Mild Hydrothermal Synthesis of the Complex Hafnium-ContainingFluorides Cs 2 [M(H 2 O) 6 ][Hf 2 F 12 ] (M = Ni, Co, Zn), CuHfF 6 (H 2 O) 4 , and Cs 2 Hf 3 Mn 3 F 20 Based on HfF 7 and HfF 6 CoordinationPolyhedra

A series of new Hf(IV)-containing fluorides with three different compositions, Cs2[M(H2O)6][Hf2F12] (M = Ni, Co, Zn), CuHfF6(H2O)4, and Cs2Hf3Mn3F20, were synthesized as high-quality single crystals via a mild hydrothermal route. The compounds with compositions of Cs2[M(H2O)6][Hf2F12] (M = Ni, Co, Zn) and CuHfF6(H2O)4 crystallize in the monoclinic space groups P21/n and P21/c, respectively, while the Cs2Hf3Mn3F20 phase crystallizes in the orthorhombic space group Pmmn. Cs2[M(H2O)6][Hf2F12] (M = Ni, Co, Zn) exhibits a complex three-dimensional (3D) crystal structure consisting of edge-sharing dimers of HfF7 polyhedra, which are linked to the divalent metal octahedra via hydrogen bonding. Cs2Hf3Mn3F20 features corner-sharing HfF7 and MnF7 dimers as well as isolated MnF6 octahedra, while the CuHfF6(H2O)4 phase exhibits a 3D structure that consists of HfF6 octahedra linked with neighboring copper octahedral units by hydrogen-bonding interactions. UV–vis spectra of the title compounds were collected and exhibi...