Rhodium complexes sulfur dioxide

Apart from anion exchange reactions the complexes are inert. One of the few reagents to bring about a change in the coordination sphere is sulfur dioxide which coordinates to rhodium without displacement of a bidentate ligand. However, the product is not well characterized and the crystals contain clathrated sulfur dioxide.250... 

However, not all bidentate ligands form complexes of this stoichiometry. Although sulfur dioxide displaces CO from a binuclear rhodium(I) complex, the product (97) retains a rhodium-rhodium bond.1048 The complexes of (98) form primarily fac products when allowed to react with rhodium trichloride.1049 The strength of the rhodium-sulfur bond is also shown in the failure of diphos or... 

Reaction with sulfur dioxide yields a o--allylic rhodium-sulfur dioxide complex (1). 

The [Rh(NH3)5(OH)] cation, and its chromium(III) analog, react very rapidly with sulfur dioxide in aqueous solution, to give O-sulfito complexes, which lose sulfur dioxide on addition of acid. Rate constants for reaction of the rhodium(III), chromium(III), and cobalt(III) complexes [M(NH3)5(OH)] with sulfur dioxide are 1.8 x 10, 2.9 x 10, and 4.7 x 10 dm mol" s", respectively. This great similarity of rates contrasts with the situation in respect of formation of carbonato complexes, where formation rate constants show a marked dependence on the p a of the aquo form of the hydroxo substrate. 

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