Metal subnitrides

Table 3.1-1 summarizes the crystallographically characterized group 1 metal suboxides, and group 2 metal subnitrides, the latter containing additional alkali or other metals [25]. 

Alkali and Alkaline Earth Metal Suboxides and Subnitrides... 

The alkali metal suboxides are well understood in terms of formation, structure, and properties, yet we still face some unsolved problems that will also be addressed in the following. In contrast, the first suboxide of barium came to light only recently [24], and one has to see whether this compound is the tip of another iceberg, as turned out to be the case with the subnitrides of alkaline earth metals. 

Tab. 3.1-1. Structurally characterized suboxides and subnitrides of alkali and alkaline earth metals, respectively, Z refers to the structural formula.

The structural principle of combining salt-like bonded units with stoichiometric amounts of alkali metal in the structure of Ba2ONa is equivalent to that which characterizes the alkali metal suboxides as well as the subnitrides of alkaline earth metals, such that a variation at least according to a general formula [Ba20 Na% can be expected. Indeed, there are indications of the existence of further suboxides in... 

The structural principle of alkali metal suboxides has been unique for many years. Early attempts to synthesize cluster-type subnitrides of Ba resulted in the only compound, Ba2N, that is isotypic with Ca2N. Beyond these, the Sr analogue Sr2N, and most recently Sr4N3 [34], have been characterized. 

All suboxides and subnitrides described in the preceding sections are metallic. In the case of the alkali metal suboxides this property has been demonstrated by measurements of the electrical conductivity [58], CS7O, for example, exhibits a free electron like behavior in the temperature dependence of its resistivity rather similar to the element Cs itself. The characteristic colors of the alkali metal suboxides have been mentioned before, and spectroscopic investigations to be discussed in the following provide a more quantitative access to the metallic properties and the underlying chemical bonding. 

A. Simon, Alkali and alkaline earth metal suboxides and subnitrides. In M. Driess and H. Noth (eds.), Molecular Clusters of the Main Group Elements, Wiley-VCH, Weinheim, 2004, pp. 246-66. 

TaN (17) A Ta metal rod in a water cooled crucible Transfered arc. N. 1-4 20-120 80 Powders are condensed on Mainly TaN, some Ta 1.9 to 9.6 a water-cooled coil subnitrides, Ta placed arround the reaction zone 277) (1966)... 

No stable, well-defined complexes with group 1 metal - metal single bonds are known to date, though related alkalide [41,42] and electride [41,43-45] compound classes with formal low oxidation state group 1 metals have been studied, and some alkali metal suboxide and subnitride materials are... 

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