{4,4′-Dimethoxy-2,2′-[2,2-dimethylpropane-1,3-diylbis(nitrilomethylidyne)]diphenolato}nickel(II)

In the title complex, [Ni(C21H24N2O4)], the NiII ion has a slightly distorted square-planar geometry, coordinated by the two N and two O atoms of a new tetradentate Schiff base ligand. The dihedral angle between the planes of the two NiNC3O chelate rings is 14.37 (12)°.

In the title complex, [Ni(C 21 H 24 N 2 O 4 )], the Ni II ion has a slightly distorted square-planar geometry, coordinated by the two N and two O atoms of a new tetradentate Schiff base ligand. The dihedral angle between the planes of the two NiNC 3 O chelate rings is 14.37 (12) .

Experimental
Crystal data [Ni(C 21  We thank Yasouj University and the University of Isfahan for partial support of this work. supporting information   (Gosden et al., 1981;Healy & Pletcher, 1978).
Recently we reported the structure of a copper(II) and nickel(II) complexes with the N,N′-bis(6-methoxysalicylidene)-1,3-diaminopropane ligand (Habibi et al., 2007a,b). The title compound is isostructural with its Cu II and Ni II analogues.

S2. Experimental
A mixture of 6-methoxysalicylaldehyde (2.0 mmol, 304 mg) and 2,2-dimethylpropane-1,3-diamine (1.0 mmol, 102 mg) was dissolved in methanol (10 ml) with stirring for 15 min at room temperature, to give a clear yellow solution. A methanol solution (10 ml) of Ni(OAc) 2 .4H 2 O (1.0 mmol, 249 mg) was then added. The mixture was refluxed for a further 45 min and then filtered. After keeping the filtrate in air for 5 d, dark green block-shaped crystals were formed at the bottom of the vessel on slow evaporation of the solvent, in about 85% yield.

S3. Refinement
All H atoms were placed in geometrically idealized positions and allowed to ride on their parent atoms, with C-H distances in the range 0.93-0.97 Å and with U iso (H) = 1.2 or 1.5 times U eq (C).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.