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

Three bis(1,2,3-triazolylidene) silver(I) complexes were synthesized, and the ruthenium complexes ([RCH2N2(NMe)C2Ph)]RuCl2(p-cymene) (R = C6H2Me3 4a₁, C6H2iPr3 4b₁) were isolated as major products with the minor C(sp(2))-H activated products ([RCH2N2(NMe)C2C6H4)]RuCl(p-cymene) (R = C6H2Me3 4a₂, C6H2iPr3 4b₂). In the related case where R = Ph, the species ([PhCH2N2(NMe)C2Ph)]RuCl2(p-cymene) 4c₁ was obtained with two C(sp(2))-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)]RuCl2 5a, 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.