Synthetic Reactions by Using Bimetallic Complexes

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In catalytic synthetic reactions, monometallic complexes have been widely used, while bimetallic complexes rarely used in practical synthesis. Precise design of bimetallic complexes is expected to realize unique chemical transformations, in which multi metal centers take part in the reactions collaboratively. In this research, homo and hetero bimetallic complexes were prepared and their catalytic activities were studied to realize organic transformations.1)Phosphido-bridged rhodium-tungsten carbonyl complexes were prepared, expecting catalytic activity of Rh(I) with the assistance by the W part as a CO donor and/or Lewis acidity. A Rh-W bimetallic complex exhibited high catalytic activity in the hydroformylation of monosubstituted alkenes even under less than 0.04 atm partial pressure of CO, with a wide functional group selectivity. A oxygen- or sulfur-bridged bimetallic were prepared and their structures were studied by X-ray crystallographic analysis. The oxygen-bridged complex exhib … More ited a unique character in the hydrogenation of alkenes; that is, outer alkenes are smoothly hydrogenated, while the ligand alkene (cyclooctadiene) is not.2)Vinyl nitrene-metal complexes, the property of which is not fully clarified yet, was found to be easily generated from azirines and vinyl azides, particularly by the treatment with rhodium(II) bimetallic complexes and copper(II) complexes. Indoles and pyrroles were prepared catalytically by aromatic C-H amination and addition reaction of active methylene compounds to the vinyl nitrene-metal complexes.3)During the course of the study on the oxidative generation of β-keto radicals from cyclopropanols, silver(I) complexes are found to show high activity. Catalytic process was accomplished by adding adequate reoxidation reagent and applied for the intramolecular ring expansion. The catalytic generation of β-keto radicals was so powerful to construct fused rings that synthesis of (-)-sordarin was achieved by using the catalysis as the key step. Less