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71.
D. Badea Dr. K. Dardenne Dr. R. Polly Dr. J. Rothe Dr. M. Hanrath M. Reimer Prof. Dr. K. Meerholz Dr. J.-M. Neudörfl Dr. E. Strub Dr. J. Bruns 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(63):e202201738
The preparation of novel technetium oxides, their characterization and the general investigation of technetium chemistry are of significant importance, since fundamental research has so far mainly focused on the group homologues. Whereas the structure chemistry of technetium in strongly oxidizing media is dominated by the anion, our recent investigation yielded the new anion. Brown single crystals of Ba[TcO3N] were obtained under hydrothermal conditions starting from Ba(OH)2 ⋅ 8H2O and NH4[TcO4] at 200 °C. crystallizes in the monoclinic crystal system with the space group P21/n (a=7.2159(4) Å, b=7.8536(5) Å, c=7.4931(4) Å and β=104.279(2)°). The crystal structure of consists of isolated tetrahedra, which are surrounded by Ba2+ cations. XANES measurements complement the oxidation state +VII for technetium and Raman spectroscopic experiments on Ba[TcO3N] single crystals exhibit characteristic Tc−O and Tc−N vibrational modes. 相似文献
72.
Joseph F. DeJesus Ryan W. F. Kerr Deborah A. Penchoff Xian B. Carroll Charles C. Peterson Polly L. Arnold David M. Jenkins 《Chemical science》2021,12(22):7882
Highly-symmetrical, thorium and uranium octakis-carbene ‘sandwich’ complexes have been prepared by ‘sandwiching’ the An(iv) cations between two anionic macrocyclic tetra-NHC ligands, one with sixteen atoms and the other with eighteen atoms. The complexes were characterized by a range of experimental methods and DFT calculations. X-ray crystallography confirms the geometry at the metal centre can be set by the size of the macrocyclic ring, leading to either square prismatic or square anti-prismatic shapes; the geometry of the latter is retained in solution, which also undergoes reversible, electrochemical one-electron oxidation or reduction for the uranium variant. DFT calculations reveal a frontier orbital picture that is similar to thorocene and uranocene, in which the NHC ligands show almost exclusively σ-donation to the metal without π-backbonding.Highly-symmetrical, thorium and uranium octakis-carbene ‘sandwich’ complexes have been prepared by ‘sandwiching’ the An(iv) cations between two anionic macrocyclic tetra-NHC ligands, one with sixteen atoms and the other with eighteen atoms. 相似文献
73.
Since the discovery of a stable "bottleable" N-heterocyclic carbene (NHC), there has been a spectacular explosion of interest in this ligand class. This interest stems from a desire to understand the fundamentals of the structure and bonding of these systems, but also because of their numerous and emerging applications in small molecule activation, homogeneous catalysis and Lewis acid-catalysed reactions. In this Tutorial Review, we introduce the reader to NHCs, cover general synthetic methods to prepare anionic tethered NHCs and their metal complexes, and discuss emerging applications in reactivity and catalytic studies. 相似文献
74.
Reaction of YI(3)(THF)(3.5) with one equivalent of the potassium beta-diketiminate (BDI) complex [HC{C(CH(3))NAr}(2)K] (Ar = 2,6-Pr(i)(2)C(6)H(3)) affords the monomeric, mono-substituted yttrium BDI complex [HC{C(CH(3))NAr}(2)YI(2)(THF)] in good yield. Reaction of with DME affords [HC{C(CH(3))NAr}(2)YI(2)(DME)] in quantitative yield, which is monomeric also. Reaction of the primary terphenyl phosphane Ar*PH(2) (Ar* = 2,6-(2,4,6-Pr(i)(3)C(6)H(2))(2)C(6)H(3)) with potassium hydride, and recrystallisation from hexane, affords the potassium primary terphenyl phosphanide complex [{Ar*P(H)K(THF)}(2)] in high yield. Compound is dimeric in the solid state, constructed around a centrosymmetric K(2)P(2) four-membered ring, the coordination sphere of potassium is supplemented with an eta(6) K[dot dot dot]C(aryl) interaction. The reaction of with one molar equivalent of in THF affords the THF ring-opened compound [HC{C(CH(3))NAr}(2)Y{O(CH(2))(4)P(H)Ar*}(I)(THF)]. Compound is formed as a mixture of endo(OR) and exo(OR) isomers (: = approximately 2 : 1) which may be separated by fractional crystallisation from hexane-toluene to give pure . Attempted alkylation of with two equivalents of KCH(2)Si(CH(3))(3) affords the potassium yttriate complex [Y{micro-eta(5):eta(1)-ArNC(CH(3))[double bond, length as m-dash]CHC([double bond, length as m-dash]CH(2))NAr}(2)K(DME)(2)] in moderate yield; contains two dianionic dianilide ligands, which are derived from C-H activation of a backbone methyl group, each bonded eta(5) to yttrium in the solid state. The reaction of with one equivalent of KC(8) affords [{HC(C[CH(3)]NAr)(2)YI(micro-OCH(3))}(2)], derived from C-O bond activation of DME, as the only isolable product in very low yield. Compounds , , , , , and have been characterised by single crystal X-ray diffraction, NMR spectroscopy and CHN microanalyses. 相似文献
75.
Chitwood DB Banks TI Barnes MJ Battu S Carey RM Cheekatmalla S Clayton SM Crnkovic J Crowe KM Debevec PT Dhamija S Earle W Gafarov A Giovanetti K Gorringe TP Gray FE Hance M Hertzog DW Hare MF Kammel P Kiburg B Kunkle J Lauss B Logashenko I Lynch KR McNabb R Miller JP Mulhauser F Onderwater CJ Ozben CS Peng Q Polly CC Rath S Roberts BL Tishchenko V Wait GD Wasserman J Webber DM Winter P Zołnierczuk PA;MuLan Collaboration 《Physical review letters》2007,99(3):032001
The mean life of the positive muon has been measured to a precision of 11 ppm using a low-energy, pulsed muon beam stopped in a ferromagnetic target, which was surrounded by a scintillator detector array. The result, tau(micro)=2.197 013(24) micros, is in excellent agreement with the previous world average. The new world average tau(micro)=2.197 019(21) micros determines the Fermi constant G(F)=1.166 371(6)x10(-5) GeV-2 (5 ppm). Additionally, the precision measurement of the positive-muon lifetime is needed to determine the nucleon pseudoscalar coupling g(P). 相似文献
76.
Aguilar-Arevalo AA Bazarko AO Brice SJ Brown BC Bugel L Cao J Coney L Conrad JM Cox DC Curioni A Djurcic Z Finley DA Fleming BT Ford R Garcia FG Garvey GT Green C Green JA Hart TL Hawker E Imlay R Johnson RA Kasper P Katori T Kobilarcik T Kourbanis I Koutsoliotas S Laird EM Link JM Liu Y Liu Y Louis WC Mahn KB Marsh W Martin PS McGregor G Metcalf W Meyers PD Mills F Mills GB Monroe J Moore CD Nelson RH Nienaber P Ouedraogo S Patterson RB Perevalov D Polly CC Prebys E Raaf JL Ray H Roe BP 《Physical review letters》2007,98(23):231801
The MiniBooNE Collaboration reports first results of a search for nu e appearance in a nu mu beam. With two largely independent analyses, we observe no significant excess of events above the background for reconstructed neutrino energies above 475 MeV. The data are consistent with no oscillations within a two-neutrino appearance-only oscillation model. 相似文献
77.
The Influence of an Internet‐Based Formative Assessment Tool on Primary Grades Students’ Number Sense Achievement
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Drew Polly Chuang Wang Christie Martin Richard G. Lambert David K. Pugalee Catharina Win Middleton 《School science and mathematics》2017,117(3-4):127-136
This study examined primary grades students’ achievement on number sense tasks administered through an Internet‐based formative assessment tool, Assessing Math Concepts Anywhere. Data were analyzed from 2,357 students in teachers’ classrooms who had participated in a year‐long professional development program on mathematics formative assessment, 1,427 students from teachers who had participated in the program in the year prior, and 9,783 students whose teachers had not participated at all. Analyses indicated that all students in the treatment group demonstrated growth, and that student achievement was influenced by the number of times the assessment was used to collect data and make instructional decisions. Further, there was a relationship between districts’ socioeconomic status and growth, meaning students from impoverished backgrounds grew more than their peers. 相似文献
78.
Prof. Dr. Polly L. Arnold M. Chem. Max W. McMullon M. Sc. Julia Rieb Prof. Dr. Fritz E. Kühn 《Angewandte Chemie (International ed. in English)》2015,54(1):82-100
Most homogeneous catalysis relies on the design of metal complexes to trap and convert substrates or small molecules to value‐added products. Organometallic lanthanide compounds first gave a tantalizing glimpse of their potential for catalytic C? H bond transformations with the selective cleavage of one C? H bond in methane by bis(permethylcyclopentadienyl)lanthanide methyl [(η5‐C5Me5)2Ln(CH3)] complexes some 25 years ago. Since then, numerous metal complexes from across the periodic table have been shown to selectively activate hydrocarbon C? H bonds, but the challenges of closing catalytic cycles still remain; many f‐block complexes show great potential in this important area of chemistry. 相似文献
79.
Judit E. Puskas Polly Chan Kimberley B. McAuley Gabor Kaszas Sohel Shaikh 《Macromolecular Symposia》2006,240(1):18-22
The carbocationic copolymerization of isobutylene (IB) and styrene (St) was investigated using real time FTIR monitoring. Depending on the concentration of the individual monomers, and their ratio in the feed, initial rapid monomer consumption was observed. Instantaneous reactivity ratios (rIB(inst) and rSt(inst)) obtained from apparent rate constants of monomer consumption strongly depended on concentration. 相似文献
80.
Real-time FTIR is a powerful tool to obtain copolymerization reactivity ratios because it allows simultaneous monitoring of individual monomer consumption rates. Based on the Mayo-Lewis equation we showed that in reactivity ratios can be defined as the ratios of apparent rate constants of monomer consumption. The validity and limitations on this new method are discussed in the isobutylene-isoprene and isobutylene-styrene carbocationic copolymerization systems. 相似文献