Cyclic Homo- and Heterohalogen Di-λ³-diarylhalonium Structures

In the context ofthe ever-growing interest in the cyclicdiaryliodoniumsalts, this work presents synthetic design principles for a new familyof structures with two hypervalent halogens in the ring. The smallestbis-phenylene derivative, [(C6H4)(2)I-2](2+), was prepared through oxidative dimerizationof a precursor bearing the ortho-disposed iodineand trifluoroborate groups. We also report, for the first time, theformation of cycles containing two different halogen atoms. Thesepresent two phenylenes linked by hetero-(I/Br) or -(I/Cl) halogenpairs. This approach was also extended to the cyclic bis-naphthylenederivative [(C10H6)(2)I-2](2+). The structures of these bis-halogen(III) rings werefurther assessed through X-ray analysis. The simplest cyclic phenylenebis-iodine(III) derivative features the interplanar angle of similar to 120 degrees,while a smaller angle of similar to 103 degrees was found for the analogousnaphthylene-based salt. All dications form dimeric pairs through acombination of pi-pi and C-H/pi interactions.As the largest member of the family, a bis-I(III)-macrocycle was alsoassembled using the quasi-planar xanthene backbone. Its geometry enablesthe two iodine(III) centers to be bridged intramolecularly by twobidentate triflate anions. In a preliminary manner, the interactionof the phenylene- and naphthalene-based bis-iodine(III) dicationswith a new family of rigid bidentate bis-pyridine ligands was studiedin solution and the solid state, with an X-ray structure showing thechelating donor bonding to just one of the two iodine centers.