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

Abstract

A number of nickel(II) dihalide complexes with small monodentate N-heterocyclic carbene ligands was synthesized and tested for their catalytic activity in the hydrosilylation of internal alkynes. The nickel(0) active species was obtained from the starting nickel(II) complex by reduction with diethylzinc. In all cases the catalytic reaction yielded the syn product selectively. The fastest catalysts reached full conversion

4‐Alkylated Silver–N‐Heterocyclic Carbene (NHC) Complexes with Cytotoxic Effects in Leukemia Cells

“…The two NHC–silver complexes of this study can be prepared via two different pathways. Because 4-methylimidazole 1 is commercially available, a short pathway leading to NHC-1 was established, a synthesis that comprises a) N-arylation,27 b) N-methylation,28 and c) complexation with silver29 to obtain the NHC-1 silver complex. The overall sequence provides a yield of 30 %, which corresponds to a mean step yield of 67 %.…”

“…The liberated imidazole derivative 12 was N-arylated [step (g)] by using bromobenzene in toluene with Pd 2 (dba) 3 and Me 4 t BuXPhos as ligand27 in good yield (78 %). The last organic reaction step of the synthetic pathway involved conversion of the imidazole derivative into an imidazolium salt28 14 from the N -aryl-4-subsituted imidazole derivative 13 by reacting with methyl iodide at reflux in THF to obtain the N 1-phenyl- N 3-methyl-4-methylimidazolium iodine salt 14 (57 %). Finally, the target silver salts were prepared by using silver(I) oxide in dichloromethane 29.…”

Nickel N-heterocyclic carbene complexes and their utility in homogeneous catalysis

“…A large number of the benzimidazole, imidazole and the triazole based N-heterocyclic carbene complexes of the type (NHC) 2 NiX 2 (343−359), [122,126] (360), [127] (361−364), [128] (365−366), [122] (367), [129] (368), [50,129] (369−371), [129] (372), [130] (373), [127] (374), [131] (375), [132] (376−377), [133] (378), [134] (379), [135] (380), [136] (381−382), [86] (383−384), [137] (385−386), [138] (387−388), [124] (389−392), [110] (393), [139] (394), [47] (395−396), [140] (397−398) [141] and (399−400) [127] were conveniently synthesized by the direct method from the reaction of a free or an in situ generated NHC ligand with a Ni(II) precursor namely, Ni(OAc) 2 , bis-indenyl nickel (Ind) 2 In the third approach, the oxidation method has been used in the preparation of the (402), [125] (403−404), [143] (405), [144] (441) [32] and (446−447) [62] Additional notable examples of the oxidation method include a large number of complexes (367−368), [145] (406−409), [146] (410−411), [40] (412), [147] (413−416), [21] (417−420), [41] (421−422), [148] (423−...…”

“…The first route is the transmetallation method (Scheme 13), which was used for preparing the following complexes (336), [120] (337), [121] (338), [122] (339−340) and [123] (341) [124] from the respective Ag−NHC complexes and (342) [125] from a Cu−NHC complex by the treatment with the Ni(II) precursors namely, (DME)NiX 2 (X = Cl, Br) and (PPh 3 ) 2 NiX 2 (X = Br, Cl).…”

“…The (338), (347), (349−350), (353−354), (356), (360), (362−363) and (365−366)complexes effectively catalyzed the hydrosilylation reactions of internal alkynes[122].…”