Ester Complexes Research Articles

Electron paramagnetic resonance of nitrosylprotoheme dimethyl ester complexes with imidazole derivatives as model systems for nitrosylhemoproteins

For the purpose of understanding the electron paramagnetic resonance (epr) spectral change of nitrosylhemoproteins under various conditions, the epr spectra for the model system have been analyzed. The model system consists of the nitrogen oxide complex of the iron(II) protoporphyrin IX dimethyl ester and various imidazole derivatives (three hindered and six unhindered imidazole derivatives). The results of the analysis indicate the existence of two molecular species in the model system, which differ in structure of the FeNO unit. These observations were compared with those for the nitrosylhemoproteins.

Studies of transition-metal oxo- and nitrido-complexes. Part 5. Oxo-osmium ester complexes with quinuclidine and related amines

The osmium(VI) ester complexes [{OsO2(O2R)(NC7H13)}2] formed by reaction of monoalkenes R (R = cyclohexene, ethylene, or stilbene) with the adduct OsO4·NC7H13(NC7H13= quinuclidine) contain an asymmetric Os2O2 bridge; in solution they have five-co-ordinate monomeric structures. With tertiary amines L (L = pyridine, methylimidazole, 5,6-dimethylbenzimidazole, or quinuclidine) they give the corresponding trans-dioxo-complexes [OsO2(O2R)(NC7H13)L]. The adduct OsO4·NC7H13 reacts with dienes R (R = cyclohexa-1,3-diene, cyclo-octa-1,5-diene, or 2,5-dimethylhexa-2,4-diene) to give products [{Os2O4(O4R)(NC7H13)2}n] or [{OsO2(O2R)(NC7H13)}2]. With alkynes R they give [{Os2O4(O4R)(NC7H13)2}n]·nS (R = C2H2, S = benzene, toluene, or carbon tetrachloride) and [{Os2O4(O4R)(NC7H13)2}n](R = PhC2H); these products have structures closely related to those of the complexes [{OsO2(O2R)L}2] derived from alkenes. Alkaloids such as strychnine and brucine which contain tertiary amine functions react with OsO4 to give oxo-osmium(VI) esters. Structures for all these complexes are proposed on the basis of vibrational and 1H n.m.r. spectra, and on that of an X-ray determination of the crystal structure of [{OsO2(O2C6H10)(NC7Hl3)}2].

The reaction of metalloporphyrins with nitrogen dioxide

The octaethylporphyrin(OEP) complexes of iron(III) chloride, iron(III) acetate, thallium(III) hydroxide, zinc(II), and cobalt(II) and the mesoporphyrin IX dimethyl ester (MPDME) complexes of zinc(II) and iron(III) chloride were reacted with a 20:1 ratio of NO 2 to metalloporphyrin in CH 2Cl 2. The +3 metalloporphyrins gave products which had a nitromethyl group in each of the four meso positions of the porphyrin ring and a chloride ion bound to the metal atom. The products of +2 metalloporphyrin reaction had a nitro group bound in each of the meso positions. The spectral and electrochemical properties of some of the products were measured. 36Cl labelled OEPFeCl was reacted with NO 2 in CH 2Cl 2. The product, meso-tetranitromethyl OEPFeCl, had 17% of the original activity which indicates that the chloride ion bound to the iron is exchanged with chloride ions formed in the reaction. The nitromethylation reaction appears to involve initially the displacement of chloride from iron(III) by NO 2 and solvent attack on the bound NO 2. The meso-nitration of the +2 metalloporphyrin by NO 2 has been proposed to proceed by a π-cation radical mechanism (E.C. Johnson and D. Dolphin, Tetrahedron Letters 2197 (1976).

Electron paramagnetic resonance of protohemin dimethyl ester complexes with sterically hindered imidazole derivatives

Electron paramagnetic resonance of protohemin dimethyl ester complexes with sterically hindered imidazole derivatives

Metal complexes of bilirubin and bilirubin dimethyl ester

A spectral study of bilirubin and bilirubin dimethyl ester complexes with a variety of metal ions indicates that bilirubin forms two different types of complexes, interacting either with the pyrrole nitrogens or with the propionic acid side chains. A combination of the two types is possible. The proposed structure of these complexes is in accord with the most recent structural information for bilirubin.

Metal complexes of amino acid phosphate esters

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMetal complexes of amino acid phosphate estersM. S. Mohan and E. H. AbbottCite this: Inorg. Chem. 1978, 17, 8, 2203–2207Publication Date (Print):August 1, 1978Publication History Published online1 May 2002Published inissue 1 August 1978https://doi.org/10.1021/ic50186a036RIGHTS & PERMISSIONSArticle Views300Altmetric-Citations30LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (596 KB) Get e-Alerts Get e-Alerts

Complexes of diethylboric esters of alkanenitronic acids with pyridine

When the diethylboric esters of alkanenitronic acids of general formula RR'C=NOOBEt2 (R=H or alkyl, and R'=alkyl or COOCH3) are treated with pyridine the intramolecular coordination bond is cleaved to give the complexes of diethylboric esters of alkanenitronic acids with pyridine.

Use of13C NMR, $$J_{13_C 15_N }$$ and $$J_{1_H 15_N }$$ data in structure and configuration analysis of heteroorganic derivatives of alkanenitronic acids

1. The general criteria for the structure analysis of the heteroorganic derivatives of alkanenitronic acids by the13C NMR method were established. 2. The pyridine complexes of the boric esters of nitronic acids exist as the trans isomers. 3. The 1,3 (O, O)-transfer of the B(C2H5)2·C5H5N fragment in (CH3O2C)CH=N(O)OBEt2· C5H5N was observed, as well as the 1,5 (O, O)-transfer of the Si(CH3)3 group in C(NO2)2 =N(O)OSiMe3, and it was found that the two NO2 groups in C(CH3)(NO2)=N(O)OSi(CH3)3 are nonequivalent.

Use of shift reagent with mtpa derivatives in 19F NMR spectroscopy: III. Determination of absolute configuration and enantiomeric purity of secondary alcohols

AbstractThe LIS values produced by Eu(fod)3 for the CF3‐19F NMR signals of the MTPA esters of different stereoisomeric secondary alcohols have been measured. The applicability of these values for assigning the absolute configuration of the alcohols has been studied. The advantages of this method over the corresponding 1H NMR method of Yamaguchi and the limits of both have been investigated. A new model of the Eu(fod)3/MTPA ester complex is given.

Isonitrile complexes derived from the nucleophilic attack of primary amines on the dithiomethyl ester complex, RuI(CO)(PPh 3) 2 (CS 2Me)

The bidentate dithiomethyl ester complex, RuI(CO)(PPh 3) 2 (CS 2Me) reacts with primary amines affording a series of novel dimeric isonitrile complexes, [RuI(CO)(CNR)(PPh 3) 2SH] 2.

The NMR spectra of porphyrins—12 : 13C and proton NMR spectra of the zinc(ii)coproporphyrin isomers2

The 13C and proton NMR spectra of the zinc(II) complexes of the tetramethyl esters of the four coproporphyrin type isomers are reported and assigned. Effects of aggregation phenomena on these shifts are discussed and a method involving addition of a slight excess of pyrrolidine is proposed for measurement of the spectra of the “monomeric” species; spectra obtained under these conditions are capable of simple, straight-forward interpretation and assignment in terms of molecular symmetry. Thus, a facile distinction between the type isomers is obtained.The “monomer” chemical shifts so derived allow consistent SCS parameters to be derived. The Cβ-Me SCS are shown to be related to the bond order of the Cβ-Cβ bond in the porphyrin ring, and are thus quite different from the corresponding SCS in pyrroles.Aggregation shifts in the 13C and proton spectra are shown to be consistent with the presence of “stacked” aggregates with the ring current of one molecule affecting the other, together with an additional effect on the chemical shifts of the meso carbons, which is probably steric in origin.

High chiral recognition in α-amino-acid and -ester complexation

Chiral cyclic polyether hosts containing one 2,2′-substituted-1,1′-binaphthyl and one 2,2′-substituted-3,3′-dimethyl-1,1′-binaphthyl units in CDCl3–CD3CN or CDCl3 have been used to extract from water differentially by factors of up to 52 the enantiomers of eight amino-acids and five amino-ester salts.

Polyelectrolyte catalysis of the alkaline hydrolysis of neutral and anionic esters

Alkaline hydrolysis of p-nitrophenyl acetate (PNPA), 4-acetoxy-3-nitrobenzoic acid (NABA). and 4-acetoxy-3-nitrobenzenearsonic acid (NABAA), has been carried out in the presence of cationic polyelectrolytes of varying degree of hydrophobic character or micelles. Ion–molecule and ion–ion reactions are accelerated by cationic polyelectrolytes, and the acceleration becomes larger with increasing hydrophobic character of the esters and/or polyelectrolytes. Polyelectrolyte catalysis is analysed in terms of saturation kinetics, and the equilibrium association constant and the rate coefficients of the polyelectrolyte–ester complex are calculated. The relative catalytic contributions of the electrostatic and hydrophobic interactions is discussed.

Monodentate amino acid ester and peptide ester complexes of cobalt(III)

Monodentate amino acid ester and peptide ester complexes of cobalt(III)

Synthesis of carbene complexes by reaction of platinum thiocarbamoyl and thio ester complexes with electrophiles

Synthesis of carbene complexes by reaction of platinum thiocarbamoyl and thio ester complexes with electrophiles

Complexes of esters of pyridine carboxylic acids. Part I. complexes with Ni(II) and Co(II) thiocyanates

The syntheses of Nickel(II) and Cobalt(II) thio- cyanate complexes of type ML n(NCS) 2 where M = Co or Ni and n = 2 for L = methyl picolinate (MP), ethyl picolinate (EP), isopropyl picolinate (IP) and n = 4 for L = ethyl nicotinate (EN) and ethyl isonicotinate (EIN), are described. The complexes have been characterised by elemental analyses, molar conductance, magnetic susceptibility, thermogravimetric, electronic and infrared spectral data. The complexes are non-electrolytes in nitrobenzene and have high spin distorted octahedral structure with N-bonded thiocyanate groups in trans-position. MP, EP and IP act as bidentate ligands coordinating through pyridine ring nitrogen and carbonyl oxygen while EN and EIN act as unidentate ligands and coordinate through ring nitrogen only. The values of splitting energy (10 Dq), Racah parameter (B) and nephelauxetic ratio (β) have been evaluated for the nickel complexes.

Reactions of π-Allylic Palladium(II) Complexes of Acetoacetate Esters with Pyridine and Its Derivatives

Abstract The π-allylic palladium(II) complexes of ethyl and benzyl acetoacetate esters react with pyridine and its derivatives to afford the terminal-carbon-bonded complexes PdCl(CH2COCH2COOCH2R)L2, where R=CH3 or C6H5, and L=pyridine or its derivative. The NMR spectra unequivocally establish the bonding type in these complexes. The pyridine and 4-methylpyridine complexes are a mixture of cis and trans isomers in a ratio of 1: 5, while 2-methyl- and 2,6-dimethyl-pyridine complexes are trans exclusively. The relative stabilities of these complexes are compared.

Evidence for nonproductive binding subsites within the active site of papain.

The reactions of several alkylating reagents with the sulfhydryl group in papain have been studied in the presence of varying concentrations of the competitive inhibitor α-N-benzoyl-D-arginine ethyl ester. The ratio of the alkylation rate constant of the papain – α-N-benzoyl-D-arginine ethyl ester complex to the rate constant with free papain is 4.3, 1.2, and 0.0 for the alkylating agents 1-chloro-3-tosylamido-4-phenyl-2-butanone, N-ethylmaleimide, and 1-chloro-3-tosylamido-7-amino-2-heptanone, respectively. These results are rationalized, along with data for the effect of α-N-benzoyl-L-arginine ethyl ester, in terms of nonproductive binding.

Reaction of titanium(IV) chloride with the ethyl esters of some β-diketo acids

The preparation and characterization of some titanium dichloro complexes of the ethyl esters of some β-diketo acids are reported. The compounds have been characterized by their elemental analysis, molecular weight determination, i.r. spectra and magnetic susceptibility.

Polymerizations of α‐olefins with BF3 complexes of acrylate esters

Polymerizations of α‐olefins with BF₃ complexes of acrylate esters