Ruthenium-Catalyzed Coupling Reactions of CO2 with C2H4 and Hydrosilanes towards Silyl Esters

Article abstract of DOI:10.1002/chem.202005083

A series of in situ-prepared catalytic systems incorporating Ru^II precursors and bidentate phosphine ligands has been probed in the reductive carboxylation of ethylene in the presence of triethylsilane as reductant. The catalytic production of propionate and acrylate silyl esters was evidenced by high-throughput screening (HTS) and implemented in batch reactor techniques. The most promising catalyst systems identified were made of Ru(H)(Cl)(CO)(PPh₃)₃ and 1,4-bis(dicyclohexylphosphino)butane (DCPB) or 1,1’-ferrocene-diyl-bis(cyclohexylphosphine) (DCPF). A marked influence of water on the acrylate/propionate selectivity was noted. Turnover numbers [mol mol(Ru)^?1] up to 16 for acrylate and up to 68 for propionate were reached under relatively mild conditions (20 bar, 100 °C, 0.5 mol % Ru, 40 mol % H₂O vs. HSiEt₃). Possible mechanisms are discussed.

Full text of DOI:10.1002/chem.202005083

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Homogeneous Catalysis |Hot Paper|
Ruthenium-Catalyzed Coupling Reactions of CO2 with C2H4 and
Hydrosilanes towards Silyl Esters
Kana Kunihiro,[a] Svetlana Heyte,[b] SØbastien Paul,[b] Thierry Roisnel,[a] Jean-
FranÅois Carpentier,*[a] and Evgueni Kirillov*[a]
Dedicated to Professor Pierre H. Dixneuf for his outstanding contribution to organometallic chemistry and catalysis.
bond to give carboxylic moieties have become powerful alter-
natives to usual methodologies.[5–7] Moreover, synthesizing car-
Abstract: A series of in situ-prepared catalytic systems in-
corporating RuII precursors and bidentate phosphine li-
boxylic derivatives from inexpensive starting materials such as
ethylene is an attractive and cost-efficient transformation.[8]
gands has been probed in the reductive carboxylation of
Pioneering studies reported by Lapidus and Ping in 1978
proved the feasibility of transforming C2H4 and CO2 into pro-
pionic acid using Rh and Pd catalysts in the presence of HBr
under very harsh conditions (Scheme 1).[9] This discovery revo-
lutionized and encouraged new developments in this area. The
synthesis of acrylic acid, a very important base chemical used
in the preparation of a variety of (co)polymers, was subse-
quently described in the 1980s.[10–23] When mixing ethylene
and CO2 in presence of 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU) and Ni complexes, Hoberg et al. reported the first isola-
tion of a stable nickelalactone intermediate;[18] yet, the reaction
was not catalytic. The first catalytic synthesis of sodium acry-
late with a turnover number (TON) of 10 was disclosed by Lim-
bach and co-workers with a Ni(COD)2/diphosphine (COD: 1,5-
cyclooctadiene) system and NaOtBu as base.[24] Upon utilizing
less nucleophilic sodium phenoxides and Zn-dust as reductant,
ethylene in the presence of triethylsilane as reductant.
The catalytic production of propionate and acrylate silyl
esters was evidenced by high-throughput screening (HTS)
and implemented in batch reactor techniques. The most
promising catalyst systems identified were made of
Ru(H)(Cl)(CO)(PPh3)3 and 1,4-bis(dicyclohexylphosphino)bu-
tane (DCPB) or 1,1’-ferrocene-diyl-bis(cyclohexylphos-
phine) (DCPF). A marked influence of water on the acry-
late/propionate selectivity was noted. Turnover numbers
[molmol(Ru)À1] up to 16 for acrylate and up to 68 for pro-
pionate were reached under relatively mild conditions
(20 bar, 1008C, 0.5 mol% Ru, 40 mol% H2O vs. HSiEt3). Pos-
sible mechanisms are discussed.
The use of cheap and non-toxic carbon dioxide for CÀC cou-
pling with unsaturated substrates (alkenes, alkynes, epoxides,
etc.) constitutes a valuable synthetic route toward carboxylic
acids and carbonates, which are commodities and highly versa-
tile starting materials toward fine chemicals.[1–3] Unfortunately,
due to the inherent stability of CO2, highly reactive and diffi-
cult to handle organometallic co-reagents are often needed.[4]
To circumvent these waste-producing synthetic routes, tremen-
dous efforts have been paid over the last 40 years, eventually
leading to efficient achievements in transition-metal catalyzed
CO2-incorporative reactions. Reductive carboxylation of unsatu-
rated hydrocarbons with CO2 and its direct insertion into CÀH
[a] K. Kunihiro, Dr. T. Roisnel, Prof. Dr. J.-F. Carpentier, Dr. E. Kirillov
CNRS, Institut des Sciences Chimiques de Rennes (ISCR), UMR 6226
Univ. Rennes
35042 Rennes Cedex (France)
E-mail: jean-francois.carpentier@univ-rennes1.fr
evgueni.kirillov@univ-rennes1.fr
[b] Dr. S. Heyte, Prof. Dr. S. Paul
CNRS, Centrale Lille, Univ. Artois, UMR 8181— UCCS— UnitØ de Catalyse et
Chimie du Solide
Univ. Lille
F-59000 Lille (France)
Supporting information and the ORCID identification number(s) for the au-
thor(s) of this article can be found under:
Scheme 1. Previous reports of metal-mediated carboxylation of olefins and
https://doi.org/10.1002/chem.202005083.
present work.
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the same group achieved TON up to 107 (Scheme 1).[25] Follow-
ing a similar strategy, Vogt and co-workers developed a pro-
cess with a Ni-DCPP (1,3-bis(dicyclohexylphosphino)propane)
catalyst relying on b-H elimination induced by a strong Lewis
acid;[26] in the presence of (over)-stoichiometric amounts of LiI,
NEt3, and Zn-dust, regeneration of the active Ni-DCPP catalyst
species was achieved, affording acrylate metal salts with TON
up to 21. Very recently, Bernskoetter and co-workers employed
a similar approach by using a phenoxide base (3-FC6H4ONa)
with TON up to 82.[27] Carboxylation reactions of alkenes using
other metal-based catalysts such as Mn, W, Fe, and Rh, have
also been studied and supported by theoretical studies, bring-
ing insights to the reaction mechanisms.[28–34] For example,
Leitner and co-workers reported a catalyst system involving
[RhCl(CO)2]2 coupled with CH3I as promoter and H2 as reduc-
tant for the „hydrocarboxylation“ of alkenes (Scheme 1).[35] Ac-
tually, this route is based on a carbonylation reaction in which
the active C1 synthon (CO) is released via a reverse water-gas-
shift reaction in the presence of H2 or alcohols. Very recently,
Iwasawa and co-workers reported the synthesis of acrylate
alkali metal salts with Ru-based catalysts (Scheme 1);[36] TON
up to 15 was achieved using 1000 equiv. of Cs2CO3 as base in
DMA (dimethylacetamide) under 3 bar C2H4/CO2. Hence, al-
though promising activities and selectivities were achieved,
most of the above protocols are plagued by the use of stoi-
chiometric amounts of metal co-reagents.
(stable liquids) make them interesting competitive reducing
agents as compared to metals and organometallic hydrides
and alkyls. Thus, the above process involving hydrosilanes as
reductants can constitute a reliable model for related carboxy-
lation processes operating with H2 and intermediated by
metal-hydrido complexes. Also, silyl acrylate esters issued from
this process are valuable precursors in the synthesis of poly(sil-
yl ester) copolymers, of interest as fouling-resistant coatings
and self-polishing materials.[40,41]
Our approach relied on the evaluation of combinations of
various ligands, especially multidentate phosphines, with
group 8 and 9 metal precursors, in the presence of different
hydrosilanes. Using a combinatorial HTS facility, series of paral-
lel 24 tests were performed, involving commercial metallic pre-
cursors such as Ru(H)(Cl)(CO)(PPh3)3, [Ru(p-cymene)Cl2]2, [Rh(n-
octanoate)2]2, Wilkinson’s catalyst and a set of diphosphine li-
gands with variable stereo-electronic features (Scheme 3). A
monohydrosilane, HSiEt3, was used for the screening. Based on
the results of preliminary investigations, the following condi-
tions were applied for the HTS experiments: solvent (toluene,
2 mL); equimolar C2H4/CO2 gas mixture (Ptotal =20 bar); Et3SiH
(0.86 mmol); [precursor]0 =[ligand]0 =0.5 mol% vs. hydrosilane;
reaction temperature=1008C; reaction time=16 h. Crude re-
actions mixtures were analyzed automatically by GC-FID (FID:
flame ionization detector) and GC-MS.
In the present study, we aimed at identifying— using high-
throughput screening (HTS) techniques— effective catalytic sys-
tems for the carboxylation of ethylene in the presence of alter-
native, readily available co-reagents, namely hydrosilanes
(Scheme 2).[37] The favored formation of the SiÀO bond [bond
dissociation energy (BDE)=460 kJmolÀ1 [38]
and the relatively
]
facile activation of the SiÀH bond (BDE=314 kJmolÀ1) make
hydrosilanes (such as Et3SiH)[38] good reductants under relative-
ly mild conditions. We thus envisioned that such reactants may
enable release of the free acrylate product from a putative
metallalactone intermediate, formed by the activation of CO2
via oxidative cyclization with ethylene.[39] Moreover, the highly
tunable reactivity of hydrosilanes and the ease of handling
Scheme 2. Possible products of the coupling reaction of CO2 with C2H4 in
Scheme 3. Main RuII and Rh(I,II) precursors and diphosphine ligands used in
the presence of Et3SiH.
this study.
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Scheme 2 summarizes the three possible different series of
products that can form through the corresponding, competing
reaction pathways, namely routes A, B, and C. Thus, besides
the reductive carboxylation reaction of ethylene (Route A) to-
wards the targeted triethylsilyl propionate (P1) and acrylate
(A1) products, subsequent over-reduction by-products can
form, namely P2, P3, propane and A2, A3, propene, respective-
ly, along with disiloxane E. Route B is the hydrosilylation reac-
tion of CO2 towards, first, triethylsilyl formate (F1) and, subse-
quently, the series of over-reduction products up to meth-
ane.[42] However, the main competitive pathway that we expe-
rienced comprises the two separate reactions between ethyl-
ene and hydrosilane, that is hydrosilylation and
dehydrogenative coupling, yielding the corresponding tetrae-
thylsilane (TES) and triethylvinylsilane (TEVS).[43] The analytical
techniques developed in this study (see the Supporting Infor-
mation for details) enabled unequivocal separation, authentica-
tion, and quantification of most of the above possible products
(except the gaseous ones); overall silane balance closures of
72–91% were obtained in most cases (see Supporting Informa-
tion).
(Scheme 3). For the first time, these group 8 metal-based sys-
tems appeared to give a direct access to silyl esters from ethyl-
ene, CO2, and hydrosilane, with moderate to high HSiEt3 con-
versions.
These reactions using the „hit“ catalyst combinations were
next reproduced in batch experiments using 50 mL-autoclaves
(entries 1–5, Table 1). The combination giving A1 in higher
amounts was Ru(H)(Cl)(CO)(PPh3)3/DCPB (entry 3, TON=13).
The related catalyst system based on the 1,1’-ferrocene-diyl-
bis(cyclohexylphosphine) (DCPF) ligand— that has a more rigid
ferrocenyl backbone but with a bite angle of 998 just slightly
larger as compared to 948 for the butylene-bridged DCPB[44]
—
returned quite similar results (Table 1, entries 3 vs. 6).
Evaluation of the influence of the alkylene chain length in
the bidentate bis(dicylohexylphosphine) ligand on the catalytic
performance was undertaken under the above-defined reac-
tion conditions. When using DCPM (bis(dicyclohexyl)phosphino
methane) instead of DCPB, high TON for the route C products
were obtained, but A1 and P1 were not detected at all
(entry 7). On the other hand, when using the homologous eth-
ylene-bridged DCPE (1,2-bis(dicyclohexylphosphino)ethane)
and propylene-bridged DCPP (1,3-bis(dicyclohexylphosphino)-
propane)ligands, low amounts of the Route A products
became detectable again (entries 8 and 9). These observations,
highlighting a monotonous dependence of the TON for car-
boxylation products with the length of the alkylene backbone,
suggest, not unexpectedly, that the PÀMtÀP bite angle has a
major influence on the activity and selectivity of the reaction.
Regarding the nature of the PR2 moieties within the chelat-
ing fragment, a comparison between DPPF and DCPF shows
that replacement of phenyl by cyclohexyl groups increases
conversions from 16 to 49% as well as selectivities toward the
Route A products (entries 5 vs. 6). In the case of DPPB ligand,
During the first series of HTS tests, many combinations were
found to enable high conversions (>60%) of Et3SiH. However,
the targeted P1 and A1 products were not the major products
obtained, as the Route C products (TES and TEVS) were detect-
ed in high yields. However, we were able to identify a few ef-
fective metal precursor/ligand combinations that produce
quantifiable and, in some cases, remarkable amounts of the
targeted P1 and A1. In particular, the following Ru-based sys-
tems were pinpointed: Ru(H)(Cl)(CO)(PPh3)3/DCPB [DCPB: 1,4-
bis(dicyclohexylphosphino)butane],
Ru(H)(Cl)(CO)(PPh3)3/PP3,
Ru(H)(Cl)(CO)(PPh3)3/DPPF (1,1’-ferrocenediyl-bis(diphenylphos-
phine)), [Ru(p-cymene)Cl2]2/DCPB and [Ru(p-cymene)Cl2]2/DPPF
Table 1. Catalytic results from batch experiments.[a]
Entry Precursor/ligand (1:1, 0.5 mol%)/additive [mol%] (vs. HSiEt3) Conv. HSiEt3[b] [mol%]
TON[c] [mol(product)mol(Ru)À1
Route A products Route B and C products
A1 P1 TES TEVS
]
F1
E
1
2
3
4
5
6
7
8
9
10[d]
11
12
13
14
15
16[e]
[Ru(p-cymene)Cl2]2/DCPB
Ru(H)(Cl)(CO)(PPh3)3/PP3
Ru(H)(Cl)(CO)(PPh3)3/DCPB
[Ru(p-cymene)Cl2]2/DPPF
Ru(H)(Cl)(CO)(PPh3)3/DPPF
Ru(H)(Cl)(CO)(PPh3)3/DCPF
Ru(H)(Cl)(CO)(PPh3)3/DCPM
Ru(H)(Cl)(CO)(PPh3)3/DCPE
Ru(H)(Cl)(CO)(PPh3)3/DCPP
Ru(H)(Cl)(CO)(PPh3)3/DCpPB[d]
Ru(H)(Cl)(CO)(PPh3)3/DCPB/H2O [10]
Ru(H)(Cl)(CO)(PPh3)3/DCPB/H2O [20]
Ru(H)(Cl)(CO)(PPh3)3/DCPB/H2O [40]
Ru(H)(Cl)(CO)(PPh3)3/DCPB/H2O [80]
Ru(H)2(CO)(PPh3)3/DCPB
>98
29
54
67
16
49
>98
55
81
44
63
83
97
89
40
68
0
0
13
0
0.2
10
0
0
0
1.3
3
0.4
0
0
16
0
0
0
0
8.0
1.0
9
5
180 traces traces
traces
4
2
53
16
4
0
1.6
2
0.4
3
74
10
3
traces
0
1.0
traces
2
26
20
2.0
180 traces
60 traces
traces
traces
12
8
4
3
4
5
6
2
3
66
26
48 traces
15
16
4
0
26
22
23
42
68
48
1
47
82
84
4
4
1
10
3
14
12
1
108 traces
7
10
1
3
Ru(H)2(CO)(PPh3)3/DCPB/H2O [20]
24
[a] Reaction conditions: toluene (20 mL), [Si-H]0 =0.43 molLÀ1, [Ru]0 =[ligand]0 =0.002 molLÀ1, CO2/C2H4 1:1 molmolÀ1, P(CO2)+P(C2H4)=20 bar; 16 h; re-
1
sults of at least duplicated experiments and averaged TON values. [b] Determined by integration of the H NMR peaks vs. those of the standard [(Me3Si)4Si].
[c] TON as determined by GC-FID using n-dodecane as internal standard. [d] DCpPB=1,4-bis(dicyclopentylphosphino)butane. [e] 4 h.
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although A1 and P1 were still formed in small amounts, a sig-
nificant difference in selectivity was observed as compared to
DCPB (see Supporting Information, Table S3). Whereas phenyl
and cyclohexyl groups are rather similar in terms of steric bulk-
iness, PCy2 moieties are much more basic than their PPh2 coun-
terparts, and this is known to dramatically affect both structur-
al arrangement and reactivity of the [(P-P)Ru] fragment. Hence,
in addition to the bite angle, basicity of the P residues is an-
other key factor in this process. Replacing the cyclohexyl by cy-
clopentyl groups on the butylene-bridged chelating phosphine
provided comparable results toward route A products (en-
tries 3 vs. 10).
Evaluation of the temperature was conducted on the most
efficient catalytic system in order to further optimize conver-
sion and selectivity (see Table S4, Supporting Information, for
details). Below 808C, route C products were mostly formed. At
1208C and above, the selectivity for Route A products de-
creased to the benefit of Route B and C products; hence, the
reaction was better conducted at 1008C.
Figure 1. Molecular structure of Ru(H)(CO)(Cl)(PPh3)(DCPB) with thermal ellip-
soids set at 50% probability.
In the literature, co-reagents such as bases,[24] methylating
reagents,[45–48] Lewis acids,[49,50] or phosphine ligands[51] are
often added to promote cleavage of metallalactones and re-
lease of the free acrylate products. Hence, to identify condi-
tions for a more selective production of the desired carboxyla-
tion products, we investigated the influence of several addi-
tives such as Al(OTf)3, KPF6, CsF, KF. Yet, no significant variations
were observed in the presence of such additives. On the other
hand, addition of water much affected triethylsilane conversion
and selectivities towards Route A products (entries 11–14).
With only 0.1 equiv. (vs. HSiEt3) of H2O, a slightly higher conver-
sion of HSiEt3 and a dramatic increase in the formation of P1
were observed (compare entries 11 and 3). With more water
(0.2 and 0.4 equiv.), the formation of propionate was favored
over acrylate with higher corresponding TONs of 42 and 68
(entries 12 and 13, respectively). Yet, addition of 0.8 equivalent
did not seem to be beneficial to the system, decreasing the
overall TON to 48 (entry 14). It is still unclear how H2O inter-
feres (vide infra). Previous work by Martin and co-workers ex-
plored the use of water in site-selective hydrocarboxylation of
unsaturated hydrocarbons with CO2: in the case of olefins,
linear carboxylic acids are formed through hypothetical hydro-
metallation.[52]
major product arising from this combination. Depending on
the reaction conditions, it is accompanied by the formation of
several other hydrido species in variable amounts. In fact, the
1
hydride region of the H NMR spectrum featured, besides the
doublet
of
triplets
at
À7.16 ppm
from
Ru(H)(-
CO)(Cl)(PPh3)(DCPB), other sets of resonances at higher field
(Figure 2a). This was even more obvious in the 1H{31P} NMR
spectrum (Figure 2b), that evidenced that those two, or possi-
bly three, additional species account for approximately 77% of
the total hydrides.[54] On the other hand, in the presence of
water [40 equiv. vs. Ru(H)(CO)(Cl)(PPh3)3 and DCPB], the NMR
spectra evidenced a more selective formation of Ru(H)(-
CO)(Cl)(PPh3)(DCPB) (ꢀ80% of the total; Figures 2c,d).[55] Al-
though the exact nature of the additional species has not
been identified yet,[56] we assume that they account for, at
least to some extent, the different selectivities observed in the
catalytic process. Surprisingly enough, preliminary catalytic ex-
periments conducted with isolated batches of Ru(H)(-
CO)(Cl)(PPh3)(DCPB) or its ferrocenyl analogue Ru(H)(-
CO)(Cl)(PPh3)(DCPF) (see Supporting Information for synthesis
and X-ray characterization) returned neither acrylate (A1) nor
propionate (P1) silyl esters, but the other side products. This
may suggest that the other hydride species are the actual
active ones in the coupling of CO2 with C2H4, although we re-
frain at this stage to overspeculate.
To get a better insight in the nature of the catalytically
active species in our system, we targeted the synthesis of
Ru(H)(CO)(Cl)(DCPB)(PPh3), which is an obvious anticipated
product from the combination of Ru(H)(CO)(Cl)(PPh3)3 and
DCPB. Following the procedure of Jia and co-workers,[53] the
precursor Ru(H)(CO)(Cl)(PPh3)3 was refluxed in the presence of
the ligand DCPB (1:1 mol ratio) in toluene under argon. Upon
work-up (see Supporting Information) and subsequent recrys-
tallization of the crude product, single-crystals of the expected
Ru(H)(CO)(Cl)(PPh3)(DCPB) were recovered; its identity was es-
tablished unambiguously by multinuclear NMR spectroscopy,
MS (see Supporting Information), and an X-ray diffraction
study (see Figure 1).
Additional in situ catalytic experiments were conducted
using the dihydro Ru(H)2(CO)(PPh3) precatalyst. Indeed, in pres-
ence of Et3SiH, the mono-hydride Ru(H)(CO)(Cl)(PPh3)3 precur-
sor is reduced to the dihydrido one and is therefore present
within the reaction medium. Consequently, its evaluation in
catalysis was undertaken. In combination with DCPB ligand
(entry 15), a better selectivity was obtained toward route A
product in comparison to the mono-hydride/DCPB catalytic
combination (entries 3 vs. 15). When adding 0.2 equivalent of
water to the system, an increase of the overall route A TONs
was observed (27 to 46, entries 15 vs. 16). In brief, both mono
However, the NMR spectra of the crude reaction mixture re-
vealed that Ru(H)(CO)(Cl)(PPh3)(DCPB) is not necessarily the
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Scheme 4. Possible mechanisms for triethylsilyl acrylate (A1) and propionate
(P1) formation.
angle of ligand can have a major influence on the feasibility of
this step, stability of the metallacycle and thus, on the overall
activity and selectivity of the reaction.[24] Such influence has
been well established in many other catalytic processes.[57,58]
Subsequent ruthenalactone cleavage by hydrosilane shall
result in the formation of the mixed hydrido/alkyl intermediate.
The latter may undergo a reductive elimination to give P1 or
afford A1 via b-H elimination step within the second cycle A1.
At this point, addition of water can affect the selectivity of the
process by stabilizing the intermediate leading to the forma-
tion of P1 via reductive elimination step. Also, formation of
TEVS suggests that silyl-ruthenium is one of the active species
in the overall process; such species may undergo ethylene in-
sertion and b-hydride elimination to give TEVS along with a
hydrido-ruthenium intermediate. Both ruthenium species may
be involved in the carboxylation processes, for example,
through capture of CO2 by the silyl-ruthenium. Such hypothet-
ic scenarios are currently explored by DFT computations; the
results will be discussed in a forthcoming paper. Current efforts
are directed at challenging such mechanistic scenarios through
DFT computations as well as at identifying the different Ru
species generated from the combination in the absence or
presence of water, preparing and isolating them, and assessing
their intrinsic reactivities.
Figure 2. a) 1H NMR and b) 1H{31P} NMR spectra of the hydride region
(400 MHz, [D8]toluene, 258C) of the crude product obtained from the reac-
tion of Ru(H)(CO)(Cl)(PPh3)3 and DCPB (1:1); c) 1H NMR and d) 1H{31P} NMR
spectra of the hydride region (400 MHz, [D8]toluene, 258C) of the crude
product obtained from the reaction of Ru(H)(CO)(Cl)(PPh3)3, DCPB and H2O
(1:1:40).
and dihydrido ruthenium precursors/DCPB combinations allow
to reach encouraging TON toward silylesters. A slight differ-
ence in selectivity is anyhow observed between the two sys-
tems: the use of Ru(H)2(CO)(PPh3) minimizes route C product
formation.
Acknowledgements
This research project was supported by the ANR-17-CE06-0006-
01 „CO22CHEM“. The authors are indebted to Dr. Elsa Caytan
from Rennes 1 University (UMS SCANMAT, Rennes, France) for
NMR analyses, to Dr. Stephan Behrens from Leibniz Institute
for Catalysis (Rostock, Germany) for his experimental contribu-
tion and to Prof. Franck Dumeignil (Univ. Lille) for stimulating
discussions and sharing expertise. The REALCAT platform is
benefiting from a state subsidy administrated by the French
National Research Agency (ANR) within the frame of the
‘Future Investments’ program (PIA), with the contractual refer-
ence ‘ANR-11-EQPX-0037’. The European Union, through the
In summary, we have investigated the metal-catalyzed syn-
thesis of esters from C2H4, CO2, and HSiEt3. Using HTS, we have
identified that the Ru(H)(Cl)(CO)(PPh3)3/DCPB combination ena-
bles to achieve moderate conversion and selectivity toward
triethylsilyl propionate and acrylate. In agreement with the for-
mation of the targeted silylester products (route A), a combina-
tion of two ruthenium catalytic cycles is tentatively proposed
in Scheme 4, as a working hypothesis (among others). Forma-
tion of the ruthenalactone[36] from C2H4 and CO2 by oxidative
addition is proposed as a key step in cycle P1. The P-Ru-P bite
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ERDF funding administered by the Hauts-de-France Region,
has co-financed the platform. Centrale Lille, the CNRS, and Lille
University as well as the Centrale Initiatives Foundation, are
thanked for their financial contributions to the acquisition and
implementation of the equipment of the REALCAT platform.
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Conflict of interest
The authors declare no conflict of interest.
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Keywords: carbon dioxide fixation · ethylene · high
throughput screening
carboxylation
·
hydrosilylation
· reductive
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Communication
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Manuscript received: November 24, 2020
Revised manuscript received: December 21, 2020
Accepted manuscript online: January 16, 2021
Version of record online: January 28, 2021
Chem. Eur. J. 2021, 27, 3997 –4003
www.chemeurj.org
4003
ꢀ 2021 Wiley-VCH GmbH