Tl 5 Te 3 adopts a common intermetallic structure type (Cr,B), and shows a superconducting transition at 3 K. Based on the structure of Tl 5 Te 3 , 20% of the thallium atoms show crystal chemical behavior consistent with Tl 2 , according to the formulation Tl (Tl) 3 (Te) 3 . These Tl atoms are susceptible to disproportionation into Tl 1 and Tl 1 . In order to explore this aspect of the electronic structure of Tl 5 Te 3 and to investigate potential mechanisms for superconductivity, semi-empirical electronic calculations were carried out on this compound. Recent experiments illustrate that Sn, as well as Bi Pb, and Cu, can substitute for one-fifth of the thallium atoms to give SnTT, Te. Both thallium sites are substituted by Sn according to the formula (Sn a,b Tl a )(Sn c,p Tl c )Te 5 . Energy density of states and crystal orbital overlap population curves for observed and hypothetical substitution patterns are examined to assess the electronic stability of these phases and to account for the observed arrangement.