HYDROGEN-BONDING IN CRYSTALS OF AN AMMONIUM CATECHOLATE NH4[C6H4(OH)2][C6H4(OH)O].0.5H2O

A discrete ammonium catecholate hydrate of the composition NH4[C6H4(OH )2][C6H4(OH)O] . 0.5 H2O has been isolated and characterized by a sing le-crystal X-ray structure analysis. The crystals are monoclinic, spac e group C2/c (No. 15), Z = 8, a = 24.613(3), b = 8.706(l), c = 11.890( 2) angstrom, beta = 1 10.56(l)-degrees. The crystal lattice features a network of hydrogen bonds, which clearly contribute significantly to the overall stability of the lattice. The water molecule is engaged as a donor and an acceptor in as many as four hydrogen bonds. Surprising ly, the crystalline compound is air-stable, while anhydrous ammonium c atecholate, as obtained by dissolving catechol in dry liquid ammonia, is quickly oxidized in air.