Synthesis and properties of the ditelluroethers m- and p-C6H4(CH2TeMe)2 and their Te(IV) derivatives: crystal structures of PhTeI2(CH2)3TeI2Ph, m-C6H4(CH2TeI2Me)2 and p-C6H4(CH2TeI2Me)2

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Abstract

The new ditelluroethers m-C6H4(CH2TeMe)2 and p-C6H4(CH2TeMe)2 have been prepared in good yield from nucleophilic reaction of m- or p-C6H4(CH2Br)2 and LiTeMe in THF solution. Reaction of the new ditelluroethers with MeI or I2 affords the light yellow m- or p-C6H4(CH2TeMe2I)2 or the red/orange m- or p-C6H4(CH2TeI2Me)2, respectively in high yield. These compounds have been characterised by IR, 1H, 13C{1H} and 125Te{1H} NMR spectroscopy and EI mass spectrometry as appropriate. The crystal structures of the di-iodo derivatives m-C6H4(CH2TeI2Me)2, p-C6H4(CH2TeI2Me)2 and the related PhI2Te(CH2)3TeI2Ph (prepared from PhTe(CH2)3TePh and diiodine in THF solution) are described. In each compound the TeI2 units are axial and significant intermolecular Te⋯I secondary contacts (≈3.6–4.1 Å) are evident, which link these covalent compounds into extended networks with each Te atom in a distorted 6-coordinate environment.

The preparations of two new ditelluroethers involving xylyl-based linkages between the Te atoms are reported; m-C6H4(CH2TeMe)2 and p-C6H4(CH2TeMe)2, together with their Te(IV) triorganotellurium iodides and diorganotellurium di-iodide derivatives. The crystal structures of m-C6H4(CH2TeI2Me)2 and p-C6H4(CH2TeI2Me)2 and the related PhTeI2(CH2)3TeI2Ph exhibit extended networks with significant Te⋯I secondary bonding interactions.

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Introduction

We have been interested for some time in the synthesis and coordination chemistry of polydentate and macrocyclic telluroether ligands with transition metal and p-block ions [1], [2], [3], [4], [5], [6], [7], [8]. Unlike thioether chemistry, where the ligand synthesis is not affected significantly by the inter-donor linkage, in telluroethers the choice of inter-donor linkage can play an important role in determining the course of the organotellurium reaction chemistry and thus, only a restricted range of linking units have been incorporated to-date [1]. However, the inter-donor unit can also influence considerably the metal binding properties of the ligands, hence we wish to extend the range of di- and poly-tellurother compounds to investigate these factors further. In the course of our characterisation of new telluroethers we often prepare methiodide or diiodide Te(IV) derivatives, since these are air-stable and therefore more easily handled, e.g. the macrocyclic Te(IV) di-iodides [11]aneS2TeI2 (1,4-dithia-8,8-diiodo-8-telluracycloundecane) and [12]aneS2TeI2 (1,5-dithia-9,9-diiodo-9-telluracyclododecane) and the telluronium species [9]aneS2TeMeI (1,4-dithia-7-methyl-7-iodo-7-telluracyclononane), [11]aneS2TeMeI (1,4-dithia-8-methyl-8-iodo-8-telluracycloundecane) and [12]aneS2TeMeI (1,5-dithia-9-methyl-9-iodo-9-telluracyclododecane) [7] and IMeRTe(CH2)3}2TeMeI (R=Me or Ph) [6].

Several classes of organotelluronium halide compounds are known, including species of general formula RTeX3, R2TeX2 and R3TeX and these have been reviewed [9]. In addition to their value in providing supporting spectroscopic characterisation for the telluroethers, these Te(IV) compounds are themselves often structurally very interesting, owing to the occurrence of secondary Te⋯X bonding interactions which can result in dimeric or higher oligomeric assemblies [9], [10]. We have previously examined the structure adopted by the telluronium derivative of the xylyl-linked o-C6H4(CH2TeMe)2 [11]. The crystal structure of o-C6H4(CH2TeMe2I) shows a weakly associated dimer, assembled through a series of secondary Te⋯I interactions to give a pseudo-cubane Te4I4 core, involving 3-coordinate (pyramidal) iodine and 6-coordinate (distorted octahedral) tellurium. The o-xylyl backbone units are oriented across the diagonal of two opposite faces of the cubane. The unusual motif in this species prompted us to probe the occurrence of secondary bonding interactions in other Te(IV) iodide compounds derived from related xylyl-based ditelluroethers.

In this paper we describe preparations for the new ditelluroethers m- and p-C6H4(CH2TeMe)2 which incorporate linkages likely to lead to extended networks upon coordination to metal ions. The preparation and spectroscopic characterisation of the tellurium(IV) derivatives m- and p-C6H4(CH2TeMe2I)2 and m- and p-C6H4(CH2TeI2Me)2 are also described. Crystal structures of the di-iodo Te(IV) species, m- and p-C6H4(CH2TeI2Me)2 and the related PhTeI2(CH2)3TeI2Ph, are presented and the structures compared with relevant literature examples.

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Results and discussion

The new xylyl-based ditelluroether compounds m- and p-C6H4(CH2TeMe)2 were obtained in good yield by reaction of freshly ground elemental tellurium with MeLi at 77 K in THF, which upon warming to room temperature produces MeTeLi. Addition of 0.5 mol. equivs. of m-C6H4(CH2Br)2 or p-C6H4(CH2Br)2 to this at 77 K and warming to RT affords the two new telluroethers m-C6H4(CH2TeMe)2 or p-C6H4(CH2TeMe)2 respectively as air-sensitive, yellow solids in good yield. These formulations follow from their 1H

Experimental

Infrared spectra were recorded as CsI discs using a Perkin–Elmer 983G spectrometer over the range 4000–200 cm−1. Mass spectra were run by electron impact on a VG-70-SE Normal geometry double focusing spectrometer or by positive ion electrospray (MeCN solution) using a VG Biotech platform. 1H NMR spectra were recorded using a Bruker AM300 spectrometer. 13C{1H} and 125Te{1H} NMR spectra were recorded using a Bruker DPX400 spectrometer operating at 100.6 or 126.3 MHz, respectively and are

Supplementary material

Crystallographic data for the structural analyses have been deposited with the Cambridge Crystallographic Data Centre, CCDC nos. 221911-221913. Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge CD2 1EZ, UK (Fax: +44-1223-336033; email: [email protected] or www:http://www.ccdc.cam.ac.uk).

Acknowledgements

We thank the EPSRC for support.

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Cited by (6)

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    Citation Excerpt :

    In addition, the well known Te⋯I secondary interactions between neighbor molecules, leading to the formation of n-dimensional polymers in the solid state, are also present in compounds 2, 3 and 4. These trends – the occurrence of intra and intermolecular Te⋯I long range, (secondary) interactions between adjacent molecules, linking them into infinite arrays – were already described in the literature [13] for this kind of ditelluroethers derivatives. Figs. 5–8 show the calculated (theoretical) absorption spectra (vertical lines are calculated electronic transitions) and the experimental spectra of 1, 2, 3 and 4.

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