metal-organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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Bis{μ-2-[2-(2-pyrid­yl)ethyl­imino­meth­yl]phenolato}bis­­[azido­zinc(II)]

aOrdered Matter Science Research Center, College of Chemistry and Chemical Engineering, Southeast UniVersity, Nanjing 210096, People's Republic of China
*Correspondence e-mail: chmsunbw@seu.edu.cn

(Received 25 March 2008; accepted 5 May 2008; online 10 May 2008)

In the centrosymmetric title dinuclear zinc(II) compound, [Zn2(C14H13N2O)2(N3)2], each ZnII ion has a slightly distorted trigonal bipyramidal geometry and is coordinated by two N atoms and one O atom from one Schiff base ligand, an O atom from the other Schiff base ligand, and another N atom from an azide ligand. The crystal structure involves inter­molecular C—H⋯N hydrogen bonds.

Related literature

For related literature, see: Tandon et al. (2000[Tandon, S. S., Chander, S. & Thompson, L. K. (2000). Inorg. Chim. Acta, E300, 683-692.]); Fu & Ye (2007[Fu, D.-W. & Ye, H.-Y. (2007). Acta Cryst. E63, m2453.]); Li & Zhang (2004[Li, Z.-X. & Zhang, X.-L. (2004). Acta Cryst. E60, m1017-m1019.]); You & Zhu (2004[You, Z.-L. & Zhu, H.-L. (2004). Z. Anorg. Allg. Chem. 630, 2754-2760.]).

[Scheme 1]

Experimental

Crystal data
  • [Zn2(C14H13N2O)2(N3)2]

  • Mr = 665.37

  • Monoclinic, P 21 /c

  • a = 9.523 (9) Å

  • b = 9.466 (9) Å

  • c = 15.853 (14) Å

  • β = 100.664 (17)°

  • V = 1404 (2) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 1.75 mm−1

  • T = 293 (2) K

  • 0.05 × 0.05 × 0.05 mm

Data collection
  • Bruker SMART 1K CCD area-detector diffractometer

  • Absorption correction: multi-scan (CrystalClear; Rigaku, 2005[Rigaku (2005). CrystalClear. Rigaku Corporation, Tokyo, Japan.]) Tmin = 0.915, Tmax = 0.915

  • 11424 measured reflections

  • 2460 independent reflections

  • 1824 reflections with I > 2σ(I)

  • Rint = 0.117

Refinement
  • R[F2 > 2σ(F2)] = 0.062

  • wR(F2) = 0.154

  • S = 1.00

  • 2460 reflections

  • 190 parameters

  • H-atom parameters constrained

  • Δρmax = 0.32 e Å−3

  • Δρmin = −0.37 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C9—H9A⋯N5i 0.97 2.58 3.198 (9) 122
Symmetry code: (i) -x+1, -y, -z.

Data collection: CrystalClear (Rigaku, 2005[Rigaku (2005). CrystalClear. Rigaku Corporation, Tokyo, Japan.]); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

Transition metal compounds containing Schiff base ligands are of great interest since many years. These compounds play an important role in the development of coordination chemistry related to their potential applications in catalysis and enzymatic reactions, magnetism and molecular architecture (You & Zhu, 2004; Li & Zhang, 2004).

We have focused on the synthesis of Schiff base complex which is formed by Cu(CH3COO)2.H2O, schiff base ligand 2-(pyridin-2-ylethyliminomethyl)phenol and sodium azide. The title dinuclear zinc(II) complex is reported here.

As shown in Fig. 1, the molecule of the title compound is composed of two ZnII atoms, two schiff base ligand 2-(pyridin-2-ylethyliminomethyl)phenol and two azido. Each ZnII atom shows a slightly distorted trigonal-bipyramidal geometry (Fu & Ye, 2007) formed by two N atoms and one O atom from one schiff base ligand (S.S. Tandon et al., 2000), the another O atom of the second schiff base, together with another N atom from azido. There are intermolecular C—H···N hydrogen bonds in the crystal structure leading to a one-dimensional supramolecular structure (Fig. 2 and Table 1).

Related literature top

For related literature, see: Tandon et al. (2000); Fu & Ye (2007); Li & Zhang (2004); You & Zhu (2004).

Experimental top

The title compound was synthesized by Cu(CH3COO)2.H2O, schiff base ligand 2-(pyridin-2-ylethyliminomethyl)phenol and sodium azide. All chemicals used (reagent grade) were commercially available. Salicylaldehyde (0.122 g, 1 mmol) was dissolved in ethanol (5 mL) and ethanol solution (5 mL) containing 2-aminoethylpyridine (0.108 g, 1 mmol) was added slowly with stirring. The resulting yellow solution was continuously stirred for about 30 min. at room temperature, and then Cu(CH3COO)2.H2O (0.200 g, 1 mmol) and sodium azide (0.13 g 2 mmol) in aqueous solution (5 mL) was added with stirring homogeneously. Colorless crystals suitable for X-ray analysis were obtained by slow evaporation at room temperature over several days.

Refinement top

Positional parameters of all H atoms were calculated geometrically.

Computing details top

Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear (Rigaku, 2005); data reduction: CrystalClear (Rigaku, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. [Symmetry code i : -x, -y, -z ]
[Figure 2] Fig. 2. One-dimensional structure in the title compound. Hydrogen bonds are shown as dashed lines. Displacement ellipsoids are drawn at the 30% probability level and all hydrogen atoms, except H9a was omitted for clarity.
Bis{µ-2-[2-(2-pyridyl)ethyliminomethyl]phenolato}bis[azidozinc(II)] top
Crystal data top
[Zn2(C14H13N2O)2(N3)2]F(000) = 680
Mr = 665.37Dx = 1.575 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 2415 reflections
a = 9.523 (9) Åθ = 3.1–27.5°
b = 9.466 (9) ŵ = 1.75 mm1
c = 15.853 (14) ÅT = 293 K
β = 100.664 (17)°Block, colorless
V = 1404 (2) Å30.05 × 0.05 × 0.05 mm
Z = 2
Data collection top
Bruker SMART 1K CCD area-detector
diffractometer
2460 independent reflections
Radiation source: fine-focus sealed tube1824 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.117
Detector resolution: 8.192 pixels mm-1θmax = 25.0°, θmin = 3.1°
thin–slice ω scansh = 1111
Absorption correction: multi-scan
(CrystalClear; Rigaku, 2005)
k = 1111
Tmin = 0.915, Tmax = 0.915l = 1818
11424 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.062Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.154H-atom parameters constrained
S = 1.00 w = 1/[σ2(Fo2) + (0.0733P)2]
where P = (Fo2 + 2Fc2)/3
2460 reflections(Δ/σ)max < 0.001
190 parametersΔρmax = 0.32 e Å3
0 restraintsΔρmin = 0.37 e Å3
Crystal data top
[Zn2(C14H13N2O)2(N3)2]V = 1404 (2) Å3
Mr = 665.37Z = 2
Monoclinic, P21/cMo Kα radiation
a = 9.523 (9) ŵ = 1.75 mm1
b = 9.466 (9) ÅT = 293 K
c = 15.853 (14) Å0.05 × 0.05 × 0.05 mm
β = 100.664 (17)°
Data collection top
Bruker SMART 1K CCD area-detector
diffractometer
2460 independent reflections
Absorption correction: multi-scan
(CrystalClear; Rigaku, 2005)
1824 reflections with I > 2σ(I)
Tmin = 0.915, Tmax = 0.915Rint = 0.117
11424 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0620 restraints
wR(F2) = 0.154H-atom parameters constrained
S = 1.00Δρmax = 0.32 e Å3
2460 reflectionsΔρmin = 0.37 e Å3
190 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.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Zn10.89278 (7)0.07610 (6)0.05279 (4)0.0388 (3)
O11.0963 (4)0.0175 (4)0.0700 (2)0.0443 (10)
N20.9352 (5)0.1930 (5)0.1691 (3)0.0437 (12)
C21.3382 (6)0.0122 (6)0.1341 (4)0.0439 (14)
H2A1.34920.07430.09040.053*
N10.8313 (5)0.2740 (5)0.0024 (3)0.0437 (12)
C11.2057 (6)0.0467 (5)0.1339 (3)0.0387 (13)
C71.0588 (7)0.2101 (6)0.2129 (4)0.0460 (14)
H7A1.06660.27500.25760.055*
C61.1919 (6)0.1403 (6)0.2022 (3)0.0407 (14)
C51.3113 (7)0.1695 (6)0.2653 (4)0.0513 (16)
H5A1.30170.23020.30990.062*
N40.6662 (7)0.1265 (5)0.0553 (3)0.0491 (13)
C100.7506 (6)0.3590 (6)0.0385 (4)0.0448 (14)
N30.7675 (7)0.0641 (6)0.0914 (4)0.0615 (15)
C80.8169 (7)0.2774 (7)0.1912 (4)0.0578 (17)
H8A0.85310.36850.21330.069*
H8B0.77820.22960.23600.069*
N50.5662 (7)0.1902 (6)0.0247 (4)0.0684 (16)
C31.4564 (7)0.0186 (7)0.1979 (4)0.0528 (16)
H3B1.54430.02310.19640.063*
C110.7189 (8)0.4943 (7)0.0084 (5)0.0626 (19)
H11A0.66200.55160.03580.075*
C140.8829 (7)0.3237 (6)0.0705 (4)0.0536 (16)
H14A0.93940.26530.09750.064*
C90.6990 (7)0.2995 (7)0.1140 (4)0.0527 (16)
H9A0.65260.20960.09800.063*
H9B0.62800.36280.12980.063*
C41.4422 (8)0.1111 (7)0.2632 (4)0.0618 (18)
H4A1.52070.13350.30530.074*
C130.8535 (9)0.4595 (7)0.1009 (5)0.071 (2)
H13A0.89010.49200.14770.085*
C120.7695 (9)0.5460 (7)0.0612 (5)0.076 (2)
H12A0.74760.63730.08100.091*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Zn10.0443 (4)0.0393 (4)0.0344 (4)0.0026 (3)0.0112 (3)0.0035 (3)
O10.041 (2)0.051 (2)0.040 (2)0.0056 (19)0.0049 (19)0.0138 (18)
N20.052 (3)0.047 (3)0.033 (3)0.009 (2)0.010 (2)0.001 (2)
C20.044 (4)0.045 (3)0.045 (4)0.001 (3)0.013 (3)0.007 (3)
N10.056 (3)0.039 (3)0.037 (3)0.002 (2)0.013 (2)0.001 (2)
C10.054 (4)0.037 (3)0.027 (3)0.004 (3)0.011 (3)0.002 (2)
C70.066 (4)0.040 (3)0.035 (3)0.004 (3)0.016 (3)0.006 (2)
C60.053 (4)0.035 (3)0.034 (3)0.002 (3)0.008 (3)0.000 (2)
C50.059 (4)0.056 (4)0.036 (4)0.002 (3)0.003 (3)0.012 (3)
N40.066 (4)0.043 (3)0.041 (3)0.007 (3)0.017 (3)0.008 (2)
C100.049 (4)0.037 (3)0.046 (4)0.006 (3)0.004 (3)0.002 (3)
N30.067 (4)0.072 (4)0.045 (3)0.022 (3)0.009 (3)0.009 (3)
C80.060 (4)0.067 (4)0.051 (4)0.013 (3)0.022 (3)0.009 (3)
N50.066 (4)0.060 (4)0.076 (5)0.003 (3)0.004 (3)0.005 (3)
C30.044 (4)0.056 (4)0.057 (4)0.003 (3)0.007 (3)0.002 (3)
C110.077 (5)0.047 (4)0.065 (5)0.017 (4)0.016 (4)0.003 (3)
C140.069 (4)0.052 (4)0.041 (4)0.008 (3)0.014 (3)0.005 (3)
C90.053 (4)0.053 (4)0.055 (4)0.013 (3)0.017 (3)0.003 (3)
C40.054 (4)0.072 (5)0.052 (4)0.004 (4)0.009 (3)0.011 (3)
C130.107 (6)0.048 (4)0.058 (5)0.016 (4)0.016 (4)0.007 (3)
C120.115 (7)0.038 (4)0.070 (6)0.003 (4)0.005 (5)0.005 (3)
Geometric parameters (Å, º) top
Zn1—N31.957 (6)N4—N51.155 (7)
Zn1—O11.986 (4)N4—N31.185 (7)
Zn1—N12.104 (5)C10—C111.380 (8)
Zn1—N22.125 (5)C10—C91.487 (8)
Zn1—O1i2.158 (4)C8—C91.515 (8)
O1—C11.342 (6)C8—H8A0.9700
O1—Zn1i2.158 (4)C8—H8B0.9700
N2—C71.262 (7)C3—C41.381 (9)
N2—C81.475 (7)C3—H3B0.9300
C2—C11.378 (8)C11—C121.373 (10)
C2—C31.398 (8)C11—H11A0.9300
C2—H2A0.9300C14—C131.383 (9)
N1—C141.350 (7)C14—H14A0.9300
N1—C101.358 (7)C9—H9A0.9700
C1—C61.423 (7)C9—H9B0.9700
C7—C61.467 (8)C4—H4A0.9300
C7—H7A0.9300C13—C121.375 (10)
C6—C51.396 (8)C13—H13A0.9300
C5—C41.369 (9)C12—H12A0.9300
C5—H5A0.9300
N3—Zn1—O1113.8 (2)N1—C10—C11119.5 (6)
N3—Zn1—N1126.5 (2)N1—C10—C9117.4 (5)
O1—Zn1—N1119.68 (18)C11—C10—C9123.1 (6)
N3—Zn1—N296.3 (2)N4—N3—Zn1132.5 (5)
O1—Zn1—N290.16 (17)N2—C8—C9111.6 (5)
N1—Zn1—N283.74 (18)N2—C8—H8A109.3
N3—Zn1—O1i97.9 (2)C9—C8—H8A109.3
O1—Zn1—O1i78.48 (16)N2—C8—H8B109.3
N1—Zn1—O1i92.66 (17)C9—C8—H8B109.3
N2—Zn1—O1i164.47 (18)H8A—C8—H8B108.0
C1—O1—Zn1130.4 (3)C4—C3—C2119.8 (6)
C1—O1—Zn1i127.3 (3)C4—C3—H3B120.1
Zn1—O1—Zn1i101.52 (16)C2—C3—H3B120.1
C7—N2—C8118.4 (5)C10—C11—C12121.4 (6)
C7—N2—Zn1123.5 (4)C10—C11—H11A119.3
C8—N2—Zn1117.2 (4)C12—C11—H11A119.3
C1—C2—C3122.1 (5)N1—C14—C13121.5 (6)
C1—C2—H2A118.9N1—C14—H14A119.3
C3—C2—H2A118.9C13—C14—H14A119.3
C14—N1—C10119.8 (5)C10—C9—C8113.4 (5)
C14—N1—Zn1121.9 (4)C10—C9—H9A108.9
C10—N1—Zn1117.9 (4)C8—C9—H9A108.9
O1—C1—C2120.0 (5)C10—C9—H9B108.9
O1—C1—C6122.4 (5)C8—C9—H9B108.9
C2—C1—C6117.6 (5)H9A—C9—H9B107.7
N2—C7—C6128.1 (5)C5—C4—C3119.3 (6)
N2—C7—H7A116.0C5—C4—H4A120.3
C6—C7—H7A116.0C3—C4—H4A120.3
C5—C6—C1119.4 (5)C12—C13—C14119.4 (7)
C5—C6—C7115.7 (5)C12—C13—H13A120.3
C1—C6—C7124.9 (5)C14—C13—H13A120.3
C4—C5—C6121.8 (6)C13—C12—C11118.4 (6)
C4—C5—H5A119.1C13—C12—H12A120.8
C6—C5—H5A119.1C11—C12—H12A120.8
N5—N4—N3175.9 (7)
N3—Zn1—O1—C196.2 (5)O1—C1—C6—C5178.0 (5)
N1—Zn1—O1—C183.7 (5)C2—C1—C6—C50.6 (8)
N2—Zn1—O1—C10.8 (4)O1—C1—C6—C72.6 (8)
O1i—Zn1—O1—C1170.2 (5)C2—C1—C6—C7178.8 (5)
N3—Zn1—O1—Zn1i93.6 (2)N2—C7—C6—C5174.0 (6)
N1—Zn1—O1—Zn1i86.5 (2)N2—C7—C6—C15.4 (10)
N2—Zn1—O1—Zn1i169.34 (19)C1—C6—C5—C40.4 (9)
O1i—Zn1—O1—Zn1i0.0C7—C6—C5—C4179.8 (6)
N3—Zn1—N2—C7120.0 (5)C14—N1—C10—C111.8 (9)
O1—Zn1—N2—C76.0 (5)Zn1—N1—C10—C11174.3 (5)
N1—Zn1—N2—C7113.8 (5)C14—N1—C10—C9178.9 (5)
O1i—Zn1—N2—C736.6 (9)Zn1—N1—C10—C96.4 (7)
N3—Zn1—N2—C870.6 (4)O1—Zn1—N3—N4120.4 (7)
O1—Zn1—N2—C8175.4 (4)N1—Zn1—N3—N459.7 (8)
N1—Zn1—N2—C855.6 (4)N2—Zn1—N3—N4146.6 (7)
O1i—Zn1—N2—C8132.9 (6)O1i—Zn1—N3—N439.5 (7)
N3—Zn1—N1—C14137.7 (5)C7—N2—C8—C9153.0 (6)
O1—Zn1—N1—C1442.4 (5)Zn1—N2—C8—C916.9 (7)
N2—Zn1—N1—C14129.0 (5)C1—C2—C3—C40.3 (10)
O1i—Zn1—N1—C1435.9 (5)N1—C10—C11—C121.3 (11)
N3—Zn1—N1—C1049.9 (5)C9—C10—C11—C12179.5 (7)
O1—Zn1—N1—C10129.9 (4)C10—N1—C14—C131.1 (9)
N2—Zn1—N1—C1043.3 (4)Zn1—N1—C14—C13173.3 (5)
O1i—Zn1—N1—C10151.8 (4)N1—C10—C9—C870.0 (7)
Zn1—O1—C1—C2176.8 (4)C11—C10—C9—C8110.8 (7)
Zn1i—O1—C1—C215.3 (7)N2—C8—C9—C1053.1 (7)
Zn1—O1—C1—C64.6 (7)C6—C5—C4—C31.3 (11)
Zn1i—O1—C1—C6163.2 (4)C2—C3—C4—C51.2 (10)
C3—C2—C1—O1178.0 (5)N1—C14—C13—C120.2 (11)
C3—C2—C1—C60.6 (8)C14—C13—C12—C110.7 (12)
C8—N2—C7—C6179.0 (5)C10—C11—C12—C130.0 (12)
Zn1—N2—C7—C69.7 (9)
Symmetry code: (i) x+2, y, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C9—H9A···N5ii0.972.583.198 (9)122
Symmetry code: (ii) x+1, y, z.

Experimental details

Crystal data
Chemical formula[Zn2(C14H13N2O)2(N3)2]
Mr665.37
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)9.523 (9), 9.466 (9), 15.853 (14)
β (°) 100.664 (17)
V3)1404 (2)
Z2
Radiation typeMo Kα
µ (mm1)1.75
Crystal size (mm)0.05 × 0.05 × 0.05
Data collection
DiffractometerBruker SMART 1K CCD area-detector
diffractometer
Absorption correctionMulti-scan
(CrystalClear; Rigaku, 2005)
Tmin, Tmax0.915, 0.915
No. of measured, independent and
observed [I > 2σ(I)] reflections
11424, 2460, 1824
Rint0.117
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.062, 0.154, 1.00
No. of reflections2460
No. of parameters190
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.32, 0.37

Computer programs: CrystalClear (Rigaku, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C9—H9A···N5i0.972.583.198 (9)121.6
Symmetry code: (i) x+1, y, z.
 

References

First citationFu, D.-W. & Ye, H.-Y. (2007). Acta Cryst. E63, m2453.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationLi, Z.-X. & Zhang, X.-L. (2004). Acta Cryst. E60, m1017–m1019.  Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
First citationRigaku (2005). CrystalClear. Rigaku Corporation, Tokyo, Japan.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationTandon, S. S., Chander, S. & Thompson, L. K. (2000). Inorg. Chim. Acta, E300, 683–692.  Web of Science CSD CrossRef Google Scholar
First citationYou, Z.-L. & Zhu, H.-L. (2004). Z. Anorg. Allg. Chem. 630, 2754–2760.  Web of Science CSD CrossRef CAS Google Scholar

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