High nuclearity bimetallic rhodium-palladium carbonyl cluster complexes.: Synthesis and characterization of Rh6(CO)16[Pd(PBut3)]3 and Rh6(CO)16[Pd(PBut3)]4

The reaction of Rh-4(CO)(12) with Pd(PBu3t)(2) yielded the high nuclearity bimetallic hexarhodium-tripalladium cluster complex Rh-6(CO)(16)[Pd(PBu3t)](3), 10, in 11% yield. Compound 10 was converted to the hexarhodium-tetrapalladium cluster Rh-6(CO)(16)[Pd(PBu3t)](4), 11, in 62% yield by reaction with an additional quantity of Pd(PBu3t)(2). Both compounds were characterized crystallographically. Structurally, both compounds consist of an octahedral cluster of six rhodium atoms with sixteen carbonyl ligands analogous to that of the known compound Rh-6(CO)(16). Compound 10 also contains three Pd(PBu3t) groups that bridge three Rh - Rh bonds along edges of the Rh-6 octahedron to give an overall D-3 symmetry to the Rh6Pd3 cluster. Compound 11 contains four edge bridging Pd(PBu3t) groups distributed across the Rh-6 octahedron to give an overall D-2d symmetry to the Rh6Pd4 cluster. Each Rh - Pd connection in both compounds contains a bridging carbonyl ligand that helps to stabilize the bond between the Pd(PBu3t) groups and the Rh atoms. Both compounds can be regarded as Pd(PBu3t) adducts of Rh-6(CO)(16).