Homo- and heteropolychalcogenide anions Ch2-, HCh-, Ch22-, Ch32-, and Ch42- (Ch = selenium and/or tellurium): solution proton, selenium-77, tellurium-123 and -125 NMR study

Abstract

The homo- and heteropolychalcogenide anions, Ch{sub n}{sup 2{minus}} (n = 1, 2, 3, 4; Ch = Se and/or Te) and the hydrochalcogenide anions, HCh{sup {minus}}, have been prepared and characterized in solution by {sup 1}H, {sup 77}Se, {sup 123}Te and {sup 125}Te nuclear magnetic resonance spectroscopy. The polychalcogenide anions were prepared in ethylenediamine and/or liquid ammonia by the reaction of the alkali-metal monochalcogenide with the appropriate chalcogen in the presence or absence of 2,2,2-crypt or by the direct reaction of the alkali metal with the chalcogen in liquid ammonia. With the exception of the pyramidal shaped TeSe{sub 3}{sup 2{minus}} anion, the polchalcogenide anions have open-chain structures. In addition, the more electronegative selenium atoms are found to be in terminal positions in the heteropolychalcogenide anions Te{sub n}Se{sub 3{minus}n}{sup 2{minus}} and Te{sub m}Se{sub 4{minus}m}{sup 2{minus}} (n = 1,2; m = 2, 3), which can be rationalixed by using the topological charge stabilization rule. The chemical shifts and unusually large spin-spin coupling constants are reported for the polychalcogenide anions and their trends discussed. 52 refs., 6 figs., 3 tabs.