In the context of
the ever-growing interest in the cyclic
diaryliodonium
salts, this work presents synthetic design principles for a new family
of structures with two hypervalent halogens in the ring. The smallest
bis-phenylene derivative, [(C6H4)2I2]2+, was prepared through oxidative dimerization
of a precursor bearing theortho-disposed iodine
and trifluoroborate groups. We also report, for the first time, the
formation of cycles containing two different halogen atoms. These
present two phenylenes linked by hetero-(I/Br) or -(I/Cl) halogen
pairs. This approach was also extended to the cyclic bis-naphthylene
derivative [(C10H6)2I2]2+. The structures of these bis-halogen(III) rings were
further assessed through X-ray analysis. The simplest cyclic phenylene
bis-iodine(III) derivative features the interplanar angle of ∼120°,
while a smaller angle of ∼103° was found for the analogous
naphthylene-based salt. All dications form dimeric pairs through a
combination of π–π and C–H/π interactions.
As the largest member of the family, a bis-I(III)-macrocycle was also
assembled using the quasi-planar xanthene backbone. Its geometry enables
the two iodine(III) centers to be bridged intramolecularly by 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 structure showing the
chelating donor bonding to just one of the two iodine centers.