The cluster cation [Os4(CO)12H4(OH)]+: preparation and crystal structure

Abstract

The cluster cation [Os₄(CO)₁₂H₄(OH)]⁺ has been prepared in high yields by the reaction of [Os₄(CO)₁₂H₄] with NOX (X = NO₃, PF₆, BF₄, or Cl) in MeCN or CH₂Cl₂. The cation is also isolated as the [Os(CO)₃(NO₃)₃]^– salt from the reaction with N₂O₄ in toluene. The salt [Os₄(CO)₁₂H₄(OH)][Os(CO)₃(NO₃)₃] crystallises in the triclinic space group P₁, with cell dimensions a= 9.701 (5), b= 11.504(6), c= 14.352(6)Å, α= 83.03(2), β= 84.79(2), γ= 85.38(2)°, and Z= 2. The structure has been solved by a combination of direct methods and Fourier-difference techniques and refined by blocked-cascade least squares to R= 0.037 for 5 538 observed reflections. The four osmium atoms in the cation define a ‘butterfly’ configuration with two triangles sharing a common edge but which are not coplanar. The space above the butterfly is occupied by the OH group. The hydrido-ligands are not located directly but the carbonyl arrangement suggests that they bridge each of the four wing-tip–hinge Os–Os ‘bonds.’