Some transition metal derivatives of ferrocene

Abstract

Complexes of the general formulation LM-X-Fc and LMFc (L = q5-C5H5, CO, PR3; X = CO, CH2, CH2CO; Fc = CsH4FeCsHs; M = Fe, W, Mo, Mn) have been prepared using the salt elimination reaction between the appropriate transition metal carbonylate anion and halo-substituted ferrocenes. The spectral and chemical properties of the complexes have been studied. The mass spectral fragmentation data reveals several examples of ligand transfer from the ferrocene iron atom to the other metal and significant metal-metal bonding. Electrochemical studies indicate that redox properties of the two metal centers are independent of one another. The acyl derivatives LMCOFc readily decarbonylate thermally to LMFc, in the case of LM = ($-C5Hs)Fe(C0)2, this being one of the few such thermal decarbonylations observed. Studies on the chemistry of the metal-carbon bond have occupied a central position in transitidn metal chemistry because of the intermediacy of such bonds in catalytic processes both industrial and biological. Recently, it has become clear that new metal-carbon bonded complexes can be synthesized and studied using special alkyl ligands that impart a greater thermal and oxidative stability in comparison with the simple alkyl ligands, methyl, ethyl, etc.2 Examples are the recent studies on the use of silylmethyl ligands to form many new complexes with very distinctive chemical characteristic~.~-~ The overall greater thermal and oxidative stability of the nonfunctionally substituted silylmethyl ligands (cf. methyl metal complexes) can, in part, be attributed to the steric bulk of the silylmethyl ligand partially protecting the central metgl atom. We have sought to find other such ligands and report here on some initial studies using ferrocene as one such ligand. This potential ligand also has a large steric requirement and also offers the opportunity to study what interactions, if any, occur between the iron atom of the ligand and the central substituted metal atom. For example, McCleverty et al., have reported that the electrochemical oxidation of a ferrocknylcarbenechromium pentacarbonyl complex exhibits a single one-electron oxidation rather than the two single one-electron oxidations expected, Le., CrO Cr+ and Fe2+ - Fe3+.6 They suggested that this resulted from the highest occupied molecular orbital of the complex encompassing both metal centers. In the present paper we report the initial resul.ts of a study using the various substituted ferrocenes as ligands u bonded to a central transition metal directly via the cyclopentadienyl ring of the ferrocene or via a bridging methylene, ketonic carbonyl, or ketenyl radical. While this work was in progress7 the preparation of some of the complexes was reported by Nesmeyanov and co-workers.8