SYNTHESIS, CHARACTERIZATION AND CRYSTAL-STRUCTURE OF HEXAKIS-(THIOUREA-S) RHENIUM(III) TRICHLORIDE TETRAHYDRATE - A POTENTIAL PRECURSOR TO LOW-VALENT RHENIUM COMPLEXES

A new rhenium(III) complex, [Re(SC(NH2)(2))(6)](3+), has been prepared by reduction of perrhenate with tin chloride in strongly acidic solut ion in the presence of thiourea. The complex has been characterized in solution and the solid state by elemental and thermal analyses, elect ronic and IR spectroscopy, conductimetric measurements, EPR spectra an d cyclic voltammetry. Stability in aqueous:solution was tested spectro photometrically. The molecular structure of the complex in the [Re(tu- S)(6)]Cl-3 . 4H(2)O salt was determined by X-ray diffraction. The comp ound is isomorphous to [Tc(tu-S)(6)]Cl-3 . 4H(2)O. The rhenium ion, si ted at an inversion center, is quasi-octahedrally coordinated by six t hiourea sulfur atoms [d(Re-S) vary from 2.412(2) to 2.429(2) Angstrom] . Average thiourea bond distances are similar to those observed for th ere analog[d(S-C) = 1.746(8) and d(C-N) = 1.32(1) Angstrom]. (C) 1997 Published by Elsevier Science Ltd.