Isolated _∞¹[ZnPn₂]⁴⁻ Chains in the Zintl Phases Ba₂ZnPn₂ (Pn = As, Sb, Bi)—Synthesis, Structure, and Bonding

Abstract

Reported are the synthesis of three new Zintl phases, Ba2ZnAs2 (I), Ba2ZnSb2 (II), Ba2ZnBi2 (III) and their structural characterization by single-crystal X-ray diffraction. They are isoelectronic and isotypic and crystallize in the orthorhombic space group Ibam, with four formula units per cell (Pearson symbol oI20; K2SiP2 type). Lattice parameters are as follows: a = 13.399(9)/14.133(3)/14.325(6); b = 6.878(5)/7.1919(15)/7.280(3); and c = 6.541(4)/6.9597(15)/7.089(3) A for I/II/III, respectively. The structure can be viewed as polyanionic chains, infinity1[ZnPn2]4- (Pn = As, Sb, Bi), running parallel to the c-axis, with Ba2+ cations separating them. The chains are made of edge-shared ZnPn4 tetrahedra, which are isosteric with the infinity1[SiS4/2] chains in SiS2. This and some other structural parallels with known Zintl phases have been discussed. The experimental results have been complemented by tight-binding linear muffin-tin orbital electronic structure calculations.

Gallium Pnictides of the Alkaline Earth Metals, Synthesized by Means of the Flux Method: Crystal Structures and Properties of CaGa2Pn2, SrGa2As2, Ba2Ga5As5, and Ba4Ga5Pn8 (Pn = P or As)

“…[34] Another relevant parallel can be drawn between the structure of Ba 4 Ga 5 P 8 , in particular, and the recently reported Ba 2 ZnPn 2 (K 2 SiP 2 type). [42] We succinctly recall that this structure contains chains of edge-shared tetrahedra (e.g., [ZnPn 4/2 ]), isosteric with those in the silicon dichalcogenides, [43] surrounded by cations. A good starting point for a discussion here is the observation that in Ba 2 ZnPn 2 , the chains are formed by Pn atoms in a ccp-like array, with zinc atoms occupying only 1 / 4 of the available tetrahedral holes.…”

Ba5Cd2Sb4O2—A New Antimonide Oxide with a Complex Structure

“…Over the past seven years, our research group has systematically explored the alkaline-earth metal and rare-earth metal antimonide systems. The resulting new compounds have often been Zintl phases [4][5][6] with complex crystal and electronic structures, and unusual properties [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Although oxide research is not our focus, it is sometimes the case that adventurous oxygen molecules find their way into our experiments and OPEN ACCESS surprise us with an atypical compound, such as the previously reported Ba 5 Cd 2 Sb 5 O x (0.5 < x < 0.7) [17].…”

New ternary phosphides and arsenides. Syntheses, crystal structures, physical properties of Eu2ZnP2, Eu2Zn2P3 and Eu2Cd2As3

“…Eu 2 ZnP 2 is the first zinc-containing compound that adopts this structure and all other known members of this structural chemistry are cadmiumbased [3,15]. Compounds with the same stoichiometry and similar chemical make up are known, such as Ba 2 ZnPn 2 (Pn ¼As, Sb, Bi) [17] or Sr 2 ZnP 2 [27], but their structures are distinctly different, based on 1 1 ½ZnPn 2 4-chains (isosteric with the 1 1 ½SiS 2 chains in SiS 2 [28]) and on defect honeycomb-like 2 (2) a U eq is defined as one third of the trace of the orthogonalized U ij tensor. [34], suggesting weak covalent bonding character.…”

“…Our previous work on pnictogen chemistry involving the systems AE-Zn-Pn and AE-Cd-Pn (AE¼ Ca, Sr, Ba, Eu and Yb; Pn¼ P, As, Sb, Bi) yielded unusual examples of polymorphic phases [15], and novel semiconductors with interesting ferromagnetic and thermoelectric properties [16][17][18][19][20]. As part of these studies, we synthesized and structurally characterized the new compounds Eu 2 ZnP 2 , Eu 2 Zn 2 P 3 and Eu 2 Cd 2 As 3 , which are at the focus of this paper.…”