Organometallic Chemistry and Homogeneous Catalysis 1, RBB
editBackground
editHistorical use of transition metal catalysts
editSabatier-Senderens process
edit- CO + 3H2 → CH4 + H2O
- heterogeneous Ni catalyst
- Named for Jean-Baptiste Senderens and Paul Sabatier, who developed it in 1902
- Sabatier also famous for the closely-related Sabatier reaction
- CO + H2 → C1 - C30 alkanes and alkenes
- heterogeneous Co or Fe catalysts
Mechanistic aspects of homogeneous catalysis
editLigand effects
editElectronic effects
editSteric effects
editLigand association and dissociation
editMigratory insertion and elimination
editThe catalytic cycle
editLutetium hydride catalysis
edit- In 1985, Tobin J. Marks found that the organolutetium compound (Cp*2LuH)2 has a far higher turnover frequency (TOF) than transition metal catalysts
- J. Am. Chem. Soc. (1985) 107, 8111–8118.
| precatalyst | name | mol prod. / mol cat. |
|---|---|---|
| RhCl(PPh3)3 | Wilkinson's catalyst | 650 |
| [Rh(COD)(PPh3)2]+ | Osborn's catalyst | 4000 |
| [Ir(COD)(py)(PCy3)]+ | Crabtree's catalyst | 6500 |
| (Cp*2LuH)2 | ? | 120000 |
- Lu(III) is hard and very electropositive
- Does not undergo oxidative addition of H2 to form Lu(V)H2
- Lanthanide contraction makes it very hard to remove electrons from Lu(III)
- Impractical due to extreme air and moisture sensitivity...
- ...but it may be possible to get the same mechanism with titanocene catalysts
Alkene isomerisation
editAlkene oxidation – the Wacker process
editAlkene polymerisation
editHeterogeneous catalysis
edit- Ziegler–Natta catalysts: TiClx / Al-R catalysis
- Phillips catalysts: CrOx on silica
Modern homogeneous catalysis
edit- Kaminsky catalysts: metallocene-based, e.g. zirconocenes
Co-catalyst: methylaluminoxane
editSpecific applications
edit- Ring-opening metathesis polymerisation of cyclic olefins
- Ring-closing metathesis