ISOCYANIDE ARENE RUTHENIUM(II) COMPLEXES AND ACTIVATION OF ALKENYLACETYLENES - SYNTHESIS AND CHARACTERIZATION OF ISOCYANIDE CARBENE RUTHENIUM AND MIXED CARBENE RUTHENIUM COMPOUNDS

[RuCl2(eta-6-arene)]2 complexes 1 (eta-6-MeC6H4(i)Pr), 2 (eta-6-C6H2Me4), and 3 (eta-6-C6Me6) react with isocyanide CNR [R = (t)Bu (a), C6H11 (b), CH2CO2C6H4Me (c), CH2CO2Et (d), (CH2)4Cl (e), and (CH2)2OSiMe3 (f)] to produce a variety of RUCl2(CNR)(eta-6-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.