Synthesis and structural characterization of group 6 transition metal complexes with terminal fluoromethylidyne (CF) ligands; a DFT/NBO/NRT comparison of bonding characteristics of terminal NO, CF and CH ligands

Abstract

A family of group 6 transition metal complexes M(C₅R₅)(CO)₂(CF) [M = Cr, Mo, W; R = H, Me] with terminal fluoromethylidyne ligands have been synthesized through the reduction of the corresponding trifluoromethyl precursors with potassium graphite or magnesium graphite. They have been characterized spectroscopically and in some cases crystallographically, although the structures show disorder between the CO and CF ligands. The MCF subunit reacts as a triple bond to form cluster complexes containing μ³-CF ligands on reaction with Co₂(CO)₈. Computational (DFT/NBO/NRT) studies on M(C₅H₅)(CO)₂(CF) [M = Cr, Mo, W] and the corresponding cationic fragments M(CO)₂(XY)⁺ illustrate significant differences in the metal–ligand bonding between CF and its isoelectronic analogue NO, as well as with its hydrocarbon analogue CH.