The distinction between valence electrons and essentially inactive core electrons is the basis of many classifying concepts in chemistry. However, it has recently been recognized that this is an oversimplification and should, at least in some areas of chemistry, be modified. Many cases are known where cations with closed d10 configurations are subject to homoatomic interactions that influence structure and properties. A characteristic and surprisingly uniform structural feature (e.g., of a number of compounds containing monovalent coinage metals) is a clusterlike assembly of d10 cations that corresponds in geometry and bond lengths to fragments of the metal structures themselves. Further evidence for a special type of bonding in such compounds is provided by their physical properties; for example, the absorption in the UV/VIS region shows a drastic redshift and the compounds are often conductors or semiconductors. The d electrons in such cases have obviously lost their pure “core” nature. All bonding models so far proposed for such systems involve mixing of higher orbitals.

Homoatomic d10–d10 Interactions: Their Effects on Structure and Chemical and Physical Properties

Homoatomare d10‐d10‐Wechselwirkungen — Auswirkungen auf Struktur‐ und Stoffeigenschaften

The increase in energy of the sp anionic band on going from oxides to the less electronegative sulfides, selenides, or tellurides (with a similar trend in neighboring columns) facilitates anion–cation redox interactions involving the d levels of transition metal cations and the sp levels of anionic species. The interactions can induce phase transitions or gradual change within a given structural model. When a cation is reduced by electron transfer to its d levels from the sp band, holes appear at the top of the latter. Interesting soft chemistry can be carried out based on redox processes that neutralize the holes with electrons. This approach also allows particular structural types to be stabilized. Three structural domains can be recognized amongst the transition elements: 1) on the left-hand side of the periodic table layered structures are observed involving M4+ and (chalcogen)2- ions; 2) formation of sets of metal-metal bonds is then observed, the geometry of which depends on both the initial electron population and the electron transfer to the metal; 3) on the right-hand side the metals in their highest oxidation state are no longer active, and the holes at the top of the sp band are taken up by a catenation of the anions, which can lead to full polymerization of the anionic sublattice.

Anion–Cation Redox Competition and the Formation of New Compounds in Highly Covalent Systems

CsCu4S3 und CsCu3S2 konnen uber Schmelzreaktionen bei Temperaturen zwischen 700 und 800°C aus Kupfer, Cs2Co3 und Schwefel erhalten werden. Ihre Kristallstruktur wurde uber Rontgendiffraktometermessungen an Einkristallen ermittelt.



CsCu4S3 (Raumgruppe P4/mmm (Nr. 123) a = 3,975(1) A, c = 9,689(3) A, Z = 2) ist schwarz, metallisch glanzend und isotyp mit dem bekannten KCu4S3.



CsCu3S2 (Raumgruppe P3m1 (Nr. 164) a = 5,469(1) A, c = 6,354(1)A, Z = 1) dagegen bildet nahezu farblose transparente Plattchen und kristallisiert mit einem neuen Strukturtyp, der verzweigte SCu-Zickzackketten mit linear koordiniertem Kupfer enthalt. Es wird eine Beschreibung auf der Basis einer hexagonal dichten Packung der Anionen gegeben.



CsCu4S3 and CsCu3S2: Sulfides with Copper in Tetrahedral and Linear Coordination



The title compounds can be prepared by fusion reaction of copper with Cs2Co3 and sulfur at temperature of 700 to 800°C. Their structure was solved from X-ray diffraction data of single crystals.



CsCu4S3 crystals (space group P4/mmm (No. 123) a = 3.975(1) A, c = 9.689(3) A, Z = 2) are shiny black and isotypic with KCu4S3.



CsCu3S2 (space group P3ml (No. 164) a = 5.469(1) A, c = 6.354(1) A, Z = 1), however, forms almost colourless transparent platelets and crystallizes with a new structure type containing two dimensional networks of branched SCu zig-zag-chains with linear coordination for copper. A description on the basis of a hexagonal close packing of anions is given.

/pdf/cscu4s3-und-cscu3s2-sulfide-mit-tetraedrisch-und-linear-xr72o6svn9.pdf

CsCu4S3 und CsCu3S2: Sulfide mit tetraedrisch und linear koordiniertem Kupfer

NaCu4S4, a simple new low-dimensional, metallic copper polychalcogenide, structurally related to CuS

Die ternaren Selenide Rb3Cu8Se6 und Cs3Cu8Se6 konnten durch Umsetzungen von Alkalimetallcarbonaten mit Kupfer und Selen in der Schmelze synthetisiert werden. Rontgenbeugungsuntersuchungen an Einkristallen fuhrten zur Struktur der isotypen Verbindungen. Die monoklinen Elementarzellen enthalten zwei Formeleinheiten. Die hochstsymmetrische Raumgruppe ist C2/m. Als Gitterkonstanten ergeben sich:



Rb3Cu8Se6: a = 1 845,8(6) pm, b = 401,0(1) pm, c = 1 021,2(3) pm, β = 104,44(2)°;



Cs3Cu8Se6: a = 1 907,6(4) pm, b = 407,8(1) pm, c = 1 044,9(3) pm, β = 106,04(3)°;



Die Atomanordnung wird als Schichtenstruktur diskutiert.



Ternary Selenides of Copper



The ternary selenides Rb3Cu8Se6 and Cs3Cu8Se6 have been synthesized by fusion reactions of alkali carbonates and selenium with copper. X-ray investigations on single crystals revealed the structure of the isotypic compounds. The monoclinic unit cells (q.v. Inhaltsubersicht) contain two formula units. The space group with the highest symmetry is C2/m. The atomic arrangement can be discussed as a layer-type structure.

Ternäre Selenide des Kupfers

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Ternäre Selenide des Kupfers