Compound (salfen)Zr(OiPr)2 (salfen = N,N’-bis(2,4-di-tert-butylphenoxy)-1,1’-ferrocene-diimine) contains a redox active ferrocene unit and can be employed in switchable catalysis. The switch between the reduced, (salfen)Zr(OiPr)2 ([Zr]red), and oxidized form, (salfen)Zr(OiPr)2[BArF] ([Zr]ox, BArF= tetrakis(3,5-bis(trifluoromethyl)phenyl)borate), was studied by cyclic voltammetry and redox reactions. Ring opening polymerization studies show an orthogonal selectivity toward cyclic esters and ethers: [Zr]red can polymerize cyclic esters, while [Zr]ox polymerizes epoxides. Diblock, PLA-PCHO, and triblock, PLA-PCHO-PLA, copolymers were prepared and characterized by size exclusion chromatography and NMR spectroscopy. The polymerization rates were compared with those of (salfan)Zr(OtBu)2 (salfan = 1,1′-di(2-tert-butyl-6-N-methylmethylenephenoxy)ferrocene), which contains a saturated linker between the ferrocene and aryloxides units. A geometry change was observed when using (salfen)Zr(OiPr)2 during lactide polymerization, and it will also be discussed.

Redox switchable (co)polymerization reactions with a zirconium compound

2019 Fall National Meeting

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