THE USE OF BIS(DIPHENYLPHOSPHINOACETYLENE) AND ITS DIGOLD DERIVATIVE AS LINKING GROUPS IN OSMIUM CLUSTER CHEMISTRY - CRYSTAL-STRUCTURES OF [(OS3(CO)11)2(DPPA)], [OS3(CO)10(DPPA)]2 AND [OS4H(CO)12AU(DPPA)]2 (DPPA = PH2PCCPPH2)

The reaction of the activated triosmium cluster, [Os3(CO)11(NCMe)] with bis(diphenylphosphinoacetylene) (dppa) at room temperature affords the linked cluster [{Os3(CO)11}2(dppa)] (1), while the reaction Of [Os3(CO)10(NCMe)2] with an excess of dppa affords the di-, tri- and tetrameric clusters [{Os3(CO)10(dppa)}2] (2), [{Os3(CO)10(dppa)}3] (3) and [{Os3(CO)10(dppa)}4] (4) in moderate yields. Similarly, the reaction of the anion [Os4H3(CO)12]- with Au2(dppa)Cl2, in the presence of excess Et3N and TlPF6, under reflux, in chloroform affords [{Os4H(CO)12Audppa}2] (5) as the only extractable product. Single crystal X-ray structural analyses of 1 and 2 show that the two triosmium cluster units are linked via coordination of one Os centre to each of the two phosphorus centres of the intact dppa ligand, while the structure of 5 shows the two tetraosmium units are linked via two mu2-bridging Au centres and terminal phosphorus centres of the two Au(dppa) ligands.