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Jacobsen H.,KemKom
Physical Chemistry Chemical Physics | Year: 2013

Analysis of the kinetic energy density within a molecule identifies patterns in its electronic structure that are intuitively linked to familiar concepts of chemical bonding. The function ν(r), termed localized-orbital locator and based on the positive-definite kinetic energy density τ+, is employed to characterize classes of covalent bonds in terms of its full topology of all critical points of rank three. Not only does ν(r) reveal patterns in chemical bonding, it also discloses features and the influence of extended electronic cores. Gradient paths define the extension of the valence space around an atomic centre; they separate various core level regions from bonding domains, and partition molecules in sensible bonded subunits. Location and ν(r)-values of critical points add a quantitative aspect to the bond characterization; profiles of unconventional chemical linkages such as charge-shift bonds emerge in a natural way. © 2013 The Owner Societies. Source


An analysis of the kinetic energy density within a molecule identifies patterns within its electronic structure that are intuitively linked to familiar concepts of chemical bonding. Proposed are bond descriptors based on local kinetic energies in an extended mapping onto a finite range of values, so called RoSE-indicators. The usefulness and performance of RoSE-indicators is judged in applications on aromaticity. Results are presented for benzene, cyclobutadiene, borazine and the cyclic hydrogen fluoride trimer as examples for agreed-upon aromaticity and antiaromaticity, as well as for questionable aromaticity. All-metal aromaticity is discussed based on results obtained for tetra aluminum dianion. © 2013 Elsevier B.V. All rights reserved. Source


Analysis of the kinetic energy density within a molecule identifies patterns in its electronic structure that are linked to the concept of charge-shift bonding. This is illustrated in a detailed study of twelve molecules, possessing carbon-carbon covalent as well as carbon-carbon charge-shift bonds in various degrees of orders, including propellanes and heteropropellanes. Regions of slow electrons are fundamental for such a correlation, and a RoSE (region of slow electrons) indicator ν±, based on the positive definite kinetic energy density τ, is employed to characterize classes of charge-shift bonds in terms of its full topology of all critical points of rank three. Not either-or anymore: Bond descriptors based on the local kinetic energy not only confirm the essence of charge-shift bonding, but also articulate this concept with nuances. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Jacobsen H.,KemKom | Cavallo L.,King Abdullah University of Science and Technology
ChemPhysChem | Year: 2012

The performance of a series of density functionals when tested on the prediction of the phosphane substitution energy of transition metal complexes is evaluated. The complexes Fe-BDA and Ru-COD (BDA=benzylideneacetone, COD=cyclooctadiene) serve as reference systems, and calculated values are compared with the experimental values in THF as obtained from calorimetry. Results clearly indicate that functionals specifically developed to include dispersion interactions usually outperform other functionals when BDA or COD substitution is considered. However, when phosphanes of different sizes are compared, functionals including dispersion interactions, at odd with experimental evidence, predict that larger phosphanes bind more strongly than smaller phosphanes, while functionals not including dispersion interaction reproduce the experimental trends with reasonable accuracy. In case of the DFT-D functionals, inclusion of a cut-off distance on the dispersive term resolves this issue, and results in a rather robust behavior whatever ligand substitution reaction is considered. Ne quid nimis: Describing chemical reactions in solution by computational techniques developed for gas-phase scenarios might produce erroneous results (see histogram). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Fortman G.C.,University of St. Andrews | Jacobsen H.,KemKom | Cavallo L.,University of Salerno | Nolan S.P.,University of St. Andrews
Chemical Communications | Year: 2011

The catalytic activity of a series of coordinatively unsaturated NHC-M(iii) (M = Rh, Ir; NHC = N-heterocyclic carbene) complexes was tested in the deuteration of secondary and tertiary silanes. Among these, [IrCl(I tBu′)2] provides the highest conversions to the deuterated species. Mechanistic studies highlight the reversible nature of the ortho-metalation reaction. © The Royal Society of Chemistry 2011. Source

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