Sn[B2O3F2]—The First Tin Fluorooxoborate as Possible NLO Material

Abstract Herein, the crystal structure as well as second‐harmonic‐generation (SHG), thermal and spectroscopic properties of Sn[B 2 O 3 F 2 ] (TFB = tin‐fluorooxo‐borate) are presented. TFB adopts a novel non‐centrosymmetric crystal structure, which is determined by single‐crystal X‐ray diffraction (XRD) ( P 31 m , Z = 1, a = 4.5072(2) Å, c = 4.7624(3) Å) and comprises [B 2 O 3 F 2 ] 2− layers consisting solely of BO 3 F tetrahedra; the covalent BF bonds are unequivocally localized via solid‐state NMR spectroscopy as well as density functional theory (DFT) calculations. TFB is insensitive to air and moisture, shows a stronger SHG intensity than K[H 2 PO 4 ] (KDP) and a bandgap of ≈5 eV. The thermal decomposition yields two new borate fluorides.