Novel compounds with gold–transition–metal bonds; crystal and molecular structure of bis(triphenylphosphine)iminium bis(tetracarbonylcobaltio)aurate(I)

Abstract

The tetrahydrothiophen group (tht) in [Au(C₆F₅)₃(tht)] can readily be replaced by carbonylmetallate anions [M(Co)_n]^–(M = Co, n= 4; M = Mn, n= 5) or [M(cp)(CO)₃]^–(M = Mo or W; cp =η-C₅H₅) to give a novel type of anionic complex of general formula [N(PPh₃)₂][(C₆F₅)₃Au–M(CO)_n] or [NBuⁿ₄][(C₆F₅)₃Au–M(cp)-(CO)₃] whose reactivity with PPh₃ depends upon M. Thus, for M = Mo or W the reaction leads to the cleavage of the metal–metal bond, for M = Mn no reaction is observed at room temperature, whilst substitution of one CO group takes place for M = Co. Reaction of the carbonylmetallates with [Au(C₆F₅)(tht)] gives rise to disproportionations affording Q[Au(C₆F₅)₂][Q = N(PPh₃)₂⁺ or NBuⁿ₄⁺] and [N(PPh₃)₂][Au{M(CO)_n}₂] or [NBuⁿ₄]-[Au{M(cp)(CO)₃}₂] which are stable at room temperature. The presence of the linear unit CO–Au–Co in [N-(PPh₃)₂][Au{Co(CO)₄}₂] has been established by a single-crystal structure determination; space group P, a= 9.610(4), b= 9.978(4), c= 11.506(5)Å, α= 97.70(2), β= 97.84(2), γ= 90.97(2)°, and Z= 1. The structure has been refined to R= 0.032 for 2 475 unique observed reflections. Both the anion and cation lie on crystallographic centres of symmetry, hence the Co–Au–Co and P–N–P moieties are linear. The Au–Co bond length is 2.509(2)Å.