Matrix-isolation and computational study of the HKrCCH center dot center dot center dot HCCH complex

The HKrCCH center dot center dot center dot HCCH complex is identified in a Kr matrix with the H-Kr stretching bands at 1316.5 and 1305 cm(-1). The monomer-to-complex shift of the H-Kr stretching mode is about +60 cm(-1), which is significantly larger than that reported previously for the HXeCCH center dot center dot center dot HCCH complex in a Xe matrix (about +25 cm(-1)). The HKrCCH center dot center dot center dot HCCH complex in a Kr matrix is formed at similar to 40 K via the attachment of mobile acetylene molecules to the HKrCCH monomers formed at somewhat lower annealing temperatures upon thermally-induced mobility of H atoms (similar to 30 K). The same mechanism was previously proposed for the formation of the HXeCCH center dot center dot center dot HCCH complex in a Xe matrix. The assignment of the HKrCCH center dot center dot center dot HCCH complex is fully supported by the quantum chemical calculations. The experimental shift of the H-Kr stretching mode is comparable with the computational predictions (+46.6, +66.0, and +83.2 cm(-1) at the B3LYP, MP2, and CCSD(T) levels of theory, respectively), which are also bigger that the calculated shift in the HXeCCH center dot center dot center dot HCCH complex. These results confirm that the complexation effect is bigger for less stable noble-gas hydrides.Peer reviewe

Reactions of Laser-Ablated U Atoms with HF: Infrared Spectra and Quantum Chemical Calculations of HUF, UH, and UF in Noble Gas Solids

Reactions of laser-ablated U atoms with HF produce HUF as the major product and UH and UF as minor products, which are identified from their argon and neon matrix infrared spectra. Our assignment of HUF is confirmed by the observation of DUF and close agreement with observed and calculated vibrational frequencies and deuterium shifts in the vibrational frequencies. Our previous observation of the UH diatomic molecule from argon matrix experiments with H₂, HD, and D₂ as reagents is confirmed through its present observation with HF and DF, and with recent higher level quantum chemical calculations. The HF reaction provides a lower concentration of F in the system and thus simplifies the fluorine chemistry relative to similar U atom reactions with F₂, and the new matrix identification of UF here is consistent with recent high level calculations on UF. In addition, we find evidence for the higher oxidation state secondary reaction products UHF₂, UHF₃, and UH₂F₂

Extending the Row of Lanthanide Tetrafluorides: A Combined Matrixâ Isolation and Quantumâ Chemical Study

Only the neutral tetrafluorides of Ce, Pr, and Tb as well as the [LnF7]3â anions of Dy and Nd, with the metal in the +IV oxidation state, have been previously reported. We report our attempts to extend the row of neutral lanthanide tetrafluorides through the reaction of laserâ ablated metal atoms with fluorine and their stabilization and characterization by matrixâ isolation IR spectroscopy. In addition to the above three tetrafluorides, we found two new tetrafluorides, 3NdF4 and 7DyF4, both of which are in the +IV oxidation state, which extends this lanthanide oxidation state to two new metals. Our experimental results are supported by quantumâ chemical calculations and the role of the lanthanide oxidation state is discussed for both the LnF4 and [LnF4]â species. Most of the LnF4 species are predicted to be in the +IV oxidation state and all of the [LnF4]â anions are predicted to be in the +III oxidation state. The LnF4 species are predicted to be strong oxidizing agents and the LnF3 species are predicted to be moderate to strong Lewis acids.Lanthanide tetrafluorides extended: Two new tetrafluorides, 3NdF4 and 7DyF4, both of which are in the +IV oxidation state, are reported; these compounds extend the examples of neutral lanthanide tetrafluorides beyond those of Ce, Pr, and Tb. The new compounds were formed by reaction of laserâ ablated metal atoms with fluorine and their stabilization and characterization by matrixâ isolation IR spectroscopy are supported by quantumâ chemical calculations (see figure).Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137267/1/chem201504182.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137267/2/chem201504182-sup-0001-misc_information.pd

New Evidence in an Old Case: The Question of Chromium Hexafluoride Reinvestigated

The question of whether or not the chromium hexafluoride molecule has been synthesized and characterized has been widely discussed in the literature and cannot, in spite of many efforts, yet be answered beyond doubt. New matrix-isolation experiments can now show, together with state-of-the-art quantum-chemical calculations, that the compound previously isolated in inert gas matrixes, was CrF₅ and not CrF₆. New bands in the matrix IR spectra can be assigned to the Cr₂F₁₀ dimer, and furthermore evidence was found in the spectra for a photodissociation or reversible excitation of CrF₅ under UV irradiation. However, even if CrF₆ is not stable at ambient conditions, its formation under high fluorine pressures in autoclave reactions cannot be excluded completely

Reaction of Laser-Ablated Uranium and Thorium Atoms with H₂Se: A Rare Example of Selenium Multiple Bonding

The compounds H₂ThSe and H₂USe were synthesized by the reaction of laser-ablated actinide metal atoms with H₂Se under cryogenic conditions following the procedures used to synthesize H₂AnX (An = Th, U; X = O, S). The molecules were characterized by infrared spectra in an argon matrix with the aid of deuterium substitution and electronic structure calculations at the density functional theory level. The main products, H₂ThSe and H₂USe, are shown to have a highly polarized actinide–selenium triple bond, as found for H₂AnS on the basis of electronic structure calculations. There is an even larger back-bonding of the Se with the An than found for the corresponding sulfur compounds. These molecules are of special interest as rare examples of multiple bonding of selenium to a metal, particularly an actinide metal

Five-Coordinate Silicon(II) Compounds with Si–M Bonds (M = Cr, Mo, W, Fe): Bis[<i>N</i>,<i>N</i>′‑diisopropylbenzamidinato(−)]silicon(II) as a Ligand in Transition-Metal Complexes

Reaction of the donor-stabilized silylene <b>1</b> with [Cr­(CO)₆], [Mo­(CO)₆], [W­(CO)₆], or [Fe­(CO)₅] leads to the formation of the transition-metal silylene complexes <b>2</b>–<b>5</b>, which contain five-coordinate silicon­(II) moieties with Si–M bonds (M = Cr, Mo, W, Fe). These compounds were characterized by NMR spectroscopic studies in the solid state and in solution and by crystal structure analyses. These experimental investigations were complemented by computational studies to gain insight into the bonding situation of <b>2</b>–<b>5</b>. The nature of the Si–M bonds is best described as a single bond

Properties of ThF_<i>x</i> from Infrared Spectra in Solid Argon and Neon with Supporting Electronic Structure and Thermochemical Calculations

Laser-ablated Th atoms react with F₂ in condensing noble gases to give ThF₄ as the major product. Weaker higher frequency infrared absorptions at 567.2, 564.8 (576.1, 573.8) cm^–1, 575.1 (582.7) cm^–1 and 531.0, (537.4) cm^–1 in solid argon (neon) are assigned to the ThF, ThF₂ and ThF₃ molecules based on annealing and photolysis behavior and agreement with CCSD­(T)/aug-cc-pVTZ vibrational frequency calculations. Bands at 528.4 cm^–1 and 460 cm^–1 with higher fluorine concentrations are assigned to the penta-coordinated species (ThF₃)­(F₂) and ThF₅^–. These bands shift to 544.2 and 464 cm^–1 in solid neon. The ThF₅ molecule has the (ThF₃)­(F₂) <i>C</i>_<i>s</i> structure and is essentially the unique [ThF₃⁺]­[F₂^–] ion pair based on charge and spin density calculations. Electron capture by (ThF₃)­(F₂) forms the trigonal bipyramidal ThF₅^– anion in a highly exothermic process. Extensive structure and frequency calculations were also done for thorium oxyfluorides and Th₂F_4,6,8 dimer species. The calculations provide the ionization potentials, electron affinities, fluoride affinities, Th–F bond dissociation energies, and the energies to bind F₂ and F₂^– to a cluster as well as dimerization energies