Synthesis of di-nitrogen Schiff-base complexes of methyltrioxorhenium(VII)
nitrogen and kept over 4 Å molecule sieves. All preparations and
manipulations were carried out under an oxygen- and water-free
nitrogen atmosphere using the standard Schlenk techniques.
121.16, 117.42 (aryl-C), 24.96 (ReCH3), 20.52, 17.43 (Ph-CH3) ppm;
IR (KBr) ν: 3091 3036 2994 2892 1633 1598 1504 1301 1197 1027
941 924 912 849 777 640 561 cm−1. MS (FAB): m/z (%) 197.0 (100)
[M+ − MTO]; elemental analysis calcd (%) C14H15N2O3Re (445.49):
C, 37.74; H, 3.39 N, 6.29. Found: C, 37.70; H, 3.59; N, 6.35.
c6: See Qiu et al.[34]
Physical Measurements
Melting points were determined on a Perkin XT-4 microscopic
analyzer. 1H NMR and 13C NMR spectra were measured in DMSO-
d6 or CDCl3 using a Bruker AC 400 spectrometer. IR spectra were
recorded on a Bruker Vector-22 spectrophotometer using KBr
pellets as the IR matrix. Mass spectra were obtained on a VG
ZAB-HS mass spectrometer. Elemental analyses were performed
on an Elementar Vario E1. Reaction products were analyzed
on a Shandong Lunan Ruihong gas chromatograph, SP-6800A,
equipped with an FID detector.
c7: See Qiu et al.[34]
c8: Yellow solid, yield 76%, m.p. 106 ◦C (decomposition); 1H
NMR (400 MHz, CDCl3) δ: 0.88–0.91 (m, 3H, CH3), 1.33–1.43 (m,
6H, CH2CH2CH2), 1.59 (s, 3H, ReCH3), 1.93–1.94 (m, 2H, CH2),
3.93∼3.96 (m, 2H, NCH2), 7.50–7.53 (m, 1H, PyH), 7.92–8.01 (m,
2H, PyH), 8.54 (s, 1H, HC N), 8.91–8.92 (d, 1H, PyH) ppm; 13C
NMR (100 MHz, CDCl3) δ: 158.98 (HC N), 149.93, 149.64, 139.65,
127.71, 127.29 (Py-C), 62.21, 31.39, 28.85, 26.75 (n-hexyl-C), 26.02
(ReCH3), 22.52, 14.02 (n-hexyl-C) ppm; IR (KBr) ν: 3094 3043 2962
2923 2857 1648 1599 1475 1300 1231 1022 936 911 855 785 645
517 cm−1. MS (ESI): 191.2 [M+ − MTO]; elemental analysis calcd
(%) C13H21N2O3Re (439.52): C, 35.52; H, 4.82; N, 6.37. Found: C,
35.24; H, 4.89; N, 6.42.
Synthesis of Di-nitrogen Schiff Bases and MTO Complexes
In a general procedure for the synthesis of the MTO complexes,
0.4 mmol of MTO was added to 0.4 mmol of the corresponding
di-nitrogen Schiff base in methanol (4 ml) at room temperature.
A yellow precipitate was formed rapidly. The precipitate was
isolated by filtration, washed with n-hexane and dried under
reduced pressure.
c9: yellow solid, yield 75%, m.p. 101 ◦C (decomposition); 1H
NMR (400 MHz, CDCl3) δ: 1.41–1.44 (m, 3H, cyclohexyl-H), 1.61 (s,
3H, ReCH3), 1.70–1.80 (m, 3H, cyclohexyl-H), 1.87–1.91 (m, 2H,
cyclohexyl-H), 2.01–2.04 (m, 2H, cyclohexyl-H), 3.69–3.74 (m, 1H,
cyclohexyl-H), 7.46–7.47 (d, 1H, PyH), 7.92–7.96 (m, 2H, PyH), 8.54
(s, 1H, HC N), 8.84–8.85 (d, 1H, PyH) ppm; 13C NMR (100 MHz,
CDCl3) δ: 157.67 (HC N), 149.80, 149.61, 138.79, 126.51, 126.19
(Py-C), 70.39, 33.12, 25.40, 25.16(cyclohexyl-C), 25.13(ReCH3)ppm;
IR (KBr) ν: 3069 3032 2977 2924 2851 1647 1601 1480 1451 1313
1057 937 916 844 772 646 519 cm−1. MS (ESI): 189.2 [M+ − MTO];
elemental analysis calcd (%) C13H19N2O3Re (437.51): C, 35.69; H,
4.38; N, 6.40. Found: C, 35.43; H, 4.49; N, 6.51.
c1: Yellow solid, yield 80%, m.p. 101 ◦C (decomposition); 1H
NMR (400 MHz, DMSO) δ: 1.89 (s, 3H, ReCH3),7.26–7.30 (m, 2H,
PhH), 7.42–7.45 (m, 2H, PhH), 7.53–7.56 (m, 1H, PyH), 7.95–7.99
(m, 1H, PyH), 8.14–8.16 (d, 1H, PyH), 8.61 (s, 1H, HC N), 8.72–8.74
(m, 1H, PyH) ppm; 13C NMR (100 MHz, DMSO) δ: 160.85 (HC N),
153.42, 149.62, 146.47, 146.44, 137.42, 125.95, 123.34, 123.25,
122.16, 116.10, 115.88 (aryl-C), 25.10 (ReCH3) ppm; IR (KBr) ν: 3114
3083 3012 2923 1954 1623 1594 1499 1242 1159 1022 944 932
908 849 785 644 551 cm−1. MS (ESI): 201.1 [M+ − MTO]; elemental
analysis calcd (%) for C13H12FN2O3Re (449.45): C, 34.74; H, 2.69; N,
6.23. Found: C, 34.92; H, 2.68 N, 6.24.
X-ray Structure Determination
Suitable crystal was obtained by slow solvent diffusion techniques
from methanol at room temperature. Diffraction data for complex
c5 were collected with a Bruker AXS APEX CCD diffractometer
equipped with a rotation anode at 113 (2) K using graphite-
monochromated Mo Kα radiation (λ = 0.71073 Å). Data were
collected over the full sphere and were corrected for absorption.
StructuresolutionswerefoundbythePattersonmethod. Structure
refinement was carried out by full-matrix least-squares on F2 using
SHELXL-97 with first isotropic and later anisotropic displacement
parameters for all non-hydrogen atoms.[35]
c2:Yellowsolid,yield:80%,m.p.112 ◦C(decomposition);1HNMR
(400 MHz, DMSO) δ: 1.89 (s, 3H, ReCH3),7.37–7.40 (m, 2H, PhH),
7.48–7.52 (m, 2H, PhH), 7.54–7.57 (m, 1H, PyH), 7.95–8.00 (m, 1H,
PyH), 8.15–8.17 (m, 1H, PyH), 8.61 (s, 1H, HC N), 8.72–8.73 (m, 1H,
PyH) ppm; 13C NMR (100 MHz, DMSO) δ: 161.58 (HC N), 153.58,
149.70, 149.14, 137.24, 131.11, 129.23, 125.92, 123.05, 121.72 (aryl-
C), 25.01 (ReCH3) ppm; IR (KBr) ν: 3074 3015 2953 1628 1592 1485
1293 1199 1093 945 933 915 859 780 643 557 cm−1. MS (ESI):
217.0 [M+ − MTO]; elemental analysis calcd (%) C13H12ClN2O3Re
(465.91): C, 33.51; H, 2.60 N, 6.01. Found: C, 33.34; H, 2.84; N, 6.07.
c3:yellowsolid, yield78%, m.p. 102 ◦C(decomposition);1HNMR
(400 MHz, DMSO) δ: 1.89 (s, 3H, ReCH3),7.30–7.34 (m, 2H, PhH),
7.54–7.57 (m, 1H, PyH), 7.61–7.65 (m, 2H, PhH), 7.95–8.00 (m, 1H,
PyH), 8.15–8.17 (m, 1H, PyH), 8.61 (s, 1H, HC N), 8.73–8.74 (m, 1H,
PyH) ppm; 13C NMR (100 MHz, DMSO) δ: 161.60 (HC N), 153.68,
149.73, 149.62, 137.18, 132.16, 125.88, 123.38, 121.57, 119.41 (aryl-
C), 24.99 (ReCH3) ppm; IR (KBr) ν: 3090 3066 3026 2910 2775 1618
15911482130710741011938912852786647557cm−1. MS(ESI):
261.0 [M+ − MTO]; elemental analysis calcd (%) C13H12BrN2O3Re
(510.36): C, 30.59; H, 2.37 N, 5.49. Found: C, 30.42; H, 2.48; N, 5.53.
c4: See Qiu et al.[34]
Catalytic Reaction
The catalytic reactions were carried out under continuous stirring
in a glass flask immersed in a water bath with temperature control.
In a typical experiment, 5 mmol of substrate, 7 ml of methanol and
0.05 mmol of the catalyst were mixed in the flask. Aqueous H2O2
(30 wt%, 10 mmol) was added to start the reaction. Samples were
taken out at regular time intervals. The products were analyzed by
gas chromatography in a capillary column using an FID detector.
c5: yellow solid, yield 76%, m.p. 104 ◦C (decomposition); 1H
NMR (400 MHz, DMSO) δ: 1.88 (s, 3H, ReCH3), 2.34 (s, 3H, PhCH3),
7.24–7.29 (m, 4H, PhH), 7.51–7.55 (m, 1H, PyH), 7.94–7.98 (m,
1H, PyH), 8.14–8.17 (m, 1H, PyH), 8.61 (s, 1H, HC N), 8.71 (d, 1H,
PyH) ppm; 13C NMR (100 MHz, DMSO) δ: 159.10 (HC N), 154.18,
149.58, 146.78, 137.07, 135.79, 131.84, 130.93, 127.35, 125.48,
Results and Discussion
Synthesis and Characterization
The route for the synthesis of the di-nitrogen Schiff bases and their
MTOcomplexesisshowninScheme 1. Thedi-nitrogenSchiffbases
were prepared smoothly according to the procedure described in
c
Appl. Organometal. Chem. 2011, 25, 54–60
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
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