Trifluoromethyl Fluorosulfonate (CF3OSO2F) and Trifluoromethoxy Sulfur Pentafluoride (CF3OSF5) - Two Gaseous Sulfur(VI) Compounds with Insulating Properties.

In this work, we analyzed trifluoromethyl fluorosulfonate (CF3OSO2F) and trifluoromethoxy sulfur pentafluoride (CF3OSF5) regarding their potential use as dielectrics by investigating some of their intrinsic and extrinsic properties. Both compounds show a higher breakdown voltage than SF6 with averaged relative breakdown voltages of 1.3±0.2 for CF3OSO2F and 1.4±0.2 for CF3OSF5 compared to SF6 with 1.0. Like the dielectric (CF3)2CFCN, both compounds decompose during the breakdown process. The decomposition products were analyzed by IR spectroscopy and GCIR methods. Furthermore, the molecular structures of both gaseous compounds CF3OSO2F and CF3OSF5 have been determined by in situ crystallization, and their physical properties were determined as well.

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.

(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)n CN+ , 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 . H13 CN reagent gave an 1892.3 absorption with shift instead, and a 12/13 isotopic frequency ratio-nearly the same as found for 13 CN+ 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)n CN+ .

Structural proof of a [C-F-C]+ fluoronium cation.

Organic fluoronium ions can be described as positively charged molecules in which the most electronegative and least polarizable element fluorine engages in two partially covalent bonding interactions to two carbon centers. While recent solvolysis experiments and NMR spectroscopic studies on a metastable [C-F-C]+ fluoronium ion strongly support the divalent fluoronium structure over the alternative rapidly equilibrating classical carbocation, the model system has, to date, eluded crystallographic analysis to confirm this phenomenon in the solid state. Herein, we report the single crystal structure of a symmetrical [C-F-C]+ fluoronium cation. Besides its synthesis and crystallographic characterization as the [Sb2F11]- salt, vibrational spectra are discussed and a detailed analysis concerning the nature of the bonding situation in this fluoronium ion and its heavier halonium homologues is performed, which provides detailed insights on this molecular structure.

Novel synthetic pathway for the production of phosgene.

Chloride ions are efficient catalysts for the synthesis of phosgene from carbon monoxide and elemental chlorine at room temperature and atmospheric pressure. Control experiments rule out a radical mechanism and highlight the role of triethylmethylammonium trichloride, [NEt3Me][Cl3], as active species. In the catalytic reaction, commercially available [NEt3Me]Cl reacts with Cl2 to form [NEt3Me][Cl3], enabling the insertion of CO into an activated Cl─Cl bond with a calculated energy barrier of 56.9 to 77.6 kJ mol−1. As [NEt3Me]Cl is also a useful chlorine storage medium, it could serve as a catalyst for phosgene production and as chlorine storage in a combined industrial process.

Cyanides, Isocyanides, and Hydrides of Zn, Cd and Hg from Metal Atom and HCN Reactions: Matrix Infrared Spectra and Electronic Structure Calculations.

Zinc and cadmium atoms from laser ablation of the metals and mercury atoms ablated from a dental amalgam target react with HCN in excess argon during deposition at 5 K to form the MCN and MNC molecules and CN radicals. UV irradiation decreases the higher energy ZnNC isomer in favor of the lower energy ZnCN product. Cadmium and mercury atoms produce analogous MCN primary molecules. Laser ablation of metals also produces plume radiation which initiates H-atom detachment from HCN. The freed H atom can add to CN radical to produce the HNC isomer. The argon matrix also traps the higher energy but more intensely absorbing isocyanide molecules. Further reactions with H atoms generate HMCN and HMNC hydrides, which can be observed by virtue of their C-N stretches and intense M-H stretches. Computational modeling of IR spectra and relative energies guides the identification of reaction products by providing generally reliable frequency differences within the Zn, Cd and Hg family of products, and estimating isotopic shifts using to 13 C and 15 N isotopic substitution for comparison with experimental data.

Matrix Isolation Spectroscopic and Relativistic Quantum Chemical Study of Molecular Platinum Fluorides PtFn (n=1-6) Reveals Magnetic Bistability of PtF4.

Molecular platinum fluorides PtFn , n=1-6, are prepared by two different routes, photo-initiated fluorine elimination from PtF6 embedded in solid noble-gas matrices, and the reaction of elemental fluorine with laser-ablated platinum atoms. IR spectra of the reaction products isolated in rare-gas matrices under cryogenic conditions provide, for the first time, experimental vibrational frequencies of molecular PtF3 , PtF4 and PtF5 . Photolysis of PtF6 enabled a highly efficient and almost quantitative formation of molecular PtF4 , whereas both PtF5 and PtF3 were formed simultaneously by subsequent UV irradiation of PtF4 . The vibrational spectra of these molecular platinum fluorides were assigned with the help of one- and two-component quasirelativistic DFT computation to account for scalar relativistic and spin-orbit coupling effects. Competing Jahn-Teller and spin-orbit coupling effects result in a magnetic bistability of PtF4 , for which a spin-triplet (3 B2g , D2h ) coexists with an electronic singlet state (1 A1g , D4h ) in solid neon matrices.

The Peculiar Interaction of Trifluoride Anions with Cryogenic Rare Gas Matrices.

In this contribution, we present theoretical modeling of the interaction between rare gas matrices and a trifluoride guest anion, as well as its quantitative effect on measured vibrational spectra. Using a combination of coupled-cluster electronic structure calculations and a many-body potential expansion coupled with permutation invariant polynomial fitting and anharmonic vibrational spectrum simulations, we shed light on the origin of the trifluoride matrix effects observed experimentally. The theoretical spectra are found to reproduce accurately the measured data while providing deeper insights into the effects of the guest-host interaction. The investigations reveal that neon can only stabilize trifluoride in hexagonal cavities formed by double vacancies, while argon can host the anion in a variety of cavities ranging from zero to two defects in the matrix. The origin of this structural variability can be traced back to the disparate strengths of the host-host interactions in neon and argon. The present work demonstrates the importance of theoretical modeling to complement matrix isolation experiments, which alone do not provide direct information about the structure of the matrices or about the physical origin of their interaction and of their spectroscopic signature.

Cleavage of the N≡N Triple Bond and Unpredicted Formation of the Cyclic 1,3-Diaza-2,4-Diborete (FB)2 N2 from N2 and Fluoroborylene BF.

A complete cleavage of the triple bond of N2 by fluoroborylene (:BF) was achieved in a low-temperature N2 matrix by the formation of the four-membered heterocycle FB(µ-N)2 BF, which lacks a trans-annular N-N bond. Additionally, the linear complex FB=N-N=BF and cyclic FB(η2 -N2 ) were formed. These novel species were characterized by their matrix infrared spectra and quantum-chemical calculations. The puckered four-membered-ring B2 N2 complex shows a delocalized aromatic two-electron π-system in conjugation with the exo-cyclic fluorine π lone pairs. This work may contribute to a rational design of catalysts based on borylene for artificial dinitrogen activation.

High-Spin Iron(VI), Low-Spin Ruthenium(VI), and Magnetically Bistable Osmium(VI) in Molecular Group 8 Nitrido Trifluorides NMF3.

Pseudo-tetrahedral nitrido trifluorides N≡MF3 (M=Fe, Ru, Os) and square pyramidal nitrido tetrafluorides N≡MF4 (M=Ru, Os) were formed by free-metal-atom reactions with NF3 and subsequently isolated in solid neon at 5 K. Their IR spectra were recorded and analyzed aided by quantum-chemical calculations. For a d2 electron configuration of the N≡MF3 compounds in C3v symmetry, Hund's rule predict a high-spin 3 A2 ground state with two parallel spin electrons and two degenerate metal d(δ)-orbitals. The corresponding high-spin 3 A2 ground state was, however, only found for N≡FeF3 , the first experimentally verified neutral nitrido FeVI species. The valence-isoelectronic N≡RuF3 and N≡OsF3 adopt different angular distorted singlet structures. For N≡RuF3 , the triplet 3 A2 state is only 5 kJ mol-1 higher in energy than the singlet 1 A' ground state, and the magnetically bistable molecular N≡OsF3 with two distorted near degenerate 1 A' and 3 A" electronic states were experimentally detected at 5 K in solid neon.

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.

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 ]- ).

Searching for Monomeric Nickel Tetrafluoride: Unravelling Infrared Matrix Isolation Spectra of Higher Nickel Fluorides.

Binary transition metal fluorides are textbook examples combining complex electronic features with most fundamental molecular structures. High-valent nickel fluorides are among the strongest known fluorinating and oxidizing agents, but there is a lack of experimental structural and spectroscopic investigations on molecular NiF3 or NiF4 . Apart from their demanding synthesis, also their quantum-chemical description is difficult due to their open shell nature and low-lying excited electronic states. Distorted tetrahedral NiF4 (D2d ) and trigonal planar NiF3 (D3h ) molecules were produced by thermal evaporation and laser ablation of nickel atoms in a fluorine/noble gas mixture and spectroscopically identified by a joint matrix-isolation and quantum-chemical study. Their vibrational band positions provide detailed insights into their molecular structures.

Insights into the Topology and the Formation of a Genuine ppσ Bond: Experimental and Computed Electron Densities in Monoanionic Trichlorine [Cl3 ].

So far, several publications have discussed the bonding concepts in polyhalides on a theoretical basis. In particular, the trichlorine monoanion is of great interest because its structure should be symmetrical and show two equidistant Cl-Cl bonds. However, apart from matrix-isolation studies, only asymmetric trichlorine anions have been reported so far. Herein, the trichlorine monoanions in 2-chloroethyltrimethylammonium trichloride [NMe3 EtCl][Cl3 ], 1, tetramethylammonium trichloride [NMe4 ][Cl3 ], 2, and tetrapropylammonium trichloride [NnPr4 ][Cl3 ], 3, are analysed. High-resolution X-ray structures and experimental charge density analyses supported by periodic quantum-chemical calculations provide insight into the influence of the crystalline environment on the structure of these [Cl3 ]- anions as well as into the progress of the bond formation between a dichlorine molecule and a Cl- anion.

Fluoro Nitrenoid Complexes FN=MF2 (M=Co, Rh, Ir): Electronic Structure Dichotomy and Formation of Nitrido Fluorides N≡MF3.

The fluoronitrenoid metal complexes FNCoF2 and FNRhF2 as well as the first ternary RhVI and IrVI complexes NIrF3 and NRhF3 are described. They were obtained by the reaction of excited Group-9 metal atoms with NF3 and their IR spectra, isolated in solid rare gases (neon and argon), were recorded. Aided by the observed 14/15 N isotope shifts and quantum-chemical predictions, all four stretching fundamentals of the novel complexes were safely assigned. The F-N stretching frequencies of the fluoronitrenoid complexes FNCoF2 (1056.8 cm-1 ) and FNRhF2 (872.6 cm-1 ) are very different and their N-M bonds vary greatly. In FNCoF2 , the FN ligand is singly bonded to Co and bears considerable iminyl/nitrene radical character, while the N-Rh bond in FNRhF2 is a strong double bond with comparatively strong σ- and π-bonds. The anticipated rearrangement of FNCoF2 to the nitrido CoVI complex is predicted to be endothermic and was not observed.

Charge-Inverted Hydrogen-Bridged Bond in HCa(µ-H)3E (E = Si, Ge, and Sn): Matrix Isolation Infrared Spectroscopic and Theoretical Studies.

Matrix isolation infrared spectroscopy combined with quantum-chemical calculations were employed to study the reactions of calcium atoms with silane, germane, and stannane in a 4 K argon matrix. The ion pairs [HCa]+ and [EH3]- (E = Si, Ge, and Sn) in both the classical structure HCaEH3 and the bridged structure HCa(µ-H)3E were identified based on the H/D isotopic substitution experiments and quantum-chemical calculations. The results show that the reaction between ground-state Ca and EH4 proceeds inefficiently, and only after the photolytic activation of Ca atoms to the Ca(1P:4s4p) state does insertion occur to give HCaEH3, which rearranges to HCa(µ-H)3E upon photolysis. Topological analysis of the electronic structure suggests that the nonclassical structure HCa(µ-H)3E is formed by the electrostatic interaction with charge-inverted hydrogen bridge bond, while HCaEH3 is dominated by (HCa)+(EH3)- ion pair interactions.

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

Invited for the cover of this issue is the group of Sebastian Riedel at Freie Universität Berlin. The image depicts an iridium rainbow reacting with dinitrogen to form iridium-nitrogen compounds. Read the full text of the article at 10.1002/chem.201905514.

Friedel-Crafts Type Methylation with Dimethylhalonium Salts.

The dimethylchloronium salt [Me2 Cl][Al(OTeF5 )4 ] is used to methylate electron-deficient aromatic systems in Friedel-Crafts type reactions as shown by the synthesis of N-methylated cations, such as [MeNC5 F5 ]+ , [MeNC5 F4 I]+ , and [MeN3 C3 F3 ]+ . To gain a better understanding of such fundamental Friedel-Crafts reactions, the role of the dimethylchloronium cation has been evaluated by quantum-chemical calculations.

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 14/15 N 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.

IR-Laser Ablation of Potassium Cyanide: A Surprisingly Simple Route to Polynitrogen and Polycarbon Species.

Pulsed laser irradiation of solid potassium cyanide (KCN) produces, besides free nitrogen and carbon atoms, the molecular species KN and KC which are potential candidates for interstellar species of potassium. Additionally, N3 , N3 - , KN3 , C3 , C3 - , and KC3 are produced and isolated in solid noble gases as well as in solid N2 . Molecular potassium nitrene (KN) reacts with dinitrogen in neon and argon matrices after photochemical excitation (λ=470 nm) forming molecular end-on (C∞v ) and side-on (C2v ) potassium azide isomers. The side-on isomer (C2v ) is thermodynamically favored at the CCSD(T)/ma-def2-TZVP level of theory. It can be obtained from the end-on isomer by UV-irradiation (λ=273 nm).