Synthesis, Structure, and Bonding in K12Au21Sn4. A Polar Intermetallic Compound with Dense Au20 and Open AuSn4 LayersInorganic Chemistry
Publication VersionPublished Version
AbstractThe new phase K12Au21Sn4 has been synthesized by direct reaction of the elements at elevated temperatures. Single crystal X-ray diffraction established its orthorhombic structure, space group Pmmn (No. 59), a = 12.162(2); b = 18.058(4); c = 8.657(2) Å, V = 1901.3(7) Å3, and Z = 2. The structure consists of infinite puckered sheets of vertex-sharing gold tetrahedra (Au20) that are tied together by thin layers of alternating four-bonded-Sn and -Au atoms (AuSn4). Remarkably, the dense but electron-poorer blocks of Au tetrahedra coexist with more open and saturated Au−Sn layers, which are fragments of a zinc blende type structure that maximize tetrahedral heteroatomic bonding outside of the network of gold tetrahedra. LMTO band structure calculations reveal metallic properties and a pseudogap at 256 valence electrons per formula unit, only three electrons fewer than in the title compound and at a point at which strong Au−Sn bonding is optimized. Additionally, the tight coordination of the Au framework atoms by K plays an important bonding role: each Au tetrahedra has 10 K neighbors and each K atom has 8−12 Au contacts. The appreciably different role of the p element Sn in this structure from that in the triel members in K3Au5In and Rb2Au3Tl appears to arise from its higher electron count which leads to better p-bonding (valence electron concentrations = 1.32 versus 1.22).
Copyright OwnerAmerican Chemical Society
Citation InformationBin Li, Sung-Jin Kim, Gordon J. Miller and John D. Corbett. "Synthesis, Structure, and Bonding in K12Au21Sn4. A Polar Intermetallic Compound with Dense Au20 and Open AuSn4 Layers" Inorganic Chemistry Vol. 48 Iss. 23 (2009) p. 11108 - 11113
Available at: http://works.bepress.com/gordon-miller/97/