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The stabilities of the Mn2+-, Co2+-, Ni2+-, Cu2+- and Zn2+-complexes with 2-(carboxymethyl)glutaric acid ( 2 ) and cis,cis-1,3,5-cyclohexanetricarboxylic acid ( 3 ) were measured potentiometrically at 25° and I = 0.5 (KNO3). Beside the complexes ML? protonated species MLH and MLH are also formed. Their stability constants are given in Table 1. A comparison between the stabilities of 2 or 3 and those of acetate, as a model for a monocarboxylate, or succinate and glutarate, as examples for dicarboxylates, indicates that in all species only one carboxylate is strongly bound whereas the second and third ones are probably not. The observation that Δlog K1 = log K ? log K as well as Δlog K2 = log K ? log K are practically constants with values of 0.34 ± 0.05 and 0.49 ± 0.07, respectively, for both ligands and the five metal ions studied is also in line with the proposed monodentate structures of the complexes ML?, MLH and MLH.  相似文献   

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Nickel Complexes of Mercaptoacetic Acid The reaction of [Cp°2Zr(OOCCH2SH‐κ1O)(OOCCH2SH‐κ2O, O′)] (Cp° = C5EtMe4) with [NiCl2(PMe2Ph)2] or [NiCl2(dppe)] (dppe = PPh2CH2CH2PPh2) in the presence of NEt3 yields the tetranuclear ZrIV/NiII complex [{Cp°2Zr(κ1O‐OOCCH2S‐κ2O′, S)(κ2O, O′‐OOCCH2S‐κ1S)Ni(PMe2Ph)}2] ( 1 ) and the chelate complexes [Ni(OOCCH2S‐κ2O, S)L2] [L = PMe2Ph ( 2 ), L2 = dppe ( 3 )]. 2 and 3 are also accessible from [NiCl2(PMe2Ph)2] or [NiCl2(dppe)] and mercaptoacetic acid in the presence of NEt3 in quantitative yield. The structure of 2 is dynamic in solution, whereby a complex with three‐coordinate nickel atom is formed. 2 and 3 were characterized spectroscopically (1H, 13C, 31P NMR and IR) and by crystal structure determination.  相似文献   

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Imidodiphosphoric Acid Esters Imidodiphosphoryl tetrachloride reacts with aliphatic alcohols (C1–C3) as well as with sodium phenolate to form tetraalkylesters or tetraphenylesters of the imidodiphosphoric acid, resp. The tetraalkylesters (alkyl = methyl, ethyl, n-propyl) are also formed by reaction of trichlorphosphazene phosphoryldichloride, Cl3P?N? POCl2, with the corresponding alcohols. The purification of the esters can be reached by destillation of their silyl derivatives followed by desilylation. The esters are associated by intermolecular O…?H…?O hydrogen bonds.  相似文献   

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Two stereoselective syntheses of nonactic acid I, the building block of the macrotetrolide antibiotic nonactin are described. The characteristic cis-configuration of the 2,5-substituents on the tetrahydrofuran ring of I is obtained in the first synthesis by catalytic hydrogenation of the furan derivative X. This key intermediate possesses the carbon skeleton and correct distribution of oxygen functions for conversin into nonactic acid. It is synthesized by an electrophilic substitution of 2-acetonylfuran (VI) with the N-cyclohexyl-N-propenyl nitrosonium ion (V) generated from the corresponding α-chloronitrone (VII) and silver fluoroborate, followed by hydrolysis and oxidation of the aldehyde group. The second synthesis starts with a diol already having the correct configuration of the side chain that contains the hydroxyl group. For this purpose threo-1-octen-5,7-diol (XV) is synthesized from acetylacetone in two steps. Oxidative cleavage of the terminal double bond of this threo-diol yields an aldehyde which is converted by a Wittig reaction, with the carbanion, obtained from diethyl α-methoxycarbonylethyl phosphonate, into the open chain intermediate, 2-methyl-6,8-dihydroxy-2-nonenoic acid methylester (XVIII). Base-catalyzed cyclisation of this α,β-unsaturated dihydroxy ester yields the methyl ester of nonactic acid (I) as the main product.  相似文献   

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The molar penamaldate value of benzylpenicilloic acid and the influence of large amounts of benzylpenicillin on the estimation of penamaldate values and penamaldate stabilities of benzylpenicilloic acid and ε-(benzylpenicilloyl-α-amido)-caproic acid have been determined. The molar penamaldate values of purified benzylpenicilloate and of benzylpenicillin hydrolyzed in alkali were equal, indicating that benzylpenicillin upon alkaline hydrolysis is converted to penicilloic acid exclusively, with no side reactions occurring to any considerable degree. Benzylpenicilloate mutarotates in neutral solution as well as in alkali, the reaction being unaffected by metal ion complexing with ethylene diamine tetraacetate. ε-(Benzylpenicilloyl-α-amido)-caproate also mutarotates in alkali; no mutarotation occurs however in neutral solution. Different mechanisms of epimerisation have therefore to be considered for the mutarotations of penicilloates and of α-amides of penicilloic acid respectively.  相似文献   

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A simple method for preparing halogenphenylesters of phosphoric, phenylphosphonic and phosphorous acid from the respective acid chlorides and phenols in the presence of various nitrogen-containing catalysts is described. Contrary to other methods, these reactions give high yields, despite of steric hindrance.  相似文献   

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On Chalcogenolates. 136. Alkyl Esters of Cyanoformic Acid and of Cyanomonothioformic Acid By use of the phase transfer catalyst 18-crown-6 the esters CH3O—CO—CN, C2H5O—CO—CN, C2H5S—CO—CN, and nC3H7S—CO—CN have been prepared by reaction of the corresponding chloro compound with potassium cyanide. The prepared compounds have been characterized by means of electron absorption, infrared, nuclear magnetic resonance (1H and 13C), and mass spectra.  相似文献   

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The values of ΔG, ΔH and ΔS for the formation of the mixed 1:1:1 lanthanide EDTA complexes with the anions of 8-hydroxyquinoline-5-sulfonic acid, iminodiacetic acid and nitrilotriacetic acid were determined by pH-titrations and a direct calorimetric method. These thermodynamic data are discussed and compared with those for the formation of the Ln(III)EDTA complexes. Contrary to current opinion it is concluded that all trivalent lanthanide aquoions have the same coordination number in dilute solution. However, in the series of the lanthanide EDTA complexes the coordination number changes between Sm and Tb. In this region, equilibria occur between two types of EDTA complexes with different numbers of coordinated water molecules: The corresponding equilibrium constants could be evaluated. The coordination number changes also in many other Ln complexes along the lanthanide series, and similar equilibria occur.  相似文献   

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