Reactions of Nitrogen Monoxide and Dioxygen with Bis(pentamethylcyclopentadienyl)vanadium Dihalides: Preparation and Structures of Oxo Derivatives of (Pentamethylcyclopentadienyl)vanadium

Reaction of Cp*₂VCl₂(Cp* = n⁵-C₅(CH₃)₅) with NO gave green Cp*VCl₂(0) (I) as the major and brown [Cp*VCl(μ-0)]₄(II) as the minor product. The structures of I and II have been determined by X-ray diffraction. I is a monomeric complex of vanadium(V) containing a V=0 bond (v(V—O) = 965 cm^-1; r(V—O) 1.576 (8) A). II is antiferromagnetic and has an almost planar eight-membered [v(μ-o)]₄ring with the Cp* and Cl ligands alternating above and below the plane; r(V—0) is 1.800 (2) A. I and II were also obtained in low yield from the reaction between Cp*₂VCl₂and 0₂, which was very slow. Reaction of Cp*₂VI₂ with NO gave [Cp*₂V(NO)]₂I₈, in which two Cp*₂VI(NO) units are linked together by three iodine molecules. The spectral properties of [Cp*₂V(NO)]₂l₈are very similar to those of Cp*₂VI(NO) published previously. There was no reaction between Cp*₂VI₂ and N₂0, but 0₂ gave two products, depending on the ratio of the reactants. With a Cp*₂VI₂:0₂ ratio of 2:1 the product was green [cp*vi(0)]2(μ-0), a vanadium(V) complex with v(V=0) at 955 cm^-1. With a Cp*₂VI₂:0₂ ratio of 4:1 the yellow, paramagnetic, vanadium(IV) complex [Cp*VI₂]₂(μ-0) (III) was obtained. The structure of III has been determined by X-ray diffraction. It has a crystallographically imposed linear and symmetrical V-O-V bridge (r(V-O) = 1.765 (1) A).