Dr. ILYA I. MOISEEV


        Kurnakov Institute of General and Inorganic Chemistry
               RAS, Moscow, Russian Federation


         COLLOIDAL METALS: A WAY TO MATERIALS FOR CATALYSIS


                                     ABSTRACT


Studies of high-disperse metal substances and materials, including colloidal 
metals, based on concepts of cluster chemistry and physics of solids are 
discussed by examples of palladium and platinum giant clusters.
        The metal clusters contain tens to hundreds metal atoms forming 
positively charged, close-packed metal cores whose the most abundant portion 
consists of the Chini "magic number" of metal atoms (Pt55, Pt309, Pd561, etc.).
The cluster core is surrounded with coordinated (PPh3, phen, dipy, O2-, Cl-) 
and outer-spheric (OAc-, PF6-) ligands. The most extensively studied giant 
clusters were characterized with HREM, electron diffraction, STM, EELS, SAXS, 
EXAFS, and elemental analysis data. The genesis of platinum metal clusters 
was traced using the temperature-programmed EXAFS in situ combined with DTA-TG.

        The Pd giant clusters with the idealized formulation Pd561phen60Xm 
(X = OAc-, PF6-) displayed high catalytic activity in the liquid-phase 
oxidation and oxidative esterification of alkenes and alkylarenes, oxidation 
of CO and alcohols, displacement of C=C and C=O double bonds, reduction of 
nitriles and nitroaromatics, acetal formation, and oxidative carbonylation 
of phenol. The Pt clusters were proved to be efficient catalysts for reductive 
dechlorination of polychloroaromatics under mild conditions.  

References:
1. I. I. Moiseev, M. N. Vargaftik. Catalysis with Palladium Clusters, 
   in: "Catalysis by Di- and Polynuclear Metal Complexes", Ed. by F.A.Cotton 
   and R.Adams, Wiley-VCH, N.Y., 1998, p.p. 395-442.
2. M.N.Vargaftik, N.Yu.Kozitsyna, N.V.Cherkashina, R.I.Rudy, D.I.Kochubey, 
   I.I.Moiseev. Strategies for Pd and Pt atom assembling, in: "Metal Clusters 
   in Chemistry", Ed. by P.Braunstein, L. A. Oro, P. R. Raithby, Wiley-VCH, 
   Weinheim, 1999, v. 3, p.p. 1364-1391.