Crown compounds for anions. MNDO calculations of the complexes of halide anions with cyclic pentameric difluoromethylidenemercury

MNDO calculations of the complexes of halide anions with cyclic pentameric difluoromethylidenemercury [CF2Hg]5 have been carried out. The complexes of the semisandwich type [L-X]- and bipyramidal complexes [X-L-X]2- with a spinning top shape have been calculated (L - macrocycle; X = F, Cl, Br, I). In both types of the complexes, the halide anions are bonded to the mercury-containing macrocycle by three generalized chemical bonds: one headlight-shaped σ-bond and two-lobed π-bonds. The studied complexes have been compared with the similar complexes of the macrocycles containing three mercury atoms. Resemblence and differences in the character of the generalized chemical bonds in dependence on the size of the cycle have been discussed. 10 refs., 2 schemes, 3 tabs