Coordinated and uncoordinated anion dictated coordination mode of PN(Me)P ligand in Pd(II) complexes and their catalytic applications

The PN(Me)P ligands based complexes [(η2-PN(Me)PPh)PdCl2] (1), [(η3-PN(Me)PPh)PdCl](OTf) (2) and [(η3-PNPiPr)PdCl] (3) (complexes 2 and 3 are pincer type) have been synthesized and characterized using standard analytical methods such as 1H NMR, 31P NMR, elemental analysis, UV–Visible spectroscopy, cyclic voltammetry and single-crystal X-ray crystallography. Formation of complexes 1 and 2 were observed under two different reaction conditions and learned about how the anions can dictate the coordination mode of PNP ligand to have different hapticity to offer different complexes. More importantly, isolation of complexes 1 and 2 filled the gap in PNP–Pd chemistry. DFT calculations have been carried out to understand the C–N bond cleavage of PN(Me)P ligand when –Ph and –iPr substituent introduced on the phosphorous. The complete reversible pattern of cyclic voltammogram of complex 3 suggests that this complex can be a better catalyst where two different oxidation states involve in the catalytic cycle. We have also performed Heck and Suzuki coupling reactions using complexes 1 and 3 and observed reasonably good yield even at relatively low temperature.