ARTICLE DOI: 10.1002/zaac.201200200 ScPdZn and ScPtZn with YAlGe Type Structure – Group-Subgroup Relation and 45 Sc Solid State NMR Spectroscopy Rolf-Dieter Hoffmann, [a] Trinath Mishra, [a] Birgit Heying, [a] Ute Ch. Rodewald, [a] Samir F. Matar,* [b] Heinz Deters, [c] Hellmut Eckert,* [c] and Rainer Pöttgen* [a] Dedicated to Professor Hartmut Bärnighausen on the Occasion of His 80th Birthday Keywords: Scandium; Superstructure; Group-subgroup relation; Electronic structure Abstract. The intermetallic compounds ScPdZn and ScPtZn were pre- pared from the elements by high-frequency melting in sealed tantalum ampoules. Both structures were refined from single crystal X-ray dif- fractometer data: YAlGe type, Cmcm, a = 429.53(8), b = 907.7(1), c = 527.86(1) pm, wR2 = 0.0375, 231 F 2 values, for ScPdZn and a = 425.3(1), b = 918.4(2), c = 523.3(1) pm, wR2 = 0.0399, 213 F 2 values for ScPtZn with 14 variables per refinement. The structures are ortho- rhombically distorted variants of the AlB 2 type. The scandium and palladium (platinum atoms) build up ordered networks Sc 3 Pd 3 and Sc 3 Pt 3 (boron networks) which are slightly shifted with respect to each other. These networks are penetrated by chains of zinc atoms (262 pm Introduction Scandium is an ambivalent element. In some cases it be- haves as a trivalent transition metal, while in other ones it adopts the position of a rare earth element. This is a conse- quence of the small size of the scandium atom which has a covalent radius of only 144 pm, [1] significantly smaller than the one of the smallest rare earth element lutetium (156 pm); [1] thus influencing the crystal chemical behavior of intermetallic scandium compounds. [2,3] Sometimes a given crystal structure shows large flexibility and scandium can also form the struc- ture type that is adopted by the corresponding lutetium com- * Prof. Dr. R. Pöttgen Fax: +49-251-83-36002 E-mail: pottgen@uni-muenster.de * Prof. Dr. H. Eckert Fax: +49-251-83-29159 E-mail: eckerth@uni-muenster.de * Dr. S. F. Matar Fax: +33-5-4000-2761 E-mail: matar@icmcb-bordeaux.cnrs.fr [a] Institut für Anorganische und Analytische Chemie Universität Münster Corrensstrasse 30 48149 Münster, Germany [b] CNRS, Université de Bordeaux, ICMCB 87 Avenue du Docteur Albert Schweitzer 33600 Pessac, France [c] Institut für Physikalische Chemie Universität Münster Corrensstrasse 30, 48149 Münster, Germany Z. Anorg. Allg. Chem. 2012, 638, (), 1–9 © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 in ScPtZn) which correspond to the aluminum positions, i.e. Zn(ScPd) and Zn(ScPt). The corresponding group-subgroup scheme and the dif- ferences in chemical bonding with respect to other AlB 2 -derived REPdZn and REPtZn compounds are discussed. 45 Sc solid state NMR spectra confirm the single crystallographic scandium sites. From elec- tronic band structure calculations the two compounds are found met- allic with free electron like behavior at the Fermi level. A larger cohe- sive energy for ScPtZn suggests a more strongly bonded intermetallic than ScPdZn. Electron localization and overlap population analyses identify the largest bonding for scandium with the transition metal (Pd, Pt). pound. This is e.g. the case for the pair LuAuSn and ScAuSn. [4,5] If scandium is too small for the structure type taken by the lutetium compound, there is another way out to adopt an al- most similar atomic arrangement. The scandium compound crystallizes with a superstructure with small distortions from the corresponding aristotype. Recent examples are the struc- tures of ScAgSn [6] and ScTSn (T = Pd, Pt). [7] If also a super- structure formation is not sufficient to fulfill the coordination requirements of scandium, the scandium compound crys- tallizes with its own structure type, e.g. Sc 4 Pt 7 Si 2 . [8] 45 Sc solid state NMR spectroscopy of such intermetallics is a useful tool to study the crystallographically different scandium sites in such structures and additionally examine vacancy formation and / or structural disorder. An overview on the 45 Sc solid state NMR spectroscopic investigation of the compounds Sc x T y X z (T = late transition metal; X = element of the 3rd, 4th, or 5th main group) is given in a recent review article. [9] In the course of our systematic investigations on structures and properties of intermetallic RE x T y Zn z compounds [10–14, and ref. therein] we were interested in the scandium based compounds ScTZn. The series of REPtZn intermetallics [13, and refs. therein] crystallizes with the orthorhombic TiNiSi type structure, while several of the REPdZn compounds [14, and refs. therein] show di- morphism, including LuPdZn with the hexagonal ZrNiAl type for the α- and the orthorhombic TiNiSi type for the β-modifi- cation. For the corresponding scandium compounds we ob-