Breaking the Tetra-Coordinated Framework Rule: New Clathrate Ba₈M₂₄P_28+δ (M=Cu/Zn)

详细信息    查看全文

• 作者：Dr. Juli-Anna Dolyniuk ; Dr. Julia V. Zaikina ; Dr. Derrick C. Kaseman ; Prof. Dr. Sabyasachi Sen and Prof. Dr. Kirill Kovnir
• 刊名：Angewandte Chemie
• 出版年：2017
• 出版时间：February 20, 2017
• 年：2017
• 卷：129
• 期：9
• 页码：2458-2462
• 全文大小：2938K
• ISSN：1521-3757

文摘

A new clathrate type has been discovered in the Ba/Cu/Zn/P system. The crystal structure of the Ba₈M₂₄P_28+δ (M=Cu/Zn) clathrate is composed of the pentagonal dodecahedra common to clathrates along with a unique 22-vertex polyhedron with two hexagonal faces capped by additional partially occupied phosphorus sites. This is the first example of a clathrate compound where the framework atoms are not in tetrahedral or trigonal-pyramidal coordination. In Ba₈M₂₄P_28+δ a majority of the framework atoms are five- and six-coordinated, a feature more common to electron-rich intermetallics. The crystal structure of this new clathrate was determined by a combination of X-ray and neutron diffraction and was confirmed with solid-state ³¹P NMR spectroscopy. Based on chemical bonding analysis, the driving force for the formation of this new clathrate is the excess of electrons generated by a high concentration of Zn atoms in the framework. The rattling of guest atoms in the large cages results in a very low thermal conductivity, a unique feature of the clathrate family of compounds.