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101.
William H. Watson Srikanth Kandala Michael G. Richmond 《Journal of chemical crystallography》2006,36(12):813-822
The tetraruthenium cluster H4Ru4(CO)12 (1) has been studied for its reactivity with the unsaturated diphosphine ligands (Z)–Ph2PCH–CHPPh2 and 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) under thermal, near-UV photolysis, and Me3NO-assisted activation. All three cluster activation methods promote loss of CO and furnish the anticipated substitution products H4Ru4(CO)10[(Z)–Ph2PCH–CHPPh2] (2) and H4Ru4(CO)10(bpcd) (3) that possess a chelating diphosphine ligand. Clusters 2 and 3 have been characterized in solution by IR and NMR spectroscopies, and these data are discussed with respect to the crystallographically determined structure for both new cluster compounds. The 31P NMR spectral data and the solid-state structures confirm the presence of a chelating diphosphine ligand in clusters 2 and 3. Cluster 2 crystallizes in the monoclinic space P21/c, a=11.768(6) ?, b=18.521(9) ?, c=20.48(1) ?, β=102.291(8)°, V=4361(4) A3, Z=4, and d
calc=1.726 Mg/m3; R=0.0225, R
w=0.0491 for 6798 reflections with I > 2σ(I). The four bridging hydrides were located in H4Ru4(CO)10[(Z)–Ph2PCH–CHPPh2] and their adopted positions are discussed relative to the solution 1H NMR spectrum. H4Ru4(CO)10(bpcd) crystallizes in the orthorhombic space Pbca, a=19.072(3) ?, b=20.169(3) ?, c=22.774(3) ?, V=8760(2) A3, Z=8, and d
calc=1.870 Mg/m3; R=0.0428, R
w=0.0896 for 10296 reflections with I > 2σ(I). Sealed NMR tubes containing clusters 2 and 3 were found to be exceeding stable towards near-UV light and temperatures up to ca. 125 °C. The surprisingly robust behavior of 2 and 3 is contrasted with the related cluster Ru3(CO)10(bpcd) that undergoes fragmentation to the donor-acceptor compound Ru2(CO)6(bpcd) and the phosphido-bridged compound Ru2(CO)6(μ–PPh2)[μ–C–C(PPh2)C(O)CH2C(O)] under mild conditions. The electrochemical properties of each substituted cluster have been investigated by cyclic voltammetry, and our findings are discussed with respect to the reported electrochemical data on the parent cluster H4Ru4(CO)12.
相似文献
Michael G. Richmond (Corresponding author)Email: |
102.
Dasari Ramesh Singanaboina Rajaram Manchala Narasimhulu Thummalpally Srikanth Reddy Kondempudi Chinni Mahesh Gajji Manasa Yenamandra Venkateswarlu 《中国化学》2011,29(11):2471-2475
An environmentally friendly and highly efficient procedure for the preparation of 1,4‐dihydropyridines by the reaction between α,β‐unsaturated aldehydes, aromatic amines and β‐keto esters in the presence of silica supported perchloric acid is described. 相似文献
103.
104.
Ammu S Dua V Agnihotra SR Surwade SP Phulgirkar A Patel S Manohar SK 《Journal of the American Chemical Society》2012,134(10):4553-4556
Chemiresistors made of thin films of single-walled carbon nanotube (CNT) bundles on cellulosics (paper and cloth) can detect aggressive oxidizing vapors such as nitrogen dioxide and chlorine at 250 and 500 ppb, respectively, at room temperature in ambient air without the aid of a vapor concentrator. Inkjet-printed films of CNTs on 100% acid-free paper are significantly more robust than dip-coated films on plastic substrates. Performance attributes include low sensor-to-sensor variation, spontaneous signal recovery, negligible baseline drift, and the ability to bend the sensors to a crease without loss of sensor performance. 相似文献
105.
In this paper, we have developed an accurate and efficient Haar wavelet method to solve film-pore diffusion model. Film-pore diffusion model is widely used to determine study the kinetics of adsorption systems. To the best of our knowledge, until now rigorous wavelet solution has been not reported for solving film-pore diffusion model. The use of Haar wavelets is found to be accurate, simple, fast, flexible, convenient, and computationally attractive. The power of the manageable method is confirmed. It is shown that film-pore diffusion model satisfactorily describes the kinetics of methylene blue adsorption onto three low-cost adsorbents, Gauva, teak and gulmohar plant leaf powders, used in this study. 相似文献
106.
107.
The kinetics for the bridge-to-chelate isomerization of the dppe ligand in H4Ru4(CO)10(dppe) have been investigated by UV-vis and NMR spectroscopies over the temperature range of 308-328 K. The isomerization of the ligand-bridged cluster 1,2-H4Ru4(CO)10(dppe) (1-br) was found to be reversible by 31P NMR spectroscopy, affording a K(eq) = 15.7 at 323 K in favor of the chelating dppe isomer 1-ch. The forward (k1) and reverse (k(-1)) first-order rate constants for the reaction have been measured in different solvents and in the presence of ligand-trapping agents (CO and PPh3). On the basis of the activation parameters and reaction rates that are unaffected by added CO and PPh3, a sequence involving the nondissociative migration of a phosphine moiety and two CO groups between basal ruthenium centers is proposed and discussed. 相似文献
108.
The copolymers from different feed ratios of N-(methacryloyloxymethyl) benzotriazole (MMBT) and methyl methacrylate (MMA) has been synthesised using free radical solution polymerization technique and characterized using FT-IR and 13C NMR spectroscopy. The thermal stability of the polymers was studied using theremogravimetrtic analysis (TGA). The corrosion behaviors of mild steel specimens dip coated with different composition of copolymers have been evaluated by potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) method. These electrochemical properties were observed in 0.1 M HCl medium. The polarization and impedance measurements showed different corrosion protection efficiency with change in composition of the copolymers. It was found that the corrosion protection properties are owing to the barrier effect of the polymer layer covered on the mild steel surfaces. However, it was observed that the copolymer obtained from 1:1 mole ratio of MMBT and MMA exhibited better protection efficiency than other combinations. 相似文献
109.
G.S.C. Srikanth Author Vitae Author Vitae 《Tetrahedron》2005,61(44):10377-10441
110.
Dmitry Gavinsky Shachar Lovett Michael Saks Srikanth Srinivasan 《Random Structures and Algorithms》2015,47(1):99-108
We prove a Chernoff‐like large deviation bound on the sum of non‐independent random variables that have the following dependence structure. The variables are arbitrary [0,1]‐valued functions of independent random variables , modulo a restriction that every Xi influences at most k of the variables . © 2014 Wiley Periodicals, Inc. Random Struct. Alg., 47, 99–108, 2015 相似文献