Exploratory Synthesis in the Solid State. Endless Wonders

Abstract

This article gives an overview of recent developments in three areas of solid state chemistry: (1) The discovery that centered and originally-adventitious interstitial elements Z are essential for the stability of M6X12-type cluster halides of group 3 and 4 metals has led to a large amount of new chemistry through tuning structures and compositions of AnM6(Z)X12Xn phases with the variables Z, x, and n. The corresponding metal-rich group 3 tellurides exhibit novel and more extensive metal aggregation, reflecting a decreased number of anions and valence electrons. (2) Many intrinsically metallic T5M3 phases with a Mn5Si3-type structure are formed by early transition metals T with main-group elements M. Each characteristically reacts with diverse elements (up to 15-20 each) to form stuffed interstitial versions T5M3Z of the same structure. The ranges of Z and some properties are described. Related reactions of hydrogen (often as an impurity) in Mn5Si3-, beta-Yb5Sb3-, and Cr5B3-type systems are extensive. Substantially all previous reports of beta-Yb5Sb3- and Cr5B3-type phases for divalent metals with pnictogen (As-Bi) and tetrel (Si-Pb) elements, respectively, have been for the hydrides, and about two-thirds do not exist without that hydrogen (or fluorine). (3) The developing chemistry of anionic polymetal cluster compounds of the main-group elements with alkali-metal cations is outlined, particularly for the triel elements In and Tl. These clusters lie to the left of what has been called the Zintl boundary, many are new hypoelectronic polyhedra, some may be centered by the same or another neighboring element, and so far all have been isolated only as neat solid state compounds in which specificity of cation-anion interactions seems important. Extended networks are also encountered.

The Crystal Orbital Hamilton Population (COHP) Method as a Tool to Visualize and Analyze Chemical Bonding in Intermetallic Compounds

“…The (second) off-diagonal contribution of the gross population in Equation (14), i.e., Re[P µν (E)S µν ], comprises the overlap-population-weighted densities-of-states and, hence, provides the essential information regarding the distributions of the electrons between the atoms in any given solid-state material. This very technique to extract the bonding information based on the overlap-population-weighted densities-of-states has been dubbed as the crystal orbital overlap population (COOP) method [25].…”

“…Under consideration of the secular determinant Equation (4), which can be transformed to it is plausible that the overlap integrals used to define the overlap-population-weighted densities-of-states in the Equation (14) can be replaced by the Hamilton matrix elements; however, it should be noted that a straightforward transformation which might be implied by the relation in the Equation (18) cannot be made. Nonetheless, using an analogy to the aforementioned overlap-population-weighted densities-of-states, the densities-of-states matrix Equation (11) is weighted by the Hamilton matrix elements resulting in the Crystal Orbital Hamilton Populations (COHP), according to…”

“…Further research on the distributions of the valence electrons in intermetallic compounds revealed additional notions, e.g., those first proposed by Zintl [5][6][7][8][9][10] and Hume-Rothery [11][12][13], respectively, to somehow correlate structural arrangements and the atoms' electronic nature. Even today, however, the existence of intermetallic compounds for which the electronic structures and, furthermore, the nature of bonding cannot be trivially categorized by applying one of the aforementioned concepts [14,15] underlines the need for different means in order to reveal the bonding nature in such materials.…”

Ru11Lu20, a New Intermetallic Compound with Eight- to Ten-Coordinate Ruthenium Atoms

“…These polyhedra are connected to a complicated three-dimensional structure. Coordination numbers of eight (cube and square antiprisms) are also observed in the cluster complex compound {Ru 5 Lu 20 }I 24 where the polyhedra are connected via common faces to a one-dimensional intermetallic structure; the chains are isolated from each other by surrounding iodide ligands.…”

“…A plethora of reduced rare-earth metal halides at the borderline between metal and salt have been obtained within the last decades [1][2][3][4][5][6][7][8][9][10][11][12]. These contain cluster complexes, most frequently of the "6-12" type, in which octahedral metal clusters {R 6 } are surrounded by twelve halide ligands (X) capping all the edges.…”