Addition of Pt(PBut3) Groups to Ru5(CO)126-C6H6)(μ5-C). Synthesis, Structures, and Dynamical Activity

The reaction of Ru5(CO)126-C6H6)(μ5-C), 7, with Pt(PBut3)2 yielded two products Ru5(CO)126-C6H6)(μ6-C)[Pt(PBut3)], 8, and Ru5(CO)126-C6H6)(μ6-C)[Pt(PBut3)]2, 9. Compound 8 contains a Ru5Pt metal core in an open octahedral structure. In solution, 8 exists as a mixture of two isomers that interconvert rapidly on the NMR time scale at 20 °C, ΔH = 7.1(1) kcal mol-1, ΔS = −5.1(6) cal mol-1 K-1, and ΔG298 = 8.6(3) kcal mol-1. Compound 9 is structurally similar to 8, but has an additional Pt(PBut3) group bridging an Ru−Ru edge of the cluster. The two Pt(PBut3) groups in 9 rapidly exchange on the NMR time scale at 70 °C, ΔH = 9.2(3) kcal mol-1, ΔS = −5(1) cal mol-1 K-1, and ΔG298 = 10.7(7) kcal mol-1. Compound 8 reacts with hydrogen to give the dihydrido complex Ru5(CO)116-C6H6)(μ6-C)[Pt(PBut3)](μ-H)2, 10, in 59% yield. This compound consists of a closed Ru5Pt octahedron with two hydride ligands bridging two of the four Pt−Ru bonds.