Synthesis and X-ray analysis of [PMePh3][Os8H(CO)22] and [Os8H(CO)22I]

Abstract

The cluster anion [Os₈H(CO)₂₂]^–(1) has been obtained from the reaction of [Os₃(CO)₁₂] in BuⁱOH and X-ray analysis of its [PMePh₃]⁺ salt shows that the anion has an unusual fused tetrahedral metal-core geometry related to that of [Os₆(CO)₁₈]. Reaction of (1) with iodine gives [Os₈H(CO)₂₂I](2) in which an overall change in cluster geometry has occurred; the reaction is reversible and heating (2) with iodide regenerates (1). Reaction of (1) with concentrated H₂SO₄ gives [Os₈H₂(CO)₂₂] which reacts with P(OMe)₃ to give [Os₈H₂(CO)₂₂{P(OMe)₃}] and with halide ions to give eventually [Os₈(CO)₂₂]^2–. Crystals of [PMePh₃][Os₈H(CO)₂₂] are triclinic, space group P, with a= 16.775(3), b= 1 3.509(2), c= 11.267(2)Å, α= 89.88(1), β= 103.97(1), γ= 96.99(1)°, and Z= 2. Refinement of atomic parameters using 5 615 absorption-corrected data converged at R= 0.0359. Crystals of [Os₈H(CO)₂₂I]·H₂O are monoclinic, space group P2₁/c, with a= 14.386(2), b= 11.037(1), c= 24.629(3)Å, β= 94.30(2)°, and Z= 4. Refinement of atomic parameters using 4 644 absorption-corrected reflections converged at R= 0.0569.