A macrocyclic silver polycarbene complex based on 1,2,4-triazole units: synthesis and postsynthetic modification

Abstract

A method for the synthesis of a new rectangular 1,2,4-triazole-containing macrocycle via photochemical [2 + 2] cycloaddition with a metal–carbene template was developed.

C3‐Symmetric Assemblies from Trigonal Polycarbene Ligands and MI Ions for the Synthesis of Three‐Dimensional Polyimidazolium Cations

“…These resonances are only slightly shifted from the equivalent resonances of the hexakisimidazolium salt H 6 ‐ 1 b (PF 6 ) 6 (Figure a). After irradiation, the olefin doublet resonances disappeared and two new characteristic peaks for the cyclobutane protons of [Ag 6 ( 2 b )](PF 6 ) 6 appeared at δ =4.41 and 4.00 ppm (both d, 3 J =4.5 Hz) (Figure c) –. Similar observations were made for the other hexanuclear silver and gold complexes upon irradiation.…”

The key role of R–NHC coupling (R = C, H, heteroatom) and M–NHC bond cleavage in the evolution of M/NHC complexes and formation of catalytically active species

“…Protonolysis reactions proceed very easily for Li/NHC 105 , 108 and Mg/NHC 112 complexes. Other complexes, including Ag I /NHC, 191 , 193 , 197 – 199 , 201 Al III /NHC, 119 In III /NHC, 119 Y III /NHC 125 and Ce III /NHC, 125 Mn I /NHC, Zn II /NHC, 213 Mo VI /NHC 130 and Ni II /NHC, 214 are also susceptible to protonolysis; the efficiency depends on the structure of NHC ligands, co-ligands and reaction conditions ( Table 1 column 3). For example, (NHC) 2 NiX 2 complexes (X = Cl, Br, I) suffer facile hydrolysis in aqueous MeCN or THF at 70 °C to give azolium salts and Ni(OH) 2 .…”

Preparation and Post-Assembly Modification of Metallosupramolecular Assemblies from Poly(N-Heterocyclic Carbene) Ligands

“…Upon irradiation, metallacycles of type 429 also react via [2 + 2] cycloaddition of two adjacent cinnamic ester groups with formation of two cyclobutane rings. Removal of the metal ions to yield the macrocyclic tetrakis­(1,2,4-triazolium) salts was also possible …”

“…Color code: silver, pink; oxygen, red; nitrogen, blue; carbon, gray. Adapted with permission from ref . Copyright 2018 Royal Society of Chemistry.…”

“…Removal of the metal ions to yield the macrocyclic tetrakis(1,2,4-triazolium) salts was also possible. 262 Modifying the linker bridging the NHC donors in bisimidazolium salts as well as changing of the terminal olefin groups for the cycloaddition proved easily possible. For example, bis-NHC proligands L130 and L131 featuring an aromatic linker and coumarin pendants were used to prepare the metallacycles 430 and 431 (Scheme 97).…”