π-Coordination vs ring-opening isomerization of 2-phenyl-1-methylenecyclopropane upon the reaction with RhCl(PPh3)3

Article abstract of DOI:10.1021/om980142q

The reactions of 2-phenyl-1-methylenecyclopropane with RhCl(PPh₃)₃ for 16 h at 50°C and at 0°C gave RhCl(η⁴-CH₂=CPhCH=CH₂)(PPh ₃)₂ (1) and RhCl-(η²-CH₂=CCH₂HPh)(PPh₃) ₂ (2) as respective isolated products. Heating of a benzene solution of 2 at 50°C turned it into 1 in a low yield (<7%), while the reactions of 2-phenyl-1-methylenecyclopropane with RhCl(PPh₃)₃ and with 2 at the same temperature afforded 1 (10%) and 2-phenyl-1,3-butadiene (14%).

Full text of DOI:10.1021/om980142q

4532
Organometallics 1998, 17, 4532-4534
π-Coor d in a tion vs Rin g-Op en in g Isom er iza tion of
2-P h en yl-1-m eth ylen ecyclop r op a n e u p on th e Rea ction
w ith Rh Cl(P P h 3)3
Kohtaro Osakada,* Hisami Takimoto, and Takakazu Yamamoto*
Research Laboratory of Resources Utilization, Tokyo Institute of Technology, 4259 Nagatsuta,
Midori-ku, Yokohama 226-8503, J apan
Received February 27, 1998
Sch em e 1
Summary: The reactions of 2-phenyl-1-methylenecyclo-
propane with RhCl(PPh3)3 for 16 h at 50 °C and at 0 °C
gave RhCl(η4-CH2dCPhCHdCH2)(PPh3)2 (1) and RhCl-
(η2-CH2dCCH2CHPh)(PPh3)2 (2) as respective isolated
products. Heating of a benzene solution of 2 at 50 °C
turned it into 1 in a low yield (<7%), while the reactions
of 2-phenyl-1-methylenecyclopropane with RhCl(PPh3)3
and with 2 at the same temperature afforded 1 (10%)
and 2-phenyl-1,3-butadiene (14%).
Sch em e 2
The transition metal complex promoted C-C bond
activation of small-membered ring molecules has been
of significant interest for the past several decades.
Methylenecyclopropane and its derivatives have high
strain energy (∆Hf larger than that of cyclopropane by
approximately 35 kcal mol-1)1 in their molecules and
are employed as the substrates for synthetic organic
reactions2 and polymer synthesis3 catalyzed by transi-
tion metals. The reactions of methylenecyclopropanes
with organotransition metal complexes afforded various
products such as 1,3-diene via ring-opening isomeriza-
tion (Sc, Rh),4 trimethylenemethane-coordinated metal
complexes (Fe, Mo),5 and organometallic compounds
formed via the insertion of a CdC double bond to the
M-C or M-Cl bond (Ti, Pd).6 Rh(I) complexes, which
were reported to cause C-C bond activation of small-
membered ring molecules,7 react also with methyl-
enecyclopropanes to form a 1,3-diene4c,8 and to generate
a trimethylenemethane complex.9 Rh complexes con-
taining η2-coordinated methylenecyclopropane were also
reported.10 The ring-opening isomerization most prob-
ably involves the initial oxidative addition of the C-C
bond to the Rh center, followed by a 1,2-hydrogen shift
to form a 1,3-diene, as shown in Scheme 1.
(1) (a) Wiberg, K. B. Angew. Chem., Int. Ed. Engl. 1986, 25, 312.
(b) Bachrach, S. M. J . Phys. Chem. 1993, 97, 4996.
(2) (a) Donaldson, W. A. Adv. Met-Org. Chem. 1991, 2, 269. (b)
Noyori, R.; Odagi, T.; Takaya, H. J . Am. Chem. Soc. 1970, 92, 5780.
(c) Noyori, R.; Kumagai, Y.; Umeda, I.; Takaya, H. J . Am. Chem. Soc.
1972, 94, 4018. (d) Noyori, R.; Ishigami, T.; Hayashi, N.; Takaya, H.
J . Am. Chem. Soc. 1973, 95, 1674. (e) Binger, P.; Schuchardt, U. Chem.
Ber. 1980, 113, 3334. (f) Yamago, S.; Nakamura, E. J . Chem. Soc.,
Chem. Commun. 1988, 1112. (g) Motherwell, W. B.; Shipman, M.
Tetrahedron Lett. 1991, 32, 1103. (h) Lautens, M.; Ren, Y.; Delanghe,
P. H. M. J . Am. Chem. Soc. 1994, 116, 8821. (i) Lautens, M.; Meyer,
C.; Lorenz, A. J . Am. Chem. Soc. 1996, 118, 10676. (j) Tsukada, N.;
Shibuya, A.; Nakamura, I.; Yamamoto, Y. J . Am. Chem. Soc. 1997,
119, 8123.
(3) (a) J ia, L.; Yang, X.; Yang, S.; Marks, T. J . J . Am. Chem. Soc.
1996, 118, 1547. (b) J ia, L.; Yang, X.; Seyam, A. M.; Albert, I. D. L.;
Fu, P.; Yang, S.; Marks, T. J . J . Am. Chem. Soc. 1996, 118, 7900.
(4) (a) Parkin, G.; Bunel, E.; Burger, B. J .; Trimmer, M. S.; van
Asselt, A.; Bercaw, J . E. J . Mol. Catal. 1987, 41, 21. (b) Brown, J . M.;
Kent, A. G. J . Chem. Soc., Perkin Trans. 2 1987, 1597. (c) Chiusoli, G.
P.; Costa, M.; Melli, L. J . Organomet. Chem. 1988, 358, 495.
(5) (a) Billups, W. E.; Lin, L.-P.; Baker, B. A. J . Organomet. Chem.
1973, 61, C55. (b) Whitesides, T. H.; Slaven, R. W. J . Organomet. Chem.
1974, 67, 99. (c) Whitesides, T. H.; Slaven, R. W.; Calabrese, J . C. Inorg.
Chem. 1974, 13, 1895. (d) Pinhas, A. R.; Samuelson, A. G.; Risemberg,
R.; Arnold, E. V.; Clardy, J .; Carpenter, B. K. J . Am. Chem. Soc. 1981,
103, 1668. (e) Allen, S. R.; Barnes, S. G.; Green, M.; Moran, G.; Trollope,
L.; Murrall, N. W.; Walch, A. J .; Sharaiha, D. M. J . Chem. Soc., Dalton
Trans. 1984, 1157.
(7) Rh complex promoted ring opening of cyclopropanes: (a) Round-
hill, D. M.; Lawson, D. N.; Wilkinson, G. J . Chem. Soc. (A) 1968, 845.
(b) Volger, H. C.; Hogeveen, H.; Gaasbeek, M. M. P. J . Am. Chem. Soc.
1969, 91, 218 and 2137. (c) Katz, T. J .; Cerefice, S. J . Am. Chem. Soc.
1969, 91, 2405. (d) Cassar, L.; Halpern, J . J . Chem. Soc., Chem.
Commun. 1970, 1082. (e) McQuillin, F. J .; Powell, K. C. J . Chem. Soc.,
Dalton Trans. 1972, 2129. (f) Ogoshi, H.; Setsune, J .-I.; Yoshida, Z.-I.
J . Chem. Soc., Chem. Commun. 1975, 572. (g) Alcock, N. W.; Brown,
J . M.; Conneely, J . A.; Williamson, D. H. J . Chem. Soc., Perkin Trans.
2 1979, 962. (h) Periana, R. A.; Bergman, R. G. J . Am. Chem. Soc.
1984, 106, 7272.
(8) J un, C.-H.; Lim, Y.-G. Bull. Korean Chem. Soc. 1989, 10, 468.
(9) Chiusoli, G. P.; Costa, M.; Schianchi, P.; Salerno, G. J . Orga-
nomet. Chem. 1986, 315, C45.
(10) Green, M.; Howard, J . A. K.; Hughes, R. P.; Kellett, S. C.;
Woodward, P. J . Chem. Soc., Dalton Trans. 1975, 2007.
(11) X-ray data of 1: triclinic, P1h (No. 2), a ) 13.395(10) Å, b )
16.613(11) Å, c ) 10.157(9) Å, R ) 92.47(7)°, â ) 103.29(7)°, γ ) 71.17-
(6)°, V ) 2080 Å3, Z ) 2, Dcalc ) 1.335 g cm-3, F(000) ) 866, µ(Mo KR)
) 5.84 cm-1 for monochromated Mo KR radiation (λ ) 0.710 69 Å). R
(Rw) ) 0.062 (0.046) for 3729 reflections with I > 3σ(I) among 9554
unique reflections (Rint ) 0.071), GOF ) 1.83.
(6) (a) Green, M.; Hughes, R. P. J . Chem. Soc., Chem. Commun.
1974, 686. (b) Mashima, K.; Takaya, H. Organometallics 1985, 4, 1464.
(c) Mashima, K.; Sakai, N.; Takaya, H. Bull. Chem. Soc. J pn. 1991,
64, 2475.
S0276-7333(98)00142-3 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 09/24/1998

Communications
Organometallics, Vol. 17, No. 21, 1998 4533
Sch em e 3
F igu r e 1. ORTEP drawing of RhCl(CH2dCHPhCHdCH2)-
(PPh3)2 (1) with 50% thermal ellipsoidal plotting. Selected
bond distances (Å) and angles (deg): Rh1-Cl1 2.459(3),
Rh1-P1 2.354(3), Rh1-P2 2.368(3), Rh1-C1 2.159(10),
Rh1-C2 2.21(1), Rh1-C3 2.144(9), Rh1-C4 2.082(10), C1-
C2 1.42(1), C2-C3 1.44(1), C2-C5 1.51(1), C3-C4 1.40-
(1), Cl1-Rh1-P1 96.90(10), Cl1-Rh1-P2 88.1(1), P1-
Rh1-P2 107.6(1), C1-C2-C3 114(1), C1-C2-C5 127.0(7),
C3-C2-C5 121(1), C2-C3-C4 118.1(10).
1,3-butadiene ligand and to Cl and PPh3 ligands, as
shown in Figure 1.11 The ligand adopts an s-cis
conformation similarly to other reported Rh(I) com-
plexes with 1,3-diene ligands.12 Complex 2 was char-
acterized based on NMR spectra. The much higher
1
magnetic field positions of the H NMR signals of two
vinylic hydrogens (δ 2.27 and 2.34) than that of unco-
ordinated 2-phenyl-1-methylenecyclopropane (δ 5.58)
and the 13C{1H} NMR signals of vinylic carbons (δ 61.5
and 34.2) with large J (RhC) values (13 and 22 Hz,
respectively) are crucial to the assignment of the
structure containing 2-phenyl-1-methylenecyclopropane,
whose CdC double bond is bonded to the Rh center in
a η2-fashion. The J (RhP) value (133 Hz) suggests a
structure with PPh3 ligands at mutually trans positions,
similarly to other RhCl(olefin)(PR3)2-type complexes.13
The reaction of CO (1 atm) with 2 to give quantitative
amounts of 2-phenyl-1-methylenecyclopropane and RhCl-
(CO)(PPh3)2 (eq 1) also supports the proposed structure.
F igu r e 2. Plots of the products of the reaction of 2-phenyl-
1-methylenecyclopropane with RhCl(PPh3)3 at 50 °C. Rela-
tive amounts of (a) 2-phenyl-1-methylenecyclopropane, (b)
2-phenyl-1,3-butadiene, (c) 1, and (d) 2 to the initial amount
of RhCl(PPh3)3 are shown. On cooling to 25 °C, the 31P-
{1H} NMR spectrum indicates the presence of 1 in a yield
higher than 80%.
The change in the amounts of organic and inorganic
products during the reaction of 2-phenyl-1-methylenecy-
clopropane with RhCl(PPh3)3 was monitored by 1H NMR
spectroscopy. Figure 2 shows the plots of the increase
in 1 and 2-phenyl-1,3-butadiene, which reached 55%
and 165%/Rh, respectively, after the reaction for 4.5 h.
The reactions of 2 at 50 °C were conducted to compare
In this paper we report the reaction of 2-phenyl-1-
methylenecyclopropane with RhCl(PPh3)3, leading to the
ring-opening isomerization or the η2-coordination of a
CdC double bond of the substrate depending on the
conditions as well as the mechanism for C-C bond
activation.
2-Phenyl-1-methylenecyclopropane reacts with RhCl-
(PPh3)3 (5:1 molar ratio) at 50 °C to give RhCl(η4-CH2d
CPhCHdCH2)(PPh3)2 (1) in 95% yield after 16 h, while
the reaction at 0 °C in toluene leads to isolation of RhCl-
(12) Rh(I)-1,3-diene complexes: (a) Schrock, R. R.; Osborn, J . A. J .
Am. Chem. Soc. 1971, 93, 2397. (b) J ohnson, B. F. G.; Lewis, J .; Yarrow,
D. J . J . Chem. Soc., Dalton Trans. 1972, 2084. (c) Abel, E. W.;
Blackmore, T.; Whitley, R. J . J . Chem. Soc., Dalton Trans. 1976, 2484.
(d) Caddy, P.; Green, M.; Howard, J . A. K.; Squire, J . M.; White, N. J .
J . Chem. Soc., Dalton Trans. 1981, 400. (e) Moreto, J .; Maruya, K.;
Bailey, P. M.; Maitlis, P. M. J . Chem. Soc., Dalton Trans. 1982, 1341.
(f) Powell, P.; Stephens, M.; Muller, A.; Drew, M. G. B. J . Organomet.
Chem. 1986, 310, 255. (g) Claret, F.; Vogel, P. Organometallics 1990,
9, 2785. (h) Murakami, M.; Itami, K.; Ito, Y. J . Am. Chem. Soc. 1996,
118, 11672. (i) Murakami, M.; Itami, K.; Ito, Y. J . Am. Chem. Soc. 1997,
119, 2950.
(13) RhCl(PR3)2(olefin)-type complexes: (a) Osborn, J . A.; J ardine,
F. H.; Young, J . F.; Wilkinson, G. J . Chem. Soc. (A) 1966, 1711. (b)
Mague, J . T.; Wilkinson, G. J . Chem. Soc. (A) 1966, 1736. (c) Tolman,
C. A.; Meakin, P. Z.; Lindner, D. L.; J esson, J . P. J . Am. Chem. Soc.
1974, 96, 2762. (d) van Gaal, H. L. M.; van den Bekerom, F. L. A. J .
Organomet. Chem. 1977, 134, 237. (e) Ohtani, Y.; Yamagishi, A.;
Fujimoto, M. Bull. Chem. Soc. J pn. 1979, 52, 2149.
(η2-CH2dCCH2CHPh)(PPh3)2 (2) (Scheme 2). Complex
2 is sparingly soluble in toluene and separated from the
solution during the reaction.
Complex 1 has a distorted piano-stool coordination
around the Rh center that is bonded to a η4-2-phenyl-

4534 Organometallics, Vol. 17, No. 21, 1998
Communications
its reactivity with RhCl(PPh3)3 toward 1,3-diene forma-
tion. Heating of a benzene solution of 2 for 7 h at 50
°C led to the formation of 1 in a low NMR yield (<7%)
and a negligible amount of 2-phenyl-1,3-butadiene. The
reaction of 2 with 2-phenyl-1-methylenecyclopropane
(1:5 molar ratio) at 50 °C gave 1 (10%) and 2-phenyl-
1,3-butadiene (14%/Rh) after 6 h. Equimolar reaction
of 2 and RhCl(PPh3)3 under similar conditions led to
formation of 1 in less than 5% of 2.
methylenecyclopropane ligand of 2 (iii) is slower than
the above two reactions and is not operative in its ring-
opening isomerization promoted by RhCl(PPh3)3 at 50
°C.
The present study has demonstrated the reaction of
2-phenyl-1-methylenecyclopropane with RhCl(PPh3)3 to
give the ring-opening isomerization product and the
complex having the substrate as the η2-bonded ligand.
The latter product undergoes intramolecular C-C bond
activation of the ligand to a limited extent in the absence
and presence of 2-phenyl-1-methylenecyclopropane.14
This contrasts with the previously reported ring-opening
reactions of 2,2-dimethylcyclopropene and allenylcyclo-
propane promoted by Co or Ir complexes via an initial
coordination of a CdC double bond followed by an
intramolecular C-C bond cleavage.15
The above results provide the relative rates of the
possible reactions involved in forming 2-phenyl-1,3-
butadiene or its Rh complex, as summarized in Scheme
3. The reaction of 2-phenyl-1-methylenecyclopropane
with RhCl(PPh3)3 to give 2-phenyl-1,3-butadiene or 1
(i) occurs more rapidly than its reaction with 2 (ii). The
intramolecular C-C bond cleavage of the 2-phenyl-1-
Ack n ow led gm en t. This work was financially sup-
ported by a Grant-in-Aid for Scientific Research from
the Ministry of Education, Science, Sports, and Culture,
J apan.
(14) Reaction ii in Scheme 3 involves oxidative addition of 2-phenyl-
1-methylenecyclopropane to the Rh center of 2. More rapid exchange
between coordinated and uncoordinated 2-phenyl-1-methylenecyclo-
propane occurs at room temperature via an associative pathway since
addition of 2-(4-fluorophenyl)-1-methylenecyclopropane to a solution
of 2 causes its conversion into RhCl(η2-CH2dCCH2CHC6H4F-p)(PPh3)2
(3). Complexes 2 and 3 are equilibrated in the presence of 2-phenyl-
1-methylenecyclopropane and 2-(4-fluorophenyl)-1-methylenecyclopro-
pane with the thermodynamic parameters ∆H° ) -10.3 kJ mol-1 and
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedure and spectroscopic and crystallographic data of the
complexes and related reactions of 2-aryl-1-methylenecyclo-
propane with RhCl(PPh3)3 (12 pages). Ordering information
is given on any current masthead page.
∆S° ) -32 J mol-1 deg-1
.
(15) (a) Foerstner, J .; Kakoschke, A.; Stellfeldt, D.; Butenscho¨n, H.;
Wartchow, R. Organometallics 1998, 17, 893. (b) Murakami, M.; Itami,
K.; Ubukata, M.; Tsuji, I.; Ito, Y. J . Org. Chem. 1998, 63, 4.
OM980142Q