metal-organic compounds
(μ-4-Bromo-2-{1-[2-(dimethylamino)ethylimino]ethyl}phenolato)bis[ethylzinc(II)]
aDepartment of Chemistry, National Chung Hsing University, Taichung 402, Taiwan, and bCollege of Design, Ling Tung University, Taichung 408, Taiwan
*Correspondence e-mail: cchlin@mail.nchu.edu.tw
The title complex, [Zn2(C2H5)2(C12H16BrN2O)2], is dimeric, bridged through the O atoms of the phenolate anions. The molecule lies on a crystallographic twofold rotation axis. Each Zn atom is pentacoordinated by two N atoms and two bridging O atoms of the tridentate salicylideneiminate ligands and one C atom from an ethyl group, forming a distorted square-pyramidal environment.
Related literature
For related literature, see: Chamberlain et al. (2001); Chen et al. (2005, 2006); Chisholm et al. (2000); Dechy-Cabaret et al. (2004); Gref et al. (1994); Jeong et al. (1997); Williams et al. (2003); Wu et al. (2005, 2006)
Experimental
Crystal data
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Data collection
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Refinement
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Data collection: SMART (Bruker, 1999); cell SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1999); software used to prepare material for publication: SHELXTL.
Supporting information
https://doi.org/10.1107/S1600536807065208/at2521sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536807065208/at2521Isup2.hkl
The ligand, 4-bromo-2-[1-(2-dimethylamino-ethylimino)ethyl]phenol was prepared by the reaction of 2-dimethylaminoethylamine (1.39 g, 22 mmol) with 5-bromo-2-hydroxyacetophenone (4.30 g, 20 mmol) in ethanol (30 ml) at room temperature for 24 h. Volatile materials were removed under vacuum and the resulting material was dissolved in hot hexane (30 ml). The solution was then cooled at 250 K for 24 h giving yellow powder.
The title complex was synthesized by the following procedures. To an ice cold solution (273 K) of 4-bromo-2-[1-(2-dimethylamino-ethylimino)ethyl]phenol (0.57 g, 2.0 mmol) in 40 ml hexane was slowly added a diethyl zinc (2.2 ml, 1 M in hexane, 2.2 mmol) solution. The mixture was stirred at room temoerature for 3 h during which the formation of yellow precipitate was observed. The resulting solid was collected by filtration and then dried under vacuum to give yellow powder. Yellow crystals was obtained from the recrystallization of a mixed dichloromethane/hexane solution.
All non-H atoms were initially located in a difference Fourier map. The methyl H atoms were then constrained to an ideal geometry with C—H distances of 0.96 Å and Uiso(H) = 1.5Ueq(C), but each group was allowed to rotate freely about its C—C bond. All other H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with C—H distances in the range 0.95–1.00 Å and Uiso(H) =1.2Ueq(C).
Poly(ε-caprolactone) (PCL) and poly(lactide) (PLA) and their copolymers have been attracting considerable attention due to their potential applications in many fields (Gref et al.,1994; Jeong et al., 1997). The major polymerization method employed to synthesize these polymers is the (ROP) of lactones/lactides. Many zinc complexes with various ligands have been reported to be effective initiators/catalyst for ROP of lactones/lactides (Chamberlain et al., 2001; Williams et al., 2003; Dechy-Cabaret et al. 2004; Chen, et al., 2005, Wu, et al., 2005; Wu et al., 2006). Tripodal tridentate ligand supported zinc complexes have been synthesized and used for the polymerization of and the polymerizations are living with relatively low polydispersities (Chisholm et al., 2000). Recently, we have synthesized a series of Schiff base zinc complexes which have shown high activity in the ROP of lactide (Chen et al., 2006). We report herein the synthesis and of a NNO-tridentate Schifff base zinc complex (I), a potential catalyst for lactide polymerization.
The solid structure of (I) reveals a dimeric Zn(II) complex (Fig. 1.) containing a Zn2O2 core bridging through the oxygen atoms of the phenolate. The geometry around Zn atom is pentacoordinated with a distorted square pyramid geometry in which two nitrogen atoms and two oxygen atoms are almost coplanar occupied the basal positions. The ethyl group is sitting on the axial position. The zinc atom is ca 0.888 Å above the O1/O1A/N1/N2 mean plane. The distances between the Zn atom and O1, O1A, N1, N2, and C13 are 2.142 (3), 2.060 (3), 2.180 (4), 2.236 (4), 2.022 (4) Å, respectively, which are all within a normal range for Schiff base Zn(II) complexes (Chen et al., 2006).
For related literature, see: Chamberlain et al. (2001); Chen et al. (2005, 2006); Chisholm et al. (2000); Dechy-Cabaret et al. (2004); Gref et al. (1994); Jeong et al. (1997); Williams et al. (2003); Wu et al. (2005, 2006).
Data collection: SMART (Bruker, 1999); cell
SAINT (Bruker, 1999); data reduction: SAINT (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1999); software used to prepare material for publication: SHELXTL (Bruker, 1999).Fig. 1. A view of the molecular structure of (I) with displacement ellipsoids shown at the 20% probability level. |
[Zn2(C2H5)2(C12H16BrN2O)2] | F(000) = 1536 |
Mr = 757.22 | Dx = 1.550 Mg m−3 |
Orthorhombic, Pbcn | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2n 2ab | Cell parameters from 3732 reflections |
a = 21.656 (6) Å | θ = 2.8–24.0° |
b = 7.839 (2) Å | µ = 3.97 mm−1 |
c = 19.114 (5) Å | T = 293 K |
V = 3244.9 (14) Å3 | Parallelpiped, yellow |
Z = 4 | 0.17 × 0.16 × 0.15 mm |
Bruker SMART 1K CCD diffractometer | 1957 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.086 |
Graphite monochromator | θmax = 26.1°, θmin = 1.9° |
φ and ω scans | h = −26→25 |
17313 measured reflections | k = −9→9 |
3207 independent reflections | l = −13→23 |
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)] = 0.040 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.107 | H-atom parameters constrained |
S = 1.00 | w = 1/[σ2(Fo2) + (0.052P)2] where P = (Fo2 + 2Fc2)/3 |
3207 reflections | (Δ/σ)max = 0.002 |
172 parameters | Δρmax = 0.68 e Å−3 |
0 restraints | Δρmin = −0.39 e Å−3 |
[Zn2(C2H5)2(C12H16BrN2O)2] | V = 3244.9 (14) Å3 |
Mr = 757.22 | Z = 4 |
Orthorhombic, Pbcn | Mo Kα radiation |
a = 21.656 (6) Å | µ = 3.97 mm−1 |
b = 7.839 (2) Å | T = 293 K |
c = 19.114 (5) Å | 0.17 × 0.16 × 0.15 mm |
Bruker SMART 1K CCD diffractometer | 1957 reflections with I > 2σ(I) |
17313 measured reflections | Rint = 0.086 |
3207 independent reflections |
R[F2 > 2σ(F2)] = 0.040 | 0 restraints |
wR(F2) = 0.107 | H-atom parameters constrained |
S = 1.00 | Δρmax = 0.68 e Å−3 |
3207 reflections | Δρmin = −0.39 e Å−3 |
172 parameters |
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 | ||
Zn | 0.93264 (2) | 0.18811 (6) | 0.70779 (3) | 0.04040 (17) | |
Br | 0.79595 (3) | 0.47079 (8) | 1.01986 (3) | 0.0781 (2) | |
O1 | 0.97357 (12) | 0.1816 (4) | 0.80980 (15) | 0.0476 (8) | |
N1 | 0.87340 (16) | 0.0062 (4) | 0.7620 (2) | 0.0462 (9) | |
N2 | 0.92031 (17) | −0.0132 (5) | 0.6261 (2) | 0.0569 (10) | |
C1 | 0.93610 (19) | 0.2386 (6) | 0.8581 (2) | 0.0424 (10) | |
C2 | 0.87745 (18) | 0.1621 (5) | 0.8681 (2) | 0.0395 (10) | |
C3 | 0.8368 (2) | 0.2322 (6) | 0.9182 (2) | 0.0461 (11) | |
H3A | 0.7984 | 0.1821 | 0.9254 | 0.055* | |
C4 | 0.8534 (2) | 0.3742 (6) | 0.9567 (2) | 0.0536 (12) | |
C5 | 0.9115 (2) | 0.4456 (6) | 0.9490 (3) | 0.0613 (14) | |
H5A | 0.9231 | 0.5387 | 0.9761 | 0.074* | |
C6 | 0.9519 (2) | 0.3770 (6) | 0.9005 (3) | 0.0566 (13) | |
H6A | 0.9911 | 0.4247 | 0.8961 | 0.068* | |
C7 | 0.85761 (18) | 0.0141 (5) | 0.8261 (3) | 0.0428 (10) | |
C8 | 0.8185 (3) | −0.1206 (7) | 0.8618 (3) | 0.0779 (17) | |
H8A | 0.8087 | −0.2092 | 0.8289 | 0.117* | |
H8B | 0.7810 | −0.0697 | 0.8786 | 0.117* | |
H8C | 0.8410 | −0.1683 | 0.9003 | 0.117* | |
C9 | 0.8539 (2) | −0.1357 (6) | 0.7177 (3) | 0.0655 (15) | |
H9A | 0.8114 | −0.1653 | 0.7279 | 0.079* | |
H9B | 0.8795 | −0.2348 | 0.7269 | 0.079* | |
C10 | 0.8600 (2) | −0.0839 (7) | 0.6419 (3) | 0.0780 (18) | |
H10A | 0.8529 | −0.1827 | 0.6125 | 0.094* | |
H10B | 0.8286 | 0.0002 | 0.6310 | 0.094* | |
C11 | 0.9207 (3) | 0.0648 (9) | 0.5561 (3) | 0.104 (2) | |
H11A | 0.9154 | −0.0223 | 0.5213 | 0.156* | |
H11B | 0.9593 | 0.1219 | 0.5486 | 0.156* | |
H11C | 0.8875 | 0.1457 | 0.5526 | 0.156* | |
C12 | 0.9678 (3) | −0.1460 (7) | 0.6266 (4) | 0.092 (2) | |
H12A | 0.9593 | −0.2274 | 0.5903 | 0.138* | |
H12B | 0.9677 | −0.2026 | 0.6711 | 0.138* | |
H12C | 1.0075 | −0.0952 | 0.6186 | 0.138* | |
C13 | 0.88570 (19) | 0.4061 (5) | 0.6884 (2) | 0.0469 (11) | |
H13A | 0.9059 | 0.4986 | 0.7132 | 0.056* | |
H13B | 0.8885 | 0.4307 | 0.6388 | 0.056* | |
C14 | 0.8200 (2) | 0.4042 (8) | 0.7084 (3) | 0.0851 (19) | |
H14A | 0.8016 | 0.5121 | 0.6970 | 0.128* | |
H14B | 0.8165 | 0.3843 | 0.7578 | 0.128* | |
H14C | 0.7992 | 0.3150 | 0.6834 | 0.128* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Zn | 0.0380 (3) | 0.0341 (3) | 0.0490 (3) | 0.0014 (2) | −0.0007 (2) | −0.0017 (2) |
Br | 0.0802 (4) | 0.0978 (5) | 0.0562 (4) | 0.0351 (3) | −0.0039 (3) | −0.0238 (3) |
O1 | 0.0353 (15) | 0.0560 (19) | 0.052 (2) | 0.0020 (14) | 0.0015 (13) | −0.0005 (15) |
N1 | 0.047 (2) | 0.032 (2) | 0.061 (3) | −0.0057 (16) | 0.0050 (18) | −0.0076 (18) |
N2 | 0.060 (3) | 0.055 (2) | 0.055 (3) | −0.012 (2) | 0.0055 (19) | −0.019 (2) |
C1 | 0.046 (2) | 0.044 (2) | 0.037 (3) | 0.006 (2) | −0.005 (2) | 0.002 (2) |
C2 | 0.043 (2) | 0.037 (2) | 0.039 (2) | 0.0009 (19) | 0.0002 (19) | 0.0008 (19) |
C3 | 0.045 (2) | 0.051 (3) | 0.042 (3) | 0.003 (2) | 0.001 (2) | 0.002 (2) |
C4 | 0.056 (3) | 0.062 (3) | 0.043 (3) | 0.020 (2) | −0.003 (2) | −0.005 (2) |
C5 | 0.069 (3) | 0.051 (3) | 0.064 (4) | 0.001 (3) | −0.016 (3) | −0.012 (3) |
C6 | 0.050 (3) | 0.056 (3) | 0.064 (4) | −0.006 (2) | −0.006 (2) | −0.007 (3) |
C7 | 0.041 (2) | 0.035 (2) | 0.052 (3) | −0.0002 (19) | 0.007 (2) | 0.001 (2) |
C8 | 0.083 (4) | 0.068 (4) | 0.083 (4) | −0.030 (3) | 0.024 (3) | 0.003 (3) |
C9 | 0.072 (3) | 0.046 (3) | 0.078 (4) | −0.022 (3) | 0.015 (3) | −0.025 (3) |
C10 | 0.065 (4) | 0.079 (4) | 0.089 (5) | −0.029 (3) | 0.006 (3) | −0.041 (3) |
C11 | 0.143 (6) | 0.114 (5) | 0.054 (4) | −0.046 (5) | 0.003 (4) | −0.021 (4) |
C12 | 0.083 (4) | 0.065 (4) | 0.128 (6) | 0.003 (3) | 0.020 (4) | −0.032 (4) |
C13 | 0.046 (2) | 0.029 (2) | 0.066 (3) | 0.0080 (19) | −0.010 (2) | 0.003 (2) |
C14 | 0.073 (4) | 0.063 (4) | 0.119 (5) | 0.021 (3) | 0.015 (4) | 0.027 (4) |
Zn—C13 | 2.022 (4) | C6—H6A | 0.9300 |
Zn—O1i | 2.060 (3) | C7—C8 | 1.516 (6) |
Zn—O1 | 2.142 (3) | C8—H8A | 0.9600 |
Zn—N1 | 2.180 (4) | C8—H8B | 0.9600 |
Zn—N2 | 2.236 (4) | C8—H8C | 0.9600 |
Br—C4 | 1.892 (4) | C9—C10 | 1.509 (7) |
O1—C1 | 1.307 (5) | C9—H9A | 0.9700 |
O1—Zni | 2.060 (3) | C9—H9B | 0.9700 |
N1—C7 | 1.273 (5) | C10—H10A | 0.9700 |
N1—C9 | 1.460 (6) | C10—H10B | 0.9700 |
N2—C10 | 1.451 (6) | C11—H11A | 0.9600 |
N2—C12 | 1.464 (6) | C11—H11B | 0.9600 |
N2—C11 | 1.471 (7) | C11—H11C | 0.9600 |
C1—C6 | 1.398 (6) | C12—H12A | 0.9600 |
C1—C2 | 1.417 (6) | C12—H12B | 0.9600 |
C2—C3 | 1.413 (6) | C12—H12C | 0.9600 |
C2—C7 | 1.475 (6) | C13—C14 | 1.472 (7) |
C3—C4 | 1.382 (6) | C13—H13A | 0.9700 |
C3—H3A | 0.9300 | C13—H13B | 0.9700 |
C4—C5 | 1.384 (6) | C14—H14A | 0.9600 |
C5—C6 | 1.383 (7) | C14—H14B | 0.9600 |
C5—H5A | 0.9300 | C14—H14C | 0.9600 |
C13—Zn—O1i | 119.14 (15) | C7—C8—H8A | 109.5 |
C13—Zn—O1 | 113.25 (15) | C7—C8—H8B | 109.5 |
O1i—Zn—O1 | 74.93 (13) | H8A—C8—H8B | 109.5 |
C13—Zn—N1 | 110.12 (16) | C7—C8—H8C | 109.5 |
O1i—Zn—N1 | 129.91 (12) | H8A—C8—H8C | 109.5 |
O1—Zn—N1 | 78.18 (13) | H8B—C8—H8C | 109.5 |
C13—Zn—N2 | 114.09 (17) | N1—C9—C10 | 109.1 (4) |
O1i—Zn—N2 | 89.20 (13) | N1—C9—H9A | 109.9 |
O1—Zn—N2 | 131.93 (14) | C10—C9—H9A | 109.9 |
N1—Zn—N2 | 78.48 (14) | N1—C9—H9B | 109.9 |
C1—O1—Zni | 136.0 (3) | C10—C9—H9B | 109.9 |
C1—O1—Zn | 112.2 (2) | H9A—C9—H9B | 108.3 |
Zni—O1—Zn | 105.00 (13) | N2—C10—C9 | 112.4 (4) |
C7—N1—C9 | 121.2 (4) | N2—C10—H10A | 109.1 |
C7—N1—Zn | 125.7 (3) | C9—C10—H10A | 109.1 |
C9—N1—Zn | 113.1 (3) | N2—C10—H10B | 109.1 |
C10—N2—C12 | 111.1 (4) | C9—C10—H10B | 109.1 |
C10—N2—C11 | 110.7 (5) | H10A—C10—H10B | 107.8 |
C12—N2—C11 | 107.3 (5) | N2—C11—H11A | 109.5 |
C10—N2—Zn | 103.4 (3) | N2—C11—H11B | 109.5 |
C12—N2—Zn | 114.4 (3) | H11A—C11—H11B | 109.5 |
C11—N2—Zn | 110.0 (3) | N2—C11—H11C | 109.5 |
O1—C1—C6 | 121.5 (4) | H11A—C11—H11C | 109.5 |
O1—C1—C2 | 120.4 (4) | H11B—C11—H11C | 109.5 |
C6—C1—C2 | 118.0 (4) | N2—C12—H12A | 109.5 |
C3—C2—C1 | 119.1 (4) | N2—C12—H12B | 109.5 |
C3—C2—C7 | 119.6 (4) | H12A—C12—H12B | 109.5 |
C1—C2—C7 | 121.4 (4) | N2—C12—H12C | 109.5 |
C4—C3—C2 | 120.8 (4) | H12A—C12—H12C | 109.5 |
C4—C3—H3A | 119.6 | H12B—C12—H12C | 109.5 |
C2—C3—H3A | 119.6 | C14—C13—Zn | 115.4 (3) |
C3—C4—C5 | 120.4 (4) | C14—C13—H13A | 108.4 |
C3—C4—Br | 119.4 (4) | Zn—C13—H13A | 108.4 |
C5—C4—Br | 120.2 (4) | C14—C13—H13B | 108.4 |
C4—C5—C6 | 119.3 (5) | Zn—C13—H13B | 108.4 |
C4—C5—H5A | 120.3 | H13A—C13—H13B | 107.5 |
C6—C5—H5A | 120.3 | C13—C14—H14A | 109.5 |
C1—C6—C5 | 122.3 (4) | C13—C14—H14B | 109.5 |
C1—C6—H6A | 118.8 | H14A—C14—H14B | 109.5 |
C5—C6—H6A | 118.8 | C13—C14—H14C | 109.5 |
N1—C7—C2 | 118.9 (4) | H14A—C14—H14C | 109.5 |
N1—C7—C8 | 123.3 (4) | H14B—C14—H14C | 109.5 |
C2—C7—C8 | 117.8 (4) |
Symmetry code: (i) −x+2, y, −z+3/2. |
Experimental details
Crystal data | |
Chemical formula | [Zn2(C2H5)2(C12H16BrN2O)2] |
Mr | 757.22 |
Crystal system, space group | Orthorhombic, Pbcn |
Temperature (K) | 293 |
a, b, c (Å) | 21.656 (6), 7.839 (2), 19.114 (5) |
V (Å3) | 3244.9 (14) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 3.97 |
Crystal size (mm) | 0.17 × 0.16 × 0.15 |
Data collection | |
Diffractometer | Bruker SMART 1K CCD |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 17313, 3207, 1957 |
Rint | 0.086 |
(sin θ/λ)max (Å−1) | 0.618 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.040, 0.107, 1.00 |
No. of reflections | 3207 |
No. of parameters | 172 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.68, −0.39 |
Computer programs: SMART (Bruker, 1999), SAINT (Bruker, 1999), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 1999).
Zn—C13 | 2.022 (4) | Zn—N1 | 2.180 (4) |
Zn—O1i | 2.060 (3) | Zn—N2 | 2.236 (4) |
Zn—O1 | 2.142 (3) | ||
C13—Zn—O1i | 119.14 (15) | O1—Zn—N1 | 78.18 (13) |
C13—Zn—O1 | 113.25 (15) | C13—Zn—N2 | 114.09 (17) |
O1i—Zn—O1 | 74.93 (13) | O1i—Zn—N2 | 89.20 (13) |
C13—Zn—N1 | 110.12 (16) | O1—Zn—N2 | 131.93 (14) |
O1i—Zn—N1 | 129.91 (12) | N1—Zn—N2 | 78.48 (14) |
Symmetry code: (i) −x+2, y, −z+3/2. |
Acknowledgements
Financial support from the National Science Council of the Republic of China is gratefully appreciated.
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Poly(ε-caprolactone) (PCL) and poly(lactide) (PLA) and their copolymers have been attracting considerable attention due to their potential applications in many fields (Gref et al.,1994; Jeong et al., 1997). The major polymerization method employed to synthesize these polymers is the ring-opening polymerization (ROP) of lactones/lactides. Many zinc complexes with various ligands have been reported to be effective initiators/catalyst for ROP of lactones/lactides (Chamberlain et al., 2001; Williams et al., 2003; Dechy-Cabaret et al. 2004; Chen, et al., 2005, Wu, et al., 2005; Wu et al., 2006). Tripodal tridentate ligand supported zinc complexes have been synthesized and used for the polymerization of lactides and the polymerizations are living with relatively low polydispersities (Chisholm et al., 2000). Recently, we have synthesized a series of Schiff base zinc complexes which have shown high activity in the ROP of lactide (Chen et al., 2006). We report herein the synthesis and crystal structure of a NNO-tridentate Schifff base zinc complex (I), a potential catalyst for lactide polymerization.
The solid structure of (I) reveals a dimeric Zn(II) complex (Fig. 1.) containing a Zn2O2 core bridging through the oxygen atoms of the phenolate. The geometry around Zn atom is pentacoordinated with a distorted square pyramid geometry in which two nitrogen atoms and two oxygen atoms are almost coplanar occupied the basal positions. The ethyl group is sitting on the axial position. The zinc atom is ca 0.888 Å above the O1/O1A/N1/N2 mean plane. The distances between the Zn atom and O1, O1A, N1, N2, and C13 are 2.142 (3), 2.060 (3), 2.180 (4), 2.236 (4), 2.022 (4) Å, respectively, which are all within a normal range for Schiff base Zn(II) complexes (Chen et al., 2006).