Synthesis, structure and properties of [1,2,4]triazolo[4,3-a]pyridin-3-ylidene rhodium and palladium complexes

Abstract

The reaction of [1,2,4]triazolo[4,3-a]pyridinium tetrafluoroborates with [RhCl(COD)]₂ and [PdCl(allyl)]₂ takes place under mild basic conditions (Et₃N, THF, room temperature) to afford the corresponding [RhCl(COD)(Tripy)] and [PdCl(allyl)(Tripy)] complexes, respectively (Tripy = [1,2,4]triazolo[4,3-a]pyridin-3-ylidene), and their structures were analysed by X-ray diffractometry and spectroscopic techniques. The σ-donor ability of the new ligands was estimated by comparative analysis of infrared ν_CO stretching frequencies of [RhCl(CO)₂(Tripy)] complexes, and proved to be strongly dependent on the substitution pattern. Additionally, a first insight into the catalytic properties of the latter in the Suzuki–Miyaura cross coupling demonstrates a good catalytic activity that enables the coupling of aryl chlorides at room temperature.