The general course of reactions and structural correlations in SN chemistry discussed in terms of a carbon and sulfur(IV) equivalence

The comparability of the thiazyl (radical dotSN) and cyano (radical dotCN) groups is discussed in terms of the element displacement principle, supported by the chemical behaviour of comparable compounds. Based on the hypothetical tautomeric equilibrium H2NSN↔HNSNH postulated in analogy to H2NCN↔HNCNH with due consideration paid to the isolated intermediates ClSN and [S4N3]Cl, possible reaction steps during the synthesis of S4N4 are outlined and evaluated critically. In addition halogenation, ring contraction and ring expansion reactions of S4N4 are included as well in the discussion.