Acyclic acid anhydrides oxidatively add to Pd(styrene)(PMe3)2 with C-O bond cleavage to give corresponding acyl(carboxylato)palladium(II) complexes 3a-3e that are isolated and identified. The acetato ligand in 3a is exchanged with added acetic acid. Treatment of 3a with formic acid at room temperature yields acetaldehyde, acetic acid and CO2. Reaction of 3a with dihydrogen liberates acetaldehyde, acetic acid and ethanol. Catalytic hydrogenolysis of octanoic and benzoic anhydrides into aldehydes and carboxylic acids was found to be catalyzed by Pd(PPh3)4.
By removing the bromide ligand in trans-[PdBr(Ph)(PMe3)2] (1) by AgBF4 in the presence and absence of pyridine, pyridine-coordinated and solvent-coordinated cationic complexes, trans-[PdPh(py)(PMe3)2]BF4 (2) and trans-[PdPh(solvent)(PMe3)2]BF4 (3), have been obtained. These cationic phenylpalladium complexes show much greater reactivities than do the parent neutral complex 1 toward olefins to give phenylated olefins by insertion followed by β-hydrogen elimination processes. Kinetic studies concerning the insertion of methyl acrylate into the phenyl-palladium bond have indicated that the reactions are first order in the phenylpalladium complexes and that addition of pyridine to a system containing 2 and methyl acrylate inhibits the insertion reaction of the olefin. The results suggest that the generation of a cationic arylpalladium complex with a vacant site is important for the olefins to be inserted.
Acyclic anhydrides oxidatively added to [Pd(styrene)(PMeR2)2] (R = Me, 2a; Ph, 2b) under mild conditions with C–O bond cleavage to give the corresponding trans-acyl(carboxylato)palladium complexes 3a—3h. Cyclic acid anhydrides also added to 2a to yield trans-acyl(carboxylato)palladium complexes 4a—4c, while reaction of 2a with phthalic anhydride afforded the palladalactone 4d generated via oxidative addition followed by decarbonylation. The acetyl(acetato)palladium complex 3a reacted with dihydrogen or formic acid to give acetaldehyde and acetic acid. Catalytic hydrogenation of acyclic anhydrides by a palladium complex was achieved to form the corresponding aldehydes and carboxylic acids.
Removal of the halide ligand X in PdR(X)L2 with AgBF4 generates solvent-coordinated cationic organopalladium complexes [PdR(s)L2]BF4 which show much higher reactivities for CO insertion than the parent neutral complexes.
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