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P.M. Reis et al. / Journal of Catalysis 235 (2005) 333–340
2. Experimental
tal analysis: calcd (%) for C4O5F6V·2H2O (329): C 14.6, H
1.2; found: C 14.5, H 0.9.
2.1. Materials
2.2. Instrumentation
The following compounds were used as received from the
supplier: carbon monoxide (Air Products), dinitrogen (Air Liq-
uid Portugal), cyclopentane (Fluka), cyclohexane (Aldrich),
pentane (Lab-Scan), hexane (Fluka), potassium peroxodisul-
fate (Fluka), ammonium peroxodisulfate (Fluka), tert-butyl hy-
droperoxide solution, 70% in water (Fluka), TFA (Aldrich),
n-butyric acid (Aldrich), and diethyl ether (Lab-Scan). The fol-
lowing complexes, applied as catalysts, were prepared accord-
ing to published methods: [VO{N(CH2CH2O)3}] 1 [28,29],
Ca[V(HIDA)2] (HIDA = basic form of 2,2ꢀ-(hydroxy-
imino)diacetic acid) 2 [30], Ca[V(HIDPA)2] (HIDPA = basic
form of 2,2ꢀ-(hydroxyimino)dipropionic acid) 3 [30], [VO(ada)
(H2O)] (ada = basic form of N-2-acetamidoiminodiacetic acid)
4 [31], [VO(Hheida)(H2O)] (Hheida = dibasic form of 2-hy-
droxyethyliminodiacetic acid) 5 [31], and [VO(CF3SO3)2] ·
2H2O 8 [32]. Complexes [VO{N(CH2COO)(CH2CH2O)
(CH2CH2OH)}] 6 and [VO(CF3COO)2] · 2H2O 7 were pre-
pared as described below, whereas VOSO4 · 5H2O 9 (Merck),
V2O4 10 (Merck), and V2O5 11 (Aldrich), the other catalysts,
were used as received.
C, H, and N elemental analyses were carried out by the
Microanalytical Service of the Instituto Superior Técnico.
Positive-ion FAB mass spectra were obtained on a Trio 2000
instrument by bombarding 3-nitrobenzyl alcohol (NBA) matri-
ces of the samples with 8 keV (ca. 1.18 × 1015 J) Xe atoms.
Mass calibration for data system acquisition was achieved us-
ing CsI. Infrared spectra (4000–400 cm−1) were recorded on
a Jasco FT/IR–430 instrument in KBr pellets. 13C-{1H} and
19F nuclear magnetic resonance (NMR) spectra were recorded
at 22 ◦C on a Varian UNITY 300 spectrometer using TMS as
internal standard (for 13C) and CFCl3 (for 19F).
Gas chromatography (GC) measurements were carried out
on a Fisons model 8160 equipped with a flame ionisation de-
tector and a capillary column (DB-WAX; column length, 30 m;
i.d., 0.32 mm). Helium was used as the carrier gas. GC-mass
spectroscopy (MS) measurements were carried out in a Fisons
Trio 2000 mass spectroscope with a coupled gas chromatograph
(Carlo Erba Instruments, Auto/HRGC/MS).
2.3. Typical carboxylation procedures and products analysis
2.1.1. Complex 6
The reaction mixtures were prepared as follows. To 0.0625
mmol of the metal complex contained in a 39.0 mL AISI
316 stainless steel autoclave equipped with a Teflon-coated
magnetic stirring bar was added the oxidant [either K2S2O8
(12.5 mmol), (NH4)2S2O8 (12.5 mmol), or t-BuOOH
(12.5 mmol)], the substrate [cyclopentane (0.90 mL,
9.58 mmol), cyclohexane (1.00 mL, 9.26 mmol), pentane
(1.00 mL, 8.68 mmol), or hexane (1.10 mL, 8.42 mmol)] and
22.0 mL of TFA. Then the autoclave was closed and flushed
with dinitrogen three times for replacing the air inside and
finally pressurized with 0–60 atm of carbon monoxide. The
reaction mixture was vigorously stirred using a magnetic stirrer
for 2–20 h at 40–150 ◦C with an oil bath. After the reaction was
complete, the autoclave was cooled using an ice bath, then de-
gassed and opened. To 2.5 mL of the filtered reaction solution
was added 6.5 mL of diethyl ether (which led to further precip-
itation) and 90 µL of n-butyric acid (as an inner standard). The
obtained mixture was stirred, then filtered off and analyzed by
gas chromatography. The reaction products (carboxylic acids)
were quantitatively analyzed by GC (1 µL samples) using the
inner standard method. The injection temperature was 240 ◦C,
and the column temperature was initially 100 ◦C for 1 min,
then increased by 10 ◦C/min (or 5 ◦C/min for the analysis of
the hexane products) to 250 ◦C and held at this value for 1 min.
In some cases, products were also identified by GC-MS and
13C-{1H} NMR of the final reaction solutions. The carboxylic
acids of all hydrocarbons were determined by both GC and
13C-{1H} NMR (in CDCl3) spectroscopy, and the esters were
identified by 13C-{1H} and 19F NMR spectroscopy. Genuine
samples of the esters were synthesized in our laboratory by the
reaction of TFA with the corresponding alcohols and their NMR
N,N-bis(2-hydroxyethyl)glycine (bicine) (0.82 g, 5.0 mmol)
and Ba(OH)2 · 8H2O (1.58 g, 5.00 mmol) were dissolved in
deionised water (20 mL) under dinitrogen. The solution was
heated and stirred for 30 min, after which VOSO4 · 5H2O
(1.26 g, 5.00 mmol) was added and the reaction mixture stirred
for another 30 min. The formed solid of BaSO4 was separated
by filtration, and the filtered dark-blue solution was concen-
trated under vacuum to yield an oily residue, which was washed
with diethyl ether by the freeze-thaw technique to give a dark-
blue solid that was filtered off, washed with diethyl ether, and
dried under vacuum. Yield 0.662 g (58%). IR (KBr): 951(m)
ν(V=O), 1442(m), 1647(w), 3385 cm−1(w,br) ν(OH). MS
(FAB+): m/z: 228 [M+]; elemental analysis: calcd (%) for
C6H11O5NV · 0.5(CH3CH2)2O (228): C 36.0, H 6.2, N 6.0;
found: C 35.6, H 6.7, N 6.5.
2.1.2. Complex 7
The synthesis was performed in two steps. In the first
step, the salt Ba(CF3COO)2 was synthesized by the reac-
tion of Ba(OH)2 · 8H2O (204.7 mg, 0.65 mmol) with TFA
(CF3COOH) (0.10 mL, 1.3 mmol) in water under dinitro-
gen (yield 89%). This salt (144.8 mg, 0.58 mmol) was then
dissolved in methanol (2 mL), and the solution was added
to a methanol solution (2 mL) of VOSO4·5H2O (146.4 mg,
0.58 mmol). The formed precipitate of BaSO4 was subse-
quently filtered off, and the filtered bright-blue solution was
concentrated under vacuum to give a brown solid, which was
dried for a few hours at 120 ◦C in an oil bath. Yield 122 mg
(72%); IR (KBr): 728 (s), 991(m) ν(V=O), 1151(m), 1205(m),
1439(m), 1676(w) ν(C=O), 3400 cm−1(w,br) ν(OH); elemen-