Room temperature operating allenylidene precatalyst [LnRuξCξCξCR2]+X- for olefin metathesis: dramatic influence of the counter anion X-

Abstract

The allenylidene-ruthenium(II) complex [(p-cymene)(PCy₃)Cl- RuξCξCξCPh₂]⁺X^-, 2a, (X^-=CF₃SO₃^-), which is pro-duced in a one-pot reaction from commercially available [RuCl₂(p- cymene)]₂, catalyses the ring-closing metathesis of N,N-diallyltosylamide at room temperature whereas 2b (X^-=BF₄^-) favours the cyclization of the 1,6-diene 3 into the five-membered heterocycle 5 without loss of atoms. The addition of BF₃·OEt₂ to 2b restores its selectivity in the RCM reaction. Catalyst 2a also promotes the metathesis of the ene-yne 6 to produce the 3-vinyl-2,5-dihydrofuran 7.