1. R. J. Lundgren and M.Stradiotto , Ligand Design in Metal Chemistry: Reactivity and Catalysis , John Wiley & Sons , Chichester, UK , 2016
2. Mesoionic compounds are defined by IUPAC as “dipolar five- (possibly six-) membered heterocyclic compounds in which both the negative and the positive charge are delocalized, for which a totally covalent structure cannot be written, and which cannot be represented satisfactorily by any one polar structure. The formal positive charge is associated with the ring atoms, and the formal negative charge is associated with ring atoms or an exocyclic nitrogen or chalcogen atom”. IUPAC. Compendium of Chemical Terminology, 2nd edn. Gold Book Compiled by A. D. McNaught and A. Wilkinson, Blackwell Scientific Publications, Oxford, 1997. XML on-line corrected version: http://goldbook.iupac.org
3. Beyond ConventionalN-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization
4. Abnormal, mesoionic and remote N-heterocyclic carbene complexes
5. Normal and Abnormal N-Heterocyclic Carbene Ligands