Nitrite-bonded nickel(II) complex of N-cyclohexyl-N-(2-pyridinylmethyl)amine; Synthesis, spectroscopic characterization, X-ray structure and DFT calculations

Abstract

A combined experimental and computational investigation on a nickel(II) complex of N-cyclohexyl-N-(2-pyridinylmethyl)amine, L, was carried out. The compound [NiL2(ONO)]NO2·½CH3CN has been prepared by the addition of L to a suspension of K4[Ni(NO2)6]·H2O in methanol and structurally characterized by a combination of analytical, spectroscopic and crystallographic methods. The nickel(II) center in the complex is surrounded by two amine nitrogen and two oxygen atoms of the nitrite ion (η2-ONO) in the basal plane and two nitrogen atoms of pyridine moieties in apical positions, forming a distorted octahedral geometry. The relative stability of the geometrical isomers (cis and trans) and linkage isomers (η1-NO2, η2-ONO and η1-ONO) of the complex were investigated by density functional theory (DFT) calculations. In support of the X-ray structure, the calculated results verified that in all cases the cis-bidentate η2-ONO isomer is more stable than the other four-coordinated nitro isomers. A further theoretical analysis of the electronic structure of the complex has also been carried out to achieve deeper insight into the properties of the relevant molecular orbitals.