Charge transfer complexes of dithioxamides with dihalogens as powerful reagents in the dissolution of noble metals

Commonly involved in the recovery/refining processes of noble metals (NMs), coordination chemistry is now required by new legislation to face requirements in the selection of ligands that must combine effectiveness with low environmental impact, in order to balance sustainability with economic development for conventional applications and for the recovery of NMs from secondary sources thus helping to convert Trash in Resource. In this paper, we review the properties of dihalogen/cyclic-dithioxamide adducts as a case-study to show how suitable complexes can provide innovation in the recovery processes of NMs from secondary sources and in the gold etching process in improving the reliability of microelectronic devices. These adducts, which do not show cytotoxicity, are capable of dissolving metal palladium and even gold in a one-step reaction and under mild conditions. In particular, Me₂dazdt·2I₂ (Me₂dazdt = N,N’-dimethyl-perhydrodiazepine-2,3-dithione) has proved to be the most effective in practical applications. It has been used in the palladium recovery from model spent three way catalysts (TWC). It selectively dissolved palladium, almost quantitatively, under mild conditions, even in a complex system such as an exhaust catalytic converter, a ceramic material that has undergone severe thermal and chemical stresses. Quite satisfactory results have also been obtained in gold recovery from selected WEEE (waste from electrical and electronic equipments) scrap and from deprocessing procedures for the failure analysis of microelectronic devices.     

Die Oxidation von Triisopropylphosphan mit Iod: Zur Rolle von trockenem und feuchtem Lösungsmittel

Oxidation of Triisopropylphosphane with Iodine: The Role of Dry or Moist Solvent i‐Pr₃P ( 1 ) and iodine give i‐Pr₃PI₂ ( 2 ). In crystals obtained from CH₂Cl₂ solution, ion pairs [i‐Pr₃PI⁺I^–] of 2 exhibiting I…I interactions are linked by CH₂Cl₂ molecules. With a second equivalent of iodine, i‐Pr₃PI⁺ I₃^– ( 3 ) is formed; the reaction of 2 with AgSbF₆ provides i‐Pr₃PI⁺SbF₆^– ( 6 ). The presence of moisture and air leads to the formation of i‐Pr₃POH⁺ salts. Solid i‐Pr₃POH⁺I^– ( 4 ) exhibits P–O–H…I cation‐anion contacts, solid (i‐Pr₃PO)₂H⁺I₃^– ( 5 ) contains a centrosymmetric P=O…H…O=P‐bridged cation. Distinguishing i‐Pr₃PI⁺ salts 2 , 3 from hydrolysis products 4 , 5 by ³¹P‐NMR in reaction mixtures is not trivial, because both kinds of cations exihibit similar ³¹P‐NMR shifts and both participate in interactions with their anions, and in equilibria with uncharged donors: rapid I⁺ transfer reactions and I…I soft‐soft interactions involving 1 , and rapid H⁺ transfer reactions and hydrogen bonds involving i‐Pr₃P=O ( 7 ).     

High order elements in finite fields arising from recursive towers

Designs, Codes and Cryptography - We illustrate a general technique to construct towers of fields producing high order elements in $$\mathbb {F}_{q^{2^n}}$$ , for odd q, and in $$\mathbb {F}_{2^{2...     

Sensitivity analysis of Mixed Tempered Stable parameters with implications in portfolio optimization

Computational Management Science - This paper investigates the use, in practical financial problems, of the Mixed Tempered Stable distribution both in its univariate and multivariate formulation....     

Kinetic Parameters of Polyethylene Degradation by the Natural Zeolite Chabazite

High-density polyethylene (PE) was subjected to thermal degradation alone and in the presence of an ammonium-exchanged zeolite chabazite (CHA/PE). The processes were carried out in a reactor connected online to a gas chromatograph/mass spectrometer in order to analyse the evolved products. Polymer degradation was also evaluated by thermogravimetry, from room temperature up to 800°C, under a dynamic nitrogen atmosphere, with multiple heating rates. From the TG curves, the activation energy relating to the degradation process was calculated by using the Flynn and Wall multiple heating rate kinetic model for pure PE and for CHA/PE. The exchanged chabazite exhibited good selectivity for the catalytic degradation of PE to low molecular mass hydrocarbons. This revised version was published online in August 2006 with corrections to the Cover Date.     

Ln3Q9 as a Molecular Framework for Ion‐Size‐Driven Assembly of Heterolanthanide (Nd,Er, Yb) Multiple Near‐Infrared Emitters

A unique example of discrete molecular entity Nd_yEr_xYb_3?(x+y)Q₉ ( 1 ) (Q=quinolinolato) containing three different lanthanides simultaneously emitting in three different spectral regions in the NIR, ranging from 900 to 1600 nm, has been synthesized and fully chararacterized. A simple molecular strategy based on tuning metal composition in the Ln₃Q₉ framework, which contains inequivalent central and terminal coordination sites, has allowed a satisfactory ion‐size‐driven control of molecular speciation close to 90 %. In 1 the central position of the larger Nd ion is well distinguished from the terminal ones of the smaller Yb³⁺ and Er³⁺, which are almost “vicariants” as found in the heterobimetallic Er_xYb_3?xQ₉ ( 2 ). The Ln₃Q₉ molecular architecture, which allows communication between the ions, has proved to afford multiple NIR emission in 1 and 2 , and is promising to develop a variety of multifunctional materials through the variation of the Ln composition.     

On the Hierarchy of d-structures

In this paper we identify and study several lattice structures in the context of directed topology. The set of d-structures on a topological space is a Heyting algebra. The implication is constructed explicitely. There is a Galois connection between the lattice of subsets of the space and the lattice of d-structures which clarifies the idea of removing a subset of the space which has only constant dipaths. Hence, variation of d-structures and variation of the “forbidden area” may be considered in one structure. Moreover, the lattice of d-structures gives rise to a lattice of directed paths between a fixed pair of points. That lattice permits us to discuss a perspective on generalised persistence. Furthermore, we consider a lattice structure in the hierarchy of structures on the n-cube.