CO substitution in HRu3(CO)10(μ-COMe) by the unsaturated diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd): Synthesis and reactivity studies of the face-capped cluster Ru3(CO)7(μ3-COMe)[μ-P(Ph)Cdouble bond; length as m-dashC(PPh

The reaction of the methylidyne-bridged cluster HRu3(CO)10(μ-COMe) (1) with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) and Me3NO furnishes HRu3(CO)8(μ-COMe)(bpcd) (2) and HRu3(CO)8(Ph2PH)[μ-PPh2Cdouble bond; length as m-dashCC(O)CH2C(O)] (3) as the major and minor products, respectively. The 1H and 31P NMR data indicate that the bpcd ligand in 2 is chelated to one of the ruthenium atoms that is bridged by the hydride and methylidyne ligands. Thermolysis of 2 is accompanied by P–Ph bond cleavage and elimination of benzene to yield Ru3(CO)7(μ3-COMe)[μ-P(Ph)Cdouble bond; length as m-dashC(PPh2)C(O)CH2C(O)] (4). Compound 4 consists of a triangular ruthenium core that is face-capped by μ3-COMe methylidyne and μ-P(Ph)Cdouble bond; length as m-dashC(PPh2)C(O)CH2C(O) phosphido ligands. The kinetics for the conversion of 2 → 4 have been measured in toluene solvent over the temperature range 320–343 K, and based on the observed activation parameters and the inhibitory effect of added CO on the reaction, a rate-limiting step involving a dissociative loss of CO is supported. Heating 4 in the presence of H2 afforded the phosphinidene-capped cluster H3Ru3(CO)7(μ3-PPh)[μ-Cdouble bond; length as m-dashC(PPh2)C(O)CH2C(O)] (5). Crystallographic analysis of 5 has confirmed the loss of the methylidyne moiety and the cleavage of the phosphido PhP–C(dione) bond, and the presence of three edge-bridging hydrides is supported by 1H NMR spectroscopy. The reaction of 4 with added PPh3 and PMe3 has been investigated; the uptake of a single phosphine ligand occurs regiospecifically at one of the phosphido-bound ruthenium centers to give Ru3(CO)6L(μ3-COMe)[μ-P(Ph)Cdouble bond; length as m-dashC(PPh2)C(O)CH2C(O)] (PPh3, 6; PMe3, 7). Compound 6 contains 48e- and exhibits a structural motif similar to that found in 4. Compound 7 readily adds a second PMe3 ligand to yield the bis-substituted cluster Ru3(CO)6(PMe3)2(μ2-COMe)[μ-P(Ph)Cdouble bond; length as m-dashC(PPh2)C(O)CH2C(O)] (8). The solid-state structure of 8 confirms the loss of two ruthenium–ruthenium bonds and the conversion of the original face-capping μ3-COMe ligand to a μ2-COMe moiety that tethers two non-bonding ruthenium centers. The two PMe3 ligands in 8 coordinate to the same ruthenium center, and the 9e- P(Ph)Cdouble bond; length as m-dashC(PPh2)C(O)CH2C(O) ligand binds all three ruthenium atoms through the phosphine, phosphido, alkene, and carbonyl moieties. Near-UV irradiation of 8 leads to loss of CO and polyhedral contraction of the triruthenium frame to yield the 48e- cluster Ru3(CO)5(PMe3)2(μ3-COMe)[μ-P(Ph)Cdouble bond; length as m-dashC(PPh2)C(O)CH2C(O)] (9).