A new ammonia adduct of an N-heterocyclic carbene (NHC) was isolated. DFT-calculations support the assumption, that reaction towards the NHC-ammonia adduct proceeds via free carbene and subsequent activation of ammonia. It is shown that this type of NHC adduct can be used as NHC transfer reagent for the synthesis of transition metal carbene complexes. Using this method, synthesis of a variety of triazolylidene-complexes is reported. Furthermore, subsequent reactions starting from the respective gold-compound are shown. In addition to the new carbene transfer method, feasibility of the traditional silver-carbene route is elucidated and a selection of new triazolylidene-compounds, generated using the silver method, is presented. The new NHC ligand represents the first example of a 1,2,3-triazolylidene with a 1,2,4-substitution pattern, thus opening a new subclass of sterically and electronically tunable N-heterocyclic carbenes to serve as ligands in the growing new class of homogenous catalysts.

N-heterocyclic carbenes via abstraction of ammonia: "Normal" carbenes with "abnormal" character

244th National Meeting (2012)

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