Hydroformylation (oxo process) template

Heck–Breslow cycle of cobalt hydroformylation: loss of CO from HCo(CO)₄, alkene coordination, 1,2-insertion into Co–H (linear alkyl), CO uptake and alkyl migration to CO, oxidative addition of H₂ and reductive elimination of the aldehyde; linear vs branched selectivity; key step: alkyl migration to CO.

What the template shows

• Heck–Breslow cycle: HCo(CO)₄ adds H and CHO across an alkene; CO and H₂ (syngas) in, aldehyde out
• Overall: R–CH=CH₂ + CO + H₂ → R–CH₂CH₂–CHO (linear) + R–CH(CH₃)–CHO (branched) (cat. HCo(CO)₄, 110–180 °C, 200–300 bar)
• HCo(CO)₃(η²-alkene)
• HCo(CO)₄ ⇌ HCo(CO)₃ + CO
• Co–H adds with Co on the terminal carbon (anti-Markovnikov), giving the linear aldehyde; Co on C2 gives the branched aldehyde RCH(CH₃)CHO.
• Linear : branched is about 3–4 : 1 with HCo(CO)₄, but about 10 : 1 or better with HRh(CO)(PPh₃)₃ and excess PPh₃, whose bulk favours the linear alkyl.
• The Rh catalyst runs the same cycle under mild conditions (about 100 °C, 10–20 bar): the low-pressure oxo process.
• Co(I)/Co(III): oxidative addition of H₂ to the 16 e⁻ acyl and reductive elimination of the aldehyde regenerate HCo(CO)₃.
• Key step: alkyl migration to CO (migratory insertion)
• In RCH₂CH₂Co(CO)₄ (18 e⁻) the Co–C bond electrons carry the alkyl onto a cis CO ligand, and a C≡O π bond moves onto oxygen: the 16-electron acyl. The CO is drawn Co⁻–C≡O⁺ so every atom keeps an octet; the other CO ligands are not drawn.
• CO ligands are named in the captions, not drawn · 16/18 e⁻ by the neutral (covalent) count · every part of this figure is editable

Drawn with 39 atoms, 8 arrows, 67 shapes – every one editable in MolDraw.

Sources

• Housecroft & Sharpe, Inorganic Chemistry, 5th ed., Pearson 2018, ch. 25 Textbook
• Crabtree, The Organometallic Chemistry of the Transition Metals, 6th ed., Wiley 2014, ch. 9 Textbook