Na12K38Tl48Au2: A Metallic Zintl Phase with Naked Icosahedral Fragments Tl77- and Tl99- Plus Au

Autor:	Zhen-Chao Dong, John D. Corbett, DaPing Huang
Rok vydání:	1998
Předmět:	Inorganic Chemistry Bond length Crystallography Valence (chemistry) Pentagonal bipyramidal molecular geometry Antiprism Zintl phase Chemistry Icosahedral symmetry Crystal structure Physical and Theoretical Chemistry Omega
Zdroj:	Inorganic Chemistry. 37:5881-5886
ISSN:	1520-510X 0020-1669
DOI:	10.1021/ic9808293
Popis:	The title compound is synthesized by direct reaction of the elements at 500 C followed by slow cooling. Na{sub 12}K{sub 38}Tl{sub 48}Au{sub 2} crystallizes hexagonal and is constituted (in terms of oxidation states) as (Na{sup +}){sub 12}(K{sup +}){sub 38}(Tl{sub 7}{sup 7{minus}}){sub 3}(Tl{sub 9}{sup 9{minus}}){sub 3}(Au{sup {minus}}){sub 2}. Both clusters have C{sub 2{nu}} symmetry and can be viewed as fragments of a centered icosahedral Tl{sub 13}. The Tl{sub 7}{sup 7{minus}} cluster is an oblate pentagonal bipyramid with an apex-apex bond distance of 3.39 {angstrom}, and Tl{sub 9}{sup 9{minus}} can be best derived from the centered icosahedron by removal of four adjoining vertexes (or as two fused pentagonal bipyramids). The isolated Au{sup {minus}} is bound in a trigonal antiprism of potassium. The compound is structurally electron-precise (Zintl phase), but it shows characteristics of a very poor metal ({rho}{sub 298} {approximately} 760 {mu}{Omega}(cm)) with a Pauli-like susceptibility of {approximately}1.4 {times} 10{sup {minus}3} emu/mol over 50--300 K after correction for Larmor precession of cluster orbitals. EHMO results for the bonding in Tl{sub 7}{sup 7{minus}} and factors that stabilize this compound are presented and discussed.
Databáze:	OpenAIRE
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