The First Organosilver(III) Fluoride, [PPh4][(CF3)3AgF]

Organosilver(III) fluoride complexes have been assigned a key role in different fluorination processes. To the best of our knowledge, however, none of them seem to have been isolated or even detected thus far. Here we report on the successful synthesis of the trifluoromethyl derivative [PPh₄][(CF₃)₃AgF], which has been isolated in high yield. The thermodynamic stability of the Ag−F bond is shown by calculation and demonstrated by multistage mass spectrometry (MSⁿ) under collision-induced dissociation (CID) conditions. Nevertheless, the substantial elongation found in the Ag−F bond (X-ray) is correlated with a marked nucleophilic character of the terminal F ligand. This Ag−F bond is, in fact, quite reactive: it suffers hydrolysis and is also solvolyzed by thiols.     

An Organogold(III) Difluoride with a trans Arrangement

The trans isomer of the organogold(III) difluoride complex [PPh₄][(CF₃)₂AuF₂] has been obtained in a stereoselective way and in excellent yield by reaction of [PPh₄][CF₃AuCF₃] with XeF₂ under mild conditions. The compound is both thermally stable and reactive. Thus, the fluoride ligands are stereospecifically replaced by any heavier halide or by cyanide, the cyanide affording [PPh₄][trans‐(CF₃)₂Au(CN)₂]. The organogold fluoride complexes [CF₃AuF_x]^? (x=1, 2, 3) have been experimentally detected to arise upon collision‐induced dissociation of the [trans‐(CF₃)₂AuF₂]^? anion in the gas phase. Their structures have been calculated by DFT methods. In the isomeric forms identified for the open‐shell species [CF₃AuF₂]^?, the spin density residing on the metal center is found to strongly depend on the precise stereochemistry. Based on crystallographic evidence, it is concluded that Auⁱⁱⁱ and Agⁱⁱⁱ have similar covalent radii, at least in their most common square‐planar geometry.     

Unusual Metal–Metal Bonding in a Dinuclear Pt–Au Complex: Snapshot of a Transmetalation Process

The dinuclear Pt–Au complex [(CNC)(PPh₃)Pt Au(PPh₃)](ClO₄) ( 2 ) (CNC=2,6‐diphenylpyridinate) was prepared. Its crystal structure shows a rare metal–metal bonding situation, with very short Pt–Au and Au–C_ipso(CNC) distances and dissimilar Pt–C_ipso(CNC) bonds. Multinuclear NMR spectra of 2 show the persistence of the Pt–Au bond in solution and the occurrence of unusual fluxional behavior involving the [Pt^II] and [Au^I] metal fragments. The [Pt^II]??? [Au^I] interaction has been thoroughly studied by means of DFT calculations. The observed bonding situation in 2 can be regarded as a model for an intermediate in a transmetalation process.     

Pd(I) phosphine carbonyl and hydride complexes implicated in the palladium-catalyzed oxo process

Reduction of compound "Pd(bcope)(OTf)2" [bcope = (c-C8H14-1,5)PCH2CH2P(c-C8H14-1,5); OTf = O3SCF3] with H2/CO yields a mixture of Pd(I) compounds [Pd2(bcope)2(CO)2](OTf)2 (1) and [Pd2(bcope)2(mu-CO)(mu-H)](OTf) (2), whereas reduction with H2 or Ph3SiH in the absence of CO leads to [Pd3(bcope)3(mu3-H)2](OTf)2 (3). Exposure of 3 to CO leads to 1 and 2. The structures of 1 and 3 have been determined by X-ray diffraction. Complex [Pd2(bcope)2(CO)2](2+) displays a metal-metal bonded structure with a square planar environment for the Pd atoms and terminally bonded CO ligands and is fluxional in solution. DFT calculations aid the interpretation of this fluxional behavior as resulting from an intramolecular exchange of the two inequivalent P atom positions via a symmetric bis-CO-bridged intermediate. A cyclic voltammetric investigation reveals a very complex redox behavior for the "Pd(bcope)(OTf)2"/CO system and suggests possible pathways leading to the formation of the various observed products, as well as their relationship with the active species of the PdL2(2+)/CO/H2-catalyzed oxo processes (L2 = diphosphine ligands).     

Evaluation and optimization of solid adsorbents for the sampling of gaseous methylated mercury species

This study evaluates the suitability of commercially available adsorbents for the measurement of gaseous organic mercury species namely monomethylmercury (MMHg) and dimethylmercury (DMHg).     

Evaluation of a hypercrosslinked polystyrene, MN-200, as a sorbent for the preconcentration of volatile organic compounds in air

Breakthrough volumes, average percentage recoveries, and storage stabilities were obtained for vapors of 8 volatile organic compounds (pentane, octane, undecane, isooctane, cyclohexane, toluene, methanol, and dichloromethane) on a new adsorbent material, Hypersol-Macronet, MN-200. Breakthrough volumes were estimated as half of the gas chromatographic specific retention volumes at 20 degrees C for the compounds. Recoveries of the adsorbates were determined by both solvent extraction and thermal desorption methods. The results obtained compare favorably with those for Tenax GR (values reported in the published literature and others obtained in our laboratory). Results of storage stability studies on MN-200 meet the criterion for acceptability (<10% loss). High adsorption capacity for very volatile and polar compounds, combined with ease of desorption of less volatile compounds, render MN-200 a highly promising adsorbent for sampling volatile organic compounds in indoor and outdoor air.     

Evaluation of Co/SSZ-13 Zeolite Catalysts Prepared by Solid-Phase Reaction for NO-SCR by Methane

Co/SSZ-13 zeolites were prepared by heating the finely dispersed mixture of NH₄-SSZ-13 and different cobalt salts up to 550 °C. Investigations by thermogravimetry – differential scanning calorimetry – mass spectrometry provided new insight into details of the solid-state reaction. Formation of Co carrying hydrate melt or volatile species was shown to proceed from chloride, nitrate, or acetylacetonate Co precursor salts upon thermal treatment. This phase change allows the transport of the Co species into the zeolite pores. The reaction of the NH₄⁺ or H⁺ zeolite cations and the mobile Co precursors generates vapor or gas products, readily leaving the zeolite pores, and cobalt ions in lattice positions suggesting that solid-state ion-exchange is the prevailing process. The obtained catalysts are of good activity and N₂ selectivity in the CH₄/NO-SCR reaction. The thermal treatment of acetate or formate salts give solid intermediates that are unable to get in contact and react with the cations in the zeolite micropores. These catalysts contain mainly Co-oxide clusters located on the outer surface of the zeolite crystallites and have poor catalytic performance.