Inorganic Chemistry
Article
DFT method. All the basis sets used are included in the Gaussian03
library.61 For d-orbital descriptions, the xy plane is defined by O1, O2,
N1, and N3 atoms coordinating the central transition metal atom (Cu
or Ni).
H]+, 506 [ZnL + Na]+, 522 [ZnL + K]+. IR spectrum, (ATR, selected
bands, νmax): 2964, 2914, 1593, 1470, 1372, 1288, 1249, 1167, 1022,
931, 825, 763, 612 cm−1. UV−vis in CHCl3, λ, nm (ε, M−1 cm−1): 431
(9279), 364 (20333), 314 (24601). The quality of the crystals was
suitable for X-ray diffraction analysis.
Synthesis of Metal Complexes and Ligand: NiIIL1. A
suspension of 5-tert-butyl-2-hydroxy-3-methylsulfanylbenzaldehyde S-
methylisothiosemicarbazone (0.96 g, 3.1 mmol) and Ni(acac)2 (0.75 g,
2.9 mmol) in pentane-2,4-dione (20 mL) and triethyl orthoformate (5
mL) were heated under argon atmosphere at 107 °C for 8 h. The
reaction mixture was allowed to cool to room temperature. The red
precipitate formed was filtered off, redissolved in methylene chloride,
and filtered. The filtrate was evaporated under reduced pressure to ca.
15 mL, and then the product was precipitated by excess ethanol,
filtered off, and dried in vacuo. Yield: 0.64 g, 45.3%. Calcd for
C20H25NiN3O3S2·0.5H2O (Mr 487.26 g/mol), %: C, 49.30; H, 5.38; N,
NiL2. A mixture of 5-tert-butyl-2-hydroxy-3-phenylsulfanylbenzalde-
hyde S-methylisothiosemicarbazide (0.76 g, 2.1 mmol) and Ni(acac)2
(0.51 g, 2.0 mmol) in pentane-2,4-dione (20 mL) and triethyl
orthoformate (5 mL) were heated under argon atmosphere and
stirring at 107 °C for 8 h. The isolated red precipitate washed with
cold ethanol (5 mL), dissolved in dichloromethane (20 mL), filtered
off, and evaporated to 1/3 of initial volume. Ethanol (15 mL) was
added, and the red crystals formed were filtered off, washed with
ethanol, and dried in vacuo. Yield: 0.27 g, 48.2%. Calcd for
C25H27NiN3O3S2·0.7H2O (Mr 552.94 g/mol), %: C, 54.30; H, 5.18;
N, 7.60; S, 11.60. Found, %: C, 54.56; H, 4.91; N, 7.45; S, 11.14. ESI-
MS (CH3OH) positive: m/z 540 [M + H]+, 562 [M + Na]+. 1H NMR
(500.32 MHz, CDCl3): δ 1.284 (s, 9H, C(CH3)3), 2.416 (s, 3H,
1
8.62; S, 13.16. Found, %: C, 49.24; H, 5.02; N, 8.86; S, 13.46. H
NMR (500.32 MHz, CDCl3): δ = 8.12 (s, 1H, CHN), 7.92 (s, 1H,
CH−N), 7.31 (s, 1H, Ar), 7.08 (s, 1H, Ar), 2.72 (s, 3H, CH3), 2.68
(s, 3H, CH3), 2.49 (s, 3H, SCH3), 2.43 (s, 3H, SCH3), 1.36 (s, 9H,
C(CH3)3). IR spectrum (ATR, selected bands, νmax): 2865, 1655,
1582, 1522, 1297, 1171, 942, 622 cm−1. UV−vis in CHCl3, λ, nm (ε,
M−1 cm−1): 474 (5169), 379 (17700), 269 (47300). X-ray diffraction
quality single crystals of NiIIL·0.5Hacac were grown from solution of
NiIIL in pentane-2,4-dione.
SCH3), 2.637 (s, 3H, CH3), 2.711 (s, 3H, CH3), 7.128 (d, 4J(H4−H6)
=
4
2 Hz, 1H, Ar−H), 7.180 (d, J(H4−H6) = 2 Hz, 1H, Ar−H), 7.340 (m,
3H, Ar−H), 7.523 (m, 1H, Ar−H), 7.537 (m, 1H, Ar−H), 7.896 (s,
1H, CH−N), 8.118 (s, 1H, CHN). UV−vis in CHCl3, λ, nm (ε,
M−1 cm−1): 471 (6615), 382 (18750). X-ray diffraction quality single
crystals were grown in an NMR tube by overlaying the solution of the
complex in CH2Cl2 with pentane.
CuIIL1. A suspension of 5-tert-butyl-2-hydroxy-3-methylsulfanylben-
zaldehyde S-methylisothiosemicarbazone (0.75 g, 2.4 mmol) and
Cu(acac)2 (0.57 g, 2.2 mmol) in pentane-2,4-dione (20 mL) and
triethyl orthoformate (5 mL) were heated under argon atmosphere at
107 °C for 8 h. The reaction mixture was allowed to cool slowly to
room temperature. The brown crystals were filtered off, redissolved in
methylene chloride, and filtered. The filtrate was evaporated under
reduced pressure to ca. 15 mL, and then the product was precipitated
by excess ethanol, filtered off, and dried in vacuo. Yield: 0.40 g, 44.0%.
Calcd for C20H25CuN3O3S2 (Mr 483.11 g/mol), %: C, 49.72; H, 5.22;
N, 8.70; S, 13.27. Found, %: C, 49.60; H, 5.21; N, 8.54; S, 12.89. ESI-
MS (CH3OH) positive: m/z 483 [M + H]+, 505 [M + Na]+, 521 [M +
K]+. IR spectrum, (ATR, selected bands, νmax): 2961, 1660, 1586,
1510, 1464, 1429, 1364, 1290, 1165, 1120, 933, 781, 645 cm−1. UV−
vis in CHCl3, λ, nm (ε, M−1 cm−1): 447 (5567), 375 (16406), 375
(16406), 332 (17126), 295 (37504). The crystals grown in pentane-
2,4-dione were of X-ray diffraction quality.
CuL2. A mixture of 5-tert-butyl-2-hydroxy-3-phenylsulfanylbenzal-
dehyde S-methylisothiosemicarbazone (0.79 g, 2.1 mmol) and
Cu(acac)2 (0.55 g, 2.0 mmol) in pentane-2,4-dione (20 mL) and
triethyl orthoformate (5 mL) were heated and stirred under argon
atmosphere at 107 °C for 8 h. The brown precipitate was filtered off
and evaporated to 1/3 of initial volume. Ethanol (15 mL) was added,
and the brown crystals formed were filtered off, washed with ethanol,
and dried in vacuo. The product was purified by column
chromatography on silica by using CH2Cl2 as an eluent. The fraction
with the brown product was evaporated to dryness. Ethanol (15 mL)
was added, and the precipitate was filtered off, washed with ethanol (5
mL), and dried in vacuo. Yield: 0.20 g, 18.4%. Calcd for
C25H27CuN3O3S2 (Mr 545.18 g/mol), %: C, 55.08; H, 4.99; N,
7.71; S, 11.76. Found, %: C, 55.10; H, 5.03; N, 7.55; S, 11.46. ESI-MS
(CH3OH) positive: m/z 483 [M + H]+, 505 [M + Na]+, 521 [M +
K]+. IR spectrum, (ATR, selected bands, νmax): 2961, 1660, 1586,
1510, 1464, 1429, 1364, 1290, 1165, 1120, 933, 781, 645 cm−1. UV−
vis in CHCl3, λ, nm (ε, M−1 cm−1): 447 (10150), 377 (23880), 334
(21590).
Oxidation of Primary Alcohol (Benzyl Alcohol) Using
TEMPO/Air and TBHP. The reactions were carried out in 20 mL
round-bottom flasks equipped with condensers under atmospheric
pressure of air. (i) TEMPO/air: Typically, to 5.0 mL of 1:1 (v/v)
MeCN/0.1 M K2CO3 aqueous solution were added 3.0 mmol of
alcohol, 3 μmol (0.1 mol % vs substrate) of catalyst, and 0.15 mmol (5
mol % vs substrate) of TEMPO. (ii) TBHP: To 5.0 mL of 1:1 (v/v)
MeCN/0.1 M K2CO3 aqueous solution were added alcohol (3.0
mmol), catalyst (3 μmol), and TBHP (15 mmol). The reaction
solutions in all cases were vigorously stirred using magnetic stirrers,
and an oil bath was used to achieve the desired reaction temperature
(50 °C). After the oxidation reaction (24 h), reaction mixtures were
neutralized by 1 mol/L HCl and then extracted with 10 mL of EtOAc.
The organic phase was used for chromatographic analyses using
acetophenone as the internal standard. Negligible reactions were
observed when the TEMPO, TBHP, or catalyst was not employed.
Peroxidative Oxidation of Sec-Alcohols Using Microwave-
Assisted Method. In a typical experiment, an alcohol substrate (5.00
mmol), TBHP (10.0 mmol), and catalyst (5 μmol, 0.1 mol % vs
substrate) were introduced to a cylindrical Pyrex tube, which was then
placed in the focused microwave reactor. The reaction mixture was
stirred under microwave irradiation (10 W power) for 240 min at 80
°C. After the reaction, the mixture was allowed to cool to ambient
temperature. The reaction samples were taken up by 5 mL of
acetonitrile with 300 μL of benzaldehyde (internal standard) and
analyzed by gas chromatography.
H2L1. Hydrogen chloride was bubbled through a solution of NiL1
(0.10 g, 0.20 mmol) in chloroform (50 mL). The red color of the
solution faded gradually and became yellow. Water (200 mL) was
added, and after vigorous stirring the organic layer was separated from
the aqueous phase using a separating funnel. This operation was
repeated 5−6 times to ensure the removal of nickel(II) from the
organic layer. The chloroform was evaporated under reduced pressure
almost to dryness, and to the remaining residue was added ethanol
(10−15 mL). The solution was allowed to stand at 4 °C overnight.
The crystals formed were separated by filtration and washed with cold
ethanol (5 mL). The crystallized product was also suitable for X-ray
diffraction measurement. Yield: 0.08 g, 95.0%. Mp: 190 °C. Calcd for
C20H27N3O3S2·0.4H2O (Mr 428.35 g/mol), %: C, 56.03; H, 6.54; N,
9.81; S, 14.93. Found, %: C, 56.22; H, 6.37; N, 9.60; S, 14.79. ESI-MS
(CH3OH) positive: m/z 422 [M + H]+, 444 [M + Na]+, 460 [M +
K]+. IR spectrum, (ATR, selected bands, νmax): 3001, 2953, 2919,
2865, 1632, 1571, 1534, 1425, 1374, 1279, 1185, 1137, 958, 743, 669,
613 cm−1. UV−vis in DMF, λ, nm (ε, M−1 cm−1): 417 (34213), 299
(18471).
[ZnIIL1]2. To H2L (0.11 g, 0.25 mmol) in chloroform (1 mL) was
added Zn(CH3COO)2·2H2O (0.06 g, 0.25 mmol) in methanol (6
mL). After 24 h the crystals formed were filtered off, washed with
methanol, and dried in air. Yield: 0.04 g, 36.0%. Calcd for
C40H50ZnN6O6S4 (Mr 967.96 g/mol), %: C, 49.68; H, 5.22; N, 8.70;
1
S, 13.24. Found, %: C, 49.24; H, 5.43; N, 8.42; S, 13.09. H NMR
(500.32 MHz, DMSO-d6): δ = 8.59 (s, 1H, CHN), 8.55 (s, 1H,
CH−N), 7.28 (d, 1H, Ar), 7.11 (s, 1H, Ar), 7.06 (s, 1H, Ar), 2.56 (s,
3H, CH3), 2.51 (s, 3H, CH3), 2.34 (s, 3H, CH3), 2.33 (s, 3H, SCH3),
1.29 (s, 9H, C(CH3)3). ESI-MS (CH3OH) positive: m/z 486 [ZnL +
O
dx.doi.org/10.1021/ic4004966 | Inorg. Chem. XXXX, XXX, XXX−XXX