Correlations of Crystal and Electronic Structure via NMR and X-ray Photoelectron Spectroscopies in the RETMAl2 (RE = Sc, Y, La–Nd, Sm, Gd–Tm, Lu; TM = Ni, Pd, Pt) Series

A total of 35 intermetallic aluminum compounds have been synthesized from the elements via arc melting and characterized by powder X-ray diffraction. A total of 15 of them have been previously reported; however, detailed property investigations were missing. Compounds of the RETMAl2 (rare earth metal RE = Sc, Y, La–Nd, Sm, Gd–Tm, Lu) series with transition metal TM = Ni, Pd, and Pt crystallize isostructurally in the orthorhombic MgCuAl2 type structure (Cmcm, oC16, fc2). Single-crystal X-ray diffraction investigations were conducted on YNiAl2, LaNiAl2, YPdAl2, ScPtAl2, and YPtAl2. The TM and Al atoms form a [TMAl2]δ− polyanion, the RE atoms reside in cavities within the framework. While the Sc, Y, La, and Lu compounds exhibit Pauli-paramagnetic behavior, consistent with all atoms being closed shell, the other RETMAl2 compounds show paramagnetism along with magnetic ordering at low temperatures, in line with an open-shell trivalent oxidation state for the RE atoms. Solid-state 27Al NMR investigations were c...