THE X-RAY STRUCTURE OF OS(CS) (PHC=CPH) (PPH3)2, A COMPLEX CONTAINING A 4-ELECTRON DONOR ACETYLENE LIGAND

Os(CS)(PhCCPh)(PPh3)2 is formed by the treatment of Os(CS)(CO)(PPh3)3 with diphenylacetylene and is an example of a complex containing a four‐electron donor acetylene ligand. Os(CS)(PhCCPh)(PPh3)2 crystallizes in the monoclinic space group P21/n with the cell dimensions a = 9.028(5), b = 25.256(2) and c = 19.22(2) Å with β = 103.8(7)°, V = 4260 Å3, Z = 4 and d(calcd) = 1.461 g cm−3 for mol.wt 937.09 g mol−1. Diffraction data were collected with a Nonius CAD‐4 diffractometer and refined to R = 4.05% and Rw = 4.19% for 1172 independent reflections. The structure can be described as a distorted trigonal bipyramid with the CS ligand occupying an axial position. The two cis‐PPh3 ligands are in equatorial sites with the acetylene occupying a position between the remaining axial and equatorial sites. The diphenylacetylene is symmetrically bound to the metal with an average OsC distance of 2.04(3) Å. The OsCS distance is unusually short at 1.79(2) Å. Copyright © 1990 John Wiley & Sons Ltd.