Molecular and crystal structure of bis-quinolizidine immonium salts. IV. Δ1(6),11(16)-didehydro-sparteinium diperchlorate

^1(6),11(16)-Didehydrosparteinium diperchlorate,M _r =431.27, (C₁₅H₂₄N₂)²⁺ ·2C1O ₄ ^– , orthorhombic, C222₁,a=9.295(1),b=12.447(1),c=16.834(2) Å,V _c =1947.5(4) ų,Z=4,D _m =1.47 g cm^–3,D _c =1.47 g cm^–3,(CuK)=31.7 cm^–1. The finalR=0.052 for 733 counter reflections. The dication and the perchlorate anions lie on two-fold axes, and one perchlorate anion is disordered in two symmetrically equivalent positions. The two independent rings of the dication have conformations intermediate between half-chair and sofa, and the quinolizidine moiety (AB system) has a planar configuration.The title compound was obtained by mercuric acetate dehydrogenation of sparteine to ^5,11-didehydrosparteine and protonation of the latter in methanol with perchloric acid.¹³C-NMR spectra in DMSO-²H₆ and in²H₂O revealed the presence of the symmetrical diimmonium structure of the salt in solution.