Wheel-to-rhomboid isomerization as well as nitrene transfer catalysis of ruthenium-thiolate wheels

Article abstract of DOI:10.1039/c6cc09903c

A unique ruthenium-thiolate molecular rhomboid (?)-[Ru(SAr)₂(CO)₂]₈, which consists of eight octahedra linked by alternate face- and vertex-sharing, was produced by isomerization of the molecular wheel (○)-[Ru(SAr)₂

Full text of DOI:10.1039/c6cc09903c

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Wheel-to-rhomboid isomerization as well as
nitrene transfer catalysis of ruthenium-thiolate
Cite this:DOI: 10.1039/c6cc09903c
wheels†
Received 13th December 2016,
Accepted 17th January 2017
a
bc
a
ad
Ken Chi-Hang Tso, Sharon Lai-Fung Chan,* Jie-Sheng Huang* and Chi-Ming Che
DOI: 10.1039/c6cc09903c
rsc.li/chemcomm
2 2 8
A unique ruthenium-thiolate molecular rhomboid (B )-[Ru(SAr) (CO) ] ,
which consists of eight octahedra linked by alternate face- and vertex-
sharing, was produced by isomerization of the molecular wheel
2 2
(J)-[Ru(SAr) (CO) ]
8
at elevated temperature. The use of
a
(J)-[Ru(SAr) (CO) ]
2 2 6
wheel for catalytic aziridination of alkenes via
nitrene transfer is also described.
The construction of metallacycles with fascinating shapes, such as
1
2
molecular polygons and wheels, constitutes an ever-increasing
area in supramolecular chemistry. As a class of molecular polygons,
molecular rhomboids assembled by metal–ligand coordination have
1,3
received considerable attention; notable examples in the literature
were assembled through a ‘‘bottom-up’’ strategy and based on
3
a,b,e
3c–h,j,l
3i
Pd(II)–pyridine,
Pt(II)–pyridine,
Pt(II)–carboxylate, or
3k
Ru(II)/Fe(II)–pyridine coordination (Fig. 1, upper left). In the
course of our studies on the reactivity and catalytic application of
ruthenium- and osmium-thiolate wheels (J)-[M(SAr) (CO) ]
2
2 n
4
(
n = 6, 8) reported recently, we came upon a molecular rhomboid
(
B)-[Ru(SAr) (CO) ] which was based on metal–thiolate coordina-
2
2 8
tion and was formed from the isomerization of a molecular wheel
J)-[Ru(SAr) (CO) (Fig. 1, lower). Such unprecedented wheel-to-
rhomboid isomerization of (J)-[Ru(SAr) (CO) , along with the
(
2
2 8
]
2
2 n
]
catalytic properties of this type of molecular wheel toward nitrene
transfer reactions, is reported herein. We examined a previous
report of chelate-induced wheel-to-square transformation, i.e. from
[
Fe(pd)(O CEt)] (pdH = 1,3-propanediol) to [{Fe O(pd) (O CEt)-
2 12 2 3 2 2
0
0
00
Fig. 1 Upper left: Literature examples of molecular rhomboids. Upper
right: Wheel-to-square transformation reported in the literature. Lower:
(tpy) } ](ClO ) (tpy = 2,2 :6 ,2 -terpyridine), upon treatment with tpy
2
4
4 8
5
Molecular rhomboid and wheel-to-rhomboid isomerization reported in
this work; the molecular rhomboid consists of eight octahedra linked by
alternate face- and vertex-sharing.
a
Department of Chemistry and State Key Laboratory of Synthetic Chemistry,
The University of Hong Kong, Pokfulam Road, Hong Kong, China.
E-mail: jshuang@hku.hk
b
c
The Hong Kong Polytechnic University Shenzhen Research Institute, China
Department of Applied Biology and Chemical Technology, The Hong Kong
Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
E-mail: sharonlf.chan@polyu.edu.hk
and NaClO resulting in major changes in the components of the
4
5
metallacycle (Fig. 1, upper right).
2 2 8
The molecular rhomboid (B )-[Ru(SAr) (CO) ] represents a
unique example of an octanuclear metallacycle consisting of eight
d
HKU Shenzhen Institute of Research and Innovation, Shenzhen 518053, China
Electronic supplementary information (ESI) available: Experimental procedures,
†
octahedra linked in an alternate face- and vertex-sharing manner
and supporting tables and figures. CCDC 1522395 and 1522396. For ESI and
6
crystallographic data in CIF or other electronic format see DOI: 10.1039/c6cc09903c (Fig. 1, lower), unlike its wheel isomer (J)-[Ru(SAr)
2
(CO)
2
]
8
and
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1
Fig. 2 H NMR spectra (in the aromatic regions) of the (J)- and (B )-
t
t
[
(
Os(S-p- BuC
6
H
4
)
2
(CO)
]
2 8
mixture (upper), (J)-[Ru(S-p- BuC
6
H
4
)
2
(CO)
2 8
]
t
middle), and (B )-[Ru(S-p- BuC
6 4 2 2 8 3
H ) (CO) ] (lower) in CDCl at 298 K.
other related octanuclear or higher-nuclearity molecular wheels in
4
,5,7
which the octahedra are linked by edge-sharing,
by alternate
8
9
edge- and vertex-sharing, or by alternate face- and edge-sharing.
Cyclic ensembles composed of edge-, vertex-, and/or face-sharing
2,8,10
polyhedra are of high importance.
The formation of
(
B)-[Ru(SAr) (CO) ] observed in this work demonstrates the
2
2 8
feasibility of utilizing alternate face- and vertex-sharing octahedra
6
to construct metallacycles with nuclearity higher than 6, which
could show intriguing structures and properties.
t
Complex (B )-[Ru(SAr)
development of the chemistry of (J)-[M(SAr)
latter was synthesized by reaction of M (CO)12 with ArSH at 120 1C
M = Ru) or 150 1C (M = Os). In the subsequent studies of these self-
assembly reactions, we found that treatment of Os (CO) with ArSH
2 2 8
6 4 2 2 8
(CO) ] was identified during our further Fig. 3 X-ray crystal structure of (B )-[Os(S-p- BuC H ) (CO) ] with omis-
4
t
t
2
(CO)
2
]
n
6 4 6 4
(n = 6, 8); the sion of all p- BuC H groups. The bonds connecting p- BuC H groups
and S atoms are shown as dashed lines. Upper: Ball and stick representa-
3
tion. Lower: Polyhedral representation.
(
3
12
t
t
(
Ar = p- BuC H ) at 160 1C afforded a mixture of two products, as characterized (B )-[Os(S-p- BuC H ) (CO) ] (Fig. 2, upper) but is
revealed by H NMR measurements (Fig. 2, upper). One product dramatically different from that of the structurally characterized
6
1
4
6
4 2
2 8
t
t
4
gave only two sets of Ar (p- BuC
highly symmetric (J)-[M(SAr)
product showed multiple sets of the Ar signals corresponding (CO)
to a structure with lower symmetry. Recrystallization of the mixture metallacycle in solution, and the signals became better resolved at
6
H
(CO)
4
) signals, like previously reported (J)-[Ru(S-p- BuC
6
H
4
)
2
(CO)
2
]
8
wheel (Fig. 2, middle). Variable-
4
1
t
2
2
]
n
wheels, whereas the other temperature (298–223 K) H NMR spectra of (B )-[Ru(S-p- BuC
6
H
4
)
2
-
2 8
] (Fig. 4) revealed some extent of fluxional behaviour of the
1
1
of products in chloroform/pentane gave a crystal suitable for low temperatures. Based on these spectral changes and the H– H
X-ray crystallographic studies. The crystal structure deter- COSY NMR spectrum (Fig. 5), the signals belong to 8 sets of the
t
mined corresponds to a centrosymmetric molecular rhomboid p- BuC H groups, in agreement with a centrosymmetric structure of
6
4
t
t
(
B)-[Os(S-p- BuC
6 4 2 2 8 6 4 2 2 8
H ) (CO) ] (Fig. 3), a structure that can account for (B )-[M(S-p- BuC H ) (CO) ] revealed by the X-ray crystal structure of
the multiple sets of Ar signals depicted in the top of Fig. 2. Attempts to the Os counterpart (Fig. 3).
t
prepare (B )-[Os(S-p- BuC
6
H
4
)
2
(CO)
2
]
8
in its pure form have not
Upon treatment with a silver(I) salt such as AgOTf, (B)-[Ru(S-
t
+
been successful. We then turned our attention to the Ru system. p- BuC
Interestingly, treatment of Ru (CO)12 with ArSH (Ar = p- BuC H
3 6 4
60 1C afforded (B )-[Ru(S-p- BuC
6
H
4
)
2
(CO)
) at suggested by the marked shift of the H NMR signals after
which was isolated addition of AgOTf to a solution of this complex in CDCl . X-ray
2 8
] can rapidly bind Ag ions in solution, as
t
1
t
1
6
H
4
) (CO) ]
2 2 8
3
with reasonable purity. This complex could also be obtained in a crystallographic studies of a crystal obtained from the reaction
t
stepwise manner, i.e., reaction of Ru (CO) with p- BuC H SH at mixture revealed a rhomboid structure with the formulation of
3
12
6
4
t
4
t
+
1
20 1C to give a (J)-[Ru(S-p- BuC
6
H
4
)
2
(CO)
]
2 8
wheel, followed by (B )-{Ag[Ru(S-p- BuC
Apart from the abovementioned wheel-to-rhomboid isomeriza-
at room tion, (J)-[Ru(SAr) (CO) wheels can also be used for nitrene
temperature (Fig. 2, lower) resembles that of the structurally transfer catalysis. To allow comparison of the catalytic activity
6 4 2 2 8
H ) (CO) ] } (Fig. 6).
t
heating of the wheel in p- BuC
6
H
4
SH at 160 1C (Scheme 1).
1
t
The H NMR spectrum of (B )-[Ru(S-p- BuC
6
H
4
)
2
(CO)
2
]
8
2
2 n
]
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1
1
Fig. 5 H– H COSY NMR spectrum (in the aromatic region) of (B )-[Ru(S-
t
6 4 2 2 8 3
p- BuC H ) (CO) ] in CDCl at 253 K.
t
6 4 2 2 8
Scheme 1 Synthesis of (B )-[Ru(S-p- BuC H ) (CO) ] .
1
Fig. 4 Variable-temperature H NMR spectra (in the aromatic regions) of
t
(
6 4 2 2 8 3
B)-[Ru(S-p- BuC H ) (CO) ] in CDCl .
between (J)-[Ru(SAr)
2
(CO)
2 n
] and its Cu(I) complex (J)-{Cu[Ru-
+
4
(
SAr) (CO) ] } (the latter is known for n = 6 but not for n = 8 ),
2
2 n
i
the structurally characterized (J)-[Ru(S-p- PrC H ) (CO) ] and
6
4 2
2 6
4
i
+
(
J)-{Cu[Ru(S-p- PrC H ) (CO) ] }
reported previously
were
6
4 2
2 6
employed in this work as examples for such studies. At a catalyst
t
+
Fig. 6 X-ray crystal structure of (B )-{Ag[Ru(S-p- BuC
6
H
4
)
2
(CO)
2
]
8
t
}
with
groups. The bonds connecting p- BuC
groups and S atoms are shown as dashed lines. Upper: Ball and stick
loading of 1 mol%, the reaction of Ph IQ NTs with styrene (3 equiv.)
t
omission of all p- BuC
6
H
4
6 4
H
i
+
6 4 2 2 6
in MeCN at 80 1C catalysed by (J)-{Cu[Ru(S-p- PrC H ) (CO) ] }
afforded the aziridination product in 82% yield, higher than the representation. Lower: Polyhedral representation.
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We gratefully acknowledge the financial support from the
Hong Kong Research Grants Council (HKU 702312P, HKU
700813P), the National Key Basic Research Program of China
(
(
(
No. 2013CB834802), the National Science Foundation of China
21401157) and the Basic Research Program of Shenzhen
No. JCYJ20160229123546997). We also thank Dr Lam Shek
and Dr Stephen Sin-Yin Chui for their great assistance with the
X-ray crystal structure determination studies.
Notes and references
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6 4 2
Scheme 2 Aziridination of alkenes catalysed by (J)-{Cu[Ru(S-p-PrC H ) -
2
013, 135, 13676; (h) I. V. Grishagin, J. B. Pollock, S. Kushal, T. R. Cook,
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+
2 6
(CO) ] } .
1
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X. Yan, Z. Zhou, M. L. Saha, Y.-C. Wang and P. J. Stang, Proc. Natl. Acad.
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i
product yield of 9% obtained for (J)-[Ru(S-p- PrC H ) (CO) ] .
6
4 2
2 6
For comparison, the same reaction catalysed by 2 mol% of
Cu(MeCN) ]PF gave the aziridine product in 40% yield. Possibly,
the Cu(I) site of (J)-{Cu[Ru(S-p- PrC
[
4
6
i
+
6
H
4
)
2
(CO)
2
]
6
}
is mainly
4
responsible for the aziridination activity and its molecular
wheel environment enhances the catalytic activity compared
with [Cu(MeCN) ]PF . (J)-{Cu[Ru(S-p- PrC H ) (CO) ] } was then
i
+
5 T. C. Stamatatos, A. G. Christou, C. M. Jones, B. J. O’Callaghan, K. A.
Abboud, T. A. O’Brien and G. Christou, J. Am. Chem. Soc., 2007, 129, 9840.
4
6
6
4 2
2 6
used as a catalyst for aziridination of styrenes with Ph IQ NR (R = Bs,
Ts, and Ns), which afforded the aziridination products in up to 95%
yield (Scheme 2).
We monitored the reaction of (J)-{Cu[Ru(S-p- PrC
with Ph IQ NR (R = Ts, Bs) in CH Cl by ESI-MS measurements,
which revealed the formation of a new cluster peak at m/z 2962 and
948 for the reaction using Ph IQ NTs and Ph IQ NBs, respectively.
This new cluster peak possibly resulted from binding of the nitrene
NR) group by the molecular wheel (see Fig. S6–S9 in the ESI†). In
6
For examples of tetra- and hexanuclear metallacycles consisting of
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i
+
6 4 2 2 6
H ) (CO) ] }
2
2
1996, 622, 579; (d) C. E. Pohl-Ferry, J. W. Ziller and N. M. Doherty, Chem.
2
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2
f ) R. Ye, Y. Qin, A.-Q. Jia, Q. Chen and Q.-F. Zhang, Inorg. Chim. Acta,
013, 405, 218.
(
the literature, catalytic applications of metal molecular wheels
remain sparse. Nitrene transfer reactions catalysed by metal com-
7
8
(a) K. L. Taft and S. J. Lippard, J. Am. Chem. Soc., 1990, 112, 9629;
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2
11
plexes have received tremendous attention, but such reactions
catalysed by molecular wheels have not been reported previously.
In summary, a novel type of molecular rhomboid, consti-
tuted by eight octahedra linked by an alternate face- and vertex-
sharing mode, has been obtained, which is remarkably stable
and could be formed by wheel-to-rhomboid isomerization of a
ruthenium-thiolate wheel at high temperature. The present
work also demonstrates the potential utility of a molecular
wheel in catalytic nitrene transfer reactions.
1
(
b) H. N. Miras, G. J. T. Cooper, D.-L. Long, H. B o¨ gge, A. M u¨ ller,
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Chem. Commun.
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