New palladacyclopentadiene complexes containing an N,P-donor setting. Crystal structure of [Pd{C4(COOMe)4}(o-Ph2PC6H4CHNiPr)]

The synthesis of palladacyclopentadiene derivatives with the mixed-donor bidentate ligands o-Ph2PC6H4CHNR (N∧P) has been achieved. The new complexes of general formula [Pd{C4(COOMe)4}(o-Ph2PC6H4CHNR)] [R=Me (1), Et (2), iPr (3), tBu (4), NHMe (5)] have been prepared by reaction between the precursor [Pd{C4(COOMe)4}]n and the corresponding iminophosphine. The polymer complex [Pd{C4(COOMe)4}]n also reacts with pyridazine (C4H4N2) to give the insoluble dinuclear complex [Pd{C4(COOMe)4}(μ-C4H4N2)]2 (6), which has been successfully employed as precursor in the synthesis of pyridazine-based palladacyclopentadiene complexes. The reaction of 6 with tertiary phosphines yielded complexes containing an N,P-donor setting of formula [Pd{C4(COOMe)4}(C4H4N2)(L)] (L=PPh3 (7), PPh2Me (8), P(p-MeOC6H4)3 (9), P(p-FC6H4)3 (10)). The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, 1H, 19F and 31P NMR). The molecular structure of complex 3 has been determined by a single-crystal diffraction study, showing that the iminophosphine acts as chelating ligand with coordination around the palladium atom slightly distorted from the square-planar geometry.