Hydrido-Rhodium(I) and -Iridium(I) complex promoted ring-opening isomerization of unsymmetrically substituted methylenecyclopropanes into 1,3-dienes. Structures of intermediates and reaction pathways

Article abstract of DOI:10.1021/om010081n

2-Phenyl-1-methylenecyclopropane and 2,2-diphenyl-1-methylenecyclopropane react with MH(CO)(PPh₃)₃ (M = Rh, Ir) to produce 1,3-dienes or the intermediate Rh and Ir complexes having a 3-butenyl ligand, depending on the conditions. The structures and chemical properties of the obtained complexes suggest plausible pathways for the ring-opening isomerization of the methylenecyclopropanes to the corresponding dienes.

Full text of DOI:10.1021/om010081n

2124
Organometallics 2001, 20, 2124-2126
Hyd r id o-Rh od iu m (I) a n d -Ir id iu m (I) Com p lex
P r om oted Rin g-Op en in g Isom er iza tion of
Un sym m etr ica lly Su bstitu ted Meth ylen ecyclop r op a n es
in to 1,3-Dien es. Str u ctu r es of In ter m ed ia tes a n d
Rea ction P a th w a ys
Yasushi Nishihara, Chikako Yoda, and Kohtaro Osakada*
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta,
Midori-ku, Yokohama 226-8503, J apan
Received February 1, 2001
Summary: 2-Phenyl-1-methylenecyclopropane and 2,2-
diphenyl-1-methylenecyclopropane react with MH(CO)-
(PPh3)3 (M ) Rh, Ir) to produce 1,3-dienes or the
intermediate Rh and Ir complexes having a 3-butenyl
ligand, depending on the conditions. The structures and
chemical properties of the obtained complexes suggest
plausible pathways for the ring-opening isomerization
of the methylenecyclopropanes to the corresponding
dienes.
Highly strained methylenecyclopropanes1 undergo
transition metal complex promoted ring opening to
afford various products, depending on the kind of
metal complex used and the reaction conditions. Rhod-
ium(I) complexes promote ring-opening addition of
methylenecyclopropane with alkenes,2 hydrosilylation
to give acyclic organosilanes,3 and intramolecular
phenylation of the cyclopropane via ring opening,2 as
well as isomerization to give 1,3-dienes or their Rh
complexes.4,5 Much less attention has been paid to
the mechanism involved in the reactions and, in par-
ticular, the roles of the Rh complexes that promote C-C
bond activation and subsequent bond formation reac-
tions to produce the functionalized products. In this
paper we report the reactions of substituted methyl-
enecyclopropanes with RhH(CO)(PPh3)3 and IrH(CO)-
(PPh3)3, leading to their ring-opening isomerization
into the corresponding 1,3-dienes, and the isolation of
the intermediate organo-rhodium and -iridium com-
plexes.
The molecular structure of 1, shown in Figure 1, verifies
the presence of a 2-phenyl-3-butenyl ligand derived from
the C-C activation of a methylenecyclopropane ring.7
The former reaction seems to involve an intermediate
Rh complex, having a structure analogous to that of 1,
but it was not found in the products due to rapid
formation of the 1,3-diene via â-hydrogen elimination.
The lack of formation of 1-phenyl-1,3-butadiene in
reaction 1 implies selective activation at the less sub-
stituted proximal C-C bond of the substrate.
2-Phenyl-1-methylenecyclopropane reacts with RhH-
(CO)(PPh3)3 at room temperature to promote smooth
ring-opening isomerization into 2-phenyl-1,3-butadiene
(eq 1), while the reaction with IrH(CO)(PPh3)3 produces
Ir(η1:η2-CH2CH(Ph)CHdCH2)(CO)(PPh3)2 (1) (eq 2).6
The reaction of 2-phenyl-1-methylenecyclopropane
with IrH(CO)(PPh3)3 at 50 °C in a 10:1 molar ratio
gives a mixture of 2-phenyl- and 1-phenyl-1,3-buta-
(1) (a) Wiberg, K. B. Angew. Chem., Int. Ed. Engl. 1986, 25, 312.
(b) Bachrach, S. M. J . Phys. Chem. 1993, 97, 4996.
(2) Chiusoli, G. P.; Costa, M.; Melli, L. J . Organomet. Chem. 1988,
358, 495.
(3) (a) Bessmertnykh, A. G.; Blinov, K. A.; Grishin, Y. K.; Donskaya,
N. A.; Tveritinova, E. V.; Yure´va, N. M.; Beletskaya, I. P. J . Org. Chem.
1997, 62, 6069. (b) Bessmertnykh, A. G.; Blinov, K. A.; Grishin, Y. K.;
Donskaya, N. A.; Tveritinova, E. V.; Beletskaya, I. P. Russ. J . Org.
Chem. (Engl. Transl.) 1969, 34, 799.
(4) Brown, J . M.; Kent, A. G. J . Chem. Soc., Perkin Trans. 2 1987,
1597.
(5) Osakada, K.; Takimoto, H.; Yamamoto, T. J . Chem. Soc., Dalton
Trans. 1999, 853.
(6) Preparation of 1: To a toluene (10 mL) solution of IrH(CO)-
(PPh3)3 (223 mg, 0.22 mmol) was added 2-phenyl-1-methylenecyclo-
propane (74 µL, 0.54 mmol) at room temperature. After 24 h the solvent
was removed by evaporation. Addition of hexane (10 mL) to the yellow
oily substance led to the formation of a pale yellow solid, which was
washed with 10 mL of hexane (four times), collected by filtration, and
dried in vacuo to give Ir(η1:η2-CH2CH(Ph)CHdCH2)(CO)(PPh3)2 (1; 171
mg, 0.20 mmol, 88%). Complex 1 crystallizes from toluene at -20 °C
as colorless crystals. Other complexes were obtained analogously from
the reactions at room temperature or at 50 °C.
10.1021/om010081n CCC: $20.00 © 2001 American Chemical Society
Publication on Web 04/24/2001

Communications
Organometallics, Vol. 20, No. 11, 2001 2125
F igu r e 1. Structure of complex 1 determined by X-ray
crystallography with 50% thermal ellipsoid plotting. Hy-
drogen atoms at the aromatic rings were omitted for
simplicity. Selected bond distances (Å) and angles (deg):
Ir1-P1 ) 2.385(4), Ir1-P2 ) 2.341(4), Ir1-C1 ) 1.65(3),
Ir1-C2 ) 2.11(1), Ir1-C4 ) 2.14(1), Ir1-C5 ) 2.12(2),
C2-C3 ) 1.54(2), C3-C4 ) 1.48(2), C4-C5 ) 1.33(2);
Ir1-C2-C3 ) 94.7(9), C2-C3-C4 ) 98(1), Ir1-C4-C3
) 95(1), Ir1-C4-C5 ) 71(1), C3-C4-C5 ) 120(2),
Ir1-C5-C4 ) 72(1).
F igu r e 2. Structure of complex 2 determined by X-ray
crystallography with 50% thermal ellipsoid plotting. Hy-
drogen atoms at the aromatic rings and solvated toluene
molecules were omitted for simplicity. Selected bond dis-
tances (Å) and angles (deg): Ir1-P1 ) 2.377(2), Ir1-P2 )
2.358(2), Ir1-C1 ) 1.869(6), Ir1-C2 ) 2.126(6), Ir1-C5
) 2.161(7), Ir1-C6 ) 2.144(7), C2-C3 ) 1.408(8), C3-C4
) 1.505(9), C4-C5 ) 1.509(9), C4-C7 ) 1.52(1), C5-C6
) 1.439(9); Ir1-C2-C3 ) 115.4(5), C2-C3-C4 ) 116.8-
(6), C3-C4-C5
) 109.5(6), C3-C4-C7 ) 116.0(6),
dienes and Ir(η1:η2-C6H4CH(Me)CHdCH2)(CO)(PPh3)2
(2) (eq 3). The molecular structure of complex 2 was
C5-C4-C7 ) 111.1(7), Ir1-C5-C4 ) 111.4(5), Ir1-C5-
C6 ) 69.8(4), C4-C5-C6 ) 121.6(6), Ir1-C6-C5 )
71.1(4).
proximal C-C bond (eq 4, Figure 3).9 Use of RhD(CO)-
confirmed by X-ray crystallography (Figure 2).8 2-Phen-
yl-1,3-butadiene and complex 2 are formed via â-hydro-
gen elimination of 1 and via orthometalation of the
phenyl group of 1, respectively. At that temperature,
the reaction produces 1-phenyl-1,3-butadiene from par-
tial activation of the more highly substituted proximal
bond of the substrate.
2,2-Diphenyl-1-methylenecyclopropane reacts with
RhH(CO)(PPh3)3 at room temperature to give Rh(η1:η2-
CH2CPh2CHdCH2)(CO)(PPh3)2 (3) via cleavage of the
(PPh3-d15)3 results in selective deuteration at the γ-posi-
tion of the ligand. The C-C bond activation appears to
involve the initial insertion of the CdC double bond into
the Rh-H bond and an ensuing â-alkyl elimination10
of the resulting cyclopropylmethyl rhodium complex
(Scheme 1).
(9) X-ray data for 3: monoclinic, C2/c (No. 15), a ) 28.705(6) Å, b )
20.170(4) Å, c ) 22.962 (4) Å, â ) 122.77(1)°, V ) 11179 Å3, Z ) 8,
Dcalcd ) 1.200 g cm-3, F(000) ) 4208, µ(Mo KR) ) 0.402 mm-1 for
monochromated Mo KR radiation (λ ) 0.710 69 Å), R (Rw) ) 0.072
(0.105) for 4727 reflections with I > 3σ(I) among 13 210 unique
reflections (Rint ) 0.065), 528 parameters, GOF ) 2.45.
(7) X-ray data for 1: monoclinic, P21/c (No. 14), a ) 14.128(3) Å, b
) 18.584(3) Å, c ) 15.013(3) Å, â ) 100.62(2)°, V ) 3874 Å3, Z ) 4,
Dcalcd ) 1.502 g cm-3, F(000) ) 1752, µ(Mo KR) ) 3.57 mm-1 for
monochromated Mo KR radiation (λ ) 0.71069 Å), R (Rw) ) 0.058
(10) â-Alkyl elimination of late-transition-metal complexes: (a)
Thompson, S. K.; Young, G. B. Organometallics 1989, 8, 2068. (b)
Alkianiec, B.; Christou, V.; Hardy, D. T.; Thompson, S. K.; Young, G.
B. J . Am. Chem. Soc. 1994, 116, 9963. (c) Hartwig, J . F.; Andersen, R.
A.; Bergman, R. G. J . Am. Chem. Soc. 1989, 111, 2717. (d) McNeill,
K.; Andersen, R. A.; Bergman, R. G. J . Am. Chem. Soc. 1997, 119,
11244. (e) Kaplan, A. W.; Bergman, R. G. Organometallics 1997, 16,
1106. (f) Thomas, B. J .; Noh, S. K.; Schulte, G. K.; Sendlinger, S. C.;
Theopold, K. H. J . Am. Chem. Soc. 1991, 113, 893. (g) Takemori, T.;
Suzuki, H.; Tanaka, M. J . Am. Chem. Soc. 1994, 116, 10779. See also:
Rybtchinski, B.; Vigalok, A.; Ben-David, Y.; Milstein, D. J . Am. Chem.
Soc. 1996, 118, 12406.
(0.057) for 4246 reflections with
I > 3σ(I) among 9166 unique
reflections (Rint ) 0.044), 460 parameters, GOF ) 1.87.
(8) X-ray data for 2: monoclinic, P21/c (No. 14), a ) 13.214(4) Å, b
) 21.397(3) Å, c ) 14.678(2) Å, â ) 93.71(2)°, V ) 4141 Å3, Z ) 4,
Dcalcd ) 1.479 g cm-3, F(000) ) 1852, µ(Mo KR) ) 3.35 mm-1 for
monochromated Mo KR radiation (λ ) 0.710 69 Å), R (Rw) ) 0.039
(0.034) for 5990 reflections with
reflections (Rint ) 0.021), 476 parameters, GOF ) 1.70.
I > 3σ(I) among 8695 unique

2126 Organometallics, Vol. 20, No. 11, 2001
Communications
Sch em e 1
Sch em e 2
F igu r e 3. Structure of complex 3 determined by X-ray
crystallography with 50% thermal ellipsoid plotting. Hy-
drogen atoms at the aromatic rings and solvated molecules
were omitted for simplicity. Selected bond distances (Å) and
angles (deg): Rh1-P1 ) 2.408(4), Rh1-P2 ) 2.376(4),
Rh1-C1 ) 1.89(1), Rh1-C2 ) 2.13(1), Rh1-C4 ) 2.12(1),
Rh1-C5 ) 2.16(1), C2-C3 ) 1.52(2), C3-C4 ) 1.54(2),
C4-C5 ) 1.36(2); Rh1-C2-C3 ) 96.0(8), C2-C3-C4 )
97(1), Rh1-C4-C3 ) 95.8(8), Rh1-C4-C5 ) 72.9(8),
C3-C4-C5 ) 116(1), Rh1-C5-C4 ) 70.0(8).
of the diene from the ligand is not plausible, the reaction
probably involves skeletal rearrangement and C-C
bond formation of the 2,2-diphenyl-3-butenyl ligand to
regenerate a cyclopropane ring11 followed by its C-C
activation, as shown in Scheme 2. Complex 3, which is
formed as the kinetic product of C-C activation of reac-
tion 5, would be transformed into the diene via a similar
pathway and regenerate the hydridorhodium complex
that promotes further ring-opening isomerization.
The reaction of 2,2-diphenyl-1-methylenecyclopropane
with RhH(CO)(PPh3)3 at 50 °C leads to its ring-opening
isomerization into 1,1-diphenyl-1,3-butadiene accompa-
nied by formation of Rh(η1:η2-C6H4C(Me)PhCHdCH2)-
(CO)(PPh3)2 (4) (eq 5). To elucidate the role of complex
Ack n ow led gm en t. This work was supported by a
Grant-in-Aid for Scientific Research on Priority Areas,
“Molecular Physical Chemistry”, from the Ministry of
Education, Science, Culture, and Sports of J apan (No.
11166221).
Su p p or tin g In for m a tion Ava ila ble: Text and tables
giving experimental procedures and crystallographic data for
1-3. This material is available free of charge via the Internet
at http://pubs.acs.org.
OM010081N
(11) Several thermally induced rearrangements of organotransition-
metal complexes occur with cyclization of the organic ligand via C-C
bond formation, giving a small ring: (a) Flood, T. C.; Bitler, S. P. J .
Am. Chem. Soc. 1984, 106, 6076. (b) Flood, T. C.; Statler, J . A.
Organometallics 1984, 3, 1795. (c) Ermer, S. P.; Struck, G. E.; Bitler,
S. P.; Richards, R.; Bau, R.; Flood, T. C. Organometallics 1993, 12,
2634. (d) Casey, C. P.; Hallenbeck, S. L.; Pollock, D. W.; Landis, C. R.
J . Am. Chem. Soc. 1995, 117, 9770. (e) J un, C.-H. Organometallics
1996, 15, 895.
3 in the above reaction, chemical properties of the
complexes were examined. Once isolated, complex 4
does not produce the 1,3-diene at elevated temperatures.
Heating 3 at 50 °C causes the liberation of 1,1-diphenyl-
1,3-butadiene in 44% yield. Since the direct elimination