Selective Cα–Cβ bond cleavage by water in allenylidene and alkenylvinylidene ruthenium complexes

Abstract

The Ru(II) complex mer,trans-[(PNP)RuCl₂(PPh₃)] [PNP = MeCH₂CH₂N(CH₂CH₂PPh₂)₂] reacts in refluxing THF with propargyl alcohols HCCCRR′OH (R = R′ = Me, Ph; R = Me, R′ = Ph) yielding either the allenylidene complex fac,cis-[(PNP)RuCl₂{CCCPh₂}] or the alkenylvinylidene derivatives fac,cis-[(PNP)RuCl₂{CC(H)C(R)CH₂}] (R = Me, Ph); treatment of all these complexes in CH₂Cl₂ or THF with water results in the formation of the ruthenium carbonyl fac,cis-[(PNP)RuCl₂(CO)] and free alkenes H₂CCRR′ (R = R′ = Me, Ph; R = Me, R′ = Ph) via regioselective C_α–C_β bond cleavage.