Schröck, JD Fellmann, J. Am. Chem. Soc. 1978, 100, 3359-3370) and potassium alkoxide, to generate tetrametallated ferrocene. Upon gentle heating, the addition of ferrocene to these solutions leads to the formation of a sparingly soluble red precipitate, largely composed of tetrametallated ferrocene (replacement of four ring hydrogen atoms by potassium atoms). In a directly subsequent reaction, this product can be converted into the corresponding carboxylic acid of ferrocene by reaction with introduced carbon dioxide. Analyses show that the processed product consists of approximately 80% of the 1,1',3,3'-tetracarboxylic acid of ferrocene, and the remaining 20% ​​consists of the corresponding 1,1',3-tri- and 1,1'-dicarboxylic acids of ferrocene. These ferrocene carboxylic acids are readily converted to the corresponding methyl esters. To achieve complete methylation, trimethylsilyldiazomethane or a solution of boron trifluoride in methanol is used as a reagent. Since the methyl ester of 1,1',3,3'-tetracarboxylic acid is considerably less soluble than the esters of tri- and dicarboxylic acids, the former can be easily obtained by filtration in good yield and purity. The methyl esters of the tri- and dicarboxylic acids in solution can be easily purified by column chromatography. The 1,1',3,3'-substituted ferrocene, in particular 1,1',3,3'-metallated ferrocene, 1,1',3,3'-ferrocene tetracarboxylic acid and 1,1',3,3'-ferrocene tetracarboxylic acid methyl ester, synthesized according to the inventive process and not claimed within the scope of the present invention, provide the basis for the simple synthesis of a large number of new compounds, preferably using processes known from the prior art. Thus, 1,1',3,3'-metallated ferrocene can be converted by oxidation into a polyferrocenyl with double linkages, which is not claimed within the scope of the present invention (Scheme 3). In contrast to known polyferrocenes with single linkages, this polyferrocenyl is characterized by double linkages of ferrocene units forming chains or networks. The strong and close linkage of the ferrocene units to one another imparts new electronic properties to such polymers. Furthermore, 1,1',3,3'-metallated ferrocene can be reacted with various electrophiles, e.g., halides, to give corresponding 1,1',3,3'-substituted ferrocene derivatives (Scheme 3). Among these, the 1,1',3,3'-halogenated ferrocene derivatives are particularly suitable for the preparation of polyferrocenyl and ferrocene-containing copolymers, which are not claimed within the scope of the present invention. The four carboxyl groups of 1,1',3,3'-ferrocenetetracarboxylic acid can be used as ligands for the complexation of metal ions. In this process, 1,1,3,3'-ferrocenetetracarboxylic acid acts as a bridging ligand and, depending on the properties of the metal ion, enables the formation of complex network- or lattice-like structures (metal-organic frameworks, MOFs). Scheme 4 schematically illustrates linkage patterns of ferrocene units in ferrocene-containing polymers not claimed within the scope of the present invention. The methyl ester groups of 1,1',3,3'-ferrocenetetramethyl esters synthesized according to the invention, such as 1,1',3,3'-ferrocenetetramethoxycarbonyl, are converted into the respective alcohol, acid chloride, amine, isocyanate and other useful functional groups by reaction with appropriate reagents (AR Petrov, K. Jess, M. Freytag, PG Jones, M. Tamm, Organometallics 2013, 32, 5946-5954). Scheme 5 shows by way of example the diverse possibilities for the derivatization and polymerization of ferrocene substituted according to the invention, starting from ferrocene metallated four times with potassium 1,1',3,3'. Its chemical, electronic, and optical properties make ferrocene and its substituted compounds versatile materials. For example, ferrocene compounds with appropriate side chains exhibit liquid-crystalline properties. The free rotation of the two cyclopentadienyl units and their respective substituents relative to each other plays a crucial role in this. Polymers made of ferrocene units, so-called polyferrocenyls, are electrically conductive and suitable as materials for the production of biotechnological sensors. This conductivity is based on overlapping, electron-occupied π-orbitals. Ferrocene compounds are reversibly oxidizable and are used as chemical or electrochemical oxidizing and reducing agents. The removal or addition of electrons shifts the energy levels for electron transitions and alters the optical properties. During oxidation, absorption lines shift towards longer wavelengths in the visible and ultraviolet ranges. These oxidation-induced shifts can be detected spectroscopically. Accordingly, ferrocene compounds are used as redox indicators in chemical sensors operating in the visible and ultraviolet ranges. The reversibility of oxidation and reduction, coupled with the ability to selectively shift redox potentials through appropriate substituents and degrees of substitution, opens up new applications in catalysis. This allows for the realization of redox processes that are inaccessible with known redox systems. Ferrocene compounds can be oxidized / reduced electrochemically or chemically and interact with target molecules as soluble or solid redox mediators. In particular, ferrocene compounds are exceptionally well-suited as SET (single electron transfer) reagents. The availability of quadruply (and also triple) substituted ferrocene compounds opens up a multitude of new possibilities in the aforementioned applications. For example, quadruply esterified 1,1',3,3'-ferrocenetetramethoxycarbonyl exhibits a remarkably high oxidation potential of ~0.75 V in cyclic voltametric measurements, compared to ~0.5 V for 1,1',3-ferrocentrimethoxycarbonyl and ~0.25 V for ferrocendimethoxycarbonyl. The present invention aims to provide a method for the production of substituted ferrocene, wherein the substituted ferrocene contains an increased proportion of quadruply substituted ferrocene. This problem is solved by a process for the preparation of substituted ferrocene, comprising a step (a) in which ferrocene (bis(η5-cyclopentadienyl)iron) is reacted with an organometallic base of lithium neopentyl (LiNp, LiCH2C(CH3)3) and an alkali alkoxide to give 1,1',3,3'-metallated ferrocene of the structure to obtain, wherein M is an alkali metal. In an alternative embodiment of the invention, in step (a) ferrocene (bis(η5cyclopentadienyl)iron) is reacted with potassium tert-pentoxide (i.e. potassium tert-amylate, KOtAm or CH3CH2C(CH3)2OK), a potassium alkoxide or a sodium alkoxide and n-butyllithium (CH3(CH2)3Li) to obtain 1,1',3,3'-metallated ferrocene of structure (I) with M = Li. Advantageous embodiments of the process according to the invention are characterized in that: - the organometallic base has the structural formula K4Np(OtAm)3 or Na4Np(OtAm)3, wherein Np is a neopentyl group with structural formula CH2C(CH3)3 and OtAm is a tert-amyl oxide group with structural formula OC(CH3)2(CH2CH3); - the reaction of ferrocene with the organometallic base is carried out in a reaction mixture containing an organic solvent, such as n-hexane, n-heptane, n-pentane, cyclohexane, or methylcyclohexane; - the reaction of ferrocene with the organometallic base is carried out in a reaction mixture containing an organic solvent selected from the group comprising methanol, ethanol, propan-1-ol, butan-1-ol, pentan-1-ol, hexan-1-ol, heptan-1-ol, and octan-1-ol. nonan-1-ol; decan-1-ol; undecan-1-ol; dodecan-1-ol; tridecan-1-ol; tetradecan-1-ol; pentadecan-1-ol; hexadecan-1-ol; octadecan-1-ol; hexacosan-1-ol; 1-triacontanol; propan-2-ol; butan-2-ol;2-methylpropan-1-ol; 2-methylpropan-2-ol; Pentan-2-ol; pentan-3-ol; 2-methylbutan-1-ol; 3-methylbutan-1-ol; 2-methylbutan-2-ol; 3-methylbutan-2-ol; 2,2-Dimethylpropan-1-ol; ethane-1,2-diol; 1,2-propanediol; propane-1,3-diol; butane-1,2-diol; butane-1,3-diol; 1,4-butanediol; 2,3-butanediol; pentane-1,5-diol; hexane-1,6-diol; octane-1,8-diol; nonane-1,9-diol; Decane-1,10-diol; propane-1,2,3-triol; cyclopentanol; cyclohexanol; Prop-2-en-1-ol; But-2-en-1-ol; Phenylmethanol; 1-Phenylethan-1-ol; 2-Phenylethan-1-ol; Diphenylmethanol; Triphenylmethanol; Polyethylene glycol derivatives and mixtures thereof; - the reaction of ferrocene with the organometallic base takes place in a protective gas atmosphere of one or more inert gases, such as argon (Ar) or nitrogen (N2); - the reaction of ferrocene with the organometallic base takes place under exclusion of oxygen (O2) and water (H2O);- in step (b) metallized ferrocene from step (a) is reacted, wherein the alkali metal M is replaced by a functional group or electrophile, such as COOH, Cl, Br, I, SO2Cl, SO2Br, SO2I or SiMe3, and 1,1',3,3'-substituted ferrocene of the structure; is obtained, wherein R is a functional group or an electrophile, such as COOH, Cl, Br, I, SO 2 Cl, SO 2 Br, SO 2 I or SiMe 3 is; - in step (b) metallized ferrocene from step (a) is reacted with I (iodine) to obtain 1,1',3,3'substituted ferrocene of structure (II) with R = I; - in step (b) metallized ferrocene from step (a) is reacted with carbon dioxide (CO2) to obtain 1,1',3,3'-ferrocenetetracarboxylic acid of the structure; - in step (b) metallated ferrocene from step (a) is reacted with carbon dioxide (CO2) and dilute hydrochloric acid to obtain 1,1',3,3'-ferrocenetetracarboxylic acid of structure (III); - the reaction in step (b) takes place in a protective gas atmosphere consisting of one or more inert gases, such as argon (Ar) or nitrogen (N2); - the reaction in step (b) takes place under exclusion of oxygen (O2) and water (H2O); - in step (c) substituted ferrocene from step (b) is reacted with another compound; - in step (c) substituted ferrocene from step (b) is esterified; - in step (c) COOH-substituted ferrocene from step (b) is reacted with trimethylsilyldiazomethane (Me3SiCHN2) or BF3 / methanol to obtain 1,1',3,3'-ferrocenetetramethoxycarbonyl of the structure wherein Me is a methyl group; - in step (c) COOH-substituted ferrocene from step (b) is reacted to obtain 1,1',3,3'-substituted ferrocene of the structure wherein X is a substituent chosen from the group comprising CH2OH, COCl, CON3, NCO, NHCOOMe, NHBoc, NH2; - in step (d) COOMe-substituted ferrocene from step (c) is purified by vacuum distillation at a temperature of 120 °C to isolate 1,1',3,3'-ferrocenetetramethoxycarbonyl of structure (V); - in step (e) purified, COOMe-substituted ferrocene from step (d) is hydrolyzed by means of an alkali to obtain 1,1',3,3'-ferrocenetetracarboxylic acid of structure (IV); - in one step (f) COOMe-substituted ferrocene from step (c) or (d) is reacted with a compound chosen from alcohols, acid chlorides, amines or isocyanates; - in one step (g) COOH-substituted ferrocene from step (e) is first reacted with Ag2CO3 or Ag2O to form Ag(I)-substituted ferrocene, and subsequently the Ag(I)-substituted ferrocene is reacted with Cl2, Br2 or I2 to obtain 1,1',3,3'-ferrocene tetrachloride, 1,1',3,3'-ferrocene tetrabromide or 1,1',3,3'-ferrocene tetraiodide; and / or - in one step (g) COOH-substituted ferrocene from step (e) is reacted with iodine to obtain 1,1',3,3'-ferrocene tetraiodide. Process steps not claimed within the scope of the present invention are characterized in that, in step (h), substituted ferrocene from step (a), (b), (c), (d), (e), (f) or (g) is polymerized to polyferrocenyl, the 1,1',3,3'-bonded ferrocene units of the structure contains; - in step (h) metallized ferrocene from step (a) is polymerized by oxidation to polyferrocenyl, which contains 1,1',3,3'-bonded ferrocene units of structure (VI); - in step (h) metallized ferrocene from step (a) is polymerized by oxidation with an oxidizing agent selected from 1,1,2,2-tetrabromoethane, CuBr-SMe2 and benzoyl chloride to polyferrocenyl, which contains 1,1',3,3'-bonded ferrocene units of structure (VI); - in one step (i) substituted ferrocene from step (a), (b), (c), (d), (e), (f) or (g) is copolymerized to form a copolymer containing 1,1',3,3'-bonded ferrocene units of structure (VI); - in step (i) COOH-substituted ferrocene from step (b) or (e) is copolymerized by Kolbe electrolysis to form a copolymer containing 1,1',3,3'-bonded ferrocene units of structure (VI); - in step (i) iodine-substituted ferrocene from step (b) or (g) is copolymerized to form a copolymer containing 1,1',3,3'-bonded ferrocene units of structure (VI); - in step (i) iodine-substituted ferrocene from step (b) or (g) is copolymerized using a reagent selected from Cu-biphenyl and Cu(I)-thiophene-2-carboxylate to form a copolymer containing 1,1',3,3'-linked ferrocene units of structure (VI); and / or - in step (i) substituted ferrocene from step (b), (c), (d), (e), (f) or (g) is copolymerized by ring-opening polymerization to form a copolymer containing 1,1',3,3'-bonded ferrocene units of structure (VI). Ferrocene substituted according to the above methods and not claimed within the scope of the present invention, and ferrocene-containing polymers contain an increased proportion of quadruply substituted ferrocene or quadruply bonded ferrocene units. Ferrocene substituted according to the inventive method and not claimed within the scope of the present invention contains ≥ 50 mol-% of 1,1',3,3'-substituted ferrocene, based on the total number of ferrocene units. Ferrocene substituted according to the inventive process and not claimed within the scope of the present invention contains ≥ 60 mol-% , ≥ 70 mol-% , ≥ 80 mol-% , ≥ 90 mol-% or ≥ 95 mol-% of 1,1',3,3'-substituted ferrocene, based on the total number of ferrocene units. Ferrocene substituted according to the inventive method and not claimed within the scope of the present invention contains 1,1',3,3'-substituted ferrocene of the structure or wherein M is an alkali metal, such as potassium, sodium or lithium, and R is a functional group or electrophile, such as Cl, Br, I, SO 2 Cl, SO 2 Br, SO 2 I or SiMe 3 is and X is a substituent chosen from the group comprising CH 2 OH, COCl, CON 3 , NCO, NHCOOMe, NHBoc, NH 2 is. Metallized ferrocene from step (b) can be polymerized to polyferrocenyl, which is not claimed within the scope of the present invention and comprises 1,1',3,3'-bonded ferrocene units (Fe(C5H3)2) of the structure contains. Polyferrocenyl not claimed within the scope of the present invention contains ≥ 20 mol-% of 1,1',3,3'-bonded ferrocene units (VI), based on the totality of all monomers of the polyferrocenyl. Polyferrocenyl not claimed within the scope of the present invention contains ≥ 30 mol-% , ≥ 40 mol-% , ≥ 50 mol-% , ≥ 60 mol-% , ≥ 70 mol-% , ≥ 80 mol-% , ≥ 90 mol-% or ≥ 95 mol-% of 1,1',3,3'-bonded ferrocene units (VI), based on the totality of all monomers of the polyferrocenyl. Substituted ferrocene from one of steps (b), (c), (d), (e), (f) or (g) can be copolymerized to form, not claimed within the scope of the present invention, a ferrocene-containing copolymer comprising 1,1',3,3'-bonded ferrocene units (Fe(C5H3)2) of the structure contains. Ferrocene-containing copolymer not claimed within the scope of the present invention contains ≥ 1 mol-% of 1,1',3,3'-bonded ferrocene units of structure (VI), based on the totality of all monomers of the ferrocene-containing copolymer. Ferrocene-containing copolymer not claimed within the scope of the present invention contains ≥ 5 mol-% , ≥ 10 mol-% , ≥ 20 mol-% , ≥ 30 mol-% , ≥ 40 mol-% or ≥ 50 mol-% of 1,1',3,3'-bonded ferrocene units of structure (VI), based on the totality of all monomers of the ferrocene-containing copolymer. Ferrocene-containing copolymer not claimed within the scope of the present invention contains ≥ 20 mol-% , ≥ 30 mol-% , ≥ 40 mol-% , ≥ 50 mol-% , ≥ 60 mol-% , ≥ 70 mol-% , ≥ 80 mol-% , ≥ 90 mol-% or ≥ 95 mol-% of 1,1',3,3'-bonded ferrocene units of structure (VI), based on the totality of all ferrocene units. In the present invention, the term "substituted ferrocene" refers to a mixture of unreacted ferrocene and various 1- or multiply substituted ferrocene compounds. "Substituted ferrocene" as used in the invention includes, among others, ferrocene compounds with the following structures and their isomers. wherein the mixture contains ≥ 5 mol-% , ≥ 10 mol-% , ≥ 20 mol-% , ≥ 30 mol-% , ≥ 40 mol-% and in particular ≥ 50 mol-% of 1,1',3,3'-substituted ferrocene of structure (IIa) and Z an alkali metal, such as potassium or sodium, a functional group or an electrophile, such as COOH, COOMe, Cl, Br, I, SO 2 Cl, SO 2 Br, SO 2 I or SiMe 3 or a substituent chosen from the group comprising CH 2 OH, COCl, CON 3 , NCO, NHCOOMe, NHBoc, NH 2 “Substituted ferrocene” within the meaning of the invention can be produced according to step (a) of the process according to the invention, in which ferrocene (Bis(η) 5 -cyclopentadienyl)iron) with an organometallic base of lithium neopentyl (LiNp, LiCH) 2 C(CH 3 ) 3 ) and an alkali alcoholate. Furthermore, “substituted ferrocene” according to the invention can be produced according to step (a) in combination with one or more of steps (b), (c), (d), (e), (f), (g). The invention will be explained in more detail below using figures and examples. Figure 1 shows the crystal structure of the organometallic base K4Np(OtAm)3, which is formed by reacting lithium neopentyl (LiNp, LiCH2C(CH3)3) with potassium alkoxide; Figure 2 shows the molecular configuration of crystalline 1,1',3,3'-ferrocenetetramethoxycarbonyl; Figure 3 shows the 1H NMR spectrum of 1,1',3,3'-ferrocenetetracarboxylic acid; Figure 4 shows the 1H NMR spectrum of a mixture of ferrocenedicarboxylic acid, ferrocenetricarboxylic acid, and ferrocenetetracarboxylic acid; Figure 5 shows the 1H NMR spectrum of 1,1',3,3'-ferrocenetetramethoxycarbonyl; Figure 6 shows the 1H NMR spectrum of 1,1',3-ferrocentrimethoxycarbonyl. Example 1: Synthesis of neopentyllithium (LiNp, LiCH2tBu) Neopentyllithium (LiNp, LiCH₂tBu) can be obtained in 60–80% yields on a gram scale (RR Schröck, JD Fellmann, J. Am. Chem. Soc. 1978, 100, 3359–3370). Potassium tert-pentoxide (i.e., potassium tert-amylate, KOtAm or CH₃CH₂C(CH₃)₂OK) was prepared on a gram scale from potassium and the corresponding alcohol. A suitable solution in cyclohexane is available from TCI Europe (1 mol / L). Solutions in toluene or THF are also available from Sigma-Aldrich. The solvent used was exclusively n-hexane, which was dried over potassium and distilled under an argon atmosphere. All steps of the synthesis were carried out under an argon atmosphere. Example 2: Synthesis of the potassium base K4Np(OtAm)4 To obtain the compound K4Np(OtAm)3(KNp·3KOtAm), LiNp (0.078 g, 1.0 mmol, 1.0 eq) and KOtAm (0.560 g, 4.5 mmol, 4.5 eq) were weighed together and dissolved in n-hexane (20 ml) with stirring at room temperature. The yellowish solution was stored at -30°C for several days, yielding the compound K4Np(OtAm)3 as colorless, very air-sensitive crystals. Yield: 0.30 g (0.61 mmol, 61%). In the reaction, an excess of 0.5 equivalents of K₄OtAm is used to achieve the desired Np / OtAm ratio of 1 / 3 and to simultaneously bind the LiOtAm formed as Li₄K(OtAm)₅ or Li₄K₄(OtAm)₈. The resulting crystalline K₄Np(OtAm)₃ corresponds to the ratio given in the formula. 1H-NMR (400 MHz, 294 K, C6D12, TMS): δ = -0.98 (s, 2H, CH2(Np)), 0.84 (t, 9H, Me (OtAm)), 0.93 (s, 18H, Me (OtAm)), 0.99 (s, 9H, tBu (Np)), 1.21 ppm (q, 6H, CH2(OtAm)).13C-NMR (101 MHz, 294 K, C6D12, TMS): δ = 10.5 (s, Me (OtAm, Ethyl)), 34.8 (s, Me (OtAm)), 35.3 (s, C (Np)), 38.7 (s, Me (Np)), 42.4 (s, CH2(OtAm)), 44.7 (s, CH2(Np)), 69.0 ppm (s, C (OtAm)). The organometallic base K4Np(OtAm)3 crystallizes in a structure (see Fig. 1) with the following parameters: Example 3: Synthesis of tetrapotassium-1,1',3,3'-ferrocene, Fe(C5H3K2)2 As described above, LiNp (0.078 g, 1.0 mmol, 1.0 eq) and KOtAm (0.560 g, 4.5 mmol, 4.5 eq) were weighed together and dissolved in n-hexane (20 mL) with stirring at room temperature. Ferrocene (0.038 g, 0.20 mmol, 0.2 eq) was then added as a solid; the solution quickly turned red and a red precipitate formed. This suspension was heated to 60°C for 1 h. After filtration and washing with n-hexane (10 mL), a red solid was obtained. Yield: 0.168 g. Hydrolysis experiments indicate the composition K₈(Fe(C₅H₃)₂)(OtAm)₄, which corresponds to an idealized yield of approximately 94%. Since the red substance is either insoluble in deuterated solvents (C6D6, C6D12) or reacts with them (d8-THF), NMR spectroscopic characterization has not been successful so far. Example 4: Synthesis of 1,1',3,3'-ferrocenetetracarboxylic acid, Fe(C5H3(COOH),)2 As described above, twice the amount of LiNp (0.156 g, 2.0 mmol, 1.0 eq) and KOtAm (1.120 g, 9.0 mmol, 4.5 eq) were weighed together and dissolved in n-hexane (40 mL) with stirring at room temperature. Ferrocene (0.076 g, 0.41 mmol, 0.2 eq) was then added as a solid; the solution quickly turned red and a red precipitate formed. This suspension was heated to 60°C for 1 h with stirring. After cooling, carbon dioxide (CO2) dried with P4O10 was passed through the suspension, causing it to quickly turn yellow. After adding hydrochloric acid (20 mL, 10%), the mixture was filtered, the precipitate was washed with acetone (10 mL), and dried under vacuum, yielding a brownish-red solid. Yield: 0.138 g (>90%). Evaluation of the NMR spectra revealed a content of approximately 77%; the impurities included the triply substituted ferrocene (Fe(C5H3(COOH)2)(C5H4COOH), 11%) (R. Deschenaux, I. Kosztics, B. Nicolet, J. Mater. Chem.1995, 5, 2291-2295 ) and the doubly substituted (literature known) ferrocene (Fe(C5H4COOH)2, 12%) ( AR Petrov, K. Jess, M. Freytag, PG Jones, M. Tamm, Organometallics 2013, 32, 5946-5954 ) are present. Fe(C5H3(COOH)2)2:1H-NMR (400 MHz, 294 K, d6-DMSO, TMS): δ = 4.85 (s, 2H, C5H3), 5.01 ppm (s, 1H, C5H3).13C-NMR (101 MHz, 294 K, d6-DMSO, TMS): δ = 74.0, 74.8, 77.5, 168.7 ppm. Mass spectrum available. Fe(C5H3(COOH)2)(C5H4COOH):1H-NMR (400 MHz, 294 K, d6-DMSO, TMS): δ = 4.49 (s, 2H, C5H4), 4.65 (s, 2H, C5H4), 4.87 (s, 2H, C5H3), 5.10 ppm (s, 1H, C5H3). Fe(C5H4COOH)2:1H NMR (400 MHz, 294 K, d6-DMSO, TMS): δ = 4.45 (s, 2H, C5H4), 4.68 ppm (s, 2H, C5H4). Example 5: Synthesis of 1,1',3,3'-ferrocenetetracarboxylic acid, Fe(C5H3(COOH)3)2 using n-butyllithium Unlike in Example 4, KOtAm (0.560 g, 4.5 mmol, 4.5 eq) was weighed out and dissolved in n-hexane (20 mL) with stirring at room temperature. A solution of n-butyllithium in n-hexane (0.625 mL, 1.0 mmol, 1.0 eq, concentration 1.6 mol / L from Sigma-Aldrich) was added dropwise, causing turbidity. Ferrocene (0.038 g, 0.2 mmol, 0.2 eq) was added as a solid to this solution; the solution quickly turned red, and a red precipitate formed. This suspension was heated to 60°C for 1 h with stirring. After cooling, carbon dioxide (CO2) dried with P4O10 was passed through the suspension, causing it to quickly turn yellow. After adding hydrochloric acid (20 ml, 10%), the mixture was filtered, the precipitate was washed with acetone (10 ml), and dried under vacuum, yielding a brownish-red solid. Yield: 0.055 g (>80%). Evaluation of the NMR spectra revealed a content of approximately...56.4%; impurities include the triply substituted ferrocene (Fe(C5H3(COOH)2)(C5H4COOH), 11.5% ( R. Deschenaux, I. Kosztics, B. Nicolet, J. Mater. Chem. 1995, 5, 2291-2295 ) and the doubly substituted (known from the literature) ferrocene (Fe(C5H4COOH)2, 11.8%) ( AR Petrov, K. Jess, M. Freytag, PG Jones, M. Tamm, Organometallics 2013, 32, 5946-5954 ). Example 6: Synthesis of 1,1',3,3'-ferrocenetetramethoxycarbonyl, Fe(C5H3(COOMe)2)2 Crude 1,1',3,3'-ferrocenetetracarboxylic acid [contaminated with Fe(C5H3(COOH)2)(C5H4COOH) and Fe(C5H4COOH)2] (0.060 g, ~0.16 mmol) was suspended in a mixture of toluene (5.0 mL) and methanol (5.0 mL). A solution of trimethylsilyldiazomethane (Me3SiCHN2) (A. Presser, A. Hüfner, Monatshefte für Chemie 2004, 135, 1015-1022) in n-hexane (1.25 mL, 0.75 mmol, 10%, 0.6 mol / L) was added while stirring. Nitrogen evolution occurred, the yellowish solution became clear and then cloudy again; stirring continued for 16 h. The tetramethyl ester of 1,1',3,3'-ferrocenetetracarboxylic acid formed was separated by filtration. Yield: 0.045 g, 0.11 mmol, 65%. The corresponding di- and triply substituted ferrocenes still present in the filtrate were obtained by column chromatography (ethyl acetate / petroleum ether 1 / 3, Rf(Fe(C5H3(COOMe)2)(C5H4COOMe)) = 0.31; Rf(Fe(C5H4COOMe)2) = 0.2). Alternatively, the methylation of 1,1',3,3'-ferrocenetetracarboxylic acid can also be carried out in a methanol / boron trifluoride·diethyl ether mixture (MeOH / BF3·Et2O, 20ml / 1ml), heating under reflux for 16h. Fe(C5H3(COOMe)2)2:1H-NMR (400 MHz, 294 K, d6-DMSO, TMS): δ = 3.85 (s, 6H, OMe), 5.01 (s, 2H, C5H3), 5.49 ppm (s, 1H, C5H3).13C-NMR (101 MHz, 294 K, d6-DMSO, TMS): δ = 52.3 (OMe), 74.3 (C5H3), 75.1 (C5H3), 168.1 (COO) ppm. Mass spectrum available. (Fe(C5H3(COOMe)2)(C5H4COOMe):1H-NMR (400 MHz, 294 K, d6-DMSO, TMS): δ = 3.83 (s, 3H, OMe), 3.84 (s, 6H, OMe), Me) 4.42 (s, 2H, C5H4), 4.87 (s, 2H, C5H4), 4.99 (s, 2H, C5H3), 5.45 ppm (s, 1H, C5H3), 13C-NMR (101 MHz, 294 K, d6-DMSO, TMS): δ = 52.0 (OMe), 52.2 (OMe), 73.1 (C5H4), 73.2 (C5H3), 74.1 (C5H4), 74.2 (C5H3), 74.6 (C5H3), 75.6 (C5H4), 169.5 (COO), 169.6 (COO) ppm. 1,1',3,3'-Ferrocenetetramethoxycarbonyl crystallizes in a structure (see Fig. 2) with the following parameters: Tricline, P1; a = 5.95 Å, b = 6.87 Å, c = 11.08 Å; α = 90°, β = 102.64°, γ = 90°; R1 = 5.0 % M = 418.18 g / mol. Example 7: Synthesis of 1,1',3,3'-ferrocenetetrachlorocarbonyl, Fe[(C5H3)(COCl)2]2 In a 1 L Erlenmeyer flask, pyridine (1.2 mL, 5 mol%) and oxalyl chloride (180 mL, 6.4 equiv) were continuously added to a fine-grained suspension of Fe[(C5H3)(COOH)2]2 (119.48 g, 0.33 mol) in CHCl3 (0.3 L). The reaction mixture was heated to 60 °C in a reflux condenser until complete dissolution after approximately 2 h. The gas produced during the reaction was passed through 10% sodium hydroxide (NaOH) solution for neutralization. The reaction mixture turned a deep red color. After the gas production subsided, the reaction mixture was stirred for 30 min. The volatile components were condensed under reduced pressure in a cold trap cooled with liquid nitrogen. The retained dark reddish-brown solid could subsequently be used for the synthesis of Fe[(C5H3)(CON3)2]2 without further purification (see below).The solid was dissolved in boiling n-heptane (300 mL for approximately 30 g) and the slightly cooled supernatant was decanted to separate a sticky black residue. The supernatant was then slowly cooled to room temperature with stirring and subsequently cooled on an ice bath. The resulting light red crystalline solid was separated by rapid filtration on a frit filter, washed with a small amount of hexane, and vacuum-dried. The yield was 95% (135.11 g, 0.31 mol) of an odorless, red, microcrystalline solid that hydrolyzes only slowly in moist air. Example 8: Synthesis of 1,1',3,3'-ferrocenetetraazidocarbonyl, Fe[(C5H3)(CON3)2]2 Example 7 is used as a starting point, but caution is advised and any contact with hot objects should be avoided. Ignition can occur in air at temperatures above 100 °C. Even small amounts (1-2 mg) of the compound decompose spontaneously at temperatures near its melting point (Tm = 112-115 °C). To an intensively stirred solution of purified Fe[(C5H3)(COCl)2]2 (87.17 g, 0.20 mol) in acetone (0.6 L), a solution of NaN3 (58 g, 4.4 equiv) in 90 mL of water was added in four rations. After a mildly exothermic reaction (possibly accompanied by product precipitation), the reaction mixture was stirred at 45–50 °C for 1 h. Subsequently, a concentrated solution of NaHCO3 (50 mL) was added dropwise, forming a viscous red suspension. With swirling of the reaction vessel, 200 mL of water were slowly added. The reaction mixture was then diluted to a volume of 2.0 L by adding ice-cold water. The fine-grained, deep red precipitate was isolated using a coarse frit filter and washed with water. A sticky residue was removed using 400 mL of CH2Cl2, the organic supernatant was separated, and the aqueous phase was extracted twice using CH2Cl2 (150 mL each time).The mixed two-phase extract was ionized by a short silicate column (H2O,. 40) directed and the product with the same solvent (Rf(CH) 2 Cl 2 ) = 0.36) eluted and via Na 2 SO 4 The mixture was dried. The solvent and residual moisture were then removed in a rotary evaporator at 50 °C under vacuum (0.03 mbar). Yield: 92–97% (85.8–90.1 g) of red-orange powder. The compound is slightly light-sensitive and should be stored in a cool, dark place in a closed container. Example 9: Synthesis of 1,1',3,3'-ferrocenetetraazidocarbonyl, Fe[(C5H3)(CON3)2]2 In a 1 L round-bottom flask, Fe[(C5H3)(COOH)2]2 (79.67 g, 0.22 mol) was suspended in 225 mL of CHCl3, and pyridine (0.5 mL, 3 mol%) and oxalyl chloride (120 mL, 6.4 equiv) were added. The reaction mixture was heated to reflux and stirred at reflux temperature for 3 h. During the first two hours, the majority of the gas, including HCl, was formed and neutralized with 10% NaOH solution. The solvent and excess oxalyl chloride were removed under vacuum to obtain Fe[(C5H3)(COCl)2]2 as a dark red solid intermediate. The intermediate was dissolved in 675 mL of acetone, and NaN3 (63.2 g, 4.4 equiv) dissolved in 90 mL of water was added with vigorous stirring. The reaction mixture was stirred at 50 °C for 1.5 h, during which NaCl was formed. Subsequently, 100 mL of saturated NaHCO3 was added, and the reaction mixture was divided between two 2 L beakers, each beaker being filled with water to a volume of 2 L.The reaction mixture in both beakers was cooled with ice to ensure complete precipitation of the product. The mixture was then filtered through a coarse glass frit filter and washed with 3-4 liters of water. The resulting red solid was dried in an air stream and under vacuum, then lightly ground and sieved. This yielded 92.4 g (200 mmol, 91% yield) of Fe[(C5H3)(CON3)2]2 as a fine reddish-brown powder, which is suitable as a starting material for the preparation of Fe[(C5H3)(NCO)2]2 and Fe[(C5H3)(NHBoc)2]2. Example 10: Synthesis of 1,1',3,3'-ferrocene tetracyanate, Fe[(C5H3)(NCO)2]2 Starting with Example 9, Fe[(C5H3)(CON3)2]2 (92.42 g, 0.20 mol) in dry toluene (0.6 L) was placed in a 1 L round-bottom flask equipped with a reflux condenser and bubble counter, and the suspension was heated to 110 °C in an oil bath. At a bath temperature of 95–100 °C, intensive nitrogen (N2) formation began. The reaction is exothermic, and its progression can be controlled by the immersion of the round-bottom flask in the oil bath. After the gas formation subsided after about 2 h, an intensely yellow suspension was obtained, which was filtered through a Celite filter under air to remove a black residue. The filtrate was concentrated under vacuum to about 75 mL and slowly cooled to 0 °C, which led to crystallization of the product. The crystallized product was isolated by further filtration, washed with a mixture of hexane and toluene in a ratio of 2:1 and dried under vacuum to obtain a yellow crystalline solid.Additional product can be extracted from the mother liquor. The product is reasonably stable but should be protected from moisture. Yield: 81% (57.1 g) of yellowish-brown, microcrystalline solid. Example 11: Synthesis of 1,1',3,3'-ferrocenetetra[amino(methoxycarbonyl)], Fe[(C5H3)(NHCOOMe)2]2 Starting from Example 10, a suspension of Fe[(C5H3)(NCO)2]2 (1.26 g, 3.61 mmol) in 10 mL of dry methanol was heated to boiling point and cooled to room temperature with stirring. The resulting yellow-orange precipitate crystallized over a period of about 12 h. The supernatant was decanted, the solid filtered, and dried under vacuum. Yield: 93% (1.60 g, 3.35 mmol) of yellow crystalline solid. Example 12: Synthesis of 1,1',3,3'-ferrocenetetra[amino(tert-butoxycarbonyl)], Fe[(C5H3)(NHCOOtBu)2]2 Starting from Example 10, dry, molten tert-butanol (6.0 g, 4.4 equiv) was added to a stirred solution of Fe[(C5H3)(NCO)2]2 (6.65 g, 19 mmol) in 20 mL of dry diethyl ether. The reaction mixture was stirred at room temperature for 24 h, after which a yellow powder was obtained as a precipitate. The powder was filtered, washed with hexane, and dried under vacuum to obtain a first fraction of 6.2 g of a yellow powder. The yellow powder was dissolved in 15 mL of hot ethyl acetate and diluted with 45 mL of hexane. The solution was filtered through a short silicate column (H2O, 40) and with approximately 200 mL of a A mixture of ethyl acetate and hexane in a 1:3 ratio (Rf = 0.31) was eluted. The eluate was concentrated with a small volume of ethyl acetate to crystallize the product. The supernatant was decanted, and the residue was dried under vacuum to obtain 1.12 g of the product as orange crystals. The overall yield was 10.99 g (17 mmol, 89%). Example 13: Synthesis of 1,1',3,3'-ferrocenetetra[amino(tert-butoxycarbonyl)], Fe[(C5H3)(NHCOOtBu)2]2 Starting from Example 8, fine-grained Fe[(C5H3)(CON3)2]2 (46.21 g, 0.10 mol) was suspended in 0.2 L of dry toluene in a 1 L Schlenk flask. Due to the strong gas formation, the volume of the suspension was limited to one-third of the volume of the reaction vessel. The reaction mixture was stirred at 110 °C for 2 h and then cooled to room temperature. The reaction progress is monitored by TLC in toluene (Rf{Fe[(C5H3)(CON3)2]2} = 0.26, Rf{Fe[(C5H3)(NCO)2]2} = 0.82, Rf{Fe[(C5H3)(NHBoc)2]2} = 0.07), since the intermediate Fe[(C5H3)(CON)2]2 is moderately stable over a short period. Careful addition of dry, molten tert-butanol (70 mL, 6.0 equiv) to the reaction mixture cooled to 0 °C and heating until reflux over 5 min yielded a brown-colored solution. After removal of the volatile components, the residue was completely dissolved in 100 mL of heated ethyl acetate.After adding 100 mL of hexane, the reaction mixture was filtered through a silicate filter pad (H15,. 100, Rf = 0.85 (EtOAc / nC 6 H 14 , 1:1), > 0.95 (EtOAc), 0.23 (CH 2 Cl 2 )) directed to black The residue and a polar, dark brown impurity were removed. Elution with the same solvent mixture (approx. 600 mL) followed by removal of the volatile components under vacuum yielded an orange, microcrystalline solid. The yield was 81–83% (52.6–53.8 g). Example 14: Synthesis of 1,1',3,3'-tetraaminoferrocene, Fe[(C5H3)(NH2)2]2 To an ice-bath-cooled, fine-grained suspension of Fe[(C5H3)(NHBoc)2]2 (37.37 g, 57.8 mmol) in degassed methanol (160 mL), acetyl chloride (25.8 g, 5.8 equiv) was added via syringe, whereupon the solid dissolved and the solution turned dark. The reaction mixture was heated to 65 °C for 1.25 h, during which time the hydrochloride salt precipitated as a yellow solid. The reaction mixture was then cooled to room temperature, and a KOH solution (9.7 g, 3.0 equiv) in 40 mL of degassed methanol was added. During the addition of the alkali, the solid dissolved, and the reaction mixture turned dark, with KCl precipitating at approximately 50 vol%. Triethylamine (4 mL, 2 vol%) was added to the yellow suspension and then immersed in a short silica gel column (H25, 15 mL) buffered with 15 mL of a 2% triethylamine solution in methanol. 40) filtered. The product was eluted with a mixture of triethylamine in methanol (2 vol%, approx. 5 × 50 mL). The volatile components were removed at 50 °C under vacuum. The crude product was treated with CH 2 Cl 2 (100 mL) extracted and filtered through a Celite filter pad (H2O, 40) filtered. The resulting yellow solid was treated with CH 2 Cl 2 (7 × 10 mL) washed. After Upon removal of the solvent under vacuum, a brown solid was obtained with a yield of 84–93% (16.4–18.1 g). When using a larger excess of KOH, the filtration had to be repeated several times. Analytically pure samples were obtained by recrystallization in methanol. The synthesis methods described above according to the invention yield mixtures of unreacted ferrocene and various 1- to 4-fold substituted ferrocene compounds with a high proportion of 1,1',3,3'-substituted ferrocene of structure (IIa), which are referred to as "substituted ferrocene". The molar fraction of 1,1',3,3'-substituted ferrocene of structure (IIa) is determined by quantitative nuclear magnetic resonance spectroscopy – hereinafter referred to as qNMR. qNMR has been established in chemical and especially pharmaceutical research for about 15 years (Importance of Purity Evaluation and the Potential of Quantitative1H NMR as a Purity Assay; GF Pauli, S.-N. Chen, C. Simmler, DC Lankin, T. Gödecke, BU Jaki, JB Friesen, JB McAlpine, JG Napolitano; J. Med. Chem., 2014, 57 (22), pp 9220-9231).The accuracy achievable with qNMR is < 0.1 mass-% and the high reliability of the measurement method has led to qNMR analyses being increasingly included in the documentation for the approval of new pharmaceuticals, e.g. by the US Food & Drug Administration. For qNMR, hydrogen and / or carbon resonance spectra can be used. For the ferrocene mixtures substituted according to the invention, 1H NMR has proven to be entirely sufficient. This is due, not least, to the fact that the characteristic 1H NMR resonance lines or resonance peaks of 1- to 4-fold substituted ferrocene are mostly significantly spaced apart from each other and from the 1H NMR resonance peaks of the ferrocene substituents as well as common solvents, such as deuterated chloroform (CDCl3). Figures 3, 4, 5 to 6 show exemplary 1H NMR spectra of some 2- to 4-fold substituted ferrocene compounds, designated (i) to (v) in Table 1. The corresponding 1H NMR resonance peaks are labeled a to k and a', b', c', and d' in Figures 3, 4, 5 to 6, and Table 1. Table 1 shows the position or shift of each 1H NMR resonance peak and its intensity or peak area. The peak area is determined using instrument-specific or generic software packages, such as INFOS (INFOS: spectrum fitting software for NMR analysis; AA Smith; J. Biomol. NMR; February 2017, Volume 67, Issue 2, pp 77-94), by nonlinear regression or Fourier analysis. Table 1 further lists the number of H atoms per molecule for each of the 1H NMR resonance peaks (a to k as well as a', b', c' and d').Table 1: Ferrocen1H NMR Resonanzlinien Table 1: Ferrocen 1H NMR Resonanzlinien. (i) a / 25,021,00 b / 44,852,13 i / 412,722,30 (ii) c / 15,100,09 d / 24,87- e / 24,650,19 f / 24,490,19 (iii) g / 44,680.32 h / 44,450,31 (iv) a' / 25,491.00 b' / 45,012,05 j / 123,856.26 (v) a' / 15,450.95 b' / 24,992.00 c' / 24,871.98 d' / 24,422.00 j / 63,849.74 k / 33.83 * pro Molekül To determine the contribution of a ferrocene compound, its normalized 1-proton contribution—hereinafter also referred to as the "1H contribution"—is first calculated, preferably using undisturbed 1H resonance peaks of the respective ferrocene compound, i.e., peaks not superimposed with other 1H resonance peaks. The 1H contribution of a ferrocene compound is calculated by: selecting m, preferably unsuperimposed, 1H NMR resonance peaks of the ferrocene compound, where m is an integer ≥ 1; dividing the peak area of ​​each of the m 1H NMR resonance peaks by the number of associated H atoms in the molecule; summing the m quotients of the respective peak area and the number of associated H atoms in the molecule; and dividing the sum by m. The calculation can be described in a compact way by the following formula. The calculation of the 1H contribution is explained in more detail below with reference to Fig. 4 and Table 2. The 1H NMR spectrum shown in Fig. 4 was measured on a mixture prepared according to the process steps of the invention, which contains 2- to 4-fold carboxylated (COOH) ferrocene compounds of type (i), (ii), and (iii). The ferrocene compound of type (i) (1,1',3,3'-ferrocenetetracarboxylic acid) includes the 1H NMR resonance peaks labeled a and b, where b is partially overlapped with the 1H NMR resonance peak d of the ferrocene compound of type (ii) (1,1',3,3'-ferrocenetricarboxylic acid) and is therefore not used for the calculation of the 1H contribution of (i). The peak area and number of associated H atoms of the 1H NMR resonance peak a of the ferrocene compound (i) (1,1',3,3'-ferrocenetetracarboxylic acid) have the values ​​1.00 and 2 respectively. Accordingly, the 1H contribution for the ferrocene compound (i) is 1.00 ÷ 2 0.5 For the ferrocene compound of type (ii) (1,1',3,3'-ferrocenetricarboxylic acid), the 1H NMR resonance peaks c, e, and f are used. The peak area and number of associated H atoms in the molecule are 0.09 and 1 for c, and 0.19 and 2 for e and f, respectively. Thus, the 1H contribution of ferrocene compound (ii) is calculated as follows: Similarly, for the 1H contribution of ferrocene compound (iii) (1,1',3,3'-ferrocenedicarboxylic acid) with the 1H NMR resonance peaks g and h, a value of [value missing] is calculated. Table 2: 1H contributions according to the NMR spectrum of Fig. 4 (i)a1,00÷2 = 0.5 (ii)c, e, f (iii)g, h ** normalized 1-proton contribution of the ferrocene compound from the associated 1 H NMR peak areas The ratios of the 1H contributions of each pair of the ferrocene compounds (i), (ii) and (iii) are consistent; it holds that From the above 1H contributions, the following molar fractions result for the ferrocene compounds (i), (ii) and (iii) Table 3: Molar fractions according to the NMR spectrum of Fig. 4 Table 3: Molar fractions according to the NMR spectrum of Fig. 4 (i) (ii) (iii) The molar fractions given in Table 3 were verified by independent 1H qNMR measurements on three calibrated mixtures. The calibrated mixtures were prepared from purified ferrocene compounds of type (i), (ii) and (iii). Purification was carried out on ferrocene 1,1',3,3'-substituted with methoxycarbonyl groups according to the procedures described above. For this purpose, 1,1'-ferrocendimethoxycarbonyl and 1,1',3-ferrocentrimethoxycarbonyl were isolated by column chromatography, and 1,1',3,3'-ferrocenetetramethoxycarbonyl was isolated by vacuum distillation at 120 °C. Subsequently, the ferrocene compounds 2- to 4-fold 1,1',3,3'-substituted with methoxycarbonyl were hydrolyzed in alkali to obtain the corresponding ferrocene carboxylic acids (i), (ii), and (iii). Using the ferrocarboxylic acids thus purified, three calibrated mixtures with different proportions of the ferrocarboxylic acids (i), (ii) and (iii) were prepared, a 1H NMR spectrum was recorded for each mixture and, as explained above, the molar proportions were calculated from the 1H contributions of the 1H NMR resonance peaks a, (c, f, e) and (g, h).The calculated proportions correspond exactly to the proportions determined by the quantitative ratios of the respective mixture. Furthermore, the results confirm the linear or proportional relationship between the measured signal, i.e., the 1H contribution, and the respective molar proportion.

Claims

Process for the preparation of substituted ferrocene and ferrocene-containing polymers, comprising a step (a) in which ferrocene (bis(η5-cyclopentadienyl)iron) is reacted with an organometallic base of lithium neopentyl (LiNp, LiCH2C(CH3)3) and an alkali alkoxide to give 1,1',3,3'-metallated ferrocene of the structure wherein M is an alkali metal, the organometallic base having the structural formula K 4 Np(OtAm) 3 or Na 4 Np(OtAm) 3 has, in which Np has a neopentyl group with structural formula CH 2 C(CH 3 ) 3 and OtAm a tert-amyl oxide group with structural formula OC(CH 3 ) 2 (CH 2 CH 3 ) is. The method according to claim 1, characterized in that the reaction of ferrocene with the organometallic base is carried out in a reaction mixture containing an organic solvent. A method according to claim 1 or 2, characterized in that in step (b) metallized ferrocene from step (a) is reacted, wherein the alkali metal M is replaced by a functional group or an electrophile selected from COOH, Cl, Br, I, SO2Cl, SO2Br, SO2I or SiMe3 and 1,1',3,3'-substituted ferrocene of the structure is obtained, wherein R is a functional group or an electrophile chosen from COOH, Cl, Br, I, SO 2 Cl, SO 2 Br, or SO 2 I or SiMe 3 is. The method of claim 3, characterized in that in step (b) metallated ferrocene from step (a) is reacted with carbon dioxide (CO2) to form 1,1',3,3'-ferrocenetetracarboxylic acid of the structure to obtain. Method according to claim 3 or 4, characterized in that in step (c) substituted ferrocene from step (b) is esterified. The method of claim 4, characterized in that in step (c) COOH-substituted ferrocene from step (b) is reacted with trimethylsilyldiazomethane (Me3SiCHN2) or BF3 / methanol to yield 1,1',3,3'-ferrocenetetramethoxycarbonyl of the structure to obtain, in which Me is a methyl group. The method according to claim 6, characterized in that in step (f) COOMe-substituted ferrocene from step (c) is reacted with a compound selected from alcohols, acid chlorides, amines or isocyanates. Substituted ferrocene, characterized in that ≥ 20 mol-%, ≥ 50 mol-%, ≥ 60 mol-%, ≥ 70 mol-%, ≥ 80 mol-%, ≥ 90 mol-% or ≥ 95 mol-% of the ferrocene units are 1,1',3,3'-substituted, based on the total number of ferrocene units, and the 1,1',3,3'-substituted ferrocene has the structure or has, wherein M is an alkali metal chosen from potassium, sodium and lithium, R is a functional group or electrophile chosen from Cl, Br, I, SO 2 Cl, SO 2 Br or SO 2 I and X a substituent chosen from the group comprising CH 2 OH, COCl, CON 3 , NCO, NHCOOMe, NHBoc, NH 2 is.

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