The first weakly coordinating anion (WCA) with reactive p-block cation (rPBC) type of [(Bi4Cl16)4-{(LSeSeL)2+}2], L = 1,3-bis(2-benzhydryl-4,6-dimethylphenyl)-1H-imidazole-2(3H), ion pair is reported. The tetranuclear anionic bismuth(III) cluster shows a new type of ladder structure with two different types of Bi(III) coordination modes. In the solid state structure, the tetranuclear bismuth(III) cluster is sandwiched by two diselenide cations through hydrogen bonding interactions. Besides, this ion pair has been efficaciously employed as catalyst in C-S cross-coupling reactions under optimized reaction condition. This ion pair depicted a wide range of substrate scope with different thiols and aryl halides. © 2019 Elsevier B.V.