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 (mu-X)(2)[Pd{kappa(2)-N2',Cl-2-(2'-NH2C6H4)C6H4}](2) [1a (X = OAc) and lb (X = C)] in high yield. Moreover, the reaction between 2-phenylaniline and Pd(OAc)(2) in one-to-one molar ratio in acid acetic at 60degreesC for 4 h, followed by a metathesis reaction with LiBr, allowed isolation of the dinuclear cyclopalladated compound (mu-Br)(2)[Pd{kappa(2) -N2',Cl-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, 1c(d1) [Pd{kappa(2)-N2',Cl-2-(2'- NH2C6H4)C6H4[(mu-Br)(2)[Pd{kappa(2)-N2',Cl-2-(2'-NH2C6H4)-3-D-C6H3] and 1c(d2) (mu-Br)(2)[Pd{kappa(2)-N2',Cl-2-(2'-NH2C6H4)-3-D-C6H3}](2) in moderate yield and with a deuterium content of ca. 60%. la and lb reacted with pyridine and PPh3 affording the mononuclear cyclopalladated compounds [Pd{kappa(2)-N2',Cl-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, la reacted with Na(acac) . H2O to give the mononuclear cyclopalladated compound 4 [Pd{kappa(2)-N2',Cl-2-(2'-NH2C6H4)C6H4}(acac)] in moderate yield. H-1 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 P1 with a = 9.9170(10), b = 10.4750(10), c = 12.0890(10) A, alpha = 98.610(10)degrees, beta = 94.034(10)degrees and gamma = 99.000(10)degrees and 4 in the monoclinic space group P2(1)/a with a = 11.5900(10), b = 11.2730(10), 12.2150(10) A, alpha = 90degrees beta = 107.6560(10)degrees and gamma= 90degrees. (C) 2004 Elsevier B.V. All rights reserved.