A. Salvini et al. / Journal of Organometallic Chemistry 690 (2005) 371–382
379
a solution of KMnO in H SO (10%), dried on anhy-
4
heated under nitrogen (5 atm at 20 °C) in the tempera-
ture range 20–150 °C.
The reaction was followed as reported in the general
2
4
drous CaCl , refluxed on sodium and distilled on
2
LiAlH . Methanol, dried as reported by Vogel [15],
4
had bp 65 °C. Tri-n-butylphosphine was distilled under
nitrogen prior to use (bp 158–160 °C/60 mmHg).
All other solvents and chemicals were reagent grade
and used without further purification.
procedure.
A sample of the solution was collected after heating
at 40 °C. After evaporation of the solvent and acetic
acid under reduced pressure the residue was dissolved
in n-heptane and analysed by IR spectroscopy: only
ꢀ
1
the bands at 2041(vs), 1971(vs) and 1628(m) cm attrib-
4
.3.1. Synthesis of ruthenium complexes
Complexes Ru H (CO) (PBu ) (1) [16], Ru(CO)2-
1
utable to the starting complex were present. The H-,
4
4
8
3 4
3
1
13
P- and C NMR spectra were recorded on the residue
dissolved in C D or in C D containing the same con-
(
MeCOO) (PBu3)2 (2) [8], Ru (CO) (l-MeCOO) (P-
2 2 4 2
Bu ) (3) [17], Ru (CO) (l-MeCOO) (PBu ) (4) [12],
6
6
6
6
3
2
4
8
4
3 2
centration of MeCOOH used for the reactivity tests.
The absorptions are reported in Table 1.
RuH (CO) (PBu ) (5) [1d], Ru H (CO) (PBu ) (6)
4
2
2
3 2
4
9
3 3
[
16], [Ru (l-H) (CO) (l-PHBu)(l-PBu ) (PBu ) (l -P)]
6 6 10 2 2 3 2 6
(
7) and [Ru (CO) (l-MeCOO) ] (12) [17] were prepared
2 4 2 n
1 31 13
4.5. Reactivity of ruthenium complexes in the presence of
acetic acid: NMR study
as described in the literature. The H-, P- and
C
NMR spectra of (1)–(4) and (6) were performed using
the same solvents (C D ) employed in experimental tests
6
6
4
.5.1. Ru (CO) (l-MeCOO) (PBu ) (3) with MeCOOH
with the aim to facilitate their identification in the course
of the reactions (Table 3).
2
4
2
3 2
A solution of (3) (24 mg, 0.029 mmol) and acetic acid
0.1 ml, 1.747 mmol) in C D (1 ml) was introduced, un-
(
der nitrogen, into a NMR sample tube.
6
6
4.4. Reactivity of ruthenium complexes in the presence of
acetic acid: IR study
After 56 h at 40 °C two singlet at 43.5 (70.4%) and
7.2 ppm (29.6%) were present in the P NMR spec-
3
1
1
trum while broad bands at 2060(vs), 1990(vs), 1950(vw)
A solution of the system under examination was
introduced in the autoclave, then N (5 atm) was added.
ꢀ
1
and 1575(w) cm were present in the IR spectrum.
The solution was evaporated to dryness and the resi-
due dissolved in C D : a broad singlet was present in the
2
IR spectra were recorded under reaction conditions
after heating the solution at the pre-fixed temperature
for the selected time.
6
6
3
1
P NMR spectrum at 44.4 ppm (70.4%), attributed to
11), together with a singlet at 17.4 ppm (29.6%), attrib-
uted to (2).
(
4
.4.1. Ru (CO) (l-MeCOO) (PBu ) (3) with MeCOOH
2
4
2
3 2
1
In the H NMR spectrum (C D ) signals attributed
6
6
A solution of (3) (120 mg, 0.144 mmol) and acetic
to (11) were present at d 0.77 (m, 9H, CH , PBu ),
1.16 (m, 6H, CH CH , PBu ), 1.30 (m, 6H, EtCH ,
PBu ), 1.63 (m, 6H, PCH , PBu ), 2.06 (s broad, 6H,
3
3
acid (0.5 ml, 8.734 mmol) in n-heptane (60 ml) was
heated under nitrogen (5 atm at 20 °C) in the tempera-
ture range 40–150 °C.
The reaction was followed as reported in the general
procedure.
3 2 3 2
3
2
3
CH COO) ppm and other resonances attributed to (2)
3
at d 0.90 (t, 18H, CH , PBu , J = 7.1 Hz), 1.30 (m,
3
3
HH
12H, CH CH , PBu ), 1.53 (m, 12H, EtCH , PBu ),
3 2 3 2 3
1.87 (m, 12H, PCH , PBu ), 2.27 (s, 6H, CH COO)
ppm.
2 3 3
4
.4.2. Ru (CO) (l-MeCOO) (PBu ) (4) with MeCOOH
4
8
4
3 2
A solution of (4) (119 mg, 93.8 lmol) and acetic acid
0.5 ml, 8.734 mmol) in n-heptane (60 ml) was heated
13
The C NMR spectrum (C D ) showed signals
6
6
(
attributed to (11) at d 13.4 (s, CH , PBu ), 20.1 (s, l-
3
3
under nitrogen (5 atm at 20 °C) in the temperature range
2
CH COO), 23.5 (s, CH COO), 24.1 (m, PCH , PBu ),
24.3 (s, CH CH , PBu ), 24.9 (m, EtCH , PBu ), 174.5
3
3
2
3
0–140 °C.
The reaction was followed as reported in the general
3 2 3 2 3
(s, COO), 183.0 (s, l-COO), 195.9 (m, CO) ppm and
procedure.
The solution recovered at the end of the experiment
was evaporated to dryness, the residue dissolved in
other resonances attributed to (2) at d 13.8 (s, CH3,
PBu ), 23.7 (s, CH COO), 23.9 (t, PCH , PBu ,
JPC = 12.7 Hz), 24.8 (t, CH CH , PBu , J = 6.3 Hz),
3
3
2
3
3
2
3
PC
1
31
C D and analysed by IR, H- and P NMR. Several
6
3
singlets were present in the P NMR spectrum besides
6
25.4 (s, EtCH , PBu ), 175.9 (s, COO), 199.0 (t, CO,
JPC = 10.9 Hz) ppm.
2 3
1
the signals at 43.5 ppm due to (11), at 17.4 (2), 38.5,
4
The IR spectrum of the same sample dissolved in n-
pentane showed the bands of the complex (11) at
3.1, 44.6, 45.4, 53.3 ppm.
ꢀ
1
057(vs), 1987(vs), 1603(w), 1563(vw) cm and those
2
of the complex (2) at 2041(s), 1971(s), 1628(vw) cm
ꢀ
1
4
.4.3. Ru(CO) (MeCOO) (PBu ) (2) with MeCOOH
2
.
2
3 2
A solution of (2) (190 mg, 0.279 mmol) and acetic
acid (0.5 ml, 8.734 mmol) in n-heptane (60 ml) was
The sample kept for 24 h at room temperature in a
C D solution, without acetic acid, was transformed in
6
6