A bulkier ligand (with large cone-angle) tends to have a higher dissociation rate than smaller ligands and electron-rich metal-centers tend to accelerate the “oxidative addition”, a key-step in the catalytic cycle.


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Note added at 1 час (2013-07-12 15:03:44 GMT)
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Bulky ligands[edit]

Bulky ligands are used to control the steric properties of a metal center. They are used for many reasons, both practical and academic. On the practical side, they influence the selectivity of metal catalysts, e.g., in hydroformylation. Of academic interest, bulky ligands stabilize unusual coordination sites, e.g., reactive coligands or low coordination numbers. Often bulky ligands are employed to simulate the steric protection afforded by proteins to metal-containing active sites. Of course excessive steric bulk can prevent the coordination of certain ligands.