Dicarbonylbis(η-cyclopentadienyl)titanium(II) chemistry: reactions with organic molecules containing C–Cl, P–Cl, O–H, and S–Cl bonds; synthesis, properties, and structures of η-acyl derivatives of titanium(IV)

Abstract

The reaction of [Ti(cp)₂(CO)₂](1)(cp =η-C₅H₅) with acyl halides RCOCl (R = Me or Ph) gives acyl derivatives of titanium(IV), [Ti(cp)₂(COR)Cl]. Under the same conditions, the reaction of (1) with alkyl iodides gives the acyl derivatives [Ti(cp)₂(COR)I](R = Me, Et, Prⁱ, or Bu^s). All the acyl derivatives are characterised by a low CO stretching frequency [ν(CO) at ca. 1 600 cm^–1]. X-Ray analysis of [Ti(cp)₂(COMe)Cl] shows that the molecule has C_s symmetry with atoms Ti and Cl and the acetyl group lying in the crystallographic mirror plane. The Ti atom has distorted tetrahedral co-ordination, and it interacts strongly with the oxygen of the acetyl group which acts as a bidentate three-electron ligand. This structure explains the observed low CO stretching frequency for the acyl unit. Reaction with MeSO₂Cl resulted in insertion of the Ti(cp)₂ unit into the S–Cl bond giving [Ti(cp)₂(O₂SMe)Cl]. Reactions of (1) with iodide, phenanthrene-9,10-quinone. and PPh₂Cl are also reported.