Reaction of [Os4(CO)1 2H3]– with [NO][PF6] in the presence of trace amounts of water; X-ray determination of the molecular structures of [Os4(CO)1 2H3(µ-OPO3H2)] and [Os4(CO)1 2H3(µ-OH)](2 : 1 ratio) in the one crystal

Abstract

The cluster anion [Os₄(CO)_{1 2}H₃]^– reacts with commercial [NO][PF₆] in acetonitrile via the in situ formation of orthophosphoric acid to give the neutral cluster species, [Os₄(CO)_{1 2}H₄], [Os₄(CO)_{1 2}H₃(µ-OPO₃H₂)], and [Os₄(CO)_{1 2}H₃(µ-OH)]. The latter two products crystallise together in a 2 : 1 ratio in the monoclinic space group P2₁/c with unit-cell dimensions a= 14.315(3), b= 30.732(4), c= 15.314(3)Å, β= 101.48(2)°, and Z= 4. The structure was solved by a combination of direct methods and Fourier-difference techniques and refined by blocked full-matrix least squares to R= 0.051 for 5 091 observed reflections. In each of the µ-OPO₃H₂ and µ-OH compounds the four osmium atoms define a ‘butterfly’ configuration with two triangles sharing a common edge but which are not coplanar, supported by the bridging oxygen linkage. The three hydrido-ligands were not located but the Os–Os bond lengths suggest that they bridge in the same arrangement as that found previously in [Os₄(CO)_{1 2}H₃I] by neutron diffraction.