Zintl arsenic

Reaction of group 15 elements like arsenic with alkali or alkaline earth metals forms Zintl anions of the general type Asn". Characterization of these species has been accomplished dissolving the solids in liquid NH3 or ethylenediamine (H2NCH2CH2NH2) and adding the macrocycle, 2,2,2-crypt (5) to complex the cations and stabilize the polyatomic anions. The fully characterized Zintl arsenic anions As4, As and Asu are shown inFigme 1. ... 

One of the most common techniques for preparing Zintl phases is by the reaction of a solution of the alkali metal in liquid ammonia with the other element. However, many of these materials are obtained by heating the elements. For example, heating barium with arsenic leads to the reaction... 

The intermetallic phase [26] Na2Tl illustrates a simple application of the Zintl-Klemm concept to a group 13 metal cluster. Complete electron transfer from Na to T1 leads to the (Na" )2Tl formulation. The Tl dianion is isoelectronic with group 15 elements and thus should form similar tetrahedral structures with six two-center two-electron bonds along the edges of the tetrahedron. Indeed, the Tl anions in the Na2Tl phase form Tl4 tetrahedra, similar to the isoelectronic P4 and As4 units in white phosphorus and yellow arsenic. 

The Structural principles of the elements can also be found in a number of ternary Zintl phases. For example, KSnSb contains (SnSb ) layers as in a-arsenic. In other ternary ZiNTL phases the anionic part of the structures resembles halo or oxo anions or molecular halides. For example, in Ba4SiAs4 there are tetrahedral SiAs particles that are isostructural to SiBr4 molecules. In Ba3AlSb3 dimeric groups Al2Sbg2 are present, with a structure as in A Clg molecules (Fig. 13.4). Ca3AlAs3 contains poly-... 

I Hume Bedford, Lamb and Spicer, loc. cit. See also Hanson, Sweetser and Feldman, J. Amer. Chem. Soc., 1934, 56, 577. For the simultaneous determination of iron, copper and arsenic, see Zintl and Schlofier, Zeitsch. angew. Chem., 1928, 41, 956. 

A typical Zintl phase is a compound like NaSi [12]. It is described by the formulation Na Si . The anion Si" has to be triply bonded, which is expressed by the symbol (3b) [13]. Si" is isoelectronic with phosphorus and arsenic (diagonal relationship) and it is, therefore, according to Klemm, a pseudo element of group 15. This means it should accomodate a structure which is typical for group 15 elements. In NaSi (3b)Sr anions form [SiJ " tetrahedra, like phosphorus and arsenic do in white phosphorus and yellow arsenic, respectively. In CaSi2, a comparable situation oecurs. According to the formulation Ca (Si )2, anions (3b)Si" are expected as well. 

Ternary Zintl phases that incorporate arsenic are exemplified by Ba4 SiAs4 (s ee Zintl Compounds). The material is made of tetrahedral SiAs4 units whose charge is compensated for by the Ba cations. 

Arsenic Inorganic Chemistry Borides Solid-state Chemistry Carbides Transition Metal Solid-state Chemistry Chalcogenides Solid-state Chemistry Electronic Structure of Solids Mixed Valence Compounds Phosphoras Inorganic Chemistry Thin Film Synthesis of Solids Zintl Compounds. 

Reaction of group 15 elements like arsenic with alkali or alkaline earth metals forms Zintl anions of the general type Characterization of these species... 

Most, if not all, solids containing Zintl ions and sequestered alkali metal ions are infinitely stable in the absence of moisture and oxygen. Since the original report of the solid state structures of (crypt-Na+)2(Pbs ) and (crypt-Na )4(Sn9 ) in 1975, " the synthetic use of crypt has now produced compounds containing Zintl ions of germanium, tin, lead, arsenic, antimony, bismuth and tellurium. " ... 

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