Bis(&mgr;-hexamethylenetetramine)bis(aquadibromocadmium)diaquadibromo cadmium dihydrate

The title compound, poly[[diaquadibromocadmium-&mgr;-(1,3,5, 7-tetraazatricyclo[3.3.1.1(3, 7)]decane-N(1):N(5))-aquacadmium-di-&mgr;-bromo-aquacadmium-&mgr;-(1, 3,5,7-tetraazatricyclo[3.3.1.1(3, 7)]decane-N(1):N(5))-di-&mgr;-bromo] dihydrate], [Cd(3)Br(6)(C(6)H(12)N(4))(2)(H(2)O)(4)].2H(2)O, is made up of two-dimensional neutral rectangular coordination layers. Each rectangular subunit is enclosed by a pair of Cd(3)(&mgr;(2)-Br)(6)(H(2)O)(3) fragments and a pair of (&mgr;(2)-hmt)Cd(H(2)O)(2)Br(2)(&mgr;(2)-hmt) fragments as sides (hmt is hexamethylenetetramine). The unique Cd(II) atom in the Cd(2)Br(2) ring in the Cd(3)(&mgr;(2)-Br)(6)(H(2)O)(3) fragment is in a slightly distorted octahedral CdNOBr(4) geometry, surrounded by one hmt ligand [2.433 (5) A], one aqua ligand [2.273 (4) A] and four Br atoms [2.6409 (11)-3.0270 (14) A]. The Cd(II) atom in the (&mgr;(2)-hmt)Cd(H(2)O)(2)Br(2)(&mgr;(2)-hmt) fragment lies on an inversion center and is in a highly distorted octahedral CdN(2)O(2)Br(2) geometry, surrounded by two trans-related N atoms of two hmt ligands [2.479 (5) A], two trans-related aqua ligands [2.294 (4) A] and two trans-related Br atoms [2.6755 (12) A]. Adjacent two-dimensional coordination sheets are connected into a three-dimensional network by hydrogen bonds involving lattice water molecules, and the aqua, bromo and hmt ligands belonging to different layers.