Structural studies of complexes of vanadium(III) and titanium(IV) with N,N-dimethylaminomethylferrocenyl

Abstract

Vanadium(III) and titanium(IV) complexes containing 12–16 valence-shell electrons have been synthesised by treatment of cyclopentadienylmetal halides with the lithium salt of N,N-dimethylaminomethylferrocene, Li(FcN). The structurally characterized products were [(η⁵-C₅H₅)₂Ti(η¹-FcN)Cl] 1, [(η⁵-C₅H₅)Ti(FcN)_xCl_3 – x)] (x = 1, complex 2; x = 2, complex 3; and x = 3, complex 4) and [V(FcN)₂Cl] 6. They contain FcN bound either monodentate, through the aromatic 2-carbon atom, or bidentate, through that carbon and the amine nitrogen. Despite employing a variety of spectroscopic techniques, we were unable to distinguish the mode of binding in any way other than a crystal structure analysis. Compound 4 changes spontaneously at room temperature into the structurally characterised [(η⁵-C₅H₅)Ti(FcN)(FcN′)] 5. The ligand FcN′ arises by metallation of one methyl group of one FcN in 4 with elimination of H(FcN). This kind of metallation has not been recognised hitherto in titanium or vanadium FcN chemistry, and it may explain why yields of required products are sometimes very low. The synthetic and structural versatility of the ligand FcN have been clearly demonstrated.