Tellurium electrodeposition from tellurium(II) and (IV) chloride salts in dichloromethane

Electrodeposition of elemental Te from [NnBu4]2[TeCl6] in a weakly coordinating solvent, dichloromethane, has been investigated. The reduction the Te(IV) complex to deposit shows very large (> 1 V) overpotential on clean Pt macrodisc electrodes and microelectrodes that is significantly reduced once deposited electrode. Corresponding studies show there no significant for deposition Te(II) complex, [NEt4]2[TeI4], under same conditions, suggesting barrier electrodeposition [TeCl6]2− arises because instability intermediate Te(III) species. Density functional theory (DFT) calculations with M06–2X density treatment solvation using polarizable continuum model confirm possible complexes, [TeCl5]2−, [TeCl4]− [TeCl3], are all unstable respect disproportionation, confirming thermodynamic Te(0) [TeCl6]2−. We propose this overcome reaction at electrode surface by catalytic mechanism which transient Lewis acidic [TeCl5]− forms acid/base adduct ([TeCl5]− —Tesurface) through p-orbital overlap surface. This shown be consistent results DFT speciation equilibria chloride complexes experiments different concentration. Our suggest formation may also play role other p-block elements.