Abstract

The synthesis and single-crystal X-ray structure determination of the title compound are described. Crystals are monoclinic, P 2₁, a 16.164(9), b 8.277(3), c 8.829(4) Ǻ, β 102.86(4)°, Z 2; 2666 independent 'observed' diffractometer data [I > 3σ(I)] were refined to a residual of 0.045. The cation is unusual amongst complexes of sarcophagine (3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) cage amines in adopting a lel₂ob conformation, seemingly in response to hydrogen bonding/crystal packing forces. In consequence, unlike the tetranitrate analogue in which Ni-N bond distances are dispersed over a narrow range (2.097(5)-2.119(5) Ǻ; mean 2.10₉ Ǻ], the coordination sphere is more distorted with one pair of Ni-N distances, cis to each other, being short at 2.081(5) and 2.086(5) Ǻ, while the other four are long, ranging from 2.116(5) to 2.135(5) Ǻ, the mean of this array being 2.11₁ Ǻ.