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Probing the molecular orbitals and charge redistribution in organometallic (PP)Pd(XX) complexes. A Pd K-Edge XANES study

Probing the molecular orbitals and charge redistribution in organometallic (PP)Pd(XX) complexes. A Pd K-Edge XANES study
Probing the molecular orbitals and charge redistribution in organometallic (PP)Pd(XX) complexes. A Pd K-Edge XANES study
Pd K-edge X-ray absorption near-edge spectroscopy (XANES) is used to probe the unoccupied molecular orbitals in bidentate diphosphine Pd complexes. Complexes containing a series of bidentate diphosphine ligands (PP) are examined to study the effect of the ligand bite angle on the charge redistribution in these complexes. Different coordinating moieties (XX) have been used to induce a range of Pd oxidation states. A full interpretation of the Pd K-edge XANES data is presented. The negative second derivative of these XANES data provides direct information on the energy and electronic distribution of the different unoccupied molecular orbitals probed. The charge redistributions within the complexes, as reflected in the effective Pd oxidation state, are indicated by both the intensity of the first edge feature, the “Pd d peak”, and the energy of the second edge feature, the “Pd p peak”, which can be easily observed in the negative second derivative of the XANES data. Additionally, the changing covalent interaction between the Pd and coordinated moieties via the Pd p orbitals is reflected directly in the energy splitting of the “Pd p” peak. Thus, investigation of these (PP)Pd(XX) complexes, some used as catalysts in organic synthesis, with XANES spectroscopy provides new essential information on their electronic properties. Further, the XANES analysis techniques described in this paper can be applied to investigate the unoccupied molecular orbitals and charge redistributions within a wide range of samples.
palladium, xanes, charge redistribution, density of states
0002-7863
777-789
Tromp, Moniek
48c1ebbb-579c-42b6-83bb-7188c668b322
van Bokhoven, Jeroen A.
ec7aff15-a681-4ae8-9a76-52b23a149f6b
van Strijdonck, Gino P.F.
ab1a4dc5-7547-42e7-b440-38ea02d463d3
van Leeuwen, Piet W.N.M.
72be186e-52c4-47fc-a129-ddc1a8294fa4
Koningsberger, Diek C.
4b5f2fc7-cfc5-4eb2-acab-9e5e0d637639
Ramaker, David E.
b6046329-366d-46f1-ab75-d30efda8f724
Tromp, Moniek
48c1ebbb-579c-42b6-83bb-7188c668b322
van Bokhoven, Jeroen A.
ec7aff15-a681-4ae8-9a76-52b23a149f6b
van Strijdonck, Gino P.F.
ab1a4dc5-7547-42e7-b440-38ea02d463d3
van Leeuwen, Piet W.N.M.
72be186e-52c4-47fc-a129-ddc1a8294fa4
Koningsberger, Diek C.
4b5f2fc7-cfc5-4eb2-acab-9e5e0d637639
Ramaker, David E.
b6046329-366d-46f1-ab75-d30efda8f724

Tromp, Moniek, van Bokhoven, Jeroen A., van Strijdonck, Gino P.F., van Leeuwen, Piet W.N.M., Koningsberger, Diek C. and Ramaker, David E. (2005) Probing the molecular orbitals and charge redistribution in organometallic (PP)Pd(XX) complexes. A Pd K-Edge XANES study. Journal of the American Chemical Society, 127 (2), 777-789. (doi:10.1021/ja048225n).

Record type: Article

Abstract

Pd K-edge X-ray absorption near-edge spectroscopy (XANES) is used to probe the unoccupied molecular orbitals in bidentate diphosphine Pd complexes. Complexes containing a series of bidentate diphosphine ligands (PP) are examined to study the effect of the ligand bite angle on the charge redistribution in these complexes. Different coordinating moieties (XX) have been used to induce a range of Pd oxidation states. A full interpretation of the Pd K-edge XANES data is presented. The negative second derivative of these XANES data provides direct information on the energy and electronic distribution of the different unoccupied molecular orbitals probed. The charge redistributions within the complexes, as reflected in the effective Pd oxidation state, are indicated by both the intensity of the first edge feature, the “Pd d peak”, and the energy of the second edge feature, the “Pd p peak”, which can be easily observed in the negative second derivative of the XANES data. Additionally, the changing covalent interaction between the Pd and coordinated moieties via the Pd p orbitals is reflected directly in the energy splitting of the “Pd p” peak. Thus, investigation of these (PP)Pd(XX) complexes, some used as catalysts in organic synthesis, with XANES spectroscopy provides new essential information on their electronic properties. Further, the XANES analysis techniques described in this paper can be applied to investigate the unoccupied molecular orbitals and charge redistributions within a wide range of samples.

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Published date: 2005
Keywords: palladium, xanes, charge redistribution, density of states

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Local EPrints ID: 46712
URI: http://eprints.soton.ac.uk/id/eprint/46712
ISSN: 0002-7863
PURE UUID: 2023c06d-0057-422a-9ba5-9f398bd2691b

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Date deposited: 16 Jul 2007
Last modified: 13 Mar 2019 21:01

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Contributors

Author: Moniek Tromp
Author: Jeroen A. van Bokhoven
Author: Gino P.F. van Strijdonck
Author: Piet W.N.M. van Leeuwen
Author: Diek C. Koningsberger
Author: David E. Ramaker

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