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111.
Grace B. Panetti Patrick J. Carroll Michael R. Gau Brian C. Manor Eric J. Schelter Patrick J. Walsh 《Chemical science》2021,12(12):4405
The super electron donor (SED) ability of 2-azaallyl anions has recently been discovered and applied to diverse reactivity, including transition metal-free cross-coupling and dehydrogenative cross-coupling processes. Surprisingly, the redox properties of 2-azaallyl anions and radicals have been rarely studied. Understanding the chemistry of elusive species is the key to further development. Electrochemical analysis of phenyl substituted 2-azaallyl anions revealed an oxidation wave at E1/2 or Epa = −1.6 V versus Fc/Fc+, which is ∼800 mV less than the reduction potential predicted (Epa = −2.4 V vs. Fc/Fc+) based on reactivity studies. Investigation of the kinetics of electron transfer revealed reorganization energies an order of magnitude lower than commonly employed SEDs. The electrochemical study enabled the synthetic design of the first stable, acyclic 2-azaallyl radical. These results indicate that the reorganization energy should be an important design consideration for the development of more potent organic reductants.The super electron donor (SED) capabilities of 2-azaallyl anions has recently been discovered and applied to diverse reactivity; their structures and electron transfer characteristics are reported herein. 相似文献
112.
For purposes of interpreting broad band electronic spectra of complexes, the 3N-5 dimensional potential energy hypersurface may be reduced substantially. Consideration of the geometry of the orbital transition involved allows selection of an appropriate cross section, depending on which features should be represented. In addition, the orbital transition geometry predicts which vibrational modes will contribute significantly to the width of the spectrum. In the particular case of the first and second spin-allowed bands in d3 and d6 complexes, α1g and ?g modes are responsible for the band width. 相似文献
113.
Noel V. Stanton Tracy Fritsch Ciaran Geraghty Mary Frances Verostek Bruce Weiner Patrick J. Parsons 《Accreditation and quality assurance》2006,11(11):590-592
Following implementation of the CLIA ‘88 laboratory regulations, the primary role of proficiency testing (external quality assessment, PT) in the U.S. has been widely viewed as one of assuring regulatory compliance. PT can also be an effective tool for detecting widespread analytical problems, subject to limitations based on the method of PT assigned value determination. A recent case study describes the role of two PT programs in detecting and resolving a calibration bias in the LeadCare blood lead analyzer, and illustrates the limitations of peer-group target determination in fulfilling that PT role. 相似文献
114.
We describe our full report of the catalytic asymmetric addition of simple and functionalized dialkylzinc reagents to a broad range of saturated ketones and enones. The functionalized organozinc reagents contain esters, silyl ethers, alkyl chlorides, and alkyl bromides. In general, the resulting tertiary alcohol products are isolated with high ee's. With some substrates, yields are low as a result of the formation of aldol byproducts. Most substrates undergo additions with good yields reaching as high as 91%. 相似文献
115.
Patrick Gredin Ariel De Kozak Michel Quarton Jean Renaudin Grard Ferey 《无机化学与普通化学杂志》1993,619(6):1088-1094
The liquid-solid phase diagram of the binary system BaF2? ScF3 is established by D.T.A. and radiocrystallography. Three fluorides are disclosed: Ba3Sc2F12, Ba5Sc3F19 and a cubic high temperature phase Ba1?xScxF2+x (x = 0.17), the structure of which derives from that of BaF2. A solid solution between BaF2 and ScF3 is also evidenced at high temperature. The ternary system BaF2? CuF2? ScF3 is investigated by radiocrystallography and an isothermal section at 670°C is given. It shows the existence of four phases: a complex quaternary fluoride Ba10Cu12ScF47, two “polytypic” phases the structure of which derives from that of BaCuF4 and a tetragonal solid solution Ba5Sc3?xCuxF19?x with 0 ≤ x ≤ 1. 相似文献
116.
Alvarez CM Alvarez MA García-Vivó D García ME Ruiz MA Saáez D Falvello LR Soler T Herson P 《Dalton transactions (Cambridge, England : 2003)》2004,(24):4168-4179
The new hydride complexes [Mo2Cp2(mu-H)(mu-PHR)(CO)4] having bulky substituents (R = 2,4,6-C(6)H2tBu3= Mes*, R = 2,4,6-C6H2Me3= Mes) have been prepared in good yield by addition of Li[PHR] to the triply bonded [Mo2Cp2(CO)4] and further protonation of the resulting anionic phosphide complex [Mo2Cp2(mu-PHR)(CO)4]-. Protonation of the Mes* compound with either [H(OEt2)2][B{3,5-C6H3(CF3)2}4] or HBF4.OEt2 gives the cationic phosphinidene complex [Mo2Cp2(mu-H)(mu-PMes*)(CO)4]+ in high yield. In contrast, protonation of the analogous hydride compounds with Mes or Cy substituents on phosphorus give the corresponding unsaturated tetracarbonyls [Mo2Cp2(mu-PHR)(CO)4]+, which are unstable at room temperature and display a cis geometry. Decomposition of the latter give the electron-precise pentacarbonyls [Mo2Cp2(mu-PHR)(mu-CO)(CO)4]+, also displaying a cis arrangement of the metal fragments. In the presence of BF4- as external anion, fluoride abstraction competes with carbonylation to yield the neutral fluorophosphide hydrides [Mo2Cp2(mu-H)(mu-PFR)(CO)4]. Similar results were obtained in the protonation reactions of the hydride compounds having a Ph substituent on phosphorus. In that case, using HCl as protonation reagent gave the chloro-complex [Mo2ClCp2(mu-PHPh)(CO)4] in good yield. The structures and dynamic behaviour of the new compounds are analyzed on the basis of solution IR and 1H, 31P, 19F and 13C NMR data as well as the X-ray studies carried out on [Mo2Cp2(mu-H)(mu-PHMes)(CO)4](cis isomer), [Mo2Cp2(mu-H)(mu-PFMes)(CO)4](trans isomer), [Mo2Cp2(mu-PHCy)(mu-CO)(CO)4](BF4) and [Mo2ClCp2(mu-PHPh)(CO)4]. 相似文献
117.
A computer algorithm is presented for the simulation of the effect of molecular tumbling on ESR spectra, and is applied to simulation of the conventional ESR signal (the absorption signal detected at the first harmonic of the modulation frequency and in-phase with the modulation frequency, in the limit of low microwave and modulation power) of axially symmetric 14N-nitroxide spin labels. The algorithm is extremely fast and is economical in terms of computer memory requirements. 相似文献
118.
Jourdain V Paillet M Almairac R Loiseau A Bernier P 《The journal of physical chemistry. B》2005,109(4):1380-1386
Sequential catalytic growth provides an efficient tool for the synthesis of carbon nanotubes periodically inserted with catalyst nanoparticles. Several synthesis parameters were found crucial in order to induce this particular growth mechanism. The presence of phosphorus is required to form metal phosphide particles active for the formation of carbon nanotubes with a matchstick morphology. The metal composition (Ni/Fe ratio) and the carbon supply have no influence on the nanofilament type but strongly affect the nanotube yield. The synthesis temperature induces important changes on both the nanofilament type and yield, which are correlated with important transformations of the catalyst layer in terms of composition, particle size, and physical state. 相似文献
119.
Patrick Gredin Gwenaël Corbel Jonathan P. Wright Nathalie Dupont Ariel de Kozak 《无机化学与普通化学杂志》2003,629(11):1960-1964
Ba3Cu2Al2F16 is monoclinic: a = 7.334(1)Å, b = 5.320(2)Å, c = 16.022(1)Å, β = 96.34(1)°, Z = 2. Its crystal structure was solved in the space group P21 (No. 4) from synchrotron X‐ray single crystal data using 2685 unique reflections (2639 with Fo/σ(Fo) > 4). The final R factor is 0.044. The structure consists of a succession along the c‐axis of the cell of three layers of two different kinds of sheets developing in the (a, b) plane. The first one, formulated [(AlF5)2]∞4— and hereafter named A, is built up from infinite cis‐chains of aluminium‐fluorine octahedra [AlF6], linked by two vertices and distanced by a. The second one, formulated [Cu2AlF11]∞4— and named B, is bidimensional. It is constituted of distorted copper‐fluorine octahedra [CuF6], linked by edges, which form infinite chains interconnected by three vertices of isolated [AlF6] octahedra. The stacking sequence of the sheets is (A, B, B)∞. The barium ions, 12‐coordinated, are inserted between the sheets. The crystal structure of Ba3Cu2Al2F16 is closely related to that of Ba4Cu2Al3F21. Only the proportion and the stacking sequence of the two kinds of sheets in the c‐direction differ, according to two different compositions and two different symmetries. 相似文献
120.
Anthony D. Wright Gabriele M. Knig Otto Sticher Paolo Lubini Patrick Hofmann Max Dobler 《Helvetica chimica acta》1991,74(8):1801-1807
Reinvestigation of the brown alga Dictyota pardalis f. pseudohamata CRIBB led to the crystallization of 1 and to the isolation of the two new dolabellane derivatives 2 and 3 . X-Ray analysis of 1 and 2 , together with detailed 1D-and 2D-NMR studies on 2 and 3 , allowed their structures to be elucidated as (1R*,3S*,7S*,11R*,4Z)-dolabella-4,8(17), 12(18)-triene-3,7-diol ( 1 ), (1R*,3S*,4S*,7S*,8S*,11R*,14R*,12E)-3,4:7,8-diepoxydolabe11-12-ene-14, 18-diol ( 2 ), and (1R*,3S*,4S*,7S*,8S*,11R*,14R*)-3,4:7,8-diepoxy-l,4,8,12,12-pentamethylbicyclo[9. 3. 0]tetra-decan-14-ol( 3 ). 相似文献