Computational Insight into the Role of Alkoxide Initiator and Oxidation State in Ring Opening Polymerization of ε-Caprolactone Catalyzed by Bis(imino)pyridine Iron Complexes

Ortuño, M. A.; Dereli, B.; Delle Chiaie, K. R.; Biernesser, A. B. ; Byers, J. A.; Cramer, C. J.
Inorg. Chem. 2018, 57, 2064 (doi:10.1021/acs.inorgchem.7b02964).

Density functional theory (DFT) is employed to characterize in detail the mechanism for the ring-opening polymerization (ROP) of ε-caprolactone catalyzed by iron alkoxide complexes bearing redox-active bis(imino)pyridine ligands. The combination of iron with the non-innocent bis(imino)pyridine ligand permits comparison of catalytic activity as a function of oxidation state (and overall spin state). The reactivities of aryl oxide versus alkoxide initiators for the ROP of ε-caprolactone are also examined. An experimental test of a computational prediction reveals an Fe(III) bis(imino)pyridine bis-neopentoxide complex to be competent for ROP of ε-caprolactone.