научная статья по теме CRYSTAL STRUCTURE OF DINUCLEAR AZIDE-BRIDGED COPPER(II) COMPLEX [CU2((3,4-MEO-BA)2EN)2( 1,1-N3)2(N3)2] {(3,4-MEO-BA)2EN = = N,N-BIS(3,4-DIMETHOXYBENZYLIDENE)-1,2-ETHANEDIAMINE} Химия

Текст научной статьи на тему «CRYSTAL STRUCTURE OF DINUCLEAR AZIDE-BRIDGED COPPER(II) COMPLEX [CU2((3,4-MEO-BA)2EN)2( 1,1-N3)2(N3)2] {(3,4-MEO-BA)2EN = = N,N-BIS(3,4-DIMETHOXYBENZYLIDENE)-1,2-ETHANEDIAMINE}»

KOOPMHH^HOHHAS XHMH3, 2011, moM 37, № 5, c. 391-395

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CRYSTAL STRUCTURE OF DINUCLEAR AZIDE-BRIDGED COPPER(II) COMPLEX [Cu2((3,4-MeO-Ba)2En)2(^u-N3)2(N3)2] {(3,4-MeO-Ba)2En = = N,N'-£/s(3,4-DIMETHOXYBENZYLIDENE)-1,2-ETHANEDIAMINE}

© 2011 S. Jalali Akerdi1, G. Grivani1, H. Stoeckli-Evans2, and A. D. Khalaji3, *

1School of Chemistry, Damghan University, Damghan, P.O. Box 36715-364, Iran 2Institute of Physics, Laboratory Physical Chemistry, University of Neuchyatel, CH-2009 Neuchatel, Switzerland 3Department of Chemistry, Faculty of Science, Golestan University, Gorgan, Iran *E-mail: alidkhalaji@yahoo.com; ad.khalaji@gu.ac.ir Received July 13, 2010

New dinuclear copper(II)-azido complex [Cu2((3,4-MeO-Ba)2En)2(^1rN3)2(N3)2] (I) ((3,4-MeO-Ba)2En = = N,N'-bis(3,4-dimethoxybenzylidene)-1,2-diaminoethane) has been synthesized and characterized by elemental analyses, FT-IR spectroscopy, and X-ray single-crystal diffraction. Complex I consists of a dinuclear unit that represents a new example of a copper(II)-azido compound and the Cu2+ ions are bridged by two azido ions in a double end-on fashion, consisting of two terminally bonded azido ligands. The Schiff base ligand (3,4-MeO-Ba)2En is chelated by two imino nitrogen atoms.

INTRODUCTION

The azido ion, N-, is one ofthe most interesting bridging molecules in inorganic coordination compounds, because the azide ion can coordinate to transition metal ions by different bridging modes, such as ^-(1,1) [1—3], ^-(1,3) [4, 5], M1,1,1) [6], and ^-(1,1,3) [7]. The cop-per(II) complexes with Schiff base ligands have attracted considerable attention in recent years due to their various interesting properties like molecular magnetism [2—7] and 1D assemblies [8]. Up to date, several dinuclear copper(II) compounds have been reported. They are based on the azido ion [2, 9, 10]. The dinuclear copper(II) complexes bridged by the azide ion have rarely been reported [11].

As an additional contribution to the synthesis, characterization, and crystal structures of copper(II) complexes with Schiff base ligands and in the course of our ongoing studies of these kinds of materials [12, 13], we describe here the synthesis and crystal structure of the new dinuclear copper(II)-azido complex [Cu2((3,4-MeO-Ba)2En)2(^1,1-N3)2(N3)2] (I):

OMe OMe

.OMe MeO

EXPERIMENTAL

All reagents and solvents were purchased from Aldrich and Merck and used without further purification. The Schiff base ligand (3,4-MeO-Ba)2En was prepared following the standard procedure [14]. The infrared spectrum was recorded on a PerkinElmer FT-IR spectrophotometer as a KBr pellet. Elemental analyses were carried out on a Heraeus CHN-O-Rapid elemental analyzer. (Although we did not experience any problem during the work, such compound as perchlorate- and azide-contain-ing compounds, being potentially explosive should be used in small quantities and handled with great care.)

Synthesis of complex I. A methanolic solution (5 ml) of(3,4-MeO-Ba)2En (1 mmol) was added to a clear solution of Cu(NO3)2 • 3H2O (1 mmol) dissolved in 20 ml of methanol, which producted immediately a blue solution. Then, 10 ml ofacetone was added to this solution, and the mixture was heated and stirred at room temperature for 1 h. The solution was allowed to stand at room temperature, and a methanolic solution of NaN3 (0.8 mmol in 10 ml) was dropwise added to give a green solution. Green single crystals ofI suitable for X-ray analysis were obtained after several days by the slow evaporation of solvents at room temperature, then collected by filtration, and dried in vacuo. The yield was 83%.

For C40H48N16O8Cu2

anal. calcd., %: C, 47.66; H, 4.80; N, 22.23. Found, %: C, 47.71; H, 4.83; N, 22.26.

IR spectrum (v, cm-1): 2062 and 2034 (N3), 1631 s (C=N).

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Table 1. Crystallographic data and experimental details for complex I*

Parameter Value

Formula weight 1008.02

Crystal system, space group Monoclinic, P2l/n

a, A 8.2617(10)

b, A 9.7017(10)

c, A 27.828(3)

P, deg 93.89l(l0)

V, A3 2225.4(4)

Z 2

mm-1 l.03

Crystal size, mm3 0.40 x 0.12 x 0.03

Index ranges h, k, l -10 < h < 10, -ll < k < ll, -33 < l < 33

Measured reflection 19262

Independent reflection/parameters 4201/302

Reflection with I > 2a(I) 2147

Rint 0.237

R (F2 > 2ct(F2)) 0.088

wR (F2) 0.146

Apmax and Apmin e AT3 0.37 and -0.49

*w = 1/[ct2(F02) + (0.0334P)2], where P = (Fo2 + 2Fc2)/3.

X-ray structure determination. Suitable crystals of I were obtained as thin green plates by slow evaporation ofsol-vents at room temperature. The intensity data were collected at 173 K (-100°C) on a Stoe Mark II-Image Plate Diffraction System[15] equipped with a two-circle goniometer and using Mo^a graphite monochromated radiation (X = = 0.71073 A). The image plate distance was 130 mm, ® rotation scans were 0°-180° at 9 = 0° and 0°-54.0° at 9 = = 90°, step A® = 1.0°, exposures of 9 mins per image, 29 range 1.76°—52.59°, dmin - dmax = 23.107-0.802 A. The structure was solved by direct methods using the SHELXS-97 program [16]. The refinement and all further calculations were carried out using SHELXL-97 [16]. The H atoms were included in calculated positions and treated as riding atoms using SHELXL default parameters. The non-H atoms were refined anisotropically using weighted full-matrix least-squares on F2. A semiem-pirical (multiscan) absorption correction was applied using the MULscanABS routine in PLATON [17]. The crystal diffracted weakly beyond 40° in 29 and, hence, the Rint value is rather high. Crystallographic details of the data collection and structure refinements are listed in Table 1. Supplementary material has been deposited with the Cambridge Crystallographic Data Centre (no.783985; deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac. uk).

RESULTS AND DISCUSSION

3,4-Dimethoxybenzaldehyde and 1,2-diaminoethane reacted in a 2 : 1 molar ratio to form the bidentate Schiff base ligand (3,4-MeO-Ba)2En [14].

The FT-IR spectra of I exhibit a strong absorption band at 2062 and 2034 cm-1 confirming the terminal and bridging coordination modes of the N- ligand in this complex. Also, the strong band at 1631 cm-1 in I is assignable to the v(C=N) stretches of the Schiffbase ligand.

The ORTEP plot of complex I is shown in Fig. 1. Selected bond lengths and bond angles are listed in Table 2. Complex I is made up of one-half [Cu((3,4-MeO-Ba)2En)(^11-N3)(N3)] moiety, while the other half being symmetry related via the center of symmetry. Each Cu2+ ion is five-coordinated with a distorted square-pyramidal geometry and is surrounded by four nitrogen atoms (N(2), N(3), N(3)i, and N(6)) in the basal plane. The fifth coordination site of the square pyramid is occupied by the one nitrogen atom N(1), from the bidentate Schiff base ligand (3,4-MeO-Ba)2En. The Cu2+ ions are bridging by two azido ligands in an end-on fashion [2, 9]. The Cu(l)-N(2), Cu(l)-N(3), Cu(l)-N(3)i, and Cu(l)-N(6) in-plane distances are 2.019(5), 2.024(5), 2.007(5), and 1.965(6) A, respectively. One nitrogen atom N(l) from the bidentate Schiff-base ligand (3,4-MeO-Ba)2En occupied the axial position (Cu(l)-N(l) 2.368(5) A). The geometry around the Cu2+ ion in I is distorted by the restricting bite of the chelate angle N(l)Cu(l)N(2) 8l.8(2)°. This angle is in a range of 82°-89° found for ethylenediamine chelate compounds and

Fig. 1. ORTEP drawing with the atom labeling scheme of I with displacement ellipsoid drawn at the 50% probability level.

Fig. 2. Crystal packing viewed along the y axis of complex I. The C—H-N interactions are shown as dotted lines.

much less than 90°. The other NCu(1)N angles are also distorted from the square-pyramidal values (Table 2).

The Schiff base ligands (3,4-MeO-Ba)2En adopts a Z,Z-configuration in this complex[18—20]. The value for the dihedral angles C(1)-N(1)-C(12)-C(13), N(1)-C(12)-C(13)-C(14), C(2)-N(2)-C(3)-C(4), and N(2)-C(2)-C(4)-C(5) are 177.2(7)°, 178.5(7)°, -178.8(7)°, and

—166.6(7)°, indicating an almost planar configuration of this moiety for the complexes studied here [18]. Selected torsion angles are given in Table 2.

The geometry ofhydrogen bonds in complex I is given in Table 3. Complex I exhibits different intra- and intermolecular hydrogen bonding patterns built up from non-classical C—H-N hydrogen bonds in the crystal structure

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Table 2. Selected bond distances and bond angles for I*

Bond d, A Bond d, A

Cu()-N(l) 2.368(5) O(4)-C(l6) 1.358(9)

Cu(l)-N(2) 2.019(5) O(4)-C(20) 1.404(9)

Cu(l)-N(3) 2.024(5) N(l)-C(l) 1.480(9)

Cu(l)-N(6) 1.965(6) N(l)-C(l2) 1.238(9)

Cu(l)-N(3)i 2.007(5) N(2)-C(2) 1.476(9)

O(l)-C(7) l.354(l0) N(2)-(3) l.28l(l0)

O(l)-C(l0) l.438(l0) N(3)-N(4) 1.220(8)

O(2)-C(8) 1.370(8) N(4)-N(5) l.l42(9)

O(2)-C(ll) 1.432(9) N(6)-N(7) l.l67(ll)

O(3)-C(l5) l.363(l0) N(7)-N(8) l.l76(ll)

O(3)-(l9) l.43l(l0)

Angle ro, deg Angle ro, deg

N(l)Cu(l)N(2) 8l.8(2) C(2)N(2)C(3) ll7.8(6)

N(l)Cu(l)N(3) 94.4(2) Cu(l)N(3)N(4) l26.l(4)

N(l)Cu(l)N(6) 94.2(2) Cu(l)N(3)Cu(l)i 104.2(2)

N(l)Cu(l)N(3)i ll4.6(2) Cu(l)iN(3)N(4) 127.5(4)

N(2)Cu(l)N(3) 9l.9(2) N(3)N(4)N(5) 177.8(7)

N(2)Cu(l)N(6) 96.2(3) Cu(l)N(6)N(7) 127.2(6)

N(2)Cu(l)N(3)i 159.9(2) N(6)N(7)N(8) 176.0(7)

N(3)Cu(l)N(6) 168.9(2) N(l)C(l)C(2) 108.6(5)

N(3)Cu(l)N(3)i 75.8(2) N(2)C(2)C(l) lll.7(6)

N(3)iCu(l)N(6) 94.3(2) N(2)C(3)C(4) 127.2(6)

C(7)0(l)C(l0) ll6.7(6) O(l)C(7)C(6) 125.9(7)

C(8)O(2)C(ll) ll5.9(6) O(l)C(7)(8) ll6.l(6)

C(l5)O(3)(l9) ll7.4(6) O(2)C(8)C(7) ll3.8(7)

C(l6)0(4)C(20) ll8.0(6) O(2)C(8)C(9) 125.4(7)

Cu(l)N(l)C(l) 99.6(4) N(l)C(l2)C(l3) 127.8(7)

Cu(l)N(l)C(l2) 143.3(5) O(3)C(l5)C(l4) 124.4(6)

C(l)N(l)C(l2) ll5.6(6) O(3)C(l5)C(l6) ll5.9(6)

Cu(l)N(2)C(2) ll0.9(4) O(4)C(l6)C(l5) ll4.7(7)

Cu(l)N(2)C(3) 130.4(5) O(4)C(l6)C(l7) 125.8(7)

Angle 9, deg Angle 9, deg

N(l)-C(l2)-C(l3)-C(l4) 178.5(7) N(2)-C(3)-(4)-C(5) -166.6(7)

N(l)-C(l2)-C(l3)-(l8) -6.7(12) N(2)-C(3)-C(4)-(9) 15.0(12)

C(l2)-N(l)-C(l)-C(2) —123.4(7) C(2)-N(2)-C(3)-C(4) —178.8

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