Heating the mixed-metal cluster PhCCo2Ni(CO)6Cp with the diphosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) in 1,2-dichloroethane proceeds by CO loss and formation of the cobalt-bridged cluster PhCCo2Ni(CO)4(η2-bma)Cp (2). The bma ligand is fluxional in solution and is in equilibrium with the cobalt-chelated isomer, as demonstrated by VT IR and 31P NMR measurements. The van’t Hoff parameters (ΔH = 1.49 ± 0.02 kcal/mol; ΔS = 12.0 ± 0.1 eu) for the chelate-to-bridge equilibrium have been evaluated from IR band-shape analyses of the in-phase anhydride carbonyl stretching band over the temperature range 173–116 K. Cluster 2 readily loses CO to furnish the cluster PhCCo2Ni(CO)3(μ,η2-bma)Cp (3), where the 6e− donor bma ligand chelates one of the cobalt centers via the phosphine groups and is tethered to the second cobalt center by the maleic anhydride π bond. Continued heating of cluster 3 is followed by the formation of 50e− cluster Co2Ni(CO)4Cp[μ2,η2,η1-C(Ph)CC(PPh2)C(O)OC(O)](μ2-PPh2) (4), which in turn gives the mononuclear complex CpNi[PPh2CPhCC(PPh2)C(O)OC(O)] (5) as the end-product of the thermolysis reaction. Each of these new compounds has been isolated and their thermolysis reactivity independently examined, allowing for the unequivocal sequence associated with the decomposition of PhCCo2Ni(CO)4(η2-bma)Cp to be established. Compounds 2–5 have been fully characterized in solution by IR and NMR(1H, 13C, 31P) spectroscopies, and the solid-state structures of all four products have been determined by X-ray crystallography. The solution spectroscopic data of the new products are compared with the X-ray diffraction structures and the structural highlights of each compound are discussed. The coordination of the maleic anhydride π bond in PhCCo2Ni(CO)3(μ,η2-bma)Cp (3) provides crucial insight into one of the necessary requirements for P–C bond cleavage of the bma ligand at a tetrahedral cluster. The reactivity of the heterometallic cluster PhCCo2Ni(CO)4(η2-bma)Cp is contrasted with its homometallic analogue PhCCo3(CO)7(η2-bma).Thermolysis of the tetrahedral cluster PhCCo2Ni(CO)6Cp (1) with the diphosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) furnishes the cobalt-bridged cluster PhCCo2Ni(CO)4(η2-bma)Cp (2). Thermolysis of 2 proceeds in a stepwise fashion to give the clusters PhCCo2Ni(CO)3(μ,η2-bma)Cp (3), and Co2Ni(CO)4Cp[μ2,η2,η1-C(Ph)CC(PPh2)C(O)OC(O)](μ2-PPh2) (4), and the mononuclear nickel complex CpNi[PPh2CPhCC(PPh2)C(O)OC(O)] (5). These compounds have been fully characterized in solution by IR and NMR spectroscopies, and the molecular structures of clusters 2–5 have been crystallographically determined.

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-PPhCC(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-PPhCC(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-PPhCC(PPh2)C(O)CH2C(O).The triruthenium cluster HRu3(CO)10(μ-PPh2) (1) reacts with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) under thermal and Me3NO activation to give H2Ru3(CO)7(bpcd)[μ,σ-PPh(C6H4)] (3) as the major isolable product. The same product is obtained from the reaction between HRu3(CO)9(μ-PPh2) (2) and bpcd at room temperature. Thermolysis of H2Ru3(CO)7(bpcd)[μ,σ-PPh(C6H4)] regenerates the μ-PPh2 moiety and leads to P–Ph bond cleavage in the bpcd ligand to furnish Ru3(CO)6(μ-CO)(μ-PPh2)[μ,η2,η1-PPhCC(PPh2)C(O)CH2C(O)] (4) as the major isolable product. Clusters 3 and 4 have been fully characterized in solution and their molecular structures have been established by X-ray crystallography.

The imido-capped cluster Ru3(CO)9(μ3-CO)(μ3-NPh) (1) reacts with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) to furnish both Ru3(CO)7(μ3-CO)(μ3-NPh)(bpcd) (2) and Ru3(CO)5(μ3-CO)(μ3-NPh)(bpcd)2 (3) as the major and minor products, respectively, under thermal and Me3NO activation. The thermolysis of cluster 2 affords the new triruthenium compounds Ru3(CO)5(μ2-CO)2(μ3-NPh)(μ2-PPh2)[μ,η1,η1-CC(PPh2)C(O)CH2C(O)] (4), Ru3(CO)6(μ2-CO)(μ3-NPh)(μ-PhCO)[μ2,η2,η1-PPhCC(PPh2)C(O)CH2C(O)] (5), and Ru3(CO)9(μ3-NPh)(μ3-PPh) (6). Compounds 2–6 have been fully characterized in solution, and the molecular structures of 2, and 4–6 have been determined. Cluster 2 exhibits a nido-NRu3 core with a face-capping μ3-CO and a chelating bpcd ligand that occupies an equatorial and axial site. VT 31P NMR data indicate that the bpcd ligand in 2 undergoes a rocking motion between the equatorial and axial sites at the attached ruthenium center at elevated temperatures. Cluster 4 possesses a similar nido polyhedral core that is tethered by a bridging phosphido group and the 3e-donor moiety μ2,η2,η1-CC(PPh2)C(O)CH2C(O). The structure of 5 reveals a hypho architecture containing a single Ru–Ru bond and where the three ruthenium centers are bridged by imido and benzoyl moieties and the seven-electron donor ligand μ2,η2,η1-PPhCC(PPh2)C(O)CH2C(O), which results from the cleavage of one the P–Ph bonds of the original bpcd ligand. The 50e cluster 6 exhibits a nido polyhedral core consisting of three Ru(CO)3 groups that are capped by a μ3-imido and μ3-phosphinidine unit. Cluster 6 represents the first structurally characterized example of a mixed PhN/PhP capped cluster belonging to the family of nido-Ru3(CO)9(μ3-EPh)2 clusters. The pertinent structural highlights associated with these clusters are discussed, and the lack of reactivity of the capping imido group with the bpcd ligand in Ru3(CO)7(μ3-CO)(μ3-NPh)(bpcd) during thermolysis is contrasted with the related benzylidyne-capped cluster PhCCo3(CO)7(bpcd).The imido-capped clusters Ru3(CO)7(μ3-CO)(μ3-NPh)(bpcd) (2) and Ru3(CO)5(μ3-CO)(μ3-NPh)(bpcd)2 (3) have been isolated from the reaction of Ru3(CO)9(μ3-CO)(μ3-NPh) (1) with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) under thermal and Me3NO activation. Thermolysis of the former product furnishes the new clusters Ru3(CO)5(μ2-CO)2(μ3-NPh)(μ2-PPh2)[μ,η1,η1-CC(PPh2)C(O)CH2C(O)] (4), Ru3(CO)6(μ2-CO)(μ3-NPh)(μ-PhCO)[μ2,η2,η1-PPhCC(PPh2)C(O)CH2C(O)] (5), and Ru3(CO)9(μ3-NPh)(μ3-PPh) (6).