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Octahedral Substitution: General Comments
[M(H
2
O)
6
]
n+
+ X
-
-----> [M(H
2
O)
5
X]
(n-x)+
+ H
2
O
Observations Implications
Rates quite similar to water exchange rates (H
2
O dissociation important factor)
Rate increases with change on anion ("Outer Sphere" Complex)
Rate unaffected by nucleophilicity, basicity, etc... (A and Ia paths thus unlikely)
Rate strongly dependent on M (suggests D or Id mechanism)
Kinetics 2
nd
order (does not eliminate any mechanism)
Intermediates not detected (very few cases, e.g. [Co(CN)
5
H
2
O]
2-
)
V
+ve, generally (careful !!!!)
