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101.
Matthias Brendel Carolin Braun Dr. Frank Rominger Prof. Dr. Peter Hofmann 《Angewandte Chemie (International ed. in English)》2014,53(33):8741-8745
For a long time d10‐ML2 fragments have been known for their potential to activate unreactive bonds by oxidative addition. In the development of more active species, two approaches have proven successful: the use of strong σ‐donating ligands leading to electron‐rich metal centers and the employment of chelating ligands resulting in a bent coordination geometry. Combining these two strategies, we synthesized bis‐NHC chelate complexes of nickel(0) and platinum(0). Bis(1,5‐cyclooctadiene)nickel(0) and ‐platinum(0) react with bisimidazolium salts, deprotonated in situ at room temperature, to yield tetrahedral or trigonal‐planar bis‐NHC chelate olefin complexes. The synthesis and characterization of these complexes as well as a first example of C? C bond activation with these systems are reported. Due to the enforced cis arrangement of two NHCs, these compounds should open interesting perspectives for bond‐activation chemistry and catalysis. 相似文献
102.
Dilcan Dirican Nils Pfister Martin Wozniak Prof. Dr. Thomas Braun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(31):6945-6963
Binary sulfur fluorides exhibit an interesting reactivity towards transition metal complexes. They open up routes for the generation of sulfur-containing building blocks. Often ligands with particular properties can be constructed. This includes their ability to transfer sulfur atoms or polysulfide units as well as fluorination reactions. This Minireview provides an insight into the reactivity of the binary and ternary sulfur halides S2Cl2, SCl2, SF4, SF6 and SF5Cl towards transition-metal compounds. 相似文献
103.
H. Braun 《The European physical journal. Special topics》2009,174(1):33-47
Large-amplitude climate shifts, the so-called Dansgaard-Oeschger events, repeatedly occurred throughout the last ice age.
These events, which are apparently threshold-crossing events, show a reported tendency to recur preferably in near multiples
of about 1470 years. Several non-linear resonance mechanisms were proposed to explain this recurrence pattern in response
to noise and/or periodic forcing. Standard methods of linear time series analysis are not sufficient to distinguish between
these hypotheses, owing to the threshold-crossing dynamics of the events. Recently, new approaches were made by means of null-hypothesis
testing with Monte Carlo methods. A major hurdle in this approach is the need of efficient, but yet simple measures of regularity
that allow to distinguish between the proposed resonance mechanisms. By means of surrogate time series (i.e. by using a large
ensemble of Dansgaard-Oeschger events as simulated with a very simple two-state model) I here test the ability of three standard
measures of periodicity to distinguish between a scenario of solely noise-induced events and a ghost stochastic resonance
scenario. Only one measure is found to be applicable for that purpose. The choice of adequate measures, which is not trivial,
should be given more attention in future studies that focus on the question what triggered threshold-crossing events such
as Dansgaard-Oeschger events. 相似文献
104.
105.
106.
M.A. Braun 《The European Physical Journal C - Particles and Fields》2008,53(1):59-63
The running coupling is introduced into the equation for the odderon via the bootstrap relation. It is shown that the previously
found odderon state with a maximal intercept, which is constructed from an antisymmetric pomeron wave function, continues
to exist in the running coupling case. Its intercept is found to remain equal to unity independent of the behaviour assumed
for the running coupling at low momenta. 相似文献
107.
Madalan AM Roesky HW Andruh M Noltemeyer M Stanica N 《Chemical communications (Cambridge, England)》2002,(15):1638-1639
A novel heterospin system, [(CuL)2Gd(TCNQ)2].TCNQ-.CH3OH.2CH3CN, is obtained by reacting the mononuclear complex, [CuL], with gadolinium(III) nitrate, followed by the substitution of the nitrato ions with anionic organic radicals. 相似文献
108.
Christiansen J Morgenstern K Schiøtz J Jacobsen KW Braun KF Rieder KH Laegsgaard E Besenbacher F 《Physical review letters》2002,88(20):206106
The intersection between dislocations and a Ag(111) surface has been studied using an interplay of scanning tunneling microscopy (STM) and molecular dynamics. Whereas the STM provides atomically resolved information about the surface structure and Burgers vectors of the dislocations, the simulations can be used to determine dislocation structure and orientation in the near-surface region. In a similar way, the subsurface structure of other extended defects can be studied. The simulations show dislocations to reorient the partials in the surface region leading to an increased splitting width at the surface, in agreement with the STM observations. Implications for surface-induced cross slip are discussed. 相似文献
109.
Braun NA Ousmer M Bray JD Bouchu D Peters K Peters EM Ciufolini MA 《The Journal of organic chemistry》2000,65(14):4397-4408
The oxidative cyclization of a phenolic amide to a spirolactam has long been regarded as an "impossible" reaction, because exposure of the substrates to a variety of oxidants results in formation of spirolactones with consequent loss of the amine segment. We recently communicated that this heretofore unknown transformation may be achieved by oxidation of oxazoline analogues of phenolic and indolic amides. Herein, we provide full details of our work. 相似文献
110.
Braun T Foxon SP Perutz RN Walton PH 《Angewandte Chemie (International ed. in English)》1999,38(22):3326-3329
Rapid and regioselective activation of the C-F bond of 2,4,6-trifluoropyrimidine occurs on reaction with [Ni(cod)(2)] (cod=1,5-cyclooctadiene) in the presence of PEt(3) to give 1, which can be converted into complex 2, containing a further N(3)-metalated pyrimidin-4-one unit. The novel pyrimidin-4-one 3 is released on protonation of 2. 相似文献