Carbonato

Other Coordination Complexes. Because carbonate and bicarbonate are commonly found under environmental conditions in water, and because carbonate complexes Pu readily in most oxidation states, Pu carbonato complexes have been studied extensively. The reduction potentials vs the standard hydrogen electrode of Pu(VI)/(V) shifts from 0.916 to 0.33 V and the Pu(IV)/(III) potential shifts from 1.48 to -0.50 V in 1 Tf carbonate. These shifts indicate strong carbonate complexation. Electrochemistry, reaction kinetics, and spectroscopy of plutonium carbonates in solution have been reviewed (113). The solubiUty of Pu(IV) in aqueous carbonate solutions has been measured, and the stabiUty constants of hydroxycarbonato complexes have been calculated (Fig. 6b) (90). 

Ratios of U and U to Th and Ra daughters, combined with differences in chemical reactivity have been used to investigate the formation and weathering of limestone in karst soils of the Jura Mountains, and of the mountains in the central part of Switzerland. Uranium contained within calcite is released during weathering, and migrates as stable uranyl(VI) carbonato complexes through the soil. In contrast, the uranium decay products, Th and Ra,... 

Ion Excha.nge, The recovery of uranium from leach solutions using ion exchange is a very important process (42). The uranium(VI) is selectively adsorbed to an anion-exchange resin as either the anionic sulfato or carbonato complexes. In carbonate solutions, the uranyl species is thought to be the tris carbonato complex, U02(C03) 3 [24646-13-7] and from sulfate solutions the anion is likely to be U02(S0 , where nis ) [56959-61-6] or 2 [27190-85-8], The uranium is eluted from the resin with a salt or acid solution of 1 AfMCl or MNO (M = H", Na", The sulfate solution is... 

Fig. 8.22) features a unique tris(bidentate) sex-tuply bridging carbonato ligand as well as three bidentate piT-carbonato ligands. Other chelating and bridging coordination modes are also known.< 2 >... 

Co(H2OMNH3)4(CI04)3. Brownish red octahedral crysts (Ref 13) prepd by the action of aq perchloric ac on Co carbonato tetra-ammino nitrate (Ref 22). Impact sensy with 2kg wt for 50% explns, 24cm- The expln is described as strong with a visible flame and loud report (Ref 25)... 

The product CO3 radical can react with a variety of inorganic ions including the carbonato complex of Pu(V). Thus, in a pulse radiolysis experiment, Pu(VI) in 0.05 M Na2C03, He saturated, there are the parallel reactions (17) and (18)... 

Each entry has the % of total metal present as the free hydrated ion, then the ligands forming complexes, in decreasing order of expected concentration. For instance, in inorganic freshwater at pH 9, Ag is present as the free aquo ion (65%), chloro-complexes (25%), and carbonato-complexes (9%). 

Carbonate is a well-established ligand, but its coordination diversity continues to surprise. Elaborate bridging modes have been reported for carbonate for example, a /i4-carbonato-bridged Co11 compound [Co2(2,2 -bipyriniidinc)(0[ I2)2(/i-C03)(//-OI I)]1 has been characterized.429... 

The (triphos)Ni0 template reacts with ethyl cyanoformate to give (220).648 The MO description and reactivity of the CS2 complex (221) has been studied in some detail.649 Treatment with 02 gives the dithiocarbonate compound (221a),650 while bubbling of C02 through a solution of (221) yields the carbonato complex (221b).651 In both cases, one of the phosphine arms has been oxidized and is found dangling. 

Stein and co-workers have reported the structure of an unusual tetranuclear platinum(II) complex possessing both ammine and carbonato ligands.325 During a study of the reaction of cisplatin with Ag+, followed by the addition of 2 -deoxyuridine to afford platinum blue -like products from aqueous solution (pH < 2), a colorless minor product was isolated from the reaction mixture. X-ray crystallography confirmed that the product was a cyclo tetra-cation... 

New reproducible syntheses of platinum(II) carbonato complexes of the type [Pt(C03)L2] (L mono- or bidentate tertiary phosphine) involve the reaction of Ag2C03 with [PtCl2L2] in water-saturated CH2C12 solution.3 Other methods of preparation include the conversion of the dichloroplatinum(II) complexes to the corresponding bis(alkoxo)- or bis(phenoxo)-platinum(II) species, followed by hydrolysis in the presence of C02. 

Ht2N(N202)] (500), stabilized with respect to NO release in aqueous solution, was also documented. During this endeavor, complex [(i-Pr3TACN)Cu(02CMe)] (bidentate acetate coordination) (501) and a carbonato-bridged complex (502) were characterized.413... 

Figure 2 Carbonato-bridged polynuclear compounds of varying nuclearity with different terminal ligands.

The zinc complex of a 14-membered CA-N2S2 dibenzo macrocycle with two pendent pyridyl-methyl groups was studied (L = 8,ll-bis(2-pyridylmethyl)5,6,7,8,9,10,16,17-octahydro-diben-zo[e,m][l,4]dithia[8,ll]diazacyclotetradecine). In solution, [ZnL]2+ takes up atmospheric carbon dioxide and transforms to the dinuclear complex [(//-C03)(ZnL)2](C104)2. The structures of both complexes have been elucidated. The zinc atoms, which are situated outside the macrocyclic ring, are unsymmetrically bridged by the //-carbonato group.739... 

Hydroxo complexes of Cd are rare. In one example, two /i-OH groups link two Cd centers to a distorted square Cd2(OH)2 (rav(Cd—O) 222.5 pm) otherwise two tetradentate N,S-donor ligands complete the coordination sphere of Cd. Remarkably, in a reaction with C02 the two /i-OH groups are replaced by one /i-carbonato group.260... 

The solubility of Tc02 nH20 in an aqueous solution was investigated by Meyer et al, [55-58], Paquette and Laurence [59] reported that carbonato- and phosphato-complex formation was likely to occur. The precipitation of Tc02-H20 is prevented in solution if the ratio... 

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