Scandium nitrides

Other Binary Compounds.—Scandium nitride and zirconium and titanium carbide do not conform with the theoretical radii. It is possible that these crystals do not consist essentially of Sc+3, N 3, Ti+4, Zr+4 and C-4 ions, especially since zirconium and titanium nitride, ZrN and TiN, also form crystals with the sodium chloride structure but possibly also the discrepancy can be attributed to deformation of the anions, which have very high mole refraction values. 

Neutral Ny is (like N5) a radical and so is likewise not expected to be reasonably stable. In an experiment of some relevance to Ny, laser-ablated scandium atoms were codeposited with argon/nitrogen at 10 K (the purpose was to study scandium nitride species) [16]. The reported IR spectra gave no indicahon of the presence of a compound with an Ny ring coordinated to scandium, a compound which has been predicted by computational methods to have a fair chance of existing [17]. 

FIGURE 11 An endohedral scandium nitride fullerene cluster (25). 

Travaglini et al. (1986) obtained pure scandium nitride ScN with such perfect stoichiometry and stability that the single crystals could be boiled for hours in a mixture of HNO3 and H2SO4 before being dissolved. ScN exhibits metallic behavior, having a carrier concentration of about 10 cm" at room temperature. A band-structure calculation was performed by Monnier et al. (1985). 

The borderline between cluster and valence compounds is clearly crossed with the scandium nitride chlorides which are unambiguously cluster compounds. Scandium shows here its difference in behavior, with compounds such as SC4CI6N, SC7CI12N (Hwu and Corbett 1986) or ScsClgN (Hwu et al. 1987), where nitrogen is an interstitial element. 

Up to 1999, only metal atoms [1-5], metal clusters [6,7], metal nitrides [55-57], and noble gas atoms [58-60] were observed to be encaged inside C60, C70, or various sizes of higher fullerenes. The experimental evidence for carbon atoms or metal-carbon compounds (carbides) being encapsulated inside fullerenes had not yet been observed. In 2000, Shinohara et al. succeeded in the first production, isolation, and spectroscopic characterization of a scandium carbide endohedral fullerene (Sc2C2) C84. Following this, the first experimental evidence based on synchrotron X-ray diffraction was presented and revealed that the Sc carbide is encapsulated in the form of a lozenge-shaped Sc2C2 cluster inside the D2d-C84 fullerene [8]. 

The volatile metal amido compounds M(NR2)X are potential precursors for solid-state materials such as metal nitrides. The metal amido compounds have also become very important synthetic starting materials for many types of compounds. The low coordination of these compounds often allows addition of molecules with suitable donor ligands. The relatively weak M—N bond allows the NR2 group to be replaced by other groups and in the case of scandium and yttrium the M—O bond is much stronger than the M—N bond. 

Hwu, S.-J., Ziebarth, R. P., von Winbush, S., Ford, J. E. Corbett, J. D. (1986). Synthesis and Structure of Double-Metal-Layered Scandium, Yttrium, and Zirconium Chloride Carbides and Nitrides, M2CI2C and M2CI2N, Inorg. Chem. 25, 283-287. 

Scandium ternary nitrides 64 4.3.2. Pyrochlore-type structure 86... 

Interstitial nitrides. Nitrided alloys 3.4.1. Scandium ternary nitrides... 

The two scandium ternary nitride phases ScTaNi- and ScNbN x were commonly prepared by nitridation of Sc—Ta (Lengauer and Ettmayer 1988) or Sc-Nb alloys in... 

---