Synthesis and structural studies of cyclopalladated complexes of secondary benzylamines

Abstract

Di-nuclear cyclopalladated acetato-bridged complexes derived from secondary benzylamines, [Pd2{(C,N)-C6H4CH2NH(R)}2(μ-OAc)2] (R = Et (1), R = t-Bu (2)) were obtained by refluxing of corresponding benzylamines and Pd(OAc)2 in a 1:1 M ratio. Complex 1 was also prepared by heating the bis-amine complex [Pd(OAc)2(PhCH2NH(Et))2] (3) in toluene at 60 °C. Complex 3 reacted with an excess of NaCl to give [Pd(Cl)2(PhCH2NH(Et))2] (4). Metathetical reaction of 1 and 2 with an excess of NaCl or NaBr afforded the corresponding dimers [Pd2{(C,N)-C6H4CH2NH(R)}2(μ-X)2] (X = Cl, R = Et (5); X = Cl, R = t-Bu (6); X = Br, R = t-Bu (7)). The cationic complex [Pd(C,N)-C6H4CH2NH(Et)(phen)]BF4 (8) can be obtained by reacting chloro bridge dimer 5 with AgBF4 and 1,10-phenanthroline (phen). Neutral ligands split the halide bridges in 6 and 7 to give monomeric complexes [Pd(C,N)-C6H4CH2NH(t-Bu)X(L)] (X = Cl, L = PPh3 (9); X = Br, L = Me3Py (10)). Complexes 1–10 were fully characterized by elemental analysis, IR and NMR spectroscopies. In addition, the crystal structures of 2, 3, 4, 8, 9 and 10 were determined by single-crystal X-ray diffraction analysis. In all these structures, the palladium atom shows a distorted or slightly distorted square-planar geometry.