| Summary: | The ammonothermal synthesis of three ammoniates of indium, namely InAlF<sub>6</sub>(NH<sub>3</sub>)<sub>2</sub>, [In(NH<sub>3</sub>)<sub>6</sub>][AlF<sub>6</sub>], and [In<sub>2</sub>F(NH<sub>3</sub>)<sub>10</sub>]<sub>2</sub>[SiF<sub>6</sub>]<sub>5</sub> ∙ 2 NH<sub>3</sub> was successful from near-ammononeutral conditions in the presence of fluoride ions. Initially, all these compounds were obtained upon corrosion of the applied liner and crucible material Si<sub>3</sub>N<sub>4</sub>, which also contains small amounts of aluminum. The syntheses were performed in supercritical ammonia (<i>T</i> = 753 K, <i>p</i> up to 307 MPa). The crystal structures were solved and refined from single crystal X-ray diffraction intensity data. InAlF<sub>6</sub>(NH<sub>3</sub>)<sub>2</sub> crystallizes as a typical layer-type structure with corner-sharing [InF<sub>4</sub>(NH<sub>3</sub>)<sub>2</sub>]<sup>–</sup> and [AlF<sub>6</sub>]<sup>3−</sup> octahedra. [In(NH<sub>3</sub>)<sub>6</sub>][AlF<sub>6</sub>] features isolated [In(NH<sub>3</sub>)<sub>6</sub>]<sup>3+</sup> and [AlF<sub>6</sub>]<sup>3−</sup> octahedra. The crystal structure of [In<sub>2</sub>F(NH<sub>3</sub>)<sub>10</sub>]<sub>2</sub>[SiF<sub>6</sub>]<sub>5</sub> ∙ 2 NH<sub>3</sub> contains [(NH<sub>3</sub>)<sub>5</sub>In–F–In(NH<sub>3</sub>)<sub>5</sub>]<sup>5+</sup> octahedra doubles next to [SiF<sub>6</sub>]<sup>2−</sup> octahedra and ammonia molecules. All intermediates have strong hydrogen bonding systems. The results from vibrational spectroscopy are reported.
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