Controlled ring-opening polymerisation of cyclic phosphates, phosphonates and phosphoramidates catalysed by heteroleptic BHT-alkoxy magnesium complexesElectronic supplementary information (ESI) available: Synthetic and polymerization experimental details, NMR spectra. See DOI: 10.1039/c7py01472d

We report here that the heteroleptic BHT-Mg(OR) complex, i.e. [(BHT)Mg(OBn)(THF)] 2 ( Mg3 ), represents an effective and versatile ring-opening polymerisation (ROP) catalyst for several cyclic ethylene phosphate monomers (CEPMs), such as ethylene phosphates with methoxy- ( MeOEP , 1 ), isopropoxy- ( i PrOEP , 2 ), and tert -butoxy- ( t BuOEP , 3 ) substituents, N , N -diethyl ethylene phosphoramidate ( Me 2 NEP , 4 ) as well as ethyl ( EtPPn , 5 ) and tert -butyl ( t BuPPn , 6 ) ethylene phosphonates. Mg3 retains its catalytic activity over a broad temperature range from −50 to 100 °C and efficiently carries out the fast and controlled polymerisation of CEPMs with sterically unhindered alkoxy groups with less than 1% chain branching even at near-complete conversion. Compared with ROP catalysed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene ( TBD ), Mg3 performs much better in the polymerisation of CEPMs with bulky groups and of monomers sensitive to strong nucleophiles, such as t BuOEP . BHT-Mg-alkoxides are readily available and effective ROP catalysts for cyclic ethylene phosphate monomers and outperform conventional organocatalysts in versatility.