научная статья по теме MOLECULAR AND CRYSTAL STRUCTURE OF BIS{1,4-BIS(1,2,4-TRIAZOL-1-YL)BUTANE}DIBROMOCADMIUM(II) Химия

Текст научной статьи на тему «MOLECULAR AND CRYSTAL STRUCTURE OF BIS{1,4-BIS(1,2,4-TRIAZOL-1-YL)BUTANE}DIBROMOCADMIUM(II)»

КООРДИНАЦИОННАЯ ХИМИЯ, 2010, том 36, № 2, с. 118-120

УДК 541.49

MOLECULAR AND CRYSTAL STRUCTURE OF ô/s{1,4-ô/s(1,2,4-TRIAZOL-1-YL)BUTANE}DIBROMOCADMIUM(II)

© 2010 L. Shen

Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, College of Material Chemistry and Chemical Engineering, Hangzhou Normal University,

Hangzhou 310036, P.R. China E-mail: shenchem@hotmail.com Received June 26, 2009

The structure of [Cd(Btb)2Br2] (I) (Btb = 1,4-bis(triazol-1-yl)butane) exhibits a two-dimensional (4,4) network through Btb-bridge in which the Cd(II) atom is in a distorted octahedral environment formed by four nitrogen atoms of the triazoles and two trans-Br atoms. The crystals are monoclinic, space group P2j/n with a = 7.6778(6), b = 18.2237(8), c = 8.7655(5) Â, в = 113.4534(19)°. The Btb ligand demonstrates the completely anti conformation.

INTRODUCTION

The construction of coordination polymers has evoked much interest not only due to their intriguing structural topologies, but also due to their potential applications in the areas of electrical, magnetic, optical, and porous properties [1—4]. The most fruitful synthetic strategy consists in taking advantage of N,N'-bidentate rigid or flexible bridging ligands to achieve these polymeric compounds. Recently, a new class of flexible ligands, [¿¿s,(1,2,4-triazol-1-yl)-alkanes] (which are flexible due to the free rotation of C—C a-bond in alkanes), has been found to be very efficient in the formation of coordination ploymers with novel structures and special properties [5—7]. Among these ligands, 1,4-bis(1,2,4-tri-azol-1-yl)butane (Btb), which is more flexible than 1,2-bis(1,2,4-triazol-1-yl)ethane and 1,2-te(1,2,4-triazol-1-yl)propane, is expected to play an important role in the construction of coordination polymers. A few reports on the crystal structures of cadmium(II), manganese(II), and iron(II) complexes with bridging Btb ligand were reported [8—11]. We recently reported a zinc(II) complex with Btb, which exhibits a one-dimensional zigzag chain [12]. As a part of our investigations of the coordination mode of this ligand in metal complexes incorporating 1,2,4-triazole derivatives, herein we report the synthesis and crystal structure of a new polymeric Cd(II) complex with Btb bridges [Cd(Btb)2Br2] (I).

EXPERIMENTAL

1,4-fts(triazol-1-yl)butane was prepared according to literature [13] and confirmed by melting point and IR. A 10 ml of aqueous solution of Btb (1 mmol) was added to a 10 ml ofmethanol of CdBr2 • 4H2O (0.5 mmol). The precipitate was filtered off after stirring for 2 h, and the mother liquid was left to stand at room temperature.

Three days later colorless crystals suitable for single-crystal X-ray determination were formed.

For C16H24Br2N12Cd (I)

anal. calcd, %: C, 29.27; H, 3.66; N, 25.61. Found, %: C, 29.22; H, 3.35; N, 25.77.

A single-crystal with dimensions of 0.30 x 0.28 x x 0.16 mm was mounted on a glass fiber and used for structure determination. Diffraction intensity data were collected at 298(1) K on a Rigaku RAXIS-RAPID diffractometer with graphite-monochromatized Mo^ radiation (k = 0.71075 A) using the ® scan technique. Observed 2173 reflections were considered (I > 2a(I)) and used for the structure refinement. Usual Lp and empirical absorption corrections were applied.

The structure was solved by direct methods and refined on F2 by full-matrix least-squares methods using SHELX-97 [14]. All non-hydrogen atoms were anisotro-pically refined. The hydrogen atoms were treated as riding atoms. Anisotropic refinement including all non-H atoms were converged to agreement factors R = 0.0493

and Rw = 0.1705, where w = 1/[0.0059(FO) +

+ 1.0000a (F0) ]/(4FO)]. Atomic scattering factors used were taken from [15]. The crystallographic data are summarized in table. The atomic coordinates and other parameters of structure I have been deposited with the Cambridge Crystallographic Data Center (no. 273262; deposit@ccdc.cam.ac.uk).

RESULTS AND DISCUSSION

The ORTEP view of the molecule structure of the centrosymmetric complex together with the atom numbering scheme is presented in Fig. 1. The Cd(II) atoms has a distorted octahedral arrangement with four triaz-

MOLECULAR AND CRYSTAL STRUCTURE

119

Fig. 1. Molecular structure of I, showing 50% probability displacement ellipsoids. Selected bond lengths and angles: Cd(1)—N(1) 2.358(3), Co(1)-N(6B) 2.348(4), Cd(1)-Br(1) 2.7472(9), N(1)-C(1) 1.366(8), N(1)-C(2) 1.326(8), N(2)-N(3) 1.347(9), N(6)-C(7) 1.342(8), N(6)-C(8) 1.323(8), N(4)-N(5) 1.350(9) A; N(1)Cd(1)N(6B) 88.37(15)°, Br(1)Cd(1)N(1) 89.99(13)°, Br(1)Cd(1)N(6B) 88.34(15)°.

Crystal data and structural refinement for complex I

N(6)ui

N(6)

ole nitrogen atoms from four Btb ligand in a basal plane. The apical position is occupied by two bromide ions with a Cd(1)-Br(1) distance of 2.7472(9) A. The Cd(1)-N bond distances of Btb (2.358(3) and 2.348(4) A) are slightly longer than the values observed in [Cd(Dca)2(Btb)]n (Dca = dicyanamide) [8]. Other angles around the Cd centers range from 88.34(15)° to 91.66(15)°, which is close to 90°.

As shown in Fig. 2, each bridging Btb ligand links Cd(II) and each Cd(II) atom bonding four Btb ligands to form a two-dimensional (4,4) network containing square Cd4(Btb)4 units. The 2D sheets are stacked in parallel along the z axis (Fig. 3). Each Btb ligand exhibits the completely anti conformation, which is different from anti-anti-gauche and anti-gauche geometry observed in {[Mn(Btb)2(H2O)2)](NO3)2(H2O)}n [9] and [Zn(Btb)(NCS)2]n [13], respectively. The dihedral angle between two triazole ring planes is 62.39°. The torsion angles C(3)-C(4)-C(5)-C(6), N(3)-C(3)-C(4)-C(5), and C(4)-C(5)-C(6)-N(4) are 175.0(6)°, 171.4(5)°, and 172.7(6)°, respectively. The Cd-Cd separation across the bridging Btb is 13.953(8) A, which is shorter than the corresponding Cd-Cd separation of 14.304(3) A in [Cd(Dca)2(Btb)]n [8]. However, this distance is apparently longer than that observed in {[Cd(Bte)2(H2O)2](NO3)2}n (Bte = 1,2-bis(1,2,4-triaz-ol-1-yl)ethane) [16], one of the few compounds also having an alkane chain as a spacer in which the Cd-Cd distance is 8.118(2) A. In fact, this confirms the impor-

Parameter Value

Formula weight 656.66

Crystal system, space group Monoclinic, P21/n

Unit cell dimensions:

a, A 7.6778(6)

b, A 18.2237(8)

c, A 8.7655(5)

ß, deg 113.4534(19)

Z 2

Pcalcd mg/m3 1.938

p., mm-1 4.565

F (000) 644.00

Crystal size, mm 0.30 x 0.28 x 0.16

9 range for data collection, deg 1.0 to 27.48

Index ranges -9 < h < 9

-23 < k < 23

-11 < l < 11

Reflections collected/unique 10752/2582 (Rint = 0.050)

Completeness to 9, % 100

Absorption correct Multi-scan

Max and min transmission 0.482 and 0.268

Data/restraints/parameters 2176/0/154

Goodness of fit on F2 1.004

Largest diff. peak and hole, e A-3 0.45 and -0.49

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120

SHEN

Fig. 2. Planar two-dimensional (4,4) network of complex I.

Fig. 3. View of the stacked sheets along the z axis of complex I.

tance of this family of ligands in adjusting the metalmetal distance.

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