6533b820fe1ef96bd127991c

RESEARCH PRODUCT

Dinuclear Palladium(II) and -(III) Compounds with O,O-Chelating Ligands. Room-Temperature Direct 2-Phenylation of 1-Methylindole

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New dinuclear palladium(III) compounds of general formula Pd2[(C6H4)PPh2]2[O–O]2Cl2, O–O being chelating phenolates C6H4OC(O)R (R = CH3, 3a; R = C2H5, 3b; R = OPh, 3c) or acetylacetonates RC(O)CHC(O)R (R = CH3, 4a; R = CF3, 4b; R = C(CH3)3, 4c), have been obtained by oxidation with PhICl2 of the corresponding palladium(II) compounds. The stability of the new compounds has been studied by 31P NMR spectroscopy from 200 to 298 K. DFT calculations of the stability of the complexes have also been performed. In agreement with these calculations, only compound Pd2[(C6H4)PPh2]2[(CF3C(O)CHC(O)CF3]2Cl2, 6b, showed the highest thermal stability. 6b was characterized by X-ray diffraction methods, presenting the longest Pd–Pd distance, 2,6403(6) A, observed among the already described discrete Pd26+compounds. The isolated palladium(II) and -(III) compounds have been tested at room temperature in the catalytic 2-phenylation of 1-methylindole with [Ph2I]PF6. With 3a as precatalyst the reaction was completed in 2 h with ...