Jahn-teller effects in the MNDO approximation: structures of the molecular cations of some simple organoberyllium compounds

Abstract

The MNDO method gives geometries for the molecular cations of organoberyllium compounds of types BeR 2 and HBeR (R = CH 3, CHCH 2, CCH, CN, C 5H 5), of C 4H 4Be and CH 3BeBeH 3 and of the series CH 4− n (BeH) n (n = 0–4) which have symmetries in precise accord with the predictions of the Jahn-Teller theorem. In the series CH 4− n (BeH) n and CH 4− n (BeH) n +, the barriers to inversion via a planar intermediate decrease with increasing n, are significantly smaller for the cations than for the neutral molecules, and are zero for CH(BeH) 3 + and C(BeH) 4 +, both of which have their minimum energy when strictly planar at carbon.