Zur Kristallchemie der Oxorhodate

Abstract

Das Review gibt einen Einblick in die Kristallchemie der Oxorhodate. Im Vergleich mit der Oxochemie anderer Edelmetalle dominiert im noch stärkeren Maße die oktaedrische Koordination des Rhodiums. Sie wird von den Oxiden Rh2O3, hp‐Rh2O3 und RhO2 vorgegeben und findet sich unabhängig von den Valenzen des Rhodiums in Oxorhodaten wieder. Bis auf wenige Ausnahmen überwiegt die Wertigkeit drei (Rh3+). Oxorhodate adaptieren die Kristallchemie der Delafossite, des K2NiF4‐Typs und dessen Varianten. Sie bilden Stapelvarianten, die sogenannten “eindimensionalen Oxide”, Perowskite, Pyrochlore, Hollandite und Spinelle. Bemerkenswert ist ein Perrhenat‐ähnliches Netzwerk in URh2O6 und eine Variante des SrCr2O4‐Typs beobachtet an β‐Sr0,97Rh2O4. Von Interesse ist Pb3Rh7O15, in dessen Oktaedergerüst einseitig offene Polyeder Pb(1)O4 und Pb(2)O6 eingebettet sind, die durch das lone pair am Pb2+ zu Polyedern des Typs Pb(1)O4LP(1) (trigonale Bipyramide) und Pb(2)O6LP(2) (überkapptes trigonales Prisma) ergänzt werden. Die Positionen der lone pairs (e2− Punktladung) wird durch Berechnungen des Madelung‐Anteils der Gitterenergie ermittelt.

Octaammine EuII and YbII Azides and Their Thermal Decompositions to the Nitrides

“…The Yb II –N bonds are again ca. 0.1–0.15 Å longer compared to the ones of the Yb III compounds reported in the literature and discussed above . The azide anions show bond lengths of 1.169(10)–1.198(12) Å, which are in good agreement with the ones obtained for compound 2 .…”

“…0.15 Å shorter due to the higher oxidation state of the central metal atoms. A report by Müller‐Buschbaum, who also worked on heteroleptic ammine complexes, states for the Yb III compound [Yb(NH 3 ) 8 ][Yb(Pyr) 6 ] (Pyr = pyrrolate), which was crystallized from liquid ammonia at –35 °C, Yb III –N distances of 2.446(2)–2.504(2) Å . Again, the coordination polyhedron was described as square‐antiprismatic with bond lengths shorter compared to our compound.…”

“…Vapor pressure measurements on the system Ln /NH 3 ( Ln = Eu, Yb) indicated the existence of hexaammine complexes of the respective metals based on chemical reasoning, which was later structurally proven by X‐ray diffraction . The considerably smaller Ln III ions form octa‐ and even nonaammine complexes, so it was expected that Ln II ions ( Ln = Eu, Yb) should also form ammine complexes of coordination numbers higher than six . Here we present the synthesis of octaammine complexes of europium(II) and ytterbium(II) azides in liquid ammonia and their characterisation by single‐crystal X‐ray diffraction.…”

Ln‐Imidazolate Frameworks: The Coordinative Demand of Ln3+ Ions and its Consequences for the Compound Constitution of Different Lanthanides

“…The structure was resolved via a Pawley‐intensity extraction21 and successive application of charge‐flipping algorithms 22. The Rietveld refinement was stable on the application of rigid body constraints for the imidazolate ring systems,23 which gave an overall satisfactory result for the structure refinement concerning atom positions and distances. Crystallographic data for the crystal X‐ray determinations are summarized in Table 1.…”

Synthesis and crystal structure of two new cerium rhodium oxides: Ce2/3−xRh3+2O4 (x∼0.12) with Ce mixed valency and Ce4+Rh3+2O5

“…Rhodium is commonly found as Rh 3 þ or Rh 4 þ in oxides [1]. Synthesis in air usually results in Rh 3 þ , which takes octahedral coordination.…”