Synthesis of Optically Active Tetrahedral Clusters through Ester Exchange Catalyzed by Lipase

Reactions of the monoanions [(η5-C5H4R)M2(CO)3]- with ArCH(Me)COOCH2C2H(μ3-C)Co2(CO)6 (4) in THF at 60 °C gave the functional cluster derivatives ArCH(Me)COOCH2C2H(μ3-C)CoM2(CO)5(η5-C5H4R) (1a−d: M2 = Mo, W; R = CO2Me, C(O)Me). Similarly, reactions of {[(η5-C5H4)C(O)OCH2(OH)CH3]M2(CO)3}- (M2 = Mo, W) with (μ3-S)M1Co2(CO)9 (M1 = Fe, Ru) gave the tetrahedral metal clusters (μ3-S)CoM2M1(CO)8[(η5-C5H4)C(O)OCH2(OH)CH3] (8a−d: M1 = Fe, Ru; M2 = Mo, W). Treatment of the two metal clusters 1a−d and three metal clusters 8a−d with methanol respectively in the presence of lipase at 50 °C for 1 h afforded the optically active cluster derivatives HOCH2C2H(μ3-C)CoM2(CO)5(η5-C5H4R) (6a−d: M2 = Mo, W; R = CO2Me, C(O)Me) and (μ3-S)CoM2M1(CO)8[(η5-C5H4)C(O)OCH3] (9a−d: M1 = Fe, Ru; M2 = Mo, W). The products were separated by silica gel chromatography. The conditions of the lipase reactions were discussed. All the compounds in the global process were characterized by element analysis, and IR and 1H NMR spectroscopy. The structures of clusters 8c and 9c have been determined by single-crystal X-ray diffraction.