Crystals of two new hexammoniates, namely, [Ga(NH3)6]I3·NH3 and [Ga(NH3)6]Br3·NH3, were grown from liquid ammonia solutions of GaI3 and GaBr3 in a wide temperature range. The known compound [Ga(NH3)5Cl]Cl2 and the new triammoniate of gallium fluoride Ga(NH3)3F3 were obtained ammonothermally during the synthesis of GaN from NH4Cl and NH4F, respectively. The compounds are characterized by crystallographic parameters derived from their X-ray diffraction data. The crystal structures of all the ammoniates feature octahedrally coordinated Ga atoms in complex ions of the general form [Ga(NH3)6–nXn](3–n)+ (n = 0, 1, 2, 4; X = F, Cl, Br, I). The extensive N–H···X hydrogen bonding networks in these compounds are analyzed. The IR and Raman spectroscopy data for [Ga(NH3)6]X3·NH3 (X = Br, I) and Ga(NH3)2F3 are provided, and the IR spectrum of Ga(NH3)3F3 is compared with those published for the monoammoniate Ga(NH3)F3 and the diammoniate Ga(NH3)2F3. Finally, the thermal deamination features of [Ga(NH3)6]X3·NH3 (X = Br, I) and Ga(NH3)3F3 are also discussed.
Invited for the cover of this issue is the group of Rainer Niewa from the Institute of Inorganic Chemistry of the University of Stuttgart. The cover image illustrates several gallium-containing species as possible intermediates of GaN crystal growth in supercritical ammonia under ammonoacidic conditions as well as crystals of solid compounds recovered from ammonia.
