Center for Molecular Modeling - B. Pinter

Trans Effect and Trans Influence: Repulsion, rather than Competition for Donation

michel — Fri, 12 Apr 2013 10:16:37 +0000

B. Pinter, V. Van Speybroeck, M. Waroquier, P. Geerlings, F. De Proft

Physical Chemistry Chemical Physics (PCCP)

15 (40), 17354-17365

2013

Abstract

The trans effect and trans influence were investigated and rationalized in the aminolysis, a typical nucleophilic substitution reaction, of trans-TPtCl2NH3 complexes (T = NH3, PH3, CO and C2H4) using energy decomposition analysis, both along the reaction paths and on the stationary points, and Natural Orbital for Chemical Valence analysis. In order to scrutinize the underlying principles and the origin of the kinetic trans effect, plausible structural constraints were introduced in the decomposition analysis, which allowed eliminating the distance dependence of the interaction energy components. It was established that the trans effect can be rationalized with the interaction of the TPtCl2 and NH3 fragments in the reactant state and TPtCl2 and (NH3)2 fragments in the transition state. It was evinced quantitatively that the σ-donor ability of T indeed controls the stability of the reactant, whereas in the case of π-acids, backdonation stabilizes the transition state, for which conceptually two mechanisms are available: intrinsic and induced π-backdonation. In the destabilization of the reactant and also in the labilization of the leaving group (trans influence) repulsion plays a more important role than orbital sharing effects, which are the cornerstones of the widely accepted interpretations of the trans influence, such as competition for donation or limitation of the donation of the leaving group by the trans ligand T. This repulsive interaction was rationalized both in terms of donated electron density and also in the molecular orbital framework. NOCV orbitals indeed clearly show that the σ-trans effect can be envisioned as a donation from the trans ligand not only to the metal but also to the σ* orbital of the metal-leaving group bond, which manifests as a repulsion between the metal and the leaving group.

DOI

http://dx.doi.org/10.1039/C3CP52383G

Private attachment

13_PCCP_15(40)17354_pinter.pdf

Spin-Polarized Conceptual Density Functional Theory Study of the Regioselectivity in Ring Closures of Radicals

wim — Mon, 03 Oct 2011 07:28:22 +0000

B. Pinter, F. De Proft, V. Van Speybroeck, K. Hemelsoet, M. Waroquier, E. Chamorro, T. Veszpremi, P. Geerlings

Journal of Organic Chemistry

72 (2), 348-356

2007

Abstract

The regioselectivity of ring-forming radical reactions is investigated within the framework of the so-called spin-polarized conceptual density functional theory. Two different types of cyclizations were studied. First, a series of model reactions of alkyl- and acyl-substituted radicals were investigated. Next, attention was focused on the radical cascade cyclizations of N-alkenyl-2-aziridinylmethyl radicals (a three-step mechanism). In both of these reactions, the approaching radical (carbon or nitrogen centered) adds to a carbon−carbon double bond within the same molecule to form a radical ring compound. In this process, the number of electrons is changing from a local point of view (a charge transfer occurs from one part of the molecule to another one) at constant global spin number Ns (both the reactant and the product ring compound are in the doublet state). It is shown that the experimentally observed regioselectivities for these ring-closure steps can be predicted using the spin-polarized Fukui functions for radical attack, (r).

DOI

http://dx.doi.org/10.1021/jo0613885

Private attachment

07 j. org. chem 72(2)348 pinter.pdf

Trans effect: withdrawing electrons from the reactive region

wim — Mon, 02 Jul 2012 13:58:30 +0000

B. Pinter, V. Van Speybroeck, M. Waroquier, P. Geerlings, F. De Proft

p. 91

Poster

Conference / event / venue

ICTAC-14

Vlissingen, The Netherlands

Tuesday, 26 June, 2012 to Saturday, 30 June, 2012

Conference reference

ICTAC-14

Trans effect: withdrawing electrons from the reactive region

wim — Mon, 07 May 2012 08:07:21 +0000

B. Pinter, V. Van Speybroeck, M. Waroquier, P. Geerlings, F. De Proft

P28

Poster

Conference / event / venue

DFTM2012

Ghent University, Het Pand, Ghent, Belgium

Sunday, 1 April, 2012 to Friday, 6 April, 2012

Abstract (private)

DFTM2012_BPinter.pdf

Conference reference

DFTM2012