DICARBONYLMOLYBDENUM AND TUNGSTEN COMPLEXES OF ALPHA,BETA-UNSATURATED ESTERS - PREPARATION, PROPERTIES AND APPLICATION IN THE COMPLEXATION OF ALPHA,BETA-UNSATURATED KETONES

摘要

Dicarbonylbis(1-oxa-1,3-diene) complexes of molybdenum and tungsten can be prepared from ethyl and methyl methacrylate by employing either (eta(6)-C6H6)Mo(CO)(3) or (CH3CH2CN)(3)W(CO)(3) in modified standard complexation reactions. The crystalline, air-sensitive compounds can be obtained in 61%-94% yield. Both NMR spectroscopic studies and the X-ray crystal structure of the tungsten methyl methacrylate complex [H2C=C(CH3)C(O)OCH3]W-2(CO)(2) suggest that: the bonding mode of the unsaturated ester ligands in these compounds differs from eta(4) to some extent, i.e. the coordination of the carbonyl fragment is an intermediate between eta(2)-pi and eta(1) at the carbonyl oxygen. The unsaturated ester ligands are labile with respect to exchange reactions, which allows other 1-oxa-1,3-dienes to replace them under very mild conditions. Most interestingly, in the case of the tungsten compounds, even complexes of temperature-sensitive alpha,beta-unsaturated ketones can thus be easily obtained in excellent yield at room temperature. [References: 27]