Alkali Metal Suboxometalates-Structural Chemistry between Salts and Metals

作者：Woersching Matthias; Hoch Constantin^*

来源：Inorganic Chemistry, 2015, 54(14): 7058-7064.

DOI：10.1021/acs.inorgchem.5b01060

The crystal structures of the new cesium-poor alkali metal suboxometalates Cs10MO5 (M = Al, Ga, Fe) show both metallic and ionic bonding following the formal description (Cs+)(10)(MO45-)(O2-) center dot 3e(-).Comparable to the cesium-rich suboxometalates Cs9MO4 (M = Al, Ga, In, Fe, Sc) with ionic subdivision (Cs+)(9)(MO45-) center dot 4e(-), they contain an oxometalate anion [(MO4)-O-III](5) embedded in a metallic matrix of cesium atoms. Columnlike building units form with prevalent ionic bonding inside and metallic bonding on the outer surface. In the cesium-rich suboxometalates Cs9MO4, additional cesium atoms with no contact to any anion are inserted between columns of the formal composition [Cs8MO4]. In the cesium-poor suboxometalates Cs10MO5, the same columns are extended by face-sharing [Cs6O] units, and no additional cesium atoms are present. The terms cesium-rich and cesium-poor here refer to the Cs:O ratio. The new suboxometalates Cs10MO5 crystallize in two modifications with new structure types. The orthorhombic modification adopts a structure with four formula units per unit cell in space group Pnnm with a = 11.158(3) angstrom, b = 23.693(15) angstrom, and c = 12.229(3) angstrom for Cs10AlO5. The monoclinic modification crystallizes with eight formula units per unit cell in space group C2/c with a = 21.195(3) angstrom, b = 12.480(1) angstrom, c = 24.120(4) angstrom, and beta = 98.06(1)degrees for Cs10AlO5. Limits to phase formation are given by the restriction that the M atoms must be trivalent and by geometric size restrictions for the insertion of [Cs6O] blocks in Cs10MO5. All of the suboxometalate structures show similar structural details and form mixed crystal series with statistical occupation for the M elements following the patterns Cs-9((MxM1-x2)-M-1)O-4 and Cs-10((MxM1-x2)-M-1)O-5. The suboxometalates are a new example of ordered intergrowth of ionic and metallic structure elements, allowing for the combination of properties related to both ionic and metallic materials.

• 出版日期2015-7-20