Diphosphine Substitution and Carbyne Ligand Transfer in the Reaction of 2,3-Bis(diphenylphosphino)maleic Anhydride (bma) with the Methylidyne-capped Clusters HCCo2MCp(CO)8 (where M=Mo, W): Synthesis and X-ray Diffraction Structures of the Vinylidene-bridged Clusters Co2MCp(CO)6[μ–C=C(H)CH2C(PPh2)C(PPh2)C(O)OC(O)

Abstract

Thermolysis of mixed-metal tetrahedrane cluster HCCo2MoCp(CO)8 (1) with the diphosphine ligand 2,3–bis(diphenylphosphino)maleic anhydride (bma) furnishes the cluster compounds HCCo2MoCp(CO)6[trans-2,3-bis(diphenylphosphino)succinic anhydride] (2), HCCo2MoCp(CO)6(bma) (3), and Co2MoCp(CO)6[μ–C=C(H)CH2C(PPh2)C(PPh2)C(O)OC(O)] (4) in low yields (<13%). The tungsten congener HCCo2WCp(CO)8 (5) reacts with bma to give Co2WCp(CO)6[μ–C=C(H)CH2C(PPh2)C(PPh2)C(O)OC(O)] (6) as the sole isolable product in 3% yield. The new clusters have been fully characterized in solution by IR and NMR spectroscopies, and the solid-state structures of the vinylidene-bridged clusters 4 and 6 established by X-ray crystallography. Clusters 4 and 6 each contain 48e- and exhibit triangular Co2M cores, with a vinylidene moiety that caps one of the Co2M faces. The reactivity differences exhibited by clusters 1 and 5 with bma are contrasted with similar data from the substitution reaction of bma with the related cluster compounds PhCCo2MoCp(CO)8 and PhCCo2WCp(CO)8. The mixed-metal cluster HCCo2MoCp(CO)8 (1) reacts with the diphosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) at elevated temperature to afford the new clusters HCCo2MoCp(CO)6[trans-2,3-bis(diphenylphosphino)succinic anhydride] (2), HCCo2MoCp(CO)6(bma) (3), and Co2MoCp(CO)6[μ–C=C(H)CH2C(PPh2)C(PPh2)C(O)OC(O)] (4). Thermolysis of HCCo2WCp(CO)8 (5) with bma furnishes only Co2WCp(CO)6[μ–C=C(H)CH2C(PPh2)C(PPh2)C(O)OC(O)] (6) in trace amounts. The presence of the face-capping vinylidene ligand in clusters 4 and 6 has been confirmed by spectroscopic methods and X-ray crystallography.