Joint X-ray and neutron diffraction refinement of the crystal and molecular structure of tri-µ-hydrido-µ-iodo-cyclo-tetrakis(tricarbonylosmium)(4 Os–Os)

Abstract

The title compound [Os₄l(CO)₁₂H₃] crystallises in the monoclinic space group C2/c with a= 17.307(8), b= 8.040(3), c= 17.760(9)Å, β= 119.80(2)°, and Z= 4. Simultaneous refinement of a single parameter set to 1 925 X-ray [(sin θ)/λ > 0.45] and 607 neutron data has led to R 0.034 (X-ray) and 0.035 (neutron). The Os atoms adopt a ‘butterfly’ configuration, with the iodine sitting on the crystallographic two-fold axis and bridging the two ‘wing-tip’ metal atoms. One hydride also lies on the two-fold axis and bridges the Os–Os ‘hinge’ bond [Os–H 1.788 (4)Å]. The other two hydrides bridge the longer Os(hinge)–Os(wing-tip) bonds and lie closer to the ‘wing-tip’ metals [Os–H 1.754(4)(two) and 1.823(5)Å(two)]. Each Os atom is also bonded to three terminal carbonyl groups.