A Transient Vanadium(III) Neopentylidene Complex. Redox Chemistry and Reactivity of the V═CH^<i>t</i>Bu Functionality

Abstract

The vanadium(III) bis(neopentyl) complex (PNP)V(CH 2 t Bu) 2 (PNP = N[4-Me-2-(P i Pr 2 )C 6 H 3 ] 2 − ), a complex readily prepared from alkylation of (PNP)VCl 2 with 2 equiv of LiCH 2 t Bu, serves as a precursor to the transient vanadium(III) alkylidene complex “(PNP)V═CH t Bu”. Two-electron oxidation of the intermediate [(PNP)V═CH t Bu] with chalcogen sources results in formation of the vanadium(V) chalcogenide series (PNP)V═CH t Bu(X) (X = O, S, Se, Te). This family of chalcogenide−alkylidenes has been studied via 51 V NMR spectroscopy in combination with DFT computational methods. The redox chemistry of [(PNP)V═CH t Bu] and the reactivity of the alkylidene ligand are explored with the substrates N 3 SiMe 3, N≡C t Bu, N 2, and azobenzene. It was discovered that N═N cleavage of the last substrate can be achieved without oxidation of the metal.