Iodine is a very large element and because of its size as well as great polarizeability, iodine can adopt oxidation states such as -1, +3, and +5. For our latest publication, see the third paper in "Current Research & Publications".
Our early work in the area of iodonium salts (iodine +3) showed the remarkable leaving group ability of the hypervalent iodine moiety found in the alkenyl(aryl)iodonium salts. Under very mild conditions, the salts, (E)-7a-c, fragment into three vinyl triflates as well as iodobenzene (eq 2).
We originally interpreted this fragmentation as evidence for the formation of a primary vinyl cation, which had been unobserved in solution. Further work from our labs as well as a lab in Japan (Okuyama's lab) indicated that the primary vinyl cation (A) shown in Scheme 2 is, indeed, not necessary to interpret the results of this thermal reaction.