摘要 :
New transition metal complexes of Co-II, Ni-II, Cu-II and Fe-III with butylmalonylbis (4-phenylsemicarbazide), H(4)BMPS, have been synthesized chemically and electrochemicaly. Attempts have been made to ascertain their probable st...
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New transition metal complexes of Co-II, Ni-II, Cu-II and Fe-III with butylmalonylbis (4-phenylsemicarbazide), H(4)BMPS, have been synthesized chemically and electrochemicaly. Attempts have been made to ascertain their probable structures on the basis of elemental analyses, molar conductivity, spectra (IR, electronic and H-1 NMR) and magnetic measurements. IR data show that H(4)BMPS acts as a bidentate or hexadentate (with two metal ions) ligand coordinating via different modes. The stereochemistry of Co-II, Ni-II, Cu-II and Fe-III complexes was investigated with the help of magnetic and spectral studies. The crystal field parameters calculated for the Co-II and Ni-II complexes agree fairly well with that reported for known octahedral complexes. [Co-2(BMPS)(H2O)(4)] has a trigonal bipyramidal structure while [Ni-2(BMPS)(H2O)(4)] has mixed stereochemistry. [References: 22]
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Interaction of lithium cyclopentadienide with a suitable partially protected a-D-allofuranose triflate, 4, epimer at C-3 of glucose, gives as a major product, besides the expected glucose-cyclopentadiene, 5, a glucose-disubstitute...
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Interaction of lithium cyclopentadienide with a suitable partially protected a-D-allofuranose triflate, 4, epimer at C-3 of glucose, gives as a major product, besides the expected glucose-cyclopentadiene, 5, a glucose-disubstituted cyclopentadiene, 6. This unprecedented behaviour, which does not occur with alpha-D-glucofuranose and other sugars, is tentatively explained by a complexation of LiCp and the oxygen atoms of the isopropylidene function of one molecule of 4 and one of 5, giving a termolecular structure as the result of a template effect. The results of other experiments, such as the use of MgCp2 in place of LiCp or the complexation of oxygen atoms by lithium triflate, which changed the selectivity of the reaction largely in favour of the monosubstitution product 5, support this hypothesis. When lithium indenide is reacted with 4, glucose-monosubstituted and glucose-disubstituted indenes, 8 and 9, respectively, are formed, and 9 is obtained with almost total diastereoselectivity. This result can also be rationalised by a stereoselective complexation of lithium, as shown by separate experiments and by molecular mechanics calculations. Methyltricarbonyl molybdenum(II) complexes have been synthesised and characterised from glucose-monosubstituted 5 and glucose-disubstituted 6 cyclopentadienes.
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RuCl3.nH(2)O in MeCN catalyzes the hydrosilylation of carbon dioxide with n-Hex(3)SiH into n-Hex(3)SiOOCH and, with Me2PhSiH, into Me2PhSiOOCH. The initial catalyst formed is trans-[(RuCl)-Cl-II(MeCN)(5)][(RuCl4)-Cl-III(MeCN)(2)],...
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RuCl3.nH(2)O in MeCN catalyzes the hydrosilylation of carbon dioxide with n-Hex(3)SiH into n-Hex(3)SiOOCH and, with Me2PhSiH, into Me2PhSiOOCH. The initial catalyst formed is trans-[(RuCl)-Cl-II(MeCN)(5)][(RuCl4)-Cl-III(MeCN)(2)], the synthesis and structural characterization of which are described. With [(RuCl)-Cl-II(MeCN)(5)][(RuCl4)-Cl-III(MeCN)(2)] as a catalyst, Me2PhSiOOCH is produced at 313 K. Analogously, Et2SiH2, Ph2SiH2, and p-C6H4-(Me2SiH)(2) yield Et2Si(OOCH)(2), Ph2Si(OOCH)(2), and p-C6H4-(Me2SiOOCH)(2), respectively. When exposed to air, the latter compounds hydrolyze spontaneously into mixtures of silanediols, linear siloxane oligomers,and polymers, and cyclic siloxane oligomers with the release of formic acid. [References: 28]
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The title complex, [CdI2(C9H11N3OS)(2)], contains distorted tetrahedral [CdI2L2] units (where L is 4-methyoxybenzaldehyde thiosemicarbazone), in which L molecules are S-bonded in a monodentate mode to the cadmium ion. Principal di...
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The title complex, [CdI2(C9H11N3OS)(2)], contains distorted tetrahedral [CdI2L2] units (where L is 4-methyoxybenzaldehyde thiosemicarbazone), in which L molecules are S-bonded in a monodentate mode to the cadmium ion. Principal dimensions include Cd-S 2.5875 (10) and 2.5795 (10) Angstrom, and Cd-I 2.7020 (4) and 2.7470 (4) Angstrom. [References: 14]
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摘要 :
The crystal structure of the title compound, C42H40O2P2, an open-chain diphosphine, is reported. The absolute structure determined by the Flack method [Flack (1983). Acta Cryst. A39, 876-881] confirms that the stereochemistry at t...
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The crystal structure of the title compound, C42H40O2P2, an open-chain diphosphine, is reported. The absolute structure determined by the Flack method [Flack (1983). Acta Cryst. A39, 876-881] confirms that the stereochemistry at the chiral centers is (2R,3R). The dihedral angles between the two rings bonded to each phosphine group are 70.94(10) and 70.20(10)degrees, and the angle between the rings of the benzyloxy groups is 59.31(13)degrees. [References: 16]
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This article reports the results of a comparative resonance Raman (rR) study of low-valent d~6 transition-metal α-diimine complexes. The α-diimine ligand used is N, N'-diisopropyl-l, 4- diaza-1,3-butadiene (~iPr-DAB) which has a...
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This article reports the results of a comparative resonance Raman (rR) study of low-valent d~6 transition-metal α-diimine complexes. The α-diimine ligand used is N, N'-diisopropyl-l, 4- diaza-1,3-butadiene (~iPr-DAB) which has a relatively simple structure and hence only a few vibrations. This simplifies the assignment of the vibrational spectra of complexes of this ligand. With the help of DFT calculations of the frontier orbitals and vibrational frequencies of (model) complexes, the rR bands are assigned unambiguously.
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Six transition-metal arene complexes containing alkynylsilyl groups have been synthesized. Direct complexation of the corresponding arenes yielded the alkynylsilylarene complexes PhC≡CMe_2SiPhCr(CO)_3 (1), n-PrC≡CMe_2SiPhCr(CO)_...
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Six transition-metal arene complexes containing alkynylsilyl groups have been synthesized. Direct complexation of the corresponding arenes yielded the alkynylsilylarene complexes PhC≡CMe_2SiPhCr(CO)_3 (1), n-PrC≡CMe_2SiPhCr(CO)_3 (2), n-PrC≡CMe _2Si-SiMe_2-SiMe_2PhCr(CO)_3 (4), and PhC≡CMe_2SiPhMo(CO)_3 (6), while PhC≡CMe _2Si-SiMe_2PhCr(CO)_3 (3) and (PhC≡CMe _2SiPh)_2Cr (7) were synthesized by modification of precomplexed arenes. The reactivity of the C≡C triple bonds of the synthesized alkynylsilyl compounds toward complexation and carbon-carbon bond-forming reactions was studied. The alkynyl groups of 1 and 6 underwent intermolecular complexation to yield the trinuclear compounds 1·Ni _2Cp_2 (8) and 6·Cp_2Mo_2(CO) 4 (9), respectively, while reaction of 7 with CpCo(PPh _3)_2 led to intramolecular [2 + 2] cycloaddition of its two alkynyl groups with formation of the dinuclear cyclobutadiene complex CpCo(PhCCSiMe_2Ph)_2Cr (10). All of these complexes were characterized by NMR, IR, and mostly also UV/vis (1, 2, 6-10) spectroscopy. The molecular and crystal structures of compounds 1, 2, and 6-10 were determined by single-crystal X-ray diffraction.
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The objective of this paper is to obtain a better insight into the sol - gel mechanism of water-based precursors for the development of thin NdBa2Cu3O7-y (NBCO) superconducting films. The influence of metal complexation behaviour ...
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The objective of this paper is to obtain a better insight into the sol - gel mechanism of water-based precursors for the development of thin NdBa2Cu3O7-y (NBCO) superconducting films. The influence of metal complexation behaviour on the formation of transparent and homogenous gels after the combination of different metal salts and ligands has been studied for several metal salts (Cu2+, Nd3+ and Ba2+). Two inorganic aqueous sol - gel precursors have been studied: a metal nitrate - citric acid-based and a metal acetate - triethanolamine-based solution. The characteristics of the precursor solution are based on the determination of the stability constants by the computer program Superquad. The prediction of the complex stability in this solution was related to the complexation of the three metal ions (Cu2+, Nd3+ and Ba2+) with a certain ligand. IR-spectroscopy was used for the determination of the gel. This resulted in a better understanding of the composition of the solution and could be used for preparation of more stable sol - gel precursors for the synthesis of homogeneous end products. These sol - gel systems were used for the deposition of highly textured superconducting thin films on SrTiO3 substrates by dip-coating. Using detailed thermal analysis, it is shown that the morphology of the films can be optimised by adjusting the parameters during thermal treatment, resulting in dense and highly textured thin films. Special attention is given to the microstructure of the thin film because of its relevance to the superconducting transport properties of the coated conductor system.
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