Cationic (tripyrrinato)palladium(II) complexes

The formation of cationic palladium(II)complexes [TrpyPdII]+X− by salt metathesis of the respective trifluoroacetates with different salts of weakly coordinating anions X− was investigated. With non-hydrolizable counterions, cationic mono- and dinuclear complexes are observed depending on the nature of the anion X− and the solvent. The mononuclear cations, which are only formed with X = BArF, most probably carry a weakly bound molecule of dichloromethane at the fourth coordination site of PdII. When treated with diazoalkanes, only these are sufficiently reactive to form carbene complexes. Four- and five coordinate Lewis base adducts [TrpyPdIIL]+ with L = CH3NC, tBuNH2, PMe3, PEt3 and PiPr3 and [TrpyPdIIL2]+ with L = PMe3 were prepared from the mononuclear cations [TrpyPdII]+BArF−. From structural studies it becomes apparent, that the formation of stable five coordinate PdII species is restricted to medium size ligands and depends on the delicate balance between the steric influence of L and the strain, which is induced on the TrpyPdII unit.