ETC and Thermal Ligand Substitution in PhCCo 3 (CO) 9 with 2,3-Bis(diphenylphosphino)- N -phenylmaleimide(bppm). X-Ray Diffraction Structure of Co 3 (CO) 6 [μ 2 ,η 2 , η 1 -C(Ph) $$$$ (O)](μ 2 -PPh 2 )

Abstract

The reactivity of the bidentate ligand 2,3-bis(diphenylphosphino)-N-phenylmaleimide (bppm) with the tetrahedrane cluster PhCCo3(CO)9 under thermolysis and ETC conditions has been studied and found to ultimately give Co3(CO)6[μ2,η2,η1-C(Ph) $${\text{C}}{\text{ = }}{\text{ = }}{\text{C(PPh}}_{\text{2}} {\text{)C(O)NPhC}}$$ (O)](μ2-PPh2) as the final product. The intermediate cluster compound PhCCo3(CO)7(bppm), which was observed by IR and 31P NMR spectroscopies, readily and rapidly transforms into the product cluster under the reactions conditions. The solid-state structure of Co3(CO)6[μ2,η2,η1-C(Ph)fptt(O)](μ2-PPh$_{2})$ was unequivocally determined by X-ray crystallography. Co3(CO)6[μ2, η2, η1-C(Ph)O(O)](μ2-PPh2) crystallizes in the monoclinic space group P2(1)/n, a = 11.825(5) A, b = 31.20(1) A, c = 11.831(5) A, β = 108.720(7)°, V = 4134(7) A3, Z = 4, d calc = 1.567 Mg/m3; R = 0.0350, R w = 0.0817 for 4747 observed reflections with I > 2σ(I). The X-ray structure confirms the coupling of the benzylidyne ligand with the bppm ligand in Co3(CO)6[μ2,η2,η1-C(Ph)O(O)](μ2-PPh2). The course of the thermolysis reaction is identical to those reactions carried out with the related diphosphine ligands bma and bpcd. The utility of electron-transfer catalysis (ETC) in the preparation of PhCCo3(CO)7(bppm) is discussed relative to the reduction potential of the bppm ligand and the tricobalt cluster PhCCo3(CO)9.