Carbenes and nitrenes. An overview

► The results of DFT and CCSD(T) calculations of a wide series of various carbenes and nitrenes are presented. ► Neglecting electron correlation, irrespective of the basis set used, gives unreliable results. ► Even simple DFT calculations give results which often nicely correlate with those of high-level calculations. ► The proclivity of carbenes and nitrenes to rearrangement is much stronger for the singlet states. ► The values of the singlet-triplet splitting ΔEST calculated at different levels of theory are strongly different.