Complex Tellurium Salts with Supramolecular

Complex Tellurium Salts with Supramolecular Bidimensional Lattices: Synthesis and X-ray Characterization of (2-Br-C5NH5)2[TeX6] (X ⴝ Cl, Br) Ramaõ Marceli Fernandes Jra, Gelson Manzoni de Oliveiraa,*, Ernesto Schulz Langa,*, and Ezequiel M. Va´zquez-Lo´pezb a b

Santa Maria, RS, Brazil, Departamento de Quı´mica, Laborato´rio de Materiais Inorgaˆnicos ⫺ Universidade Federal de Santa Marıá Vigo, Galicia, Spain, Departamento de Quı´mica Inorgańica, Facultade de Quı´mica, Universidade de Vigo

Received June 21st, 2004.

Abstract. The reaction of tellurium(IV) tetrahalides with hydrochloric and hydrobromic acid leads to the formation of (H3O)2[TeX6], which reacts subsequently with (2-Br-C5NH5)⫹X⫺ to afford (2-Br-C5NH5)2[TeCl6] (1) and (2-Br-C5NH5)2[TeBr6] (2). The structure of the complex salts were analysed by X-ray diffractometry affording the centrosymmetric space groups P21/n (monoclinic, 1) and P1¯ (triclinic, 2). Interionic hydrogen bondings hold their lattices in bidimensional supramolecular arrays not yet described in the literature. The lone electron pair of the AX6E-system of the hexahalotellurates [TeX6]2⫺ (X ⫽ Cl, Br) seems to be fully de-

localized since only small octahedral deviations were observed for the anionic species. The structures of the title compounds were refined with the Te atoms occupying sites with full point symmetry, approximately m3¯m. In both cases the Te atoms enclose centers of inversion and the octahedrally dynamic structures are enforced and stabilized along the supramolecular lattices by the crystal field of the 2-Br-pyridinium cations.

Keywords: Chalcogen halides; Hexahalotellurates; Octahedral distortion in hexahalotellurates

Komplexe Tellursalze mit supramolekularen zweidimensionalen Gittern: Synthese und Kristallstrukturen von (2-Br-C5NH5)2[TeX6] (X ⴝ Cl, Br) Inhaltsübersicht. Die Reaktion von Tellurtetrahalogeniden mit Salzsäure und Bromwasserstoffsäure führt zur Bildung von (H3O)2[TeX6], die sich mit (2-Br-C5NH5)⫹X⫺ zu (2-Br-C5NH5)2[TeCl6] (1) und (2-Br-C5NH5)2[TeBr6] (2) umsetzen lassen. Die Kristallstrukturanalysen der komplexen Salze führen zu den zentrosymmetrischen Raumgruppen P21/n (monoklin, 1) und P1¯ (triklin, 2). Interionische Wasserstoffbrückenbindungen erzeugen zweidimensionale supramolekulare Anordnungen, die bisher in der Literatur nicht beschrieben sind. Das freie Elektronenpaar des AX6E-Systems der

Hexahalogenotellurate [TeX6]2⫺ (X ⫽ Cl, Br) scheint völlig delokalisiert zu sein, da nur sehr geringe Abweichungen von der Oktaedersymmetrie der Anionen beobachtet werden. Die Strukturen der Titelverbindungen wurden mit den Te-Atomen auf angenäherten Punktlagen m3¯m verfeinert. In beiden Fällen besetzen die TeAtome Inversionszentren, und ihre oktaedrisch-dynamischen Strukturen werden durch Kristallfeldeffekte der 2-Brompyridinium-Kationen im Gitter erzwungen und stabilisiert.

Introduction

and possible distortions of the octahedral structure [4⫺7]. Some authors gave special attention to the cation-anion interaction through hydrogen bonding [8⫺10] and Valle and coworkers [11] in earlier reports have studied the possible effects of hydrogen bondings on the distortion of the hexachlorotellurate(IV) ion. To explain the distortion around the tellurium atom in the crystal structures of some reported compounds, the authors [11] have considered their hydrogen bonding systems and postulated that in compounds with undistorted [TeX6]2⫺, hydrogen bondings either are not present or form a symmetric net around the halogen atoms; on the other hand, all compounds with distorted [TeX6]2⫺-ions would possess asymmetric hydrogen bondings: the N⫺H···C1 and N⫺H···Br hydrogen bonds in protonated amines, amides or amino acids weaken the Te⫺X bonds with a resultant distortion of the TeX6 octahedron. More recently, looking for symmetry rules for the stereochemistry of the lone-pair electrons in AX6E (X ⫽ CI, Br, I) systems, Abriel [12] showed that a comparison of

Structural and bonding properties of chalcogen halides have been, in general, an attractive subject of structural chemistry. The stereochemistry of the chalcogen halides exhibits a large range because of the strongly variable stereochemical activity of the inert electron pairs in the valence shell of the chalcogen atom [1, 2]. The major interest on the investigations of hexahalotellurates [TeX6]2⫺ has been in the field of structural considerations involving the rules of the VSEPR theory [3] and their implications with respect to the seven ⫺ one “lone” ⫺ electron pairs of the tellurium atom,

* Prof. Dr. Gelson Manzoni de Oliveira * Prof. Dr. Ernesto Schulz Lang Departamento de Quı´mica Universidade Federal de Santa Marıá 97105-900 Santa Marıá, RS/Brazil E-mail: [email protected] Z. Anorg. Allg. Chem. 2004, 630, 2687⫺2691

DOI: 10.1002/zaac.200400320

 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim

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some compounds with [MX6]2⫺ anions (M ⫽ Sn, Te; X ⫽ C1, Br) and cations containing N⫺H functions allows to conclude that the neighbourhood of a more or less acid N⫺H function is not the decisive factor for distortion. According Abriel, looking at the point symmetry of the Te atoms, the existence of a center of symmetry always produces a non-distorted anion, or, distortion is allowed only with the Te atom in a noncentrosymmetric point symmetry group. As the distorted species show an increasing ionic character of the longer Te⫺X bonds, these more polarized halogen ligands are able to form hydrogen-bridged connections to neighbouring N atoms. Most of the complex hexahalotellurates salts with cations containing N⫺H functions reported up to date show interionic N⫺H···X interactions, and these secondary bondings can reach very different linkage models. In opposition, simultaneous cation/anion interactions through halogen atoms and hydrogen bondings have not yet been described in the literature to date, since, to our knowledge, it is not very usual that the investigated positive counter ions ⫺ protonated nitrogen compounds on the whole ⫺ enclose an halogen atom [13]. Also to investigate this possibility of double, interionic interaction, as well their effects on the stereochemistry of the lone-pair electrons in AX6E (X ⫽ CI, Br) systems, we have synthesized and report the X-ray structural characterization of (2-Br-C5NH5)2[TeCl6] (1) and (2-Br-C5NH5)2[TeBr6] (2). In both compounds the 2-Br-pyridinium cations are linked to the [TeX6]2⫺ anions through hydrogen bondings, in 2 there are additional weak interionic Br···Br contacts; the effective interactions hold the

ionic species 1 and 2 in supramolecular, bidimensional arrays along their lattices. Such a novel assembling model was not yet reported in the literature for this type of compound.

Results and Discussion The successful refinements of the X-ray measures of (2-Br-C5NH5)2[TeCl6] (1) and (2-Br-C5NH5)2[TeBr6] (2) have shown that 1 belongs to the monoclinic space group P21/n and 2 to the triclinic one P1¯ . Both space groups present symmetry centers, and the asymmetric units of 1 and 2 contain one cation (2-Br-C5NH5)⫹ and half [TeX6]2⫺anion, this means, one Te0,5X3-moiety. The whole (2-Br-C5NH5)2[TeX6] neutral species are generated through an inversion center on the asymmetric units, and the tellurium atoms of 1 and 2 lie in the special crystallographic positions (0.5, 0, 0.5) and (0.5, 0.5, 0), respectively. There are no asymmetrical trans-X⫺Te⫺X bonds in the octahedral anions [TeCl6]2⫺ (1) and [TeBr6]2⫺ (2), and this should be significant in the (later) discussion about distortions of the octahedrons. The crystal data and experimental conditions are given in Table 1. Figures 1 and 2 show sections of adjacent nets of (2-Br-C5NH5)2[TeCl6] and (2-Br-C5NH5)2[TeBr6], coupled through three-centered hydrogen bondings (dotted lines). In the case of 2 (Figure 2), interionic, likewise three-centered, non bonding Br···Br-interactions (broader dotted lines) could be also detected. Selected bond distances (for secondary interactions in spotted lines) and angles of both complexes are listed in Tables 2 and 3.

Table 1 Crystal data and structure refinement for 1 and 2 Empirical formula Formula weight Temperature/ °K ˚) Radiation/ λ (A Crystal system, space group ˚ Unit cell dimensions a, b, c/ A α, β, γ (°) ˚3 Volume/ A Z, Calculated density (g.cm⫺3) Absorption coefficient (mm⫺1) F(000) Crystal size/ mm θ range/ ° Limiting indices Reflections collected Reflections unique Completeness to theta max. Absorption correction Max. and min. transmission Refinement method Data / restraints / parameters Goodness-of-fit on F2 Final R indices [I>2σ (I)] R indices (all data) Extinction coefficient Largest diff. peak and hole/ e.A⫺3

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C5H5BrCl3NTe0.50 (1) 329.16 293(2) 0.71073 monoclinic, P21/n a ⫽ 9.0530(14) b ⫽ 10.7917(17) c ⫽ 10.6513(17) β ⫽ 110.990(3) 977.8(3) 4, 2.236 6.4201 616 0.7 x 0.5 x 0.35 2.56 ⫺ 30.50 ⫺12ⱕhⱕ12, ⫺15ⱕkⱕ15, ⫺15ⱕlⱕ15 11765 2963 [Rint ⫽ 0.0254] 99.4 % semi-empirical from equivalents 1 and 0.547427 full-matrix least-squares on F2 2963 / 0 / 98 1.079 R1 ⫽ 0.0213, wR2 ⫽ 0.0570 R1 ⫽ 0.0235, wR2 ⫽ 0.0581 0.0236(7) 0.706 and ⫺1.404


C5H5Br4NTe0.50 (2) 462.54 293(2) 0.71073 triclinic, P1¯ a ⫽ 7.4105(2) b ⫽ 8.426(3) c ⫽ 9.385(2) α ⫽ 73.77(2) β ⫽ 68.36(2) γ ⫽ 82.402(18) 522.7(3) 2, 2.939 6.705 416 0.13 x 0.1 x 0.09 3.02 ⫺ 29.02 ⫺1 ⱕ h ⱕ 10, ⫺11 ⱕ k ⱕ 11, ⫺12 ⱕ l ⱕ 12 3392 2779 [Rint ⫽ 0.0263] 99.7 % semi-empirical from equivalents 0.9809 and 0.4832 full-matrix least-squares on F2 2779 / 0 / 98 1.066 R1 ⫽ 0.0404, wR2 ⫽ 0.1007 R1 ⫽ 0.0611, wR2 ⫽ 0.1093 0.033(2) 1.117 and ⫺1.489

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Complex Tellurium Salts with Supramolecular Bidimensional Lattices

In the complex salt (2-Br-C5NH5)2[TeCl6] each cationic moiety (2-Br-C5NH5)⫹ links bidimensionally two vicinal anions [TeCl6]2⫺ through two NH···Cl bridges {bond ˚ ; H(6)···Cl(2) ⫽ lengths: H(6)···Cl(1) ⫽ 2.467(1) A ˚ 2.869(2) A; bond angles: N(6)⫺H(6)···Cl(1) ⫽ 149.00(11)°; N(6)⫺H(6)···Cl(2) ⫽ 120.95(11)°}, so that each octahedral TeCl6 unit is equatorially connected ⫺ through four cations ⫺ to four adjacent [TeCl6]2⫺ anions. The arrangement of the hydrogen bondings causes an alternated orientation in zigzag of the octahedrons TeCl6 in the crystal lattice of 1 along the face parallel to the b axis and diagonal to the ac axes. The bidimensional restraint of the supramolecular arrangement of (2-Br-C5NH5)2[TeCl6] can be explained by the fact that there are no cationic interactions (NH···Cl) with the axial chlorine atoms of the anionic octahedral species. The Te⫺Cl bond distances in the [TeCl6]2⫺ anions ⫺ see Figure 1 ⫺ are respectively 2.5539(5) {Cl(1)⫺Te}, 2.5464 ˚ {Cl(3)⫺Te}, the three trans{Cl(2)⫺Te} and 2.5316 A chlorine bonds have the same lengths. Minor octahedral distortion appears also in the bond angles: all the transCl⫺Te⫺Cl bonds are fully linear with angles of 180.0°, but the cis-Cl⫺Te⫺Cl bonds are not entirely perpendicular,

Fig. 1 Projection of a segment of adjacent chains of (2-Br-C5NH5)2[TeCl6] linked through three-centered N⫺H···Cl hydrogen bondings (dotted lines) and the bidimensional supramolecular arrangement of the monoclinic cell. Symmetry transformations used to generate equivalent atoms: #1 1⫺x, 1⫺y, 1⫺z; #2 1/2⫹x, 1/2⫺y, 1/2⫹z; #3 ⫺1/2⫹x, 1/2⫺y, ⫺1/2⫹z.

showing small orthogonal deviations. Nevertheless these deflections (maximum: ± 0.337°) are always twofold (cis) compensated as shown in Table 2, so that a mean point symmetry m3¯ m can be attributed to the octahedral anion [TeCl6]2⫺. In the crystal lattice of (2-Br-C5NH5)2[TeBr6] (2) the interionic NH···Br interactions produce a stout approximation of the counter-ions, what brings the Br (counter) atoms close to each other. These contacts, however, can not be viewed as secondary interactions, since the Br⫺Br distances are related merely to the sum of the van der Waals radii. It is known that for [Ph3AsBr]2[TeBr6], for example, the shortest Br···Br interionic distances are 383.7 and 379.0(3) pm, even if the relative orientation of the ions should promote secondary Br⫺Br interactions [14]. In 2 each single cationic unit (2-Br-C5NH5)⫹ is associated with three [TeBr6]2⫺ anions (see Figure 2): two vicinal through ˚; two NH···Br bridges {bond lengths: H(6)···Br(2) ⫽ 2.72 A ˚ H(6)···Br(4) ⫽ 2.85 A; bond angles: N(6)⫺H(6)···Br(2) ⫽ 136.0°; N(6)⫺H(6)···Br(4) ⫽ 134.6°} and the third one ⫺ of the adjacent net ⫺ by means of two Br···Br non ˚ bonding interactions, with lengths of 3.663(4) A ˚ {Br(1)···Br(4)#3} and 3.683(1) A {Br(1)···Br(2)#2}.

Fig. 2 Segment of adjacent chains of (2-Br-C5NH5)2[TeBr6] connected through three-centered N⫺H···Br hydrogen bondings and Br···Br non bonding interactions (dotted lines) and the supramolecular array of the lattice. Symmetry transformations used to generate equivalent atoms: #1 x, 1⫹y, z; #2 x, 1⫹y, 1⫹z; #3 ⫺x, 1⫺y, 1⫺z.

˚ and angles/° for 2 Table 3 Selected bond lengths/A ˚ and angles/° for 1 Table 2 Selected bond lengths/A Bond-lengths C(1)⫺Br Cl(1)⫺Te Cl(2)⫺Te Cl(3)⫺Te H(6)···Cl(1) H(6)···Cl(2)

1.863(2) 2.5539(5) 2.5464(5) 2.5316(5) 2.467(1) 2.869(2)

Bond angles N(6)···H(6)···Cl(1)

149.00(11)

N(6)···H(6)···Cl(2) Cl(3)⫺Te⫺Cl(2) Cl(3)⫺Te⫺Cl(2)#1 Cl(3)⫺Te⫺Cl(1) Cl(3)#1⫺Te⫺Cl(1) Cl(2)⫺Te⫺Cl(1) Cl(2)⫺Te⫺Cl(1)#1

120.95(11) 89.66(2) 90.34(2) 90.060(2) 89.94(2) 90.31(2) 89.69(2)

Symmetry transformations used to generate equivalent atoms: #11⫺x, 1⫺y, 1⫺z.

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Bond lengths C(1)⫺Br(1) Br(2)⫺Te(1) Br(3)⫺Te(1) Br(4)⫺Te(1) H(6)···Br(2) H(6)···Br(4)#1 Br(1)···Br(4)#3 Br(1)···Br(2)#2

1.850(6) 2.7016(8) 2.6951(12) 2.7028(10) 2.72 2.85 3.663(4) 3.683(1)

Bond angles N(6)⫺H(6)···Br(2)

136.0

N(6)⫺H(6)···Br(4) Br(1)···Br(4)#3⫺Te#2 Br(1)···Br(2)#2⫺Te#2 Br(2)⫺Te(1)⫺Br(1)#1 Br(2)⫺Te(1)⫺Br(1) Br(2)#1⫺Te(1)⫺Br(1) Br(2)⫺Te(1)⫺Br(3)#1 Br(1)⫺Te(1)⫺Br(3)#1 Br(2)⫺Te(1)⫺Br(3) Br(1)⫺Te(1)⫺Br(3)

134.6 99.40(1) 98.88(1) 88.63(3) 91.37(3) 88.63(3) 91.13(3) 90.18(3) 88.87(3) 89.82(3)

Symmetry transformations used to generate equivalent atoms: # 1x, 1⫹y, z; #2 x, 1⫹y, 1⫹z; #3 ⫺x, 1⫺y, 1⫺z.  2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim

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The angles of these weak interactions are 99.40(1)° {Br(1)···Br(4)#3⫺Te#2} and 98.88(1)° {Br(1)···Br(2)#2⫺Te#2}. Every one of the four equatorial halogen atoms of the octahedrons TeBr6 performs two “secondary interactions“: one hydrogen bonding and other of the Br···Br type. The four Br···Br non bonding interactions involve two oppose (2-Br-C5NH5)⫹ cations, the four NH···Br bonds engage four vicinal (coupled in two chains) cationic species. Also in this compound there are no secondary interactions regarding the two axial bromine atoms. Because of this reinforced approximations the supramolecular arrangement of 2 is compact and denser than the crystalline assembly of 1 (Calculated density: 2.939 g.cm⫺3, see Table 1), although the lattice of the later belongs to a space group of higher symmetry (P21/n) than that of 2. The Te⫺Br bonds in the anion [TeBr6]2⫺ are somewhat symmetrical than the Te⫺Cl bonds in [TeCl6]2⫺, with lengths of 2.7016(8) {Br(2)⫺Te}, 2.6951(12) {Br(3)⫺Te}, and ˚ {Br(4)⫺Te}, the three trans Te⫺Br bonds present 2.7028 A also the same distances. The trans-Br⫺Te⫺Br bonds are linear with angles of 180.0°, and the cis-Br⫺Te⫺Br bonds present small orthogonal deviations. The deflections are also cis compensated and proportionally bigger than in case of [TeCl6]2⫺ (maximum: ± 1.37°). By comparison of some own results with reported [TeX6]2⫺ and [SnX6]2⫺ salts, Abriel [12] has pointed out that only very small distortions from m3¯ m symmetry are observed for the investigated MX6 octahedrons; it should also be noted that this kind of distortion always appears by refining atomic positions with the central atom not occupying a site with full point symmetry (here m3¯ m), hence the octahedrons found should be only quite regular. Abriel has also postulated that the packing of cations and anions fixes the point symmetry of the Te atom: with a center of symmetry for this Te position, a non-distorted [TeX6]2⫺ ion results. Only small deviations from ideal m3¯ m symmetry (of the same order of magnitude as in [SnX6]2⫺ ions) will be allowed when the point group is of lower symmetry than m3¯ m, since this crystal field stabilizes the octahedrally enforced dynamic structure. With a noncentrosymmetric point symmetry for the Te atom, the [TeX6]2⫺ group will be statically distorted, and ⫺ according to Pearson [15] ⫺ the resulting symmetry must be 4mm, 2mm or 3m (displaying the three orientations of one component of the T1u deformation vibration of the octahedron). Besides the discussion about the symmetry decreasing of the ion [TeX6]2⫺ related to its IR-active deformation, it is especially significant the earlier introduction of the concepts of dynamical and statical distortion of the ion [TeX6]2⫺. The dynamical distortion involves only small deviations of the octahedral symmetry m3¯ m, a severe distortion ⫺ or statical distortion ⫺ implicates a configuration in which [TeX6]2⫺ belongs to a point group of lower symmetry. We assume that this effect should be caused by the “confinement” in the structure ⫺ instead of free delocalisation ⫺, of the lone electron pair existing in the AX6E system. The structures of our title compounds 2690


(2-Br-C5NH5)2[TeCl6] (1) and (2-Br-C5NH5)2[TeBr6] (2) were refined with the Te atoms occupying sites with full point symmetry, approximately m3¯ m, with small deviations. In both cases {[TeCl6]2⫺ and [TeBr6]2⫺} the Te atoms enclose centers of inversion, and this ⫺ according Abriel ⫺ should mean the occurrence of non-distorted [TeX6]2⫺ ions. The small octahedral deviations observed for the anions [TeCl6]2⫺ and [TeBr6]2⫺ allow us to consider them as dynamically distorted octahedrons, with the (octahedrally) enforced dynamic structures stabilized by the crystal field of the cations (2-Br-C5NH5)⫹ along their supramolecular lattices.

Experimental The crystallographic structures of 1 and 2 were solved by direct methods (SHELXS-97 [16]). Refinements were carried out with the SHELXL⫺97 [17] package. All refinements were made by full⫺matrix least⫺squares on F2 with anisotropic displacement parameters for all non-hydrogen atoms. Hydrogen atoms were included in the refinement in calculated positions. Further details of the crystal structures investigations are available free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; fax: ⫹44 1223 336033; e-mail: [email protected]) as Supplementary publication No. CSD 244372 (1) and 244373 (2). The title compounds 1 and 2 were prepared starting from TeCl4 and TeBr4 in hydrochloric and hydrobromic acid with 2-bromopyridine, according to Scheme 1:

TeX4 ⫹ 4 HX

⫹2H2O ⫺2H2O 씮 (H3O)2[TeX6] ⫹ 2 QX 씮 (Q)2[TeX6] ⫹ 2 HX (Q ⫽ 2-Br-C5NH5; X ⫽ Cl, Br)

Scheme 1 The reaction of tellurium(IV)tetrahalides with hydrochloric and hydrobromic acid leads to the formation of (H3O)2[TeX6], which reacts subsequently with 2-Br-C5NH5⫹X⫺ to afford the desired products.

Preparation of (2-Br-C5NH5)2[TeCl6] (1) After dissolving 0.270 g of tellurium tetrachloride (1 mmol) and 0.51 ml of 2⫺bromopyridine (2 mmol) in 20 ml of dichloromethane, 0.3 ml of hydrochloric acid 12 M was added. The mixture was stirred for 2 h with precipitation of a yellow substance. The solid was recrystallized from hot THF. Properties: remarkably stable, yellow crystalline substance; C10H10Br2Cl6N2Te (658.322). Yield: 0.625 g (95 % based on tellurium tetrachloride taken). Melting point: 134 °C (decomposition); C, H, N-Analysis, Found: C, 18.10; H, 1.66; N, 4.18 %. Calc.: C, 18.24 ; H, 1.53 ; N, 4.25 %.

Preparation of (2-Br-C5NH5)2[TeBr6](2) Tellurium tetrabromide (0.45 g, 1 mmol) and 2⫺bromopyridine (0.51 ml, 2 mmol) were dissolved in 20 ml of dichloromethane and 0.5 ml of HBr 47M was added. The solution was stirred for 3 h,

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Complex Tellurium Salts with Supramolecular Bidimensional Lattices resulting a reddish-brown precipitate. After addition of 8 ml of hot methanol the mixture was stirred for 5 minutes and then filtered. The product crystallizes by slow evaporation of a saturated solution of dichloromethane /methanol. Properties: very stable, red crystals; C10H10N2Br8Te (925.004). Yield: 0.66 g (72 % based on tellurium tetrabromide taken). Melting point: 47 °C (decomposition). C, H, N-Analysis, Found: C, 14.19; H, 1.15; N, 3.12 %. Calc.: C, 14.10; H, 1.08; N, 2.99 %.

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[7] L.-J. Baker, C. E. F. Rickard, M. J. Taylor, Polyhedron 1995, 14, 401. [8] P. L’Haridon, H. Jedrzejczak, S. Szwabski, Acta Crystallogr. 1979, B35, 1843. [9] H. Ishida, S. Kashino, Acta Crystallogr. 1998, C54, 1811. [10] M. H. Ben Ghozlen, J. W. Bats, Acta Crystallogr. 1982, B38, 1308. [11] G. Valle, U. Russo, S. Calogero, Inorg. Chim. Acta 1980, 45, L277. [12] W. Abriel, Acta Crystallogr. 1986, B42, 449. [13] N. Kuhn, A. Abu-Rayyan, K. Eichele, C. Piludu, M. Steimann, Z. Anorg. Allg. Chem. 2004, 630, 495. [14] S. Chitsaz, B. Neumüller, K. Dehnicke, Z. Naturforsch. 1999, 54b, 1092. [15] R. G. Pearson, Symmetry Rules for Chemical Reactions, p. 199 ft. New York, John Wiley, 1976. [16] G. M. Sheldrick, SHELXS-97, Program for Crystal Structure Solution, University of Göttingen, Germany, 1997. [17] G. M. Sheldrick, SHELXL-97, Program for Crystal Structure Refinement, University of Göttingen, Germany, 1997.


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