Simple Synthesis of CpNi(NHC)Cl Complexes (Cp = Cyclopentadienyl; NHC = N-Heterocyclic Carbene)

Abstract

The reaction of saturated and unsaturated imidazolium salts with nickelocene in refluxing THF results in the formation of NHC complexes of general formula CpNi(NHC)Cl (NHC ) SIMes (2), IPr (3), SIPr ( 4)). This protonation of Cp 2 Ni was also tested using phosphonium salts, and the reaction of nickelocene with triethylphosphonium chloride leads to CpNi(PEt 3 )Cl ( 5). All compounds were characterized by NMR and X-ray crystallography. The catalytic activity of the NHC compounds was tested in aryl amination (Buchwald-Hartwig reaction) and in aryl halide dehalogenation reactions.

Synthesis, Structure, and Polymerization Activity of Cyclopentadienylnickel(II) N‐Heterocyclic Carbene Complexes: Selective Cross‐Metathesis in Metal Coordination Spheres

“…The presence of ligand L1 does not produce a significant distortion in the Ni coordination sphere when compared with related complexes. [1][2][3] …”

“…[1] A number of complexes of the general formula [(RC 5 H 4 )Ni(X)(NHC)] (X = Cl, Br, I; NHC = N-heterocyclic carbene) have since been prepared by us [2] and others [3] in a similar fashion since this seminal publication. Complexes of this type display catalytic activity in aryl dehalogenation and aryl amination, [3a] styrene polymerization in the presence of MAO, [2] and hydrothiolation of alkynes.…”

Well‐Defined Allylnickel Chloride/N‐Heterocyclic Carbene [(NHC)Ni(allyl)Cl] Complexes as Highly Active Precatalysts for CN and CS Cross‐Coupling Reactions

“…However, only aryl bromides could be coupled with less basic amines such as anilines at higher temperatures and longer reaction times (100 8C, 24 h). Similar conditions were described for Nolans system [13] employing [CpNiA C H T U N G T R E N N U N G (NHC)Cl] as precatalysts in aryl amination reactions (105 8C, 7-20 h). Compared to these precedents, our system provides better conversions under milder conditions.…”

“…These complexes are easily reduced to the active Ni(0) species (the former in the presence of NHC ligands) without the aid of external reductants. In addition, a family of phosphane-free Ni(II)-NHC complexes of composition [CpNiA C H T U N G T R E N N U N G (NHC)Cl] [13] have been reported to exhibit only moderate catalytic activity in both aryl halide dehalogenation and aryl amination reactions. Such a low ac-tivity could be the result of the lack of an easy reduction of Ni(II) precursors to Ni(0) species.…”

Metal compounds with rigid polyaromatic ligands. Catalytic consequences

“…59 Los complejos a base de paladio 3A, 3B y 7C, fueron preparados siguiendo un protocolo para compuestos de paladio similares. 60 Todos los nuevos complejos fueron caracterizados mediante técnicas espectroscópicas de RMN, espectrometría de masas y análisis elemental.…”