Giant palladium clusters as catalysts of oxidative reactions of olefins and alcohols

• Published in: Journal of molecular catalysis 1989-08, Vol.53 (3), p.315-348
• Main Authors: Vargaftik, M.N., Zagorodnikov, V.P., Stolarov, I.P., Moiseev, I.I., Kochubey, D.I., Likholobov, V.A., Chuvilin, A.L., Zamaraev, K.I.
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0304-5102
• DOI: 10.1016/0304-5102(89)80066-5

Giant cationic palladium clusters approximated as Pd 561L 60(OAc) 180 (L = phen, bipy) and Pd 561phen 60O 60(PF 6) 60 were synthesized and characterized with high resolution TEM, SAXS, EXAFS, IR and magnetic susceptibility data. The results of these studies suggest that L and O ligands are bound to Pd atoms located on the surfaces of close-packed metal skeletons of the clusters, while OAc −1 and PF 6 − anions are outer-sphere ligands. Under mild conditions (293–363 K, l atm) the giant palladium clusters catalyze oxidative acetoxylation of ethylene into vinyl acetate, propylene into allyl acetate, and toluene into benzyl acetate; oxidation of primary aliphatic alcohols into esters; and conversion of aldehydes into acetals. Kinetics of oxidative acetoxylation of ethylene and propylene in solutions of the giant clusters were studied. A mechanism for these reactions is proposed, which includes the following steps: coordination of reagents by the cluster, oxidative addition of alkene to a Pd—Pd fragment and transfer of an electron pair from a Pd—H, Pd—vinyl, or Pd—allyl fragment to a coordinated molecule of oxidant (O 2, peroxide, Pd(II)).