排序方式: 共有75条查询结果,搜索用时 15 毫秒
51.
A new methodology has been developed based on Pd(OAc)2 and 4-aminobenzoic acid catalytic system for the Sonogashira cross-coupling reaction at ambient temperature under copper and amine free conditions. The newly developed catalytic system is conveniently applicable to the aryl iodides and terminal acetylenes. The catalytic system is much efficient because of the use of easily available and low cost additive. 相似文献
52.
Effect of variable viscosity on boundary layer flow along a continuously moving plate with variable surface temperature 总被引:1,自引:0,他引:1
V.?M.?SoundalgekarEmail author H.?S.?Takhar U.?N.?Das R.?K.?Deka A.?Sarmah 《Heat and Mass Transfer》2004,40(5):421-424
Flow of an incompressible viscous fluid past a continuously moving semi-infinite plate is studied by taking into account variable viscosity and variable temperature. Velocity and temperature profiles are shown graphically whereas the numerical values of the skin-friction and the rate of heat transfer are listed in a table. The effect of different parameters on the flow field is discussed. 相似文献
53.
Acetanilide palladacycle: an efficient catalyst for room‐temperature Suzuki–Miyaura cross‐coupling reaction 下载免费PDF全文
Anindita Dewan Zenith Buragohain Manoj Mondal Gayatri Sarmah Geetika Borah Utpal Bora 《应用有机金属化学》2014,28(4):230-233
The catalytic activity of three acetanilide palladacycles derived from easily accessible and commercially available acetanilide derivatives, viz. N‐phenylacetamide ( L1 ), N‐(4‐chlorophenyl)acetamide ( L2 ) and N‐(4‐methylphenyl)acetamide ( L3 ) has been examined in Pd‐catalyzed Suzuki–Miyaura reaction of arylboronic acid with aryl bromides at room temperature. The complex 1L3 exhibited efficient activity in the Suzuki–Miyaura reaction (up to 99% isolated yield) under mild reaction conditions. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
54.
55.
Kokil Saikia Biswajit Deb Bibek Jyoti Borah Podma Pollov Sarmah Dipak Kumar Dutta 《Journal of organometallic chemistry》2012,696(26):4293-4297
New palladium complexes of the type [PdCl2(η2–P∩P)] (1a,1b) and [PdCl2(η2–P∩S)] (1c,1d) have been synthesised by the reaction of PdCl2 with P,P and P,S type bidentate ligands in 1:1 mol ratio, where, P∩P = 9,9–dimethyl-4,5-bis(diphenylphosphanyl) xanthene {Xantphos}(a) or bis(2-diphenylphosphanylphenyl)ether{DPEphos}(b); P∩S = 9,9-dimethyl-4,5-bis(diphenyl -phosphanyl) xanthenemonosulfide {Xantphos(S)}(c) or bis(2-diphenylphosphanyl phenyl) ether monosulfide {DPEphos(S)}(d). The complexes are characterized by elemental analyses, mass spectrometry, 1H, 13C and 31P NMR spectroscopy together with the single crystal X-ray structure determination of 1a and 1d. The palladium atom in all the complexes occupies the centre of a slightly distorted square planar environment formed by a P atom, a P/S atom and two Cl atoms. The catalytic activities of 1a–1d investigated for Suzuki–Miyaura cross-coupling reactions at room temperature exhibit higher yield of the coupling products than catalysed by PdCl2 itself. Among 1a–1d, the palladium complexes of bidentate phosphine (1a, 1b) show higher efficacy than their monosulfide analogues (1c, 1d). However, the recycling experiments with the catalysts for a selected coupling reaction between 4-bromobenzonitrile and phenylboronic acid exhibit that 1c and 1d are more efficient than 1a and 1b, which may be due to the donor effect of the P,S ligands during catalytic reaction. 相似文献
56.
Bhaskar Jyoti Sarmah 《Journal of organometallic chemistry》2010,695(6):781-785
The complex [Ru(CO)2(triphos-κ2P)Cl2] (1) underwent decarbonylation in dichloromethane solution under air over a period of about two weeks to afford the chelated monocarbonyl complex [Ru(CO)(triphos-κ3P)Cl2] (2). The Single Crystal X-ray structure of 2 showed a slightly distorted metal centred complex. The catalytic activity of one of the complexes [Ru(CO)(triphos-κ3P)Cl2] (2) was examined in the transfer hydrogenation of aromatic carbonyl compounds and was found to be efficient with conversion up to 100% in the presence of isopropanol/NaOH. 相似文献
57.
Podma Pollov Sarmah Bibek Jyoti Borah Alexandra M.Z. Slawin Dipak Kumar Dutta 《Journal of organometallic chemistry》2010,695(24):2603-2608
The dimeric rhodium precursor [Rh(CO)2Cl]2 reacts with quinoline (a) and its three isomeric carboxaldehyde ligands [quinoline-2-carboxaldehyde (b), quinoline-3-carboxaldehyde (c), and quinoline-4-carboxaldehyde (d)] in 1:2 mole ratio to afford complexes of the type cis-[Rh(CO)2Cl(L)] (1a-1d), where L = a-d. The complexes 1a-1d have been characterised by elemental analyses, mass spectrometry, IR and NMR (1H, 13C) spectroscopy together with a single crystal X-ray structure determination of 1c. The X-ray crystal structure of 1c reveals square planar geometry with a weak intermolecular pseudo dimeric structure (Rh?Rh = 3.573 Å). 1a-1d undergo oxidative addition (OA) with different electrophiles such as CH3I, C2H5I and I2 to give Rh(III) complexes of the type [Rh(CO)(COR)Cl(L)I] {R = -CH3 (2a-2d), R = -C2H5 (3a-3d)} and [Rh(CO)Cl(L)I2] (4a-4d) respectively. 1b exhibits facile reactivity with different electrophiles at room temperature (25 °C), while 1a, 1c and 1d show very slow reactivity under similar condition, however, significant reactivity was observed at a temperature ∼40 °C. The complexes 1a-1d show higher catalytic activity for carbonylation of methanol to acetic acid and methyl acetate [Turn Over Frequency (TOF) = 1551-1735 h−1] compared to that of the well known Monsanto’s species [Rh(CO)2I2]− (TOF = 1000 h−1) under the reaction conditions: temperature 130 ± 2 °C, pressure 33 ± 2 bar, 450 rpm and time 1 h. The organometallic residue of 1a-1d was also isolated after the catalytic reaction and found to be active for further run without significant loss of activity. 相似文献
58.
Pankaj Hazarika Diganta Kalita Swapnalee Sarmah Ruli Borah Nashreen S. Islam 《Polyhedron》2006,25(18):3501-3508
Two new dinuclear oxo-bridged peroxo complexes of tungsten with coordinated dipeptides of the type, Na2[W2O3(O2)4(glycyl-glycine)2] · 3H2O (1) and Na2[W2O3(O2)4(glycyl-leucine)2] · 3H2O (2) have been synthesized from the reaction of H2WO4, 30% H2O2 and the respective dipeptide at pH ca. 2.5. Synthesis of the compounds, in addition to pH, is sensitive to reaction temperature and concentrations of the components. The compounds were characterized by elemental analysis, spectral and physico-chemical methods including thermal analysis. In the dimeric complexes the two W(VI) centres with edge bound peroxo groups are bridged by an oxo group. The dipeptides occurring as zwitterions bind the metal centers through O (carboxylate) atoms leading to hepta co-ordination around each W(VI). Thermal stability of the compounds as well as their stability in solution were determined. The compounds are highly stable toward decomposition in solutions of acidic as well as physiological pH. These compounds, besides another similar dimeric compound Na2[W2O3(O2)4(cystine)] · 4H2O (3) efficiently oxidized bromide to a bromination competent intermediate in phosphate buffer at physiological pH, a reaction in which only two of the peroxide groups of the complex species were found to be active. The complexes could also mediate bromination of organic substrate in aqueous-organic media. 相似文献
59.
A highly efficient and recyclable silica-supported palladium catalyst for alcohol oxidation reaction
A silica supported palladium catalyst (SiO2@APTES-Pd) showed excellent activity and reusability for selective oxidation of alcohols to corresponding carbonyl compounds with H2O2 as oxidant under base free environment. A wide range of alcohols including aliphatic alcohols are tolerated as substrates with a low loading of palladium (0.1 mol %). 相似文献
60.
Dr. Aparna G. Nair Arathi Das Nayana Edavan Chathoth Manash Pratim Sarmah Dr. Padmesh Anjukandi 《Chemphyschem》2023,24(22):e202300445
Organic light-emitting diodes (OLEDs) have become one of the most popular lighting technologies since they offer several advantages over conventional devices. In carbazole-benzophenone (CzBP) OLED devices, the polymeric form of the compound is previously reported to be Thermally Activated Delayed Fluorescence (TADF)-active (ΔEST ≈0.12 eV), while the monomer ( CzBP ) (ΔEST≈0.39 eV) does not. The present study examines the effect of chemical tailoring on the optical and photophysical properties of CzBP using DFT and TDDFT methods. The introduction of a single −NO2 group or di-substitution (−NO2, −COOH or −CN) in the selected LUMO region of the reference CzBP monomer significantly reduces ΔEST≈0.01 eV, projecting these systems as potential TADF-active emitters. Furthermore, the chemical modification of CzBP -LUMO alters the two-step TADF mechanism (T1→T2→S1) in CzBP (ES₁>ET2>ET₁) to the Direct Singlet Harvesting (T1→S1) mechanism (ET2>ES₁>ET₁), which has recently been identified in the fourth-generation OLED materials. 相似文献