Syntheses of a 2,6-bis-(methylphospholyl)pyridine ligand and its cationic Pd(II) and Ni(II) complexes – application in the palladium-catalyzed synthesis of arylboronic esters

2,6-Bis(2,5-diphenylphospholyl-1-methyl)pyridine (2) was prepared from the reaction of 2,5-diphenylphospholide anion with 2,6-bis(chloromethyl)pyridine. The X-ray crystal structure of 2 was recorded. Reaction of 2 with [Pd(COD)Cl2] in the presence of AgBF4 yields the cationic complex [Pd(2)Cl][BF4] (3). The analogous Ni complex [Ni(2)Br][BF4] (4) was prepared in a similar way by reacting ligand 2 with [NiBr2(DME)] in the presence of AgBF4 and its formulation was confirmed by an X-ray crystal structure study. Complex 3 efficiently catalyzes the coupling between pinacolborane and iodo and bromoarenes with good TON (up to 1 × 105 with iodo derivatives and 8.9 × 103 with bromo derivatives).