Iridium , hexaaqua complexes

Ru-O distances which are 212 pm in both complexes. For [Cp M(H20)3] (M = Rh, Ir) there is an even more dramatic increase of the water exchange rate constant (14 orders of magnitude) when compared with the corresponding hexaaqua-ion [M(H20)6p. This increase in reactivity is also related to a mechanistic changeover from an mechanism towards a more dissociative activation mode. In both cases the rhodium compound is significantly more reactive than the iridium one. 

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