Ring-opening and double-metallation reactions of the N-Heterocyclic carbene ligand in Cp*(IXy)Ru (IXy=1,3-bis(2,6-dimethylphenyl)imidazol-2-ylidene) complexes. Access to an anionic fischer-type carbene complex of ruthenium

An N-heterocylic carbene (NHC) ring-opening reaction was observed upon treatment of the silyl complex Cp*(IXy-H)(H)RuSiH(2)Mes [1; IXy = 1,3-bis(2,6-dimethylphenyl)imidazol-2-ylidene; IXy-H = 1-(2-CH2C6 H-3-6-methyl)-3-(2,6-dimethylphenyl)imidazol-2-ylidene-1-yl (the deprotonated form of IXy); Cp* = eta(5)-C5Me5] with LiCH2SiMe3. This reaction results in formation of a novel, anionic Fischer-type carbene complex Cp*(H)Ru{kappa(2)-CHN(Xyl)CH[Si(CH2SiMe3)Me-3]N(Xyl)Li} (4). This ring-opening reaction demonstrates a new pathway for NHC degradation via the cooperation of ruthenium, silicon, and lithium. Additionally, treatment of the dinitrogen complex Cp*(IXy-H)Ru(N-2) with LiCH2SiMe3 led to the doubly-metallated complex [Cp*(IXy-2H)Ru]Li (5), which exhibits a solid-state polymeric structure and metallation of both xylyl groups of the IXy ligand. Finally, removal of a hydride from 4, achieved with two equiv of B(C6F5)(3), led to C-H activation of the Cp* ligand and formation of an unusual, formally dianionic eta(5)-Me4C5CH2B(C6F5)(3) ligand in a ruthenium carbene complex [eta(5)-Me5C5CH2B(C6F5)(3)](H)Ru {kappa(3)-CHN(Xyl)CH[SiH(CH2SiMe3)Mes]N(Xyl)} (7). (C) 2014 Elsevier Ltd. All rights reserved.