Improved synthetic routes to N-heterocyclic carbene-metal-diketonato complexes of gold and copper

In our search for simple synthetic routes to N-heterocyclic carbene (NHC)-metal complexes and their derivatives, we herein report an operationally simple, expedient and scalable method to obtain the widely used NHC-metal-diketonates. The reported complexes are synthesized for the first time under mild, aerobic conditions and in excellent yields in a sustainable manner. The protocol is general with regards to the anionic co-ligand and the ancillary carbene ligands. The spectroscopic and crystallographic characterization of the complexes reveal a bidentate binding mode of the diketonate ligand to copper while the gold-congener is C-bound. Finally, the reported Au complex was shown to be an efficient pre-catalyst for the hydrocarboxylation of alkynes.

Automated summary

In this study, a simple and scalable method for synthesizing widely used NHC-metal-diketonate complexes was reported. The complexes were synthesized for the first time under mild, aerobic conditions and in excellent yields. Characterization of the complexes revealed a bidentate binding mode of the diketonate ligand to copper and a C-bound binding mode to gold. Furthermore, the gold complex showed high efficiency as a pre-catalyst for the hydrocarboxylation of alkynes.