Cationic and charge-neutral calcium tetrahydroborate complexes and their use in the controlled ring-opening polymerisation of rac-lactide

The first cationic main group tetrahydroborate complexes are reported. [Ca(BH4)(THF)(5)][BPh4] and the charge neutral (Tp(tBu,Me))Ca(BH4)(THF) are initiators for the living ring opening polymerization of rac-lactide, the latter producing PLA with high levels of heterotactic enrichment. These represent a new class of ROP initiators for main group metals.