Chelating Ruthenium Phenolate Complexes: Synthesis, General Catalytic Activity, and Applications in Olefin Metathesis Polymerization

Article abstract of DOI:10.1002/chem.201403580

Cyclic Ru-phenolates were synthesized, and these compounds were used as olefin metathesis catalysts. Investigation of their catalytic activity pointed out that, after activation with chemical agents, these catalysts promote ring-closing metathesis (RCM), enyne and cross-metathesis (CM) reactions, including butenolysis, with good results. Importantly, these latent catalysts are soluble in neat dicyclopentadiene (DCPD) and show good applicability in ring-opening metathesis polymeriyation (ROMP) of this monomer. Olefin metathesis catalysis: Investigation of the catalytic activity of Ru phenolate catalysts pointed out that, after activation with chemical agents, these catalysts promote ring-closing metathesis (RCM), enyne, and cross-metathesis (CM) reactions, including butenolysis, with good results (see scheme, Mes=2,4,6-trimethylphenyl, Cy=cyclohexyl). The phenolanate catalysts, well soluble in dicyclopentadiene (DCPD), also show good applicability in ring-opening metathesis polymerization (ROMP) of this monomer.

Full text of DOI:10.1002/chem.201403580

DOI: 10.1002/chem.201403580
Full Paper
&
Synthetic Methods
Chelating Ruthenium Phenolate Complexes: Synthesis, General
Catalytic Activity, and Applications in Olefin Metathesis
Polymerization
Anna Kozłowska,[a] Maciej Dranka,[b] Janusz Zachara,[b] Eva Pump,[c] Christian Slugovc,[c]
Krzysztof Skowerski,*[d] and Karol Grela*[a]
Abstract: Cyclic Ru-phenolates were synthesized, and these
compounds were used as olefin metathesis catalysts. Investi-
gation of their catalytic activity pointed out that, after activa-
tion with chemical agents, these catalysts promote ring-clos-
ing metathesis (RCM), enyne and cross-metathesis (CM) reac-
tions, including butenolysis, with good results. Importantly,
these latent catalysts are soluble in neat dicyclopentadiene
(DCPD) and show good applicability in ring-opening meta-
thesis polymeriyation (ROMP) of this monomer.
Introduction
vated by chemical or physical methods. In addition, such
latent catalysts shall exhibit high solubility in a monomer (no
co-solvent needed) and high thermal stability.[5] The few Ru
catalysts that amply fulfill these prerequisites, and have been
successfully used in ROMP of DCPD, are complexes bearing bi-
dentate Schiff base ligands (e.g., 2 and 3 in Figure 1).[6]
Catalytic olefin metathesis has become a powerful tool for the
formation of carbon–carbon bonds in organic and polymer
chemistry.[1] The success of olefin metathesis has spurred in-
tense investigation for new catalysts for this transformation.[2]
Most of the efforts in designing new catalysts concentrated on
finding more efficient ones, such as Grubbs II-generation cata-
lyst (1).[1,2] However, very reactive catalysts do not always give
good results in ring-opening metathesis polymerization
(ROMP) of some monomers, like dicyclopentadiene (DCPD), es-
pecially when an industrial scale is considered.[3,4]
To solve this problem, a number of latent Ru-catalysts have
been developed in recent years.[5] The use of such catalysts in
ROMP allows for the catalyst to be mixed with the monomer
with no polymerization at RT, in order to give enough time to
handle the formulation. Once required, the catalyst can be acti-
Figure 1. Grubbs (1) and two selected Schiff-base-bearing catalysts (2 and
3). Mes=2,4,6-trimethylphenyl, Cy=cyclohexyl.
Recently, we reported the synthesis of chelating ruthenium
sulfonamides (4, Figure 2),[7a] a new family in the kingdom of
ruthenium-based metathesis catalysts bearing altered anionic
ligands.[8] These complexes exhibit nearly no activity in meta-
thesis reactions; however, they can be easily “turned on” by
the addition of some Brønsted acids.
[a] A. Kozłowska, Prof. Dr. K. Grela
Faculty of Chemistry, Biological and Chemical Research Centre
University of Warsaw
˙
Zwirki i Wigury 101, 02-089 Warsaw (Poland)
E-mail: klgrela@gmail.com
Homepage: http://www.karolgrela.eu/
[b] Dr. M. Dranka, Prof. J. Zachara
Faculty of Chemistry
Warsaw University of Technology
Noakowskiego 3, 00-664 Warsaw (Poland)
[c] E. Pump, Prof. Dr. C. Slugovc
Institute of Chemistry and Technology
Graz University of Technolgy
Stremayrgasse 9, 8010-Graz (Austria)
[d] K. Skowerski
Apeiron Synthesis S.A.
´
Dunska 9, 54-427 Wrocław (Poland)
E-mail: krzysztof.skowerski@apeiron-synthesis.com
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201403580.
Figure 2. Ru-amide (4) and planned Ru-phenolate (5a) complexes and Hov-
eyda–Grubbs catalyst (6). py=pyridine
Chem. Eur. J. 2014, 20, 14120 – 14125
14120
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Results and Discussion
For the next step, we were interested in analogous NHC-con-
taining Ru-phenolate salts, such as compound 5a (see Fig-
ure 2)[7b] These—at the time—conjectural complexes can be
considered analogues of 6, the so-called Grubbs–Hoveyda II-
generation catalyst, which contains in its structure a phenol-
ether fragment that coordinates to
a
metal center
(Figure 2).[2,9–11] Hoveyda-type complexes became a very suc-
cessful and popular class of olefin metathesis catalysts, the ac-
tivity of which could be fine-tuned by altering the strength of
the Ru···O(ether) chelate.[2] Recently, Pietraszuk et al. have pub-
lished independently on similar structures containing a cyclic
Ru-phenolate fragment.[7c]
Here, we present a full account of the preparation, charac-
terization, and catalytic activity of three representative II-gener-
ation complexes (5a–c) that bear the cyclic Ru-phenolate frag-
ment. The syntheses presented in Scheme 1 were performed
Figure 3. Molecular structure of 5a (thermal ellipsoids at 50% probability
level; hydrogen atoms and co-crystallized n-heptane omitted for clarity).
Figure 4. The molecular structure of 5b (thermal ellipsoids at 50% probabili-
ty level; hydrogen atoms omitted for clarity).
Scheme 1. Preparation of complexes 5a–c. SIMes and IMes are N-heterocy-
clic carbene ligands.
metal center by replacing one of the chlorine atoms alters the
geometry around the ruthenium center. The Ru(1)ÀO(1) bond
lengths in 5a (2.120(3) ꢁ) and 5b (2.1152(16) ꢁ) are significant-
ly shorter than the analogous Ru(1)ÀO(1) bond equal to
2.261(3) ꢁ in the Hoveyda catalyst 6.[9a] The observed bond
lengths of the NHC carbon C(1) are longer: 2.065(5)–2.072(2) ꢁ
compared with 1.981(5) ꢁ in 6.[9a] To validate if these structural
changes influence the chemical activity of 5a and b, we used
a standard set of metathesis reactions.
using corresponding propenyl phenols (7a,b) in dichlorome-
thane at reflux, with 1a and 1b[12] as a ruthenium source. As
noted previously,[7a] addition of tricyclohexylphosphine (PCy3)
(3 equiv relative to the Ru complex) leads to higher yields of
the products. Catalysts 5a–c were isolated by column chroma-
tography as air-stable solids and characterized spectroscopical-
ly.[13]
Single crystals of compounds 5a and 5b (see Figures 3 and
4) suitable for X-ray diffraction analysis were grown at RT from
n-heptane solutions (for crystallographic details see Supporting
Information).
Ring closing metathesis (RCM) of diethyldiallyl malonate 8
promoted by phenolate 5a was chosen as the first assay
(Scheme 2). Figure 5 shows that although 5a is inactive in the
model reaction, the addition of trimethylsilyl chloride (TMSCl)
or etheral solution of HCl (10 mol% each) causes a dramatic in-
crease in activity. Interestingly, a non acidic additive, C2Cl6
(10 mol%) also exhibits a detectable activation potential.[14]
The comparative screening of catalysts 5a–c and 6 in the
RCM of 8, presented in Figure 6, shows some basic structure–
activity relationships. Complex 5a, activated by TMSCl, exhibits
This allowed us to confirm the molecular assignment of new
Hoveyda-type catalysts. The coordination geometry of the
ruthenium center in both complexes is a distorted square pyra-
mid, the apex of which is formed by the carbene atom C(22)
with a RuÀC bond of 1.844(5) and 1.832(2) ꢁ for 5a and 5b, re-
spectively. The fact that the phenol anion coordinates with the
Chem. Eur. J. 2014, 20, 14120 – 14125
www.chemeurj.org
14121
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Table 1. Comparative study of catalysts 5a–c and 6.[a]
Entry Substrate(s)
Product(s)
Cat. Yield
(Conv.)
[%][b]
Scheme 2. Model RCM reaction of 8.
5a (60)
5b (64)
5c (13)
1
6[c] 99
5a 90
5b 98
5c 83
6[c] 63
5a 55
5b 81
5c 52
2
3[d]
6[c] (95)
5a (31)
5b (91)
5c (13)
4[e]
Figure 5. Activity of 5a in RCM of 8 in the presence of various activating
agents. Conditions as in Scheme 2.
5a 96
5c 83
5
[a] Conditions: CH2Cl2 (0.1m), 408C, 2 h, catalyst 1 mol%, TMSCl 10 mol%.
[b] Conversion was determined by GC for entries 1 and 4 using durene as
an internal standard. [c] Catalyst 6 was used without TMSCl. [d] E/Z ratio:
9:1 (for cat. 6, 5a, and 5b), 5:1 (for 5c). [e] Conditions: toluene (0.1m),
808C, overnight, cat. 2 mol%, TMSCl 20 mol%. 2-Butene 18 was used as
a standard solution (1 m) in CH2Cl2. E/Z-ratio was not determined.
diacetoxy-2-butene 15 (2 equiv) was, under chosen conditions,
quite challenging, even for the active Hoveyda catalyst 6. Inter-
estingly, the nitro-substituted 5b was very effective in this case
(entry 3). Butenolysis of methyl oleate (17) was chosen next
(entry 4); in this case, catalysts 5a and 5c gave the lowest con-
versions of 17, while 5b was again the catalyst of choice, pro-
viding similar results to 6. Finally, CM between estrone deriva-
tive 21 and 2-methylbut-2-ene 22 (3 equiv) proceeded very
well, even with only 1 mol% of the catalysts 5a and 5c.
The results presented in Table 1 show that the newly ob-
tained phenolate catalysts, when activated, can be used in typ-
ical olefin metathesis transformations, usually leading to good
results, even with a loading of 1–2 mol%. As expected, the ob-
served levels of activity were not higher than those exhibited
by the known and successful catalyst 6; however, the new cat-
alysts have special properties, such as chemo-switchability and
solubility in a wide spectrum of solvents. Importantly, the new
complexes 5a–c are characterized by their high solubility both
in polar and non polar solvents, including pentane. This prop-
erty can be utilized, for example, to polymerize some non
polar monomers, such as dicyclopentadiene (DCPD), without
using any additional co-solvent.[15]
Figure 6. Comparative test of catalysts 5a–c and 6 in RCM of 8. Conditions
as in Scheme 2.
activity comparable to that of Hoveyda catalyst 6. Interestingly,
the electron-withdrawing effect of the nitro group placed at
the para position, with respect to the phenolate fragment,
caused catalyst 5b to initiate slower than 5a. However, the
overall conversion obtained with this catalyst was the highest
in the series. Replacing the SIMes ligand with the Me2IMes[12]
ligand significantly reduced the activity of the resultant catalyst
5c.
Next, catalysts 5a–c (1–2 mol%) were screened in a selected
set of RCM, enyne, and CM reactions in the presence of TMSCl
(Table 1). The first entry is a ring-closing metathesis reaction of
diethylallylmethallyl malonate 10. Due to steric effects, this
substrate is more challenging in RCM than 8; however, good
performance of the studied catalysts was observed for 1 mol%
loading (Table 1, entry 1). Enyne cycloisomerisation (entry 2)
also proceeded well with the new catalysts (5c again gave the
lowest yield). The CM reaction of allylbenzene 14 and cis-1,4-
To gain more information about the specific behavior of
phenolate-type catalysts (5a–c) in ROMP, we studied their per-
formance in polymerization of endo,exo-bicyclo[2.2.1]hept-5-
Chem. Eur. J. 2014, 20, 14120 – 14125
www.chemeurj.org
14122
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
a polystyrene standard. Two activation modes were investigat-
ed: 1) activation by temperature, and 2) chemo-activation by
the addition of HCl. As seen in Table 2 (entries 5 and 7), the re-
activity of 5a can be enhanced by temperature. The conver-
sion was improved from 58% at RT to 73% at 808C. However,
no completion was reached, because the catalyst decomposes
within 24 h under both reaction conditions. With the addition
of HCl (10 equiv) in diethyl ether, the reaction at RT leads to
full conversion in less than 1 h. The obtained polymers
(entry 6) were found to have a higher molecular weight and
slightly broader weight distribution (153 kgmolÀ1, 1.8) than
those produced with Hoveyda catalyst 6 (89 kgmolÀ1, 1.3).
These results were not improved when HCl was added at
808C, as revealed by gel permeation chromatography (GPC)
data (entry 8).
Scheme 3. ROMP benchmark reaction.
ene-2,3-dicarboxylic acid dimethyl ester (24 Scheme 3), before
focusing on DCPD. This reaction has been used in previous re-
ports for benchmarking novel initiator systems,[16] because
polymers of 24 are rarely prone to degradation by secondary
metathesis (back-biting) reactions.[17] Accordingly, the number-
average molecular weight (Mn) of the polymers produced read-
ily permits the assessment of the initiation efficiency of the
novel catalysts, because it is indirectly proportional to the ratio
of initiation rate to propagation rate constants (ki/kp).
Due to the industrial importance of poly(DCPD) as a valuable
material,[15] there is a strong need to develop well-defined cata-
lysts for effective ROMP reactions of DCPD. To get a first im-
pression about the switchability of initiator 5a in DCPD, simul-
taneous thermal analysis (STA) was conducted with and with-
out the addition of HCl. For this purpose, initiator (100 ppm)
was added to DCPD (1 mL). The formulation was then homo-
genized, cooled with liquid N2 and placed in DSC pans. The
measurements were commenced at 208C with a heating rate
of 38CminÀ1. The polymerization exotherm was read out as
a function of temperature. Switching temperatures for the ini-
tiators were equalized to the onset temperature of the exo-
thermic heat flow. Without HCl, an onset temperature of 728C
was found for initiator 5a. Moreover, a mass loss of 38% was
observed, which was due to a retro-Diels–Alder reaction occur-
ring to its volatile educt, cyclopentadiene at 698C
(Scheme 4).[15d]
For a first estimation, only the initiator 5a was used in
a benchmark reaction with 24 and the results were compared
with data obtained for well-established olefin metathesis initia-
tors M31,[18] 1, and 6. Catalyst M31 is characterized by a fast in-
itiation and is well-suited for performing controlled/living poly-
merization, producing polymers with short chain lengths and
a polydispersity index (PDI) of <1.1. In contrast, a relatively
high Mn and PDI (ꢀ300 kgmolÀ1 and >2, respectively) can be
attributed to a slow, non concurrent initiation, as with 1. Hov-
eyda catalyst 6 is a compromise, showing a Mn value of
89 kgmolÀ1 and a PDI of 1.3. Results are summarized in
Table 2.
Table 2. ROMP benchmark reaction of 24.[a]
[b]
Entry Reference Initiator Solvent T [8C] t [h] Mn [kgmolÀ1
]
PDI[b]
1
2
3
4
5
6
7
8
[16e]
[16e]
[16e]
[16g]
M31
1
6
M31
5a
CH2Cl2 RT
CH2Cl2 RT
CH2Cl2 RT
toluene 80
toluene RT
0.1 62
1.05
2.3
1.3
6
292
0.5 89
0.5 54
24 n.d. (58% conv.)
0.5 153
24 n.d. (73% conv.)
0.5 213
1.1
5a+HCl toluene RT
5a toluene 80
5a+HCl toluene 80
1.8
1.8
Scheme 4. Competing thermal degradation and ROMP of DCPD (25).
[a] Conditions: [mon]=0.1m, [mon]/[Ru]=300 [b] Determined by GPC in
THF on the basis of polystyrene calibration. n.d.=not determined.
In contrast, HCl-activated polymerization already occurs
below 508C (an exact value could not be determined as STA
has a domain of uncertainty in the low-temperature area).
However, the marginal mass loss of less than 6%, is assigned
to toluene, which was added in exactly this amount to DCPD.
This result is the final proof that full polymerization occurred.
Next, complexes 5a and 5b were tested in bulk polymeri-
zation in neat DCPD. The commercially available catalyst 1 was
utilized as reference material, because it is known to show suf-
ficient mechanical properties of industrially produced poly-
(DCPD).[15d] Because of the good solubility of catalysts 5a and
5b in DCPD, we performed the polymerization in the neat mo-
nomer, without any co-solvent. Again, the influence of temper-
The reactions were carried out under inert conditions, using
the Schlenk technique. We investigated the activity of pure
and HCl-activated 5a at RT and elevated temperature (808C).
In both cases, toluene was selected as a solvent, because the
presence of a chloride source might influence the reactivity of
the complex. The monomer was added in an excess of
300 equiv with respect to the initiator. After completion of the
polymerization (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
analysed by gel permeation chromatography in THF against
Chem. Eur. J. 2014, 20, 14120 – 14125
www.chemeurj.org
14123
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
an oil bath heated to 608C resulted in fast and quantitative
polymerization, leading to a hard polymer (entry 11). Finally, it
should be stressed that, after addition of an acidic activator,
both 5a and 5b did not initiate immediately, leaving some
time to handle the reaction mixture. All these facts can be of
some value in terms of possible practical applications of these
complexes. To obtain exact values for mechanical properties of
the obtained poly(DCPD) samples, tensile strength tests were
performed under the conditions presented in entries 2 and 6
of Table 3. In this case a pre-prepared mixture, containing
30 mL of toluene per 1 mL of monomer, was used to maintain
the monomer, liquidized for better handling at RT. Both initia-
tors were dissolved in the appropriate amount of toluene to
reach a total concentration of 60 mL of toluene per 1 mL of
DCPD. Additionally, HCl (10 equiv) was added to the
DCPD/[5a] formulation. The molds were put in the oven for
24 h at 808C. Tensile strength measurement revealed that poly-
(DCPD) test bars, initiated with the HCl-activated 5a, exhibit
a Young’s modulus (E) of (1.75Æ0.10) GPa and maximum strain
(Rm) of (29Æ2) MPa. Mechanical properties are in accordance
with tensile strength values obtained with 1 (1.6–1.9 GPa, 40–
50 MPa, elongation at yield or break 4–5%) which are repre-
sentative for industrially produced and applied poly(DCPD).[20]
Table 3. ROMP of DCPD.
Additive[a] T [8C] t [min]
Entry Catalyst
(monomer/
Yield of
poly(DCPD) poly(DCPD)
[%][b]
Form of
catalyst
ratio)
1
2
3
4
5
6
7
8
9
10
1 (16000)
1 (50000)
none
none
28
80
28
28
80
80
80
80
80
80
28–
60
30
>99
>99
n.d.
90
>99
>99
97
75
>99
85
solid, hard
solid, hard
liquid
24 h
180
960
10
5a (16000) none
5a (16000) none
5a (31000) HCl
5a (40000) HCl
5a (62500) HCl
5a (125000) HCl
5b (31000) HCl
5b (31000) p-TsOH
solid, soft
solid, hard
solid, hard
solid, soft
solid, soft
solid, hard
solid, soft
solid, hard
30
120
120
10
60
11[c] 5b (16000) HCl
24 h
+10
min
>99
[a] For entries 4–11, 4 equiv (rel. to catalyst) of the additive was used.
[b] The yield was calculated based on the weight of obtained solid mate-
rial. n.d.=not determined, [c] The reaction was carried out at 288C for
24 h, HCl was added, and the reaction continued at 608C for 10 min.
ature and additives on the performance of phenolate catalysts
in polymerization and on the nature of the resultant poly-
(DCPD)[19] was studied.
Conclusion
The first reactions (Table 3, entries 1, 3, and 4) were conduct-
ed at 288C without any additives. No co-solvent was required
to dissolve 5a in the monomer, whereas a stock solution of
1 in DCM had to be used because this catalyst is insoluble in
neat DCPD. Importantly, although 1 initiated the reaction
almost immediately after addition, no visual signs of polymeri-
zation were observed even after 3 h when 5a was used, which
proves that the initiation can be nicely controlled in this case.
After a prolonged time, the progress of the reaction with
a phenolate catalyst can be observed, because after 16 h a ge-
latinous polymer was isolated with a 90% yield.
In summary, we synthesized three cyclic Ru-phenolates (5a–c)
and studied their effectiveness as catalysts in olefin metathesis
reactions.[7b] The investigation of their catalytic activity showed
that, after activation with some chemical agents, they promote
RCM, enyne, and CM reactions, including butenolysis, with
good results. Catalysts 5a and 5b also show applicability in
ROMP of DCPD. Practical advantages of using these particular
complexes are their solubility in neat DCPD and the possibility
of delaying the initiation of the polymerization reaction until
a specific time.
As expected, addition of HCl or p-TsOH and increasing tem-
perature significantly improved the yield of polymerization
promoted by 5a and 5b (activation properties of TMSCl were
estimated by us as being between those of HCl and p-TsOH).
By using 5a and HCl, we were able to obtain solid poly(DCPD)
with an almost quantitative yield after 30 min in a reaction car-
ried out at 808C and with a monomer to catalyst ratio of
40000:1 (entry 6). Further decrease of the catalyst loading re-
sulted in the isolation of the soft form of poly(DCPD), but still
in excellent yields (Table 3, entries 7–8). At this point, we decid-
ed to take advantage of the lower activity of the nitro-substi-
tuted 5b to prove the possibility of prolonged storage of the
catalyst–monomer mixture. We intentionally ran this experi-
ment with relatively high catalyst loading (Table 3, entry 11) to
show that even increased amounts of the initiator do not ini-
tiate the polymerization. Contrary to benchmark polymeri-
zation with monomer 24, which yielded 52% of polymer, we
were pleased to see no sign of the reaction even after keeping
the DCPD/catalyst mixture at 288C for 24 h. After that time,
however, addition of HCl and placing the reaction vessel into
Experimental Section
For full details on synthetic procedures, characterization, and
screening of complexes 5a–c, and for details of X-ray measure-
ments of 5a and 5b, see the Supporting Information. CCDC-
1013670 (5a) and CCDC-1013671 (5b) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Representative synthesis of a phenolate complex (5a)
A Schlenk flask equipped with a magnetic stirring bar was charged
under argon with Grubbs II-generation complex
1 (200 mg,
0.236 mmol), propenyl phenol derivative 7a (63 mg, 0.47 mmol),
dry DCM (7 mL) and PCy3 (132 mg, 0.47 mmol). The reaction mix-
ture was stirred for 5 h at 508C. After this time, solvent was evapo-
rated by vacuum and crude product was purified by column chro-
matography (SiO2, 10% ethyl acetate/c-hexane). After removal of
solvents, complex 5a remained as a green solid (152 mg, 78%
1
yield). Analytical data: H NMR (500 MHz, CD2Cl2): d=15.85 (s, 1H),
7.07 (s, 1H), 7.00–6.96 (m, 3H), 6.66 (d, J=8.4 Hz, 1H), 6.44 (dd, J=
Chem. Eur. J. 2014, 20, 14120 – 14125
www.chemeurj.org
14124
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
plex (5d) was formed. This complex
was characterized by X-ray diffraction,
but was not tested in olefin metathe-
sis.J. N. Coalter III, J. C. Huffman, K. G.
Caulton, Chem. Commun. 2001,
1158–1159.
7.7, 1.4 Hz, 1H), 6.24 (s, 1H), 6.20 (t, J=7.2 Hz, 1H), 4.01–3.96 (m,
1H), 3.83–3.70 (m, 2H), 3.64–3.59 (m, 1H), 2.63 (s, 3H), 2.54 (s, 3H),
2.50 (s, 3H), 2.35 (s, 3H), 2.27 (s, 3H), 1.66–1.50 (m, 13H), 1.29 (s,
3H), 1.11–0.70 ppm (m, 20H); 13C NMR: (126 MHz, CD2Cl2): d=
281.36, 222.21, 221.66, 180.31, 148.30, 139.54, 139.17, 138.78,
137.63, 137.32, 136.98, 134.69, 130.23, 130.05, 129.70, 129.00,
122.38, 116.17, 111.26, 32.52, 32.39, 29.45, 28.92, 28.23, 28.15,
28.12, 28.04, 27.34, 27.03, 21.33, 21.14, 19.40, 18.92, 18.66,
16.76 ppm; 31P NMR (202 MHz, CD2Cl2): d=29.11 ppm; IR (film from
DCM): n˜ =2925, 2849, 1890, 1583, 1463, 1335, 1266, 1132, 849,
752 cmÀ1; MS (MALDI TOF) m/z (%): 828.34 [M+].
[11] For other representative Ru–benzylidene complexes with phenol-de-
rived anionic ligands, see: a) J. C. Conrad, D. Amoroso, P. Czechura,
G. P. A. Yap, D. E. Fogg, Organometallics 2003, 22, 3634–3636; b) S.
Monfette, D. E. Fogg, Organometallics 2006, 25, 1940–1944; c) J. C.
Conrad, H. H. Parnas, J. L. Snelgrove, D. E. Fogg, J. Am. Chem. Soc. 2005,
127, 11882–11883; d) S. Monfette, K. D. Camm, S. I. Gorelsky, D. E. Fogg,
Organometallics 2009, 28, 944–946.
[12] R. Kadyrov, A. Rosiak, J. Tarabocchia, A. Szadkowska, M. Bieniek, K. Grela,
“New Concepts in Designing Ruthenium based Second Generation
Olefin Metathesis Catalysts and their Application” in Catalysis of Organic
Reactions: Twenty-second Conference, (Ed.: M. L.Prunier), Chemical In-
dustries Series, Vol. 123, CRC Press, 2008, pp 568.
[13] Full details on synthetic procedures, characterization, and screening of
complexes 5a–c, and details of X-ray measurements are included in the
Supporting Information.
Acknowledgements
A.K. and K.G. are grateful to the National Science Centre
(Poland) for the NCN MAESTRO Grant No. DEC-2012/04A/ST5/
00594. Apeiron Synthesis acknowledges the Operation Pro-
gramme Innovative Economy (PO IG) for financial support
within POIG 1.4–4.1. Programme. E.P. gratefully acknowledges
Chemical Monthly for financial support of this work. The au-
thors acknowledge WTZ PL10/2014 cooperation.
[14] At present we have no explanation of the exact activating mechanism
of C2L6. However, the potency of this compound, as well as CCl4 and
CBr4, was noted before for a nitronate–Ru complex. For details, see: T.
´
´
Wdowik, C. Samojłowicz, M. Jawiczuk, M. Malinska, K. Wozniak, K. Grela,
Chem. Commun. 2013, 49, 674–676.
[15] a) C. Slugovc, Macromol. Rapid Commun. 2004, 25, 1283–1297; b) J. C.
Mol, J. Mol. Catal. A 2004, 213, 39–45; c) M. S. Trimmer, “Commercial
Applications of Ruthenium Olefin Metathesis Catalysts in Polymer Syn-
thesis” in Handbook of Metathesis Vol. 3 (Ed.: R. H. Grubbs), Wiley-VCH,
Weinheim, 2003, pp. 407–418; d) A. Leitgeb, J. Wappel, C. A. Urbina-
Blanco, S. Strasser, C. Wappl, C. S. J. Cazin, C. Slugovc, Monatsh. Chem.
2014, 145, 1513–1517.
[16] a) X. Gstrein, B. Burtscher, A. Szadkowska, M. Barbasiewicz, F. Stelzer, K.
Grela, C. Slugovc, J. Polym. Sci. Part A 2007, 45, 3494–3500; b) S. Slu-
govc, A. M. Z. Slawin, S. P. Nolan, Chem. Eur. J. 2010, 16, 9215–9225;
c) A. Szadkowska, X. Gstrein, C. Burtscher, K. Jarzembska, K. Wozniak, C.
Slugovc, K. Grela, Organometallics 2010, 29, 117–124; d) C. A. Urbina-
Blanco, A. Leitgeb, C. Slugovc, X. Bantreil, H. Clavier, A. M. Z. Slawin, S. P.
Nolan, Chem. Eur. J. 2011, 17, 5045–5053; e) A. Leitgeb, M. A. Szadkow-
ska, M. Barbasiewicz, K. Grela, C. Slugovc, J. Polym. Sci. Part A 2011, 49,
3448–3454; f) C. A. Urbina-Blanco, X. Bantreil, J. Wappel, T. E. Schmid,
A. M. Z. Slawin, C. Slugovc, C. S. J. Cazin, Organometallics 2013, 32,
6240–6247; g) E. Pump, A. Poater, M. Zirngast, A. Torvisco, R. Fischer, L.
Cavallo, C. Slugovc, Organometallics 2014, 33, 2806–2813.
[17] a) S. Riegler, S. Demel, G. Trimmel, C. Slugovc, F. Stelzer, J. Mol. Catal. A:
Chemical 2006, 257, 53–58; b) C. Slugovc, S. Demel, S. Riegler, J. Ho-
bisch, F. Stelzer, J. Mol. Catal. A 2004, 213, 107–113.
[18] D. Burtscher, C. Lexer, K. Mereiter, R. Winde, R. Karch, C. Slugovc, J.
Polym. Sci. Part A 2008, 46, 4630–4635.
[19] T. A. Davidson, K. B. Wagener, J. Mol. Catal. A 1998, 133, 67–74.
[20] a) Polymer material property database EFUNDA (http://www.efunda.
com/materials/polymers/properties/polymerdatasheet.cfmMajor-
ID=PDCP&MinorID=1); b) C. Slugovc, “Industrial Applications of Olefin
Metathesis Polymerization” in Olefin Metathesis: Theory and Practice,
1st ed. (Ed.: K. Grela), Wiley, Hoboken, Weinheim, 2014, p. 329–333.
Keywords: carbenes
metathesis · ruthenium
· catalysis · NHC ligands · olefin
[1] a) Handbook of Metathesis, 1edst ed(Ed.: R. H. Grubbs), Wiley-VCH, Wein-
heim, 2003; b) Olefin Metathesis: Theory and Practice, 1edst ed(Ed.: K.
Grela), Wiley, Hoboken, 2014.
[2] a) C. Samojłowicz, M. Bieniek, K. Grela, Chem. Rev. 2009, 109, 3708–
3742; b) G. C. Vougioukalakis, R. H. Grubbs, Chem. Rev. 2010, 110, 1746–
1787.
[3] For an interesting commentary, see: D. Stoianova, “Latent Metathesis
Catalysts and ROMP of Reactive Monomers” in All Things Metathesis:
http://allthingsmetathesis.com/latent-metathesis-catalysts-romp/. Last
accessed on 07/27/13.
[4] A significant fraction of initiators for industrial-scale ROMP of DCPD are
still based on ill-defined catalyst systems. For example, see: H. Li, Z.
Wang, B. He, J. Mol. Catal. A 1999, 147, 83–88.
[5] For reviews, see: a) A. Szadkowska, K. Grela, Curr. Org. Chem. 2008, 12,
1631–1647; b) Y. Vidavsky, A. Anaby, N. G. Lemcoff, Dalton Trans. 2012,
41, 32; c) a recent example from our laboratory: A. Szadkowska, A.
Makal, K. Wozniak, R. Kadyrov, K. Grela, Organometallics 2009, 28, 2693–
2701.
[6] For review, see: R. Drozdzak, B. Allaert, N. Ledoux, I. Dragutan, V. Dragu-
tan, F. Verpoort, Coord. Chem. Rev. 2005, 249, 3055–3074.
[7] a) C. Pietraszuk, S. Rogalski, B. Powała, M. Mie˛tkiewicz, M. Kubicki, G.
´
Spꢂlnik, W. Danikiewicz, K. Wozniak, A. Pazio, A. Szadkowska, A. Kozłow-
ska, K. Grela, Chem. Eur. J. 2012, 18, 6465–6469; b) K. Skowerski, M. Bi-
eniek, Polish Patent Appl. P-400162 (27.07.20012.); c) P. Zak, S. Rogalski,
M. Kubicki, P. Przybylski, C. Pietraszuk, Eur. J. Inorg. Chem. 2014, 1131–
1136.
˙
[8] For a recent review on Ru-catalysts bearing “pseudo-halide” anionic li-
gands, see: E. B. Anderson, M. R. Buchmeiser, Synlett 2012, 185–207.
[9] a) S. B. Garber, J. S. Kingsbury, B. L. Gray, A. H. Hoveyda, J. Am. Chem.
Soc. 2000, 122, 8168–8179; b) S. Gessler, S. Randl, S. Blechert, Tetrahe-
dron Lett. 2000, 41, 9973–9976.
Received: May 19, 2014
[10] It was reported that in a reaction of sodium salt of 2,6-dimethylphenol
with (PCy3)2RuCl2=CHPh an analogous I-generation Ru-phenolate com-
Published online on September 9, 2014
Chem. Eur. J. 2014, 20, 14120 – 14125
www.chemeurj.org
14125
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim