Exchange of ammine- and fluorido-ligands in complex salts: The series [Cr(NH3)6][AlF6], [Cr(NH3)5F][SiF6] and K2[Cr(NH3)4F2][Si(NH3)0.5F5.5]2

The three amminechromium(III) complex compounds [Cr(NH3)(6)][AlF6], [Cr(NH3)(5)F][SiF6] and K-2[Cr(NH3)(4)F-2][Si(NH3)(0.5)F-5.5](2) were obtained from ammonothermal synthesis at T-max=724 K and p(max)=2120 bar. Crystal structures were determined from single crystal X-ray diffraction. The gradual exchange of ammine ligands by fluoride ligands in the amminechromium(III) ions is reflected by an intriguing change in color. The mutual ligand exchange between ammonia ligands and fluoride ions occurs in both the cations and the anions, indicating the various dissolved species present under the synthetic conditions.