2-thiophenyltellurium derivatives: alternative synthetic routes and structural characterization

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) dichlorides, ArTpnTeCl 2 (Ar = 1-C 10 H 7 , Npl; 2,4,6-Me 3 C 6 H 2 , Mes). Oxidative addition of α-bromo- N , N -diethylacetamide 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, δ ( 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 tellurium lone pair repulsion to widen the equatorial C–Te–C angle to the extent of 108°. In the crystal lattices 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.