Synthesis of the scandium chloride hydrates ScCl3•3H2O and Sc2Cl4(OH)2•12H2O and their characterisation by X-ray diffraction, 45Sc NMR spectroscopy and DFT calculations

The compounds ScCl3 center dot 3H(2)O (SCTH) and [{Sc(H2O)(5)(mu-OH)}(2)]Cl-4 center dot H2O (SCOH), have been synthesised and characterised by single-crystal XRD, Sc-45 NMR spectroscopy and DFT calculations, with the crystal structure of SCTH reported here for the first time. From Sc-45 NMR measurements under static and MAS conditions, both chemical shift and quadrupolar coupling parameters have been determined. The quadrupolar coupling constants chi for the octahedrally coordinated scandium sites in SCTH are 2.0 +/- 0.1 MHz for Sc(1) and 3.81 +/- 0.05 MHz for Sc(2). For SCOH, where the hepta- coordination of the single scandium site constitutes a less symmetric electronic environment, 14.68 +/- 0.05 MHz was found. DFT calculations for the static SCTH structure consistently overestimate the quadrupolar coupling constants, indicating the possible presence of crystal water dynamics on the NMR time scale.