Simple but Stronger UO, Double but Weaker UNMe Bonds: The Tale Told by Cp2UO and Cp2UNR

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The free energies of reaction and the activation energies are calculated, with DFT (B3PW91) and small RECP (relativistic core potential) for uranium, for the reaction of Cp2UNMe and Cp2UO with MeCCMe and H3Si-Cl that yields the corresponding addition products. CAS(2,7) and DFT calculations on Cp2UO and Cp2UNMe give similar results, which validates the use of DFT calculations in these cases. The calculated results mirror the experimental reaction of [1,2,4-(CMe3)3C5H2]2UNMe with dimethylacetylene and [1,2,4-(CMe3)3C5H2]2UO with Me3SiCl. The net reactions are controlled by the change in free energy between the products and reactants, not by the activation energies, and therefore by the ... continued below

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LPCNO, CNRS-UPS-INSA, INSA Toulouse; Institut Charles Gerhardt, CNRS, Universite Montpellier; Laboratoire de Chimie et Physique Quantiques, CNRS, IRSAMC, Universite Paul Sabatier; Andersen, Richard; Barros, Noemi; Maynau, Daniel et al. June 27, 2007.

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The free energies of reaction and the activation energies are calculated, with DFT (B3PW91) and small RECP (relativistic core potential) for uranium, for the reaction of Cp2UNMe and Cp2UO with MeCCMe and H3Si-Cl that yields the corresponding addition products. CAS(2,7) and DFT calculations on Cp2UO and Cp2UNMe give similar results, which validates the use of DFT calculations in these cases. The calculated results mirror the experimental reaction of [1,2,4-(CMe3)3C5H2]2UNMe with dimethylacetylene and [1,2,4-(CMe3)3C5H2]2UO with Me3SiCl. The net reactions are controlled by the change in free energy between the products and reactants, not by the activation energies, and therefore by the nature of the UO and UNMe bonds in the initial and final states. A NBO analysis indicates that the U-O interaction in Cp2UO is composed of a single U-O bond with three lone pairs of electrons localized on oxygen, leading to a polarized U-O fragment. In contrast, the U-NMe interaction in Cp2UNMe is composed of a and component and a lone pairof electrons localized on the nitrogen, resulting in a less polarized UNMe fragment, in accord with the lower electronegativity of NMe relative to O. The strongly polarized U(+)-O(-) bond is calculated to be about 70 kcal mol-1 stronger than the less polarized U=NMe bond.

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  • Journal Name: Organometallics; Journal Volume: 26; Journal Issue: 20; Related Information: Journal Publication Date: September 24, 2007

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  • Report No.: LBNL-119E
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 926496
  • Archival Resource Key: ark:/67531/metadc899330

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  • June 27, 2007

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  • Sept. 27, 2016, 1:39 a.m.

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  • Oct. 3, 2016, 2:21 p.m.

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LPCNO, CNRS-UPS-INSA, INSA Toulouse; Institut Charles Gerhardt, CNRS, Universite Montpellier; Laboratoire de Chimie et Physique Quantiques, CNRS, IRSAMC, Universite Paul Sabatier; Andersen, Richard; Barros, Noemi; Maynau, Daniel et al. Simple but Stronger UO, Double but Weaker UNMe Bonds: The Tale Told by Cp2UO and Cp2UNR, article, June 27, 2007; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc899330/: accessed October 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.