title: Mapping the Trajectory of Nucleophilic Substitution at Silicon Using a peri-Substituted Acenaphthyl Scaffold.
abstract: The second-order nucleophilic substitution (SN2) reaction at a silicon atom is scrutinized by means of snapshots along a pseudoreaction coordinate. Phosphine and fluoride represent both attacking and leaving groups in the modeled SN2 reaction. In the experimentally obtained 5-diphenylphosphinoacenaphth-6-yl-dimethylfluorosilane, 1, the phosphine and fluorosilane moieties are forced into immediate proximity through an acenaphthyl scaffold, that is, they exhibit peri interactions that serve as the model of the reactant ion-molecule complex and starting point for a theoretical potential-energy surface (PES) scan. Upon dissociation of fluoride, the experimentally obtained silylphosphonium cation 2 serves as a model of the product and end point of the PES scan. The pseudoreaction pathway is studied using geometric, energetic, spectroscopic, molecular-orbital, and topological real-space bonding indicators. It becomes evident that it is crucial to combine such methods to understand the pseudoreaction because they reveal different aspects based on different sensitivity to dispersive, electrostatic, and polar-covalent contributions to bonding, as shown by the reduced density gradient analysis. For example, atoms-in-molecules theory describes a late topological catastrophe, whereas the electron localizability indicator describes an early concerted reaction and natural resonance theory describes a more gradual change of properties. This case study encourages the use of a well-balanced toolbox equipped with complementary methods to emphasize different aspects of bonding.
authors.affiliation: Institut für Anorganische Chemie und Kristallographie, Fachbereich 2-Biologie/Chemie, Universität Bremen, Leobener Straße NW2, 28359, Bremen, Germany.|Current address: Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Hupf
authors.affiliation: Institut für Anorganische Chemie und Kristallographie, Fachbereich 2-Biologie/Chemie, Universität Bremen, Leobener Straße NW2, 28359, Bremen, Germany.|Centre of Supramolecular Organic and Organometallic Chemistry, Department of Chemistry, Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, 11 Arany Janos Street, 400028, Cluj-Napoca, Romania.
authors.forename: Marian
authors.initials: M
authors.lastname: Olaru
authors.affiliation: Centre of Supramolecular Organic and Organometallic Chemistry, Department of Chemistry, Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, 11 Arany Janos Street, 400028, Cluj-Napoca, Romania.
authors.forename: Ciprian I
authors.initials: CI
authors.lastname: Raţ
authors.affiliation: Institut für Anorganische Chemie und Kristallographie, Fachbereich 2-Biologie/Chemie, Universität Bremen, Leobener Straße NW2, 28359, Bremen, Germany.
authors.forename: Malte
authors.initials: M
authors.lastname: Fugel
authors.affiliation: Laboratory of Crystallography, University of Bayreuth, 95440, Bayreuth, Germany.
authors.forename: Christian B
authors.initials: CB
authors.lastname: Hübschle
authors.affiliation: Institut für Anorganische Chemie und Kristallographie, Fachbereich 2-Biologie/Chemie, Universität Bremen, Leobener Straße NW2, 28359, Bremen, Germany.
authors.forename: Enno
authors.initials: E
authors.lastname: Lork
authors.affiliation: Institut für Anorganische Chemie und Kristallographie, Fachbereich 2-Biologie/Chemie, Universität Bremen, Leobener Straße NW2, 28359, Bremen, Germany.
authors.forename: Simon
authors.identifier: http://orcid.org/0000-0002-3377-9474
authors.initials: S
authors.lastname: Grabowsky
authors.affiliation: Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Mebs
authors.affiliation: Institut für Anorganische Chemie und Kristallographie, Fachbereich 2-Biologie/Chemie, Universität Bremen, Leobener Straße NW2, 28359, Bremen, Germany.
authors.forename: Jens
authors.identifier: http://orcid.org/0000-0002-8548-1821
authors.initials: J
authors.lastname: Beckmann
keywords: bonding indicators; nucleophilic substitution; peri-interactions; reaction mechanisms; silicon