Ba3Pt4Al4鈥擲tructure, Properties, and Theoretical and NMR Spectroscopic Investigations of a Complex Platinide Featuring Heterocubane [Pt4Al4] Units

详细信息    查看全文

• 作者：Frank Stegemann ; Christopher Benndorf ; Timo Bartsch ; Rachid St. Touzani ; Manfred Bartsch ; Helmut Zacharias ; Boniface P. T. Fokwa ; Hellmut Eckert ; Oliver Janka
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：November 16, 2015
• 年：2015
• 卷：54
• 期：22
• 页码：10785-10793
• 全文大小：591K
• ISSN：1520-510X

文摘

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]^{未鈭?/sup> 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鈥揚t covalent bonds are present, while a significant electron transfer from Ba to the [Pt₄Al₄]未鈭?/sup> network is found. By X-ray photoelectron spectroscopy measurements the Pt 4f_5/2 and 4f_7/2 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. 27Al 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.}