Pentamethylcyclopentadienyltrimethylgermane: A Nontoxic Entry to Mid-Valent Monopentamethylcyclopentadienylvanadium Chloride Complexes

The reaction of [VCl₃(thf)₃] with [Ge(C₅Me₅)Me₃] provides an efficient and nontoxic alternative synthesis for the vanadium(III) trimer [{VCp*(μ-Cl)₂}₃] (Cp* = η⁵-C₅Me₅) (1). The trinuclear structure of 1 is preserved in aromatic hydrocarbon solvents and can be easily oxidized with [FeCp₂](BPh₄) to give [{VCp*(μ-Cl)₂}₃](BPh₄). In contrast, 1 undergoes dissociation in coordinating solvents to form mononuclear species [VCp*Cl₂(L)] (L = thf, py), which can be reduced with magnesium to afford dinuclear mixed-valence V(III)/V(II) [(VCp*)₂(μ-Cl)₃] or V(II) [{VCp*(py)(μ-Cl)}₂] derivatives. The latter compound reduces in two electrons the N═N bond of azobenzene at room temperature to give the vanadium(III) derivative [{VCp*(μ-Cl)}₂(μ–η²:η²-N₂Ph₂)], which undergoes cleavage of the N–N bond at 90 °C to form the imido-bridged dinuclear vanadium(IV) complex [{VCp*Cl(μ-NPh)}₂].