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152.81, 140.69, 136.03, 124.97, 123.61, 121.25, 66.07, 56.26, 54.99, 2.453 (m, 2 H, morpholine ring), 2.202 (s, 6 H, CH3), 2.067 (s, 6 H,
53.65, 48.03, 35.04, 34.18, 31.77, 29.63 ppm.
CH3) ppm.
H2L2 and H2L3: These ligands were prepared in 63 and 71 % yields,
respectively, by the procedure outlined for H2L1 by using 2,4-di-
methylphenol (1.221 g, 10 mmol) or 2-tert-butyl-4-methylphenol
(1.642 g, 10 mmol) in place of 2,4-di-tert-butylphenol.
[MoVIO2(L3)] (3): Complex 3 was prepared similarly to 1 with H2L3
instead of H2L1 (0.483 g,
1
mmol), yield 0.401
g (66 %).
C30H44MoN2O5 (608.64): calcd. C 59.20, H 7.29, N 4.60; found C
59.11, H 6.88, N 4.48. Crystals of 3 suitable for X-ray diffraction were
grown through the slow evaporation of a MeCN solution at room
Data for H2L2: C24H34N2O3 (398.538): calcd. C 72.33, H 8.60, N 7.03;
temperature. IR: νmax = 2868, 2915, 2956 (alkyl), 1462, 1442, 1306,
˜
found C 72.13, H 8.52, N 7.12. IR: νmax = 3155 (–OH), 2958, 2913,
˜
1243, 1229, 1149, 1116, 923 (MoO2)asym, 901 (MoO2)sym, 863, 820,
2861 (alkyl), 1486, 1377, 1308, 1283, 1218, 1115, 1071, 862, 768,
1
756, 598, 569, 552 cm–1. H NMR ([D6]DMSO): δ = 6.957–6.953 (d, 2
741, 618, 580 cm–1 1H NMR ([D6]DMSO): δ = 9.203 (s, 2 H, –OH),
.
H, Ar), 6.872–6.869 (d, 2 H, Ar), 4.091–4.056 (d, J = 14.0 Hz, 2 H,
NCH2Ar), 3.998–3.965 (d, J = 13.2 Hz, 2 H, NCH2Ar), 3.830–3.774 (t,
2 H, NCH2CH2), 3.722–3.667 (t, 2 H, NCH2CH2), 3.910–3.878 (m, 2 H,
morpholine ring), 3.318–3.316 (m, 2 H, morpholine ring), 2.961–
2.932 (m, 2 H, morpholine ring), 2.741–2.711 (m, 2 H, morpholine
ring), 2.218 (s, 6 H, CH3), 1.332 [s, 18 H, –C(CH3)3] ppm.
6.807–6.802 (d, 2 H, Ar), 6.727–6.724 (d, 2 H, Ar), 3.655–3.632 (t, 4
H, NCH2CH2), 3.326 (s, 4 H, NCH2Ar), 2.570–2.540 (m, 2 H, morph-
oline ring), 2.483–2.454 (m, 2 H, morpholine ring), 2.293–2.264 (m,
2 H, morpholine ring), 2.136 (s, 6 H, CH3), 2.077 (s, 6 H, CH3) ppm.
13C NMR (CDCl3): δ = 152.16, 131.35, 128.44, 127.80, 125.49, 121.54,
60.09, 55.65, 54.99, 53.63, 47.95, 20.47, 16.03 ppm.
Oxotransfer Activity: A solution of benzoin (1.06 g, 5 mmol), cata-
lyst (0.0030 g, 5.72 μmol) and DMSO (1 mL) in acetonitrile (10 mL)
was maintained at 80 °C for 24 h. The progress of the reaction was
monitored by HPLC with MeCN/H2O/TFA mixtures (60:40:0.02).
Data for H2L3: C30H46N2O3 (482.69): calcd. C 74.65, H 9.61, N 5.80;
found C 74.54, H 9.52, N 5.82. IR: ν
= 3190 (–OH), 2872, 2910,
˜
max
2953 (alkyl), 1478, 1445, 1356, 1286, 1231, 1180, 1118, 1023, 862,
812, 773, 548, 519, 502 cm–1 1H NMR ([D6]DMSO): δ = 9.451 (s, 2
.
H, –OH), 6.900–6.894 (d, 2 H, Ar), 6.779–6.763 (d, 2 H, Ar), 3.744–
3.717 (t, 4 H, NCH2CH2), 3.506 (s, 4 H, NCH2Ar), 3.341–3.324 (m, 4 H,
morpholine ring), 2.675–2.645 (m, 2 H, morpholine ring), 2.439–
2.318 (m, 2 H, morpholine ring), 2.168 (s, 6 H, CH3), 1.130 [s, 18 H,
–C(CH3)3] ppm. 13C NMR (CDCl3): δ = 152.90, 136.76, 128.87, 127.34,
127.22, 122.09, 66.07, 55.76, 54.89, 53.48, 47.98, 34.72, 29.58, 20.83
ppm.
Molybdenum Hydroxylase Activity
– Catalytic Oxidation
of Pyrogallol: The molybdenum hydroxylase activities of all cis-
[MoO2]2+ complexes were determined at pH 7 in acetonitrile. The
reactions were followed by UV/Vis spectroscopy by monitoring the
absorbance increment at λ = 417 nm owing to the formation of the
oxidized product, purpurogallin. The reaction was initiated by the
addition of a solution of pyrogallol (1 mL, 2.5 × 10–2
phate buffer solution (pH 7, 1 , 1 mL), followed by the addition of
H2O2 solution (1 mL, 2.5 × 10–2
) and the catalyst solution (1 mL,
2.5 × 10–4
). The UV/Vis spectra of the resulting solutions were
M) to phos-
M
Further details of the 13C NMR spectroscopic data and assignments
of important signals are given in Table S2.
M
M
[MoVIO2(L1)] (1): To a suspension of H2L1 in MeOH (0.567 g,
1 mmol, 10 mL) was added a filtered solution of [MoVIO2(acac)2]
(0.326 g, 1 mmol) in MeOH (10 mL) with stirring to afford a clear
orange solution after ca. 15 min. The orange solution was then
heated under reflux for 3 h with a hot water bath. The yellow solid
that separated as the reaction mixture cooled to room temperature
was collected by filtration, washed with cold MeOH and dried under
vacuum, yield 0.485 g (70 %). C36H56MoN2O5 (692.80): calcd. C
62.41, H 8.15, N 4.04; found C 61.85, H 7.98, N 4.01. Crystals of 1
suitable for X-ray diffraction were grown through the slow evapora-
then recorded every 3 min in repeat scan mode for 2 h. The steady-
state kinetics was determined similarly over 3 min, and the initial
rates were calculated from the slopes of the absorbance versus time
plots. The initial reaction rates were then fitted to the Michaelis–
Menten equation and Lineweaver–Burk plots to calculate the maxi-
mal velocity (Vmax), Michaelis constant (KM) and catalytic constant
or turnover number (kcat) from the nonlinear curve with the Origin
8.0 software.
Acknowledgments
tion of a MeOH solution at room temperature. IR: νmax = 2954, 2903,
˜
2866 (tert-butyl), 1467, 1442, 1361, 1240, 1204, 1170, 1119, 933
M. R. M. thanks the Science and Engineering Research Board
(SERB), Government of India, New Delhi for financial support of
the work (grant number EMR/2014/000529). B. U. is thankful to
the Indian Institute of Technology (IIT) Roorkee for an MHRD
fellowship.
(MoO2)asym, 906 (MoO2)sym, 843, 753, 600, 555, 496 cm–1 1H NMR
.
([D6]DMSO): δ = 7.175–7.170 (d, 2 H, Ar), 7.080–7.069 (d, 2 H, Ar),
4.159–4.122 (d, J = 14.8 Hz, 2 H, NCH2Ar), 4.043–4.005 (d, J =
15.2 Hz, 2 H, NCH2Ar), 3.912–3.880 (t, 2 H, NCH2CH2), 3.826–3.774
(t, 2 H, NCH2CH2), 3.735–3.680 (m, 2 H, morpholine ring), 2.980–
2.948 (m, 2 H, morpholine ring), 2.768–2.738 (m, 2 H, morpholine
ring), 2.070–2.069 (m, 2 H, morpholine ring), 1.353 [s, 18 H,
–C(CH3)3], 1.251 [s, 18 H, –C(CH3)3] ppm.
[MoVIO2(L2)] (2): This complex was prepared similarly to 1 with
H2L2 (0.399 g, 1 mmol) instead of H2L1, yield 0.398 g (76 %).
C24H32MoN2O5 (524.46): calcd. C 54.96, H 6.15, N 5.34; found C
54.58, H 6.25, N 5.26. Crystals of 2 suitable for X-ray diffraction were
grown through the slow evaporation of a DMSO solution at room
Keywords: Molybdenum · Tripodal ligands · Oxido
ligands · Oxidation · Kinetics
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temperature. IR: ν
= 2961, 2919, 2878 (alkyl), 1464, 1310, 1248,
˜
max
1214, 1142, 1113, 918 (MoO2)asym, 870 (MoO2)sym, 834, 762, 750,
585, 552, 515 cm–1 1H NMR ([D6]DMSO): δ = 6.939–6.935 (d, 2 H,
.
Ar), 6.843–6.838 (d, 2 H, Ar), 4.368–4.332 (d, J = 14.4 Hz, 2 H,
NCH2Ar), 3.909–3.873 (d, J = 14.4 Hz, 2 H, NCH2Ar), 4.169–4.116 (t,
2 H, NCH2CH2), 3.743–3.703 (t, 2 H, NCH2CH2), 3.185–3.163 (m, 2 H,
morpholine ring), 2.670–2.600 (m, 4 H, morpholine ring), 2.471–
Eur. J. Inorg. Chem. 0000, 0–0
11
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