Synthesis of stable phosphomide ligands and their use in Ru-catalyzed hydrogenations of bicarbonate and related substrates

Article abstract of DOI:10.1002/cssc.201200732

New benzoyl- and naphthoyl-substituted phosphines have been synthesized, which are stable to air and moisture. Testing these so-called phosphomide ligands in the presence of different ruthenium precursors, the hydrogenation of sodium bicarbonate (NaHCO₃) to sodium formate (NaHCO₂) proceeded with good catalyst turnover numbers in the range of 1300-1600 at 80 °C and a total pressure of hydrogen of 60 bar in the absence of amines or other additives. Similarly, catalytic hydrogenations of carbon dioxide, cinnam-, and benzaldehyde were possible with these new ruthenium complexes. As an intermediate of the catalytic cycle the defined ruthenium complex [(η⁶-C₆H₆)-RuCl₂(Cy ₂P(1-naphthoyl)] (Cy=cyclohexyl) was prepared and characterized by X-ray crystallography. Ruthenium and phosphor work wonders: Air-stable ruthenium phosphomide complexes are active catalysts in the hydrogenation of sodium bicarbonate, carbon dioxide, and carbonyl compounds. Hydrogenation proceeds with high catalyst turnover numbers in the absence of amines or other additives. The application range of these new ruthenium catalysts also includes the hydrogenation of cinnamaldehyde and benzaldehyde. Copyright

Full text of DOI:10.1002/cssc.201200732

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DOI: 10.1002/cssc.201200732
Synthesis of Stable Phosphomide Ligands and their Use in
Ru-Catalyzed Hydrogenations of Bicarbonate and Related
Substrates
Saravanan Gowrisankar, Christopher Federsel, Helfried Neumann, Carolin Ziebart,
Ralf Jackstell, Anke Spannenberg, and Matthias Beller*[a]
New benzoyl- and naphthoyl-substituted phosphines have
been synthesized, which are stable to air and moisture. Testing
these so-called phosphomide ligands in the presence of differ-
ent ruthenium precursors, the hydrogenation of sodium bicar-
bonate (NaHCO3) to sodium formate (NaHCO2) proceeded with
good catalyst turnover numbers in the range of 1300–1600 at
808C and a total pressure of hydrogen of 60 bar in the ab-
sence of amines or other additives. Similarly, catalytic hydroge-
nations of carbon dioxide, cinnam-, and benzaldehyde were
possible with these new ruthenium complexes. As an inter-
mediate of the catalytic cycle the defined ruthenium complex
[(h6-C6H6)-RuCl2(Cy2P(1-naphthoyl)] (Cy=cyclohexyl) was pre-
pared and characterized by X-ray crystallography.
Introduction
Organometallic complexes with phosphine ligands represent
the most important catalysts for the homogeneous hydrogena-
tion of unsaturated compounds, such as olefins, alkynes, ke-
tones, etc.[1] More recently, these catalysts became also of in-
terest for hydrogen storage and the utilization of C1 building
blocks. In this respect, especially molecular-defined complexes
of ruthenium and iridium have been investigated for the cata-
lytic hydrogenation of carbon dioxide and bicarbonate.[2]
In general, well-known triaryl- or trialkylphosphines (R3P, I) are
used to modify and control the activity and selectivity of the
respective active metal centers.
Figure 1. Comparison between phosphines and phosphomide ligands.
secondary phosphines with carboxylic acid derivatives and
should be less prone towards P-oxidation.
Based on our continuing interest in the refinement of
carbon dioxide,[3] we became attracted to investigate the cata-
lytic potential of less common phosphorous ligands for the re-
duction of bicarbonate and CO2. More specifically, we had the
idea to use acyl-substituted phosphorus ligands (R2PCOR, II),
which have been largely neglected in homogeneous cataly-
sis.[4] These so-called phosphomide ligands (Figure 1) are char-
acterized by decreased s-donor and increased p-acceptor abili-
ties relative to traditional triaryl- or trialkylphosphines. Because
Herein, we describe the preparation of several new phos-
phomide ligands, which are surprisingly stable to air and mois-
ture. For the first time the catalytic potential of this class of li-
gands is demonstrated in the hydrogenation of carbon dioxide
to formic acid derivatives, sodium bicarbonate to sodium for-
mate, and cinnamaldehyde and benzaldehyde to the corre-
sponding alcohols.
of the assumed labile PÀCO bond, only few studies on the Results and Discussion
electronic properties of phosphomide ligands and the catalytic
Synthesis of phosphomide ligands
behavior of corresponding complexes have been reported so
far.[4] Additionally, such ligands might be conveniently pre-
pared relative to traditional phosphines by direct reaction of
Previous reports suggested that phosphomide ligands are ef-
fectively prepared from alkylsilylphosphines, dialkylphosphines,
and metalated phosphides by reaction with ketene, benzoyl
chloride, or other acid chlorides, respectively.[5] However, a vari-
ety of sterically hindered phosphomides can be conveniently
synthesized from commercially available acid chlorides and
secondary phosphines (Scheme 1). Notably, this method gives
easy access to new phosphomides (L8–L20) from aromatic,
heteroaromatic, and aliphatic carboxylic acids. As an example,
the reaction of benzoyl chloride with diadamantylphosphine in
the presence of triethylamine immediately gives a bright
[a] Dr. S. Gowrisankar, Dr. C. Federsel, Dr. H. Neumann, C. Ziebart,
Dr. R. Jackstell, Dr. A. Spannenberg, Prof. Dr. M. Beller
Leibniz-Institut fꢀr Katalyse e.V.
Universitꢁt Rostock
Albert-Einstein-Straße 29a, 18059 Rostock (Germany)
Fax: (+49)381-1281-5000
E-mail: matthias.beller@catalysis.de
Supporting Information for this article is available on the WWW under
http://dx.doi.org/10.1002/cssc.201200732.
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lysts. Interestingly, our new ligands gave rise to also more
active catalysts relative to [Ru(Me-allyl)2(cod)] in the presence
of commercially available ligands, such as triphenylphosphine
(PPh3), tricyclohexylphosphine (PCy3), dicyclohexylphosphine
(PHCy2), 1,1’-bis(diphenylphosphino)-ferrocene (dppf), 1,2,-bis-
(diphenylphosphino)ethane (dppe), di(1-adamantyl)-n-butyl-
phosphine (BuPAd2), and di(1-adamantyl)-benzylphosphine
(BzPAd2). With all these ligands, only a low yield of the desired
sodium formate (<18%) was obtained (Table 1, entry 1–7).
Conversely, experiments performed in the presence of L8 pro-
vided formate in 36% yield with a catalyst turnover number
(TON) of 875. Due to this promising result, we tested ligands
L9–L20 under similar reaction conditions in the same model
reaction (Table 1). Applying L14 gave rise to a yield in formate
Scheme 1. General synthesis of phosphomide ligands.
Table 1. Catalytic hydrogenation of bicarbonate to formate: Variation of
ligands (L1–L20).[a]
orange solution of diadamantyl benzoyl phosphine (L8) as the
only phosphorus-containing product. In general, the new
phosphomides are obtained in good yield (>70%) and high
purity (>90%) simply by filtration and removal of the solvent.
Notably, most of the prepared ligands are remarkably stable to
air and moisture. Hence, even after several days in THF/H2O
only a negligible amount of hydrolysis and impurities was de-
tected by 31P NMR spectroscopy (see the Supporting Informa-
tion).[6]
Ligand
Yield
[%]
TON
73
Ligand
Yield
[%]
TON
389
3
16
7
7
170
170
437
–
3
–
73
The unusual stability of different ligands stems from the in-
creased steric protection of bulky cyclohexyl, tert-butyl, or ada-
mantyl substituents on the phosphorous atom. This may also
prevent the coplanar orientation between the carbonyl group
and the lone electron pair of the phosphorus atom, which is
required for the conjugation/delocalization of phosphomide
ligands.
18
36
872
13
30
316
729
14
23
340
559
Catalytic tests: Hydrogenation of NaHCO3, CO2, cinnamalde-
hyde, and benzaldehyde
In the past two decades a variety of rhodium-, iridium-, and
ruthenium-based complexes have been developed for the hy-
drogenation of CO2 to formic acid derivatives.[7] The insertion
of CO2 into ruthenium hydride complexes was intensively stud-
ied with water-soluble phosphine ligands, such as triphenyl-
phosphine monosulfonate (TPPMS), triphenylphosphine trisul-
fonate (TPPTS), P(CH2OH)3, P(CH2CH2CH2OH)3, P(CH2CH2CN)3,
P(CH2)6N3, and 1,3,5-triaza-7-phosphaadamantane.[8] However,
much less work is known[9] on the related reduction of bicar-
bonates and the reported catalyst activities are significantly
lower[9a,e] relative to the reduction of CO2.
65
60
53
1575
20
486
1454[b]
1284[c]
13
15
21
316
364
510
12
16
12
292
389
292
To compare the activity of P-containing catalysts appropri-
ately, initially different commercially available ruthenium com-
plexes such as [RuCl2(C6H5)]2, [Ru(Me-allyl)2(cod)] (cod=1,5-cy-
clooctadiene), and [RuCl2(cod)] were tested for the hydrogena-
tion of sodium bicarbonate at a H2 pressure of 60 bar and
a temperature of 808C in methanol without any phosphine
ligand present. As expected, no desired reduction was ob-
served. However, in combination with L8, both [RuCl2(C6H6)]2
and [Ru(Me-allyl)2(cod)] generated active hydrogenation cata-
[a] Reaction conditions: NaHCO3 (1.6 g, 0.0190 mol), [Ru(Me-allyl)2(cod)]
(2.5 mg, 7.84ꢁ10À6 mol), L1–L20 (2.0 equiv), 808C, H2 (60 bar), 20 h. Yield
based on H NMR signals of sodium formate with THF used as an internal
standard. TON=mol of sodium formate/per mol of catalyst.
[b] [RuCl2(C6H5)]2 and L14 (2.0 equiv). [c] [RuCl2(cod)].
1
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We failed to obtain crystals of other ruthenium precursors,
such as [Ru(Me-allyl)2(cod)] and [RuCl2(cod)] suitable for X-ray
analysis. We also failed to obtain crystals of the defined ruthe-
nium carbonato complex 2[11] and the corresponding dihydride
complex 3[12] under different reaction conditions. These were
important intermediates in the catalytic cycle for the hydroge-
nation of bicarbonate.
Table 2. Ru/L14-catalyzed hydrogenation of sodium bicarbonate, carbon
dioxide, and carbonyl compounds.
Entry
Product
T
[8C]
P(H2/CO2)[a]
Yield
[%]
TON
1[b]
2[c]
3[d]
4[e]
sodium formate
methyl formate
benzyl alcohol
(E)-3-phenylprop-2-en-1-ol
80
100
80
60:0
30:30
50:0
50:0
15
20
64
87
7188
4126
1600
1764
As shown in Figure 2, in complex 1 the ruthenium atom is
coordinated to the benzene ring, two chloride atoms, and the
80
[a] Pressures are in bar. [b] NaHCO3 (1.26 g, 0.015 mol), [Ru(Me-allyl)2(cod)]
(0.313ꢁ10À6 mol), 20 h, L14 (2.0 equiv). [c] NEt3 (2 mL), MeOH (40 mL).
[d] Benzaldehyde (2.0 g, 0.0196 mol), tBuOK (0.45 mmol), catalyst (7.84ꢁ
10À6 mol). [e] Cinnamaldehyde (0.0159 mol), tBuOK (0.45 mmol), catalyst
(7.84ꢁ10À6 mol).
of 65% and a TON of 1575 after 20 h. By lowering the catalyst
amount, a remarkable TON of 7188 was achieved (Table 2,
entry 1). To the best of our knowledge, this is the highest TON
so far reported for the hydrogenation of bicarbonates using
purely hydrogen pressure without any additives. Notably, also
L14 was air-stable and could be conveniently handled in air.[10]
Subsequently, we set out to see whether the catalytic
system comprising [Ru(Me-allyl)2(cod)]/L14 could be applied
more generally for the hydrogenation of carbonyl compounds
and CO2. Methyl formate was produced from CO2 hydrogena-
tion with a TON of 4126 (Table 2, entry 2), whereas benzyl alco-
hol was produced from benzaldehyde without optimization in
64% yield and with a TON of 1600 (Table 2, entry 3). In addi-
tion, the hydrogenation of ethyl cinnamate to (E)-3-phenyl-
prop-2-en-1-ol was achieved in 87% yield and a TON of 1764
(Table 2, entry 4).
Figure 2. ORTEP representation of [(h6-C6H6)RuCl2(Cy2P(1-naphthoyl)]. Dis-
placement ellipsoids are drawn at the 30% probability level. Selected bond
lengths (ꢂ) and angles (8): Ru1ÀP1 2.3764(6), Ru1ÀCl1 2.4033(6), Ru1ÀCl2
2.3985(7), C1ÀO1 1.219(3), P1ÀRu1ÀCl1 89.29(2), P1ÀRu1ÀCl2 86.62(2), Cl1À
Ru1ÀCl2 88.21(2), C1ÀP1ÀRu1 105.95(7).
P-bonded phosphomide ligand.[10] The coordination geometry
at the ruthenium center can be described as a piano-stool
geometry.
Synthesis of a defined Ru phosphomide complex
Conclusions
The active catalyst species in the hydrogenations above are
likely to be monomeric ruthenium phosphomide complexes.
In this respect, the ability of ruthenium dimers, such as
[(h6-C6H6)RuCl2]2, to convert into monomeric ruthenium(II) com-
plexes of the general formula [RuCl2(h6-C6H6)L] (L=phosphine
donor ligand) through cleavage of the chloride bridges is well
documented. Under our conditions, the optimum ratio of
ruthenium dimer and ligand was found to be 1:2. Isolation of
the resulting complex [(h6-C6H6)RuCl2(Cy2P(1-naphthoyl)] (1)
was achieved in 86% yield by mixing [RuCl2(C6H5)]2 with two
equivalents of L14 in MeOH at 508C for 5 h (Scheme 2).
We have demonstrated that new phosphomides can be readily
prepared from carboxylic acid chlorides and secondary phos-
phines. This class of ligands has been largely neglected in cat-
alysis; however, with appropriate substituents they are remark-
ably stable to air and moisture. Combinations of phospho-
mides with commercially available ruthenium precursors gen-
erate active catalysts for the hydrogenation of carbonyl com-
pounds, carbon dioxide, and bicarbonate. In the case of
bicarbonate, improved catalyst TONs relative to previously
known catalyst systems have been achieved.
Experimental Section
General procedure for the forma-
tion of sodium formate: Dissolv-
ing [Ru(Me-allyl)2(cod)] (2.5 mg,
7.84ꢁ10À6 mol)
and
L14
(2.0 equiv) in MeOH (40 mL) led to
the immediate formation of a light
yellow solution. NaHCO3 (1.6 g,
0.0190 mol) was placed in an auto-
Scheme 2. Reaction conditions for the formation of 1: [(h6-C6H6)RuCl2]2 (1.0 equiv), Cy2P(1-naphthoyl) (2.0 equiv),
MeOH, 508C, 5 h.
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clave (100 mL) and the preformed catalyst solution was then
added. The autoclave was deoxygenated and then filled with H2
(60 bar) at room temperature. The reaction mixture was stirred
(400 rpm) for 20 h at 808C. Subsequently, the autoclave was
cooled with ice water and the pressure was slowly released. The
solution was fully evaporated in a rotary evaporator and the for-
mate content (white powder) was determined by H NMR spectros-
copy in D2O with THF as an internal standard and a relaxation time
of 20 s.
give L8 as an orange solid (2.15 g, 74%). The crude product was
recrystallized from MeOH. This synthesis produced the desired
product in high purity (>95%) as determined spectroscopically.
1H NMR (300 MHz, CDCl3): d=8.10–8.03 (m, 2H), 7.51–7.43 (m, 1H),
7.40–7.32 (m, 2H), 2.05–1.93 (m, 6H), 1.92–1.77 (m, 12H), 1.68–
1.54 ppm (m, 12H); 13C NMR (75 MHz, CDCl3): d=218.53, 217.84,
144.35, 143.90, 133.20, 128.91, 128.75, 128.39, 128.37, 43.51, 43.37,
41.54, 41.41, 38.60, 38.30, 36.86, 36.79, 28.92, 28.81 ppm; 31P NMR
(121 MHz, CDCl3): d=39.43 ppm; IR (neat): n˜ =2896, 2844, 1632,
1196, 1171, 797, 689 cmÀ1; MS (EI): m/z (%): 406 (84) [M]+, 407 (34),
135 (100).
1
Formation of methyl formate: The synthesis of methyl formate
was performed in a similar way as the synthesis of sodium formate.
MeOH (40 mL) was used and NEt3 (2 mL) was added to the catalyst
solution. CO2 (30 bar) and H2 (30 bar) were added at room temper-
ature to the solution and the reaction mixture was stirred at 1008C
for 20 h. The product was analyzed by GC (HP 6890N) with a HP5
column (30 m) with an internal diameter of 0.32 mm; film thickness
of 0.25 mm; N2 as carrier gas; inlet temperature of 2708C; injection
volume of 1 mL; split ratio of 50:1; flow rate of 0.6 mLminÀ1 (up to
Diadamantyl o-anisoyl phosphine (L9): o-Anisoyl chloride (1.0 g,
5.88 mmol) was added dropwise over about 20 min to a solution
of diadamantylphosphine (1.77 g, 5.88 mmol) and triethylamine
(0.72 g, 7.0 mmol) in THF (10 mL) and stirred for 5 h. The mixture
was quenched with H2O (10 mL) and the product was extracted
with CH2Cl2 (2ꢁ50 mL). The combined CH2Cl2 extracts were
washed with water (20 mL), dried over Na2SO4, and evaporated to
give L9 as a yellow solid (2.0 g, 78%). The crude product was re-
crystallized from MeOH. This synthesis always gave rise to the de-
sired product in high purity (>95%) as determined spectroscopi-
cally. 1H NMR (300 MHz, CDCl3): d=8.01–7.93 (m, 1H), 7.47–7.37 (m,
1H), 7.02–6.91 (m, 2H), 3.88 (s, 3H), 2.19–2.05 (m, 6H), 2.05–1.84
(m, 12H), 1.80–1.63 ppm (m, 12H); 13C NMR (75 MHz, CDCl3): d=
219.3, 218.6, 156.37, 156.33, 135.05, 134.59, 132.91, 132.54, 132.28,
119.71, 111.88, 111.86, 55.74, 41.38, 41.26, 39.18, 38.88, 36.93, 28.99,
28.89 ppm; 31P NMR (121 MHz, CDCl3): d=51.93 ppm.
20 min), then increasing by 0.5 mLminÀ1 steps up to 2.1 mLminÀ1
,
temperature of 358C (up to 20 min), then increasing by 208CminÀ1
steps up to 2958C (17 min), detector temperature of 3008C, H2
flow of 30 mLminÀ1, air flow of 300 mLminÀ1, and makeup flow of
25 mLminÀ1, with diglyme used as an internal standard. The yields
are expressed as the ratio of mols of product per mol of NEt3 used.
Synthesis of [(h6-C6H6)RuCl2(Cy2P(1-naphthoyl)] (1): MeOH (3 mL)
was added to a Schlenk tube containing [(h6-C6H6)RuCl2]2 (100 mg,
0.20 mmol, 1.0 equiv) and Cy2P(1-naphthoyl) (154 mg, 0.44 mmol,
2.0 equiv). The resulting solution was stirred for 5–6 h at 508C
under argon, and then the solvent was removed. The crude materi-
al was washed three times with heptane. Removal of solvent and
drying in vacuum produced 1 (108 mg) in 86% yield as an air-
stable orange powder. Crystals suitable for X-ray analysis were ob-
tained from recrystallization in CHCl3/heptane. The crude product
Diadamantyl 2-(trifluoromethyl)benzoyl phosphine (L10): 2-(Tri-
fluoromethyl)benzoyl chloride (1.0 g, 7.1 mmol) was added drop-
wise over about 20 min to a solution of diadamantylphosphine
(2.16 g, 7.1 mmol) and triethylamine (0.87 g, 8.5 mmol) in THF
(10 mL) and stirred for 5 h. The mixture was quenched with H2O
(10 mL) and the product was extracted with CH2Cl2 (2ꢁ50 mL). The
combined CH2Cl2 extracts were washed with water (20 mL), dried
over Na2SO4, and evaporated to give L10 as an orange solid
(2.15 g, 74%). The crude product was recrystallized from MeOH.
This synthesis produced the desired material in high purity (>
95%) as determined spectroscopically. 1H NMR (300 MHz, CDCl3):
d=8.45–8.37 (m, 1H), 7.73–7.64 (m, 1H), 7.62–7.45 (m, 2H), 1.86–
1.70 (m, 18H), 1.73–1.53 ppm (m, 12H); 13C NMR (75 MHz, CDCl3):
d=219.1, 218.4, 143.93, 143.47, 133.43, 133.10, 131.44, 131.30,
127.78, 127.72, 126.55, 125.48, 121.84, 41.40, 41.27, 39.70, 39.39,
36.77, 28.91, 28.80 ppm; 31P NMR (121 MHz, CDCl3): d=52.90 ppm;
IR (neat): n˜ =2897, 2846, 1638, 1310, 1141, 766, 652 cmÀ1; MS (EI):
m/z (%): 474 (13) [M]+, 135 (100), 173 (34); HRMS (ESI): m/z calcd
for C28H35F3OP+H+: 475.23721 [M+H+]; found: 475.23811.
1
was analyzed by NMR spectroscopy. H NMR (300 MHz, CDCl3): d=
8.71–8.66 (m, 1H), 8.61–8.54 (m, 1H), 8.02–7.96 (m, 1H), 7.91–7.84
(m, 1H), 7.57–7.44 (m, 2H), 5.48 (s, 6H), 2.80–2.58 (m, 2H), 2.40–
2.25 (m, 2H), 1.80–0.83 ppm (m, 18H); 13C NMR (75 MHz, CDCl3):
d=215.54, 215.46, 134.81, 134.49, 134.37, 134.31, 130.07, 129.02,
128.91, 126.93, 124.88, 124.57, 88.83, 88.80, 35.48, 35.25, 31.20,
31.13, 29.73, 29.07, 28.27, 28.13, 27.23, 27.12, 26.07 ppm; 31P NMR
(121 MHz, CDCl3): d=47.98 ppm; IR (neat): n˜ =2923 cmÀ1 (C=O);
high resolution (HR) MS (ESI): m/z calcd for C29H35Cl2NaOPRu+:
625.07403 [M+Na+]; found: 625.07453.
Crystal
data
for
[(h6-C6H6)RuCl2(Cy2P(1-naphthoyl)]·2CHCl3:
¯
C31H37Cl8OPRu, M=841.25; triclinic; space group P1; a=11.5804(4),
b=11.7775(4), c=13.1399(5) ꢂ; a=94.561(3), b=97.392(3), g=
97.949(3)8; V=1751.5(1) ꢂ3; T=150(2) K; Z=2; m=1.129 mmÀ1
;
30258 reflections measured; 8374 independent reflections (Rint
=
Diadamantyl 1-naphthoyl phosphine (L11): 1-Naphthoyl chloride
(1.0 g, 5.26 mmol) was added dropwise over about 20 min to a so-
lution of diadamantylphosphine (1.6 g, 5.26 mmol) and triethyla-
mine (0.64 g, 6.3 mmol) in THF (10 mL) and stirred for 5 h. The mix-
ture was quenched with H2O (10 mL) and the product was extract-
ed with CH2Cl2 (2ꢁ50 mL). The combined CH2Cl2 extracts were
washed with water (20 mL), dried over Na2SO4, and evaporated to
give L11 as an orange solid (1.91 g, 80%). The crude product was
recrystallized from MeOH. This synthesis always produced the de-
sired material in high purity (>95%) as determined spectroscopi-
cally. 1H NMR (300 MHz, CDCl3): d=8.69–8.60 (m, 1H), 8.57–8.49 (m,
1H), 7.93–7.86 (m, 1H), 7.83–7.75 (m, 1H), 7.56–7.36 (m, 3H), 2.14–
1.99 (m, 6H), 1.98–1.75 (m, 6H), 1.85–1.75 (m, 6H), 1.68–1.54 ppm
(m, 12H); 13C NMR (75 MHz, CDCl3): d=221.9, 221.2, 141.55, 141.2,
134.11, 134.08,133.24, 132.85, 128.91, 128.86, 128.49, 128.21,
0.0317); final R values (I>2s(I)): R1 =0.0312, wR2 =0.0661; final R
values (all data): R1 =0.0478, wR2 =0.0684; 379 refined parameters.
Data were collected on a STOE IPDS II diffractometer using graph-
ite monochromatic MoKa radiation. The structure was solved by
direct methods and refined by full-matrix least-squares procedures
on F2 with the SHELXTL software package.[13]
Diadamantyl benzoyl phosphine (L8): Benzoyl chloride (1.0 g,
7.1 mmol) was added dropwise over about 20 min to a solution of
diadamantylphosphine (2.16 g, 7.1 mmol) and triethylamine
(0.87 g, 8.5 mmol) in THF (10 mL) and stirred for 5 h. The mixture
was quenched with H2O (10 mL) and the product was extracted
with CH2Cl2 (2ꢁ50 mL). The combined CH2Cl2 extracts were
washed with water (20 mL), dried over Na2SO4, and evaporated to
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126.44, 125.58, 124.26, 124.24, 41.59, 41.46, 39.37, 39.07, 36.89,
28.96, 28.85 ppm; 31P NMR (121 MHz, CDCl3): d=49.80 ppm; IR
(neat): n˜ =2887, 2842, 1621, 1165, 1057, 772 cmÀ1; MS (EI): m/z (%):
456 (48) [M]+, 155 (100), 457 (17); HRMS (ESI): m/z calcd for
C31H38OP+H+: 457.26548 [M+H+]; found: 457.26450.
124.34, 124.33, 33.04, 32.87, 31.17, 31.04, 29.84, 29.72, 27.49, 27.36,
27.30, 27.18, 26.29 ppm; 31P NMR (121 MHz, CDCl3): d=28.79 ppm;
IR (neat): n˜ =2924, 2850, 1627, 1447, 1234, 1133, 779, 495 cmÀ1; MS
(EI): m/z (%): 352 (14) [M]+, 155 (100), 156 (13); HRMS (ESI): m/z
calcd for C23H30OP+H+: 353.20288 [M+H+]; found: 353.20213.
Di-tert-butyl 1-naphthoyl phosphine (L12): 1-Napthoyl chloride
(1.0 g, 5.26 mmol) was added dropwise over about 20 min to a so-
lution of di-tert-butylphosphine (0.76 g, 5.26 mmol) and triethyla-
mine (0.64 g, 6.3 mmol) in THF (10 mL) and stirred for 5 h. The mix-
ture was quenched with H2O (10 mL) and the product was extract-
ed with CH2Cl2 (2ꢁ50 mL). The combined CH2Cl2 extracts were
washed with water (20 mL), dried over Na2SO4, and evaporated to
give L12 as an orange solid (1.4 g, 89%). Purification of the crude
product by flash column chromatography (silica gel) using initially
hexane and finally ethyl acetate/hexane (5:95) as eluent gave rise
to the title compound as a yellow oil. This synthesis produced the
desired material in high purity (>95%) as determined spectroscop-
ically. 1H NMR (300 MHz, CDCl3): d=8.57–8.48 (m, 1H), 8.48–8.41
(m, 1H), 7.91–7.83 (m, 1H), 7.79–7.71 (m, 1H), 7.54–7.33 (m, 3H),
1.18 (s, 9H), 1.14 ppm (s, 9H); 13C NMR (75 MHz, CDCl3): d=222.15,
221.50, 140.98, 140.55, 134.14, 134.11, 132.12, 132.16, 131.83,
129.06, 129.06, 129.01, 128.52, 128.16, 128.50, 125.53, 124.23,
124.21, 34.22, 33.93, 30.56, 30.40 ppm; 31P NMR (121 MHz, CDCl3):
d=53.33 ppm; IR (neat): n˜ =2943, 2894, 2860, 1626, 1166, 1056,
793 cmÀ1; MS (EI): m/z (%): 155 (100) [M]+, 300 (56); HRMS (ESI): m/
z calcd for C19H26OP+H+: 301.17158 [M+H+]; found: 301.17192.
Diadamantyl 2-naphthoyl phosphine (L15): 1-Naphthoyl chloride
(1.0 g, 5.26 mmol) was added dropwise over about 20 min to a so-
lution of diadamantylphosphine (1.6 g, 5.26 mmol) and triethyla-
mine (0.64 g, 6.3 mmol) in THF (10 mL) and stirred for 5 h. The mix-
ture was quenched with H2O (10 mL) and the product was extract-
ed with CH2Cl2 (2ꢁ50 mL). The combined CH2Cl2 extracts were
washed with water (20 mL), dried over Na2SO4, and evaporated to
give L15 as an orange solid (1.59 g, 67%). The crude product was
recrystallized from MeOH. This synthesis produced the desired ma-
terial in high purity (>95%) as determined spectroscopically.
1H NMR (300 MHz, CDCl3): d=8.69–8.60 (m, 1H), 8.57–8.49 (m, 1H),
8.91–8.85 (m, 1H), 7.98–7.89 (m, 2H), 7.83–7.75 (m, 2H), 7.56–7.41
(m, 2H), 2.10–1.98 (m, 6H), 1.96–1.86 (m, 6H), 1.86–1.78 (m, 6H),
1.64–1.56 ppm (m, 12H); 13C NMR (75 MHz, CDCl3): d=217.30,
216.55, 141.73, 141.27, 135.82, 132.79, 132.53, 130.04, 128.54,
128.45, 127.79, 126.68, 123.19, 123.1043.52, 43.39, 41.63, 41.50,
38.66, 38.37, 36.87, 28.93, 28.82 ppm; 31P NMR (121 MHz, CDCl3):
d=38.46 ppm; IR (neat): n˜ =2895, 2845, 1614, 1117, 747 cmÀ1; MS
(EI): m/z (%): 456 (22) [M]+, 135 (100), 155 (72); HRMS (ESI): m/z
calcd for C31H38OP+H+: 457.26548 [M+H+]; found: 457.2645.
(E)-1-(Diadamantylphosphino)-3-phenylprop-2-en-1-one
(L16):
Diphenyl 1-naphthoyl phosphine (L13): 1-Naphthoyl chloride
(1.0 g, 5.26 mmol) was added dropwise over about 20 min to a so-
lution of diphenylphosphine (0.98 g, 5.26 mmol) and triethylamine
(0.64 g, 6.31 mmol) in THF (10 mL) and stirred for 5 h. The mixture
was quenched with H2O (10 mL) and the product was extracted
with CH2Cl2 (2ꢁ50 mL). The combined CH2Cl2 extracts were
washed with water (20 mL), dried over Na2SO4, and evaporated to
give L13 as an orange solid (1.45 g, 80%). The crude product was
recrystallized or filtered through a small column. This synthesis
produced the desired material in high purity (>95%) as deter-
mined spectroscopically. 1H NMR (300 MHz, CDCl3): d=8.58–8.49
(m, 1H), 8.31–8.22 (m, 1H), 7.81–7.75 (m, 1H), 7.74–7.68 (m, 1H),
7.41–7.31 (m, 5H), 7.26–7.16 ppm (m, 6H); 13C NMR (75 MHz,
CDCl3): d=216.49, 215.55, 137.45, 137.03, 134.92, 134.68, 133.92,
132.95, 132.89, 131.95, 130.03, 129.76, 129.46, 128.90, 128.71,
128.61, 128.35, 128.14, 126.85, 126.53, 125.73, 125.46, 124.35 ppm;
31P NMR (121 MHz, CDCl3): d=18.81 ppm; IR (neat): n˜ =3050, 2922,
1632, 1058, 781, 740, 693 cmÀ1; MS (EI): m/z (%): 340 (6) [M]+, 155
(100), 156 (20), 201 (10); HRMS (ESI): m/z calcd for C23H18OP+H+:
341.10898 [M+H+]; found: 341.10857.
Cinnamoyl chloride (1 g, 6.0 mmol) was added dropwise over
about 20 min to a solution of diadamantylphosphine (1.82 g,
7.1 mmol) and triethylamine (1.0 g, 7.2 mmol) in THF (10 mL) and
stirred for 5 h. The mixture was quenched with H2O (10 mL) and
the product was extracted with CH2Cl2 (2ꢁ50 mL). The combined
CH2Cl2 extracts were washed with water (20 mL), dried over
Na2SO4, and evaporated to give L16 as an orange solid (1.95 g,
75%). The crude product was recrystallized from MeOH. This syn-
thesis produced the desired material in high purity (>95%) as de-
1
termined spectroscopically. H NMR (300 MHz, CDCl3): d=7.91 (dd,
J=4.8 Hz, 1H), 7.55–7.46 (m, 2H), 7.36–7.29 (m, 3H), 6.83–6.71 (m,
1H), 2.06–1.81 (m, 18H), 1.67–1.59 ppm (m, 12H); 13C NMR
(75 MHz, CDCl3): d=216.34, 145.16, 144.90, 134.83, 134.69, 134.15,
130.60, 128.98, 128.65, 41.58, 41.45, 38.46, 36.89, 28.94, 28.83 ppm;
31P NMR (121 MHz, CDCl3): d=42.44 ppm; IR (neat): n˜ =2896, 2844,
1603, 1135, 754, 689 cmÀ1; MS (EI): m/z (%): 432 (14) [M]+, 131 (65),
135 (100); HRMS (ESI): m/z calcd for C29H38OP+H+: 433.26548
[M+H+]; found: 433.26638.
(Diadamantylphosphino)(quinolin-2-yl)methanone (L17): Quino-
line-2-carbonyl chloride (1.0 g, 5.21 mmol) was added dropwise
over about 20 min to a solution of diadamantylphosphine (1.57 g,
5.21 mmol) and triethylamine (0.63 g, 8.5 mmol) in THF (10 mL)
and stirred for 5 h. The mixture was quenched with H2O (10 mL)
and the product was extracted with CH2Cl2 (2ꢁ50 mL). The com-
bined CH2Cl2 extracts were washed with water (20 mL), dried over
Na2SO4, and evaporated to give L17 as a dark violet solid (1.96 g,
82%). The crude product was recrystallized from MeOH. This syn-
thesis gave rise to the desired material in high purity (>95%) as
determined spectroscopically. 1H NMR (300 MHz, CDCl3): d=8.21
(d, J=8.5 Hz, 1H), 8. 61 (d, J=8.9 Hz, 1H), 7.88 (d, J=8.5 Hz, 1H),
7.78–7.25 (m, 1H), 7.70–7.62 (m, 1H), 7.56–7.49 (m, 1H), 2.12–1.89
(m, 12H), 1.85–1.75 (m, 6H), 1.65–1.54 ppm (m, 12H); 13C NMR
(75 MHz, CDCl3): d=219, 157.1, 157.4, 141.1, 137.1, 131.1, 129.9,
129.5, 128.5, 127.5, 117.7, 41.6, 41.4, 39.2, 38.8, 36.9, 29.1,
28.9 ppm; 31P NMR (121 MHz, CDCl3): d=45.75 ppm; IR (neat): n˜ =
Dicyclohexyl 1-naphthoyl phosphine (L14): 1-Naphthoyl chloride
(1.0 g, 5.26 mmol) was added dropwise over about 20 min to a so-
lution of dicyclohexylphosphine (1.04 g, 5.26 mmol) and triethyla-
mine (0.64 g, 6.31 mmol) in THF (10 mL) and stirred for 5 h. The
mixture was quenched with H2O (10 mL) and the product was ex-
tracted with CH2Cl2 (2ꢁ50 mL). The combined CH2Cl2 extracts were
washed with water (20 mL), dried over Na2SO4, and evaporated to
give L14 as an orange solid (1.45 g, 78%). The crude product was
recrystallized from MeOH. This synthesis produced the desired ma-
terial in high purity as determined spectroscopically. 1H NMR
(300 MHz, CDCl3): d=8.53–8.44 (m, 1H), 8.27–8.20 (m, 1H), 7.94–
7.85 (m, 1H), 7.82–7.75 (m, 1H), 7.53–7.37 (m, 3H), 1.88–1.74 (m,
2H), 1.74–1.43 (m, 8H), 1.29–0.86 ppm (m, 12H); 13C NMR (75 MHz,
CDCl3): d=222.2, 221.7, 139.89, 139.50, 134.06, 134.03, 132.84,
130.61, 130.32, 129.03, 129.98, 128.43, 127.99, 126.51, 125.48,
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2899, 2846, 1732, 1634, 902, 828, 750 cmÀ1; MS (EI): m/z (%): 457
(22) [M]+, 322 (100), 135 (86); HRMS (ESI): m/z calcd for
C30H37NOP+H+: 458.26073 [M+H+]; found: 458.26148.
Acknowledgements
This work has been funded by the State of Mecklenburg–Western
Pomerania, the BMBF, and the DFG (Leibniz Prize). We thank Dr.
W. Baumann, and Mrs. S. Buchholz (LIKAT) for their support. We
thank Dr. Ronaldo Mariz (Product Manager Catalysis, Sigma–Al-
drich, Switzerland) for commercializing the new ligands.
(Dimethylphosphino)(pyridin-2-yl)methanone (L18): Picolinoyl
chloride·HCl (1.0 g, 5.6 mmol) was added dropwise over about
20 min to a solution of diadamantylphosphine (1.7 g, 5.6 mmol)
and triethylamine (0.68 g, 6.7 mmol) in THF (10 mL) and stirred for
5 h. The mixture was quenched with H2O (10 mL) and the product
was extracted with CH2Cl2 (2ꢁ50 mL). The combined CH2Cl2 ex-
tracts were washed with water (20 mL), dried over Na2SO4, and
evaporated to give L18 as a dark violet solid (1.59 g, 70%). The
crude product was recrystallized or filtered through a small
column. This synthesis produced the desired material in 90%
purity as determined spectroscopically. 1H NMR (300 MHz, CDCl3):
d=8.72–8.65 (m, 1H), 7.83–7.69 (m, 2H), 7.39–7.33 (m, 1H), 2.05–
1.84 (m, 12H), 1.84–1.78 (m, 6H), 1.63–1.54 ppm (m, 12H); 13C NMR
(75 MHz, CDCl3): d=220.19, 219.52, 158.31, 157.89, 149.16, 136.89,
136.88, 126.77, 120.92, 120.87, 41.45, 41.31, 38.84, 38.52, 36.82,
28.92, 28.82 ppm; 31P NMR (121 MHz, CDCl3): d=43.18 ppm; IR
(neat): n˜ =3391, 2901, 2847, 1721, 1449, 1138 cmÀ1; MS (EI): m/z
(%): 409 (1) [M]+, 135 (100), 155 (63), 352 (5).
Keywords: homogeneous catalysis · hydrogenation · nmr
spectroscopy · phosphomide ligands · ruthenium
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(Diadamantylphosphino)(furan-2-yl)methanone (L19): Furan-2-
carbonyl chloride (1.0 g, 7.7 mmol) was added dropwise over
about 20 min to
a solution of diadamantylphosphine (2.2 g,
7.7 mmol) and triethylamine (0.922 g, 8.5 mmol) in THF (10 mL)
and stirred for 5 h. The mixture was quenched with H2O (10 mL)
and the product was extracted with CH2Cl2 (2ꢁ50 mL). The com-
bined CH2Cl2 extracts were washed with water (20 mL), dried over
Na2SO4, and evaporated to give L19 as an orange solid (2.5 g,
82%). The crude product was recrystallized from MeOH. This syn-
thesis produced the desired material in high purity (>95%) as de-
1
termined spectroscopically. H NMR (300 MHz, CDCl3): d=7.57–7.51
(m, 1H), 7.47–7.43 (m, 1H), 6.46–6.39 (m, 1H), 2.07–1.94 (m, 6H),
1.94–1.78 (m, 12H), 1.70–1.55 ppm (m, 12H); 13C NMR (75 MHz,
CDCl3): d=202.48, 201.88, 158.25, 157.51, 147.24, 121.94, 121.79,
112.04, 112.02, 41.58, 41.44, 38.55, 38.25, 36.83, 28.88, 28.77 ppm;
31P NMR (121 MHz, CDCl3): d=41.99 ppm; IR (neat): n˜ =2899, 2883,
2845, 1612, 1244, 765 cmÀ1; MS (EI): m/z (%): 397 (8) [M]+, 135
(100). HRMS (ESI): m/z calcd for C25H34O2P+H+: 397.22909 [M+H+];
found: 397.22969.
(Diadamantylphosphino)(thiophen-2-yl)methanone (L20): Benzo-
yl chloride (1.0 g, 6.8 mmol) was added dropwise over about
20 min to a solution of diadamantylphosphine (2.05 g, 6.8 mmol)
and triethylamine (0.82 g, 8.1 mmol) in THF (10 mL) and stirred for
5 h. The mixture was quenched with H2O (10 mL) and the product
was extracted with CH2Cl2 (2ꢁ50 mL). The combined CH2Cl2 ex-
tracts were washed with water (20 mL), dried over Na2SO4, and
evaporated to give L20 as an orange solid (2.02 g, 72%). The crude
product was recrystallized from MeOH. This synthesis produced
the desired material in high purity (>95%) as determined spectro-
scopically. 1H NMR (300 MHz, CDCl3): d=8.04–7.96 (m, 1H), 7.61–
7.56 (m, 1H), 7.09–7.02 (m, 1H), 2.07–1.94 (m, 6H), 1.94–1.79 (m,
12H), 1.68–1.57 ppm (m, 12H); 13C NMR (75 MHz, CDCl3): d=
207.34, 152.37, 151.75, 134.52, 134.47, 134.37, 128.09, 41.57, 41.44,
38.60, 38.29, 36.84, 28.90, 28.79 ppm; 31P NMR (121 MHz, CDCl3):
d=44.38 ppm; IR (neat): n˜ =2903, 2885, 2845, 1610, 1197, 798,
727 cmÀ1; MS (EI): m/z (%): 412 (36) [M]+, 135 (100). HRMS (ESI): m/
z calcd for C25H34OPS+H+: 413.20625 [M+H+]; found: 413.20692.
[6] As an example ligands L8, L11, and L14 were treated with D2O. Even
after a week in solution, there was no decomposition detected. Howev-
er, treatment of the ligands with D2O, [D6]THF, [D4]MeOH under an air
atmosphere for 1–2 weeks in solution resulted in
a considerable
amount of decomposition detected by 31P NMR (see the Supporting In-
formation). Selected L8, L11, and L14 ligands are commercialized by
Sigma–Aldrich. These ligands are available under the trademark names
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemSusChem 2013, 6, 85 – 91 90

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of Ad-BellGiPhos-Bz (L8: Sigma–Aldrich Catalog No.: 744816), Ad-BellGi-
Phos-1-Nap (L11: Sigma–Aldrich Catalog No.: 744913), and Cy-BellGi-
Phos-1-Nap (L14: Sigma–Aldrich Catalog No.: 744700).
[10] CCDC 880410 contains the supplementary crystallographic data (1) for
this paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/
data_request/cif.
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1
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Received: October 2, 2012
Published online on December 28, 2012
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