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100.57 MHz on a Varian Mercury 400, using solvent resid-
ual peak as reference. 31P{1H} NMR spectra were regis-
tered at 121.421 MHz on a Varian VXR 300, using
H3PO4 (85%) as external standard: downfield values were
taken as positive. All 13C{1H} and 31P{1H} NMR spectra
were acquired using a broad band decoupler.
hex-2-en-1-one (72.6 ll, 0.75 mmol) was added, followed
by pressurization with 25 bar of H2 at room temperature.
The tube was placed into the NMR probe and 31P{1H}
1
and H NMR spectra were acquired in 10 ꢁC steps from
room temperature to 60 ꢁC. The tube was kept for 3 h at
60 ꢁC, before cooling it again to room temperature.
An analogous study in the absence of substrate was car-
ried out applying the same experimental conditions.
High-pressure NMR experiments were performed on a
Bruker ACP 200 spectrometer operating at 200.13 and
1
81.01 MHz for H and 31P{1H} NMR, respectively. The
10 mm-o.d. sapphire tube was purchased from Saphikon,
Milford, NH, while the titanium high-pressure charging
head was constructed at ICCOM-CNR (Firenze, Italy)
[8]. Caution: Since high gas pressures are involved, safety
precautions must be taken at all stages of studies involving
high-pressure NMR tubes.
The reaction mixtures were analyzed with a Shimadzu
GC-14A gas chromatograph equipped with a packed col-
umn (length 2 m, diameter, 3.17 mm) and a flame ioniza-
tion detector. A column of the type FFAP (‘free fatty
acids phase’ supported on Chromosorb G AW-DMCS
5%) was used to analyze the hydrogenation products of
the a,b-unsaturated ketones studied in this work, except
for methyl vinyl ketone for which a PPG column (Polypro-
pylenglicol LB-550-X 15% supported on Chromosorb W)
was employed.
4.4.2. High pressure NMR study with
RuH(CO)2(OAc)(PnBu3)(PPh3) in the presence of
substrate
The dihydride 3 (18.0 mg, 0.025 mmol) was dissolved
in a Schlenk tube containing degassed C6D6 (1.8 ml).
To this solution was added HOAc (1.4 ll, 0.025 mmol)
and the obtained solution was stirred for 2 days at room
temperature. The solution was transferred under nitrogen
into a 10 mm-OD sapphire NMR tube. 31P{1H} and H
1
NMR spectra showed the complete conversion of 3 into
the monohydride 2 already at room temperature. To this
solution were sequentially added under nitrogen HOAc
(1.4 ll, 0.025 mmol) and cyclohex-2-en-1-one (72.6 ll,
0.75 mmol). The sapphire tube was pressurized with H2
(20 bar) at room temperature and 31P{1H} and 1H
NMR spectra were acquired at the same temperature.
GC-MS spectra were collected using a Shimadzu GC-
17A QP5050A instrument.
Elemental analyses were performed with a Perkin–Elmer
2400 Series II CHNS/O analyzer.
The NMR tube was then heated to 60ꢁ
C and
maintained at this temperature for 20 min. During this
time 2 was transformed quantitatively into 3. The
NMR tube was cooled to room temperature and the
gas was released. A GC-MS analysis of the solution
showed the formation of the allylic alcohol (75%)
together with the saturated ketone (15%) and the satu-
rated alcohol (4%).
4.3. Catalytic reactions
4.3.1. General procedure
Typically, in a glass vial placed in a stainless-steel
autoclave, previously evacuated by a vacuum pump, were
introduced 4.0 ml of a toluene solution containing the cat-
alytic precursor (1.5 · 10À5 mol) and the substrate (1.5 ·
10À3 mol) under dry nitrogen. The autoclave was then pres-
surized at room temperature with H2, placed in a thermo-
static oil bath at the desired temperature ( 1 ꢁC) and
rocked for the desired time. At the end of the reaction,
the autoclave was cooled to room temperature and the gas-
eous contents were vented off. The product composition of
the solutions was analyzed by GC-MS and by GC using
pure compounds as standards.
4.5. X-ray data collection and structure determination of
Ru(CO)2(OAc)2(PnBu3)(PPh3)
A suitable single crystal of 1 was analyzed with an Enraf
Nonius CAD4 automatic diffractometer with Mo Ka radi-
ation (graphite monochromator) at room temperature.
Unit cell parameters were determined from a least-squares
refinement of the setting angles of 25 carefully centred
reflections. Crystal data and data collection details are
given in Tables 1 and 2, respectively. Lorentz-polarization
and absorption corrections were applied [9a]. Atomic scat-
tering factors were taken from Ref. [9b] and an anomalous
dispersion correction, real and imaginary part, was applied
[9c]. The structure was solved by direct methods and
refined by full-matrix F2 refinement. Anisotropic thermal
parameters were assigned to all non-hydrogen atoms and
hydrogen atoms were introduced in their calculated posi-
tions applying a riding model with thermal parameters
20% larger than those of the respective carbon atoms. All
calculations were performed on a PC using the WINGX
package [9d] with SIR-97 [9e], SHELX-97 [9f] and ORTEP-3
[9g] programs.
4.4. Operando high-pressure NMR studies in C6D6
4.4.1. High pressure NMR study with
Ru(CO)2(OAc)2(PnBu3)(PPh3) with or without substrate
Complex 1 (15.5 mg, 0.025 mmol) was dissolved in a
Schlenk tube containing degassed C6D6 (1.8 ml). The
resulting solution was then transferred under nitrogen into
a sapphire NMR tube, which was introduced at room tem-
perature into the NMR probe. 31P{1H} and 1H NMR spec-
tra were acquired at room temperature. Then the sapphire
tube was removed from the NMR probe-head and cyclo-
Micoli, Francesca
