Supramolecular Architecture in Some 4-Halophenylboronic Acids

Crystal structures of 4-chloro- and 4-bromophenylboronic acids ( 1 and 2 ) and hydrates of 2 and 4-iodophenylboronic acid in two different forms ( 2a, 3a, and 3b ), which were characterized by single-crystal X-ray diffraction methods, are reported. In structures 1 and 2, −B(OH) 2 forms a syn − anti conformation, but it exists in syn − syn as well as anti − anti conformations in the hydrated structures 2a, 3a, and 3b . In all the structures, the molecules are held together by O−H···O interactions formed by −B(OH) 2 groups. The C−H···X (X = Cl, Br, and I) interactions play an important role in crystal packing. In 2, Br···Br interactions are also observed. Interestingly, all the three hydrates form similar types of three-dimensional structures with the formation of channels, which are occupied by water molecules. The two hydrates of 4-iodophenylboronic acid ( 3a and 3b ) are distinguishable on the basis of O···O short contacts, with an identical host lattice of the boronic acid.