Formation of the Sub-oxide Sc 4 Au 2 O 1- x and the Drastically Negative 27 Al NMR Shift in Sc 2 Al

During attempts to synthesize Sc AuAl in the cubic Gd RhIn-type structure, the solid solution Sc Au Al in the PbCl -type structure formed instead. Subsequently, the solid solution Sc Au Al was investigated with respect to its existence range along with the structure types formed for different compositions with = 0, 0.25, 0.5, 0.75, and 1. According to X-ray powder diffraction studies, Sc Al and nominal Sc Au Al crystallized in the hexagonal Ni In-type structure ( 6 / ), while Sc Au Al , Sc Au Al , and Sc Au were found to crystallize in the orthorhombic PbCl -type structure ( ). The crystal structures of Sc Au and Sc Au Al were refined from single-crystal data (Sc Au: = 648.0(1), = 467.2(1), = 835.2(2) pm, 2 = 0.0382, 535 values, 25 variables; Sc Au Al : = 632.48(5), = 472.16(3), = 848.67(6) pm, 2 = 0.0484, 540 values, 21 variables). Contamination with air during the synthesis of Sc Au led to the discovery of a compound adopting the cubic W Co C-type structure (stuffed cubic Ti Ni type). Using Sc O as a defined oxygen source led to samples with high amounts of Sc Au O . All intermetallic compounds exhibited paramagnetic behavior in the investigated temperature range of 2.1 to 300 K, and no superconductivity was observed at low temperatures and low fields. Sc Au and Sc Al were investigated by Al and Sc solid-state NMR investigations. For Sc Al, one signal was found in the Al NMR spectra in line with the crystal structure; however, an extremely negative resonance shift of δ = -673 ppm was observed. In both compounds, two Sc resonances were observed, in line with the proposed crystal structure. Finally, it was observed that the stability of Sc Au in air is limited. This was investigated thermal analysis and (temperature-dependent) powder X-ray diffraction. DFT calculations helped in assessing charge analysis, electronic properties, and chemical bonding.