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User:Benjah-bmm27/degree/3/PGP

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Organometallic Chemistry and Homogeneous Catalysis 2, PGP

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Feedstocks

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aldehydes from alkenes, by Rh catalysis (hydroformylation)
methanol by Cu catalysis
alkanes and alkenes by Fe catalysis (Fischer-Tropsch)
    • Methanol
alkanes, alkenes, aromatics by zeolite catalysis
formaldehyde and ethers, e.g. MTBE
acetic acid by Ir catalysis (Cativa process)

Hydroformylation

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Hydroformylation is formally the addition of a molecule of formaldehyde across the C=C double bond of an alkene.

R2C=CR2 + HCHO → R2CH–CR2CHO

Formaldehyde isn't actually used. Synthesis gas (a mixture of hydrogen and carbon monoxide, H2 + CO) is used instead.

Regioselectivity

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Hydroformylation of monosubstituted alkenes (vinyl alkanes, if you like: RHC=CH2) can give two possible regioisomers: linear (n) and branched (iso)

Cobalt carbonyl catalysis of hydroformylation

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  1. Dissociation of a CO ligand generates HCo(CO)3: Co(I), d8, 16 e, vacant coordination site
  2. Coordination of alkene generates HCo(CO)3(alkene): Co(I), d8, 18 e, coordinatively saturated
  3. Migration of hydride from Co to alkene C generates Co(CO)3(alkyl): Co(I), d8, 16 e, coordinatively unsaturated
  4. Coordination of a new CO ligand to Co gives Co(CO)4(alkyl): Co(I), d8, 18 e, coordinatively saturated
  5. Migratory insertion of alkyl (formally R) to one of the CO ligands gives Co(CO)3(acyl): Co(I), d8, 16 e, coordinatively unsaturated
  6. Oxidative addition of H2 generates H2Co(CO)3(acyl): Co(III), d6, 18 e, coordinatively saturated, octahedral molecular geometry
  7. Reductive elimination of acyl hydride (aldehyde!) regenerates HCo(CO)3

Acetic acid synthesis by methanol carbonylation

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MMA synthesis

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