Reactions of µ-hydroxo-dicobalt(III) complexes. Part XII. Equilibrium and kinetic studies on hydroxo-bridge cleavage reactions of two triply-bridged dicobalt(III) complexes in aqueous perchloric acid solutions

Abstract

3 J. D. Edwards and A. G. Sykes, unpublished work.9, 735.(2). The co-ordinated water molecules in ( 111) and (IV) can be replaced by anions to give complex cations of the type (V) and (VI), where NH, and bridging NH,and OH-ligands have been omitted for clarity. Derivatives of (111) in which X = F-, N3-, and NCS-,1° and of ( 111) and (IV) with X = NO,-11*12 have been reported. Bridging ligands Y can be RC0,-(where R = H, alkyl, or aryl) l3 and NO,-l2 for derivatives of (111), and CH,C02for (IV). Previously it has been assumed that the water ligands in ( 111) and (IV), and the X groups in (V), occupy cis-positions. However recent X-ray studies on the nitrate salt of (111) have shown

Preparation, structure, and interconversion kinetics of mono- and binuclear aquo(nitrilotriacetato)cobaltate(III) complexes

“…While the last referenced work was in progress, we had become engaged in a similar type of preparative investigation since we wished to use the compound Co(NTA)(OH2)2 in an extension of our carbon dioxide uptake studies. 4 We found it rather easy to prepare aqueous solutions of the diaquo compound by decarboxylation of the carbonato congener Co(NTA)C032", as reported in our kinetic study of the latter process.5 However, our attempts to prepare pure solid samples of complexes of the formula [€ ( )( ) ( 20)]• 20 by the published procedures1"3 failed, our purified product inevitably turning out to be K2[Co(NTA)2(OH)2]. Our kinetic studies of the acid-catalyzed hydrolysis of this di-^-hydroxo species confirm some of the findings of Thacker and Higginson3 which have been sufficiently extended to enable further clarification of the chemistry of this interesting system, as well as of related ja-hydroxo-cobalt(III) species.…”

Reactivity of the tri-µ-hydroxo-bis[triamminecobalt(III)] ion in halide media

“…Table 6 contains the pseudo-first-order rate constants for the third stage of the acid hydrolysis of [(NH3)3C~(p-OH),Co(NH3),l3+ as a function of [Cl-] and [Br-] at constant [H+]. The right-hand column shows that the rate of the reaction is first order with respect to m -1 , equation (5). Based on these results we can propose the mechanism shown in Scheme 2 for the third step of the acid hydrolysis of…”