In coordination chemistry, the first coordination sphere refers to the array of molecules and ions (the ligands) directly attached to the central metal atom. The second coordination sphere consists of molecules and ions that attached in various ways to the first coordination sphere.
The first coordination sphere refers to the molecules that are attached directly to the metal. The interactions between the first and second coordination spheres usually involve hydrogen-bonding. For charged complexes, ion pairing is important.
In hexamminecobalt(III) chloride ([Co(NH3)6]Cl3), the cobalt cation plus the 6 ammonia ligands comprise the first coordination sphere. The coordination sphere of this ion thus consists of a central MN6 core "decorated" by 18 N−H bonds that radiate outwards.
Metal ions can be described as consisting of series of two concentric coordination spheres, the first and second. More distant from the second coordination sphere, the solvent molecules behave more like "bulk solvent." Simulation of the second coordination sphere is of interest in computational chemistry. The second coordination sphere can consist of ions (especially in charged complexes), molecules (especially those that hydrogen bond to ligands in the first coordination sphere) and portions of a ligand backbone. Compared to the first coordination sphere, the second coordination sphere has a less direct influence on the reactivity and chemical properties of the metal complex. Nonetheless the second coordination sphere is relevant to understanding reactions of the metal complex, including the mechanisms of ligand exchange and catalysis.
Mechanisms of metalloproteins often invoke modulation of the second coordination sphere by the protein.
The rates at which ligands exchange between the first and the second coordination sphere is the first step in ligand substitution reactions. In associative ligand substitution, the entering nucleophile resides in the second coordination sphere. These effects are relevant to practical applications such as contrast agents used in MRI.
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The course will provide a synopsis of the chemistry of f elements (lanthanides and actinides) covering structure, bonding, redox and spectroscopic properties and reactivity. The coordination and organ
Ce cours présente les fondements du droit foncier et les apports des principaux instruments de gestion foncière pour la mise en œuvre du développement territorial.
Le cobalt est l'élément chimique de numéro atomique 27, de symbole Co. Le cobalt de structure électronique [Ar] 4s2 3d7 est le second élément du huitième groupe secondaire, ce métal de transition fait partie du groupe du fer. Le corps simple cobalt a des propriétés physiques assez voisines de celles du fer et du nickel. D'un point de vue chimique, il est moins réactif que le fer. Le cobalt est aussi un élément du groupe 9, dont les trois premiers Co, Rh et Ir constituent le groupe du cobalt.
redresse=.67|vignette|Exemple de complexe aqua octaédrique. En chimie de coordination, un complexe aqua est un complexe de coordination homoleptique formé d'un ion métallique et de molécules d'eau coordonnées comme ligands. Ces complexes sont l'espèce prédominante des solutions aqueuses de nombreux sels métalliques tels que les nitrates, sulfates et perchlorates. Ils ont pour formule générale . Leurs propriétés sous-tendent de nombreux aspects de la chimie environnementale, biologique et industrielle.
A metal ion in aqueous solution or aqua ion is a cation, dissolved in water, of chemical formula [M(H2O)n]z+. The solvation number, n, determined by a variety of experimental methods is 4 for Li+ and Be2+ and 6 for most elements in periods 3 and 4 of the periodic table. Lanthanide and actinide aqua ions have higher solvation numbers (often 8 to 9), with the highest known being 11 for Ac3+. The strength of the bonds between the metal ion and water molecules in the primary solvation shell increases with the electrical charge, z, on the metal ion and decreases as its ionic radius, r, increases.
Examine la gestion foncière, le droit de la propriété, la coordination avec les municipalités et les défis liés aux projets d'aménagement du territoire.
Explore la dynamique du travail d'équipe, en mettant l'accent sur les commentaires, la collaboration et les expériences d'apprentissage au sein d'une équipe.
Discute de l'organisation des assistants de cours, en mettant l'accent sur les responsabilités, la coordination et l'interaction des élèves pendant les exercices.
Communities are shared areas on the Zenodo platform where projects, institutions, domains, and conferences can curate and manage their research outputs. An EPFL community https://zenodo.org/communities/epfl was created in 2013, mainly as a light-weight sol ...
2024
Cupredoxins are widely occurring copper-binding proteins with a typical Greek-key beta barrel fold. They are generally described as electron carriers that rely on a T1 copper centre coordinated by four ligands provided by the folded polypeptide. The discov ...
The combination of palladium salts and bipyridyl ligands can lead to the formation of a large variety of coordination complexes, with different shapes and sizes, displaying a very versatile host-guest chemistry. Increasing their structural complexity remai ...