Mesoionic Triazolylidene Nickel Complexes: Synthesis, Ligand Lability, and Catalytic C–C Bond Formation Activity

Synthesis, Structures and Properties of Half‐Sandwich Nickel(II) Complexes with Backbone‐Modified NHC Ligands

“…Non‐equivalence of these hydrogen atoms bonded to the same carbon atom originates from the restricted rotation of the Ni–C carbene or N–C Bn bonds. Similar dynamic behaviour was observed for some dialkyl or mixed alkyl‐aryl nickel NHC complexes 6c,6f,10,23. The nature of such restricted rotation has been attributed mainly to steric factors related to the bulkiness of halogen or Cp ligands, although electronic factors cannot be completely excluded 6d,6f.…”

“…This procedure, developed by Abernethy et al, has proved to be versatile and has resulted in a considerable number of different NHC complexes of the general formula [Ni(η 5 ‐C 5 H 4 R)(X)(NHC)] ( 1 , R = H or alkyl; X = Cl, Br or I) 6,7. These complexes serve as precatalysts in a remarkably broad range of transformations, such as amination of aromatic halides,6a,6i polymerization of styrene,6b,6f polymerization of methyl methacrylate,8 Suzuki–Miyaura cross‐coupling,6g,9,10 polymerization of phenylacetylene,6f regioselective hydrothiolation of alkynes,11 hydrosilylation of aldehydes, ketones and imines,12 and α‐arylation of acyclic ketones 13…”

Metal Complexes of Click-Derived Triazoles and Mesoionic Carbenes: Electron Transfer, Photochemistry, Magnetic Bistability, and Catalysis

“…Until now, this route has worked the best for synthesizing palladium complexes, where precursors such as Pd(OAc) 2 or Pd(acac) 2 were used for this purpose (Scheme ). Additionally, nickel complexes have been prepared by this route by using nickelocene as a precursor . In some cases, the halides, which are counter‐anions in the triazolium salts, end up as ligands on the central metal atoms.…”

“…Nickel complexes have also been reported with monodentate triazolylidene ligands L15 . Depending on the reaction conditions, three different types of nickel complexes could be isolated ( 103 , 104 + , and 105 , Figure ) . These complexes were used as pre‐catalysts for the Suzuki‐Miyaura cross‐coupling reaction.…”

“…These complexes were used as pre‐catalysts for the Suzuki‐Miyaura cross‐coupling reaction. Even though the complexes formed somewhat active catalysts, their lifetime turned out to be a problem, and this was ascribed to the lability of the Ni‐triazolylidene bond . A trinuclear nickel complex, 106 , containing additional cyclopentadienyl (Cp) ligands was also recently reported.…”