Phosphine addition to pyruvoyl ligands of iron complexes: Formation of zwitterionic metallalactones

Article abstract of DOI:10.1021/om800804b

Tertiary phosphines react, at -80 °C, with the pyruvoyl-substituted iron complex (CO)₄Fe[C(O)C(O)CH₃](CO₂CH ₃) (1) to give rise to phosphonium-substituted metallalactones fac-(CO)₃e[C(O)C(CH₃

Full text of DOI:10.1021/om800804b

216
Organometallics 2009, 28, 216–224
Phosphine Addition to Pyruvoyl Ligands of Iron Complexes:
Formation of Zwitterionic Metallalactones
J. Y. Salau¨n,*,† R. Rumin,† F. Setifi,†,‡ S. Triki,† and P. A. Jaffre`s†
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, and De´partement de Chimie, Faculte´ des Sciences, UniVersite´
Ferhat Abbas, de Se´tif Alge´ria
ReceiVed August 19, 2008
Tertiary phosphines react, at -80 °C, with the pyruvoyl-substituted iron complex
(CO)4Fe[C(O)C(O)CH3](CO2CH3) (1) to give rise to phosphonium-substituted metallalactones fac-
(CO)3Fe[C(O)C(CH3)(PR3)OC(O)](CO2CH3) (2). These zwitterionic compounds are formed by an initial
addition of the phosphine to the noncoordinated carbonyl of the pyruvoyl unit followed by the addition
of the oxygen of this CdO on a terminal carbonyl. They display an anionic metal center substituted by
three organic ligands and a positive charge located on a phosphonium group. Attempts to extend the
reaction to the related cationic pentacarbonyl pyruvoyl-substituted iron complex failed, as no reaction
was observed with the same reagents. However, the expected products of these reactions, cationic
phosphonium metallalactones {(CO)4Fe[C(O)C(CH3)(PR3)OC(O)]}+, were obtained by acidic dissociation
of the alkoxycarbonyl ligand of the relevant zwitterionic metallalactones.
Scheme 1
Introduction
Catalytic carbonylation reactions are thought to take place
from organometallic intermediates displaying carbonylated
organic ligands. To appraise the involvement of such entities
in the course of these reactions, the synthesis and the study of
stable complexes of Pt, Mn, Co, or Fe bearing one or two
carbonylated ligands have been performed.1 Although sequential
double migratory insertion of carbon monoxide into a [M]-R
bond affording a [M]C(O)C(O)R linkage is only found to occur
under very specific conditions,2-4 the possible intervention of
R,ꢀ-dicarbonylated groups in multiple carbonylation processes
has however been considered. It has been found that complexes
containing a single [M]C(O)C(O)R chain can be thermally
decarbonylated, giving rise to the corresponding [M]C(O)R
compound ([M] ) Mn(CO)5 and R ) CH3, Ph;5 [M] ) trans-
Pd or Pt(PPh3)2Cl and R ) Ph;6 [M] ) trans-[Pt(PPh3)2(CO)]+
and R ) Ph7). Model compounds for dicarbonylation (those
displaying an R,ꢀ-dicarbonylated ligand and an alkyl ligand)
are also found to undergo thermal decarbonylation. Thus trans-
[PhC(O)C(O)]Pt(PPh3)2(C2H5)8 and cis-(CO)4Fe[C(O)CO2-
C2H5](CH3)9 give rise to trans-[PhC(O)]Pt(PPh3)2[C(O)C2H5]
and cis-(CO)4Fe(CO2C2H5)[C(O)CH3], respectively, which are
formed by insertion of the carbon monoxide molecule, released
by decarbonylation of the RC(O)C(O) group, into the metal alkyl
bond. A second reaction is also observed during decarbonylation
of the iron complex at 6 °C: CH3C(O)CO2C2H5 is formed by a
Csp2-Csp3 carbon-carbon coupling between the two organic
ligands. Complexes displaying the cis-[M][C(O)C(O)R][C(O)R′]
geometry, which might be expected to produce tricarbonylated
organic compounds under thermal treatment, also display a
decarbonylation reaction affording cis-[M][C(O)R][C(O)R′]
complexes ([M] ) Pt(PPh3)2 R ) CH3, C2H5, Ph, OCH3, R′ )
C2H5, Ph;10 [M] ) Fe(CO)4, R ) R′ ) OCH3 or R ) CH3 and
R′ ) OCH311). However, the iron complexes again display a
carbon-carbon coupling process upon decarbonylation, giving
rise to dimethyloxalate or methylpyruvate (dicarbonylation). The
complex cis-(CO)4Fe[C(O)C(O)CH3](CO2CH3) (1), which is
also a model compound for the study of the tricarbonylation
process, has been unexpectedly found to generate upon heating
at 15 °C the metallalactonic complex (CO)4-
* To whom correspondence should be addressed. E-mail Jean-
Yves.Salaun@univ-brest.fr.
† Universite´ de Bretagne Occidentale.
‡ Universite´ Ferhat Abbas.
(1) des Abbayes, H.; Salau¨n, J. Y. Dalton Trans. 2003, 1041, and
references therein.
(2) Geoffroy, G. L.; Sheridan, J. B.; Bassner, S. L.; Kelley, C. Pure
Appl. Chem. 1989, 61, 1723.
(3) Cassar, L. Ann. N.Y. Acad. Sci. 1980, 333, 208.
(4) Gregg, B. T.; Cutler, A. R. Organometallics 1998, 17, 4169.
(5) Casey, C. P.; Bunnel, C. A.; Calabrese, J. C. J. Am. Chem. Soc.
1976, 98, 1166.
(6) Sen, A.; Chen, J. T.; Veller, W. M.; Whittle, J. Am. Chem. Soc.
1987, 109, 148.
(7) Huang, T. M.; You, Y. J.; Yang, C. S.; Tzeng, W. H.; Chen, J. T.;
Cheng, M. C.; Wang, Y. Organometallics 1991, 10, 1020.
(8) Chen, J. T.; Huang, T. M.; Cheng, M. C.; Wang, Y. Organometallics
1991, 10, 2838.
Fe[C(O)C(CH3)(OCH3OC(O)] (Scheme 1), which is formally
(9) Sabo-Etienne, S.; Larsonneur, A. M.; des Abbayes, H. J. Chem. Soc.,
Chem. Commun. 1989, 1671.
(10) 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.
(11) Laurent, P.; Salau¨n, J. Y.; Le Gall, G.; Sellin, M.; des Abbayes, H.
J. Organomet. Chem. 1994, 466, 175.
10.1021/om800804b CCC: $40.75
2009 American Chemical Society
Publication on Web 12/12/2008

Zwitterionic Metallalactones
Organometallics, Vol. 28, No. 1, 2009 217
Scheme 2
obtained by an addition of the oxygen of the ꢀ-carbonyl of the
pyruvoyl ligand on the alkoxycarbonyl and by a migration of
the OR group of this last ligand toward the carbon of the
ꢀ-carbonyl.12
This reaction appears to be very similar to the ring-chain
tautomerism observed in organic chemistry for γ-keto-esters,13
the organometallic complex being considered as a γ-keto-ester
with a metal inserted into the link bridging the two organic
functions. However, unlike the organic process, metallalactone
formation is not reversible and does not require acid or base
catalysis. Carrying out this reaction in the presence of different
nuclophiles (NuH ) ROH, RSH14 or Nu- ) RO-, RS-, and
carbanions15,16) has been found to induce the formation of Nu-
performed with tertiary phosphines (neutral nucleophiles with
no mobile group). These nucleophiles may be expected either
to attack the electrophilic ꢀ-carbonyl of the pyruvoyl ligand,
thereby inducing formation of a phosphonium-substituted met-
allalactone, or, as usually observed, to substitute a terminal
carbonyl of the metal center.
Results and Discussion
In organic chemistry, addition of primary or secondary
phosphines to the carbonyl group of ketones or aldehydes
affording R-hydroxyphosphines has been known for a long
time.19 On the other hand, reactions performed with tertiary
phosphines are more scarce and R-hydroxyphosphonium cations
are obtained only in the presence of a strong acid.20 In
organometallic chemistry however, additions of nucleophiles
including phosphines on unsaturated ligands (alkenes, alkynes,
etc.) are numerous, while examples describing the counterpart
of the organic reaction of addition of tertiary phosphines on
carbonyls are scarce. They have always been performed on η2-
acyl ligands and they give rise to η2-phosphonium C-O
groups.21 The complexes formed are found to be stable for
phosphines already linked to the metal via another coordinating
group,21a-e while adducts obtained by intermolecular attack of
monophosphines (PR3; R ) CH3; C2H5; etc.) seem more difficult
to obtain.21f,g An addition of a phosphine to a terminal carbonyl
has also been reported; it is claimed that an intermediate
displaying a [M]C(O)-phosphonium group is formed.22 The
facile addition of nucleophiles to the ꢀ-carbon of the pyruvoyl
ligand of 1 observed in our laboratory and giving rise to
metallalactones prompted us to try to achieve similar reactions
with tertiary phosphines with the aim of performing for the first
substituted metallalactones (CO)4Fe[C(O)C(CH3)(Nu)OC(O)]
and fac{(CO)3Fe[C(O)C(CH3)(Nu)OC(O)](CO2CH3)},23 respec-
tively (Scheme 2).
Mechanistically, the reaction proceeds (1) by specific addition
of the nucleophiles on the ꢀ-carbonyl of the pyruvoyl ligand,
which then appears as the most electrophilic site of the molecule
(even more than the terminal carbonyls) and (2) by a ring
formation resulting from an attack of the oxygen of this
ꢀ-carbonyl on a terminal carbonyl and not, as previously
supposed, on the alkoxycarbonyl ligand. An analogous observa-
tion has been made for a reaction between a hydride and a
phenylglyoxyl manganese complex.17 Successful use of the same
process in the reaction of the related acetyl complex cis-
(CO)4Fe[C(O)C(O)CH3][C(O)CH3] with the same nucleophiles
confirms that the presence of an alkoxycarbonyl ligand is not
required for the formation of metallalactones.18 As mentioned
above, nucleophiles displaying mobile protons, NuH, af-
ford
neutral
bisubstituted
metallalactones
(CO)4-
Fe[C(O)C(CH3)(Nu)OC(O)], while anionic nucleophiles, Nu-,
give rise to trifunctionalized anionic metallalactones fac-
{(CO)3Fe[C(O)C(CH3)(Nu)OC(O)](CO2CH3)}-. The present
article describes the results obtained when the reaction is
(19) (a) See for example: Houben-Weil Methoden der Organishen
Chemie; Georg Thieme Verlag: Stuttgart, Germany, 1963; pp29 and 98.
(b) Epstein, M.; Buckler, S. A. Tetrahedron 1962, 18, 1231. (c) Buckler,
S. A.; Epstein, M. Tetrahedron 1962, 18, 1211.
(20) (a) Evangelidou-Tsolis, E.; Ramirez, F.; Pilot, J. F.; Smith, C. P.
Phophorus Relat. Group V Elem. 1974, 4, 109. (b) Lee, S. W.; Trogler,
W. C. J. Org. Chem. 1990, 55, 2644.
(21) (a) Skagestad, V.; Tilset, M. Organometallics 1994, 13, 3134. (b)
Tikkanen, W.; Ziller, J. W. Organometallics 1991, 10, 2266. (c) Grimmet,
D. L.; Labinger, J. A.; Bonfiglio, J. N.; Masuo, S. T.; Shearin, E.; Miller,
J. S. Organometallics 1983, 2, 1325. (d) Labinger, J. A.; Bonfiglio, J. N.;
Grimmet, D. L.; Masuo, S. T.; Shearin, E.; Miller, J. S. Organometallics
1983, 2, 733. (e) Karsch, H. H.; Mu¨ller, G.; Kru¨ger, C. J. Organomet. Chem.
1984, 273, 195. (f) Arnold, J.; Tilley, T. D.; Rheingold, A. L.; Geib, S. J;
Arif, A. M. J. Am. Chem. Soc. 1989, 111, 149. (g) Bonnesen, P. V.; Yau,
P. K. L.; Hersh, W. H. Organometallics 1987, 6, 1587.
(12) Sellin, M.; Luart, D.; Salau¨n, J. Y.; Laurent, P.; Toupet, L.; des
Abbayes, H. J. Chem. Soc., Chem. Commun. 1996, 857.
(13) Valter, R. E.; Flitsh, R. E. Ring-Chain Tautomerism; Plenum: New
York, 1985.
(14) Cabon, P.; Sellin, M.; Salau¨n, J. Y.; Patinec, V.; des Abbayes, H.;
Kubicki, M. Organometallics 2002, 21, 2196.
(15) Cabon, P.; Rumin, R.; Salau¨n, J. Y.; Triki, S.; des Abbayes, H.
Organometallics 2005, 24, 1709.
(16) Cabon, P.; Rumin, R.; Salau¨n, J. Y.; des Abbayes, H.; Triki, S.
Eur. J. Inorg. Chem. 2006, 1515.
(17) Selover, J. C.; Vaughn, G. D.; Strouse, C. E.; Gladysz, J. A. J. Am.
Chem. Soc. 1986, 108, 1455.
(18) Salau¨n, J. Y.; Rumin, R.; des Abbayes, H.; Triki, S. J. Organomet.
Chem. 2006, 691, 3667.
(22) Doherty, S.; Waugh, M.; Scanlan, T. H.; Elsegood, M. R. J.; Clegg,
W. Organometallics 1999, 18, 679.
(23) Sellin, M.; Luart, D.; Salau¨n, J. Y.; Laurent, P.; Toupet, L.; des
Abbayes, H. Organometallics 1996, 15, 521.

218 Organometallics, Vol. 28, No. 1, 2009
Salau¨n et al.
Scheme 3
time an addition of these reagents on a non-η2-carbonyl and to
obtain stable metallalactones substituted by phosphonium
groups.
Reaction of (CO)4Fe[C(O)C(O)CH3](CO2CH3) (1) with
P(CH3)3, P(C2H5)3, P(n-Bu)3, and P(CH3)2(C6H5). As shown
by an IR monitoring of the reactions, 1 in solution in CH2Cl2
at -80 °C reacts instantaneously with 1 equiv of these slightly
hindered phosphines to afford a series of new complexes (2).
The IR spectra of these compounds exhibit three strong νCtO
bands between 2080 and 1990 cm-1, very similar to those
observed for the related anionic trifunctionalized metallalactones
fac-{(CO)3Fe[C(O)C(CH3)(Nu)OC(O)](CO2CH3)}- (Scheme 2),
which are obtained by reaction of 1 with anionic nucleophiles
(Nu-) (three bands between 2084 and 1970 cm-1).15,16 Since
the noncyclic compound fac-[(CO)3Fe(CO2CH3)3]- displays only
two bands in this area, as required by C3V symmetry (at 2080
and 2015 cm-1),23 the observation of the third IR-active νCtO
is presumed to result from the presence of a metallacycle on
complexes 2. The existence of a metallacycle, the fac-trisub-
stitution, and the anionic character of the metal center of
complexes 2 are confirmed by their 13C NMR data (see
Experimental Section). The fact that most of the resonances of
these complexes are split into doublets suggests the formation
of two isomers (Scheme 3) made possible by the presence of
two different substituents on the quaternary carbon of the cycle
in addition to the presence of three different organic substituents
in fac positions on the metal center.
are observed at 32.0 and 30.7 ppm for 2a (60/40), 41.2 and
39.3 ppm for 2b (66/33), 44.4 and 42.7 ppm for 2c (55/45),
and 28.8 and 24.4 ppm for 2d (55/45). There is no clear relation
between the ratio of the two isomers and the electronic or steric
effects of the phosphines. An attempt to modify these ratios by
increasing the bulkiness of the alkoxycarbonyl ligand, using the
related complex (CO)4Fe[C(O)C(O)CH3][CO2C(CH3)3] (1a),
failed, as the ratios of the different metallalactonic isomers
obtained with this complex are very similar to those observed
with 1. All data are in good agreement with a zwitterionic
structure of 2 in which a negative charge is located on the
trifunctionalized metal center, while the phosphonium group is
associated with the positive charge. Conclusive evidence of the
structure is provided by the X-ray diffraction study performed
on isomer 2b(1) of complex 2b.
Structural Study of Complex 2b(1). Single crystals of 2b(1)
were grown from a hexanes/dichloromethane mixture (90:10)
at -30 °C. An ORTEP diagram of the complex is displayed in
Figure 1, crystallographic data are given in Table 1, and selected
bond lengths and angles are gathered in Table 2.
Figure 1 shows only one isomer of the expected zwitterionic
trifunctionalized metallalactone substituted by a phosphonium
group. Many attempts to collect data for a crystal containing
the second isomer (2b(2)) which was present in solution failed
(proportions of the two isomers: 66/33). The same proportion
between these two products was also observed in the remaining
solution after crystallization or when crystals are dissolved at
low temperature in CD2Cl2. These results suggest that either
2b(2) crystallizes together with 2b(1) but not as single crystals
or if 2b(1) is the only isomer present in the solid state, a rapid
isomerization could occur between these two compounds (during
the crystallization and the dissolving of 2b(1)). This isomer-
ization could result, as reported for ruthenium alkoxycarbonyl
The signals of the three terminal carbonyls (six signals
observed for the two isomers) are found between 205 and 207
ppm and fall within the range of the resonances observed for
23
anionic homologues fac-[(CO)3Fe(CO2CH3)3]-
or fac-
{(CO)3Fe[C(O)C(CH3)(Nu)OC(O)](CO2CH3)}- (from 209 to
206 ppm)15,16 but differ from those of neutral metallalactones
(CO)4Fe[C(O)C(CH3)(Nu)OC(O)] (from 200 to 198 ppm).14
These data clearly show a trisubstitution and an increase of the
electron density of the metal center of complexes 2. The absence
of coupling constants between the signals of the terminal
carbonyls and the phosphorus suggests that the phosphine is
not complexed to the metal. The presence of a metallacycle is
shown by the resonances of the quaternary carbon of the ring
between 83.8 and 86.2 ppm (two signals arising from the
presence of the two isomers). The location of the phosphonium
1
group on this sp3 carbon leads to the large observed JC-P
coupling constants (from 40 to 63 Hz). Smaller interactions are
also observed between the phosphorus and the methyl group
which also link to the sp3 carbon, seen at 20-23 ppm (2JC-P
)
4.6-8.4 Hz). It is worth noting that no coupling is measured
between the phosphorus and the cyclic C(O) acyl bound to the
metal at 269.2-273.3 ppm (2J), whereas a small coupling, 3JC-P
) 6-7.5 Hz (through the oxygen), is observed for the cyclic
C(O)O at 213.9-219.1 ppm. 31P NMR spectra of 2 confirm
the formation of two isomers for each product. Two resonances
Figure 1. ORTEP view of 2b(1) (50% probability ellipsoid)
showing the asymmetric unit, the atom labeling scheme, and the
molecular structure.

Zwitterionic Metallalactones
Organometallics, Vol. 28, No. 1, 2009 219
Table 1. Crystallographic Data for Compounds 2b(1) and 5b
metallacycle of -1.206(8) Å. The methyl group (second
substituent of the cyclic quaternary carbon) is then found in a
pseudoaxial location (dihedral angle C(9)-C(7)-C(6)-Fe(1)
) 104.9(6)°; distance to the median plane: 1.473(8) Å). The
metallacycle is not rigorously planar, as C(7) and O(7) display
deviations from the C(6)-Fe(1)-C(8) plane of 0.27(1) and
0.13(1) Å, respectively; O(7) and C(7) are located on the same
side of this plane. The coordination around the metal center of
2b (1) can be described as a distorted octahedron. As already
observed for anionic metallacyclic iron complexes, the axial
alkoxycarbonyl ligand is slightly bent toward the metallacycle:
C(1)-Fe(1)-C(6) ) 87.2(3)° and C(1)-Fe(1)-C(8) ) 84.8(3)°.
The presence of a five-membered metallacycle in the complex
infers the observation of a small bite angle: C(6)-Fe(1)-C(8)
) 82.7(4)°. This size falls within the range of the values
measured for similar angles of homologous iron metalla-
cycles;12,14-18,25 it is smaller than the angles measured between
two nonchelating organic ligands (for example a value of
88.5(2)° is reported for cis-(CO)4Fe(CO2C2H5)226). It is worth
noting that C(2)-Fe(1)-C(3), the opposite angle on the metal
center, displays a higher value than expected (96.4(3)°).
2b(1)
5b
formula
fw
C15H21FeO8P
416.14
C28H36B2F8Fe2O14P2
943.83
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
orthorhombic
P212121
9.409(2)
10.736(2)
17.932(3)
90
90
90
1811.5(6)
4
triclinic
P1
j
11.365(1)
13.080(1)
14.277(2)
111.19(1)
94.81(1)
99.01(1)
1931.5(4)
2
Z
cryst size (mm)
0.26 × 0.06 × 0.05
0.16 × 0.14 × 0.11
Dcalcd (g cm-3
F(000)
)
1.526
1.623
864
0.960
100(2)
960
0.934
170(2)
abs coeff, µ (mm-1
T (K)
)
2θ limits (deg)
reflns collected
reflns unique/Rint
7.34-50.06
6.70-253.72
6751
15 304
2550/0.0851
1886/221
0.0709
0.0991
1.026
5107/0.0383
3738/505
0.0466
0.0974
1.017
reflns with I > 2σ(I)/Nv
R1a
wR2b
GooFc
Reaction of (CO)4Fe[C(O)C(O)CH3](CO2CH3) (1) with
Bulky Phosphines P(C6H5)3 or P(C6H11)3. Reaction of 1
with P(C6H5)3. At -80 °C, no reaction is observed between
P(C6H5)3 and 1; changes in the IR spectrum of the starting
compound are detected only after 24 h at 10 °C. The 13C NMR
spectrum of the crude product of this reaction shows a failure
in the formation of the phosphonium-substituted metallalactone
that might be expected (no signal with a large interaction with
a phosphorus at ∼80-90 ppm corresponding to a quaternary
metallacyclic carbon substituted by a phosphonium). The
products of the reaction appraised by 13C and 31P NMR are
Fe(CO)4[P(C6H5)3] (33%; 31P NMR: 71.7 ppm; 13C NMR:
∆Fmax/∆Fmin (e Å-3
)
0.513/-0.399
0.10(4)
+0.611/-0.334
Flack param
b
a R1 ) ∑|Fo - Fc|/Fo. wR2 ) {∑w(Fo - Fc2)2]/∑w(Fo )2]}1/2
.
2
2
c
GooF ) {∑w(Fo - Fc2)2]/(Nobs - Nvar.)}1/2
.
2
Table 2. Selected Bond Lengths (Å) and Bond Angles (deg) for
2b(1)
Fe(1)sC(1)
Fe(1)sC(2)
Fe(1)sC(3)
Fe(1)sC(4)
Fe(1)sC(8)
Fe(1)sC(6)
P(1)sC(7)
1.983(8)
1.820(10)
1.823(10)
1.799(9)
1.953(9)
1.958(8)
1.829(8)
O(7)sC(8)
O(7)sC(7)
O(6)sC(6)
O(8)sC(8)
C(9)sC(7)
C(7)sC(6)
1.407(9)
1.429(8)
1.224(9)
1.218(9)
1.531(10)
1.562(11)
213.33 ppm, d, JC-P) 18.7 Hz),27 Fe(CO)3[P(C6H5)3]2 (25%;
2
2
31P NMR: 82.3 ppm; 13C NMR: 214.15 ppm, t, JC-P) 28.3
Hz),27,28 and the two mer isomers of (CO)3Fe-
[P(C6H5)3](CO2CH3)[C(O)C(O)CH3], 3a(1) and 3a(2) (Scheme
4), displaying, in the 31P NMR singlets at 42.85 ppm (20%)
and 42.95 ppm (20%). Formation of 3a(1) and 3a(2) in the
absence of their fac isomers is shown in the 13C NMR by the
presence of two pairs of signals of 2:1 intensities corresponding
to the terminal carbonyls. The specific formation of the mer
isomers by substitution of a terminal carbonyl of 1 by a bulky
phosphine is not surprising, as a similar result has already been
observed for the related complex (CO)4Fe(CO2CH3)2.29
C(4)sFe(1)sC(2)
C(4)sFe(1)sC(3)
C(2)sFe(1)sC(3)
C(4)sFe(1)sC(8)
C(2)sFe(1)sC(8)
C(3)sFe(1)sC(8)
C(4)sFe(1)sC(6)
C(2)sFe(1)sC(6)
C(3)sFe(1)sC(6)
C(8)sFe(1)sC(6)
C(4)sFe(1)sC(1)
C(2)sFe(1)sC(1)
C(3)sFe(1)sC(1)
C(8)sFe(1)sC(1)
94.6(4)
95.2(3)
96.4(3)
88.0(3)
90.1(4)
172.4(4)
90.8(3)
170.9(3)
90.3(4)
82.7(4)
172.8(4)
86.5(4)
91.8(3)
84.8(3)
C(6)sFe(1)sC(1)
C(8)sO(7)sC(7)
O(7)sC(7)sC(9)
O(7)sC(7)sC(6)
C(9)sC(7)sC(6)
O(7)sC(7)sP(1)
C(9)sC(7)sP(1)
C(6)sC(7)sP(1)
O(6)sC(6)sC(7)
O(6)sC(6)sFe(1)
C(7)sC(6)sFe(1)
O(8)sC(8)sO(7)
O(8)sC(8)sFe(1)
O(7)sC(8)sFe(1)
87.2(3)
116.2(6)
109.6(6)
109.3(6)
107.9(6)
105.2(5)
110.6(5)
114.3(5)
115.5(7)
130.9(6)
113.4(5)
112.8(7)
130.5(7)
116.7(6)
The complexation of the phosphine to the metal center of
3a(1) and 3(a)2 is shown by the couplings observed in the 13
C
NMR between the phosphorus and the different carbons linked
2
to the iron: 254.57 ppm (d, JP-C ) 20.6 Hz) and 255.03 ppm
complexes, from a hopping of the alkoxy group of the
alkoxycarbonyl ligand from one terminal carbonyl to
another.24Unlike the related anionic complexes {(CO)3-
2
2
(d, JP-C ) 19.2 Hz) for Fe-C(O)C(O); 206.50 ppm (d, JP-C
2
) 14.6 Hz) and 206.70 ppm (d, JP-C ) 13.5 Hz) for the two
2
axial CtO; 204.95 ppm (d, JP-C ) 7.5 Hz) and 204.90 ppm
Fe[C(O)C(CH3)[CH(CO2C2H5)2]OC(O)](CO2R)}- (R
)
2
(d, JP-C ) 7.5 Hz) for the equatorial CtO; 198.35 ppm (d,
OCH3;16 CH318), respectively obtained as a single isomer, which
display their diethylmalonyl groups and methoxycarbonyl or
acetyl ligands in a trans position with respect to the medium
plane of the metallacyle, the alkoxycarbonyl ligand and the
phosphonium group of 2b(1) are located in cis positions relative
to the same plane.
(25) (a) Pettersen, R. C.; Cihonski, J. L.; Young, F. R.; Levenson, R. A.
J. Chem. Soc., Chem. Commun. 1975, 370. (b) Hoffmann, K.; Weiss, E. J.
Organomet. Chem. 1977, 128, 389. (c) Aime, S.; Milone, L.; Sappa, E.;
Tiripicchio, A.; Manotti Lanfredi, A. M. J. Chem. Soc., Dalton Trans. 1979,
1664. (d) Karel, K. J.; Tulip, T. H.; Ittel, S. D. Organometallics 1990, 9,
1276.
(26) Luart, D.; le Gall, N.; Salau¨n, J. Y.; Toupet, L.; des Abbayes, H.
Inorg. Chim. Acta 1999, 9, 166.
(27) Whitmire, K. H.; Lee, T. R. J. Organomet. Chem. 1985, 282, 95.
(28) Inoue, H.; Takei, T.; Heckmann, G.; Fluck, E. Z. Naturforsch. 1991,
46b, 682.
To minimize steric interactions between these two groups,
the bulky phosphonium adopts a pseudoequatorial position
shown by a torsion angle of 131.7(4)° for P(1)-C(7)-C(6)-Fe(1)
and by a distance between P(1) and the median plane of the
(29) Sellin, M.; Luart, D.; Salau¨n, J. Y.; Laurent, P.; des Abbayes, H.
J. Organomet. Chem. 1998, 562, 183.
(24) Gargulak, J. D.; Gladfelter, W. L. Organometallics 1994, 13, 698.

220 Organometallics, Vol. 28, No. 1, 2009
Salau¨n et al.
Scheme 4
Scheme 5
2JP-C ) 14.0 Hz) and 198.30 ppm (d, 2JP-C ) 14.2 Hz) for the
As no trace of formation of the metallalactone,
C(O)OCH3. A similar interaction is also displayed by the
(CO)4Fe[C(O)C(CH3)(OC2H5)OC(O)], that might be expected
was observed, the terminal carbonyls appear to be the most
electrophilic sites of this cationic species. Tertiary phosphines,
which are not supposed to react easily with terminal carbonyls,
might, by an addition to the ꢀ-carbonyl of 4, induce the forma-
3
ꢀ-carbonyl of the pyruvoyle ligand at 201.58 ppm (d, JP-C
)
16.2 Hz) and at 201.20 ppm (d, 3JP-C ) 16.0 Hz). The coupling
constants between the phosphorus of the phosphine and either
the R-C(O) of the pyruvoyl or the carbonyl of the alkoxycar-
bonyl are equivalent, making any assignment of an exact
geometry to 3a(1) or 3a(2) very difficult. Due to their low
stability, several attempts at separation of these two complexes
failed.
tion
of
the
cationic
metallalactones
{(CO)4-
Fe[C(O)C(CH3)(PR3OC(O)]}+ (5) (Scheme 5). Unfortunately,
as shown by an IR monitoring, no reaction is observed at -40
°C between 4 and P(CH3)3 or [P(C6H5)3]. Raising the temper-
ature to 20 °C leads only to a decomposition of the starting
complex (probably by decarbonylation of the pyruvoyl ligand).
A possible decomposition of lactones 5 was also considered;
however, their isolation as stable compounds by reaction of
complexes 2 with HBF4 (see below) proved this hypothesis to
be wrong and confirms the low electrophilicity of the ꢀ-carbonyl
of pyruvoyl ligands in cationic species.
By Dissociation of the Alkoxycarbonyl Ligand of 2.
Dissociation of alkoxycarbonyl ligands in the presence of a
strong acid is a well-known process.30 This reaction has already
been reported for alkoxycarbonyl iron complexes and yielded,
after release of alcohol, several cationic iron carbonylated
species.11,14,31 Reaction of complexes 2 with 1.1 equiv of
HBF4[O(CH3)2] in THF at -20 °C is found to afford very
rapidly a series of new complexes 5, whose low solubility in
nonpolar solvents suggests a cationic nature. Their IR spectra
(performed in THF) display a set of three broad νCtO bands
between 2147 and 2056 cm-1. The broadness of these signals
can explain the presence of only three bands instead of the four
signals required by a M(CO)4 fragment with C2V symmetry and
generally observed for cis-disubstituted iron carbonyl com-
plexes.11,12,14-16,23,31 The wave numbers measured for these
νCtO bands fall within the range of those observed for neutral
disubstituted iron complexes, 2138-2040 cm-1. They are
significantly different from their homologous monosubstituted
cationic iron complexes (which exhibit three bands between
2195 and 2130 cm-1) and from the νCtO bands observed for
the starting zwitterionic complexes 2 (from 2080 to 1989 cm-1),
Reaction of 1 with P(C6H11)3. As observed for P(C6H5)3, a
reaction between 1 and P(C6H11)3 is obtained only at 15 °C (IR
monitoring). As shown by its NMR data, the crude product of
the reaction is composed of Fe(CO)4[P(C6H11)3] (55%),
Fe(CO)3[P(C6H11)3]2 (traces), (CO)4Fe[C(O)C(CH3)(OCH3)OC-
(O) (15%), and
a
single mer isomer of (CO)3-
Fe[P(C6H11)3](CO2CH3)[C(O)C(O)CH3] (3b) (25%) (data arising
from these different complexes are detailed in the Experimental
Section). The formation of the methoxy-substituted metallalac-
tone very likely results from a direct thermolysis of 1, which
has been reported to occur at 15 °C.12 Unexpectedly, only one
mer isomer of 3b is formed; the value observed for the coupling
constant between the phosphorus and the R-carbonyl of the
pyruvoyl (20.6 Hz) compared to that of 12.1 Hz measured for
the alkoxycarbonyl ligand could suggest for this compound a
structure with the phosphine in a trans position with respect to
the pyruvoyl group. However, as this difference in the coupling
constants was not observed for the related complexes 3(a)1 and
3(a)2, this assignment remains tentative.
Attempts to Obtain Phosphonium-Substituted Cationic
Metallalactones {(CO)4Fe[C(O)C(CH3)(PR3)OC(O)]}+ (5):
R ) CH3, 5a; R ) C2H5, 5b; R ) n-Bu, 5c; PR3
)
P(CH3)2(C6H5), 5d. By Reaction of PR3 with
{(CO)5Fe[C(O)C(O)CH3]}+. The formation of phosphonium-
substituted metallalactones by nucleophilic additions of tertiary
phosphines on 1 confirms the high electrophilicity of the
ꢀ-carbonyl of the pyruvoyl ligand of neutral iron complexes.
The nucleophilicity of this carbon has however not been
observed for similar pyruvoyl-substituted cationic complexes.
Indeed, by addition of EtONa on {(CO)5Fe[C(O)C(O)CH3]}+
(4) we observed the selective formation of cis-
(CO)4Fe(CO2C2H5)[C(O)C(O)CH3] formed by addition of the
nucleophile on one of the terminal carbonyls of the complex.14
(30) Fernandez, M. J.; Rodriguez, M. J.; Oro, L. A. J. Organomet. Chem.
1992, 438, 337.
(31) Salau¨n, J. Y.; le Gall, G.; Laurent, P.; des Abbayes, H. J.
Organomet. Chem. 1992, 441, 99.

Zwitterionic Metallalactones
Organometallics, Vol. 28, No. 1, 2009 221
Table 3. Selected Bond Lengths (Å) and Bond Angles (deg) for 5b
Fe(0)sC(01)
Fe(0)sC(02)
Fe(0)sC(03)
Fe(0)sC(04)
Fe(0)sC(08)
Fe(0)sC(06)
P(0)sC(07)
Fe(1)sC(1)
Fe(1)sC(2)
Fe(1)sC(3)
Fe(1)sC(4)
Fe(1)sC(8)
Fe(1)sC(6)
P(1)sC(7)
1.803(5)
1.875(5)
1.847(6)
1.839(5)
2.013(5)
1.962(5)
1.857(5)
1.822(5)
1.871(5)
1.860(6)
1.829(5)
1.981(5)
1.977(5)
1.840(5)
O(07)sC(08)
O(07)sC(07)
O(06)sC(06)
O(08)sC(08)
C(09)sC(07)
C(07)sC(06)
1.362(5)
1.450(5)
1.221(5)
1.200(5)
1.529(6)
1.555(6)
O(7)sC(8)
O(7)sC(7)
O(6)sC(6)
O(8)sC(8)
C(9)sC(7)
C(7)sC(6)
1.400(5)
1.433(5)
1.204(5)
1.194(5)
1.531(6)
1.564(6)
C(04)sFe(0)sC(02)
C(04)sFe(0)sC(03)
C(02)sFe(0) sC(03)
C(04)sFe(0)sC(08)
C(02)sFe(0)sC(08)
C(03)sFe(0)sC(08)
C(04)sFe(0)sC(06)
C(02)sFe(0)sC(06)
C(03)sFe(0)sC(06)
C(08)sFe(0)sC(06)
C(04)sFe(0)sC(01)
C(02)sFe(0)sC(01)
C(03)sFe(0)sC(01)
C(08)sFe(0)sC(01)
C(4)sFe(1)sC(2)
C(4)sFe(1)sC(3)
C(2)sFe(1) sC(3)
C(4)sFe(1)sC(8)
C(2)sFe(1)sC(8)
C(3)sFe(1)sC(8)
C(4)sFe(1)sC(6)
C(2)sFe(1)sC(6)
C(3)sFe(1)sC(6)
C(8)sFe(1)sC(6)
C(4)sFe(1)sC(1)
C(2)sFe(1)sC(1)
C(3)sFe(1)sC(1)
C(8)sFe(1)sC(1)
93.3(2)
92.2(2)
94.5(2)
90.2(2)
90.3(2)
174.4(2)
84.1(2)
172.3(2)
92.8(2)
82.5(2)
171.8(2)
93.3(2)
92.0(2)
85.0(2)
92.9(2)
91.1(2)
97.4(2)
85.9(2)
91.5(2)
170.8(2)
88.9(2)
173.9(2)
88.4(2)
82.8(2)
174.2(2)
88.9(2)
94.1(2)
88.5(2)
C(06)sFe(0)sC(01)
C(08)sO(07)sC(07)
O(07)sC(07)sC(09)
O(07)sC(07)sC(06)
C(09)sC(07)sC(06)
O(07)sC(07)sP(0)
C(09)sC(07)sP(0)
C(06)sC(07)sP(0)
O(06)sC(06)sC(07)
O(06)sC(06)sFe(0)
C(07)sC(06)sFe(0)
O(08)sC(08)sO(07)
O(08)sC(08)sFe(0)
O(07)sC(08)sFe(0)
C(6)sFe(1)sC(1)
C(8)sO(7)sC(7)
O(7)sC(7)sC(9)
O(7)sC(7)sC(6)
C(9)sC(7)sC(6)
O(7)sC(7)sP(1)
C(9)sC(7)sP(1)
C(6)sC(7)sP(1)
O(6)sC(6)sC(7)
O(6)sC(6)sFe(1)
C(7)sC(6)sFe(1)
O(8)sC(8)sO(7)
O(8)sC(8)sFe(1)
O(7)sC(8)sFe(1)
88.7(2)
117.5(3)
110.4(4)
108.9(4)
108.4(4)
105.9(3)
110.7(3)
112.5(3)
118.0(4)
127.9(4)
113.9(3)
116.3(4)
128.4(4)
115.3(3)
88.7(2)
118.1(4)
110.7(4)
108.5(4)
110.2(4)
105.4(3)
111.3(3)
110.7(3)
118.5(4)
128.5(4)
112.9(3)
116.0(4)
129.0(4)
115.0(3)
Figure 2. ORTEP view of 5b (50% probability ellipsoids) showing
the asymmetric unit, the atom-labeling scheme, and the molecular
structure of the two molecular units, 5b(0) and 5b(1).
whose metal center displays an anionic character. These data
suggest for these cationic complexes the presence of a disub-
stituted neutral metal center and a positive charge located on a
phosphonium group. The 13C NMR spectra of cations 5 confirm
the neutral nature of their metal center; the resonances of their
terminal carbonyls (four signals between 199.6 and 194.35 ppm)
are located between those of cationic monosubstituted iron
compounds (196.1-190.4 ppm) and of anionic complexes
enantiomeric, as they display similar structures with an S C07
for 5b(0) and an R C7 for 5b(1) asymmetric carbons and as
they can be related to each other by a virtual mirror plane located
in a horizontal position orthogonally to the projection plane of
Figure 2. 5b(0) and 5b(1) are however crystallographically
independent molecules, and due to the presence of an inversion
-
23
(209.6 ppm for (CO)3Fe(CO2CH3)3 or from 207.05 to 205.04
ppm for the zwitterionic metallalactones 2). These chemical
shifts are similar to those displayed by a neutral metallalactone
(from 199.4 to 196.7 ppm). Due to the conversion of the
alkoxycarbonyl ligand of each isomer of complexes 2 into a
terminal carbonyl, each formed complex 5 is present as only a
single isomer whose 13C NMR spectra exhibit four resonances
corresponding to the four terminal carbonyls. The nonequiva-
lence of the two axial carbonyls is induced by the presence of
two different substituents on the cyclic sp3 carbon of the
metallacycle. The resonances of these sp3 metallacyclic carbons
are observed at ∼89.5 ppm, and the presence of the phospho-
nium substituent is shown by large JC-P coupling constants
(between 52 and 63 Hz).
j
center required by the space group of crystallysation (P1), their
respective enantiomers are also present in the unit cell. The two
enantiomers 5b(0) and 5b(1) display only slight differences in
their bond lengths and angles. As observed for the zwitterionic
compound 2b(1), the bulky P(C2H5)3 phosphonium group adopts
a pseudoequatorial position with distances to the metallacyclic
median plane of 1.216(5) Å for P(1) and 1.251(6) Å for P(0)
(vs 1.206(8) Å for 2b(1)). The methyl group, the other
substituent of the C(7) (or C(07)) metallacyclic sp3 carbons, is
then located in pseudoaxial position with C(9) or C(09) median
plane distances of -1.496(6) and -1.465(6) Å, respectively.
The metallacycle of 5b(0) is quasi-planar, with distances
between C(07) and O(07) and the C(06)-Fe(0)-C(08) plane
of -0.146(8) and 0.056(7) Å, respectively. C(07) and O(07)
are located from each side of this plane. On the other hand,
C(7) and O(7), their homologues of the second form, 5b(1),
are situated on the same side of this metallacyclic medium plane
with distances between these two atoms and the C(6)-Fe(1)-C(8)
plane of -0.336(8) and -0.141(7) Å, respectively. This
molecule 5b(1) then displays a less planar metallacycle than
that of 5b(0). As observed for the zwitterionic complex 2b(1),
Structural Study of Complex 5b. An X-ray diffraction study
performed on 5b confirmed the structure proposed for the
compounds of this series. Single crystals of 5b were obtained
from a CH2Cl2 solution at -30 °C. The ORTEP diagram of the
complex is displayed in Figure 2; crystallographic data are given
in Table 1 (see Experimental Section), and selected bond lengths
and angles are gathered in Table 3.
Complex 5b is found in the crystal as two entities: 5b(0)
and 5b(1) (Figure 2). These two forms can be described as

222 Organometallics, Vol. 28, No. 1, 2009
Salau¨n et al.
mL of a hexanes/CH2Cl2 (95:5) mixture to give after 12 h at -30
°C white crystals of 2.
the coordination polyhedra around the metal centers of 5b(0)
and 5b(1) are distorted octahedra built of four terminal carbonyls
and the chelate. Again the bite angles of the metallacycles are
small (C(06)-Fe(0)-C(08) ) 82.5(2)°; C(6)-Fe(1)-C(8) )
82.8(2)°) and their opposite angles on the metal centers are
found larger than 90°, with C(03)-Fe(0)-C(02) ) 94.5(2)° and
C(3)-Fe(1)-C(2) ) 97.4(2)°. The two axial terminal carbonyls
are also bent toward the metallacycles. This is shown by an
average value of 87.5° for the angles C(1)-Fe(1)-C(6),
C(1)-Fe(1)-C(8), C(4)-Fe(1)-C(6), and C(4)-Fe(1)-C(8)
and their homologues of the 5b(0) molecular unit.
Reaction of 1 with P(CH3)3 Preparation of 2a. The reaction,
which was performed with a 1 M solution of P(CH3)3 in THF (1.5
mL), afforded after crystallization 310 mg of 2a (55% yield). IR
(CH2Cl2, cm-1): νCtO 2080 (s), 2015 (s), 1990 (s); ν(CdO) 1695(w),
1655 (m), 1640 (w).
1
Major isomer (60%). H NMR (CD2Cl2, 263 K, δ ppm): 3.39
(s, 3 H, OCH3); 1.79 (d, 2JP-H ) 14.5 Hz, 9 H, PCH3); 1.41 (d,3JP-H
) 16.3 Hz, 3 H, CCH3). 13C{1H} NMR (CD2Cl2, 263 K, δ ppm):
270.61 (s, cyclic CdO); 214.25 (d, 3JC-P ) 7.4 Hz, cyclic C(O)O);
203.38 (s, C(O)OCH3); 206.71 (s), 206.39 (s), 205.33 (s) (3 terminal
1
CO); 83.80 (d, JC-P ) 62.6 Hz, cyclic quaternary carbon); 51.29
(s, OCH3); 21.15 (d, 2JC-P ) 8.2 Hz, CCH3); 7.70 (d, 1JC-P ) 51.4
Conclusion
Hz, PCH3). 31P{1H} NMR (CD2Cl2, 263 K, δ ppm): 32.0.
The reactions of an iron complex containing a pyruvoyl
ligand, with tertiary phosphines, has allowed the high electro-
philicity of the ꢀ-carbonyl of this polycarbonylated ligand of
neutral complexes to be confirmed. For the first time, the
addition of these phosphines has been performed on a non-η2-
coordinated CdO. This reaction has been found to give rise to
stable metallactones whose metallacycle formation results from
an addition of the oxygen of the ꢀ-carbonyl of the pyruvoyl to
a terminal carbonyl. These lactones display original zwitterionic
geometries with an anionic charge located on the trisubstituted
metal center and a cationic phosphonium group. However, the
reaction seems limited to neutral compounds, as a similar
cationic pyruvoyl iron complex was found to be unreactive
toward the same phosphines. Cationic lactones, though not
directly available from pyruvoyl cationic compounds, are
obtained by dissociation in acidic medium of the alkoxycarbonyl
ligand of the zwitterionic species 2. These display a neutral metal
center and a positive phosphonium group.
1
Minor isomer (40%). H NMR (CD2Cl2, 263 K, δ ppm): 3.37
2
(s, 3 H, OCH3); 1.80 (d, JP-H ) 14.5 Hz, 9 H, PCH3); 1.40 (d,
3JP-H ) 14.7 Hz, 3 H, CCH3). 13C{1H} NMR (CD2Cl2, 263 K, δ
3
ppm): 273.54 (s, cyclic CdO); 214.05 (d, JC-P ) 7.5 Hz, cyclic
C(O)O); 200.75 (s, C(O)OCH3); 207.05 (s), 205.93 (s), 205.25 (s)
1
(3 terminal CO); 84.30 (d, JC-P ) 61.5 Hz, cyclic quaternary
2
carbon); 50.95 (s, OCH3); 20.20 (d, JC-P ) 7.6 Hz, CCH3); 6.90
(d, 1JC-P ) 51.4 Hz, PCH3). 31P{1H} NMR (CD2Cl2, 263 K, δ ppm):
30.7. Anal. Calcd for C12FeH15O8P: C, 38.53; Fe, 14.93; H, 4.04;
P, 8.28. Found: C, 39.05; Fe, 14.61; H, 4.35; P, 8.15.
Reaction of 1 with P(C2H5)3. Preparation of 2b. The reaction
was performed with a 1 M solution of P(C2H5)3 in THF (1.5 mL).
It was found to afford after crystallization 312 mg of 2b (50% yield).
IR (CH2Cl2, cm-1): νCtO 2080 (s), 2005 (s), 1989 (s); ν(CdO)
1680(w), 1640 (m), 1610 (sh).
1
Major isomer (66%). H NMR (CD2Cl2, 263 K, δ ppm): 3.45
(s, 3 H, OCH3); 1.92 (m, 6 H, PCH2); 1.55 (d, 3JP-H ) 12.0 Hz, 3
H, CCH3); 1.39 (m, 9 H, PCH2CH3). 13C{1H} NMR (CD2Cl2, 263
3
K, δ ppm): 270.07 (s, cyclic CdO); 213.90 (d, JC-P ) 7.0 Hz,
cyclic C(O)O); 202.91 (s, C(O)OCH3); 206.35 (s), 206.11 (s),
Experimental Section
1
205.04 (s) (3 terminal CO); 85.60 (d, JC-P ) 52.0 Hz, cyclic
2
All reactions were carried out using Schlenk techniques under a
dry, oxygen-free argon atmosphere. All solvents were purified by
preliminary distillation from an appropriate drying agent.32 CD2Cl2
and D8-THF were stored over molecular sieves under an inert
atmosphere until needed. Infrared spectra were recorded in the range
2300-1600 cm-1 in solution in CH2Cl2 or THF using a FT-IR
Nexus Nicolet spectrometer. 1H and 13C NMR spectra were recorded
at 0 °C in CD2Cl2 or D8-THF on Bruker AMX-3 300, Bruker DRX
400, or Bruker DRX 500 spectrometers. Chemical shifts were
measured relative to residual protonated solvents for 1H 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”. Fe(CO)5, MeONa, CH3C(O)CO2H, and the different
phosphines were purchased from commercial sources and used as
received. Complex 1 was prepared as described elsewhere15 by
reaction of ClC(O)C(O)Me33 with [(CO)4Fe(CO2Me)]-.34
quaternary carbon); 50.91 (s, OCH3); 22.60 (d, JC-P ) 7.0 Hz,
2
1
CCH3); 13.95 (d, JC-P ) 12.7 Hz, PCH2CH3); 11.09 (d, JC-P
)
44.2 Hz, PCH2). 31P{1H} NMR (CD2Cl2, 263 K, δ ppm): 41.2.
Minor isomer (33%). H NMR (CD2Cl2, 263 K, δ ppm): 3.42
1
3
(s, 3 H, OCH3); 1.85 (m, 6 H, PCH2); 1.53 (d, JP-H ) 10.0 Hz,
3H, CCH3); 1.35 (m, 9H, PCH2CH3). 13C{1H} NMR (CD2Cl2, 263
K, δ ppm): 272.88 (s, cyclic CdO); 218.82 (s, cyclic C(O)O);
200.64 (s, C(O)OCH3); 206.63 (s), 205.60 (s), 205.10 (s) (3 terminal
1
CO); 86.21 (d, JC-P ) 50.1 Hz, cyclic quaternary carbon); 50.59
(s, OCH3); 21.95 (d, 2JC-P ) 5.0 Hz, CCH3); 14.25 (d, 1JC-P ) 38
Hz, PCH2); 14.05 (d, 3JC-P ) 10.0 Hz, PCH2CH3). 31P{1H} NMR
(CD2Cl2, 263 K, δ ppm): 39.3. Anal. Calcd for C15FeH21O8P: C,
43.29; Fe, 13.42; H, 5.09; P, 7.44. Found: C, 43.75; Fe, 13.32; H,
5.35; P, 7.15.
Reaction of 1 with P(n-Bu)3. Preparation of 2c. The reaction,
which was performed with 303 mg (375 µL) of P(n-Bu)3, afforded
after crystallization 340 mg of 2c (45% yield). IR (CH2Cl2, cm-1):
Reaction of
1 with P(CH3)3, P(C2H5)3, P(n-Bu)3, or
ν
CtO 2080 (s), 2018 (s), 1992 (s); ν(CdO) 1675(w), 1630 (m), 1615
P(CH3)2(C6H5). General procedure: One equivalent of the appropri-
ate phosphine (1.5 mmol) was added with stirring to a solution of
1 (450 mg, 1.5 mmol) in 30 mL of CH2Cl2 at -80 °C. Monitoring
of the reaction showed the instantaneous disappearance of the two
(sh).
1
Major isomer (55%). H NMR (CD2Cl2, 263 K, δ ppm): 3.47
(s, 3 H, OCH3); from 1.65 to 1.55 (m, 18 H, CH2); 1.43 (d, JP-H
3
) 11.0 Hz, 3 H, CCH3); 1.25 (t, 3JH-H ) 7.0 Hz, 9 H, P(CH2)3CH3).
13C{1H} NMR (CD2Cl2, 263 K, δ ppm): 269.68 (s, cyclic CdO);
214.04 (br s, cyclic C(O)O); 202.97 (s, C(O)OCH3); 207.04 (s),
206.46 (s), 205.32 (s) (3 terminal CO); 85.48 (d, 1JC-P ) 40.0 Hz,
cyclic quaternary carbon); 50.92 (s, OCH3); 22.63 (d, 2JC-P ) 4.6
Hz, CCH3); 24.8 (s), 24.45 (s), 24.30 (s) (3 CH2); 13.89 (s, CH3).
31P{1H} NMR (CD2Cl2, 263 K, δ ppm): 44.4.
νCtO bands of the starting complex, which were replaced by three
new bands in the νCtO area. After 15 min at -80 °C, the
temperature of the solution was raised to -10 °C and the solvent
evaporated to dryness. The off-white residue was washed at -10
°C with three portions of hexanes (20 mL) extracted with 3 × 20
(32) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals; Pergamon Press: New York, 1980.
(33) Ottenheijm, H. C. J.; Tijhuis, M. W. Org. Synth. 1983, 61, 1.
(34) McLean, J. L., Ph.D. Thesis, New York University, 1974.
1
Minor isomer (45%). H NMR (CD2Cl2, 263 K, δ ppm): 3.48
3
(s, 3 H, OCH3); from 1.65 to 1.55 (m, 18 H, CH2); 1.45 (d, JP-H
) 12.0 Hz, 3 H, CCH3); 1.29 (t, 3JH-H ) 7.0 Hz, 9 H, P(CH2)3CH3).

Zwitterionic Metallalactones
Organometallics, Vol. 28, No. 1, 2009 223
13C{1H} NMR (CD2Cl2, 263 K, δ ppm): 272.90 (s, cyclic CdO);
214.04 (br s, cyclic C(O)O); 200.65 (s, C(O)OCH3); 207.36 (s),
205.88 (s), 205.05 (s) (3 terminal CO); 86.17 (d, 1JC-P ) 43.7 Hz,
cyclic quaternary carbon); 50.66 (s, OCH3); 24.7 (s), 24.15 (s) (2
Reaction of 1 with P(C6H5)3. The yellow oil was obtained in
80% yield. IR (CH2Cl2, cm-1): νCtO 2105 (m), 2035 (s), 2010 (s);
ν
(CdO) 1705(br), 1630 (br), 1600 (br,sh). 1H NMR (CD2Cl2, 263 K,
δ ppm): from 7.90 to 7.15 (m, 46 H, aromatic); 3.68 (br s, 3 H,
OCH3); 2.26 (br s, 3 H, CCH3). The 31P{1H} NMR (CD2Cl2, 263
K, δ ppm) and the 13C{1H} NMR (CD2Cl2, 263 K, δ ppm) spectra
of the mixture allowed the identification of the following products.
Fe(CO)4[P(C6H5)3] (33%): 31P{1H} NMR 71.7 ppm; 13C NMR
2
1
CH2); 22.72 (d, JC-P ) 5.0 Hz, CCH3); 18.15 (d, JC-P ) 30 Hz,
PCH2); 17.25 (s CH2CH3). 31P{1H} NMR (CD2Cl2, 263 K, δ ppm):
42.7. Anal. Calcd for C21FeH33O8P: C, 50.42; Fe, 11.16; H, 6.65;
P, 6.19. Found: C, 50.77; Fe, 12.97; H, 5.48; P, 7.08.
Reaction of 1 with P(CH3)2(C6H5). Preparation of 2d. The
process was performed with 210 mg (215 µL) of P(n-Bu)3. We
obtained after crystallization 392 mg of 2d (60% yield). IR (CH2Cl2,
cm-1): νCtO 2080 (s), 2008 (s), 1995 (s); ν(CdO) 1700(br), 1635
(br), 1615 (sh).
213.33 ppm, (d, JC-P ) 18.7 Hz).27 Fe(CO)3[P(C6H5)3]2) (25%):
2
2
31P{1H} NMR 82.3 ppm; 13C NMR 214.15 ppm, (t, JC-P ) 28.3
Hz).27,28 3a(1) and 3a(2): 31P{1H} NMR 42.85 (20%) and 42.95
2
ppm (20%); 13C NMR 255.03 (d, JC-P ) 19.2 Hz), 254.57 (d,
2JC-P ) 20.6 Hz), Fe-C(O); 206.70 (d, 2JC-P ) 13.6 Hz), 206.50
1
2
2
Major isomer (55%). H NMR (263 K, δ ppm): CD2Cl2, from
(d, JC-P ) 14.6 Hz, 2 axial CtO); 204.95 (d, JC-P) 7.5 Hz),
2
3
7.35 to 6.95 (m, 5 H, aromatic); 3.25 (s, 3 H, OCH3); 1.75 (d,
2JP-H ) 46.5 Hz, 6 H, PCH3); 1.38 (d, 3JP-H ) 6.7 Hz, 3 H, CCH3.
13C{1H} NMR (CD2Cl2, 263 K, δ ppm): 272.81 (s, cyclic CdO);
217.07 (d, 3JC-P ) 7.1 Hz, cyclic C(O)O); 201.22 (s, C(O)OCH3);
206.46 (s), 206.06 (s), 205.40 (s) (3 terminal CO); from 135 to
204.90 (d, JC-P ) 7.5 Hz, equatorial CtO); 201.58 (d, JP-C
)
16.2 Hz), 201.20 (d, 3JP-C ) 16.0 Hz), C(O)CH3; 198.30 (d, 2JC-P
2
) 14.2 Hz), 198.35 (d, JC-P ) 14.0 Hz), C(O)OCH3; 51.66 (s),
51.19 (s), OCH3; 22.88 (s), 22.53 (s), C-CH3. Numerous signals
are observed between 133 0.0 and 127.5 (aromatic carbons).
Reaction of 1 with P(C6H11)3. Preparation of 3b. The oil was
obtained in 70% yield. 1H NMR (CD2Cl2, 263 K, δ ppm): 3.72 (s,
1.6H, OCH3); 3.35 (s, 1H, OCH3); from 2.70 to 1.50 (m, 60 H,
cyclohexyl and CCH3). According to its 31P and its 13C NMR spectra
this oil was found to contain traces of Fe(CO)3[P(C6H11)3]2: 31P{1H}
1
115 (6 aromatic carbons); 84.78 (d, JC-P ) 57.4 Hz, cyclic
2
quaternary carbon); 51.20 (s, OCH3); 22.07 (d, JC-P ) 8.4 Hz,
CCH3); 5.50 (d, 1JC-P ) 38.78 Hz, PCH3). 31P{1H} NMR (CD2Cl2,
263 K, δ ppm): 28.8.
1
Minor isomer (45%). H NMR (CD2Cl2, 263 K, δ ppm): from
7.35 to 6.95 (m, 5 H, aromatic); 3.27 (s, 3 H, OCH3); 1.78 (d,
2JP-H ) 48.7 Hz, 6 H, PCH3); 1.35 (d, 3JP-H ) 6.5 Hz, 3 H, CCH3).
13C{1H} NMR (CD2Cl2, 263 K, δ ppm): 269.26 (s, cyclic CdO);
219.07 (d, 3JC-P ) 6.2 Hz, cyclic C(O)O); 203.60 (s, C(O)OCH3);
206.81 (s), 206.06 (s), 205.22 (s) (3 terminal CO); from 135 to
2
NMR 89.1; 13C{1H} NMR 216.60 (t, JC-P ) 26.9 Hz); 55% of
Fe(CO)4[P(C6H11)3]: 31P{1H} NMR 81.7; 13C{1H} NMR 214.20 (d,
2JC-P ) 19.0 Hz); 15% of (CO)4Fe[C(O)C(CH3)(OCH3)OC4(O)-
(Fe-C4)]12,14 (the proportion of this complex was evaluated by
1
comparison of its OCH3 signal at 3.35 ppm in the H NMR with
1
115 (6 aromatic carbons); 85.90 (d, JC-P ) 57.56 Hz, cyclic
its homologue of 3b at 3.72 ppm); and 25% of one isomer of the
mer-P(C6H11)3](CO)3Fe[C(O)C(O)CH3](CO2CH3) complex (3b):
2
quaternary carbon); 50.64 (s, OCH3); 20.68 (d, JC-P ) 6.9 Hz,
1
CCH3); 6.0 (d, JC-P ) 39.1 Hz, PCH3). 31P{1H} NMR (CD2Cl2,
2
31P{1H} NMR 48.3; 13C NMR 254.60 (d, JP-C ) 20.6 Hz,
263 K, δ ppm): 24.4. Anal. Calcd for C17FeH17O8P: C, 46.82; Fe,
12.72; H, 3.93; P, 7.10. Found: C, 47.21; Fe, 12.65; H, 4.22; P,
7.05.
Fe-C(O)); 206.50 (d, 2JP-C ) 14.6 Hz, 2 axial CtO); 204.15 (d,
3
2JP-C ) 9.4 Hz, equatorial CtO); 200.20 (d, JP-C ) 15.2 Hz,
2
C(O)CH3); 196.10 (d, JP-C ) 12.1 Hz, C(O)OCH3); 51.0 (s,
Crystallographic Analyses. Crystallographic data of compounds
2b(1) and 5b were collected at 100 and 170 K, respectively, on an
Xcalibur 2 diffractometer (Oxford Diffraction) using graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å). The two
structures were solved by direct methods and successive Fourier
difference syntheses and were refined on F2 by weighted anisotropic
full-matrix least-squares methods35 except the C15 carbon atom
of 2b(1), which was refined isotropically. All the non-hydrogen
atoms were refined anisotropically. All the hydrogen atoms were
calculated for both structures and therefore included as isotropic
fixed contributors to Fc. The thermal ellipsoid drawings were made
with the ORTEP program.36 Data collection and data reduction were
done with the CRYSALIS-CCD and CRYSALIS-RED programs.37
All other calculations were performed with standard procedures
(embedded with WinGX suite of programs).38 Pertinent crystal data
and structure refinement and selected bond distances and angles
are listed in Tables 1-3, respectively. Complete crystallographic
data, in CIF format, are included in the Supporting Information.
OCH3); 22.7 (s, CH3). Numerous signals were observed between
37.5 and 26.8 ppm in the 13C NMR; they correspond to the carbons
of the different cyclohexyl groups.
Preparation of Cationic Metallalactones 5. General procedure:
To 1 mmol of a lactone 2 in solution in 40 mL of THF at -20 °C
was added under stirring 1.1 equiv of HBF4 · O(C2H5)2 (150 µL).
After 10 min the solvent was evaporated under vacuum to give a
pale green, oily residue. This residue was washed with two portions
of hexanes at 0 °C and extracted at this temperature by three
portions (20 mL) of a CH2Cl2/hexanes (90:10) mixture. The volume
of the solution obtained was reduced under vacuum at -40 °C to
give a white precipitate. After filtration 5 was obtained as a white
powder, which was washed with two portions of hexanes at -10
°C.
Preparation of 5a. Following the general procedure, 375 mg
of 2a was found to afford 360 mg (85% yield) of 5a, obtained as
a white powder. IR (THF, cm-1): νCtO 2145 (s), 2100 (s), 2070
1
(s); ν(CdO) 1705(s), 1680 (s). H NMR (CD2Cl2, 263 K, δ ppm):
Reaction of
1 with Bulky Phosphines P(C6H5)3 or
2
3
1.92 (d, JP-H ) 23.8 Hz, 9 H, PCH3); 1.62 (d, JP-H ) 25.2 Hz,
3 H, CCH3). 13C{1H} NMR (CD2Cl2, 263 K, δ ppm): 254.8 (s,
cyclic CdO); 198.0 (s, cyclic C(O)O); 199.5 (s), 199.4 (s), 197.7
P(C6H11)3. Preparation of 3a and 3b. General procedure: To a
solution of 1 (450 mg, 1.5 mmol) in 30 mL of CH2Cl2 at -20 °C
was added under stirring 1.1 equiv of the phosphine (P(C6H5)3, 430
mg; P(C6H11)3, 460 mg). The temperature was raised to 10 °C, and
the solution was stirred at this temperature for 24 h. After
evaporation of the solvent the oily residue was extracted by two
portions of 15 mL of a hexanes/dichloromethane (90/10%) mixture
at 0 °C. The solvent was removed to yield a yellow oil.
1
(s), 196.2 (s) (4 terminal CO); 89.6 (d, JC-P ) 63.0 Hz, cyclic
2
1
quaternary carbon); 20.5 (d, JC-P ) 6.5 Hz, CCH3); 6.3 (d, JC-P
) 55.5 Hz, PCH3). 31P NMR{1H} (CD2Cl2, 263 K, δ ppm): 37.8.
Anal. Calcd for BC11F4FeH12O7P: C, 30.74; Fe, 12.99; H, 2.81; P,
7.21. Found: C, 30.91; Fe, 12.48; H, 4.35; P, 6.85.
Preparation of 5b. The general procedure performed with 2b
(416 mg) was found to give rise to 330 mg (yield 70%) of 5b. IR
(THF, cm-1): νCtO 2140 (s), 2085 (br, s), 2057 (s); ν(CdO) 1723(s),
1692 (s). 1H NMR (CD2Cl2, 263 K, δ ppm): 2.37 (m, 6H, PCH2);
1.62 (d, 3JP-H ) 13.5 Hz, 3 H, CCH3); 1.35 (dt, 3JP-H ) 18.5 Hz,
3JH-H ) 7 Hz, 9 H, CH2CH3). 13C{1H} NMR (CD2Cl2, 263 K, δ
(35) Sheldrick, M. SHELX97. Programs for Crystal Structure Analysis;
University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(36) Johnson, C. K. ORTEP, Rep. ONL-3794, Delft, The Netherlands,
1985.
(37) CRYSALIS-CCD 170; Oxford Diffraction, 2002.
(38) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.

224 Organometallics, Vol. 28, No. 1, 2009
Salau¨n et al.
3
ppm): 252.65 (s, cyclic CdO); 195.33 (d, JC-P ) 5 Hz cyclic
ν
CtO 2147 (m), 2087 (sh), 2059 (s); ν(CdO) 1713(m), 1685 (m). 1H
C(O)O); 199.08(s), 198.94 (s), 195.85 (s), 194.42 (s) (4 terminal
CO); 89.8 (d, JC-P ) 51.0 Hz, cyclic quaternary carbon); 21.98
NMR (CD2Cl2, 263 K, δ ppm): from 7.81 to 7.45 (m, 5 H,
1
2
2
aromatic); 2.32 (d, JH-P ) 14.5 Hz, 3H, PCH3); 2.26 (d, JH-P
)
2
1
14.0 Hz, 3H, PCH3); 1.65 (d, 3JP-H ) 15.5 Hz, 3 H, CCH3). 13C{1H}
NMR (CD2Cl2, 263 K, δ ppm): 254.87 (s, cyclic CdO); 197.87
(d, JC-P ) 6.0 Hz, CCH3); 11.72 (d, JC-P ) 55.0 Hz, PCH2).
6.52(d, 2JC-P ) 6.0 Hz, CH2CH3). 31P{1H} NMR (CD2Cl2, 263 K,
δ ppm): 45.3. Anal. Calcd for BC14F4FeH18O7P: C, 35.63; Fe, 11.83;
H, 4.34; P, 6.56. Found: C, 36.02; Fe, 12.35; H, 4.49; P, 6.75.
Preparation of 5c. According to the general procedure the
transformation of 500 mg of 2c afforded 330 mg of 5c (60% yield).
IR (THF, cm-1): νCtO 2139 (s), 2085 (br, s), 2056 (s); ν(CdO)
1721(s), 1692 (s). 1H NMR (CD2Cl2, 263 K, δ ppm): 2.24 (m, 6H,
PCH2); 1.68 (d, 3JP-H ) 13.9 Hz, 3 H, CCH3); 1.59 (m, 6 H, CH2)
1.50 (m, 6 H, CH2CH3) 0.97 (m, 9 H, CH2CH3). 13C{1H} NMR
(CD2Cl2, 263 K, δ ppm): 253.58 (s, cyclic CdO); 196.99 (s, cyclic
C(O)O); 199.12(s), 198.75 (s), 195.74 (s), 194.35 (s) (4 terminal
3
(d, JC-P ) 6.3 Hz, cyclic C(O)O); 199.60(s), 197.57 (s), 197.49
1
(s), 195.95 (s) (4 terminal CO); 89.74 (d, JC-P ) 61.5 Hz, cyclic
quaternary carbon); 20.66 (d, 2JC-P ) 6.5 Hz, CCH3); 5.80 (d, 1JC-P
) 70.0 Hz, PCH3); 5.42 (d, 1JC-P ) 67.0 Hz, PCH3). 31P{1H} NMR
(CD2Cl2, 263 K, δ ppm): 30.2. Anal. Calcd for BC16F4FeH14O7P:
C, 39.07; Fe, 11.35; H, 2.87; P, 6.30. Found: C, 39.52; Fe, 11.65;
H, 3.05; P, 6.15.
Acknowledgment. We thank the “Service de RMN,
Faculte´ des Sciences et Technologie, Universite´ de Bretagne
Occidentale” for its assistance for data recording.
1
CO); 89.32 (d, JC-P ) 52.0 Hz, cyclic quaternary carbon); 21.49
1
(s, CCH3); 17.72 (d, JC-P ) 41.0 Hz, PCH2); 24.23, 24.01 (s, 2
CH2); 13.22 (s, CH2CH3). 31P{1H} NMR (CD2Cl2, 263 K, δ ppm):
40.8. Anal. Calcd for BC20F4FeH30O7P: C, 43.20; Fe, 10.04; H,
5.44; P, 5.56. Found: C, 43.62; Fe, 9.75; H, 5.55; P, 5.75.
Preparation of 5d. The general procedure gave rise (starting
from 440 mg of 2d) to 320 mg (65% yield) of 5d. IR (THF, cm-1):
Supporting Information Available: X-ray structural information
for complexes 2b(1) and 5b. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM800804B