Ca10Pt7Tt3 (Tt = Si, Ge): New Platinide Phases Featuring Electron-Rich 4c鈥?e Bonded [Pt7Tt3]20鈥?/sup> Intermetalloid Clusters

详细信息    查看全文

• 作者：Isa Doverbratt ; Sim茅on Ponou ; Sven Lidin ; Daniel C. Fredrickson
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：November 5, 2012
• 年：2012
• 卷：51
• 期：21
• 页码：11980-11985
• 全文大小：302K
• 年卷期：v.51,no.21(November 5, 2012)
• ISSN：1520-510X

文摘

Two new phases Ca₁₀Pt₇Tt₃ (with Tt = Si, Ge) were obtained by reacting stoichiometric mixtures of the elements at high temperature. Their structures were refined from single crystal X-ray diffraction data. They are isostructural and crystallize in the Ba₁₀Al₃Ge₇ type structure, space group P6₃/mcm (No. 193) with a = b = 8.7735(3) 脜, c = 13.8260(5) 脜, V = 921.66(6) 脜³, Z = 2 for Tt = Si, and a = b = 8.7995(6) 脜, c = 13.9217(14) 脜, V = 933.56(16) 脜³ for Tt = Ge phase. The most interesting structural features in these phases are the propeller shape {Pt₇Tt₃} (Tt = Si, Ge) intermetalloid clusters in a D_3h local symmetry. LMTO electronic structure calculations and COHP analyses reveal that both Ca₁₀Pt₇Tt₃ (Tt = Si, Ge) phases are charge optimized, which is not predicted by the classical Zintl concept and the octet or Wade鈥揗ingo鈥檚 rules, but rather by a more complex bonding model based on the unprecedented electron-rich 4c鈥?e multicenter bonding. The clusters are best described as three-condensed trigonal planar [TtPt₃]^{8鈥?/sup> units, resulting in a central Pt atom also with a trigonal planar coordination of three symmetrical equivalent Si/Ge atoms that are further connected to two terminal Pt atoms each. The 鈥渢refoil鈥?electron-rich multicenter bonding is proposed here for the first time, and may be viewed as a unique bonding feature with potential relevance for the catalytic properties of the noble metal platinum.}