Carbon–oxygen and carbon–sulfur bond activation of vinyl esters, ethers and sulfides by low valent ruthenium complexes

Abstract

[Ru(cod)(cot)] (1) (cod: 1,5-cyclooctadiene, cot: 1,3,5-cyclooctatriene) reacts with phenyl vinyl ether and vinyl sulfides in the presence of the bidentate depe ligand affording the zerovalent (η²-vinyl ether or sulfide)ruthenium(0) complexes, [Ru(η²-C₂H₃YR)(cod)(depe)] [RY = PhO (2a), PhS (2b), PhCH₂S (2c), EtS (2d), Me₂CHS (2e), depe: 1,2-bis(diethylphosphino)ethane]. Whereas the vinyl ether or sulfide ligand is selectively displaced in 2a, 2d and 2e by monodentate phosphines giving [Ru(cod)(depe)L] [L = PMe₃ (3a), PMe₂Ph (3b)], partial exchange reactions of either the vinyl sulfide ligand or cod take place for 2b and 2c affording 3a and b and [Ru(η²-C₂H₃SR)(depe)(L)₂] [L = PMe₃, R = Ph (4a), L = PMe₂Ph, R = Ph (4b); L = PMe₃, R = CH₂Ph (4c)]. The intermolecular C–S bond cleavage takes place in 4a promoted by MeI to form [Ru(I)(η¹-C₂H₃)(depe)(PMe₃)₂] 5 with liberation of MeSPh. On the other hand, reactions of 1 with vinyl carboxylates in the presence of tertiary phosphines such as PMe₃, PEt₃ or depe give a series of (η¹-vinyl)ruthenium(II) complexes cis-[Ru(η¹-C₂H₃)(η¹-OCOR′)(PMe₃)₄] [R′ = Me (6a), Et (6b), ^tBu (6c), Ph (6d)], mer-[Ru(η¹-C₂H₃)(η²-OCOR′)(PEt₃)₃] [R′ = Me (7a), Et (7b), ^tBu (7c), Ph (7d), C(Me)CH₂ (7e)], trans-[Ru(η¹-C₂H₃)(η¹-OCOR′)(depe)₂] [R′ = Me (8a), Et (8b), ^tBu (8c), Ph (8d), C(Me)CH₂ (8e)]. The structures of 2a, 2b, 3a, and 8a have been determined by X-ray crystallography. A mechanism including prior co-ordination of the vinylic moiety has been proposed for the C–O bond cleavage reaction on ruthenium(0).