Phenyl-1,2,3-triazol-5-ylidenes

Albrecht [133] and Sankararaman [174] have independently synthesized the cyclometallated phenyl-1,2,3-triazol-5-ylidenes complexes 77a-b (Scheme 11). Both groups have found that the cyclometallation is selective for aryl groups in the 1-position of the l,2,3-triazol-5-ylidenes units presumably because the direct attachment to the nitrogen atom increases the acidity of the 1-substituted aryl group, making the deprotonation more facile. It is noted that 77b is a catalyst for the stereoselective hydroarylation of alkynes [174]... 

Triplet energy transfer measurements from porphyrin and phthalocyanine sensitizers give the triplet energies of six (Z)-A4,A4-diethyl-2-(alkyl, aryl)-A1-(3-phenyl-77/-pyrazolo[5,l-r-][l,2,4]triazol-7-ylidene)benzene-l,4-diamine azomethine dyes 154 with adsorption maxima in ethanol at 546-633 nm to lie in the range of 115-88 kJmoF1 <2003PPS563> (Figure 24). 

In the reaction of 5-phenyl-3-methyl-2-imino-l,3,4-oxadiazoline and EMME at 130°C for 30 min, N-( 1,3,4-oxadiazolin-2-ylidene)aminomethy-lenemalonate (66) was obtained in 34% yield (70AP501). The reaction of 5-amino-4-phenyl-1,2,3-triazole and EMME in the presence of acetic acid in boiling benzene for 30 hr, or in boiling toluene for 3 hr, gave (1,2,3-triazol-5-ylamino)methylenemalonate (67) in 64-89% yields [71JCS (02156]. 

For instance, a new bidentate NHC pyrazolate ligand precursor featuring a methylene spacer between the benzimidazol-2-ylidene and the pyrazolate moieties has been used to obtain four new luminescent platinum(ii) complexes along with either phenyl-pyridine or pyridine-triazole luminophores/ ... 

This section focuses solely on the use of a commercially available triazolin-5-ylidene carbene, viz. l,3,4-triphenyl-4,5-dihydro-l//-l,2,4-triazol-5-ylidene. When the stoichiometric reaction between this ligand and [RuCl2(/i-cymene)]2 was carried out in THF, a mixture of product and starting dimer was obtained. NMR analysis showed that coordination of the incoming carbene to the Ru center was accompanied by an orf/to-metaUation of the phenyl substituent in position 1, thereby releasing one equivalent of HCl in solution. Addition of a base (EtN/-Pr2 in excess) drove the reaction to completion and prevented side reactions between the protic acid and the highly reactive free carbene species. Thus, a single adduct could be obtained selectively and quantitatively (Eq. 

In contrast to Ru-24, the reaction between [RUCI2 (p-cymene)]2 as a precursor and an NHC carbene of 1,3,4-triphenyl-triazol-5-ylidene resulted in ortlio-metallation of the phenyl ring in position 1 to form Ru-32.Although the controllability was lower than Ru-24, Ru-32 could polymerize MMA and styrene derivatives (Mw/Mn 1.5). By using other ligands, the p-cymene complexes with a series of NHC ligands were successfully synthesized and used for the metal-catalyzed... 

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