Showing papers on "Aquation published in 1984"

Synthetically versatile (trifluoromethanesulfonato)metal amine complexes

Abstract: Synthese des complexes M(NH 3 ) 5 (OSO 2 CF 3 ) n+ , M(NH 2 CH 3 ) 5 (OSO 2 CF 3 ) 2+ , cis-M(en) 2 (OSO 2 CF 3 ) 2 + et trans-M(en) 2 Cl(OSO 2 CF 3 ) + avec M=metal trivalent. Constantes de vitesse d'aquation

Post-column reaction detector for platinum(II) antineoplastic agents.

Abstract: The development and evaluation of a post-column reaction detector sensitive to platinum(II) complexes is presented in which sodium bisulfite is used as the derivatizing agent with potassium dichromate as an activating agent. The influences of mobile phase changes (i.e., pH, organic modifiers, electrolytes), oxygen, metal ions, and order of reagent addition on reaction kinetics and product yield are defined and used in optimization of detector response. Detection at lambda/sub max/ 290 nm results in an on-line post-column sensitivity of 40-60 ng/mL for selected cis-dichloroplatinum complexes and a sensitivity of 300-1200 ng/mL for four (substituted)-malonato-platinum complexes. The reaction detector is used to monitor the kinetics of aquation of cisplatin (CDDP) and to quantitate CDDP degradation in plasma. As the sensitivity for CDDP in plasma is comparable to that achieved from high pressure liquid chromatography (HPLC) effluent fractionation/off-line flameless atomic absorption (AAS) quantitation, significant utilitiy for this time-efficient post-column reactor in clinical analysis is suggested. 33 references, 8 figures, 2 tables.

Phosphorus-31 NMR and kinetic studies of the formation of ortho-, pyro-, and triphosphato complexes of cis-dichlorodiammineplatinum(II)

Abstract: Les reactions de cis-dichlorodiammino-Pt(11) avec di- et triphosphate de 25 a 40°C. L'etape initiale est un melange d'aquation et de complexation de phosphates

Aquation of chloropentaammine and chloropentakis(methylamine) complexes of cobalt(III) and chromium(III): comparative activation volumes and mechanistic implications

Abstract: Volumes d'activation pour l'aquation de Co(NH 2 CH 3 ) 5 Cl 2+ , trans-Co(NH 3 ) 4 (NH 2 CH 3 )Cl 2+ et Cr(NH 2 CH 3 ) 5 Cl 2+ . Il y aurait un mecanisme d'interechange dissociant dans tous les cas

Spontaneous solvolysis reactions of some palladium(II)-diethylenetriamine complexes in aqueous solution: equilibrium and kinetic data

Abstract: Etude de solvolyse sur les complexes de type Pd(R 5 dien)X (2−n)+ (R 5 dien=diethylenetriamine substituee par methyl ou ethyl). Les constantes d'aquation et d'anation inverse dependent beaucoup de la nature de R 5 dien

Photochemistry of the supercomplex obtained on complexation of the hexacyanocobaltate(III) anion by a polyammonium macrocyclic receptor

Abstract: Enclosure of Co(CN)63–into a polyammoniumm macrocyclic ligand partially hinders the CN– photoaquation reaction, showing that it may be possible to control and orient the ligand photosubstitution reactions of transition metal complexes by using appropriate receptor molecules.

Stereochemical aspects of the thermal substitution reactions of cobalt(III) complexes

Abstract: Comparaison entre theorie et experience pour les aquations spontanees et induites de cis- et trans-Co(en) 2 AX 4+ , isomerisation cis-trans de Co(en) 2 A(HO) m+ et racemisation de cis-Co(en) 2 A(H 2 O) m+

Transfer Chemical Potentials for Cobalt(III) and Chromium(III) Complexes from Water into Aqueous Methanol; their Relevance to Reactivity Trends for Cobalt(III)-Chloride Aquation

Abstract: We report solubilities of a number of cobalt(III) and chromium(III) complex salts in methanol-water mixtures. From these, and published solubilities of salts of other complexes of these metals, we have calculated transfer chemical potentials from water into aqueous methanol for a variety of cationic and anionic complexes of cobalt(III) and chromium(III), using the assumption δmμ⊖(Ph4As+) + δmμ⊖(BPh 4 − ). The established trends are discussed in terms of electrostatic factors and of the hydrophilicity or hydrophobicity of the ligands present. The effects of single ion assumptions on conclusions of initial state-transition state analyses of solvent effects on reactivity are assessed with particular reference to aquation of thetrans-[Co(en)2Cl2]+ andtrans-[Co(py)4Cl2]+ cations.

Characterisation of cis-[CoCl2L]+ and two diastereoisomeric trans-[CoCl2L]+ complexes and studies of the aquation kinetics (L = C-meso-5,12-dimethyl-1,4,8,11-tetra-azacyclotetradecane)

Abstract: The complex cis-[CoCl2L]ClO4 and two diastereoisomeric trans-[CoCl2L]ClO4 complexes have been isolated and characterised (α- and β-trans isomers; L = C-meso-5,12-dimethyl-1,4,8,11-tetra-azacyclotetradecane). The two trans isomers differ in the configuration at the chiral secondary NH centres (in principle ten diastereoisomers are possible). The β-trans isomer is found in conjunction with the cis isomer and isomerisation of cis-[CoCl2L]ClO4 in hot dilute hydrochloric acid gives β-trans-[CoCl2L]+. The aquation kinetics of the three isomers have been studied over a temperature range and activation parameters determined. At 25 °C the values of kaq. are 2.4 × 10–5 s–1(α-trans), 5.5 × 10–5 s–1(β-trans), and 8.7 × 10–2 s–1(cis isomer). Configurations for the complexes are considered in detail, and their reactivities in aquation discussed.

Synthesis and aquation kinetics of the cis-dichloro- and three diastereoisomeric trans-dichloro-complexes of cobalt(III) with the macrocyclic ligand C-rac-5,12-dimethyl-1,4,8,11-tetra-azacyclotetradecane

Abstract: The synthesis and characterisation of cis-[CoCl2L]Cl and three diastereoisomeric trans-[CoCl2L]ClO4 complexes [designated (B), (C), and (D)] are described (L = C-rac-5,12-dimethyl-1,4,8,11-tetra-azacyclotetradecane). Ten diastereoisomeric trans-[CoCl2L]+ complexes are in principle possible. Isomer (B) is pale green, is aquated without isomerisation (kaq.25= 4.5 × 10–5 s–1), and has the trans III (RSSR) configuration of the chiral nitrogen centres, with one equatorial and one axial methyl substituent (confirmed by 1H n.m.r. measurements). This isomer is comparable with the ‘aquation-inert’[CoCl2-(cyclam)]+ isomer (cyclam = 1,4,8,11-tetra-azacyclotetradecane). Isomer (C) is bright green, is aquated more rapidly than isomer (B)(kaq.25= 6.5 × 10–4 s–1) to give a green chloroaqua-complex indicating retention of configuration, and could have a configuration with two equatorial methyl groups. Isomer (D), which is deep green, is prepared by isomerisation of cis-[CoCl2L]Cl in HCl solution. Isomer (D) is aquated quite rapidly (kaq.25= 9.0 × 10–4 s–1) with isomerisation to give a violet chloroaqua-species, and probably has a configuration with two equatorial methyl groups and two ‘twist-boat’ six-membered chelate rings. Activation parameters for aquation of the cis and trans complexes have been determined, and their relative reactivites are discussed. The ability of the macrocyclic ligand to fold in the transition state of a dissociative aquation reaction is shown to be important in determining the reactivities of the complexes.

Kinetics and mechanism of the reactions of sulfito complexes in aqueous solution. Formation, aquation, and intramolecular electron-transfer reactions of the trans-aquo(sulfito-O)bis(ethylenediamine)cobalt(III) ion

Abstract: Mesures des vitesses de fixation reversible rapide de SO 2 par le complexe du titre. Intermediaires formes

Base hydrolysis of mono-alkylsubstituted chloropentaamminecobalt(III) complexes

Abstract: The preparation of the series ofcis- andtrans-[Co(NH3)4(RNH2)Cl]2+ complexes (withcis, R = Me orn-Pr andtrans, R = Me, Et,n-Pr,n-Bu ori-Bu) is described The uv-visible spectra indicate a decrease of the ligand field on increasing chain length Infrared spectra show an enhanced Co-Cl bond strength compared to the pentaammine Partial molar volumes of the complex cations do not reveal steric compression From proton exchange studies in D2O it follows that [Co(NH3)5Cl]2+ and thecis- andtrans-[Co(NH3)4-(CH3NH2)C1]2+ complexes exchange the amine protons on the grouptrans to the chloro faster than those on thecis A coordinated methylamine group exchanges its amine protons slower than a corresponding NH3 group in the parent pentaammine, but the methyl introduction accelerates the exchange of the other NH3 groups The aquation of thetrans-alkylamine complexes (studied at 52° C) is acceleratedca 10 times compared to the parent pentaammine, irrespective of the nature of the alkyl group Thecis complexes do not show this acceleration of aquation In base hydrolysis (studied at 25° C) thecis complexes are the most reactive (a factor 20 over the parent ion) Thecis/trans product ratio in base hydrolysis and the competition ratio in the presence of azide ions were calculated from the 500 MHz1H nmr spectra, which display distinctly different alkyl resonances for each individual complex Thecis ions react under stereochemical retention of configuration; thetrans compounds give 10±1%trans tocis rearrangement The ionic strength (⩽4 mol dm−3) and the pH do not affect this result The same product ratio is obtained in methanol-water and DMSO-water mixtures Ammoniation in liquid ammonia gives the same ratios as in base hydrolysis, base-catalyzed solvolysis in neat methylamine gives stereochemical retention for both thecis- andtrans-methylamine ion The product competition ratio (Co-N3)/(Co-OH2) for thecis compounds and the bulkier amines (R =n- andi-Bu), 15–25% at 1 mol dm−3N 3 − , isca twice that of thetrans compounds and the pentaammine The results are interpreted in the classical conjugate base mechanism, and discussed in the context of current ideas about stereochemistry of base hydrolysis

Anionopentaaminecobalt(III) complexes with polyamine ligands. XIX: Computer simulated intermediates for dissociative aquation reactions

Abstract: Strain energy minimization calculations have been performed for several octahedral chloropenta-amine cobalt(III) complexes with polyamine ligands. Similar calculations on the five-coordinate residue obtained by removal of the chloro ligand allow an estimation of the geometry and energy of a potential intermediate in a chloride release reaction proceeding via a dissociative mechanism. In all cases the five-coordinate residue is less strained than the six-coordinate octahedron and the non-replaced ligands play an essential role in determining the resulting distortion. Thus for the series mer-CoCl(NN)(dien)2+ (NN = en, (NH3)2,tn), the total strain energy difference between the minimized ground state and the minimized five-coordinate residue is 12.2, 18.3 and 25.8 kJ mol-1, respectively. This order is identical (where data are available) to that of the rate constants (and activation energies) for thermal aquation, Hg2+ assisted aquation and mer → fac-dien isomerization in this series. Similar calculations have been performed for a series of trans-CoCl2(N4)+ systems and again the energy differences are in the approximate order of the rates of thermal aquation. In the case of N4 = (NH3)2, the energy difference between trans-and cis-CoCl(NH3)4(OH2)2+ products is about 1 kJ mol-1, the trans-isomer being the more stable.

Interpretation of kinetic data for the reaction of azide with aquapentaamminechromium(III) and the reverse (aquation) reaction

Abstract: Constantes de vitesse au 1er ordre pour la formation de Cr(NH 3 ) 5 N 3 2+ et son aquation. Parametres d'activation

Photophysical and photochemical properties of cobalt(III) phosphite complexes

Abstract: Etude de l'emission a partir de l'etat 3 T 1g de [Co(P) 6 ](ClO 4 ) 3 avec P=P(OCH 2 ) 3 CCH 3 et a partir de [Co(pom-pom) 3 ](ClO 4 ) 3 avec pom-pom=(CH 3 O) 2 PCH 2 CH 2 P(OCH 3 ) 2 . Photolyse de Co(pom-pom) 3 3+ conduisant a une photoaquation. Etude cinetique

Substitution reactions of five-coordinate complexes. 1. Formation and aquation kinetics of the (acido)(rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)copper(II) (blue) cation

Abstract: Constantes de vitesse de formation et d'aquation de 7 complexes (acido)(rac-hexamethyl-5,5,7,12,12,14 tetraaza-1,4,8,11 cyclotetradecane)

Photochemical studies of chromium (III) complexes. Photoisomerization and photochemical ammine ligand aquation of the isomeric ammineaquachromium (III) complexes

Abstract: Reactions photochimiques de 8 complexes differents, a 366 et 546 nm. Les rendements quantiques pour l'isomerisation et la perte de NH 3 coordine ne presentent pas de relation avec la longueur d'onde. Les distributions des produits des reactions photochimiques sont differentes de celles des reactions thermiques a 60-80°C

Salt and medium effects in the aquation ofcis-amminebromobis(ethylenediamine)cobalt(III) ion

Abstract: The aquation kinetics ofcis-[Co(NH3)Br(en)2]2+ were studied in aqueous and mixed aqueous-nonaqueous solvents in the presence of KBr, KCl, LiCl, NaNO3 and NaClO4 as supporting electrolytes. It was found that the association between the complex ion and Cl−, Br− and NO3− ions takes place. The association constants, KIP, were evaluated from kinetic measurements. The kinetic parameters in the studied media are related to the influence of the cosolvents on the solvation spheres of the reactants and activated complex.

Photochemistry of the cis- and trans-dibromobis(ethylenediamine)ruthenium(III) cations

Abstract: Irradiation par champ de coordinat de la substitution de coordinat et la solvolyse des trans- et cis- [Ru(en) 2 Br 2 ] + respectivement en trans- et cis-[Ru(en) 2 Br(H 2 O)] 2+

The volume profile for the aquation reactions of trans-[CoBr(NO2)(en)2]+ and trans-[CoCl(N3)(en)2]+

Abstract: For the aquation of trans-[CoBr(NO2)(en)2]+, the activation volume at atmospheric pressure (ΔV\eweq) is 0.3±0.2 cm3 mol−1 at 10 °C, and the reaction volume (ΔV) is −10.4±0.1 cm3 mol−1 at 7.4 °C, both in pure water. For trans-[CoCl(N3)(en)2]+, ΔV\eweq is 0.7±0.6 cm3 mol−1 at 30 °C in 0.011 M HClO4 (1 M=1 mol dm−3) and ΔV is −11.0±0.6 and −11.4±0.3 cm3 mol−1 at 25 °C in 0.008 M HClO4, thus yielding the trans and the cis aqua products respectively.

Mutarotation of D(+)-glucose. III. Evidence for cooperative and competitive nucleophilic catalysis by molybdenum(VI) and tungsten(VI) anions

Abstract: The rate of mutarotation of α-D(+)-glucose is subject to general base catalysis by a variety of oxo anions. The relative magnitudes of the second-order rate constants are B4O72->W7O246->Mo7O246- > HCO3->WO42->MoO42- Catalysis by W7O246- and Mo7O246- is competitive but that by WO42- and MoO42- is cooperative. A mechanism for catalysis by the polymeric anions is proposed which involves ion-pair formation between the anion and the conjugate acid of glucose. Specifically oriented aquation sheaths about the charged ions cause them to act as enhanced nucleophiles in the rate-determining step to form the aldehyde intermediate. Activation parameters support this model.

The kinetics of base hydrolysis of trans-dichlorotetrakis(alkylamine)-rhodium(III) ions

Abstract: The observed pseudo-first-order rate constants for the base hydrolysis of the series of complexes trans-[Rh(NH2R)4Cl2]+(R = H, Me, Et, or Prn) have been found to depend on hydroxide ion according to Kobs.=k1+k2[OH–]. The k1 term is believed to be the aquation pathway which is operative in the bromide interchanges of these complexes, whereas the k2 term corresponds to the SN1 (c.b.)(conjugate base) mechanism. Values of the activation parameters for the base hydrolysis have also been determined and are discussed in relation to the results for similar rhodium(III), cobalt(III), and chromium(III) complexes. It is concluded that in complexes of this type rhodium(III) is less able to participate in π bonding than are cobalt(III) and chromium(III).

A Simple Method for the Preparation of Pentaammine Complexes Containing Anions Derived from Acids of Low Volatility

Abstract: A method applicable to the preparation of complexes of the type [MX(NH3)5]Z+, with M = Co(III), Rh(III), Cr(III), has been used to prepare the new compounds [CoH2PO3(NH3)5](ClO4)2, [Rh(TS)(NH3)5] (TS)2(TS = p-toluenesulfonate, C7H7SO3) and |RhH2PO2(NH3)5|(ClO4)2 and also to improve the synthesis of the known compounds [CoPO4(NH3)5]z+ and [CrPO4(NH3)5]. The method involves heating a salt of [MY(NH3)5]Z+ (where Y is the anion of an acid that can be easily displaced) in molten HX. The acid HX used should be anhydrous or contain as little water as possible to avoid partial or total aquation.