Synthesis and application of a new selenoplatinum catalyst

Article abstract of DOI:10.1016/j.tetlet.2004.12.039

The reaction of 4-methyl-5-ethoxycarbonyl-1,2,3-selenadiazole with (PPh₃)₄Pt leads to the formation of a new platinum-containing heterocyclic system. It was found that the selenoplatinum complex is a selective catalyst for the hydrosilylation of terminal alkynes to yield β-(Z)- and β-(E)-silylethylenes.

Full text of DOI:10.1016/j.tetlet.2004.12.039

Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 1001–1003
Synthesis and application of a new selenoplatinum catalyst
*
Pavel Arsenyan, Kristine Oberte, Kira Rubina and Sergey Belyakov
Latvian Institute of Organic Synthesis, Aizkraukles 21, Riga, LV 1006, Latvia
Received 4 October 2004; revised 26 November 2004; accepted 8 December 2004
3 4
Abstract—The reaction of 4-methyl-5-ethoxycarbonyl-1,2,3-selenadiazole with (PPh ) Pt leads to the formation of a new platinum-
containing heterocyclic system. It was found that the selenoplatinum complex is a selective catalyst for the hydrosilylation of ter-
minal alkynes to yield b-(Z)- and b-(E)-silylethylenes.
ꢀ
2004 Elsevier Ltd. All rights reserved.
Recently, the syntheses and use of selenium-containing
1
compounds in organic synthesis has increased. The
was studied for the hydrosilylation of terminal acetyl-
enes with phenyldimethylsilane. The new catalyst
enables the synthesis of previously unknown b-(Z)-
silylethylenes.
interest in 1,2,3-selenadiazoles stems from the fact that
they undergo a wide variety of reactions as 1,3-dipoles
or as a source of selenium and have attracted much
attention for the synthesis of different organoselenium
compounds. The reactions of 1,2,3-selenadiazoles with
low-valent transition metal compounds have previously
been used to prepare a variety of selenium-containing
complexes. Reaction of cyclohepteno-1,2,3-selenadiaz-
The reaction of 4-methyl-5-ethoxycarbonyl-1,2,3-selena-
5
diazole (1) with 1 equiv of tetrakis(triphenylphosph-
ino)platinum(0) in toluene at 140 ꢁC in a Pierce vial
for 3 h led to the formation of a new platinum-contain-
ing heterocyclic system. This reaction involved the inser-
tion of di(triphenylphosphino)platinum into the
selenadiazole ring yielding the six-membered ring 2.
During the second step a 1,3-dipole formed from selena-
diazole 1 by thermal elimination of nitrogen adds to
intermediate 2 with the elimination of triphenylphos-
5
ole with a two fold excess of (g -C H ) Mo (CO) leads
5
5 2
2
4
to the formation of a dimolybdenum complex in 10%
2
yield. It has been shown that cyclopentadienylcobalt
diselenolenes may be produced by interaction of di(tri-
phenylphosphino)- or dicarbonylcyclopentadienyl co-
balt(0) with 4,5-disubstituted 1,2,3-selenadiazoles in
6
phine to yield the new heterocycle 3. The platinum is
covalently bonded to two selenium atoms and has an
intramolecular donor–acceptor bond with nitrogen,
3
a,b
the presence of elemental selenium.
lates have been synthesized using nanocarbonyldiiron.
Heating Pd (dba) and 1,2,3-selenadiazoles with 1 equiv
Diiron diseleno-
3
c
and
a coordinate bond with triphenylphosphine
2
3
of trialkylphosphine led to the formation of a complex
4
(Scheme 1). Compound 3 was obtained in 35% yield as
dark-violet crystals after recrystallization from hexane.
Previously palladium-containing heterocycles with
similar structures were prepared by Morley and co-
a,b
containing Se, N, Se tridentate ligands.
A selenaketo-
carbene complex containing platinum was obtained
from cycloocteno-1,2,3-selenadiazole and tetrakis(tri-
4
c
4b
phenylphosphino)platinum(0) in high yield.
workers in 1999. The desired product was formed
from the selenadiazole and (PPh ) Pd at 60 ꢁC in benz-
3
4
We now present a totally new type of platinum complex
prepared from 4-methyl-5-ethoxycarbonyl-1,2,3-selena-
diazole and tetrakis(triphenylphosphino)platinum(0).
The catalytic application of this selenoplatinum complex
ene after 1 h and in low yield. In our case the molecular
structure of selenoplatinum heterocycle 3 was estab-
7
lished by X-ray analysis. The atomic labeling and the
ORTEP view of 3 is presented in Figure 1. The Pt1–
˚
Se2 bond length in the six-membered ring (2.345 A) is
shorter than the Pt1–Se9 bond length in the five-mem-
˚
bered ring (2.394 A). Heterocycle 3 is stabilized by the
Keywords: Hydrosilylation; Molecular structure; Platinum; Selenadiaz-
ole; Selenium.
triphenylphosphine ligand, the Pt1–P10 bond length is
˚
*
Corresponding author. Tel.: +371 753 1028; fax: +371 755 0338;
e-mail: pavel.arsenyan@lycos.com
2.259 A, and the intramolecular Pt1–N6 bond is
˚
2.079 A. The bond lengths in 3 are in accord with Pt–Se
0
040-4039/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.12.039

1002
P. Arsenyan et al. / Tetrahedron Letters 46 (2005) 1001–1003
˚
2.377–2.479 A) and Pt–P (2.229–2.305 A) bond dis-
˚
(
8
tances of previously published structures. The Se2–
Pt1–Se9 angle is almost linear (176.48ꢁ). The methyl
groups of the ethoxycarbonyl substituent at C3 appear
disordered in the crystal structure.
9
a
According to literature data the hydrosilylation of tri-
chloro(ethynyl)silane with trichloro-, dimethylchloro-,
and trimethylsilanes in the presence of Speierꢀs catalyst
yields two b-(E)- and a-silylethylenes. However, hydro-
silylation of alkylalkoxyethynylsilanes with chloroalkyl-
silanes catalyzed by H PtCl Æ6H O gives only the b-(E)-
2
6
2
9
b,c
isomer.
In the synthesis of methylarylsilanes, the
hydrosilylation reaction predominantly forms the b-
(
the only product (Table 1).
E)-ethylene, which in the case of ethynylsilatrane is
9
d,e
Hydrosilylation in the
Scheme 1. Interaction of 4-methyl-5-ethoxycarbonyl-1,2,3-selenadiaz-
ole 1 with tetrakis(triphenylphosphino)platinum(0).
presence of rhodium catalysts occurs less selectively to
afford both the hydrosilylation products and the prod-
ucts of a dehydrocondensation. It should be noted that
the b-(Z)-isomer was not obtained in the previously de-
scribed experiments.
We have found that the new selenoplatinum complex 3
can catalyze the hydrosilylation of tert- butyl-, trimeth-
ylsilyl-, phenyl-, and methoxycarbonyl substituted acet-
ylenes with dimethylphenylsilane in good yields (74–
8
0%). 3,3-Dimethylbut-1-yne reacts with dimethylphen-
ylsilane at 50 ꢁC in 2 h and in 80% yield almost stereo-
specifically to give the b-(E)-isomer 4E with only
traces of the Z-isomer. In the case of trimethylsilylacet-
ylene, hydrosilylation also occurred stereospecifically to
give b-(E)-1-trimethylsilyl-2-dimethylphenylsilylethylene
(
5E). In contrast the use of Speierꢀs catalyst gave a reg-
9e
ioisomeric ratio of 96% (5E) to 4% (the a-isomer).
Reaction of the silane with phenylacetylene led to the
formation of a stereoisomeric mixture. b-(E)-2-Dimeth-
ylphenylsilylstyrene (6E) was obtained in 75% yield as
the major product along with the b-(Z)-isomer 6Z in
1
5% yield. According to H NMR spectroscopy the
2
alkene double bond protons of 6Z appeared as doublets
3
at 5.65 and 5.98 ppm ( J = 3.0 Hz). Inspection of the
literature data showed that no platinum catalysts had
previously been reported for the synthesis of b-(Z)-iso-
mers by hydrosilylation. Analysis of the product mixture
after hydrosilylation of methyl propiolate showed that
methyl b-(Z)-2-dimethylphenylsilylacrylate 7Z was
formed in a small excess in comparison to the 7E iso-
˚
Figure 1. Molecular structure of 3. Selected bond lengths (A) and
angles (ꢁ): Pt1–Se2 2.3448(7), Pt1–Se9 2.3941(7), Pt1–P10 2.2596(12),
Pt1–N6 2.071(5), Se9–C8 1.859(5), Se2–C3 1.836(6), N6–C8 2.323(7),
N6–C7 1.434(8), N6–N5 1.295(7), N6–C4 2.398(8), C8–C7 1.322(9),
C7–N5 2.189(9), N5–C4 1.420(9), Se9–Pt1–Se2 176.48(3), Se9–Pt1–P10
1
0
mer. It should be noted that selenoplatinum catalyst
can be almost quantitatively recovered from the reac-
8
9
1
1
7.61(3), Se9–Pt1–N6 82.93(13), Se2–Pt1–P10 90.83(4), Se2–Pt1–N6
8.73(13), P10–Pt1–N6 170.33(14), Pt1–Se9–C8 95.4(2), Pt1–Se2–C3
03.6(2), Pt1–N6–C8 92.0(2), Pt1–N6–C7 123.0(4), Pt1–N6–N5
30.4(5), Pt1–N6–C4 101.0(3).
3
tion mixture by column chromatography on silica gel
and reused more than five times (Scheme 2).
Table 1. Addition of dimethylphenylsilane to terminal acetylenes
9d,e
R
3
2 6
[H PtCl ]
Regioisomer ratio (%)
Yield (%)
Regioisomer ratio (%)
a
b-(E)
b-(Z)
a
b-(E)
b-(Z)
t
Bu
—
—
—
—
4E 99
5E 99
6E 75
7E 45
Traces
Traces
6Z 25
7Z 55
80
74
79
76
4
96
76
69
40
—
—
—
—
Me
Ph
3
Si
24
31
60
COOMe

P. Arsenyan et al. / Tetrahedron Letters 46 (2005) 1001–1003
1003
R
R
14.4, 24.9, 25.5, 61.6, 62.0, 128.0, 128.2, 128.7, 131.5,
35.1, 135.4, 165.8, 166.2. Anal. Calcd for
C H N O PPtSe : C, 41.53; H, 3.60; N, 3.23. Found:
1
4E - 7E
PhMe SiH
3
0
31
2
4
2
2
SiMe Ph
2
C, 41.42; H, 3.58; N, 3.26.
. Single-crystal X-ray diffraction: Nonius KappaCCD
R
+
7
3
˚
SiMe Ph
difractometer (Mo Ka-radiation, k = 0.71073 A; T =
2
2
93(2) K). The structure was solved by direct methods
SIR-97, Altomare, A.; Burla, M. C.; Camalli, M.;
6
Z - 7Z
(
Cascarano, G. L.; Giacovazzo, C.; Guagliardi, A.; Moli-
terni, A. G. G.; Spagna, R. J. Appl. Cryst. 1999, 32, 115)
Scheme 2. Hydrosilylation of terminal acetylenes with dimethylphen-
ylsilane in the presence of catalyst 3.
2
and refined by FMLS on F (Sheldrick, G. M. SHELXL-97,
Program for Crystal Structure Refinement, Universit a¨ t
G o¨ ttingen, G o¨ ttingen (Germany), 1997) in anisotropic
approximation. Hydrogen atoms were refined by the
Despite the reports on the platinum catalysts of Kar-
1
1
riding model. C30
let crystals, 0.10 · 0.11 · 0.26 mm; monoclinic, space
group P2 /c (No 14); a = 9.2592(1), b = 15.5252(3),
c = 23.8922(5) A,
31 2 4 2 r
H N O PPtSe , M = 867.55, dark-vio-
stedt et al. and Lewis et al. our attempts to use catalyst
in the hydrosilylation of vinylsilanes with phenyldi-
methylsilane failed.
3
1
˚
˚
3
b = 110.609(1)ꢁ,
V = 3214.7(1) A ;
À1
À3
Z = 4; l = 6.715 mm
;
q
calcd = 1.792 g cm
;
15535
In summary, we have presented a method for the synthe-
sis of a new type of platinum heterocycle and it crystal
structure. It was found that the selenoplatinum com-
pound acted as a selective catalyst in hydrosilylation
reactions to yield b-(Z)- and b-(E)-silylethylenes.
reflections (2hmax = 60ꢁ), 9289 unique (Rint = 0.034), 360
parameters; largest max/min in final difference Fourier
˚
synthesis: 6.113 e A
À3.904 e A
À3
˚
(0.807 A from Pt atom)/
max/min transmission 0.5532/0.2742;
˚
À3
R = 0.078 (for 6386 reflections with I > 2r(I)), wR (on
F ) = 0.172. CCDC-233367 contains supplementary crys-
2
tallographic data for this paper. These data can be
obtained free of charge via www.ccdc.acm.ac.uk/conts/
retrieving.html.
Acknowledgements
8
. (a) Dey, S.; Jain, V. K.; Knoedler, A.; Kaim, W.; Zalis, S.
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J. D. Angew. Chem., Int. Ed. Engl. 1989, 28, 1047–1049.
. (a) Sheludyakov, V. D.; Zhun, V. I.; Lakhtin, V. G.;
Bochkarev, V. N.; Slyusarenko, T. F.; Nosova, V. N.;
Kisin, A. V. Zh. Obsch. Khim. 1984, 54, 640–646; (b)
Voronkov, M. G.; Yarosh, O. G.; Tsvetaeva, L. V.;
Sigalov, M. G.; Gromkova, R. A. Zh. Obsch. Khim. 1974,
44, 1747–1750; (c) Voronkov, M. G.; Yarosh, O. G.;
Pestunovich, V. A.; Sigalov, M. G.; Tsvetaeva, L. V. Izv.
Akad. Nauk SSSR, Ser. Khim. 1974, 2066–2070; (d)
Lukevics, E.; Sturkovich, R. Ya.; Pudova, O. A. J.
Organomet. Chem. 1985, 292, 151–158; (e) Lukevics, E.;
Pudova, O.; Sturkovich, R.; Gaukhman, A. J. Organomet.
Chem. 1988, 346, 297–303; (f) Marciniec, B.; Gulinski, J.;
Urbaniak, W.; Kornetka, Z. W. In Comprehensive Hand-
book on Hydrosilylation; Marciniec, B., Ed.; Pergamon:
Oxford, 1992.
Financial support of this work by the Latvian Council
of Science (grant no 189) is gratefully acknowledged.
9
References and notes
1
. (a) Ando, W.; Tokitoh, N. Heteroatom Chem. 1991, 1; (b)
Reid, D. H. In Comprehensive Heterocyclic Chemistry II:
A Review of the Literature 1982–1995; Torr, R. C. S., Ed.;
Pergamon: Oxford, 1996; Vol. 4, pp 743–777; (c) Regidz,
M.; Krill, S. Phosphorus Sulfur Silicon Relat. Elem. 1996,
9
9, 15–31.
2
. Cervantes-Lee, F.; Parkanyi, L.; Kapoor, R. N.; Mayr, A.
J.; Pannell, K. H.; Pang, Y.; Barton, T. J. J.Organomet.
Chem. 1998, 562, 29–33.
3
. (a) Knebel, J.; Morley, C. P.; Wilke, G.; Kruger, C.;
Wallis, J. M. J. Organomet. Chem. 1987, 334, C39–C40;
(
b) Morley, C. P. Organometallics 1989, 8, 800–804; (c)
Morley, C. P.; Vaughan, R. R. J. Chem. Soc., Dalton
Trans. 1993, 703–706.
. (a) Ford, S.; Morley, C. P.; Di Vaira, M. Chem. Commun.
10. General procedure for the hydrosilylation reactions: The
reactions were conducted in Pierce reactors at 80 ꢁC. A
mixture of hydrosilane (0.5 mmol), terminal acetylene
4
À6
1998, 1305–1306; (b) Ford, S.; Khanna, P. K.; Morley, C.
P.; Di Vaira, M. J. Chem. Soc., Dalton Trans. 1999, 791–
(0.5 mmol) and catalyst 3 (1 · 10 mol) was heated
for 2 h. The ratio of isomers was determined on the basis
1
7
1
96; (c) Khanna, P. K.; Morley, C. P. J. Chem. Res. (S)
995, 64–65.
of GC–MS and H NMR spectra. b-(E)-2-Dimethylphe-
nylsilylstyrene (6E). GC–MS (m/z): 238 [M ] (32), 223
+Å
+
Å
+Å
5
6
. Lalezari, I.; Shafiee, A.; Yalpani, M. J. Org. Chem. 1971,
836–2842.
[M ÀCH ] (39), 207 [M À2 CH ] (5), 197 (15), 145 (24),
Å
3
3
+
1
2
135 [M ÀPhCH@CH] (100), 105 (20). H N MR
(200 MHz, CDCl , 298 K): 0.26 (6H, s), 5.65 (1H, d,
. General procedure for the synthesis of 3,5-dimethyl-1,7-
diselena-3a,4-diaza-7a-triphenylphosphino-7a-platinaind-
ene-2,6-dicarboxylic acid diethyl ester (3): Selenadiazole 1
3
J = 3.0 Hz), 5.98 (1H, d, J = 3.0 Hz), 7.29–7.55 (10H,
arom). Methyl b-(Z)-2-phenyldimethylsilylacrylate (7Z).
+
Å
+Å
(
(
0.05 mmol) and tetrakis(triphenylphosphino)platinum
0.05 mmol) were dissolved in 5 mL of toluene. The
GC–MS (m/z): 220 [M ] (5), 205 [M ÀCH ] (100), 189
3
+Å
(15), 175 (57), 151 (84), 143 (40), 135 [M ÀCH@CHCO-
1
OMe] (45), 121 (40). H NMR (200 MHz, CDCl , 298 K):
reaction mixture was heated at 130 ꢁC for 1 h. The solvent
was evaporated and the residue purified by column
chromatography on silica gel using petroleum ether/
3
0.41 (6H, s), 3.69 (3H, s), 5.97 (1H, d, J = 3.2 Hz), 6.85
(1H, d, J = 3.2 Hz), 7.32–7.38 (3H, arom), 7.46–7.55 (2H,
arom).
1
dichloromethane (1:5, R
f
= 0.60), mp = 210–212 ꢁC.
H
NMR (200 MHz, CDCl , 298 K): 1.22 (3H, t, J = 6.5 Hz),
3
11. (a) Karstedt, B. D.; Bruce, D. P16134j Ger. Offen
2,307,085, 1973; CA 1974, 80; (b) Lewis, L. N.; Coborn,
R. E.; Grade, H.; Bryant, G. L.; Sumpter, C. A.; Scott, R.
A. Organometallics 1995, 14, 2202–2213.
1
.29 (3H, t, J = 6.5 Hz), 2.78 (3H, s), 2.90 (3H, s), 4.35
2H, q, J = 6.5 Hz), 4.38 (2H, q, J = 6.5 Hz), 7.45–7.74
(
(
1
3
3
15H, arom). C NMR (50.31 MHz, CDCl , 298 K): 13.6,