yM 541.49


1Department of Public Subject, Shangqiu Medical College, Shangqiu, 476100 P.R. China 2Engineering Research Center of Functional Material Preparation, Shangqiu Normal University, Shangqiu, 476000 P.R. China *E-mail: wangna_sqnu@126.com Received February 1, 2015

A new dinuclear zinc(II) complex, [Zn2Br2L2] (I), was prepared from 4-methyl-2-[(2-methylaminoethyl-imino)methyl]phenol (HL) with zinc bromide in methanol. Self-assembly of I with ammonium thiocyanate in methanol afforded the mononuclear complex [Zn(L)(HL)]2[Zn(NCS)4] (II). Structures of complexes I, II have been characterized by elemental analysis, IR spectra and single crystal X-ray diffraction (CIF files CCDC nos. 1046617 (I), 1046618 (II)). Complex I possesses a crystallographic two-fold rotation axis symmetry, with Zn-'-Zn separation of 3.106(1) A. Complex II contains two mononuclear zinc(II) complex cations and one [Zn(NCS)4] complex anion. The Zn(1) atom in I is in a tetrahedral coordination. The Zn(2) atom in I and the Zn atoms in II are in octahedral coordination. Crystals of I, II complexes are stabilized by hydrogen bonds.

DOI: 10.7868/S0132344X15090066


Schiff bases are a kind of versatile ligands in coordination chemistry which are readily synthesized from the reaction of primary amines with carbonyl-con-taining compounds. In recent years, much work has been carried out on the syntheses and properties of Schiff bases and their complexes [1—5]. Schiff bases derived from salicylaldehyde and primary amines constitute one of the most relevant synthetic ligand systems with importance in asymmetric catalysis and they appear to be of importance for a broad range of transition-metal catalyzed reactions including lactide polymerization, epoxidation of olefins, hydroxylation and asymmetric ring opening of epoxides [6—10]. Although a number of Schiff bases and their complexes have been studied, the relationship between the self-assembly processes and structures has seldom been reported. In the present work, we report the synthesis, structural and spectroscopic properties of two new Schiff base zinc(II) complexes, [Zn2Br2L2] (I) and [Zn(L)(HL)]2[Zn(NCS)4] (II), where L is the monoanionic form of 4-methyl-2-[(2-methylamino-ethylimino)methyl]phenol (HL):




Materials and physical measurements. 5-Methyl-salicylaldehyde and N-methylethane-1,2-diamine with AR grade were purchased from Lancaster. Other reagents and solvents were purchased from Shanghai Chemical Reagent Company and used as received. The mono-Schiff base HL was prepared according to the literature method [11]. C, H, and N elemental analyses were performed on a PerkinElmer 240C elemental analyzer. IR spectra were measured with a Nicolet FT-IR 170-SX spectrophotometer.

Synthesis of I. HL (2.0 mmol, 0.385 g) and zinc bromide (2.0 mmol, 0.450 g) were mixed in methanol. The mixture was stirred at room temperature for 30 min to give a slight yellow solution. Yellow blocklike single crystals of complex I, suitable for X-ray dif-

Table 1. Crystallographic data and structure refinement information for complexes I and II

Parameter Value


Fw 673.06 1195.45

Crystal shape/colour Block/yellow Block/slight yellow

Crystal size (mm) 0.25 x 0.23 x 0.22 0.17 x 0.13 x 0.13

Crystal system Monoclinic Orthorhombic

Space group C2/c Pna2i

a, A 23.463(3) 21.060(1)

b, A 8.896(1) 15.3115(7)

c, A 16.733(2) 17.0041(8)

P, deg 131.748(3)

V, A3 2605.9(6) 5483.2(4)

Z 4 4

^(MoJa), mm-1 4.933 1.507

0.3719/0.4100 0.7837/0.8281

Pcalcd g cm-3 1.716 1.448

Reflections collected 11174 48054

Independent reflections (Rint) 2418 (0.0542) 8998 (0.0496)

Observed reflections (I > 2ct(I)) 1832 7182

Numbers of parameters 151 658

Restraints 1 5

Goodness of fit on F2 1.058 1.059

R1, wR2 (I> 2ct(I)) 0.0520, 0.1341 0.0501, 0.1102

R1, wR2 (all data) 0.0742, 0.1459 0.0705, 0.1186

APma« Apmim « A_3 0.906, -1.037 0.571, -0.437

fraction, were obtained after slow evaporization of the solution in air. The yield was 72%.

For C22H3oN4O2Br2Zn2

anal. calcd., %: Found, %:

C, 39.26; C, 39.39;

H, 4.49; H, 4.56;

N, 8.32. N, 8.17.

IR data (KBr; v, cm-1): 3231 w v(N-H), 1623 s, v(C=N).

Synthesis of II. Complex I (0.1 mmol, 67.3 mg) and ammonium thiocyanate (0.2 mmol, 15.2 mg) were mixed in methanol. The mixture was stirred at room temperature for 30 min to give a slight yellow solution. Slight yellow block-like single crystals of complex II, suitable for X-ray diffraction, were obtained

after slow evaporization of the solution in air. The yield was 31%.

For C48H62N12O4S4Zn3

anal. calcd., %: C, 48.22; H, 5.23; N, 14.06. Found, %: C, 48.08; H, 5.35; N, 13.97.

IR data (KBr; v, cm-1): 3210 w v(N-H), 2077 s v(NCS), 1622 s v(C=N).

X-ray crystallography of I, II. Diffraction intensities for the complexes were collected at 298(2) K using Bruker SMART CCD detector with Mola radiation (X = 0.071073 nm). The collected data were reduced using SAINT [12], and multi-scan absorption corrections were performed using SADABS [13]. Structures were solved by direct method and

Table 2. Selected bond distances (À) and angles (deg) for complexes I, II*

Bond d, A Bond d, A

Zn(1)—O(1) Zn(2)—N(1) Zn(2)-N(2) Zn(1)-N(1) Zn(1)-N(3) Zn(1)-N(2) Zn(2)-O(3) Zn(2)-N(7) Zn(2)-O(4) Zn(3)-N(11) Zn(3)-N(9) 1.974(4) 2.111(5) 2.195(5) I 2.103(5) 2.112(4) 2.201(5) 2.078(3) 2.111(5) 2.184(4) 1.944(8) 2.003(8) Zn(1)-Br(1) Zn(2)-O(1) I Zn(1)-O(1) Zn(1)-O(2) Zn(1)-N(4) Zn(2)-N(5) Zn(2)-N(6) Zn(2)-N(8) Zn(3)-N(10) Zn(3)-N(12) 2.3566(9) 2.163(4) 2.109(3) 2.151(4) 2.214(6) 2.090(4) 2.177(5) 2.225(5) 1.955(9) 2.026(8)

Angle ro, deg Angle ro, deg

O(1)Zn(1)O(1A) O(1)Zn(1)Br(1) N(1)Zn(2)O(1) O(1)Zn(2)N(2) N(2)Zn(2)N(2A) N(1)Zn(1)O(1) O(1)Zn(1)N(3) O(1)Zn(1)O(2) N(1)Zn(1)N(2) N(3)Zn(1)N(2) N(1)Zn(1)N(4) N(3)Zn(1)N(4) N(2)Zn(1)N(4) O(3)Zn(2)N(7) O(3)Zn(2)N(6) N(7)Zn(2)N(6) N(5)Zn(2)O(4) N(6)Zn(2)O(4) N(5)Zn(2)N(8) N(6)Zn(2)N(8) N(11)Zn(3)N(10) N(10)Zn(3)N9 N(10)Zn(3)N(12) 87.4(2) 114.71(12) 82.42(16) 159.63(17) 96.9(3) I 84.31(16) 95.77(15) 85.89(14) 79.5(2) 101.1(2) 96.94(19) 78.03(19) 96.0(3) 96.93(16) 164.7(2) 96.1(2) 95.85(16) 88.12(19) 101.68(19) 99.4(2) 115.1(3) 105.6(3) 104.1(4) O(1)Zn(1)Br(1A) Br(1)Zn(1)Br(1A) O(1)Zn(2)O(1A) N(1)Zn(2)N(2) O(1)Zn(2)N(2A) I N(1)Zn(1)N(3) N(1)Zn(1)O(2) N(3)Zn(1)O(2) O(1)Zn(1)N(2) O(2)Zn(1)N(2) O(1)Zn(1)N(4) O(2)Zn(1)N(4) O(3)Zn(2)N(5) N(5)Zn(2)N(7) N(5)Zn(2)N(6) O(3)Zn(2)O(4) N(7)Zn(2)O(4) O(3)Zn(2)N(8) N(7)Zn(2)N(8) O(4)Zn(2)N(8) N(11)Zn(3)N(9) N(11)Zn(3)N(12) N(9)Zn(3)N(12) 112.59(11) 112.62(6) 78.2(2) 79.32(18) 95.30(17) 174.96(19) 102.30(17) 82.72(15) 161.8(2) 89.5(2) 94.15(18) 160.66(18) 86.30(16) 176.13(18) 80.4(2) 85.75(14) 82.32(15) 90.60(17) 80.47(18) 161.83(18) 110.3(3) 109.6(3) 112.1(3)

* Symmetry code for A: - x, y, 1/2 — z.

refined against F2 by full-matrix least-squares method using SHELXTL [14]. All non-hydrogen atoms were refined anisotropically. The amino and hydroxyl H were located from difference Fourier maps and refined isotropically, with N—H and O—H distances restrained to 0.90(1) and 0.85(1) A, respectively. The remaining hydrogen atoms were placed in calculated positions and constrained to ride on their parent atoms. A summary of the crys-tallographic data are given in Table 1. Coordinate bond lengths and angles are listed in Table 2.

Supplementary data for the structures have been deposited with the Cambridge Crystallographic Data Centre (nos. 1046617 (I) and 1046618 (II); deposit@ ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).


The synthesis procedures for complexes I, II are shown in Scheme. Complex I was prepared by reaction of the mono-Schiff base with zinc bromide in methanol. Complex II was prepared by reaction of I with ammonium thiocyanate in methanol.

The molecular structure of complex I is shown in Fig. 1a. X-ray crystallography reveals that the complex possesses a two-fold ratation axis symmetry with the axis passesses through the two Zn atoms. The two Zn atoms are bridged by two phenolate groups. The Zn---Zn separation is 3.106(1) Á. The Zn(1) atom is coordinated by two phenolate O atoms from two Schiff base ligands and two Br atoms, forming a tetrahedral coordination. The Zn(2) atom is coordinated by two phenolate O, two imino N and two amino N atoms from two Schiff base ligands, forming an octahedral coordination. The coordinate bond lengths in complex I are comparable to those reported in similar zinc(II) complexes [15, 16]. Molecule of I is butterfly-shaped with the dihedral angle formed by the two benzene rings of 70.8(3)°.

In the crystal structure of complex I, molecules are linked via intermolecular N(2)—H(2)---Br(1) hydrogen bonds (N(2)—H(2) 0.90(1), H(2)-Br(1)i 2.76(3), N(2)-Br(1)i 3.607(5) Á, N(2)—H(2)---Br(1)i 158(7)°; symmetry code: i —x, y, 1/2 — z), forming 1D chains running along y axis (Fig. 2a).

The molecular structure of complex II is shown in Fig. 1b. X-ray crystallography reveals that the complex contains two [Zn(L)(HL)] cations and one [Zn(NCS)4] anion. The difference Fourier map of the complex reveals that there are H atoms attached to O(2) and O(4) atoms. The two [Zn(L)(HL)] units are linked together by intermolecular O(2)—H(2)---O(3) and O(4)-H(4^)-O(1) hydrogen bonds (O(2)-H(2) 0.85(1), H(2)-O(3) 1.61(1), O(2)-O(3) 2.455(5) Á, O(2)—H(2)--O(3) 176(8)°; O(4)-H(4^) 0.85(1),



Fig. 1. The molecular structure of complexes I (a) and II (b). In I, atoms labeled with the suffix A are at the symmetry position —x, y, 1/2 - z. Thermal ellipsoids are at the 30% probability level. Hydrogen atoms except for the amino H (for I, II) and hydroxyl H (for II) are omitted for clarity.

H(44)-"O(1) 1.62(2), O(4)-O(1) 2.456(5) Â, O(4)-H(4^)-O(1) 169(8)°). The Zn atoms in the cat

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