Synthesis and Characterization of Unusual Polar Intermetallics

Li17Ag3Sn6: A Polar Intermetallic π-System with Carbonate-like [AgSn3]11- Anions and Trefoil Aromatic [Ag2Sn3]6- Layers

“…Thus, the electron allocation can be approximated as Li 17 [{AgSn 3 } - x {Ag 2 Sn 3 } - y ] with ( x + y = 17). Furthermore, we can assume that the isolated trigonal planar AgSn 3 units are isoelectronic with the 24-electron anions, [CO 3 ] 2- and [SiP 3 ] 5- , and formulated as [AgSn 3 ]. − …”

“…Our work probes the efficacy of the Zintl concept in rationalizing the stoichiometry, structure, and chemical bonding of complex electron-deficient Zintl phases exhibiting novel π-bonds. Their chemical bonding is reflected by their unusual crystal structures related to unsaturated hydrocarbons . Several examples have been discovered, including the novel anionic zigzag chains, [InIn−Ge], - in the semiconductor SrCa 2 In 2 Ge .…”

“…The anionic chains of the electron-deficient Zintl phase, with short In−In bonding distances, were characterized as being analogous and isoelectronic with an allyl anion chain [CHCH−CH 2 ] ∞ . Similarly, the [Ga] 2- zigzag chains in CaGa have been likened to polyacetylene 23a. Later, the polar intermetallic Ca 5 In 9 Sn 6 was discovered and found to exhibit an unprecedented intergrowth structure of Zintl and normal intermetallic layers …”

“…As in Zintl phases, intermetallic phases formed between late transition and posttransition metals with one or more of the electropositive alkali or alkaline earth metals often exhibit a variety of complex anionic structures. 23c, Formal charge transfer is anticipated to occur from the most electropositive metal to the covalent framework of late transition and/or posttransition metals. Several studies on transition metal polar intermetallics and compounds (e.g., borides, pnictides, and chalcogenides) have shown the effectiveness of the Zintl picture, in the framework of the rigid band, as a starting point in rationalizing crystal structures with respect to stoichiometry, chemical bonding, and properties. ,,,− The variety of structural anionic units (e.g., clusters, networks, and frameworks) in these compounds were observed to follow electronic valence rules consistent with the characteristic chemistry of the component elements. More interestingly, the various combinations of late transition metals with post-transition metals also provide interesting chemical solid-state systems wherein interplay of electronic and magnetic effects can be investigated.…”

“…Similar alkaline earth metal phases such as SrZnGe and CaCuSi, with anionic hexagonal nets (AlB 2 -structure type), have also been prepared . Moreover, chemical bonding of the complex late-transition metal polar intermetallics were successfully rationalized using the extended-Zintl concept. 23a,9a,− However, just how far to the left of the Zintl border would the effective charge transfer from the electropositive metals to the electronegative metal partners persist is yet to be determined.…”