The unanti-cipated oxidation of a tertiary amine in a tetra-cyclic glyoxal-cyclam condensate yielding zinc(II) coordinated to a sterically hindered amine oxide.

The complex, tri-chlorido-(1,4,11-tri-aza-8-azonia-tetra-cyclo-[6.6.2.0(4,16).0(11,15)]hexa-decane 1-oxide-κO)zinc(II) monohydrate, [ZnCl(3)(C(12)H(23)N(4)O)]·H(2)O, (I), has monoclinic symmetry (space group P2(1)/n) at 120†K. The zinc(II) center adopts a slightly distorted tetra-hedral coordination geometry and is coordinated by three chlorine atoms and the oxygen atom of the oxidized tertiary amine of the tetra-cycle. The amine nitro-gen atom, inside the ligand cleft, is protonated and forms a hydrogen bond to the oxygen of the amine oxide. Additional hydrogen-bonding inter-actions involve the protonated amine, the water solvate oxygen atom, and one of the chloro ligands.