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Four-electron oxidation of the quadruply bonded W(2)(II,II) compound W(2)(2,2'-dipyridylamide)(4), 1, results in the formation of a novel, diamagnetic ditungsten terminal oxo compound [W(2)O(2,2'-dipyridylamide)(4)](2+), 2. In contrast to the chemical inertness of mononuclear tungsten oxo species, 2 undergoes a four-electron reduction including oxygen-atom transfer in reactions with excess tri-tert-butylphosphine in acetonitrile to recover 1. This unusual chemically reversible multielectron reactivity is ascribed to the cooperation of W-O and W-W multiple bonding. 相似文献
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H. Allrecht H. Ehrlichmann T. Hamacher A. Krüger A. Nau A. Nippe M. Reidenbach M. Sch?fer H. Schr?der H. D. Schulz et al. 《Zeitschrift fur Physik C Particles and Fields》1992,54(1):13-19
We have measured theR value in non-resonante
+
e
– annihilation using the ARGUS detector at the storage ring DORIS II. At a centre-of-mass energy
GeV the ratio of the hadronic cross-section to the -pair cross section in lowest order QED has been determined to beR=3.46±0.03±0.13. In addition, we have measured the charged-particle multiplicities in non-resonant hadron production at
GeV just below theB
threshold and in (4S) resonance decays. For the average charged-particle multiplicities in continuum events and (4S)B
decays we obtain n>cont=8.35±0.02±0.20 and n>(4s)=10.81±0.05±0.23.Supported by the German Bundesministerium für Forschung und Technologie, Contract no. 054DO51P 相似文献
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Corey P. Burns Xin Yang Joshua D. Wofford Dr. Nattamai S. Bhuvanesh Prof. Michael B. Hall Prof. Michael Nippe 《Angewandte Chemie (International ed. in English)》2018,57(27):8144-8148
We present an investigation of isostructural complexes that feature unsupported direct bonds between a formally trivalent lanthanide ion (Dy3+) and either a first‐row (Fe) or a second‐row (Ru) transition metal (TM) ion. The sterically rigid, yet not too bulky ligand PyCp22? (PyCp22?=[2,6‐(CH2C5H3)2C5H3N]2?) facilitates the isolation and characterization of PyCp2Dy?FeCp(CO)2 ( 1 ; d(Dy–Fe)=2.884(2) Å) and PyCp2Dy?RuCp(CO)2 ( 2 ; d(Dy–Ru)=2.9508(5) Å). Computational and spectroscopic studies suggest strong TM→Dy bonding interactions. Both complexes exhibit field‐induced slow magnetic relaxation with effectively identical energy barriers to magnetization reversal. However, in going from Dy?Fe to Dy?Ru bonding, we observed faster magnetic relaxation at a given temperature and larger direct and Raman coefficients, which could be due to differences in the bonding and/or spin–phonon coupling contributions to magnetic relaxation. 相似文献
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F. Burgstaller H. F. Launer F. T. Carson D. T. Jackson J. L. Parsons W. Nippe N. I. Nikitin und I. A. Nagrodsky 《Fresenius' Journal of Analytical Chemistry》1938,115(7-8):289-292
Ohne Zusammenfassung 相似文献
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The heterometallic complexes CrCrM(dpa)(4)Cl(2) (dpa = 2,2'-dipyridylamide) featuring linear Cl-Cr≡Cr···M-Cl chains can regiospecifically be modified via axial ligand substitution to yield OTf-Cr≡Cr···M-Cl chains (OTf = triflate) with M being Fe, Mn, or Co. The effect of OTf substitution on the Cr side of the molecule has an unusual and profound structural impact on the square-pyramidal transition metal M. Specifically, elongation of the four equatorial M-N(py) bonds and the axial M-Cl bonds by 0.03 and 0.09 ? for Fe and 0.07 and 0.11 ? for Mn is observed. The longer M-Cl and M-N(py) bonds result from subtle interactions between the equatorial dpa ligand and the three metal ions. The equatorial dpa ligand responds to the introduction of the more labile OTf ligand at Cr by binding more strongly to this Cr ion which in turn weakens bonding to M. The ligand field experienced by M can be tuned by changing the Cr axial ligand, and this effect is observed in electrochemical measurements of the iron compounds. 相似文献
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Trevor P. Latendresse Veacheslav Vieru Apoorva Upadhyay Nattamai S. Bhuvanesh Liviu F. Chibotaru Michael Nippe 《Chemical science》2020,11(15):3936
Lanthanide metallocenophanes are an intriguing class of organometallic complexes that feature rare six-coordinate trigonal prismatic coordination environments of 4f elements with close intramolecular proximity to transition metal ions. Herein, we present a systematic study of the structural and magnetic properties of the ferrocenophanes, [LnFc3(THF)2Li2]−, of the late trivalent lanthanide ions (Ln = Gd (1), Ho (2), Er (3), Tm (4), Yb (5), Lu (6)). One major structural trend within this class of complexes is the increasing diferrocenyl (Fc2−) average twist angle with decreasing ionic radius (rion) of the central Ln ion, resulting in the largest average Fc2− twist angles for the Lu3+ compound 6. Such high sensitivity of the twist angle to changes in rion is unique to the here presented ferrocenophane complexes and likely due to the large trigonal plane separation enforced by the ligand (>3.2 Å). This geometry also allows the non-Kramers ion Ho3+ to exhibit slow magnetic relaxation in the absence of applied dc fields, rendering compound 2 a rare example of a Ho-based single-molecule magnet (SMM) with barriers to magnetization reversal (U) of 110–131 cm−1. In contrast, compounds featuring Ln ions with prolate electron density (3–5) don''t show slow magnetization dynamics under the same conditions. The observed trends in magnetic properties of 2–5 are supported by state-of-the-art ab initio calculations. Finally, the magneto-structural relationship of the trigonal prismatic Ho-[1]ferrocenophane motif was further investigated by axial ligand (THF in 2) exchange to yield [HoFc3(THF*)2Li2]− (2-THF*) and [HoFc3(py)2Li2]− (2-py) motifs. We find that larger average Fc2− twist angles (in 2-THF* and 2-py as compared to in 2) result in faster magnetic relaxation times at a given temperature.Lanthanide ferrocenophanes are an intriguing class of organometallic complexes that feature rare six-coordinate trigonal prismatic coordination environments of 4f elements with close intramolecular proximity to iron ions. 相似文献
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Gabrielle M. Risica Veacheslav Vieru Branford O. Wilkins Trevor P. Latendresse Joseph H. Reibenspies Nattamai S. Bhuvanesh Gregory P. Wylie Liviu F. Chibotaru Michael Nippe 《Angewandte Chemie (International ed. in English)》2020,59(32):13335-13340
We report the first f‐block‐ruthenocenophane complexes 1 (Dy) and 2 (Tb) and provide a comparative discussion of their magnetic structure with respect to earlier reported ferrocenophane analogues. While axial elongation of the rare trigonal‐prismatic geometry stabilizes the magnetic ground state in the case of Dy3+ and results in a larger barrier to magnetization reversal (U), a decrease in U is observed for the case of Tb3+. 相似文献