Silica-supported Z-selective Ru olefin metathesis catalysts

Article abstract of DOI:10.1016/j.mcat.2019.110743

Recently reported thiolate-coordinated ruthenium alkylidene complexes show promise in Z-selective and stereoretentive olefin metathesis reactions. Herein we describe the immobilization of three Ru complexes containing a bulky aryl thiolate on mesostructured silica via surface organometallic chemistry. The applied methodology gives isolated catalytic sites homogeneously distributed on the silica surface. The catalytic results with two model substrates show comparable Z-selectivities to those of the homogeneous counterparts.

Full text of DOI:10.1016/j.mcat.2019.110743

MolecularCatalysis483(2020)110743
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Molecular Catalysis
journal homepage: www.elsevier.com/locate/mcat
Silica-supported Z-selective Ru olefin metathesis catalysts
Marc Renom-Carrascoa, Philipp Maniaa, Reine Sayaha, Laurent Veyrea, Giovanni Occhipintib,
Vidar R. Jensenb, Chloé Thieuleuxa,*
a Université de Lyon, Institut de Chimie de Lyon, C2P2 UMR 5265 CNRS-Université Lyon 1-CPE Lyon, ESCPE Lyon. 43, Bd du 11 Novembre 1918, 69616 Villeurbanne,
France
b Department of Chemistry, University of Bergen, Allégaten 41, N-5007 Bergen, Norway
A R T I C L E I N F O
A B S T R A C T
Keywords:
Recently reported thiolate-coordinated ruthenium alkylidene complexes show promise in Z-selective and ste-
reoretentive olefin metathesis reactions. Herein we describe the immobilization of three Ru complexes con-
taining a bulky aryl thiolate on mesostructured silica via surface organometallic chemistry. The applied meth-
odology gives isolated catalytic sites homogeneously distributed on the silica surface. The catalytic results with
two model substrates show comparable Z-selectivities to those of the homogeneous counterparts.
Olefin metathesis
Z-selectivity
Ruthenium
NHC
Supported complexes
1. Introduction
isolated sites for the immobilization of organometallic complexes. This
feature, in combination with the rigidity of the surface (not present in
Olefin metathesis is a well-known and established reaction for the
formation of C]C bonds [1]. Since its discovery, many generations of
catalysts, with improved activities and stabilities, have been developed.
However, the olefin metathesis product is a thermodynamic mixture of
the two alkene stereoisomers (Z and E), with the E-isomer normally
being the favored one. In 2009, the first highly Z-selective olefin me-
tathesis catalysts, based on Mo and W, were reported by Schrock and
Hoveyda [2]. Improved versions of these catalysts [3] and also a highly
E-stereoretentive catalyst [4] were later reported. The evolution of Z-
selective and stereoretentive Ru-olefin metathesis catalysts has fol-
lowed a similar chronology, starting by the reports of Grubbs and co-
workers in 2011 [5]. Since then, two kinds of Z-selective Ru olefin
metathesis catalysts and one highly stereoretentive have been reported
(Fig. 1): cyclometalated N-heterocyclic carbene (NHC) architectures [6]
and 2,4,6-arylbenzenethiolate-Ru complexes [7], and catecholthiolate-
Ru complexes [8].
The immobilization of complexes onto solid supports is a recurrent
strategy to avoid some of the problems associated with homogeneous
catalysis [9]. Numerous groups have reported the immobilization of Ru
olefin metathesis catalysts on different supports [10]. Here, we have
chosen mesostructured silica supports, since they provide high surface
areas, a good chemical stability and big pores avoiding mass transfer
limitation during the catalytic reaction. They can be functionalized
with homogeneously distributed organic tethers/ligands, which inter-
molecular distance can be controlled. This key asset allows to generate
polymers for example), avoids any possible interaction between the
metallic centers and allows the selective coordination of the complex on
a single surface site. As any other heterogeneous support, it also allows
an easy recovery of the metal (no pollution of the reaction products)
and a good reusability if the active centers are still alive after catalysis.
In this context, our group has already reported the usefulness of this
kind of supports by immobilizing Ru olefin metathesis complexes on
surface NHC ligands and, besides high catalytic performances, we also
showed the presence of additional interactions between the silica sur-
face and the metal when flexible tethers are used [11]. These specific
interactions were found to provide an extra stabilization of the sup-
ported complexes. More recently, we also demonstrated that the an-
choring of Ru-alkylidene complexes could also be successful by an an-
ionic exchange of the chloride by a propyl or phenyl thiolate (Fig. 2)
[12].
The success of this latter methodology prompted us to investigate
the immobilization of different Ru-alkylidene complexes through a
sterically demanding aryl thiolate, mimicking the molecular structure
of the Jensen-Occhipinti complexes (Fig. 1), in order to obtain, for the
first time, an immobilized Z-selective Ru olefin metathesis catalyst. The
results presented below demonstrate that the supported catalyst can
perform as well as the molecular analogue.
⁎ Corresponding author.
E-mail address: thieuleux@cpe.fr (C. Thieuleux).
https://doi.org/10.1016/j.mcat.2019.110743
Received 30 September 2019; Received in revised form 18 November 2019; Accepted 12 December 2019
2468-8231/©2019ElsevierB.V.Allrightsreserved.

M. Renom-Carrasco, et al.
MolecularCatalysis483(2020)110743
Fig. 1. Reported Z-selective and stereoretentive Ru olefin metathesis catalysts.
2,6-diphenylphenol (1) (10 g, 40.6 mmol), NH4OAc (616 mg, 20 mol%)
and CH3CN (200 mL) and stirred for 4 h at room temperature. Then, the
solvent was removed under vacuum and the residual was taken with
EtOAc (200 mL) and washed with H2O (3 × 100 mL). The organic
phases were dried with anhydrous Na2SO4, filtered and concentrated.
The product (2) was purified by flash column chromatography (95:5,
Petroleum ether/EtOAc). Yield: 11.5 g = 87 %.
NaH (60 % mineral oil, 1.52 g, 38 mmol) and dry DMF (20 mL) were
put into a three-neck flask equipped with a condenser and an addition
funnel under Ar. Compound 2 (9.9 g, 30.4 mmol) was dissolved in dry
DMF (30 mL) and added slowly via the addition funnel. Then, di-
methylthiocarbamoyl chloride (4.5 g, 36.5 mmol) dissolved in dry DMF
(20 mL) was added in the same way. The mixture was heated at 100 °C
for 2 h. After cooling to room temperature, the solution was added into
a 2 % w/w KOH aqueous solution (500 mL), the precipitate was filtered
and washed with H2O (3 × 300 mL). The product (2b) was purified by
column chromatography (95:5, Petroleum ether/EtOAc). Yield:
10.0 g = 80 %. A mixture of compound 2b (10.0 g, 24.3 mmol) and
Ph2O (30 mL) was heated to 245 °C under Ar for 72 h. Then, most of the
Ph2O was removed under vacuum and the concentrate was purified by
flash column chromatography (85:15, Petroleum ether/EtOAc) to give
product 2c. Yield: 8.8 g = 88 %. Under Argon, DIBAL-H (1 M in THF,
45 mL, 45 mmol) was added dropwise onto a vigorously stirred mixture
of compound 2c (8.8 g, 21.3 mmol) and dry Et2O (170 mL) at 0 °C. The
reaction was stirred for 4 h at reflux temperature, whereupon more
DIBAL-H (1 M in THF, 28 mL, 28 mmol) was added. The mixture was
allowed to reflux overnight. Then, the reaction was cooled down to
room temperature and added slowly into a mixture of crushed ice
(500 mL) and concentrated H2SO4 (50 mL). The product was extracted
with Et2O (3 × 200 mL) and the combined organic phases were washed
with an aqueous solution of potassium sodium tartrate (15 % w/w,
200 mL), dried with anhydrous Na2SO4, filtered and concentrated. The
crude mixture was purified by flash column chromatography (99:1,
Petroleum ether/EtOAc) to render product 3. Yield: 5.4 g = 85 %.
p-Methoxybenzyl chloride (1050 μL, 7.6 mmol) was added to a so-
lution of compound 3 (2.0 g, 5.9 mmol) and K2CO3 (1.6 g, 11.7 mmol)
in acetone (60 mL) under Ar. The mixture was refluxed overnight. Then
it was filtered, washed with DCM and the filtrate concentrated under
vacuum. The product (4) was purified by flash column chromatography
(99:1, Petroleum ether/EtOAc). Yield: 2.2 g = 81 %.
Fig. 2. Reported Ru olefin metathesis catalysts supported on SiO2 via a thiolate
tether.
2. Experimental section
2.1. General information
All reactions related to surface-modifications were carried out under
Argon using standard Schlenk techniques and dry degassed solvents.
TEOS was distilled from Mg. Et3N was distilled from CaH2. 1-hexene
and 4-Phenyl-1-butene were distilled from Na, degassed and stored for
4 h over activated Selexsorb CD®. Dodecane was distilled from Na and
degassed.
Elemental analyses were performed under inert atmosphere at the
Mikroanalytisches Labor Pascher, Remagen, Germany. N analysis was
based on the method of Dumas (instrument: N-analyser from Pascher).
Ru, S, and Si analyses were performed by dissolution of the sample with
acids and determination of the element concentration by ICP-AES (in-
strument: iCap 6500 from Thermo Fisher Scientific). Liquid 1H NMR
spectra were recorded on a Bruker AC 300 MHz. Proton chemical shifts
are reported in ppm (δ) with the solvent reference relative to tetra-
methylsilane (TMS) employed as the internal standard (CDCl3
δ
=7.26 ppm; CD2Cl2, δ =5.32 ppm). Liquid 13C NMR spectra were re-
corded on a Bruker AC 300 MHz operating at 75 MHz, with complete
proton decoupling. Carbon chemical shifts are reported in ppm (δ) re-
lative to TMS with the respective solvent resonance as the internal
standard (CDCl3, δ =77.16 ppm; CD2Cl2, δ =54.00 ppm). CP-MAS
NMR spectra were recorded on a Bruker Advance 300 MHz spectro-
meter with a conventional double resonance 4 mm CP-MAS probe. The
MAS frequency was set to 10 kHz for all the 1H and 13C experiments
reported here. N2 adsportion-desorption experiments were carried out
on a Belsorb Japan system. DRIFT analyses were performed on a Nicolet
6700 FT-IR Spectrometer from Thermo Scientific. TEM micrographs
were performed using a JEOL 2100 F electron microscope. The accel-
eration voltage was 200 kV. The samples were prepared by dispersing a
drop of the ethanol suspension of a ground sample on a Cu grid covered
by a carbon film.
Compound 4 (600 mg, 1.3 mmol) was dissolved in dry DMF (11 mL)
and dry Et3N (11 mL) and Ar was bubbled in the solution for 1 h. Then,
PdCl2(PPh3)2 (136 mg, 15 mol%), CuI (74 mg, 30 mol%) and ethynyl-
trimethylsilane (572 μL, 4.1 mmol) were added. The mixture was stirred
at 100 °C overnight. The solvent was removed under vacuum and the
crude mixture was redissolved in EtOAc, filtered through a short pad of
Celite and concentrated. The crude mixture was dissolved in dry MeOH
(10 mL) and dry THF (10 mL), K2CO3 (1.0 g, 7.3 mmol) was added and
the mixture was stirred at room temperature for 4 h. Then, the solvent
was removed under vacuum and the crude redissolved in DCM, filtered
and concentrated. The mixture was purified by flash column chroma-
tography (98:2, Petroleum ether/EtOAc) to give S-(p-Methoxybenzyl)-
4-ethynyl-2,6-diphenylthiophenol (5). Yield: 370 mg = 70 %.
2.2. Catalysis synthesis
2.2.1. Synthesis of S-(p-Methoxybenzyl)-4-ethynyl-2,6-diphenylthiophenol
(5)
The synthesis of 5 was carried out as shown in Scheme 1 and as
detailed below.
N-bromosuccinimide (7.5 g, 42 mmol) was added into a mixture of
2

M. Renom-Carrasco, et al.
MolecularCatalysis483(2020)110743
Scheme 1. Synthesis of alkyne 5. NBS: N-bromosuccinimide, ACN: acetonitrile, DMF: N,N-dimethylformamide, DIBAL-H: diisobutylaluminium hydride, PMBCl = 4-
methoxybenzyl chloride, TMS: trimethoxysilyl, THF: tetrahydrofuran.
Scheme 2. Synthesis of the hybrid silica material. TFA: tri-
fluoroacetic acid.
2.2.2. Synthesis of azidopropyl silica material 7
The synthesis of 8 was carried out as shown in Scheme 2 and as
detailed below.
To the dry material, a solution of the Ru precursor (HG-II, HG-II-NCO
or M31, 0.2 mmol) in toluene (8 mL) was added. The mixture was
stirred for 20 h at room temperature. Subsequently, the solvent was
filtered off and the material washed with dry DCM (3 × 10 mL). In the
case of C3, the material was washed with DCM containing 1 % pyridine,
to make sure that the pyridine ligand was not lost during washing. The
material was dried under vacuum (10–2 mbar) for 20 h.
A homogeneous solution of P123 (8.4 g), H2O (333 mL) and HCl 37
% (878 μL) was added into a mixture of TEOS (20 mL, 90 mmol) and
(azidopropyl)triethoxysilane (6) (560 mg, 2.25 mmol). The reaction
mixture was stirred for 2 h at room temperature and then warmed up to
45 °C, at which NaF (154 mg, 3.67 mmol) was added when the solution
reached 40 °C. The mixture was stirred at this 45 °C for 72 h. The re-
sulting solid was filtered and washed with H2O, EtOH, acetone and
Et2O. The surfactant was removed by Soxhlet extraction with EtOH
during 48 h. The solid was then filtered, washed with acetone and Et2O
and dried at 135 °C under vacuum (10–2 mbar). The resulting material
was suspended in HCl 2 M (500 mL) and stirred at 45 °C for 2 h. After
filtration, washing with H2O, EtOH, acetone and Et2O and drying at
135 °C under vacuum (10–2 mbar) gave 4.2 g of material 7 were ob-
tained as a white powder.
2.3. Experimental procedure for the catalytic tests
The immobilized catalyst (≈ 10 mg, ≈ 1 μmol of Ru) was weighed
in a 2 mL vial with a stirring magnet inside the glovebox. Then, the
substrate (1 mmol) and the internal standard (dodecane) were added,
the vial was capped, and the reaction was stirred at the desired tem-
perature (20 or 40 °C) still inside the glovebox. Samples were collected
at different times. Yields and Z-selectivity were analyzed by GC using
the dodecane as reference.
2.2.3. Immobilization of the ligand on the silica surface
3. Results and discussion
Alkyne 5 (650 mg) and material 7 (1.78 g) were dispersed in dry
DMF (30 mL) and dry Et3N (3 mL), and the solution was degassed
bubbling Ar for 30 min. Then, CuI (120 mg) was added and the mixture
was stirred under Ar for 4 days at 50 °C. After this time, the solution was
filtered and washed with acetone to recover the unreacted alkyne. The
material from the filter was washed with an EDTA solution [5 g of
EDTA + 40 mL of H2O + 30 mL of DMF + 0.5 mL of Et3N], H2O, EtOH,
acetone and Et2O and then dried under vacuum (10–2 mbar) at 135 °C
overnight. 2.1 g of material 7b were obtained as a white powder.
Material 7b (2.1 g) was dispersed in trifluoroacetic acid (42 mL) and
anisole (12.6 mL) and stirred for 72 h at room temperature. After this
time, the solution was filtered and washed with H2O, acetone and Et2O
and then dried under vacuum (10–2 mbar) at 135 °C overnight. The
obtained material (1.9 g) was suspended in dry toluene (160 mL) and
dry Et3N (25 mL) under Ar, whereupon TMSBr (11.4 mL) was added.
The mixture was stirred at room temperature for 72 h. The solid was
filtered under Ar, washed with dry toluene, dry MeOH and dry Et2O and
then dried at 135 °C under vacuum (10–2 mbar). 2.1 g of material 8
were obtained as a white powder.
3.1. Synthesis and characterizations
Our approach was designed as follows: i) preparation of a bulky
thiol, similar to the one present in JO-1, bearing a terminal alkyne
moiety; ii) synthesis of a mesostructured silica material featuring a
flexible azidopropyl group on the surface; iii) immobilization of the
alkyne-thiol on the surface via a copper-catalyzed azide-alkyne cy-
cloaddition (CuAAC); iv) immobilization of Ru olefin metathesis cata-
lysts to the thiols via anion exchange [13].
The synthesis of the bulky thiol bearing an alkyne moiety started by
brominating the commercially available 2,6-diphenylphenol 1 to give
bromophenol 2 (Scheme 1). Formation of the carbamate, followed by a
Newman-Kwart rearrangement and cleavage of the thiocarbamate gave
bromothiophenol 3. The latter compound was protected as 4-methox-
ybenzyl thioether – stable enough to withstand the subsequent reac-
tions and with a deprotection methodology suitable to be carried out
when supported on the silica material.1 Finally, a Sonogashira coupling
2.2.4. Immobilization of the catalyst via anion exchange
1 Other protecting groups were tested without success. Protection as tri-
methylsilyl thioether was attempted in different conditions, but no silylation
product was ever observed probably due to the steric hindrance of the two
ortho-phenyl substituents. The protection as tert-butyl thiocarbonate proceeded
well, but it was partially deprotected during the subsequent Sonogashira
Material 8 (400 mg), dry toluene (4 mL) and potassium bis(tri-
methylsilyl)amide, KHMDS, (0.5 M solution in toluene, 1 mL) were
stirred for 2 h at room temperature under Ar atmosphere. The solvent
was filtered off and the material washed with more toluene (3 × 8 mL).
3

M. Renom-Carrasco, et al.
MolecularCatalysis483(2020)110743
with ethynyltrimethylsilane and subsequent desilylation yielded com-
pound 5, bearing a terminal alkyne and a protected thiol.
In parallel, a mesostructured hybrid silica material containing azi-
dopropyl surface fragments was prepared by a sol-gel process using a
templating route (Scheme 2) [14]. This was achieved by co-hydrolysis
and co-condensation of one equivalent of (azidopropyl)triethoxysilane
and 40 equivalents of tetraethoxysilane in the presence of Pluronic® P-
123 as the structure-directing agent. A subsequent acidic treatment was
used to hydrolyze the remaining ethoxy groups on the silica surface.
This methodology allows for an accurate control of the loading and a
homogeneous distribution of the azidopropyl units inside the silica pore
channels [14]. At this point, alkyne 5 was anchored to the surface via a
CuAAC. The reaction was monitored by the appearance of signals in the
aromatic region of the 13C CP-MAS NMR spectrum and by the decrease
of the ν(N]N) band from the azido-group in the DRIFT spectrum
(Figures S12 and S16). Elemental analysis indicated that 66 % of the
azido groups reacted to give the cycloaddition product. The deprotec-
tion of the thiol involved a treatment with neat trifluoroacetic acid in
the presence of anisole. A quantitative deprotection was accomplished
as observed by the complete disappearance of the 4-methoxybenzyl
peaks by NMR (Figure S12). Finally, the silica surface was passivated by
treating the material with bromotrimethylsilane in the presence of
triethylamine as the base.2 In this way, we were able to produce ma-
terial 8 at the gram-scale without affecting the structure of the silica
material, as shown by N2 adsorption-desorption isotherms and TEM
microscopy (Figures S1 and S17).
As the last step, the catalyst was immobilized on the silica surface
via an anionic exchange of one chloride by the thiolate tether. We had
already observed that KHMDS was incompatible with Ru olefin me-
tathesis catalysts [12], thus material 8 was first deprotonated with the
base and all the excess removed by washings with toluene. The thiolate-
containing material was then stirred with the corresponding Ru pre-
cursor in toluene to afford catalysts C1, C2, and C3 (Scheme 3). The
color of the final supported complexes was a lighter version of their
homogeneous precursors: green for C1 and C2 and orange-brownish for
C3. 13C CP-MAS NMR showed the expected signals after the im-
mobilization of the Ru complexes (Figures S13, S14 and S15): aromatic
peaks (δ = 120−140 ppm) from the mesitylene and alkylidene moi-
eties, a peak at δ ≈ 50 ppm corresponding to aliphatic carbons attached
to a nitrogen, and the rest of aliphatic peaks at δ = 10−20 ppm. As
expected from the fact that 13C labels were not used, the carbenic signal
was not observed. The difficulty in observing such carbenic signals,
even using cutting edge NMR methods such as Dynamic Nuclear Po-
larization, is due to the inherent large CSA [15] for this type of com-
plexes and the absence of protons in the vicinity of the carbenic carbon.
The S/Ru ratios found by elemental analysis correspond to 45 %
grafting of thiolate groups for C1, 58 % for C2 and 72 % for C3.3 As we
had already observed with other thiolate linkers [12], the grafting
yields are much higher than those obtained when grafting Ru olefin
metathesis catalysts through the NHC moiety [11].
Scheme 3. Immobilization of different homogeneous catalysts on material 8 to
give catalysts C1, C2 and C3.
3.2. Catalytic tests
Next, we turned to the exploration of the metathesis activity and
selectivity of these complexes (Table 1). The turnover number (TON)
towards the desired product and the Z-selectivity of each catalyst was
investigated in different conditions under inert atmosphere. The
homometathesis of 1-hexene (S1) with catalyst C1 at room temperature
achieved a TON of 98 and a moderate Z-selectivity of 63 % after 7 h of
reaction (entry 3). These results are comparable to those of its homo-
geneous counterpart JO-1 after the same reaction time (TON = 99 and
68 % of Z-isomer, entry 2). Both catalysts are still far from the activities
of the non-Z-selective HG-II standard (TON = 583 at 7 h, entry 1). In-
terestingly, while JO-1 shows the higher Z-selectivities at short reaction
times (81 % of Z after 1 h), C1 displays a profile with a maximum of Z-
selectivity after a few hours (see Fig. 3). This finding might seem
counterintuitive, since the reversibility of the metathesis reaction
should drag the product selectivity to the thermodynamic equilibrium
(16 % of Z-5-decene). Thus, the Z-selectivity should in theory decrease
with time, as observed with JO-1 (Table 1, entry 2). A plausible ex-
planation for the observed behavior might be that this supported cat-
alyst, which is very sterically hindered due to its ligands and to the
presence of the silica surface, may require a longer induction period to
get activated and to reach its most Z-selective conformation. Then, after
reaching a maximum, the ratio of Z-isomer starts decreasing, as ex-
pected. Another observation from the kinetic profile (Fig. 3) is that the
catalyst loses almost all activity after 7−8 h. An increase of the tem-
perature to 40 °C (Table 1, entry 4) accelerated the reaction, but did not
affect the Z-selectivity or the catalyst TON. Unfortunately, these cata-
lysts (both the homogeneous and the supported one) decompose very
fast, leading to isomerization catalysts (probably Ru hydrides) which
lost all the metathesis activity, thus preventing their recyclability.
However, this findings proof that the main deactivation pathway of the
catalyst doesn’t follow a bimolecular process, as it is often observed in
metal catalysis [16], but an intramolecular process as the rigidity of the
silica and the homogeneous distribution of the catalysts along the
surface hamper the possibility of two metallic centers getting in close
proximity.
In order to prevent the formation of Ru hydride species that lead to
higher isomerization degrees, different additives commonly used to this
aim [17] were tested. DMAN (1,8-bis(dimethylamino)naphthalene), a
strong and bulky base used to trap any proton in solution, produced the
opposite effect, slightly increasing the amount of isomerization but
without affecting the metathesis activity (entries 5 and 6). Tricyclo-
hexylphosphine oxide reduced the amount of isomerization products
and increased the Z-selectivity up 78 %, however, at expenses of the
activity (entry 7). The use of 1,4-benzoquinone as additive completely
suppressed isomerization but also the metathesis activity (TON = 9
after 7 h, entry 8). Solvents, such as DCM or THF (entries 9 and 10),
greatly reduced the catalyst activity. However, THF enhanced the Z-
(footnote continued)
coupling. A most robust protection as n-butyl thioether was perfectly suitable
for the preparation of the material, however, no conditions were found for its
deprotection once supported.
2 The thiol group was not silylated during the passivation of the surface.
Attempts to prepare the trimethylsilyl thioether in homogeneous conditions
were unsuccessful, probably due to the steric hindrance of the two ortho-phenyl
substituents.
3 Due to the lower stability of M31 compared to HG-II, degradation of the
catalysts probably occurred during the immobilization giving a Ru/S ratio of
1.1. The correct yield of immobilization was calculated from the N/S ratio (see
Supporting Information).
4

M. Renom-Carrasco, et al.
MolecularCatalysis483(2020)110743
Table 1
Catalytic results on the homometathesis of 1-hexene (S1) and 4-phenyl-1-butene (S2).
#
catalyst
additive
T (°C)
t (h)
side products (%)[a],[b]
yield P1 (%)[b]
TON to P1
% Z-selectivity[b],[c]
1
2
HG-II
JO-1
–
–
20
20
7
1
7
1
7
3
7
7
7
7
7
7
7
3
7
1
7
7
4.9
0.8
6.9
6.3
20.0
27.5
45.0
46.0
6.6
58.3
2.3
9.9
3.9
9.8
10.1
10.7
9.6
5.5
0.9
0.8
1.5
5.5
4.7
0.5
1.4
1.8
0
583
23
99
39
98
101
107
96
55
9
16
81
68
49
63
63
63
65
78
50
41
70
55
60
81
76
71
–
3
C1
–
20
4
5
6
7
8
9
10
11
12
13
14
C1
C1
C1
C1
C1
C1
C1
C2
C2
C2
C3
–
40
20
20
20
20
20
20
20
40
20
20
DMAN (2 eq./cat)
DMAN (20 eq./cat)
OPCy3 (5 eq./cat)
p-BQ (5 eq./cat)
0.0
DCM (200 μl)
26.1
54.0
20.9
21.1
0.4
3.8
16.9
0
8
THF (200 μl)
15
55
47
5
14
18
0
–
–
in air
–
15
C3
pyridine (50 eq./cat)
20
#
16
17
catalyst
HG-II
JO-1
additive
–
–
T (°C)
40
40
t (h)
7
0.2
0.6
7
7
7
7
side products (%)[d],[b]
23.6
7.8
18.1
76.0
54.5
0.9
yield P2 (%)[b]
TON to P2
% Z-selectivity[b],[c]
25.7
4.1
9.6
9.9
5.1
1.4
1.8
257
41
96
99
51
14
18
21
84
78
74
71
81
77
18
19
20
21
C1
C2
C2
C3
–
–
40
40
40
40
in air
–
25.4
[a] includes n-pentene, n-hexene and n-heptene isomers (except S1) and 4-nonene. [b] calculated from GC analysis using dodecane as internal standard. [c] % of Z-
isomer in the product (P1 or P2) [d] includes phenylpropene, phenylbutene and phenylpentene isomers (except S2) and 1,5-diphenyl-2-pentene and 1,4-diphenyl-2-
butene. DMAN = 1,8-Bis(dimethylamino)naphthalene. p-BQ = para-benzoquinone.
Fig. 3. Evolution of the metathesis reactions of Table 1, entry 3 and entry 18 vs time.
selectivity to 70 %.
favor a particular conformation of the thiolate ligand which is much
more Z-selective. We therefore added an excess of pyridine to the re-
action (entry 15), but in that case no activity was detected after 7 h.
This might be explained by the fact that the coordinatively saturated Ru
complex is overstabilized by the excess of pyridine or due to a pyridine-
triggered catalyst decomposition via a nucleophilic attack on the alky-
lidene.
The use of 4-phenyl-1-butene (S2) as substrate resulted in similar
activities, but with more isomerization. However, due to the increased
bulkiness of the substrate, the Z-selectivities were also superior,
showing again a maximum at around 7 h (Fig. 3). The selectivity of C1
was again similar to that of its homogeneous counterpart JO-1. The
TONs were also comparable (Table 1, entry 17 vs 18), but the reaction
mediated by C1 was slower and the catalyst lost its metathesis activity
Catalyst C2, equivalent to C1 but bearing an isocyanate instead of
chloride, displayed lower activities and slightly lower Z-selectivities
(Table 1, entry 11 vs 3). Jensen and co-workers had reported that its
homogeneous analogue JO-2 performed better when used in air – with
increased Z-selectivity and less isomerization at the expense of catalytic
activity [7b] Indeed, when testing C2 in air (entry 13), we observed a
remarkable increase in Z-selectivity (reaching 81 %) and less iso-
merization products. However, the activity dropped significantly. In the
case of C3, bearing an indenylidene moiety and a coordinated pyridine,
a fast decomposition of the catalyst (little activity after 1 h) but high Z-
selectivities (up to 76 %) were observed (entry 14). These selectivities
are comparable to those obtained with C1 in THF (entry 10). In both
cases the presence of a coordinating molecule (THF or pyridine) might
5

M. Renom-Carrasco, et al.
MolecularCatalysis483(2020)110743
after 7−8 h. As with 1-hexene, C2 exhibited lower activities and en-
hanced Z-selectivity when used in air (entries 19 and 20). The Z-se-
lectivity of C3 in metathesis of S2 was good (77 %) but the activity was
very low (TON = 18 after 7 h).
(c) A.J. Jiang, Y. Zhao, R.R. Schrock, A.H. Hoveyda, Highly Z-Selective metathesis
homocoupling of terminal olefins, J. Am. Chem. Soc. 131 (2009) 16630–16631.
[3] (a) S.C. Marinescu, R.R. Schrock, P. Müller, M.K. Takase, A.H. Hoveyda, Room-
temperature Z-Selective homocoupling of α-Olefins by tungsten catalysts,
Organometallics 30 (2011) 1780–1782;
(b) E.M. Townsend, J. Hyvl, W.P. Forrest, R.R. Schrock, P. Müller, A.H. Hoveyda,
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demanding arenethiolate ligands, Organometallics 33 (2014) 5334–5341;
(c) J.K. Lam, C. Zhu, K.V. Bukhryakov, P. Müller, A.H. Hoveyda, R.R. Schrock,
Synthesis and evaluation of molybdenum and tungsten monoaryloxide halide al-
kylidene complexes for Z-Selective cross-metathesis of cyclooctene and Z-1,2-
Dichloroethylene, J. Am. Chem. Soc. 138 (2016) 15774–15783;
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of linear (Z)‐α,β‐Unsaturated esters by catalytic cross‐metathesis. The influence of
acetonitrile, Angew. Chem. Int. Ed. 55 (2016) 13210–13214;
4. Conclusions
To conclude, we have successfully developed a series of hetero-
genized Z-selective 2,4,6-triphenylbenzenethiolate-Ru olefin metathesis
catalysts. To reach this goal, a mesostructured hybrid silica material
containing a sterically demanding aryl thiol on the surface has been
prepared and the complex was generated in situ by an anionic exchange.
The activity of these new catalysts was found comparable to those of
their homogeneous counterparts, with TONs on up to 107 at Z-se-
lectivities of 63 %, with the advantage that the supported catalyst can
be easily removed. Z-selectivities of up to 81 % could be achieved at
very low TON (TON = 5). The similar activities between the homo-
geneous and heterogeneous counterparts suggest that the deactivation
pathway for this type of Ru complexes is more likely intramolecular and
not intermolecular. Remarkably, the fact that no activity/selectivity is
lost during immobilization is promising for the immobilization of re-
lated more active Z-selective or stereoretentive thiolate-coordinated
ruthenium-based olefin metathesis catalysts.
(e) M. Joo Koh, T.T. Nguyen, J.K. Lam, S. Torker, J. Hyvl, R.R. Schrock,
A.H. Hoveyda, Molybdenum chloride catalysts for Z-selective olefin metathesis
reactions, Nature 542 (2017) 80–85.
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Kinetically E-selective macrocyclic ring-closing metathesis, Nature 541 (2017)
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tathesis, J. Am. Chem. Soc. 133 (2011) 8525–8527;
(b) B.K. Keitz, K. Endo, M.B. Herbert, R.H. Grubbs, Z-selective homodimerization
of terminal olefins with a ruthenium metathesis catalyst, J. Am. Chem. Soc. 133
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Author contribution
(b) G. Occhipinti, V. Koudriavtsev, K.W. Törnroos, V.R. Jensen, Theory-assisted
development of a robust and Z-selective olefin metathesis catalyst, Dalton Trans. 43
(2014) 11106–11117;
(c) W. Smit, V. Koudriavtsev, G. Occhipinti, K.W. Törnroos, V.R. Jensen,
Phosphine-based Z-Selective ruthenium olefin metathesis catalysts,
Organometallics 35 (2016) 1825–1837;
(d) G. Occhipinti, K.W. Törnroos, V.R. Jensen, Pyridine-stabilized fast-initiating
ruthenium monothiolate catalysts for Z-Selective olefin metathesis, Organometallics
36 (2017) 3284–3292;
(e) V.R. Jensen, G. Occhipinti, Pyridine-stabilized fast-initiating ruthenium
monothiolate catalysts for Z-Selective olefin metathesis, Int. Patent Appl. (2017)
WO 2017009232.
Dr. Renom-Carrasco: Designed and performed experiments, pre-
pared the materials and performed catalytic tests, wrote the paper
Dr. Philipp Mania: Performed research on ligand development
Dr. Reine Sayah: Designed and performed experiments concerning
the ligands
M. Laurent Veyre: Ran analyses and performed characterization of
materials (TEM, Adsorption experiments)
Dr. Giovanni Occhipinti: Designed and performed experiments
concerning the preparation of molecular complexes and catalytic tests
Prof. Vidar R. Jensen: Supervised and designed research on the
molecular complexes, wrote the paper
[8] (a) R.K.M. Khan, S. Torker, A.H. Hoveyda, Readily accessible and easily modifiable
Ru-Based catalysts for efficient and Z-Selective ring-opening metathesis poly-
merization and ring-opening/cross-metathesis, J. Am. Chem. Soc. 135 (2013)
10258–10261;
(b) M. Joo Koh, R.K.M. Khan, S. Torker, M. Yu, M.S. Mikus, A.H. Hoveyda, High-
value alcohols and higher-oxidation-state compounds by catalytic Z-selective cross-
metathesis, Nature 517 (2015) 181–186;
Dr. C. Thieuleux: Supervised and designed research on the catalytic
materials, wrote the paper
(c) T.S. Ahmed, R.H. Grubbs, Fast-initiating, ruthenium-based catalysts for im-
proved activity in highly E-Selective cross metathesis, J. Am. Chem. Soc. 139 (2017)
1532–1537.
Declaration of Competing Interest
[9] C. Copéret, A. Comas-Vives, M.P. Conley, D.P. Estes, A. Fedorov, V. Mougel,
H. Nagae, F. Núñez-Zarur, P.A. Zhizhko, Surface organometallic and coordination
chemistry toward single-site heterogeneous catalysts: strategies, methods, struc-
tures, and activities, Chem. Rev. 116 (2016) 323–421.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
[10] (a) M.R. Buchmeiser, K. Grela (Ed.), Olefin Metathesis - Theory and Praxis, J. Wiley
& Sons, 2014, pp. 495–514;
(b) L. Xia, T. Peng, G. Wang, X. Wen, S. Zhang, L. Wang, Grubbs catalysts im-
mobilized on merrifield resin for metathesis of leaf alcohols by using a convenient
recycling approach, ChemistryOpen, (2019), pp. 45–48;
Acknowledgements
The authors gratefully acknowledge financial support from the
Research Council of Norway via the GASSMAKS program (grant number
208335) and the FRIPRO program (262370). The authors would also
like to acknowledge Prof. Christophe Copéret for fruitful discussions.
(c) H. Balcar, J. Čejka, Mesoporous molecular sieves as advanced supports for
olefin metathesis catalysts, Coord. Chem. Rev. (2013), pp. 3107–3124.
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C. Copéret, R.J.P. Corriu, E. Jeanneau, A. Mehdi, C. Réyé, L. Veyre, C. Thieuleux,
Tailored Ru‐NHC heterogeneous catalysts for alkene metathesis, Chem. Eur. J. 15
(2009) 11820–11823;
(b) M.K. Samantaray, J. Alauzun, D. Gajan, S. Kavitake, A. Mehdi, L. Veyre,
M. Lelli, A. Lesage, L. Emsley, C. Copéret, C. Thieuleux, Evidence for metal–surface
interactions and their role in stabilizing well-defined immobilized Ru–NHC alkene
metathesis catalysts, J. Am. Chem. Soc. 135 (2013) 3193–3199.
[12] M. Renom-Carrasco, P. Mania, R. Sayah, L. Veyre, G. Occhipinti, D. Gajan,
A. Lesage, V.R. Jensen, C. Thieuleux, Supported Ru olefin metathesis catalysts via a
thiolate tether, Dalton Trans. 48 (2019) 2886–2890.
Appendix A. Supplementary data
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.mcat.2019.110743.
[13] C. Copéret, M. Chabanas, R. Petroff Saint-Arroman, J.-M. Basset, Homogeneous and
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