J. Chil. Chem. Soc, 54, N° 2 (2009)

X-RAY CRYSTALLOGRAPHIC STRUCTURAL STUDY ON A NEW COORDINATION POLYMER: CATENA-di-μCHLORO-BIS[(di-2-PYRIDYLDISULFIDE- k² N, N') COPPER(I)]

 

 

IVÁN BRIT0¹*, ALDO MUNDACA¹, ALEJANDRO CÁRDENAS², JOSELYN ALBANEZ¹, JAVIER VALLEGOS¹, DANITZA VARGAS¹ AND MATÍAS LÓPEZ-RODRÍGUEZ³

 

¹Departamento de Química, Facultad de Ciencias Básicas, Universidad de Antofagasta, Casilla 170, Antofagasta-Chile.

²Departamento de Física, Facultad de Ciencias Básicas, Universidad de Antofagasta, Casilla 170, Antofagasta-Chile.

³instituto de Bio-Orgánica Antonio González', Universidad de La Laguna, Astrofísico Francisco Sánchez N" 2, La Laguna, Tenerife, España.

^*e-mail: ibrito@uantof.cl

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ABSTRACT

In title compound, [CuC1(C₁₀H₈N₂S₂)]_n, (I) each Cu(I) ion coordinates to two nitrogen atoms from two different ligands and to two chloro ions which bridge to another Cu(I) to complete a planar four-membered Cu₂Cl₂ ring.The Cu⁺ coordination geometry is best described as a slightly distorted tetrahedron. The structure consists of CuCl cores connected by 2, 2'-dypyridyldisulfide ligand and form a two-dimensional extended polymeric network in which the 2, 2'-dipyridyldisulfide ligand bridges Cu atoms. The title compound is isostructural with di-u-chlorido-bis[(di-2-pyridyldisulnde-K² N, N') copper(I)], (II)', which is a zero-dimensional binuclear compound. The two structures differ due conformational flexibility of ligand, which have axial conformation in (I) and equatorial conformation in (II), torsion angles S-S-C-N (axial ring) 168.8(4)°; for (I) and 72.0(3)° for (II) respectively.

Keywords: Coordination polymes, disulfides, x-ray diffraction.

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INTRODUCTION

The design of molecular architectures in the solid state is a subject of current investigations. In particular, the formation of coordination networks, hybrid metallo-organic molecular assemblies, has attracted much attention over the last decade ². These networks, based on the formation of coordination bonds, may be defined as infinite structures resulting from iterative self-assembly process between organic and metallic tectons (active building blocks). The generation of coordination networks in the solid-state results on one hand from the binding events taking place between the coordinating sites located on the organic tecton and the available coordination sites on the metal centre thus defining the assembling cores, and on the other hand, the iteration of the binding process allowing the translation of the assembling cores which become nodes of the network. The dimensionality of the network, i.e. 1-, 2- or 3-D, is defined by the number of translations of one or several assembling cores into one, two or three directions of space respectively. Copper(I) halides³ have been employed as inorganic components in the construction of novel coordination polymers with various structural motifs. Among those copper halide motifs, the rhombic Cu₂X₂ secondary building units formed by two X- atoms linking two neighboring Cu(I) atoms, have been found to be characteristic of excellent planar 4-connecting nodes whose remaining coordination sites of the Cu(I) atoms are bridged by the N,N'- bridging ligands, being facile at constructing multidimensional coordination frameworks. Many of the architectures reported to date are based upon rigid linear linker ligands ", with only recent efforts focusing on the use of ligands showing conformational flexibility ^5-7 probably due to the flexibility of the backbones, which makes it more difficult to predict and control the final coordination networks.

EXPERIMENTAL

A colorless solution of 2, 2'-dipyridyldisulfide (0.720 g, 327 mmol) in CH₃CN (5 ml) was added dropwise to a yellow-green suspension of CuCl (0.042 g, 0.42 mmol) in CH₃CN (15 ml) forming a yellow solution. The vessel was sealed and left to stand at room temperature. After one hour small red crystals of the title compound were isolated in ca. 50% yield. Anal. cal. for CuCl (C₁₀H₈N₂S₂)_n: C, 37.61; H, 2.53; N, 8.77 %. Found: C, 37.63; H, 2.44; N, 8.84 %. IR (KBr; cm^-1): 1578 (s), 1556 (m), 1446 (m), 1021 (m), 775 (s), 753 (s), 710 (m), 645 (w), 489 (m).

RESULTS AND DISCUSSION

Part of the polymeric structure of the title compound, (I), is shown in Fig. 1 and selected geometric parameters are given in Table II. It crystallizes as red block, which were found to be stable to air and light. In title compound, [CuC1(C₁₀H₈N₂S₂)]_n, (I) the Cu⁺ cation has a four-coordinate environment completed by two N atoms of the 2, 2'-dypyridyldisulfide ligand and by two Cl anions. The Cu⁺ coordination geometry is best described as a slightly distorted tetrahedron, [Cu1-N1 =2.074(3)A,Cu1-N2'=2.088(3)Å(i = -x,y-l/2,-z+3/2); Cul-CU = 2.3720(12) Å, Cu1-CU¹¹ = 2.4070(12) Å (ii = -x, -y+1, -z+1)], with bond angles ranging from 103.36(14) to 119.6(2)° (See Table II). The material is composed of two-dimensional extended polymeric network with a rhombic CuC1₂ core often encountered in compound formed between copper(I) chloride and nitrogen donor ligands ^16>'. The Cu-N bond distance, 2.081(3) Å is normal for a Cu(I) ion bonded to an unsatured nitrogen atom in the cyclic ligand (the mean Cu(I)-N bond distance determined for such compounds is 2.04 Å) ^{19i 22}. The title compound have C-S-S-C torsion angle -85.08(17)° and S-S bond lengths 2.0411(17) Å, normal for metal complex with aromatic disulfides in the axial conformation (N-C-S-S torsion angles near 90° ) (see Table III). The title compound is isostructural with di-μ-chlorido-bis[(di-2-pyridyldisulfide-K² N, N') copper(I)], (II)¹, which is zero-dimensional dinuclear compound. The two structures differ due to the conformational flexibility of ligand which is gauche in (II) and anti in (I). In (I) the distance between two Cu atoms located at each extremity of the tecton is 8.305 Å and 10.084 Å in the [010] and [001] directions respectively. The Cu-Cu distance between halide bridged centers is 2.9637(12) Å. This distance is similar than the observed for compound (II) [3.076(3) Å] and is slightly longer than the sum of the van der Waals radii of copper (I) [2.8 Å]. Coordination to CuC1 has caused a change in the conformation of ligand passing of a equatorial (uncoordinated ligand) to axial conformation ⁸. A search in the Cambridge Structural Database (version 5.30) ⁹ for compounds formed between 2,2-dipyridyl disulfide ligand and transition metal ions yielded twenty-two structures with axial conformation, and two structures S,S'-bis(3-(Ethoxycarbonyl)pyridin-2-yl)disulfide ¹⁰ and S,S'-bis(3-(n-Butoxycarbonyl)pyridin-2-yl)disulfide ¹¹ with a equatorial conformation. The C—S bond length of 1.761(3) A is between the value for a C—S single and double-bond ¹² and is shorter than to those observed in organic disulfides with an equatorial conformation.

Crystallographic data (excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC- 711383. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: (+44) 1223-336-033; e-mail: deposit@ccdacam.ac.uk)

 

 

 

 

ACKNOWLEDGEMENTS

This work was supported by a grant from the Universidad de Antofagasta (DI-1324-06). The authors thanks the Spanish Research Council (CSIC) for the provision of a free-of-charge license for the Cambridge Structural Database system. AM thanks the Universidad de Antofagasta for a PhD fellowship.

 

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(Received: September 8, 2008 - Accepted: January 28, 2009)