Single-Crystal Structures and Vibrational Spectra of Li[SCN] and Li[SCN] · 2H₂O

Abstract

The crystal structure of Li[SCN] · 2 H 2 O has been determined by single-crystal X-ray diffraction on commercially available material. Crystals of this compound are colorless, transparent and hygroscopic. Li[SCN] · 2H 2 O adopts the orthorhombic space group Pnma with the cell parameters a = 572.1(3), b = 809.3(4) and c = 966.9(4) pm and Z = 4. Li[SCN] was obtained by dehydration of the afore-mentioned dihydrate and also crystallizes orthorhombically in Pnma with the lattice parameters a = 1215.1(3), b = 373.6(1) and c = 529:9(2) pm (Z = 4). Both compounds contain Li+ cations in sixfold coordination. Four water molecules and two nitrogen-attached thiocyanate anions [SCN]- arrange as trans-octahedra [Li(OH 2 ) 4 (NCS) 2 ] - in the case of Li[SCN] · 2 H 2 O. Anhydrous Li[SCN] displays fac-octahedra [Li(NCS) 3 (SCN) 3 ] 5- with six thiocyanate anions grafting via both nitrogen and sulfur atoms, three each. Infrared and Raman spectra of both compounds were recorded and a DSC=TG measurement was performed on Li[SCN] · 2 H 2 O.