Cleavage of Ru-3(CO)(12) by N-heterocyclic carbenes: Isolation of cisand trans-Ru(NHC)(2)(CO)(3) and reaction with O-2 to form Ru(NHC)(2)(CO)(2)(CO3)

The N-heterocyclic carbenes (NHCs) 1,3-dialkyl-4,5-dimethylimidazol-2-ylidene (alkyl = ethyl, IEt2Me2; isopropyl, IiPr2Me2) and 1,3-di-isopropylimidazol-2-ylidene (IiPr2) cleave Ru3(CO)12 at room temperature to give the mononuclear complexes Ru(NHC)2(CO)3 (NHC = IEt2Me2 1; IiPr2Me2 2; IiPr2, 3). X-ray crystallography reveals that 1 contains trans-NHC ligands whereas 2 and 3 have an unexpected cis arrangement of carbenes. Exposure of 1−3 to air in the solid state or upon reaction with O2 in solution yields the carbonato complexes Ru(NHC)2(CO)2(CO3) (NHC = IEt2Me2 4, IiPr2Me2 5, IiPr2, 6).