title: Palladium(II) containing γ-Keggin silicodecatungstate that efficiently catalyzes hydration of nitriles.
abstract: A mixture of Pd(OAc)(2) and TBA(4)[γ-SiW(10)O(34)(H(2)O)(2)] (TBA-SiW10, TBA = [(n-C(4)H(9))(4)N](+)) showed high catalytic activities for hydration of various kinds of structurally diverse nitriles including aromatic, aliphatic, heteroaromatic, and double bond-containing ones. For hydration of 3-cyanopyridine, the turnover frequency was 860 h(-1), and the turnover number reached up to 670. A dipalladium-substituted γ-Keggin silicodecatungstate, [γ-H(2)SiW(10)O(36)Pd(2)(OAc)(2)](4-) (I), was successfully synthesized by the reaction of [γ-SiW(10)O(34)(H(2)O)(2)](4-) with Pd(OAc)(2) in a mixed solvent of acetone and water. The crystal structure of I was a monomeric, dipalladium-substituted, γ-Keggin silicodecatungstate with bidentate acetate ligands. Compound I showed similar activities and selectivities to those of a simple mixture of Pd(OAc)(2) and TBA-SiW10. The kinetic, mechanistic, and density functional theory calculation studies show that the dipalladium site plays an important role in the present hydration, and the nucleophilic attack of a hydroxide or water to the nitrile carbon atom is included in the rate-determining step.
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-8656, Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Hirano
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Uehara
authors.forename: Keigo
authors.initials: K
authors.lastname: Kamata
authors.forename: Noritaka
authors.initials: N
authors.lastname: Mizuno
mesh_terms: D000085:Acetates / Q000737:chemistry; D002384:Catalysis; D018360:Crystallography, X-Ray / Q000379:methods; D006878:Hydroxides / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D009570:Nitriles / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D017655:Silicon Compounds / Q000737:chemistry*; D017973:Tungsten Compounds / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D000085:Acetates; D006878:Hydroxides; D008024:Ligands; D009570:Nitriles; D017655:Silicon Compounds; D017973:Tungsten Compounds; D014867:Water; D010165:Palladium