title: Quantitative Index of the Relative Ease of Formation and σ-Bonding Strength of N-Heterocyclic Carbenes.
abstract: An energy-based index of the ease of N-heterocyclic carbene (NHC) formation either by deprotonation of precursor salts to give neutral NHCs or deprotonation of heterocyclic mesomeric betaines to give anionic NHCs is described. This index (CREF; Carbene Relative Energy of Formation), which is easily calculated using DFT methods, also gives a quantitative measure of the relative σ-donor strength of NHCs. CREF index values for a wide range of known and unknown NHC ring systems are reported and their significance discussed.
authors.affiliation: Lennard-Jones Laboratories, School of Physical and Geographical Sciences, Keele University , Staffordshire ST5 5BG, U.K.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Ramsden
authors.affiliation: Laboratory of Theoretical Methods and Computations, National Medicines Institute , 30/34 Chełmska Street, 00-725 Warsaw, Poland.
authors.forename: Wojciech P
authors.initials: WP
authors.lastname: Oziminski