CROWN COMPOUNDS FOR ANIONS - MNDO CALCULATIONS OF COMPLEXES OF HALIDEANIONS WITH CYCLIC PENTAMERIC DIFLUOROMETHYLIDENEMERCURY

Molecular and electronic structures of complexes of halide anions with cyclic pentameric difluoromethylidenemercury [CF2Hg](5) have been stu died by the MNDO method. Calculations have been performed for [L-X](-) halfsandwich complexes and bipyramidal complexes [X-L-X](2-) having a shape of a spinning top (L is the mercury-containing macrocycle; X = F, Cl, Pr, or I). It has been shown that in complexes of both types, h alide anions are bonded to the mercury-containing macrocycle via three generalized chemical bonds: one headlight-shaped sigma-bond and two t wo-lobe n-bonds. The complexes studied have been compared with the ana logous complexes of the macrocycles containing three mercury atoms. Th e similarity and differences in the character of the generalized chemi cal bonds in relation to the size of the cycle have been considered.