Solvent dependence of ligand substitution kinetics of nickel(II)

Self Cite

Kinetics and thermodynamics of dissociation of nickel(I1)-isoquinoline complexes in tetrahydrofuran. Effect of trace water on ligand substitution kiiletics 1842 (1983) Rate constants and associatctl activation parameters for the dissociation of ( s~l v )~~i ( i s o t l~~i~i ) " (solv = solvent, isoquin = isoquinolinc) were dctcmmincd in tetlahydrofur;~~~ ('I'HF) over the r;unge IS to 35°C by stoppctl-flow spcctrophotornctry.Comparison of the cnthalpy of activation A H ; for the, dissociation of (so~v)~Ni(isoquin)" in THF with previous results in othcr solvents reveals that the linear rclation bctwccn AH,: for the dissociation of this ion in the various solvcnts and the Gutrnann donicity can bc extended to THF. From this relation the donor number of THF is fount1 to be 18.8 + 0.5. in agreement with the value 19.3 rcportcd from othcr methods. Dissociation of(~olv)~Ni(isoquin)" in THF is controlled by an [,,-type mechanism, as was previously observed in othcr protic and aprotic solvents. The rate of dissociation in THF is strongly affected by the frcc-water conccntration in the rncdium.

“…The pathways can be represented by [8] Any condition that influences the rate-controlling step, represented by eq. 191, will affect k,,.…”

Section: Resultsmentioning

confidence: 99%

Kinetics and thermodynamics of dissociation of nickel(II)–isoquinoline complexes in tetrahydrofuran. Effect of trace water on ligand substitution kinetics

Chattopadhyay¹,

Kratochvil²

1983

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“…The limits of the first line of evidence have already been tested by Chattopadhyay and Coetzee (6). Their work establishes that n (and AHL* -AHex*) is a moderately sensitive function of the choice of L. Moreover, the ordering of solvents with respect to the magnitude of n is not constant as L varies.…”

Section: Role Of Solvent In Solvent Exchange Reactionsmentioning

confidence: 98%

Solvent Effects on Solvent Exchange Reactions at Nickel(II) Centers

Langford¹,

Tong²,

Merbach³

1975

. Can. J. Chem. 53, 702 (1975).Several recent correlations relating kinetics of Ni(I1) complex formation and solvent exchange to solvent properties are examined after collection of literature and new experiments on solvent exchange kinetics at Ni(I1) when only rile solvent is varied (entering group, leaving group, and nonlabile ligands held constant). The results indicate solvent exchange is remarkably insensitive to bulk solvent. It is suggested that this implies that the interesting correlations of complex formation rates with solvents introduced by Bennetto and Caldin provide a means to study the solvent dependence of the encounter equilibria between a Ni(I1) complex and a ligand L. The linear relationship between enthalpies and entropies of activation for reactions at Ni(I1) in different media is attributed to the changes in the ligands bound to the Ni(I1) center but not undergoing substitution in the reaction observed. Chem.53,702 (1975

“…J. Chem. Downloaded from www.nrcresearchpress.com by 34 proton is attached to a tertiary ring carbon and this may hinder the process of proton removal. This large catalytic effect is not reproduced in the reaction of any other metal ion with the en01 tautomer of a P-diketone.…”

Section: P I )mentioning

confidence: 99%

Catalysis of the deprotonation of β-diketones during formation of the 1:1 metal complexes

Blanco¹,

Hynes²

1992

. Can J. Chem. 70, 2285Chem. 70, (1992. Catalytic effects on the deprotonation rate constants of P-diketones were observed during kinetic studies of the formation reactions of the 1 : 1 complexes of these ligands. When vanadium(IV), chromium(III), iron(III), cobalt(II), nickel(II), copper(II), and uranium(V1) react with pentane-2,4-dione, heptane-3,5-dione, 1,1,1-trifluoropentane-2,4-dione, 4,4,4-trifluoro-1 -(2-thieny1)-butane-1,3-dione, I-phenylbutane-l,3-dione, and 2-acetylcyclohexanone a significant catalytic effect on the rate of ionization of the keto tautomer of the ligand was observed. A considerable enhancement of the rate of ionization of the en01 tautomers of these ligands was observed during the com lex formation reactions with Cu2+. A mechanism is proposed that accounts for these catalytic effects. In the case of C U~ the increased rate of proton removal from the ligands may be rationalized in terms of the relatively large reduction potential of this metal ion. CARLOS A. BLANCO et MICHAEL J. HYNES. Can. J. Chem. 70, 2285Chem. 70, (1992. On a observe des effets catalytiques sur les constantes de vitesse de dkprotonation des P-dicCtones au cours d'ktudes cinetiques sur les reactions de formation des complexes 1 : 1 de ces coordinats. Lorsqu'on fait reaction du vanadium(IV), du chrome(III), du fer(III), du cobalt(II), du nickel(II), du cuivre(I1) et de I'uranium(V1) avec la pentane-2,4-dione, l'heptane-3,5-dione, la 1,1,1-trifluoropentane-2,4-dione, la 4,4,4-trifluoro-1-(2-thiCny1)-butane-1,3-dione, la 1-phenylbutane-1,3-dione et la 2-acetylcyclohexanone, on observe un effet catalytique important sur la vitesse d'ionisation du tautomtre cetonique du coordinat. On a observk une augmentation considkrable de la vitesse d'ionisation des tautomeres Cnoliques de ces coordinats au cours des reactions de formation de complexes avec le CU". On propose un mecanisme qui explique ces effets catalytiques. Dans le cas du Cu2+, on peut rationaliser I'accCICration de la vitesse d'enl2vement du proton des coordinats en fonction d'un relativement grand potentiel de reduction de cet ion metallique.[Traduit par la redaction]