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

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.