Organometallics
Article
but could stabilize the cationic species and also improve the
solvation of the ammonium salts on the other. It also has to be
considered that when using toluene a water phase can be
gradually formed during the reaction. This may have an
influence on the activity when compared with that of THF,
which is completely miscible with water. The different
of NaHBEt
3
in THF (3.1 mL, 3.1 mmol, 2.5 equiv) was added
dropwise. The white suspension was heated at reflux for 16 h to give a
red solution. The solution was filtered to remove a small amount of
white precipitate, and the solvent volume was reduced under vacuum
to ∼5 mL. Pentane (40 mL) was slowly added to give [(triphos)Ru-
(
H) (CO)] (2, 750 mg, 0.99 mmol, 83% yield) as a light yellow solid
2
after filtration. All spectroscopic data are identical to those reported in
the literature.
solubilities of NH in THF and toluene also have to be taken
14
3
into account regarding the activity of the catalytic system. In
this context, it is still not clear which effect is the most relevant
to explain the significant higher activity in toluene compared to
that of the catalysis run in THF. Further investigations into
how the triphos-ligand can be modified to improve the catalyst
performance and on the role of different solvents in the
catalytic system are ongoing.
General Procedure for NMR-Scale Conversion of [(Triphos)-
Ru(H) (CO)] (2) to [(Triphos)Ru(H)(X)(CO)] (1 and 3). A Teflon
2
capped NMR tube was charged with [(triphos)Ru(H)
mg, 0.026 mmol, 1 equiv), [NH ][Cl] (14 mg, 0.26, 10 equiv), or
(CO)] (2, 20
2
4
[
NH ][Br] (25 mg, 0.26, 10 equiv) and pyridine-d (0.5 mL). The
4
5
solution was mixed and placed in an oil bath at 110 °C and checked
periodically by 31P{ H} and H NMR spectroscopy.
1
2
31
1
(
a) For [NH ][Cl]: After 25 h, the P{ H} NMR spectrum
4
showed mostly 1 (83%) with a small amount of 2 (7%) and several
EXPERIMENTAL SECTION
unidentified products (10%).
■
31
1
(
b) For [NH ][Br]: After 16 h, the P{ H} NMR spectrum
4
General Considerations. All manipulations were carried out
under an anaerobic atmosphere of argon in a glovebox or using
standard Schlenk line techniques. All nondeuterated solvents were
dried using an MBraun SPS-800 solvent purification system and
degassed prior to use, except for anhydrous pentane which was
purchased and degassed prior to use. All reagents were purchased from
Aldrich, except for [(PPh ) Ru(H)(Cl)(CO)], which was purchased
showed mostly [(triphos)Ru(H)(Br)(CO)] (5, 82%) with several
3
1
1
unidentified products (18%). P{ H} NMR (81.0 MHz, pyridine-d ,
5
2
2
2
δ): 50.6 (dd, J = 39 Hz, J = 17 Hz, 1P), 13.3 (dd, J = 39 Hz,
PP
PP
PP
2
2
2
1
JPP = 32 Hz, 1P), 0.7 (dd, J = 33 Hz, J = 17 Hz, 1P). H NMR
PP
PP
(
1
(
200.2 MHz, pyridine-d , δ): 8.14−7.77 (m, 12H, Ph), 7.31−6.98 (m,
5
8H, Ph), 3.11−2.88 (m, 2H, CH P), 2.59−2.49 (m, 4H, CH P), 1.68
2
2
3
3
2 2
s, 3H, CH ), −5.73 (dt, J = 92 Hz, J = 17 Hz, 1H, RuH).
General Procedure for the Conversion of [(Triphos)Ru(H)-
from Alfa Aesar. Liquid reagents were distilled prior to use, and all
others were used without further purification. [(triphos)Ru(H)(Cl)-
CO)] (1) was prepared by literature methods. Dichloromethane-d
3
HP
HP
1
2
(Cl)(CO)] (1) to [(Triphos)Ru(H) (CO)] (2) with Ammonia and
(
2
2
1
2
1
Hydrogen. [(Triphos)Ru(H)(Cl)(CO)] (1, 50 mg, 0.063 mmol)
and THF (20 mL) were added to two separate premex autoclaves (60
mL, stainless steel) equipped with a magnetically coupled propeller
blade stirrer, under an inert argon atmosphere. One autoclave was
and THF-d were dried over CaH prior to distillation. H, H{ H},
8
2
1
3
1
31
1
19
1
C{ H}, P{ H}, and F{ H} NMR spectra were recorded on a
1
13
Bruker Avance 200 or 400 MHz spectrometer. H and C chemical
shifts are reported relative to residual solvent signals of CD Cl (5.32
2
2
charged with NH (6 bar) and hydrogen gas (20 bar), while the other
3
and 54.0 ppm), THF-d (5.38 and 67.21 ppm), and pyridine-d (8.74
8
5
1
31
1
was charged with only hydrogen (20 bar). The autoclave was heated to
165 °C for 1.5 h with vigorous stirring (200−300 rpm). The
autoclaves were vented, and the solution was added to a round-
bottomed Schlenk flask (100 mL) in the glovebox. The solvent was
removed under reduced pressure, the light yellow residue was partially
pp for H). P{ H} chemical shifts are referenced to an external 85%
solution of phosphoric acid, and F{ H} chemical shifts are referenced
to external neat CFCl . The C NMR data were assigned by HSQC
19
1
13
3
and HMBC spectra. FAB and HR mass spectrometry was measured at
the Mass Spectrometry Facility (Institute of the Organic Chemistry,
University Heidelberg). Gas chromatography was performed on an
Agilent 6890N modular GC base equipped with a split-mode capillary
injection system and a flame ionization detector using a BGB-5
capillary column (Agilent 122−1033; 30 m × 0.32 mm × 0.25 μm; He
flow 1.0 mL/min, program: initial 50 °C for 2 min, ramp 6 °C/min,
dissolved in THF-d (0.5 mL), and the composition was determined
8
by 31P{ H} NMR spectroscopy.
1
(
a) For NH3 and H : The reaction mixture contained mostly
2
[
(triphos)Ru(H) (CO)] (2, 85%), a small amount of [(triphos)Ru-
2
(
H)(Cl)(CO)] (1, 6%), and 1−2 unidentified products (9%).
31 1
(
b) For H : In this case, the P{ H} NMR of the residue was also
3
00 °C for 10 min). Starting materials and products had the following
2
checked in CD Cl due to the low solubility of 1 in THF. The reaction
retention times: cyclohexanone (t = 10.49 min), octanal (t = 13.47
2
2
R
R
mixture contained [(triphos)Ru(H)(Cl)(CO)] (1, 67%), [(triphos)-
min), octylamine (tR = 14.54 min), 1-octanol (tR = 15.16 min),
hexanitrile (tR = 15.40 min), acetophenone (tR = 15.60 min),
dioctylamine (tR = 31.34 min), 18crown6 (tR = 34.79 min), and
trioctylamine (tR = 41.71 min). All in situ IR experiments were
performed using a ReactIR 45m, purchased from Mettler Toledo with
a titanium autoclave from Paar Instruments and an integrated ATR
probe. Elemental analyses were performed in the “Mikroanalytisches
Ru(H) (CO)] (2, 27%), and 1−2 unidentified products (6%).
2
General Procedure for Catalyst Screening of 1 and 2 with
Additives. To a premex autoclave (60 mL, stainless steel) equipped
with a magnetically coupled propeller blade stirrer was added the
catalyst (1 (36 mg, 0.046 mmol); 2 (37 mg, 0.046 mmol)), toluene
(17 mL), 1-octanol (3.0 g, 23 mmol), and the additive, under an inert
argon atmosphere. The autoclave was sealed, and NH (6 bar) was
3
̈
Laboratorium der Chemischen Institute der Universitat Heidelberg”.
introduced at room temperature as a gas. The autoclave was heated to
General Procedure for the Catalyst Tests Given in Table 1
and Monitoring Reactivity over Time of Catalyst System D and
Complexes 1 and 2. To a Parr autoclave (160 mL, stainless steel
V4A) equipped with a magnetically coupled inclined blade stirrer was
added 0.14 mmol of catalyst (D: triphos (88 mg); (PPh ) Ru(H)-
1
65 °C for 15 h with vigorous stirring (200−300 rpm). A sample of
the product mixture was analyzed by GC, and the conversion of 1-
octanol and the yield of 1-octylamine were calculated based on GC
area %.
3
3
(
Cl)(CO) (133 mg); 1 (111 mg); 2 (106 mg); and 3 (128 mg)), THF
(a) Catalyst 1, no additive, and catalyst resting state determination:
When cooled, the autoclave was vented and flushed with argon for 20
min. In a glovebox, the mixture was added to a round-bottomed
Schlenk flask (100 mL), and the solvent was removed under vacuum.
Pentane was added to the high boiling residue to give a yellow
precipitate. The mixture was filtered, and the residue was dissolved in
(
30 mL) and 1-octanol (9.1 g, 50 mmol) under an inert argon
atmosphere. The Parr autoclave was sealed, and NH (7.2 g, 500
3
mmol) was introduced at room temperature as condensed liquid. The
autoclave was heated to 155 °C for 24 h with vigorous stirring (200−
5
00 rpm). A sample was removed periodically, and the product
CD
(H)
Cl
(CO)] (2) as the only product. Product distribution: 1-octanol
2
. The 31P{ H} and H NMR spectra showed [(triphos)Ru-
1
1
mixture was analyzed by GC (30 m RTX5-0.32 mm, 1,5 μm; 60-4-
2
2
2
80/20), and the conversion of 1-octanol and the yield of 1-
octylamine were calculated based on GC area%.
(37%), octylamine (52%), dioctylamine (6%), hexanenitrile (3%), and
other (2%).
Synthesis of [(Triphos)Ru(H) (CO)] (2). A round-bottomed
2
Schlenk flask (100 mL) was charged with [(triphos)RuHCl(CO)]
(b) Catalyst 1 + [NH ][Cl]: additive, [NH ][Cl] (25 mg, 0.46
4
4
(1, 980 mg, 1.2 mmol, 1 equiv) and THF (25 mL). A 1.0 M solution
mmol); product distribution, 1-octanol (33%), octylamine (54%),
H
Organometallics XXXX, XXX, XXX−XXX