Revisiting the Effect of f-Functions in Predicting the Right Reaction Mechanism for Hypervalent Iodine Reagents

TL;DR

This study demonstrates that f-functions in basis sets are crucial for accurately predicting reaction mechanisms and barriers in hypervalent iodine reagents, impacting the understanding of key steps like bond cleavage and formation.

Contribution

The paper revisits the role of f-functions in basis sets, showing their importance in correctly modeling hypervalent iodine reaction mechanisms and energy barriers.

Findings

f-functions are essential for correct rate-determining step prediction

f-functions significantly influence reaction barrier calculations

Different hypervalent twist modes reveal varied effects of f-functions

Abstract

To understand the effect of f-functions in predicting the right reaction mechanism for hypervalent iodine reagents, we adopt the Ahlrichs basis set family def2-SVP and def2-TZVP to revisit the potential energy surfaces of IBX-mediated oxidation and Togni I's isomerisation. Our results further prove that f-functions (in either Pople, Dunning, or Ahlrichs basis set series) are indispensable to predict the correct rate-determining step of hypervalent iodine reagents. The f-functions have a significant impact on the predicted reaction barriers for processes involving the I-X (X = O, OH, CF$_3$, etc.) bond cleavage and formation, e.g. in the reductive elimination step or the hypervalent twist step. We furthermore explore two hypervalent twist modes that account for the different influences of f-functions for IBX and Togni I. Our findings may be helpful for theoretical chemists to appropriately study the reaction mechanism of hypervalent iodine reagents.