Ruthenium Amide Complexes – Synthesis and Catalytic Activity in Olefin Metathesis and in Ring-Opening Polymerisation

Article abstract of DOI:10.1002/ejic.201800251

A set of olefin metathesis catalysts bearing a ruthenium amide moiety was synthesised. In the ruthenium amide form these complexes exhibit very low activity in standard metathesis reactions. However, a dramatic increase of activity was observed upon in si

Full text of DOI:10.1002/ejic.201800251

DOI: 10.1002/ejic.201800251
Full Paper
Olefin Metathesis
Ruthenium Amide Complexes – Synthesis and Catalytic Activity
in Olefin Metathesis and in Ring-Opening Polymerisation
Anna Gawin,[a][‡] Eva Pump,[b] Christian Slugovc,[b] Anna Kajetanowicz,*[a] and Karol Grela*[a]
Abstract: A set of olefin metathesis catalysts bearing a ruth- ber of model ring-closing metathesis, cross-metathesis and
enium amide moiety was synthesised. In the ruthenium amide enyne transformations. Moreover, such activated complexes
form these complexes exhibit very low activity in standard me- proved to be very effective catalysts for bulk polymerisation
tathesis reactions. However, a dramatic increase of activity was of dicyclopentadiene (DCPD). The influence of factors such as
observed upon in situ activation with trimethylsilyl chloride or temperature and the nature of additives on the properties of
HCl, allowing successful application of such catalysts in a num- poly-DCPD was examined.
Introduction
In the past decade, the development of well-defined catalysts
has established olefin metathesis as a useful synthetic tool in
both organic and materials chemistry.[1] The transformation it-
self has been known for many years, as early examples of these
metal-mediated reactions in ring-opening metathesis polymeri-
sation (ROMP) of cyclic olefins date back to the 1960s.[2] Ring-
closing metathesis (RCM), acyclic diene metathesis, cross-
metathesis (CM), ring-opening metathesis (ROM) and combina-
tions of these more recently explored transformations have now
developed into powerful methods leading to previously diffi-
cult-to-reach synthetic targets.[3]
As the number of applications utilising olefin metathesis cat-
alysts is growing constantly, research into more efficient com-
plexes with high stability and, at the same time, high activity
and selectivity remains a key concern for the organic and phar-
maceutical communities. On the other hand, intensive research
is also carried out on the synthesis of latent catalysts, the initia-
tion of which can be easily controlled, thermally, chemically
or photochemically.[4] Such a possibility is beneficial mainly in
Figure 1. Examples of well-defined ruthenium catalysts of general use
([Ru-1] to [Ru-3]) and latent catalysts for ROMP (the rest).[5a–c,7]
ROMP.[5] The availability of well-defined ruthenium-based cata-
lysts (Figure 1) resistant to moisture, oxygen and the presence
of various functional groups, as well as optimisation of the reac-
Recently, we reported the synthesis of new ruthenium
tion conditions, have significantly extended the scope and ap-
phenolate chelate complexes bearing altered anionic ligands
plication of this process and made it widely used in synthesis.[6]
(Figure 2, [Ru-10]).[8] These complexes exhibit almost no activ-
ity in metathesis reactions, but they can easily be switched on
by adding Brønsted acids. Detailed research on their catalytic
activity has shown that after activation with, for example, HCl,
Me3SiCl or C2Cl6, they promote RCM, enyne and CM reactions,
including butenolysis, with good results. Catalyst [Ru-10] dem-
onstrated high usefulness in the ROMP of dicyclopentadiene
(DCPD), which is related to its good solubility in neat DCPD as
well as with an easy-to-control initiation process and therefore
[a] Biological and Chemical Research Centre, Faculty of Chemistry,
University of Warsaw,
Żwirki i Wigury Street 101, 02-089 Warsaw, Poland
E-mail: prof.grela@gmail.com
anna.kajetanowicz@gmail.com
http://www.karolgrela.eu/
[b] Institute of Chemistry and Technology, Graz University of Technolgy,
Stremayrgasse 9, 801-0 Graz, Austria
[‡] Apeiron Synthesis S.A.,
was commercialised under the trade name LatMetTM [9]
.
Duńska 9, 54-427 Wrocław, Poland
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.201800251.
The same switchability in the presence of Lewis acids was
observed during a collaboration with Pietraszuk et al. on Ru
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chloride (Scheme 1 a–c) followed by Stille cross-coupling with
tri-n-butylvinyltin to produce styrenes 3a–3c in good yields.
With styrenes 3a–3c in hand the reaction with [Ru-3] (com-
mercially available Umicore M31 ruthenium indenylidene com-
plex) was performed in toluene at 80 °C (Scheme 2). Since previ-
ous studies showed that the addition of an excess of pyridine
to the reaction mixture leads to higher yields,[10] the same strat-
egy was applied here. New complexes were isolated by column
chromatography and characterised by standard analytical tech-
niques.
Figure 2. Our previously synthesised latent Ru catalysts bearing anionic
benzylidene ligands.
complexes bearing amidobenzylidene chelating ligands (Fig-
ure 2, [Ru-11] and [Ru-12]).[10] In this preliminary study the
addition of Me3SiCl or HCl caused a significant increase in cata-
lytic activity in two RCM reactions. The mechanism of activation
of these complexes in the presence of HCl was also thoroughly
investigated by FTIR spectroscopy and DFT calculations.[11]
Herein, we extend this preliminary study by synthesis of more
structurally diverse analogues of [Ru-11] and [Ru-12] (Figure 3)
and checking their activity in model RCM, CM and enyne reac-
tions of functionalised substrates. In addition to transformations
of small molecules, we also explored their utilisation in the pro-
duction of macromolecules, by exploiting the potential switch-
ability of such catalysts, which can be of key importance in
ROMP of some monomers.
Scheme 2. Synthesis of complexes [Ru-12]–[Ru-14].
Next, an alternative method of synthesis of complexes
[Ru-12]–[Ru-14] was tested (Scheme 3). In the first step, the
reaction between the previously obtained benzylidene ligand
precursors 3a–3c and the Grubbs second-generation complex
(Gru-II) in the presence of 3 equiv. of free tricyclohexylphos-
phane (PCy3) was performed. The reaction was carried out in
toluene at 70 °C and monitored by TLC. When full conversion
of [Ru-1] was observed, 3 equiv. of pyridine were added. This
pathway enabled the synthesis of complexes [Ru-12]–[Ru-14]
from more stable Gru-II, although the amide complexes were
obtained in lower yields as compared with the procedure de-
scribed in Scheme 2.
Figure 3. Structural modifications of [Ru-12] examined in this study.
Results and Discussion
Complexes with Modified Amido Benzylidene Ligands
In the first stage of the study, the main focus was on preparing
analogues of the previously obtained third-generation complex
[Ru-12] containing different substituents Z that can modify the
acidity of the amido group. To do so, the corresponding ligand
precursors 3a–3c were obtained in two-step synthesis starting
from commercially available 2-bromoaniline (1, Scheme 1).
Compound 1 was transformed into amido-bearing ligand pre-
cursors by reaction with the appropriate acid anhydride or
Scheme 3. Alternative synthesis of complexes [Ru-12]–[Ru-14].
Amido Complexes with Modified NHC Ligands
Next we investigated the influence of the N-heterocyclic carb-
ene (NHC) ligand on the behaviour of this class of complexes.
The first attempt to form complexes containing a modified NHC
was the reaction of 3a with [Ru-15], which is an SIPr analogue
Scheme 1. Synthesis of ligands 3a–3c.
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of [Ru-3]. The ligand-exchange reaction was performed in tolu- plexes [Ru-19] and [Ru-20] in 62 and 80 % yield, respectively.
ene at 80 °C in presence of an excess of pyridine (Scheme 4). Due to low solubility of [Ru-19] and [Ru-20] in toluene, these
Addition of the amidobenzylidene ligand precursor (3a) in por- complexes precipitated from the reaction mixture as pure prod-
tions significantly increased the yield. Complex [Ru-16] was iso- ucts, and further purification was not required in these cases
lated as a green solid in 80 % yield.
(Scheme 6).
Activity Studies
Prior to ROMP tests, the general activity of amido complexes in
standard metathesis reactions was briefly examined. The struc-
tures of complexes used in tests are shown in Figure 4.
Scheme 4. Synthesis of complex [Ru-16].
To obtain another complex with modified NHC ligand we
used [Ru-17], the so-called Turbo-IMes Grubbs-type com-
plex,[12] as starting material. Complex [Ru-18] was obtained by
a pathway similar to that presented in Scheme 3. Ligand precur-
sor 3a and 2 equiv. of PCy3 were added to [Ru-17] followed by
an excess of pyridine. Complex [Ru-18] was isolated as a green
solid in 70 % yield (Scheme 5).
Figure 4. Structure of complexes utilised in this study.
Previously, we showed that this type of Ru complexes are
inactive in metathesis in the Ru amide form, and they had to be
activated, for example, by addition of Me3SiCl as the activating
agent.[10] So, catalysts [Ru-12]–[Ru-14], [Ru-16] and [Ru-18]–
[Ru-20] (1 mol-%) were screened in a selected set of RCM,
enyne and CM reactions in the presence of Me3SiCl as activator
(Table 1). The reactions were conducted for 2 h at 40 °C and
then the reaction mixtures were analysed by GC with durene
as internal standard. When diallyl tosylamide (S1), a straightfor-
ward substrate in RCM, was tested, all amido complexes (1 mol-
%, see Figure 4, entry 1) gave complete reaction. Similarly high
conversions (> 94 %) were reached when a second standard
model substrate,[13] namely, diethyl diallylmalonate (S2; Table 1,
entry 2) was used.
Scheme 5. Synthesis of complex [Ru-18].
Amido Complexes Bearing Various Pyridine Derivatives
To complete the picture, we obtained complexes with a modi-
Proline-derived S3 and allyl-decorated barbiturate S4 were
fied pyridine ligand. For that purpose we treated Grubbs sec- chosen as examples of more functionalised substrates, the com-
ond-generation catalyst [Ru-1] with 3a in the presence of 3- plexity of which resembles that of simple active pharmaceutical
bromopyridine or 4-dimethylaminopyridine (DMAP). The reac- ingredients synthesised by the pharmaceutical industry.[14]
tions were performed in toluene at 80 °C and provided com- Again, RCM of tert-butyl-2-(diallylcarbamoyl)pyrrolidine-1-carb-
Scheme 6. Synthesis of complexes [Ru-19] and [Ru-20].
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Table 1. Comparative study of catalysts [Ru-12]–[Ru-14], [Ru-16] and
[Ru-18]–[Ru-20].[a]
Scheme 7. Model CM reaction of substrates S6a and S6b. Conditions: CH2Cl2
(0.1
M), 40 °C, 3 h, catalyst 1 mol-%, Me3SiCl 10 mol-%; E/Z ratio of P6 was
not determined.
amide complexes activated by HCl (10 mol-%) the SIPr-bearing
complex [Ru-16] exhibited the highest activity, followed by
[Ru-12] and [Ru-13] (Table 2). The latter SIMes amide complex
exhibited slightly lower activity than [Ru-3].
Scheme 8. Model RCM reaction of substrate S7.
Table 2. Conversions reached in the presence of ruthenium amide complexes
in the RCM reaction of S7.[a]
Entry
[Ru]
Additive
Conversion [%][b]
1
2
3
4
5
[Ru-3]
–
–
48
5
55
44
82
[Ru-12]
[Ru-12]
[Ru-13]
[Ru-16]
HCl (10 mol-%)
HCl (10 mol-%)
HCl (10 mol-%)
[a] Conditions: CH2Cl2 (0.1
M), 40 °C, 2 h, catalyst 1 mol-%, Me3SiCl 10 mol-
%. [b] Conversion was determined by GC with durene as internal standard;
yields after purification by column chromatography. [c] t = 5 min. [d] t =
15 min.
[a] Conditions: CH2Cl2 (0.1
Conversion was determined by GC with durene as internal standard.
M
), 40 °C, 2 min, [Ru] 1 mol-%, HCl 10 mol-%. [b]
Attempts to decrease catalyst loading have been an impor-
tant area of research in recent years.[16] It is essential because
it can lead to lower costs and minimisation of ruthenium resi-
dues in products.[17] We studied it for the RCM reaction of S1
(Scheme 9), which was performed in refluxing CH2Cl2. Using
500 ppm of the representative [Ru-12] gave greater than 80 %
conversion [turnover number (TON) = 1760], and 50 ppm gave
20 % (TON = 4400; Figure 5 and Table 3). General-purpose cata-
lysts, such as [Ru-1] or recently developed CAAC complexes can
lead to much higher TONs in easy RCM reactions,[16b] the
present results are, to the best of our knowledge, quite high for
the latent catalysts.
oxylate (S3) proceeded well, full conversion was reached in the
presence of all tested complexes and product P3 could be iso-
lated in high yield. Good reactivity of selected Ru amide com-
plexes was observed also when 5,5-diallyl-1,3-dimethylpyrim-
idine-2,4,6(1H,3H,5H)-trione (S4) was used as starting material
(Table 1, entry 4). Next, the amido complexes were found to be
effective catalysts of enyne cycloisomerisation (Table 1, entry
5). When [1-(allyloxy)prop-2-yne-1,1-diyl]dibenzene (S5) was
utilised, quantitative conversion was reached in all cases.
Finally the moderately challenging CM reaction between
estrone derivative S6a and cis-1,4-diacetoxy-2-butene (S6b,
2 equiv.) was examined with selected Ru amido complexes.[15]
Also in this case the reaction proceeded smoothly and the de-
sired product P6 was obtained in moderate to high yield
(Scheme 7). Importantly, this reaction finally showed the differ-
ences in catalytic activity of the studied complexes.
To underline the differences in catalyst activity, we selected
three representative complexes [Ru-12], [Ru-13] and [Ru-16]
as well as commercially available Ind-III ([Ru-3]) for the RCM
reaction of diethyl allylmethallylmalonate (a standard substrate
Scheme 9. Model RCM reaction of S1 at low loading.
To evaluate the potential of the amide catalysts in ROMP, the
of medium difficulty; Scheme 8).[13a,13b] From the tested Ru performances of selected complexes [Ru-12], [Ru-18] and
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Figure 5. Activity of [Ru-12] in the model RCM reaction of S1.
Table 3. Conversions and TONs reached in the presence of [Ru-12] in RCM
reaction of S1.[a]
First, initiators [Ru-12], [Ru-18] and [Ru-20] were employed
for benchmark reaction with S8 at room temperature in differ-
ent solvents (CH2Cl2, CCl4 and toluene) without the addition of
acid. After 20 h the conversions of polymerisations were deter-
Entry
Ru [ppm]
Conversion [%][b]
TON
1
2
500
50
88
22
1760
4400
1
mined by H NMR spectroscopy by evaluating the ratio of the
double-bond signals (at δ = 6.27 and 6.27 ppm for the mono-
mer S8 and the area between 5.62 and 5.09 ppm for the poly-
mer). We would expect an increase in activity from toluene to
dichloromethane to tetrachloromethane, as activation in pres-
ence of chloride seems obvious for this type of catalysts. How-
ever, this trend was not obtained in our studies, as shown in
Table 4. While catalysts [Ru-12] and [Ru-20] showed hardly any
activity in toluene (14 and 1 %, respectively), catalyst [Ru-18]
gave an impressive conversion of 40 %. However, the values are
not representative, as all three catalysts showed limited solubil-
ity in toluene: catalyst [Ru-18] dissolved the best followed by
[Ru-12] and finally [Ru-20], which is in accordance with the
activities. In dichloromethane, (pre-)catalyst [Ru-18] showed
the worst performance (18 %) closely followed by [Ru-12]
(23 %). On the contrary, [Ru-20] nearly reached full conversion
(up to 96 %). On changing the solvent to tetrachloromethane,
again deviating behaviour was found for the three catalysts:
[Ru-12] showed the highest conversion (83 %), while for
[Ru-20] polymerisation terminated at 71 % (instead of 96 % in
dichloromethane), which might be traced back to decomposi-
tion of the catalyst, as suggested by a colour change. The low-
est activity (52 % conversion) was found for [Ru-18], which
seems to be the most suitable catalyst in this context, as it has
the best solubility in toluene and the highest robustness in all
three solvents.
[a] Conditions: CH2Cl2 (0.1 M), 40 °C, 30 min, [Ru-12], HCl 1 mol-%. [b] Conver-
sion was determined by GC with durene as internal standard.
[Ru-20] were tested in polymerisation with endo,exo-bicyclo-
[2.2.1]hept-5-ene-2,3-dicarboxylic acid dimethyl ester (S8) as
monomer (Scheme 10).
Scheme 10. Benchmark ROMP reaction of S8.
This reaction is well-established for benchmarking initiator
systems,[8,18] because the resulting polymers are hardly prone
to degradation by secondary metathesis reactions (e.g., backbit-
ing).[19] Accordingly, the number-average molecular weight Mn
of the produced polymers readily permits assessment of the
initiation efficiency of the catalysts, as it is indirectly propor-
tional to the ratio of initiation rate to propagation rate con-
stants ki/kp. We investigated the activity of the catalysts at room
temperature in different solvents (toluene, CH2Cl2 and CCl4) and
the role of HCl activation at room temp. and elevated tempera-
ture (40, 80 °C) in CH2Cl2 and toluene. The standardised proto-
col was followed under inert conditions by using Schlenk tech-
niques: the (pre)catalyst was dissolved in the respective solvent,
and then the monomer was added in an excess of 300 equiv.
with respect to the initiator. After completion of the polymerisa-
tion (monitored by TLC), the reaction was quenched by the
addition of an excess of ethyl vinyl ether. Subsequently the
polymers were precipitated in cold methanol, dried and ana-
lysed by gel permeation chromatography in THF against a poly-
styrene standard.
Table 4. Conversion of the ROMP benchmark reaction of S8 in toluene, CH2Cl2
and CCl4.[a]
Entry
Solvent
Conversion [%][b]
[Ru-12]
[Ru-18]
[Ru-20]
1
2
3
toluene
CH2Cl2
CCl4
14
23
83
40
18
52
1
96
71
[a] Reaction conditions: [mon] = 0.1
M, [mon]/[Ru] = 300, room temp. [b]
Conversion of polymerisation was determined by 1H NMR spectroscopy after
20 h.
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Table 5. ROMP benchmark reaction of S8.[a]
Entry
Solvent
T [°C]
[Ru-3]
[Ru-12]
[Ru-18]
[Ru-20]
Mn [kg/mol]
PDI
Mn [kg/mol]
PDI
Mn [kg/mol]
PDI
Mn [kg/mol]
PDI
1
2
3
CH2Cl2
CH2Cl2
toluene
25
40
80
62[8]
55
–
1.05
1.07
–
60.4
52.4
65.0
1.2
1.3
1.3
82.6
63.4
59.7
1.7
1.5
1.4
106.4
89.7
63.0
1.7
1.8
2.1
[a] Conditions: [mon] = 0.1 M, [mon]/[Ru] = 300, [HCl]/[Ru] = 10, reaction time: 20 h. Determined by GPC in THF on the basis of polystyrene calibration.
The addition of 10 equiv. of HCl (with respect to initiator) to the initiators were taken as equal to the onset temperature of
the reactions in CH2Cl2 (Table 4, entry 2) after 20 h led to com- the exothermic heat flow.
pletion of the polymerisations initiated with catalysts [Ru-18]
and [Ru-20] after 30 min. The progress of polymerisation initi-
ated by [Ru-12] remained unchanged at 23 %, which was not
surprising, as a preceding colour change from green to brown
indicated decomposition of the catalyst within the first 20 h. To
investigate the influence of acid on the performance of [Ru-
12], [Ru-18] and [Ru-20], 10 equiv. HCl was added from the
beginning to the previously described protocol at 25 °C, at
40 °C (both in CH2Cl2) and at 80 °C (toluene). For comparison,
[Ru-3] was purchased as a commercial initiator that is suitable
for performing living polymerisation. Its fast initiation at room
temperature leads to a short chain length of 62 kg/mol and a
polydispersity index (PDI) of < 1.1.[20] Results of all polymerisa-
tions are summarised in Table 5. In all cases, completion of
polymerisation was found after less than 20 h. Although these
results clearly indicate that the activity of chemo-activated
complexes can be further improved by raising the reaction tem-
perature, none of the catalysts is characterised by living polym-
erisation character. Considering Mn values, catalyst [Ru-12] ap-
proaches most closely the defined requirements, but the PDI of
1.3 is still too high. Initiators [Ru-18] and [Ru-20] showed more
latent behaviour, similar to an analogous Hoveyda–Grubbs-type
catalyst with naphthalene ligand (Mn = 89 kg/mol and PDI =
1.3).[18d] In toluene at 80 °C this trend completely stagnates,
most probably for two reasons: worse solubility of the catalyst
in toluene and decomposition of the catalyst at elevated tem-
perature. The effect is small but apparent when comparing re-
sults at 40 and 80 °C: in the case of [Ru-12], an increased Mn
(52.4–65.0 kg/mol with unchanged PDI) was found, whereas for
[Ru-20] the PDI rose from 1.8 to 2.1 although Mn decreased.
Only (pre-)catalyst [Ru-18] showed a steady improvement of
both Mn and PDI with increasing reaction temperature.
Scheme 11. ROMP benchmark reaction of DCPD.
A mass loss is expressed in an endotherm originating from
a retro-Diels–Alder reaction of the monomer occurring at 69 °C
to give volatile cyclopentadiene.[2] Without the addition of HCl,
no polymerisation exotherm was found (mass loss: 62 %). In-
deed, the addition of acid could improve results, but still no
complete conversion was observed (mass loss: 47.7 %), due to
poor solubility of the (pre-)catalyst and its subsequent decom-
position. The atypical DSC curves (see the Supporting Informa-
tion) suggest that no polymerisation exotherm was found be-
cause of the poor solubility of the catalyst.
To obtain mechanical properties of the obtained poly-DCPD
materials, tensile strength tests were performed with the
above-mentioned concentrations (100 ppm of initiator). For this
experiment, a pre-prepared mixture containing 30 μL of toluene
per 1 mL of monomer was used to keep the monomer liquid-
ised to allow better handling at room temperature. Initiators
[Ru-12], [Ru-18] and [Ru-20] were dissolved in the appropriate
amount of CH2Cl2 (as the solubility in toluene was unsatisfac-
tory) and mixed with the liquidised monomer to reach a total
concentration of 60 μL solvent/mL DCPD. Additionally, 9 equiv.
of HCl were added to the DCPD/[Ru] formulation and the
moulds were put in an oven to cure the polymer for 24 h at
75 °C. Although all test bars entrapped some air (originating
from CH2Cl2) tensile strength measurement revealed that poly-
DCPDs initiated with [Ru-12] and [Ru-20] exhibit Young's
moduli E of 1.6–1.9 GPa and maximum stresses Rm of 45 and
53 MPa, respectively (see the Supporting Information). Mechan-
ical properties are in accordance with experimentally observed
values of poly-DCPD prepared with commercially available Ind-II
(1.6–1.9 GPa, 40–50 MPa, elongation at yield or break: 4–5 %),
which are representative for industrially produced and applied
poly-DCPD.[22]
Next, complexes [Ru-12], [Ru-18] and [Ru-20] were tested
in bulk polymerisation in neat DCPD (S9, cf. Scheme 11). Com-
mercially available indenylidene second-generation catalyst
Ind-II was utilised as reference material, since it is known to
give sufficient mechanical properties of industrially produced
poly-DCPD.[21] To get a first impression of the switchability, initi-
ator [Ru-20] was used (with and without acid) for simultaneous
thermal analysis with DCPD as monomer. For this purpose, initi-
ator (100 ppm dissolved in toluene) was added to DCPD (1 mL).
Subsequently, the formulation was homogenised, cooled with
liquid N2 and placed in differential scanning calorimetry (DSC)
pans. The measurements were commenced at 20 °C with a
Conclusions
heating rate of 3 °C/min. The polymerisation exotherm was read We have synthesised new olefin metathesis catalysts [Ru-12]–
out as a function of temperature; switching temperatures for [Ru-14], [Ru-16] and [Ru-18]–[Ru-20]. After activation with tri-
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[Ru-14]: (62 % method I, 44 % method II). 1H NMR (400 MHz,
CD2Cl2): δ = 16.81 (s, 1 H), 8.68 (d, J = 5.2 Hz, 1 H), 8.35 (t, J =
7.8 Hz, 1 H), 7.92–7.81 (m, 1 H), 7.77 (d, J = 8.0 Hz, 1 H), 7.55 (d, J =
5.2 Hz, 1 H), 7.41 (t, J = 7.6 Hz, 1 H), 7.25 (s, 2 H), 7.09–6.99 (m, 3
H), 6.80 (d, J = 6.6 Hz, 4 H), 6.66 (d, J = 8.3 Hz, 1 H), 6.46 (t, J =
7.2 Hz, 1 H), 4.22–3.89 (m, 4 H), 2.74 (s, 6 H), 2.42 (s, 6 H), 2.27 (s, 3
H), 1.94 (s, 6 H) ppm. 13C NMR (101 MHz, CD2Cl2): δ = 309.6, 214.7,
153.1, 150.8, 141.1, 140.3, 138.8, 138.3, 137.7, 136.4, 135.7, 131.0,
129.9, 129.7, 128.6, 128.3, 127.8, 126.7, 124.1, 121.8, 117.0, 116.2,
methylsilyl chloride or HCl they can be used as very active cata-
lysts for numerous metathesis reactions, such as RCM, enyne
cycloisomerisation and CM, also with more functionalised sub-
strates such as S3, S4 and S6a. Moreover, due to their latency
and possibility of on-demand activation, the Ru amide com-
plexes can be used in ROMP of DCPD (S8) and endo,exo-
bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid (S9). Although
the best catalysts ([Ru-12], [Ru-18] and [Ru-20]) produced
poly-DCPD that showed reasonable results in mechanical tests,
52.0, 20.9, 19.1, 18.0 ppm. IR (film CH2Cl2): ν = 2955, 2912, 1600,
˜
the low solubility of the new complexes in non-polar solvents 1583, 1458, 1447, 1314, 1259, 1152, 1020, 957, 853, 826, 751, 655,
565 cm–1. HRMS (ESI, m/z) [M – Cl]+ calcd. 745.2150, found 745.2159.
could restrict their commercial applications, as compared to the
fully soluble LatMet catalyst family.[8]
[Ru-16]: (88 % method I, 53 % method II). 1H NMR (400 MHz,
CD2Cl2): δ = 17.23 (s, 1 H), 8.48 (d, J = 20.8, Hz, 1 H), 7.66–7.63 (m,
1 H), 7.62–7.53 (m, 2 H), 7.46–7.37 (m, 2 H), 7.44–7.38 (m, 1 H), 7.28
(d, J = 7.5 Hz, 2 H), 6.87–6.80 (m, 1 H), 6.78–6.67 (m, 5 H), 4.42–4.19
(m, 2 H), 4.19–4.02 (m, 2 H), 3.95–3.75 (m, 2 H), 3.40–3.03 (m, 2 H),
Experimental Section
General Procedure for Synthesis of Complexes (Method I): A
Schlenk flask equipped with a magnetic stirring bar was charged
under argon with complex [Ru-3] (0.13 mmol), the first portion of
ligand (3a–3c) (0.13 mmol), anhydrous toluene (7 mL) and anhy-
1.44 (d, J = 14.6 Hz, 6 H), 1.36–1.26 (m, 6 H), 1.22–1.11 (m, 6 H),
0.65–0.25 (m, 6 H) ppm. 13C NMR (101 MHz, CD2Cl2): δ = 312.1,
311.7, 215.6, 151.9, 151.1, 148.9, 137.1, 136.7, 131.0, 129.7, 124.9,
124.6, 123.5, 122.4, 121.2, 119.6, 31.9, 28.7, 28.2, 26.9, 26.2, 22.7,
drous pyridine/DMAP/3-bromopyridine (0.27 mmol). The reaction
22.4, 13.9 ppm. IR (film CH2Cl2): ν = 3284, 3063, 2965, 2928, 2869,
˜
mixture was stirred for 15 min at 70 °C. Than the second portion of
1932, 1726, 1618, 1578, 1539, 1461, 14057, 1326, 1267, 1237, 1160,
3a–3c (0.13 mmol) was added and the reaction was allowed to
1048, 932, 760, 724, 694, 550, 458 cm–1. MS (FD, m/z): 806.2 [M]+.
proceed for 15 min. After this time the resulting mixture was puri-
1
fied by column chromatography with 10–30 % hexane/ethyl acet-
[Ru-18]: (70 % method II). H NMR (400 MHz, CD2Cl2): δ = 17.12 (s,
ate. After evaporation of solvents, the resulting solid was collected,
dissolved in CH2Cl2 and washed a few times with n-pentane to give
the pure product.
1 H), 8.45 (d, J = 8.3 Hz, 1 H), 7.48–7.37 (m, 2 H), 7.31 (s, 2 H), 7.26
(dd, J = 6.6, 1.4 Hz, 2 H), 6.95 (s, 2 H), 6.93–6.89 (m, 1 H), 6.88–6.75
(m, 3 H), 2.51 (s, 6 H), 2.33 (s, 6 H), 1.85 (s, 6 H), 1.58 (s, 6 H) ppm.
13C NMR (101 MHz, CD2Cl2): δ = ppm: 314.0, 177.6, 161.9, 161.6,
153.5, 151.8, 148.9, 139.7, 138.0, 137.5, 136.2, 134.4, 130.4, 129.5,
127.2, 124.6, 123.5, 122.7, 120.9, 20.9, 18.6, 17.6, 8.8 ppm. IR (film
General Procedure for Synthesis of Complexes (Method II): A
Schlenk flask equipped with a magnetic stirring bar was charged
under argon with complex [Ru-1] (0.053 mmol), ligand (3a–3c)
(0.116 mmol), tricyclohexylphosphane (0.159 mmol) and anhydrous
toluene (4 mL). The reaction mixture was stirred for 15 min at 70 °C.
Then anhydrous pyridine/DMAP/3-bromopyridine (0.27 mmol) was
added and the reaction mixture was heated for a further 15 min.
The resulting mixture was purified by column chromatography with
10–30 % hexane/ethyl acetate. After evaporation of solvents, the
resulting solid was collected, dissolved in CH2Cl2 and washed a few
times with n-pentane to give the pure product.
CH2Cl2): ν = 3654, 3441, 2922, 1609, 1564, 1484, 1462, 1359, 1291,
˜
1235, 1144, 1133, 1034, 942, 857, 757, 701, 589 cm–1. HRMS (ESI,
m/z) [M + Na]+ calcd. 771.1627; found 771.1611.
[Ru-19]: (62 % method I, 38 % method II). 1H NMR (400 MHz,
CDCl3): δ = 16.92 (s, 1 H), 8.55 (d, J = 8.4 Hz, 1 H), 7.63–7.48 (m, 1
H), 7.39 (s, 1 H), 7.29–7.21 (m, 3 H), 7.10 (d, J = 5.6 Hz, 1 H), 6.92 (s,
2 H), 6.77 (d, J = 4.0 Hz, 2 H), 6.65–6.48 (m, 1 H), 4.30–3.68 (m, 4 H),
2.60 (s, 6 H), 2.45 (s, 6 H), 1.90 (s, 6 H) ppm. 13C NMR (101 MHz,
CDCl3): δ = 213.6, 153.4, 152.4, 150.7, 149.2, 139.2, 138.9, 138.3,
132.0, 129.9, 124.8, 124.1, 122.6, 121.4, 120.5, 51.9, 21.2, 18.9,
[Ru-12]: (85 % method I, 54 % method II). 1H NMR (400 MHz,
CD2Cl2): δ = 17.46 (s, 1 H), 8.67 (d, J = 4 Hz, 1 H), 7.51 (m, 2 H),
7.40–7.14 (m, 2 H), 7.01–6.97 (m, 4 H), 6.9 (t, J = 7.4 Hz, 1 H), 6.63
(dd, J = 7.4, 1.4 Hz, 1 H), 4.14–3.35 (m, 4 H), 2.82, 2.56, 2.43, 2.32,
2.16 (br. s, 18 H) ppm. 13C NMR (101 MHz, CD2Cl2): δ = 301.4, 218.6,
150.4, 150.1, 137.5, 137.3, 131.5, 130.9, 130.1, 129.2, 128.2, 128.0,
127.9, 127.4, 126.6, 126.3, 125.7, 124.9, 123.7, 122.5, 122.5, 121.3,
18.0 ppm. IR (film CH2Cl2): ν = 2912, 1721, 1628, 1577, 1480, 1447,
˜
1266, 1228, 1160, 1123, 1041, 760, 732, 696, 576 cm–1. HRMS (ESI,
m/z) [M – Cl]+ calcd. 765.0990; found 765.0988.
1
[Ru-20]: (80 % method I). H NMR (400 MHz, CD2Cl2): δ = 17.06 (s,
1 H), 8.42 (d, J = 8.3 Hz, 1 H), 7.37 (m, 1 H), 7.21 (s, 2 H), 6.91 (s, 2
H), 6.81 (s, 2 H), 6.74–6.47 (m, 2 H), 6.03 (d, J = 7.4 Hz, 2 H), 4.06 (s,
4 H), 2.89–2.44 (m, 18 H), 1.94 (s, 6 H) ppm. 13C NMR (101 MHz,
CD2Cl2): δ = 214.9, 157.8, 153.5, 151.2, 148.5, 138.7, 138.4, 130.1,
129.7, 123.4, 122.4, 120.8, 107.1, 51.8, 38.8, 20.8, 18.8, 17.8 ppm. IR
51.6, 35.2, 29.6, 22.3, 20.7, 18.4, 13.8 ppm. IR (film CH2Cl2): ν = 3284,
˜
3024, 2918, 2858, 1942, 1727, 1621, 1578, 1537, 1485, 1458, 1448,
1417, 1282, 1266, 1240, 1231, 1204, 1160, 1034, 930, 852, 761, 724,
695, 578, 423 cm–1. MS (ESI, m/z) [M – Cl]+: 687.2. Complex [Ru-12]
was described previously.[10]
(film CH2Cl2): ν = 3325, 2911, 1621, 1562, 1541, 1394, 1229, 1146,
˜
[Ru-13]: (72 % method I, 47 % method II). 1H NMR (400 MHz,
CD2Cl2): δ = 16.80 (s, 1 H), 8.17 (d, J = 8.5 Hz, 1 H), 7.42 (d, J =
4.9 Hz, 3 H), 7.38–7.28 (m, 1 H), 7.03 (s, 3 H), 6.95–6.89 (m, 2 H),
1032, 806, 578, 515 cm–1. HRMS (ESI, m/z) [M – Cl]+ calcd. 730.2307;
found 730.2309.
6.59 (t, J = 7.2 Hz, 2 H), 6.49 (dd, J = 7.6, 1.4 Hz, 1 H), 3.73 (s, 4 H), Representative Procedure for Catalytic Test RCM of Substrate
2.38–1.52 (m, 18 H), 0.97 (s, 9 H) ppm. 13C NMR (101 MHz, CD2Cl2):
δ = 221.1, 195.1, 160.9, 158.2, 150.2, 149.2, 136.1, 135.8, 129.9, 129.5,
129.0, 128.8, 123.3, 121.4, 119.6, 117.9, 117.0, 77.5, 51.3, 28.6, 27.9,
S1: Comparative RCM experiments with substrate S1 (CH2Cl2, c =
0.1 , 40 °C) were performed as follows. The catalyst (1 mol-%,
500 ppm or 50 ppm) and an ethereal solution of HCl (0.0399 mmol,
M
27.7, 20.8 ppm. IR (film CH2Cl2): ν = 3356, 2916, 1699, 1604, 1584, 10 mol-%) were added in a single portion to a stirred solution of
˜
1518, 1482, 1445, 1263, 1153, 1043, 757, 694, 577 cm–1. HRMS (ESI, S1 (100 mg, 0.399 mmol) and durene (internal standard, 54 mg,
m/z) [M – Cl]+ calcd. 691.2586, found 691.2599.
0.399 mmol) in CH2Cl2 (4 mL) under argon in a Schlenk tube at
Eur. J. Inorg. Chem. 2018, 1766–1774
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1772 © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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40 °C, and the reaction mixture was stirred for 2 h at the same
temperature. Aliquots (0.05 mL), taken in regular intervals, were
quenched immediately with an ice-cold solution of ethyl vinyl ether
(0.1 mL) in CH2Cl2 (0.5 mL) and analysed by GC by using an EP
Clarus 580 chromatograph with InertCap MS5/Sil column.
Clarus 580 chromatograph with InertCap MS5/Sil column. After
complete conversion the solvent was evaporated, and the crude
mixture was purified by column chromatography. The column was
eluted with cyclohexane/ethyl acetate (10 % v/v). The product was
obtained as a colourless oil. 1H NMR (200 MHz, CDCl3): δ = 7.10–
7.40 (m, 10 H), 6.20–6.27 (m, 1 H), 6.16–6.18 (m, 1 H), 5.31 (dd, J =
17.7, 0.8 Hz, 1 H), 5.10 (dd, J = 11.2, 0.8 Hz, 1 H), 4.11 (q, J = 7.1 Hz,
1 H) ppm. 13C NMR (50 MHz, CDCl3): δ = 171.1, 143.6, 143.3, 129.7,
127.9, 127.8, 124.8, 117.5, 94.5, 60.3 ppm. Analytical data were in
good agreement with previously reported values.[24]
Representative Procedure for Catalytic Test RCM of Substrate
S2: Comparative RCM experiments with substrate S2 (CH2Cl2, c =
0.1 M, 40 °C) were performed as follows. The catalyst (0.00204 mmol,
1 mol-%) and Me3SiCl (0.0204 mmol, 10 mol-%) were added in a
single portion to a stirred solution of substrate S2 (50 mg,
0.204 mmol) and durene (internal standard, 27 mg, 0.204 mmol) in
CH2Cl2 (2 mL) under argon in a Schlenk tube at 40 °C, and the
reaction mixture was stirred for 2 h at the same temperature. Ali-
quots (0.05 mL), taken in regular intervals, were quenched immedi-
ately with an ice-cold solution of ethyl vinyl ether (0.1 mL) in CH2Cl2
(0.5 mL) and analysed by GC by using an EP Clarus 580 chromato-
graph with InertCap MS5/Sil column.
Representative Procedure for Catalytic Test CM Reaction of
Substrates S6a and S6b: Comparative CM experiments with sub-
strates S6a and S6b (CH2Cl2, c = 0.1
M, 40 °C) were performed as
follows. The catalyst (0.0034 mmol,
1
mol-%) and Me3SiCl
(0.034 mmol, 10 mol-%) were added in a single portion to a stirred
solution of S6a (120 mg, 0.34 mmol), S6b (117 mg, 0.68 mmol,
2 equiv.) and durene (internal standard, 45 mg, 0.34 mmol) in
CH2Cl2 (7 mL) under argon in a Schlenk tube at 40 °C, and the
reaction mixture was stirred for 2 h at the same temperature. After
2 h the solvent was evaporated, and the crude mixture was purified
by column chromatography. The column was eluted with cyclohex-
ane/ethyl acetate (10 % v/v). The product was obtained as a white
Representative Procedure for Catalytic Test RCM of Substrate
S3: Comparative RCM experiments with substrate S3 (CH2Cl2, c =
0.1 M, 40 °C) were performed as follows. The catalyst (0.0034 mmol,
1 mol-%) and Me3SiCl (0.034 mmol, 10 mol-%) were added in a
single portion to a stirred solution of substrate S3 (100 mg,
0.34 mmol) and durene (internal standard, 32 mg, 0.34 mmol) in
CH2Cl2 (2 mL) under argon in a Schlenk tube at 40 °C, and the
reaction mixture was stirred for 2 h at the same temperature. Ali-
quots (0.05 mL), taken in regular intervals, were quenched immedi-
ately with an ice-cold solution of ethyl vinyl ether (0.1 mL) in CH2Cl2
(0.5 mL) and analysed by GC by using an EP Clarus 580 chromato-
graph with InertCap MS5/Sil column. After complete conversion the
solvent was evaporated, and the crude mixture was purified by col-
umn chromatography. The column was eluted with cyclohexane/
ethyl acetate (10 % v/v). The product was obtained as a brown oil.
1H NMR (400 MHz, CDCl3): δ = 5.84–5.64 (m, 2 H), 4.57–4.05 (m, 5
H), 3.53–3.29 (m, 2 H), 2.13–1.93 (m, 2 H), 1.87–1.68 (m, 2 H), 1.34–
1.27 (m, 9 H) ppm. 13C NMR (101 MHz, CDCl3): δ = 171.2, 170.8,
154.4, 153.7, 126.1, 126.0, 124.9, 124.7, 79.4, 74.3, 57.6, 57.5, 53.1,
52.9, 46.8, 46.7, 30.2, 29.3, 28.4, 28.2, 24.2, 23.7 ppm. Analytical data
were in good agreement with previously reported values.[23]
1
solid. H NMR (400 MHz, CDCl3, E isomer): δ = 7.73 (d, J = 8.0 Hz, 1
H), 7.30 (dd, J = 8.0, 2.0 Hz, 1 H), 6.34–6.27 (m, 1 H), 6.19–6.11 (m,
1 H), 5.00 (d, J = 6.0 Hz, 2 H), 3.37–3.35 (m, 2 H), 3.13–3.09 (m, 2 H),
3.00–2.93 (m, 3 H), 2.88–2.84 (m, 1 H), 2.76–2.71 (m, 1 H), 2.63–2.61
(m, 1 H), 2.52–2.41 (m, 7 H), 2.14–1.85 (m, 7 H), 1.37 (s, 3 H) ppm.
13C NMR (101 MHz, CDCl3, E isomer): δ = 220.8, 171.7, 170.9, 148.6,
138.1, 137.5, 133.5, 126.5, 125.6, 121.6, 118.8, 64.9, 50.5, 48.0, 44.3,
38.1, 36.0, 33.7, 31.7, 29.5, 27.6, 26.4, 25.9, 21.7, 20.9, 13.9 ppm. IR
(KBr): ν = 3453, 2930, 2871, 1737, 1495, 1376, 1223, 1155, 1020, 958,
˜
888, 824, 777 cm–1. HRMS (ESI): m/z [M + Na]+. HRMS calcd.
261.1830, found. 261.1835.
Representative Procedure for Catalytic Test RCM of Substrate
S7: Comparative RCM experiments with substrate S7 (CH2Cl2, c =
0.1 M, 40 °C) were performed as follows. The catalyst (0.00197 mmol,
1 mol-%) and an ethereal solution of HCl (0.0197 mmol, 10 mol-%)
were added in a single portion to a stirred solution of substrates
(50 mg, 0.197 mmol) and durene (internal standard, 68 mg,
0.197 mmol) in CH2Cl2 (2 mL) under argon in a Schlenk tube at
40 °C, and the reaction mixture was stirred for 2 h at the same
temperature. Aliquots (0.05 mL), taken in regular intervals, were
quenched immediately with an ice-cold solution of ethyl vinyl ether
(0.1 mL) in CH2Cl2 (0.5 mL) and analysed by GC by using an EP
Clarus 580 chromatograph with InertCap MS5/Sil column.
Representative Procedure for Catalytic Test RCM of Substrate
S4: Comparative RCM experiments with substrate S4 (CH2Cl2, c =
0.1 M, 40 °C) were performed as follows. The catalyst (0.00423 mmol,
1 mol-%) and Me3SiCl (0.0197 mmol, 10 mol-%) were added in a
single portion to a stirred solution of substrate S4 (100 mg,
0.423 mmol) and durene (internal standard, 57 mg, 0.423 mmol) in
CH2Cl2 (4.3 mL) under argon in a Schlenk tube at 40 °C, and the
reaction mixture was stirred for 2 h at the same temperature. Ali-
quots (0.05 mL), taken in regular intervals, were quenched immedi-
ately with an ice-cold solution of ethyl vinyl ether (0.1 mL) in CH2Cl2
(0.5 mL) and analysed by GC by using an EP Clarus 580 chromato-
graph with InertCap MS5/Sil column.
Representative Procedure for ROMP of S8 in Solution: The ap-
propriate complex (0.00159 mmol, 1 equiv.) was weighed in a
Schlenk flask and dissolved in toluene/CH2Cl2/CCl4 (3.8 mL, c[S8] =
0.1
M). The reaction mixture was either maintained at room temper-
ature or heated to 40 or 80 °C with or without the addition of 2
M
Representative Procedure for Catalytic Test Cycloisomerisation
of Substrate S5: Comparative enyne experiments with substrate
S5 (CH2Cl2, c = 0.1 M, 40 °C) were performed as follows. The catalyst
ethereal HCl (7.9 μL, 0.0159 mmol, 10 equiv.). A solution of the
monomer (100 mg, 0.48 mmol, 300 equiv.) in toluene (1 mL) was
added. The conversion of the reaction was monitored by TLC [cyclo-
hexane/ethyl acetate (25 % v/v)] by staining with KMnO4 solution.
After full conversion, the reaction mixture was quenched by addi-
tion of ethyl vinyl ether (200 μL). Subsequently, the solvent was
evaporated and the polymer was dissolved in CH2Cl2, precipitated
in cold methanol and finally dried in vacuo. 1H NMR spectra were
recorded in CDCl3 for unfinished polymerisation after 24 h. For this
a 200 μL sample of the reaction mixture was taken, quenched with
ethyl vinyl ether (50 μL) and dried in vacuo.
(0.00201 mmol, 1 mol-%) and Me3SiCl (0.0201 mmol, 10 %mol) were
added in a single portion to a stirred solution of substrate S6
(100 mg, 0.201 mmol) and durene (internal standard, 27 mg,
0.201 mmol) in CH2Cl2 (2 mL) under argon in a Schlenk tube at
40 °C, and the reaction mixture was stirred for 2 h at the same
temperature. Aliquots (0.05 mL), taken in regular intervals, were
quenched immediately with an ice-cold solution of ethyl vinyl ether
(0.1 mL) in CH2Cl2 (0.5 mL) and analysed by GC by using an EP
Eur. J. Inorg. Chem. 2018, 1766–1774
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© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
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Acknowledgments
A. G., A. K. and K. G. are grateful to the National Science Centre
(Poland) for the NCN MAESTRO Grant No. DEC-2012/04/A/ST5/
00594. The study was carried out at the Biological and Chemical
Research Centre, University of Warsaw, established within the
project co-financed by European Union from the European Re-
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Keywords: Metathesis · Ruthenium · Polymerization ·
Homogeneous catalysis · Carbene ligands
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Received: February 22, 2018
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