Mesoionic thiazol-5-ylidenes as ligands for transition metal complexes

Abstract

The first examples of thiazol-5-ylidene complexes featuring group 9, 10 and 11 metal centers, have been prepared by deprotonation of a series of 2,3,4-triaryl-susbtituted thiazolium salts in the presence of the corresponding transition metal precursor.

Silver‐Catalyzed Amidiniumation of Alkynes: Isolation of a Silver Intermediate, Synthesis of Enamine Amido Carbene Precursors, and an Unprecedented Umpolung of Propiolamide

“…X -ray crystallography undoubtedly confirmed the formation of 11 (Figure 2). [15] TheA u À Cb ond [2.005- (8) ] is similar to that observed for the abnormal thiazol-5ylidene gold complex [2.005 14] [20] and shorter than those in vinyl gold complexes (2.04-2.06 ), [19] thus indicating that 11 is more like an abnormal carbene (aNHC) complex than av inyl gold complex. Thea urated species 11 represents as carce example of an onheteroatom-substituted carbene coinage-metal complex.…”

Silver‐Catalyzed Amidiniumation of Alkynes: Isolation of a Silver Intermediate, Synthesis of Enamine Amido Carbene Precursors, and an Unprecedented Umpolung of Propiolamide

“…X‐ray crystallography undoubtedly confirmed the formation of 11 (Figure 2). 15 The AuC bond [2.005(8) Å] is similar to that observed for the abnormal thiazol‐5‐ylidene gold complex [2.005(14) Å]20 and shorter than those in vinyl gold complexes (2.04–2.06 Å),19 thus indicating that 11 is more like an abnormal carbene ( a NHC) complex than a vinyl gold complex. The aurated species 11 represents a scarce example of a nonheteroatom‐substituted carbene coinage‐metal complex 21.…”

“…The gold species 5 represents a rare gold intermediate in gold‐catalyzed exo ‐dig cyclization of terminal alkynes. Only one isolable vinyl gold species derived from a terminal alkyne was reported by Hashmi and co‐workers before 20a. Interestingly, hydolysis of 5 with HOTf can immediately afford the bis(hydroxyimidazol)ium salt 2 b with excellent yield, thus indicating the formation of B during the process [Eq.…”

Synthesis and Catalytic Activity of Coumarin‐ and Chrysin‐Tethered Triazolylidene Gold(I) Complexes

“…These type of ligands where the carbene center is not flanked by heteroatoms in both sides of their structures, have attracted a great deal of attention as they have demonstrated enhanced σ‐donor properties compared to classical N‐heterocyclic carbenes (NHCs) . Among the several types of mesoionic carbenes available in the literature (Scheme ) including pyrazol‐4‐ylidenes ( A ), imidazol‐5‐ylidenes ( B ), thiazol‐5‐ylidenes ( C ) and oxazol‐4‐ylidenes ( D ), the coordination chemistry of 1,2,3‐triazolylidenes ( E ) have found a wide range of applications as ligands for transition metals, typically employed in a variety of homogeneous catalysis processes …”