Replacement by Nucleophilic Attack

Ligand Replacement by Nucleophilic Attack A. The Simple Rate Law and Nature of the Reactions 

The vast majority of ligand-replacement reactions fit into this category. Most conform to a simple two-term rate law of Eq. (1)  

The ligand-dependent pathway, represented by the 2[Y] term, is readily understood as a nucleophilic attack of Y at the metal ion. Thus, increasing steric hindrance at the metal atom markedly retards the reaction, exemplified by reaction (2), in which bulkier iV-substituents, R, on the diethylenetriamine (dien) ligand reduce 2 (9)- 

A counterbalancing example of the retarding effects of bulky entering groups is afforded by reaction (3), in which the use of amines (am) of increasing size progressively diminishes the 2 values (10). 

A second classical test for detecting associative or dissociative pathways is the effect of electronic charge on substitution rates. A number of comparative studies have revealed only small changes in rate con- 

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The amino group of 6-(dimethylamino]fulvene is itself readily replaced by nucleophilic attack. The following reactions serve as examples [73,247] ... 

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