A novel hydrogen-bonded cyclic dibromide in an organic diammonium salt

Abstract

The organic diammonium salt N,N'-dibenzyl-N,N,N',N'-tetramethylethylenediammonium dibromide dihydrate, (dbtmen)Br-2.2H(2)O (1), was prepared by the reaction of N,N,N',N'-tetramethylethylenediamine (tmen) with benzyl bromide.1 crystallizes in the triclinic space group P 1 bar with the following unit cell dimensions for C20H34Br2N2O2 (M = 494.31): a = 8.6672(6) angstrom, b = 11.7046(8) angstrom, c = 11.7731(8) angstrom, alpha = 76-988(8)degrees, beta = 88-978(8)degrees, gamma = 76.198(8)degrees, V = 1129.26(13) angstrom(3), Z = 2. Three components, namely the (dbtmen)(2+) dication, two bromide anions and two crystal water molecules constitute the structural arrangement of 1.H2O molecules are linked to bromide anions via O-(HBr)..Br hydrogen bonding interactions resulting in the formation of a four-membered (O2Br2) cyclic dibromide. The (O2Br2) units and the dications are arranged as alternating layers extending in the crystallographic bc plane. The arrangement of anions and cations may be viewed as atypical lamellar structure. The crystal water molecules can be removed by heating 1 at 140 degrees C and the anhydrous dibromide thus formed can be fully rehydrated as evidenced by IR spectra and X-ray powder patterns.