The complex [Cp*RuCl(COD)] reacts with LH 2 Cl 2 (L = bis(3-methylimidazol-2-ylidene)) and LiBu n in tetrahydrofuran at 65 °C furnishing the bis-carbene derivative [Cp*RuCl(L)] (2). This compound reacts with NaBPh 4 in MeOH under dinitrogen to yield the labile dinitrogen-bridged complex [{Cp*Ru(L)} 2 (μ-N 2 )][BPh 4 ] 2 (4). The dinitrogen ligand in 4 is readily replaced by a series of donor molecules leading to the corresponding cationic complexes [Cp*Ru(X)(L)][BPh 4 ] (X = MeCN 3, H 2 6, C 2 H 4 8a, CH 2 CHCOOMe 8b, CHPh 9). Attempts to recrystallize 4 from MeNO 2 /EtOH solutions led to the isolation of the nitrosyl derivative [Cp*Ru(NO)(L)][BPh 4 ] 2 (5), which was structurally characterized. The allenylidene complex [Cp*RuCC CPh 2 (L)][BPh 4 ] (10) was also obtained, and it was prepared by reaction of 2 with HCCC(OH)Ph 2 and NaBPh 4 in MeOH at 60 °C. Complexes 3, 4, and 6 are efficient catalyst precursors for the transfer hydrogenation of a broad range of ketones. The dihydrogen complex 6 has proven particularly effective, reaching TOF values up to 455 h −1 at catalyst loadings of 0.1% mol, with a high functional group tolerance on the reduction of a broad scope of aryl and aliphatic ketones to yield the corresponding alcohols.

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An efficient ruthenium-catalyzed N-alkylation of amines, amides and sulfonamides has been developed employing novel pentamethylcyclopentadienylruthenium (II) complexes bearing the methylene linked bis(NHC) ligand bis(3-methylimidazol-2-ylidene)methane. The acetonitrile complex 2 has proven...