The Utilization of Solid State Chemistry Reaction Routes as New Syntheses Strategies for the Coordination Chemistry of Rare Earth Amides

Abstract

Solvent free high-temperature reactions in melts are well known procedures in Solid-State Chemistry. Although the reaction conditions are extreme considering the properties of organic ligands they can also be utilized for Coordination Chemistry and offer a fruitful alternative to usual solvent treatments. This includes the chemistry of organic amides of the rare earth elements. The avoidance of any solvent renders novel homoleptic complexes accessible but also implies difficulties bound to the solid state of the reaction mixtures. The high chemical affinity of the rare earth elements towards halides and especially oxygen limits known homoleptic amides obtained via solvent treatments mostly to multi-chelating ligands like porphyrines, calix-pyrroles etc. With no special conditions met like a high steric demand, solvent molecules as cocoordinating partners enforce the formation of heteroleptic species. This influence can be avoided by the use of completely solvent free reactions, such as melt reactions in which a solid is reacted directly with a melt or with a substance under solvothermal conditions. The high reactivity of the rare earth metals allows the direct oxidation with amines and thus to use high-temperature reactions for the formation of rare earth amides. This includes homoleptic com- Die Anwendung Festkörper-chemischer Synthesemethoden als neue Synthesestrategie für die Koordinationschemie von Selten-Erd-AmidenInhaltsübersicht. Solvensfreie Reaktionen bei hohen Temperaturen sind gut bekannte Vorgehensweisen in der Festkörperchemie. Obgleich die Reaktionsbedingungen extrem bezüglich der Eigenschaften organischer Liganden sind, können sie für die Koordinationschemie genutzt werden und bieten eine Erfolg versprechende Alternative zu gewöhnlichen Reaktionen in Lösungsmitteln. Dies schließt die Chemie organischer Selten-Erd-Amide ein. Die Vermeidung jedweder Lösemittel macht neuartige, homoleptische Komplexe zugänglich, sie bringt aber auch Schwierigkeiten mit sich, die mit dem festen Zustand des gesamten Reaktionsgemenges verbunden sind. Die hohe chemische Affinität der Selten-Erd-Elemente zu den Halogenen und allen voran zu Sauerstoff beschränkt die Bildung homoleptischer Amide zumeist auf die Verwendung multichelatisierender Liganden, wie z.B. mit Porphyrinen oder Calix-Pyrrolen. So keine besonderen Bedingungen wie ein hoher sterischer Anspruch eingehalten werden, erzwingen Solvens-Moleküle als co-koordinierende Teilchen die Bildung von heteroleptischen Verbindungen. Dieser Einfluss kann vermieden werden, wenn stattdessen vollständig solvensfreie Synthesen durchgeführt werden. Gerade die Schmelzsynthese bietet solche Möglichkeiten, da ein Feststoff direkt mit einer Schmelze reagiert oder mit einer Substanz unter solvothermalen Bedingungen. Die hohe Reaktivität der Metalle erlaubt deren direkte Oxidation mit Aminen und damit, derar-811pounds from simple ligands. Crystallization under reaction conditions is possible; no re-crystallization step is necessary preventing the risk of a change of the chemical char...

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