Halogen bonds of iodonium ions: a world dissimilar to silver coordination

A distinct difference between the three-center halogen bond and the analogous three-center coordinative bond of silver is demonstrated by computational, X-ray crystallographic and solution NMR spectroscopic investigations of their complexes with a bidentate Lewis base. Iodine(I) preferentially forms an entropically favored monomeric complex, whereas silver(I) forms enthalpically favored dimeric complexes. Counterion coordination considerably influences the structure of the silver complexes in the solution and solid state, whereas it does not have notable effect on the analogous halogen bond.