RELATIVE AROMATICITY IN HETEROPOLAR INORGANIC ANALOGS OF BENZENE

Ab initio electronic structure calculations have been carried out on a series of heteropolar inorganic analogues of hydrocarbons in order to evaluate reaction energies for an isodesmic reduction by ethane and homodesmotic reactions as indicators of the relative aromaticities of the recently synthesized X3Y3R6 rings where XY is BP and AlN. Calculations where XY is CC and BN are also reported to establish the scale. Optimized geometries and energies through RHF/6-31G* are reported for both reactions, and energies at the SCF optimized geometries including fourth-order Moller-Plesset perturbation corrections are reported for the homodesmotic reaction. The homodesmotic reactions are taken to be the most useful index and give the results with MP4(SDQ) of CC (22.1 kcal/mol) >> BP (12.7 kcal/mol) approximately BN (11.1 kcal/mol) > AlN (1.9 kcal/mol).