Reversible aryl C–H bond activation in the reaction between HRu3(CO)9,10(μ-PPh2) and the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd): X-ray diffraction structures of H2Ru3(CO)7(bpcd)[μ,σ-PPh(C6H4)] and Ru3(CO)6(μ-CO)(μ-PPh

The reaction between HRu3(CO)10(μ-PPh2) (1) and the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) proceeds rapidly in the presence of Me3NO to furnish H2Ru3(CO)7(bpcd)[μ,σ-PPh(C6H4)] (3). Treatment of the nonacarbonyl cluster HRu3(CO)9(μ-PPh2) (2) with bpcd at room temperature affords cluster 3 as the major product in addition to cluster 1. Thermolysis of cluster 3 in 1,2-dichloroethane yields Ru3(CO)6(μ-CO)(μ-PPh2)[μ,η2,η1-PPhCdouble bond; length as m-dashC(PPh2)C(O)CH2C(O)] (4) as the major isolable product. The highlights associated with the production of cluster 4 involve the reductive elimination of the orthometalated aryl group with one of the two bridging hydrides in 3 and cleavage of one of the P–Ph bonds of the bpcd ligand, followed by the release of benzene from the transient sigma-bound Ru–Ph group. Both H2Ru3(CO)7(bpcd)[μ,σ-PPh(C6H4)] and Ru3(CO)6(μ-CO)(μ-PPh2)[μ,η2,η1-PPhCdouble bond; length as m-dashC(PPh2)C(O)CH2C(O)] have been isolated and characterized in solution by IR and NMR (31P and 1H) spectroscopies, in addition to X-ray crystallography. The solid-state structure of H2Ru3(CO)7(bpcd)[μ,σ-PPh(C6H4)] confirms the presence of an orthometalated μ2-phosphido moiety and a chelating bpcd ligand. The crystal structure of cluster 4 consists of a triangular Ru3 core where one face is capped by the 6e-donor ligand μ,η2,η1-PPhCdouble bond; length as m-dashC(PPh2)C(O)CH2C(O).