Electrocatalytic hydrogen evolution mediated by an organotelluroxane macrocycle stabilized through secondary interactions.

A discrete liphophilic organotelluroxane macrocycle has been found to catalyse the hydrogen evolution reaction (HER) by proton reduction efficiently. The macrocycle is synthesized via chloride abstraction from bis( p -methoxyphenyl) tellurium dichloride ( p -MeOC 6 H 5 ) 2 TeCl 2 (1) by silver salts AgMX 4 (MX 4 = BF 4 - , and ClO 4 - ) resulting in in situ generated di-cationic tetraorganoditelluroxane units; two such units are held together by two weak anions μ 2 -MX 4 , bridging to form 12-membered di-cationic macrocycles [(( p -MeO-C 6 H 4 ) 2 Te) 2 (μ-O)(μ 2 -F 2 BF 2 ) 2 ] 2+ (2) and [(( p -MeO-C 6 H 4 ) 2 Te) 2 (μ-O)(μ 2 -O 2 ClO 2 ) 2 ] 2+ (3) stabilized via Te-(μ 2 -BF 4 /ClO 4 ), with secondary interactions. The charge is balanced by the presence of two more anions, one above and another below the plane of the macrocycle. Similar reaction at higher temperatures leads to the formation of telluronium salts R 3 TeX [X = BF 4 - (4), ClO 4 - (5)] as a major product. The BF 4 - anion containing macrocycle and telluronium salt were monitored using 19 F NMR. HRMS confirmed the structural stability of all the compounds in the solution state. The organotelluroxane macrocycle 2 has been found to act as an efficient electrocatalyst for proton reduction in an organic medium in the presence of p -toluene sulfonic acid as a protic source.