Carbonyltrichlorotris(dimethylphenylphosphine)technetium-ethanol (1/1), the first seven-co-ordinate complex of technetium; position of this molecule in the C3v family

Abstract

The preparation and the crystal and molecular structure of the title complex are reported. The co-ordination polyhedron is that of a distorted capped octahedron (C_3v symmetry). The technetium atom is seven-co-ordinate and bonded to three phosphine ligands (capped face), three chlorine ligands (uncapped face), and to the carbonyl group, which occupies the unique capping position. Crystals are monoclinic, space group P2₁/c, with cell dimensions a= 11.732(9), b= 11.807(9), c= 23.588(12)Å, and β= 103.42(8)° The structure has been refined by least squares to a conventional R of 0.093 for 1 794 observed reflections, Metal-ligand bond lengths are: Tc-CO 1.86(2), Tc-Cl 2.48(1), and Tc-P 2.44(1)Å. Seven-co-ordinate complexes are briefly reviewed; in particular, a description of C_3v symmetry and its distortions has been developed in terms of repulsion theory and the angular-overlap model.