Abstract
The crystal and molecular structure of hexachlorobis(triethylphosphine)dirhenium(III), Re2Cle[P(C2H6)3]2, has been deter- mined by single-crystal X-ray diffraction methods. The green crystals belong to the monoclinic system, space group P2i/n, with a = 7.644 ± 0.003 A, * = 10.985 ± 0.005 Á, c = 14.206 ± 0.006 Á, ß = 96.5 ± 0.1°, density by flotation 2.29 ± 0.02 g cm-3; calculated density (for Z = 2) 2.30 g cm-1. Using 911 reflections above background collected on a manually operated counter diffractometer, the structure was solved by conventional Patterson and Fourier methods and refined by full-matrix least squares to final unweighted and weighted residuals of 0.052 and 0.063, respectively. The molecular structure is similar to that of the Re2Cls2- anion, with one of the chlorine atoms in each half of the centrosymmetric anion replaced by a triethyl- phosphine group. The Re-Re distance is 2.222 ± 0.003 A, and the molecule possesses the eclipsed configuration, indicative of the fact that the component of the quadruple bond is preserved for nonredox substitution reactions of Re2CIs2-. A struc- tural trans effect is observed, the Re-Cl bonds opposite the Re-P bonds being 2.352 (7) A long while the cis Re-Cl bonds are
2.296 (5) Along.