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Theoretical studies and structural analysis of models of surface organometallic centres

Theoretical studies and structural analysis of models of surface organometallic centres
Theoretical studies and structural analysis of models of surface organometallic centres

Theoretical calculations utilizing the density functional theory (DFT) method are presented here from the point of view of their applicability in modelling catalytic rhodium gem dicarbonyl, Rh(CO)2, species on silica surface. The surface rhodium gem dicarbonyls were modelled by [Rh(CO)2(OSiH3)], [Rh(CO)2(OHSiH3)]+, [Rh(CO)2(ClSiH3)]+, [Rh(CO)2(Cl)(OSiH3)]-, [Rh(CO)2(Cl)(OHSiH3)], [Rh(CO)2(Cl)(ClSiH3)]. In all model structures the rhodium atoms are assumed to have the oxidation state of +1.

The geometries were optimized using the hybrid B3LYP exchange-correlational functional and effective core potential basis set of Hay and Wadt, LanL2DZ was used on the Rh atoms while 6-31G** basis set was applied on the rest of the system. We also presented the DFT-B3LYP predictions of their vibrational frequencies, charge distribution, and HOMO-LUMO energy gaps. The result shows Rh-O distance within the suggested experimental range for both O-2 and OH- ligands. Combination of geometry optimization, frequency calculation and HOMO-LUMO energy gap, shows [Rh(CO)2(Cl)(ClSiH3)] to best model the surface Rh1(CO)2 with [Rh(CO)2(Cl)(OHSiH3)] being the other closest possibility.

The flexibility of octasilsesquioxanes, R'nRmSi8O12 (m=8-n, n=0,1,2) and their incompletely condensed polyhedral oligosilsesquioxanes, R8Si8O12 which are of great interest due to their striking structural similarity with silica polymorphs, is analyzed using crystal data extracted from the Cambridge Crystallographic Database (CSD). The results are represented as histograms and scattergrams.

University of Southampton
Adnan, Rohana Binti
825dc606-a026-4501-8303-2fbf224bff07
Adnan, Rohana Binti
825dc606-a026-4501-8303-2fbf224bff07

Adnan, Rohana Binti (2000) Theoretical studies and structural analysis of models of surface organometallic centres. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Theoretical calculations utilizing the density functional theory (DFT) method are presented here from the point of view of their applicability in modelling catalytic rhodium gem dicarbonyl, Rh(CO)2, species on silica surface. The surface rhodium gem dicarbonyls were modelled by [Rh(CO)2(OSiH3)], [Rh(CO)2(OHSiH3)]+, [Rh(CO)2(ClSiH3)]+, [Rh(CO)2(Cl)(OSiH3)]-, [Rh(CO)2(Cl)(OHSiH3)], [Rh(CO)2(Cl)(ClSiH3)]. In all model structures the rhodium atoms are assumed to have the oxidation state of +1.

The geometries were optimized using the hybrid B3LYP exchange-correlational functional and effective core potential basis set of Hay and Wadt, LanL2DZ was used on the Rh atoms while 6-31G** basis set was applied on the rest of the system. We also presented the DFT-B3LYP predictions of their vibrational frequencies, charge distribution, and HOMO-LUMO energy gaps. The result shows Rh-O distance within the suggested experimental range for both O-2 and OH- ligands. Combination of geometry optimization, frequency calculation and HOMO-LUMO energy gap, shows [Rh(CO)2(Cl)(ClSiH3)] to best model the surface Rh1(CO)2 with [Rh(CO)2(Cl)(OHSiH3)] being the other closest possibility.

The flexibility of octasilsesquioxanes, R'nRmSi8O12 (m=8-n, n=0,1,2) and their incompletely condensed polyhedral oligosilsesquioxanes, R8Si8O12 which are of great interest due to their striking structural similarity with silica polymorphs, is analyzed using crystal data extracted from the Cambridge Crystallographic Database (CSD). The results are represented as histograms and scattergrams.

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Published date: 2000

Identifiers

Local EPrints ID: 464219
URI: http://eprints.soton.ac.uk/id/eprint/464219
PURE UUID: cd08fc36-a253-452f-9826-a98ed8545b0e

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Date deposited: 04 Jul 2022 21:37
Last modified: 16 Mar 2024 19:20

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Contributors

Author: Rohana Binti Adnan

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