Synthesis and reactivity of bimetallic palladium(II) methyl complexes with new functional phosphine ligands

Bimetallic palladium(II) methyl complexes, [Pd(dppmpH)(CH3)(μ-Cl)]2 (1) and [Pd(dippmpH)(CH3)(μ-Cl)]2 (2) were synthesized by the reaction of (COD)Pd(CH3)(Cl) (COD = 1,5-cyclooctadiene) with the new functional phosphine ligands 2-diphenylphosphino-4-methylphenol (dppmpH) and 2-diisopropylphosphino-4-methylphenol (dippmpH). The homolytic cleavage of the CH3–Pd bond was found to occur when complexes 1 and 2 were heated or photolyzed to form a methyl radical and the corresponding oxygen-bridged bimetallic palladium(II) complexes, [Pd(dppmp)(Cl)]2 (3) and [Pd(dippmp)(Cl)]2 (4), respectively. The molecular structures of complexes 1, 3 and 4 were determined by single-crystal X-ray diffraction. Reaction of small molecules, such as CO, SO2 and CH2CH2, with complexes 1 and 2 was observed and characterized by IR, 1H, 13C and 31P{1H} NMR spectroscopy.