Structural studies of technetium complexes. III. The crystal structure of Tris[2-aminobenzenethiolato(2–)-S, N]technetium(VI) : a trigonal-prismatictechnetium geometry

Abstract

Tris[2-aminobenzenethiolato(2–)-S,N]technetium(VI), Tc(NHC₆H₄S)₃, has been prepared by the reaction of ammonium pertechnetate with 2-aminobenzenethiol in 0.1 M hydrochloric acid solution at room temperature. The crystal structure of Tc(NHC₆H₄S)₃ has been determined by single-crystal X-ray diffraction methods at 17ºC. Crystals are orthorhombic, space group P2₁2₁2₁, with a 10.696(2), b 11.363(1), c l5.220(2) Å, and Z 4. Automatic diffractometry has provided significant Bragg intensities for 1413 independent reflections, and the structure of the correct enantiomorph has been refined by full-matrix least-squares methods to R 0.044. The compound, which is isostructural with the molybdenum analogue, consists of discrete molecules of Tc(NHC₆H₄S)₃. The environment about the technetium atom closely approximates a trigonal-prismatic geometry. This is the first example where this geometry has been established with technetium. Differences in detail between the structures of TC(NHC₆H₄S)₃ and its molybdenum analogue are discussed. In particular the S₃N₃ coordination polyhedron in TC(NHC₆H₄S)₃is contracted and the distortions from ideal trigonal-prismatic geometry are less than in the molybdenum analogue.