Dinuclear μ-alkylidene complexes of transition metals as models for the transformation of CH2X2 (X=Cl, Br, I) into malonic acid derivatives by double carbonylation reactions

Article abstract of DOI:10.1016/0022-328X(89)85121-6

The carbonylation of the μ-alkylidene complexes Fe2(CO)8CH2 (1) and Pd2I2(PPh2CH2PPh2)2CH2 (2) has been studied under a variety of conditions.In the presence of an alcohol ROH, complex 1 gives mainly the acetate CH3CO2R, the product of monocarbonylation, whereas under the same conditions complex 2 gives the malonate CH2(CO2R)2, the product of dicarbonylation.The mechanisms of both reactions are discussed.From the fraction involving 1 a mononuclear complex resulting from the dimerization of ketene has been isolated, and its structure established by an X-ray diffraction study.Olefins such as ethene and norbornene are able to trap the ketene intermediate.The possible participation of such μ-alkylidene complexes in the direct transformation of CH2X2 (X=Cl, Br, I) into malonic acid derivatives is discussed.