{6,6′-Diethoxy-2,2′-[4,5-dimethyl-o-phenylenebis(nitrilomethylidyne)]di­phenolato}nickel(II) dihydrate

In the title complex, [Ni(C₂₆H₂₆N₂O₄)]·2H₂O, the Ni^II ion, lying on a twofold crystallographic rotation axis, has a square-planar geometry, being coordinated by the N₂O₂ unit of the tetra­dentate Schiff base ligand. The asymmetric unit of the title compound comprises one-half of the complex mol­ecule and one of the water mol­ecules of crystallization. The water H atoms form bifurcated O—H...(O,O) hydrogen bonds with the O atoms of the phenolato and eth­oxy groups with R₁²(5) and R₁²(6) ring motifs. The dihedral angle between the central benzene ring and the two outer benzene rings are 4.07 (11) and 3.99 (12)°. The dihedral angle between the two O–Ni–N coordination planes is only 0.77 (11)°. In the crystal structure, the mol­ecules are linked together into extended chains along the c axis by inter­molecular O—H...O and C—H...O inter­actions. An inter­esting feature of the crystal structure is a short inter­molecular C ... C [3.355 (3) Å] contact, which is shorter than the sum of the van der Waals radii. The crystal structure may be further stabilized by inter­molecular π–π inter­actions [centroid–centroid distances in the range 3.5758 (13)–3.6337 (13) Å].

Key indicators

• Single-crystal X-ray study
• T = 294 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.046
• wR factor = 0.122
• Data-to-parameter ratio = 21.8

checkCIF/PLATON results

No syntax errors found



Alert level C
            Value of measurement temperature given =   294.000
            Value of melting point given =     0.000
PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       2.62 Ratio
PLAT222_ALERT_3_C Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       3.06 Ratio

Alert level G
PLAT720_ALERT_4_G Number of Unusual/Non-Standard Labels ..........          2

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Schiff base complexes are some of the most important stereochemical models in transition metal coordination chemistry, with their ease of preparation and structural variations (Granovski et al., 1993). Metal derivatives of Schiff bases have been studied extensively, and copper(II) and Ni(II) complexes play a major role in both synthetic and structural research (Elmali et al., 2000; Blower, 1998; Granovski et al., 1993; Li & Chang, 1991; Shahrokhian et al., 2000). Tetradentate Schiff base metal complexes may form trans or cis planar or tetrahedral structures (Elmali et al., 2000).

The Ni^II ion of the title compound (Fig. 1), shows a square planar geometry which is coordinated by two imine N atoms and two phenol O atoms of the tetradentate Schiff base ligand and lies across a crystallographic twofold rotation axis. The bond lengths (Allen et al.,, 1987) and angles are within normal ranges and are comparable with the related structures (Clark et al., 1968, 1969, 1970). The water H atoms form bifurcated O—H(O,O) intermolecular hydrogen bonds with the oxygen atoms of the phenolato- and ethoxy groups with R²₁(5) and R²₁(6) ring motifs (Bernstein et al., 1995), which may, in part, influence the molecular configuration (Fig. 1). The dihedral angle between the central benzene ring and the two outer benzene rings are 4.07 (11) and 3.99 (12)°. The dihedral angle between the two coordination planes O1—Ni1—N1 and O1A—Ni1—N1A is 0.77 (11)°. In the crystal structure the complex and two water molecules, association of which form the title compound, are linked together into 1-D extended chains by intermolecular O—H···O and C—H···O interactions along the c axis (Fig. 2). The interesting feature of the crystal structure is a short intermolecular C1···C7ⁱⁱⁱ [3.355 (3) Å; (iii) 1 - x, -y, 1 - z ] contact, shorter than the sum of the van der Waals radius of carbon atoms. The crystal structure is further stabilized by intermolecular π-π [Cg1···Cg3ⁱⁱⁱ = 3.5758 (13) Å; Cg2···Cg2ⁱⁱⁱ = 3.6085 (11) Å; Cg2···Cg3ⁱⁱⁱ = 3.6337 (13) Å, Cg1, Cg2 and Cg3 are the centroid of the Ni1/N1/C8/C8A/N1A, C1–C6, and Ni1/O1/C1/C6/C7/N1 rings, respectively].

Related literature

For bond-length data, see Allen et al. (1987). For related structures see, for example: Clark et al. (1968, 1969, 1970). For the applications and bioactivity of Schiff base complexes see, for example: Elmali et al. (2000); Blower (1998); Granovski et al. (1993); Li & Chang, (1991); Shahrokhian et al. (2000). For hydrogen-bond motifs, see: Bernstein et al. (1995).

S2. Experimental

A chloroform solution (40 ml) of [N,N'-Bis(3-ethoxy-salicylidene)- 4,5-dimethyl-phenylenediamine (1 mmol) was added to a ethanol solution (20 mL) of NiCl₂.6H₂O (1.05 mmol, 237 mg). The mixture was refluxed for 30 min and then filtered. After keeping the filtrate in air, deep-red block-shaped crystals were formed at the bottom of the vessel on slow evaporation of the solvent.

S3. Refinement

The water H-atoms were located from the difference Fourier map and constrained to refine with the carrier atom after O—H distance restraint of 0.82 (1) Å. The rest of the hydrogen atoms were positioned geometrically [C—H = 0.95–97 Å] and refined using a riding approximation model. A rotating-group model was used for the methyl groups.

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures

	Fig. 1. The title molecular compound, showing 50° probability displacement ellipsoids and the atomic numbering, hydrogen bonds are shown as dashed lines. Symmetry code for suffix A: -x + 1, y, -z + 1/2.
	Fig. 2. A crystal packing excerpt of the title compound viewed down the b-axis, showing 1-D extended chains along the c-axis. Intermolecular interactions are drawn as dashed lines.

{6,6'-Diethoxy-2,2'-[4,5-dimethyl-o- phenylenebis(nitrilomethylidyne)]diphenolato}nickel(II) dihydrate

Crystal data

[Ni(C26H26N2O4)]·2H2O	F(000) = 1104
Mr = 525.23	Dx = 1.419 Mg m^−3
Orthorhombic, Pbcn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2ab	Cell parameters from 2497 reflections
a = 12.8706 (4) Å	θ = 2.7–22.3°
b = 16.1130 (4) Å	µ = 0.83 mm^−1
c = 11.8546 (3) Å	T = 294 K
V = 2458.45 (12) Å^3	Block, red
Z = 4	0.30 × 0.16 × 0.08 mm

Data collection

Bruker APEXII CCD area-detector diffractometer	3517 independent reflections
Radiation source: fine-focus sealed tube	2007 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.065
ϕ and ω scans	θmax = 29.8°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −17→17
Tmin = 0.790, Tmax = 0.935	k = −22→22
16330 measured reflections	l = −16→11

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.046	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.122	H-atom parameters constrained
S = 1.01	w = 1/[σ^2(Fo^2) + (0.0543P)^2 + 0.1108P] where P = (Fo^2 + 2Fc^2)/3
3517 reflections	(Δ/σ)max < 0.001
161 parameters	Δρmax = 0.29 e Å^−3
0 restraints	Δρmin = −0.51 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Ni1	0.5000	−0.00935 (2)	0.2500	0.04044 (15)
O1	0.44372 (13)	0.07589 (9)	0.33400 (13)	0.0501 (4)
O2	0.38481 (16)	0.21443 (10)	0.42373 (15)	0.0716 (6)
N1	0.44336 (14)	−0.09376 (10)	0.33719 (15)	0.0398 (4)
C1	0.38667 (17)	0.06930 (14)	0.4246 (2)	0.0441 (5)
C2	0.3505 (2)	0.14350 (15)	0.4772 (2)	0.0524 (6)
C3	0.2894 (2)	0.14174 (16)	0.5706 (2)	0.0605 (7)
H3A	0.2659	0.1912	0.6020	0.073*
C4	0.2614 (2)	0.06548 (19)	0.6203 (2)	0.0660 (8)
H4A	0.2193	0.0646	0.6841	0.079*
C5	0.2961 (2)	−0.00668 (16)	0.5746 (2)	0.0566 (7)
H5A	0.2790	−0.0568	0.6088	0.068*
C6	0.35820 (19)	−0.00679 (13)	0.4755 (2)	0.0451 (6)
C7	0.39054 (17)	−0.08387 (14)	0.42982 (19)	0.0441 (5)
H7A	0.3725	−0.1315	0.4695	0.053*
C8	0.46786 (17)	−0.17483 (13)	0.29740 (18)	0.0412 (5)
C9	0.43332 (19)	−0.24982 (14)	0.3410 (2)	0.0498 (6)
H9A	0.3879	−0.2497	0.4020	0.060*
C10	0.4649 (2)	−0.32468 (14)	0.2957 (2)	0.0519 (6)
C11	0.3545 (2)	0.29234 (15)	0.4698 (3)	0.0759 (9)
H11A	0.3783	0.2974	0.5471	0.091*
H11B	0.2794	0.2979	0.4687	0.091*
C12	0.4041 (3)	0.35795 (18)	0.3968 (3)	0.1078 (13)
H12A	0.3824	0.4119	0.4219	0.162*
H12B	0.3832	0.3500	0.3198	0.162*
H12C	0.4783	0.3537	0.4022	0.162*
C13	0.4247 (3)	−0.40558 (15)	0.3438 (2)	0.0791 (10)
H13A	0.3822	−0.3943	0.4086	0.119*
H13B	0.4823	−0.4399	0.3656	0.119*
H13C	0.3841	−0.4338	0.2877	0.119*
O1W	0.38489 (17)	0.20940 (12)	0.15851 (16)	0.0853 (6)
H1W1	0.3725	0.1955	0.2239	0.128*
H2W1	0.4475	0.2018	0.1648	0.128*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni1	0.0477 (2)	0.0286 (2)	0.0450 (3)	0.000	0.00116 (19)	0.000
O1	0.0667 (11)	0.0307 (8)	0.0530 (10)	0.0029 (8)	0.0057 (9)	−0.0006 (7)
O2	0.1017 (15)	0.0353 (9)	0.0778 (13)	0.0146 (9)	0.0068 (11)	−0.0068 (9)
N1	0.0447 (11)	0.0313 (9)	0.0434 (11)	0.0007 (8)	0.0005 (9)	−0.0028 (8)
C1	0.0453 (13)	0.0388 (12)	0.0481 (14)	0.0059 (10)	−0.0064 (11)	−0.0071 (11)
C2	0.0561 (15)	0.0429 (14)	0.0582 (16)	0.0118 (12)	−0.0078 (12)	−0.0123 (12)
C3	0.0610 (17)	0.0553 (16)	0.0651 (18)	0.0144 (13)	−0.0023 (14)	−0.0211 (14)
C4	0.0646 (17)	0.0690 (19)	0.0643 (18)	0.0047 (14)	0.0141 (14)	−0.0177 (15)
C5	0.0582 (16)	0.0584 (16)	0.0533 (17)	−0.0020 (12)	0.0091 (13)	−0.0069 (12)
C6	0.0447 (13)	0.0418 (13)	0.0487 (15)	0.0012 (10)	−0.0008 (10)	−0.0074 (11)
C7	0.0470 (13)	0.0392 (12)	0.0461 (14)	−0.0042 (10)	0.0000 (11)	−0.0020 (10)
C8	0.0496 (13)	0.0312 (11)	0.0429 (13)	0.0000 (9)	−0.0010 (10)	−0.0010 (9)
C9	0.0603 (15)	0.0384 (12)	0.0507 (14)	0.0005 (11)	0.0115 (12)	0.0003 (11)
C10	0.0660 (16)	0.0321 (12)	0.0576 (15)	−0.0057 (10)	0.0056 (12)	0.0027 (10)
C11	0.079 (2)	0.0387 (15)	0.111 (2)	0.0179 (14)	−0.0129 (18)	−0.0251 (16)
C12	0.161 (4)	0.0409 (17)	0.122 (3)	0.016 (2)	−0.011 (3)	−0.0029 (18)
C13	0.111 (3)	0.0372 (15)	0.089 (2)	−0.0093 (15)	0.0313 (19)	0.0036 (14)
O1W	0.1029 (16)	0.0723 (14)	0.0809 (14)	0.0234 (12)	−0.0218 (12)	0.0009 (11)

Geometric parameters (Å, º)

Ni1—O1^i	1.8447 (15)	C7—H7A	0.9300
Ni1—O1	1.8447 (15)	C8—C9	1.387 (3)
Ni1—N1	1.8573 (17)	C8—C8^i	1.396 (4)
Ni1—N1^i	1.8573 (17)	C9—C10	1.381 (3)
O1—C1	1.306 (3)	C9—H9A	0.9300
O2—C2	1.380 (3)	C10—C10^i	1.410 (5)
O2—C11	1.423 (3)	C10—C13	1.514 (3)
N1—C7	1.301 (3)	C11—C12	1.508 (4)
N1—C8	1.424 (2)	C11—H11A	0.9700
C1—C6	1.415 (3)	C11—H11B	0.9700
C1—C2	1.427 (3)	C12—H12A	0.9600
C2—C3	1.358 (3)	C12—H12B	0.9600
C3—C4	1.410 (4)	C12—H12C	0.9600
C3—H3A	0.9300	C13—H13A	0.9600
C4—C5	1.358 (3)	C13—H13B	0.9600
C4—H4A	0.9300	C13—H13C	0.9600
C5—C6	1.421 (3)	O1W—H1W1	0.8226
C5—H5A	0.9300	O1W—H2W1	0.8179
C6—C7	1.417 (3)
O1^i—Ni1—O1	83.75 (10)	N1—C7—H7A	117.2
O1^i—Ni1—N1	178.81 (7)	C6—C7—H7A	117.2
O1—Ni1—N1	95.21 (7)	C9—C8—C8^i	119.32 (13)
O1^i—Ni1—N1^i	95.21 (7)	C9—C8—N1	127.2 (2)
O1—Ni1—N1^i	178.81 (7)	C8^i—C8—N1	113.45 (11)
N1—Ni1—N1^i	85.84 (11)	C10—C9—C8	121.4 (2)
C1—O1—Ni1	127.19 (14)	C10—C9—H9A	119.3
C2—O2—C11	117.8 (2)	C8—C9—H9A	119.3
C7—N1—C8	120.49 (18)	C9—C10—C10^i	119.14 (14)
C7—N1—Ni1	125.80 (15)	C9—C10—C13	120.3 (2)
C8—N1—Ni1	113.61 (14)	C10^i—C10—C13	120.54 (14)
O1—C1—C6	124.54 (19)	O2—C11—C12	106.4 (2)
O1—C1—C2	118.4 (2)	O2—C11—H11A	110.5
C6—C1—C2	117.1 (2)	C12—C11—H11A	110.5
C3—C2—O2	125.3 (2)	O2—C11—H11B	110.5
C3—C2—C1	121.8 (2)	C12—C11—H11B	110.5
O2—C2—C1	112.9 (2)	H11A—C11—H11B	108.6
C2—C3—C4	120.5 (2)	C11—C12—H12A	109.5
C2—C3—H3A	119.8	C11—C12—H12B	109.5
C4—C3—H3A	119.8	H12A—C12—H12B	109.5
C5—C4—C3	119.7 (3)	C11—C12—H12C	109.5
C5—C4—H4A	120.2	H12A—C12—H12C	109.5
C3—C4—H4A	120.2	H12B—C12—H12C	109.5
C4—C5—C6	121.1 (2)	C10—C13—H13A	109.5
C4—C5—H5A	119.5	C10—C13—H13B	109.5
C6—C5—H5A	119.5	H13A—C13—H13B	109.5
C1—C6—C7	121.4 (2)	C10—C13—H13C	109.5
C1—C6—C5	119.8 (2)	H13A—C13—H13C	109.5
C7—C6—C5	118.8 (2)	H13B—C13—H13C	109.5
N1—C7—C6	125.7 (2)	H1W1—O1W—H2W1	93.7
O1^i—Ni1—O1—C1	−177.9 (2)	C2—C1—C6—C7	−179.8 (2)
O1—Ni1—N1—C7	−4.77 (19)	O1—C1—C6—C5	179.7 (2)
N1^i—Ni1—N1—C7	175.8 (2)	C2—C1—C6—C5	0.0 (3)
O1—Ni1—N1—C8	178.82 (14)	C4—C5—C6—C1	1.5 (4)
N1^i—Ni1—N1—C8	−0.62 (11)	C4—C5—C6—C7	−178.6 (2)
Ni1—O1—C1—C6	0.5 (3)	C8—N1—C7—C6	−177.5 (2)
Ni1—O1—C1—C2	−179.89 (15)	Ni1—N1—C7—C6	6.3 (3)
C11—O2—C2—C3	0.2 (4)	C1—C6—C7—N1	−3.4 (4)
C11—O2—C2—C1	−179.2 (2)	C5—C6—C7—N1	176.7 (2)
O1—C1—C2—C3	178.9 (2)	C7—N1—C8—C9	6.6 (4)
C6—C1—C2—C3	−1.4 (3)	Ni1—N1—C8—C9	−176.77 (19)
O1—C1—C2—O2	−1.6 (3)	C7—N1—C8—C8^i	−174.9 (2)
C6—C1—C2—O2	178.1 (2)	Ni1—N1—C8—C8^i	1.8 (3)
O2—C2—C3—C4	−178.1 (2)	C8^i—C8—C9—C10	3.0 (4)
C1—C2—C3—C4	1.3 (4)	N1—C8—C9—C10	−178.6 (2)
C2—C3—C4—C5	0.3 (4)	C8—C9—C10—C10^i	1.0 (5)
C3—C4—C5—C6	−1.7 (4)	C8—C9—C10—C13	−179.1 (2)
O1—C1—C6—C7	−0.2 (4)	C2—O2—C11—C12	178.9 (2)

Symmetry code: (i) −x+1, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1W1···O1	0.82	2.50	3.087 (2)	129
O1W—H1W1···O2	0.82	2.39	3.145 (3)	152
O1W—H2W1···O1^i	0.82	2.47	3.083 (3)	133
O1W—H2W1···O2^i	0.82	2.41	3.121 (3)	146
C7—H7A···O1W^ii	0.93	2.57	3.383 (3)	146

Symmetry codes: (i) −x+1, y, −z+1/2; (ii) x, −y, z+1/2.