Iridium pentaammine

Y. Harel, A. W. Adamson. Photocalorimetry. 4. Enthalpies of Substitution Reactions of Rhodium(III) and Iridium(lll) Pentaammine Halides and of Ruthenium(II) Hexaammine. J. Phys. Chem. 1986, 90, 6690-6693. 

COBALT(III), RHODIUM(III), AND IRIDIUM(III) CARBONATO COMPLEXES OF THE PENTAAMMINE TYPE... 

The procedure described here is based on the observation that amine monohydroxo complexes of cobalt(III), rhodium(IIl), and iridium(III) react directly with carbon dioxide to form the corresponding carbonato complexes,2 3 without effect on the configuration of the amine ligands.4 The amine monoaqua complex is allowed to react with lithium carbonate or carbon dioxide gas at room temperature at pH 8.0 for a few minutes, and the carbonato complex is isolated by adding alcohol. The procedure has been used to prepare salts of the following cations pentaammine(carbonato)-cobalt(III),2 ds-ammine(carbonato)bis(ethylenediamine)cobalt(III),5 trans-... 

The time required for the preparation and isolation of the crude complex is 1 hr. Crystallization of the complex from aqueous NaCp3S03 solution requires 4 hr. Pentaammine(trifluoromethanesulfonato-0)iridium(III) trifluoromethanesul-fonate (0.50 g, 0.69 mmol) is added to distilled deionized water (5 mL) in a 20-mL round-bottomed flask, and the solution is heated to 80° for 10 min. The solution is filtered, and the solvent is removed by rotary evaporation (60°) to give [Ir(NH3)s(0H2)](CF3S03)3 as a white powder. The white powder is washed from the flask with diethyl ether (3 x 10 mL) and then air-dried. Yield 0.52 g (100%). 

Preparation and recrystallization of the complex requires —20 hr. Pentaammine-(trifluoromethanesuIfonato-O)iridium(III) trifluoromethanesulfonate (O.SO g, 0.69 mmol) is dissolved in dry liquid anunonia (20 mL) contained in a SO-mL round-bottomed flask that can be fitted with a mercury bubbler. The flask is initially cooled in a Dry Ice/acetone bath to prevent excessive splashing of the solvent and hence loss of complex. 

Pentaammine(trifluoromethanesulfonato-0)iridium(III) trifluoromethanesul-fonate is a white powder that is air-stable provided it is not subjected to prolonged exposure to atmospheric moisture. The complex may be kept for many months in a desiccator over a suitable drying agent (silica gel, CaCL) without any noticeable decomposition. The aquation rate constant for the complex is 2.6 x 10 sec" at 25° (0.1 M CF3SO3H), and at elevated temperatures (60-80°) the rate of substitution is quite rapid in both aqueous and nonaqueous solvents. When dissolved in poorly coordinating solvents such as acetone or tetrahydrothiophene 1,1-dioxide (sulfolane), the solvent-substituted species are themselves comparatively labile, and many substitution reactions may be performed in these solvents. " ... 

Chromium(II) reactions with pentaammine rhodiuin(lll) and iridium(lll) complexes are much slower and involve more than one step (Table III), Final... 

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