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A Transient Vanadium(III) Neopentylidene Complex. Redox Chemistry and Reactivity of the VCHtBu Functionality

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posted on 2009-02-09, 00:00 authored by Uriah J. Kilgore, Caitlin A. Sengelaub, Hongjun Fan, John Tomaszewski, Jonathan A. Karty, Mu-Hyun Baik, Daniel J. Mindiola
The vanadium(III) bis(neopentyl) complex (PNP)V(CH2tBu)2 (PNP = N[4-Me-2-(PiPr2)C6H3]2), a complex readily prepared from alkylation of (PNP)VCl2 with 2 equiv of LiCH2tBu, serves as a precursor to the transient vanadium(III) alkylidene complex “(PNP)VCHtBu”. Two-electron oxidation of the intermediate [(PNP)VCHtBu] with chalcogen sources results in formation of the vanadium(V) chalcogenide series (PNP)VCHtBu(X) (X = O, S, Se, Te). This family of chalcogenide−alkylidenes has been studied via 51V NMR spectroscopy in combination with DFT computational methods. The redox chemistry of [(PNP)VCHtBu] and the reactivity of the alkylidene ligand are explored with the substrates N3SiMe3, NCtBu, N2, and azobenzene. It was discovered that NN cleavage of the last substrate can be achieved without oxidation of the metal.