Co-ordination complexes of niobium and tantalum. Part XIII. Thiocyanato-alkoxo-bipyridyl complexes of niobium(V) and tantalum(V)

Abstract

Crystalline complexes of the composition M(NCS)₂(OR)₃(bipy)(M = Nb or Ta; R = Me or Et) have been prepared. Methoxo- and ethoxo-derivatives, respectively, of niobium and tantalum are isomorphous. Molecular-weight determinations in benzene show that the complexes are dimeric. The presence of two bridging alkoxo-groups, nitrogen-bonded isothiocyanates in the terminal position, and normal bidentate co-ordination of bipyridyl is indiacated by spectral evidence. Accordingly, Nb^V and Ta^V are surrounded in these asymmetrical ligand spheres by eight donor atoms.