CYCLOPENTADIENYL-RUTHENIUM AND CYCLOPENTADIENYL-OSMIUM CHEMISTRY .34. REACTIONS OF 1-ALKYNES WITH SIGMA-VINYL-RUTHENIUM COMPLEXES - X-RAY STRUCTURES OF RU(ETA-3-CH(CO2ME)C(CO2ME)C=CHPH)(PPH3)(ETA-C5H5) AND RU(ETA-C5H5)(ETA-5-C3(CO2ME)3CHCTBUCH(CO2ME))

Reactions between HC2R (R = Ph, tBu) and the chelate vinyl ester complex RuC(CO2Me)CHC(O)OMe(PPh3)(η-C5H5) have given η3-allyl derivatives Ruη3-CH(CO2Me)C(CO2Me)CCHR(PPh3)(η-C5H5), as shown by an X-ray structure of the phenyl derivative. Similarly, the reaction between HC2Ph and RuC(OMe)CH(CO2Me)(PPh3)2(η-C5H5) gave Ruη3-CH(CO2Me)C(OMe)CCHPh(PPh3)(η-C5H5). These reactions probably proceed via displacement of the ester carbonyl group or PPh3 by the 1-alkyne, which isomerises to the corresponding vinylidene before a formal insertion into the Ru-C(sp2) bond. Complexes containing cyclic adducts of the 1-alkyne and the butadienyl ligand, namely Ru(η-C5H5)η5-C3(CO2Me)3CHCRCH(CO2Me), were obtained from RuC(CO2Me)C(CO2Me)C(CO2Me)CH(CO2Me)(PPh3)(η-C5H5) and HC2R (R = Ph, tBu), as shown by an X-ray structure of the t-butyl derivative. A small amount of an η5-vinylcyclohexadienyl complex was also obtained from the reaction with HC2Ph. In these reactions, the 1-alkyne does not isomerise, probably for steric reasons; the first step may involve replacement of PPh3 by the alkyne, rather than formation of an η1-butadienyl complex. © 1990.