Magnesium Promoted Active and Isoselective ROP of rac‐Lactide and ϵ‐Caprolactone Under Mild Conditions

A novel amidophosphine sulfur‐supported magnesium complex, [Ph2P(S)NCH2CH2N−(CH2CH2)O]Mg(C4H9)(THF)] (2) enabling efficient ring‐opening polymerization of rac‐lactide (LA) and ϵ‐caprolactone (CL) is disclosed. Achieved incredible selectivity for ROP of rac‐lactide for the first time using a magnesium catalyst affording isoselective PLA with a Pi value of 0.77. The polymerization of rac‐LA as well as ϵ‐CL proceeded under mild reaction conditions in absence of any external initiator, to yield corresponding polyesters with a great control over the molecular weight. The kinetic studies reveal that both sulfur and magnesium centers simultaneously work together to drive high yield and selectivity. A facile protocol for synthesis of PCL and PLA is developed via the ring‐opening polymerization of ϵ‐caprolactone and rac‐lactide under mild conditions in the presence of magnesium complex as the catalyst in the absence of any external initiator.