Catalytic CO2 hydrosilylation with [Mn(CO)5Br] under mild reaction conditions

Article abstract of DOI:10.1016/j.poly.2021.115242

Carbon dioxide hydrosilylation with earth-abundant transition-metal catalysts is an attractive alternative for the design of greener and cost-effective synthetic strategies. Herein, simple [Mn(CO)₅Br] is an efficient precatalyst in the hydrosilylation of carbon dioxide with Et₃SiH under mild reaction conditions. Using THF as a solvent, triethylsilylformate Et₃SiCH(O)O was obtained in 67% yield after 1 h at 50 °C and 4 bar of CO₂ pressure. The selectivity of the reaction was tuned by changing the solvent to a mixture of THF and toluene producing bis(triethylsilyl)acetal (Et₃SiO)₂CH₂ in 86% yield. The CO₂ hydrosilylation was also effective at room temperature and atmospheric pressure using either THF or the mixture THF/toluene as the solvent resulting in high Et₃SiH conversion (92%–99%) but with a decrease in the selectivity. Radical trapping experiments indicated the participation of radical species in the catalytic mechanism. To the best of our knowledge, this is the first report on CO₂ hydrosilylation catalyzed by transition-metal radical intermediates.

Full text of DOI:10.1016/j.poly.2021.115242

Polyhedron 203 (2021) 115242
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Catalytic CO hydrosilylation with [Mn(CO) Br] under mild reaction
2
5
conditions
⇑
Tania González, Juventino J. García
Facultad de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history:
Carbon dioxide hydrosilylation with earth-abundant transition-metal catalysts is an attractive alternative
for the design of greener and cost-effective synthetic strategies. Herein, simple [Mn(CO) Br] is an efficient
precatalyst in the hydrosilylation of carbon dioxide with Et SiH under mild reaction conditions. Using
THF as a solvent, triethylsilylformate Et SiCH(O)O was obtained in 67% yield after 1 h at 50 °C and
bar of CO pressure. The selectivity of the reaction was tuned by changing the solvent to a mixture
of THF and toluene producing bis(triethylsilyl)acetal (Et SiO) CH in 86% yield. The CO hydrosilylation
was also effective at room temperature and atmospheric pressure using either THF or the mixture
THF/toluene as the solvent resulting in high Et SiH conversion (92%–99%) but with a decrease in the
selectivity. Radical trapping experiments indicated the participation of radical species in the catalytic
Received 12 March 2021
Accepted 24 April 2021
Available online 29 April 2021
5
3
3
4
2
Keywords:
Hydrosilylation
Manganese
Homogeneous catalysis
Carbon dioxide reduction
3
2
2
2
3
mechanism. To the best of our knowledge, this is the first report on CO
sition-metal radical intermediates.
2
hydrosilylation catalyzed by tran-
Ó 2021 Elsevier Ltd. All rights reserved.
1
. Introduction
2
The most commonly observed products in the CO hydrosilyla-
tion are silylformates (see Scheme 1) [13–30]. Silylformates can be
hydrolyzed to obtain formic acid or used as formyl synthons
[17,25,31]. Other rarer products include bis(silyl)acetals
[13,15,25,32–43], methoxysilanes [13,15,48,20,33,34,36,44–47],
and methane [33,37,44,49] (Scheme 1). Methylamines and for-
mamides can be synthesized in the presence of amines [16,50–59].
Even though earth-abundant 3d transition metals are generally
2
Increasing CO emissions and their impact on global warming
have led us to reassess our fossil fuel economy. Carbon dioxide is
a renewable, non-toxic, abundant, and ubiquitously distributed
feedstock. It could also become an energy carrier through its con-
version to methanol, DME, methane, and formic acid [1–8]. Among
2
the multiple chemical transformations of CO , its reduction to C1
products has attracted significant attention because these are valu-
able raw materials for fine chemicals and fuels.
of low cost and toxicity, their application in CO
has remained overlooked. In recent years, reports on the CO
2
hydrosilylation
2
In recent decades, research efforts to develop cost-effective car-
bon dioxide reduction have increased. However, CO is a highly
2
stable and inert compound, and strategies involving the use of cat-
alysts and high-energy reagents are needed [5]. Direct catalytic
hydrogenation is one of the most relevant reductive transforma-
hydrosilylation with earth-abundant metals have appeared
[13,14,23,24,27,45]. Baba and coworkers published very relevant
contributions on this area in 2012 and 2013 [14,23]. They used
Cu(OAc)
2
2
ÁH O
with 1,2-bis(diisopropylphosphino)-benzene as
to obtain silylformate achieving a TON
ligand under 1 atm of CO
2
tions of CO
and strong bases are usually required [6,9]. In contrast, the
hydrosilylation of CO is a thermodynamically favored reaction
2
due to its atom economy but high pressures of H
2
of 70,000 after 24 h, which is the highest reported so far for this
reaction with transition metal-based catalysts even among
noble-metal catalysts for CO hydrosilylation. In 2014, Chirik and
2
2
that can be carried out under mild reaction conditions without
the need for a base to stabilize the product [10–12]. Furthermore,
hydrosilanes are safe and easily handled reductant agents. There-
coworkers reported a catalytic precursor of Co(I) with a PNP pincer
ligand to synthesize silylformates, bis(silyl)acetals, as well as
methoxysilanes using CO
Our group has evaluated Fe(0) and Ni(I) compounds as precata-
lysts in the CO hydrosilylation (Scheme 2, García 2013 and 2018).
Using commercial [Fe (CO)12 without ancillary ligands, we
obtained silylformates in good yields [24]. The Ni(I) complex
(dippe)Ni(m-H)] [25] was also an efficient pre-catalyst for the
2
and phenylsilanes [13].
2 2
fore, the hydrosilylation of CO is a convenient alternative to CO
reduction with hydrogen.
2
3
]
⇑
Corresponding author.
E-mail address: juvent@unam.mx (J.J. García).
[
2
https://doi.org/10.1016/j.poly.2021.115242
277-5387/Ó 2021 Elsevier Ltd. All rights reserved.
0

T. González and J.J. García
Polyhedron 203 (2021) 115242
2
Scheme 1. Reduction products of the CO hydrosilylation.
at room temperature and atmospheric pressure after 24–48 h but
using an excess of silane (5 eq. Si–H bonds) over carbon dioxide.
They also achieved the CO
2
hydrosilylation to silylformate using
an excess of CO obtaining a quantitative conversion of silane.
2
The selective synthesis of methoxysilanes is of great interest due
to their potential as methanol precursors [34,36,45,47,48,73].
In the search for more efficient, simple, and cost-effective man-
ganese-based catalytic systems for CO
2
hydrosilylation, we report
Br] as a pre-
here CO hydrosilylation with Et SiH using [Mn(CO)
2
3
5
catalyst under mild reaction conditions. The optimized catalytic
system yielded the bis(silyl)acetal and silyl formate reduction
products with good yields and selectivity. Mercury drop test and
inhibition of the catalytic activity by TEMPO are consistent with
a free radical mechanism. To the best of our knowledge, this may
be the first CO
2
hydrosilylation system catalyzed by radical transi-
tion metal species.
2
. Results and discussion
2
.1. Catalytic CO hydrosilylation
2
Commercially available [Mn(CO)
precursor in the CO hydrosilylation with triethylsilane. Thus, high
Et SiH conversion was observed after 24 h under relatively mild
reaction conditions (60 °C and 4 bar of CO ) with moderate selec-
tivity to the silylformate Et SiCO H (44%); the bis(silyl)acetal
reduction product (Et SiO) CH (13%) was also observed. Other
products such as Et SiOH, Et SiOSiEt , and Et SiO(CH CH were
5
Br] was evaluated as a catalyst
2
3
2
3
2
3
2
2
3
3
3
3
2
)
3
3
also detected. Some of these byproducts are the result of the
tetrahydrofuran ring-opening, similar reactivity with THF and fur-
ther polymerization have been reported before by Jansen and Pitter
Scheme 2. Selected examples of earth-abundant metal catalysts used for CO
hydrosilylation.
2
with Ru complexes [28]. Consequently, the reaction of Et
THF in the presence of [Mn(CO) Br] was assessed, and Et
CH and Et SiOSiEt were observed (see Supporting information
(SI), Table S1). Furthermore, minimum amounts of residual water
from the solvent were found to affect the catalytic activity favoring
3
SiH with
2 3
Si(CH ) -
5
3
CO
the first Zn catalyst ([Tris(2-pyridylthio)methyl]zinc hydride) for
the CO hydrosilylation to silylformates in 2012 [26]. Five years
later, they tested the zinc and magnesium catalytic systems [Tism
2
hydrosilylation with Et
3
SiH. Parkin and coworkers reported
3
3
3
2
3 3 3 3
the hydrolysis of Et SiH to Et SiOH and Et SiOSiEt . Drying the sol-
i
i
Prbenz]ZnH and [Tism Prbenz]MgH with B(C
6
F
5
)
3
, which could
vent with activated alumina significantly improved the catalytic
activity and the selectivity to the formation of silylformate (see
Table S2 in SI). Optimized conditions yielded 64% of silylformate
and 15% of silylacetal after just an hour at 50 °C (see Table 1, entry
5). This reaction also proceeded at room temperature and atmo-
spheric pressure with a change in selectivity (Table 1, entries 7–9).
selectively form bis(silyl)acetal and methane as products; bis(si-
lyl)acetals are rarely obtained [32,34–37,39–43], and they are valu-
able precursors of anhydrous formaldehyde [60]. Rodriguez and
coworkers also achieved selective hydrosilylation of CO
lyl)acetal with the bis(phosphino)boryl nickel hydride catalyst in
the presence of B(C [32].
In recent years, manganese catalysts have been used in the
hydrogenation of CO [61–63] as well as in the hydrosilylation of
olefins, alkynes, and carbonyl compounds [64–72]. However, man-
ganese catalysts had not been applied to the hydrosilylation of CO
until the recent work by Gonsalvi and coworkers [45] where Mn(I)
carbonyl complexes bearing a PNP pincer ligand catalyzed the CO
2
to bis(si-
6 5 3
F )
2.2. Solvent effect
2
Considering the results described above, other solvents were
evaluated to minimize the undesired products from the reaction
2
with THF. Some Et
observed in CH CN. When non-polar solvents were used there
was no significant catalytic activity (Table 2). However, traces of
Et SiOEt were detected with dioxane as a solvent similar to the
3
SiH conversion to silylformate (33%) was
2
3
reduction to methoxysilanes (Scheme 2, Gonsalvi 2019). They
reached high methoxysilane yields (84–99%) with a TON of 100
3
2

T. González and J.J. García
Polyhedron 203 (2021) 115242
Table 1
Carbon dioxide hydrosilylation with [Mn(CO)
5
Br] in THF as solvent.a
Entry
mol% [Mn]
P (bar)
t (h)
T (°C)
% silyl formate
% bis(silyl) acetal
% other productsb
% conversionc
1d
2
3
4
5
6
7
8
1.5
1
1.5
2
3
3
3
3
3
3
4
4
4
4
4
2
1
1
4
4
4
4
1
1
1
1
1
1
5
20
1
1
1
1
50
50
50
50
50
50
40
rt
55
50
54
67
64
54
37
18
14
62
nd
nd
19
3
3
6
15
4
17
48
21
18
nd
nd
25
17
29
26
21
35
42
26
12
19
28
nd
>99
70
86
>99
>99
93
96
92
47
>99
28
9
rt
e
10
11
12
50
50
50
f
g
3
1.5
h
nd
a
b
c
d
e
f
General reaction conditions: catalyst (7.5–20 mmol), Et
Et SiOSiEt , Et SiOH and products from the solvent were observed see SI.
Conversion based on Et SiH.
mmol of Et SiH.
Mercury drop test.
3
SiH 0.5 mmol, THF 5 mL. Yields were determined by GC–MS. r.t. = room temperature, n.d. = not detected.
3
3
3
3
1
3
TEMPO (1 mmol) was added.
Spin adducts with TEMPO, see Table 4.
g
Table 2
2 5
Solvent effect in the CO hydrosilylation with [Mn(CO)
Br].a
Entry
Solvent
% silylformate
% bis(silyl)acetal
% other productsb
n.d.
% conversionc
1
2
3
4
5
6
7
8
Toluene
Dioxane
MeCN
THF
THF/toluene (1:50)
THF/Toluene (1:10)
THF/Toluene (1:5)
THF/Toluene (2:3)
n.d.
<1
33
55
<1
1
n.d.
n.d.
n.d.
19
61
79
n.d.
<1
78
>99
93
95
d
<1
45
e
25
31
15
10
23
3
30
86
47
99
>99
a
General reaction conditions: catalyst 15 mmol, Et
Et SiOSiEt , Et
3 3 3
3
SiH 1 mmol, solvent 5 mL. Chromatographic yield. n.d. = not detected.
SiOH and products with the solvent were observed see SI.
Conversion based on Et SiH.
b
c
3
d
3
Et SiOEt was detected.
THF ring-opening reaction (see Table S1 in SI). Highly polar sol-
vents may promote the CO hydrosilylation [45,50]. However, sol-
vents such as DMSO and DMF present high boiling points making it
difficult to workup the corresponding product. Alternatively, the
use of a toluene and THF mixture minimized the undesired prod-
ucts and shifted the selectivity towards the bis(silyl)acetal (Table 2,
while PhSiH
3
gave only 6% of methoxysilane. Also, control experi-
2
ments without a catalytic precursor were carried out, and no prod-
ucts from carbon dioxide hydrosilylation were detected.
2.3. Mechanistic studies
entries 5–8). The reduction of CO
because anhydrous formaldehyde can be produced from bis(silyl)
acetals while CO reduction to formaldehyde is difficult to control
via hydrogenation.
The hydrosilylation reaction in the mixture THF/toluene was
also achieved using milder reaction conditions (Table 3). Under
atmospheric pressure and room temperature, a quantitative con-
2
to bis(silyl)acetal is of interest
Stoichiometric and homogeneity tests were performed to get
some insights into the catalytic mechanism. Additionally, the pres-
ence of radical intermediates was assessed by radical trapping
experiments with TEMPO. The mercury drop test was performed
for both the catalytic hydrosilylation in THF and the mixture of
THF/toluene. There was no significant change in the conversion
and selectivity in either case (see Table 1, entry 10; and Table 3,
entry 10); these results underscore the homogeneous nature of
the catalytic system. Nevertheless, it is well known that carbonyl
manganese complexes are feasible to form radical species that
can be active as catalytic intermediates in a variety of processes
[66–70,74–77]. Considering this as well as the reactivity observed
with THF (vide supra), experiments to evaluate the presence of free
2
version of Et
of the system changed to increase the proportion of silylformate
see Table 3, entry 7).
The CO hydrosilylation using other silanes was also assessed,
3
SiH was observed after 20 h; however, the selectivity
(
2
but overall lower yields were observed (see SI, Table S3). With
TMDS as a reducing agent, a 37% yield of silylformate was afforded
3

T. González and J.J. García
Polyhedron 203 (2021) 115242
Table 3
2 5
CO hydrosilylation with [Mn(CO)
Br] in a mixture of THF/toluene as solvent.a
Entry
mol% [Mn]
P (bar)
t (h)
T (°C)
Silyl formate
Bis(silyl)acetal
Other productsb
Conversion (%)c
1
2
3
4
5
6
7
8
1.5
1
4
4
6
2
1
1
1
4
4
4
4
1
1
1
1
1
6
20
1
1
1
1
50
50
50
50
50
40
rt
3
2
3
1
10
26
37
4
2
6
86
80
86
77
22
34
34
19
80
69
nd
10
15
11
19
27
40
25
11
14
24
19
99
97
>99
97
59
>99
96
34
96
>99
19
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
rt
9
1
1
40
50
50
d
0
1
e
f
nd
a
3
General reaction conditions: catalyst 15–40 mmol, Et SiH 1 mmol, THF/Toluene (4.0 mL/0.8 mL). Yields were determined by GC–MS. n.d. = not detected, r.t. = room
temperature.
b
Et SiOSiEt , Et SiOH and products with the solvent were observed see SI.
3 3 3
c
d
e
Conversion based on Et
3
SiH.
Mercury drop test.
TEMPO (1 mmol) was added.
radicals were performed with TEMPO as a radical trap. Thus, the
catalytic CO hydrosilylation was completely inhibited in the pres-
ence of TEMPO. Furthermore, stable radical adducts with TEMPO
were detected by GC–MS (see Table 4) indicating a homolytic
cleavage of the silane Si–H bond.
to produce a silylformate radical. Subsequent hydrogen atom
transfer from [Mn(CO) H] to the silyl radical Et SiC
(O)OH, which can be further hydrosilylated following the same
mechanistic pathway to the bis(silyl)acetal reduction product.
2
5
3
SiÅ yields Et
3
5
Noteworthy, the hydrogen atom transfer from [Mn(CO) H] to a-
Moreover, stoichiometric reactions with Et
3
SiH and [Mn(CO)
5
-
methylstyrene was reported by Halpern and Sweany in 1977
Br] were performed at room temperature and atmospheric pres-
sure in a THF/toluene mixture. After just half an hour, the
[76]. More recently, Wang and Yang showed selective hydrosilyla-
tion of alkynes by radical intermediates generated from [Mn
2
(-
compounds [Mn(CO)
5
H] and [Mn
2
(CO)10] were detected by GC–
CO)10] in the presence of dialuroyl peroxide and Ph MeSiH [66].
2
MS (see Scheme 3A, signal 2 and Scheme 3B, signal 6). The silane
was fully consumed (see Scheme 3A, signal 3), and triethylsilyl
bromide was formed (Scheme 3B, signal 4). An independent test
3
. Conclusion
using [Mn
clear carbonyl [Mn
hydrosilylation. As found, the Mn(0) precursor did not show any
catalytic activity under these reaction conditions (see Table 1,
2
(CO)10] was performed to elucidate whether the binu-
(CO)10 participates in the catalytic CO
2
The results reported herein prove the catalytic efficiency of sim-
ple commercial [Mn(CO) Br] without any additives or elaborated
ancillary ligands for the mild hydrosilylation of CO with Et SiH.
The optimized reaction conditions produced triethylsilylformate
in 67% yield and using a mixture of solvents gave bis(triethylsi-
lyl)acetal in 86% yield. Mechanistic studies are indicative of the
radical nature of the catalytic intermediates. We postulated a
hydrogen atom transfer mechanistic pathway involving the Mn(I)
2
]
5
2
3
1
entry 12). The formation of [Mn(CO)
NMR at À7.9 ppm, and IR-ATR (2014 and 1981 cm
Schemes 3C and D respectively) in agreement with the reported
data [71,76,78].
5
H] was confirmed by
H
)
À1
(
Considering the current results and closely related hydrogen
atom transfer reactions (HATR) [66,67,76], a radical hydrogen
transfer mechanism is postulated as shown in Scheme 4. First,
hydride [Mn(CO)
the best of our knowledge, this is the first report on the CO
5 5
H] and the formation of radical [(CO) MnÅ]. To
2
hydrosilylation catalyzed by transition-metal radical intermedi-
ates. These findings may improve the field of radical-mediated
[
Mn(CO)
generate [(CO)
Et SiH to yield [Mn(CO)
5
Br] suffers a homolytic cleavage of the Mn-Br bond to
MnÅ], which performs a hydrogen abstraction from
H] and Et SiÅ. The last one reacts with CO
5
CO
2
transformations catalyzed by earth-abundant metal
3
5
3
2
complexes.
Table 4
Radical trapping adducts with TEMPO and Et
SiH in the presence of [Mn(CO)
5
Br].a
3
Entry
Solvent
% a
% b
% c
b
1
THF/Toluene (1:5)
THF
3
3
7
18
9
6
c
2
a
b
c
2
Reaction conditions: catalyst 15 mmol, THF 5 mL, 1 h at 50 °C, 4 bar of CO . Chromatographic yield.
1
3
mmol of Et SiH.
3
Et SiH (0.5 mmol).
4

T. González and J.J. García
Polyhedron 203 (2021) 115242
Scheme 3. Stoichiometric CO
2
hydrosilylation. A & B: GC–MS characterization; C: H1 RMN; D: IR-ATR.
4
. Experimental section
(<0.005 mmHg) at 40 °C. TEMPO was purified by sublimation at
reduced pressure at room temperature. Deuterated solvents
4.1. General considerations
8 8
(THF-d and toluene d ) were purchased from Cambridge Isotope
Laboratories and stored over 3 Å molecular sieves. GC–MS determi-
nations were made using an Agilent 5975C system equipped with a
All manipulations were performed under argon atmosphere in
an MBraun Unilab Pro SP glovebox (<0.5 ppm of H O and <2 ppm
of O ) or using standard Schlenk techniques in an inert-gas/vac-
uum double manifold. All reagents were purchased as reagent
grade and stored in the glovebox before use unless otherwise
noted. Regular THF was dried and degassed using an MB-SPS-800
solvent drying system. Toluene was dried and distilled over Na
with benzophenone as an indicator. Molecular sieves (3 Å) and
activated alumina were dried under vacuum at 150 °C for 4 h. Car-
bon dioxide and argon (both 99.998%) from Praxair were used
30 m DB-5MS capillary column (0.25 mm  0.25
lm). Infrared ATR
2
analyses were carried out in a Perkin Elmer FT-IR Spectrometer
Frontier L1280101. NMR spectra were recorded at room tempera-
ture either on a Bruker AC-400 MHz or a Bruker AC-300 MHz
spectrometer.
2
4.2. General procedure for the catalytic CO
2
hydrosilylation with [Mn
(
CO) Br]
5
without further purification. Commercial [Mn(CO)
from Strem Chemicals) was sublimated under vacuum
5
Br] (purchased
In a typical assay, a 125 mL stainless steel Parr autoclave was
loaded with 4.2 mg (15 mmol) of the complex [Mn(CO) Br] and
5
5

T. González and J.J. García
Polyhedron 203 (2021) 115242
2 5
Scheme 4. Mechanistic proposal for the CO hydrosilylation with [Mn(CO) Br].
5
9 mg (0.5 mmol) of Et
3
SiH in 5 mL of THF. The solvent was passed
An aliquot was then taken and the flask was closed. Later, the reac-
tion mixture was stirred for half an hour at room temperature, and
another aliquot was taken. Both aliquots were analyzed immedi-
ately by GC–MS and infrared ATR spectroscopy. The NMR assay
was prepared using a Wilmad NMR tube with 16.4 mg (0.14 mmol)
through an alumina microcolumn immediately before use. The sys-
tem was pressurized, and the reaction mixture was stirred and
heated in an oil bath. After the reaction time was reached, the reac-
tion mixture was exposed to air and analyzed immediately by GC/
MS.
of Et
and toluene d
tone/N bath and charged with CO
temperature after 24 h.
3
SiH, and 19.2 mg (0.07 mmol) of [Mn(CO)
5
Br], THF (0.14 mL)
8
(ca. 0.7 mL). The mixture was then cooled in an ace-
1
4.3. Atmospheric pressure CO
2
hydrosilylation
2
2
. H NMR was acquired at room
Atmospheric pressure reactions were prepared in a 50 mL Sch-
3
lenk flask with 2.1 mg of [Mn(CO) Br] (7.5 mmol) and 29 mg of Et -
SiH (0.25 mmol) in 2.5 mL of solvent. The reaction mixture was
degassed by three freeze-pump-thaw cycles and charged with
5
CRediT authorship contribution statement
Tania Gonzalez: Investigation, Writting original draft. Juven-
tino Garcia: Supervision, Project administration, Writing-review
and editing.
2
CO (1 atm). The reaction mixture was stirred and heated in an
oil bath. After the reaction time was reached, the crude reaction
mixture was analyzed by GC/MS.
4.4. Mercury drop tests
Declaration of Competing Interest
Mercury drop tests were performed following the above general
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
procedure but a mercury drop (230 mg, 1.1 mmol) was added to
the reaction mixture on this occasion. The reaction crude was fil-
tered and analyzed by GC–MS.
4.5. Radical trapping experiments
Acknowledgments
The reaction mixture was prepared according to the general
Financial support by CONACYT (A1-S-7657) and DGAPA-UNAM
procedure, but 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) was
added in stoichiometric amounts (1 mmol, 156 mg) to the reaction
mixture. The autoclave was heated in an oil bath at 50 °C for an
hour, and then the crude reaction mixture was analyzed by GC–MS.
(
IN-200119) are acknowledged. T.G. thanks CONACYT for the Ph.D.
studies grant 607079. We also thank Dr. Alma Arévalo for technical
assistance.
4.6. Stoichiometric reactions
Appendix A. Supplementary data
Stoichiometric amounts of Et
3
SiH (0.2 mmol, 23.7 mg) and [Mn
MS, 1H NMR, and ATR spectra of products and Mn complexes.
GC traces of relevant experiments and additional support tables.
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.poly.2021.115242.
(
CO)
were loaded into a 50 mL Schlenk flask, the flask was degassed by
three freeze-pump-thaw cycles and charged with CO (0.77 bar).
5
Br] (0.2 mmol, 55 mg) and 1 mL of solvent (THF/toluene, 1:5)
2
6

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