Coordination chemistry and catalysis with hemilabile oxygen-phosphorus ligands

Metal–dihydrogen and σ-bond coordination: the consummate extension of the Dewar–Chatt–Duncanson model for metal–olefin π bonding

Dielectric and acid−base bifunctional effects are elucidated in heterogeneous aminocatalysis using a synthetic strategy based on bulk silica imprinting. Acid−base cooperativity between silanols and amines yields a bifunctional catalyst for the Henry reaction that forms α,β-unsaturated product via quasi-equilibrated iminium intermediate. Solid-state UV/vis spectroscopy of catalyst materials treated with salicylaldehyde demonstrates zwitterionic iminium ion to be the thermodynamically preferred product in the bifunctional catalyst. This product is observed to a much lesser extent relative to its neutral imine tautomer in primary amine catalysts having outer-sphere silanols partially replaced by aprotic functional groups. One of these primary amine catalysts, consisting of a polar outer-sphere environment derived from cyano-terminated capping groups, has activity comparable to that of the bifunctional catalyst in the Henry reaction, but instead forms the β-nitro alcohol product in high selectivity (∼99%). Th...

Acid−Base Bifunctional and Dielectric Outer-Sphere Effects in Heterogeneous Catalysis: A Comparative Investigation of Model Primary Amine Catalysts

Durch die vor einigen Jahren gefundene photochemische Reaktion von n- und π-Donatoren mit Metallcarbonylen oder deren Derivaten kann man ein breites Spektrum neuer Metallcarbonyl-Derivate herstellen, welche thermisch nicht oder nur mit schlechten Ausbeuten zu erhalten sind. — Praparative Verfahren werden beschrieben. An ausgewahlten Beispielen wurde der Reaktionsmechanismus dieser photochemisch induzierten Substitutionsreaktionen aufgeklart und versucht, einen Einblick in die Polaritat der Metall-Liganden-Bindung zu erhalten. — Dieser Beitrag soll einen Uberblick uber die in letzter Zeit auf diesem Gebiet erschienenen Arbeiten geben.

Photochemische Substitutionen an Metallcarbonylen und deren Derivaten

Understanding the fate of an electronically excited molecule constitutes an important task for theoretical chemistry, and practical implications range from the interpretation of atto- and femtosecond spectroscopy to the development of light-driven molecular machines, the control of photochemical reactions, and the possibility of capturing sunlight energy. However, many challenging conceptual and technical problems are involved in the description of these phenomena such as 1) the failure of the well-known BornOppenheimer approximation; 2) the need for accurate electronic properties such as potential energy surfaces, excited nuclear forces, or nonadiabatic coupling terms; and 3) the necessity of describing the dynamics of the photoexcited nuclear wavepacket. This review provides an overview of the current methods to address points 1) and 3) and shows how time-dependent density functional theory (TDDFT) and its linear-response extension can be used for point 2). First, the derivation of Ehrenfest dynamics and nonadiabatic Bohmian dynamics is discussed and linked to Tully's trajectory surface hopping. Second, the coupling of these trajectory-based nonadiabatic schemes with TDDFT is described in detail with special emphasis on the derivation of the required electronic structure properties.

Trajectory‐Based Nonadiabatic Dynamics with Time‐Dependent Density Functional Theory

Infrared Spectra and Structures of Metal Carbonyl Derivatives. III. Acetylene and Olefin Derivatives of Group VI Metal Carbonyls

Publisher Summary This chapter discusses coordinately bonded derivatives In the years following World War II, the increasingly large body of experimental data inconsistent with widely held beliefs led to a reassessment of the mechanism of bonding in certain transition metal complexes Common characteristics in complexes exhibiting anomalous behavior are the availability of filled metallic d orbitals and of vacant ligand orbitals with which they could interact The accepted bonding mechanism may be exemplified by consideration of bonding in the octahedral metal carbonyls, for example, Cr(CO)6 The chapter discusses anionic derivatives The anionic derivatives of the group VIB metal carbonyls may be classified (a) Carbonyl metallate ions M(CO)52–, M2(CO)I02–, M3(CO)142–, and possibly higher homologs in which the metal atoms are joined by metal-metal bonds; (b) complex products of the base reactions of the hexacarbonyls, many of which are polynuclear and contain hydroxo or other bridging groups, some of which can be precipitated as the hydrides with strong acids; and (c) Mixed complexes of the zerovalent metal carbonyls and anionic substituents The chapter reviews the π-Arene derivatives of the group VIB metal carbonyls

Ingo W. Stolz

Papers

Infrared Spectra and Structures of Metal Carbonyl Derivatives. III. Acetylene and Olefin Derivatives of Group VI Metal Carbonyls

Substitution Products of the Group VIB Metal Carbonyls

Evidence for the Existence of Group VI Metal Pentacarbonyls

The Infrared Spectrum and Evidence for the Structure of a New Metal Carbonyl

Photochemical Formation of Some Metal Hexacarbonyl-Acetonitrile Derivatives