Crystal and molecular structure of 2,2′-bipyridyldichloro(trimethyl)tantalum(V)

Abstract

Crystals of the title compound are monoclinic, space group P2₁/m, a= 7·549(8), b= 12·422(12), c= 8·558(9)Å, β= 109·7(2)°, Z= 2. The structure was solved from diffractometer data by Patterson and Fourier methods, and refined by least squares to R 0·08 for 762 independent reflections. A disordered structure model was refined space group P2₁/m. In each individual molecule, the tantalum atom has a distorted capped trigonal prismal environment, with one chlorine atom in the unique capping position [2·540(10)Å]; the nitrogen atoms [2·291(21)Å], one chlorine atom, and one methyl group form the capped quadrilateral face with two methyl groups [2·24(4) and 2·16(6)Å] occupying the remaining edge. The molecule was refined with imposed m symmetry, so that the two sites in the quadrilateral face occupied by a chlorine atom and a methyl group were given equivalent mean scattering factors. The choice of geometry for this seven-co-ordinate (with five unidenta ligands) complex has been rationalised by considering the ligand–ligand repulsions and the constraints imposed by the bidentate 2,2′-bipyridyl ligand.