Solid state compounds with tin-tin bonding.: Yb36Sn23:: A novel compound containing oligomeric tin anions

Reaction of appropriate amounts of the elements in Ta at 1100 degrees C leads to formation of the title phase in high yield. Hydrogen impurities in small amounts do not obscure its formation. Yb36Sn23 crystallizes in tetragonal space group P4/mbm (No. 127) with a = 12.3869(5) Angstrom, c = 22.935(1) Angstrom, Z = 2. The structure features a linear tin hexamer, five dimers, and seven isolated tin atoms per formula unit. These proportions lead to a closed-shell oxidation state count for simple octet assignments (Yb+2)(36)(Sn-6(-14))(Sn-2(-6))(5)(Sn-4)(7) and a Zintl phase classification. Dimensionally, all cations appear to be Yb-II. The hexamer of tin atoms has as its genesis the close contact of Sn atoms that center confacial square antiprismatic arrangements of Yb atoms (closely related to the parent W5Si3 structure). These interconnect with elongated square prisms in a 6:1 proportion to generate the n = six member of Parthe's homologous series A(5n+6)B(3n+5). Electrical conductivity measurements as a function of temperature show that the compound is a poor metal (rho(298) approximate to 130 mu Omega.cm). The latter property is not uncommon for compounds containing clusters of the early p elements.