Dinuclear ortho-metalated palladium(II) compounds with N, N- and N, O-donor bridging ligands. synthesis of new palladium(III) complexes

摘要

New dinuclear ortho-metalated palladium(II) compounds with N, N′-diarylformamidinates, Pd_2[(C_6H _4)PPh_2]_2[R′NC(H)NR′]_2 (R′ = C_6H_5, 3a; R′ = p-CH_3C _6H_4, 3b; R′ = p-CH_3OC_6H _4, 3c) and N, O-donor ligands, Pd_2[(C_6H _4)PPh_2]_2[N, O]_2 (N, O = succinimidate (5), phtalimidate (6), 2-hydroxypyridinate (7), acetanilidate (8)) have been synthesized and characterized by NMR spectroscopy and X-ray diffraction methods. The oxidation with iodobenzene dichloride gave new and rare Pd_2~(6+) compounds, Pd_2[(C_6H_4)PPh _2]_2[R′NC(H)NR′]_2Cl_2 (R′ = C_6H_5, 4a; R′ = p-CH_3C _6H_4, 4b). DFT calculations on the Pd_2~(4+) → Pd_2~(6+) oxidation reaction show that the substituents on the amidinate N atoms have a greater effect on the reaction energy than the substituents on the C atom. DFT calculations also confirm that for Pd_2[(C_6H_4)PPh_2] 2[N, O]_2 compounds the symmetric isomers with N atoms trans to O atoms are the most stable complexes. The palladium dimers were tested as precursors of catalysts in tandem diboration/arylation/oxidation reactions.