Ester Complexes Research Articles

Preparation and Characterization of Boronic Ester Complexes of o‐ Mercapto‐azomethines

Preparation and Characterization of Boronic Ester Complexes of o‐ Mercapto‐azomethines

Steric Versus Electronic Effects in the Ligation Behavior of Trivalent Phosphorus Compounds:59Co AND31P NMR Spectroscopic Studies

Abstract Using NMR techniques, the role of electronic and steric influences in phosphorus(III) ester complexes of the type CoL6 3+ and AgLn + (where n = 1–4) are assessed.

Unexpected intramolecular nucleophilic substitution in an anionic Fe2(CO)6 complex with an organosulfur ligand. A novel preparation of Fe2(CO)6 complexes of dithioformic acid esters

Le carbanion forme par deprotonation par le diisopropylamidure de Li, de (μ-CH 2 S 2 )Fe 2 (CO) 6 subit une attaque nucleophile intramoleculaire sur Fe pour donner une liaison C−Fe et un anion a centre S. L'alkylation forme ensuite un coordinat alkylthio pontant dont on etudie la structure moleculaire

L-CYSTEINE COMPOUNDS WITH TWO ASYMMETRIC CENTRES AND THE RELATED CADMIUM COMPLEXES

Abstract The cadmium complexes of L-cysteine alkyl esters have been shown to polymerize methylthiirane stereospecifically and stereoelectively. A series of L-cysteine esters with two asymmetric carbon atoms is prepared by reacting L-cysteine with the racemic mixture of various secondary alcohols: CH3CH(OH)R (with R [dbnd] C2H5, CH(CH3)2, C(CH3)3, C6H13, CH2C6H5) in the presence of dried HCl. It is shown that, under same experimental conditions, l-phenyl ethanol (R [dbnd] C6H5) gives rise to S-substitution instead of esterification. The structure of the resulting compound is confirmed, in particular, on the basis of 13C and 1H NMR spectra whose lines are assigned by comparison with spectra of model compound. The cadmium complexes of the various diastereoisomeric derivates of L-cysteine are prepared and characterized. Cadmium bis 2-octyl ester cysteinate is the first example of cadmium L-cysteinate derivate soluble in organic solvents. It is shown that all these complexes act as initiators for the polymeriz...

Q-band electron paramagnetic resonance study of nitrosylprotoheme dimethyl ester complexes with N-,O-, and S-donor ligand as model systems for nitrosylhemoproteins

Electron paramagnetic resonance (epr) spectra (at X- and Q band frequency) of nitrosyl(proto-porphyrin IX dimethyl ester) iron( II) complexes with a trans axial ligand of nitrogen-, oxygen-, and sulfur-donor ligand, in the trozen glass state at 77°K, have been investigated in order to understand the epr spectra of nitrosylhemoproteins. The Q-band spectra resolved the spectral features more clearly than the X-band spectra and distinctly exhibited two groups of absorptions, which were attributable to two molecular species. Significant relations were found between two g values (e.g., g x-g z, g x-g y) and between the g value and the degree of the hyperfine splitting in central absorption. The epr parameters were not very sensitive to the π-bonding ability of the axial ligand, but registered the steric interaction of the axial ligand with porphynnato core. These findings can be utilized in the characterization of an axial ligand trans to the nitrosyl group in nitrosylhemoproteins.

Aromatic hydroxylation of acetanilide and aniline by hemin2̄thiolester complex as a cytochrome P-450 model

Acetanilide and aniline hydroxylations with a hemin–thiol compound and Cu(II)-containing systems were studied under various conditions as models of cytochrome P-450 monooxygenases. Thereby the determination method of acetaminophenols was established using liquid chromatography. The reactions were characterized by the yield of hydroxylated products and the product ratio. The model system containing thioglycolate ester simulated the acetanilide hydroxylation with liver microsomal fraction in both conversion of the substrate and product ratio ( p-:m-:o-acetaminophenol). Hydroxylation of acetanilide and aniline was enhanced upon addition of additional reducing agents or thiol compounds to the hemin–thioglycolate ester complex, suggesting an involvement of the similar reaction profile of cytochrome P-450 monooxygenases requiring NAD(P)H as a reducing agent. The hemin–thioglycolate ester complex is thus concluded to be a good chemical model of cytochrome P-450-dependent monooxygenases.

Niobium organometallic chemistry : IX. CS 2 complexes: synthesis, reactivity and their use as ligand; crystal structure of (n-C 4H 9)(ν 5-C 5H 5) 2Nb(μ-CS 2)W(CO) 5

Carbon disulphide reacts with niobium complexes [Nb(η-C 5H 5) 2(Me) 2] and [Nb(η-C 5H 5) 2H (CH 2CHC 2H 5)] to produce the new η 2-CS 2 derivatives [Nb(η-C 5H 5) 2(Me)(η 2-CS 2)] ( 1) and [Nb(η-C 5H 5) 2(Bu) (η 2-CS 2)] ( 2) respectively. Treatment of 1 and 2 with methyl iodide affords the respective cationic η 2- dithioalkyl ester complexes [Nb(η-C 5H 5) 2(Me) {η 2-C(S)SMe}] I ( 3) and [Nb(η-C 5H 5) 2(Bu) {η 2-C(S)SMe}] I ( 4). Hetero-dinuclear complexes [(Bu)-(η-C 5H 5) 2Nb(η-CS 2)M(CO) n ] (M  Cr, Mo, W; n  5. M  Fe; n  4) and [(Bu)-(η-C 5H 5) 2Nb(μ-CS 2)Mn(CO) 2(η-CH 3C 5H 4)] and an homodinuclear complex [(Bu)(η-C 5H 5) 2Nb(μ-CS 2)Nb(η-C 5H 5) 2(Bu)] have been synthesized. The structure of the niobium—tungsten derivative has been determined by single-crystal X-ray diffraction. Crystal data are space group P2 1/ c, a 12.935(4), b 12.742(4), c 14.565(4) Å, β 103.27(3)°, Z  4. The Nb(μ-CS 2)W unit is planar within ±0.06 Å. The CS 2 group is η 2-bonded to niobium through a CS linkage and σ-bonded to manganese through the other sulfur atom. The 13C NMR spectra indicate that 2 has a larger σ-donor/π-acceptor ratio than CO.

Electron paramagnetic resonance study of nitrosylprotoheme dimethyl ester complexes with aliphatic nitrogenous bases: Characterization of the axial ligand trans to the nitrosyl group in nitrosylhemoproteins

The interaction of nitrosyl(protoporphyrin IX dimethyl ester) iron (II) (Fe(PPDME)(NO)) with aliphatic amines, anilines, and cyclic imines has been studied by electron paramagnetic resonance (EPR) measurements at room temperature and at 77K. At room temperature, the bases studied here were divided into two groups according to the exchange rate between two EPR-positive species, Fe(PPDME)(NO) and Fe(PPDME)(NO)B, in equilibrium; Fe(PPDME)(NO) + B ▪ Fe(PPDME)-(NO)B. The Fe(PPDME)(NO)-base system with a fast exchange rate on the EPR time scale had a smaller equilibrium constant ( K) than that with a slow rate. The EPR spectra of the Fe(PPDME)(NO)-base system both at room temperature and at 77K were markedly influenced by the steric interaction of the base with the porphyrin core.

ChemInform Abstract: PHOSPHONATE ESTER COMPLEXES OF METHYLTIN CHLORIDES. FORMATION CONSTANT AS A FUNCTION OF NUCLEAR SPIN COUPLING CONSTANT

Chemischer InformationsdienstVolume 13, Issue 14 Article ChemInform Abstract: PHOSPHONATE ESTER COMPLEXES OF METHYLTIN CHLORIDES. FORMATION CONSTANT AS A FUNCTION OF NUCLEAR SPIN COUPLING CONSTANT R. C. REITER, R. C. REITERSearch for more papers by this authorN. TAKAHASHI, N. TAKAHASHISearch for more papers by this authorR. K. BUNTING, R. K. BUNTINGSearch for more papers by this authorG. W. CALDWELL, G. W. CALDWELLSearch for more papers by this author R. C. REITER, R. C. REITERSearch for more papers by this authorN. TAKAHASHI, N. TAKAHASHISearch for more papers by this authorR. K. BUNTING, R. K. BUNTINGSearch for more papers by this authorG. W. CALDWELL, G. W. CALDWELLSearch for more papers by this author First published: April 6, 1982 https://doi.org/10.1002/chin.198214077AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume13, Issue14April 6, 1982 RelatedInformation

Equilibrium binding of amphotericin B and its methyl ester and borate complex to sterols

Scatchard analysis of the binding of amphotericin B to sterols in egg phosphatidylcholine/sterol vesicles revealed that amphotericin B was bound to ergosterol by approximately one order of magnitude more tightly than to cholesterol. Amphotericin B methyl ester formed a tighter complex with each of the sterols investigated than did amphotericin B, but the difference in the apparent binding constants toward ergosterol and cholesterol was not as large as with amphotericin B. Amphotericin B borate formed weaker complexes with vesicle-bound sterols than amphotericin B and amphotericin B methyl ester.

Organometallic compounds in organic synthesis. Part 13. Stereoselectivity of complexation of cyclohexadiene esters

Complexation of cyclohexadienes with Fe(CO)3 as the entering group are subject to classical steric hindrance by alkyl groups, but CO2R and related groups introduce a competing factor because they favour sterically the entering group, probably through an intermediate complex. Increase of π-electron availability in the initial 1,4-diene by the attachment of OMe reduces this influence, probably because it favours direct olefin complexation. Non-polar conditions increase the directing effect of CO2R, but complete stereospecificity cannot be achieved except through additional alkyl substitution. Nevertheless, many stereoisomeric pairs can be separated and the route leads to precursors of a number of sterically defined products which are otherwise not readily accessible.

Phosphonate ester complexes of methyltin chlorides. Formation constants as a function of nuclear spin coupling constant

Phosphonate ester complexes of methyltin chlorides. Formation constants as a function of nuclear spin coupling constant

Komplexe zweifach positiver Übergangsmetallkationen mit Hydrazido-thiophosphorsäure-estern/ Complexes of Divalent Transition Metals with Hydrazido Thiophosphoric Acid Esters

Abstract Dihydrazido thiophosphoric acid phenyl ester, (NH2NH)2P(= S)-OC6H5 (DHTPPH), forms a 2:1 complex with manganese(II) chloride: [Mn(II)(DHTPPh)2Cl2], soluble in methanol. Solvolysis yields the corresponding methyl ester complex. With water in methanol the dihydrazidothiophosphato complex [Mn(II){(NH2NH)2P(= O)S}2] is formed. Monohydrazido thiophosphoric acid diphenyl ester NH2NH-P(= S)(OC6H5)2 (MHTPPh) gives various complexes with first row transition metals: [M(II)(MHTPPh)nX2], n = 2, 4; X = halogen. The nickel complex (n = 4; X = Cl) is characterized by elemental analysis and spectroscopic methods. MHTPPh is monodentate through the terminal N atoms of the hydrazido groups. Iron(II) and cadmium complexes have different compositions (n- 2; X = Cl) and therefore different structures, probably with MHTPPh as a bidentate chelate ligand.

Synthesis and characterization of Tris[(S)-1-dithiocarboxypyrrolidine-2-carboxylato(2 -)-S,S']cobalt(III), a complex derived from the (S)-proline residue

The ammonium salt of (S)-1-dithiocarboxypyrrolidine-2-carboxyic acid and its tris-chelated cobalt(III) complex have been prepared and characterized. The ammonium salt of the complex anion is soluble in water whereas the fully protonated form is soluble in some organic solvents. These diamagnetic cobalt(III) compounds and the corresponding neutral methyl ester complex are shown by 13C n.m.r. spectroscopy to have the facial geometrical structure. The complex anion was successfully separated into diastereomeric Δ(SSS) and λ(SSS) forms (S refers to the asymmetric carbon atom in each of the proline moieties) by using Sephadex DEAE anion-exchange resin with aqueous ammonium chloride eluent. The more easily eluted species has the Δ absolute configuration at the dissymmetric cobalt atom as assigned from its circular dichroism spectrum.

CH-Acidity of amino-acid esters co-ordinated to cobalt(III). Racemization during the formation of peptides

Several dipeptide complexes of general formula [Co(tren)(NH2CHRCONHCHR′COOCH3)][CH3C6H4SO3-p]3 have been obtained by coupling a chelated ester complex with a free amino-acid ester. The rate of the reaction appears to be quite sensitive to steric hindrance. With chiral amino-acids, the product is a mixture of diastereomers; this result is consistent with a fast racemization coupled with a slight asymmetric induction. The half-life for proton exchange in the complex [Co(en)2(GlyOCH3)][CH3C6H4SO3-p]3 under the conditions of peptide synthesis is 20 s. The hydrolysis of this ester in methanol (1 mol dm–3 in H2O) is nevertheless faster than recemization.

Preparation and properties of phosphine complexes of nickel-containing cyclic amides and esters [(PR3)nNiCH2CH(R1)COZ (Z = NR2, O)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPreparation and properties of phosphine complexes of nickel-containing cyclic amides and esters [(PR3)nNiCH2CH(R1)COZ (Z = NR2, O)]Takakazu Yamamoto, Kohji Igarashi, Sanshiro Komiya, and Akio YamamotoCite this: J. Am. Chem. Soc. 1980, 102, 25, 7448–7456Publication Date (Print):December 1, 1980Publication History Published online1 May 2002Published inissue 1 December 1980https://doi.org/10.1021/ja00545a009RIGHTS & PERMISSIONSArticle Views700Altmetric-Citations51LEARN 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 (1 MB) Get e-Alerts Get e-Alerts

Evidence for cobalt(II) catalysis and for an intermediate dioxygen adduct in the autoxidation of cobalt(II) chloride complexes of ethyl phosphinite, phosphonite, and phosphite esters

Evidence for cobalt(II) catalysis and for an intermediate dioxygen adduct in the autoxidation of cobalt(II) chloride complexes of ethyl phosphinite, phosphonite, and phosphite esters

Possible side-reactions with diazocarbonyl dipeptide esters as protein modifying reagents

The reaction of diazocarbonyl compounds with chymotrypsinogen and chymotrypsin in the presence of cupric ions was accompanied by the oxidative destruction of tryptophan and methionine residues and to a lesser extent of tyrosine and cystine residues of the proteins. Cu2+/diazoacetyl-DL-norleucine methyl ester complex was found to promote the oxidation of cystine residues of the proteins while the similar complex with the L-isomer of the diazocarbonyl compound was ineffective. Inclusion of α-aminocarbonyl compounds in the reaction medium not only prevented the Cu2+ ion mediated decomposition responsible for the diminution in the potency of the diazocarbonyl compound as a modifying agent, but also permitted the reaction to be accomplished over the pH range of 4.5 to 7.0. The side reactions, namely the oxidative destruction of amino acids could be minimized by exclusion of oxygen from the reaction medium.

Evidence for organoironcarbonylate anion formation in nucleophilic addition to tetracarbonyliron complexes of acrylate esters

Sequential addition of stabilized anions and alkyl iodides to tetracarbonyliron complexes of methyl acrylate and methyl crotonate affords products consistent with regiospecific generation and alkylation of an organoironcarbonylate anion intermediate.

Nickel complexes of the methyl esters of dithiocarbazic and N-substituted dithiocarbazic acids

The nickel complexes of the methyl esters of dithiocarbazic acid NH2NHC(=S)SMe (L), 2-methyldithiocarbazic acid NH2NMeC(=S)SMe (MeL), 2-n-butyldithiocarbazic acid, NH2NBuC(=S)SMe (BuL), 3,3-dimethyldithiocarbazic acid NMe2NHC(=S)SMe (Me2L), 3-phenyldithiocarbazic acid NHPhNHC(=S)SMe (PhL), and 3,3-diphenyldithiocarbazic acid NPh2NHC(=S)SMe (Ph2L) have been investigated. L, MeL, BuL, and Me2L can act as neutral ligands giving the high-spin complexes [NiL3]X2, [Ni(MeL)3]X2, [Ni(BuL)3]X2(X = Cl, Br, or I), and [Ni(Me2L)2Cl2]; L and Me2L can act also in deprotonated form at N(2) giving the low-spin complexes [Ni(L – H)2] and [Ni(Me2 L – H)2]. PhL and Ph2L act only in deprotonated form at N(2) giving the low-spin [Ni(PhL – H)2] and [Ni(Ph2L – H)2] respectively. MeL and BuL can be deprotonated at N(3) after co-ordination giving the low-spin complexes [Ni(MeL – H)2] and [Ni(BuL – H)2]. The complexes have been characterized by their electronic and i.r. spectra.