Reaktionen mit Cyanamiden und die Bildung von Cyanamiden der Selten-Erd- und der Übergangsmetalle
Zusammenfassung der Projektergebnisse
An explorative expedition on the application of SSM reactions has been demonstrated for syntheses of many new compounds and families of compounds. SSM reactions for preparations of carbodiimides and tetracyanamidosilicates ignite when the starting materials are being heated up above temperatures between 400 and 550 °C to form mostly air stable compounds that are being purified from the coproduced salt (LiCI) by washing with water. The choice and the high purity of starting materials are most important in SSM reactions. Covalently bound anions can remain intact during reactions and may even transform to yield dimeric or trimeric anions. In addition, ions may be combined to form larger anionic units or to form mixed anion compounds. A broad chemistry of nitridoborates involves several different anions ((BN)n-, {BN2)3- (BN3)6- (B2N4)8-, (B3N6)9-) and combinations thereof being combined in structures. Reactions designed to synthesize higher carbon nitride anions such as the expected carbonate analogue (CNs)^ or the oxalate analogue (C2N4)6- failed In favour of compounds being formed with the carbodiimide ion. Reactions can be controlled by the choice of starting materials and their compositions being used in reactions in order to reach for an intended material. The course of a reaction can be controlled via analytical studies by monitoring thermal effects such as the exothermic effect related to the ignition temperature and the melting temperature with the coproduced salt. However, these parameters may be considerably altered when a reactive flux is being used. In addition, it may be regarded that reactions may proceed even below the ignition temperature with expectedly slower speed. In case of the formation of a carbon nitride material a slow reaction progress even allowed the isolation of intermediate products being formed during the successive condensation reaction below Tj. Compound classes such as carbodiimides and tetracyanamidosilicates could be developed empirically by rational SSM reactions. The knowledge and experience from these reactions can be certainly transferred onto new systems. However, important questions regarding the course of SSM reactions still must be studied in more detail.
