42
W.Y. Fan et al. / Polyhedron 96 (2015) 38–43
obtained was carried out using Bruker-AXS Smart Apex CCD
Single-Crystal Diffractometers. Data were obtained at 100(2) K
chromatographed on silica gel (100–200 mesh). The product was
obtained by eluting out with 1:1 ethyl acetate:acetone. The
purified product was dried via rotary evaporation and redissolved
in acetone. X-ray quality crystals of 2 were grown by slow evapo-
ration of acetone solvent at room temperature. Yield: 34.7 mg,
67%. ESI-MS (m/z): 505.9 [CoCl(dmg)(dmgH)(NH2Ph(OCH3)3)]À.
Elemental analyses (%): C, 39.84 (expected 40.21); H, 5.59 (5.36);
N 12.00 (13.79).
with graphite monochromated Mo K
a radiation (k = 0.7107 Å).
Data collection was performed with SMART CCD system. Infrared
spectra were obtained on a Shimadzu IR-Prestige 21 spectrometer.
6.2. Electrochemical experiments
Cyclic voltammetry experiments were carried out with the
Metrohm Autolab PGSTAT302N potentiostat using a 3-electrode
system. The working electrode used was a 1 mm glassy carbon disk
(Cypress system), together with a platinum counter electrode
6.6. Synthesis of [Co(NCS)2]
KSCN (0.5756 g, 5.92 mmol) was added to
a solution of
(Metrohm) and
a silver wire miniature reference electrode
CoCl2Á6H2O (0.5788 g, 2.43 mmol) in 30 mL of acetone. The mix-
ture was stirred at room temperature for 2 h, and filtered to
remove the precipitate. The solvent was removed via rotary evap-
oration to obtain the product. Yield: 0.25 g, 38%. IR (DMF):
(Cypress Systems) immersed in acetonitrile. Before each scan, the
sample solution was purged with nitrogen gas and the working
electrodes were polished with alumina oxide (0.3 lm grain size)
on a Buehler Ultra-pad polishing cloth. The working electrodes
were subsequently washed with deionized water, acetone and
dried before use. The potentials were calculated with ferrocene
as an internal standard added into the sample solution at the start
of the measurements [13]. The sample solution consisted of 1 mM
of the cobalt complex and 0.1 M of the supporting electrolyte,
m
SCN = 2075 cmÀ1
.
6.7. Synthesis of [Co(dmgH)2(NCS)2]
Co(NCS)2 (0.2202 g, 1.26 mmol) was dissolved in 15 mL of ace-
tone, and dimethylglyoxime (0.3275 g, 2.82 mmol) was added to
the resulting blue solution. The mixture was stirred for 3.5 h in
the presence of air. The precipitated product was filtered by suc-
tion filtration, washed with cold acetone and air dried to give a
Bu4NPF6
(tetrabutylammonium
hexafluorophosphate)
in
acetonitrile.
For the controlled potential electrolysis experiment, a solution
of 1 mM of each of the cobalt complexes with 50 mM CH3COOH
in 0.1 M Bu4NPF6 in acetonitrile was electrolyzed at À1.60 V vs
Fc+/Fc in a gas-tight electrochemical cell. The experiment was car-
ried out three times enabling the average value for the current and
electrolysis period to be calculated. The content of the reaction
headspace was sampled with a 1 cm3 syringe and injected into a
residual analyzer (Pfeiffer PrismaPlus) tuned to monitor signals
at m/z = 2, corresponding to H2 production. The Faraday yield
(>80% for all complexes) was determined by calibrating to the sig-
nal produced by a known pressure of H2 from a H2 cylinder (Soxal,
99.99%).
brown product. Yield: 0.312 g, 61%. IR (DMF):
m .
SCN = 2109 cmÀ1
6.8. Synthesis of [Co(dmgH)2(py)(NCS)] (complex 3)
Co(dmgH)2(NCS)2 (0.4893 g, 1.20 mmol) was suspended in
25 mL of methanol and pyridine (0.2023 g, 2.56 mmol) was added.
The mixture was stirred at room temperature for 1 h. 40 mL of
water was added with stirring, and the suspension was cooled in
an ice bath for 10 min. The precipitated product was collected
via suction filtration, washed with 2:1 water/methanol, followed
by diethyl ether, and air dried to give an orange product. X-ray
quality crystals of 6 were grown via solvent diffusion of Et2O into
a concentrated solution of 6 in CHCl3 at room temperature. Yield:
6.3. Synthesis of [Co(dmgH)2Cl2]
0.2564 g, 50%. IR (DMF):
m
SCN = 2113 cmÀ1. ESI-MS (m/z): 424.7
CoCl2Á6H2O (0.50 g, 2.10 mmol) and dimethylglyoxime (0.49 g,
4.202 mmol) were added to 50 mL of acetone. The initial blue solu-
tion was aerated and stirred for 6 h before being left to dry over-
night under ambient conditions. A green powder was obtained.
Yield 0.62 g (82%).
[Co(NCS)(dmg)(dmgH)(py)]À. Elemental analyses (%): C, 39.84
(expected 39.44); H, 4.88 (4.49); N, 16.91 (19.71); S, 6.23 (7.52).
6.9. Synthesis of [Co(dmgH)2(py)Cl] (complex 4)
Co(dmgH)2Cl2 (0.1773 g, 0.491 mmol) was suspended in 10 mL
of methanol before adding pyridine (0.0396 g, 0.501 mmol). The
mixture was stirred at room temperature for 1.5 h and filtered to
remove the precipitate. The solvent of the resultant filtrate was
removed via rotary evaporation to obtain a brown product. Yield:
0.1036 g, 52%. ESI-MS (m/z): 404.9 [CoCl(dmg)(dmgH)(py)]À.
6.4. Synthesis of [Co(dmgH)2(NH2Ph)Cl] (complex 1)
Co(dmgH)2Cl2 (32.3 mg, 89.7
lmol) and aniline (9.2 mg,
98.7 mol) were added to 8 mL of methanol and stirred in air at
l
room temperature for 1 h. The initial yellow solution turned red
upon aniline addition. The crude product was filtered and the fil-
trate was column chromatographed on silica gel (100–200 mesh).
The product was obtained by eluting out with 100% ethyl acetate.
X-ray quality crystals of 1 were grown via solvent diffusion of
hexane into a concentrated solution of 1 obtained from column
chromatography at room temperature. Yield: 23.6 mg, 63%. ESI-MS
(m/z): 416.0 [CoCl(dmg)(dmgH)(NH2Ph)]À. Elemental analyses
(%): C, 44.36 (expected 40.25); H, 5.21 (5.07); N, 14.81 (16.77).
Acknowledgment
W.Y. Fan thanks NUS for a research grant 143-000-553-112.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
6.5. Synthesis of [Co(dmgH)2(NH2C6H2(OMe)3)Cl] (complex 2)
Co(dmgH)2Cl2 (36.7 mg, 101.9
lmol) and 3,4,5-trimethoxyani-
References
line (20.5 mg,112.1 mol) were added to 8 mL of methanol and
l
stirred in air at room temperature for one hour. The initial yellow
solution turned red upon the addition of 3,4,5-trimethoxyaniline.
The crude product was filtered and the filtrate was column