Synthesis and properties of N₃ and CN delivery compounds and related precursors for nitride and ceramic fabrication

The simple azido and cyano compounds Cl₂AsN₃, Br ₂AsN₃, (C₆H₅)SiH₂N ₃, (C₆H₅)SiH₂CN and p-(tolyl)SiH₂CN have been prepared for the first time by metathesis reactions involving the corresponding halides and NaN₃, LiN ₃ and LiCN. These compounds represent a highly reactive and efficient family of delivery reagents for the preparation of N₃ and CN molecular precursors to bulk ceramics and nitride thin films. They are isolated as low volatility liquids and characterized by spectroscopic methods and chemical analysis. Ab initio simulations were used to elucidate the structural and vibrational properties of the simpler, fully inorganic Cl ₂AsN₃ and Br₂AsN₂ species. This theoretical treatment was extended to include the hypothetical H ₂AsN₃ and HClAsN₃ derivatives which are particularly desirable as single-source low-temperature As-N sources for the formation of highly sought after, metastable GaAs_1-xN_x materials for solar cell applications. The practical utility of the title molecules is also demonstrated by synthesizing several representative compounds of B, Be, Ga and Al, which are of interest for the development of open frameworks, optoelectronic nitrides and refractory B-C-N hybrids. The cyanide derivatives (C₆H₅)SiH₂CN and p-(tolyl)SiH ₂CN react readily with Be and B halides to yield crystalline Be(CN)₂ and amorphous B-C-N. The latter is crystallized upon heating to form graphite-like polymorphs with homogeneous nanoscale morphologies. The azide derivatives Cl₂AsN₃, Br₂AsN₃ and (C₆H₅)SiH₂N₃ react readily with GaBr₃, GaCl₃ and BBr₃ to produce high yields of the previously reported Br₂GaN₃, Cl₂GaN ₃ and Br₂BN₃, respectively. The latter is shown to possess a trimeric molecular structure in which the α-nitrogen of the azide group bridges the boron atoms to form cyclohexane-like B₃N ₃ rings.