Cyclic Homo- and Heterohalogen Di-λ3-diarylhalonium Structures

Abstract

In the context of the ever-growing interest in thecyclic diaryliodonium salts, this work presents synthetic designprinciples for a new family of structures with two hypervalenthalogens in the ring. The smallest bis-phenylene derivative,[(C6H4)2I2]2+, was prepared through oxidative dimerization of aprecursor bearing the ortho-disposed iodine and trifluoroborategroups. We also report, for the first time, the formation of cyclescontaining two different halogen atoms. These present twophenylenes linked by hetero-(I/Br) or -(I/Cl) halogen pairs.This approach was also extended to the cyclic bis-naphthylenederivative [(C10H6)2I2]2+. The structures of these bis-halogen(III)rings were further assessed through X-ray analysis. The simplestcyclic phenylene bis-iodine(III) derivative features the interplanarangle of ∼120°, while a smaller angle of ∼103° was found for the analogous naphthylene-based salt. All dications form dimeric pairsthrough a combination of π−π and C−H/π interactions. As the largest member of the family, a bis-I(III)-macrocycle was alsoassembled using the quasi-planar xanthene backbone. Its geometry enables the two iodine(III) centers to be bridged intramolecularlyby two bidentate triflate anions. In a preliminary manner, the interaction of the phenylene- and naphthalene-based bis-iodine(III)dications with a new family of rigid bidentate bis-pyridine ligands was studied in solution and the solid state, with an X-ray structureshowing the chelating donor bonding to just one of the two iodine centers.