A gold(I) N-heterocyclic carbene (NHC) complex mediated hydroamination of an alkyne has been modeled using density functional theory (DFT) study. In this regard, alkyne and amine coordination pathways have been investigated for the hydroamination reaction between two representative substrates, namely, MeC≡CH and PhNH(2), catalyzed by a gold(I) NHC based (NHC)AuCl-type precatalyst, namely, [1,3-dimethylimidazol-2-ylidene]gold chloride. The amine coordination pathway displayed a lower activation barrier than the alkyne coordination pathway. The catalytic cycle is proposed to proceed via a crucial proton-transfer step occurring between the intermediates [(NHC)AuCH═CMeNH(2)Ph](+) (D) and [(NHC)Au(PhNHMeC═CH(2))](+) (E), the activation barrier of which was found to be significantly reduced by a proton relay mechanism process assisted by the presence of any adventitious H(2)O molecule or even by any of the reacting PhNH(2) substrates. The final hydroaminated enamine product, PhNHMeC═CH(2), was further seen to be stabilized in its tautomeric imine form PhN═CMe(2).

A series of palladium complexes of the abnormal N-heterocyclic carbene ligands of the type (a-NHC)PdI2(L) [L = NC5H5(1-3)b and PPh3(1-3)c] effectively catalyzed the Hiyama coupling of aryl bromides and iodides with PhSi(OMe)3 under the highly desired fluoride-free conditions. Interestingly enough, the pyridine based trans-(1-3)b complexes and a PPh3 derived cis-3c complex exhibited higher yields than the related PPh3 derived trans-(1-2)c complexes. The superior performances of the pyridine based trans-(1-3)b complexes and the PPh3 derived cis-3c complex have been correlated to a tighter binding of the a-NHC ligand to the palladium center in these complexes, leading to a greater (a-NHC) ligand influence on the metal center partaking in the catalysis.

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A series of nickel‐based chiral bifunctional catalysts (1d–3d) with N‐heterocyclic carbene (NHC) ligands derived from (1R)‐(–)‐menthol, (1S)‐(–)pinene, and (1R)‐(+)‐camphor have been successfully designed for asymmetric Michael addition reactions under base‐free conditions. The NHC complexes, namely, [1‐R‐3‐{N‐(phenylacetamido)}imidazol‐2‐ylidene]2Ni [R = (1S)‐menthyl (1d), (1S)‐pinane (2d), and (1R)‐isobornyl (3d)], bearing chiral ancillaries on the amido‐functionalized side arms of the NHC ligands, performed the bifunctional catalysis of the asymmetric base‐free Michael addition reaction of the α‐methyl cyano ester substrates ethyl 2‐cyanopropanoate (4), isopropyl 2‐cyanopropanoate (5), and tert‐butyl 2‐cyanopropanoate (6) with the activated olefinic substrates methyl vinyl ketone (7) and acrylonitrile (8) in 63–98 % yields with enantiomeric excess (ee) values of 2–75 % at room temperature in 8 h. More interestingly, only the longest of the three catalysts, the menthol derivative 1d, showed significant chiral induction of up to 75 % ee; this has been attributed to the reduction of the steric influence owing to the relatively distant dispositions of the chiral ancillaries from the catalytically active metal center that arise as a consequence of the cis geometries of 1d–3d.

Synthesis, structure and density functional theory (DFT) studies of a series of new ruthenium complexes, [1-(R)-3-N-(benzylacetamido)imidazol-2-ylidene]RuCl(p-cymene) [R = Me (1c), i-Pr (2c), CH 2 Ph (3c); p-cymene = 4-i-propyltoluene] supported over N /O-functionalized N-heterocyclic carbene (NHC) ligands are reported. In particular, the ruthenium (1-3)c complexes were synthesized from the respective silver complexes, [1-(R)-3-N-(benzylacetamido)imidazol-2-ylidene] 2 Ag + Cl − [R = Me (1b), i-Pr (2b), CH 2 Ph (3b)] by the treatment with [Ru(p-cymene)Cl 2 ] 2 in 65-76% yields. The molecular structures of (1-3)c revealed the chelation of the N-heterocylic carbene ligand through the carbene center and an amido sidearm of the ligand in all of the three complexes. The density functional theory studies on the ruthenium (1-3)c complexes indicated strong binding of the NHC ligand to the metal center as was observed from the deeply buried NHC-Ru σ-bonding molecular orbitals.