An ab initio study resulting in a greater understanding of the HSAB principle

Abstract

The quantitative applicability of the hard-soft acid-base (HSAB) principle has been tested. Complexes of HF and Ag+ with several bases (HF, HCl, HBr, H₂O, H₂S, H₂Se, NH₃, PH₃, and AsH₃) have been studied at the HF, MP2, and QCISD(T) levels with 6-311+G** basis sets. Ab initio pseudopotential calculations have been performed for the molecules containing heavier elements, viz., Br, Se, As, and Ag⁺. For the hard acid HF, the HSAB principle has been found to be valid even at the HF level. Correlation is important for soft-soft interactions. The maximum hardness principle has been found to be valid for reactions of HF. Reaction of hard acids like H⁺, Li⁺, and Na⁺ have also been studied at the MP2/6-311+G** Level. Out of 45 reaction which are not in conformity with the HSAB priniciple.