Synthesis of 1,3-diaryltriazenido triruthenium and triosmium clusters: Crystal structures of [Ru-3(mu-H)(CO)(10)(mu-C6F5NNNC6F5)] and [Os-3(CO)(11)Cl(eta(2)-C6F5NNNC6F5)]

New clusters [Ru-3(mu-H)(CO)(10)(mu-RNNNR)](R = p-C(6)F(4)X; X = F 1, Pr 2, I 3 or H 4) were obtained from reactions of RN=NNHR with [Ru-3(CO)(12)] in toluene at 80 degrees C under vacuum, while the linear triosmium clusters [Os-3(CO)(11)Cl(eta(2)-RNNNR)] (R = p-C(6)F(4)X; X = F 5, Br 6, I 7 or H 8) were obtained from RN=NNHR with [Os-3(CO)(11)(NCMe)] in CH2Cl2 at 60 degrees C under vacuum. The crystal structures of [Ru-3(mu-H)(CO)(10)(mu-C6F5NNNC6F5)] 1 and [Os-3(CO)(11)Cl(eta(2) -C6F5NNNC6F5)] 5 have been determined by single-crystal X-ray crystallography. The structure of 1 shows that the triazenide ligand bridges one Ru-Ru vector in the cluster at axial sites and forms a five-membered ring with pi delocalization over the whole system. A hydride ligand was located which bridges another Ru-Ru vector equatorially and displays interesting fluxionality in solution. The chloride ligand in complex 5 co-ordinates equatorially at the first Os atom, while the triazenide occupies an axial and an equatorial site on the third Os in the linear cluster and forms a four-membered ring with pi delocalization over the whole system. The linear cluster [Os3H(CO)(11)(eta(2)-C6F5NNNC6F5)], precursor of 5, was also obtained. Carbon-13 NMR studies of this cluster and the mechanism of its formation are reported.