The Electrochemical Synthesis of Polycationic Clusters

Abstract

As a new method for the synthesis of chalcogen polycationic clusters, the electrochemical dissolution of elemental tellurium in ionic liquids (IL) or in liquid SO2 is presented. ILs used are ethylmethylimidazolium triflate [OTf](-) and tetraalkylammonium triflylimide [NTf2](-). Tristriflylmethanide [CTf3](-) was used as [BuMeIm][CTf3] as the electrolyte in SO2. This allowed for the isolation of [Te4][CTf3]2, [Te6][OTf]4, and [Te8][NTf2]2 containing the square [Te4](2+), the prismatic [Te6](4+), and the novel barrelane-shaped [Te8](2+). The compounds are novel compositions as they do not contain the usual halometalate anions, but rather common weakly coordinating anions. The (125)Te NMR spectrum of an IL solution containing [Te8](2+) features only one broad signal at 2700 ppm. DFT calculations show that slight concerted displacements within the [Te8](2+) cluster lead to a fluxional molecular structure and a fast valence isomerism with a very low activation barrier of about 8 kJ mol(-1).

Controlled Synthesis of Polyions of Heavy Main-Group Elements in Ionic Liquids

“…A variety of homoatomic polycations of group 15 or 16 elements has been synthesized in ILs [26,27,31,99,101,102,103,104] and several influencing reaction parameters were deduced.…”

“…Apart from Te 4 2+ , which proves a dominance in Lewis-acidic AlCl 3 -containing ILs similar to Bi 5 3+ , several other tellurium polycations (Figure 5) were accessed in ILs [26,27,31,101,102,103]. Thereby, the utilization of an IL as reaction medium can lead to extraordinary properties of the reaction product as the following example demonstrates: Te 4 [Bi 0.67 Cl 4 ] obtained from a gas-phase transport reaction is an conventional semiconductor.…”

“…They obtained Te 4 [CTf 3 ] 2 , Te 6 [Otf] 4 , and Te 8 [NTf 2 ] 2 after one to three weeks depending on the chosen IL and voltage [102]. By applying 4 V in the IL [EMIm][OTf], a red-violet anodic solution was obtained which yielded [Te 6 ][OTf] 4 upon layering or washing with liquid SO 2 at −60 °C.…”

“…Synopsis of tellurium homopolycations accessible in ILs: ( a ) Te 4 2+ e.g., in Te 4 [AlCl 4 ] 2 [101] or “Te 4 1.78+ ” in Te 4 [Bi 0.74 Cl 4 ] [31]; ( b ) Te 8 2+ in Te 8 [NTf 2 ] 2 [102]; ( c ) Te 6 4+ in Te 6 [OTf] 4 [102]; ( d ) Te 6 2+ in Te 6 [WOCl 4 ] 2 [101]; ( e ) ${}_{\infty }{}^{1}false[$Te 8 ] 2+ in [Te 8 ] 2 [Ta 4 O 4 Cl 16 ] [103]; and ( f ) ${}_{\infty }{}^{1}false[$Te 8 ] 2+ in Te 8 [Bi 4 Cl 14 ] [26]. …”

The First Step of the Oxidation of Elemental Sulfur: Crystal Structure of the Homopolyatomic Sulfur Radical Cation [S8].+

“…[1] Lately,t he synthetic strategies and methods that were very successful in the past did not allow for further progress.Nevertheless,byusing new methods and techniques,s pectacular results were still obtained even recently.F or instance,e vidence for the first homopolyatomic phosphorus cation [P 9 ] + was obtained by using modern weakly coordinating anions instead of classical hexafluorometallates such as [AsF 6 ] À . [3] Recently,i onic liquids as reaction media [4] and electrochemical syntheses [5] were introduced as new strategies for the field of homopolyatomic cations of the heavier chalcogen elements. [3] Recently,i onic liquids as reaction media [4] and electrochemical syntheses [5] were introduced as new strategies for the field of homopolyatomic cations of the heavier chalcogen elements.…”