Oxidation reactions of a nucleophilic palladium carbene: mono and bi-radical carbenes

摘要

Palladium(ii) cationic carbene radical and neutral bi-radical complexes were synthesized from a previously reported Pd(ii) carbene in the presence of one and two electron oxidants. When [{PC(sp(2))P}Pd-tBu(PMe3)] (1, [PC(sp(2))P](tBu) = (bis[2-(di-iso-propylphosphino)-4-tertbutylphenyl]methylene)) was treated with [Cp2Fe][X] (X = BAr4F, Ar-F = 3,5-(CF3)(2)C6H3, or PF6), the corresponding radical cationic complexes [{PC(sp(2))P}Pd-tBu(PMe3)][X] (2: X = BAr4F, 3: PF6) were isolated and characterized. Magnetic moment measurements and EPR spectroscopy indicated the presence of a ligand centered unpaired electron. In the presence of two electron oxidants such as 1,8-naphthylene disulfide or 9,10-anthracenedione, 1 converts to [{PC(sp(2))P}(PdS)-Pd-tBu(C10H6)SPd{PC(sp(2))P}(tBu)] (4) or [{PC(sp(2))P}(PdO)-Pd-tBu(C14H10)OPd{PC(sp(2))P}(tBu)] (5), respectively. Single crystal X-ray diffraction and EPR spectroscopy confirmed the bi-radical nature of 4 and 5.