Comparison Cp* With Cp
| Cp-metals and color | ||
|---|---|---|
| Compound | Cp | Cp* |
| Cp2Fe | yellow | yellow |
| CpTiCl3 | yellow | red |
| 2 | red-violet | |
| 2 | red | |
| Cp*Re(CO)3 | colorless | |
| Cp*Mo(CO)2CH3 | orange | |
The pentamethylcyclopentadienyl ligand (Cp*) is an important ligand in organometallic compounds arising from the binding of the five ring-carbon atoms in C5Me5−, or Cp*−, to metals. Relative to the more common cyclopentadiene (Cp) ligand, Cp* offers certain features that are often advantageous. Being more electron-rich, Cp* is a stronger donor and is less easily removed from the metal. Consequently its complexes exhibit increased thermal stability. Its steric bulk allows the isolation of complexes with fragile ligands. Its bulk also attenuates intermolecular interactions, decreasing the tendency to form polymeric structures. Its complexes also tend to be highly soluble in non-polar solvents.
Read more about this topic: Cyclopentadienyl Complex
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