Reversible interconversion between mu,eta(2):eta(2)- and mu(3),eta(2):eta(2):eta(2)-C-60 on a carbido pentaosmium cluster framework

Abstract

Decarbonylation of Os-5(CO)(14)(PPh3) by 2 equiv of Me3NO/CH3CN at room temperature followed by reaction with C-60 in refluxing chlorobenzene produces Os5C(CO)(11)(PPh3)(mu (3),eta (2): eta (2):eta (2)-C-60) (1) in 44% yield. Thermal treatment of 1 at 80 degreesC under 1 atm of carbon monoxide affords Os5C(CO)(12)(PPh3)(mu,eta (2):eta (2)-C-60) (2) in good yield (72%). Upon thermolysis of 2 at 132 degreesC, 2 is cleanly reconverted to 1 (73%) by loss of a carbonyl ligand. Reaction of I with benzyl isocyanide at room temperature gives the addition product Os5C(CO)(11)(CNCH2C6H5)(PPh3)(mu (3),eta (2) :eta (2):eta (2):eta (2)-C-60) (3) in 85% yield. Thermolysis of 3 at 100 degreesC forms the isomeric Os5C(CO)(11)(CNCH2C6H5)(PPh3)(mu eta (2):eta (2)-C-60) (4) in 64% yield. Treatment of 4 with 1 equiv of Me3NO/ CH3CN at room temperature followed by heating at 132 degreesC in chlorobenzene gives Os5C(CO)(10)(CNCH2C6H5)(PPh3)(mu (3),eta (2):eta (2):eta (2)-C-60) (5) in 71% yield. Compound 5 can be alternatively prepared from the reaction of 1 with excess Ph3P=NCH2Ph at room temperature in 59% yield. Heating a chlorobenzene solution of 5 at 55 degreesC under 3 atm of carbon monoxide produces 4 as the only major product (16%). Treatment of Ru5C(CO)(11)(PPh3)(mu (3),eta (2):eta (2):eta (2)-C-60) (1') with benzyl isocyanide at room temperature forms Ru5C(CO)(11)(CNCH2C6H5)(PPh3)(mu (3),eta (2): eta (2):eta (2)-C-60) (3') in 90% yield. Reaction of 1' with benzyl isocyanide at a slightly elevated temperature of 40 degreesC affords Ru5C(CO)(10)(CNCH2C6H5)(PPh3)(mu (3),eta (2):eta (2):eta (2)-C-60) (5') in an almost quantitative yield of 96%. Compounds 1-5, 3', and 5', isolated as crystalline solids, have been characterized by microanalytical and spectroscopic methods. Molecular structures of 1-4 and 5' have been elucidated by X-ray crystallographic studies.