Novel C-C and C-C-P coupling reactions using an allenylidenerhodium complex as a precursor

Full text of DOI:10.1021/ja953911v

J. Am. Chem. Soc. 1996, 118, 2495-2496
Communications to the Editor
Scheme 1a
2495
Novel C-C and C-C-P Coupling Reactions Using
an Allenylidenerhodium Complex as a Precursor
Ralf Wiedemann, Paul Steinert, Olaf Gevert, and
Helmut Werner*
Institut fu¨r Anorganische Chemie der
UniVersita¨t Wu¨rzburg, Am Hubland, D-97074 Wu¨rzburg
Germany
ReceiVed NoVember 21, 1995
After we had recently shown that the Selegue method for
the preparation of transition-metal allenylidenes1 can also be
applied to the synthesis of the square-planar rhodium complexes
trans-[RhCl(dCdCdCRR′)(PiPr3)2],2 we started to investigate
the reactivity of these molecules. In this paper we describe two
types of C-C and C-C-P coupling reactions involving the
rhodium-bonded allenylidene unit which finally lead to vinyl-
allenes and a highly unsaturated Wittig-type ylide.
Compound 1, which was prepared from [RhCl(PiPr3)2]2 and
HCtCCPh2OH,2a reacted with NaC5H5 in THF at room
temperature to give the half-sandwich type complex 2 as a dark-
green solid in 62% yield. If, however, instead of sodium
cyclopentadienide the vinyl Grignard reagent CH2dCHMgBr
(in toluene/THF) was used as the substrate, not only the
substitution of chloride by the C-nucleophile but also coupling
of the vinyl and the allenylidene ligand occurred. The π-allylic
complex 3 (Scheme 1), which forms red air-sensitive crystals,
was isolated in 61% yield.3 With regard to the mechanism of
this reaction, we assume that initially a four-coordinate inter-
mediate A is generated which rearranges by migratory insertion
to give 3. In this context it should be mentioned that the
vinylidene compounds trans-[RhCl(dCdCHR)(PiPr3)2] (R )
H, tBu, Ph) react with CH2)CHMgBr to yield the isolable
products trans-[Rh(CHdCH2)(dCdCHR)(PiPr3)2], which upon
heating (45-50 °C, benzene) slowly isomerize to give the
π-butadienyl complexes [Rh(η3-CH2CHCdCHR)(PiPr3)2].4
Treatment of a solution of 3 at 10 °C in benzene with CO
led to a rapid change of color from red to light-yellow and fi-
nally to the isolation of yellow crystals of trans-[Rh{η1-
C(CHdCH2)dCdCPh2}(CO)(PiPr3)2] 4 in 65% yield.5 The
addition of CO to the metal center is accompanied by a π-σ
conversion of the C5 ligand, possibly via an 18-electron
intermediate [Rh(η3-CH2CHCdCdCPh2)(CO)(PiPr3)2]. The
X-ray crystal structure analysis of 4 reveals a square-planar
coordination sphere around rhodium with the two phosphines
in a trans disposition.6 The C1-C4-C5 chain is almost linear
a
L ) PiPr3.
(177.5(5)°) with the vinyl carbon atoms C2 and C3 lying in the
same plane as Rh, C1, C4, and C5.
The cleavage of the Rh-C σ-bond in 4 by an equimolar
amount of acetic acid in benzene at 10 °C proceeded smoothly
and gave, besides trans-[Rh(η1-O2CCH3)(CO)(PiPr3)2],7 quan-
titatively the new vinylallene 5. One characteristic feature of
the 13C NMR spectrum of 58 is the low-field signal at δ 210.20
for the central CdCdC carbon atom, the position of which is
typical for organic allenes.9
A second C3 + C2 + P coupling reaction with complex 1 is
even more exceptional. If a solution of 1 and phenylacetylene
in benzene was stirred for 20 h at 10 °C, a gradual change of
color from red to bright-red occurred, and, after removal of the
solvent, light-red crystals of 6 (Scheme 2) were isolated from
CH2Cl2/pentane in practically quantitative yield. Both the
elemental analysis and the mass spectrum of 6 indicated that a
1:1 adduct of 1 and the alkyne was formed which according to
the 31P NMR spectrum contained two distinctly different PiPr3
groups.10 As the X-ray structural analysis confirmed,11 one of
(1) Selegue, J. P. Organometallics 1982, 1, 217-218.
(2) (a) Werner, H.; Rappert, T. Chem. Ber. 1993, 126, 669-678. (b)
Werner, H.; Rappert, T.; Wiedemann, R.; Wolf, J.; Mahr, N. Organome-
tallics 1994, 13, 2721-2727.
(6) Molecular structure of complex 4. Principal bond lengths (Å) and
interbond angles (deg): Rh-C1 2.143(5), Rh-C36 1.814(6), Rh-P1 2.359-
(1), Rh-P2 2.340(1), C1-C2 1.481(6), C1-C4 1.308(6), C2-C3 1.311-
(7), C4-C5 1.332(6), C36-O 1.166(8), P1-Rh-P2 164.92(4), C1-Rh-
C36 165.8(2), C1-Rh-P1 91.8(1), C1-Rh-P2 93.0(1), P1-Rh-C36
89.1(2), P2-Rh-C36 89.7(2), Rh-C1-C2 116.9(3), Rh-C1-C4 127.0-
(3), Rh-C36-O 172.6(5), C1-C2-C3 126.2(5), C2-C1-C4 116.0(4),
C1-C4-C5 177.5(5).
(3) Selected spectroscopic data of 3: 1H NMR (C6D6, 400 MHz) δ 4.79
1
1
3
1
2
1
2
(dd, JH -H ) 12.1, JH -H ) 6.8 Hz, H2CCH C), 3.01 (d, JH -H ) 6.8 Hz,
H2 (syn) of CH2), 2.45 (dd, JP -H ) 5.8, JH -H ) 12.1 Hz, H3 (anti) of
CH2); 13C{1H} NMR (C6D6, 100.6 MHz) δ 183.11 (s, CdCdCPh2), 113.19
(ddd, JRh-C ) 54.0, JP-C ) 17.1 and 16.7 Hz, CdCdCPh2), 106.89 (m,
H2CCHC), 79.74 (s, CPh2), 50.32 (m, CH2).
2
3
1
3
(7) (a) Ohgomori, Y.; Yoshida, S.; Watanabe, Y. J. Chem. Soc., Dalton
Trans. 1987, 2969-2974. (b) Scha¨fer, M.; Wolf, J.; Werner, H. J.
Organomet. Chem. 1995, 476, 85-91.
(4) Wiedemann, R.; Wolf, J.; Werner, H. Angew. Chem. 1995, 107,
1359-1361. Angew. Chem., Int. Ed. Engl. 1995, 34, 1244-1246.
(8) Selected spectroscopic data of 5: 13C{1H} NMR (C6D6, 100.6 MHz)
δ 210.2 (s, CdCdC), 132.54 (s, CHdCH2), 117.02 (s, CHdCH2), 111.97
(s, dCPh2), 97.94 (s, dCHCHdCH2).
(5) Selected spectroscopic data of 4: IR (C6H6) ν(CtO) ) 1930 cm-1
;
1H NMR (C6D6, 200 MHz) δ 6.84 (dd, JH -H ) 17.0, JH -H ) 9.5 Hz,
1
2
1
3
CH1dCH2), 5.97 (dd, JH -H ) 17.0, JH -H ) 3.1 Hz, H2 (trans to H1) of
(9) Munson, J. W. The Chemistry of Ketenes, Allenes and Related
Compounds; Patai, S., Ed.; Wiley: New York, 1980; Vol. 1, Chapter 5.
(10) Selected spectroscopic data of 6: 1H NMR (C6D6, 400 MHz) δ
1
2
2
3
CH2), 5.11 (dd, JH -H ) 9.5, JH -H ) 3.1 Hz, H3 (cis to H1) of CH2);
13C{1H} NMR (C6D6, 50.3 MHz) δ 209.92 (t, JP-C ) 3.2 Hz, CdCdCPh2),
195.12 (dt, JRh-C ) 55.8, JP-C ) 22.3 Hz, RhCO), 144.45 (s, br, CHdCH2),
118.76 (dt, JRh-C ) 27.0, JP-C ) 11.4 Hz, RhC), 117.80 (s, CH2), 98.37
(s, CPh2); 31P{1H} NMR (C6D6, 81.0 MHz) δ 47.33 (d, JRh-P ) 135.1
Hz).
1
3
2
3
2.36 (dd, JP -H ) 9.6, JP -H ) 5.6 Hz, CHPiPr3); 13C{1H} NMR (CDCl3,
100.6 MHz) δ 187.49 (s, CdCdCPh2), 108.87 (s, CPh2), 106.69 (m,
2
1
1
1
CdCdCPh2), 71.80 (d, JP-C ) 6.8 Hz, CHCPhC), 20.94 (ddd, JRh-C
)
65.8, JP-C ) 25.8 and 10.6 Hz, CHPiPr3); 31P{1H} NMR (CDCl3, 162.0
0002-7863/96/1518-2495$12.00/0 © 1996 American Chemical Society

2496 J. Am. Chem. Soc., Vol. 118, No. 10, 1996
Communications to the Editor
Scheme 2a
with CO (C6H6, 10 °C, 30 s). The rhodium containing products
are trans-[RhCl(CO)(PiPr3)2]16 and [RhCl(CO)2]2.17 Ylide 7
was isolated upon extraction of the product mixture with pentane
1
as a violet solid and characterized by H, 13C, and 31P NMR
spectroscopic data. The influence of the butatrienyl substituent
on the electronic properties of the ylide carbon is reflected by
the signal of the PdCH proton which appears at δ 3.05 and is
shifted ca. 4 ppm downfield compared with the PdCH2
resonance of iPr3PdCH2.18
In conclusion, the results reported in this paper illustrate that
not only carbene-19 and vinylidenerhodium complexes20 but also
the related allenylidene compounds can be used as starting
materials for C-C and even C-C-P coupling reactions.
Experiments presently in progress are aimed to find out whether
migratory insertion reactions, similar to the key step in the
formation of 3, can also occur with ligands other than vinyl
groups.
a
L ) PiPr3.
Acknowledgment. We are grateful for financial support of this work
from Volkswagenstiftung, Deutsche Forschungsgemeinschaft (SFB
347), and Fonds der Chemischen Industrie. We also thank Dr. Justin
Wolf for helpful advice.
the phosphines is still coordinated to the metal center while the
other is part of a π-bonded unsaturated ylide which is formed
from the allenylidene, the alkyne, and the phosphine. The PC5
ligand is coordinated like a π-allyl unit; however, the distances
between the rhodium and the carbon atoms C1, C2, and C3
differ by ca. 0.15 Å. The bond length P2-C1 (1.752(3) Å) is
significantly shorter than a P-C single bond but quite similar
to that of [RhCl{η3-anti-CH(PiPr3)C(Ph)dO}(PiPr3)] (1.799-
(4) Å)12 and of metal-substituted ylides.13 Although the carbon
atoms of the dCdCPh2 unit are not coplanar with the allylic
fragment, the C3-C4-C5 chain is almost linear (177.3(4)°)
with C3-C4 and C4-C5 distances that are comparable to those
in the allenylidene complex trans-[RhCl{dCdCdC(Ph)Tol}-
(PiPr3)2] (1.24(1) and 1.37(1) Å)2b and in 2 (1.29(2) and 1.39-
(2) Å).14
Supporting Information Available: Experimental procedures and
analytical and spectroscopic data for compounds 2-7, details of the
X-ray analysis of 4 and 6, tables of the bond lengths and bond angles,
and atomic positional and anisotropic thermal parameters (26 pages).
This material is contained in libraries on microfiche, immediately
follows this article in the microfilm version of the journal, can be
ordered from the ACS, and can be downloaded from the Internet; see
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instructions.
JA953911V
(15) Selected spectroscopic data of 7: 1H NMR (C6D6, 400 MHz) δ
3.05 (d, JP-H ) 15.2 Hz, CHPiPr3); 13C{1H} NMR (C6D6, 100.6 MHz) δ
45.88 (d, JP-C ) 100.8 Hz, iPr3PdCHR); 31P{1H} NMR (C6D6, 162.0 MHz)
δ 33.57 (s)
(16) (a) Busetto, C.; D’Alfonso, A.; Maspero, F.; Perego, G.; Zazzetta,
A. J. Chem. Soc., Dalton Trans. 1977, 1828-1834. (b) Wang, K.; Rosini,
G. P.; Nolan, S. P.; Goldman, A. S. J. Am. Chem. Soc. 1995, 117, 5082-
5088.
(17) McCleverty, J. A.; Wilkinson, G. Inorg. Synth. 1968, 8, 211-214.
(18) Ko¨ster, R.; Simic, D.; Grassberger, M. A. Justus Liebigs Ann. Chem.
1970, 739, 211-219.
(19) (a) Wulff, W. D. In ComprehensiVe Organic Synthesis; Trost, B.
M., Fleming, I., Eds.; Pergamon Press: New York, 1991; Vol. 5. (b) Fryzuk,
M. D.; Gao, X.; Rettig, S. J. Organometallics 1995, 14, 4236-4241 and
references therein.
The free ylide 7,15 which to the best of our knowledge is
unknown as yet, can be generated on treatment of complex 6
MHz) δ 52.90 (dd, JRh-P ) 179.6, JP-P ) 14.3 Hz, Rh-P1), 39.29 (dd,
JRh-P ) 4.2, JP-P ) 14.3 Hz, C-P2); MS (70 eV) m/z (%) ) 750 (2) [M+].
(11) Molecular structure of complex 6. Principal bond lengths (Å) and
interbond angles (deg): Rh-P1 2.295(1), Rh-C1 2.170(4), Rh-C2 2.046-
(3), Rh-C3 2.024(3), Rh-Cl 2.388(1), C1-P2 1.752(3), C1-C2 1.455-
(4), C2-C3 1.429(4), C3-C4 1.276(4), C4-C5 1.327(4), P1-Rh-Cl
94.93(4), P2-C1-C2 126.1(2), C1-C2-C3 116.7(3), C2-C3-C4 144.2-
(3), C3-C4-C5 177.3(4).
(12) Werner, H.; Mahr, N.; Frenking, G.; Jonas, V. Organometallics
1995, 14, 619-625.
(13) Inter alia: (a) Fachin, G.; Bertani, R.; Zanotto, L.; Galligaris, M.;
Nardin, G. J. Organomet. Chem. 1989, 366, 409-420. (b) Werner, H.;
Schippel, O.; Wolf, J.; Schulz, M. J. Organomet. Chem. 1991, 417, 149-
162.
(20) (a) Bruce, M. I. Chem. ReV. 1991, 91, 197-257. (b) Fryzuk, M.
D.; Huang, L.; McManus, N. T.; Paglia, P.; Rettig, S. J.; White, G. S.
Organometallics 1992, 11, 2979-2990. (c) Wiedemann, R.; Steinert, P.;
Wolf, J.; Werner, H. J. Am. Chem. Soc. 1993, 115, 9864-9865. (d)
Wakatsuki, Y.; Yamazaki, H. J. Organomet. Chem. 1995, 500, 349-362.
(14) Windmu¨ller, B. Ph.D. Thesis, University Wu¨rzburg, to be submitted.