1-2 COMPLEX OF 1,4,7,10,13,16-HEXAOXACYCLOOCTADECANE (18-CROWN-6) WITH N-M-BROMOPHENYLUREA

C7H7BrN2O.1/2C12H24O6, M(r) = 347.2, monoclinic, P2(1)/c, a = 8.910 (3), b = 24.924 (8), c = 8.391 (4) angstrom, beta = 122.00 (1)-degrees, V = 1580.3 (10) angstrom 3, Z = 4, D(x) = 1.46 Mg m-3, lambda-(Mo K-alpha) = 0.71069 angstrom, mu = 2.77 mm-1, F(000) = 712, T = 293 K, final R = 0.067 for 1229 observed reflections. The host 18-crown-6 molecule lies about a crystallographic centre of symmetry. This centre relates the two guest bromophenylurea molecules which lie on either side of the host molecule almost perpendicular to the macrocyclic ring. Each guest molecule is hydrogen bonded to two adjacent O atoms of the crown ether by means of one H atom from each amino group. The complex adopts the biangular conformation of the macrocycle and is evidence for the formation of a discrete 1:2 crown ether-urea molecular complex.