Square pyramidal dialkoxo-bound monooxo-vanadium(V) complex and its behavior in solution.

Interest in vanadium chemistry has increased since the recognition of the involvement of vanadium ions in many important biological systems.1 The distinctive preference of the vanadium ion for N/O donor atom types has prompted the synthesis and characterization of many model complexes containing N/O donor ligands, the spectroscopic properties and solution behavior of which have been investigated.2 A short vanadium-oxygen bond length (1.72 Å) for the coordination environment of the vanadium(V) center in vanadate-dependent bromoperoxidase, based on the EXAFS,3 increased interest in alkoxo-bound vanadium(V) model complexes. In addition, crystallographic studies on chloroperoxidase (at 2.1-Å resolution) showed a five-coordinate trigonal bipyramidal vanadium center as an active site, where three nonprotein oxygen atoms are situated at short distances from the vanadium(V) center (average 1.65 Å).4 While five-coordinate monooxo-vanadium(IV) model complexes5,6 are common, only a few five-coordinate monooxo-vanadium(V) model complexes5b,6,7 are known. In this study, we report the synthesis and structural characterization of a five-coordinate square pyramidal dialkoxo-bound monooxo-vanadium(V) complex and its behavior in solution.