Iridium complexes nitrito-nitro

One example will suffice to show the value of making use of reaction mechanisms in syntheses. This approach allowed us to prepare the new nitrito (M-ONO) complexes [M(ONO)(NH3)5] " of rhodium(iii) and of iridium(iii), although their nitro (M-NOj) compounds had been known for about a century. The success we had with this started with our detailed kinetic study of the apparently simple Reaction (14). 

This mechanistic concept for the formation of nitrito-complexes of cobalt(iii) suggests that other analogous metal systems should yield similar materials. However, the corresponding nitrito-complexes of rhodium(iii) and of iridium(iii) were not known. One reason that previous investigators had not been successful in preparing these is that the platinum group metal complexes are usually very slow to react and rather drastic reaction conditions had been used. As a result, the stable nitro-product rather than the kinetic nitrito-product was isolated. Since the formation of M-ONO does not involve M-O bond cleavage, the reaction as shown in (18) is expected to occur even under rather mild experimental conditions. This was found to be the case and salts of the new complexes [M(ONO)(NH3)5] where M = rhodium(iii), iridium(iii) or plati-num(iv) have been prepared. ... 

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