Synthesis and solid state structures of increasingly sterically crowded 1,4-diiodo-2,3,5,6-tetraarylbenzenes: a new series of bulky benzenes and aryls

Abstract

A series of very bulky 1,4-diiodo-2,3,5,6-tetraarylbenzenes I₂Ar₄C₆ (Ar = 4-^tBuC₆H₄, 1; Ar = 3,5-^tBu₂C₆H₃, 2; Ar = 2,4,6-Me₃C₆H₂, 3) have been prepared by a rapid, convenient procedure involving sequential reaction of hexabromobenzene with the appropriate Grignard reagent in excess, followed by addition of excess elemental iodine. The new materials 2 and 3 were isolated in 18 and 28% yields, respectively. The solid state structures of 1–3 have been investigated by single crystal X-ray techniques. Interesting distortions in the structures of these hexasubstituted benzenes are observed upon the increasing steric pressures in 1–3. For example, while the structures of 1 and 2 contain central planar benzene rings, steric interactions in 3 produce a non-planar central benzene ring. Regardless of these factors, the carbon–iodine bond lengths in 1–3 are essentially constant (2.108–2.118 Å).