Electronic spectrum and magnetic properties of a dinuclear nickel(II) complex with two nickel(II) ions of C2-twisted octahedral geometry

A dinickel(II) complex [Ni-2(sym-hmp)(2)](BPh4)(2)center dot 3.5DMF center dot 0.5(2-PrOH) (1) was synthesized with a dinucleating ligand, 2,6-bis[(2-hydroxyethyl)methylaminomethyl]-4-methyl-phenol [H(sym-hmp)]. The complex 1 (C90H118.50B2N7.50Ni2O10) crystallized in the triclinic space group P1 1 with dimensions a = 14.7446(4) angstrom, b = 15.4244(4) angstrom, c = 18.7385(6) angstrom, alpha = 86.9495(9)degrees, beta = 76.7263(10)degrees, gamma = 86.5370(8)degrees, and V = 4136.8(2) angstrom(3) and with Z = 2; this is isomorphous to a previous cobalt(II) complex [Co-2(sym-hmp)(2)] (BPh4)(2). Single-crystal X-ray analysis revealed a bis(mu-phenoxo) dinickel(II) core structure containing two distorted octahedral nickel(II) ions of C-2 symmetry. The order of the coordination bond lengths is Ni-O(phenoxo) < Ni-O(hydroxy) < Ni-N. The electronic spectrum of 1 was typical for the octahedral nickel(II) complexes, but the axial elongation and the C-2-twist of the equatorial plane were found after a detailed analysis. The bond angles obtained by the electronic spectrum agreed with the crystallograph obtained bond angles within 2.3 degrees. The order of the AOM parameters was e(sigma,O(phenoxo)) > e(sigma,O(hydroxy)) > e(sigma,N), which was consistent with the order of the coordination bond lengths. Magnetic susceptibility data for 1 were fitted well with the parameters 2J = -69.7 cm (1), D = 0.00 cm (1), g = 2.17, and TIP = 265 x 10 (6) cm(3) mol (1). The result indicates significant antiferromagnetic exchange interaction and negligible zero-field splitting, while the isostructural cobalt(II) complex showed an anisotropic behavior. (C) 2010 Elsevier B. V. All rights reserved.