The synthesis, molecular and electronic structure of cyanovinylidene complexes

Reaction of the readily available metal acetylide complexes Ru(CCC6H4R-4)(PPh3)2Cp (R = OMe, Me, H, CN, CO2Me), Ru(CCFc)(PPh3)2Cp and Fe(CCC6H4R-4)(dppe)Cp (R = Me, H) with 1-cyano-4-dimethylaminopyridinium tetrafluoroborate affords cyanovinylidene complexes [Ru{CC(CN)C6H4R-4}(PPh3)2Cp]BF4, [Ru{CC(CN)Fc}(PPh3)2Cp]BF4 and [Fe{CC(CN)C6H4R-4}(dppe)Cp]BF4 in an experimentally simple fashion. These synthetic studies are augmented by refinements to the preparation of the key iron reagents FeCl(dppe)Cp and Fe(CCC6H4R-4)(dppe)Cp. Molecular structure determinations, electrochemical measurements, representative IR spectroelectrochemical studies and DFT studies have been used to provide insight into the electronic structure of the cyanovinylidene ligand, and demonstrate that despite the presence of the cyano-substituted methylidene fragment, reduction takes place on the vinylidene Cα carbon.