Bis 2,4,6-trimethylphenyl

Second-generation ruthenium-carbene complex, (tricyclohexylphosphine-[l,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene]ruthenium (IV) dichloride),4e was purchased from Strem Chemicals. 

Tricyclohexylphosphine[l,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene]ruthenium... 

The versatile starting material lCp RuCI 4 (1) reacts rapidly with sterically demanding phosphines (PCy and P Pr ) as well as with the nucleophilic carbene ligands (L) to give deep blue, coordinatively unsaturated Cp Ru(L)CI complexes 2-8 (L= l,.Tbis(2,4,6-lrimethylphenyl) (IMes. 2) 1,3-R2-imidazol-2-ylidene = cyclohcxyl (ICy, 3) 4-methylphenyl (ITol, 4) 4-chlorophenyl (IPCl, 5) adamanlyl (lAd, 6) 4..5-dichloro-1,3-bis(2.4,6-trimethylphenyl) (IMesCI, 7) and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidenc (IPr. 8) in high yields according to Eq. (4). 

Cahonic iridium complexes bearing imidazol-2-ylidene hgands were applied as TH catalysts by Hillier et al. [48]. Here, [lr(cod)(py)(L)]Pp6 (L= IMes, l,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (53a), IPr, l,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (53b) and ICy, l,3-bis(cyclohexyl)imidazol-2-ylidene (53c) were employed as catalysts for TH from 2-propanol to various unsaturated substrates, and compared to [lr(cod)(py)(PCy3)]PF6 and complexes formed in situ from [Ir(cod)(py)2]PF,5 and diazabutadienes (RN=CHCH=NR, DAB-R R = cyclohexyl, DAB-Cy 2,4,6-trimethylphenyl, DAB-Mes adamantyl, DAB-Ad 2,4,6-trimethoxyphenyl, DAB-trimethoxyphenyl). AH complexes were achve catalysts for the TH of acyclic ketones, with complex 53c being the most achve, showing 100% conversion of BuC(0)Me and PhC(0)Ph in 25 and lOmin, respechvely, using 0.025 mol% of catalyst and KOH in PrOH at reflux (Scheme 4.20). 

Unpronounced polarization of regular C-H bonds such as methyl or ethyl groups does not lead us to expect the formation of dihydrogen bonds. Actually, an analysis of the Cambridge Structure Database [2] reveals numerous C-H- - -H-C contacts with H- - -H distances of 2.500 A or even more where the angular distribution is ideally isotropic. The latter is typical of nondirec-tional van der Waals interactions. The C-H and B-H bonds in the molecule l,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene- BH3 are obviously more... 

The ligand l,3-bis(2,2", 6,6"-tetramethyl-m-terphenyl-5 -yl)imidazole-2-ylidene) ITmt was designed to facihtate the formation of low-coordinate species. It has a much higher overall degree of bulkiness than the well-known l,3-bis(2,4,6-trimethylphenyl)imidazoline-2-ylidene (IMes), but in the vicinity of the carbene center it is less severe because of the absence of substituents in the ortho-position. 

An N-heterocyclic carbene ligand, formed from l,3-bis-(2,4,6-trimethylphenyl)-3//-imidazol-l-ium chloride and cesium carbonate, with dipalladium tris(dibenzylideneacetone) gave excellent yields (93-96% yields) in the Suzuki coupling of 2-chloropurines and arylboronic acids in anhydrous dioxane <2001TL8751>. The combination of an imidazolium-carbene and nickel(O) bis(cyclooctadiene) formed a catalyst capable of insertion into the C-F bond of 6-fluoropurine nucleosides (Scheme 35) <20050L1149>. 

The rhodium A-heterocyclic carbine complex [Rh(IMes)(COD)] [IMes = A,A -bis(2,4,6-trimethylphenyl)imidazol-2-ylidine COD = cycloocta-1,5-diene] catalyses the 4 + 2 + 2-carbocyclization of 1,6-enynes (191) to carbocycles [(192) and (193)] (Scheme 54).226 Computational and experimental evidence of a new reaction pathway for the diastereospecific intermolecular rhodium-catalysed 4 + 2 + 2-carbocyclization (g) reactions of 1,6-enynes with r-components has been reported.227... 

Bis[2,4,6-trimethylphenyl] Tellurium2 A solution of 4.94 g (10 mmol) of bis[2,4,6-trimethylphenyl] ditellurium in 150 ml of toluene and 1.40 g (22 mmol) of electrolytic copper are placed in a 250-ml flask fitted with a reflux condenser. The mixture is heated under reflux for 12 h, filtered, and the filtrate is evaporated to dryness to give the pure product m.p. 123-125°. 

Jones and co-workers investigated reactions of the stable carbene 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene with a series of halide sources... 

The reversible FeTe1 FeTe11 couple of an N-heterocyclic carbene dinuclear FeTe1 complex, (p-pdt) [FeI(CO)2(PMe3)][FeI(CO)2(IMes)] (IMes= l,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), complex D, has led to the isolation of the mixed-valent cationic complex D as a biomimetic of the 2Fe2S subsite of the oxidized H cluster in... 

Angeletakis [2] prepared metathesis-curable dental compositions using 1,3-bis-(2,4,6-trimethylphenyl)-2-(imidazolidinylideii ) dichloro(o-isopropoxy-... 

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