2-Thiophenyltellurium derivatives: Alternative synthetic routes and structural characterization Ashok K.S. Chauhan a,⇑ , Poornima Singh a , Ramesh C. Srivastava a , Ray J. Butcher b , Andrew Duthie c a Department of Chemistry, University of Lucknow, Lucknow 226007, India b Department of Chemistry, Howard University, Washington, DC 20059, USA c School of Life and Environmental Sciences, Deakin University, Geelong 3217, Australia article info Article history: Received 14 March 2011 Received in revised form 20 May 2011 Accepted 31 May 2011 Available online 6 June 2011 Keywords: Tellurated thiophene Detelluration Secondary bonding interactions Sterically inactive lone pair abstract Grignard reagent prepared from 2-thiophenyl bromide in THF consumes elemental tellurium readily at room temperature and provides a route to obtain bis(2-thiophenyl)ditelluride, Tpn 2 Te 2 (1, Tpn = 2- C 4 H 3 S) in good yield. It can also thiophenylate aryltellurium(II) bromides, producing solutions of mixed aryl(heteroaryl)tellurides, which when chlorinated give crystalline aryl(heteroaryl)tellurium(IV) dichlo- rides, ArTpnTeCl 2 (Ar = 1-C 10 H 7 , Npl; 2,4,6-Me 3 C 6 H 2 , Mes). Oxidative addition of a-bromo-N,N-diethylac- etamide to (2-thiophenyl)tellurium(II) bromide, gave the mixed alkyl(heteroaryl)tellurium(IV) dibromide, (Et 2 NCOCH 2 )TpnTeBr 2 . Ditelluride 1 can be detellurated by electrolytic copper to the bis(2- thiophenyl)telluride, Tpn 2 Te (2). Chemical shifts, d( 1 H, 13 C and 125 Te) for (2-thiophenyl)tellurium(IV) halides are reported. Crystal structures of Tpn 2 TeBr 2 (2b), Tpn 2 TeI 2 (2c) and Mes(Tpn)TeCl 2 (2e) have been determined unambiguously. In the case of 2e, steric repulsion of the mesityl ligand counters the tel- lurium lone pair repulsion to widen the equatorial C–Te–C angle to the extent of 108°. In the crystal lat- tices of 2b and 2c, the intermolecular TeX secondary bonds give rise to an interesting tetrameric supramolecular architecture with S 2 symmetry that defies the stereochemical activity of the lone pair on the central tellurium atom. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction The tellurated thiophene derivatives, Tpn 2 TeX 2 (Tpn = 2-C 4 H 3 S), Tpn 2 Te and Tpn 3 TeBr were first reported in 1929 [1,2] using TeBr 2 as precursor. The mono and ditellurides, (Tpn 2 Te, Tpn 2 Te 2 ), have since been prepared by the use of 2-thiophenyllithium [3,4] and also characterized crystallographically [5,6]. Though the formation of TpnTeCl 3 has been implied in one of the preparations of Tpn 2 Te 2 (from TeCl 4 and TpnHgCl) [7,8], no trihalide has so far been iso- lated. In the other cases too, characterization has mostly been lim- ited to elemental analyses and 1 H NMR data. Surprisingly, insertion of elemental tellurium into the Mg–C(Tpn) bond has not been exploited as a synthetic route to obtain 2-thiophenyltellurium derivatives, though this synthetic protocol is known for other aryl- tellurium derivatives [9]. This communication details (i) an improved alternative synthe- sis of bis(2-thiophenyl)ditelluride, Tpn 2 Te 2 (1), its detelluration to the corresponding monotelluride, Tpn 2 Te (2), oxidative halogen- ations to trihalides TpnTeX 3 (X = Cl (1a), Br (1b), I (1c)) and dihalides Tpn 2 TeX 2 (X = Cl (2a), Br (2b), I (2c)) and preparation of mixed diaryl- and alkylaryltellurium(IV) dihalides ArTpnTeCl 2 (Ar = 1-C 10 H 7 , Npl (2d), 2,4,6-Me 3 C 6 H 2 , Mes (2e)) and (Et 2 N- COCH 2 )TpnTeBr 2 (2f); (ii) 1 H, 13 C and 125 Te NMR spectra of the sol- uble compounds and (iii) structure elucidation of 2b, 2c and 2e by single-crystal X-ray diffraction. Our interest in this area derives from earlier work on the characterization of functionalized organo- tellurium(II and IV) derivatives synthesized directly from elemen- tal tellurium, including those derived from 2-acetylthiophene [10,11]. The carbonyl O atom of each acylmethyl groups in (RCOCH 2 ) 2 TeX 2 is invariably involved in intramolecular 1,4-TeO non-covalent interactions, with cisoidal orientation of the organic ligands imparting C 2v symmetry to the (C–C(O)–CH 2 –) 2 TeX 2 skele- tal framework in the solid state. Interestingly, in case of (TpnC- OCH 2 ) 2 TeBr 2 , one of the 2-thiophenoylmethyl ligands adopts trans disposition with respect to the other and its carbonyl O atom is devoid of the 1,4-TeO interaction [11]. This observation emphasizes the role of the ring heteroatom as the cisoidal con- former would cause concentration of electron density in the domain of the lone pair at the central Te atom. As even subtle changes in electronic factors can be useful in the field of material science, systematic preparation and characterization of the tellu- rated thiophene derivatives was considered worthwhile so that a comparison with the phenyltellurium analogues could be made. 0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2011.05.039 ⇑ Corresponding author. Tel.: +91 9415010763; fax: +91 522 2338531. E-mail addresses: akschauhan2003@yahoo.co.in (A.K.S. Chauhan), poornima05- singh@yahoo.co.in (P. Singh), rameshlko@yahoo.co.nz (R.C. Srivastava), rbutcher99 @yahoo.com (R.J. Butcher), aduthie@deakin.edu.au (A. Duthie). Inorganica Chimica Acta 376 (2011) 80–86 Contents lists available at ScienceDirect Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica