Mechanistic studies on ligand substitution in hexaaquarhodium(III) ion by salicylaldoxime

929-931The kinetics of formation of [Rh(OH2)4(SalH)j2+ from [Rh(OH2)6]3+ has been studied spectrophotometrically by following the appearance of a characteristic peak of the product complex (λmax=345 nm) as a function of substrate and ligand concentrations, temperature and solvent polarity. The rate of the reaction is found to be first order each in [substrate] and [ligand]. Activation parameters (H≠ = 54.4 kJ mol-1, S≠= - 77.0 JK-1 mol-1), compared with that of the water-exchange, suggest an associative mode of activation. Solvent effect study also helps to lead to the same mechanistic conclusion

Ligand substitution in [Rh(OH₂)₆P]³⁺ by <img src='/image/spc_char/beta.gif' border=0> diketones: Applicability of ligand constants

247-252The kinetics of anation of [Rh(OH2)6P]3+ by -diketones has been followed spectrophotometrically at different temperatures with different ligand concentrations. The reaction is pH dependent. The rate and activation parameters (calculated from Eyring plots), compared with H2O-exchange and other anation studies, indicate an associative mode of activation with the incoming ligand participation in the transition state. A correlation of rate constants with the ligand constant values (-1.82, -1.78 and -1.73 V for pentane-2,4-dione, 1-phenylbutane-1,3-dione and 1,3-diphenylpro-pane-1 ,3-dione respectively)has been attempte

Kinetics and mechanism of the interaction of L- cysteine with diaquaethylenediamineplatinum(II) perchlorate in aqueous solution

863-866The kinetics of the interaction of L-cysteine with [Pt(en)(H20)2]2+ has been studied spectrophotometrically as a function of [Pt(en(H20)2+], [L-cysteinel, pH and temperature. The reaction has been monitored at 230 nm, where the spectral difference is maximum although the λmax, of the L-cysteine saturated product is at 213 nm. The activation parameters have been evaluated from temperature coefficient of the reaction rates. The low value of ΔH# (61.1 kJ mol-1) and large negative value of ΔS# (- 83 J k-1 mol-1) indicate an associative mode of activation for the substitution process. The additional advantage of using aquaamine complexes as an amino acid binder is also discussed

Kinetic and mechanistic studies on the interaction of thiosemicarbazide <span style="font-size:14.0pt;font-family:"Times New Roman";mso-fareast-font-family: "Times New Roman";mso-ansi-language:EN-US;mso-fareast-language:EN-US; mso-bidi-language:AR-SA">with <i>cis </i>- diaquaethylenediamine platinum (II) ion</span>

453-457Kinetics of interaction of thiosemicarbazide with [Pt(en)(H2O2)2+ has been studied spectrophotometrically as a function of [Pt(en)(H2O2)2+ , [thiosemicarbazide] and temperature at a particular pH(4.0) where the substrate complex exists predominantly as the diaqua species and the ligand thiosemicarbazide as a neutral molecule. Th<span style="font-size:14.0pt;font-family:HiddenHorzOCR; mso-bidi-font-family:HiddenHorzOCR">e interaction reaction shows distinct two step consecutive process, the first step is the ligand assisted anation and the second step is the chelation step. The activation parameters for both the steps are evaluated (ΔH1≠= 35 .69 ± 0.80 k J mol -1, ΔS1≠ = -166± 2.54 JK-1 mol -1 and ΔH2≠= 44.54 ± 1.32 k J mol -1 , ΔS2≠ = -182 ± 4. 18 JK-1 mol -1 ).</span

Kinetics and mechanism of the interaction of L- cysteine with diaquaethylenediamineplatinum(II) perchlorate in aqueous solution

863-866The kinetics of the interaction of L-cysteine with [Pt(en)(H20)2]2+ has been studied spectrophotometrically as a function of [Pt(en(H20)2+], [L-cysteinel, pH and temperature. The reaction has been monitored at 230 nm, where the spectral difference is maximum although the λmax, of the L-cysteine saturated product is at 213 nm. The activation parameters have been evaluated from temperature coefficient of the reaction rates. The low value of ΔH# (61.1 kJ mol-1) and large negative value of ΔS# (- 83 J k-1 mol-1) indicate an associative mode of activation for the substitution process. The additional advantage of using aquaamine complexes as an amino acid binder is also discussed