Wynand J. Louw

Kinetics and mechanisms of reactions of gold(III) complexes III. Substitution reaction of tetrachlorogold(III) with ethylenediamine

Abstract The kinetics of the reaction [AuCl 4 ] − + en → (where en is ethylenediamine), have been studied in acid medium at different temperature and pH values and the following reaction scheme is suggestd: Also included are some tentative results suggesting At 25°C values of k 1 =4.7 × 10 2 M −1 sec −1 , k 2 =1.72 × 10 1 M −1 sec −1 , k 3 =(1.2 ± .7) × 10 −4 sec −1 were obtained The activitation parameters were found to be: ΔH 1 * =15.6 kcal mole −1 , ΔH 2 * =in 13.8 kcal mole −1 , ΔH 1 * =+6.0 e.u., ΔS 2 * =−7.0 e.u.

An investigation into the mechanisms of the substitution reactions by ethylenediamine and diethylenetriamine in tetrachlorogold(III)

Abstract It is shown that the reaction AuCl 4 − +enH + → (en = ethylenediamine) in aqueous acid medium obeys the same rate law as the reaction with the diethylenetriamine ligand viz . which is derived from the reaction scheme

Kinetics and mechanisms of reactions of goldIII complexes. IV. Substitution reaction by diethylenetriamine in tetrachlorourate(III)

The reaction AuCl4−+dien→Au(dien)Cl2+3Cl− (diendiethylenetriamine) in aqueous acid medium obeys the rate law kobs = k3K′a[H+] + k1k4Ka′Kak2[H+]2[Cl−][dienH33+], derived from a consideration of the reaction scheme where dienH33+ ⇋ dienH22+ + H+ is the principle equilibrium between the amine species. The data were taken at various amine, hydrogen ions and chloride ion concentrations as well as different temperatures. The various rate constants at 25 °C have the values k3 = 7.3 sec−1M−1 and k4 = 1.2 × 103 sec−1M−1. The activation parameters ΔH3∗ = 12.9 kcal mol−1, ΔH4∗ = 13.8 kcal mol−1 ,ΔS3∗ = −20.5 e.u. and ΔS4∗ = +2 e.u. were evaluated.

Preparation of (η-cyclo-octa-1,5-diene)halogenohydridobis(phosphine)-iridium(III) salts and kinetic study of the oxidative-addition reactions of (η-cyclo-octa-1,5-diene)bis(phosphine)iridium(I) salts with hydrohalogenic acids: evidence for anionic intermediates

The complexes [IrH(X)(cod)L2][PF6][cod = cyclo-octa-1,5-diene, X = Cl, Br, or I, L = PPh2(OMe) or PMePh2; X = Cl or Br, L = PEtPh2] and [IrHX2(cod)L](X = Br or I, L = PMePh2 or PEtPh2) have been synthesised from HX (X = Cl, Br, or I) and the salts [Ir(cod)L2][PF6][L = PPh2(OMe), PMePh2, or PEtPh2]. The equilibrium (i)[Ir(cod)L2]++ Cl–⇌[IrCl(cod)L]+ L (i) exists due to steric crowding, and explains the presence of the second chloride in the end product. Kinetic studies on both the oxidative-addition reactions of [Ir(cod)L2]+ and [lrCl(cod)L] with HCl have revealed that the nucleophilic attack of Cl– precedes the protonation of the complexes.

Kinetics and mechanism of reactions of gold(III) complexes. VI. Substitution reactions by methyl substituted diethylenetriamines in tetrachlorogold(III)

Abstract The reaction, AuCl4− + am→AuCl2am+ + 2Cl− where am = xN, yN′-(x+y)methylethylenediamine (x = 1, 2; y = 0, 1, 2) in aqueous acid medium obeys the rate law where k and k′ are constants. The formation of ion pairs between the protonated amines and chloride ion is considered as a possibility for explaining this rate law. Data ware taken at different amine, hydrogen, and chloride ion concentrations and temperatures.

Kinetics and mechanisms of reactions of gold(III) complexes. II. The formation and equilibrium hydrolysis of tetrabromoaurate(III)

Abstract The first two hydrolysis steps of the tetrabromoaurate(III) ion have been studied over a range of temperature and bromide and hydrogen ion concentrations. Both steps follow the normal two-term rate law for square planar equilibrium solvolysis, with a direct hydrogen ion concentration dependence incorporated in the second order term. In the formation of tetrabromoaurate(III) from tetrachloroaurate(III) only one reaction was observed. On the basis of the experimental data this appears to be the displacement of the first chloride.

Preparation of the five-co-ordinate complexes [PdX2(PMe2Ph)3](X = Cl, Br, or I) and the crystal and molecular structure of dichlorotris-[dimethylphenylphosphine]palladium

The preparation of tris(dimethylphenylphosphine) dihalogenopalladium(II) complexes and the crystal structure of dichlorotris(dimethyIphenylphosphine)palladium(II) are reported. The co-ordination of the palladium ion is distorted square pyramidal with one palladium–chloride bond of 2.96 A.The possibility of the five-co-ordinate complex being a tight ion-pair. [PdX(PMe2Ph)3][X], is discussed in terms of the u.v.–visible spectra of [PdX2(PMe2Ph)3] and [PdX(PMe2Ph)3][PF6].

KINETICS AND MECHANISM OF THE SUBSTITUTION REACTIONS OF FOUR‐ AND FIVE‐COORDINATE IRIDIUM(I) COMPLEXES. THE DETECTION OF A STABLE REACTION INTERMEDIATE

Abstract The substitution reactions of the four- (X = Cl) and five- (X = I, SCN) coordinate complexes CODIr(phen)X with ethylenediamine have been studied kinetically. The mechanism for the five-coordinate system was dissociative. A stable four- or five-coordinate intermediate CODIr(phen)(en) + hat been detected in the substitution reaction the four-coordinate system.

Mechanism of the reaction of hydrogen and phenylacetylene with IrH(CO)(PPh3)3. Kinetic evidence for the co-ordinatively unsaturated IrH(CO)(PPh3) species in solution as reactive intermediates and for the reaction of hydrogen with the co-ordinatively saturated IrH(CO)(PPh3)3 species

A kinetic study of the reaction between IrH(CO)(PPh3)3 and H2 or PhCCH provided evidence for the existence of the co-ordinatively unsaturated intermediate IrH(CO)(PPh3) in solution, as well as a direct attack of hydrogen on the co-ordinatively saturated IrH(CO)(PPh3)3.

Kinetic evidence for a possible end-on oxidative addition of dioxygen to a five-co-ordinate iridium(I) complex

Kinetic measurements have been shown dioxygen to react faster with the five-co-ordinate complex [(cod)Ir(phen)I](cod = cyclo-octa-1,5-diene; phen = 1,10-phenanthroline) than with the four-co-ordinate complex [(cod)Ir(phen)]Cl to form the peroxide complex [(cod)Ir(phen)O2]X (X = Cl, I).