Crystal Structure, Spectroscopic Investigations, and Physical Properties of the Ternary Intermetallic REPt2Al3 (RE = Y, Dy–Tm) and RE2Pt3Al4 Representatives (RE = Tm, Lu)

Abstract

Abstract:The REPt 2 Al 3 compounds of the late rare-earth metals (RE = Y, Dy-Tm) were found to crystallize isostructural. Single-crystal X-ray investigations of YPt 2 Al 3 revealed an orthorhombic unit cell (a = 1080.73(6), b = 1871.96(9), c = 413.04(2) pm, wR2 = 0.0780, 942 F 2 values, 46 variables) with space group Cmmm (oC48; q 2 pji 2 hedb). A comparison with the Pearson database indicated that YPt 2 Al 3 forms a new structure type, in which the Pt and Al atoms form a [Pt 2 Al 3 ] δ− polyanion and the Y atoms reside in the cavities within the framework. Via a group-subgroup scheme, the relationship between the PrNi 2 Al 3 -type structure and the new YPt 2 Al 3 -type structure was illustrated. The compounds with RE = Dy-Tm were characterized by powder X-ray diffraction experiments. While YPt 2 Al 3 is a Pauli-paramagnet, the other REPt 2 Al 3 (RE = Dy-Tm) compounds exhibit paramagnetic behavior, which is in line with the rare-earth atoms being in the trivalent oxidation state. DyPt 2 Al 3 and TmPt 2 Al 3 exhibit ferromagnetic ordering at T C = 10.8(1) and 4.7(1) K and HoPt 2 Al 3 antiferromagnetic ordering at T N = 5.5(1) K, respectively. Attempts to synthesize the isostructural lutetium compound resulted in the formation of Lu 2 Pt 3 Al 4 (Ce 2 Ir 3 Sb 4 -type, Pnma, a = 1343.4(2), b = 416.41(8), c = 1141.1(2) pm), which could also be realized with thulium. The structure was refined from single-crystal data (wR2 = 0.0940, 1605 F 2 values, 56 variables). Again, a polyanion with bonding Pt-Al interactions was found, and the two distinct Lu atoms were residing in the cavities of the [Pt 3 Al 4 ] δ-framework. X-ray photoelectron spectroscopy (XPS) measurements were conducted to examine the electron transfer from the rare-earth atoms onto the polyanionic framework.

Synthesis, magnetic and NMR spectroscopic properties of the MAl5Pt3 series (M = Ca, Y, La–Nd, Sm–Er)

“…All Pt sites exhibit a coordination number of seven with a highly asymmetrical coordination environment and interatomic Al-Pt distances between 247 and 270 pm. These agree well with those in binary (AlPt: 248-273 pm; 81,82 Al 2 Pt: 256 pm; 83 Al 3 Pt 2 : 255-286 pm 63,64 ) and ternary intermetallics (YAlPt: Al-Pt 308-336 pm, 74 YAl 2 Pt: Al-Pt 287-305 pm, 75 YAl 3 Pt 2 : Al-Pt: 329-348 pm 77 ) as well as with the sum of the covalent radii (Pt + Al = 129 + 125 = 254 pm 73 ). The respective homoatomic distances (YAl 5 Pt 3 : Pt-Pt: 306 pm; Al-Al: 273-293 pm) agree with what is observed in elemental Al (286 pm 84 ), therefore suggesting partial bonding contributions while the Pt-Pt distances are significantly longer compared to the distances found in the elemental Pt (277 pm 85 ) or the sum of the covalent radii (Al: 250 pm; Pt: 258 pm).…”

“…This has been shown for quite some instances, e.g., Ba 3 Al 4 Pt 4 94 and the REAl 3 Pt 2 (RE = Y, Dy-Tm) series. 77 Since the most electronegative elements acquire additional electron density, shifts of the binding energies of the Pt 4f lines towards lower binding energies can be observed in the respective XPS measurements. [94][95][96][97] In general, the Pt 4f states can be chosen as a reference as they are intense and sharp enabling the detection of already small shifts.…”

“…). Similar distances can be observed in ternary compounds of the Y-Al-Pt system like YAlPt (TiNiSi type, Y-Al: 308-336 pm; Y-Pt: 257-267 pm),74 YAl 2 Pt (MgAl 2 Cu type, Y-Al: 287-305 pm; Y-Pt: 287-308 pm),75 Y 4 Al 24 Pt 9 (own type, Y-Al: 304-321 pm; Y-Pt: 328-336 pm),76 YAl 3 Pt 2 (own type, Y-Al: 329-348 pm; Y-Pt: 301-316 pm),77 YAl 2 Pt 5 (ZrAl 5 Ni 2 type, Y-Al: no contacts; Y-Pt: 288-302 pm),78 …”

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

“…When the platinum compounds are considered first, the observed binding energies for ScPtAl 2 [ E b (Pt 4f 7/2 ) = 71.5 eV], YPtAl 2 [ E b (Pt 4f 7/2 ) = 70.9 eV], and LuPtAl 2 [ E b (Pt 4f 7/2 ) = 71.2 eV] exhibit binding energies equal to or lower in comparison with elemental Pt [ E b (Pt 4f 7/2 ) = 71.2 eV]. The one found for YPtAl 2 matches the observations made for Ba 3 Pt 4 Al 4 [ E b (Pt 4f 7/2 ) = 70.9 eV] or YPt 2 Al 3 [ E b (Pt 4f 7/2 ) = 70.4 eV] and can be explained by a higher electron density at the Pt atoms, in line with an electron transfer from the less electronegative RE and Al atoms. The values for the scandium and lutetium compounds are close to the values of elemental Pt; hence, no distinct electron transfer seems to take place.…”

Compounds with Polar Metallic Bonding

“…They give an excellent example on how electronic structure and crystallographic distortion mutually interact. • Fabian Eustermann, Simon Gausebeck, Carsten Dosche, Mareike Haensch, Gunther Wittstock and Oliver Janka present an article entitled 'Crystal Structure, Spectroscopic Investigations, and Physical Properties of the Ternary Intermetallic REPt 2 Al 3 (RE = Y, Dy-Tm) and RE 2 Pt 3 Al 4 Representatives (RE = Tm, Lu)'[20]. Here, structural and chemical modifications go hand in hand with symmetry reduction, magnetic interactions and with gradual polarity changes.…”