Reactions of nickel complexes NiL2X2 [L N-(2-aminoethyl)aziridine, X = Cl,
Br] with formaldehyde in the presence of ammonia lead primarily to inner-sp
here transformation of the ligand L into piperazine. The subsequent inner-s
phere condensation with formaldehyde and ammonia results in formation of po
lyaza macromolecules of cyclic and chain (polymeric) structures, in which t
he piperazine units are linked through iminodimethylene bridges.