Adduct Formation Reactions Research Articles

The thermodynamic and kinetic stabilities of some Tetra-μ-carboxylatodirhodium(II) adducts

The stability constants and forward and reverse rate constants have been determined for adduct formation reactions involving tetra-μ-acetato, tetra-μ-propionate and tetrakis-μ-methoxyacetatodirhodium(II) with the ligands pyridine, picolinic acid, niacin and isonicotinic acid. The experimentally observed stability trend is isonicotinic acid > pyridine ⋍ niacin ⪢ picolinic acid. It appears that the π bonding ability of the ligands determines the order of stability of these adducts. The variation of the stabilities of the adducts formed from different tetra-μ-carbox-ybtodlrhodium(II) complexes and a given ligand is related to an inductive effect as well as the lipophylic nature of the carboxylate side chain. The more hydropholic character of the propionate species apparently exerts a desolvating effect at the two axial positions resulting in a more rapid ligand exchange.

Thermodynamics and kinetics of some tetra-.mu.-carboxylato-dirhodium(II) adduct formation reactions

Thermodynamics and kinetics of some tetra-.mu.-carboxylato-dirhodium(II) adduct formation reactions

Coordination compounds of hydrazine derivatives with transition metals. XIV. Nickel(II) chelates with bidentate aroylhydrazones and their reactions with heterocyclic bases

Both cationic and neutral bis(ligand)nickel(II) chelates derived from some bidentate aroylhydrazones have been prepared and characterized. Whatever the solubility permits, the reaction of the neutral bis-(ligand)chelates, NiL 2, with some heterocyclic bases were studied spectrophotometrically in benzene solution. The stability constants as well as the thermodynamic parameters (ΔG, ΔH, ΔS) for the adduct formation reaction have been measured. Stable solid mono-, bis- and tetrapyridinate adducts have been isolated from the crystallization of neutral bis(ligand) chelates from pyridine solutions.

Coordination compounds of hydrazine derivatives with transition metals—XI Reaction of heterocyclic bases with nickel(II) chelates of hydrazine-s-methyldithiocarboxylate schiff bases

The reaction of some nickel(II) chelates of the type Ni(R 1R 2·C N N CSSCH 3) 2 with heterocyclic bases have been studied both in benzene and neat base solutions. Spectrophotometric titrations reveal the formation of bis adducts with benzaldehyde Schiff base. In case of acetone, ethyl methyl ketone and cyclohexanone derivatives only mono adducts were identified. The stability constants as well as the thermodynamic parameters (Δ G, Δ H and Δ S) for the adduct formation reactions have been measured. The role of steric factors imposed by the parent nickel(II) chelate as well as the heterocyclic base molecule are emphasized. From the spectral and magnetic measurements of the nickel(II) chelates in neat base solutions, pseudooctahedral and distorted square pyramidal configurations respectively are assigned for the bis and mono adducts.

Studies on the sulfur-containing chelating agents. XLIII. The reaction of thio .BETA.-diketones and the related compounds with iron(II) in the presence of pyridine.

The formations of the adduct complex of the type (ligand)2 Fe (II) (base) n (n=1 or 2) were observed in the reacton of some thio-β-diketones, and the corresponding β-diketones with iron (II) ion in the presence of pyridine base. Paramagnetic shifts were observed in γ-picoline adducts. The use of thiothenoyltrifluoroacetone, thiodibenzoylmethane and dibenzoylmethane gave satisfactory result in the determination of less than 60μg of iron as an extraction-spectrophotometric reagent, based on their adduct formation reaction with pyridine.

The extraction of iron(III) from aqueous sulphate solutions by the primary amines 3,5,5-trimethylhexylamine and n-dodecylamine

The compound isolated from the organic phase when 3,5,5-trimethylhexylammonium sulphate in isopentanol extracts iron(III) from an acid sulphate solution has been isolated and recrystallized from ethanol and has been shown to have the stoicheiometric formula (RNH 3) 2FeOH(SO 4) 2. C 2H 5OH, where R is 3,5,5-trimethylhexyl. It has been shown that the extraction of iron(III) occurs by an adduct formation reaction between a primary amine sulphate molecule and the species FeOHSO 4 and (FeOHSO 4) 2 from the aqueous phase, and not by an anion exchange reaction as suggested previously[1]. A dimeric structure is suggested for the complex crystallized from ethanol and magnetic and spectral evidence is presented for the presence of the dihydroxy-bridged unit Fe(OH) 2Fe in the complex and not the FeOFe unit.

Flavin-Sulfite Complexes and Their Structures

Abstract The interaction of free flavocoenzymes with sulfite is described. The synthesis of a few flavin sulfite complexes isolated in the crystalline state and the elucidation of their structure by light and infrared absorption spectroscopy are described. It was found that sulfite binds at the N-5 position of the flavin molecule. Elemental analysis data show that one sulfite molecule is bound per flavin molecule. The flavin sulfite adduct formation is dependent on the absolute concentrations of the reactants, temperature, and pH but is not affected by oxygen or light. The reacting nucleophile species was found to be SO3= rather than HSO3-. The adduct formation reaction is reversible in the pH range g2. At pH l0 the flavin sulfite complex is hydrolyzed yielding a sulfate flavin ratio of 0.95. The light absorption spectrum of the flavin adduct is similar to but not identical with that of the 1,5-dihydroflavin, the latter showing considerable absorption in the visible region whereas the former shows only very little absorption. A number of flavin derivatives were investigated and the dissociation constants of the adducts and the rate constant of the formation of the complex determined. A good correlation was found between the dissociation constants of the sulfite adducts and the oxidation reduction potentials of the corresponding flavoquinones. The mechanism of the formation of the adduct and the possible biological significance of these findings is discussed. The flavin sulfite interaction is also compared with the sulfite interaction occurring with other compounds of biological interest.

Adducts of copper(II) β-diketone chelates with tertiary alkylamines and alkylamine hydrochlorides

Adduct formation of Cu(chelate) 2 (chelate = anion of thenoyltrifluoroacetone, TTA, and trifluoroacetylacetone, TFA) with alkylamines and alkylamine hydrochlorides, S (S = tri- n-butylamine, TBA, tri- n-hexylamine, THA, tri- n-octylamine, TOA, tri- n-laurylamine, TLA, tri- n-hexylamine hydrochloride, THA·HCl, tri- n-octylamine hydrochloride, TOA·HCl and tri- n-laurylamine hydrochloride, TLA·HCl) have been studied spectrophotometrically. Visible and i.r. spectra suggest that alkylamines and alkylamine hydrochlorides form different adducts through bonding of different atoms. In the alkylamines the nitrogen atom is bonded to copper(II) while in the alkylamine hydrochlorides the chlorine atom is bonded to copper(II). Equilibrium constants for the adduct-formation reactions are calculated from the spectral change upon addition of the adduct-forming ligands. It is found that alkylamines and alkylamine hydrochlorides do not interact with Cu(chelate) 2 to the same extent. Furthermore, the complexes species, TOA·HTTA and TOA·HCl·HTTA, do not interact with Cu(chelate) 2.