Crystal structure of bis-{2-[(E)-(4-meth-oxy-lbenz-yl)imino-meth-yl]phenolato-κ(2) N,O (1)}nickel(II).

The asymmetric unit of the title compound, [Ni(C15H14NO2)2], comprises an Ni(II) cation, lying on an inversion centre, and a Schiff base anion that acts as a bidentate ligand. The Ni(II) cation is in a square-planar coordination environment binding to the imine N and phenolate O atoms of the two Schiff base ligands. The N- and O-donor atoms of the two ligands are mutually trans, with Ni-N and Ni-O bond lengths of 1.9191 (11) and 1.8407 (9) Å, respectively. The plane of the meth-oxy-benzene ring makes a dihedral angle of 84.92 (6)° with that of the phenolate ring. In the crystal, mol-ecules are linked into screw chains by weak C-H⋯O hydrogen bonds. Additional C-H⋯O hydrogen bonds, together with C-H⋯π contacts, arrange the mol-ecules into sheets parallel to the ac plane.

Chemical context

Schiff bases have often been used as chelating ligands in coordination chemistry as they readily form stable complexes with most transition metal ions (Kalita et al., 2014 ▶; Mohamed et al., 2010 ▶). Metal complexes of Schiff bases containing nitro­gen and other donor atoms have received attention because of their stability, biological activity (Islam et al., 2014 ▶) and potential applications in other fields, such as catalysis (Mohd Tajuddin et al., 2012 ▶).

The title compound, bis­{2-[(E)-(4-meth­oxy­lbenz­yl)imino­meth­yl]phenolato-κ2 N,O 1}nickel(II), (I), is related to bis­{2-[1-(benzyl­imino)­eth­yl]phenolato}palladium(II) (Mohd Tajuddin et al., 2010 ▶) in terms of the geometry around the metal centre. However, we have extended our investigation to include a nickel compound with a Schiff base ligand that has a 4-meth­oxy substituent on the phenyl ring of the benzyl unit bound to the imine N atom (Fig. 1 ▶).

Figure 1

The mol­ecular structure of (I), showing 50% probability displacement ellipsoids and the atom-numbering scheme. The symmetry-related Schiff base ligand is generated by the symmetry code (−x + 1, −y, −z + 1).

Structural commentary

The asymmetric unit of (I) consists of an NiII cation that lies on an inversion centre and a Schiff base anion that functions as a bidentate ligand (Fig. 1 ▶). The N2O2 donor set of the chelating Schiff base ligands has the N1 and O1 donor atoms mutually trans, in a distorted square-planar coordination geometry, with O1—Ni1—N1 = 92.30 (4)° and O1—Ni1—N1i = 87.70 (4)° [symmetry code: (i) −x + 1, −y, −z + 1] and a maximum deviation from the NiN2O2 least-squares plane of 0.731 (1) Å for the N1 atom. The Ni1—N1 and Ni1—O1 bond lengths in the N2O2 coordination plane are 1.9191 (11) and 1.8407 (9) Å, respectively. These are similar to those observed in the other closely related NiII complexes with N2O2-coord­inating Schiff base ligands (Bahron et al., 2011 ▶; Mohd Tajuddin et al., 2010 ▶). Other bond lengths and angles observed in the structure are also normal. The meth­oxy substituent is coplanar with the ring to which it is bound, the C15—O2—C12—C13 torsion angle being 3.93 (2)°. The plane of the meth­oxy­benzene ring (C9–C14) makes a dihedral angle of 84.92 (6)° with that of the phenolate benzene ring (C1–C6). A weak intra­molecular C14—H14⋯O1 contact is also observed that affects the overall mol­ecular conformation.

Supra­molecular features

In the crystal (Fig. 2 ▶), mol­ecules are linked into screw chains by weak C11—H11A⋯O2 inter­actions (Fig. 2 ▶ and Table 1 ▶). Additional C5—H5A···Cg1 contacts link mol­ecules into chains along the c-axis direction (Fig. 3 ▶ and Table 1 ▶) resulting in sheets parallel to the ac plane and stacked along the b axis (Fig. 4 ▶).

Figure 2

Screw chains of mol­ecules of (I) linked by C—H⋯O contacts (shown as dashed lines).

Table 1

Hydrogen-bond geometry (Å, °)

Cg1 is the centroid of the C1–C6 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C11—H11A⋯O2i	0.95	2.47	3.3709 (17)	158
C14—H14A⋯O1ii	0.95	2.57	3.2281 (17)	126
C5—H5A⋯Cg1iii	0.95	2.68	3.3918 (13)	132

Symmetry codes: (i) ; (ii) ; (iii) .

Figure 3

C—H⋯π contacts for (I), shown as dotted lines, with ring centroids shown as coloured spheres. Cg1 is the centroid of the C1–C6 ring.

Figure 4

The packing of (I), viewed along the b axis, showing the stacking of sheets of NiII complex mol­ecules. Only H atoms involved in weak C—H⋯O inter­actions are shown for clarity.

Database survey

A search of the Cambridge Structural Database (Version 5.35, November 2013 with 3 updates; Allen, 2002 ▶) reveals a total of 1191 NiII complexes with an NiN2O2 coordination sphere. No fewer than 333 of these had the NiII atom chelated by two 3-(imino­meth­yl)phenolate residues. No corresponding structures with a benzyl or substituted benzyl unit bound to the imino N atom were found. However, extending the search to allow additional substitution on the phenolate ring resulted in seven discrete structures including the closely related bis­(2-[(E)-(4-fluoro­benz­yl)imino­meth­yl]-6-meth­oxy­phenolato-κ2 N,O 1)nickel(II) (Bahron et al., 2011 ▶) and bis­{2-[(benzyl­imino)­meth­yl]-5-meth­oxy­phenolato}nickel(II) (Gou et al., 2013 ▶)

Synthesis and crystallization

N-4-Meth­oxy­benzyl­salicyl­idene­imine (5 mmol, 0.6041 g) was dissolved in ethanol (15 ml). An ethano­lic solution of nickel(II) acetate tetra­hydrate (2.5 mmol, 0.6216 g) was added dropwise to the former solution and the mixture heated under reflux for 4 h, producing a green solid. The solid was filtered off, washed with ice-cold ethanol and air-dried at room temperature. The solid product was recrystallized from chloro­form, yielding green crystals (yield 43.3%; m.p. 469–472 K). Analytical data for [Ni(C28H30N2O4)]: C 66.82, H 5.23, N 5.19%; found: C 67.03, H 5.28, N 5.15%. IR (KBr, cm−1): ν(C=N) 1605 (s), ν(C—N) 1391 (s), ν(C—O) 1325 (s), ν(Ni—O) 598 (w), ν(Ni—N) 437 (w).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▶. All H atoms were positioned geometrically and allowed to ride on their parent atoms, with C—H = 0.95 for aromatic, 0.99 for CH2 and 0.98 Å for CH3 hydrogens. The U iso(H) values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating-group model was used for the methyl groups.

Table 2

Experimental details

Crystal data
Chemical formula	[Ni(C15H14NO2)2]
M r	539.23
Crystal system, space group	Monoclinic, P21/c
Temperature (K)	100
a, b, c (Å)	12.1847 (2), 5.6738 (1), 17.7620 (3)
β (°)	95.682 (1)
V (Å3)	1221.92 (4)
Z	2
Radiation type	Mo Kα
μ (mm−1)	0.84
Crystal size (mm)	0.52 × 0.30 × 0.16
Data collection
Diffractometer	Bruker APEXII CCD area detector
Absorption correction	Multi-scan (SADABS; Bruker, 2009 ▶)
T min, T max	0.670, 0.876
No. of measured, independent and observed [I > 2σ(I)] reflections	14541, 3542, 3092
R int	0.019
(sin θ/λ)max (Å−1)	0.703
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.028, 0.074, 1.05
No. of reflections	3542
No. of parameters	170
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	0.42, −0.32

Computer programs: APEX2 and SAINT (Bruker, 2009 ▶), SHELXTL (Sheldrick, 2008 ▶), PLATON (Spek, 2009 ▶), Mercury (Macrae et al., 2006 ▶) and publCIF (Westrip, 2010 ▶).

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S160053681401650X/sj5419sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S160053681401650X/sj5419Isup2.hkl

CCDC reference: 1014286

Additional supporting information: crystallographic information; 3D view; checkCIF report

[Ni(C15H14NO2)2]	F(000) = 564
Mr = 539.23	Dx = 1.466 Mg m−3
Monoclinic, P21/c	Melting point = 469–472 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 12.1847 (2) Å	Cell parameters from 3542 reflections
b = 5.6738 (1) Å	θ = 1.7–30.0°
c = 17.7620 (3) Å	µ = 0.84 mm−1
β = 95.682 (1)°	T = 100 K
V = 1221.92 (4) Å3	Needle, green
Z = 2	0.52 × 0.30 × 0.16 mm

Bruker APEXII CCD area-detector diffractometer	3542 independent reflections
Radiation source: sealed tube	3092 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.019
φ and ω scans	θmax = 30.0°, θmin = 1.7°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −17→17
Tmin = 0.670, Tmax = 0.876	k = −7→7
14541 measured reflections	l = −24→24

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.074	H-atom parameters constrained
S = 1.05	w = 1/[σ2(Fo2) + (0.0313P)2 + 0.7976P] where P = (Fo2 + 2Fc2)/3
3542 reflections	(Δ/σ)max < 0.001
170 parameters	Δρmax = 0.42 e Å−3
0 restraints	Δρmin = −0.32 e Å−3

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.

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 F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

	x	y	z	Uiso*/Ueq
Ni1	0.5000	0.0000	0.5000	0.01253 (7)
O1	0.58126 (8)	−0.03642 (16)	0.41876 (5)	0.01676 (19)
O2	−0.03916 (8)	−0.2287 (2)	0.34237 (6)	0.0272 (2)
N1	0.42000 (8)	0.2622 (2)	0.45360 (6)	0.0142 (2)
C1	0.60209 (10)	0.1191 (2)	0.36758 (6)	0.0141 (2)
C2	0.68624 (10)	0.0696 (3)	0.31981 (7)	0.0164 (2)
H2A	0.7260	−0.0744	0.3255	0.020*
C3	0.71053 (10)	0.2297 (3)	0.26525 (7)	0.0176 (2)
H3A	0.7676	0.1945	0.2343	0.021*
C4	0.65287 (11)	0.4428 (3)	0.25451 (7)	0.0182 (3)
H4A	0.6698	0.5501	0.2163	0.022*
C5	0.57101 (10)	0.4940 (2)	0.30048 (7)	0.0157 (2)
H5A	0.5315	0.6380	0.2938	0.019*
C6	0.54531 (10)	0.3354 (2)	0.35715 (6)	0.0138 (2)
C7	0.45329 (10)	0.3875 (2)	0.39913 (7)	0.0146 (2)
H7A	0.4130	0.5271	0.3857	0.018*
C8	0.31199 (10)	0.3363 (2)	0.47834 (7)	0.0163 (2)
H8A	0.2966	0.5015	0.4629	0.020*
H8B	0.3151	0.3279	0.5342	0.020*
C9	0.22048 (10)	0.1787 (2)	0.44360 (7)	0.0159 (2)
C10	0.16960 (11)	0.2254 (3)	0.37107 (7)	0.0209 (3)
H10A	0.1939	0.3559	0.3436	0.025*
C11	0.08462 (11)	0.0860 (3)	0.33834 (7)	0.0235 (3)
H11A	0.0517	0.1204	0.2888	0.028*
C12	0.04753 (10)	−0.1046 (3)	0.37812 (7)	0.0194 (3)
C13	0.09757 (11)	−0.1573 (3)	0.44988 (8)	0.0216 (3)
H13A	0.0735	−0.2887	0.4770	0.026*
C14	0.18353 (11)	−0.0150 (3)	0.48172 (8)	0.0203 (3)
H14A	0.2176	−0.0518	0.5307	0.024*
C15	−0.08444 (12)	−0.4144 (3)	0.38380 (9)	0.0274 (3)
H15A	−0.1488	−0.4812	0.3537	0.041*
H15B	−0.1069	−0.3521	0.4314	0.041*
H15C	−0.0287	−0.5376	0.3947	0.041*

	U11	U22	U33	U12	U13	U23
Ni1	0.01363 (11)	0.01119 (12)	0.01281 (10)	0.00205 (8)	0.00150 (7)	0.00034 (8)
O1	0.0207 (4)	0.0148 (5)	0.0153 (4)	0.0041 (4)	0.0044 (3)	0.0021 (3)
O2	0.0239 (5)	0.0353 (6)	0.0210 (5)	−0.0062 (5)	−0.0041 (4)	−0.0053 (4)
N1	0.0138 (4)	0.0131 (5)	0.0157 (4)	0.0010 (4)	0.0010 (3)	−0.0012 (4)
C1	0.0146 (5)	0.0148 (6)	0.0126 (5)	−0.0009 (5)	−0.0009 (4)	−0.0015 (4)
C2	0.0158 (5)	0.0168 (6)	0.0165 (5)	0.0003 (5)	0.0013 (4)	−0.0021 (5)
C3	0.0159 (5)	0.0198 (7)	0.0174 (5)	−0.0029 (5)	0.0025 (4)	−0.0026 (5)
C4	0.0187 (5)	0.0181 (6)	0.0179 (5)	−0.0039 (5)	0.0016 (4)	0.0015 (5)
C5	0.0156 (5)	0.0133 (6)	0.0176 (5)	−0.0021 (5)	−0.0007 (4)	0.0011 (5)
C6	0.0144 (5)	0.0134 (6)	0.0133 (5)	−0.0008 (4)	−0.0009 (4)	−0.0009 (4)
C7	0.0149 (5)	0.0123 (6)	0.0160 (5)	0.0010 (5)	−0.0012 (4)	−0.0009 (5)
C8	0.0159 (5)	0.0149 (6)	0.0183 (5)	0.0039 (5)	0.0029 (4)	−0.0004 (5)
C9	0.0140 (5)	0.0171 (6)	0.0167 (5)	0.0049 (5)	0.0026 (4)	−0.0008 (5)
C10	0.0201 (6)	0.0250 (7)	0.0178 (5)	0.0023 (5)	0.0027 (4)	0.0036 (5)
C11	0.0221 (6)	0.0340 (8)	0.0141 (5)	0.0021 (6)	0.0000 (4)	0.0007 (6)
C12	0.0163 (5)	0.0243 (7)	0.0174 (5)	0.0023 (5)	0.0006 (4)	−0.0057 (5)
C13	0.0212 (6)	0.0214 (7)	0.0216 (6)	−0.0012 (5)	−0.0007 (5)	0.0019 (5)
C14	0.0187 (6)	0.0227 (7)	0.0185 (6)	0.0009 (5)	−0.0030 (4)	0.0029 (5)
C15	0.0219 (6)	0.0282 (8)	0.0317 (7)	−0.0039 (6)	0.0007 (5)	−0.0100 (7)

Ni1—O1	1.8407 (9)	C6—C7	1.4374 (16)
Ni1—O1i	1.8407 (9)	C7—H7A	0.9500
Ni1—N1	1.9191 (11)	C8—C9	1.5123 (18)
Ni1—N1i	1.9191 (11)	C8—H8A	0.9900
O1—C1	1.3095 (15)	C8—H8B	0.9900
O2—C12	1.3717 (16)	C9—C14	1.3892 (19)
O2—C15	1.427 (2)	C9—C10	1.3986 (17)
N1—C7	1.2977 (16)	C10—C11	1.384 (2)
N1—C8	1.4887 (15)	C10—H10A	0.9500
C1—C6	1.4123 (18)	C11—C12	1.392 (2)
C1—C2	1.4221 (16)	C11—H11A	0.9500
C2—C3	1.3813 (18)	C12—C13	1.3898 (18)
C2—H2A	0.9500	C13—C14	1.3967 (19)
C3—C4	1.402 (2)	C13—H13A	0.9500
C3—H3A	0.9500	C14—H14A	0.9500
C4—C5	1.3810 (17)	C15—H15A	0.9800
C4—H4A	0.9500	C15—H15B	0.9800
C5—C6	1.4080 (17)	C15—H15C	0.9800
C5—H5A	0.9500
O1—Ni1—O1i	180.000 (1)	C6—C7—H7A	116.9
O1—Ni1—N1	92.30 (4)	N1—C8—C9	110.50 (10)
O1i—Ni1—N1	87.70 (4)	N1—C8—H8A	109.5
O1—Ni1—N1i	87.70 (4)	C9—C8—H8A	109.5
O1i—Ni1—N1i	92.30 (4)	N1—C8—H8B	109.5
N1—Ni1—N1i	180.00 (6)	C9—C8—H8B	109.5
C1—O1—Ni1	128.67 (8)	H8A—C8—H8B	108.1
C12—O2—C15	117.36 (11)	C14—C9—C10	117.60 (12)
C7—N1—C8	114.59 (11)	C14—C9—C8	122.03 (11)
C7—N1—Ni1	124.19 (9)	C10—C9—C8	120.37 (12)
C8—N1—Ni1	121.22 (8)	C11—C10—C9	121.56 (13)
O1—C1—C6	123.41 (11)	C11—C10—H10A	119.2
O1—C1—C2	118.82 (12)	C9—C10—H10A	119.2
C6—C1—C2	117.77 (11)	C10—C11—C12	119.86 (12)
C3—C2—C1	120.40 (12)	C10—C11—H11A	120.1
C3—C2—H2A	119.8	C12—C11—H11A	120.1
C1—C2—H2A	119.8	O2—C12—C13	124.20 (13)
C2—C3—C4	121.55 (12)	O2—C12—C11	115.95 (12)
C2—C3—H3A	119.2	C13—C12—C11	119.84 (13)
C4—C3—H3A	119.2	C12—C13—C14	119.37 (13)
C5—C4—C3	118.84 (12)	C12—C13—H13A	120.3
C5—C4—H4A	120.6	C14—C13—H13A	120.3
C3—C4—H4A	120.6	C9—C14—C13	121.74 (12)
C4—C5—C6	120.87 (12)	C9—C14—H14A	119.1
C4—C5—H5A	119.6	C13—C14—H14A	119.1
C6—C5—H5A	119.6	O2—C15—H15A	109.5
C5—C6—C1	120.55 (11)	O2—C15—H15B	109.5
C5—C6—C7	118.67 (12)	H15A—C15—H15B	109.5
C1—C6—C7	120.51 (11)	O2—C15—H15C	109.5
N1—C7—C6	126.28 (12)	H15A—C15—H15C	109.5
N1—C7—H7A	116.9	H15B—C15—H15C	109.5
N1—Ni1—O1—C1	22.59 (11)	Ni1—N1—C7—C6	9.30 (18)
N1i—Ni1—O1—C1	−157.41 (11)	C5—C6—C7—N1	−178.90 (12)
O1—Ni1—N1—C7	−19.81 (11)	C1—C6—C7—N1	7.05 (19)
O1—Ni1—N1—C8	159.85 (9)	C7—N1—C8—C9	99.88 (13)
O1i—Ni1—N1—C8	−20.15 (9)	Ni1—N1—C8—C9	−79.80 (11)
Ni1—O1—C1—C6	−13.67 (17)	N1—C8—C9—C14	95.30 (14)
Ni1—O1—C1—C2	166.19 (9)	N1—C8—C9—C10	−84.93 (14)
O1—C1—C2—C3	−179.94 (11)	C14—C9—C10—C11	0.7 (2)
C6—C1—C2—C3	−0.06 (18)	C8—C9—C10—C11	−179.09 (12)
C1—C2—C3—C4	−0.79 (19)	C9—C10—C11—C12	0.5 (2)
C2—C3—C4—C5	0.89 (19)	C15—O2—C12—C13	3.9 (2)
C3—C4—C5—C6	−0.13 (19)	C15—O2—C12—C11	−175.51 (13)
C4—C5—C6—C1	−0.71 (18)	C10—C11—C12—O2	178.05 (12)
C4—C5—C6—C7	−174.76 (11)	C10—C11—C12—C13	−1.4 (2)
O1—C1—C6—C5	−179.33 (11)	O2—C12—C13—C14	−178.31 (13)
C2—C1—C6—C5	0.80 (17)	C11—C12—C13—C14	1.1 (2)
O1—C1—C6—C7	−5.40 (18)	C10—C9—C14—C13	−1.0 (2)
C2—C1—C6—C7	174.74 (11)	C8—C9—C14—C13	178.78 (12)
C8—N1—C7—C6	−170.38 (11)	C12—C13—C14—C9	0.1 (2)

D—H···A	D—H	H···A	D···A	D—H···A
C11—H11A···O2ii	0.95	2.47	3.3709 (17)	158
C14—H14A···O1i	0.95	2.57	3.2281 (17)	126
C5—H5A···Cg1iii	0.95	2.68	3.3918 (13)	132