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 15�C. Crystals are
orthorhombic, space group Pcmn, with a 8.936(1), b 15.681(1), c 28.445(7) �, 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 �, 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.