Preparation and X-ray structure of bis(1-methyl-3-ethylbenzimidazolidine-2-ylium) tetrafluoroborate

The title compound, C 20 H 24 B 2 F 8 N 4 , crystallises monoclinic (space group C2, Z= 4, a = 23.797(5) A, b = 8.330(2) A, c = 11.471(2) A, β = 90.17(2)° R = 0.084 for 1922 [I ≥ 2σ(I)]. The most notable features are the values of the C-C bond length [1.47(1) A], of the adjacent endocyclic N-C bond length [1.363(1) A], the torsion angle about the central C-C bond [83°] and the nearly trigonal planar environment of the nitrogen atom.