21Among many transition metal complexes, nickel(II) complexes are interesting, because they provide us complicated features, giving paramagnetic properties with blue color in some cases and diamagnetic properties with yellow color in other cases. 1 We previously reported on dinuclear nickel(II) complexes with some organic chelate ligands having strong-donor atoms, such as thiolate-sulfur and amino-nitrogen, which have square-planar nickel(II), resulting in the diamagnetic property of dinuclear complexes. 2 We also obtained the mixed-spin state of nickel(II) complexes with the coexistence of paramagnetic and diamagnetic nickel(II) ions in the same molecule by introducing an additional donor group to the dinuclear systems.3-5 When chelate ligands have weaker donor atoms, such as pyridine-nitrogen, octahedral paramagnetic nickel(II) complexes were formed. 6 The magnetic interaction between paramagnetic nickel(II) ions is antiferromagnetic in most cases. We observed a ferromagnetic interaction in a dinuclear complex of nickel(II) pivalate.7 Such a ferromagnetic behavior is interesting as a potential magnetic material. Recently we synthesized a dinuclear nickel(II) complex having two-μ-phenolato and μ-aqua bridges with N, N′-disalicylidene-2,2′-(ethylenedioxy)bis(ethylamine) (H2dee), [Ni2(dee)2(μ-H2O)]·2C2H5OH (1), from a reaction of nickel(II) salt and H2dee. 8 In this study, we isolated another dinuclear nickel(II) complex and determined the crystal structure of this complex, which shows a dinuclear core with two-phenolatooxygen bridges and a methanol bridge, as shown in Fig. 1. The presence of the neutral methanol molecule as the bridging group is unique, which was deduced from a charge balance consideration. This paper describes the synthesis, crystal structure, temperature dependence of the magnetic susceptibility, and the electronic spectra of [Ni2(dee)2(μ-CH3OH)]·2CH3OH (2).The ligand H2dee was synthesized by a method described in the literature. 8 The complex was prepared by a 1:1 reaction of H2dee and nickel(II) salt in methanol. To a solution of H2dee (36 mg, 0.1 mmol) in 10 cm 3 of methanol was added 24 mg (0.1 mmol) of nickel(II) chloride hexahydrate. The reaction mixture was stirred overnight at room temperature. The resulting clear-green solution was left for several days to give green crystals. The crystals were collected and dried under a vacuum. Yield, 30 mg (33%). Anal. Found: C, 56.24; H, 5.93; N, 6.16%. Calcd for C43H56N4Ni2O11: C, 56.00; H, 6.12; N, 6.07%. Single crystals suitable for the X-ray structure analysis were obtained from the methanol solution, and the crystal structure was determined by the X-ray diffraction method.