Synthesis of 1,3-diaryltriazenido triruthenium and triosmium clusters: crystal structures of [Ru 3 (µ-H)(CO) 10 (µ-C 6 F 5 NNNC 6 F 5 )] and [Os 3 (CO) 11 Cl(η 2 -C 6 F 5 NNNC 6 F 5 )]

New clusters [Ru3(µ-H)(CO)10(µ-RNNNR)](R =p-C6F4X; X = F 1, Br 2, I 3 or H 4) were obtained from reactions of RNNNHR with [Ru3(CO)12] in toluene at 80 °C under vacuum, while the linear triosmium clusters [Os3(CO)11Cl(η2-RNNNR)](R =p-C6F4X; X = F 5, Br 6, I 7 or H 8) were obtained from RNNNHR with [Os3(CO)11(NCMe)] in CH2Cl2 at 60 °C under vacuum. The crystal structures of [Ru3(µ-H)(CO)10(µ-C6F5NNNC6F5)]1 and [Os3(CO)11Cl(η2-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 π 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 π delocalization over the whole system. The linear cluster [Os3H(CO)11(η2-C6F5NNNC6F5)], precursor of 5, was also obtained. Carbon-13 NMR studies of this cluster and the mechanism of its formation are reported.