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1.
K. Yuvaraj Iskander Douair Dafydd D. L. Jones Laurent Maron Cameron Jones 《Chemical science》2020,11(13):3516
An extremely bulky, symmetrical three-coordinate magnesium(i) complex, [{(TCHPNacnac)Mg}2] (TCHPNacnac = [{(TCHP)NCMe}2CH]−, TCHP = 2,4,6-tricyclohexylphenyl) has been prepared and shown to have an extremely long Mg–Mg bond (3.021(1) Å) for such a complex. It was shown not to react with either DMAP (4-dimethylaminopyridine) or CO. Three unsymmetrical 1 : 1 DMAP adducts of less bulky Mg–Mg bonded species have been prepared, viz. [(ArNacnac)Mg–Mg(DMAP)(ArNacnac)] (ArNacnac = [(ArNCMe)2CH]− Ar = 2,6-xylyl (Xyl), mesityl (Mes) or 2,6-diethylphenyl (Dep)), and their reactivity toward CO explored. Like the previously reported bulkier complex, [(DipNacnac)Mg–Mg(DMAP)(DipNacnac)] (Dip = 2,6-diisopropylphenyl), [(DepNacnac)Mg–Mg(DMAP)(DepNacnac)] reductively trimerises CO to give a rare example of a deltate complex, [{(DepNacnac)Mg(μ-C3O3)Mg(DMAP)(DepNacnac)}2]. In contrast, the two smaller adduct complexes react with only two CO molecules, ultimately giving unusual ethenediolate complexes [{(ArNacnac)Mg{μ-OC(H) C(DMAP−H)O}Mg(ArNacnac)}2] (Ar = Xyl or Mes). DFT calculations show the latter reactions to proceed via reductive dimerizations of CO, and subsequent intramolecular C–H activation of Mg-ligated DMAP by “zig–zag” [C2O2]2− fragments of reaction intermediates. Calculations also suggest that magnesium deltate complexes are kinetic products in these reactions, while the magnesium ethenediolates are thermodynamic products. This study shows that subtle changes to the bulk of the reacting 1 : 1 DMAP–magnesium(i) adduct complexes can lead to fine steric control over the products arising from their CO reductive oligomerisations. Furthermore, it is found that the more activated nature of the adduct complexes, relative to their symmetrical, three-coordinate counterparts, [{(ArNacnac)Mg}2], likely derives more from the polarisation of the Mg–Mg bonds of the former, than the elongated nature of those bonds.Subtle changes to the bulk of 1 : 1 adducts of DMAP with magnesium(i) complexes leads to steric control over the products arising from their reductive oligomerisations of carbon monoxide. 相似文献
2.
Reactivity of [M2(μ‐Cl)2(cod)2] (M=Ir,Rh) and [Ru(Cl)2(cod)(CH3CN)2] with Na[H2B(bt)2]: Formation of Agostic versus Borate Complexes 下载免费PDF全文
K. Bakthavachalam K. Yuvaraj Mohammad Zafar Prof. Dr. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17291-17297
Treatment of [M2(μ‐Cl)2(cod)2] (M=Ir and Rh) with Na[H2B(bt)2] (cod=1,5‐cyclooctadiene and bt=2‐mercaptobenzothiazolyl) at low temperature led to the formation of dimetallaheterocycles [(Mcod)2(bt)2], 1 and 2 ( 1 : M=Ir and 2 : M=Rh) and a borate complex [Rh(cod){κ2‐S,S′‐H2B(bt)2}], 3 . Compounds 1 and 2 are structurally characterized metal analogues of 1,5‐cyclooctadiene. Metal–metal bond distances of 3.6195(9) Å in 1 and 3.6749(9) Å in 2 are too long to consider as bonding. In an attempt to generate the Ru analogue of 1 and 2 , that is [(Rucod)2(bt)2], we have carried out the reaction of [Ru(Cl)2(cod)(CH3CN)2] with Na[H2B(bt)2]. Interestingly, the reaction yielded agostic complexes [Ru(cod)L{κ3‐H,S,S′‐H2B(bt)2}], 4 and 5 ( 4 : L=Cl; 5 : L=C7H4NS2). One of the key differences between 4 and 5 is the presence of different ancillary ligands at the metal center. The natural bond orbital (NBO) analysis of 1 and 2 shows that there is four lone pairs of electrons on each metal center with a significant amount of d character. Furthermore, the electronic structures and the bonding of these complexes have been established on the ground of quantum‐chemical calculations. All of the new compounds were characterized by IR, 1H, 11B, 13C NMR spectroscopy, and X‐ray crystallographic analysis. 相似文献
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4.
Jeremy C. Mullins Dr. K. Yuvaraj Yixiao Jiang Dr. Gerard P. Van Trieste III Dr. Asim Maity Prof. David C. Powers Prof. Cameron Jones 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(65):e202202103
UV irradiation of solutions of a guanidinate coordinated dimagnesium(I) compound, [{(Priso)Mg}2] 3 (Priso=[(DipN)2CNPri2]−, Dip=2,6-diisopropylphenyl), in either benzene, toluene, the three isomers of xylene, or mesitylene, leads to facile activation of an aromatic C−H bond of the solvent in all cases, and formation of aryl/hydride bridged magnesium(II) products, [{(Priso)Mg}2(μ-H)(μ-Ar)] 4 – 9 . In contrast to similar reactions reported for β-diketiminate coordinated counterparts of 3 , these C−H activations proceed with little regioselectivity, though they are considerably faster. Reaction of 3 with an excess of the pyridine, p-NC5H4But (pyBut), gave [(Priso)Mg(pyButH)(pyBut)2] 10 , presumably via reduction of the pyridine to yield a radical intermediate, [(Priso)Mg(pyBut⋅)(pyBut)2] 11 , which then abstracts a proton from the reaction solvent or a reactant. DFT calculations suggest two possible pathways to the observed arene C−H activations. One of these involves photochemical cleavage of the Mg−Mg bond of 3 , generating magnesium(I) doublet radicals, (Priso)Mg⋅. These then doubly reduce the arene substrate to give “Birch-like” products, which subsequently rearrange via C−H activation of the arene. Circumstantial evidence for the photochemical generation of transient magnesium radical species includes the fact that irradiation of a cyclohexane solution of 3 leads to an intramolecular aliphatic C−H activation process and formation of an alkyl-bridged magnesium(II) species, [{Mg(μ-Priso−H)}2] 12 . Furthermore, irradiation of a 1 : 1 mixture of 3 and the β-diketiminato dimagnesium(I) compound, [{(DipNacnac)Mg}2] (DipNacnac=[HC(MeCNDip)2]−), effects a “scrambling” reaction, and the near quantitative formation of an unsymmetrical dimagnesium(I) compound, [(Priso)Mg−Mg(DipNacnac)] 13 . Finally, the EPR spectrum (77 K) of a glassed solution of UV irradiated 3 is dominated by a broad featureless signal, indicating the presence of a doublet radical species. 相似文献
5.
Susheel Kalia Sarita Kango Amit Kumar Yuvaraj Haldorai Bandna Kumari Rajesh Kumar 《Colloid and polymer science》2014,292(9):2025-2052
Hybrid nanomaterials have received voluminous interest due to the combination of unique properties of organic and inorganic component in one material. In this class, magnetic polymer nanocomposites are of particular interest because of the combination of excellent magnetic properties, stability, and good biocompatibility. Organic–inorganic magnetic nanocomposites can be prepared by in situ, ex situ, microwave reflux, co-precipitation, melt blending, and ceramic–glass processing and plasma polymerization techniques. These nanocomposites have been exploited for in vivo imaging, as superparamagnetic or negative contrast agents, drug carriers, heavy metal adsorbents, and magnetically recoverable photocatalysts for degradation of organic pollutants. This review article is mainly focused on fabrication of magnetic polymer nanocomposites and their applications. Different types of magnetic nanoparticles, methods of their synthesis, properties, and applications have also been reviewed briefly. The review also provides detailed insight into various types of magnetic nanocomposites and their synthesis. Diverse applications of magnetic nanocomposites including environmental and biomedical uses have been discussed. 相似文献
6.
The synthetic utility of trifluoromethanesulphonic anhydride (triflic anhydride, TA) without additive or base for the high-yielding synthesis of a wide variety of 1,2-benzisoxazoles from 2-hydroxyaryl aldoximes and ketoximes under mild conditions has been carried out for the first time. As a continuation of our study, syntheses of isoxazolo and isothiazolo quinolones have also been demonstrated using triflic anhydride under similar conditions. This method is simple and has benefits from the easy way to isolate the products in excellent yields.
[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] 相似文献
7.
Gurumurthy Hegde Govindaswamy Shanker S. M. Gan A. R. Yuvaraj Syed Mahmood Uttam Kumar Mandal 《Liquid crystals》2016,43(11):1578-1588
Azobenzene derivatives containing phenyl/4-halogen-phenyl 4-{(E)-[4-(pent-4-en-1-yloxy)phenyl]diazenyl}benzoate group with different electronegative substituent (H, F, Cl, Br and I) at other end was synthesised. These azo-based benzoate derivatives have been characterised by FTIR, 1H-NMR, 13C-NMR, elemental analyser, POM and UV-Vis spectroscopy. Photosaturation at 358 nm obtained after 82 s of UV irradiation and the longest thermal back relaxation time of 45 h recorded by UV-Vis. The azo derivative could be possible photolock under UV light, as observed by the improved thermal back relaxation time. The resulting photolockable chain of azobenzene might prove valuable in the development of optical device application. These azobenzene moieties also exhibit liquid crystalline behaviour with respect to the halogen substitution as an electron withdrawing group shows that strong structure property relationship exists among them. 相似文献
8.
Zinc micro and nanostructures were synthesized in vacuum by condensing evaporated zinc on Si substrate at different gas pressures. The morphology of the grown Zn structures was found to be dependent on the oxygen partial pressure. Depending on oxygen partial pressure it varied from two-dimensional microdisks to one-dimensional nanowire. The morphology and structural properties of the grown micro and nanostructures were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Transmission electron microscopy (TEM) studies on the grown Zn nanowires have shown that they exhibit core/shell-like structures, where a thin ZnO layer forms the shell. A possible growth mechanism behind the formation of different micro and nanostructures has been proposed. In addition, we have synthesized ZnO nanocanal-like structures by annealing Zn nanowires in vacuum at 350 °C for 30 min. 相似文献
9.
Determination of hexavalent chromium by on-line dialysis ion chromatography in a matrix of strong colourants and trivalent chromium 总被引:3,自引:0,他引:3
Ganeshjeevan R Chandrasekar R Yuvaraj S Radhakrishnan G 《Journal of chromatography. A》2003,988(1):151-159
Hexavalent chromium detection in the presence of a high load of colourants without any false positive and in-procedure oxidation of Cr(III) is an important area of study. Colourants are a class of interfering substances in many spectroscopic analyses and chromatographic separations and detection. A purification method using an on-line dialysis technique for ion chromatography (IC) has been developed to remove water-soluble anionic dyes and particulate colourants and other substances to facilitate Cr(VI) quantification and the method is discussed. The dialysis was optimized with Cr(VI) standard solutions for quantification. The efficacy of the procedure for the removal of anionic dyes and detection of Cr(VI) was checked with a Cr(VI) spiked synthetic preparation containing a water-soluble dye and trivalent chromium. Soluble Cr(VI) extracted with organic dyes from environmental samples was analyzed. The method has a detection limit of 5 microg/l, recovery rate of 100% and analysis time less than 20 min. 相似文献
10.
Design,synthesis, and antimicrobial activity of novel 5-substituted indole-2-carboxamide derivatives
Mane Yogesh D. Sarnikar Yuvaraj P. Surwase Santosh M. Biradar Dhanraj O. Gorepatil Pratapsinha B. Shinde Vishnu S. Khade Bhimrao C. 《Research on Chemical Intermediates》2017,43(2):1253-1275
Research on Chemical Intermediates - A series of novel, bioactive 5-substituted indole-2-carboxamide derivatives (10a–t and 14a–k) are synthesized by the coupling of 5-substituted... 相似文献