N-Heterocyclic carbene-induced transmethylation in tungsten imido alkylidene bistriflates: unexpected formation of an N-heterocyclic olefin complex.

The reaction of [W(N-2,6-PrCH)(CHCMePh)(OTf)(DME)] (DME = 1,2-dimethoxyethane, OTf = CFSO) with the N-heterocyclic carbene (NHC) 1,3-bis(2,4,6-trimethylphenyl)imidazolidin-2-ylidene (IMesH) leads to DME activation followed by transmethylation and in due consequence to the formation of the N-heterocyclic olefin complex [W(N-2,6-PrCH)(CHCMePh)(OTf)(IMesHCH)] along with [W(N-2,6-PrCH)(CHCMePh)(OTf)(IMesH)(κ-O(CH)OMe)], [1,3-bis(2,4,6-trimethylphenyl)-2-methylimidazolidinium (OTf)] and [1,3-bis(2,4,6-trimethylphenyl)-2-H-imidazolidinium (OTf)]. A reaction pathway is proposed and confirmed by the use of C-labelled compounds; structures of the products were verified by NMR and/or single-crystal X-ray analysis.

Phosphenium Hydride Reduction of [(cod)MX] (M = Pd, Pt; X = Cl, Br): Snapshots on the Way to Phosphenium Metal(0) Halides and Synthesis of Metal Nanoparticles.

The outcome of the reduction of [(cod)PtX] (X = Cl, Br; cod = 1,5-cyclooctadiene) with N-heterocyclic phosphenium hydrides NHP-H depends strongly on the steric demand of the N-aryl group R and the nature of X. Reaction of [(cod)PtCl] with NHP-H featuring bulky N-Dipp groups produced an unprecedented monomeric phosphenium metal(0) halide [(NHP)(NHP-H)PtCl] stabilized by a single phosphine ligand. The phosphenium unit exhibits a pyramidal coordination geometry at the phosphorus atom and may according to DFT calculations be classified as a Z-type ligand.

Application of imidazolinium salts and N-heterocyclic olefins for the synthesis of anionic and neutral tungsten imido alkylidene complexes.

The synthesis, single crystal X-ray structure and activity in olefin metathesis of novel anionic tungsten imido alkylidene complexes [1,3-bis-(2,4,6-trimethylphenyl)imidazolinium](+) [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(2,5-Me2Pyr)2Cl](-), [1,3-bis-(2,4,6-trimethylphenyl)imidazolinium](+) [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(2,5Me2Pyr)2(OC6F5)](-), and [1,3-bis-(2,6-diisopropylphenyl)imidazolinium](+) [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(2,5-Me2Pyr)Cl2](-) are reported. Additionally, the first example of a bis(N-heterocyclic olefinium) alkylidene tungstate, W(N-2,6-iPr2C6H3)(CHCMe2Ph)(2-methylene-1,3,4,5-tetramethyl-imidazoline)2(OTf)2, is described, including preparation, crystal structure and catalytic activity.

Neutral and Cationic Molybdenum Imido Alkylidene N-Heterocyclic Carbene Complexes: Reactivity in Selected Olefin Metathesis Reactions and Immobilization on Silica.

The synthesis and single-crystal X-ray structures of the novel molybdenum imido alkylidene N-heterocyclic carbene complexes [Mo(N-2,6-Me2C6H3)(IMesH2)(CHCMe2Ph)(OTf)2] (3), [Mo(N-2,6-Me2C6H3)(IMes)(CHCMe2Ph)(OTf)2] (4), [Mo(N-2,6-Me2C6H3)(IMesH2)(CHCMe2Ph)(OTf){OCH(CF3)2}] (5), [Mo(N-2,6-Me2C6H3)(CH3CN)(IMesH2)(CHCMe2Ph)(OTf)](+)BArF(-) (6), [Mo(N-2,6-Cl2C6H3)(IMesH2)(CHCMe3)(OTf)2] (7) and [Mo(N-2,6-Cl2C6H3)(IMes)(CHCMe3)(OTf)2] (8) are reported (IMesH2=1,3-dimesitylimidazolidin-2-ylidene, IMes=1,3-dimesitylimidazolin-2-ylidene, BArF(-)=tetrakis-[3,5-bis(trifluoromethyl)phenyl] borate, OTf=CF3SO3(-)). Also, silica-immobilized versions I1 and I2 were prepared. Catalysts 3-8, I1 and I2 were used in homo-, cross-, and ring-closing metathesis (RCM) reactions and in the cyclopolymerization of α,ω-diynes.