Pyridine Iodine(I) Cations : Kinetic Trapping as a Sulfonate Complexes

Seven pyridine iodine(I) sulfonate complexes were prepared and isolated at low temperatures and characterized by X-ray diffraction analysis. The inherently instable pyridine iodine(I) cations are stabilized by an oxygen of sulfonate anions via the I···O halogen bond. In these complexes, the iodine atom of the pyridine iodine(I) cation acts as an electron acceptor and the sulfonate oxygen as the electron donor. These complexes are stable enough in the crystalline state, yet decompose rapidly under ambient conditions, also being unstable in solution. The (pyridine)N–I bond lengths [2.140(3) - 2.197(2) Å] and the I···O halogen bonds [2.345(6) - 2.227(3) Å] are analogous to (imide)N–I···O–N-pyridine uncharged halogen-bonded complexes formed from N-haloimides and pyridine N-oxides, thus confirming the existence of elusive pyridine iodine(I) cation.