SYNTHESIS AND REACTION OF RHENIUM ENYNE, AND VINYLALKENYLIDENE COMPLEXES

Reaction of Cp*Re(CO)2(THF) with HC=CC(CH3)=CH2 produced the conjugated enyne complex Cp*(CO)2Re[eta2-HC= CC(CH3)=CH2] (1). Attempted preparation of an eta3-propargyl complex by protonation of 1 with HBF4 failed. Thermolysis of 1 led to the corresponding alkenylidene complex Cp*(CO)2Re=C=CHC(CH3)=CH2 (2), which reacted with HBF4 to give the cationic alkylidyne complex [Cp*(CO)2Re=CCH=C(CH3)2][BF4] (3). Nucleophiles including NaCH(CO2C2H5)2, PMe3, and NaBH4 attack regioselectively at the gamma-carbon of the alkylidyne ligand of 3. Both the conjugated enyne complex 1 and vinylalkenylidene complex 2 underwent reaction with dimethyl acetylenedicarboxylate (DMAD), eventually producing dimethyl 4-methylphthalate (9).