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3,3,3-Trichloropropyl-1-triphenylphosphonium chloride is conveniently prepared from 2-chloroethanol, triphenylphosphine, and trichloroacetic acid. Deprotonation of this reagent generates 3,3,3-trichloropropyl-1-triphenylphosphorane, which reacts with aldehydes to give trichloromethylated (Z)-olefins, which are useful for the synthesis of (Z)-1,3-enynes, (Z,Z)-1-chloro-1,3-dienes, and 1,3-diynes in high yields and stereospecificities. 相似文献
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Tidmarsh IS Laye RH Brearley PR Shanmugam M Sañudo EC Sorace L Caneschi A McInnes EJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(22):6329-6338
A family of high nuclearity oxo(alkoxo)vanadium clusters in unprecedentedly low oxidation states is reported, synthesised from simple vanadium diketonate precursors in alcohols under solvothermal conditions. Crystal structures of [V18(O)12(OH)2(H2O)4(EtO)22(O2CPh)6(acac)2] (1), [V16Na2(O)18(EtO)16(EtOH)2(O2CPh)6(HO2CPh)2]infinity (2), [V13(O)13(EtO)15(EtOH)(RCO2)3] in which R=adamantyl (3) or Ph3C (4), and [V11(O)12(EtO)13(EtOH)(Ph3CCO2)2(MePO3)] (5) are reported, revealing these to be {VIII 16VIV 2} (1), {VIII 9VIV 3VV} (3 and 4) and {VIII 3VIV 8} (5) clusters, while 2 consists of isolated {VIII 8VIV 8} clusters bridged into polymeric chains by {Na2(OEt)2} fragments. Solvothermal conditions are essential to the formation of these species, and the level of oxidation of the isolated clusters is in part controlled by the crystallisation time, with the lowest mean-oxidation-state species being isolated by direct crystallisation on controlled cooling of the reaction solutions. 相似文献
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Tidmarsh IS Laye RH Brearley PR Shanmugam M Sañudo EC Sorace L Caneschi A McInnes EJ 《Chemical communications (Cambridge, England)》2006,(24):2560-2562
The solvothermal synthesis, crystal structure and preliminary magnetic studies are reported of the first high nuclearity V(III)-based polyoxo(alkoxo)vanadium cage, a V(III)16V(IV)2 complex. 相似文献
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Maheswaran Hariharasarma Charles H. Lake Gary M. Gray 《Journal of chemical crystallography》1999,29(1):87-91
Bis(dibenzo[d,f][1,3,2]dixoaphosphepin) ligands are extensively used in catalysts for asymmetric alkene hydroformylation; however, few crystal structures of complexes of these ligands have been reported. In this paper, the synthesis and X-ray crystal structure of cis-{(±)-6,6-[[1,1-biphenyl]-2,2-diylbis(oxy)]bis-dibenzo[d,f][1,3,2]dioxaphosphepin} diiodoplatinum (II)·dichloromethane are presented. This complex crystallizes in the triclinic space group P1¯ with a = 12.0842(2,3) b = 12.6993(15) c = 13.2801(18) Å; = 85.852(10), = 76.723(13), = 72.400(12)°, V = 1890.7(10) Å3 and Z = 4. The diastereomer that has crystallized has an R*R*R*(S*S*S*) configuration. This X-ray crystal structure supports previous observations that bis(phosphite) ligands with bridging groups derived from 2,2-biphenol can exhibit a wide range of bite angles (>20°). 相似文献
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Myers TW Kazem N Stoll S Britt RD Shanmugam M Berben LA 《Journal of the American Chemical Society》2011,133(22):8662-8672
Electrophilic activation and subsequent reduction of substrates is in general not possible because highly Lewis acidic metals lack access to multiple redox states. Herein, we demonstrate that transition metal-like redox processes and electronic structure and magnetic properties can be imparted to aluminum(III). Bis(iminopyridine) complexes containing neutral, monoanionic, and dianionic iminopyridine ligands (IP) have been characterized structurally and electronically; yellow (IP)AlCl(3) (1), deep green (IP(-))(2)AlCl (2) and (IP(-))(2)Al(CF(3)SO(3)) (3), and deep purple [(IP(2-))Al](-) (5) are presented. The mixed-valent, monoradical complex (IP(-))(IP(2-))Al is unstable toward C-C coupling, and [(IP(2-))Al](2-)(μ-IP-IP)(2-) (4) has been isolated. Variable-temperature magnetic susceptibility and EPR spectroscopy measurements indicate that the biradical character of the ligand-based triplet in 2 is stabilized by strong antiferromagnetic exchange coupling mediated by aluminum(III): J = -230 cm(-1) for ? = -2J(?(L(1))·?(L(2))). Coordination geometry-dependent (IP(-))-(IP(-)) communication through aluminum(III) is observed electrochemically. The cyclic voltammogram of trigonal bipyramidal 2 displays successive ligand-based oxidation events for the two IP(1-/0) processes, at -0.86 and -1.20 V vs SCE. The 0.34 V spacing between redox couples corresponds to a conproportionation constant of K(c) = 10(5.8) for the process (IP(-))(2)AlCl + (IP)(2)AlCl → 2(IP(-))(IP)AlCl consistent with Robin and Day Class II mixed-valent behavior. Tetrahedral 5 displays localized, Class I behavior as indicated by closely spaced redox couples. Furthermore, CV's of 2 and 5 indicate that changes in the coordination environment of the aluminum center shift the potentials for the IP(1-/0) and IP(2-/1-) redox couples by up to 0.9 V. 相似文献
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Hydroxo‐Bridged Dimers of Oxo‐Centered Ruthenium(III) Triangle: Synthesis and Spectroscopic and Theoretical Investigations
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Apoorva Upadhyay Jitendrasingh Rajpurohit Mukesh Kumar Singh Richa Dubey Anant Kumar Srivastava Prof. Dr. Ashutosh Kumar Prof. Dr. Gopalan Rajaraman Prof. Dr. Maheswaran Shanmugam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(20):6061-6070
The homometallic hexameric ruthenium cluster of the formula [RuIII6(μ3‐O)2(μ‐OH)2((CH3)3CCO2)12(py)2] ( 1 ) (py=pyridine) is solved by single‐crystal X‐ray diffraction. Magnetic susceptibility measurements performed on 1 suggest that the antiferromagnetic interaction between the RuIII centers is dominant, and this is supported by theoretical studies. Theoretical calculations based on density functional methods yield eight different exchange interaction values for 1 : J1=?737.6, J2=+63.4, J3=?187.6, J4=+124.4, J5=?376.4, J6=?601.2, J7=?657.0, and J8=?800.6 cm?1. Among all the computed J values, six are found to be antiferromagnetic. Four exchange values (J1, J6, J7 and J8) are computed to be extremely strong, with J8, mediated through one μ‐hydroxo and a carboxylate bridge, being by far the largest exchange obtained for any transition‐metal cluster. The origin of these strong interactions is the orientation of the magnetic orbitals in the RuIII centers, and the computed J values are rationalized by using molecular orbital and natural bond order analysis. Detailed NMR studies (1H, 13C, HSQC, NOESY, and TOCSY) of 1 (in CDCl3) confirm the existence of the solid‐state structure in solution. The observation of sharp NMR peaks and spin‐lattice time relaxation (T1 relaxation) experiments support the existence of strong intramolecular antiferromagnetic exchange interactions between the metal centers. A broad absorption peak around 600–1000 nm in the visible to near‐IR region is a characteristic signature of an intracluster charge‐transfer transition. Cyclic voltammetry experiments show that there are three reversible one‐electron redox couples at ?0.865, +0.186, and +1.159 V with respect to the Ag/AgCl reference electrode, which corresponds to two metal‐based one‐electron oxidations and one reduction process. 相似文献
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S. P. Palanisamy G. Maheswaran C. Kamal G. Venkatesh 《Research on Chemical Intermediates》2016,42(12):7823-7840
The corrosion of reinforced steel in concrete in 3.5 % NaCl without and with Prosopis juliflora extract at different time intervals has been studied using various techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization study (PDS) and atomic force microscopy (AFM). The results obtained by electrochemical measurements (EIS and PDS) showed that the extract inhibited corrosion by forming a protective layer on the surface of the embedded steel and by altering the reactions of the cathodic and anodic sites of the steel. Further, the AFM images supported the formation of the protective layer over the surface of the embedded steel by inhibitor molecules. The adsorption of the inhibitor molecules over the surface of the embedded steel obeyed the Temkin isotherm. Density functional theory (DFT) calculations for major ingredients of the extract have been carried out. From the results of the DFT calculations, the influence of major ingredients on the anti–corrosion potential of the plant extract has been correlated. The mechanism of inhibitive action of the P. juliflora extract has also been proposed. 相似文献
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Crich D Krishnamurthy V Brebion F Karatholuvhu M Subramanian V Hutton TK 《Journal of the American Chemical Society》2007,129(33):10282-10294
Primary allylic selenosulfates (seleno Bunte salts) and selenocyanates transfer the allylic selenide moiety to thiols giving primary allylic selenosulfides, which undergo rearrangement in the presence of PPh3 with the loss of selenium to give allylically rearranged allyl alkyl sulfides. This rearrangement may be conducted with prenyl-type selenosulfides to give isoprenyl alkyl sulfides. Alkyl secondary and tertiary allylic disulfides, formed by sulfide transfer from allylic heteroaryl disulfides to thiols, undergo desulfurative allylic rearrangement on treatment with PPh3 in methanolic acetonitrile at room temperature. With nerolidyl alkyl disulfides this rearrangement provides an electrophile-free method for the introduction of the farnesyl chain onto thiols. Both rearrangements are compatible with the full range of functionality found in the proteinogenic amino acids, and it is demonstrated that the desulfurative rearrangement functions in aqueous media, enabling the derivatization of unprotected peptides. It is also demonstrated that the allylic disulfide rearrangement can be induced in the absence of phosphine at room temperature by treatment with piperidine, or simply by refluxing in methanol. Under these latter conditions the reaction is also applicable to allyl aryl disulfides, providing allylically rearranged allyl aryl sulfides in good yields. 相似文献