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991.
D. W. Johnson Jr. P. K. Gallagher M. F. Yan H. Schreiber 《Journal of solid state chemistry》1979,30(3)
Measurement of the divalent iron content in acid dissolved MnZn ferrites, fired in controlled atmospheres at various temperatures and quenched, allows calculation of cation vacancy contents. Addition of Ti4+ to these ferrites resulted in the introduction of vacancies at the rate of about 0 to 0.3 per Ti4+ depending on heat treatment conditions. Data are presented whereby the vacancy content with Ti4+ can be calculated based on the oxygen content of the undoped ferrite as available in the literature. Ti4+ stabilizes the hexagonal hematite-like structure and the phase boundary is presented as a function of Ti4+ and temperature. The vacancy contents at the phase boundary in Ti4+-doped ferrite as a function of temperature are in agreement with those calculated from the literature for undoped MnZn ferrites. Finally, the total oxygen content of coexisting spinel and hexagonal phases is presented. 相似文献
992.
The SCF Xα SW method can be used to obtain uniquely all the multiplets arising from the d → d transitions in the square planar metal complex PtCl2?4. The agreement with the experimental absorption spectrum and the singlet transition assignments in the region ≈ 3.0–4.5 eV is excellent. 相似文献
993.
Cycloelimination of Imidazolidin‐2‐ylidene N‐Heterocyclic Carbenes: Mechanism and Insights into the Synthesis of Stable “NHC‐CDI” Amidinates 下载免费PDF全文
Aleksandr V. Zhukhovitskiy Julie Geng Prof. Dr. Jeremiah A. Johnson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5685-5688
We report the discovery that 1,3‐bis(aryl)imidazolidin‐2‐ylidenes, one of the most widely studied classes of N‐heterocyclic carbenes (NHCs), undergo quantitative conversion to zwitterionic “NHC‐CDI” amidinates upon heating to ≈100 °C in solution. The mechanism of this novel NHC decomposition process is studied in detail. These studies enabled the rational synthesis of a new class of bench stable amidinates from a panel of NHCs and carbodiimides. We expect these constructs to find utility in a variety of applications. 相似文献
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The proton and carbon-13 NMR spectra of 2,3,6 -tri-O-methyl-β-cyclodextrin in deuteriochloroform have been fully and unambiguously assigned using homonuclear and selective heteronuclear spin decoupling and two-dimensional homo- and heteronudear correlation NMR spectroscopy. Corrections are made to some earlier literature assignments. 相似文献
999.
1000.
David C. Johnson II 《Tetrahedron letters》2004,45(46):8483-8487
The benzyl groups of β-hydroxy-N-benzyl sulfonamides are labile toward hydrogenolysis-unlike N-benzyl sulfonamides lacking the β-hydroxy moiety. We find that N-acyl-N-benzyl sulfonamides undergo hydrogenolysis under very mild conditions. Based upon these observations, we developed a reversible safety-catch method using tert-butoxycarbonyl moieties to activate N-benzyl sulfonamides toward hydrogenolysis. We also explored the utility of the safety-catch activation method for other nitrogen-based functionality such as N-benzyl carboxamides, imides, and related functionality. 相似文献