- Synthesis of xylylene-bridged dipalladium complexes with imidazole and triazole-based di-N-heterocyclic carbene (NHC) ligands
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The di-N-heterocyclic carbene (NHC) dipalladium complexes, [(PdPyBr2)2(di-NHCimi)] and [(PdPyBr2)2(di-NHCtri)], di-NHCimi and di-NHCtri represent an imidazolylidene and a triazolylidene, respectively, featuring a 1,4-xylylene spacer between the carbene units, have been prepared. The influences of the imidazolylidene and triazolidene backbone and different substituents on the catalytic activity have been investigated in the Mizoroki-Heck reaction of styrene with bromobenzene.
- Du, Yufeng,Tang, Huiling,Ding, Hong,Shi, Yanhui,Cao, Changsheng,Pang, Guangsheng
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p. 735 - 739
(2016/12/30)
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- Tris(carbene)borate ligands featuring imidazole-2-ylidene, benzimidazol-2-ylidene, and 1,3,4-triazol-2-ylidene donors. Evaluation of donor properties in four-coordinate {NiNO}10 complexes
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The synthesis and characterization of new tris(carbene)borate ligand precursors containing substituted benzimidazol-2-ylidene and 1,3,4-triazol-2-ylidene donor groups, as well as a new tris(imidazol-2-ylidene) borate ligand precursor are reported. The relative donor strengths of the tris(carbene)borate ligands have been evaluated by the position of νNO) in four-coordinate {NiNO}10 complexes, and follow the order: imidazol-2-ylidene > benzimidazol-2-ylidene > 1,3,4-triazol-2-ylidene. There is a large variation in νNO), suggesting these ligands to have a wide range of donor strengths while maintaining a consistent ligand topology. All ligands are stronger donors than Tp* and Cp*.
- Mu?oz, Salvador B.,Foster, Wallace K.,Lin, Hsiu-Jung,Margarit, Charles G.,Dickie, Diane A.,Smith, Jeremy M.
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p. 12660 - 12668
(2013/02/22)
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- Preparation and N-alkylation of 4-Aryl-1,2,4-triazoles
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Heating of N,N-dimethylformamide azine dihydrochloride {N-[(dimethylamino) methylene]-N,N-dimethylhydrazonoformamide dihydrochloride} with anilines in the absence of a solvent gave a range of 4-aryl-1,2,4-triazoles by direct transamination. Ortho-substituents were tolerated. Some triazoles were converted into symmetrically and nonsymmetrically substituted bistriazolium salts, one of which was converted into a dicopper complex. Georg Thieme Verlag Stuttgart - New York.
- Holm, Stefanie C.,Siegle, Alexander F.,Loos, Christian,Rominger, Frank,Straub, Bernd F.
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experimental part
p. 2278 - 2286
(2010/08/20)
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- The 1,2,4-triazolyl cation: Thermolytic and photolytic studies
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The generation of the 1,2,4-triazolyl cation (1) has been attempted by the thermolysis and photolysis of 1-(1,2,4-triazol-4-yl)-2,4,6-trimethylpyridinium tetrafluoroborate (2) and the thermolysis of 1- and 4-diazonium-1,2,4-triazoles, using mainly mesitylene as the trapping agent. Thermolysis of 2 gave mostly 1,2,4-triazole, together with 3-(1,2,4-triazol-4-yl)-2,4,6-trimethylpyridine, 4-(1,2,4-triazol-4-ylmethyl)-2,6-dimethylpyridine, and 4-(2,4,6-trimethylbenzyl)-2,6-dimethylpyridine. Thermolysis, of each of the diazonium salts in the presence of mesitylene again gave mainly triazole together with very low yields of 1-(1,2,4-triazol-1-yl)-2,4,6-trimethylbenzene and the corresponding -4-yl isomer in about the same ratio. On the other hand, photolysis of 2 in mesitylene gave mainly 1-(1,2,4-triazol-1-yl)-2,4,6-trimethylbenzene. A photoinduced electron transfer from mesitylene to 2 has been observed and preliminary laser flash photolyses of 2 and the corresponding 2,4,6-triphenylpyridinium salt have been carried out. The observed transients are explained as arising from the first excited states of the pyridinium salts rather than from 1. Ab initio MO calculations are reported and indicate that the predicted electronic ground-state of the triazolyl cation is a triplet state of B1 symmetry with five π electrons, which corresponds to a diradical cation (1c). Possible mechanisms for the formation of the various products are proposed.
- Abramovitch,Beckert,Gibson Jr.,Belcher,Hundt,Sierra,Olivella,Pennington,Sole
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p. 1242 - 1251
(2007/10/03)
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- ATTEMPTED GENERATION AND STRUCTURE OF THE 4-(1,2,4-TRIAZOYL) CATION
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4-(and 1-) Amino-1,2,4-triazoles have been treated with nitrosonium tetrafluoroborate or with isoamyl nitrile and acetic acid in the presence of mesitylene.The main product is 1,2,4-triazole, together with a small amount of the 1- and trace amounts of the 4-mesityl derivatives.Ab initio calculations of the putative 4-(1,2,4-triazoyl) cation show the electronic ground state to be a closed shell singlet 1A1 (4? e) (3), with a low-lying 3B1 triplet (4) only 1 kcal/mol above it; the ?-cation (1) is not a local minimum on the potential energy surface.Possible explanations of the results are proposed.
- Abramovitch, Rudolph A.,Gibson, Harry H.,Nguyen, Terry,Olivella, Santiago,Sole, Albert
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p. 2321 - 2324
(2007/10/02)
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