Addition of Alkynes to Coordinated Allyl Ether in Ruthenium(II) Chelate Complexes

Reactions of the ruthenium chelate complex [Ru(η5:η2-C5Me4CH2OCH2CHCH2)(CO)Cl] (1) with acetylenes R1C⋮CR2 in the presence of AgBF4 give the cationic diene chelates [Ru(η5:η4-C5Me4CH2OCH2CHCHCR1CHR2)(CO)]+BF4- (2a, R1 = R2 = Ph; 3a, R1 = R2 = Me; 4a, R1 = Me, R2 = Ph; 4b, R1 = Ph, R2 = Me; 5a, R1 = H, R2 = CO2Me; 5b, R1 = CO2Me, R2 = H; 6a, R1 = H, R2 = CH2OMe) and {Ru[η5:η4-C5Me4CH2OCH2C(CH2)CHCHPh](CO)}+BF4- (7). The crystal structures of [2a‘ ‘]+PF6- and [7]+PF6- have been determined. The formation of complexes 2−6 is the result of regiospecific addition of acetylenes PhC⋮CMe, MeC⋮CMe, PhC⋮CMe, HC⋮CCO2Me, and HC⋮CCH2OMe to the terminal carbon of the allylic ether, while phenylacetylene adds to the internal carbon of the olefin. The unsymmetric acetylenes (PhC⋮CMe, HC⋮CCO2Me) give predominantly the isomers 4a and 5a, where the allylic C−H has added to the acetylenic carbon bearing the less bulky substituent. The complex [Ru(η5:η2-Me4C5CH2OCH2CHCH2)(η1-C⋮CPh)(CO)] (8) was synthesized by the reaction of 1...