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

Abstract

Reactions of the monoanions [(η 5-C5H4R)M2(CO)3]- with ArCH(Me)COOCH2C2H(μ 3-C)Co2(CO)6 (4) in THF at 60 °C gave the functional cluster derivatives ArCH(Me)COOCH2C2H(μ 3-C)CoM2(CO)5(η 5-C5H4R) (1a−d: M2 = Mo, W; R = CO2Me, C(O)Me). Similarly, reactions of {[(η 5-C5H4)C(O)OCH2(OH)CH3]M2(CO)3}- (M2 = Mo, W) with (μ 3-S)M1Co2(CO)9 (M1 = Fe, Ru) gave the tetrahedral metal clusters (μ 3-S)CoM2M1(CO)8[(η 5-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(μ 3-C)CoM2(CO)5(η 5-C5H4R) (6a−d: M2 = Mo, W; R = CO2Me, C(O)Me) and (μ 3-S)CoM2M1(CO)8[(η 5-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.

Synthesis and Characterization of Tetrahedral Ru3O Clusters with Intrinsic Framework Chirality: A Chiral Probe of the Intact Cluster Catalysis Concept

“…The motivation for this work was to demonstrate the implication of intact metal clusters in catalytic reactions, since intrinsically chiral metal clusters used as catalysts for the conversion of prochiral substrates may give rise to an enantiomeric excess of the chiral products, subject to the condition that the metal cluster stays intact throughout the catalytic process. So far, this demonstration still remains to be done, because only very few intrinsically chiral metal clusters have been separated into their enantiomers, 13a, and in these cases the clusters either showed no catalytic activity or became active only under UV irradiation, which caused racemization of the cluster framework 15a. Whereas the intrinsically chiral metal clusters known so far, based on a tetrahedral framework with four different vertices, contain a M 3 S, ,, a M 3 (CR), 13a,b or a M 4 framework with different metal atoms, we report here homometallic trinuclear clusters containing a chiral Ru 3 O skeleton capped by a μ 3 -oxo ligand, the three ruthenium atoms being coordinated to three different arene ligands.…”

“…So far, this demonstration still remains to be done, because only very few intrinsically chiral metal clusters have been separated into their enantiomers, 13a, and in these cases the clusters either showed no catalytic activity or became active only under UV irradiation, which caused racemization of the cluster framework 15a. Whereas the intrinsically chiral metal clusters known so far, based on a tetrahedral framework with four different vertices, contain a M 3 S, ,, a M 3 (CR), 13a,b or a M 4 framework with different metal atoms, we report here homometallic trinuclear clusters containing a chiral Ru 3 O skeleton capped by a μ 3 -oxo ligand, the three ruthenium atoms being coordinated to three different arene ligands. Because of the three different arene ligands, the tetrahedral Ru 3 O framework is intrinsically chiral, as the four vertices of the tetrahedron are different.…”

“…Metal clusters with a chiral framework have been extensively studied ever since the pioneering work of Vahrenkamp and Richter, who were the first to prepare tetrahedral M 3 S clusters with three different metal atoms . The motivation for this work was to demonstrate the implication of intact metal clusters in catalytic reactions, since intrinsically chiral metal clusters used as catalysts for the conversion of prochiral substrates may give rise to an enantiomeric excess of the chiral products, subject to the condition that the metal cluster stays intact throughout the catalytic process.…”

A topological analysis of the bonding interaction within the tri-nuclear heterometallic cluster [Mo–Ru–Co(µ3–S)(CO)8(Cp)COOCH3], (Cp = η5-C5H4)

“…The Gaussian 09 program [14] was utilized in this work to perform all DFT calculations of the trinuclear cluster using the PBE1PBE [15] functional. The X-ray diffraction structure of the investigated compounds [13] served as the basis for geometry optimization. The effective core potential LanL2DZ [16] was used with an additional set of fpolarization functions for Mo, Co, and Ru atoms.…”