A comparative study of new platinum methyl complexes cis-(dfmp)2Pt(Me)2 and trans-(dfmp)2Pt(Me)X (dfmp = (C2F5)2MeP; X = O2CCF3, OTf, OSO2F) with previously reported acceptor chelate analogues ...(dfepe)Pt(Me)X (dfepe = (C2F5)2PCH2CH2P(C2F5)2; X = Me, O2CCF3, OTf, OSO2F) is presented. In contrast to (dfepe)Pt(Me)2, which is inert to both H2 and CO addition, cis-(dfmp)2Pt(Me)2 reacts readily to form (dfmp)4Pt and cis-(dfmp)(CO)Pt(Me)2, respectively. Similarly, whereas (dfepe)Pt(Me)2 is stable up to 180 °C, thermolysis of cis-(dfmp)2Pt(Me)2 in benzene-d 6 at 80 °C leads to ethane reductive elimination and production of (dfmp)4Pt. Dissolving cis-(dfmp)2Pt(Me)2 in neat trifluoroacetic, triflic, or fluorosulfonic acid at ambient temperature cleanly produces the corresponding trans-(dfmp)2Pt(Me)(X) complexes. Attempted isolation of trans-(dfmp)2Pt(Me)(O2CCF3) resulted in dfmp loss and reversible formation of the crystallographically characterized dimer, (dfmp)Pt(Me)(μ-O2CCF3)2. Monitoring the thermolysis of trans-(dfmp)2Pt(Me)(X) complexes by 31P NMR in their respective neat acids reveals a kinetic protolytic stability that is dependent on the nature of the trans X ligand: whereas trans-(dfmp)2Pt(Me)(O2CCF3) is less stable than the corresponding (dfepe)Pt(Me)(O2CCF3) complex, trans-(dfmp)2Pt(Me)(OTf) and trans-(dfmp)2Pt(Me)(OSO2F) are significantly more resistant to protolytic cleavage than the chelating analogues. Thermolysis in CF3CO2D or DOTf resulted in deuteration of the methyl ligand prior to methane loss, indicating the reversible formation of a methane adduct intermediate.
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The comparative reactivity properties of previously reported trans-(dfmp)2Pt(Me)X (dfmp = (C2F5)2MeP; X = O2CCF3, OTf, OSO2F) with small molecules are presented. Anionic ligand displacement by CO ...depends upon X and the corresponding acid solvent. In trifluoroacetic acid, treatment of trans-(dfmp)2Pt(Me)(O2CCF3) with CO results in loss of dfmp to form the mixed phosphine/carbonyl product (dfmp)(CO)Pt(Me)(O2CCF3). However, in triflic and fluorosulfonic acids trans-(dfmp)2Pt(Me)(X) compounds react with CO to form trans-(dfmp)2Pt(Me)(CO)+(X)-. trans-(dfmp)2Pt(Me)(X) systems react with H2 under both acidic and aprotic conditions to form trans-(dfmp)2Pt(H)(X); trans-(dfmp)2Pt(H)(OTf) has been crystallographically characterized. Treatment of trans-(dfmp)2Pt(H)(OTf) with CO or dfmp gives trans-(dfmp)2Pt(H)(CO)+ or (dfmp)3Pt(H)+, respectively. In contrast to trans-(dfmp)2Pt(Me)(OTf), which releases methane in HOTf, trans-(dfmp)2Pt(Me)(OSO2F) in FSO3H at 80 °C cleanly produces the reductive elimination product MeOSO2F. Carbonylation of trans-(dfmp)2PtMe(CO)+X- under 1000 psi CO in turn cleanly produces MeC(O)X at ambient temperatures. The mechanism of reductive elimination from these Pt(II) precursors is discussed.
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The crystal structure of the title compound, (bicyclo2.2.1hepta-2,5-diene)dichloroplatinum(II), PtCl2(C7H8), has been determined from single-crystal X-ray analysis. The coordination sphere about the ...Pt atom is pseudo-square planar, with shorter Pt-C distances than in the corresponding dichloro(cyclooctadiene)platinum(II) complex.
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The first examples of structurally-characterized 2- and 3-coordinate Pt(0) complexes with π-acceptor perfluoroalkylphosphine ligands (PFAP’s) is reported. Addition of ethylene to (dfebp)2Pt ...(dfebp=(C2F5)2PtBu) results in facile and reversible equilibria with the ethylene adducts (dfebp)2Pt(C2H4) and (dfebp)Pt(C2H4)2. Display omitted
The synthesis and structural characterization of 2- and 3-coordinate Pt(0) complexes with π-acceptor perfluoroalkylphosphine ligands (PFAP’s) is reported. (dfebp)2Pt (dfebp=(C2F5)2PtBu) was prepared in moderate yield by either thermolysis of (cod)Pt(Ph)2 in neat dfebp or, more efficiently, by the treatment of (nbe)3Pt with 2equiv. dfebp in the presence of H2. Addition of 1equiv. CF3CO2H to (dfebp)2Pt generates the expected Pt(II) trans-(dfebp)2Pt(O2CCF3)(H) product, while treatment with the mesitylenium acid (C6Me3H4)+B(C6F5)4− leads to phosphine loss and formation of the arene complex (η6-C6Me3H3)Pt(dfebp)(H)+(B(C6F5)4)−. Addition of ethylene to (dfebp)2Pt results in facile and reversible equilibria with the ethylene adducts (dfebp)2Pt(C2H4) and (dfebp)Pt(C2H4)2, which have been quantified by VT NMR spectroscopy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The XENON1T liquid xenon time projection chamber is the most sensitive detector built to date for the measurement of direct interactions of weakly interacting massive particles with normal matter. ...The data acquisition system (DAQ) is constructed from commercial, open source, and custom components to digitize signals from the detector and store them for later analysis. The system achieves an extremely low signal threshold below a tenth of a photoelectron using a parallelized readout with the global trigger deferred to a later, software stage. The event identification is based on MongoDB database queries and has over 97% efficiency at recognizing interactions at the analysis energy threshold. A readout bandwidth over 300 MB/s is reached in calibration modes and is further expandable via parallelization. This DAQ system was successfully used during three years of operation of XENON1T.
In this paper, we describe the XENON100 data analyses used to assess the target-intrinsic background sources radon (\(^{222}\)Rn), thoron (\(^{220}\)Rn) and krypton (\(^{85}\)Kr). We detail the event ...selections of high-energy alpha particles and decay-specific delayed coincidences. We derive distributions of the individual radionuclides inside the detector and quantify their abundances during the main three science runs of the experiment over a period of \(\sim\) 4 years, from January 2010 to January 2014. We compare our results to external measurements of radon emanation and krypton concentrations where we find good agreement. We report an observed reduction in concentrations of radon daughters that we attribute to the plating-out of charged ions on the negatively biased cathode.
We report on the response of liquid xenon to low energy electronic recoils below 15 keV from beta decays of tritium at drift fields of 92 V/cm, 154 V/cm and 366 V/cm using the XENON100 detector. A ...data-to-simulation fitting method based on Markov Chain Monte Carlo is used to extract the photon yields and recombination fluctuations from the experimental data. The photon yields measured at the two lower fields are in agreement with those from literature; additional measurements at a higher field of 366 V/cm are presented. The electronic and nuclear recoil discrimination as well as its dependence on the drift field and photon detection efficiency are investigated at these low energies. The results provide new measurements in the energy region of interest for dark matter searches using liquid xenon.
We report the first dark matter search results from XENON1T, a \(\sim\)2000-kg-target-mass dual-phase (liquid-gas) xenon time projection chamber in operation at the Laboratori Nazionali del Gran ...Sasso in Italy and the first ton-scale detector of this kind. The blinded search used 34.2 live days of data acquired between November 2016 and January 2017. Inside the (1042\(\pm\)12) kg fiducial mass and in the 5, 40 \(\mathrm{keV}_{\mathrm{nr}}\) energy range of interest for WIMP dark matter searches, the electronic recoil background was \((1.93 \pm 0.25) \times 10^{-4}\) events/(kg \(\times\) day \(\times \mathrm{keV}_{\mathrm{ee}}\)), the lowest ever achieved in a dark matter detector. A profile likelihood analysis shows that the data is consistent with the background-only hypothesis. We derive the most stringent exclusion limits on the spin-independent WIMP-nucleon interaction cross section for WIMP masses above 10 GeV/c\({}^2\), with a minimum of 7.7 \(\times 10^{-47}\) cm\({}^2\) for 35-GeV/c\({}^2\) WIMPs at 90% confidence level.
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