On New Alkaline Sulfatometallates: Cs ₆ [(WO ₂ ) ₂ O(SO ₄ ) ₄ ], K ₈ [(MoO ₂ ) ₂ (SO ₄ ) ₆ ], K _7.9 Sr _0.1 [(WO <sub>2

The new sulfatotungstate Cs 6 [(WO 2 ) 2 O(SO 4 ) 4 ] exhibits a hitherto unknown anion with an unusual W–O–W angle of 180° and edge‐sharing WO 6 and SO 4 polyhedra. It crystallises in the monoclinic space group P 2 1 / c (no. 14) with Z = 2, determined by single‐crystal X‐ray diffraction. K 8 [(MoO 2 ) 2 (SO 4 ) 6 ] and K 7.9 Sr 0.1 [(WO 2 ) 2 (SO 4 ) 6 ] crystallise isotypic to each other in the monoclinic space group P 2 1 / n (no. 14) with Z = 2. Na 4 [MoO 2 (SO 4 ) 3 ] crystallises in the orthorhombic non‐centrosymmetric space group P 2 1 2 1 2 1 (no. 19) with Z = 4, confirmed by second harmonic generation measurements. UV–vis measurements show a bright absorption below 400 nm for all compounds due to the ligand‐to‐metal charge transfer (LMCT) in tungstate and molybdate moieties. In the fluorescence spectra Cs 6 [(WO 2 ) 2 O(SO 4 ) 4 ], K 8 [(MoO 2 ) 2 (SO 4 ) 6 ] and K 7.9 Sr 0.1 [(WO 2 ) 2 (SO 4 ) 6 ] show an emission of the LMCT. Further, all compounds were characterised by FT‐IR spectroscopy and thermogravimetric analysis. Latter reveals remarkably high thermal stabilities, especially for Cs 6 [(WO 2 ) 2 O(SO 4 ) 4 ].