Homogeneous Catalysis with Dicationic PdII Complexes: Aldol reaction of methyl isocyanoacetate with benzaldehyde

A series of dicationic PdII‐acetonitrile complexes containing bi‐ and tridentate nitrogen and bidentate phosphine ligands (some of which are chiral) has been prepared as their BF4 salts. The molecular structures for two of these, [Pd(CH3CN)2(bipy)] (BF4)2 (4) and [Pd(CH3CN)((pybox)(i‐Pr))] (BF4)2((S,S)‐pybox(i‐Pr) = 2,6‐bis[(S)‐4′‐isopropyloxazolin‐2′‐yl]pyridine, 5) have been determined by X‐ray diffraction. All of these complexes are shown to be effective homogeneous catalysts for the aldol‐type condensation of the isonitrile, methyl isocyanoacetate, with benzaldehyde. Two isonitrile complexes, [Pd(2,2′‐bipyridyl)(CNCH2COOCH3)2] (BF4)2 and [Pd((S,S)‐pybox(i‐Pr))(CNCH2COOCH3)] (BF4)2, have also been prepared.