Synthesis of the cluster dianion [Os11C(CO)27]2- by pyrolysis and its reactions with electrophiles; X-ray structure analysis of the mixed-metal derivative [PMePh3][Os11C(CO)27Cu(NCMe)]·CH 2Cl2 and the hydrido derivative [PMePh3][Os11C(CO)27H]

The new cluster species [Os11C(CO)27]2- (2) has been identified as one of the products resulting from the pyrolysis of [Os3(CO)12]. It reacts with [Cu(NCMe)4] BF4 to yield the monoanion [Os11C(CO)27Cu(NCMe)]- (4) and [Os11C(CO)27Cu(NCMe)2] (5). The reaction of (2) with iodine-iodide produces a series of iodo-clusters [Os11C(CO)27I]- (8) and [Os11C(CO)27I2] (9) which are converted back into (2) by addition of halide ions. The unstable monoanionic species [Os11C(CO)27M(PMe2Ph)]- [M = Au (3) or Cu (7)] are obtained on reaction of (2) with [M(PMe2Ph)]+, and further reaction of (3) yields [Os11C(CO)27Au(PMe2Ph)2] (6). The dianionic cluster (2) reacts with acid to give the monoanion [Os11C(CO)27H]- (10) and [Os11C(CO)27H2] (11). The reaction with Hg(C6Cl5) (O2CCF3) yields initially the unstable monoanion [Os11C(CO)27Hg(C6Cl5)]- (12) which is rapidly converted into the known cluster dianion [Os20Hg(C)2(CO)48]2-. X-Ray analysis of the [PMePh3]+ salts of (4) and (10) reveal identical Os11 core geometries, but in (4) the copper ligand occupies a μ3-bridging position, while the hydride in (10) appears to be located in an interstitial site.