Electrophilic substitution of platinum(II) complexes with thiophene derivatives

Article abstract of DOI:10.1246/cl.2008.542

The reaction of aryl(halo)platinum(II)(bpy) complexes with thiophene derivatives causes novel electrophilic substitution in the presence of AgNO ₃/KF as an activator to form thienyl complexes in 65-91% yields. The related reaction with (dihalo)

Full text of DOI:10.1246/cl.2008.542

542
Chemistry Letters Vol.37, No.5 (2008)
Electrophilic Substitution of Platinum(II) Complexes with Thiophene Derivatives
Atsunori Mori,ꢀ1 Atsushi Sugie,1 Hirotoshi Furukawa,1 Yuji Suzaki,2 Kohtaro Osakada,2 and Munetaka Akita2
1Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501
2Chemical Resources Laboratory, Tokyo Institute of Technology, R1-3 4259 Nagatsuta, Yokohama 226-8503
(Received March 4, 2008; CL-080240; E-mail: amori@kobe-u.ac.jp)
The reaction of aryl(halo)platinum(II)(bpy) complexes with
Worthy of note is that this is a new class of reactivity in
platinum(II) complexes5 to allow intermolecular electrophilic
substitution with a heteroaromatic compound in the presence
of AgNO3/KF without participation of proximal chelation by
a heteroatom.6 It should also be pointed out that the platinum
carbon bond formation occurred smoothly at the CH bond
when a thiophene derivative bearing a carbon–bromine bond
was employed.7,8
thiophene derivatives causes novel electrophilic substitution in
the presence of AgNO3/KF as an activator to form thienyl com-
plexes in 65–91% yields. The related reaction with (dihalo)-
platinum(II) also takes place to afford dithienylplatinum(II)
complexes.
Mechanistic studies on a transition-metal-catalyzed reaction
with a stoichiometric amount of the metal complex is a powerful
tool for the understanding of the reaction pathway involving sev-
eral fundamental reactions and the actual structure of each key
intermediate. We have previously reported that palladium-cata-
lyzed CH arylation and CH homocoupling reactions in the pres-
ence of a silver salt as an activator.1,2 The mechanistic studies
have also been performed with a stoichiometric palladium(II)
complex and it was found that the reaction of arylpalladium(II)
complex 1 with a thiophene derivative 2 afforded the CH aryla-
tion product 3 in good yields (eq 1).3 These findings suggest that
the key of the catalytic CH arylation reaction is the electrophilic
substitution of arylpalladium(II) complex with thiophene. How-
ever, detection of aryl(thienyl)palladium(II) complex has been
unsuccessful probably owing to the facile reductive elimination
leading to 3. Accordingly, we envisaged to switch the metal spe-
cies to platinum, which would retard the reductive elimination
step, to afford aryl(thienyl)platinum complex. Herein, we report
that aryl(thienyl)platinum complex is obtained by the reaction
of the corresponding halide with thiophene derivatives in the
presence of a silver salt.
Table 1 shows that such electrophilic substitution reaction
proceeds with several platinum complexes and thiophene
derivatives. In addition to platinum(II) iodide complex, it
was found that the chloride complex underwent the reaction
smoothly to afford the corresponding aryl(thienyl) complex in
excellent yields.9
Aryl(thienyl)platinum complex 5be was isolated as single
crystals and characterized by X-ray crystallography.10 Figure 1
Table 1. The reaction of [Pt(Aryl)(X)(bpy)] (4) with thiophene
derivatives 2a
Aryl
N
N
Aryl
S
N
N
AgNO3/KF
Pt
Pt
2
+
X
R
4
5
Aryl
X
I
Thiophene 2
Product Yield/%
Br
5aa
5ab
91
87
Br
S
(4a)
(2a)
n-C6H13
R
Aryl
N
N
R
4a
I
AgNO3/KF
Br
S
Pd
(1)
+
Aryl
S
(2b)
S
I
2
3
CH3
Cl
Cl
Cl
2a
5ba
5bc
5bd
74
65
73
1
(4b)
The reaction of the arylplatinum(II) complex 4a4 with 2,3-
dibromothiophene (2a) was first examined with AgNO3/KF as
an activator under similar conditions to those carried out in the
reaction of the corresponding palladium complex and found to
Br
S
4b
(2c)
1
CHO
S
afford platinum complex 5aa in 91% yield. H NMR spectrum
4b
of the product shows that satellite of 195Pt was observed in the
signals of ꢀ-H signal of the thiophene [J(PtH) = 54.6 Hz] and
ortho-H signal of the aryl moiety [J(PtH) = 51.6 Hz] suggesting
that the complex possesses both platinum–aryl and platinum–
thienyl bonds (see Supporting Information). It has been com-
pletely unsuccessful to detect such arylthienyl complex when
the stoichiometric reaction is carried out with the corresponding
arylpalladium(II) complex 1.3 On the other hand, the obtained
platinum(II) complex 5aa was quite stable in DMSO-d6 and
no reductive elimination was found to occur upon heating at
100 ꢁC for 17 h.
(2d)
COOEt
S
4b
4b
Cl
Cl
5be
5bf
74
78
(2e)
S
(2f)
aThe reaction was carried out with [Pt(Aryl)(X)(bpy)] (4)
(0.05 mmol) and 2 (0.12 mmol) at 50 ꢁC for 5 h in the presence
of AgNO3 (0.2 mmol) and KF (0.2 mmol) in DMSO.
Copyright Ó 2008 The Chemical Society of Japan

Chemistry Letters Vol.37, No.5 (2008)
543
Masui, A. Mori, Org. Lett. 2005, 7, 5083. See also: c) A. R.
Murphy, P. C. Chang, P. VanDyke, J. Liu, J. M. J. Frechet,
V. Subramanian, D. M. Delongchamp, S. Sambasivan, D. A.
Fischer, E. K. Lin, Chem. Mater. 2005, 17, 6033. d) B. C.
Bishop, K. M. J. Brands, A. D. Gibb, D. J. Kennedy, Synthesis
2004, 43. e) C. A. Zificsak, D. J. Hlasta, Tetrahedron 2004, 60,
8991.
A. Sugie, K. Kobayashi, Y. Suzaki, K. Osakada, A. Mori,
Chem. Lett. 2006, 35, 1100.
a) T. Yagyu, Y. Suzaki, K. Osakada, Organometallics 2002,
21, 2088. b) Y. Suzaki, T. Yagyu, Y. Yamamura, A. Mori,
K. Osakada, Organometallics 2002, 21, 5254. c) Y. Suzaki,
K. Osakada, Bull. Chem. Soc. Jpn. 2004, 77, 139.
C(10)
C(16)
C(14)
C(9)
C(15)
C(17)
C(11)
C(8)
C(18)
C(19)
C(20)
C(21)
C(12)
Pt(1)
N(1)
N(2)
C(13)
C(2)
C(3)
C(1)
C(22)
C(4)
C(14)
3
4
S(1)
O(2)
C(14)
C(7)
C(5)
O(1)
C(6)
Figure 1. ORTEP drawing of 5be (50% probability). Hydrogen
atoms were omitted for clarity.
5
a) K. Osakada, Transmetalation, in Current Methods in
Inorganic Chemistry, ed. by H. Kurosawa, A. Yamamoto,
Elsevier Science, Amsterdam, 2003, Vol. 3, pp. 233–291. b)
K. Osakada, T. Yamamoto, Coord. Chem. Rev. 2000, 198,
379. c) K. Osakada, Platinum ꢂ-Bond Complexes, in Compre-
hensive Organometallic Chemistry III, Elsevier Science,
Amsterdam, 2003, Vol. 8, pp. 445–610.
J. Brooks, Y. Babayan, S. Lamansky, P. I. Djurovich, I. Tsyba,
R. Bau, M. E. Thompson, Inorg. Chem. 2002, 41, 3055, and
references therein.
a) S. Murai, F. Kakiuchi, S. Sekine, Y. Tanaka, A. Kamatani,
M. Sonoda, N. Chatani, Nature 1993, 366, 529. b) H.
Weissman, X. Song, D. Milstein, J. Am. Chem. Soc. 2001,
123, 337. c) S. Oi, S. Fukita, N. Hirata, N. Watanuki, S.
Miyano, Y. Inoue, Org. Lett. 2001, 3, 2579. d) J.-Y. Cho,
M. K. Tse, D. Holmes, R. E. Maleczka, Jr., M. R. Smith, III,
Science 2002, 295, 305. e) C. Jia, D. Piao, J. Oyamada, W.
Lu, T. Kitamura, Y. Fujiwara, Science 2000, 287, 1992. f) T.
Satoh, Y. Kawamura, M. Miura, M. Nomura, Angew. Chem.,
Int. Ed. Engl. 1997, 36, 1740. g) K. Oguma, M. Miura, T.
Satoh, M. Nomura, J. Am. Chem. Soc. 2000, 122, 10464.
h) H. Chen, S. Schlecht, T. C. Semple, J. F. Hartwig, Science
2000, 287, 1995. i) M. Miura, M. Nomura, Topics in Current
Chemistry, 2002, Vol. 219, p. 211.
a) S. Pivsa-Art, T. Satoh, Y. Kitamura, M. Miura, M. Nomura,
Bull. Chem. Soc. Jpn. 1998, 71, 467. b) A. Yokooji, T.
Okazawa, T. Satoh, M. Miura, M. Nomura, Tetrahedron
2003, 59, 5685. c) Y. Kondo, T. Komine, T. Sakamoto, Org.
Lett. 2000, 2, 3111. d) J. C. Lewis, S. H. Wiedemann, R. G.
Bergman, J. A. Ellman, Org. Lett. 2004, 6, 35. e) N. Kamigata,
M. Yoshikawa, T. Shimizu, J. Fluorine Chem. 1998, 87, 91.
The stoichiometric reactions of arylpalladium(II) bromide and
chloride were confirmed to proceed similarly to that of iodide.
depicts the molecular structure of 5be with a square-planar coor-
dination around the Pt center. The thienyl ligand bonds to plat-
inum center through its ꢁ-carbon (Pt(1)–C(1) = 1.989(6) A).
˚
The reaction of [Pt(X)2(bpy)] (X = Cl and I) (6)4 was also
found to proceed with thiophene through the electrophilic substi-
tution reaction (eq 2).2 Similarly to the case of the reaction of
aryl(halo)platinum complex 5, chloride and iodide were found
to react to afford 7. The reaction of 6 with 2,3-dibromothiophene
(2a) in the presence of AgNO3 and KF in DMSO afforded
dithienyl complex 7 in 70% yield (X = I) and 65% yield
(X = Cl), respectively. The complex 7 is considered to be a
platinum analogue for the supposed intermediate of the homo-
coupling reaction catalyzed by a palladium complex.
6
7
Br
Br
Br
Br
Br
Br
X
X
N
N
N
N
AgNO3/KF
S
Pt
(2)
+
Pt
S
DMSO,
50 °C, 5 h
S
X = I: 70%
X = Cl: 65%
6a: X = I
6b: X = Cl
7
In summary, electrophilic substitution of thiophene deriva-
tives with platinum complex to form aryl(thienyl)platinum(II)
and dithienylplatinum(II) complexes proceeds by the addition
of AgNO3/KF. The results support that the CH substitution
reactions of thiophene derivatives proceeds via such an electro-
philic substitution reaction. The reactions of platinum complexes
4 and 6 are a class of new reactivity in platinum chemistry to
provide a pathway to thienylplatinum(II) complex, where the
presence of carbon–halogen bond is tolerable.11
8
9
This work was partially supported by a Grant-in-Aid for
Scientific Research on Priority Areas, ‘‘Advanced Molecular
Transformation of Carbon Resources’’ by Ministry of Education,
Culture, Sports, Science and Technology, Japan.
10 Crystal data for 5be: C24H22N2O2PtS: fw 597.60, triclinic,
ꢀ
˚
space group P1 (No. 2), a ¼ 10:0772ð6Þ A, b ¼ 10:0956ð5Þ
ꢁ
ꢁ
˚
˚
A, c ¼ 12:8026ð9Þ A, ꢁ ¼ 66:951ð5Þ , ꢀ ¼ 73:933ð5Þ , ꢃ ¼
ꢁ
3
61:988ð4Þ , V ¼ 1051:2ð1Þ A , Z ¼ 2, Dcalcd ¼ 1:888 gꢂcmꢃ3
,
˚
no. of unique reflections = 3729 (I > 3ꢂðIÞ), R ¼ 0:028,
Rw ¼ 0:036. Crystallographic data reported in this manuscript
have been deposited with Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC-682142.
Copies of the data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the
Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge, CB2 1EZ, UK; fax: +44 1223 336033; or
deposit@ccdc.cam.ac.uk).
References and Notes
1
a) A. Mori, A. Sekiguchi, K. Masui, T. Shimada, M. Horie,
K. Osakada, M. Kawamoto, T. Ikeda, J. Am. Chem. Soc.
2003, 125, 1700. b) K. Masui, A. Mori, K. Okano, K.
Takamura, M. Kinoshita, T. Ikeda, Org. Lett. 2004, 6, 2011.
See also: c) J. Hassan, C. Gozzi, M. Lemaire, C. R. Acad.
Sci. Paris, Ser. IIc: Chimie/Chemistry 2000, 3, 517. d) C.
Gozzi, L. Lavenot, K. Ilg, V. Penalva, M. Lemaire, Tetra-
hedron Lett. 1997, 38, 8867.
11 Supporting Information is available electronically on the
CSJ-Journal Web site, http://www.csj.jp/journals/chem-lett/
index.html.
2
a) K. Masui, H. Ikegami, A. Mori, J. Am. Chem. Soc. 2004,
126, 5074. b) K. Kobayashi, A. Sugie, M. Takahashi, K.
Published on the web (Advance View) April 12, 2008; doi:10.1246/cl.2008.542