- Influence of axial ligands on diverse properties in three trinickel string complexes
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Three new trinickel string complexes, [Ni3(dpa)4(3-nba) 2](1), [Ni3(dpa)4(4-nba)2]·(CH 3OH) (2), and [Ni3(dpa)4(3,5-dnba)2](3) where dpa- is the anion of 2,2-dipyridylamine, 3-nba- is 3-nitrobenzoate anion, 4-nba is 4-nitrobenzoate anion, and 3,5-dnba- is 3,5-dinitrobenzoate anion, were synthesized in good yield and characterized by X-ray crystallography, infrared spectra, elemental analysis, magnetic susceptibility, cyclic voltammogram (CV), UV-vis spectra, fluorescence spectra, and TG analysis. The magnetic susceptibilities suggested that the terminal Ni atoms in all three complexes are in high-spin state while the central Ni atom is in a low-spin state. The CVs of complexes 1-3 showed reversible one-electron redox waves at E1/2 = 1.1395 V for 1, 1.108 V for 2, and 1.109 V for 3 corresponding to Ni3 7+/Ni3 6+. The Ni-Ni distances in three complexes are somewhat different, indicating the axial nitrobenzoate ligands have significant effect on the structural assembly. Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.
- Zhang, Jing,Zhu, Long-Guan
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p. 1071 - 1077
(2013/01/14)
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- CLEAVAGE OF THE PHENACYL ESTERS OF CARBOXYLIC AND THIOCARBOXYLIC ACIDS BY METAL ALKOXIDES
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During the cleavage of phenacyl esters with general formula XC6H4COCH2OCOR by metal alkoxides in alcohols and in ether-alcohol solutions the acids, esters, and ethers are formed as a result of cleavage of the C-C bond.The solvent participates in the formation of the ether and gives rise to transesterification of RCOOCH3 with catalytic participation of the metal alkoxide.The reactivity of the phenacyl esters of the thio acids is much higher.Before dissociation the esters of substituted benzoins C6H5COCH(OCOCH3).C6H4X-4 undergo irreversible rearrangement with the formation of isomeric products.
- Morozov, A. A.
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p. 1138 - 1143
(2007/10/02)
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- Studies of the Borderline between Concerted and Stepwise Mechanisms of Elimination : E1cB Elimination of Fluoren-9-ylmethyl Carboxylate Esters
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Rates of β-elimination of carboxylate leaving groups from fluoren-9-ylmethyl carboxylate esters in methanolic sodium methoxide at 25 deg C are reported.An E1cB mechanism with rate-determining formation of a carbanion intermediate is assigned on the basis of near identity of measured elimination rates and rates of carbanion formation predicted from a Taft correlation, and the similarity with elimination of 1-(1-acetoxy-1-methylethyl)indene for which the mechanism has been established by Ahlberg and Thibblin.Values of ρ=0.42 and βlg=0.27 measured for substituted benzoate leaving groups are a little larger than expected (ca. 0.24 and 0.18, respectively) and the discrepancy is tentatively ascribed to conformational enhancement of remote substituent effects, rather than to a contribution of E2 elimination.The effects of alkyl and aryl substitution α to the leaving group are discussed, especially in relation to the borderline between concerted and stepwise mechanisms.The measurements fail to confirm an earlier inference that the borderline shows a discontinuity in transition-state structure at the point of mechanistic change.
- O'Ferrall, Rory A. More,Larkin, Finbar,Walsh, Peter
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p. 1573 - 1580
(2007/10/02)
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- Kinetics and Mechanism of Ru(III)-catalysed Oxidation of Aromatic Aldehydes by Sodium Metaperiodate in Alkaline Medium: A Change in Mechanism from Hydride Loss in Acid Medium to Proton Loss in Alkaline Medium
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The title reactions are first order in the substrate and first order in the catalyst, the order with respect to periodate being zero.The dependence on alkali is unity.The reactivity order is p-nitro > m-nitro > m-bromo > m-methoxy > p-bromo > p-chloro- > H ca. p-methyl > p-methoxy.The pH-rate profile attains a minimim at neutral pH and the rate increases on either regions of this pH.The Hammett plot shows a fair linearity with a ρ-value of + 1.66 pointing to a rate-limiting proton loss.A mechanism involving the complexation of the monoanion of the aldehydes with the Ru(III) followed by rate-limiting proton loss is postulated.Activation parameters have been computed.
- Radhakrishnamurti, P. S.,Misra, P. C.
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p. 427 - 430
(2007/10/02)
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