Crystal structure of bis­{μ-2-meth­oxy-6-[(methyl­imino)­meth­yl]phenolato}bis­({2-meth­oxy-6-[(methyl­imino)­meth­yl]phenolato}nickel(II)) involving different coordination modes of the same Schiff base ligand

The structure of the title compound, [Ni2(C9H10NO2)4], is built up by discrete centrosymmetric dimers. Two nitro­gen and three oxygen atoms of two Schiff base ligands singly deprotonated at the phenolate site form a square-pyramidal environment for each metal atom. The ligands are bonded differently to the metal centre: one of the phenolic O atoms is bound to one nickel atom, whereas another bridges the two metal atoms to form the dimer. The Ni—N/O distances fall in the range 1.8965 (13)–1.9926 (15) A, with the Ni—N bonds being slightly longer; the fifth contact of the metal to the bridging phenolate oxygen atom is substanti­ally elongated [2.533 (1) A]. A similar coordination geometry was observed in the isomorphous Cu analogue previously reported by us [Sydoruk et al. (2013). Acta Cryst. E69, m551–m552]. In the crystal, the [Ni2L4] mol­ecules form sheets parallel to the ab plane with the polar meth­oxy groups protruding into the inter­sheet space and keeping the sheets apart. Within a sheet, the mol­ecules are stacked relative to each other in such a way that the Ni2O2 planes of neighbouring mol­ecules are orthogonal.