Triazolylidene ligand

Very recently, transition metal complexes were reported where 1,2,3-triazolium salts served as precursors for 1,2,3-triazolylidene ligands (Mathew, Neels et al. 2008). However, application of these carbene complexes as catalysts in organic synthesis has not been reported so far. We tried to apply an in situ procedure in Suzuki reaction using Pd2(dba)3,... 

Scheme 3.6 Selective protonation of the abnormal triazolylidene ligand in the mixed bis(carbene) ruthenium complex 28 to form the olefin metathesis active species A.

A series of ruthenium complexes bearing triazolylidene ligands was syn-thethized and evaluated for catalytic water oxidation with CAN as a sacrificial... 

Till now, triazolylidene and thiazolylidene have been scarcely studied as TM ligands, althongh they find numerous applications in organocatalysis. The stabiUty of complexes binding these types of NHC has not been extensively reported and could explain why their use remains scarce. As an example, metathesis ruthenium-based catalyst (170) first synthesized by Fiirstner exhibited a moderate activity in metathesis transformations in relation to its poor stability in solution. This problem of reactivity/stability has been pointed out in others reports. ... 

A carbene derived from triazole was used in IPA with K2CO3 as base, for direct reductive amination of aldehydes with primary amines to form secondary amine products [179]. Other recent examples include (1) a base-free catalyzed reduction of a series of C=0 bonds and of the C=N bond of benzylideneaniline (>99 % conversion was achieved in 48 h, with 0.1 mol% catalyst) [180] (2) heteroditopic dicarbene Rh(I) and Ir(I) complexes containing 1,2,3-triazolylidene-imidazolyli-dene ligands, mostly tested on acetophenone but with one imine example [181] (3) Ir complexes of A-benzyl-substituted A-heterocyclic carbenes where 0.5 mol% catalyst is used with 5 % KOH in IPA in reductions to give products in >99 %... 

Herrmann and co-workers reported the first use of chiral NHC complexes in asymmetric hydrosilylations in 1996. The hydrosilylation of acetophenone in the presence of catalyst 111 at 20 °C gave more than 90% conversion into the desired silyl ether and afforded optical inductions of up to 30% ee (Figure 13.20). Subsequently, Enders and co-workers reported the preparation of chiral [(triazolylidene)Rh(COD)] complexes 112, which incorporated the C -symmetrical NHC ligand for the asymmetric hydrosilylation of methyl ketones. After hydrolysis, the desired alcohols were obtained in 40 90% yield and up to 44% Recently, Ros et al. reported the evaluation of... 

Sluijter SN, Elsevier CJ. Synthesis and reactivity of heteroditopic dicarbene rhodium(I) and iridium(I) complexes bearing chelating 1,2,3-triazolylidene—itnidazolylidene ligands. Organometallics. 2014 33 6389-6397. 

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