Cyclohexenyl [2.2]paracyclophane complexes of ruthenium( II): Highly fluxional agostics from the sequential reduction of arenes

Abstract

Reduction of the (arene)(paracyclophane)ruthenium( II) complex [RU(η 6-C 6Me 6)(η 6-C 16H 16][BF 4] 2 ( 1b) with Na[BH 4] gives in contrast to the analogous RedAl reduction a mixture of ruthenium(O) diene products, chiefly the 1,3-diene complex [Ru(η 4-1,3-C 6Me 6H 2) (η 6-C 16H 16)] ( 2C). Complex 2c reacts with aqueous H[BF 4] to generate the agostic species [Ru(η 3-C 6Me 6H 3)(η 6-C 16H 16)][BF 4] ( 3). The complex is highly fluxional with the single endo agostic hydrogen atom exchanging rapidly between the two terminal olefinic carbon atoms of the cyclohexadiene unit. The formulation of the complex has been confirmed by the preparation of the di-deutero analogue.