Rhodium complexes of 1,4-disubstituted-1,2,3-butatrienes: Their preparation and reactivity

Article abstract of DOI:10.1246/cl.2003.16

The 1,4-disubstituted butatrienes, (Z)-R-CH=C=C=CH-R (1, R = SiMe₃, t-Bu), reacted with RhCl(PAr₃)₃ (Ar = Ph, p-tolyl) to give rhodium-(Z)-butatriene complexes 3. The butatrienes coordinated to Rh with the central double b

Full text of DOI:10.1246/cl.2003.16

16
Chemistry Letters Vol.32, No.1 (2003)
Rhodium Complexes of 1,4-Disubstituted-1,2,3-butatrienes: Their Preparation and Reactivity
Noriyuki Suzuki,ꢀ Yoshiyuki Fukuda,y Chae Eun Kim,# Hidemichi Takahara,y Masakazu Iwasaki,y Masahiko Saburi,y
Masayoshi Nishiura, and Yasuo Wakatsuki##
RIKEN (The Institute of Physical and Chemical Research), Wako, Saitama 351-0198
yDepartment of Environmental Engineering, Faculty of Engineering, Saitama Institute of Technology, Okabe, Saitama 369-0293
(Received August 14, 2002; CL-020693)
The 1,4-disubstituted butatrienes, (Z)-R-CH=C=C=CH-R
(1, R = SiMe3, t-Bu), reacted with RhCl(PAr3)3 (Ar = Ph, p-
tolyl) to give rhodium-(Z)-butatriene complexes 3. The buta-
trienes coordinated to Rh with the central double bond in an ꢀ2-
fashion. (Z)-Butatrienes on 3 isomerized to (E)-form at 70 ꢁC to
afford (E)-butatriene complexes 4 with excellent E=Z ratios
(E=Z = 97/3–99/1). The molecular structure of 4b (R = SiMe3,
Ar = p-tolyl) was determined by X-ray diffraction analysis.
Hydrosilation of 1 was catalyzed by rhodium complexes to give
allenes as major products accompanied by 1,3-dienes as minor
ones, which are results of 2,1-addition and 2,3-anti-addition of the
silane.
Scheme 1. Formation of Rh-(Z)-butatriene complexes.
Quaternary cumulene carbons (13C NMR: 1a: 182.99, 1b:
160.17 ppm) appeared upfield owing to coordination to rhodium
(3a: 156.97, 3b: 158.60, 3c: 131.47 ppm), and methines in the
butatrienes at the sp2-carbon region. Two trimethylsilyl (3a,b) or
tert-butyl (3c) groups, methines, and quaternary carbons in 3 were
observed as single signals showing their symmetrical structure.
These results indicated that butatrienes 1 coordinated to rhodium
with the central double bond in an ꢀ2-fashion as well as the known
rhodium-butatriene complexes.3;17{19 X-ray diffraction analysis
of 3b supported this structure although the refinement was not
satisfactory because of disorder observed in the solvated diethyl
ether molecule. The butatriene moiety was slightly bent out and
the trimethylsilyl groups were located away from the metal.
To our interest, coordinated (Z)-butatriene moieties in 3
isomerized to an (E)-form by heating in benzene at 70 ꢁC for 3 h to
give (E)-butatriene complexes 4 (Scheme 2). 1H and 13C NMR
spectroscopy showed that four carbons in the butatriene unit are
unequivalent.20 Figure 1 illustrates the molecular structure of
4b.21 The butatriene bonds to rhodium in an ꢀ2-fashion as well as
3b, and other structural features were similar to the reported
complexes. It should be noted that the E=Z ratios (4/3) in
equilibria are extremely high (97/3–99/1). Similar equilibrium
was also observed in the zirconium complexes 2. The ratio,
however, was 3/1–9/1. It is probably due to steric repulsion
between bulky trimethylsilyl or tert-butyl groups in 3. To the best
of our knowledge, this is the first example of E=Z isomerization of
ꢁ-coordinated butatrienes on transition metals, although its
mechanism is still vague.
1,2,3-Butatrienes have long attracted organometallic chem-
ists because of their highly unsaturated structure.1{4 However,
reactivity and transformation of the coordinated butatrienes on
metal complexes have been rarely described,5;6 although some
catalytic reactions were reported.7{9 Besides, most examples
described transition metal complexes of 1,1,4,4-tetrasubstituted
butatrienes. There have been only a few reports on transition
metal complexes of 1,4-disubstituted butatrienes probably
because of their unavailability.10 Straightforward and highly
selective synthesis of (Z)-R–CH=C=C=CH–R (1a: R = Me3Si,
1b: R = t-Bu) from 1-alkynes in the presence of ruthenium
catalysts was reported from our laboratory.11{13 This prompted us
to study the reactivity of (Z)-1,4-disubstituted butatrienes with
transition metal complexes.
R
R
H
R
H
+
'Cp2Zr'
C
C C C
(1)
Cp2Zr
1
R
a: R = SiMe3
b: R = t-Bu
2
We recently reported the preparation of zirconocene com-
plexes of 1. Their structures are 1-zirconacyclopent-3-ynes (2)
that are the first isolated and structurally characterized five-
membered cyclic alkynes (Eq 1).14 In the most of known
mononuclear butatriene complexes, butatrienes coordinated to
metals in an ꢀ2-ꢁ-coordination mode.15 It must be of interest to
examine if 1 gives a metallacyclopentyne or an ꢀ2-ꢁ-complex
with other metals, in particular, late-transition metals. Herein we
report the synthesis of rhodium-1,4-disubstituted butatriene
complexes, E=Z isomerization of 1 on the metal, and rhodium-
catalyzed reactions of 1.
H
H
R
R
R
H
C
C
PA r3
PAr 3
C
C
Cl Rh
Ar3P
Cl Rh
Ar3P
C
C
C
Benzene
70 °C, 3h
C
H
R
3a-c
4a-c
Butatriene 1 was mixed with an equimolar rhodium complex,
RhCl(PAr3)3 (Ar = Ph, p-tolyl), in benzene at room temperature.
After stirring for 1 h, the formation of butatriene complex 3 was
observed by NMR spectroscopy in good yields (Scheme 1).16
a: 58%, E/Z = 97/3
b: 89%, E/Z = 97/3
c: 83%, E/Z = 99/1
Scheme 2. Isomerization of butatrienes on Rh complexes.
Copyright ꢀ 2003 The Chemical Society of Japan

Chemistry Letters Vol.32, No.1 (2003)
17
1
2
A. Nakamura, P.-J. Kim, and N. Hagihara, J. Organomet. Chem., 3, 7 (1965).
a) K. K. Joshi, J. Chem. Soc. A, 1966, 594. b) D. Bright and O. S. Mills, Chem.
Commun., 1966, 211.
3
L. Hagelee, R. West, J. Calabrese, and J. Norman, J. Am. Chem. Soc., 101,
4888 (1979).
4
5
6
7
U. Schubert and J. Gronen, Organometallics, 6, 2459 (1987).
¨
A. Maercker and A. Groos, Angew. Chem., Int. Ed. Engl., 35, 210 (1996).
L. Stehling and G. Wilke, Angew. Chem., Int. Ed. Engl., 27, 571 (1988).
M. Iyoda, S. Tanaka, H. Otani, M. Nose, and M. Oda, J. Am. Chem. Soc., 110,
8494 (1988).
8
9
T. Kusumoto and T. Hiyama, Bull. Chem. Soc. Jpn., 63, 3103 (1990).
L. Stehling and G. Wilke, Angew. Chem., Int. Ed. Engl., 24, 496 (1985).
10 a) A. Nakamura, Bull. Chem. Soc. Jpn., 38, 1868 (1965). b) R. O. Angus, Jr.,
M. N. Janakiraman, R. A. Jacobson, and R. P. Johnson, Organometallics, 6,
1909 (1987).
11 Y. Wakatsuki, H. Yamazaki, N. Kumegawa, T. Satoh, and J. Y. Satoh, J. Am.
Chem. Soc., 113, 9604 (1991).
ꢀ
Figure 1. Molecular structure of 4b; selected bond lengths (A)
and angles (deg).
12 Y. Wakatsuki, H. Yamazaki, N. Kumegawa, and P. S. Johar, Bull. Chem.
Soc. Jpn., 66, 987 (1993).
13 a) Y. Suzuki, R. Hirotani, H. Komatsu, and H. Yamazaki, Chem. Lett., 1999,
1299. b) M. Ogasawara, H. Ikeda, K. Ohtsuki, and T. Hayashi, Chem. Lett.,
2000, 776. c) T. Ohmura, S. Yorozuya, Y. Yamamoto, and N. Miyaura,
Organometallics, 19, 365 (2000).
Hiyama reported that hydrosilation of 1,1,4,4-tetrakis(tri-
methylsilyl)butatriene catalyzed by rhodiumcomplexes gave 1,2-
addition products in which a silyl group attached at the terminal
position.8 When 1 was treated with diphenylsilane in the presence
of a catalytic amount of RhCl(PPh3)3, hydrosilated products were
obtained in moderate yields (Scheme 3).22 Contrary to the
previous results, allenes 5 were obtained as major products. These
have a silyl group at the internal position as a result of 2,1-
addition, while 2,3-addition gave 1,3-dienes 6 as minor products.
Interestingly, 6 is formally an anti-addition product. A reaction of
1a using Ph2SiD2 (97%D) gave deuterated products 7 and 8.
Deuterium was incorporated at C1 in 7 and C3 in 8 (96 and
97%D). It should be noted that D was not attached at the other
carbons. The possibility that (Z)-1 isomerized to 1,3-enyne 9 and
this accepted hydrosilation to give 6 can be ruled out. However, it
is not clear yet whether 6 formed via direct anti-addition of Si–H
on (Z)-1 or syn-addition to (E)-1 that was isomerized from (Z)-1.
Further investigation is now in progress.
14 N. Suzuki, M. Nishiura, and Y. Wakatsuki, Science, 295, 660 (2002).
15 Cumulenylidene complexes are also known, see: M. I. Bruce, Chem. Rev.,
98, 2797 (1998) and the references cited therein.
16 3a: 1H NMR (C6D6, Me4Si) d ¼ À0:14 (s, 18H), 6.71 (d, 3JRh-H ¼ 2:6 Hz,
2H), 7.01–7.13 (m, 18H), 7.90–7.97 (m, 12H). 13C NMR (C6D6, Me4Si)
d ¼ À0:67, 124.34, 127.77 (3JP-C ¼ 5:0 Hz), 129.45, 132.95 (1JP-C
¼
¼
1
2
21:2 Hz), 135.15 (2JP-C ¼ 6:1 Hz), 156.97 (q, JRh-C ¼ 12:9, JP-C
1
3:4 Hz). 31P NMR (C6D6, H3PO4) d ¼ 31:2 (d, JP-Rh ¼ 138:1 Hz). 29Si
3
NMR (C6D6, Me4Si) d ¼ À11:5 (d, JSi-Rh ¼ 3:2 Hz). Anal. Calcd for
C
46H50ClP2RhSi2: C 64.29H 5.86, Found:C 64.72, H5.84. Yield 83% by 1H
NMR (35% isol.).
17 P. J. Stang, M. R. White, and G. Maas, Organometallics, 2, 720 (1983).
18 a) H. Werner, M. Laubender, R. Wiedemann, and B. Windmuller, Angew.
¨
Chem., Int. Ed. Engl., 35, 1237 (1996). b) K. Ilg and H. Werner, Chem.—Eur.
J., 7, 4633 (2001).
19 J.-D. van Loon, P. Seiler, and F. Diederich, Angew. Chem., Int. Ed. Engl., 32,
1187 (1993).
20 4a: 1H NMR (C6D6, Me4Si) d ¼ À0:18 (s, 9H), 0.33 (s, 9H), 5.71 (dd,
5JH-H ¼ 3:0, 3JRh-H ¼ 3:0 Hz, 1H), 6.02 (dd, 5JH-H ¼ 3:0, 3JRh-H ¼ 3:0 Hz,
1H), 7.06 (m, 18H), 7.90 (m, 12H). 13C NMR (C6D6, Me4Si) d ¼ À0:40,
0.40, 116.22, 122.16, 127.66 (3JP-C ¼ 4:5 Hz), 129.69, 131.85 (1JP-C
¼
¼
1
2
21:2 Hz), 135.21 (2JP-C ¼ 5:9 Hz), 154.66 (q, JRh-C ¼ 13:4, JP-C
R
R
1
2
3:7 Hz), 157.07 (q, JRh-C ¼ 15:1, JP-C ¼ 3:9 Hz). 31P NMR (C6D6,
Ph2HSi
1
H3PO4) d ¼ 39:3 (d, JP-Rh ¼ 134:3 Hz). 29Si NMR (C6D6, Me4Si) d ¼
4 mol%
RhCl(PPh3)3
3
3
5a: 43%, 5b: 41%
À4:9 (d, JSi-Rh ¼ 3:7 Hz), À8:0 (d, JSi-Rh ¼ 1:8 Hz). Anal. Calcd for
R
H
R
H
C
46H50ClP2RhSi2: C 64.29, H 5.86, Found: C 64.04, H 5.87. Yield 58% by
+ Ph2SiH2
C C C C
R
in Et2O
rt, 1h
1H NMR (17% isol.).
21 4b: Crystal data: C52H62ClP2RhSi2, fw=943.50, orthorhombic, space
R
1
ꢀ
group = Pna2(1), a ¼ 33:305ð4Þ, b ¼ 11:4630ð12Þ, c ¼ 12:9333ð13Þ A,
a: R = SiMe3
b: R = t-Bu
SiHPh2
ꢀ 3
V ¼ 4937:5ð9Þ A , Z ¼ 4, Dcalcd ¼ 1:269 g/cm3, R ¼ 0:057, Rw ¼ 0:125.
6a: 23%, 6b: 2%
Data were collected on Bruker APEX diffractometer with a CCD area
detector, using graphite monochromated Mo Ka radiation at 110 K. A total
of 37042 reflections was measured. The structure was solved by direct
methods and refined on F2 by full-matrix least-squares techniques. The final
cycle of least-squares refinement was based on 14067 observed reflections
(I ꢂ 2sðIÞ) with 535 variable parameters. The data were deposited in
Cambridge Crystallographic Data Centre (CCDC 191256).
(97%)
D
(96%)
D
SiMe3
R
SiMe3
Me3Si
Me3Si
R
Ph2DSi
SiDPh2
7
8
9
Scheme 3. Hydrosilation of butatrienes catalyzed by Rh complexes.
22 Typically, to a solution of RhCl(PPh3)3 (18.5 mg, 0.02 mmol) in diethyl
ether (0.5 mL) were added 1a (99 mg, 0.5 mmol) and diphenylsilane
(184 mg, 1 mmol). The mixture was stirred at room temperature for 1 h.
Usual workup gave 5a and 6a (Y. 35% and 16% isolated). Yields were
determined by GC. 5a: 1H NMR (C6D6) d ¼ À0:01 (s, 9H), 0.06 (s, 9H),
1.37 (dd, J ¼ 15, 2.8 Hz, 1H), 1.48 (dd, J ¼ 15, 2.8 Hz, 1H), 4.5 (t,
The authors are grateful to Ms. Keiko Yamada for elemental
analysis. Dr. Hiroyuki Koshino is appreciated for characterization
of hydrosilation products by NMR. A part of this work was
financially supported by Mitsubishi Chemical Corporation Fund.
J ¼ 2:8 Hz, 1H), 5.38 (s, 1H, Si-H), 7.1–7.2 (m, 6H), 7.65–7.69 (m, 4H). 13
C
NMR (C6D6) d ¼ À0:77, À0:64, 17.57, 75.96, 78.15, 128.24, 129.98,
133.98, 135.99, 211.41. 6a: 1H NMR (C6D6) d ¼ 0:07 (s, 9H), 0.22 (s, 9H),
5.33 (s, 1H, Si-H), 6.05 (d, J ¼ 19:0 Hz, 1H), 6.49 (d, 4J ¼ 1:0 Hz, 1H), 7.16
(dd, 3J ¼ 19:0, 4J ¼ 1:0 Hz, 1H), 7.39 (m, 4H), 7.42 (m, 2H), 7.58 (dd,
J ¼ 7:8, 1.5 Hz, 4H). 13C NMR (C6D6) d ¼ À1:32, 0.46, 128.32, 130.00,
134.23, 136.22, 136.25, 147.44, 153.73, 155.65.
References and Notes
#
On leave from Dae-gu Christian University, Korea (JISTEC Winter Institute
Program, 2002)
## Current address: RIKEN Venture OM Chemtech Ltd., Wako, Saitama 351-
0198