1,2,3-Triazolylidene ruthenium(ii)(η6-arene) complexes: synthesis, metallation and reactivity

Abstract

Three bis(1,2,3-triazolylidene) silver(I) complexes were synthesized, and the ruthenium complexes ([RCH₂N₂(NMe)C₂Ph)]RuCl₂(p-cymene) (R = C₆H₂Me₃4a₁, C₆H₂iPr₃4b₁) were isolated as major products with the minor C(sp²)–H activated products ([RCH₂N₂(NMe)C₂C₆H₄)]RuCl(p-cymene) (R = C₆H₂Me₃4a₂, C₆H₂iPr₃4b₂). In the related case where R = Ph, the species ([PhCH₂N₂(NMe)C₂Ph)]RuCl₂(p-cymene) 4c₁ was obtained with two C(sp²)–H activated products [PhCH₂N₂(NMe)C₂C₆H₄)]RuCl(p-cymene) 4c₂ and [(C₆H₄)CH₂N₂(NMe)C₂Ph)]RuCl(p-cymene) 4c₃ derived from metallation of the N and C-bound arene rings. Heating a solution of 4a₁ at 45 °C over three weeks resulted in a ruthenium(II)(1,2,3-triazolylidene) complex [(C₆H₂Me₃)CH₂N₂(NMe)C₂Ph)]RuCl₂5a, where the pendant mesityl group on the triazolylidene moiety displaced the p-cymene ligand. The complexes 4a₁, 4b₁, 4c₁ and 5a displayed moderate catalytic activities in base-free oxidation of benzyl alcohols to benzaldehydes and oxidative homocoupling of benzyl amines to imines using oxygen as oxidant.