A theoretical study on the existence and structures of some hypothetical first-row transition-metal M(NCN) compounds

Abstract

The family of quasi-binary cyanamides/carbodiimides of general formula M(NCN) containing divalent 3d transition metals (M = Mn, Fe, Co, Ni and Cu) has been studied by density-functional means; until now, such light transition-metal compounds have not yet been prepared. Twenty-eight structural models have been considered based on known compounds having NCN2- and other tri-atomic anionic entities (e. g., thiocyanates). After performing LDA geometry optimizations, the relative energetic orderings are interpreted in terms of geometrical factors such as molar volumes and effective coordination numbers; dense structures with octahedral metal coordinations and high-spin electronic configurations are to be expected, especially for the earlier metals (Mn and Fe). Based on GGA total-energy calculations, there is a chance to synthesize these enthalpically unstable compounds, not from the elements but via appropriate exchange reactions employing fairly stable cyanamide/carbodiimide precursors and yielding stable or volatile metal halides which can be removed from the chemical equilibria. © 2005 Verlag der Zeitschrift für Naturforschung.