Products of the pyrolysis of [Os3(CO)11{P(OMe)3}]; the molecular and crystal structure of [Os5C(CO)13H{OP(OMe)2}{P(OMe)3}

Abstract

The pyrolysis of [Os3(CO)11{P(OMe)3}] leads to the formation of four cluster carbonyl complexes containing five Os atoms which have been characterised as [Os5C(CO)14H{OP(OMe)2}](3), [Os5C(CO)13H{OP(OMe)2}{P(OMe)3}](7a), [Os5C(CO)13H{OP(OMe)OP(OMe)2}](5), and [Os5(CO)15{P(OMe)}](2) by spectroscopic and X-ray single-crystal analyses. The full crystal structure of (7a) is reported; the complex crystallises in the triclinic space group P, with a= 11.623(2), b= 15.937(2), c= 18.515(4)A, α= 104.01(2), β= 98.85(2), γ= 91.65(1)°, and Z= 4. The structure has been solved by a combination of multisolution Σ2 sign expansion and Fourier-difference techniques, and refined by blocked full-matrix least squares to R= 0.054 for 8 446 unique observed diffractometer data. The nature and mode of co-ordination of the ligands derived from the phosphite group varies from complex to complex, and there is a stepwise progression for the first three compounds in which replacement of a carbonyl group is followed by an eventual linking of two phosphite ligands on the cluster surface. The structures of the four complexes are discussed briefly in terms of the number of electrons present.