Ligand degradation and phosphorus scavenging in the reaction between 1,2-bis(diphenylphosphino)benzene (dppbz) and Ru6(μ6-C)(CO)17: Synthesis and X-ray structure of the edge-bridged square-pyramidal cluster HRu6(μ5-C)(μ3-P)(CO)14(dppbz)

Thermolysis or Me₃NO activation of the hexaruthenium cluster Ru₆(μ₆-C)(CO)₁₇ in the presence of the diphosphine ligand 1,2-bis(diphenylphosphino)benzene (dppbz) does not furnish the expected dppbz-substituted cluster Ru₆(μ₆-C)(CO)₁₅(dppbz) but rather HRu₆(μ₅-C)(μ₃-P)(CO)₁₄(dppbz), whose edge-bridged square-pyramidal structure has been established by X-ray crystallography. Accompanying the opening of the original closo Ru₆ polyhedron is the dephosphination of a second dppbz ligand through three rapid P-C bond cleavages, leading to the capture of the phosphorus atom as a face-capping phosphido ligand. This unprecedented reactivity between Ru₆(μ₆-C)(CO)₁₇ and the dppbz ligand is discussed relative to other diphosphine ligands.