Both nickel(II) and copper(II) complexes of the sterically hindered linear tetraamines 1,3,5,7-tetra-azabicyclo [3.3.l]nonane-3,7-bis( ethanamine (4) and 3,3′-(ethane-1,2-diyl)bis(1,3,5,7-tetraaza-bicyclo [3.3.1] nonane (7) have been prepared from reaction of ethane-1,2-diamine complexes with formaldehyde and ammonia or by reaction of the metal salt with the quaternary 'hexamminium' cation (8) and ammonia, respectively. Spectroscopic properties and kinetics of the acid hydrolyses of these complexes are reported. Observed pseudo-first-order rate constants are of the order of 10^-1 s^-1 at 25° in 1 mol dm^-3 HCl/NaCl; acid dependencies are reported. In addition to (4), a further acid-stable and presumably macrocyclic compound could be produced from reaction of [cu(en)₂]²⁺ with formaldehyde and ammonia, assigned tentatively as (9). Further reaction of the nickel(II) complex of (4) with formaldehyde and nitroethane yielded the macrocyclic complex of (10), which was characterized by a crystal structure analysis. Reduction with zinc amalgam yielded an amine-substituted macrocyclic complex from the nitro-substituted precursor. The title complex [Ni(10)](ClO₄)₂.H₂O crystallized in the space group P2₁/n, a 14.367(2), b 13.099(2), c 12.325(3) Å , β 101.01(1)º. The nickel(II) was located in a square plane of two secondary (Ni-N 1.92 Å ) and two tertiary nitrogens (Ni-N 1.93 Å ); the 'football' formed as one cap from ammonia and formaldehyde condensation was clearly defined.