Pincer-type di(1,2,4-triazolin-5-ylidene)Pd(II) complexes and their catalytic activities towards Cu- and amine-free Sonogashira reaction

Pd(II) complexes [PdBr(A-kappa(CNC)-C-3)]Br (1) and [PdBr(B-kappa(CNC)-C-3)]Br (2) with new CNC pincer-type ligands derived from 1,2,4-triazolin-5-ylidenes have been synthesized and characterized by multinuclei NMR spectroscopies, ESI mass spectrometry and X-ray diffraction analysis. The more soluble complex 1 proved to be an efficient pre-catalyst in copper- and amine-free Sonogashira reaction with high turnover numbers. The potential for recycling of the catalyst was also demonstrated.