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Convenient syntheses of novel ruthenium catalysts bearingN-heterocyclic carbenes

Journal of Organometallic Chemistry
Publication Date
DOI: 10.1016/s0022-328x(99)00435-0
  • Ruthenium
  • Carbenes
  • Alkyne Coupling
  • Homogeneous Catalysis


Abstract The 16-electron ruthenium(II) complexes Cp*Ru[ C(R)N(H)CC(H)N (R)]Cl (Cp*=η 5-C 5Me 5; R=Cy (ICy), 1a; Mes (IMes), 1b) containing N-heterocyclic carbenes are easily accessible in quantitative yields from [Cp*Ru(OMe)] 2 (Me=CH 3) and the corresponding 1,3-diorganylimidazolium chloride by methanol elimination. Compounds 1a–b can also be prepared in 75–80% yield by treating the commercially available polymeric ruthenium(III) compound [Cp*RuCl 2] n with the free 1,3-diorganylimidazolin-2-ylidenes in 1 to 1.5 molar amounts. 1a reacts with CO, PPh 3, pyridine and ethyl diazoacetate (EDA) affording the 18-electron derivatives Cp*Ru(ICy)(L)Cl (L=CO, 2; PPh 3, 3; py, 4; CHCO 2Et, 5). The mixed dicarbene complex 5 is the first isolable ruthenium cyclopentadienyl species bearing a CHCO 2Et moiety. Compounds 1a–b catalyze the carboncarbon coupling of terminal alkynes HCCR (R=Ph, SiMe 3, t Bu, p-Tol) under mild conditions, with the selectivity strongly depending on the substituent R.

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