Cobaltcarbonyl complexes - Tunable catalysts for the carbonylation of epoxides

Poly(hydroxyalkanoates) establish an important family of thermoplastic materials which can be synthesized from epoxides and CO either directly through a recently discovered, alternating copolymerization reaction or via a lactone intermediate. A mixture of Co(acac)₃ and Et₃A1 is a known but poorly understood catalyst system for the formation of low molecular weight PHB (polyhydroxybutyrate) from propylene oxide and CO. We investigated this catalyst system by online ATR-IR spectroscopy and found it to produce mixtures of β-butyrolactone (primary product) and polyester. In contrast to this less selective mixture we present here a new catalyst comprising Co ₂(CO)₈/R₃Al for the highly chemo- and regioselective β-butyrolactone formation from propylene oxide and carbon monoxide.