Spotlight on Ligand Effects in 1,2,3-Triazolylidene Gold Complexes for Hydroamination Catalysis: Synthesis and Catalytic Application of an Activated MIC Gold Triflimide Complex and Various MIC Gold Chloride Complexes

The control of catalytic properties through ligand design is at the heart of homogeneous catalysis. Herein we report on ligand effects in six 1,3,4-substituted 1,2,3-triazolylidene gold complexes as precatalysts for the intermolecular hydroamination catalysis of alkynes with amines. Mainly silver-free protocols have been followed for the synthesis of the complexes and for the catalytic reactions. All of the novel gold complexes have been fully characterized, one of them being, to the best of our knowledge, the first 1,2,3-triazolylidene-based mesoionic carbene (MIC) gold complex with a weakly coordinating second ligand. In contrast to expectations, the gold complexes bearing the most strongly electron donating MICs did not display the best conversion in catalysis. According to our investigations the stability of the complex is a determining factor in the present case. The MIC gold bistriflimide complex shows activity in hydroamination catalysis without the need for an activating additive.