Synthesis and Structure of Silver and Rhodium 1,2,3-Triazol-5-ylidene Mesoionic Carbene Complexes

Abstract

New mono- and bidentate 1,2,3-triazol-5-ylidene mesoionic carbene (MIC) ligands have been synthesized and reacted with silver oxide, forming cationic 1:2 and 2:2 Ag:MIC ([AgL2]Br and [Ag2L2]­[Ag2Br4]) complexes, respectively. These complexes have been isolated and characterized. They were further found to be potent transmetalation agents toward rhodium, resulting in the preparation of mono- and bimetallic rhodium complexes. The reaction of the 2:2 Ag:L complex with [Rh­(COD)2]­BF4 results in the first reported example of a cationic bimetallic rhodium MIC complex. This complex was fully characterized, and its X-ray structure is reported. Interestingly, this complex exhibits various secondary noncovalent interactions in the solid state of the general type C–H···X, where X = F, Cl.

Application of 1,2,3-triazolylidenes as versatile NHC-type ligands: synthesis, properties, and application in catalysis and beyond

“…Despite the large scope of the CuAAC reaction, the vast majority of the ligands reported to date are monodentate and bear alkyl or aryl wingtip groups. Whilst some work has been carried out in increasing the functionality of the ligands, this area is still Journal Name 34 This complex is derived from a related ditriazolium salt that lacks stabilising pyrrol substituents, suggesting that donor substituents may play an important role.…”

Versatile bonding and coordination modes of ditriazolylidene ligands in rhodium(iii) and iridium(iii) complexes

“…The 1 H NMR spectrum of the triazolylidene silver complexes showed a symmetric linker which suggests a dimeric [Ag 2 (trz^E^trz) 2 ] 2+ species rather than a chelating [Ag(trz^E^trz)] + monomer, in agreement with results by Crudden and co-workers. 15 The formation of the silver triazolylidene proceeded at elevated temperatures when using the N-ethyl triazolium salts (refluxing MeCN), while N-aryl triazolium salts reacted under milder conditions and provided the desired triazolylidene silver intermediate at room temperature. Triazolylidene silver complexes were also formed in the absence of a chloride additive, though significant decomposition was observed and yields were typically much lower, presumably because the triazolylidene silver unit is less stabilized by tetrafluoroborate as compared to chlorides.…”

“…To date, two approaches for linking 1,2,3-triazolium salts via either the triazole C4 or N3 position were reported, involving a di-alkyne and a di-azide precursor, respectively. For example, C4-linked ditriazolium salts with rigid aryl-bridges have been metalated with rhodium, 15 ruthenium, 16 nickel, 17 and palladium, 18 leading to bimetallic systems (Fig. 1, A) or CNC-type pincer complexes (B).…”

Copper(I) Complexes of Mesoionic Carbene: Structural Characterization and Catalytic Hydrosilylation Reactions

“…A recent emerging class of carbenes are abnormal, or latterly called mesoionic carbenes, MIC [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. One interesting subclass of these MICs are 1,2,3-triazol-5-ylidenes [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. Since their first report in 2008 by the Albrecht group [ 36 ] these carbenes now belong to one of the “hot topics” in organometallic chemistry.…”

“…Since their first report in 2008 by the Albrecht group [ 36 ] these carbenes now belong to one of the “hot topics” in organometallic chemistry. In the field of catalysis, especially the carbene derivatives of 1,2,3,-triazoles, so-called triazolylidenes, have proven to show superior effects on the catalytic performances in several catalytic processes [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. One reason for this is their easy accessibility, through the copper(I) catalyzed click [3+2] cycloaddition reaction between azides and alkynes [ 51 , 52 ].…”