Mixed-membered-bisfulvalene dimetal-complexes via metallocene-substituted norbornenyl alcohols

Abstract

A proven synthetic method for mixed-metal [0.0] bimetallocenophanes containing Fe, Ru and Co is presented in detail. Utilising norbonenyl alcohol precursors, doubly lithiated ruthenocene or ferrocene were reacted with bicyclo[2.2.1]-hept-2-en-7-one (norborn-2-en-7-one) to yield a mixture of stereoisomeric alcohols, or respectively spiro-ethers, which can be separated by means of chromatography. The initially formed alcoholates were further reacted with diethylchlorophosphate to yield the respective chloro-substituted derivatives. Subsequent reductive cleavage of the chlorine-carbon bonds by lithium-powder in DME afforded the metallocene-substituted norbornenyl carbanions, which eliminated ethylene at ambient temperature to form dilithium metallocenylenebis(cyclopentadienvlides). In a final step, reaction with cobalt dichloride produced the mixed-metal bimetallocenophanes 1,1′-(1,1′-cobaltocenediyl)-ferrocene and 1,1′-(1,1′-cobaltocenediyl)-ruthenocene respectively. Target-compounds isolated as monocationic hexafluorophosphate salts as well as isolable intermediate products were characterized mainly by NMR-, IR- and MS-techniques. The X-ray structures of 1,1′-(1,1′-cobaltoceniumdiyl)-ruthenocene PF 6 − and selected norbornenols are presented. anti-, anti-Bisnorbornenol 1b exhibits significant sandwich plane distortions induced by hydrogen bridges. The dimers formed in the solid state resemble covalent ansa-type conformations. Furthermore, the synthetic route of reacting mono- and dilithiometallocenes with norbornenone was applied to the lithium and dilithium acetylides of ethynyl and 1,1′-diethynylferrocene. The attempted extension of the described synthetic concept to mono- and dinorbornenol-substituted ferrocenylethynes for the final conversion to ferrocene-1,1′-bis(ethynylcyclopentadienides) did not allow the preparation of the desired ethyne-spacered bimetallocenophane species.