III International Conference

PP-I-68ADSORPTION OF RHODIUM (I) DICARBONYL ON ZEOLITE: AN EMBEDDEDCLUSTER DENSITY FUNCTIONAL STUDYLaletina S.S., Shor E.A., Shor A.M., Nasluzov V.A.Institute of Chemistry and Chemical Technology, SB RAS, Krasnoyarsk, RussiaE-mail: shkulepo@rambler.ruThe structure and bonding of rhodium dicarbonyl cation located in faujasite cavities wasstudied computationally by DFT method in combination with scheme of cluster modelsembedded in an elastic polarizable environment that allows one to account for electrostaticfield and mechanical constraint of substrate. According to our calculation bonding ofRh(CO) 2 + at two oxygen atoms of support near an aluminum center, belonging one twelve–ring of the supercage wall is energetically most preferred.Mononuclear rhodium complexes supported on surface of covalent oxides, e.g. zeolites,are active catalysts of such reactions as, for example, methanol carbonylation, alkenehydroformylation and polymerization. To understand origin of the chemical reactivity of thesecomplexes, it is of necessity to investigate structure of catalytically active center at atomisticlevel. Here we report the characterization of rhodium dicarbonyl anchored at internal surfaceof faujasite.Experimental studies using EXAFS and IR spectroscopies has identified the surfacerhodium species on NaY as site isolated rhodium dicarbonyls [1]. Basing on the measuredparameters three models of the local structure of surface rhodium complex have beensuggested. They differ by the number of support oxygen atoms (2 or 3) to which rhodiumdicarbonyl complex Rh(CO) + 2 is bonded; the Rh-O bond distances vary in a range 2.10-2.15Å. However, on the basis of experimental data only it was impossible to distinguish thesemodels. To assist in discrimination of the models theoretical calculations [1] have beenperformed that indicated that Rh(CO) + 2 is bonded to two oxygen centers nearby Al center.This earlier study was carried out using isolated cluster models to represent zeolite substrate.To avoid artificial distortion of model clusters special restrictions on movement of clustercenters were imposed. Present computational study was aimed to re-investigate these systemswith more accurate theoretical approach – the elastic polarizable environment clusterembedding approach, EPE [2], which allows to relax all degrees of freedom of embeddedcluster and take into account electrostatic field as well as polarization of the clusterenvironment by the active center. Moreover, several sites for coordination of Rh(CO) + 2 thatdiffer by the crystallographic position of the oxygen atoms to be involved in the bonding have129