Gravar-mail: Synthesis and structure of an aryl­tellurenium(II) cation; [4-tert-butyl-2,6-bis­(1-pentyl-1H-benz­imidazol-2-yl-κN (3))phenyl-κC (1)]tellurium(II) (1,4-dioxane)tri­iodido­mercurate(II)