Tris{2-methoxy-6-[(4-methylphenyl)iminiomethyl]phenolate-κ2 O,O′}tris(thiocyanato-κN)lanthanum(III)

In the title compound, [La(NCS)3(C15H15NO2)3], the metal centre is nine-coordinated by six O atoms from three zwitterionic Schiff base 2-methoxy-6-[(4-methylphenyl)iminiomethyl]phenolate (L) ligands and three terminal N atoms of the thiocyanate ions in a monocapped square-antiprismatic environment. The L ligands chelate the LaIII ion with strong La—O(deprotonated phenolic) bonds [2.435 (3)–2.464 (3) Å] and significantly longer La—O(methoxy) bonds [2.801 (3)–2.831 (3) Å]. The La—N bond lengths range from 2.541 (4) to 2.605 (4) Å.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: PV2228).

S1. Comment
The rare earth complexes prepared by ligands derived from o-vanillin have been reported in the past decades due to the intriguing biological activities of o-vanillin and the varied structures and behaviors of the Schiff bases (Yeap et al., 2003).
For these reasons, we have been engaged in the syntheses of new analogous Schiff bases derived from o-vanillin and their rare metal complexes. For the past few years we have synthesized and reported several Schiff complexes (Zhao et al., 2007;Liu et al., 2009). Herein, we describe the crystal structure of a new lanthanum(III) complex, (I).
The structure of the title compound is shown in Fig. 1  (phenolic) distances. The La-N bonds vary from 2.541 (4)Å to 2.605 (4) Å. These bond lengths correspond to those previously observed (Liu et al., 2009). While in contract to the isomorphous Ce III complex, the La-X (X = O/N) are slightly longer than the corresponding distances reported in the Ce III complex (Liu et al., 2009), which can be attribute to a decrease in the ionic radii from La III to Ce III due to the lanthanide contraction. Because of the geometric and chemical environment requirements of the chelating groups the coordination geometry deviates considerably from the distorted capped square antiprism geometry (Fig. 2). In the HL ligands, the protons of the phenolic groups are considered to have transferred to N-imine atoms, which are involved in intramolecular hydrogen bonds (Table 1) that probably forces them to assume nearly planar conformations.
A solid product (HL) was separated from the solution after stirring for about 10 min. and was purified by recrystallization from ethanol.
To a methanol solution of N-3-methoxysalicylidene-p-toluidine (HL) (3 mmol, 10 ml) was dropped 1 mmol La(Cl 3 ) 3 .6H 2 O (dissolved in methanol) under stirring condition and the mixture solution was still stirred at room temperature for 8 h to give a purplish red solution. The deposit was filtered out and the solution was kept for evaporating.
The red crystals of the title compound (I) were formed after several days.

S3. Refinement
The H atoms bonded to C and N atoms were positioned geometrically and refined using a riding model with C-H distances: 0.96, 0.93 and 0.86 Å for aliphatic, aromatic and imino H-atoms, respectively, and U iso (H) = 1.5U eq (C- aliphatic) or 1.2U eq (the rest of the parent atoms).

Figure 1
The molecular structure of the title complex, showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 30% probability level.  The coordination environment of the lanthanum(III) atom, showing the monocapped square antiprism.

Tris{2-methoxy-6-[(4-methylphenyl)iminiomethyl]phenolate-κ 2 O,O′}tris(thiocyanato-κN)lanthanum(III)
Crystal data  Hydrogen site location: inferred from neighbouring sites H-atom parameters constrained where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.002 Δρ max = 0.53 e Å −3 Δρ min = −0.54 e Å −3 Special details Experimental. HL product: yield = 80%, (m.p. 373-374 K). Analysis calculated for C 15 H 15 NO 2 : C 74.66, H 6.27, N 5.81%; found: C 74.62, H 6.31, N 5.77%. 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.