Catalytic Synthesis and Characterization of Biodegradable ...

Chapter 2
was first synthesized according to the method described in a previous report 29 with some
modifications as follows. A solution of cobalt acetate tetrahydrate (0.75 g, 3.0 mmol) in
methanol (200 mL) was added to a solution of the ligand, H2L 1 (1.81 g, 3.0 mmol), in CH2Cl2
(20 mL) via a cannula under an atmosphere of argon. A brick-red precipitate was observed
before all of the cobalt acetate solution was added. The residue on the wall of the reaction
flask was rinsed with methanol (20 mL), and the collected mixture was allowed to stir for a
further 15 min at room temperature, and then for 30 min at 0 . The solids were collected by
filtration and rinsed with cold (0 ) methanol (3 × 50 mL) before drying at 60 in a vacuum
for 24 h. The product L 1 -Co II was obtained in 95% yield. FT-IR (KBr): 1610 (s, C=N), 1595
(s, Ar–ring), 1527 (s, Ar–ring), 1254 (s, C–O), 572 cm -1 (w, Co–O). ESI-MS: m/z = 603.6
(C36H52N2O2Co) + .
(2,4-Dinitrophenolato)(R,R)-N,N�-(1,2-cyclohexene)bis(3,5-di-tert-butylsalicylideneiminat
o)]cobalt(III) (L 1 -Co III -dnp) was synthesized according to a method described in the
literature with modifications as follows. 22, 29 To a stirred solution of L 1 -Co II (1.48 g, 2.0 mmol)
in CH2Cl2 (150 mL), 2,4-dinitrophenol (0.368 g, 2.0 mmol, 1 equiv.) in CH2Cl2 (20 mL) was
added. The solution was stirred under dry oxygen at room temperature for 60 min. The
solvents were removed under vacuum to leave a crude dark solid in an approximately 100%
yield. The residue was further rinsed with a mixture of diethyl ether and hexane, and then
dried at 60 under vacuum for 24 h, yielding a dark needle-like crystal (1.47 g, 94%). FT-IR
(KBr): 1624 (s, C=N), 1610 (s, Ar–ring), 1566 (w, N=O), 1525 (s, Ar–ring), 1327 (s, N=O),
1252 (s, C–O), 1063 (w, C–N), 571 cm -1 (w, Co–O). C42H55N4O7Co (786.8): Calcd. C 64.11,
H 7.05, N 7.12; Found C 64.01, H 7.01, N 6.94. ESI-MS: m/z = 786.3, (C42H55N4O7Co) + ,
603.5 (C36H52N2O2Co) + , 183.2 (C6H3N2O5) - . Crystal data for L 1 -Co III -dnp: C42H55CoN4O20,
M = 786.83, Triclinic space group P 1.
a = 11.2788(13) Å, b = 14.4552(17) Å, c = 14.5806(17)
Å, � = 90.382(2), = 108.936(2), � = 111.141(2), V = 2076.5(4) Å 3 , Z = 2, Dcalcd = 1.258 g
cm -3 , (Mo K ) = 0.466 mm -1 . The data were collected at 293 K. Of the 11165 reflections,
7503 were unique (Rint = 0.017). The non-hydrogen atoms were anisotropically refined. The
hydrogen atoms were geometrically positioned and refined as riding atoms. The final cycle of
the full-matrix least-squares refinement converged with R = 0.0447 and Rw = 0.1040 based on
6046 reflections with I > 2(I).
(2,4-Dinitrophenolato)[N,N�-ethylenebis(3,5-di-tert-butylsalicylideneiminato)]cobalt(I
II) (L 2 -Co III -dnp) was synthesized by a procedure similar to that of L 1 -Co III -dnp. Yield: 89%.
IR (KBr): 1626 (s, C=N), 1596 (s, Ar–ring), 1569 (w, N=O), 1521 (s, Ar–ring), 1331 (s, N=O),
1257 (s, C–O), 1065 (w, C–N), 583 cm -1 (w, Co–O). C38H49N4O7Co (732.8): Calcd. C 62.29,
H 6.74, N 7.65; Found C 62.12, H 6.67, N 7.52. ESI-MS: m/z = 603.5 (C32H46N2O2Co) + ,
183.2 (C6H3N2O5) - .
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