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31.
Dipl.‐Chem. Fabian Schax Dr. Eckhard Bill Dr. Christian Herwig Prof. Dr. Christian Limberg 《Angewandte Chemie (International ed. in English)》2014,53(47):12741-12745
The reaction of a tripodal trisilanol with n‐butyllithium and CrCl2 results in a dinuclear CrII complex ( 1 ), which is capable of cleaving O2 to yield in a unique complex ( 2 ) with an asymmetric diamond core composed of two CrIV?O units. Magnetic susceptibility data reveal significant exchange coupling of CrII (S=2) in 1 and large zero‐field splitting for CrIV (S=1) in 2 owing to strong spin–orbit coupling of the ground state. The CrIV?O compound can also be generated using PhIO, and evidence was gathered that although it is the stable product isolated after excessive O2 treatment, it further activates O2 to yield an intermediate species that oxidizes THF or Me‐THF. By extensive 18O labeling studies we were able to show, that in the course of this process 18O2 exchanges its label with siloxide O atoms of the ligand via terminal oxido ligands. 相似文献
32.
Philip Boehm Sven Roediger Alessandro Bismuto Bill Morandi 《Angewandte Chemie (International ed. in English)》2020,59(41):17887-17896
An efficient palladium‐catalyzed chlorocarbonylation of aryl (pseudo)halides that gives access to a wide range of carboxylic acid derivatives has been developed. The use of butyryl chloride as a combined CO and Cl source eludes the need for toxic, gaseous carbon monoxide, thus facilitating the synthesis of high‐value products from readily available aryl (pseudo)halides. The combination of palladium(0), Xantphos, and an amine base is essential to promote this broadly applicable catalytic reaction. Overall, this reaction provides access to a great variety of carbonyl‐containing products through in situ transformation of the generated aroyl chloride. Combined experimental and computational studies support a reaction mechanism involving in situ generation of CO. 相似文献
33.
A sequence of random variables X0,X1, … with values in {0, 1, …, n} representing a general finite-state stochastic process with absorbing state 0 is said to be directionally biased towards 0, if, for all j > 0, ϵj: = infk>0 {j − E[Xk | Xk−1 = j]} > 0. For such sequences, let t be the expected value of the time to absorption at 0. For a fixed set of biases, the least upper bound for this time can be computed with an algorithm requiring O(n2) steps. Simple upper bounds are described. In particular, t ≤ E[bx0], where bi = Σj≤i 1/¯ϵj and ¯ϵj = minl≥j {ϵl}. If all ϵj ≤ ϵj + 1 (so ¯ϵj = ϵj) and ϵn < 1, this bound for t is the best possible. For certain finite stochastic processes which we term conditionally independent of X0 = i, b(i) bounds the expected time given X0 = i. Similar results are given for lower bounds. The results of this paper were designed to be a useful tool for determining rates of convergence of stochastic optimization algorithms. © 1996 John Wiley & Sons, Inc. 相似文献
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Density Functional Theory (DFT) has been applied to characterize the early stages of the reaction of dioxygenation of [(triphos)M(catecholate)]+ complexes [M = Co(III), Ir(III); triphos = MeC(CH2PPh2)3], which have been considered to be models of ring-opening dioxygenases. The structural features of the starting complexes and of the intermediate complexes formed by addition of O2 to the coordinated catecholato ion are well reproduced. The calculations showed that this preliminary stage can be obtained only when the oxygen molecule attacks the molecule on the catecholato site. 相似文献
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Duboc-Toia C Hummel H Bill E Barra AL Chouteau G Wieghardt K 《Angewandte Chemie (International ed. in English)》2000,39(16):2888-2890
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Scott B. Guthery 《Journal of Number Theory》1974,6(3):201-210
If f is a monotone function subject to certain restrictions, then one can associate with any real number x between zero and one a sequence {an(x)} of integers such that . In this paper properties of the function F defined by , where g is any function satisfying the same restrictions as f, are discussed. Principally, F is found to be useful in finding stationary measures on the sequences {an(x)}. 相似文献