Synthesis and Structural Characterization of the First Bis(benzimidazolin-2-ylidene) Complexes of Nickel(II)

Abstract

The reaction of Ni(OAc) 2 with the benzimidazolium salts 1,3-dimethylbenzimidazolium iodide (1), 1,3-bis(2-propenyl)benzimidazolium bromide (2), 1,3-dipropylbenzimidazolium bromide (3), 1-(2propenyl)-3-methylbenzimidazolium bromide ( 6), and 1-propyl-3-methylbenzimidazolium iodide (7) in molten [Bu 4 N]X (X ) Br, I, BF 4 ) as ionic liquid afforded novel square-planar nickel(II) bis(benzimidazolin-2-ylidene) complexes of the general formula trans-[NiX 2 (NHC) 2 ] (X ) I, NHC ) 1,3-dimethylbenzimidazolin-2-ylidene, 8; X ) Br, NHC ) 1,3-bis(2-propenyl)benzimidazolin-2-ylidene, 9; X ) Br, NHC ) 1,3-dipropylbenzimidazolin-2-ylidene, 10; X ) Br, NHC ) 1-(2-propenyl)-3-methylbenzimidazolin-2-ylidene, 11; X ) I, NHC ) 1-propyl-3-methylbenzimidazolin-2-ylidene, 12). X-ray diffraction studies of 8-12 reveal a square-planar coordination geometry for all complexes with the carbene ligands arranged in a trans fashion.

[NiX2(NHC)2] Complexes in the Hydrosilylation of Internal Alkynes

“…In the cases in which the melting point of the imidazolium salt was too high for the reaction to occur successfully an additional low-melting salt, tetrabutylammonium halide, was added as a solvent, in an adaptation of the original procedure reported by Huynh et al [18] After aqueous work-up and purification, the [NiX 2 (NHC) 2 ] complexes were obtained as stable, orange-red to purple powders. Complexes 3c, 3d, 4a and 4f have been synthesized before, following these literature procedures.…”

Ligand Exchange at a Gold(I) Carbene Complex

“…Complexes with benzimidazolin-2-ylidene donors can be obtained from coordinatively unsaturated transition metal complexes and the free benzimidazolin-2-ylidene [11,12] or by cleavage of dibenzotetraazafulvalenes in the presence of suitable transition metal compounds [13,14]. The most facile routes to benzimidazolin-2-ylidene complexes, however, is the in situ deprotonation of a benzimidazolium salt in the presence of a metal complex bearing basic ligands like [Pd(OAc) 2 ] [15 -17] or [Ni(OAc)] [18,19]. Alternatively, the carbene transfer reaction can be based on NHC complexes possessing a labile M-C NHC bond, which allows a transfer of the carbene ligand to another metal center [20].…”

Normal and abnormal carbene complexes derived from thiazole: Preparation and a preliminary investigation of their relative catalytic performance

“…Representative molecular structure of the cationic complex 2b (50% probability ellipsoids, hydrogen atoms, counter ions and second independent molecule omitted). The Ni-Br bond length of 2.3099(9) Å in 1a is significantly shorter than in other normal 2-imidazolylidene nickel complexes [30,31]. The two rather similar Pd-Br bond distances in the abnormal(N) and abnormal(S) thiazolylidene complexes 2b and 3b (ca.…”

“…All the product complexes display a single signal in their 31 P NMR spectra indicating the presence of two trans-orientated phosphine groups. Phenyl protons and carbon atoms of these ligands resonate in the same region as previously found for related pyridylidene complexes [15].…”