Isocyanide arene-ruthenium(II) complexes and activation of alkenylacetylenes: Synthesis and characterization of isocyanide carbene- and mixed carbene-ruthenium compounds

Article abstract of DOI:10.1021/om00055a055

[RuCl₂(η⁶-arene)]₂ complexes 1 (η⁶-MeC₆H₄ⁱPr), 2 (η⁶-C₆H₂Me₄), and 3 (η⁶-C₆Me₆) react with isocyanide CNR [R = ^tBu (a), C₆H₁₁ (b), CH₂CO₂C₆H₄Me (c), CH₂CO₂Et (d), (CH₂)₄Cl (e), and (CH₂)₂OSiMe₃ (f)] to produce a variety of RuCl₂(CNR)(η⁶-arene) derivatives 4-6, which give a C≡N absorption in the infrared at high wavenumbers between 2165 and 2206 cm^-1. (C₆Me₆)Cl₂RuCN(CH₂) ₂OSiMe₃ (6f) on reaction with KF in methanol affords the carbene complex (C₆Me₆)Cl₂Ru:CNHCH₂CH₂O (8). Cyclic voltammetry of complexes 4-6 shows that only with the most electron-releasing arene C₆Me₆ a reversible oxidation occurs, at 1.06-1.15 V_SCE for complexes 6a-f and at 0.80 V_SCE for 8. Complexes 6a, 6e, and 8 activate isopropenylacetylene, via an allenylidene intermediate, and in the presence of methanol give access to alkenylcarbene complexes containing the Ru=C(OMe)CH=CMe₂ moiety 7a,e and the mixed carbene complex 9.