Formation of anionic trifunctionalized metallalactones by nucleophilic addition at the β-carbonyl of a pyruvoyl ligand

Article abstract of DOI:10.1021/om049030r

Anionic nucleophilic reagents Nu^- = CH₃O^-, C₂H₅O^-, t-BuO^-, CH ₃S^-, and P(C₆H₅)₂ ^- were found to react with (CO)<

Full text of DOI:10.1021/om049030r

Organometallics 2005, 24, 1709-1717
1709
Formation of Anionic Trifunctionalized Metallalactones
by Nucleophilic Addition at the â-Carbonyl of a Pyruvoyl
Ligand
P. Cabon, R. Rumin, J. Y. Salau¨n,* S. Triki, and H. des Abbayes
Laboratoire de Chimie, Electrochimie Mole´culaires et Chimie Analytique, UMR CNRS 6521,
Universite´ de Bretagne Occidentale, UFR Sciences et Techniques, 6 Avenue le Gorgeu,
CS 93837, 29238 Brest Ce´dex, France
Received December 8, 2004
Anionic nucleophilic reagents Nu- ) CH3O-, C2H5O-, t-BuO-, CH3S-, and P(C6H5)2- were
found to react with (CO)4Fe(CO2CH3)[C(O)C(O)CH3] to afford two isomers of anionic
trifunctionalized metallalactones, {(CO)3Fe[C(O)C(CH3)(Nu)OC(O)](CO2CH3)}-, whose forma-
tion resulted from an addition of the nucleophile to the â carbonyl of the pyruvoyl ligand. In
this reaction, the metallacycle formation was found to occur by a further addition of the
oxygen of the same â carbonyl on a terminal carbonyl. In acidic medium, these anionic
complexes evolved into neutral metallalactones (CO)4Fe[C(O)C(CH3)(Nu)OC(O)] already
obtained by performing the same reaction with pronucleophiles (Nu-H type reagents).
Achievement of (CO)4Fe[C(O)C(dCH2)OC(O)] when the reaction was performed with t-BuO-
could result from an intermediate formation of the enolate form of the pyruvoyl ligand [Fe]-
C(O)-C(dCH2)-O- under basic conditions.
Scheme 1
Introduction
For their possible involvement in double-carbonyla-
tion catalytic processes, a wide variety of organometallic
complexes bearing two carbonylated ligands in cis
position have been described.1 Possible models for
tricarbonylation displaying the [M][C(O)R][C(O)C(O)-
R′] pattern are more scarce;1 they have generally been
found to be thermally subjected to an exclusive decar-
bonylation giving rise to diacyl, acyl-alkoxycarbonyl, or
bis-alkoxycarbonyl complexes. However, together with
this decarbonylation, a carbon-carbon coupling process
giving rise to organic diketones, keto-esters, or diesters
has sometimes been observed.2
To our knowledge, the thermal behavior of cis-
(CO)4Fe[C(O)C(O)CH3](CO2CH3) (1a) is the only excep-
tion to these observations. This complex, which can be
considered as a model for the so far elusive tricarbon-
ylation reactions, has been found to evolve thermally
into a metallalactone, 2a (Scheme 1), formed by a
cyclization process occurring between its two carbonyl-
ated ligands. 2a was formally obtained by a C-O
coupling between the oxygen of the â carbonyl of the
pyruvoyl and the carbon of the alkoxycarbonyl ligand
and by a migration of the alkoxy group of this last ligand
toward the carbon of the â carbonyl of the pyruvoyl.3
This process looked very similar to the ring-chain
isomerism observed for organic γ-keto-esters.4 The
similarity between the two mechanisms seemed plau-
sible, as 1a can be considered as a γ-keto-ester with a
metal inserted into its organic chain. However, the
reaction performed from 1a was irreversible and did not
require acid or basic catalysis as it does for γ-keto-esters.
The achievement of a similar reaction in the presence
of a series of Nu-H type nucleophiles (pronucleophiles)
allowed us to show the â-carbonyl of the pyruvoyl to be
the more electrophilic site of 1a. Under these conditions
it was presumed that metallalactone 2 formation could
occur by an attack of the nucleophile reagent at the â
carbonyl of the pyruvoyl and that a further addition of
the oxygen of this group on the carbonyl of the alkoxy-
carbonyl that could induce the elimination of methanol.
These reactions were found to afford quantitatively and
under mild conditions Nu-substituted metallalactones
2 with Nu ) O-CH3, O-C2H5, S-CH3, P(C6H5)2, or
P(C6H11)2 (Scheme 1).5
* To whom correspondence should be addressed. E-mail:
Jean-Yves.Salaun@univ-brest.fr.
(1) des Abbayes, H.; Salau¨n, J. Y. Dalton Trans. 2003, 1041.
(2) Salau¨n, J. Y.; Laurent, P.; des Abbayes, H. Coord. Chem. Rev.
1998, 178-180, 353.
(3) Sellin, M.; Luart, D.; Salau¨n, J. Y.; Laurent, P.; Toupet, L.; des
Abbayes, H. J. Chem. Soc., Chem. Commun. 1996, 857.
(4) Walter, R. E.; Flitsh, W. Ring-chain tautomerism; Plenum
Press: New York, 1985.
10.1021/om049030r CCC: $30.25 © 2005 American Chemical Society
Publication on Web 03/05/2005

1710 Organometallics, Vol. 24, No. 7, 2005
Cabon et al.
Table 1. Bond Lengths (Å) and Bond Angles (deg)
for 1a
Fe-C(1)
Fe-C(2)
Fe-C(3)
Fe-C(4)
Fe-C(5)
Fe-C(7)
C(1)-O(1)
C(2)-O(2)
C(3)-O(3)
1.827(2)
1.848(2)
1.853(2)
1.833(2)
2.023(2)
2.001(2)
1.127(3)
1.126(2)
1.119(3)
C(4)-O(4)
C(5)-O(5)
C(5)-C(6)
C(6)-O(6)
C(6)-C(9)
C(7)-O(7)
C(7)-O(8)
C(8)-O(8)
1.125(3)
1.203(2)
1.563(3)
1.197(3)
1.497(2)
1.206(2)
1.353(2)
1.455(3)
C(1)-Fe-C(2)
C(1)-Fe-C(3)
C(1)-Fe-C(4)
C(1)-Fe-C(5)
C(1)-Fe-C(7)
C(2)-Fe-C(3)
C(2)-Fe-C(4)
C(2)-Fe-C(5)
C(2)-Fe-C(7)
C(3)-Fe-C(4)
C(3)-Fe-C(5)
C(3)-Fe-C(7)
C(4)-Fe-C(5)
94.50(8)
93.38(9)
170.21(9)
85.52(7)
84.68(9)
93.36(8)
91.26(8)
179.28(9)
90.36(8)
94.19(9)
87.36(8)
175.93(7)
88.63(7)
C(4)-Fe-C(7)
C(5)-Fe-C(7)
Fe-C(5)-O(5)
Fe-C(5)-C(6)
Fe-C(7)-O(7)
Fe-C(7)-O(8)
O(5)-C(5)-C(6)
C(5)-C(6)-O(6)
C(5)-C(6)-C(9)
O(6)-C(6)-C(9)
O(7)-C(7)-O(8)
C(7)-O(8)-C(8)
87.37(9)
88.93(8)
124.3(1)
119.9(1)
126.3(2)
112.7(1)
115.7(1)
119.3(2)
116.5(2)
123.9(2)
121.0(2)
115.6(1)
Figure 1. Molecular structure of 1a with probability
ellipsoids drawn at the 50% level. Hydrogen atoms have
been omitted for clarity.
However, achievement of an analogous metallalactone
{(CO)4Mn[C(O)C(H)(C6H5))OC(O)]}- by reaction of
Mn(CO)5[C(O)C(O)C6H5] with Li(C2H5)3BH suggested
that, for this complex, the formation of the lactonic ring
initiated by H- could be performed by a cyclization of
the phenylglyoxyl ligand on a terminal CO.6 To check
that the presence of an alkoxycarbonyl ligand with a
mobile alkoxy group is essential for the achievement of
metallalactones by cyclization of a pyruvoyl ligand, we
reinvestigated the mechanism of formation of these
metallalactones by inducing the reactions with anionic
nucleophiles. The results of this study will be the topic
of this paper.
Table 2. Bond Lengths (Å) and Bond Angles (deg)
for 5
Fe-C(1)
Fe-C(2)
Fe-C(3)
Fe-C(4)
Fe-C(5)
Fe-C(6)
C(1)-O(1)
C(2)-O(2)
1.948(3)
1.791(3)
1.791(3)
1.800(3)
1.935(3)
2.101(3)
1.192(4)
1.074(3)
C(3)-O(3)
C(4)-O(4)
C(5)-O(5)
C(5)-C(7)
C(6)-O(6)
C(6)-O(7)
O(7)-C(7)
C(7)-C(8)
1.099(3)
1.125(4)
1.170(4)
1.599(4)
1.161(4)
1.398(3)
1.352(4)
1.291(4)
C(1)-Fe-C(2)
C(1)-Fe-C(3)
C(1)-Fe -C(4)
C(1)-Fe-C(5)
C(1)-Fe-C(6)
C(2)-Fe-C(3)
C(2)-Fe-C(4)
C(2)-Fe-C(5)
C(2)-Fe-C(6)
C(3)-Fe-C(4)
C(3)-Fe-C(5)
C(3)-Fe-C(6)
C(4)-Fe-C(5)
91.5(1)
94.8(1)
91.8(1)
96.5(1)
174.8(1)
90.6(1)
99.7(1)
171.9(1)
93.7(1)
167.6(1)
87.7(1)
85.1(1)
81.1(1)
C(4)-Fe-C(6)
C(5)-Fe-C(6)
O(6)-C(6)-O(7)
Fe-C(5)-O(5)
Fe-C(5)-C(7)
O(5)-C(5)-C(7)
Fe-C(6)-O(6)
Fe-C(6)-O(7)
C(6)-O(7)-C(7)
C(5)-C(7)-O(7)
C(5)-C(7)-C(8)
O(7)-C(7)-C(8)
87.3(1)
78.3(1)
Results and Discussion
107.6(3)
121.8(2)
113.6(2)
124.7(2)
131.2(2)
121.2(2)
108.5(2)
118.1(2)
127.9(3)
114.0(3)
Preparation and Properties of Complex 1a. cis-
Fe(CO)4(CO2CH3)[C(O)C(O)CH3] (1a) was prepared, as
previously described,5 by reacting, at -80 °C, [Fe(CO)4-
(CO2CH3)]- 7 with pyruvoyl chloride.8 The complex,
isolated as a pale yellow powder, was found to be stable
below 20 °C. Suitable crystals for an X-ray diffraction
study were only recently obtained from a hexane/
dichloromethane (90/10) mixture, at -30 °C. Figure 1
displays the ORTEP drawing of the molecule; selected
bonds and angles are listed in Table 1 and crystal-
lographic data gathered in Table 3.
To our knowledge, 1a is the first structurally char-
acterized iron complex with a ligand displaying a double
C(O) chain described in the literature. As revealed by
this study, the coordination about its metal center can
be described as a distorted octahedron with angle values
between ligands in trans positions from 170.21(9)°
(C(1)-Fe-C(4)) to 179.28(9)° (C(2)-Fe-C(5)) and be-
tween ligands in cis position from 85.52(7)° (C(1)-Fe-
C(5)) to 94.50(8)° (C(1)-Fe-C(2)). The relatively long
Fe-terminal carbonyl distances (from 1.827(2) to 1.853-
(2) Å) compared with an average of 1.80 Å observed for
similar bonds could result from a reduced back-donation
induced by the electron-withdrawing alkoxycarbonyl
and pyruvoyl ligands. In the pyruvoyl fragment, the acyl
carbonyls are in s-trans conformation as seen in most
complexes displaying an R-keto acyl ligand.9-14 The
torsion angle O(5)-C(5)-C(6)-O(6) measured between
these two carbonyls is 141.7(2)°. This value is smaller
than its homologues generally observed for R-keto acyl
complexes (157-177°)9,10,13,15,16 but larger than analo-
gous angles of a manganese17 and a platinum12 complex
(112° and 127°, respectively). The iron pyruvoyl (Fe-
C(5) ) 2.023(2) Å) and iron methoxycarbonyl (Fe-C(7)
) 2.001(2) Å) distances are normal;11,18 they can be
(9) Casey, C. P.; Bunnel, C. A.; Calabrese, J. C. J. Am. Chem. Soc.
1976, 98, 1166.
(10) Huang, T. M.; You, Y. J.; Yang, C. S.; Tzeng, W. H.; Chen, J.
T.; Cheng, M. C.; Wang, Y. Organometallics 1991, 10, 1020.
(11) Do¨tz, K. H.; Wenicker, U.; Mu¨ller, G.; Alt, H. G.; Seyferth, D.
Organometallics 1986, 5, 2570.
(12) You, Y. J.; Chen, J. T.; Cheng, M. C.; Wang, Y. Inorg. Chem.
1991, 30, 3621.
(13) Sen, A.; Chen, J. T.; Vetter, W. M.; Whittle, R. R. J. Am. Chem.
Soc. 1987, 109, 148.
(14) Chen, J. T.; Yeh, Y. S.; Yang, C. S.; Tsai, F. Y.; Huang, G. L.;
Shu, B. C.; Huang, T. M.; Chen, Y. S.; Lee, G. H.; Cheng, M. C.; Wang,
C. C.; Wang, Y. Organometallics 1994, 13, 4804.
(5) Cabon, P.; Sellin, M.; Salau¨n, J. Y.; Patinec, V.; des Abbayes,
H.; Kubicki, M. M. Organometallics 2002, 21, 2196.
(6) Selover, J. C.; Vaughn, G. D.; Strouse, C. E.; Gladysz, J. A. J.
Am. Chem. Soc. 1986, 108, 1455.
(15) Dobryzynski, E. D.; Angelici, R. J. Inorg. Chem. 1975, 14, 59.
(16) Vetter, W. M.; Sen, A. J. Organomet. Chem. 1989, 378, 485.
(17) Sheridan, J. B.; Johnson, J. R.; Handwerker, B. M.; Geoffroy,
G. L.; Rheingold, A. L. Organometallics 1988, 7, 2404.
(7) McLean, J. L. Ph.D. Thesis, New York University, 1974.
(8) Ottenheijm, H. C. J.; Tijhuis, M. W. Org. Synth. 1983, 61, 1.

Anionic Trifunctionalized Metallalactones
Organometallics, Vol. 24, No. 7, 2005 1711
Table 3. Crystallographic Data for Compounds
1a and 5
Scheme 2
1a
5
formula
fw
cryst syst
space group
a (Å)
b (Å)
c (Å)
C9H6O8Fe
297.99
triclinic
P1h
6.3286(7)
8.776(1)
10.946(1)
87.08(1)
89.52(1)
68.99(1)
566.7(2)
2
C8H2O7Fe
265.95
monoclinic
P21/c
11.5836(9)
6.9549(5)
12.4252(9)
90
105.260(7)
90
Scheme 3
R (deg)
â (deg)
γ (deg)
V (Å3)
965.7(2)
4
Z
cryst size (mm)
0.21*0.18*0.07 0.15*0.11*0.08
Dcalcd (g cm-3
F(000)
)
1.75
1.83
300
528
abs coeff, µ (mm-1
T (K)
)
1.356
1.574
100
288
2θ limits (deg)
5.0-63.46
5303
5.00-70.12
10 494
3819/0.051
1653/145
0.032
no. of reflns collected
no. of reflns unique/Rint
3185/0.031
no. of reflns with I > 4σ(I)/Nv 2164/187
R(Fo)a
0.026
Rw(Fo)b
0.028
0.035
1.055
+0.477/-0.305
0.000
the pyruvoyl at a terminal carbonyl, we carried on with
this study by reacting 1a with anionic nucleophiles
Nu- ) CH3O-, C2H5O-, t-BuO-, CH3S-, and (C6H5)2P-.
Reactions of Cyclization of 1a Induced by RO-
Nucleophiles. Although 1a displayed an alkoxycarbon-
yl together with the pyruvoyl ligand, its reactions with
anionic reagents were found to reveal interesting infor-
mation about the mechanism of cyclization of the
pyruvoyl ligand.
GOFc
1.095
∆Fmax/∆Fmin (e Å-3
∆/F
)
0.465/-0.263
0.003
a R ) ∑|Fo - Fc|/Fo. b Rw ) [(∑wFo - Fc)2/w(Fo)2]1/2
.
c GOF )
[(∑w|Fo| - |Fc|)2/(Nobs - Nvar)]1/2. w ) 4Fo2/(σ2(Fo2) + (0.02Fo2)2).
compared to long Fe-C carbene bonds in a variety of
iron carbene complexes.19 The carbon-carbon and car-
bon-oxygen distances of these two ligands are also
normal. Nonbonding repulsions between the pyruvoyl
and the methoxycarbonyl linked to Fe(CO)4 are mini-
mized by a staggered relationship between these two
ligands. The dihedral angle between the Fe-C(O)
pyruvoyl plane (Fe-C(7)-O(7)) and the equatorial plane
of the complex (Fe-C(3)-C(2)-C(5)-C(7)) is 29.61°,
whereas its homologue between the Fe-C(O) alkoxy-
carbonyl plane and the same equatorial plane is 41.93°.
To check the possibility of performing the cyclization
of a pyruvoyl ligand into a metallalactone on a complex
that did not display an alkoxycarbonyl ligand, we made
use of the well-known mobility of alkoxy groups of
alkoxycarbonyl ligands on iron complexes.20 This mobil-
ity, generally shown by rapid exchanges with alcohols,
allowed us, by reacting 1a with HBF4,5 to obtain the
ionic complex 3. The stability of this cation clearly
showed that no spontaneous cyclization of the pyruvoyl
ligand by a nucleophilic attack of the oxygen of the â
carbonyl of this ligand at a terminal carbonyl occurred.
Moreover, we showed that by reaction with anionic
nucleophiles 3 was not found to afford a metallalactone.
Thus, by reaction with C2H5ONa, the cis complex 1b
(Scheme 2) was formed whose spectroscopic character-
istics were very close to those reported for 1a.5 The
formation of the ethoxycarbonyl ligand was indicative,
on this cationic complex, of an enhanced electrophilicity
of the terminal carbonyls compared to that of the â acyl
of the pyruvoyl.
Addition of CH3ONa to 1a. IR monitoring of the
reaction performed at -10 °C showed the formation (3
h) of a new complex characterized by three νCtO bands
at 2069, 2004, and 1987 cm-1 and by three νCdO at
1678, 1639, and 1592 cm-1. This compound, which was
isolated as a pale yellow powder, was only sparingly
soluble in THF. Its IR and NMR characteristics sug-
gested for this complex the metallalactonic anionic
trifunctionalized structure 4a (R ) CH3; Nu ) OCH3)
displayed in Scheme 3. Its IR νCtO frequencies were
halfway between the values observed for the same
oscillators of the starting neutral complex 1a (2130-
2050 cm-1) and those measured for the monofunction-
alized anionic iron complex [Fe(CO)4(CO2CH3)]- (1910
cm-1).7 They were very close to the νCtO observed for
the trifunctionalized anion [Fe(CO)3(CO2R)3]- (two bands
about 2080 and 2015 cm-1), obtained by reaction of RO-
with cis-(CO)4Fe(CO2R)2.21 The values measured for the
νCtO of 4a suggested a strong delocalization of the
negative charge of the complex along electron-with-
drawing carbonylated organic ligands. The observation
of three bands (two νCtO are expected for a C3v
symmetry) could result from the presence on the com-
plex of a metallacycle with an asymmetric carbon. The
13C NMR spectrum of 4a was also consistent with the
proposed structure. The presence on the metallacycle
of a quaternary carbon bearing two different substitu-
ents together with an alkoxycarbonyl ligand in axial
position on the metal brought about the possible forma-
tion of two isomers of 4a. Indeed, the two signals of
equal intensities observed for the quaternary carbon of
the cycle at 111.0 and 109.7 ppm as well as for the cyclic
As this result did not answer the question of the
possible formation of a metallalactone by cyclization of
(18) Luart, D.; Le Gall, N.; Salau¨n, J. Y.; Toupet, L.; des Abbayes,
H. Inorg. Chim. Acta 1999, 291, 166.
(19) Schubert, U. Coord. Chem. Rev. 1984, 55, 261.
(20) Sellin, M.; Luart, D.; Salau¨n, J. Y.; Laurent, P.; des Abbayes,
H. J. Organomet. Chem. 1998, 562, 183.
(21) Sellin, M.; Luart, D.; Salau¨n, J. Y.; Laurent, P.; Toupet, L.; des
Abbayes, H. Organometallics 1996, 15, 521.

1712 Organometallics, Vol. 24, No. 7, 2005
Cabon et al.
Scheme 4
process between 1a and CH3ONa, careful monitoring
of the reaction between 1a and CH3ONa never allowed
the transient detection of 2a, whose formation would
be required by the cyclization of the pyruvoyl on the
alkoxycarbonyl ligand. Furthermore, contrary to the
reaction of 1a with CH3ONa, the addition of this last
reagent to 2a was not quantitative. These results made
the formation of the lactone by cyclization of the
pyruvoyl on a terminal carbonyl the more plausible
hypothesis.
Reaction of 1a with C2H5ONa. This process showed
that the mechanism of formation of 4 could be more
complex. When performed at 0 °C, the reaction afforded
numerous compounds whose IR and 13C NMR spectra
were very close to those displayed by 4a. The 13C NMR
spectrum of the crude product of this reaction exhibited
six signals between 276 and 265 ppm (M-cyclic C(O)),
five resonances for the metallalactonic quaternary
carbon between 111.6 and 109.5 ppm, six peaks corre-
sponding to OCH2- (59.9-57.5 ppm), and only three
signals between 51.2 and 50.4 ppm for OCH3. When
reacted with HCl at -70 °C, this mixture of compounds,
which were very probably anionic trifunctionalized
complexes 4, afforded quantitatively a mixture of 50%
of 2a and 50% of its ethyl homologue 2b.22 These results
were clearly indicative of an exchange between the two
alkoxy groups that could afford eight isomers of 4. Such
exchanges have already been observed between the
alkoxy of alkoxycarbonyl ligands of iron complexes and
alcohols;20 however, they were never performed by
reaction of alkoxycarbonyl iron complexes with alcoho-
lates.21 Careful monitoring of the reaction between 1a
and 1 equiv of C2H5ONa or performing the same
reaction in the presence of 0.5 equiv of C2H5ONa showed
the absence of alkoxy-alcoholate exchange on 1a prior
to the formation of the mixture of complexes 4. The
same lack of exchange was noticed between anion 4a
and C2H5ONa or C2H5OH. In the same way although
the neutral lactone 2a reacted with C2H5ONa to afford
an analogous mixture of 4, no exchange prior to the
anion formation could be detected. It must also be
mentioned that, contrary to the easy exchange reactions
observed between alcohols and the alkoxy substituent
of organic lactones in acidic media,23 such a process was
not observed between 2a and C2H5OH even in the
presence of HCl. Under these last reaction conditions,
decomposition of 2a rapidly occurred. All these results
showed that exchange processes were concomitant with
the metallalactonic ring formation affording 4.
M-C(O) acyl (271.4 and 265.5 ppm) and for the methyl
substituent of this quaternary carbon (21.5 and 20.6
ppm) strongly suggest the formation of an equimolecular
mixture of two isomers of 4a. Four methoxy resonances
were also found at 51.1, 50.6, 50.5, and 50.4 ppm, and
the signals corresponding to the terminal carbonyls and
to the cyclic C(O)O linked to the metal were observed
as 10 peaks between 222.1 and 206.4 ppm. Among these
signals, the two more deshielded resonances (222.1,
220.0 ppm) were attributed to the M-C(O)O group of
the cycle. By comparison with the resonances of analo-
gous neutral complexes, the signals of this anionic
compound were shifted by about 10 ppm toward the
lower fields.3,5
The exclusive formation of the trifunctionalized anion
4a by reaction of 1a with CH3ONa strongly suggested
the formation of the metallalactone to occur via a
cyclization of the pyruvoyl at a terminal carbonyl
(Scheme 4, path a). This result brought up the question
of the formation of only 2a when the isomerization of
1a was induced by CH3OH.5 An answer to this problem
was given by the reaction of 4a with HCl. We already
described the instantaneous evolution in acidic media
of anionic trifunctionalized complexes {(CO)3Fe[C(O)R]2-
(CO2R′)}- displaying at least one alkoxycarbonyl ligand.
Neutral complexes (CO)4Fe[C(O)R]2 were then quanti-
tatively formed, and elimination of alcohol was ob-
served.21 In the same way, when the mixture of isomers
of 4a was reacted with HCl at -70 °C, the instantaneous
and quantitative formation of the already structurally
characterized neutral metallacyclic lactone 2a (Nu )
OCH3) was observed (Scheme 3). This reaction con-
firmed the structure attributed to 4a and also showed
that this last complex with H+ as counterion evolved
into 2a with liberation of CH3OH. This observation
explained the production of only 2a when the cyclization
of 1a was induced by Nu-H reagents. The formation of
the metallalactonic cycle of this process could then be
achieved by an attack of the oxygen of the pyruvoyl on
a terminal carbonyl (Scheme 4, path a), as the reaction
would afford 4a with H+ as counterion that would evolve
instantaneously into 2a under the reaction conditions.
On the other hand, the formation of 4a via the addition
of the pyruvoyl at the alkoxycarbonyl as displayed by
path b of Scheme 4 cannot be completely dismissed.
To check the possible validity of this last assumption,
we reacted CH3ONa with the metallalactone 2a, which
would be the intermediate species of this process. This
reaction was found to afford, within 3 h, 4a as a mixture
of isomers (50/50, 60% yield). However, although the
rate of this last reaction was similar to that of the
Reaction of 1c (R ) t-Bu) with MeONa. Surpris-
ingly, although easy exchanges were observed between
CO2t-Bu ligands of (CO)4Fe(CO2t-Bu)2 and methanol,20
such reactions were not observed when 1c was reacted
with CH3ONa. Again IR monitoring of the reaction
showed the formation of trifunctionalized anions, but
the 13C NMR spectrum of the crude product of the
reaction clearly showed the formation of only two
isomers of the anionic lactone 4c (R ) t-Bu, Nu )
OCH3). The characteristics of these isomers were very
close to those displayed by 4a, and as shown by the
relative intensities of the two signals observed at 271.15
(22) This compound had already been specifically obtained by
inducing the cyclisation of 1a with C2H5OH via the intermediate
formation of 1b: (CO)4Fe(CO2C2H5)[C(O)C(O)CH3].5
(23) des Abbayes, H. Bull. Soc. Chim. Fr. 1970, 3671.

Anionic Trifunctionalized Metallalactones
Organometallics, Vol. 24, No. 7, 2005 1713
Scheme 5
Scheme 6
Figure 2. Molecular structure of 5 with probability
ellipsoids drawn at the 40% level. Hydrogen atoms have
been omitted for clarity.
showed 1J interactions between the two protons and the
methylene signal at 89.7 ppm and confirmed the pro-
posed structure. The formation of 5 by reaction of
t-BuONa with 1a or 1c could occur either by a proton
abstraction with elimination of tBuOH from the anionic
intermediates of type 4 (4d or4e, Scheme 3) by a
reaction analogous to the process already observed,
under basic conditions, for a Pd π allyl lactone24 or, as
described for a malonyl ligand of a rhenium complex,25
by the intermediate formation, in the presence of
t-BuONa, of the enolate of the pyruvoyl ligand of 1a or
1c, enolates that could undergo a cyclization on a
terminal carbon and then give rise to trifunctionalized
methylene metallalactonic anions 6a or 6c, which, in
the presence of HCl, would afford 5 (Scheme 6).
The molecular structure of 5 was determined by a
single-crystal X-ray study. Pale yellow monocrystals of
this product were grown from a hexane/dichloromethane
(90/10) solution at -30 °C. An ORTEP drawing of the
complex is depicted in Figure 2. Selected bond lengths
and angles are listed in Table 2, and crystallographic
data are gathered in Table 3.
and 264.5 (M-C(O)) and at 110.9 and 109.6 ppm
(quaternary carbon of the metallacycle), their relative
proportions were estimated to be 55/45%. This result
was indicative of a low steric effect of the alkoxy group
in the course of the reaction. Treatment of these two
isomers with HCl at 0 °C afforded the neutral metal-
lalactone 2a in 80% yield together with 20% of the
starting complex 1c. The absence of formation of O-tBu-
substituted neutral metallalactone confirmed the non-
occurrence of any exchange in the course of formation
of 4c. The presence of 1c as a final product of the
reaction can be explained, as already supposed for a Mn
metallalactone,6 by an electrophilic addition of H+ on
the lactonic cyclic oxygen followed by a ring opening of
the lactone with release of methanol (Scheme 5).
As suggested from Figure 2, the metallacycle of the
complex is quasi planar. Both atoms C(7) and O(7)
deviate from the plane defined by C(5), Fe, C(6) by only
0.07 Å. The acyl oxygen atoms O(5) and O(6) (0.09 and
0.06 Å) as well as the methylene carbon C(8) (0.25 Å)
are also only slightly removed from this plane. The
presence in the metallacycle of the sp2 carbon linked to
the methylene group is indicated by a higher value of
the C(5)-C(7)-O(7) angle, 118.1(2)°, compared to an
average of 109° measured for homologous angles of iron
metallalactones with an sp3 carbon.3,5 This large angle
brings about a small C(6)-O(7)-C(7) angle (108.5(2)°
vs 118°) and a large iron-acyl-oxygen angle (Fe-C(6)-
O(7)) of 121.2(2)° (vs an average of 115.5°). The geom-
etry around the iron atom shows distortions from
idealized octahedral. As generally observed for five-
membered iron metallacycles,3,5,26 the angle between the
two acyls of the metallacycle (C(6)-Fe-C(5): 78.3 (1)°)
is smaller than their homologues of a noncyclic bis-
Reaction of 1a or 1c with t-BuONa: Formation
of a Methylene-Substituted Metallalactone 5. As
shown by IR monitorings, these reactions were again
found to induce the formation of trifunctionalized
anions. We were unfortunately unable to obtain correct
1H or 13C NMR spectra of these complexes. When
treated with HCl at -80 °C, these intermediates re-
spectively evolved into the structurally characterized
neutral methylene metallalactone 5 (Scheme 6). This
complex was the only product of the reaction performed
with the anion resulting from the addition of t-BuONa
to 1a (60% yield), while the anions obtained by reaction
of 1c with t-BuONa, under the same conditions, were
found to give rise to 43% 5 and 13% 1c, whose formation
could be explained as above. In the IR, the CdO and
CtO stretching bands of 5 were similar to those
displayed by 2a; however, an additional band (probably
a νCdC) was observed at 1618 cm-1. The 1H NMR
spectrum of this complex displayed two broad signals
at 5.07 and 4.86 ppm, suggesting the presence of a
methylene group. In 13C NMR the signals of the car-
bonyls were similar to those observed for 2a except the
resonance of the cyclic C(O), which, due to its conjuga-
tion with the CdCH2 group, was shielded by about 9
ppm at 236.9 ppm. The cyclic carbon bound to the
methylene was found at 157.5 ppm and the methylene
carbon at 89.7 ppm. 13C-1H NMR HMQC sequences
(24) Carfagna, C.; Gatti, G.; Mosca, L.; Paoli P.; Guerri, A. Orga-
nometallics 2003, 22, 3967.
(25) O’Connor, J. M.; Uhrhammer, R.; Rheingold, A. L.; Roddick,
D. M. J. Am. Chem. Soc. 1991, 113, 4530.
(26) (a) Aime, S.; Milone, L.; Sappa, E.; Tiripicchio, A.; Manotti,
Lanfredi, A. M. J. Chem. Soc., Dalton Trans. 1979, 1664. (b) Hoffmann,
K.; Weiss, E. J. Organomet. Chem. 1977, 128, 399. (c) Karel, K. J.;
Tulip, T. H.; Ittel, S. D. Organometallics 1990, 9, 1276. (d) Pettersen,
R. C.; Cihonski, J. L.; Young, F. R.; Levenson, R. A. J. Chem. Soc.,
Chem. Commun. 1975, 370.

1714 Organometallics, Vol. 24, No. 7, 2005
Cabon et al.
alkoxycarbonyl iron complex (88.5° is observed for the
cis-(CO)4Fe(CO2tBu)2).27 The two axial CtO also present
a significant bending toward the metallacyclic ring:
C(3)-Fe-C(4) ) 167.6(1)°. Surprisingly the molecule
displays a very long Fe-terminal CO bond: Fe-C(1) )
1.948(3) Å. The lengthening of this Fe-CtO bond trans
from the C(O)O group could result from an electronic
delocalization along the metallacycle. Compared to other
metallalactones, the presence of the methylene group
on the metallacycle of 5 induces significant modifica-
tions of interatomic distances. Thus, the Fe-acyl (Fe-
C(5) ) 1.935(3) Å), C(dCH2)-O (C(7)-O(7) ) 1.352(4)
Å), and C(O)-O (C(6)-O(7) ) 1.398(3) Å) bonds are
shorter than expected, whereas C(O)-C(CdH2) (C(5)-
C(7) ) 1.599(4) Å) and Fe-C(O)O (Fe-C(6) ) 2.101(3)
Å) distances are longer than their homologues of other
iron metallalactones.3,5 The very short value between
O(6) and O(7) (2.070(3) Å) is also worth noting; it is
associated with a small O(6)-C(6)-O(7) angle: 107.6(3)°.
Generalization of the Reaction of Formation of
Metallalactones. To expand the scope of the reaction
of cyclization of pyruvoyl iron complexes into metalla-
lactones, we tried to perform the process by using RS-,
PR2-, NR2-, and H- as nucleophiles. According to the
procedure described for the reaction between 1a and
CH3ONa, CH3SNa was found to react in 1.5 h at -30
°C to afford the anionic complex 4f (Scheme 3), display-
ing in its IR νCO stretching bands very close to those
observed for 4a (three νCtO at 2068 (s), 2005 (s), and
1987 (s) cm-1 and two νCdO at 1646 (s) and 1593 (m)
cm-1). The 13C NMR spectrum of the product of the
reaction confirmed the formation of an anionic trifunc-
tionalized metallalactone, as it displayed an acyl carbon
at 259.6 ppm, a carbonyl (cyclic CO2 group) at 222.8
ppm, and an unresolved broad signal between 207.7 and
209.3 ppm for the other CO of the molecule. The
resonance of the quaternary carbon of the metallacycle,
now substituted by a SCH3 group, was observed at 95.5
ppm (a shielding of 15 ppm compared to its homologue
substituted by a OCH3 group), whereas the signals of
the CH3 were found at 50.3 (OCH3), 22.6 (CH3-C), and
12.5 ppm (SCH3). The formation of a second isomer of
this product (15%) was shown by the presence of minor
peaks at 259.7, 223.0; 97.0; 51.0 and 12.2 ppm. When
reacted with 1 equiv of HCl at -80 °C, this mixture of
complexes afforded quantitatively the SCH3-substituted
of equal intensities at 30.2 and 24.6 ppm. When treated
with HCl at low temperature, this mixture afforded
quantitatively the PPh2-substituted neutral lactone 2d.
The presence of the P(C6H5)2 group on the sp3 carbon
of the metallacycle was shown in the 13C NMR by the
large coupling constant observed for the signal of this
carbon at 101.1 ppm (JC-P ) 35.6 Hz) and by the lower
interactions of the phosphorus with the acyl carbon at
252.7 ppm (JC-P ) 8.7 Hz) and with the methyl at 23.1
(JC-P ) 17.4 Hz). J3 interactions P-CH3 were also
detected by 31P-1H NMR HMBC sequences. In the 31
P
NMR, 2d displayed one signal at 10.9 ppm, which was
indicative of an uncomplexed large cone angle phos-
phine.28 This absence of coordination of the phosphine
to the metal was confirmed by the lack of interaction
between the phosphorus and the terminal carbonyl
carbons.
Two other nucleophiles, NaH and LiNEt2, were also
reacted with 1a; at low temperature they were found
unreactive and, at 0 °C, the only products of the
reactions were Fe(CO)5 and organic compounds.
Conclusions
This work clearly established that addition of alco-
holates to pyruvoyl-substituted cationic iron complexes
occurred on a terminal carbonyl, affording an alkoxy-
carbonyl ligand. On the other hand, on neutral iron
complexes, the â carbonyl of the pyruvoyl was shown
to be the most electrophilic site of the molecule, as the
reactions of 1a or 1c with anionic nucleophiles (Nu-)
were found to give rise to anionic trifunctionalized Nu-
substituted metallalactones 4 (Nu ) OCH3, OC2H5,
SCH3, P(C6H5)2) formed by addition of the nucleophile
on the â carbonyl of the pyruvoyl followed by the
metallalactone formation probably performed by an
attack of the oxygen of this â carbonyl on a terminal
carbonyl of the complex. These anionic lactones 4 were
generally obtained as a mixture of isomers. In acidic
medium, they quantitatively afforded neutral metalla-
lactones 2. This last process was shown to be reversible,
as the reaction of RO- with 2 gave rise to 4 by addition
of the reagent on a terminal carbonyl. However, the
yield of this last reaction was found to be rather low.
When a stronger base (t-BuO-) was added to 1a or 1c,
the major product of the process, after reaction with
HCl, was a methylene-substituted metallalactone 5,
whose formation could result from the cyclization of the
enolized form of the pyruvoyl ligand on a terminal
carbonyl of the complex. The original compounds 1a and
5 were characterized structurally.
neutral metallalactone 2c, characterized by IR and 13
C
NMR. These characteristics were very similar to those
displayed by 2a except, in the 13C NMR, the resonance
of the quaternary carbon of the cycle substituted by the
SCH3 group, which is shielded by 12.5 ppm compared
to its OCH3 homologue. Again, by reaction with 1 equiv
of CH3ONa, 2c gave rise to 4f (as a mixture of 85/15
isomers) in 30% yield. An analogous process was ob-
served when 1a was reacted with (C6H5)2PLi. As shown
by the 13C NMR spectrum of the product of the reaction
(CdO at 267.5 and 253.3 ppm; C(CH3)(PPh2) (broad
signals) at 91.35 and 90.2 ppm and CH3 at 21.2 and 19.6
ppm), an anionic PPh2-substituted trifunctionalized
metallalactone 4g was formed as a mixture of two
isomers (50/50). The formation of these two isomers was
confirmed by the presence in the 31P NMR of two signals
Experimental Section
All manipulations were performed under a dry oxygen-free
argon atmosphere using standard Schlenk techniques. Hexane
and THF were distilled under nitrogen from sodium/benzophe-
none. CH2Cl2 was dried with CaH2. CD2Cl2 and D8-THF were
stored on molecular sieves in a Schlenk storage flask until
needed. Fe(CO)5, CH3ONa, C2H5ONa, t-BuONa, HCl (1 M in
ether), and BuLi (1.6 M in hexanes) were used as received from
8
Aldrich. CH3SNa,29 (C6H5)2PLi,30 and ClC(O)C(O)CH3 were
prepared by literature methods. ClC(O)C(O)CH3 was obtained
(28) Rahman, M. M.; Liu, H. Y.; Eriks, K.; Prock, A.; Giering, W. P.
Organometallics 1989, 8, 1.
(29) Wark, T. A.; Stephen, D. W. Organometallics 1989, 8, 2836.
(27) Luart, D.; Le Gall, N.; Salau¨n, J. Y.; Toupet, L.; des Abbayes,
H. Inorg. Chim. Acta 1999, 291, 166.

Anionic Trifunctionalized Metallalactones
Organometallics, Vol. 24, No. 7, 2005 1715
as a mixture with HC(O)OCH3 and ClC(O)CH3. The respective
percentages of these compounds were evaluated by H NMR.
(t, J ) 7.5 Hz, 3H, CH3). 13C{1H} NMR (CD2Cl2, 273 K; δ,
ppm): 246.0 (CdO); 201.6 (2), 199.4 (1), 198.4 (1) (CtO); 198.0
(CdO); 193.2 (CO2C2H5); 62.8 (OC2H5); 23.2 (CH3); 14.5 (CH3).
Anal. Calc for C10FeH8O8: C, 38.50; Fe, 17.90; H, 2.59.
Found: C, 38.70; Fe, 17.75; H, 2.65. 1c: We were unable to
get crystals of 1c. However, after evaporation of the solution
to dryness, 1c was obtained as an oily residue in 70% yield
(4.76 g). IR (hexane, cm-1): ν(CtO) 2118 (m), 2070 (w, sh),
2060 (m, sh), 2045 (s); ν(CdO) 1730 (br), 1663 (m, sh), 1618
(br). 1H NMR (CD2Cl2, 273 K; δ, ppm): 2.23 (s, 3H, CH3), 1.36
(s, 9H, CH3). 13C{1H} NMR (CD2Cl2, 273 K; δ, ppm): 246.8
(CdO); 201.9 (2), 199.4 (1), 198.8 (1) (CtO); 198.4 (CdO); 191.9
(CO2t-Bu); 84.6 (Ot-Bu); 28.3 (CH3); 23.3 (CH3). Correct
analysis of this complex was not obtained.
Preparation of the Cationic Complex 3. To a solution
of 100 mg (0.33 mmol) of 1a in 10 mL of THF was added, at
-40 °C, 2.5 equiv (0.825 mmol, 0.110 mL) of HBF4, O(CH3)2.
The solution was stirred for 1 h at -40 °C. Pale yellow crystals
slowly separated. After filtration these crystals were washed
with three portions (5 mL) of THF at -50 °C and dried under
vacuum to give 46 mg (40%) of 3. 1H NMR (CD3CN, 273 K; δ,
ppm): 2.80 (s, 3H, CH3). 13C{1H} NMR (CD3CN, 273 K; δ,
ppm): 231.5 (CdO); 196.1 (4), 190.4 (1) (CtO); 189.5 (CdO);
24.6 (CH3). Probably due to its high sensitivity to moisture,
we were unable to obtain a correct IR spectrum and micro-
analysis of this complex.
Reaction of 3 with C2H5ONa: Formation of 1b. A
solution of 20 mg (0.283 mmol) of C2H5ONa in 5 mL of THF
was added dropwise to a stirred suspension of 100 mg (0.283
mmol) of 3 in 30 mL of THF at -40 °C. Within 15 min the
solid in suspension gradually disappeared and a yellow solu-
tion was obtained. The solvent was then removed under
vacuum at 0 °C. The remaining residue was washed at
-70 °C with two portions of 5 mL of hexanes and extracted
with 2 × 15 mL of a hexanes/CH2Cl2 (95:5) mixture. After
concentration of the so obtained solution to about 10 mL at
-50 °C, 53 mg (60% yield) of 1b was obtained as a pale yellow
crystalline solid.
Reactions of Complexes 1 with Anionic Nucleophiles
Nu-: General Procedure for the Preparation of 4. Nu-M+
(1 mmol) in solution in 5 mL of THF was added dropwise to 1
mmol of 1 in solution in 20 mL of THF at -30 °C. The reaction,
which was monitored by IR, was complete after 1.5 h. The
solvent was then removed and the oily residue washed at 0
°C with two portions of 10 mL of hexanes to afford 4 as a pale
yellow powder. We were unable to obtain correct analysis of
these anionic complexes.
1
Infrared spectra were recorded in solution in hexanes, CH2-
Cl2, or THF on a Nicolet Nexus 470 spectrometer. 1H, 13C, and
31P NMR spectra were recorded (unless otherwise stated) at 0
°C in CD2Cl2 (neutral compounds) or in D8-THF (anionic
complexes) on a Bruker AMX-3 300 or on a Bruker DRX 400
spectrometer. NMR HMQC sequences were performed on a
Bruker DRX 500. Chemical shifts were measured relative to
1
residual protonated solvents for H NMR spectra and to the
solvent resonance for 13C NMR spectra. 31P spectra were
externally referenced to H3PO4 (85%). Elemental analyses were
performed by the Service Central D’analyses du CNRS.
Crystallographic Analyses. Crystallographic data of com-
pounds 1a and 5 were collected (T ) 100 K for 1a, T ) 288 K
for 5) on an Xcalibur 2 diffractometer (Oxford diffraction). The
two structures were solved by direct methods and successive
Fourier difference syntheses and were refined on F by weighted
anisotropic full-matrix least-squares methods.31 For compound
1a, the hydrogen atoms were located by difference Fourier
maps and refined isotropically, while those of compound 5 were
calculated [d(C-H) ) 0.95 Å; thermal parameters Uiso
)
1.3Ueq(C)] and therefore included as isotropic fixed contributors
to Fc. Scattering factors and corrections for anomalous disper-
sion were taken from International Tables for X-ray Crystal-
lography.32 The thermal ellipsoid drawings were made with
the ORTEP program.33 All calculations were performed on an
Alphastation 255 4/233 computer. Pertinent crystal data, bond
distances, and bond angles of both compounds are listed in
Tables 1-3. Complete crystallographic data, in CIF format,
are included in the Supporting Information.
Preparation of Complexes 1a, 1b, and 1c. Syntheses of
complexes 1b and 1c were performed by following the method
of preparation of 1a:5 A solution of pyruvoyl chloride (20 mmol,
2.07 g) in 5 mL of THF was added dropwise to a stirred
solution of 20 mmol of [(CO)4Fe(CO2R)]- 7 in THF at -70 °C.
[(CO)4Fe(CO2R)]- was obtained by reaction at 0 °C of 20 mmol
of the appropriate alcoholate (CH3ONa: 1.08 g; C2H5ONa: 1.36
g; t-BuOK: 2.24 g) with Fe(CO)5 in excess (40 mmol, 7.95 g,
5.33 mL). The orange-brown solution of the anion slowly
turned yellow-green as, in IR, the ν(CtO) bands of the anions
at 1915, 1890, and 1870 cm-1 were replaced by four bands at
2125, 2075, 2070, and 2060 cm-1. After 2 h at -20 °C, the
solvent was evaporated to dryness and the residue washed at
-70 °C with two portions (5 mL) of hexanes. Neutral com-
plexes 1 were extracted, at 0 °C, from the residue by three
fractions (20 mL) of hexanes/CH2Cl2 (95:5) for 1a or 1b or
hexanes for 1c. These different fractions were joined, and
concentration of the extract to approximately half its volume
and cooling to -40 °C resulted in crystallization of pale yellow
solid of pure 1a or 1b, which were washed twice with a
minimum of hexanes at -70 °C and dried under vacuum. 1a:
yield: 60% (3.57 g). IR (hexane, cm-1): ν(CtO) 2125 (m), 2075
(w, sh), 2070 (m, sh), 2060 (s); ν(CdO) 1740 (br), 1665 (w, sh),
1630 (br). 1H NMR (CD2Cl2, 273 K; δ, ppm): 3.56 (s, 3H,
OCH3), 3.22 (s, 3H, CH3). 13C{1H} NMR (CD2Cl2, 273 K; δ,
ppm): 245.7 (CdO); 201.3 (2), 199.2 (1), 198.2 (1) (CtO); 198.1
(CdO); 193.9 (CO2CH3) 50.5 (OCH3); 23.0 (CH3). Anal. Calc
for C9FeH6O8: C, 36.28; Fe, 18.74; H, 2.03. Found: C, 36.42;
Fe, 18.65; H, 2.11. 1b: yield: 55% (3.43 g). IR (hexane, cm-1):
ν(CtO) 2120 (w), 2085 (w, sh), 2075 (m, sh), 2065 (s); ν(CdO)
1730 (br), 1660 (sh), 1625 (br). 1H NMR (CD2Cl2, 273 K; δ,
ppm): 4.06 (q, J ) 7.5 Hz, 2H, CH2), 2.23 (s, 3H, CH3), 1.17
Formation of 4a. Complex 1a (1 mmol, 300 mg) was
reacted with 54 mg (1 mmol) of CH3ONa to afford 240 mg (yield
80%) of 4a. IR (THF, cm-1): ν(CtO) 2069 (s), 2004 (s), 1987
1
(s); ν(CdO) 1678 (sh), 1639 (m), 1592 (w). H NMR (D8-THF,
273 K; δ, ppm): 3.30 (br s, 3H, OCH3), 3.11 (br s, 3H, OCH3),
1.15 (br s, 3H, CH3). 13C{1H} NMR (THF, 273 K; δ, ppm):
271.4, 265.5 (CdO); 222.1, 220.0 (cyclic C(O)O-); 209.15, 209.0,
208.8, 208.5, 208.1, 207.9 207.35, 206.4 (CtO and C(O)O-);
111.0, 109.7 (cyclic quaternary carbon); 51.1, 50.6, 50.5, 50.4
(OCH3); 21.5, 20.6 (CH3).
Reaction of 1a with C2H5ONa. 1a (1 mmol, 300 mg) was
reacted with 68 mg (1 mmol) of C2H5ONa to give rise to 250
mg of trifunctionalized anionic lactones 4. IR (THF, cm-1):
ν(CtO) 2068 (s), 2003 (s), 1985 (s); ν(CdO) 1667 (sh), 1638
1
(m), 1591 (w). H NMR (D8-THF, 273 K; δ, ppm): numerous
signals between 3.50 and 0.80. 13C{1H} NMR (THF, 273 K; δ,
ppm): 276.2, 271.5, 270.0, 265.55, 265.4, 264.9. (CdO); 222.5,
222.3, 222.0, 219.9 (cyclic C(O)O-); 211.6, 209.2, 209.1, 209.0,
208.8, 208.5, 208.4, 208.2, 208.1, 207.9, 207.6, 207.5, 207.4,
207.3, 206.6, 206.5, 206.4 (CtO and C(O)O-); 111.6, 111.0,
110.9, 109.7 109.5 (cyclic quaternary carbons); 59.9, 59.3, 59.0,
58.9, 58.3, 57.5 (OCH2) 51.2, 50.5, 50.4, (OCH3); 22.4, 21.5,
21.1, 20.6, 19.5 (CH3).
(30) Legzdins, P.; Ross, K. J.; Sayers, S. F.; Rettig, S. J. Organo-
metallics 1997, 16, 190.
(31) Fair C. K. MolEN, An Interactive Intelligent System for Crystal
Structure Analysis, User Manual; Enraf-Nonius: Delft, The Nether-
lands, 1990.
(32) International Tables for X-Ray Crystallography; Kynoch
Press: Birmingham, U.K., 1975; Vol. 4.
(33) Johnson, C. K. ORTEP, Rep. ONL-3794; Delft, The Nether-
lands, 1985.

1716 Organometallics, Vol. 24, No. 7, 2005
Cabon et al.
13C NMR Monitoring of the Reaction. To 7 mg of C2H5-
ONa in an NMR tube was added a cold solution of 1a (30 mg)
in 0.7 mL of D8-THF. The spectra recorded at -30 °C were
not found to display characteristic signals corresponding to
1b: CdO at 246, CO2 at 193.2, CH2 at 62.8, or CH3 at 14.5
ppm.
Reaction Performed with 0.5 Equiv of C2H5ONa. 1a (1
mmol, 300 mg) was reacted with 34 mg (0.5 mmol) of C2H5-
ONa at -30 °C; after the usual treatment, the 13C NMR
spectrum of the crude product of the reaction was not found
to display any signals corresponding to 1b.
Reaction of 1c with CH3ONa. 1c (1 mmol, 340 mg) was
allowed to react with 54 mg (1 mmol) of CH3ONa to afford
300 mg (70% yield) of 4c. IR (THF, cm-1): ν(CtO) 2066 (s),
2002 (s), 1981 (s); ν(CdO) 1678 (sh), 1639 (s), 1590 (m). 1H
NMR (D8-THF, 273 K; δ, ppm): 3.30 (br s, 3H, OCH3), 1.65
(br s, 9H, Ot-Bu), 0.8 (br s, 3H, CH3). 13C{1H} NMR (THF,
273 K; δ, ppm): (two isomers 60/40) 271.15, 264.4 (CdO);
224.1, 219.0 (cyclic C(O)O-); numerous signals between 209.8
and 207.5 (CtO and C(O)O-); 110.9, 109.6 (cyclic quaternary
carbon); 79.25 (C t-Bu); 51.4, 50.4 (OCH3); 28.5, 30.5 (CH3
t-Bu); 20.5, 19.8 (CH3).
IR monitoring, the reaction was very fast even at low temper-
ature. After 15 min at -70 °C, the solvent was removed under
vacuum and the residue washed with two portions of 5 mL of
hexanes at -70 °C. Complexes 2 were extracted from the
residue by a hexanes/CH2Cl2 (90/10) mixture (2 × 25 mL). The
reduction of this solution to ∼20 mL under vacuum at -40 °C
afforded pale yellow crystals of 2, which, after filtration, were
washed twice with 5 mL of hexane at -70 °C.
Preparation of 2a by Reaction of 4a with HCl. 4a (176
mg) was reacted with 0.5 mL of 1 N HCl in ether to give 97
mg (yield: 65%) of 2a. IR (hexane, cm-1): ν(CtO) 2125 (m),
2085 (sh), 2060 (sh), 2050 (s); ν(CdO) 1720 (m), 1685 (sh). 1H
NMR (CD2Cl2, 273 K; δ, ppm): 3.35 (s, 3H, OCH3), 1.4 (s, 3 H,
CH3). 13C{1H} NMR (CD2Cl2, 273 K; δ, ppm): 245.8 (CdO);
199.7, 199.1, 198.7, 198.0 (terminal CtO) 196.8 (cyclic C(O)O);
109.8 (cyclic quaternary carbon); 50.5 (OCH3); 16.1 (CH3). Anal.
Calc for C9FeH6O8: C, 36.27; Fe, 18.74; H, 2.03. Found: C,
35.95; Fe, 18.53; H, 2.18.
Reaction of HCl with the Trifunctionalized Lactones
4 Formed by Addition of C2H5ONa to 1a. A 175 mg portion
of the mixture of the lactones 4 obtained by reaction of 1a with
C2H5ONa was reacted with 0.5 mL of 1 N HCl in ether to afford
105 mg of a pale yellow powder composed of a 50/50 mixture
of 2a and 2b. These two complexes were not separated. IR
(hexane, cm-1): ν(CtO) 2125 (m), 2085 (sh), 2060 (sh), 2050
Reaction of 1a with t-BuONa. 1a (1 mmol, 300 mg) was
reacted with 95 mg (1 mmol) of t-BuONa to form 225 mg (yield:
60%) of an anionic complex which could be 4d. The presence
of paramagnetic impurities in the crude product could explain
the very poor resolution of the NMR spectra of this complex,
1
(s); ν(CdO) 1720 (m), 1685 (sh). H NMR: (CD2Cl2, 273 K; δ,
ppm): 3.63 (q, J ) 6.5 Hz, 2H, OCH2), 3.34 (s, 3H, OCH3) 1.40
(s, 6H, CH3) 1.14 (t, J ) 6.5 Hz, 3H, CH3). 13C{1H} NMR (CD2-
Cl2, 273 K; δ, ppm): The two products were identified by their
13C NMR specific resonances. 2a: 50.5 (OCH3) and 16.1 (CH3)
and 2b 59.1 (OCH2), 16.6 (CH3), and 14.9 ppm (CH3).5
Reaction of the Anionic Lactone 4c with HCl. 4c (0.5
mmol, 170 mg) was reacted with 0.5 mL of 1 N HCl in ether
to afford 120 mg of a pale yellow powder composed of 80% 2a
and 20% 1c. The presence of these complexes was shown in
13C NMR by their specific resonances: 245.8, 196.8, 109.8, 50.5,
and 16.1 ppm for 2a and 246.8, 201.9, 191.9, 84.6, 28.3, and
23.3 ppm for 1c.
Reaction of 4d or 4e with HCl: Formation of 5. 4d or
4e formed in situ respectively by reaction of 1 mmol (300 mg)
of 1a or 340 mg of 1c with 100 mg of t-BuONa was reacted
with 1 mL of 1 N HCl in ether. 4d gave rise specifically to 5,
which was obtained as a white powder in 60% yield (160 mg).
IR (hexane, cm-1): ν(CtO) 2134 (m), 2083 (sh), 2074 (m), 2056
(s); ν(CdO) and ν(CdC) 1725 (m), 1688 (m) 1618 (m). 1H NMR
(CD2Cl2, 273 K; δ, ppm): 5.07 (br s, 1H, CH2), 4.86 (br s, 1H,
CH2). 13C{1H} NMR (CD2Cl2, 273 K; δ, ppm): 236.9 (CdO);
198.6 (2), 199.1, 198.0, 196.9, 196.1 (terminal CtO and C(O)O),
157.5 (cyclic CdCH2); 89.7 (CH2). NMR HMQC sequences
showed interactions between the two protons and the carbon
at 89.7 ppm. Anal. Calc for C8FeH2O7: C, 36.13; Fe, 21.00; H,
0.76. Found: C, 36.75; Fe, 20.72; H, 1.05. Under the same
reaction conditions, 4e afforded 115 mg of 5 (43% yield) and
45 mg of 1c (13% yield). 1c was extracted from the crude
product by five portions of 5 mL of hexanes at -70 °C, while
5 was purified by crystallization from a CH2Cl2/hexanes
mixture (5/95) at -30 °C. Both complexes were characterized
in 13C NMR by comparison with authentic samples.
which was only characterized by its IR spectrum: (THF, cm-1
)
ν(CtO) 2069 (s), 2007 (s), 1988 (s); ν(CdO) 1678 (sh), 1640
(s), 1612 (m).
Reaction of 1c with t-BuONa. 1c (1 mmol, 340 mg) was
reacted with 1 mmol (95 mg) of t-BuONa to give rise to 310
mg (yield: 75%) of an anionic complex which could be 4e. For
the same reason as for the preceding complex, no suitable
NMR spectrum was obtained. IR (THF, cm-1): ν(CtO) 2068
(s), 2005 (s), 1982 (s); ν(CdO) 1673 (sh), 1636 (s), 1585 (m).
Reaction of 1a with CH3SNa. 1a (1 mmol, 300 mg) was
reacted with 1 mmol (70 mg) of CH3SNa29 to afford 275 mg
(yield: 80%) of 4f. IR (THF, cm-1): ν(CtO) 2068 (s), 2005 (s),
1987 (s); ν(CdO) 1646 (s), 1593 (m). 1H NMR (D8-THF, 273 K;
δ, ppm): 3.5 (br s, 3H, OCH3), 2.1 (br s, 2.55 H, SCH3), 1.9 (br
s, 0.45 H, SCH3) 1.5 (br s, 2.55 H, CH3) 1.4 (br s, 0.45 H, CH3).
13C{1H} NMR (THF, 273 K; δ, ppm): (two isomers 85/15) 259.6,
(CdO); 222.8, (cyclic C(O)O-); 209.3, 208.4, and 207.7 (CtO
and C(O)O-); 95.5 (cyclic quaternary carbon); 50.3 (OCH3);
22.6 (CH3); 12.5(SCH3). The presence of a second isomer (15%)
is shown by the following resonances: 259.7 (CdO); 223.0
(cyclic C(O)O-); 97.0 (cyclic quaternary carbon); 51.0 (OCH3);
12.2(SCH3).
Reaction of 1a with P(C6H5)2Li. 1a (1 mmol, 300 mg) was
reacted with 200 mg (1 mmol) of P(C6H5)2Li30 to form 340 mg
(yield: 75%) of 4g. IR (THF, cm-1): ν(CtO) 2072 (s), 2012 (s),
1994 (s); ν(CdO) 1637 (s), 1615 (s). 1H NMR (D8-THF, 273 K;
δ, ppm): from 8.1 to 6.9 (broad signal, 10 H, C6H5), 3.3 (br s,
3H, OCH3), 1.5 (br s, 3 H, CH3). 13C{1H} NMR (THF, 273 K;
δ, ppm): (two isomers 50/50) 267.5, 253.3 (CdO); 226.0, 214.5,
214.1, 207.2, and 205.8 (cyclic C(O)O; CtO and C(O)O-);
91.35, 90.2 (cyclic quaternary carbon); 50.4 (OCH3); 21.2 and
19.6 (CH3). The poor resolution of the spectrum precludes the
evaluation of the 31P-13C coupling. 31P NMR (D8-THF, 273 K;
δ, ppm): 30.2, 24. 6 (two signals of equal intensities).
Reaction of 1a with NaNH2 or LiN(C2H5)2. As shown by
IR, 1 mmol of 1a reacts in 2 h time at -10 °C with 1 mmol of
NaNH2 or LiN(C2H5)2 to afford Fe(CO)5 and organic products.
Reaction of 1a with NaH. No reaction was observed
between these two compounds even at room temperature.
Reactions of the Anionic Trifunctionalized Metalla-
lactones 4 with HCl; Preparation of the Neutral Lac-
tonic Complexes 2: General Procedure. A 1 N solution of
HCl in ether (0.5 mL) was added to a suspension of 0.5 mmol
of complexes 4 in 50 mL of THF at - 70 °C. As shown by an
Reaction of 4f with HCl. 4f (184 mg 0.5 mmol) was
reacted with 0.5 mL of 1 N HCl in ether to give rise to 87 mg
(yield: 60%) of 2c. IR (hexane, cm-1): ν(CtO) 2127 (s), 2077
(m), 2066 (s), 2049 (s); ν(CdO) 1726 (m), 1706 (sh), 1696 (sh).
1H NMR (CD2Cl2, 273 K; δ, ppm): 2.13 (s, 3H, SCH3), 1.64 (s,
3 H, CH3). 13C{1H} NMR (CD2Cl2, 273 K; δ, ppm): 244.5
(CdO); 199.7 (2), 198.2, 197.0, 196.3 (terminal CtO) and cyclic
C(O)O); 97.4 (cyclic quaternary carbon); 21.6 (CH3) 12.6
(SCH3). Anal. Calc for C9FeH6O7S: C, 34.42; Fe, 17.78; H, 1.93.
Found: C, 34.54; Fe, 17.65; H, 2.05.
Reaction of 4g with HCl. 4g (245 mg, 0.5 mmol) was
reacted with 0.5 mL of 1 N HCl in ether to form 125 mg (yield:
55%) of 2d. IR (hexane, cm-1): ν(CtO) 2120 (m), 2075 (m, sh),

Anionic Trifunctionalized Metallalactones
Organometallics, Vol. 24, No. 7, 2005 1717
2065 (m, sh), 2045 (s); ν(CdO) 1710 (m, br), 1695 (sh). 1H NMR
(CD2Cl2, 273 K; δ, ppm): from 7.9 to 7.3 (m, 10H, C6H5), 1.51
(d, JP-H ) 11.2 Hz, 3 H, CH3). 31P{1H} NMR (CD2Cl2, 273K; δ,
ppm): 10.9. 13C{1H} NMR (CD2Cl2, 273 K; δ, ppm): 252.7 (d,
JP-C ) 8.7 Hz) (CdO); 200.8, 198.2 (2), 197.4 196.3 (terminal
CtO) and cyclic C(O)O); from 135.2 to 136.1 (m, 4C); 133.9
(d, JP-C ) 15 Hz, 1C); 132.7 (d, JP-C ) 16.5 Hz, 1C); 130.4 (bs,
1C); 130.1 (bs, 1C); 128.8 (bs, 4C); 101.1 (cyclic quaternary
carbon); (d, JP-C ) 35.6 Hz); 23.1 (d, JP-C ) 17.4 Hz (CH3).
13C{1H,31P} NMR: 135.9 (2C (ortho)); 135.7 (2C (ortho)); 133.9
(1C (R)); 132.7 (1C (R)); 130.4 (1C (para)); 130.1 (1C (para));
128.9 (2C (meta)); 128.8 (2C (meta)). Anal. Calc for C20-
FeH13O7P: C, 53.12; Fe, 12.85; H, 2.90; P, 6.85. Found: C,
53.32; Fe, 12.70; H, 2.95; P, 6.91.
NMR, the so formed products were similar to those already
obtained by reaction of 1a with C2H5ONa (numerous isomers).
(2) 2a (150 mg, 0.5 mmol) was allowed to react with 0.25 mmol
of C2H5ONa (18 mg). After evaporation of the solvent, the 13
C
NMR spectrum of the residue showed the formation of the
same mixture of complexes 4 together with 50% of unchanged
2a.
Reaction of 2c with CH3ONa. 2d (160 mg, 0.5 mmol) was
reacted with 0.5 mmol of CH3ONa (28 mg) to give 92 mg of 4f
(50% yield). As observed for the reaction between 1a and
CH3SNa, the 13C NMR spectrum of the product of the reaction
showed only the formation of two isomers of 4f (85/15).
Reaction of 2a with C2H5OH or C2H5OH and HCl. C2H5-
OH (20 equiv, 1.180 mL) was added to a solution of 1 mmol of
2a in solution in 25 mL of CH2Cl2 at 0 °C. The solution was
stirred for 5 h at this temperature. The solvent was removed
and the 13C NMR spectrum of the residue was found un-
changed. If 1 equiv of HCl was added to the solution, as shown
by IR, a decomposition of 2a occurred, affording Fe(CO)5
together with organic compounds.
Reactions of Metallalactones 2 with RO-: General
Procedure. To a solution of 0.5 mmol of lactone 2 in 20 mL
of THF at -5 °C was added 1 equiv of solid RO-. The reaction,
which was monitored by IR, was complete after 2 h at this
temperature. The solvent was then removed and the residue
washed with two portions of 10 mL of hexanes at -70 °C. The
composition of the so obtained white powder was determined
by 13C NMR.
When C2H5ONa (1 mmol, 68 mg) or C2H5OH (20 mmol,
1.180 mL) was reacted with 4a in THF solutions at 0 °C (5 h
stirring), no reaction was observed by 13C NMR.
Reaction of 2a with CH3ONa. 2a (150 mg) was reacted
with 30 mg of CH3ONa to give 97 mg (55% yield) of 4a, whose
13
C NMR spectrum was similar to that obtain by reaction of
Supporting Information Available: X-ray structural
information for complexes 1a and 5. This material is available
free of charge via the Internet at http://pubs.acs.org.
CH3ONa with 1a (mixture of isomers: 50/50)
Reaction of 2a with C2H5ONa. (1) 2a (150 mg, 0.5 mmol)
was allowed to react with 0.5 mmol (35 mg) of C2H5ONa to
afford 82 mg (∼45% yield) of a mixture of 4. As shown by 13
C
OM049030R