title: Unsymmetrical NCN-pincer mononuclear and dinuclear nickel(ii) complexes of N-heterocyclic carbene (NHC): synthesis, structure and catalysis for Suzuki-Miyaura cross-coupling.
abstract: This report describes the synthesis and characterization of a family of unsymmetrical NCN pincer Ni(ii) complexes 2-8 with NHC-triazole arms. All of these complexes have been fully characterized by X-ray single crystal analysis, NMR spectroscopy, and elemental analysis. Complexes 2 and 4-6 were square planar with a chloride trans to the carbene carbon atoms. Complex 3 was a paramagnetic octahedral complex with its central metal surrounded by two NCN pincer ligands. Complexes 7 and 8 contain [(NHC)2Ni2-OH] moieties bearing a OH bridge. Both the [(NHC)2Ni2-OH] complexes 7 and 8 and [(NCNHCN)Ni-Cl] complexes 2 and 4-6 were synthesized similarly via the reactions of the in situ formed Ag-NHCs from the corresponding imidazolium salts with [NiCl2(PPh3)2]. The catalytic activities of all complexes for Suzuki-Miyaura cross-coupling were examined. Under the optimized conditions, complex 4 was active in the Suzuki-Miyaura cross-coupling reactions of aryl iodides and aryl bromides at 110 °C. Aryl chlorides were successfully coupled in the presence of triphenylphosphine as an additive.
authors.affiliation: School of Materials Science and Engineering, Wuhan Textile University, Wuhan 430200, People's Republic of China. gushaojin@hotmail.com.
authors.forename: Shaojin
authors.identifier: http://orcid.org/0000-0001-8305-7691
authors.initials: S
authors.lastname: Gu
authors.affiliation: School of Materials Science and Engineering, Wuhan Textile University, Wuhan 430200, People's Republic of China. gushaojin@hotmail.com.
authors.forename: Jiehao
authors.initials: J
authors.lastname: Du
authors.affiliation: School of Materials Science and Engineering, Wuhan Textile University, Wuhan 430200, People's Republic of China. gushaojin@hotmail.com.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Huang
authors.affiliation: School of Materials Science and Engineering, Wuhan Textile University, Wuhan 430200, People's Republic of China. gushaojin@hotmail.com.
authors.forename: Yun
authors.initials: Y
authors.lastname: Guo
authors.affiliation: School of Materials Science and Engineering, Wuhan Textile University, Wuhan 430200, People's Republic of China. gushaojin@hotmail.com.
authors.forename: Ling
authors.initials: L
authors.lastname: Yang
authors.affiliation: School of Materials Science and Engineering, Wuhan Textile University, Wuhan 430200, People's Republic of China. gushaojin@hotmail.com.
authors.forename: Weilin
authors.initials: W
authors.lastname: Xu
authors.affiliation: Department of Chemistry, Zhejiang University, Hangzhou, 310028, People's Republic of China. chenwzz@zju.edu.cn.
authors.forename: Wanzhi
authors.initials: W
authors.lastname: Chen