The X-ray structure of Os(CS)(PhCCPh)(PPh3)2, a complex containing a four-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 ų, 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 R_w = 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.