Synthesis, magnetic and NMR spectroscopic properties of the MAl 5 Pt 3 series (M = Ca, Y, La-Nd, Sm-Er).

Following recent investigation in the ternary system Sr-Al-Pt led to the discovery of SrAl 5 Pt 3 which crystallizes in the orthorhombic YNi 5 Si 3 type ( Pnma ) structure. Interestingly, only two more aluminum representatives, CeAl 5 Pt 3 and EuAl 5 Pt 3 , have been reported to adopt this structure type. Therefore, we decided to investigate the existence range of compounds adopting the YNi 5 Si 3 type structure. Besides the already known Sr, Ce and Eu members, the series could be extended to Ca, Y and La-Nd as well as Sm-Er. All compounds were synthesized from the elements and characterized by powder X-ray diffraction. While for CaAl 5 Pt 3 and LaAl 5 Pt 3 also the respective M 2 Al 16 Pt 9 members were observed, the other compounds could be obtained either as X-ray pure materials or with small amounts of Al 3 Pt 2 as a side phase. The structure of ErAl 5 Pt 3 could be refined from single crystal data, verifying that also the small rare-earth elements adopt the YNi 5 Si 3 type structure. Selected members of the series were furthermore characterized by magnetization and susceptibility measurements. Since YAl 5 Pt 3 could be obtained as a phase pure material and exhibits no paramagnetic behaviour it was investigated by 27 Al MAS NMR investigations. Also, XPS measurements were conducted on this compound to gain an insight into the charge distribution. Finally, quantum-chemical calculations supported the NMR measurements and gave an insight into the chemical bonding and the charge distribution.