MOLECULAR STRUCTURE OF NICKEL(II) AND COPPER(II) N, N′-ETHYLENE-BIS(ACETYLACETONEIMINATES) MO2N2C12H18 ACCORDING TO GAS-PHASE ELECTRON DIFFRACTION DATA AND QUANTUM-CHEMICAL CALCULATIONS

The molecular structure of nickel(II) and copper(II) N, N'-ethylene-bis(acetylacetoneiminates), NiO2N2C12H18 and CuO2N2C12H18, at 442(5) K and 425(5) K, respectively. Both molecules have C-2 symmetry with a nearly planar MN2O2 coordination site and internuclear distances rh(1)(MO) = 1.862(10)/1.923(17) angstrom and rh(1)(M-N) = 1.879(10)/1.947(18) angstrom for Ni(acacen) and Cu(acacen), respectively. The structure of free molecules is close to the structure of molecules in crystal. The DFT/B3LYP quantum-chemical calculations (CEP-31G and 6-31G* basis sets) gave a molecular structure that agreed satisfactorily with the one found in experiment. The low-spin (1)A and high-spin (3)A states of the Ni(acacen) molecule were considered. It was found that a change in multiplicity caused significant changes in the geometrical and electronic structure of the MN2O2 coordination site. As shown by experiment and calculations for the NiO2N2C12H18 molecule, the low-spin (1)A state is the ground state. The internal rotation of CH3(CN) and CH3(CO) methyl groups was studied by the B3LYP/CEP-31G method. It was shown that steric hindrances led to a high rotation barrier of the CH3(CN) group.