Vanadium, niobium and tantalum

Abstract

This report summarizes the literature from 2007 pertaining to the chemistry of the group 5 elements. Novel coordination and organometallic compounds are included, along with selected applications in the areas of catalysis and bioinorganic/medicinal chemistry. HighlightsHighlights from 2007 include the ingenious use of the vanadium(IV/V) redox couple to sufficiently stabilize a monomeric phosphorus radical to allow its isolation and characterization, 4 the first example of a tantalum complex incorporating both alkyl and aquo ligands at the metal centre, 55 and a new family of Nb-and Ta-based olefin polymerization catalysts supported by bridged calixarene ligands. 79 2 Coordination chemistry Vanadium One of the attractive features of the chemistry of vanadium is the accessibility of the metal in several oxidation states, and whilst this may present a challenge to the synthetic chemist, the variety of ligands available for use in a supporting role ensures that most of the desired complexes can be isolated. Once tamed, the metal can be put to work in number of different roles and clever use of the resonance stabilization of the vanadium(IV/V) redox couple has enabled isolation of a monomeric phosphorus radical for the first time by Cummins and co-workers (1). 4 The redox chemistry of vanadium supported by a s,p,s-tripyrrole ligand set has been exploited in the cleavage of a coordinated dinitrogen molecule, in this case to afford a mixed-valent nitride-bridged complex (2).