D. Schultz and J. R. Nitschke
red overnight at room temperature. The solution was then concentrated
to approximately 1 mL under dynamic vacuum and was triturated with
tert-butanol (30 mL). The dark red solid that precipitated was filtered
hydrate (0.0048 g, 0.017 mmol), and tetrakis(acetonitrile)copper(I) tetra-
fluoroborate (0.0083 g, 0.026 mmol) in deuterium oxide (0.5 mL) were
added to an NMR tube with a Teflon screw cap. All materials dissolved
to give a dark red/purple solution. The atmosphere in the tube was
purged of oxygen by means of three evacuation/argon-fill cycles. The re-
action was followed by using NMR spectroscopy, and the minority spe-
cies present initially disappeared over the course of 12 h at 323 K. After
this time, only signals corresponding to complexes 1 and 2 were observed
in the NMR and ESIMS spectra.
1
and dried under dynamic vacuum (0.216 g, 91%). H NMR (400 MHz,
3
00 K, D
2
O): d=9.01 (s, 2H; imine), 7.95 (t, J=7.7 Hz, 2H; 4-pyridine),
7
.84 (d, J=7.6 Hz, 2H; 3-pyridine), 7.55 (d, J=8.6 Hz, 2H; phenyl), 7.46
(
(
d, J=7.6 Hz, 2H; 5-pyridine), 7.26 (d, J=8.6 Hz, 2H; phenyl), 2.04 ppm
1
3
s, 6H; CH
3 2
); C NMR (100.62 MHz, 300 K, D O): d=161.3, 159.0,
1
50.3, 149.5, 143.2, 139.2, 129.5, 127.6, 127.0, 123.0, 24.9 ppm; ESIMS:
À
m/z: À614.1 [M ].
Selective substitution of ethanolamine by sulfanilic acid within complex 1
in the presence of complex 2 (Scheme 3): Sulfanilic acid (0.0073 g,
0.042 mmol) was added to a mixture of 1 (0.0101 g, 0.021 mmol) and 2
(0.0118 g, 0.021 mmol) in deuterium oxide (0.5 mL) and the atmosphere
in the tube was purged of oxygen by means of three evacuation/argon-fill
cycles. The tube was left overnight at room temperature, after which only
signals corresponding to 2, 3, and protonated ethanolamine were ob-
served in the NMR (Figures S1 and S2 in the Supporting Information)
and ESIMS spectra. This mixture was stable at 508C for 10 d.
Iron complex 4: Pyridine-2,6-dicarbaldehyde (0.0292 g, 0.216 mmol),
ethanolamine (0.0264 g, 0.432 mmol), and iron(II) sulfate heptahydrate
(
0.0301 g, 0.108 mmol) were added to a 10 mL Schlenk flask containing
water (3 mL). All starting materials dissolved to give a dark purple solu-
tion. The flask was sealed and the atmosphere was purged of oxygen by
means of three evacuation/argon-fill cycles. The reaction was stirred for
2
4 h at room temperature before volatile compounds were removed
under dynamic vacuum to give a dark purple product, which was deter-
1
mined to be pure from its NMR spectrum (0.0642 g, 99%). H NMR
Selective simultaneous formation of complexes 1 and 4 (Scheme 4): Pyri-
dine-2,6-dicarbaldehyde (0.0095 g, 0.07 mmol), 6-methylpyridine-2-carbal-
dehyde (0.0085 g, 0.07 mmol), ethanolamine (0.0129 g, 0.21 mmol),
iron(II) sulfate heptahydrate (0.0096 g, 0.035 mmol), and tetrakis(aceto-
nitrile)copper(I) tetrafluoroborate (0.011 g, 0.035 mmol) in deuterium
oxide (0.5 mL) were added to an NMR tube with a Teflon screw cap. All
materials dissolved to give a dark red/purple solution. The atmosphere in
the tube was purged of oxygen by means of three evacuation/argon-fill
cycles. The tube was left overnight at room temperature, after which only
signals corresponding to complexes 1 and 4 were observed in the NMR
spectrum (Figures S3 and S4 in the Supporting Information).
(
(
(
400 MHz, 300 K, D
brs, 8H; NCH CH
100.62 MHz, 300 K, D
2
O): d=8.54 (brs, 10H; imine, 3,4,5-pyridine), 3.07
1
3
2
2
OH), 2.79 ppm (brs, 8H; NCH
2 2
CH OH); C NMR
2
+
O): d=171.8, 160.3, 138.2, 128.5, 60.0, 59.0 ppm;
2
ESIMS: m/z: 249.1 [M ].
Iron complex 5: Pyridine-2-carbaldehyde (0.2386 g, 2.228 mmol), ethanol-
amine (0.1366 g, 2.236 mmol), and iron(II) sulfate heptahydrate (0.2040 g,
0
.734 mmol) were added to a 50 mL Schlenk flask containing methanol
(
5 mL). All materials dissolved to give a purple solution. The flask was
sealed and the atmosphere was purged of oxygen by means of three evac-
uation/argon-fill cycles. The reaction was stirred overnight at room tem-
perature before volatile compounds were removed under dynamic
vacuum to give a dark purple product, which was determined to be pure
from its NMR spectrum (0.441 g, 100%). Signals corresponding to the
fac and mer diastereomers of the complex were observed in the NMR
Kinetic substitution of ethanolamine by sulfanilic acid within complex 1
(Scheme 4): Sulfanilic acid (0.0121 g, 0.07 mmol) was added to the mix-
ture of complexes 1 and 4 obtained in the previous experiment and the
atmosphere in the tube was purged of oxygen by means of three evacua-
tion/argon-fill cycles. Immediately after addition of sulfanilic acid (ca.
5 min) only signals corresponding to complexes 3 and 4 were observed in
the NMR spectra (Figures S5 and S6 in the Supporting Information).
These two products were observed to decrease in intensity over the
course of several hours at 258C, with an estimated half-life of about 24 h.
spectra in an almost statistical ratio of 1:3; a slight excess of the mer
1
form was noted. H NMR (400 MHz, 300 K, D
2
O): d=9.25 (s, 1H; mer-
imine), 9.18 (s, 1H; mer-imine), 9.13 (s, 1H; mer-imine), 9.06 (s, 0.84H;
fac-imine), 8.08–8.33 (m, 8H; mer, 1.68H; fac), 7.44–7.59 (m, 3H; mer,
0
1
1
1
1
.84H; fac), 7.31 (d, 1H; mer), 7.12 (d, 0.84H; fac), 3.20–3.96 ppm (m,
1
3
13
2H; mer, 3.36H; fac); C NMR (100.62 MHz, 300 K, D
2
O): d=173.9,
Multiple products were observed in the C NMR spectrum (Figure S7 in
1
the Supporting Information, the H NMR spectrum was extremely
73.8, 173.5, 173.4, 159.3, 159.0, 158.7, 158.5, 155.8, 155.5, 155.2, 154.9,
39.5, 139.3, 139.2, 139.1, 130.03, 129.98, 129.7, 129.6, 128.8, 128.6, 128.5,
I
broad), and peaks in the ESIMS spectrum were assigned to multiple Cu
II
2
+
and Fe complexes containing mixtures of both ethanolamine and sulfa-
28.4, 61.2, 60.8, 60.5, 59.4, 59.1, 58.9 ppm; ESIMS: m/z: 253.4 [M ].
nilate residues.
Iron complex 6: Pyridine-2-carbaldehyde (0.008 g, 0.075 mmol), sulfanilic
acid (0.013 g, 0.075 mmol), sodium bicarbonate (0.0063 g, 0.075 mmol),
and iron(II) sulfate heptahydrate (0.007 g, 0.025 mmol) in deuterium
oxide (0.5 mL) were added to an NMR tube with a Teflon screw cap. All
materials dissolved to give a purple solution. The atmosphere in the tube
was purged of oxygen by means of three evacuation/argon-fill cycles. The
reaction was monitored by means of NMR spectroscopy, and after 24 h
at room temperature only signals corresponding to complex 6 were ob-
served in the spectra. Signals corresponding to the fac and mer diastereo-
mers of the complex were observed in the NMR spectra in an almost
Selective simultaneous formation of complexes 2 and 5 (Scheme 5):
Tris(2-aminoethyl)amine (0.0021 g, 0.014 mmol), pyridine-2-carbaldehyde
(
0.0091 g, 0.084 mmol), ethanolamine (0.0026 g, 0.042 mmol), and iron(II)
sulfate heptahydrate (0.0076 g, 0.027 mmol) in deuterium oxide (0.5 mL)
were added to an NMR tube with a Teflon screw cap. All materials dis-
solved to give a dark purple solution. The atmosphere in the tube was
purged of oxygen by means of three evacuation/argon-fill cycles. The
tube was left overnight at room temperature, after which only signals cor-
responding to complexes 2 and 5 were observed in the NMR spectra
(
Figures S8 and S9 in the Supporting Information) and ESIMS spectra.
statistical ratio of 1:3; a slight excess of the mer form was noted.
1
H NMR (400 MHz, 300 K, D
H; mer-imine), 8.99 (s, 1H; mer-imine), 8.96 (s, 0.79H; fac-imine), 8.73
d, 1H; mer), 8.58 (m, 1H; mer, 0.79H; fac), 8.41 (m, 1H; mer, 0.79H;
2
O): d=9.41 (s, 1H; mer-imine), 9.37 (s,
Selective substitution of ethanolamine by sulfanilic acid within iron com-
plex 5 (Scheme 5): Sulfanilic acid (0.0073 g, 0.042 mmol) was added to
the mixture of complexes 2 and 5 obtained in the previous experiment
and the atmosphere in the tube was purged of oxygen by means of three
evacuation/argon-fill cycles. The tube was left overnight at room temper-
ature, after which, the signals corresponding to complexes 2, 6, and pro-
tonated ethanolamine predominated the NMR spectra (Figures S10 and
S11 in the Supporting Information ).
1
(
fac), 8.29 (t, 1H; mer), 8.13 (d, 1H; mer), 8.07 (t, 1H; mer), 7.99 (m, 1H;
mer, 0.79H; fac), 7.73 (m, 3H; mer, 1.58H; fac), 7.60 (m, 3H; mer), 7.48
(
0
m, 3H; mer), 7.33 (d, 2H; mer), 6.95 (d, 2H; mer), 6.76 (m, 2H; mer,
1
3
.79H; fac), 6.16 (d, 2H; mer), 5.46 ppm (d, 1.58H; fac); C NMR
O): d=176.7, 176.3, 175.4, 174.3, 158.8, 158.7,
(
100.62 MHz, 300 K, D
2
1
1
1
58.4, 158.1, 156.3, 153.5, 152.5, 150.1, 149.0, 144.1, 143.5, 140.5, 139.92,
39.87, 139.6, 139.4, 132.4, 132.04, 132.01, 131.5, 130.4, 130.0, 129.8, 129.7,
28.0, 127.56, 127.59, 127.2, 127.0, 123.3, 122.8, 122.6, 122.3, 116.0 ppm.
Selective simultaneous formation of complexes 1 and 2 (Scheme 2):
Tris(2-aminoethyl)amine (0.0025 g, 0.017 mmol), pyridine-2-carbaldehyde
Acknowledgements
(
0
0.0055 g, 0.051 mmol), 6-methylpyridine-2-carbaldehyde (0.0062 g,
.051 mmol), ethanolamine (0.0031 g, 0.051 mmol), iron(II) sulfate hepta-
This work was made possible by the Swiss National Science Foundation.
We thank P. Perrottet for mass spectrometric analyses.
3664
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 3660 – 3665