Stereospecific chlorotelluration of terminal acetylenes

Chlorotelluration of terminal acetylenes, RCH CH (R - Ph, 1; 4- MeC6H4, 2; t-Bu, 3) with aryltellurium trichlorides and TeCl4 in refluxing toluene affords (2-chloro-2-organylvinyl)tellurium(IV) dichlorides, Ar [R(Cl)C-CH] TeCl2 (Ar = 1-C10H7, 1Aae3Aa; 2,4,6- Me3C6H2, 1Ba-3Ba; 4-MeOC6H4, 1Ca) and [t-Bu(Cl)-C] CH](2)TeCl2, 3a respectively. These Te(IV) derivatives on reduction with Na2S2O5 give the corresponding vinyltellurides as oils, except (2,4,6-Me3C6H2)[Ph(Cl)C=CH]Te (1B) which is a crystalline solid. The dibromides (1Ab-3Ab, 1Bb-3Bb, 3b) and diiodides (1Ac-3Ac, 1Bc-3Bc, 1Cc) were obtained by the oxidative addition of dihalogens to the tellurides. The stereochemistry of the products has been established with the help of X-ray diffraction studies of 1Aa, 1Ba, 1Bc, 1Cc, 3Aa, 3a and 1B. Intramolecular Te center dot center dot center dot Cl attractive interactions appear to favor the (Z) conformation adopted by the 2-chloro-2-organylvinyltellurium group irrespective of the steric demand of the aryl ligand of the Te(IV) electrophile and the terminal acetylene substituent. The intermolecular Te center dot center dot center dot X secondary bonding interactions give rise to dimeric units in the lattices of 1-naphthyl- and anisyltellurium(IV) derivatives, but are absent among the mesityl analogues, consistent with the larger steric requirement of the latter ligand. (C) 2012 Elsevier B.V. All rights reserved.