title: Ba3Pt4Al4-Structure, Properties, and Theoretical and NMR Spectroscopic Investigations of a Complex Platinide Featuring Heterocubane [Pt4Al4] Units.
abstract: Ba3Pt4Al4 was prepared from the elements in niobium ampules and crystallizes in an orthorhombic structure, space group Cmcm (oP44, a = 1073.07(3), b = 812.30(3), c = 1182.69(3) pm) isopointal to the Zintl phase A2Zn5As4 (A = K, Rb). The structure features strands of distorted [Pt4Al4] heterocubane-like units connected by condensation over Pt/Al edges. These are arranged in a hexagonal rod packing by further condensation over Pt and Al atoms with the barium atoms located inside cavities of the [Pt4Al4](δ-) framework. Structural relaxation confirmed the electronic stability of the new phase, while band structure calculations indicate metallic behavior. Crystal orbital Hamilton bonding analysis coupled with Bader effective charge analysis suggest a polar intermetallic phase in which strong Al-Pt covalent bonds are present, while a significant electron transfer from Ba to the [Pt4Al4](δ-) network is found. By X-ray photoelectron spectroscopy measurements the Pt 4f5/2 and 4f7/2 energies for Ba3Pt4Al4 were found in the range of those of elemental Pt due to the electron transfer of Ba, while PtAl and PtAl2 show a pronounced shift toward a more cationic platinum state. (27)Al magic-angle spinning NMR investigations verified the two independent crystallographic Al sites with differently distorted tetrahedrally coordinated [AlPt4] units. Peak assignments could be made based on both geometrical considerations and in relation to electric field gradient calculations.
authors.forename: Frank
authors.initials: F
authors.lastname: Stegemann
authors.forename: Christopher
authors.initials: C
authors.lastname: Benndorf
authors.forename: Timo
authors.initials: T
authors.lastname: Bartsch
authors.affiliation: Institut für Anorganische Chemie, RWTH Aachen , Landoltweg 1, D-52074 Aachen, Germany.
authors.forename: Rachid St
authors.initials: RS
authors.lastname: Touzani
authors.affiliation: Physikalisches Institut, Universität Münster , Wilhelm-Klemm-Strasse 10, D-48149 Münster, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Bartsch
authors.affiliation: Physikalisches Institut, Universität Münster , Wilhelm-Klemm-Strasse 10, D-48149 Münster, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Zacharias
authors.affiliation: Institut für Anorganische Chemie, RWTH Aachen , Landoltweg 1, D-52074 Aachen, Germany.|Department of Chemistry, University of California Riverside , California 92521, United States.
authors.forename: Boniface P T
authors.initials: BP
authors.lastname: Fokwa
authors.affiliation: Instituto de Física de São Carlos, Universidade de São Paulo , São Carlos-SP 13566-590, Brazil.
authors.forename: Hellmut
authors.initials: H
authors.lastname: Eckert
authors.forename: Oliver
authors.initials: O
authors.lastname: Janka