Preparation of Ru(η3-2-alkenylallyl)(CO)Cl(PPh3)2 complexes via carbometallation of allenes with alkenyl ruthenium complexes

Alkenyl ruthenium complex, Ru(CHCHR)(Cl)(CO)(PPh3)2 1, reacted with allenes 2 to give η3-allyl ruthenium complexes, Ru(η3-2-alkenylallyl)(Cl)(CO)(PPh3)2 3, in good yields. The reaction depends on the structure of the alkenyl group. When R was phenyl or methoxycarbonyl group, the carbometallated complex 3 was yielded as a sole product. However, when R was butyl or trimethylsilyl group, besides the carbometallation product as main product, was obtained a small amount of 2-unsubstituted η3-allyl ruthenium complex which was formed via β-elimination of the alkenyl complex followed by the reaction with allene. Structure of 3 was determined by the X-ray crystal structure analysis.