Monodentate bicarbonato complexes

Values of the Acid Dissociation Constant (K) and Ring-Opening Rate Constant (k2) of [L4Co(02COH)]2 + and the Decarboxylation Rate Constant (k2) of the Corresponding Monodentate Bicarbonato Complexes (at 25.0 °C,... 

The kinetics of the formation of carbonato complexes by CO2 uptake reaction has been extensively investigated (3). The two methods of study, the equilibrium method and acidification method , genuinely devised by Harris and co-workers were adapted to the stopped-flow kinetics measurement (63). The following general reaction scheme was proposed by them for the formation of monodentate carbonato/bicarbonato complexes by the C02 uptake reaction of M-OH(K-1)+ species (Scheme 2). 

Rate constants and activation parameters are also given for loss of carbon dioxide from the intermediate d5-[Rh(en)2(C03H)(OH2)]. Here the rhodium(III) system has two advantages over its cobalt(III) counterpart, for not only is it possible to obtain kinetic data for the monodentate bicarbonato intermediate but also there is no concomitant isomerization to complicate the carbon dioxide loss kinetics in the rhodium(III) case. In the reverse direction, kinetic parameters were obtained for the reaction of c/5-[Rh(en)2(OH2)(OH)] and of d5-[Rh(en)2(OH)2] with carbon dioxide-(bi)carbonate. The products are cw-[Rh(en)2(C03)(0H2)] and d5-[Rh(en)2(C03)(0H)] there is no mention of a bidentate carbonato product. Kinetics of decarboxylation of the new complexes trans-[Rh(en)2(C03)(0H2)] and rra 5-[Rh(en)2(C03)2]" have been reported, with values for rate constants and activation parameters given. The bis(carbonato) complex loses both carbonate ligands at low pHs, but only one carbonate when pH > 6.5. The kinetics of the reverse carbonate-formation reactions, from trans-... 

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