The cyclopalladation reaction of 2-phenylaniline revisited

2-Phenylaniline reacted with Pd(OAc)2 in toluene at room temperature for 24 h in a one-to-one molar ratio and with the system PdCl2, NaCl and NaOAc in a 1 (2-phenylaniline):1 (PdCl2):2 (NaCl):1 (NaOAc) molar ratio in methanol at room temperature for one week to give the dinuclear cyclopalladated compounds (μ-X)2[Pd{κ2-N2′,C1-2-(2′-NH2C6H4)C6H4}]2 [1a (X = OAc) and 1b (X = Cl)] in high yield. Moreover, the reaction between 2-phenylaniline and Pd(OAc)2 in one-to-one molar ratio in acid acetic at 60 °C for 4 h, followed by a metathesis reaction with LiBr, allowed isolation of the dinuclear cyclopalladated compound (μ-Br)2[Pd{κ2-N2′,C1-2-(2′-NH2C6H4)C6H4}]2 (1c) in moderate yield. A parallel treatment, but using monodeuterated acetic acid (DOAc) as solvent in the cyclopalladation reaction, allowed isolation of a mixture of compounds 1c, 1cd1 [Pd{κ2-N2′,C1-2-(2′-NH2C6H4)C6H4](μ-Br)2[Pd{κ2-N2′,C1-2-(2′-NH2C6H4)-3-d-C6H3] and 1cd2 (μ-Br)2[Pd{κ2-N2′,C1-2-(2′-NH2C6H4)-3-d-C6H3}]2 in moderate yield and with a deuterium content of ca. 60%. 1a and 1b reacted with pyridine and PPh3 affording the mononuclear cyclopalladated compounds [Pd{κ2-N2′,C1-2-(2′-NH2C6H4)C6H4}(X)(L)] [2a (X = OAc, L = py), 2b (X = Cl, L = py), 3a (X = OAc, L = PPh3) and 3b (X = Cl, L = PPh3)] in a yield from moderate to high. Furthermore, 1a reacted with Na(acac) · H2O to give the mononuclear cyclopalladated compound 4 [Pd{κ2-N2′,C1-2-(2′-NH2C6H4)C6H4}(acac)] in moderate yield. 1H NMR studies in CDCl3 solution of 2a, 2b, 3a, 3b and 4 showed that 2a and 3a presented an intramolecular hydrogen bond between the acetato ligand and the amino group, and were involved in a dynamic equilibrium with water present in the CDCl3 solvent; and that the enantiomeric molecules of 2b and 4 were in a fast exchange at room temperature, while they were in a slow exchange for 2a, 3a and 3b. The X-ray crystal structures of 3b and 4 were determined. 3b crystallized in the triclinic space group View the MathML source