Abstract
The Formation of a hypervalent X–Se–X bond in a TB, together with a non-polar I–I bond in an MC, was superior to that of a couple of dipolar I-X bonds in MC’s (RSeXX′R′: R, R′ = Me or Ph; X, X′ = Cl,Br, or I). The stability of the X–Se–X bonds depended much more on the difference of their elecrtonegativities than that of the I-X bonds: MC’s of IX of selenides were formed in solution when X was only Br or I.