1,3-Dipolar cycloaddition of nitrones to transition metal-bound isocyanides: DFT and HSAB principle theoretical model together with analysis of vibrational spectra

Abstract

The hard and soft acids and bases (HSAB) principle together with the density functional theory (DFT) calculations were used to analyze the driving forces of the hypothetical 1,3-dipolar cycloaddition (CA) of the nitrone CH2=N(Me) O to the uncomplexed C NMe and to isocyanide ligands in various transition metal complexes. The calculated activation (Delta G(s)(not equal)) and reaction (Delta G(s)) energies depend from the electronic chemical potential (mu), the global electrophilicity (omega) and nucleophilicity (N) indexes of the dipolarophiles, the static charge transfer "nucleophile -> electrophile" (Delta N-0), and the maximum amount of electronic charge that the electrophile system may accept (Delta N-max). Thus, the HSAB principle may be successfully apply for the study of reactivity of such compounds. The Delta G(s)(not equal) and Delta G(s) and the calculated stretching vibration frequencies v(C N) of isocyanides well correlated with each other, i.e. higher values of v(C N) correspond to lower values of Delta G(s)(not equal) and Delta G(s). The application of the reactivity descriptors discussed in this work is a possible alternative and a complement addition to the estimates based on the classical frontier molecular orbital (FMO) theory. (C) 2015 Elsevier B.V. All rights reserved.

C1 St Petersburg State Univ, Inst Chem, St Petersburg 198504, Russia.