Structural studies of technetium complexes. V. The preparation and crystal structure of Dichlorobis(diethyldithiocarbamato)thionitrosyltechnetium(III)

Abstract

Dichlorobis(diethyldithiocarbamato)thionitrosyltechnetium(III), [Tc(S₂CNEt₂)₂Cl₂(NS)], has been prepared by the reaction of [Tc(S₂CNEt₂)₂N] with either disulfur dichloride or thionyl chloride. The crystal structure of [TC(S₂CNEt₂)₂Cl₂(NS)] has been determined by single-crystal X-ray diffraction methods at 15ºC. Crystals are orthorhombic, space group P_cmn, with a 8.936(1), b 15.681(1), c 28.445(7) Å, and Z 8. Automatic diffractometry has provided significant Bragg intensities for 2078 independent reflections, and the structure has been refined by full-matrix least-squares methods to R 0.078. The crystal lattice is disordered across a non-crystallographic mirror plane, the degree of disorder being 4.0(2)% for the crystal described above, and 21.9(7)% for another crystal initially used to obtain an intensity data set. There are two independent molecules of [Tc(S₂CNEt₂)₂Cl₂(NS)] in the asymmetric unit, and in each the technetium atom is seven-coordinate with a pentagonal-bipyramidal coordination environment. The Tc=N=S bonding is linear with Tc=N c. 1.75 and N=S c. 1.52 Å, which indicates that the thionitrosyl group is a three-electron donor with a formal positive charge. This is only the third crystal structure of a complex containing the thionitrosyl group to be determined, and the first for technetium.