Deprotonation of iron vinylidene complexes containing a dppe ligand

Article abstract of DOI:10.1021/om061005t

Two iron complexes each containing a 1-ferra-2,5-diphospha-[2.1.1] ring are prepared by deprotonation reaction of cationic vinylidene complexes [Fe]=C=C(Ph)CH₂R⁺ ([Fe] = (η⁵-C ⁵H⁵)(dppe)Fe, R = CH= CH² and Ph). The deprotonation takes place at the methylene proton of the dppe ligand, which is followed by an intramolecular addition giving the product. For similar vinylidene complexes with R = CN, p-C₆₄-CN, and p-C ₆H₄CF₃, the deprotonation reaction gave the cyclopropenyl complexes. The deprotonation of the vinylidene complex with R = C₆F₅ gave both the cyclopropenyl complex and the product containing a 1-ferra-2,5-diphospha-[2.1.1] ring system. The electron-withdrawing ability of the substituent near the C_γ-methylene group of the vinylidene ligand determines the selectivity of deprotonation. Characterizations of vinylidene, cyclopropenyl complexes, and a complex containing a 1-ferra-2,5-diphospha-[2.1.1] ring are carried out using single-crystal X-ray diffraction analysis.

Full text of DOI:10.1021/om061005t

1250
Organometallics 2007, 26, 1250-1255
Deprotonation of Iron Vinylidene Complexes Containing a dppe
Ligand
Yung-Sheng Yen, Ying-Chih Lin,* Yi-Hung Liu, and Yu Wang
Department of Chemistry, National Taiwan UniVersity, Taipei, Taiwan 106, Republic of China
ReceiVed NoVember 1, 2006
Two iron complexes each containing a 1-ferra-2,5-diphospha-[2.1.1] ring are prepared by deprotonation
reaction of cationic vinylidene complexes [Fe]dCdC(Ph)CH2R+ ([Fe] ) (η5-C5H5)(dppe)Fe, R ) CHd
CH2 and Ph). The deprotonation takes place at the methylene proton of the dppe ligand, which is followed
by an intramolecular addition giving the product. For similar vinylidene complexes with R ) CN, p-C6H4-
CN, and p-C6H4CF3, the deprotonation reaction gave the cyclopropenyl complexes. The deprotonation
of the vinylidene complex with R ) C6F5 gave both the cyclopropenyl complex and the product containing
a 1-ferra-2,5-diphospha-[2.1.1] ring system. The electron-withdrawing ability of the substituent near the
Cγ-methylene group of the vinylidene ligand determines the selectivity of deprotonation. Characterizations
of vinylidene, cyclopropenyl complexes, and a complex containing a 1-ferra-2,5-diphospha-[2.1.1] ring
are carried out using single-crystal X-ray diffraction analysis.
accessible ruthenium vinylidene complexes containing a -CH2R
group bound to Câ. With the presence of a terminal vinyl group
suitably placed at a proper site, the ruthenium vinylidene
complex displays novel intramolecular metathesis reactivity
between the two CdC double bonds.8 Encouraged by the rich
chemistry of ruthenium vinylidene complexes, we set out to
explore the chemical reactivity of iron complexes. Since
relatively few vinylidene complexes of iron with a dppe ligand9
have been obtained, we therefore studied the iron complexes
with such a ligand. Interestingly, deprotonation could take place
either at the methylene group on Cγ of the vinylidene ligand or
at the methylene group of the dppe ligand.
Introduction
Vinylidene complexes of various metals1 commonly function
as strategic intermediates for catalytic conversion of alkynes
such as cycloaromatization of conjugated enediynes,2 dimer-
ization of terminal alkynes,3 and addition of oxygen, nitrogen,
and carbon nucleophiles to alkynes.4 Recently, the importance
of vinylidene intermediates in catalysis has been pointed out.5
Therefore the synthesis and stoichiometric reactivity of these
unsaturated ligands are under active investigation.6 The forma-
tion of metal vinylidene intermediates has been used to promote
new carbon-carbon bond forming reactions by the addition of
carbon centers to the electrophilic vinylidene carbon atom. The
reactivity of ruthenium vinylidene complexes finds their ap-
plications broadly in synthetic chemistry; however, studies on
iron complexes with highly unsaturated carbon-rich ligands such
as acetylide, vinylidene, and allenylidene are relatively scarce.7
We previously reported8 synthesis of a number of ruthenium
cyclopropenyl complexes by deprotonation reaction of readily
Results and Discussion
Iron Acetylide and Vinylidene Complexes. The reported
preparation of iron acetylide complexes in the literature10 via
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10.1021/om061005t CCC: $37.00 © 2007 American Chemical Society
Publication on Web 01/27/2007

Deprotonation of Iron Vinylidene Complexes
Organometallics, Vol. 26, No. 5, 2007 1251
Scheme 1
Figure 1. Molecular structure of complex 4d (hydrogen atoms
and phenyl groups on dppe except the ipso carbon are removed
for clarity). Thermal ellipsoids are shown at the 30% level. Selected
bond lengths [Å] and angles [deg]: Fe(1)-P(1), 2.207(1); Fe(1)-
P(2), 2.199(1); Fe(1)-C(1), 1.766(4); C(1)-C(2), 1.320(5); C(2)-
C(3), 1.532(5); C(4)-C(5), 1.268(7); P(1)-Fe(1)-P(2), 84.81(4);
Fe(1)-C(1)-C(2), 178.7(3); C(1)-C(2)-C(3), 120.7(3); C(2)-
C(3)-C(4), 114.2(3).
alcohols or water to give alkoxycarbene or acyl complexes,
respectively.13,14 The reaction is thought to proceed by nucleo-
philic attack at the vinylidene R carbon, followed by a proton
shift from the oxonium ion to the â-carbon. However, vinylidene
complexes 4 and 4* are inert to alcohols and water, giving no
alkoxy carbene complexes.
deprotonation of the vinylidene intermediate was modified to
give [Fe]CtCPh (3, [Fe] ) (η5-C5H5)(dppe)Fe) and [Fe*]Ct
CPh, (3*, [Fe*] ) (η5-C5Me5)(dppe)Fe) both with moderate
yields without isolation of the vinylidene precursor. Reaction
of the iron acetylide complex 3 with ICH2CN at room
temperature afforded the cationic vinylidene complex {[Fe]d
CdC(Ph)CH2CN}I (4a). Similarly, preparation of various
vinylidene complexes [Fe]dCdC(Ph)CH2R+ (4b, R ) p-C6H4-
CN; 4c, R ) p-C6H4CF3; 4d, R ) CHdCH2; 4e, R ) Ph; 4f,
R ) C6F5) have been successfully accomplished by reacting 3
with corresponding primary alkyl halides in CH2Cl2 at room
temperature all with high yields. All iron vinylidene complexes
4a-f display a characteristic deep red color in CDCl3. Pen-
tamethyl-cyclopentadienyl vinylidene complexes [Fe*]dCd
C(Ph)CH2R+ (4a*, R ) CN; 4b*, R ) p-C6H4CN) can also be
prepared from electrophilic addition of primary alkyl halides
to the acetylide ligand of complex 3*.
Synthesis of Cyclopropenyl Complexes. Deprotonation of
n
the vinylidene complex 4a by Bu4NOH in acetone induces a
cyclization reaction affording the neutral cyclopropenyl complex
5a in high yield; see Scheme 1. The same reaction is also
observed in THF and CH2Cl2. Complex 5a is stable in benzene,
toluene, and hexane but unstable in CHCl3 and MeOH, in which
5a is protonated to give back 4a quantitatively. Formation of
the cyclopropenyl ring from the vinylidene ligand should
generate a stereogenic carbon center giving two doublet 31P
resonances at δ 109.7 and 107.9 with 2JP-P ) 33.0 Hz assignable
to the dppe ligand in the 31P NMR spectrum of 5a.8 Single
crystals of 5a were obtained by slow evaporation of a diethyl
ether solution of 5a at low temperature. The solid-state
structure of 5a is determined by an X-ray diffraction analysis.
An ORTEP drawing of 5a is shown in Figure 2. The cyclo-
propenyl ring is clearly seen with the cyano group bound to
the unique sp3 carbon of the cyclopropenyl ligand. The Fe-
C(1) bond length is 1.903(4) Å and the C(1)-C(4) bond length
of 1.328(5) Å is a double bond, indicating coordination of the
sp2 carbon of the cyclopropenyl ligand. The bond angles Fe-
C(1)-C(4) and C(1)-C(4)-C(5) of 163.3(3)° and 155.0(3)°,
respectively, are both far greater than that of an idealized C(sp2)
hybridization. The C(1)-C(2) and C(2)-C(4) bond lengths of
1.580(5) and 1.489(6) Å, respectively, are significantly different,
consistent with the favorable cleavage of the C(1)-C(2) bond
of 5a in acid.
Distinctive spectroscopic data of 4a consist of a strongly
deshielded CR resonance as a triplet at δ 353.4 with JP-C
)
32.7 Hz in the 13C NMR spectrum.11 In the 13C NMR spectrum
of 4a* a strongly deshielded CR resonance as a triplet at δ 346.6
with JP-C ) 32.4 Hz is also observed. Single crystals of 4d
suitable for X-ray diffraction analysis were obtained by recrys-
tallization from acetone/diethyl ether. An ORTEP drawing is
shown in Figure 1. The coordination around the Fe atom can
be described as a three-legged piano stool. The Fe-C(1) bond
length of 1.766(4) Å is in the range of a regular iron-carbon
double bond in other crystallographically characterized iron
vinylidene complexes.12 The C(1)-C(2) bond length of 1.320-
(5) Å is a typical double bond. The bond angles Fe-C(1)-
C(2) and C(1)-C(2)-C(3) are 178.7(3)° and 120.7(3)°, respec-
tively. Cationic vinylidene complexes are known to react with
The same deprotonation-induced cyclization process in
acetone takes place for a number of vinylidiene complexes. We
prepared similar cyclopropenyl complexes (5b, R ) p-C6H4-
CN; 5c, R ) p-C6H4CF3; 5a*, R ) CN; 5b*, R ) p-C6H4CN);
(10) (a) Connelly, N. G.; Gamasa, M. P.; Gimeno, J.; Lapinte, C.; Lastra,
E.; Maher, J. P.; Le Narvor, N.; Rieger, A. L.; Rieger, P. H. J. Chem. Soc.,
Dalton Trans. 1993, 2575. (b) Bitcon, C.; Whiteley, M. W. J. Organomet.
Chem. 1987, 336, 385.
(11) (a) Allen, D. L.; Gibson, V. C.; Green, M. L.; Skinner, T. F.;
Bashikin, J.; Grebenik, P. D. J. Chem. Soc., Chem. Commun. 1983, 895.
(b) Consiglio, G.; Morandini, F. Chem. ReV. 1987, 87, 761.
(12) (a) Selegue, J. P. J. Am. Chem. Soc. 1982, 104, 119. (b) Gamasa,
M. P.; Gimeno, J.; Lastra, E.; Mart´ın, B. M. Organometallics 1992,
11, 1373. (c) Iyer, R. S.; Selegue, J. P. J. Am. Chem. Soc. 1987, 109,
910.
(13) Antonova, A. B.; Johanson, A. A. Russ. Chem. ReV. 1989, 58, 693
(Usp. Khim. 1989, 587, 1197).
(14) (a) Davison, A.; Solar, J. P. J. Organomet. Chem. 1978, 155, C8.
(b) Jolly, P. W.; Pettit, R. J. Organomet. Chem. 1968, 12, 491. (c) Bell, R.
A.; Chisholm, M. H.; Couch, D. A.; Rankel, C. A. Inorg. Chem. 1977, 16,
677. (d) Bell, R. A.; Chisholm, M. H. Inorg. Chem. 1977, 16, 687. (e)
Gamasa, M. P.; Gimeno, J.; Lastra, E.; Lanfranchi, M.; Tiripicchio, A. J.
Organomet. Chem. 1992, 430, C39.

1252 Organometallics, Vol. 26, No. 5, 2007
Yen et al.
The 31P NMR spectrum of 6d in C6D6 shows two doublet
resonances at δ 90.0 and 44.9 with 2JP-P ) 45.5 Hz assignable
to two different phosphorus atoms, with the latter shifted upfield
1
significantly. The H NMR spectrum of 6d shows resonances
at δ 5.86 and 4.96 assignable to the vinyl group. The 13C NMR
spectrum shows a doublet of doublets signal at δ 140.5 with
JP-C ) 9.5, 6.4 Hz assignable to CR, confirming the nucleophilic
addition at the R-carbon of the vinylidene ligand. The doublet
of doublets resonance at δ 57.9 with JP-C ) 36.1 and 18.1 Hz
assignable to CH resulted from deprotonation of the dppe
ligand shifted significantly toward the downfield region
1
from that of a regular CH2 of dppe. In the 2D H-13C HSQC
1
NMR spectrum correlation between H resonances at δ 4.60
with one proton and 13C resonance at δ 57.9 as well as the
correlation between 2.54, 1.98 (1H two protons) and 32.5 (13C)
assignable to the bridging group of the dppe ligand clearly
reveal the site of deprotonation. Formation of complex 6d
resulted from initial deprotonation of the dppe ligand to afford
a zwitterionic intermediate followed by an intramolecular
addition of the ethanide carbon atom to CR of the vinylidene
ligand. Formation of a few related complexes of Fe and Ru as
a result of similar intramolecular coupling between a deproto-
nated dppe ligand and a vinylidene moiety has been reported.18
Recently, Gimeno and his co-workers have studied intramo-
lecular carbon-carbon coupling of a dppm ligand with a
vinyilidene and allenyidene moiety in an indenyl-ruthenium
system.19
Figure 2. Molecular structure of complex 5a (hydrogen atoms and
phenyl groups on dppe except the ipso carbon are removed for
clarity). Thermal ellipsoids are shown at the 30% level. Selected
bond lengths [Å] and angles [deg]: Fe(1)-P(1), 2.164(1); Fe(1)-
P(2), 2.156(1); Fe(1)-C(1), 1.903(4); C(1)-C(2). 1.580(5); C(1)-
C(4), 1.328(5); C(2)-C(4), 1.489(6); P(1)-Fe(1)-P(2), 87.06(3);
Fe(1)-C(1)-C(2), 135.2(3); Fe(1)-C(1)-C(4), 163.3(3); C(2)-
C(1)-C(4), 60.9(3); C(1)-C(2)-C(4), 51.2(2); C(1)-C(4)-C(2),
67.9(3).
see Scheme 1. Spectroscopic data of complexes 5b, 5c, 5a*,
and 5b* are all consistent with their formula.
Single crystals of 6d suitable for X-ray diffraction analysis
are obtained by slow evaporation from a hexane solution. An
ORTEP drawing is shown in Figure 3, with representative bond
lengths and bond angles. Complex 6d contains a 1-ferra-2,5-
diphospha-[2.1.1] ring system. The central coordination sphere
of the iron atom contains a Cp ring, a vinylic carbon, and two
phosphorus atoms. The vinylic R-carbon C(1) bonds both to
the iron atom and to one (C(17)) of the carbons in the ethylene
bridge of the dppe ligand. The four-membered ring has bond
angles of 68.84(9)°, 86.94(10)°, 88.6(2)°, and 98.7(2)° at Fe,
P(1), C(17), and C(1), respectively. The C(1)-C(17) bond length
of 1.551(4) Å is relatively long. The Fe-C(1) bond length is
2.045(3) Å, slightly longer than a normal Fe-C(sp2) bond.20-22
The five-membered ring shows less sign of strain, although the
P(2)-C(18)-C(17) angle of 102.2(2)° is rather acute. The
C(1)-C(2) bond length of 1.339(4) Å is typical for a carbon-
carbon double bond, and substituents on these two carbon atoms
are nearly coplanar.
Previously, iron cyclopropenyl derivatives in which the iron
bonds to C(sp3) of the cyclopropenyl ring have been prepared
by the reaction of cyclopropenylium salts with sodium dicar-
bonyl(cyclopentadienyl)ferrate.15 However, a derivative in which
the metal is bound to the C(sp2) of the three-membered ring is
rare.16 A few structurally different transition metal cyclopro-
penylidene complexes, mostly prepared from dichlorocyclopro-
pene,16 and a number of π-cyclopropene complexes17 are also
known. Our synthetic strategy provides a convenient route to a
metal-coordinated cyclopropenyl moiety with a M-C(sp2)
bonding.
Alternative Intramolecular Addition of Iron Vinylidiene
Complexes. In the deprotonation reaction of 4d, with R ) CHd
CH2 no cyclopropenyl complex is observed. Instead, the
deprotonation of 4d at one methylene proton of the dppe
n
ligand by Bu4NOH is followed by an intramolecular nucleo-
Deprotonation of the vinylidene complex 4e with R ) Ph
gave similar metallacyclic complex 6e exclusively. Both met-
allacyclic derivatives 6d and 6e are air-stable orange solids.
Noticeably, the 31P NMR spectrum of 6e shows that there are
Z-form and E-form isomers in a 6:1 ratio. In refluxing THF the
E isomer is converted to the Z isomer. Previously, it has been
philic addition of the deprotonated carbon to CR of the
vinylidene ligand, affording complex 6d (see Scheme 1). The
orange solid product 6d is air stable at room temperature. A
neutral ruthenium cyclopropenyl triphenylphosphine complex8
with a vinyl substituent at the three-membered ring could be
prepared from deprotonation of their vinylidene precursor. The
relatively more acidic proton of the dppe ligand in the cationic
iron complex 4d could direct the reaction to proceed via a
different route.
(18) (a) Adams, R. D.; Davison, A.; Selegue, J. P. J. Am. Chem. Soc.
1979, 101, 7232. (b) Bruce, M. I.; Cifuentes, M. P.; Humphrey, M. G.;
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429, C19.
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C.; Borge, J.; Garc´ıa-Granda, S. Organometallics 1997, 16, 4453. (b)
Cadierno, V.; Gamasa, M. P.; Gimeno, J.; Mart´ın-Vaca, B. M. J. Organomet.
Chem. 2001, 617-618, 261.
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Chem. 1977, 135, 361.
(15) (a) Gompper, R.; Bartmann, E. Angew. Chem., Int. Ed. Engl. 1978,
17, 456. (b) Gompper, R.; Bartmann, E. Angew. Chem., Int. Ed. Engl. 1985,
24, 209. (c) Morton, M. S.; Selegue, J. P. J. Organomet. Chem. 1999, 578,
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(16) (a) Kirchgassner, U.; Piana, H.; Schubert, U. J. Am. Chem. Soc.
1991, 113, 2228. (b) Miki, S.; Ohno, T.; Iwasaki, H.; Yoshida, Z. I. J.
Phys. Org. Chem. 1988, 1, 333.
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P.; Reisch, J. W.; Rheingold, A. L. Organometallics 1985, 4, 1754. (c)
Hughes, R. P.; Kla¨ui, W.; Reisch, J. W.; Mu¨ller, A.; Rheingold, A. L.
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A. K.; Amma, E. L. Organometallics 1982, 1, 443.

Deprotonation of Iron Vinylidene Complexes
Organometallics, Vol. 26, No. 5, 2007 1253
diphosphabicyclo[2.1.1]hexane complex 6. For the iron complex
containing a pentafluorophenyl group at Cγ of the vinylidene
ligand, the deprotonation reaction could take place at both sites
and a mixture was obtained.
Experimental Section
General Procedures. All manipulations were performed under
an atmosphere of dry nitrogen using vacuum-line and standard
Schlenk techniques. Solvents were dried by standard methods and
distilled under nitrogen before use. All reagents were obtained from
commercial suppliers and used without further purification. Com-
pounds [Fe]-CtC-Ph (3, [Fe] ) (η5-C5H5)(dppe)Fe) and [Fe*]-
CtC-Ph, (3*, [Fe*] ) (η5-C5Me5)(dppe)Fe) were prepared by
following the methods reported in the literature.10 Infrared spectra
were recorded on a Nicolet-MAGNA-550 spectrometer. The C, H,
and N analyses were carried out with a Perkin-Elmer 2400
microanalyzer. Mass spectra (FAB) were recorded using a JEOL
SX-102A spectrometer; 3-nitrobenzyl alcohol (NBA) was used as
the matrix. NMR spectra were recorded on a Bruker AC-300
instrument or a DMX 500 FT-NMR spectrometer at room temper-
ature using SiMe4 or 85% H3PO4 as standard.
Figure 3. Molecular structure of complex 6d (hydrogen atoms
and phenyl groups on dppe except the ipso carbon are
removed for clarity). Thermal ellipsoids are shown at the 30% level.
Selected bond lengths [Å] and angles [deg]: Fe(1)-P(1), 2.147-
(1); Fe(1)-P(2), 2.156(1); Fe(1)-C(1), 2.045(3); C(1)-C(2), 1.339-
(4); C(1)-C(17), 1.551(4); C(2)-C(3), 1.535(5); C(4)-C(5),
1.248(6); P(1)-Fe(1)-P(2), 87.73(4); C(1)-Fe(1)-P(1), 68.84-
(9); Fe(1)-P(1)-C(17), 86.94(10); Fe(1)-C(1)-C(2), 139.7(2); Fe-
(1)-C(1)-C(17), 98.7(2); C(1)-C(2)-C(3), 124.4(3); C(1)-
C(17)-P(1), 88.6(2).
Synthesis of {[Fe]dCdC(Ph)CH2CN}I, 4a. To a Schlenk flask
charged with 3 (0.10 g, 0.161 mmol) in CH2Cl2 (15 mL) was added
ICH2CN (0.11 mL, 1.64 mmol) under nitrogen. The resulting
solution was stirred at room temperature for 5 h, then the solvent
was reduced to about 5 mL. The mixture was slowly added to
vigorously stirred diethyl ether (50 mL). The gray precipitate thus
formed was filtered off and washed with diethyl ether and dried
under vacuum to give 4a (99 mg, yield 78%, mp ) 197 °C, dec).
Spectroscopic data for 4a: 1H NMR (CDCl3) δ 7.45-6.79 (m, 25H,
Ph), 5.31 (s, 5H, Cp), 3.48-3.12 (m, 4H, CH2CH2 of dppe), 2.64
(s, 2H, CH2CN); 13C NMR (CDCl3) δ 353.4 (t, JP-C ) 32.7 Hz,
reported that in the ruthenium indenyl complex the steric
requirements of the indenyl ligand and the bulky tBu group on
the alkenyl group would favor the E configuration.19b,23 When
a less sterically demanding phenyl group replaces the tBu group,
a mixture of Z-form and E-form isomers was obtained. In our
system the steric hindrance between the Cp ring and the
substituents on Câ probably is insignificant, therefore giving
the Z-form as the more stable isomer.
CR), 135.0-124.8 (Câ, Ph), 118.0 (CN), 89.2 (Cp), 27.9 (t, JP-C
)
22.6 Hz, dppe), 14.7 (CH2CN); 31P NMR (CDCl3) δ 93.4 (s, dppe);
MS m/z 660.2 (M+ - I), 519.1 (M+ - I, C2PhCH2CN). Anal. Calcd
for C41H36NFeIP2 (787.43): C, 62.54; H, 4.61; N, 1.78. Found:
C, 62.81; H, 4.52; N, 1.91.
Interestingly, deprotonation of the vinylidene complex 4f with
a C6F5 group was observed to give a mixture of the cyclopro-
penyl complex 5f and the metallacyclic complex 6f in a
2:8 ratio. The presence of the electron-withdrawing C6F5
group enhances the acidity of the neighboring methylene
proton, making protons at the dppe and vinylidene ligand
comparable in acidity. Therefore the deprotonation could
take place at each site. For 6f two isomers (Z/E) are observed
in a 13:1 ratio. Spectroscopic data for complex 6f (Z-form)
are in accordance with the proposed structure. No attempt was
made to isolate the cyclopropenyl compound 5f from the
mixture.
Synthesis of {[Fe]dCdC(Ph)CH2R}X (4b, R ) p-C6H4CN,
X ) Br; 4c, R ) p-C6H4CF3, X ) Br; 4d, R ) CHdCH2, X )
I; 4e, R ) Ph, X ) Br; 4f, R ) C6F5, X ) Br). Synthesis of
4b-f followed the same procedure as that used for the preparation
of 4a. Spectroscopic data of 4b (yield 87%, mp ) 190 °C, dec):
1H NMR (CDCl3) δ 7.42-6.52 (m, 29H, Ph), 5.21 (s, 5H, Cp),
3.17-3.06 (m, 4H, CH2CH2 of dppe), 3.02 (s, 2H, CH2); 13C NMR
(CDCl3) δ 357.3 (t, JP-C ) 32.7 Hz, CR), 144.3-127.5 (Ph), 118.8
(CN), 109.8 (Câ), 88.8 (Cp), 31.7 (CH2), 28.7 (t, JP-C ) 22.7 Hz,
CH2); 31P NMR (CDCl3) δ 94.1 (s, dppe); MS m/z 736.2 (M+
-
Br), 519.1 (M+ - Br, C2PhCH2(p-C6H4CN)). Anal. Calcd for
C47H40NBrFeP2 (816.49): C, 69.13; H, 4.94; N, 1.72. Found: C,
69.19; H, 4.90; N, 1.65. Spectroscopic data of 4c (yield 83%): 1H
NMR (CDCl3) δ 7.34-6.49 (m, 29H, Ph), 5.16 (s, 5H, Cp), 3.08-
3.05 (m, 4H, CH2CH2 of dppe), 2.97 (s, 2H, CH2); 13C NMR
(CDCl3) δ 357.8 (t, JP-C ) 33.2 Hz, CR), 138.0-125.0 (Ph), 88.7
(Cp), 31.4 (CH2), 28.6 (t, JP-C ) 23.1 Hz, CH2); 31P NMR (CDCl3)
δ 94.9 (s, dppe); MS m/z 779.3 (M+ - Br), 519.2 (M+ - Br, C2-
PhCH2(p-C6H4CF3)). Anal. Calcd for C47H40F3FeBrP2 (859.48): C,
65.68; H, 4.69. Found: C, 65.74; H, 4.78. Spectroscopic data of
4d (yield 92%): 1H NMR (CDCl3) δ 7.41-6.63 (m, 25H, Ph),
5.28 (m, 1H, CHd), 5.17 (s, 5H, C5H5), 4.82 (dd, 1H, J ) 10.3
Hz, J ) 1.35 Hz, CH2), 4.61 (dd, 1H, J ) 16.9 Hz, J ) 1.35 Hz,
CH2), 3.30-3.07 (m, 4H, CH2CH2 of dppe), 2.35 (d, 2H, J ) 6.13
Hz, CH2); 13C NMR (CDCl3) δ 359.3 (t, Jp-c ) 32.8 Hz, CR),
137.8-126.8 (Ph, Câ, CHd), 116.6 (dCH2), 88.4 (Cp), 51.5 (CH2),
30.1 (CH2), 28.2 (t, Jp-c ) 22.9 Hz, CH2CH2 of dppe); 31P NMR
(CDCl3) δ 94.4 (s, dppe); MS m/z 660.3 (M+ - I). Anal. Calcd for
C42H39FeIP2 (788.43): C, 63.98; H, 4.99. Found: C, 63.80; H, 4.97.
Concluding Remarks
In the deprotonation reaction of iron vinylidene complexes
containing a dppe ligand, various electron-withdrawing groups
at Cγ of the vinylidene ligand control the site of deprotonation
reaction, leading to different products. Neutral iron cyclopro-
penyl complexes 5a-c containing a bidentate dppe ligand are
obtained from the deprotonation of an iron complex with an
electron-withdrawing group such as CN or p-C6H4CN at Cγ of
the vinylidene ligand. Namely, the deprotonation takes place
at the Cγ-methylene group of the vinylidene ligand. For
complexes without an electron-withdrawing group, deprotona-
tion takes place at the dppe ligand, affording the 1-ferra-2,5-
(23) Reger, D. L. Acc. Chem. Res. 1988, 21, 229.

1254 Organometallics, Vol. 26, No. 5, 2007
Yen et al.
Spectroscopic data of 4e (yield 91%): 1H NMR (CDCl3) δ 7.41-
6.54 (m, 30H, Ph), 5.18 (s, 5H, Cp), 3.44 (m, 2H, CH2 of dppe),
3.19 (m 2H, CH2 of dppe), 2.95 (s, 2H, CH2); 13C NMR (CDCl3)
δ 358.9 (t, JP-C ) 32.7 Hz, CR), 138.6-126.2 (Ph, Câ), 88.5 (Cp),
31.7 (CH2Ph), 28.6 (t, JP-C ) 23.0 Hz, CH2); 31P NMR (CDCl3) δ
94.4 (s, dppe). Anal. Calcd for C46H41FeBrP2 (791.48): C, 69.80;
H, 5.22. Found: C, 69.75; H, 5.57. Spectroscopic data of 4f (yield
86%): 1H NMR (CDCl3) δ 7.40-6.53 (m, 25H, Ph), 5.23 (s, 5H,
Cp), 3.16 (m, 4H, CH2CH2 of dppe), 2.87 (s, 2H, CH2); 13C NMR
(CDCl3) δ 352.7 (t, JP-C ) 32.4 Hz, CR), 137.0-127.7 (Ph, Câ),
88.9 (Cp), 28.1 (t, JP-C ) 23.0 Hz, CH2), 19.1 (CH2); 31P NMR
620.1 (M+ - CH(p-C6H4CF3)), 519.1 (M+ - CH(p-C6H4CF3), C2-
Ph). Anal. Calcd for C47H39F3FeP2 (778.57): C, 72.50; H, 5.05.
Found: C, 72.61; H, 4.95. Spectroscopic data of 5a* (yield 85%):
1H NMR (C6D6) δ 7.82-6.52 (m, 25H, Ph), 2.68 (m, 1H, dppe),
2.04-1.84 (m, 3H, dppe), 1.59 (s, 15H, C5Me5), 0.34 (s, CH); 31
P
NMR (C6D6) δ 105.8, 101.1 (2d, JP-P ) 13.1 Hz, dppe); MS m/z
730.2 (M+ + 1), 690.2 (M+ - CHCN). Anal. Calcd for C46H45-
NFeP2 (729.62): C, 75.72; H, 6.22; N, 1.92. Found: C, 75.65; H,
6.34; N, 1.90. Spectroscopic data of 5b* (yield 83%): 1H NMR
(C6D6) δ 7.98-6.32 (m, 29H, Ph), 2.46 (m, 1H, dppe), 2.18-2.00
(m, 3H, dppe), 1.52 (s, 15H, C5Me5), 0.70 (s, 1H, CH); 31P NMR
(C6D6) δ 107.1, 103.2 (2d, JP-P ) 13.4 Hz). Anal. Calcd for C52H49-
NFeP2 (805.71): C, 77.51; H, 6.13; N, 1.74. Found: C, 77.42; H,
6.40; N, 1.70.
(CDCl3) δ 93.7 (s, dppe); MS m/z 801.1 (M+ - Br), 724.1 (M+
-
Br, Ph), 519.1 (M+ - Br, Ph, C2CH2C6F5). Anal. Calcd for
C46H36F5FeBrP2 (881.43): C, 62.68; H, 4.12. Found: C, 62.47; H,
4.29.
Synthesis of 6d and 6e. To a 15 mL acetone solution of 4d
(0.26 g, 0.33 mmol) was added a solution of nBu4NOH (1.5 mL, 1
M in MeOH). The mixture was stirred at room temperature for 2
h, and the solvent was removed under vacuum. The residue was
washed with 10 mL of MeOH to give an orange precipitate, which
was filtered off and washed with 2 × 5 mL of MeOH and 10 mL
of diethyl ether, then dried under vacuum. The product was
analytically pure and was identified as 6d (0.23 g 92% yield).
Spectroscopic data of 6d: 1H NMR (C6D6) δ 7.98-6.89 (m, 25H,
Ph), 5.86 (m, 1H, CHd), 4.96 (m, 2H, dCH2), 4.60 (m, 1H, CH
on dppe), 3.98 (s, 5H, Cp), 3.35 (m, 2H, CH2), 2.54 (m, 1H, CH2
of dppe), 1.98 (m, 1H, CH2 of dppe); 13C NMR (C6D6) δ 149.8-
125.4 (Ph, CHd), 140.5 (dd, JP-C ) 9.5, 6.4 Hz, CR), 113.4 (d
CH2), 75.4 (Cp), 57.9 (dd, JP-C ) 36.1 Hz, JP′-C ) 18.1 Hz, CH),
41.8 (CH2), 32.5 (d, JP-C ) 33.7 Hz, CH2); 31P NMR (C6D6) δ
90.0, 44.9 (2d, JP-P ) 45.5 Hz, dppe); MS m/z 660.1 (M+). Anal.
Calcd for C42H38FeP2 (660.52): C, 76.37; H, 5.80. Found: C, 76.41;
H, 5.92. Complex 6e (0.17 g, 73% yield, mp ) 209 °C) was
prepared similarly from 4e (0.26 g, 0.33 mmol). Spectroscopic data
of 6e: 1H NMR (CDCl3) δ 8.00-6.95 (m, 30H, Ph), 4.81-4.66
(m, 1H, CHPPh2), 3.99 (s, 5H, Cp), 3.82 (m, 2H, CH2Ph), 2.57-
2.43 (m, 1H, CH2PPh2), 2.01 (m, 1H, CH2PPh2); 31P NMR (C6D6)
δ 89.8, 45.4 (2d, JP-P ) 45.3 Hz); MS m/z 710.2 (M+). Anal. Calcd
for C46H40FeP2 (710.58): C, 77.75; H, 5.67. Found: C, 77.91; H,
5.72.
Synthesis of {[Fe*]dCdC(Ph)CH2R}X (4a*, R ) CN, X )
I; 4b*, R ) p-C6H4CN, X ) Br). Syntheses of 4a* and 4b*
followed the same procedure as that used for the preparation of
4a. Spectroscopic data for 4a* (yield 90%): 1H NMR (CDCl3) δ
7.57-6.91 (m, 25H, Ph), 3.22 (m, 2H, dppe), 2.78 (m, 2H, CH2-
CH2 of dppe), 2.41 (s, 2H, CH2), 1.60 (s, 15H, C5Me5); 13C NMR
(CDCl3) δ 346.6 (t, J ) 32.4 Hz, CR), 133.3-127.8 (Ph), 118.0
(CN), 116.2 (Câ), 101.0 (C5Me5), 30.1 (t, JP-C ) 22.6 Hz, CH2),
16.3 (CH2CN), 10.5 (C5Me5); 31P NMR (CDCl3) δ 88.6 (s, dppe);
MS m/z 730.2 (M+ - I), 690.1 (M+ - I, CH2CN), 589.2 (M+ - I,
CH2CN, C2Ph). Anal. Calcd for C46H46NFeIP2 (857.53): C, 64.42;
H, 5.41; N, 1.63. Found: C, 64.37; H, 5.58; N, 1.59. Spectroscopic
data for 4b* (yield 90%): 1H NMR (CDCl3) δ 7.47-6.58 (m, 29H,
Ph), 3.36 (s, 2H, CH2), 3.36 (m, 2H, dppe), 3.01 (m, 2H, dppe),
1.63 (s, C5Me5); 13C NMR (CDCl3): δ 352.1 (t, J ) 32.7 Hz, CR),
143.7-126.9 (Ph), 118.8 (CN), 109.7 (Câ), 100.4 (C5Me5), 32.8
(CH2), 31.9 (t, JP-C ) 21.3 Hz, CH2, dppe), 11.9 (C5Me5); 31P NMR
(CDCl3) δ 89.9 (s, dppe); MS m/z 806.4 (M+ - Br), 690.4 (M+
-
Br, CH2-p-C6H4CN). Anal. Calcd for C52H50NFeBrP2 (886.62): C,
70.44; H, 5.68; N, 1.58. Found: C, 70.72; H, 5.82; N, 1.49.
Synthesis of 5a. To a 15 mL acetone solution of 4a (0.40 g,
n
0.51 mmol) was added a solution of Bu4NOH (1.3 mL, 1 M in
MeOH). The mixture was stirred at room temperature for 2 h to
give an orange microcrystalline precipitate, which was filtered off
and washed with 2 × 5 mL of acetone and 10 mL of diethyl ether,
then dried under vacuum. The product was analytically pure and
was identified as 5a (0.30 g, 90% yield, mp ) 174 °C, dec).
Spectroscopic data of 5a: 1H NMR (C6D6) δ 7.85-6.55 (m, 25H,
Ph), 4.59 (s, Cp), 2.60-2.50 (m, 1H, dppe), 2.08-1.89 (m, 3H,
dppe), 0.13 (s, CH); 13C NMR (C6D6) δ 143.7-125.0 (CR, Ph),
139.9 (t, CR, JP-C ) 7.8 Hz), 118.8 (CN), 81.0 (Cp), 29.1 (dd,
Deprotonation of 4f. To a 15 mL acetone solution of 4f (0.21
g, 0.24 mmol) was added a solution of nBu4NOH (1.3 mL, 1 M in
MeOH). The mixture was stirred at room temperature for 2 h to
give an orange microcrystalline precipitate, which was filtered off
and washed with 2 × 5 mL of acetone and 10 mL of diethyl ether,
then dried under vacuum. The mixture was further extracted with
MeOH twice to give the product identified as 6f (0.12 g, 63% yield).
Spectroscopic data of 6f: 1H NMR (C6D6) δ 7.94-6.90 (m, 25H,
JP-C ) 34.0 Hz, JP’-C ) 15.1 Hz, CH2 of dppe), 27.4 (dd, JP-C
)
34.0 Hz, JP’-C ) 15.1 Hz, CH2 of dppe), 5.35 (d, CH, 3JP-C ) 2.9
Hz); 31P NMR (C6D6) δ 109.7, 107.9 (2d, JP-P ) 33.0 Hz, dppe);
MS m/z 660.2 (M+ + 1), 519.1 (M+ + 1 - C(Ph)CHCN). Anal.
Calcd for C41H35NFeP2 (659.49): C, 74.67; H, 5.35; N, 2.12.
Found: C, 74.65; H, 5.45; N, 2.09. Synthesis of 5b,c followed the
same procedure as that used for the preparation of 5a. Spectroscopic
data of 5b (yield 82%): 1H NMR (C6D6) δ 7.90-6.42 (m, 25H,
Ph), 4.19 (s, Cp), 2.68-2.50 (m, 1H, dppe), 2.17-1.87 (m, 3H,
dppe), 0.89 (s, CH); 13C NMR (CD2Cl2) δ 162.5 (Ph), 148.7-120.5
(CR, Ph), 104.4 (CN), 79.5 (Cp), 31.0 (CH), 28.4 (dd, JP-C ) 33.7
Hz, JP′-C ) 15.2 Hz, CH2 of dppe), 26.6 (dd, JP-C ) 26.7 Hz,
JP’-C ) 15.1 Hz, CH2 of dppe); 31P NMR (C6D6) δ 109.8, 107.7
(2d, JP-P ) 33.0 Hz, dppe); MS m/z 736.2 (M+ + 1), 519.1 (M+
+ 1 - C(Ph)CH(p-C6H4CN)). Anal. Calcd for C47H39NFeP2
(735.58): C, 76.74; H, 5.34; N, 1.90. Found: C, 76.81; H, 5.23;
N, 1.87. Spectroscopic data of 5c (yield 72%): 1H NMR (C6D6) δ
7.91-6.54 (m, 29H, Ph), 4.21 (s, 5H, Cp), 2.69-2.54 (m, 1H,
dppe), 2.17-1.90 (m, 3H, dppe), 1.00 (s, 1H, CH); 31P NMR (C6D6)
δ 109.9, 108.0 (2d, JP-P ) 34.0 Hz, dppe); MS m/z 779.2 (M+),
Ph), 4.69 (1H, JP-Ha ) 45.21 Hz, JP′-Ha ) 7.36 Hz, JHa-Hb,c
)
3.50 Hz, CH), 3.90 (s, 5H, Cp), 3.84 (d, 1H, J ) 14.6 Hz, CH2),
3.63 (d, 1H, J ) 13.5 Hz, CH2C6F5), 2.67 (m, 1H, JP-Hb ) 43.23
3
2
Hz, JP′-Hb ) 10.35 Hz, JHb-Ha ) 3.91 Hz, JHb-Hc ) 13.98 Hz,
2
dppe), 2.11 (m, 1H, JP-Hc ) 13.12 Hz, JP′-Hc ) 5.17 Hz, JHc-Hb
) 13.11 Hz, dppe); 31P NMR (C6D6) δ 89.7, 45.4 (2d, JP-P ) 45.5
Hz, dppe). Anal. Calcd for C46H35F5FeP2 (800.53): C, 69.01; H,
4.41. Found: C, 68.85; H, 4.72. Monitoring the same reaction in a
smaller scale by 31P NMR indicated formation of the cyclopropenyl
complex 5f as revealed by a set of two doublet resonances at δ
109.6 and 108.5 with J ) 32.1 Hz. The ratio of 5f:6f was 1:4. No
attempt was made to isolate complex 5f. While complex 5f is only
slightly soluble in MeOH, purification of the desired product 6f
was carried out by methanol extraction.
Structure Determination of Complexes 4d, 5a, and 6d. Single-
crystal X-ray diffraction data were measured on a Bruker SMART
Apex CCD diffractometer using µ(Mo KR) radiation (λ ) 0.71073
Å). The data collection was executed using the SMART program;

Deprotonation of Iron Vinylidene Complexes
Organometallics, Vol. 26, No. 5, 2007 1255
cell refinement and data reduction were performed with the SAINT
program. The structure was determined using the SHELXTL/PC
program and refined using full-matrix least-squares.24 Crystal-
lographic refinement parameters25 of complexes 4d, 5a, and 6d and
selected bond distances and angles are listed in the Supporting
Information.
Acknowledgment. Financial support from the National
Science Council of Taiwan is gratefully acknowledged.
Supporting Information Available: Complete crystallographic
data for 4d, 5a, and 6d (CIF). This material is available free of
charge via the Internet at http://pubs.acs.org.
OM061005T
(24) (a) The SADABS program is based on the method of Blessing;
see: Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33. (b)
SHELXTL: Structure Analysis Program, version 5.04; Siemens Industrial
Automation Inc.: Madison, WI, 1995.
(25) GOF ) [∑[w(F2 - F2 )2]/(n - p)]1/2, where n and p denote the
o
c
number of data and parameters. R1 ) (∑||Fo| - |Fc||)/∑|Fo|, wR2 ) [∑-
[w(Fo2 - Fc )2]/∑[w(Fo )2]]1/2 where w ) 1/[σ2(F2 ) + (aP)2 + bP] and P
2
2
o
2
) [(max; 0, F2 ) + 2Fc ]/3.
o