Zwitterionic Iron(II) Compounds: Synthesis, Reactivity, and Catalytic Carbonylative Polymerization of Cyclic Ethers

The generality of the zwitterionic strategy to design catalysts for carbonylative polymerization of cyclic ethers has been validated by applying it to Fe. The acyl group of the zwitterionic Fe catalyst is less electrophilic than that of the zwitterionic Ni catalyst, but the thermal stability of the octahedral Fe complex allows the copolymerization to be carried out at relatively high temperatures. The selectivity for carbonylative enchainment achieved at such temperatures with the Fe catalyst is markedly better than that previously achieved with the Ni analogs at room temperature.