Monothiolate ruthenium alkylidene complexes with tricyclic fluorinated N-heterocyclic carbene ligands

Article abstract of DOI:10.1016/j.mencom.2019.01.011

New monothiolate ruthenium alkylidene complexes bearing bulky tricyclic N-heterocyclic carbene ligands decorated with two geminal trifluoromethyl groups were synthesized. Their catalytic activity in representative olefin metathesis reactions, such as ring closing metathesis of diallyltosylamine and selfmetathesis of allylbenzene, has been evaluated.

Full text of DOI:10.1016/j.mencom.2019.01.011

Mendeleev
Communications
Mendeleev Commun., 2019, 29, 38–40
Monothiolate ruthenium alkylidene complexes with
tricyclic fluorinated N-heterocyclic carbene ligands
Timur R. Akmalov,a Salekh M. Masoud,a Daria V. Vorobyeva,a Fedor M. Dolgushin,a
Sergey E. Nefedovb and Sergey N. Osipov*a
a A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow,
Russian Federation. Fax: +7 499 135 5085; e-mail: osipov@ineos.ac.ru
b N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 119991 Moscow,
Russian Federation
DOI: 10.1016/j.mencom.2019.01.011
F3C
F3C
F3C
F3C
O
New monothiolate ruthenium alkylidene complexes bearing
bulky tricyclic N-heterocyclic carbene ligands decorated with
two geminal trifluoromethyl groups were synthesized. Their
catalytic activity in representative olefin metathesis reactions,
such as ring closing metathesis of diallyltosylamine and self-
metathesis of allylbenzene, has been evaluated.
O
Me
Me
N
N
Me
N
N
Me
Cl
Me
Cl
Me
Me
Ph
Me
Ru
Ru
Me
S
Ph
Ph
S
O
O
Pri
Ph
Pri
Ph
Ph
Over the past decade, olefin metathesis along with the advent
of efficient ruthenium alkylidene complexes have experienced a
dramatic development becoming the highly versatile method for
the catalytic construction of carbon–carbon bonds.1 Ruthenium
metathesis catalysts bearing N-heterocyclic carbene (NHC) ligands,
commonly used for various synthetic purposes in academia, have
nowadays begun finding industrial applications.2
Despite substantial progress in the area highlighting the great
potential of these ligands, the particular attention is focused
on complexes with unsymmetrical NHCs possessing the unique
capability of rapid fine-turning of their catalytic properties by
modifying the NHC stereoelectronics.3 The most attractive recent
examples include the application of chelating unsymmetrical
NHC ligands in the Ru-catalyzed Z-selective cross-metathesis
(CM).4 The further development of new catalytic systems bearing
unsymmetrical NHC ligands is therefore of current interest.
We have recently developed an efficient procedure for the
preparation of novel olefin metathesis catalysts of Hoveyda–Grubbs
type based on the sterically demanding unsymmetrical NHC
ligands bearing two geminal trifluoromethyl groups.5
NHC demonstrated promising results in self-metathesis of allyl
benzene, outperforming commercially available Hoveyda–Grubbs
catalyst HG-II (e.g., remarkably low content of isomerization
products along with almost quantitative yields of metathesis
product were observed).5(d)
At the same time, Jensen et al. have recently reported a series
of highly Z-selective olefin metathesis catalysts derived from G-II
and HG-II catalysts via a simple substitution of one chlorine atom
by the bulky 2,4,6-triphenylbenzenethiolate group.6 Meanwhile,
significant amounts of isomerization products has been observed in
the reaction mixtures.6(a) Thus, inspired by Jensen’s work and by
own findings,5(d) we decided to install into complexes 2a,b, which
are able to hamper the isomerization pathways, the sterically
bulky thiolate group and to check the performance and selectivity
of resulting complexes 3a and 3b (Scheme 1).
Ph
F3C
O
F3C
Me
Ph
Ph
N
N
Cl
Me
SK
4
The both types of complexes 1a–c and 2a,b have exhibited
a good catalytic activity in the ring closing metathesis (RCM) of
diallyl and allylmetallyl malonates as well as in CM of allyl ben-
zene. Noteworthy, the catalysts 2a,b comprising sterically rigid
Me
Me
Ru
O
R
Cl
THF, room temperature,
3–5 h
Pri
Me
Me
2a R = Me
2b R = H
F3C
F3C
Me
N
N
Cl
Me
O
CF3
Me
OR
O
F3C
F3C
Me
Me
N
N
Cl
Me
Me
Ru
O
CF3
Cl
Me
N
N
Me
Cl
Me
Ru
R
Ph
Me
Pri
Ru
O
R
S
O
1a R = Me
1b R = Et
1c R = (CH2)2CHMe2
Cl
Pri
Pri
Ph
Ph
3a R = Me, 36%
3b R = H, 64%
2a R = Me
2b R = H
Active in RCM and preventing isomerization in CM
Scheme 1
© 2019 Mendeleev Communications. Published by ELSEVIER B.V.
on behalf of the N. D. Zelinsky Institute of Organic Chemistry of the
Russian Academy of Sciences.
– 38 –

Mendeleev Commun., 2019, 29, 38–40
For this purpose, starting complexes 2a,b were treated with
1.2 equivalent of potassium thiolate 4 prepared from 2,4,6-triphenyl-
benzenethiol and potassium hydride.6(a) The reactions proceed at
room temperature in anhydrous THF under argon atmosphere for
3 h to afford desired complexes 3a,b as air stable light green solids
in 36 and 64% yields, respectively (see Scheme 1).
Table 1 Activity of catalysts 3a,b in RCM of diallyltosylamine 5 as
compared to that of HG-II and 2a,b.
Entry
[Ru]
T/°C
t/h
Yield of 6 (%)
1
2
3
HG-II
2a
30
30
30
1
1
100
100
The obtained compounds were fully characterized by 1H, 19
F
2b
1
4
57
82
and 13C NMR spectroscopy and elemental analysis. In 1H NMR
spectra of 3a,b measured at room temperature, the signals of
intrinsic benzylidene protons were observed around 14.96 and
13.65 ppm, respectively, as singlets in each case. Their 13C NMR
spectra of NHCs contained the corresponding resonances at
215.8 (3a) and 215.1 ppm (3b) attributed to the carbene center,
which are in the expected range for aryl-substituted
imidazolylidenes (see Online Supplementary Materials for the
complete NMR data). In addition, single crystals of good quality
for X-ray analysis were isolated for ruthenium complex 3b by
slow diffusion of hexane into its concentrated solution in a
mixture of benzene and CH2Cl2 (Figure 1).†
24
100
4
3a
30
1
4
40
62
24
48
86
100
5
6
3b
3b
30
24
48
0
5
100
1
4
61
81
24
48
95
100
The single crystal X-ray analysis of 3b revealed the presence
of two independent molecules (A and B) in the crystal cell, wherein
chloride anion of A is hydrogen bonded with solvate molecule of
CH2Cl2 (distance C···Cl 3.584 Å) leading to some discrepancies
in the values of bond length and valence angles. The analogous
hydrogen bond with CH2Cl2 has been previously reported for a
similar monothiolate IMes-complex.6(a)
To ensure that the obtained complexes are metathesis active,
their performance was checked on the model RCM reaction of
diallyltosylamine 5 (Scheme 2) under the standard conditions
[Ru] (1 mol%)
N
N
toluene (0.1 M)
Ts
5
Ts
6
Scheme 2
for evaluation of olefin metathesis catalysts.10 Commercially
available complex RuCl2(H2IMes)[=CH(2-PriOC6H4)] HG-II
[H2IMes = bis(mesityl)imidazolinylidene] was used as reference
catalyst.11 As a result, new catalysts 3a and 3b were proved to be
less active as compared with their dichloride precursors 2a and
2b as well as with reference catalyst HG-II (Table 1). Neverthe-
less, the full conversion can be slowly achieved in 24 h for 3a
(see Table 1, entry 4) and 48 h for 3b at 100°C (see Table 1,
entry 6), which reflects the high stability of catalysts in solution.
Next, an efficiency of new complexes in the self-metathesis
of allylbenzene 7 (Scheme 3) was estimated. Complexes 3a,b
demonstrated a lower catalytic activity and selectivity in this
reaction in comparison with their dichloride precursors 2a,b
(Table 2). The best yield of metathesis product (37%) has been
achieved for catalyst 3a at 35°C in THF in 2 h (see Table 2,
entry 4). The enhanced catalyst loading (1 mol%) led to the
better yield of 8 (77%, see Table 2, entry 6), but the content of
isomerization products (ISO, primarily styrenes 9 and 10, see
Scheme 3) increased several times. Nevertheless, the ISO content
in most trails of new catalysts was noticeably lower as compared
to HG-II (see Table 2, entry 1). At the same time, catalysts 3a
and 3b did not induce Z-selectivity comparable to their nearest
analogue containing IMes ligand6(a) in this reaction. In all cases,
the E/Z ratios have not exceeded 4:1.
F(5)
C(15)
F(4)
F(6)
F(2)
O(1)
C(12)
C(13)
C(11)
C(9)
F(3)
C(17)
C(14)
C(8)
C(10)
N(2)
C(6)
C(5)
F(1)
C(7)
C(16)
N(1)
C(2)
C(19)
C(3)
C(22)
S(1)
C(1)
C(18)
C(4)
C(21)
Ru(1)
Cl(1)
Ph
C(20)
Ph
C(47)
C(48)
C(23)
C(24)
C(40)
C(49)
C(50)
C(51)
C(39)
C(32)
O(2)
C(31)
C(57)
C(53)
C(52)
C(54)
C(56)
Ph
Figure 1 Molecular structure of complex 3b (two independent molecules,
molecule A) showing thermal ellipsoids at the 50% probability level. Only
the support carbons of Ph-substituents of arylthiolate ligand are shown.
Hydrogen atoms are omitted for clarity. For bond lengths and angles, see
Online Supplementary Materials.
†
[Ru]
Crystal data for 3b: C56H49ClF6N2O2RuS, M = 1107.01, triclinic, space
Ph
–
Ph
+
Ph
THF (3 M)
group P1 (no. 2), at 120 K: a = 11.6280(13), b = 21.281(2) and c =
8
7
= 22.280(3) Å, a = 113.133(2)°, b = 92.415(3)°, g = 102.219(3)°,
V = 4906.7(10) Å3, Z = 4, dcalc = 1.499 g cm–3. X-ray analysis was
performed on a Bruker AXS SMART 1000 instrument equipped with
graphite monochromator and CCD-detector operating at l(MoKa) =
= 0.71073 Å, w-scanning, 2qmax = 60°, 28598 measured reflections,
19669 independent reflections with F2 > 2s(I), m = 0.540 mm–1, R1 =
= 0.0506, wR2 = 0.0806. Corrections for absorption were made using
SADABS software.7 The structure was solved by direct method and refined
by full-matrix least squares method for F2 with anisotropic parameters
for all non-hydrogen atoms. All calculations were performed in the
SAINT8 and SHELXTL-979 software packages.
Me
+
Ph
Ph
Ph
10
9
ISO
Scheme 3
In conclusion, the synthesis of new monothiolate ruthenium
alkylidene complexes bearing bulky tricyclic NHC ligands
decorated with the two geminal trifluoromethyl groups has
been developed. The complexes synthesized have exhibited a
moderate catalytic activity in RCM of diallyltosylamine reaching
CCDC 1866377 contains the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via http://www.ccdc.cam.ac.uk.
– 39 –

Mendeleev Commun., 2019, 29, 38–40
Table 2 Activity of catalysts 3a,b in self-metathesis of allylbenzene 7 as
3 (a) J. Tornatzky, A. Kannenberg and S. Blechert, Dalton Trans., 2012,
41, 8215; (b) F. Hamad, T. Sun, S. Xiao and F. Verpoort, Coord. Chem.
Rev., 2013, 257, 2274; (c) T. P. Montgomery, A. M. Johns and R. H.
Grubbs, Catalysts, 2017, 7, 87; (d)V. Paradiso,V. Bertolasi, C. Costabile,
compared to that of HG-II and 2a,b.a
Cat. loading
(mol%)
Yield of
Yield of
ISO (%)
Entry
[Ru] cat.
HG-II
2a
t/h
8b (%)
˛
T. Caruso, M. Dabrowski, K. Grela and F. Grisi, Organometallics, 2017,
36, 3692; (e) P. Małecki, K. Gajda, O.Ablialimov, M. Malin´ska, R. Gajda,
K. Woz´niak, A. Kajetanowicz and K. Grela, Organometallics, 2017, 36,
2153.
4 (a) K. Endo and R. H. Grubbs, J. Am. Chem. Soc., 2011, 133, 8525;
(b) B. K. Keitz, K. Endo, P. R. Patel, M. B. Herbert and R. H. Grubbs,
J. Am. Chem. Soc., 2012, 134, 693; (c) M. B. Herbert, B. A. Suslick, P. Liu,
L. Zou, P. K. Dornan, K. N. Houk and R. H. Grubbs, Organometallics,
2015, 34, 2858; (d)A. Dumas, R. Tarrieu, T. Vives, T. Roisnel, V. Dorcet,
O. Baslé and M. Mauduit, ACS Catal., 2018, 8, 3257.
5 (a) S. M. Masoud, A. K. Mailyan, V. Dorcet, T. Roisnel, P. H. Dixneuf,
C. Bruneau and S. N. Osipov, Organometallics, 2015, 34, 2305; (b) S. M.
Masoud, M. A. Topchiy, A. S. Peregudov, T. Roisnel, P. H. Dixneuf,
C. Bruneau and S. N. Osipov, J. Fluorine Chem., 2017, 200, 66;
(c) S. M. Masoud, A. K. Mailyan, A. S. Peregudov, C. Bruneau and
S. N. Osipov, Mendeleev Commun., 2016, 26, 474; (d) S. M. Masoud,
T. R. Akmalov, K. A. Palagin, F. M. Dolgushin, S. E. Nefedov and S. N.
Osipov, Eur. J. Org. Chem., 2018, 5988; (e) T. R.Akmalov, S. M. Masoud,
D. A. Petropavlovskikh, M. A. Zotova, S. E. Nefedov and S. N. Osipov,
Mendeleev Commun., 2018, 28, 609.
1
2
3
4
5
6
7
0.1
1
2
74
75
14
15
0.1
0.1
0.1
0.1
1.0
1.0
1
2
76
78
<1
<1
2b
1
2
75
77
<1
<1
3a
1
2
23
37
<1
<1
3b
1
2
8
12
<1
<1
3a
1
2
75
77
2
2
3bc
1
4
31
46
2
6
aAllylbenzene (3 mol dm–3), 35°C. Conversions and yields were determined
by 1H NMR spectroscopy. b E/Z ratios in all cases were in a range of 4:1 to
5:1, respectively. c Reaction temperature was 60°C.
6 (a) G. Occhipinti, F. R. Hansen, K. W. Tornroos and V. R. Jensen,
J. Am. Chem. Soc., 2013, 135, 3331; (b) G. Occhipinti, V. Koudriavtsev,
K. W. Tornroos and V. R. Jensen, Dalton Trans., 2014, 43, 11106;
(c) W. Smit, V. Koudriavtsev, G. Occhipinti, K. W. Tornroos and V. R.
Jensen, Organometallics, 2016, 35, 1825; (d) G. Occhipinti, K. W. Tornroos
and V. R. Jensen, Organometallics, 2017, 36, 3284.
7 G. M. Sheldrick, SADABS, Bruker AXS Inc., Madison, WI, 1997.
8 SMART, v. 5.051 and SAINT, v. 5.00, Area Detector Control and Integration
Software, Bruker AXS Inc., Madison, WI, 1998.
the full conversion under heating in THF for two days. In the
case of self-metathesis of allyl benzene, these new catalysts
were less active then their dichloride precursors demonstrating
from moderate to good yields along with an acceptable content
of isomerization products under increased catalyst loading. The
revealed data can be useful in the design and synthesis of novel
more selective olefin metathesis catalysts.
9 G. M. Sheldrick, SHELXTL, v. 5.10, Bruker AXS Inc., Madison, WI,
1997.
This work was supported by the Russian Science Foundation
(grant no. 16-13-10364).
10 (a) M. Bieniek, R. Bujok, M. Cabaj, N. Lugan, G. Lavigne, D. Arlt
and K. Grela, J. Am. Chem. Soc., 2006, 128, 13652; (b) Ł. Gułajski,
A. Michrowska, R. Bujok and K. Grela, J. Mol. Catal. A: Chem., 2006,
254, 118; (c) A. Michrowska, R. Bujok, S. Harutyunyan, V. Sashuk,
G. Dolgonos and K. Grela, J. Am. Chem. Soc., 2004, 126, 9318.
11 J. S. Kingsbury, J. P. A. Harrity, B. L. Gray and A. H. Hoveyda, J. Am.
Chem. Soc., 1999, 121, 791.
Online Supplementary Materials
Supplementary data associated with this article can be found
in the online version at doi: 10.1016/j.mencom.2019.01.011.
References
1 (a) Handbook of Metathesis, 2nd edn., eds. R. H. Grubbs, A. G. Wenzel,
D. J. O’Leary and E. Khosravi, Wiley-VCH, Weinheim, 2015; (b) Olefin
Metathesis: Theory and Practice, 1st edn., ed. K. Grela, John Wiley and
Sons, Hoboken, 2014.
2 (a) M. Scholl, S. Ding, C. W. Lee and R. H. Grubbs, Org. Lett., 1999,
1, 953; (b) S. B. Garber, J. S. Kingsbury, B. L. Gray and A. H. Hoveyda,
J. Am. Chem. Soc., 2000, 122, 8168; (c) L. Jafarpour, H. J. Schanz,
E. D. Stevens and S. P. Nolan, Organometallics, 1999, 18, 5416.
Received: 17th September 2018; Com. 18/5692
– 40 –