In the title complex, [Ni(C
21H
14Br
2N
2O
2)], the Ni
II atom is coordinated by the two imine N and two phenolate O atoms of the Schiff base ligand in a tetrahedrally distorted square-planar geometry. The Ni—N and Ni—O distances are within the ranges expected for Ni–Schiff base derivatives. Intermolecular C—H
O hydrogen bonds link the molecules into centrosymmetric dimers, forming
(12) (
A) and
(10) (
B) rings. These dimers combine to form a supramolecular
ABAB… aggregate which propagates along the [100] direction.
Supporting information
CCDC reference: 256993
The ligand 4-bromo-2-[2-(5-bromo-2-hydroxybenzylideneaminomethyl)phenyliminomethyl]phenol (H2L) was prepared by condensation of 5-bromosalicylaldehyde (10 mmol, 2.01 g) and 2-aminobenzylamine (5 mmol, 0.61 g) in methanol (50 ml). The reaction mixture was stirred for 1 h and the resulting solution was used without further purification. Ni(ClO4)2·6H2O (1 mmol, 0.366 g) was dissolved in methanol (20 ml) and the methanol solution of the ligand (H2L, 1 mmol) was added dropwise. A brown compound, NiL, (I), was obtained on keeping the solution at room temperature (298 K) for three days. Recrystallization from dichloromethane yielded single crystals of (I), which were collected by filtration and air-dried (yield 65%). Analysis found: C 46.31, H 2.55, N 5.16%; calculated for C21H14Br2N2O2NI; C 46.24, H 2.57, N 5.14%. IR (cm−1): 1605 (C—N), 1320 (C—O), 2300–2840 (N—H), 535 (Ni—N), 405 (Ni—O). The broad band around 620 nm in the UV spectrum can be assigned to d–d transition in the complex and suggests an approximate square-planar or tetrahedral metal coordination.
Data collection: SMART (Bruker, 1998); cell refinement: SMART (Bruker, 1998); data reduction: SMART; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and CAMERON (Watkin et al., 1993); software used to prepare material for publication: SHELXL97 and PARST95 (Nardelli, 1995).
{4-Bromo-2-[2-(5-bromo-2- oxidobenzylideneaminomethyl)phenyliminomethyl]phenolato-
κ4O,
N,
N',
O'}nickel(II)
top
Crystal data top
[Ni(C21H14Br2N2O2)] | Z = 2 |
Mr = 544.87 | F(000) = 536 |
Triclinic, P1 | Dx = 1.873 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 7.228 (5) Å | Cell parameters from 110 reflections |
b = 10.834 (7) Å | θ = 1.2–26.0° |
c = 12.831 (8) Å | µ = 5.16 mm−1 |
α = 100.09 (1)° | T = 293 K |
β = 99.83 (1)° | Needle, brown |
γ = 95.63 (1)° | 0.35 × 0.12 × 0.10 mm |
V = 966.2 (11) Å3 | |
Data collection top
Bruker SMART CCD area-detector diffractometer | 3752 independent reflections |
Radiation source: fine-focus sealed tube | 2981 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.024 |
ϕ and ω scans | θmax = 26.0°, θmin = 1.6° |
Absorption correction: multi-scan (SADABS; Sheldrich, 1996) | h = −8→8 |
Tmin = 0.299, Tmax = 0.597 | k = −13→13 |
9936 measured reflections | l = −15→15 |
Refinement top
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)] = 0.033 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.082 | H-atom parameters constrained |
S = 1.02 | w = 1/[σ2(Fo2) + (0.0412P)2 + 0.2635P] where P = (Fo2 + 2Fc2)/3 |
3752 reflections | (Δ/σ)max = 0.001 |
253 parameters | Δρmax = 0.74 e Å−3 |
0 restraints | Δρmin = −0.39 e Å−3 |
Crystal data top
[Ni(C21H14Br2N2O2)] | γ = 95.63 (1)° |
Mr = 544.87 | V = 966.2 (11) Å3 |
Triclinic, P1 | Z = 2 |
a = 7.228 (5) Å | Mo Kα radiation |
b = 10.834 (7) Å | µ = 5.16 mm−1 |
c = 12.831 (8) Å | T = 293 K |
α = 100.09 (1)° | 0.35 × 0.12 × 0.10 mm |
β = 99.83 (1)° | |
Data collection top
Bruker SMART CCD area-detector diffractometer | 3752 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrich, 1996) | 2981 reflections with I > 2σ(I) |
Tmin = 0.299, Tmax = 0.597 | Rint = 0.024 |
9936 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.033 | 0 restraints |
wR(F2) = 0.082 | H-atom parameters constrained |
S = 1.02 | Δρmax = 0.74 e Å−3 |
3752 reflections | Δρmin = −0.39 e Å−3 |
253 parameters | |
Special details top
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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Br1 | 0.15193 (6) | 0.31365 (4) | 0.97644 (3) | 0.06638 (14) | |
Br2 | 0.38440 (6) | 0.88639 (4) | 0.06741 (3) | 0.06703 (14) | |
Ni | 0.25506 (5) | 0.48784 (4) | 0.46153 (3) | 0.03464 (12) | |
O1 | 0.2083 (3) | 0.5570 (2) | 0.59536 (16) | 0.0418 (5) | |
O2 | 0.3168 (3) | 0.6568 (2) | 0.45556 (16) | 0.0437 (5) | |
N1 | 0.1594 (3) | 0.3215 (2) | 0.47186 (19) | 0.0354 (6) | |
N2 | 0.3346 (3) | 0.4315 (2) | 0.33175 (19) | 0.0364 (6) | |
C1 | 0.1910 (4) | 0.5004 (3) | 0.6751 (2) | 0.0372 (7) | |
C2 | 0.1931 (5) | 0.5738 (3) | 0.7784 (3) | 0.0449 (8) | |
H2 | 0.2016 | 0.6614 | 0.7870 | 0.054* | |
C3 | 0.1829 (5) | 0.5190 (3) | 0.8651 (3) | 0.0476 (8) | |
H3 | 0.1874 | 0.5693 | 0.9324 | 0.057* | |
C4 | 0.1657 (4) | 0.3880 (3) | 0.8536 (2) | 0.0437 (8) | |
C5 | 0.1528 (4) | 0.3124 (3) | 0.7554 (2) | 0.0439 (8) | |
H5 | 0.1353 | 0.2249 | 0.7481 | 0.053* | |
C6 | 0.1659 (4) | 0.3674 (3) | 0.6646 (2) | 0.0384 (7) | |
C7 | 0.1380 (4) | 0.2877 (3) | 0.5618 (2) | 0.0402 (7) | |
H7 | 0.1005 | 0.2022 | 0.5582 | 0.048* | |
C8 | 0.0813 (4) | 0.2291 (3) | 0.3753 (2) | 0.0396 (7) | |
C9 | −0.0956 (5) | 0.1594 (3) | 0.3643 (3) | 0.0490 (8) | |
H9 | −0.1649 | 0.1718 | 0.4191 | 0.059* | |
C10 | −0.1669 (6) | 0.0710 (3) | 0.2698 (3) | 0.0617 (10) | |
H10 | −0.2827 | 0.0214 | 0.2625 | 0.074* | |
C11 | −0.0674 (6) | 0.0565 (3) | 0.1871 (3) | 0.0605 (10) | |
H11 | −0.1166 | −0.0022 | 0.1240 | 0.073* | |
C12 | 0.1062 (5) | 0.1292 (3) | 0.1977 (3) | 0.0482 (8) | |
H12 | 0.1717 | 0.1201 | 0.1410 | 0.058* | |
C13 | 0.1825 (5) | 0.2155 (3) | 0.2923 (2) | 0.0403 (7) | |
C14 | 0.3681 (5) | 0.2981 (3) | 0.3073 (3) | 0.0436 (8) | |
H14A | 0.4576 | 0.2795 | 0.3662 | 0.052* | |
H14B | 0.4204 | 0.2824 | 0.2422 | 0.052* | |
C15 | 0.3598 (4) | 0.4982 (3) | 0.2605 (2) | 0.0395 (7) | |
H15 | 0.3887 | 0.4568 | 0.1966 | 0.047* | |
C16 | 0.3472 (4) | 0.6300 (3) | 0.2708 (2) | 0.0379 (7) | |
C17 | 0.3652 (4) | 0.6861 (3) | 0.1820 (3) | 0.0446 (8) | |
H17 | 0.3762 | 0.6364 | 0.1170 | 0.054* | |
C18 | 0.3666 (5) | 0.8132 (3) | 0.1905 (3) | 0.0484 (8) | |
C19 | 0.3590 (5) | 0.8884 (3) | 0.2881 (3) | 0.0543 (9) | |
H19 | 0.3633 | 0.9755 | 0.2939 | 0.065* | |
C20 | 0.3453 (5) | 0.8360 (3) | 0.3762 (3) | 0.0507 (8) | |
H20 | 0.3431 | 0.8882 | 0.4416 | 0.061* | |
C21 | 0.3343 (4) | 0.7036 (3) | 0.3701 (2) | 0.0392 (7) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Br1 | 0.0905 (3) | 0.0754 (3) | 0.0369 (2) | 0.0132 (2) | 0.01485 (19) | 0.01729 (18) |
Br2 | 0.0848 (3) | 0.0696 (3) | 0.0559 (2) | 0.0092 (2) | 0.0183 (2) | 0.0327 (2) |
Ni | 0.0384 (2) | 0.0337 (2) | 0.0302 (2) | 0.00363 (16) | 0.00510 (16) | 0.00402 (16) |
O1 | 0.0528 (13) | 0.0383 (12) | 0.0337 (11) | 0.0064 (10) | 0.0098 (10) | 0.0040 (9) |
O2 | 0.0593 (14) | 0.0367 (12) | 0.0341 (12) | 0.0024 (10) | 0.0095 (10) | 0.0062 (9) |
N1 | 0.0385 (14) | 0.0347 (14) | 0.0317 (13) | 0.0034 (11) | 0.0060 (11) | 0.0047 (11) |
N2 | 0.0363 (13) | 0.0367 (14) | 0.0347 (14) | 0.0057 (11) | 0.0060 (11) | 0.0033 (11) |
C1 | 0.0299 (15) | 0.0440 (18) | 0.0360 (17) | 0.0042 (13) | 0.0056 (13) | 0.0039 (14) |
C2 | 0.053 (2) | 0.0424 (19) | 0.0379 (18) | 0.0085 (15) | 0.0094 (15) | 0.0010 (14) |
C3 | 0.0491 (19) | 0.058 (2) | 0.0332 (17) | 0.0092 (16) | 0.0082 (14) | 0.0002 (15) |
C4 | 0.0426 (18) | 0.056 (2) | 0.0330 (17) | 0.0067 (15) | 0.0073 (14) | 0.0107 (15) |
C5 | 0.0485 (19) | 0.047 (2) | 0.0365 (18) | 0.0052 (15) | 0.0069 (14) | 0.0116 (15) |
C6 | 0.0353 (16) | 0.0432 (18) | 0.0340 (17) | 0.0032 (14) | 0.0038 (13) | 0.0042 (14) |
C7 | 0.0428 (18) | 0.0371 (17) | 0.0396 (18) | 0.0047 (14) | 0.0065 (14) | 0.0066 (14) |
C8 | 0.0466 (18) | 0.0347 (17) | 0.0342 (16) | 0.0040 (14) | 0.0026 (14) | 0.0033 (13) |
C9 | 0.054 (2) | 0.0430 (19) | 0.0444 (19) | −0.0040 (16) | 0.0050 (16) | 0.0042 (15) |
C10 | 0.067 (2) | 0.048 (2) | 0.057 (2) | −0.0114 (18) | −0.0020 (19) | 0.0004 (18) |
C11 | 0.083 (3) | 0.043 (2) | 0.043 (2) | −0.003 (2) | −0.0016 (19) | −0.0034 (16) |
C12 | 0.071 (2) | 0.0385 (19) | 0.0352 (17) | 0.0136 (17) | 0.0084 (16) | 0.0047 (14) |
C13 | 0.0528 (19) | 0.0322 (17) | 0.0351 (17) | 0.0115 (14) | 0.0049 (14) | 0.0046 (13) |
C14 | 0.052 (2) | 0.0412 (18) | 0.0393 (17) | 0.0141 (15) | 0.0129 (15) | 0.0049 (14) |
C15 | 0.0346 (16) | 0.050 (2) | 0.0313 (16) | 0.0039 (14) | 0.0022 (13) | 0.0062 (14) |
C16 | 0.0329 (15) | 0.0430 (18) | 0.0368 (17) | 0.0027 (13) | 0.0023 (13) | 0.0105 (14) |
C17 | 0.0401 (18) | 0.055 (2) | 0.0380 (18) | 0.0041 (15) | 0.0037 (14) | 0.0124 (15) |
C18 | 0.0474 (19) | 0.056 (2) | 0.047 (2) | 0.0035 (16) | 0.0083 (15) | 0.0259 (17) |
C19 | 0.066 (2) | 0.0412 (19) | 0.060 (2) | 0.0049 (17) | 0.0154 (19) | 0.0189 (17) |
C20 | 0.064 (2) | 0.0401 (19) | 0.050 (2) | 0.0069 (17) | 0.0191 (17) | 0.0087 (16) |
C21 | 0.0384 (17) | 0.0408 (18) | 0.0372 (17) | 0.0021 (14) | 0.0042 (13) | 0.0090 (14) |
Geometric parameters (Å, º) top
Br1—C4 | 1.904 (3) | C8—C9 | 1.391 (5) |
Br2—C18 | 1.905 (3) | C9—C10 | 1.391 (5) |
Ni—O1 | 1.850 (2) | C9—H9 | 0.9300 |
Ni—O2 | 1.859 (2) | C10—C11 | 1.376 (5) |
Ni—N2 | 1.875 (3) | C10—H10 | 0.9300 |
Ni—N1 | 1.901 (3) | C11—C12 | 1.387 (5) |
O1—C1 | 1.299 (4) | C11—H11 | 0.9300 |
O2—C21 | 1.306 (4) | C12—C13 | 1.387 (4) |
N1—C7 | 1.299 (4) | C12—H12 | 0.9300 |
N1—C8 | 1.439 (4) | C13—C14 | 1.501 (5) |
N2—C15 | 1.286 (4) | C14—H14A | 0.9700 |
N2—C14 | 1.477 (4) | C14—H14B | 0.9700 |
C1—C6 | 1.414 (5) | C15—C16 | 1.423 (5) |
C1—C2 | 1.417 (4) | C15—H15 | 0.9300 |
C2—C3 | 1.359 (5) | C16—C17 | 1.401 (4) |
C2—H2 | 0.9300 | C16—C21 | 1.403 (4) |
C3—C4 | 1.392 (5) | C17—C18 | 1.361 (5) |
C3—H3 | 0.9300 | C17—H17 | 0.9300 |
C4—C5 | 1.361 (4) | C18—C19 | 1.382 (5) |
C5—C6 | 1.411 (4) | C19—C20 | 1.364 (5) |
C5—H5 | 0.9300 | C19—H19 | 0.9300 |
C6—C7 | 1.416 (4) | C20—C21 | 1.416 (5) |
C7—H7 | 0.9300 | C20—H20 | 0.9300 |
C8—C13 | 1.387 (4) | | |
| | | |
O1—Ni—O2 | 82.64 (10) | C10—C9—H9 | 120.6 |
O1—Ni—N2 | 172.20 (10) | C11—C10—C9 | 120.4 (4) |
O2—Ni—N2 | 92.46 (10) | C11—C10—H10 | 119.8 |
O1—Ni—N1 | 92.65 (10) | C9—C10—H10 | 119.8 |
O2—Ni—N1 | 172.06 (10) | C10—C11—C12 | 120.2 (3) |
N2—Ni—N1 | 92.87 (11) | C10—C11—H11 | 119.9 |
C1—O1—Ni | 127.9 (2) | C12—C11—H11 | 119.9 |
C21—O2—Ni | 127.22 (19) | C13—C12—C11 | 120.4 (3) |
C7—N1—C8 | 115.7 (3) | C13—C12—H12 | 119.8 |
C7—N1—Ni | 124.0 (2) | C11—C12—H12 | 119.8 |
C8—N1—Ni | 119.82 (19) | C12—C13—C8 | 119.0 (3) |
C15—N2—C14 | 116.6 (3) | C12—C13—C14 | 122.6 (3) |
C15—N2—Ni | 125.8 (2) | C8—C13—C14 | 118.4 (3) |
C14—N2—Ni | 117.6 (2) | N2—C14—C13 | 108.4 (2) |
O1—C1—C6 | 123.4 (3) | N2—C14—H14A | 110.0 |
O1—C1—C2 | 119.4 (3) | C13—C14—H14A | 110.0 |
C6—C1—C2 | 117.2 (3) | N2—C14—H14B | 110.0 |
C3—C2—C1 | 121.4 (3) | C13—C14—H14B | 110.0 |
C3—C2—H2 | 119.3 | H14A—C14—H14B | 108.4 |
C1—C2—H2 | 119.3 | N2—C15—C16 | 125.8 (3) |
C2—C3—C4 | 120.3 (3) | N2—C15—H15 | 117.1 |
C2—C3—H3 | 119.8 | C16—C15—H15 | 117.1 |
C4—C3—H3 | 119.8 | C17—C16—C21 | 120.8 (3) |
C5—C4—C3 | 120.9 (3) | C17—C16—C15 | 118.2 (3) |
C5—C4—Br1 | 119.6 (3) | C21—C16—C15 | 120.7 (3) |
C3—C4—Br1 | 119.4 (2) | C18—C17—C16 | 120.2 (3) |
C4—C5—C6 | 119.7 (3) | C18—C17—H17 | 119.9 |
C4—C5—H5 | 120.2 | C16—C17—H17 | 119.9 |
C6—C5—H5 | 120.2 | C17—C18—C19 | 120.2 (3) |
C5—C6—C1 | 120.4 (3) | C17—C18—Br2 | 119.3 (3) |
C5—C6—C7 | 118.9 (3) | C19—C18—Br2 | 120.5 (3) |
C1—C6—C7 | 120.5 (3) | C20—C19—C18 | 120.5 (3) |
N1—C7—C6 | 126.7 (3) | C20—C19—H19 | 119.7 |
N1—C7—H7 | 116.6 | C18—C19—H19 | 119.7 |
C6—C7—H7 | 116.6 | C19—C20—C21 | 121.4 (3) |
C13—C8—C9 | 121.1 (3) | C19—C20—H20 | 119.3 |
C13—C8—N1 | 118.5 (3) | C21—C20—H20 | 119.3 |
C9—C8—N1 | 120.4 (3) | O2—C21—C16 | 123.6 (3) |
C8—C9—C10 | 118.9 (3) | O2—C21—C20 | 119.6 (3) |
C8—C9—H9 | 120.6 | C16—C21—C20 | 116.8 (3) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C9—H9···O2i | 0.93 | 2.68 | 3.484 (4) | 145 |
C14—H14A···O2ii | 0.97 | 2.51 | 3.403 (4) | 152 |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x+1, −y+1, −z+1. |
Experimental details
Crystal data |
Chemical formula | [Ni(C21H14Br2N2O2)] |
Mr | 544.87 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 7.228 (5), 10.834 (7), 12.831 (8) |
α, β, γ (°) | 100.09 (1), 99.83 (1), 95.63 (1) |
V (Å3) | 966.2 (11) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 5.16 |
Crystal size (mm) | 0.35 × 0.12 × 0.10 |
|
Data collection |
Diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrich, 1996) |
Tmin, Tmax | 0.299, 0.597 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9936, 3752, 2981 |
Rint | 0.024 |
(sin θ/λ)max (Å−1) | 0.617 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.033, 0.082, 1.02 |
No. of reflections | 3752 |
No. of parameters | 253 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.74, −0.39 |
Selected geometric parameters (Å, º) topBr1—C4 | 1.904 (3) | Ni—N1 | 1.901 (3) |
Br2—C18 | 1.905 (3) | O1—C1 | 1.299 (4) |
Ni—O1 | 1.850 (2) | O2—C21 | 1.306 (4) |
Ni—O2 | 1.859 (2) | N1—C7 | 1.299 (4) |
Ni—N2 | 1.875 (3) | N2—C15 | 1.286 (4) |
| | | |
O1—Ni—O2 | 82.64 (10) | O1—Ni—N1 | 92.65 (10) |
O1—Ni—N2 | 172.20 (10) | O2—Ni—N1 | 172.06 (10) |
O2—Ni—N2 | 92.46 (10) | N2—Ni—N1 | 92.87 (11) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C9—H9···O2i | 0.93 | 2.68 | 3.484 (4) | 145 |
C14—H14A···O2ii | 0.97 | 2.51 | 3.403 (4) | 152 |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x+1, −y+1, −z+1. |
Comparison of geometric parameters (Å, °) of similar NiII–Schiff base complexes top | D1a | D2b | A1c | A2d | A3e |
Ii | 0.104 (3) | 0.002 (1) | 9.37 (7) | 19.70 (5) | 18.99 (6) |
Iii | 0.044 (2) | 0.002 (2) | 6.1 (2) | 9.9 (2) | 4.0 (2) |
Iiii | 0.08 | 0.06 | 8.9 (3) | 4.0 (2) | 4.9 (3) |
Iiv | 0.213 (4) | 0.013 (3) | 29.3 (3) | 11.0 (3) | 25.7 (3) |
Iv | 0.004 | 0.029 | 43.5 (1) | 24.9 (2) | 19.0 (2) |
Notes: (i) this work; (ii) [Ni(salchd)] (de Castro et al., 2001); (iii) [Ni(-)(chxn)(sal)2] (Wojtczak et al., 1997); (iv) [Ni(salpd)] (Arici et al., 2001); (v) [Ni(-)(chxn)(hapi)2] (Szlyk et al., 1999); (a) the maximum deviation from the N2O2 plane; (b) the deviation of the Ni atom from the least squares N2O2 plane; (c) the dihedral angle between the two chelating rings; (d) the angle between the N2O2 plane and the N1···O1 plane; (e) the angle between the N2O2 plane and the N2···O2 plane. |
Multidentate Schiff base ligands and their nickel(II) complexes have been studied extensively because of their preparative accessibility and structural variability (Garnovskii et al., 1993). In addition to their diverse chelating ability, magnetic properties and applications in catalysis, the Schiff base ligands derived from salicylaldimine can serve as efficient models for biologically important systems (Long, 1995). In general, nickel(II) complexes of diamine Schiff bases display square-planar metal coordination (Elerman et al., 1996; Sony et al., 2004). When the substituents in the imine bridge are bulkier or the substitution is asymmetric, the metal coordination often exhibits tetrahedral distortion (Elmali et al., 2000; de Castro et al., 2001). As part of systematic studies of the characterization of tetradentate nickel(II)–diamine complexes (Datta et al., 2003), and to build up a hierarchy for such systems, the synthesis, spectroscopy and X-ray structural studies of the title complex, (I), were undertaken.
The crystal structure of (I) (Fig. 1) is built from discrete NiL units (where L is the tetradentate Schiff base ligand) in which each NiII ion is coordinated by two imine N and two phenolate O atoms. The coordination polyhedron around the metal centre is close to square-planar, the N2O2 plane being slightly tetrahedrally distorted [maximum deviation of 0.104 (3) Å for atom N2]. The Ni atom [deviation 0.002 (1) Å] is well within the plane defined by atoms N1, N2, O1 and O2. The distortion of the metal coordination geometry from an ideal square-planar arrangement is revealed by the cisoid O—Ni—O angle of 82.64 (10)° (Table 1) and the dihedral angle of 8.2 (1)° between the two Ni/N/O planes. Similar distortions in the metal coordination geometry have been reported for tetradentate nickel(II)–Schiff base complexes (Arici et al., 2001; Elmali et al., 2000; de Castro et al., 2001) where the substituents in the imine bridge are bulkier.
The tetradentate ligand consists of three essentially planar parts, viz. two 5-bromosalicylideneimine groups [O1/N1/Br1/C1–C7 (L1) and O2/N2/Br2/C15–C21 (L2)], and the bridging benzyl moiety [C8–C14 (L3)]. The maximum deviation of an atom from the L1, L2 and L3 least-squares planes is 0.085 (3) Å for atom C7 in L1; the corresponding deviations of the Ni atom from the L1 and L2 planes are 0.467 (1) and 0.438 (1) Å, respectively. The dihedral angle between L1 and L2 is 8.8 (1)°, indicating a flat arrangement of the two bromosalicylideneimine groups in the molecule. This geometry is similar to that observed in the [Ni(salchd)] (de Castro et al., 2001) and [Ni(-)(chxn)(sal)2] (Wojtczak et al., 1997) complexes [salchd is bis(salicylidene)cyclohexane-1,2-diaminate, chxn is ?? and sal is salicylidene??] (see Table 3). The pronounced distortion of the planar geometry in [Ni(salpd)] [salpd is bis(salicylidene)-2,2-dimethyl-1,3-propanediaminate; Arici et al., 2001] and [Ni(-)(chxn)(hapi)2] (hapi is ??; Szlyk et al., 1999) complexes (see Table 3), where the bridging moiety between the two imine N atoms has methyl substitution, is due to the steric requirements imposed by the interaction between the bulky methyl group and other H atoms of the ligand. The whole ligand in (I), however, is not planar; the bridging benzyl moiety (L3) is inclined to the 5-bromosalicylideneimne planes L1 and L2 by 56.2 (1) and 60.7 (1)°, respectively. The bridging chelate ring composed of atoms Ni, N1, C8, C13, C14 and N2 has a distorted boat conformation, with ring puckering parameters (Cremer & Pople, 1975) Q = 0.684 (3) Å, θ = 97.5 (3)° and ϕ = 68.5 (3)°. The distances of the two para-positioned boat atoms, N1 and C14, from the mean plane of the six atoms are 0.435 (2) and 0.715 (3) Å, respectively. The Ni—N and Ni—O bond distances (Table 1) are in good agreement with those observed in similar NiII–Schiff base complexs (Santos et al., 2000; Szlyk et al., 1999). ??The fact that the Ni—N bond distances in (I) are slightly longer than those in these related compounds may be attributed to the steric hindrance of the benzyl group between the N atoms, which is bulkier than the bridging groups in these related compounds. The slightly longer Ni—N bond distances in (I) may be attributed to the steric hindrance of the bulky benzyl group between the N atoms. Other bond distances and angles in (I) are within the ranges found for related structures (Elmali et al., 2000; Elerman et al., 1998).
Molecules of (I) are linked by two different C—H····O hydrogen bonds (Table 2) into centrosymmetric dimers, in which one of the phenolate O atoms acts as a double acceptor. Phenyl atom C9 at (x, y, z) acts as a hydrogen-bond donor to O2 at (-x, −y + 1, −z + 1), thus forming a dimer characterized by an R22(12) motif (A) with an inversion centre at (0, 1/2, 1/2). Similarly, atom C14 at (x, y, z) acts as a donor to atom O2 at (-x + 1, −y + 1, −z + 1), generating an R22(10) ring (B) with an inversion centre at (1/2, 1/2, 1/2). These two dimers combine to form a supramolecular aggregate, ABAB···, which propagates along [100] (Fig. 2). The observed Ni···Ni distance, 3.480 (3) Å, in (I) is well within the values reported [3.201 (1)–3.582 (1) Å] for analogous Schiff base complexes (de Castro et al., 2001; Encan et al., 1997; Wojtczak et al., 1997) with Ni···Ni interactions.