Trigonal Prismatic Coordination. The Crystal and Molecular Structure of Tris(cis-l,2-diphenylethene-l,2-dithiolato)Rhenium

The crystal and molecular structure of tris(cis-1,2-diphenylethene-1,2-dithiolato)rhenium, Re(S₂C₂(C₆H₅)₂)₃, has been determined from three-dimensional X-ray data. The neutral complex crystallizes in space group PI of the triclinic system, with two molecules in a cell of a = 19.73, b = 11.94, c = 9.87 A, α = 120.1, IS = 73.6, γ = 102.5°. The crystal structure consists of the packing of discrete monomeric molecules, the closest Re-Re distance being approximately 9.5 A. In the molecule, rhenium is surrounded by six equidistant sulfur atoms in a trigonal prismatic coordination. The sides of the prism are near perfect squares with an average edge of 3.043 A. No significant differences appear between the intra- and closest interligand sulfur-sulfur distances. Hence, the ReS₆ trigonal prism is essentially perfect. The phenyl rings are twisted out of the planes of the five-membered chelate rings and appear not to be conjugated with them. While no crystallographic symmetry conditions are imposed on the molecule, the coordination geometry is clearly Dsh and the over-all molecular symmetry belongs nearly to the point group C₃.