Regioselective hydrosilylation of terminal alkynes using pentamethylcyclopentadienyl iridium(III) metallacycle catalysts

Article abstract of DOI:10.1016/j.molcata.2016.07.014

Pentamethylcyclopentadienyl iridium(III) metallacycles catalyse the hydrosilylation of alkynes using triethylsilane and no additive. The reactions proceed rapidly and efficiently at low catalyst loadings and under mild reaction conditions. If catalyses st

Full text of DOI:10.1016/j.molcata.2016.07.014

Accepted Manuscript
Title: Regioselective hydrosilylation of terminal alkynes using
pentamethylcyclopentadienyl iridium(III) metallacycle
catalysts
´
Author: Yann Corre Christophe Werle Lydia Brelot-Karmazin
Jean-Pierre Djukic Francine Agbossou-Niedercorn Christophe
Michon
PII:
S1381-1169(16)30264-3
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2016.07.014
MOLCAA 9948
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Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
19-4-2016
1-6-2016
6-7-2016
´
Please cite this article as: Yann Corre, Christophe Werle, Lydia Brelot-
Karmazin, Jean-Pierre Djukic, Francine Agbossou-Niedercorn, Christophe Michon,
Regioselective hydrosilylation of terminal alkynes using pentamethylcyclopentadienyl
iridium(III) metallacycle catalysts, Journal of Molecular Catalysis A: Chemical
http://dx.doi.org/10.1016/j.molcata.2016.07.014
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Regioselective hydrosilylation of terminal alkynes using
pentamethylcyclopentadienyl iridium(III) metallacycle catalysts
Yann Corre,a,b Christophe Werlé,c Lydia Brelot-Karmazin,c Jean-Pierre Djukic,c Francine
Agbossou-Niedercorn,*a,b Christophe Michon*a,b
a Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181 - UCCS - Unité de Catalyse et Chimie du
Solide, F-59000 Lille, France.
b Unité de Catalyse et de Chimie du Solide, CNRS UMR 8181, Ecole Nationale Supérieure de Chimie de Lille,
Bât C7, Av. Mendeleïev, Cité Scientifique, CS 90108, Villeneuve d’Ascq Cedex, France
c Institut de Chimie de Strasbourg, UMR 7177, Université de Strasbourg, 4 rue Blaise Pascal, F-67000
Strasbourg, France
christophe.michon@ensc-lille.fr, francine.agbossou@ensc-lille.fr
Fax: (+)33-320436561, Tel.: (+)33-320436863
1

Abstract
Pentamethylcyclopentadienyl iridium(III) metallacycles catalyse the hydrosilylation of
alkynes using triethylsilane and no additive. The reactions proceed rapidly and efficiently at
low catalyst loadings and under mild reaction conditions. If catalyses starting from terminal
alkynes lead selectively to (Z)-alkenylsilanes in high yields, reactions are less efficient and
selective starting from internal alkynes due to steric hindrance and the possible formation of
isoquinolinium salts. Mass spectrometry highlights up to two consecutive 1,2-insertions of
alkynes could take place into the catalyst iridium-carbon bond.
Keywords: iridium; metallacycles; half-sandwich; hydrosilylation, alkynes.
2

1. Introduction
Selective reduction of alkynes to alkenes is an important reaction in organic and
polymer chemistry [1]. If semihydrogenation of alkynes has been successfully studied mainly
by Lindlar reduction [2], the metal-catalysed hydrosilylation of alkynes is an interesting direct
and atom-economic reaction which provides versatile alkenylsilanes [3]. However, the control
of the reaction’s stereo- and regiochemistry remains challenging depending on several factors
like the structure of the catalyst, the nature of reagents (e.g. alkyne and silanes) and reaction
parameters (e.g. solvent and temperature). The hydrosilylation of terminal alkynes shall lead
to -(E)- and less frequent -(Z)-linear vinylsilanes, through respectively anti-Markovnikov
syn-addition and anti-Markovnikov anti-addition [3n,v]. Futhermore, the synthesis of
branched -vinyl silanes through Markovnikov addition is rare [3a,o,u].
The stereoselective synthesis and reactivity of metallacycles like iridium(III) complex
1 and chromiumtricarbonylbound iridacycle 2 have been studied by some of us for several
years (Scheme 1) [4]. Complexes of type 2 were found to display novel catalytic properties
for the conversion of terminal aromatic alkynes into racemic N-phenyl, 1-arylethylamines by
tandem hydroamination and hydrosilylation/protodesilation reactions under mild “one pot”
conditions (Scheme 2 a) [5].
Scheme 1.
3

Scheme 2.
The peculiar efficiency of such catalysts in promoting hydrosilylation was assigned to the
intervention of iridium–hydrido intermediate 3 (Scheme 1) [4e,5,6], a key species for the
transfer of the hydritic H atom to the electrophilic imine substrate. Recently, we showed the
combination of iridacycle 1 with sodium tetrakis(3,5-trifluoromethyl)phenyl]borate,
NaBArF24, as an additive could catalyse the hydrosilylation of various ketimines and
aldimines at low catalyst loadings and under mild reaction conditions (Scheme 2 b) [7].
Finally, other reports stated the efficiency of such iridacycles for other reactions [8] like
hydrogenation [9] and transfer hydrogenation [10]. Regarding the reactivity of iridacycles
with alkynes, we and others demonstrated complexes of type 4 could be obtained from a
double 1,2-insertion of a terminal aromatic alkyne like phenylacetylene (Scheme 1) [5,11]. A
recent report have revealed such 1,2-alkyne insertion could compete with a vinylidene
rearrangement/1,1-insertion depending the nature of the iridium(III) metallacycle. Indeed, the
reaction of fluorinated iridacycles with diphenylacetylene derivatives was shown to afford
ninemembered metallacycle complexes of type 5 by way of a sequential vinylidene
rearrangement, 1,1-insertion of the vinylidene ligand, and the 1,4-iridium migration to the Ar
group (Scheme 1) [11a]. Considering our previous results on hydrosilylation of imines as well
as on tandem hydroamination-hydrosilylation reactions, we investigated iridium(III)
metallacycles as catalysts for the hydrosilylation of alkynes.
2. Results and discussion
Screening of reaction conditions (e.g. solvent, temperature, time) and catalysts was
performed on the hydrosilylation of phenylacetylene 6a with triethylsilane (Table 1). Among
the various solvents screened, tetrahydrofuran (THF) led to a moderate yield and a poor
selectivity (entry 1). If the use of toluene and 1,4-dioxane afforded higher yields and a
selectivity for (E)-product 8a (entries 2-4), acetonitrile allowed the reaction to proceed well in
4

favor of the (Z)-product 7a provided the reaction temperature was kept at 80°C for 20 hours,
yields being barely not improved at 100°C (entries 5, 6). By comparison, chlorinated solvents
had to be preferred considering reactions proceeded well at 40°C in favor of (Z)-product 7a. If
dichloromethane led to an almost quantitative yield and a fair selectivity for 7a in 20 hours
without the use of AgBF4 or NaBArF24 (entries 7, 8, 9), 1,1’,2,2’-tetrachloroethane gave
better results in only 2 hours (entry 10). Finally, alcohols could not be used because of their
spontaneous reactivity with silanes. Hence, as already noticed in our previous studies [4,5,7],
a strong polar solvent had to be preferred to activate the catalyst by dissociation of the Ir-Cl
bond. Though the use of acetonitrile, a greener solvent, afforded fair yields and selectivities at
80°C and 20 hours of reaction, the non-coordinating dichloromethane and 1,1’,2,2’-
tetrachloroethane led to better results in only few hours. In presence of our iridium(III)
catalysts, nitrile solvents had another drawback due to their reactivity with silane reagents at
high temperatures (entries 5,6) [5,7]. Within the most efficient and selective reaction
conditions, catalyst 1 proved to be slightly more active than catalyst 2 (entries 10, 11). Yield
and selectivity were also high using 1 mol% of catalyst 1 though the reaction time had to be
extended to 3 hours (entries 12, 13). A preliminary kinetic study performed at 40°C and 1
mol% catalyst loading allowed us to determine a half-life of 1.6 hour (94 minutes) along with
a turnover number (TON) of 50 and a turnover frequency (TOF) of 31. However, the data
could not be fitted with any simple kinetic law. A further decrease of the catalyst loading to
0.1 mol% led to a much slower reaction with a slightly reduced yield and a significant
increase of TON and TOF values (entry 14). However, decreasing the amount of catalyst to
0.01 mol% resulted in a very low yield and showed the catalyst limits (entry 15).
Table 1: hydrosilylation of phenylacetylene 6a - effects of solvent, temperature and time.
Entry
Cat.
(%)
Solvent
T
(°C)
t
(h)
Yield
(%)[a]
Selectivity[a]
(Z) / (E) / (gem)
TON[b] TOF[c]
1
2
3
4
5
6
7
1 (2.5)
1 (2.5)
1 (2.5)
THF
60
80
100
80
80
100
40
20
20
10
20
20
20
20
39
83
87
85
72
78
95
51
37
21
1
89
0
41
57
71
91
8
8
7
8
7
3
8
5
16
33
35
34
29
31
38
0.8
1.7
3.5
1.7
1.5
1.6
1.9
toluene
toluene
1 (2.5) dioxane[d]
1 (2.5)
1 (2.5)
1 (2.5)
CH3CN
CH3CN
CH2Cl2
92
12
83
5

8
1 (2.5)
1 (2.5)
1 (2.5)
2 (2.5)
1 (1.0)
1 (1.0)
1 (0.1)
CH2Cl2
CH2Cl2
TCE
TCE
TCE
TCE
TCE
TCE
40
40
40
40
40
40
40
40
2
20
2
2
2
3
20
62
57
0
92
-
3
-
6
9
9
9
13
3
5
-
40
-
20
-
9[e]
10
11
12
13
14
91
86
71
90
87
11
92
91
86
86
81
8
2
0
5
5
6
0
36
36
71
90
870
11
18
18
36
30
44
0.2
15[f] 1 (0.01)
1
[a] determined by H NMR using 1,3,5-trimethoxybenzene as an internal reference. [b] Turnover
number = mol of product/mol of catalyst. [c] Turnover frequency = mol of product/mol of
catalyst/hour. [d] 1,4-dioxane. [e] reaction with 5 mol% of AgBF4 or NaBArF24, sodium tetrakis(3,5-
trifluoromethyl)phenyl]borate. [f] 10 mL solvent and 0.1 eq. of 1,3,5-trimethoxybenzene.
Various silane reagents [12] could be used for the hydrosilylation of phenylacetylene
6a (Table 2). Interestingly, reactions using affordable triethylsilane could be run in 2 hours
and at 40°C affording (Z)-product in good yield, selectivity, TON and TOF (entry 1).
However, an increase of temperature and time resulted in the partial isomerization of (Z)-
product 7a into (E)-product 8a (entry 2). Within the same reaction conditions (e.g. 2 hours
and 40°C), the reaction with triphenylsilane allowed also the selective hydrosilylation of 6a
into (Z)-product 7a but in lower yield, TON and TOF. An increase of the reaction time and
temperature led to the complete isomerization of 7a into (E)-product 8a (entries 3, 4). If
sterically hindered 1,1,1,3,5,5,5-heptamethyltrisiloxane afforded selectively (Z)-product 7a at
60°C in 20 hours, a double reaction time led exclusively to the (E)-product 8a (entries 5, 6).
Otherwise, the use of triethoxysilane required a stronger heating and showed only the (E)-
product formation (entries 7, 8). Finally, inexpensive hydrosilylation reagents like
tetramethyldisiloxane (TMDS) and polymethylhydroxysiloxane (PMHS) led to complex
mixtures (entries 9, 10).
The reaction scope was then studied using the best silane reagent and reaction
conditions (Table 3). The hydrosilylation of phenylacetylene 6a proceeded in fair yields at
40°C with high selectivities for (Z)-product 7a using triethyl- or triphenylsilane. If the use of
triethylsilane led to the (Z)-alkenylsilane 7b from para-fluorinated reagent 6b in good yield
and selectivity, triphenylsilane afforded only the (E)-product 8b in a modest yield.
Table 2: hydrosilylation of phenylacetylene 6a - effects of silanes and temperature.
6

Entry
Silane
Cost[a]
T
t
Yield
Selectivity[b]
TON[c] TOF[d]
(€/mmol) (°C) (h) (%)[b] (Z) / (E) / (gem)
1
2
3
4
5
Et3SiH
Et3SiH
Ph3SiH
0.41
0.41
1.64
1.64
0.38
40
60
40
2
25
2
91
93
80
65
87
92
38
100
0
6
60
0
100
0
2
2
0
0
0
36
37
32
26
35
18
1.9
16
1.1
1.8
Ph3SiH
100 24
(Me3SiO)2-
Si(Me)H
(Me3SiO)2-
Si(Me)H
(EtO)3SiH
(EtO)3SiH
TMDS
60
60
40
100 24
70
60
20
40
2
100
6
0.38
100
0
100
-
0
40
1.0
7
8
9
0.79
0.79
0.11
0.01
0
63
-
-
-
-
-
25
-
-
1.0
-
100
50 100[e]
40 100[e]
unidentified
products
10
PMHS
-
-
1
[a] According to ref. 12 and www.sigmaaldrich.com. [b] determined by H NMR using 1,3,5-
trimethoxybenzene as an internal reference. [c] Turnover number = mol of product/mol of catalyst. [d]
Turnover frequency = mol of product/mol of catalyst/hour. [e] determined by GC and GC-MS.
The same tendency could be observed with para-methoxy and meta-methyl derivatives 6c and
6d with higher yields and reduced selectivities. By comparison, dimethylamino substrate 6e
led to an opposite trend. Indeed, whereas the use of triethylsilane led to the (E)-alkenylsilane
8e in fair yield and selectivity, triphenylsilane afforded both (Z)- and (E)-products, 7e and 8e,
in a good yield. We could also notice alkyl substrates 6f and 6g displayed poor reactivities.
Table 3: substrate scope.
Entry
R1
R2
Silane
T
t
Yield
Selectivity
(°C) (h) (%)[a] 7a-j / 8a-j / 9a-j
(Z) / (E) / (gem)
1
2
3
4
5
6
7
8
9
6a
6a
6b
6b
6c
6c
6d
6d
6e
Ph
H
H
H
H
H
H
H
H
H
Et3SiH
40
2
2
2
2
2
2
2
2
2
91
80
74
22
86
85
93
100
81
92
100
93
0
6
0
2
0
2
0
1
2
2
5
0
Ph
Ph3SiH 40
Et3SiH 40
Ph3SiH 40
Et3SiH 40
Ph3SiH 40
Et3SiH 40
Ph3SiH 40
p-F-(C6H4)
p-F-(C6H4)
p-MeO-(C6H4)
p-MeO-(C6H4)
m-Me-(C6H4)
m-Me-(C6H4)
p-NMe2-(C6H4)
5
100
30
98
5
69
0
93
0
95
81
Et3SiH
40
19
7

10
11
12
13
14
15
16
17
18
19
20
21
22
6e
6f
p-NMe2-(C6H4)
n-pentyl
n-pentyl
cyclopropyl
cyclopropyl
CO2Et
CO2Et
Ph
H
H
H
H
H
H
H
Ph3SiH 40
Et3SiH 40
Ph3SiH 40
Et3SiH 40
Ph3SiH 40
Et3SiH 40
Ph3SiH 40
12
2
86
33
0
55
0
41
100
-
4
0
-
6f
2
-
6g
6g
6h
6h
6i
2
0
-
-
-
2
0
13[b]
-
-
-
2
100
-
0
0
-
2
0
-
CO2Et Et3SiH
CO2Et Et3SiH
80
80
20
20
20
20
20
20
62[c]
6
42
100
-
58
0
-
6i[d]
Ph
0
-
6i
Ph
CO2Et Ph3SiH 80
0
35[e]
-
6j
6j[d]
Ph
Me
Me
Me
Et3SiH
Et3SiH
80
80
0
100
50
-
0
0
-
Ph
8
50
-
6j
Ph
Ph3SiH 80
0
1
[a] determined by H NMR using 1,3,5-trimethoxybenzene as an internal reference and by GC. [b]
same result in 20h and 14% yield of (E)-selectivity if 80°C during 20h. [c] mixture of -(E)- and -
(Z)-products as respect to phenyl substituent. [d] in CH3CN. [e] mixture of - and -(E)-products as
respect to phenyl substituent.
8

Indeed, no reaction was observed with reagent 6g and the hydrosilylation of 6f proceeded
only with the use of triethylsilane to lead to the (E)-product 8f in a low yield. Ethylpropiolate
6h displayed also a poor reactivity independently of the reaction time and temperature.
Finally, the hydrosilylation of internal alkynes 6i and 6j was investigated. If no reactions were
observed while using triphenylsilane, modest to average yields were obtained with
triethylsilane and the use of acetonitrile as a solvent resulted also in lower reactivities.
Reagent 6i led to both (Z)- and (E)-products, 7i and 8i, in a fair yield, and substrate 6j
afforded exclusively (E)-products 8j in a modest yield.
As a preliminary study regarding the possible active species involved in the catalytic
process of such alkyne hydrosilylation reactions [3s, 13, 14], we performed an analysis by
electrospray ionization mass spectrometry on the reaction mixture obtained from the
quantitative reaction of phenylacetylene 6a and complex 2 (Scheme 3, Figure 1).
Along this study, complex 2 had to be preferred to 1 because of its higher stability when
analysed in methanol by mass spectrometry. Species 10 and 11 could be characterized
unambiguously along with complexes 12 and 13a. Hence, if complex 10 resulted from a
single 1,2-insertion of terminal alkyne 6a into the iridium-CAr bond of complex 2, species 11
was issued from a double 1,2-insertion of 6a and no vinylidene rearrangement/1,1-insertion
could be evidenced. Our previous studies on tandem hydroamination and
hydrosilylation/protodesilylation reactions demonstrated complex 11, once isolated, had no
catalytic activity [5]. Hence, single and double 1,2-insertion of terminal alkyne 6a proved to
compete, one leading to an active catalyst and the other to an inert species. Otherwise,
complex 13a and complex 12 which had been previously linked to the catalyst resting state
[7] were also observed.
Scheme 3.
9

Figure 1. ESI(+)-MS analysis in methanol of the crude mixture resulting from the catalytic
hydrosilylation of reagent 6a.
Another analysis by electrospray ionization mass spectrometry was performed on the
crude mixture resulting from the quantitative reaction of iridium(III) complex 2 with internal
alkyne 6i (Scheme 4, Figure 2). The use of silver tetrafluoroborate was shown to be critical to
stabilize the formed species. If complex 13b appeared as the first reaction intermediate linked
to the catalyst resting state [7], the main species observed at m/w 656 was likely to be
complex 14 and/or 15 as the result of a single 1,2-insertion of internal alkyne 6i into complex
2 iridium-CAr bond.
Scheme 4. Reaction of complex 2 with AgBF4 and phenylpropiolate.
10

Figure 2. ESI(+)-MS analysis in methanol of the crude mixture resulting from the
stoechiometric hydrosilylation of reagent 6i.
In addition, thanks to the stabilizing effect of tetrafluoroborate anion, minor species 17 was
observed at m/w 328 and confirmed by X-ray diffraction analysis. Indeed, characterization of
single crystals grown by diffusion of the reaction crude mixture (dichloromethane solution) in
hexane helped to confirm the synthesis of species 17 (Figure 3, Table 4). That compound shall
be prepared from complex 15 by, first, the formation of intermediate 16, which is a
pyridoisoquinolinium moiety bound to the iridium center and, second, the release of
pentamethylcyclopentadienyl iridium(III) fragment (Scheme 3). It is worth to note such
reaction pathway was already observed when pentamethylcyclopentadienyl rhodium(III)
complexes and O2 were used to catalyse oxidative C−H activation/annulation reactions and
produce various related isoquinolinium salts [15].
Figure 3. Ortep plot of 17 in the solid state. Thermal ellipsoids are drawn at a 50%
probability level. Hydrogen atoms are omitted for clarity. CCDC 1473938 [16].
11

On the whole, if isoquinolinium salt 17 could be synthesised to the detriment of the catalytic
hydrosilylation of alkynes, its characterization confirmed a single 1,2-insertion of internal
alkyne into the catalyst iridium-CAr bond was likely to occur. However, we could not find
evidences of a double 1,2-insertion of internal alkynes or of a vinylidene rearrangement/1,1-
insertion. Hence, the reaction mechanism shall start by the insertion of alkyne reagent into the
iridium-CAr bond of the dechlorinated species A (Scheme 5).
Scheme 5. Proposed reaction mechanism.
While a first equivalent of A inserts the alkyne reagent forming species B and C, a second
equivalent of A reacts with triethylsilane to afford iridium hydride complex 3 (Schemes 1 and
5) and triethylsilyl cation. The latter can then react with species B and C to lead to
intermediates D and E which react further with hydride 3 to form (Z)- and (E)-alkenylsilane
12

products and release cationic iridium species A. If the low reactivity and selectivity observed
for the hydrosilylation of internal alkynes may be related to their implicit steric hindrance and
the possible formation of isoquinolinium salts, the selective synthesis of (Z)-alkenylsilanes
from terminal alkynes proved to depend on both electronic and steric parameters of the
substrates as well as on the reaction temperature (Tables 2 and 3, Scheme 5). According
previous studies on iridium and rhodium catalysts [13c-e], (Z)-alkenylsilanes 7a-j shall be the
kinetic products formed through anti-additions leading to intermediates D (Scheme 5).
Isomerization appeared privileged by high reaction temperature and time (Table 1). It may
occur through 2-vinyl species F or zwitterionic carbenes G to generate intermediates E
which shall then react with iridium hydride 3 and afford (E)-alkenylsilanes 8a-j as the
thermodynamic products (Scheme 5).
Conclusion
Pentamethylcyclopentadienyl iridium(III) metallacycles were shown to catalyse the
hydrosilylation of alkynes using triethylsilane and no additive. The reactions could proceed
rapidly and efficiently at low catalyst loading and under mild conditions. If the catalyses
starting from terminal alkynes led selectively to (Z)-alkenylsilanes in high yields, reactions
were less efficient and selective starting from internal alkynes due to steric hindrance and the
possible formation of isoquinolinium salts. Isomerization from (Z)- to (E)-alkenylsilanes
appeared privileged by high reaction temperature and time. A study by mass spectrometry
showed single and double alkyne 1,2-insertion could take place into the catalyst iridium-
carbon bond but no vinylidene rearrangement/1,1-insertion could be evidenced. Whereas a
single insertion was observed for internal alkynes, a double 1,2-insertion was possible using
terminal alkynes but led to an inert catalytic species.
3. Experimental section
3.1.
General data
All solvents were dried using standard methods. All commercial reagents were used as
received unless otherwise stated. Unless stated, all reactions were carried out under a dry
1
nitrogen atmosphere. H (300 MHz) and 13C (75 MHz) spectra were acquired on a Bruker
Avance spectrometer. Chemical shifts are reported downfield of Me4Si in ppm and coupling
constants are expressed in Hz. Gas chromatography analyses were done on GC Shimadzu
13

2010+ with FID detectors using Supelco SPB-5 column (30 m, 0.25 mm, 0.25 μm) and with
nitrogen as gas carrier. GC-MS analyses were performed on a Shimadzu QP2010+ (EI mode)
using Supelco column SLBTM-5ms (30 m, 0.25 mm, 0.25 μm). Analytical thin layer
chromatography (TLC) was performed on Merck pre-coated 0.20 mm silica gel Alugram Sil
60 G/UV254 plates. Flash chromatography was carried out with Macherey silica gel
(Kielselgel 60). MS-ESI and HRMS-ESI analyses were performed at CUMA-University Lille
Nord de-France.
Table 4. Crystal data and structure refinement compound 17.
Compound 17 CCDC
Temperature
Empirical formula
Formula weight
Wavelength
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α(°)
173 K
C22H18NO2BF4
415.18
0.71073 (MoK)
Monoclinic
P21/c
27.6525 (14)
10.2341 (5)
14.1072 (7)
90
β (°)
102.6830(10)
90
3894.9(3)
 (°)
Volume(Å3)
Z
8
Crystal dim (mm)
0.40 x 0.25 x 0.18
1.416
Density (g.cm-3)
Absorption coefficient
Absorption (max. and min. transmission)
F(000)
0.115 mm-1
0.7458 and 0.6373
1712
1.510 to 29.050
-37, 37 / -13, 13 / -19, 19
31007
10348 [R(eq.) = 0.0841]
543
2θ limits (deg)
Limits hkl
Reflections collected
Independent reflections
Num. of var.
GOF
0.876
Final R indices
R indices (all data)
R = 0.0552, wR = 0.1293
Rall = 0.1593, wRall = 0.1652
3.2.
General procedure for the catalysis
Under nitrogen, alkyne reagent (0.15 mmol, 1 eq.) and selected iridium(III) catalyst (x
mol%) were introduced in a Schlenk tube along with internal reference 1,3,5-
trimethoxybenzene (1 eq.). TCE solvent (2 mL) was added followed by silane reagent
14

(0.18 mmol, 1.2 eq.). The reaction mixture was then heated at the selected temperature
under stirring. In order to follow the progress of the reaction, aliquots (0.1 mL) were
taken at defined times, filtered through Celite with a CH2Cl2 wash (3 mL), evaporated
under vacuum and analysed by 1H NMR.
Acknowledgements
The Université Lille 1 and Région Nord-Pas de Calais are acknowledged for a PhD fellowship
(Y. C.). The Agence Nationale de la Recherche (project ANR-10-BLAN-0736 administered
by the University of Strasbourg) is thanked for a PhD funding (C. W.). The CNRS, the
Chevreul Institute (FR 2638), the Ministère de l’Enseignement Supérieur et de la Recherche,
the Région Nord – Pas de Calais and the FEDER are acknowledged for supporting and
funding partially this work. Mrs C. Delabre (UCCS) is thanked for GC and GC-MS analyses.
Mrs N. Duhal and C. Lenglart (CUMA, Lille University) are thanked for HRMS analyses.
15

References:
[1] (a) H.-U. Blaser, A. Schnyder, H Steiner, R ssler, P Baumeister, In Handbook of
Heterogeneous Catalysis; Wiley−VCH Verlag GmbH & Co. KGaA: Weinheim,
Germany, 2008; pp 3284−3308. (b) D. Heller, A. H. De Vries, J. G. De Vries, In
Handbook of Homogeneous Hydrogenation; de J. G. Vries, C. J. Elsevier, Eds.;
Wiley−VCH: Weinheim, Germany, 2007; Vol 3, pp 1483−1516. (c) A. Molnar, A.
Sarkany, M. Varga, J. Mol. Catal. A: Chem. 173 (2001) 185−221
[2] By hydrogenation: (a) S. Furukawa, T. Komatsu, ACS Catal. 6 (2016) 2121−2125; (b) K.
C. Szeto, W. Sahyoun, N. Merle, J. L. Castelbou, N. Popoff, F. Lefebvre, J. Raynaud, C.
Godard, C. Claver, L. Delevoye, R. M. Gauvin, M. Taoufik, Catal. Sci. Technol. 6 (2016)
882-889; (c) T. Mitsudome, M. Yamamoto, Z. Maeno, T. Mizugaki, K. Jitsukawa, K.
Kaneda, J Am Chem Soc 137 (2015) 13452−13455; (d) W. Y. Siau, Y. Zhang, Y.
Zhao, Top. Curr. Chem. 327 (2012) 33–58; (e) Y. Lee, Y. Motoyama, K. Tsuji, S. H.
Yoon, I. Mochida, H Nagashima, ChemCatChem 4 (2012) 778−781; (f) H. Sajiki, S.
Mori, T. Ohkubo, T. Ikawa, A. Kume, T. Maegawa, Y. Monguchi, Chem. Eur. J. 14
(2008) 5109−5111; (g) J. J. Brunet, P. J. Caubere, J. Org Chem 49 (1984) 4058−4060;
(h) J. Rajaram, A. P. S. Narula, H. P. S. Chawla, S. Dev, Tetrahedron 39 (1983)
2315−2322; (i) H. Lindlar, R. Dubuis, Organic Syntheses 46 (1966) 89−92; (j) H.
Lindlar, Helv. Chim. Acta 35 (1952) 446−456
[3] By hydrosilylation: (a) M. Iglesias, M. Aliaga-Lavrijsen, P. J. Sanz Miguel, F. J.
Fernández-Alvarez, J. J. Pérez-Torrente, L. A. Oro, Adv. Synth. Catal. 357 (2015) 350–
354; (b) Z. Mo, J. Xiao, Y. Gao, L. Deng, J. Am. Chem. Soc. 136 (2014) 17414-17417;
(c) M. Iglesias, P. J. Sanz Miguel, V. Polo, F. J. Fernández-Alvarez, J. J. Pérez-Torrente,
L. A. Oro, Chem. Eur. J. 19 (2013) 17559–17566; (d) S. Ding, L.-J. Song, L. W. Chung,
X. Zhang, J. Sun, Y.-D. Wu, J. Am. Chem. Soc. 135 (2013) 13835−13842; (e) R. Cano,
M. Yus, and D. J Ram n, ACS Catal. 2 (2012) 1070−1078; (f) K. Igawa, D. Yoshihiro,
N. Ichikawa, N. Kokan, K. Tomooka, Angew. Chem. Int. Ed. 51 (2012) 12745–12748;
(g) M. Iglesias, M. Pérez-Nicolás, P. J. Sanz Miguel, V. Polo, F. J. Fernández-Alvarez, J.
J. Pérez-Torrente, L. A. Oro, Chem. Commun. 48 (2012) 9480–9482; (h) Y. Sumida, T.
Kato, S. Yoshida, T. Hosoya, Org. Lett. 14 (2012) 1552–1555; (i) W. A. Solomonsz, G.
A. Rance, M. Suyetin, A. La Torre, E. Bichoutskaia, A. N. Khlobystov, Chem. Eur. J. 18
(2012) 13180–13187; (j) G. F. Silbestri, J. C. Flores, E. de Jes s, Organometallics 31
(2012) 3355−3360; (k) Y. Kawasaki, Y. Ishikawa, K. Igawa, K. Tomooka, J. Am. Chem.
16

Soc. 133 (2011) 20712−20715; (l) L. Busetto, M. C. Cassani, C. Femoni, M. Mancinelli,
A. Mazzanti, R. Mazzoni, G. Solinas, Organometallics 30 (2011) 5258–5272; (m) N.
Kato, Y. Tamura, T. Kashiwabara, T. Sanji, M. Tanaka, Organometallics 29 (2010)
5274–5282; (n) B. Marciniec, H. Maciejewski, C. Pietraszuk and P Pawluć in
Hydrosilylation: A Comprehensive Review on Recent Advances, ed. B. Marciniec,
Springer, Heidelberg, 2009; (o) J. J. Hu, F. Li, T. S. A. Hor, Organometallics 28 (2009)
1212–1220; (p) M. V. Jiménez, J. J. Pérez-Torrente, M. I. Bartolomé, V. Gierz, F. J.
Lahoz, L. A. Oro, Organometallics 27 (2008) 224–234; (q) A. Hamze, O. Provot, J.-D.
Brion, M. Alami, J. Organomet. Chem. 693 (2008) 2789–2797; (r) V. S. Sridevi, W. Y.
Fan, W. K. Leong, Organometallics 26 (2007) 1157-1160; (s) L. Yong, K. Kirleis, H.
Butenschön, Adv. Synth. Catal. 348 (2006) 833–836; (t) Y. Liu, S. Yamazaki, S.
Yamabe, J. Org. Chem. 70 (2005) 556-561; (u) C. Menozzi, P. I. Dalko, J. Cossy, J. Org.
Chem. 70 (2005) 10717–10719; (v) B. M. Trost, Z. T. Ball, Synthesis (2005) 853-887.
[4] (a) W. Iali, F. La Paglia, X.-F. Le Goff, D. Sredojevic , M. Pfeffer, J.-P. Djukic, Chem.
Commun. 48 (2012) 10310–10312; (b) J.-P. Djukic, W. Iali, M. Pfeffer, X.-F. LeGoff,
Chem. Eur. J. 18 (2012) 6063–6078; (c) J.-P. Djukic, W. Iali, M. Pfeffer, X.-F. LeGoff,
Chem. Commun. 47 (2011) 3631–3633; (d) J.-P. Djukic, C. Boulho, D. Sredojevic, C.
Scheeren, S. Zaric, L. Ricard, M. Pfeffer, Chem. Eur. J. 15 (2009) 10830–10842; (e) C.
Scheeren, F. Maasarani, A. Hijazi, J.-P. Djukic, M. Pfeffer, S. D. Zaric, X.-F. LeGoff, L.
Ricard, Organometallics 26 (2007) 3336–3345.
[5] W. Iali, F. La Paglia, X.-F. Le Goff, D. Sredojevic , M. Pfeffer, J.-P. Djukic, Chem.
Commun. 48 (2012) 10310-10312.
[6] Y. Hu, L. Li, A. P. Shaw, J. R. Norton, W. Sattler, Y. Rong, Organometallics 31 (2012)
5058−5064
[7] Y. Corre, W. Iali, M. Hamdaoui, X. Trivelli, J.-P. Djukic, F. Agbossou-Niedercorn, C.
Michon, Catal. Sci. Tech. 5 (2015) 1452-1458.
[8] (a) C. Michon, K. MacIntyre, Y. Corre, F. Agbossou-Niedercron, ChemCatChem 8 (2016)
1755-1762; (b) Y.-F. Han, G.-X. Jin, Chem. Soc. Rev. 43 (2014) 2799-2823.
[9] (a) W. Tang, C. Lau, X. Wu, J. Xiao, Synlett 25 (2014) 81-84; (b) J. Wu, J. H.
Barnard, Y. Zhang, D. Talwar, C. M. Robertson, J. Xiao, Chem. Commun. 49 (2013)
7052-7054; (c) B. Villa-Marcos, W. Tang, X. Wu, J. Xiao, Org. Biomol. Chem. 11
(2013) 6934–6939.
[10] (a) H. Y. T. Chen, C. Wang, X. Wu, X. Jiang, C. R. A. Catlow, J. Xiao, Chem. Eur. J. 21
(2015) 16564-16577; (b) D. Talwar, H. L. Yi, E. Durham, J. Xiao, Chem. Eur. J. 21
17

(2015) 5370-5379; (c) D. Talwar, X. Wu, O. Saidi, N. P. Salguero, J. Xiao, Chem. Eur. J.
20 (2014) 12835-12842; (d) S. Sabater, M. Baya, J. A. Mata, Organometallics 33 (2014)
6830−6839; (e) Y. Wei, D. Xue, Q. Lei, C. Wang, J. Xiao, Green Chem. 15 (2013) 629-
634; (f) N. Pannetier, J.-B. Sortais, J.-T. Issenhuth, L. Barloy, C. Sirlin, A. Holuigue, L.
Lefort, L. Panella, J. G. de Vries, M. Pfeffer, Adv. Synth. Catal. 353 (2011) 2844–2852;
(g) S. Arita, T. Koike, Y. Kayaki, T. Ikariya, Organometallics 27 (2008) 2795-2802.
[11] (a) Y. Ikeda, S. Kodama, N. Tsuchida, Y. Ishii, Dalton Trans. 44 (2015) 17448–17452;
(b) M. Valencia, M. Martín-Ortiz, M. Gómez-Gallego, C. Ramírez de Arellano, M. A.
Sierra, Chem. Eur. J. 20 (2014) 3831–3838; (c) D. L. Davies, O. Al-Duaij, J. Fawcett, K.
Singh, Organometallics 29 (2010) 1413–1420; (d) L. Li, Y. Jiao, W. W. Brennessel, W.
D. Jones, Organometallics 29 (2010) 4593–4605.
[12] D. Addis, S. Das, K. Junge, M. Beller, Angew. Chem. Int. Ed. 50 (2011) 6004–6011.
[13] (a) S. Sridevi, W. Y. Fan, W. K. Leong, Organometallics 26 (2007) 1157-1160; (b) C.
Vicent, M. Viciano, E. Mas-Marzá, M. Sanaú, E. Peris, Organometallics 25 (2006) 3713–
3720; (c) C.-H. Jun, R. H. Crabtree, J. Organomet. Chem., 447 (1993) 177-187; (d) I.
Ojima, N. Clos, R. J. Donovan, P. Ingallina, Organometallics, 9 (1990) 3127-3133 ; (e) J.
E. Hill, T. A. Nile, J. Organomet. Chem., 137 (1977) 293-300; (f) A. J. Chalk, J. F.
Harrod, J. Am. Chem. Soc. 89 (1967) 1640–1647.
[14] (a) M. Iglesias, F. J. Fernández-Alvarez, L. A. Oro, ChemCatChem, 6 (2014) 2486–
2489; (b) T. T. Metsänen, P. Hrobárik, H. F. T. Klare, M. Kaupp, M. Oestreich, J. Am.
Chem. Soc. 136 (2014) 6912–6915; (c) W. Wang, P. Gu, Y. Wang, H. Wei,
Organometallics 33 (2014) 847–857; (d) M. Iglesias, P. J. Sanz-Miguel, V. Polo, F. J.
Fernández-Alvarez, J. J. Pérez-Torrente, L. A. Oro, Chem. Eur. J. 19 (2013) 17559–
17566; (e) J. Yang, P. S. White, M. Brookhart, J. Am. Chem. Soc. 130 (2008) 17509–
17518.
[15] (a) C.-Z. Luo, P. Gandeepan, J. Jayakumar, K. Parthasarathy, Y.-W. Chang, C.-H.
Cheng, Chem. Eur. J. 19 (2013) 14181–14186; (b) G. Zhang, L. Yang, Y. Wang, Y. Xie,
H. Huang, J. Am. Chem. Soc. 135 (2013) 8850−8853.
[16] CCDC 1473938 for compound 17. Selected bond lengths (Å): C27-N2 1.383(3), C27-
C28 1.442(3), C28-C33 1.403(3), C33-C34 1.435(3), C34-C35 1.347(3), C35-N2
1.426(3). These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
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Graphical abstract
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