Nucleophilic attack on η3-allyl and η2-tetrahydroborate complexes of ruthenium(ii)

Abstract

Reaction of [Ru(CO)(η³-C₃H₅)Cl(PMe₂Ph)₂], 1, with CO and Ag⁺ yielded 2A and 2B, isomers of [Ru(CO)₂(η³-C₃H₅)(PMe₂Ph)₂]⁺. Treatment of 2B with BH₄⁻ gave [Ru(CO)₂(CH₂CH₂CH₂)(PMe₂Ph)₂], 7, and [Ru(η²-BH₄)(CO)H(PMe₂Ph)₂], 6, subsequently obtained from [Ru₂(CO)₂Cl₄(PMe₂Ph)₄] and NaBH₄. Chloride attacked the metal in 2B, yielding [Ru(CO)₂(η¹-C₃H₅)Cl(PMe₂Ph)₂], 8, which then reformed 1. Lability of the Ru–HB bond trans to hydride allowed nucleophilic access to the metal in 6, with low-temperature formation of [Ru(η¹-BH₄)(CO)H(L)(PMe₂Ph)₂] (11, 12, 13, L = PMe₂Ph, CO, 4-methylpyridine, respectively). On warming with excess L, these gave H₃B·L and [Ru(CO)(H)₂L(PMe₂Ph)₂] (5, 4, 14, respectively). For L = C₂H₄, low-temperature NMR studies revealed a rapid equilibrium between 6, C₂H₄ and [Ru(η¹-BH₄)(CO)(η²-C₂H₄)H(PMe₂Ph)₂], 16, with slower conversion to [Ru(η²-BH₄)(CO)Et(PMe₂Ph)₂], 17.