ScPdSi- crystal structure and Si/Sc solid state MAS NMR spectroscopic investigations.

The silicide ScPdSi was synthesized from the elements by arc-melting. Its structure was refined from single crystal X-ray diffractometer data: Immm, LiCuP type, a = 397.12(6), b = 945.4(1), c = 1314.4(2) pm, wR = 0.0245, 578 F values and 29 parameters. The palladium atoms have slightly distorted tetrahedral silicon coordination and a condensation of these PdSi tetrahedra leads to a two-dimensional substructure which is condensed via Si pairs (234 pm Si-Si), forming the [PdSi] polyanionic network. The ScPdSi structure contains three crystallographically independent scandium sites with coordinations Sc1@PdSiSc, Sc2@PdSiSc and Sc3@PdSiSc. ScPdSi is a Pauli paramagnet with a low susceptibility of 2.9(5) × 10 emu mol at room temperature. The Si MAS-NMR spectrum confirms the presence of two crystallographically distinct sites in a 2 : 1 ratio. Likewise, the three crystallographic scandium sites are well-differentiated by three Sc MAS NMR signals in the expected 2 : 2 : 1 ratio. Unambiguous assignments could be made based on the comparison of the nuclear electric quadrupolar coupling parameters with predicted values from WIEN2k calculations.