Catalytic Synthesis and Characterization of Biodegradable ...

Synthesis and Electrochemistry of Schiff Base Cobalt(III) Complexes and Their
Catalytic Activity for Copolymerization of Epoxide and Carbon Dioxide
(2,4-Dinitrophenolato)[(R,R)-N,N�-1,2-diphenylethylenebis(3,5-di-tert-butylsalicylide
neiminato)]cobalt(III) (L 3 -Co III -dnp) was synthesized by a method similar to that of
L 1 -Co III -dnp. Yield: 90%. IR (KBr): 1625 (s, C=N), 1597 (s, Ar–ring), 1555 (w, N=O), 1525
(s, Ar–ring), 1310 (s, N=O), 1269 (s, C–O), 1056 (w, C–N), 571 cm -1 (w, Co–O).
C50H57N4O7Co (884.9): Calcd. C 67.86, H 6.49, N 6.33; Found C 66.05, H 6.34, N 5.97.
ESI-MS: m/z = 883.8, (C50H57N4O7Co) + , 701.5 (C44H54N2O2Co) + , 183.2 (C6H3N2O5) - .
(2,4-Dinitrophenolato)[N,N�-2,2-dimethyl-1,3-propylenebis(3,5-di-tert-butylsalicylide
neiminato)]cobalt(III) (L 4 -Co III -dnp) was synthesized by a procedure similar to that of
L 1 -Co III -dnp. Yield: 95%. IR (KBr): 1625 (s, C=N), 1601 (s, Ar–CH), 1568 (s, N=O), 1522 (s,
Ar–ring), 1318 (s, N=O), 1261 (s, C–O), 1061 (w, C–N), 575 cm -1 (w, Co–O). C41H55N4CoO7
(774.8): Calcd. C 63.55, H 7.15, N 7.23; Found C 63.39, H 7.06, N 7.14. ESI-MS: m/z =
774.1 (C41H55N4O7Co) + , 591.4 (C35H52N2O2Co) + , 183.1 (C6H3N2O5) - .
Typical Copolymerization Procedure
A mixture of the cobalt complex(0.1 mmol) and tetra(n-butyl)ammonium bromide
(Bu4NBr)(0.1 mmol) was dissolved in 3.5 mL of racemic propylene oxide (rac-PO) under a
nitrogen atmosphere. The mixture was injected into a high pressure reactor equipped with a
magnetic stirrer under a CO2 atmosphere. The reactor with a 2.5 MPa CO2 pressure was
placed in an oil bath. The mixture was stirred at 40 for the allotted reaction time and then
vented in a fume hood. A small aliquot of the polymerization mixture was sampled from the
reactor for the 1 H NMR spectroscopic analysis. The remaining polymerization mixture was
then dissolved in CH2Cl2, quenched with 5% HCl in methanol, and transferred to a
pre-weighed vial. The product mixture was dried under vacuum to a constant weight. The
crude yield was carefully determined after subtracting the catalyst weight. The product was
then dissolved in CH2Cl2 and precipitated from methanol again. The polymer was collected
by filtration and dried under vacuum to a constant weight. Analytical data for the typical
product (with the L 1 -Co III -dnp catalyst) was as follows. IR (KBr): 1749 (s, C=O), 1609 (w,
Ar-ring), 1580 (w, N=O), 1531 (w, Ar-ring), 1314 (s, N=O), 1235 cm -1 (s, C-O). 1 H NMR
(500 MHz, CDCl3, ppm): = 1.24 (–CHCH3), 4.19 (–CH2CH–), 4.90 (–CH2CH–). 13 C NMR
(400 MHz, CDCl3, ppm): = 16.1 (–CH3), 72.3 (–CH2–), 69.1 (–CH–), 154.1 (C=O) .
References
1. J. K. Lee, S. W. Park, J. W. Lee, M. R. Kim, Polym. Int. 2006, 55, 849.
2. H. Sugimoto, S. Inoue, J. Polym. Sci., Part A: Polym. Chem. 2004, 42, 5561.
3. D. J. Darensbourg, R. M. Mackiewicz, A. L. Phelps, D. R. Billodeaux, Acc. Chem. Res.
2004, 37, 836.
4. M. Cheng, E. B. Lobkovsky, G. W. Coates, J. Am. Chem. Soc. 1998, 120, 11018.
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