Bond Analysis Of Metal-Element Interactions In Molecules And Solids Applying Embedding And Density Functional Techniques

Description

Dissertation Zur Erlangung des naturwissenschaftlichen Doktorgrades der Julius-Maximilians-Universität Würzburg. Deutchland, Würzburg, 2009. – 189 p.Since Lewis’ electronic structure revolution, many exceptional and intriguing bonding situations have been discovered, among them agostic, multi-centered, metallic, dispersive, aromatic, anti-aromatic and multiple bonding up to quintuple bonds etc. The interaction between metal atoms and light main-group elements, especially carbon, has been of general interest ever since and determines the chemical behavior of a complete section of chemistry: organometallics. Not only because of the broad applicability of organometallic compounds in e.g. catalysis or bio-inorganicchemistry, but also due to their complicated electronic structure and intriguing bonding situations, the metal–non-metal bond has been of broad interest for all kinds ofchemists. Within this thesis two sub-classes of organometallics are investigated: I) transition-metal complexes, with a focus on carbene and borylene species, and II) lithium-organic compounds, especially methyl derivatives.Concurrently with the discovery of novel bonding situations, a plethora of methods have been developed to classify, describe and understand the chemical bond. The valence bond (VB) and molecular orbital (MO) theories have risen as two independent concepts to describe a broad range of bonding situations, both promoted by rivaling groups of supporters. However, the many useful schemes, which are available for the analysis of the chemical bond, may emphasize different aspects of bonding and hence yield varying chemical interpretations. One category focuses on the electronic restructuring accompanying the bond formation process, namely the natural bond orbitals, the atoms in molecules approach or the electron localization function, along with many variants of population schemes. A second group is based on the decomposition of the bond energy into chemically significant contributions, for instance the Kitaura-Morokuma approach or the extended transition state scheme.In the following first part of this thesis, the basic formalism, applicability and shortcomings of the herein applied theoretical and quantumchemical tools are presented. Density functional theory is introduced, since it is the underlying technique used to obtain the molecular charge density that can be evaluated by bond analysis tools.ContentsIntroduction and Theoretical BackgroundIntroductionFoundations of Density Functional TheoryFundamentals: the Schrödinger Equation and the Hartree-Fock ApproximationFrom Hohenberg-Kohn theorems to the Kohn-Sham approachThe Hohenberg-Kohn TheoremsThe Kohn-Sham ApproachFunctionals and Electron Holes – on LDA, GGA and HybridsDensity Matrices and Electron HolesModern FunctionalsShortcomings of the DFT ApproachIntroduction to Density-Based Topological ToolsThe Quantum Theory of Atoms in MoleculesBasic FormalismShortcomings, Criticism and DevelopmentsReal Space Functions for the Description of Electron LocalizationThe Electron Localization FunctionThe Electron Localizability IndicatorComparison and CriticismChemical Bonding in Transition Metal CompoundsIntroductionBonding Patterns in Dinuclear Iron Complexes – an Overview of Metal–Metal InteractionsComputational DetailsBridged-to-Terminal Metamorphosis in Fe2CO9Metal–Metal Interactions in Supported Diiron ComplexesConclusionsExtension of the Fischer/Schrock ConceptComputational DetailsFischer and Schrock CarbenesComparison between Singlet and Triplet Borylenes and CarbenesExemplary Fischer- and Schrock-type Borylene ComplexesOutlookDependency of AIM and ELF Results for Bonding Analyses on Exchange Correlation FunctionalsComputational DetailsOptimized StructuresQTAIM AnalysisELF AnalysisConclusionsStructure and Bonding in Supported Dinuclear Cobalt and Nickel Borylene ComplexesCompuational DetailsExperimental Background and Structure DeterminationBonding AnalysisConclusionsMain Group Metals: Li–C Bonding and Intermolecular Interactions in Methyl LithiumIntroductionAggregation of LiR – Structure Forming PrinciplesPrevalent Bonding Concepts in Organolithlium CompoundsComputational MethodsPeriodic SimulationsBasic FormalismGaussian Basis Sets in Solid State CalculationsEmbedding TechniquesPolarizable Continuum ModelsPeriodic Electrostatic Embedded Cluster ModelValidation of Embedding Techniques for Modeling Environmental Effects in Polar Organolithium CompoundsComputational DetailsEmbedded Cluster CalculationsSolid State CalculationsFunctionalsBasis SetsQM Cluster DefinitionsLocation of BCPs and AIM Basin IntegrationModeling Solid State Effects in MeLiConclusionsUnderstanding the Structure-Reactivity Relationship of Methyllithium Base AdductsComputational DetailsStructure Formation and Agostic InteractionsExperimental Background and X-Ray Structure DeterminationOptimized StructuresAgostic InteractionsElectronic Structure AnalysisGeneral Aspects of Li–C Bonding in MeLi Clusters and AdductsPolarity Changes upon Deaggregation and Lewis Base CoordinationConclusionsSummarySummaryZusammenfassungReferencesAppendix AAppendix BAppendix CList of CompoundsList of PublicationsDanksagung