Synthesis, Characterization, and Crystal Structures of a Series of Osmium−Rhodium Mixed-Metal Carbonyl Clusters: [N(PPh3)2][Os6Rh(μ-H)2(CO)20], [Os6Rh(μ-H)7(μ-CO)(CO)18], [Os6Rh(μ-H)9(CO)18], and [Os3Rh(μ-CO)(CO)9(μ4-η2-PhC2Ph)(μ2-η1:η2-PhC2PhH)]

The reaction between [N(PPh 3 ) 2 ][Os 3 (μ-H)(CO) 11 ] and [Rh(COD) 2 ][SbF 6 ] (COD = cycloocta-1,5-diene) yields the known cluster [Os 3 Rh(μ-H) 3 (CO) 10 (COD)] ( 1 ) and the new complex [N(PPh 3 ) 2 ][Os 6 Rh(μ-H) 2 (CO) 20 ] ( 2 ). Subsequent reaction of 1 with CO gas in CH 2 Cl 2 produces [Os 3 Rh(μ-H) 3 (CO) 12 ] ( 4 ). Compound 1 also reacts with 1 equiv of [N(PPh 3 ) 2 ][Os 3 (μ-H)(CO) 11 ] to give 2 . Hydrogenation of 1 results in the hydrogen-rich cluster [Os 6 Rh(μ-H) 9 (CO) 18 ] ( 5 ) in moderate yield. Reaction of 1 with diphenylacetylene affords [Os 3 Rh(μ-CO)(CO) 9 (μ 4 -η 2 -PhC 2 Ph)(μ 2 -η 1:η 2 -PhC 2 PhH)] ( 6 ). On the other hand, the unsaturated cluster [Os 3 (μ-H) 2 (CO) 10 ] reacts with [Rh(dppm) 2 ][BF 4 ] (dppm = bis(diphenylphosphino)methane) to give [Os 6 Rh(μ-H) 7 (μ-CO)(CO) 18 ] ( 3 ) in good yield. The crystal structures of 2, 3, 5, and 6 were determined. Clusters, 2, 3, and 5 consist of a central rhodium atom linking two triosmium units; however, the rhodium atom of 2 bridges two triosmium units, while 3 and 5 possess a sandwich-type structure. Complex 6 has a butterfly arrangement of three osmium atoms and one rhodium atom which contains a diphenylacetylene fragment in a μ 4 -η 2 arrangement and an alkenyl group in a μ 2 -η 1:η 2 configuration.