Cleavage of Ru₃(CO)₁₂ by N-Heterocyclic Carbenes: Isolation of <i>cis</i>- and <i>trans</i>-Ru(NHC)₂(CO)₃ and Reaction with O₂ To Form Ru(NHC)₂(CO)₂(CO₃)

Abstract

The N-heterocyclic carbenes (NHCs) 1,3-dialkyl-4,5-dimethylimidazol-2-ylidene (alkyl = ethyl, IEt 2 Me 2; isopropyl, I i Pr 2 Me 2 ) and 1,3-di-isopropylimidazol-2-ylidene (I i Pr 2 ) cleave Ru 3 (CO) 12 at room temperature to give the mononuclear complexes Ru(NHC) 2 (CO) 3 (NHC = IEt 2 Me 2 1; I i Pr 2 Me 2 2; I i Pr 2, 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 O 2 in solution yields the carbonato complexes Ru(NHC) 2 (CO) 2 (CO 3 ) (NHC = IEt 2 Me 2 4, I i Pr 2 Me 2 5, I i Pr 2, 6 ).