609810-30-2Relevant academic research and scientific papers
Arene C-H bond activation and arene oxidative coupling by cationic palladium(II) complexes
Ackerman, Lily J.,Sadighi, Joseph P.,Kurtz, David M.,Labinger, Jay A.,Bercaw, John E.
, p. 3884 - 3890 (2008/10/08)
N,N′-Diaryl-α-diimine-ligated Pd(II) dimethyl complexes (tBu(2)ArDABMe)PdMe2 and {(CF(3))(2)Ar_DABMe}PdMe2 {tBu(2)ArDABMe: ArN=C(CH3)-C(CH3)=NAr, Ar = 3,5-di-tert-butylphenyl; (CF(3))(2)Ar_DABMe: Ar = 3,5-bis(trifluoromethyl)phenyl} undergo protonolysis with HBF4(aq) in trifluoroethanol (TFE) to form cationic complexes [(α-diimine)Pd(CH3)(H2O)][BF4]. The cations activate benzene C-H bonds at room temperature. Kinetic analyses reveal trends similar to those observed for the analogous platinum complexes: the C-H activation step is rate-determining (KIE = 4.1 ± 0.5) and is inhibited by H2O. The kinetic data are consistent with a mechanism in which benzene substitution proceeds by a solvent- (TFE-) assisted associative pathway. Following benzene C-H activation under 1 atm O2, the products of the reaction are biphenyl and a dimeric μ-hydroxide complex, [(α-diimine)Pd(OH)]2[BF4]2. The Pd(0) formed in the reaction is reoxidized by O2 to the dimeric μ-hydroxide complex after the oxidative C-C bond formation. The regioselectivity of arene coupling was investigated with toluene and α,α,α-trifluorotoluene as substrates.
