ABSTRACT
New well-defined, paramagnetic nickel complexes have been prepared and characterized by X-ray crystallography. The complexes were found to be active for the cross-coupling of alkyl electrophiles (especially ethyl 2-bromobutyrate) with alkyl Grignard reagents. The ligand architecture in these new complexes could potentially be rendered chiral, opening up future possibilities for performing asymmetric cross-coupling reactions.
Subject(s)
Aminophenols/chemical synthesis , Coordination Complexes/chemical synthesis , Nickel/chemistry , Crystallography, X-Ray , Models, Molecular , Molecular ConformationABSTRACT
The synthesis of a bis(amino)amide nickel pincer complex bearing a perfluoroethyl ligand was effected by reaction of the corresponding nickel chloride complex with cesium fluoride and trimethyl(pentafluoroethyl)silane. Electrochemical experiments revealed that the oxidation of the LNi-C(2)F(5) complex occurs at the same potential as the LNi-Cl derivative, but reduction of the LNi-C(2)F(5) complex occurs at slightly more positive potentials. The similarity of the electrochemical data was corroborated by density functional theory (DFT), which predicts that the energies of the HOMOs (HOMO = highest occupied molecular orbital) and LUMOs (LUMO = lowest unoccupied molecular orbital) of the LNi-C(2)F(5) and LNi-Cl complexes are equal in magnitude. DFT also revealed that the HOMOs of the bis(amino)amide nickel pincer complexes are primarily ligand in character, while the LUMOs are predominantly metal in character, supporting redox-activity with this ligand.
