Selective hydrogenation of ruthenium acylphosphine complexes

Article abstract of DOI:10.1021/om4008086

Hydrogenation of a benzene ruthenium chloride dimer in the presence of novel acylphosphine (phosphomide) ligands resulted in the formation of corresponding ruthenium(II)-benzyl phosphine complexes. Here, selective reduction of the carbonyl group to a methylene unit takes place with molecular hydrogen under mild conditions in good yield. This approach provides an alternative synthesis of ruthenium phosphine complexes of benzyl and heterobenzyl phosphine ligands.

Full text of DOI:10.1021/om4008086

Article
pubs.acs.org/Organometallics
Selective Hydrogenation of Ruthenium Acylphosphine Complexes
Saravanan Gowrisankar,† Helfried Neumann, Anke Spannenberg, and Matthias Beller*
Leibniz-Institut fur Katalyse e.V. an der Universitat Rostock, Albert-Einstein-Strasse 29a, 18059 Rostock, Germany
̈
̈
S
* Supporting Information
ABSTRACT: Hydrogenation of a benzene ruthenium chloride dimer in
the presence of novel acylphosphine (phosphomide) ligands resulted in
the formation of corresponding ruthenium(II)−benzyl phosphine
complexes. Here, selective reduction of the carbonyl group to a
methylene unit takes place with molecular hydrogen under mild
conditions in good yield. This approach provides an alternative synthesis
of ruthenium phosphine complexes of benzyl and heterobenzyl
phosphine ligands.
Scheme 1. Reactivity of Ir− and Ru−Acylphosphine
Complexes
INTRODUCTION
■
Phosphorus-based ligands have been proven to be essential in
homogeneous catalysis and organometallic chemistry. In
contrast to the usually applied aryl and alkyl phosphines,
acylphosphines (phosphomides) are an under-represented class
of compounds, which are rarely used in catalysis.1 In general,
acylphosphines are believed to be unstable and difficult to
handle. Nevertheless, in 1952, the first synthesis of an acetyl
phosphine was described starting from acetyl bromide and
diethyl phosphine.2 Still today, most of the known acyl-
phosphines are synthesized by condensation of acid chlorides
with the respective secondary phosphine in the presence of a
base such as NEt3 or K2CO3 in an inert solvent.3 Alternatively,
highly reactive silyl phosphines can be used for the synthesis of
cyclic carboxylic monophosphines or difunctional acyl-
phosphines based on dicarboxylic acids.4 In agreement with
the rare catalytic investigations, the preparation and basic
organometallic chemistry of acylphosphine transition-metal
complexes has also been largely neglected. In fact, only four
examples of such complexes have been explored in more detail.
The synthesis of acylphosphine molybdenum5 and iron6
complexes relies on a controllable migration of acyl groups
from metal to phosphine ligands. A more straightforward
synthesis was developed by Clarke et al., who showed that aroyl
phosphines form stable complexes by combination with
[Cp*RhCl2]2. The resulting rhodium phosphomide complexes
were applied in the hydroformylation of 1-hexene.7 Recently,
Stambuli et al. synthesized acylphosphine-ligated iridium
complexes using [Cp*IrCl2]2 as precursor.8 Interestingly, the
latter group demonstrated that an alkyl group of the
acylphosphine ligand coordinated to the iridium center is
dehydrogenated in the β−γ position to an olefin (Scheme 1).
For some time, we were attracted to the development of
improved catalysts for hydrogenation of carbon dioxide to
formic acid derivatives, which is of interest for novel hydrogen
storage systems.9 In this respect, very recently, we succeeded
generating active catalysts for the hydrogenation of sodium
bicarbonate by a combination of phosphomides with
commercially available ruthenium precursors.1 On the basis of
this work, we decided to prepare ruthenium complexes with
acylphosphine ligands and examined their behavior in the
presence of hydrogen. In this paper, we show for the first time
unexpected hydrogenations of well-defined ruthenium(II)-
arene−acylphosphine complexes, which were synthesized
straightforward from acylphosphine ligands and the
[RuCl2(η6-C6H6)]2 dimer.
RESULTS AND DISCUSSION
■
At the start of this work, 1-naphthoylchloride was reacted with
dicyclohexyl phosphine in the presence of triethylamine, which
led immediately to a bright orange solution of dicyclohexyl 1-
naphthoyl phosphine L1.10 Likewise, other acylphosphine
ligands such as (dicyclohexyl phosphino)(furan-2-yl)-
Received: August 12, 2013
Published: December 9, 2013
© 2013 American Chemical Society
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Table 1. Different Hydrogenation Experiments of Ruthenium Dimer with Phosphomide Ligand (L1)
ab
,
yield (%)
entry
1
temp (°C)
H2 (bar)
time (h)
1a
2a
50
50
5
5
86
85
58
66
90
10
0
0
c
2
0
0
d
3
RT
RT
40
24
3
4
60
10
60
60
60
0
e
5
1.5
1.5
5
10
90
e
6
40
f
7
50
80
8
80
12
0
0
a
b
c
d
Reaction conditions: 0.05 mmol [RuCl2(η6-C6H6)]2, 0.1 mmol ligand (L1), 2 mL of MeOH. Isolated yield. CHCl3 was used as solvent. Ligand
e
f
L1 (0.2 mmol). Ratio of 1a and 2a was determined by 31P NMR. Precipitation (55%) as a red solid and from the reaction mixture 25% are
obtained.
methanone (L2), (dicyclohexyl phosphino)(thiophen-2-yl)-
methanone (L3), and dicyclohexyl benzoyl phosphine (L4)
were successfully prepared starting from 2-furoyl chloride, 2-
thiophenecarbonyl chloride, and benzoyl chloride, respectively.
Notably, all of these acylphosphine ligands are stable to air and
moisture. Surprisingly, ligand L1 was even stable in water
(D2O) for several days (see Supporting Information).
Next, the acylphosphine ligands L1−L3 were allowed to
react in methanol at ambient temperature with the ruthenium
complexes Ru(Me-allyl)2(COD) and [RuCl2(COD)]n. We
expected that the COD (cis,cis-cycloocta-1,5-diene) group
would be rapidly displaced by the dicyclohexyl 1-naphthoyl
phosphine ligand under this condition. However, both Ru(Me-
allyl)2(COD) and [RuCl2(COD)]n precursors gave only a
mixture of products, which was difficult to purify. In contrast,
the reaction of the ruthenium dimer [RuCl2(η6-C6H6)]2 with
L1 gave the well-defined complex 1a [RuCl2(η6-C6H6)(Cy2P-
(1-naphthoyl))] in methanol as well in chloroform at 50 °C
(Table 1, entries 1 and 2). Carrying out the reaction with 4
equiv of the ligand (L1) gave the same product (Table 1, entry
3).
Under the optimized reaction conditions (MeOH at 60 bar
of H2 at 50 °C using 0.5 equiv of [RuCl2(η6-C6H6)]2 and 1.0
equiv of the ligand), we examined the reaction of related
ligands (dicyclohexyl phosphino)(furan-2-yl)methanone (L2)
and (dicyclohexyl phosphino)(thiophen-2-yl)methanone (L3)
and ruthenium benzene dimer. Again, the conversion of both
ligands L2 and L3 proceeded with complete reduction (99%)
of the acyl group giving 54 and 60% yield of corresponding
complexes 2b and 2c, as shown in Scheme 2.
Scheme 2. Synthesis of Ruthenium Benzyl-Type Phosphine
a
Complexes
Then, we started carrying out a set of hydrogenation
experiments to study the behavior of complex 1a and
acylphosphine ligand L1 under this condition. Obviously, a
ruthenium hydride complex was expected to be formed by
hydrogenolysis since a large number of ruthenium complexes
are known to activate molecular hydrogen. Instead, to our
surprise, we obtained a mixture of 1a and the reduced complex
2a [RuCl2(η6-C6H6)(Cy2P(1-methylnaphthyl))] under 10 bar
H2 at 40 °C after 5 h (Table 1, entry 5). Apparently, the
carbonyl group of the ligand L1 in complex 1a is partially
reduced to a methylene unit. To improve the yield of 2a, we
increased the pressure to 60 bar of hydrogen, and the ratio of
1a/2a was increased to 10:90. Full conversion toward 2a was
observed at 50 °C and 60 bar of hydrogen, yielding 80% of 2a.
Increasing the reaction temperature further from 50 to 80 °C
and increasing the time to 12 h gave only decomposition
products (Table 1, entries 6−8). To the best of our knowledge,
such hydrogenation of acylphosphine ligands is not known yet.
a
Reaction conditions: [RuCl2(η6-C6H6)]2 (0.5 equiv), ligand (L1−L3)
(1.0 equiv), 2 mL of MeOH, 60 bar H2, 50 °C, 5 h. Isolated yield.
It should be noted that this hydrogenation constitutes a
convenient way to synthesize benzyl-type phosphine ruthenium
complexes starting from easily accessible aroyl phosphine
complexes since the synthesis of free benzyl-type ligands is
often tedious. For example, in the case of 1-methylnaphthyl
dicyclohexyl phosphine, which is not described in the literature,
we were able to obtain the borane adduct, but the release of the
free ligand with morpholine failed.11 Notably, the binding of
the phosphine ligand in complex 2a should be stronger
compared to the binding of the acylphosphine in 1a. Indeed, a
31P NMR experiment with equimolar amounts of 2a and ligand
L1 in CDCl3 showed no formation of 1a, indicating that no
ligand exchange occurred.
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The structure of complex 2a was confirmed by X-ray analysis
time nor increasing the temperature from 50 to 80 °C gave rise
to the formation of complex 6. Also, other experiments starting
from 3 and 4 failed to give complex 6.
1
and was additionally characterized by H, 13C, 31P NMR, and
1
high-resolution mass spectroscopy. More specifically, the H
The unusual complex 4 was characterized by 1H, 13C, and 31
P
NMR spectra show a doublet at 3.98 (d, J = 10.7 Hz, 2H),
which can be assigned to the CH2 protons of the alkyl moiety.
The 31P NMR shifts of 2a and 1a at 39.01 and 48.07 ppm,
respectively, show the expected downfield shift, while 28.79
ppm was observed in the case of the free ligand L1. The
molecular structure of 2a shows the piano-stool geometry at the
ruthenium center, which is coordinated by a benzene molecule,
two chlorine atoms, and the benzyl phosphine ligand (Figure
1).
NMR, and high-resolution mass spectroscopy (HRMS) as well
as X-ray crystal structure analysis (Figure 2). Again, we
Figure 2. Molecular structure of complex 4. The thermal ellipsoids
correspond to 30% probability. Hydrogen atoms (except H2 and H26)
are omitted for clarity.
observed piano-stool geometry at the ruthenium center. In the
solid state, the phosphine ligand in 4 coordinates only via the
phosphorus atom to the ruthenium center, and no additional
coordination via oxygen is observed. The NMR spectrum of
complex 4 mixed with D2O confirmed the existence of the free
OH group by diminishing the signal at 4.5 ppm. To the best of
our knowledge, no example of such ruthenium complex has
been reported.12
In conclusion, we describe the synthesis of ruthenium
complexes 2a−c, 3, and 4 with benzyl-type phosphine ligands
from air-stable acylphosphine ligands L1−L4. These ligands
can be easily obtained from the reaction of acid chlorides and
dialkyl phosphine in good yields. The formation of the novel
Figure 1. Molecular structure of complex 2a. The thermal ellipsoids
correspond to 30% probability. Hydrogen atoms are omitted for
clarity.
Using dicyclohexyl benzoyl phosphine (L4) in this hydro-
genation reaction, an interesting difference of reactivity was
observed giving insight into the detailed pathway of the
reaction. Unpredictably, the addition of dicyclohexyl benzoyl
phosphine (L4) to the ruthenium dimer followed by hydro-
genation resulted in the formation of the dicyclohexyl-
phosphino-1-hydroxybenzyl ruthenium complex 4 and not
the expected complex 6 (Scheme 3). Neither a longer reaction
Scheme 3. Reactions of Ligand L4 and Complex 3
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1H, CH), 7.35−7.30 (m, 1H, CH), 6.50−6.44 (m, 1H, CH),
2.09−1.92 (m, 2H, Cy), 1.82−1.52 (m, 10H, Cy), 1.34−0.97 (m, 10H,
Cy). 13C NMR (75 MHz, CDCl3): δ 202.3, 201.8, 156.4, 155.8, 146.7,
119.5, 119.4, 111.9, 32.1, 31.9, 30.3, 30.1, 29.7, 29.5, 27.2, 27.0, 26.9,
26..8, 26.1. 31P NMR (121 MHz, CDCl3): δ 18.9. IR (neat, cm−1):
2920, 2848, 1615, 1446, 1253, 1025, 787. MS (EI): 292 (56) [M]+, 95
(100), 128 (44), 197 (33), 209 (47). HRMS calcd for C17H26O2P (M
+ H)+ 293.16649; found 293.16662. Anal. Calcd for C17H25O2P: C,
69.84; H, 8.62; P, 10.59. Found: C, 70.04; H, 8.78; P, 10.66.
complexes proceeds via regioselective CO hydrogenation of
the acylphosphine ligand.
EXPERIMENTAL SECTION
■
General Considerations. All reactions were performed under
argon by using standard Schlenk techniques. All solids were weighed in
air. Dicyclohexyl phosphine and Et3N were purchased from Sigma-
Aldrich and used as received. Acid chlorides were purchased from
Strem and Sigma-Aldrich. [RuCl2(η6-C6H6)]2 complex was commer-
cially available from Sigma-Aldrich. All other reagents were purchased
from common suppliers and used without further purification.
Heptane and methanol were distilled in an argon atmosphere over
lithium hydride and magnesium turnings, respectively. Chloroform was
distilled over P2O5.
(Dicyclohexylphosphino)(thiophen-2-yl)methanone (L3).
Following the procedure for the preparation of L1, the reaction of
thiophene-2-carbonyl chloride (1g, 6.8 mmol), dicyclohexyl phosphine
(1.21 g, 6.08 mmol), and triethylamine (0.81 g, 8.0 mmol) in THF (10
mL) gave 1.78 g (85%) of a yellow solid. Purification of the crude
1
product is analogous to L1. H NMR (300 MHz, CDCl3): δ 7.97−
7.91 (m, 1H, thiophenyl), 7.65−7.59 (m, 1H, thiophenyl), 7.13−7.10
(m, 1H, thiophenyl), 2.09−1.94 (m, 2H, Cy), 1.85−1.53 (m, 10H,
Cy), 1.32−0.98 (m, 10H, Cy). 13C NMR (75 MHz, CDCl3): δ 206.8,
206.2, 149.6, 149.1, 133.9, 133.9, 127.9, 32.4, 32.2, 30.3, 30.2, 29.7,
29.6, 27.2, 27.1, 27.0, 26.9, 26.1. 31P NMR (121 MHz, CDCl3): δ 19.7.
IR (neat, cm−1): 2924, 2847, 1607, 1404, 800, 742. MS (EI): 308 (47)
[M]+, 111 (100), 197 (25), 225 (27). HRMS calcd for C17H26OPS (M
+ H)+ 309.14365; found 309.14381. Anal. Calcd for C17H25OPS: C,
66.20; H, 8.17; P, 10.04; S, 10.40. Found: C, 66.24; H, 8.23; P, 10.01;
S, 10.45.
Analytical Methods. NMR data were recorded on Bruker ARX
1
300 and Bruker ARX 400 spectrometers. 13C and H NMR spectra
were referenced to signals of deutero solvents and residual protonated
solvents, respectively. 31P NMR chemical shifts are reported relative to
85% H3PO4. Gas chromatography analysis was performed on an
Agilent HP-5890 instrument with a FID detector and HP-5 capillary
column (polydimethylsiloxane with 5% phenyl groups, 30 m, 0.32 mm
i.d., 0.25 μm film thickness) using argon as carrier gas. Gas
chromatography−mass analysis was carried out on a Agilent HP-
5890 instrument with an Agilent HP-5973 mass selective detector (EI)
and HP-5 capillary column (polydimethylsiloxane with 5% phenyl
groups, 30 m, 0.25 mm i.d., 0.25 μm film thickness) using helium
carrier gas. ESI HR-MS measurements were performed on an Agilent
1969A TOF mass spectrometer. The combustion analysis data for P
were collected using the UV/vis spectrometer Lamda 2 (Perkin-
Elmer), while the combustion data for C/H/S were obtained from a
C/H/N/S Mikroanalysator−TruSpec CHNS Micro (Leco). Suitable
samples for correct elementary analysis of all ruthenium complexes
were obtained by washing the crude product several times with
methanol and subsequently drying the material in high vacuum.
Diffraction data were collected on a Bruker Kappa APEX II Duo
diffractometer using graphite monochromated Mo Kα radiation. The
structures were solved by direct methods and refined by full-matrix
least-squares procedures on F2 with the SHELXTL software package.13
XP (Bruker AXS) was used for graphical representations.
Dicyclohexyl Benzoyl Phosphine (L4). Following the procedure
for the preparation of L1, the reaction of benzoyl chloride (1g, 7.14
mmol), dicyclohexyl phosphine (1.47 g, 7.14 mmol), and triethylamine
(0.87 g, 8.57 mmol) in THF (10 mL) gave 1.55 g (72%) of a yellow
1
solid. Purification of the crude product is analogous to L1. H NMR
(300 MHz, CDCl3): δ 8.04−7.96 (m, 2H, Ph), 7.59−7.50 (m, 1H,
Ph), 7.49−7.39 (m, 2H, Ph), 2.09−1.93 (m, 2H, Cy), 1.85−1.55 (m,
10H, Cy), 1.36−0.98 (m, 10H, Cy). 13C NMR (75 MHz, CDCl3): δ
218.0, 217.4, 142.2, 141.7, 133.1, 128.4, 128.1, 128.0, 32.3, 32.1, 30.8,
30.6, 29.7, 29.5, 27.4, 27.2, 27.1, 27.0, 26.2. 31P NMR (121 MHz,
CDCl3): δ 19.3. IR (neat, cm−1): 2917, 2849, 1633, 1445, 1209, 1167,
777, 692. MS (EI): 302 (100) [M]+, 197 (35), 219 (23). HRMS calcd
for C19H28OP (M + H)+ 303.18723; found 303.18770. Anal. Calcd for
C19H27OP: C, 75.47; H, 9.00; P, 10.24. Found: C, 75.35; H, 9.02; P,
10.22.
Synthesis of [RuCl2(η6-C6H6)(Cy2P(1-naphthoyl))] 1a. To a
Schlenk tube containing [RuCl2(η6-C6H6)]2 (50 mg, 0.10 mmol) and
Cy2P(1-naphthoyl) (77 mg, 0.22 mol) was added MeOH (3 mL). The
resulting solution was stirred for 5−6 h at 50 °C under argon, and then
the solvent was removed. After washing the crude material three times
with heptane and drying in vacuum, the desired product was obtained
as an orange powder (108 mg, 89%). 1H NMR (300 MHz, CDCl3): δ
8.54 (d, J = 7.7 Hz, 1H, naphthyl), 8.63 (d, J = 8.1 Hz, 1H, naphthyl),
8.05 (d, J = 8.1 Hz, 1H, naphthyl), 7.93 (d, J = 7.7 Hz, 1H, naphthyl),
7.74−7.50 (m, 3H, naphthyl), 5.55 (s, 6H, benzene), 2.74 (br s, 2H,
Cy), 2.39 (br s, 2H, Cy), 1.86−0.89 (m, 18H, Cy). 13C NMR (75
MHz, CDCl3): δ 215.5, 215.4, 134.4, 134.2, 130.0, 129.0, 128.8, 126.9,
124.8, 124.5, 88.8, 88.7, 35.4, 35.2, 31.1, 31.0, 29.7, 28.2, 28.1, 27.2,
27.0, 26.0. 31P NMR (121 MHz, CDCl3): δ 48.0. IR (neat, cm−1)
ν(CO): 2923 cm−1. HRMS calcd for C29H35Cl2OPRuNa (M +
Na)+ 625.07403; found 625.07453. Anal. Calcd for C29H35Cl2OPRu:
C, 57.81; H, 5.85; P, 5.14. Found: C, 57.61; H, 5.79; P, 5.22.
Synthesis of [RuCl2(η6-C6H6)(Cy2P(1-methylnaphthyl))] 2a. A
mixture of [RuCl2(η6-C6H6)]2 (25 mg, 0.05 mmol, 1.0 equiv) and
dicyclohexyl 1-naphthoyl phosphine (L1) (35.2 mg, 0.1 mmol, 2.0
equiv) was given in a 12 mL vial equipped with a stirring bar, septum,
and needle. After flashing with argon, 2 mL of MeOH was added, and
the vial was placed in an alloy plate, which was transferred to a 300 mL
autoclave of the 4560 series from Parr Instruments under argon
atmosphere. The autoclave was then filled with 60 bar H2 at room
temperature. The reaction mixture was stirred (400 rpm) for 5 h at 50
°C. Next, the autoclave was cooled with ice water, and the pressure
was slowly released. The cold reaction solution was dark and contained
a red brown residue. The solution over the solid was carefully
decanted, and the solid was washed three times with 1−2 mL of
Dicyclohexyl 1-Naphthoyl Phosphine (L1). At room temper-
ature, 1-naphthoyl chloride (1g, 5.26 mmol) was added dropwise over
a period of 20 min to a solution of dicyclohexyl phosphine (1.04 g,
5.26 mmol) and triethylamine (0.64 g, 6.31 mmol) in THF (10 mL),
and the resulting mixture was stirred for 5 h. Next, the mixture was
quenched with H2O (10 mL), and the product was extracted with
CH2Cl2 (2 × 50 mL). The combined CH2Cl2 extracts were washed
with water (20 mL), dried over Na2SO4, and evaporated to give L1 as
a yellow solid (1.45 g, 78%). For purification, the crude product was
dissolved in a mixture of 1 mL of chloroform and 8 mL of methanol
and was kept overnight in the refrigerator (+8 °C). After being washed
with heptane, the title compound was obtained as an analytically pure
yellow solid. 1H NMR (300 MHz, CDCl3): δ 8.57 (d, J = 7.9 Hz, 1H,
arom), 8.37−8.30 (m, 1H, arom), 7.98 (d, J = 8.6 Hz, 1H, arom), 7.88
(d, J = 8.0 Hz, 1H, arom), 7.63−7.46 (m, 3H, arom), 2.13−1.98 (m,
2H, Cy), 1.96−1.53 (m, 10H, Cy), 1.36−0.93 (m, 10H, Cy). 13C
NMR (75 MHz, CDCl3): δ 222.1, 221.6, 139.8, 139.4, 134.0, 134.0,
132.8, 130.5, 130.2, 128.9, 128.9, 128.3, 127.9, 126.4, 125.4, 124.2,
33.0, 32.8, 31.1, 31.0, 29.7, 29.6, 27.4, 27.3, 27.2, 27.1, 26.2. 31P NMR
(121 MHz, CDCl3): δ 28.8. IR (neat, cm−1): 2924, 2850, 1627, 1447,
1234, 1133, 779, 495. MS (EI): 352 (14) [M]+, 155 (100), 156 (13).
HRMS calcd for C23H30OP (M + H)+ 353.20288; found 353.20213.
Anal. Calcd for C23H29OP: C, 78.38; H, 8.29; P, 8.79. Found: C,
78.62; H, 8.10; P, 8.80.
(Dicyclohexylphosphino)(furan-2-yl)methanone (L2). Follow-
ing the procedure for the preparation of L1, the reaction of furan-2-
carbonyl chloride (1g, 7.66 mmol), dicyclohexyl phosphine (1.37 g,
6.92 mmol), and triethylamine (1.28 g, 9.0 mmol) in THF (10 mL)
gave 1.789 g (84%) of a yellow solid. Purification of the crude product
1
is analogous to L1. H NMR (300 MHz, CDCl3): δ 7.59−7.55 (m,
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MeOH. Then, the complex was dried under vacuum, and the desired
complex was obtained in 55% (32 mg) yield as a stable orange powder.
Crystallization from CHCl3/heptane gave at −28 °C red crystals
suitable for X-ray analysis. Further product can be achieved from the
reaction solution. After removing MeOH, the dark residue was solved
in a mixture of CHCl3 and heptane. From the solution, 15 mg (25%)
of red crystals was obtained at −28 °C. 1H NMR (300 MHz, CDCl3):
δ 8.38 (d, J = 8.9 Hz, 1H, naphthyl), 7.80 (d, J = 8.0 Hz, 1H,
naphthyl), 7.72 (d, J = 8.3 Hz, 1H, naphthyl), 7.58−7.33 (m, 3H,
naphthyl), 7.21 (d, J = 7.0 Hz, 1H, naphthyl), 5.72 (s, 6H, benzene),
3.98 (d, J = 10.7 Hz, 2H, CH2), 2.37 (m, 2H, Cy), 2.11 (m, 2H, Cy),
1.78 (m, 2H, Cy), 1.69−0.68 (m, 16H, Cy). 13C NMR (75 MHz,
CDCl3): δ 133.9, 133.1, 133.0, 128.4, 127.4, 127.3, 127.2, 127.2, 126.0,
125.8, 125.1, 125.0, 87.0, 86.9, 35.9, 29.8, 29.0, 27.4, 27.3, 27.1, 27.0,
26.2. 31P NMR (121 MHz, CDCl3): δ 39.1. HRMS (ESI) m/z+ calcd
for C29H37Cl2PRuNa (M + Na)+ 611.09477; found 611.09616. Anal.
Calcd for C29H37Cl2PRu: C, 59.18; H, 6.34; P, 5.26. Found: C, 59.19;
H, 6.44; P, 5.25.
Calcd for C25H33Cl2OPRu: C, 54.35; H, 6.02; P, 5.61. Found: C,
54.48; H, 6.12; P, 5.68.
Synthesis of [RuCl2(η6-C6H6)(Cy2P(phenyl)methanol)] 4.
Following the procedure for the preparation of 2a, the reaction of
[RuCl2(η6-C6H6)]2 (25 mg, 0.05 mmol, 1 equiv) and dicyclohexyl
benzoyl phosphine (L4) (30.3 mg, 0.1 mmol, 2.0 equiv) gave 23 mg
(42%) of a ocher solid. Recrystallization from CHCl3/heptane gave
red crystals suitable for X-ray analysis. 1H NMR (400 MHz, CDCl3): δ
7.39−7.31 (m, 2H, Ph), 7.31−7.21 (m, 3H, Ph), 5.95−5.88 (s, 1H,
CH), 5.65 (s, 6H, benzene), 4.40 (s, 1H, OH), 2.41−2.22 (m, 2H,
Cy), 1.96−1.43 (m, 12H, Cy), 1.42−0.87 (m, 8H, Cy). 13C NMR
(100 MHz, CDCl3): δ 128.2, 128.2, 128.1, 128.0, 128.0, 127.9, 87.2,
87.1, 73.1, 72.8, 38.3, 38.1, 37.4, 37.3, 31.9, 30.4, 30.3, 29.7, 28.8, 27.8,
27.7, 27.7, 27.6, 27.2, 27.1, 26.5, 26.3. 31P NMR (121 MHz, CDCl3): δ
37.6. HRMS (ESI) m/z+ calcd for C25H35ClOPRu (M − Cl)+
521.11528; found 521.11566. Anal. Calcd for C25H35Cl2OPRu: C,
54.15; H, 6.36; P, 5.59. Found: C, 54.04; H, 6.45; P, 5.52.
Crystal Data for 4: C26.5H36.5Cl6.5OPRu, M = 733.52, triclinic, space
group P1, a = 14.6405(5) Å, b = 15.2404(5) Å, c = 16.8663(6) Å, α =
̅
Crystal Data for 2a: C30H41Cl2OPRu, M = 620.57, triclinic, space
group P, a = 9.4204(1) Å, b = 10.1326(2) Å, c = 16.0790(3) Å, α =
92.781(1)°, β = 106.513(1)°, γ = 96.699(1)°, V = 1456.06(4) Å3, T =
150(2) K, Z = 2, 27 297 reflections measured, 6670 independent
reflections (Rint = 0.0245), final R values (I > 2σ(I)): R1 = 0.0255, wR2
= 0.0707, final R values (all data): R1 = 0.0320, wR2 = 0.0753, 347
parameters; presence of CH3OH in the crystal lattice.
94.309(2)°, β = 97.282(2)°, γ = 115.195(2)°, V = 3342.7(2) Å3, T =
150(2) K, Z = 4, 75 677 reflections measured, 15 344 independent
reflections (Rint = 0.0461), final R values (I > 2σ(I)): R1 = 0.0533, wR2
= 0.1381, final R values (all data): R1 = 0.0679, wR2 = 0.1474, 606
parameters. The asymmetric unit of compound 4 contains two
complex molecules (only one of them is depicted in Figure 2) and
three solvent molecules (CHCl3). Contributions of further disordered
solvents were removed from the diffraction data with PLATON/
SQUEEZE [Spek, A. L. Acta Crystallogr. 2009, D65, 148−155].
Synthesis of 5. The D2O experiment was carried out in an NMR
tube by adding 0.2 mL of D2O to 4 dissolved in CDCl3. The crude
Synthesis of [RuCl2(η6-C6H6)(Cy2P(furan-2-ylmethyl))] 2b.
Following the procedure for the preparation of 2a, the reaction of
[RuCl2(η6-C6H6)]2 (25 mg, 0.05 mmol, 1 equiv) and (dicyclohexyl
phosphino)(furan-2-yl)methanone (L2) (29.2 mg, 0.1 mmol, 2 equiv)
gave 29 mg (54%) of an orange solid. 1H NMR (300 MHz, CDCl3): δ
7.34−7.21 (m, 1H, furanyl), 6.32−6.28 (m, 1H, furanyl), 6.04−5.99
(m, 1H, furanyl), 5.69 (s, 6H, benzene), 3.57 (d, J = 9.1 Hz, 2H, CH2),
2.36−2.19 (m, 2H, Cy), 2.19−1.03 (m, 2H, Cy), 2.00−1.64 (m, 8H,
Cy), 1.56−1.37 (m, 2H, Cy), 1.37−1.09 (m, 8H, Cy). 13C NMR (75
MHz, CDCl3): δ 149.6, 141.0, 141.0, 111.0, 108.7, 108.7, 86.9, 86.8,
38.4, 38.1, 28.7, 28.6, 28.5, 27.6, 27.4, 27.3, 26.3, 18.1. 31P NMR (121
MHz, CDCl3): δ 33.9. HRMS (ESI) m/z+ calcd for C23H33ClOPRu
(M − Cl)+ 495.09958; found 495.09917. Anal. Calcd for
C23H33Cl2OPRu: C, 52.27; H, 6.29; P, 5.86. Found: C, 52.26; H,
6.33; P, 5.89.
1
product was analyzed by H NMR (300 MHz, CDCl3): δ 7.41−7.22
(m, 5H), 5.97 (d, J = 6.3 Hz, 1H), 5.72 (s, 6H), 2.43−2.23 (m, 2H),
2.05−1.43 (m, 15H), 1.43−1.13 (m, 5H).
ASSOCIATED CONTENT
* Supporting Information
NMR spectra of products. This material is available free of
charge via the Internet at http://pubs.acs.org.
■
S
AUTHOR INFORMATION
Corresponding Author
*E-mail: matthias.beller@catalysis.de.
■
Synthesis of [RuCl2(η6-C6H6)(Cy2P(thiophen-2-ylmethyl))] 2c.
Following the procedure for the preparation of 2a, the reaction of
[RuCl2(η6-C6H6)]2 (25 mg, 0.05 mmol, 1 equiv) and (dicyclohexyl
phosphino)(thiophen-2-yl)methanone (L3) (30.8 mg, 0.1 mmol, 2
Present Address
†Division of Organic Chemistry, Institute of Chemical and
Engineering Sciences, 8 Biomedical grove, Neuros, #07-01,
Singapore 138665.
1
equiv) gave 33 mg (60%) of an orange solid. H NMR (300 MHz,
CDCl3): δ 7.18−7.13 (m, 1H, thiophenyl), 6.95−6.99 (m, 1H,
thiophenyl), 6.85−6.80 (m, 1H, thiophenyl), 5.66 (s, 6H, benzene),
3.78 (d, J = 9.1 Hz, 2H, CH2), 2.46−2.30 (m, 2H, Cy), 2.18−2.05 (m,
2H, Cy), 2.00−1.70 (m, 8H, Cy), 1.57−1.40 (m, 2H, Cy), 1.40−1.18
(m, 2H, Cy). 13C NMR (75 MHz, CDCl3): δ 128.3, 127.8, 127.0,
124.4, 86.9, 86.9, 38.0, 37.8, 29.0, 28.9, 27.6, 27.4, 27.3, 27.2, 26.3. 31P
NMR (121 MHz, CDCl3): δ 32.9. HRMS (ESI) m/z+ calcd for
C23H33ClPRuS (M − Cl)+ 511.07695; found 511.07765. Anal. Calcd
for C23H33Cl2PRuS: C, 50.73; H, 6.11; P, 5.69; S, 5.89. Found: C,
50.98; H, 6.21; P, 5.71; S, 5.85.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work has been funded by the State of Mecklenburg−
Western Pomerania, the BMBF, and the DFG (Leibniz Prize).
We thank S. Leiminger for excellent technical assistance. For
analytical support, we are grateful to Dipl. Ing.-A Koch and Drs.
W. Baumann and C. Fischer. We also thank A. Lehmann for
determining the combustion analysis data (all LIKAT).
Synthesis of [RuCl2(η6-C6H6)(Cy2P(benzoyl))] 3. A mixture of
[RuCl2(η6-C6H6)]2 (125 mg, 0.25 mmol, 1.0 equiv) and dicyclohexyl
benzoyl phosphine (L4) (165 mg, 0.55 mmol, 2.2 equiv) was dissolved
in MeOH. The reaction mixture was stirred for 5 h at 50 °C. The
solution was fully evaporated in a vacuum and washed three times with
heptane. Then, the complex was dried under vacuum to give 221 mg
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■
1
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