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191.
A novel organoantimony complex of 6-cyclohexyl-6,7-dihydrodibenzo[c,f] [1,5]azastibocin-12(5H)-yl nitrate ( 2 ) was synthesized and systematically characterized by techniques such as NMR spectra, TG-DSC, and X-ray diffraction. It was found that the complex 2 exhibits relatively strong Lewis acidity (3.3 < Ho ≤ 4.8) and could be employed as a water tolerant Lewis acid catalyst for the synthesis of synthetically valuable benzimidazole derivatives starting from aldehydes and arylenediamines. This catalytic system shows excellent tolerance toward a wide variety of functional groups, such as methyl, methoxyl, fluoro, chloro, bromo, nitro, cyan, trifluoromethyl, 1-naphthaldehyde, furfural and n-butyl, together with facile reusability in 5 times scale enlarged synthesis. 相似文献
192.
Dr. Oliver Hegen Jens Braese Prof. Dr. Alexey Y. Timoshkin Prof. Dr. Manfred Scheer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(2):485-489
A new class of neutral bidentate ligands with pnictogenyl-functional sites has been obtained. The reaction of tmeda⋅(BH2I)2 ( 1 , tmeda=tetramethylethylendiamine) with different phosphanides yields the corresponding bidentate phosphanylboranes tmeda⋅(BH2PH2)2 ( 2 a ), tmeda⋅(BH2PPh2)2 ( 2 b ), and tmeda⋅(BH2tBuPH)2 ( 2 c ). This reaction strategy could be further extended to synthesize the first bidentate arsanylborane tmeda⋅(BH2AsPh2)2 ( 3 ). Depending on the substituents on the phosphorus, these compounds form different AuI complexes, to build either polymeric tmeda⋅(BH2PH2AuCl)2 ( 4 a ), or monomeric tmeda⋅(BH2PPh2AuCl)2 ( 4 b ) products. These compounds form also neutral oligomeric group 13/15 chain-like molecules by coordination to a boron moiety such as tmeda⋅(BH2PH2BH3)2 ( 5 a ) and tmeda⋅(BH2AsPh2BH3)2 ( 5 b ). DFT calculations provide insight into the differences between the syntheses of mono- and bidentate pnictogenylboranes. 相似文献
193.
Considering the importance of silylene ligands in transition metal-mediated catalytic reactions, we have scrutinized eight novel monodentate ( 1 – 4 ) and bidentate ( 1 ′ - 4 ′ ) derivatives of 2,5-diX-cyclopentasilylene-2,4-dienes (X = NH2, OH, PH2, and SH), at M06/6-311++G** level of theory. To probe the complexation ability of our scrutinized silylene ligands with Rh atom ( 1 Rh - 4 Rh and 1 ′ Rh - 4 ′ Rh , respectively), thermodynamic and structural parameters such as complexation energy (ΔECom), singlet-triplet energy gap (ΔEs-t), bond length, along with NBO and atoms in molecules analyses are provided. In going from less electron donating groups (EDGs) to more EDGs (NH2 > OH > PH2 > SH), the σ -donor strength and ligand flexibility increase. Structures 1 and 1 ′ turn out as the most nucleophilic species for showing the highest nucleophilicity (N = 5.47 and 5.40 eV, respectively). Furthermore, they exhibit the highest proton affinity values (PA = 271.46 and 271.23 kcal/mol, respectively). The results indicate that bidentate coordination mode of silylene leads to a stronger Si-Rh complex. The overall orders of σ -donation ability for monodentate and bidentate silylene ligands are 1 > 2 > 3 > 4 and 1 ′ > 2 ′ > 3 ′ > 4 ′ , respectively. 相似文献
194.
We demonstrate a dramatic increase in the signal-to-noise ratio (SNR) of a nuclear quadrupole resonance (NQR) signal by using a polarization enhancement technique. By first applying a static magnetic field to pre-polarize one spin subsystem of a material, and then allowing that net polarization to be transferred to the quadrupole subsystem, we increased the SNR of a sample of ammonium nitrate by one-order of magnitude. 相似文献
195.
Oxoanionic Noble Metal Compounds from Fuming Nitric Acid: The Palladium Examples Pd(NO3)2 and Pd(CH3SO3)2
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Jörn Bruns Prof. Dr. Thorsten Klüner Prof. Dr. Mathias S. Wickleder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1294-1301
The oxidation of elemental palladium at 100 °C in a mixture of fuming nitric acid and a pyridine‐SO3 complex leads to the anhydrous nitrate Pd(NO3)2 (monoclinic, P21/n, Z=2, a=469.12(3) pm, b=593.89(3) pm, c=805.72(4) pm, β=105.989(3)°, V=215.79(2) Å3). The Pd2+ ions are in square‐planar coordination with four monodentate nitrate groups which are connected to further palladium atoms, leading to a layer structure. The reaction of elemental palladium with a mixture of fuming nitric acid and methanesulfonic acid at 120 °C leads to single crystals of Pd(CH3SO3)2 (monoclinic, P21/n, Z=2, a=480.44(1) pm, b=1085.53(3) pm, c=739.78(2) pm, β=102.785(1)°, V=376.254(17) Å3). Also in this structure the Pd2+ ions are in square‐planar coordination with four monodentate anions; however, the connection to adjacent palladium atoms leads to a chain‐type structure. The thermal decomposition of the compounds has been investigated by means of DSC/TG measurements. Furthermore, IR and Raman spectra have been recorded, and an assignment of the observed vibrational frequencies has been carried out based on theoretical investigations. 相似文献
196.
Screening of N,N‐bidentate and N,N,N‐tridentate pyridine‐based ligands in the catalytic allylic oxidation of cyclic olefins
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A variety of chiral N,N‐bidentate and N,N,N‐tridentate ligands based on the pyridine framework, namely C2‐symmetric dipyridylmethane and terpyridine, N‐(p‐toluensulfinyl)iminopyridines and two kinds of iminopyridines, has been assessed in the asymmetric copper(I)‐catalysed allylic oxidation of cyclic olefins. Catalytic activity and enantioselectivity were found to be highly dependent upon the framework of the ligands, which afforded cycloalkenyl benzoates in low to moderate yields and enantioselectivities. The best yields (up to 70%) and enantioselectivities (up to 53% enantiomeric excess) were obtained with an iminopyridine based on camphane and quinoline skeletons. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
197.
William?H.?WatsonEmail author Tao?Chen Michael?G.?RichmondEmail author 《Journal of chemical crystallography》2004,34(11):765-771
Refluxing 2,3-dichloromaleic anhydride with p-anisidine in benzene with water removal gives the condensation product 2,3-dichloro-N-(p-MeOC6H4)maleimide (1) 75% yield. This new maleimide compound reacts with added ethanethiol in the presence of Et3N or DBU to furnish the bidentate sulfide ligand 2,3-bis(ethylthio)-N-(p-MeOC6H4)maleimide (2) in 85% yield. Each product has been characterized in solution by IR, NMR, and UV-vis spectroscopies, and the solid-state structure of 2,3-bis(ethylthio)-N-(p-MeOC6H4)maleimide was unequivocally established by single-crystal X-ray diffraction analysis. 2,3-bis(Ethylthio)-N-(p-MeOC6H4)maleimide crystallizes in the monoclinic space group C2/c, a = 20.035(3)Å, b = 9.188(1)Å, c = 16.887(2)Å, = 93.696(2)°, V = 3102.3(8)Å3, Z = 8, and Dcalcd = 1.385 mg/m3; R = 0.0268, Rw = 0.0676 for 2025 reflections with I > 2 (I). The nature of the LUMO in 2,3-bis(ethylthio)-N-(p-MeOC6H4)maleimide (2) has been determined by extended Hückel molecular orbital calculations, and these data are discussed relative to the cyclic voltammetry results and other structurally relevant compounds prepared in our labs. 相似文献
198.
基于氟钛配合物的原位水解以及硝酸镧电位滴定法建立了测定钛合金化铣腐蚀溶液中总氟化物浓度的新方法。在六次甲基四胺(HMTA)缓冲溶液中,氟钛配合物发生原位水解并释放出游离氟离子,以氟离子选择电极(F-ISE)为指示电极进行测定。对影响测定的各项参数(如p H值、HMTA溶液用量、钛离子浓度等)做了条件实验并予以优化。实验结果表明Ti(Ⅳ)浓度在0~20 g/L范围内对于氟离子测定无干扰,方法的相对标准偏差(RSDs,n=6)在0.27%~0.62%之间,加标回收率在99.5%~101.1%之间。此外,本文对氟钛配合物原位水解反应的机理也进行了探讨,溶液中氟钛配合物的主要存在形式为TiF_6~(2-),适宜的酸度是水解反应进行的必要条件,HMTA作为缓冲溶液为水解反应持续进行提供恒定的p H环境,La(NO_3)_3作为氟清除剂降低游离氟离子浓度促进水解反应的进行,伴随滴定过程氟钛配合物发生完全水解。 相似文献
199.
Rasim Tanbug Kristin Kirschbaum A. Alan Pinkerton 《Journal of chemical crystallography》1999,29(1):45-55
Two energetic salts of the melaminium cation have been prepared and structurally characterized from room temperature X-ray single crystal diffraction data. Melaminium dinitramide (I), triclinic, P1¯, a = 6.6861(11), b = 6.9638(16), c = 10.447(2) Å , = 99.07(3), = 98.30(3), = 108.50(3)°, V = 445.6(2) Å3, and Z = 2. Melaminium nitrate (II), monoclinic, P21/c, a = 3.5789(7), b = 20.466(4), c = 10.060(2) Å, = 94.01(2)°, V = 735.0(3) Å3, and Z = 4. The crystal structures of both salts show distinct monoprotonated melaminium cations and dinitramide- or nitrate anions, respectively. Efficient packing in the solid state is achieved by extensive hydrogen bonding between two-dimensional zigzag ribbons of the melaminium cations and the respective anions resulting in high densities of the solid state structures of 1.74 (I) and 1.71 g/cm3 (II). 相似文献
200.
Gezina Beurskens C. F. Martens R. J. M. Nolte Paul T. Beurskens J. M. M. Smits 《Journal of chemical crystallography》1995,25(7):425-427
The crystal and molecular structure of a pyridine complex of anhydrous copper(II)nitrate is described. The structure has been solved by vector search methods and refined by least-squares methods to R1=0.049 [I>2(I)]. The complex lies on a twofold axis parallel toa, and two solvent pyridine molecules lie on twofold axes parallel toc. The copper atom is coordinated by four pyridyl groups and two monodentate NO3 groups. Crystal data: C30H30N8O6Cu, orthorhombic, space group Pnna(52),a=14.446(7),b=12.154(5),c=16.881(4) Å,V=2964(2) Å3,Z=4. 相似文献