New bulky phosphinopyridine ligands. P~N~C Tridentates in palladium complexes

The sterically bulky pyridinyl phosphine (PN) ligands have been prepared from the phosphinylation of 2,4-di-tertbutyl-6-methylpyridine. Due to the steric hindrance, substitution reaction of these PN ligands with (COD) PdMeCl yields the chloro-bridged dipalladium species [(PN)2Pd2Me2Cl2], in which the PN ligand acts as a monodentate. Treatment of these dimeric palladium compounds with AgBF4 in the presence of acetonitrile gives the corresponding C–H activation metal complex [(PNC)Pd(CH3CN)]BF4. Both spectral and X-ray single-crystal characterization of these palladium complexes are presented.