Organic synthesis via transition metal complexes. 112. Reactivity enhancement of group VI Fischer carbene complexes by copper and rhodium catalysts: Experimental proof of a carbene rhodium complex as an intermediate

Article abstract of DOI:10.1021/om0103207

Rhodium(I) compounds were found to efficiently catalyze reactions of Fischer carbene complexes. It was shown that the thermally quite unreactive tungstaoctatetraenes 14a-d were readily transformed into spiro-fused vinylcyclopentadienes 15a-d in the presence of catalytic amounts of RhCl₃·3H₂O in MeOH or [(COD)RhCl]₂. A reactivity enhancement was observed also for the transformation of the tungsten complex 8a into vinylcyclopentadiene 10a. Experimental proof for the intermediacy of carbene rhodium complexes in these reactions was provided by preparation of the rhodaoctatetraene 16c from the reaction of the tungsten compound 14c with a stoichiometric amount of [(COD)RhCl]₂. The carbene rhodium compound 16c was transformed into the vinylcyclopentadiene 15c thermally in a smooth reaction and showed a catalytic activity similar to [(COD)RhCl]₂. Not only rhodium but also copper compounds were found to be good catalysts for the π-cyclization of tungstaoctatetraenes.

Full text of DOI:10.1021/om0103207

3
574
Organometallics 2001, 20, 3574-3581
Or ga n ic Syn th esis via Tr a n sition Meta l Com p lexes. 112.1
Rea ctivity En h a n cem en t of Gr ou p VI F isch er Ca r ben e
Com p lexes by Cop p er a n d Rh od iu m Ca ta lysts:
Exp er im en ta l P r oof of a Ca r ben e Rh od iu m Com p lex a s
a n In ter m ed ia te
Inigo G o¨ ttker-Schnetmann, Rudolf Aumann,* and Klaus Bergander
Organisch Chemisches Institut der Universit a¨ t M u¨ nster, Corrensstrasse 40,
D-48149 M u¨ nster, Germany
Received April 17, 2001
Rhodium(I) compounds were found to efficiently catalyze reactions of Fischer carbene
complexes. It was shown that the thermally quite unreactive tungstaoctatetraenes 14a -d
were readily transformed into spiro-fused vinylcyclopentadienes 15a -d in the presence of
catalytic amounts of RhCl
observed also for the transformation of the tungsten complex 8a into vinylcyclopentadiene
0a . Experimental proof for the intermediacy of carbene rhodium complexes in these reactions
was provided by preparation of the rhodaoctatetraene 16c from the reaction of the tungsten
compound 14c with a stoichiometric amount of [(COD)RhCl] . The carbene rhodium
compound 16c was transformed into the vinylcyclopentadiene 15c thermally in a smooth
reaction and showed a catalytic activity similar to [(COD)RhCl] . Not only rhodium but also
3
‚3H
2 2
O in MeOH or [(COD)RhCl] . A reactivity enhancement was
1
2
2
copper compounds were found to be good catalysts for the π-cyclization of tungstaocta-
tetraenes.
In tr od u ction
Application of Fischer carbene complexes to organic
has been shown by us for the first time that rhodium
compounds would catalyze an insertion of alkynes into
WdC and CrdC bonds of 4-amino-1-metalla-1,3-buta-
2
synthesis has been amply demonstrated over the past
8
dienes (M ) Cr, W) and of 6-amino-1-metalla-1,3,5-
3
decades. Even though transfer reactions of carbene
9
hexatrienes to give cyclopentadienes at temperatures
ligands from one metal to another have been reported,
they have not been considered a means to properly
adjust the reactivity of carbene complexes to a certain
as low as 20 °C (Scheme 1). Concerning the mechanism
(
4) (a) Fischer, E. O.; Beck, H.-J . Angew. Chem. 1970, 82, 44-45;
4
,5
synthetic goal. A brand new field of investigations is
now directed toward a reactivtiy enhancement of car-
bene complexes in catalytic processes involving carbene
transfer reactions. The investigation was initiated by
Angew. Chem., Int. Ed. Engl. 1970, 9, 72-73. (b) O¨ fele, K.; Herberhold,
M. Angew. Chem. 1970, 82, 775-776; Angew. Chem. 1970, 9, 739-
7
40. (c) Fischer, E. O.; Beck, H.-J .; Kreiter, C. G.; Lynch, J .; M u¨ ller,
J .; Winkler, E. Chem. Ber. 1972, 105, 162-172. (d) Casey, C. P.;
Anderson, R. L. J . Chem. Soc., Chem. Commun. 1975, 895-896. (e)
Kreiter, C. G.; O¨ fele, K.; Wieser, G. W. Chem. Ber. 1976, 106, 1749-
6
7
Sierra et al. and Narasaka et al., who, independently
of each other, reacted Fischer carbene chromium com-
plexes with olefins at ambient temperatures in the
presence of catalytic amounts of palladium compounds
and obtained coupling products of the carbene ligand
with the olefin instead of cyclopropanation products of
the olefin, in line with expectation of the chemistry of
palladium but not of chromium carbene complexes. It
1
758. (f) Ashworth, T.; Berry, M.; Howard, J . A. K.; Laguna, M.; Stone,
F. G. A. J . Chem. Soc., Dalton Trans. 1980, 1615-1624. (g) Berry, M.;
Martin-Gil, J .; Howard, J . A. K.; Stone, F. G. A. J . Chem. Soc., Dalton
Trans. 1980, 1625-1629. (h) Edwards, B. H.; Rausch, M. D. J .
Organomet. Chem. 1981, 210, 91-96. (i) Aumann, R.; Fischer, E. O.
Chem. Ber. 1981, 114, 1853-1857. (j) Wengrovius, J . H.; Schrock, R.
P. Organometallics 1982, 1, 148-155. (k) Theopold, K. H.; Bergmann,
R. G. J . Am. Chem. Soc. 1983, 105, 464-475. (l) Aumann, R.; Heinrich,
H.; Henkel, G.; Dartmann, M.; Krebs, B. Z. Naturforsch. 1983, 38b,
1325-1331. (m) Fischer, E. O.; B o¨ ck, M.; Aumann, R. Chem. Ber. 1983,
1
1
16, 3618-3623. (n) Fischer, E. O.; B o¨ ck, M. Monatsh. Chem. 1984,
15, 1159-1164. (o) Fehlhammer, W. P.; Achatz, D.; Plaia, U.; V o¨ lkl,
*
To whom correspondence should be addressed. Fax: ++49 251
33 6502. E-mail: aumannr@uni-muenster.de.
1) For part 111 see: G o¨ ttker-Schnetmann, I.; Aumann, R.; Kataeva,
O.; Holst, Ch.; Fr o¨ hlich, R. Organometallics 2001, 20, 2889-2904.
2) Fischer, E. O.; Maasb o¨ l, A. Angew. Chem. 1964, 76, 645-645;
Angew. Chem., Int. Ed. Engl. 1964, 3, 580-580.
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A. Z. Naturforsch. 1987, 42b, 720-727. (p) J ordi, L.; Moret o´ , J . M.;
Ricart, S.; Vi n˜ as, J . M. Organometallics 1992, 11, 3507-3510.
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F.-M.; Rajender Reddy, K.; Chen, Y.-C.; Lee, K.-J .; Lee, J .-H.; Lee, G.-
H.; Peng, S.-M.; Liu, S.-T. Organometallics 1999, 18, 2145-2154. (d)
Liu, S.-T.; Rajender Reddy, K. Chem. Soc. Rev. 1999, 28, 315-322.
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C.; Manche n˜ o, M. J .; G o´ mez-Gallego, M. J . Am. Chem. Soc. 2001, 123,
851-861.
8
(
(
(
Soc. Rev. 1999, 28, 187-198. (b) Wulff, W. In Comprehensive Orga-
nometallic Chemistry, Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.;
Pergamon Press: New York 1995; Vol. 12, Chapter 5.3. (c) Doyle, M.
P. In Comprehensive Organometallic Chemistry, Abel, E. W., Stone,
F. G. A., Wilkinson, G., Eds.; Pergamon Press: New York 1995; Vol.
2, Chapters 5.1 and 5.2. (d) Barluenga, J . Pure Appl. Chem. 1999,
1, 1385-1391. (e) Barluenga, J .; Fa n˜ an a´ s, F. J . Tetrahedron 2000,
6, 4597-4628. (f) Herndon, J . W. Coord. Chem. Rev. 1999, 181, 177-
42. (g) Herndon, J . W. Tetrahedron 2000, 56, 1257-1280.
1
7
5
2
(7) Sakurai, H.; Tanabe, K.; Narasaka, K. Chem. Lett. 1999, 75-
76.
(8) G o¨ ttker-Schnetmann, I.; Aumann, R. Organometallics 2001, 20,
346-354.
1
0.1021/om0103207 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 07/13/2001

Carbene Rhodium Complex as an Intermediate
Organometallics, Vol. 20, No. 16, 2001 3575
Sch em e 1. Rh od iu m -Ca ta lyzed In ser tion of a n Alk yn e in to a MdC Bon d Exem p lified by Tw o Differ en t
Rou tes to Vin ylcyclop en ta d ien es fr om (1-Alk yn yl)ca r ben e Com p lexes 1
of such transformation, up to date no experimental
evidence could be provided that showed that carbene
palladium or carbene rhodium complexes were involved
as intermediates. With regard to the formation of
vinylcyclopentadienes from group VI carbene complexes
and alkynes it was shown that the alkyne insertion step
was catalyzed by rhodium(I) species, but it was not
obvious that rhodaoctatetraenes thus generated would
undergo a π-cyclization to vinylcyclopentadienes 4 and
It was shown in recent studies that an addition of
2-amino-1,3-butadienes 7a ,b to (1-alkynyl)carbene com-
plexes 1a ,b resulted in formation of conjugated metal-
laoctatetraenes 8a -d as the major products as well as
[4+2]-cycloadduct 9a as the minor product (Scheme 2).11
The latter compound underwent a spontaneous cycliza-
tion at 20 °C to produce the tetracyclic compound 12a ,
while the 1-metallaoctatetraenes 8 exhibited a remark-
able thermal stability and even at 65 °C did not undergo
a π-cyclization (as anticipated on the basis of earlier
6
faster than the respective chroma- or tungstaocta-
1
2
tetraenes (Scheme 1).
studies ) to possibly afford vinylcyclopentadienes 10
and cycloheptatrienes 11, respectively. Heating of com-
pounds 8a -d to 65 °C resulted in formation of un-
We present experimental proof that it is not only the
insertion of an alkyne into a MdC bond that can be
catalyzed by rhodium but also the π-cyclization of the
resulting 1-metalla-1,3,5-hexatriene unit to a cyclopen-
tadiene. We now report on the preparation of a rhoda-
octatetraene from the reaction of a tungstaoctatetraene
with a stoichiometric amount of [(COD)RhCl]2 and its
smooth transformation into a vinylcyclopentadiene. It
was further demonstrated that the rhodaoctatetraene
thus generated was active as catalyst in this reaction.
Furthermore, we report on the first example of a copper-
catalyzed reaction of a carbene complex.
1
3
tractable mixtures, while 1-tungsta-1,3,5,7-octatetra-
ene 8e gave the cyclohexadiene derivative in 10% yield,
1
4
but no cyclopentadiene.
Resu lts a n d Discu ssion
While the 1-tungsta-1,3,5,7-octatetraene 8a did not
undergo a π-cyclization at 65 °C (Scheme 2), this
compound could be smoothly transformed into the
vinylcyclopentadiene 10a in the presence of the rhodium
catalyst [(COD)RhCl]2 (2.5 mol %, 20 °C, 36 h, THF)
(Scheme 3). Now, this catalyzed reaction not only
provides a synthetically valuable access to the formation
of cyclopentadienes from Fischer carbene complexes but
also supports the assumption (vide supra) that the
π-cyclization of metallaolefins can indeed be catalyzed
by rhodium species.
Vin ylcyclop en ta d ien e 10a by a Rh od iu m -Ca ta -
lyzed π-Cycliza tion of 1-Tu n gsta -1,3,5,7-octa tetr a -
en es 8a . In view of our recent finding that the insertion
of alkynes 2 into MdC bonds of cross-conjugated 1-met-
1
allahexatrienes (OC)5MdC(OEt)C(dCHNR2)CdCR Ph
9
5
(
(M ) W, Cr) as well as 1-metalla-1,3-butadienes
8
OC)5MdC(OEt)CdC(Ph)NR2 2 (M ) W, Cr) could be
efficiently catalyzed by rhodium(I) compounds at 20 °C,
and the 1-metallaolefins resulting thereby underwent
a π-cyclization to vinylcyclopentadienes 4 and 6, respec-
tively (Scheme 1), we anticipated that it would be not
only the insertion of an alkyne into a MdC bond but
also the subsequent π-cyclization step of the 1-metal-
laoctatetraenes 8 to vinylcyclopentadienes 10 that pos-
sibly might be catalyzed by rhodium species.1
(
11) Aumann, R.; G o¨ ttker-Schnetmann, I.; Wibbeling, B.; Fr o¨ hlich,
R. Tetrahedron Lett. 1998, 39, 795-798.
12) For the chemistry of 1-metalla-1,3,5-hexatrienes see: (a) Au-
(
mann, R. Eur. J . Org. Chem. 2000, 17-31. (b) Meyer, A. G.; Aumann,
R. Synlett 1995, 1011-1013. (c) Aumann, R.; Meyer, A. G.; Fr o¨ hlich,
R. Organometallics 1996, 15, 5018-5027. (d) Aumann, R.; K o¨ ssmeier,
M.; Zippel, F. Synlett 1997, 621-623. (e) Aumann, R.; K o¨ ssmeier, M.;
J a¨ ntti, A. Synlett 1998, 1120-1122. (f) Aumann, R.; Heinen, H.;
Hinterding, P.; Str a¨ ter, N.; Krebs, B. Chem. Ber. 1991, 124, 2343-
0
2
343. (g) Aumann, R.; Heinen, H.; Hinterding, P.; Str a¨ ter, N.; Krebs,
B. Chem. Ber. 1991, 124, 1229-1236. (h) Aumann, R.; Fr o¨ hlich, R.;
Prigge, J .; Meyer, O. Organometallics 1999, 18, 1369-1380. (i) Wu,
H.-P.; Aumann, R.; Fr o¨ hlich, R.; Wegelius, E.; Saarenketo, P. Orga-
nometallics 2000, 19, 2373-2381. (j) Wu, H.-P.; Aumann, R.; Venne-
Dunker, S.; Saarenketo, P. Eur. J . Org. Chem. 2000, 3463-3473. (k)
Aumann, R.; K o¨ ssmeier, M.; M u¨ ck-Lichtenfeld, Ch.; Zippel, F. Eur. J .
Org. Chem. 2000, 37-49. (l) Aumann, R.; K o¨ ssmeier, M.; Roths, K.;
Fr o¨ hlich, R. Tetrahedron 2000, 56, 4935-4949.
(13) Aumann, R.; G o¨ ttker-Schnetmann, I. Unpublished results.
(14) Similar results have been independently reported by: Barlu-
enga, J .; Aznar, F.; Barluenga, S.; Fern a´ ndez, M.; Mart ´ı n, A.; Garc ´ı a-
Granda, S.; Pi n˜ era-Nicol a´ s, A. Chem. Eur. J . 1998, 4 (11), 2280-2298.
(
9) Aumann, R.; G o¨ ttker-Schnetmann, I.; Fr o¨ hlich, R.; Meyer, O.
Eur. J . Org. Chem. 1999, 2545-2561 and 3209.
10) The appearance of a 1-rhoda(II)-1,3,5-hexatriene species, ob-
(
tained from a o-dialkynyl-substituted diazoacetophenone and catalytic
rhodium(II) octanoate and subsequent π-cyclization to a cyclopenta-
diene, was postulated by: (a) Padwa, A.; Kassir, J . M.; Xu, S. L. J .
Org. Chem. 1997, 62, 1642-1652. For a general review of (related)
rhodium(II)-mediated cyclizations involving carbene rhodium com-
plexes obtained from diazo compounds see: (b) Padwa, A. J . Orga-
nomet. Chem. 2000, 610, 88-101. For further work: (c) Padwa, A.;
Weingarten, M. D. J . Org. Chem. 2000, 65, 3722-3732.

3
576 Organometallics, Vol. 20, No. 16, 2001
G o¨ ttker-Schnetmann et al.
Sch em e 2. Ad d ition of 2-Am in o-1,3-bu ta d ien es 7 to (1-Alk yn yl)ca r ben e Com p lexes 1 a n d Th er m a lly
In d u ced Cycliza tion of Ad d u cts
Sch em e 3. F a cile Tr a n sfor m a tion th e 1-Tu n gsta -1,3,5,7-octa tetr a en e 8a in to Vin ylcyclop en ta d ien e 10a by
Mea n s of a Rh od iu m (I) Ca ta lyst
Sp ir o-F u sed Vin ylcyclop en t a d ien es 15 b y a
(identified by TLC), but no organic product could be
detected. If 2.0 mol % RhCl3‚3H2O and MeOH were used
(instead of [(COD)RhCl]2), compound 15c was formed
in ca. 10% yield at 20 °C after 12 h, but most of the
starting material remained unchanged. Optimal yields
of compounds 15a -d in the range of 71-76% were
obtained in THF or toluene at 70 °C both with [(COD)-
RhCl]2 (reaction time ca. 12 h) and with RhCl3‚3H2O
and MeOH (reaction time of ca. 4 h) (Scheme 4). Since
it was anticipated that a transmetalation of the carbene
ligand from tungsten to rhodium might possibly be
involved in this process, we were aiming for the prepa-
ration of such a carbene rhodium complex.
Rh od iu m -Ca ta lyzed π-Cycliza tion of Cr oss-Con -
ju ga ted Tu n gsta octa tetr a en es 14. Further examples
of rhodium-catalyzed π-cyclization reactions of metal-
laolefins are provided in Scheme 4. It was shown, for
example, that (rapidly interconverting) tungstaocta-
1
5
tetraenes 14/14′, which are obtained in 48-86% yields
by addition of 1,3,3-trimethyl-2-(1-propen-3-ylidene)-
indolines 13 to (1-alkynyl)carbene tungsten complexes
1
a ,c (R ) Ph, cyclohexenyl), are quite stable in solution
1
even at 80-100 °C. Even at 110 °C these compounds
could be recovered almost completely after 14 h, while
a CdC bond isomerization and a subsequent π-cycliza-
tion to a cyclopentadiene derivatives 15 were observed
to a very minor extent only. However formation of
vinylcyclopentadienes 15 from compounds 13 is dra-
matically improved by rhodium catalysts (Scheme 4).
In our initial studies on the reactions shown in
Scheme 4 both [(COD)RhCl]2 and RhCl3‚3H2O in MeOH
were applied as catalysts in the temperature range from
Sta ble Rh od iu m Ca r ben e Com p lex 16c Obta in ed
by Tr a n sm eta la tion . We finally succeeded in provid-
ing experimental proof of the intermediacy of rhodium
carbene complexes in the catalytic reactions described
in Scheme 4 and prepared the carbene rhodium complex
1
6c by transmetalation of the carbene ligand of the
tungsten complex 14c with a stoichiometric amount of
(COD)RhCl]2 (Scheme 5). The carbene tungsten com-
1
6
2
0 to 70 °C. Addition of 2.5 mol % of [(COD)RhCl]2 to
[
a solution of compound 14c in THF at 20 °C after 12 h
resulted in production of W(CO)6 in trace amounts
pound 14c was consumed almost completely at 20 °C
in 1.5 h to give colorless hexacarbonyltungsten and a
new yellow-orange compound. Workup by flash chro-
matography on silica gel afforded the red rhodaocta-
tetraene 16c in 69% yield. On the basis of its 13C NMR
spectra (at 150, 100, and 90 MHz), the latter compound
was unambiguously identified as a carbene rhodium
(
15) Compounds 14b-d were obtained in 82-86% yields, whereas
compound 14a was obtained in 48% yield together with a second isomer
in 33% yield. For a detailed discussion see ref 1.
(
16) [(COD)RhCl]
2
was proven to be an adequate catalyst in acid
O)/MeOH is an more active
sensitive systems: see ref 8. RhCl
catalyst but due to formation of HCl only applicable on acid resistant
systems: see ref 9.
3
‚(3H
2
1
103
13
complex by its doublet at δ 291.1, J ( Rh, C) ) 44 (

Carbene Rhodium Complex as an Intermediate
Organometallics, Vol. 20, No. 16, 2001 3577
Sch em e 4. In flu en ce of Rh od iu m Ca ta lysts on th e π-Cycliza tion of Cr oss-Con ju ga ted
Tu n gsta octa tetr a en es 14/14′ Gen er a ted fr om (1-Alk yn yl)ca r ben e Com p lexes 1a ,c1
Sch em e 5. Tr a n sm eta la tion of a Ca r ben e Liga n d fr om th e Tu n gsten Com p lex 14c to a Rh od iu m Moiety
a n d F or m a tion of a Vin ylcyclop en ta d ien e Der iva tive 15c by π-Cycliza tion
1
Hz, typical of a RhdC unit.17,18 It should be noted that
this is the first example of a transmetalated carbene
complex, which has been explicitly shown to be an
intermediate in a catalyzed reaction of a Fischer carbene
complex.
(17) Carbene rhodium complexes of the type RhdC(OR)C are not
According to NMR measurements, the COD ligand
reported to our knowledge; those of the type RhdC(OM)C are scarcely
reported: (a) Erker, G.; Lecht, R.; Tsay, Y.-H.; Kr u¨ ger, C. Chem. Ber.
4
retains its η coordination throughout the reaction. Two
1
987, 120, 1763-1765. (b) Erker, G.; Mena, M.; Hofmann, U.; Menj o´ n,
of the four olefinic protons of compound 16c as well as
the carbon atoms of the COD ligand trans to chloride
are significantly shifted upfield (CH of COD: δ 5.76,
B.; Petersen, J . L. Organometallics 1991, 10, 291-298. (c) Yeston, J .
S.; Bergmann, R. G. Organometallics 2000, 19, 2947-2949.
(18) For pioniering work on carbene rhodium complexes of the type
2 2
RhdC(NR ) see: (a) Cardin, D. J .; Doyle, M. J .; Lappert, M. F. J .
5
.58, 3.62, and 3.10; CH: 103.8 and 103.0 [CH each, d
Chem. Soc., Chem. Commun. 1972, 927-928. (b) Coleman, A. W.;
Hitchcock, P. B.; Lappert, M. F.; Maskell, R. K.; M u¨ ller, J . H. J .
Organomet. Chem. 1985, 296, 173-196. (c) Cetinkaya, B.; Hitchcock,
P. B.; Lappert, M. F.; Shaw, D. B.; Spyropoulos, K.; Warhust, N. J . W.
J . Organomet. Chem. 1993, 459, 311-317. Synthetic strategies toward
1
103
13
each, J ( Rh, C) ) 4.3 Hz], 70.3 and 67.2 [CH each,
1
103
13
d each, J ( Rh, C) ) 14.3 Hz]), while the proton signal
NC(R)dCHCHdC(R) is shifted downfield to δ 10.19
(compound 14c: δ 9.04) apparently due to an anisotropic
2
the generation of carbene rhodium complexes of the type RhdCR have
been developed by the Werner group: (d) Schwab, P.; Mahr, N.; Wolf,
J .; Werner, H. Angew. Chem. 1993, 105, 1498-1500; Angew. Chem.,
Int. Ed. Engl. 1993, 32, 1480-1482. (e) Schwab, P.; Werner, H. J .
Chem. Soc., Dalton Trans. 1994, 3415-3425. (f) Werner, H. J .
Organomet. Chem. 1995, 500, 331-336. (g) Werner, H.; Schwab, P.;
Bleuel, E.; Mahr, N.; Steinert, P.; Wolf, J . Chem. Eur. J . 1997, 3 (8),
1
1
deshielding. It was explicitly proven by ( H, H)COSY,
1
13
1
13
(
H, C)GHSQC, and ( H, C)GHMBC experiments that
the connectivity of the carbon skeleton of the carbene
ligand in compound 14c and compound 16c was identi-
1
1
375-1384. (h) Bleuel, E.; Gevert, O.; Laubender, M.; Werner, H.
cal. The H NMR spectrum shows two independent sets
Organometallics 2000, 19, 3109-3114. (i) Werner, H.; Schwab, P.;
Bleuel, E.; Mahr, N.; Windm u¨ ller, B.; Wolf, J . Chem. Eur. J . 2000, 6
of signals in a ratio of ca. 95:5 tentatively assigned to
stereoisomers 16c and 16c′ on the basis of NOE and
ROESY experiments at 273 K, 600 MHz in [D8]toluene.
(
24), 4461-4470. (j) Bleuel, E.; Webernd o¨ rfer, B.; Werner, H. J .
Organomet. Chem. 2001, 617, 502-510.

3
578 Organometallics, Vol. 20, No. 16, 2001
G o¨ ttker-Schnetmann et al.
While an interconversion of the tungsten compounds
4c and 14c′ could be proven by spin-saturation transfer
It was shown that rhodaoctatetraene 16c was indeed
catalyzing formation of the vinylcylopentadiene 15c
from tungstaoctatetraene 14c. In the presence of 4 mol
% of rhodaoctatetraene 16c, the tungsten compound 14c
was smoothly transformed into the cyclopentadiene 15c
1
1
9
experiments, this was not the case for the rhodium
compounds 16c and 16c′ within a similar temperature
range. A coordination of a carbon monoxide ligand to
rhodium is excluded on the basis of 1 C NMR and IR
measurements. MALDI-TOF experiments show mass
3
according to NMR spectra in [D ]toluene at 70 °C within
8
10 h (74% isolated yield), while a small signal at δ 10.02,
+
+
peaks at M - COD and M - Cl and a coincidence of
the observed and the simulated isotope pattern. The
elemental analysis found C, 68.55; H, 6.00; and N, 1.54
is slightly critical with respect to the nitrogen value
attributed to RhdC(OEt)C(R)dCHCH of compound 16c,
was persistently visible during the reaction time. Some
further information on the nature of intermediates was
derived from monitoring the stoichiometric transmeta-
lation of the tungstaoctatetraene 14c with [(COD)RhCl]2
into the rhodaoctatetraene 16c at 30 °C and its subse-
quent transformation into the cyclopentadiene 15c at
70 °C. After ca. 30 min at 70 °C a new carbene rhodium
complex, characterized by a carbon signal at δ 267.3 [d,
(calcd C, 68.87; H, 6.37; N, 2.06), if a molecular formula
C39H43ClNORh is assumed for compound 16c.
Structural information obtained from NOE and ROE-
SY experiments (600 MHz, 273 K) comprise a positive
signal enhancement of one of the olefinic protons of the
COD ligand proton at δ 3.56, which is located trans to
the chloro ligand, the geminal dimethyl group C(CH3)2,
and the (high-field) proton NC(R)dCHCHdC(R) at δ
1
1
103
13
J ( Rh, C) ) 48 Hz], two CO signals at 208.3 [d,
103
13
1
103
13
J ( Rh, C) ) 45 Hz] and 186. 0 [d, J ( Rh, C) ) 91
Hz], as well as a proton doublet at 10.70, was detected
as a transient species. This compound certainly contains
a RhdC(OEt)C(R)dCH unit and two CO units replacing
the COD ligand (which was detected in metal-free COD
6
.12 on irradiation of the (low-field proton) NC(R)d
CHCHdC(R). An intensity enhancement was found also
for the signals NCH3 and PhCHdC(Ph) on irradiation
of NC(R)dCHCHdC(R). It was shown by 1H NMR
experiments that the isomers 16c and 16c′ do not
interconvert on the NMR time scale. A spin-saturation
transfer between the two olefinic COD protons at the
position trans to the chloro ligand is not observed,
indicating a high rotation barrier of the RhdC bond.
An apparent increase in the back-donation from rhod-
ium atom to the carbene carbon atom20 is reflected also
by a higher isomerization barrier of the enamine double
bond NC(R)dCH in the rhodium compounds 16c and
1
in the NMR spectrum). After 4 h at 70 °C the H NMR
spectra were essentially identical to those previously
obtained on thermolysis of the carbene rhodium complex
16c at 70 °C, 4 h, including the aforementioned broad
signals assigned to formation of polymers and a slight
drop in chemical yields of compound 15c.
F ir st Exa m p le of a Cop p er -Ca ta lyzed Rea ction
of a F isch er Ca r ben e Com p lex. On the basis of the
finding that reactions of Fischer carbene complexes can
be efficiently catalyzed by transmetalation, we are
currently investigating different metal systems with
respect to their catalytic influence on the reaction course
of Fischer carbene complexes. Here we wish to report
that also copper(I) compounds might serve as efficient
catalysts for the π-cyclization of metallaolefins. It was
found, for example, that formation of the vinylcyclo-
pentadiene 15c from tungstaoctatetraene 14c is strongly
enhanced by CuI in the presence of Et3N (5 mol % CuI
and 8 mol % Et3N in toluene; 70 °C, 16 h, 74% yield of
compound 15c).
2
1
1
6c′ compared to the tungsten compounds 14 and 14′.
On the basis of the ROE enhancements, the plane
defined by the square-planar coordination sphere at
rhodium appears to be perpendicular toward the plane
defined by the carbene unit, in line with earlier reports
2
2
on N-heterocyclic carbene rhodium complexes.
The thermally induced transformation of the rhoda-
octatetraene 16c into the vinylcyclopentadiene 15c
1
13
could be monitored by H and C NMR spectra in [D8]-
toluene at 70 °C, 4 h. Compound 15c was obtained in
this experiment in a somewhat lower isolated yield of
Attem p ted Ster eoin d u ction of π-Cycliza tion In -
d u ced by Rh od iu m (I) a n d Cop p er (I) Ca ta lysts in
th e P r esen ce of Ch ir a l Au xilia r ies. In view of the
fact that rotation of the RhdC bond in compound 16c
was found to be appreciably hindered (vide supra), we
investigated the influence of chiral ligands, like DIOP
or BINAP, in the enantioselectivity of the rhodium-
catalyzed π-cyclization leading to formation of vinyl-
cyclopentadiene 15c (Scheme 6). Similar experiments
were performed with copper catalysts and chiral amines.
6
%
3% than under conditions of the cataysis with 2 mol
RhCl3‚3H2O (76% isolated yield) (Scheme 5). This
drop in chemical yield was attributed to a partial metal-
induced polymerization of compound 15c in more con-
centrated solution, particularly since additional broad
signals were observed in this case both in the aromatic
1
and in the aliphatic region of the H NMR spectra.
(
19) For a detailed discussion of chemical exchange phenomena in
compounds 14 see ref 1.
20) For a discussion of the rotation parameters of the RhdC bond
(
Compound 14c was reacted with solutions of 2.5 mol
% [(COD)RhCl]2 and 7 mol % (-)-DIOP and (-)-BINAP
in toluene, respectively. The efficiency of our catalytic
system was reduced noticeably by the addition of the
phosphorus ligands with respect to the reaction time,
which had to be tripled at 70 °C to 36 h for a complete
conversion, even though the overall yields remained
unchanged. Analysis of the reaction mixture on a chiral
HPLC column (ChiraGrom HPLC column, UV detector
in N-heterocyclic carbene rhodium complexes see: Doyle, M. J .;
Lappert, M. F. J . Chem. Soc., Chem. Commun. 1974, 679-680. While
2 2
Lappert’s carbene rhodium complexes of the RhdC(NR ) type exhibit
a strong σ-donation of the carbene ligand and a weak π-back-donation
of the metal, Werner’s compounds of type RhdCR as well the
2
compounds studied in this paper show a strong σ-donation and strong
1
3
π-back-donation according to the C chemical shift of the RhdC bond.
X-ray data are provided in refs 18b-f.
(
21) A weak back-donation would be equivalent to a more R,ω-
-
zwitterionic carbiminium rhodate structure Rh-C(OEt)dC(R)CHd
CHC(R)dN . In fact the zwitterionic character of tungstaoctatetraenes
+
1
4 due to the electron-withdrawing CO ligands should be higher than
that of compound 16c.
22) For examples see: (a) Enders, D.; Gielen, H.; Runsink, J .;
(
210 nm) and n-hexane as eluant) showed that a 1:1
(
mixture of enantiomers 15c was obtained. Reaction of
compound 14c in the presence of 5 mol % CuI and 7
Breuer, K.; Boehm, K. Eur. J . Inorg. Chem. 1998, 913-919. (b)
References 18b-f.

Carbene Rhodium Complex as an Intermediate
Organometallics, Vol. 20, No. 16, 2001 3579
Sch em e 6. Attem p ted Ch ir a l In d u ction by a Rh od iu m -Ca ta lyzed π-Cycliza tion
mol % (-)-sparteine, 14 mol % (+)-methoxyproline, or
4 mol % (+)-1-phenylethylamine in toluene or 1,2-
dichloroethane afforded vinylcyclopentadiene 15c after
2-16 h at 70 °C, but no enantioselectivity was observed
in these transformations.
with n-pentane/diethyl ether (20:1) afforded compound 10a
(133 mg, 0.38 mmol, 76%, R
f
) 0.7 in n-pentane/diethyl ether,
1
20:1, pale yellowish oil).
1
Con clu sion
A strong reactivity enhancement of the π-cyclization
of tungstaoctatetraenes 8 and 14 to give vinylcyclopen-
tadienes 10a and 15a -d was achieved in the presence
of catalytic amounts of rhodium(I) catalysts. Evidence
is presented that the catalysis involves the intermediate
formation of rhodium carbene complexes, since the
rhodaoctetraene 16c could be generated and isolated by
transmetalation of the carbene ligand from the tung-
staoctatetraene 14c with stoichiometric amounts of
1H NMR (400 MHz, C
.21 (2 H, m, m-H Ph), 7.13 (1 H, m, p-H Ph), 6.07 (1 H, d, J
6
6
D , 300 K): δ 7.48 (2 H, m, o-H Ph),
4
7
)
3
4
2.0 Hz, 5-H), 6.02 (1 H, m, 2′-H), 5.36 (1 H, d, J ) 2.0 Hz,
-H), 3.72 (4 H, m, 2 OCH ), 3.60 (2 H, m, OCH CH ), 2.93
and 2.66 (2:2 H, m each, 2 NCH ), 2.30 and 2.27 (1:1 H, m
each, 6′-H ), 2.00 (2 H, m, 3-H ), 1.63 (2 H, m, 5′-H ), 1.52 (2
). 13C NMR
H, m, 4′-H ), 1.11 (3 H, t, J ) 6.9 Hz, OCH CH
100 MHz, C , C2), 142.9 (C , C4), 136.4
and 136.1 (C each, C1′ and i-C Ph), 128.7 (CH, m-C Ph), 127.7
2
2
3
2
2
2
2
[(COD)RhCl]2. The carbene rhodium complex 16c has
3
2
2
3
been smoothly transformed into the vinylcyclopenta-
diene 15c. It was shown for the first time that copper-
(
6
q
D
6
, 300 K): δ 169.7 (C
q
q
(
I) compounds are good catalysts for reactions of Fischer
(CH, p-C Ph), 126.0 (CH, o-C Ph), 124.1 (CH, C2′), 121.7 (CH,
C5), 97.8 (CH, C3), 80.6 (C , C1), 68.2 (2 OCH ), 65.2 (OCH
CH ), 48.3 (2 N(CH ), 26.3 (CH , C6′), 61.1 (CH , C3′), 23.9
CH , C5′), 23.0 (CH , C4′), 14.7 (OCH CH ). IR (diffuse
carbene complexes.
q
2
2
-
3
2
2
2
(
2
2
2
3
Exp er im en ta l Section
NMR: Bruker AM 360, Bruker AMX 400, and Varian U 600.
-1
reflection), cm (%): 2926 (56), 2849 (46), 1616 (18), 1568 (25),
+
1203 (56), 1112 (100). MS (70 eV), m/e (%): 351 (3) [M ], 322
1
13
All new compounds were routineously analyzed by H, C,
(31), 266 (100), 237 (30), 178 (22), 165 (37), 152 (27). Anal.
Calcd for C23H29NO (351.5): C, 78.59; H, 8.32; N, 3.98.
2
Found: C, 78.50; H, 8.50; N, 3.80.
Sp ir o[2-eth oxy-3-(1-p h en yl-2-m eth ylp r op -1-en yl)cyclo-
p en t a d ien e-1,2′-N-m et h yl-3′,3′-d im et h ylin d olin e] (15a ).
Compound 15a was obtained from pentacarbonyl[1-ethoxy-2-
(1,2-diphenylethenyl)-4-(1,3,3-trimethylindolin-2-ylidene)but-
2-en-1-ylidene]tungsten (14a) (284 mg, 0.40 mmol) and [(COD)-
1
1
1
13
1
13
DEPT, ( H, H)COSY, ( H, C)GHSQC, and ( H, C)GHMBC
experiments on a Bruker AMX 400. NOE-DIFF experiments
were performed on a Bruker AM 360. ROESY experiments as
well as dynamic NMR experiments were performed on a
Varian U 600. IR: FT-IR BIO-RAD DIGILAB DIVISION FTS-
4
(
5. MS: FINNIGAN MAT8200 and LAZARUS III DE23
MALDI). Elemental analyses: HERAEUS CHN-O Rapid.
Column chromatography: Merck silica gel 60F. Flash chro-
matography was performed under an argon pressure of 1.2
RhCl]
by flash chromatography on silica gel (110 mg, 0.28 mmol, 71%,
) 0.8 in n-pentane/diethyl ether, 20:1, pale yellowish oil).
RhCl O) (2.6 mg, 0.01 mmol) and 0.3 mL of MeOH were
somewhat more efficient catalysts, which gave compound 14a
at 70 °C, 4 h in 72% yield.
2
(2 mg, 0.004 mmol) in 3.5 mL of toluene at 70 °C, 12 h
bar. TLC: Merck silica gel 60F254. R
tests. All reactions were performed under argon. CH
quality), 1,2-dichloroethane, diethyl ether, n-pentane, THF,
toluene C , and [D ]toluene were used as purchased and not
f
values are based on TLC
R
f
2
2
Cl (p.a.
3
‚(3H
2
6
D
6
8
dried. Compounds 1 were prepared according to ref 24,
compound 8a according to ref 11, and compounds 14 according
to ref 1.
[
1-(Cycloh ex-1-en yl)-2-eth oxy-4-p h en yl-2,4-cyclop en ta -
d ien -1-yl]m or p h olin e (10a ). Pentacarbony[(2Z)-5-(cyclohex-
-enyl)-1-ethoxy-3-phenyl-2,4-pentadien-1-ylidene]tungsten (1a)
337 mg, 0.50 mmol) and [(COD)RhCl] (6 mg, 0.012 mmol)
were stirred for 36 h at 20 °C in 3.5 mL of THF until compound
a was consumed (TLC test). Chromatography on silica gel
1
(
2
1
(23) The mass spectrometer LAZARUS III DE was provided by Dr.
H. Luftmann, Organisch-Chemisches Institut der Universit a¨ t M u¨ nster.
Data sets were collected with LeCroy DSO 9450A instrumentation.
(
24) (a) Aumann, R.; Nienaber, H. Adv. Organomet. Chem. 1997,
1, 163-242. (b) Aumann, R.; Fr o¨ hlich, R.; Meyer, O.; Prigge, J .
Organometallics 1999, 18, 1369-1380.
1H NMR (400 MHz, C
7.20 (2 H, m, m-H Ph), 7.17 (1 H, m, 6′-H), 7.07 (1 H, m, p-H
4
6
6
D , 300 K): δ 7.26 (2 H, m, o-H Ph),

3
580 Organometallics, Vol. 20, No. 16, 2001
G o¨ ttker-Schnetmann et al.
Ph), 6.95 (1 H, m, 4′-H), 6.80 (1 H, m, 5′-H), 6.45 (1 H, m, 7′-
pale yellowish oil). RhCl
3
‚(3H
2
O) (2.6 mg, 0.01 mmol) and 0.3
3
3
H), 6.01 (1 H, d, J ) 6.1 Hz, 4-H), 5.65 (1 H, d, J ) 6.1 Hz,
-H), 3.75 (2 H, m, OCH ), 2.59 (3 H, s, NCH ), 1.81 and 1.68
3:3 H, s each, 7-CH and 8-H ), 1.42 and 1.35 [3:3 H, s each,
mL of MeOH instead of [(COD)RhCl]
compound 15c in 75% yield. Application of the copper catalyst
CuI (4.8 mg, 0.025 mmol) and Et N (4 mg, 0.04 mmol) at 70
°C for 16 h gave compound 15c in 75% yield. Experiments
toward attempted stereoinduction with different catalystss
2
at 70 °C for 12 h gave
5
2
3
(
3
3
3
3
13
3
′-(CH
3
)
6
2
], 0.76 (3 H, t, J ) 7.1 Hz, OCH
, 300 K): δ 161.4 (C , C2), 152.3 (C
, i-C Ph), 140.3 (C , C3′a), 138.1 (CH, C4), 132.8 and 131.6
each, C6 and C7), 130.0 (CH, o-C Ph), 128.2 (CH, m-C Ph),
,C6′), 126.7 (CH, p-C Ph), 124.9 (CH, C5), 120.8 (CH,
C4′), 117.6 (CH, C5′), 116.2 (C , C3) 106.6 (CH, C7′), 88.4 (C
C1), 65.1 (OCH ), 46.9 (C , C3′), 30.5 (NCH ), 29.1 and 22.3
], 23.3 and 21.9 (CH each, 7-CH and C8), 15.7
). IR (diffuse reflection), cm (%): 2924 (57), 2856
2
CH
3
). C NMR (100
MHz, C
D
6
q
q
, C7′a), 141.8
(
(
C
C
q
q
(a) 2.5 mol % [(COD)RhCl]
2
and 5 mol % (-)-DIOP or
q
(-)-BINAP in toluene, (b) 5 mol % CuI and 7 mol % of (-)-
sparteine in 1,2-dichloroethane, (c) 5 mol % CuI and 14 mol %
of (+)-methoxyproline in toluene, (d) 5 mol % CuI and 14 mol
% of (+)-1-phenylethylamine in toluenesgave compound 15c
in each case as racemic mixtures. The stoichiometric reaction
1
27.5 (C
q
q
q
,
2
q
3
[
(
(
(
CH
3
, 3′-(CH
CH
3
)
2
3
3
-
1
OCH
2
3
of CuI, 1.5 equiv of Et N, and compound 14c yielded compound
3
29), 1605 (39), 1557 (16), 1483 (100), 1445 (49), 1363 (26), 1300
35). MS (70 eV), m/e (%): 385 (31) [M ], 370 (69), 356 (100),
15c after 60 h at 20 °C, but no isolable copper carbene could
be detected. The rhodium compound 16c was obtained from
+
3
26 (26), 210 (21), 158 (30). Anal. Calcd for C27
H
31NO (385.6):
compound 14c (378 mg, 0.50 mmol) and [(COD)RhCl] (126
2
mg, 0.26 mmol) in 10 mL of dichloromethane at 20 °C, 1.5 h
(compound 14c was nearly totally consumed according to a
TLC test), flash chromatography on silica gel with n-pentane/
C, 84.11; H, 8.10; N, 3.63. Found: C, 84.14; H, 8.07; N, 3.61.
Sp ir o[2-eth oxy-3-(1-p h en ylp r op -1-en yl)cyclop en ta d i-
en e-1,2′-N-m et h yl-3′,3′-d im et h ylin d olin e] (15b ). Com-
pound 15b was obtained from pentacarbonyl[1-ethoxy-2-(1-
phenylprop-1-enyl)-4-(1,3,3-trimethylindolin-2-ylidene)but-2-
en-1-ylidene]tungsten (14b) (348 mg, 0.50 mmol) and [(COD)-
diethyl ether, 1:1 (234 mg, 69%, R ) 0.4 in n-pentane/diethyl
f
ether, 1:1). An analytically pure sample of solid 16c was
obtained from a filtered benzene solution of compound 16c by
careful removal of the solvent at 0 °C. Rearrangement of
compound 16c (103 mg, 0.15 mmol) was studied by monitoring
the NMR spectra in [D ]toluene. Compound 15c was isolated
8
from this sample after 4 h at 70 °C by flash chromatography
on silca gel (41 mg, 63%). Stoichiometric reaction of compound
RhCl]
h by flash chromatography on silica gel (137 mg, 0.37 mmol,
4%, R ) 0.9 in n-pentane/diethyl ether, 20:1, pale yellowish
oil). RhCl ‚3H O (2.6 mg, 0.01 mmol) and 0.3 mL of MeOH
instead of [(COD)RhCl] gave compound 15b in 74% yield at
2
(2.5 mg, 0.005 mmol) in 3.5 mL of toluene at 70 °C, 12
7
f
3
2
2
7
0 °C, 4 h.
1
4c (179 mg, 0.25 mmol) with [(COD)RhCl]
mmol) in [D ]toluene at 30 °C was monitored by H NMR
experiments to give a complete transformation into compound
6c and W(CO) after 1 h. At 70 °C after 4 h compound 15c
69 mg, 64% after chromatography) was obtained. H and
2
(63 mg, 0.13
1
8
1
(
6
1
13
C
NMR spectra after 60, 120, and 240 min at 70 °C showed
additional signals of a carbonyl carbene rhodium complex as
a transient species. Reaction of compound 14c (179 mg, 0.25
mmol) in [D
8
]toluene and 4 mol % carbene rhodium complex
1
6c (7 mg, 0.01 mmol) gave compound 15c (80 mg, 74%) after
1
2 h at 70 °C.
1H NMR (400 MHz, C
D , 300 K): δ 7.27 (2 H, m, o-H Ph),
6 6
.19 (2 H, m, m-H Ph), 7.14 (1 H, m, 6′-H), 7.08 (1 H, p-H Ph),
.95 (1 H, m, 4′-H), 6.78 (1 H, m, 4-H), 6.42 (1 H, m, 7′-H),
7
6
6
5
3
3
.14 (1 H, d, J ) 6.1 Hz, 4-H), 5.82 (1 H, q, J ) 7.1 Hz, 7-H),
3
.66 (1 H, d, J ) 6.1 Hz, 5-H), 3.62 (2 H, m, OCH
2
), 2.58 (3 H,
3
s, NCH
H, s each, 3′-(CH
NMR (100 MHz, C
C7′a), 140.3 (C , C3′a), 139.4 (C
, C6), 129.7 (CH, o-C Ph), 128.3 (CH, m-C Ph), 127.5 (CH,
C6′), 127.1 (CH, p-C Ph), 126.1 (CH, C7), 125.6 (CH, C5), 120.8
3
), 1.66 (3 H, d, J ) 7.1 Hz, 8-H
3
), 1.43 and 1.34 [3:3
3
13
3
)
2
], 0.65 (3 H, t, J ) 7.2 Hz, OCH
, 300 K): δ 161,7 (C , C2), 152.2 (C
, i-C Ph), 137.1 (CH, C4), 136.4
2
CH
3
).
C
6
D
6
q
q
,
q
q
(C
q
1H NMR (400 MHz, C
D , 300 K): δ 7.33 (2 H, m, o-H 12-
6 6
Ph), 7.16 (1 H, m, 6′-H), 7.07 (4 H, m, o-H 7-Ph and m-H 6-Ph),
7.03 (1 H, m, p-H 6-Ph), 6.95 (3 H, m, m-H 7-Ph and 4′-H),
6.88 (1 H, p-H 7-Ph), 6.79 (2 H, m, 5′-H and 7-H), 6.43 (1 H,
(
(
2
CH, C4′), 118.8 (C
q
, C3), 117.6 (CH, C5′), 106.4 (CH, C7′), 88.4
, C1), 66.5 (OCH ), 47.2 (C , C3′), 30.4 (NCH ), 29.0 and
each, 3′-(CH ], 15.5 (OCH CH ), 15.1 (CH , C8).
C
q
2
q
3
2.0 [CH
3
3
)
2
2
3
3
-
1
IR (diffuse reflection), cm (%): 2975 (12), 2861 (10), 1605
3
3
(51), 1556 (22), 1483 (100), 1443 (40), 1361 (32), 1300 (55). MS
m, 7′-H), 6.12 (1 H, d, J ) 6.2 Hz, 4-H), 5.67 (1 H, d, J ) 6.2
+
(
3
(
3
70 eV), m/e (%): 371 (37) [M ], 356 (87), 342 (100), 327 (15),
12 (24), 284 (15), 268 (12), 210 (22), 182 (21), 167 (19), 158
33). Anal. Calcd for C26 29NO (371.5): C, 84.06; H, 7.87; N,
.77. Found: C, 83.85; H, 7.93; N, 3.63.
Hz, 5-H), 3.75 (2 H, m, OCH
2
), 2.61 (3 H, s, NCH
], 0.63 (3 H, t, 3J ) 7.0 Hz,
, 300 K): δ 163.9 (C
, C3′a), 139.6 (C , C6), 137.6
, i-C 7-Ph), 136.6 (CH, C4), 136.5 (C , i-C 6-Ph), 130.3 (CH,
3
), 1.47 and
3 2
1.36 [3:3 H, s each, 3′-(CH )
1
3
H
OCH
C2), 152.1 (C
(C
2
CH
3
). C NMR (100 MHz, C
6
D
6
q
,
q
, C7′a), 140.2 (C
q
q
Sp ir o[2-e t h oxy-3-(1,2-d ip h e n yle t h e n yl)cyclop e n t a -
q
q
d ien e-1,2′-N-m eth yl-3′,3′-d im eth ylin d olin e] (15c) a n d
η -Cyclooct a d ie n e [1-e t h oxy-2-(1,2-d ip h e n yle t h e n yl)-
o-C 6-Ph), 129.9 (CH, C7), 129.7 and 128.7 (CH each, m-C 6-Ph
and o-C 7-Ph), 128.4 (CH, m-C 7-Ph), 127.7 and 127.6 (CH
each, C6′ and p-C 6-Ph), 127.0 (CH, p-C 7-Ph), 125.7 (CH, C5),
4
4
-(1,3,3-t r im et h ylin d olin -2-ylid en e)b u t -2-en -1-ylid en e]-
r h od iu m Ch lor id e (16c). Compound 15c was obtained from
pentacarbonyl[1-ethoxy-2-(1,2-diphenylethenyl)-4-(1,3,3-tri-
methylindolin-2-ylidene)but-2-en-1-ylidene]tungsten (14c) (378
120.9 (CH, C4′), 118.9 (C
C7′), 88.7 (C , C1), 67.2 (OCH
29.1 and 22.0 [CH each, 3′-(CH
q
, C3), 117.7 (CH, C5′), 106.5 (CH,
), 47.4 (C , C3′), 30.4 (NCH ),
], 15.6 (OCH CH ). IR
q
2
q
3
3
3
)
2
2
3
-
1
mg, 0.50 mmol) and [(COD)RhCl]
mL of toluene at 70 °C, 12 h by flash chromatography on silica
gel (164 mg, 76%, R ) 0.8 in n-pentane/diethyl ether, 10:1,
2
(2.5 mg, 0.005 mmol) in 3.5
(diffuse reflection), cm (%): 2975 (21), 2863 (14), 1605 (56),
1554 (13), 1484 (100), 1445 (35), 1299 (33). MS (70 eV), m/e
+
f
(%): 433 (47) [M ], 418 (100), 404 (99), 372 (24), 284 (13), 268

Carbene Rhodium Complex as an Intermediate
Organometallics, Vol. 20, No. 16, 2001 3581
(19), 215 (34), 178 (24), 159 (37). Anal. Calcd for C31
H
31NO
of toluene at 70 °C after 12 h by flash chromatography on silica
(
433.6): C, 85.87; H, 7.21; N, 3.23. Found: C, 85.63; H, 7.54;
gel (160 mg, 73%, R
f
) 0.9 in n-pentane/diethyl ether, 20:1,
O (2.6 mg, 0.01 mmol) and 0.3 mL of
N, 3.16.
yellowish oil). RhCl ‚3H
3
2
MeOH instead of [(COD)RhCl]
2
gave compound 15d in 74%
yield at 70 °C, 12 h.
1H NMR (400 MHz, C
Hz, 4-H), 7.47 (2 H, m, o-H 13-Ph), 7.24 (2 H, o-H 12-Ph), 7.08
2 H, m, m-H 13-Ph), 7.02 (2 H, m, m-H 12-Ph), 6.97 (4 H, m,
-H, 10-H, p-H 12- and 13-Ph), 6.86 (1 H, m, 9-H), 6.64 (1 H,
3
6
6
D , 300 K): δ 10.19 (1 H, d, J ) 13.4
1H NMR (400 MHz, C
D , 300 K): δ 7.38 (2 H, m, o-H Ph),
6 6
(
8
7.15 (3 H, m, m-H Ph and 6′-H), 7.01 (1 H, m, p-H Ph), 6.97 (1
H, m, 4′-H), 6.79 (1 H, m, 5′-H), 6.56 (1 H, s, 7-H), 6.43 (1 H,
3
s, 13-H), 6.24 (1 H, m, 11-H), 6.12 (1 H, d, J ) 13.4 Hz, 5-H),
.00 and 5.26 (1:1 H, m each, OCH ), 5.76 and 5.58 [1:1 H, m
3
6
2
m, 7′-H), 6.34 (1 H, d, J ) 6.0 Hz, 4-H), 5.76 (1 H, m, 9-H),
3
each, COD-CH cis to Cl], 3.62 and 3.10 [1:1 H, m, each, COD-
CH trans to Cl]; 2.67, 2.38, 2.13, 2.07, 1.97, 1.83 and 1.71 (1:
5.74 (1 H, d, J ) 6.0 Hz, 5-H), 3.94 and 3.73 (1:1 H, m each,
OCH
2:2 H, m each, 10-H
3′-(CH ) ], 0.75 (3 H, t,
2
), 2.58 (3 H, s, NCH
-13-H
J ) 7.1 Hz, OCH CH ). 13C NMR (100
3
); 2.20, 2.06, 1.57 and 1.48 (1:1:2:
2
1
:1:1:1:1:1 H, m each, COD), 2.34 (3 H, s, NCH
3
), 2.02 and
], 1.19 (3 H, t, J ) 7.1 Hz,
). C NMR (100 MHz, C , 300 K): δ 291.1 [C , d,
, C6), 162.0 (CH, C4), 144.0
, i-C 13-Ph), 140.4 (C , C7a),
, i-C 12-Ph), 131.2 (CH, C13), 129.8
2
2
), 1.46 and 1.38 [3:3 H, s each,
3
3
.95 [3:3 H, s each, 7-(CH
3
)
2
3
2
2
3
1
3
MHz, C D , 300 K): δ 163.3 (C , C2), 152.2 (C , C7′a), 140.3
(C , C3′a), 139.1 (C , C8), 138.4 (C , i-C Ph), 136.8 (C , C6),
q q q q
136.4 (CH, C4), 129.2 (CH, o-C Ph), 128.7 (CH, C9), 128.5 (CH,
C7), 128.4 (CH, m-C Ph), 127.6 (CH, C6′), 126.8 (CH, p-C Ph),
OCH
2
CH
3
6
D
6
q
6
6
q
q
1
13
103
J ( C, Rh) ) 45 Hz, C2], 169.0 (C
, C3), 143.8 (C , C11a), 141.3 (C
38.4 (C , C12), 138.2 (C
q
(C
q
q
q
q
1
q
q
and 129.7 (CH each, o-C 12- and 13-Ph), 128.4 and 128.3 (CH
each, m-C 12- and 13-Ph), 128.0 (CH, C8), 127.1 and 127.0
125.6 (CH, C5), 120.9 (CH, C4′), 118.9 (C
C5′), 106.5 (CH, C7′), 88.7 (C , C1), 67.0 (OCH
30.4 (NCH ), 29.0 and 22.0 [3′-(CH ]; 28.7, 25.9, 23.3 and 22.4
each, C10-C13), 15.7 (OCH CH ). IR (diffuse reflection),
q
, C3), 117.7 (CH,
q
2
), 47.2 (C , C3′)
q
(
CH each, p-C 12- and 13-Ph), 122.6 and 122.1 (CH each, C9
and C10), 108.0 (CH, C11), 103.8 and 103.0 [CH each, COD-
CH cis to Cl], 96.1 (CH, C5), 75.2 (OCH ), 70.3 and 67.2 [CH
each, d each, J ( C, Rh) ) 15.0 and 14.8 Hz, COD-CH trans
to Cl], 48.0 (C , C7); 34.3, 32.4, 29.6 and 27.8 (CH each, COD);
8.8, 28.8 and 28,7 [CH and 7-(CH ], 15.1
OCH CH
3
3 2
)
(CH
2
1
2
3
-
cm (%): 2929 (30), 1604 (73), 1556 (25), 1484 (100), 1360
2
1
13
103
(32), 1338 (38), 1298 (54). MS (70 eV), m/e (%): 437 [M
422 (87), 408 (100), 302 (14), 283 (18), 171 (54), 158 (22). Anal.
Calcd for C31 35NO (437.6): C, 85.08; H, 8.06; N, 3.20,
+
] (43),
q
2
2
3
each, NCH
3
1
3
)
2
H
-
Found: C, 85.26; H, 8.31; N, 3.01.
(
(
(
[
2
3
). IR (diffuse reflection), cm (%): 2973 (15), 2871
13), 1561 (92), 1308 (40), 1189 (90), 1172 (100), 1118 (60). MS
MALDI, DCTB, 337.0 nm, 3 ns): 644 [M - Cl], 571(573)
M
+
Ack n ow led gm en t . This investigation was sup-
ported by the Deutsche Forschungsgemeinschaft (grant
of the Graduiertenkolleg “Hochreaktive Mehrfachbin-
dungssysteme” at M u¨ nster to I.G.-S.) and the Fonds der
Chemischen Industrie. The authors thank Mrs. K.
Gottschalk, M u¨ nster, for her assistance with the chiral
HPLC instrumentation.
+
- COD]. Anal. Calcd for C39H43NOClRh (680.1): C, 68.87;
H, 6.37; N, 2.06. Found: C, 68.55; H, 6.00; N, 1.54.
Sp ir o[2-eth oxy-3-(1-cycloh ex-1-en yl-2-p h en yleth en yl)-
cyclop en t a d ien e-1,2′-N-m et h yl-3′,3′-d im et h ylin d olin e]
(
15d ). Compound 15d was obtained from pentacarbonyl[1-
ethoxy-2-(1-cyclohex-1-enyl-2-phenylethenyl)-4-(1,3,3-trimethyl-
indolin-2-ylidene)but-2-en-1-ylidene]tungsten (14d ) (381 mg,
0
.50 mmol) and [(COD)RhCl]
2
(2.5 mg, 0.005 mmol) in 3.5 mL
OM0103207