Ferrocene organic chemistry

Gan, K.-S. Hor, T. S. A. l,l -Bis(diphenylphosphine) ferrocene. Coordination chemistry, organic synthesis, and catalysis. VCH Weinheim, Germany. In Ferrocenes-Homogeneous Catalysis, Organic Synthesis, Materials Science, Togni, A., Hayashi, T., Eds., 1995, p 3. 

In organic chemistry this stabilizing effect is well known the stability of carbanions is known to be enhanced by nitro groups. The stability of the cyclopentadienide anion is increased by complexing with a typical Lewis acid so that it becomes less reactive. For example, ferrocene is not ionized in nitromethane solution. Addition of a Lewis acid such as aluminum chloride facilitates the occurrence of intramolecular race-mization (75) a process which is believed to involve ionic intermediates [16). This belief is supported by kinetic evidence and the failure of the reaction to occur in nearly inert solvents like methylene chloride and in those of high donidty. Whereas the former do not support the solvation of the cation formed in the process of ionization, the latter will react preferentially with the Lewis acid, which is then no longer available for the stabilization of the carbanion. 

The original concepts of metal-ligand bonding were essentially related to the dative covalent bond the development of organometallic chemistry has revealed a further way in which ligands can supply more than one electron pair to a central atom. This is exemplified by the classical cases of bis(benzene)chromium and bis(cyclopentadienyl)iron, trivial name ferrocene. These molecules are characterised by the bonding of a formally unsaturated system (in the organic chemistry sense, but expanded to include aromatic systems) to a central atom, usually a metal atom. 

Cymantrene (6) demonstrates a considerable amount of organic chemistry just as does ferrocene. No organic photochemistry has been found in cy-mantrenyl systems, however, due to the customary complication of photo-chemically induced decarbonylation. E. O. Fischer55 has investigated this in some detail and three representative reactions are listed here. 

The organometallic ferrocene moiety is an attractive redox center to integrate into macrocyclic polyether ligands because, apart from its established functional group organic chemistry, ferrocene itself is elec-trochemically well behaved in most common solvents undergoing a reversible one-electron oxidation (43). 

Like the CSH5 ring in ferrocene and CpMn(CO)3 (see later), the C4H4 ring undergoes typical aromatic electrophilic substitution reactions. There is quite an extensive organic chemistry of the derivatives. Finally, it is possible to obtain free cyclobutadiene for use in in situ organic reactions by oxidative decomposition ... 

There is a very large number of complexes which contain one or two Cp groups per iron atom the best known is the unusually stable ferrocene for which a vast organic chemistry is known.117 It undergoes Friedel-Crafts acylation, sulfonation, and metallation by alkyllithiums, and so on. An example is the reaction... 

A26. M. Rosenblum, Chemistry of the Iron Group Metallocenes Ferrocene, Rutheno-cene, Osmocene. Wiley (Interscience), New York, 1965. Only vol. 1 published, which is an excellent introduction to the organic chemistry of ferrocene and its two congeners, but unfortunately not yet completed by the appearance of vol. 2. 

P. L. Pauson Compounds derived from cyclopentadiene, pp. 107-140a (197) an account of metal cyclopentadienyls, and the organic chemistry of ferrocene. A50. G. A. Olah, ed., Friedel-Crafts and Related Reactions. Wiley (Interscience), New York, 1965. 

Metallocene chemistry, i.e. organic chemistry of ferrocene and related molecules... 

The initial problem was in the attempt to prepare a variety of correct intermediate and final derivatives of ferrocene. These compounds first became available in the 1970s [73, 94], when the a-ferrocenyl alkyl amines were shown also to play an essential role, and when the He-3CR of ferrocene was first introduced [94]. These derivatives are now widely used as catalysts in organic chemistry [95], as illustrated by the U-4CR of 2h being the first chiral amine component that fulfilled all essential aspects (Scheme 4.17 see also Scheme 4.14) however, the individual steps of such U-4CRs did not yet proceed in sufficient yield and stereoselectivity. The final yields of cleaving 18o into 31A and the simultaneous re-synthesis of the amine 2h were poor, though hope remains (with some justification) that closely related U-4CRs with a-ferrocenyl- J-hydroxyethylamine derivatives will be developed. 

Another cooperative effort arose between Samuel McManus of the University of Alabama in Huntsville and our group. This cooperation produced results in pure heterocyclic organic chemistry, oxazoline polymerizations,96 and siloxane polymers.97 Oxysilane ferrocene-containing polymers were explored.98,99 Several bis(dimethylamino)silanes were made and reacted with 1,1 -bis(hydroxymethyl)ferrocene to give the early ferrocene oxysilane polymers 69 and 70 (Scheme 1.12).98... 

Little, W. F., Survey of Progress in Chemistry, 1963, 1, 133 (review on sandwich compounds, especially organic chemistry of ferrocene). 

The method for preparation of ferrocene (70) [104], applied to indeno-phanes, links the two most extensively investigated two-layered molecules in organic and metal organic chemistry, [22](l,4)cyclophane (8) and ferrocene (70) respectively (Fig. 126) [103, 105]. 

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