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 PdCl 2 (PhCN) 2 in benzene yields the neutral Pd–C,N,N pincer complexes Pd(OAc)(κ 3 ‐C,N,N‐L) ( 1 ) and PdCl(κ 3 ‐C,N,N‐L) ( 2 ), respectively. In the presence of NaBAr′ 4 [Ar′ = 3,5‐(CF 3 ) 2 C 6 H 3 ], 2 reacts in CH 2 Cl 2 with MeCN, PPh 3 , or PH[ o ‐MeO(C 6 H 4 )] 2 to give the cationic palladium( II ) pincer complexes [Pd(CH 3 CN)(κ 3 ‐C,N,N‐L)]BAr′ 4 ( 3 ), [Pd(PPh 3 )(κ 3 ‐C,N,N‐L)]BAr′ 4 ( 4 ) and {Pd[PH( o ‐MeOC 6 H 4 ) 2 ](κ 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 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)