SYNTHESIS AND CARBON-CARBON BOND-FORMING REACTIONS OF TUNGSTEN, MOLYBDENUM, AND RHENIUM ENOLATES

Alkylation of sodium cyclopentadienyl(tricarbonyl)metallates of tungsten and molybdenum with alpha -chloro ketones and alpha -chloro esters gives stable tungsten and molybdenum enolates. Similar alkylation of sodium pentacarbonylrhenate provides rhenium enolates. Compounds lose carbon monoxide and rearrange to eta **3 -oxaallyl complexes upon irradiation. These compounds react with benzaldehyde to give transition metal aldolates, which may be converted into the silylated aldol and the corresponding metal chloride upon reaction with trimethylsilyl chloride. Rhenium enolate undergoes thermal aldol reaction with benzaldehyde and suffers exchange of one carbonyl ligand upon being heated with triphenylphosphine. The resulting cis monophosphine complex and an aldol compound both react with triphenylphosphine in refluxing acetonitrile to give a complex in which the enolate moiety has been transferred from rhenium to the nitrile function. Several schemes for establishing catalytic cycles based on the foregoing reactions are suggested.