Synthesis and Structural Characterization of η6-Arene Ruthenium Complexes Bearing Pentadienyl and Oxopentadienyl Ligands

Abstract

General methodology for the synthesis of cationic ruthenium(II) η5-pentadienyl compounds stabilized by the (η6-C6Me6)Ru fragment has been developed. Pentadienyl compounds [(η6-C6Me6)Ru{η5-CH2C(R2)CHC(R4)CH(R5)}]BF4 (R2 = R4 = R5 = H, 2-BF4; R2, R4 = H, R5 = Me, 3; R2, R4 = Me, R5 = H, 4) can be prepared in good yields from reactions of the labile dication [(η6-C6Me6)Ru(acetone)3](BF4)2 (1) with 1-trimethylsilyl-2,4-pentadiene, 1-trimethylsilyl-2,4-hexadiene, and 2,4-dimethyl-1-trimethylstannyl-2,4-pentadiene, respectively. Compound 3 is isolated in 90% yield as a mixture of the syn and anti isomers. In contrast, the reaction of pentadienyllithium with [(η6-C6Me6)RuCl2]2 provides a nonselective reaction, which affords a mixture of isomeric η1-, η3-, and η5-coordinated pentadienyl complexes, [(η6-C6Me6)Ru(η5-CH2CHCHCHCH2)]Cl (2-Cl), [(η6-C6Me6)Ru(η3-CH2CHCHCHCH2)Cl] (5), and [(η6-C6Me6)Ru(η1-CH2CHCHCHCH2)Cl]2 (6); the reaction of 1,4-pentadiene and [(η6-C6Me6)RuCl2]2 in ethanolic carbonate similarly gives a...