Rabindra K. Nanda

KINETICS OF ANATION OF CIS-DIAQUO-BIS-(1,3-DIAMINOPROPANE) COBALT(III) BY OXALATE

Abstract The kinetics of anation of cis-diaquobis(1,3-diaminopropane) cobalt(III) by oxalic acid and bioxalate anion have been studied at 35°, 40° and 45°C, I=1.0 M(NaClO4). The observed rate law for the formation of Co(tmd)2C2O+ 4, is valid in the range of [Ox]T=0.03–0.50 M, pH=0.3–2.03. The anation rate constants, k1 and k2, for cis-{Co(tmd)2(OH2)3+ 2, H2C2O4) and cis-{Co(tmd)2(OH2)3+ 2, HC2O4-] ion pairs respectively are found to be virtually the same (k1=10.7 × 10−4 sec−1 and k2=11.0 × 10−4 sec−1 at 40°C). Temperature independent oxalic acid and bioxalate ion-pair association constants (Q1 and Q2) are 1.7(±0.3)M−1 and 11.5(±0.7)M−1, respectively. The activation enthalpy and entropy for k1 and k2 paths are 122.6 kJ mol−1 89.5 JK−1 mol−1 and 103.8 kJ mol−1, 29.3 JK−1 mol−1, respectively. The anation of cis-{Co(tmd)2(OH2)3+ 2, X} ion pairs (X=H2C2O4 or HC2O− 4) is believed to involve Id mechanism. The reaction is catalysed by NO− 3.

Kinetics of acid and base catalysed hydrolysis ofcis-?- andcis-?2-[Co(trien)(aniline)Cl]2+ cations

SummaryThe rate of hydrolysis of the title cations obey the rate law:-d ln[Complex]/dt=kobs=k0+k1[OH−] in the range: 1≤pH≤3. The rate and activation parameters for acid and base hydrolysis (k0 and k1 paths respectively) are reported in the 40–60 °C range.

Kinetics of aquation of Pentaammine(substituted salicylato)cobalt(III) complexes by ferric ion

SummaryThe aquation of pentaammine (substituted salicylato) cobalt(III) complexes [(NH3)5CoO2CC6H3(X)OH]2+,X = 5-SO3, 5-Br, 5-NO2, and 3-NO2 in the presence of ferric ion was studied spectrophotometrically in the 65°–80° range. Ferric ion catalyses the aquation of the substratesvia formation of a reactive binuclear species.

Metal ion catalysed aquation of carboxylatoamine cobalt(III) complexes. Kinetics of copper(II) catalysed aquation ofcis(diformato)bis(ethylenediamine)cobalt(III) ion

SummaryThe aquation ofcis-[(en)2Co(CO2H)2]+ tocis-[(en)2Co(OH2)(CO2H)]2+ is catalysed by Cu2+ and the rate equation, −d[complex]t/dt=(kCu[Cu2+]+kH [H+]) [complex)T is valid at [Cu2+]T=0.01–0.1, I=0.5 and [HClO4]=0.005 mol dm−3. The rate measurements are reported at 30, 35, 40 and 45°C and the rate and activation parameters for the Cu2+ and H+-catalysed paths are: kH(35°C)=(2.44±0.09)×10−2 dm3 mol−1 s−1, ΔH‡=83±13 kJ mol−1, ΔS‡=−8±42 JK−1 mol−1, kCu′(35°C)=(3.30±0.09)×10−3 dm3 mol−1 s−1, ΔH‡=73.2±6.1 kJ mol−1, ΔS‡=−55±20 JK−1 mol−1. The formate-bridged innersphere binuclear complex,cis-[(en)2Co{(O2CH)2Cu}]3+ may be involved as the catalytically active intermediate in the copper(II)-catalysed path, just as the corresponding H+-bridged species presumed to be present in the acidcatalysed path.

Reactions of coordinated ligands, Part III(1). Kinetics of lodination of malonate and pyruvate in malonato(pentaammine)-cobalt(III), malonato-bis-(ethylenediamine)cobalt(III) and pyruvato(pentaammine)cobalt(III) ions

SummaryThe kinetics of iodination of malonate and pyruvate in the title complexes are reported at 35.0 °C and I=0.3 M. The reaction is first order in substrate and zeroth order in [I2]. This result is commensurate with rate determining enolisation of the active methylene and methyl groups of the malonate and pyruvate respectively. The reaction is catalysed by H2O, OH− and by the buffer anions used. The rate data suggest that the malonate methylene group in the [Co(en)2-O2CCH2CO2]2+ chelate is considerably more active towards electrophilic substitution than is the case in [Co(NH3)5O2CCH2CO2]2+.

Reactions of coordinated ligands, part II1). Kinetics of iodination of salicylate in bis(ethylenediamine)(salicylato)cobalt(III) cation

SummaryThe rates of iodination of Salicylate in the bis-(ethylenediamine)(salicylato)cobalt(lII) complex and free Salicylate have been measured in acetate buffer at 40° and I = 0.1 M. The reaction is catalysed by acetate and water. The reactivity order for both acetate- and water-catalysed paths is: [HSal]− < [(en)2CoSal]+ < [Sal]2−, where [HSaI]− and [Sal]2− stand for the phenol and phenate forms of Salicylate respectively. Chelation of [Sal]2− to cobalt(III) results in a rate reduction of its iodination by 107.

Synthesis, characterisation and acid and iron(III) catalysed aquation oftrans-bis(Hmalonato)bis(trimethylenediamine) cobalt(III) ion

SummaryTrans-bis(malH)bis(tmd)cobalt(III) (malH2=HO2CCH2CO2H; tmd=trimethylenediamine) has been synthesised and its acid and FeIII catalysed aquation have been investigated in the temperature range 30–45°C. The major product in both cases iscis-[Co(tmd)2(malH)-OH2]2. The rate laws of the acid and FeIII catalysed aquations are given by

Kinetics and mechanism of base hydrolysis of trans- bis(Hmalonato)bis(ethylenediamine)cobalt(III) ion

- d ln[complex]_\tau /dt = k_0 + k_1 [H^ + ]