Trends in Covalency for d- and f-Element Metallocene Dichlorides Identified Using Chlorine K-Edge X-ray Absorption Spectroscopy and Time-Dependent Density Functional Theory.
We describe the use of Cl K-edge X-ray absorption spectroscopy (XAS) and both ground-state and time-dependent hybrid density functional theory (DFT) to probe the electronic structure and determine the degree of orbital mixing in M-Cl bonds for (CMe)MCl (M = Ti, 1; Zr, 2; Hf, 3; Th, 4; U, 5), where w...
| Publicado en: | Journal of the American Chemical Society Vol. 131; no. 34; pp. 12125 - 12137 |
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| Autores principales: | , , , , , , , , , |
| Formato: | Artículo |
| Publicado: |
American Chemical Society
9/2/2009
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| Materias: | |
| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=44230185&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 44230185 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 9/2/2009 vid: 131 iid: 34 pid: 997 pub: American Chemical Society artinfo: ui: 44230185 10.1021/ja9015759 ppf: 12125 ppct: 12 formats: tig: atl: Trends in Covalency for d- and f-Element Metallocene Dichlorides Identified Using Chlorine K-Edge X-ray Absorption Spectroscopy and Time-Dependent Density Functional Theory. aug: au: Kozimor, Stosh A. Ping Yang Batista, Enrique R. Boland, Kevin S. Burns, Carol J. Clark, David L. Conradson, Steven D. Martin, Richard L. Wilkerson, Marianne P. Wolfsberg, Laura E. affil: Los Alamos National Laboratory, Los Alamos, New Mexico 87545 W.R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 su: Metallocenes Chlorine Extended X-ray absorption fine structure Density functionals Radioactive substances Cathode rays sug: subj: Metallocenes Chlorine Extended X-ray absorption fine structure Density functionals Radioactive substances Cathode rays ab: We describe the use of Cl K-edge X-ray absorption spectroscopy (XAS) and both ground-state and time-dependent hybrid density functional theory (DFT) to probe the electronic structure and determine the degree of orbital mixing in M-Cl bonds for (CMe)MCl (M = Ti, 1; Zr, 2; Hf, 3; Th, 4; U, 5), where we can directly compare a class of structurally similar compounds for d- and f-elements. Pre-edge features in the Cl K-edge XAS data for the group IV transition-metals 1-3 provide direct evidence of covalent M-Cl orbital mixing. The amount of Cl 3p character was experimentally determined to be 25%, 23%, and 22% per M-Cl bond for 1-3, respectively. For actinides, we find a pre-edge shoulder for 4 (Th) and distinct and weak pre-edge features for U, 5. The amount of Cl 3p character was determined to be 9% for 5, and we were unable to make an experimental determination for 4. Using hybrid DFT calculations with relativistic effective core potentials, the electronic structures of 1-5 were calculated and used as a guide to interpret the experimental Cl K-edge XAS data. For transition-metal compounds 1-3, the pre-edge features arise due to transitions from Cl 1s electrons into the 3d-, 4d-, and 5d-orbitals, with assignments provided in the text. For Th, 4, we find that 5f- and 6d-orbitals are nearly degenerate and give rise to a single pre-edge shoulder in the XAS. For U, 5, we find the 5f- and 6d-orbitals fall into two distinct energy groupings, and Cl K-edge XAS data are interpreted in terms of Cl 1s transitions into both 5f- and 6d-orbitals. Time-dependent DFT was used to calculate the energies and intensities of Cl 1s transitions into empty metal-based orbitals containing Cl 3p character and provide simulated Cl K-edge XAS spectra for 1-4. For 5, which has two unpaired 5f electrons, simulated spectra were obtained from transition dipole calculations using ground-state Kohn-Sham orbitals. To the best of our knowledge, this represents the first application of Cl K-edge XAS to actinide systems. Overall, this study allows trends in orbital mixing within a well-characterized structural motif to be identified and compared between transition-metals and actinide elements. These results show that the orbital mixing for the d-block compounds slightly decreases in covalency with increasing principal quantum number, in the order Ti > Zr ≈ Hf, and that uranium displays approximately half the covalent orbital mixing of transition elements. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2009 holdings: @attributes: islocal: N |
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