Valence bond and molecular orbital studies of the A-F bond lengths in some AF_n type molecules and their fluorinated cations

摘要

The results of ab initio MP2(full)/cc-pVTZ and DFT MPW1PW91/cc-pVTZ molecular orbital calculatons of the bond lenths are reported for non-hypercoordinate and hypercooredinate systems of the general type AF~q+_n,with q>=0 and A=N,P,O,S and Cl.They show that except for OF~2+_4 the bond lengths decrease as the cationic character increases.Increased-valence structures are used to provide valence bond (VB) rationlizations for the bond length shortenings.In these valence bond structures,the degree of multiple bonding increases as the cationic character increases.