Synthesis, characterization, and reactivity of neutral and cationic Pd-C,N,N pincer complexes

The ortho-palladation of the iminophosphane ligand 6-phenyl-2-[(2,6-diisopropylphenyl)imino]pyridine (HL) with Pd(OAc)(2) and PdCl2(PhCN)(2) in benzene yields the neutral Pd-C,N,N pincer complexes Pd(OAc)(kappa(3)-C,N,N-L) (1) and PdCl(kappa(3)-C,N,N-L) (2), respectively. ln the presence of NaBAr'(4) [Ar' = 3,5-(CF3)(2)C6H3], 2 reacts in CH2Cl2 with MeCN, PPh3, or PH[o-MeO(C6H4)](2) to give the cationic palladium(II) pincer complexes [Pd(CH3CN)(kappa(3)-C N,N-L)]BAr'(4) (3), [Pd(PPh3)(kappa 3-C, N,N-L)]BAr'(4) (4) and {Pd[PH(o-MeOC6H4)(2)]-(kappa (3)-C N,N-L)}BAr'(4) (5), respectively. Complexes 1-5 have been characterized by multinuclear NMR and IR spectroscopy. The solid-state structures of 1 and 2 have been determined by single-crystal X-ray diffraction techniques. Both the neutral compounds I and 2 and the cationic derivatives 3, 4, and 5 were tested as catalyst precursors for the Suzuki cross-coupling of 4-bromo- and 4-chloroacetophenone with pherrylboronic acid. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).