Clusters and networks of the early p-block elements in the solid state: Mixed cations as a way to structural novelties

The discovery of Tt₉4− (Tt = Si, Ge, Sn, Pb) in “neat solids”,1 stimulated the search for other, yet to be discovered Zintl phases with novel isolated clusters or with clusters that have already been made by solution routes.{09}For that matter, we began thorough and systematic studies over the binary A-Tt systems (A = alkali metal), and later, as the work advanced, we extended this series towards the pseudo-binary systems with mixed alkali metals. After exploring a great deal of compositions within the pseudo-binary systems with mixed alkali metals, we have invariably embarked on exploring analogous systems with the help of mixtures of alkali and alkaline-earth metals (AE).; The major part of the work presented in this dissertation deals with the synthesis and structural characterization of a variety of novel intermetallic compounds. A few noteworthy examples are: (1) A₈Na₁₆ Si₁₃₆ and A₈Na₁₆Ge₁₃₆ (A = Cs, Rb) with the clathrate-II structure; (2) A₃Na₁₀ Sn₂₃ (A = Cs, Rb, K) with a layered structure, an intergrowth between the clathrate-II and the Zintl phase NaSn; (3) Rb₂₀Na ₁₂Sn₁₀₀ with the chiral clathrate structure; (4) CS ₃₀Na₃Sn₁₆₂ with the clathrate-III structure; (5) Ba ₁₆Na₂₀₄Sn₃₁₀ with isolated tetramers of pentagonal dodecahedra Sn, which are “excised” motifs from clathrate-II; (6) A₄Li₂Sn₈ (A = Rb, K) with unprecedented arachno-Sn₈6− clusters; (7) RbLi ₇Ge₈ with isolated giant truncated tetrahedra of Ge ₁₂12−. Similar clusters of tin, Sn₁₂ 12− were found in [AE]Na₁₀Sn₁₂ (AE = Ca, Sr).; Another part of this dissertation concentrates on the next step along this line of research, namely to try to synthesize heteroatomic clusters isoelectronic with those of group 14 by a combination of elements from groups 13 (Tr) and 15 (Pn), respectively. However, so far, we have not been able to realize this in the solid state, since all probed reactions either produced novel compounds with extended structures based on TrPn₄-tetrahedra or yielded several compounds, adopting already known structure types.; All of the above-mentioned compounds nicely illustrate the delicate balance between packing efficiency and electronic requirements, which explains the stabilization of these, otherwise inaccessible in pure binary systems, novel compounds.; 1The use of “neat solids” here (after Corbett, J. D. in Structure and Bonding 1998, 87, 157) is to distinguish solids made by solid-state reactions from “molecular” solids crystallized from solution.