Synthesis, Characterization, and Reactivity of Neutral and Cationic Pd–C,N,N Pincer Complexes

Abstract

AbstractThe 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)(κ3‐C,N,N‐L) (1) and PdCl(κ3‐C,N,N‐L) (2), respectively. In the presence of NaBAr′4 [Ar′ = 3,5‐(CF3)2C6H3], 2 reacts in CH2Cl2 with MeCN, PPh3, or PH[o‐MeO(C6H4)]2 to give the cationic palladium(II) pincer complexes [Pd(CH3CN)(κ3‐C,N,N‐L)]BAr′4 (3), [Pd(PPh3)(κ3‐C,N,N‐L)]BAr′4 (4) and {Pd[PH(o‐MeOC6H4)2](κ3‐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 1 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 phenylboronic acid. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)