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].