A Cornucopia of Iridium Nitrogen Compounds Produced from Laser‐Ablated Iridium Atoms and Dinitrogen

The reaction of laser‐ablated iridium atoms with dinitrogen molecules and nitrogen atoms yield several neutral and ionic iridium dinitrogen complexes such as Ir(N2), Ir(N2)+, Ir(N2)2, Ir(N2)2−, IrNNIr, as well as the nitrido complexes IrN, Ir(N)2 and IrIrN. These reaction products were deposited in solid neon, argon and nitrogen matrices and characterized by their infrared spectra. Assignments of vibrational bands are supported by ab initio and first principle calculations as well as 14/15N isotope substitution experiments. The structural and electronic properties of the new dinitrogen and nitrido iridium complexes are discussed. While the formation of the elusive dinitrido complex Ir(N)2 was observed in a subsequent reaction of IrN with N atoms within the cryogenic solid matrices, the threefold coordinated iridium trinitride Ir(N)3 could not be observed so far

Forecasting the Risk of Speculative Assets by Means of Copula Distributions

The GARCH(1,1) model and its extensions have become a standard econometric tool for modeling volatility dynamics of financial returns and port-folio risk. In this paper, we propose an adjustment of GARCH implied conditional value-at-risk and expected shortfall forecasts that exploits the predictive content of uncorrelated, yet dependent model innovations. The adjustment is motivated by non-Gaussian characteristics of model residuals, and is implemented in a semiparametric fashion by means of conditional moments of simulated bivariate standardized copula distributions. We conduct in-sample forecasting comparisons for a set of 18 stock market indices. In total, four competing copula-GARCH models are contrasted against each other on the basis of their one-step ahead forecasting performance. With regard to forecast unbiasedness and precision, especially the Frank-GARCH models provide most conservative risk forecasts and out-perform all rival models

A combined quantum-chemical and matrix-isolation study on molecular manganese fluorides

Molecular manganese fluorides were studied using quantum-chemical calculations at DFT and CCSD(T) levels and experimentally by matrix-isolation techniques. They were prepared by co-deposition of IR-laser ablated elemental manganese or manganese trifluoride with F2 in an excess of Ne, Ar, or N2 or with neat F2 at 5–12 K. New IR bands in the Mn–F stretching region are detected and assigned to matrix-isolated molecular MnFx (x = 1–3)

[P4H]+[Al(OTeF5)4]−: protonation of white phosphorus with the Brønsted superacid H[Al(OTeF5)4](solv)

A sustainable transformation of white phosphorus (P4) into chemicals of higher value is one of the key aspects in modern phosphorus research. Even though the chemistry of P4 has been investigated for many decades, its chemical reactivity towards the simplest electrophile, the proton, is still virtually unknown. Based on quantum-chemical predictions, we report for the first time the successful protonation of P4 by the Brønsted acid H[Al(OTeF5)4](solv). Our spectroscopic results are in agreement with acid-mediated activation of P4 under protonation of an edge of the P4-tetrahedron and formation of a three-center two-electron P–H–P bond. These investigations are of fundamental interest as they permit the activation of P4 with the simplest electrophile as a new prototype reaction for this molecule

Friedel-Crafts Type Methylation with Dimethylhalonium Salts

The dimethylchloronium salt [Me2Cl][Al(OTeF5)(4)] is used to methylate electron-deficient aromatic systems in Friedel-Crafts type reactions as shown by the synthesis ofN-methylated cations, such as [MeNC5F5](+), [MeNC5F4I](+), and [MeN3C3F3](+). To gain a better understanding of such fundamental Friedel-Crafts reactions, the role of the dimethylchloronium cation has been evaluated by quantum-chemical calculations

Investigation of molecular alkali tetrafluorido aurates by matrix‐isolation spectroscopy

Molecular alkali tetrafluorido aurate ion pairs M[AuF4] (M=K, Rb, Cs) are produced by co‐deposition of IR laser‐ablated AuF3 and MF in solid neon under cryogenic conditions. This method also yields molecular AuF3 and its dimer Au2F6. The products are characterized by their Au–F stretching bands and high‐level quantum‐chemical calculations at the CCSD(T)/triple‐ζ level of theory. Structural changes in AuF4− associated with the coordination of the anion to different alkali cations are proven spectroscopically and discussed

Conductivity and Redox Potentials of Ionic Liquid Trihalogen Monoanions [X3]−, [XY2]−, and [BrF4]− (X=Cl, Br, I and Y=Cl, Br)

The ionic liquid (IL) trihalogen monoanions [N2221][X3]− and [N2221][XY2]− ([N2221]+=triethylmethylammonium, X=Cl, Br, I, Y=Cl, Br) were investigated electrochemically via temperature dependent conductance and cyclic voltammetry (CV) measurements. The polyhalogen monoanions were measured both as neat salts and as double salts in 1‐butyl‐1‐methyl‐pyrrolidinium trifluoromethane‐sulfonate ([BMP][OTf], [X3]−/[XY2]− 0.5 M). Lighter IL trihalogen monoanions displayed higher conductivities than their heavier homologues, with [Cl3]− being 1.1 and 3.7 times greater than [Br3]− and [I3]−, respectively. The addition of [BMP][OTf] reduced the conductivity significantly. Within the group of polyhalogen monoanions, the oxidation potential develops in the series [Cl3]−>[BrCl2]−>[Br3]−>[IBr2]−>[ICl2]−>[I3]−. The redox potential of the interhalogen monoanions was found to be primarily determined by the central halogen, I in [ICl2]− and [IBr2]−, and Br in [BrCl2]−. Additionally, tetrafluorobromate(III) ([N2221]+[BrF4]−) was analyzed via CV in MeCN at 0 °C, yielding a single reversible redox process ([BrF2]−/[BrF4]−)

Investigation of Molecular Iridium Fluorides IrFn (n=1–6): A Combined Matrix-Isolation and Quantum-Chemical Study

The photo-initiated defluorination of iridium hexafluoride (IrF6) was investigated in neon and argon matrices at 6 K, and their photoproducts are characterized by IR and UV-vis spectroscopies as well as quantum-chemical calculations. The primary photoproducts obtained after irradiation with λ=365 nm are iridium pentafluoride (IrF5) and iridium trifluoride (IrF3), while longer irradiation of the same matrix with λ=278 nm produced iridium tetrafluoride (IrF4) and iridium difluoride (IrF2) by Ir−F bond cleavage or F2 elimination. In addition, IrF5 can be reversed to IrF6 by adding a F atom when exposed to blue-light (λ=470 nm) irradiation. Laser irradiation (λ=266 nm) of IrF4 also generated IrF6, IrF5, IrF3 and IrF2. Alternatively, molecular binary iridium fluorides IrFn (n=1–6) were produced by co-deposition of laser-ablated iridium atoms with elemental fluorine in excess neon and argon matrices under cryogenic conditions. Computational studies up to scalar relativistic CCSD(T)/triple-ζ level and two-component quasirelativistic DFT computations including spin-orbit coupling effects supported the formation of these products and provided detailed insights into their molecular structures by their characteristic Ir−F stretching bands. Compared to the Jahn-Teller effect, the influence of spin-orbit coupling dominates in IrF5, leading to a triplet ground state with C4v symmetry, which was spectroscopically detected in solid argon and neon matrices

Non-classical polyinterhalides of chlorine monofluoride: experimental and theoretical characterization of [F(ClF)3]−

We present the synthesis and characterization of the first non-classical Cl(I) polyinterhalide [NMe4][F(ClF)3] as well as the homologous polychloride [NPr3Me][Cl7]. Both salts were obtained from the reaction of the corresponding ammonium chlorides with ClF or Cl2, respectively. Quantum-chemical investigations predict an unexpected planar structure for the [F(ClF)3]− anion

(Noble Gas)n-NC+ Molecular Ions in Noble Gas Matrices: Matrix Infrared Spectra and Electronic Structure Calculations

An investigation of pulsed-laser-ablated Zn, Cd and Hg metal atom reactions with HCN under excess argon during co-deposition with laser-ablated Hg atoms from a dental amalgam target also provided Hg emissions capable of photoionization of the CN photo-dissociation product. A new band at 1933.4 cm−1 in the region of the CN and CN+ gas-phase fundamental absorptions that appeared upon annealing the matrix to 20 K after sample deposition, and disappeared upon UV photolysis is assigned to (Ar)nCN+, our key finding. It is not possible to determine the n coefficient exactly, but structure calculations suggest that one, two, three or four argon atoms can solvate the CN+ cation in an argon matrix with C−N absorptions calculated (B3LYP) to be between 2317.2 and 2319.8 cm−1. Similar bands were observed in solid krypton at 1920.5, in solid xenon at 1935.4 and in solid neon at 1947.8 cm−1. H13CN reagent gave an 1892.3 absorption with shift instead, and a 12/13 isotopic frequency ratio–nearly the same as found for 13CN+ itself in the gas phase and in the argon matrix. The CN+ molecular ion serves as a useful infrared probe to examine Ng clusters. The following ion reactions are believed to occur here: the first step upon sample deposition is assisted by a focused pulsed YAG laser, and the second step occurs on sample annealing: (Ar)2++CN→Ar+CN+→(Ar)nCN+