Ammonothermal Synthesis and Characterization of First Amidozincate Hydroxides

Abstract

The first alkali metal amidozincate hydroxides Na 3 [Zn(NH 2 ) 4 ](OH) and Na 3 [Zn(NH 2 ) 3 ](OH) 2 were obtained from supercritical ammonia under ammonobasic conditions at 823 K and 250 MPa, and 623 K and 159 MPa, respectively. Crystal structures have been refined against single crystal X-ray diffraction intensity data. Coordination environments of the cations as well as the rather open crystal structure and low density of Na 3 [Zn(NH 2 ) 4 ](OH) suggest the initial formation of a monoammoniate, prior loss of ammonia during depressurizing and recovery of the product.While Na 3 [Zn(NH 2 ) 4 ](OH) contains mutually isolated amidozincate ions next to hydroxide ions, Na 3 [Zn(NH 2 ) 3 ](OH) 2 is the first amidozincate realizing a condensation of the complex anionic substructure so far. Both compounds are regarded possible intermediates in an ammonothermal zinc nitride synthesis and give insights into the action of impurities during ammonothermal processes. Raman spectroscopic measurements support the assignment of amide and hydroxide groups.