Coordination chemistry of cyclopentadienyl ester-disubstituted ligands. Synthesis and solid state structures of [Na([18]-crown-6)][C5H3(CO2Et)2-1,2] and [Mn{C5H3(CO2Ph)2-1,2}(CO)3]

Article abstract of DOI:10.1021/om000662x

The disubstituted alkyl- and aryloxycarbonylcyclopentadienides of sodium Na[C₅H₃(CO₂R)₂-1,2] [R = Me (3a), Et (3b), Ph (3c)] are obtained in a two-step synthesis. The known Na[C₅H₄(CO₂R)] [R = Me (1a), Et (2b)] and the hitherto unknown Na[C₅H₄(CO₂Ph)] (1c), prepared from NaCp and dialkyl- or diphenyl carbonate, are subsequently reacted with the corresponding chloroformates ROCOCl to give 3 contamined with variable amounts of 1,3 isomers. Treatment of 3b with [18]-crown-6 affords the buff-colored crystalline salt [Na([18]-crown-6)][C₅H₃(CO₂Et)₂-1,2] (4b). Reactions of 4b and 3c with MBr(CO)₅ [M = Mn, Re] or [RuCl₂(CO)₃]₂ lead to the respective metal complexes [M{η⁵-C₅H₃(CO₂R)₂-1,2}(CO)₃] [R = Et and M = Mn (5b) or Re (6b), R = Ph and M = Mn (5c)] and [Ru{C₅H₃(CO₂Et)₂-1,2}(CO)]₂ (7b). The solid state structure of 4b reveals ion pairs in which the anion adopts an idealized C_2v conformation and chelates the sodium (κ²O,O′-coordination). The structure of [Mn{C₅H₃(CO₂Ph)₂-1,2}(CO)₃] (5c) confirms the expected η⁵-coordination of the Cp ring and exhibits significant torsion angles between the Cp ring and carboxylate groups.

Full text of DOI:10.1021/om000662x

282
Organometallics 2001, 20, 282-288
Coor d in a tion Ch em istr y of Cyclop en ta d ien yl
Ester -Disu bstitu ted Liga n d s. Syn th esis a n d Solid Sta te
Str u ctu r es of [Na ([18]-cr ow n -6)][C5H3(CO2Et)2-1,2] a n d
[Mn {C5H3(CO2P h )2-1,2}(CO)3]
Luigi Busetto,*,† M. Cristina Cassani,† Valerio Zanotti,†
Vincenzo G. Albano,*,‡ and Piera Sabatino‡
Dipartimento di Chimica Fisica ed Inorganica, Universita` degli Studi di Bologna,
Viale Risorgimento 4, I-40136 Bologna, Italy, and Dipartimento di Chimica “G. Ciamician”,
Universita` degli Studi di Bologna, Via Selmi 2, I-40126, Bologna
Received August 1, 2000
The disubstituted alkyl- and aryloxycarbonylcyclopentadienides of sodium Na[C5H3(CO2R)2-
1,2] [R ) Me (3a ), Et (3b), Ph (3c)] are obtained in a two-step synthesis. The known Na-
[C5H4(CO2R)] [R ) Me (1a ), Et (2b)] and the hitherto unknown Na[C5H4(CO2Ph)] (1c),
prepared from NaCp and dialkyl- or diphenyl carbonate, are subsequently reacted with the
corresponding chloroformates ROCOCl to give 3 contamined with variable amounts of 1,3
isomers. Treatment of 3b with [18]-crown-6 affords the buff-colored crystalline salt [Na-
([18]-crown-6)][C5H3(CO2Et)2-1,2] (4b). Reactions of 4b and 3c with MBr(CO)5 [M ) Mn,
Re] or [RuCl2(CO)3]2 lead to the respective metal complexes [M{η5-C5H3(CO2R)2-1,2}(CO)3]
[R ) Et and M ) Mn (5b) or Re (6b), R ) Ph and M ) Mn (5c)] and [Ru{C5H3(CO2Et)2-
1,2}(CO)]2 (7b). The solid state structure of 4b reveals ion pairs in which the anion adopts
an idealized C2v conformation and chelates the sodium (κ2O,O′-coordination). The structure
of [Mn{C5H3(CO2Ph)2-1,2}(CO)3] (5c) confirms the expected η5-coordination of the Cp ring
and exhibits significant torsion angles between the Cp ring and carboxylate groups.
In tr od u ction
thesis of sodium 1,2-di(methoxycarbonyl)cyclopenta-
dienide from reaction of methyl chloroformate and
sodium cyclopentadienide.5 The subsequent NMR analy-
sis showed that the product contained 20% of 1,3
isomer.6 By analogy Arthurs7a described in detail the
reaction of KC5H5 with MeOCOCl that gave a complex,
time-dependent, mixture of bi- and trisubstituted cy-
clopentadienide salts together with several organic
byproducts; these results were confirmed in a very
recent work.7b
With the aim of investigating the chemistry of bis-
alkoxy- or bisaryloxycarbonylcyclopentadienyl ligands
here we report their synthesis, and spectroscopic and
X-ray crystallographic characterization. The coordinat-
ing properties are also presented and discussed.
Cyclopentadienyl ligands (Cp) have a wide range of
applications in organometallic chemistry and catalysis.
Replacements of one or more of the cyclopentadienyl
ring hydrogens with different functional groups can
change both electronic properties and range of applica-
tions of the related metal complexes.1 This is especially
true for Cp with attached carbonyl COX (X ) OR, NHR)
functionalities because they may offer different coordi-
nation modes, i.e., κ2O,O′-chelation of the carbonyl
oxygen atoms or η5-coordination of the ring carbons,
depending on the nature of the metal center.2
The chemistry of mono- or pentasubstituted-Cp rings
with alkoxycarbonyl groups CO2R (R ) Me, Et) has been
thoroughly developed and studied by Rausch1a,3 and
Bruce, respectively.2a,4 However bisalkoxycarbonylcy-
clopentadienyl ligands have been scarcely, if at all,
investigated due to the lack of selective, good yield
syntheses. In 1959 Peter described the low-yield syn-
(3) (a) Hart, W. P.; Macomber, D. W.; Rausch, M. D. J . Am. Chem.
Soc. 1980, 102, 1196. (b) Hart, W. P.; Shihua, D.; Rausch, M. D. J .
Organomet. Chem. 1985, 282, 111. (c) Rausch, M. D.; Lewinson, J . F.;
Hart, W. P. J . Organomet. Chem. 1988, 358, 161. (d) J ones, S. S.;
Rausch, M. D.; Bitterwolf, T. E. J . Organomet. Chem. 1990, 396, 279.
(e) Ogasa, M.; Mallin, D. T.; Macomber, D. W.; Rausch, M. D.; Rogers,
R. D.; Rollins, A. N. J . Organomet. Chem. 1991, 405, 41. (f) J ones, S.
S.; Rausch, M. D.; Bitterwolf, T. E. J . Organomet. Chem. 1993, 450,
27. (g) Bitterwolf, T. E.; Gallagher, S.; Rheingold, A. L.; Yap, G. P. A.
J . Organomet. Chem. 1997, 545-546, 27.
(4) Bruce, M. I.; Humphrey P. A.; Williams, M. L. Aust. J . Chem.
1997, 50, 1113.
(5) Peters, D. J . Chem. Soc. 1959, 1757.
(6) Okuyama, T.; Ikenouchi, Y.; Fueno, T. J . Am. Chem. Soc. 1978,
100, 6162.
† Dipartimento di Chimica Fisica ed Inorganica.
‡ Dipartimento di Chimica “G. Ciamician”.
(1) (a) Macomber, D. W.; Hart, W. P.; Rausch, M. D. Adv. Organom.
Chem. 1982, 21, 1. (b) J aniak, C.; Schumann, H. Adv. Organomet.
Chem. 1991, 33, 291. (c) Coville, N. J .; du Plooy, K. E.; Pickl, W. Coord.
Chem. Rev. 1992, 116, 1. (d) Haltermann, R. L. Chem. Rev. 1992, 92,
965. (e) Hays, M. L.; Hanusa, T. P. Adv. Organomet. Chem. 1996, 40,
117. (f) Cuenca, T.; Royo, P. Coord. Chem. Rev. 1999, 193-195, 447-
498.
(2) (a) Bruce, M. I.; White, A. H. Aust. J . Chem. 1990, 43, 949. (b)
Oberhoff, M.; Duda, L.; Karl, J .; Mohr, R.; Fro¨lich, R.; Grehl, M.; Erker,
G. Organometallics 1996, 15, 4005. (c) Klass, K.; Duda, L.; Kleigrewe,
N.; Erker, G.; Fro¨lich, R.; Wegelius E. Eur. J . Inorg. Chem. 1999, 11.
(7) (a) Arthurs, M.; Al-Daffaee, H. K.; Haslop, J .; Kubal, G.; Pearson,
M. D.; Thatcher, P.; Curzon, E. J . Chem. Soc., Dalton Trans. 1987,
2615. (b) Lei, Y. X.; Cerioni, G.; Rappoport, Z. J . Org. Chem. 2000, 65,
4028.
10.1021/om000662x CCC: $20.00 © 2001 American Chemical Society
Publication on Web 12/09/2000

Cyclopentadienyl Ester-Disubstituted Ligands
Organometallics, Vol. 20, No. 2, 2001 283
Resu lts a n d Discu ssion
resonance form not present in the 1,3 isomers.2b,c,4,8
While the separation of 3a -c salts from the neutral
byproduct [C5H5CO2R]2 was easily performed due to
their different solubility in ether, the separation of the
1,2 from the 1,3 isomer was achieved exploiting the
peculiar chelating properties of the ortho isomers. We
discovered that, by adding an equimolar amount of [18]-
crown-6 to 3b, it was possible to precipitate the crown
ether complex of the 1,2 isomer [Na([18]-crown-6)]-
[C5H3(CO2Et)-1,2] (4b) as buff-colored, air-stable crys-
tals soluble in chlorinated solvents. The NMR spectrum
in CDCl3 of 4b (1H NMR δ 6.92, d, 2H; 5.91, t, 1H; 3J )
3.6 Hz; corresponding 13C NMR Cp signals at δ 122.2,
111.5, and 109.8) is very similar to that of 3b in D2O.
The IR absorptions in THF (range 2300-1500 cm-1) of
3b and 4b are identical and show a strong broad band
at 1680 cm-1 originating from the conjugated CdO and
CdC system.8d In the solid state the ester carbonyl
stretching frequency of 4b occurs at 1695 cm-1, a 32
cm-1 shift to higher frequency with respect to the
uncoordinated 3b (1663 cm-1). This behavior, usually
exhibited from enolate salts,9 can be explained assuming
that in solution 4b does not retain the solid state
structure due to the quite loose encapsulation of the
sodium ion in the [18]-crown-6 (see further on). This
method of separation allowed us to obtain a highly pure
sample of 4b, which in THF solution frees type 3 ortho-
disubstituted Cp derivatives.
Syn t h esis a n d Ch a r a ct er iza t ion of [C5H 3(CO2-
R)2]-. Following what was previously reported on the
synthesis of the polysubstituted-Cp-containing ester
functionalities, we have used, as starting material, the
monosubstituted Cp [C5H4CO2R]- [R ) Me (1a ), Et
(1b)], prepared as described by Rausch3a,b from sodium
cyclopentadenide and dimethyl or diethyl carbonate
(eq 1).
NaCp + (RO) CO
f Na[C5H4CO2R] + ROH (1)
2
R ) Me, Et
We have prepared the new Na[C5H4CO2Ph] (1c) in a
similar manner by reacting NaCp with diphenyl car-
bonate (PhO)2CO in tetrahydrofuran at room temper-
ature. The substantial difference observed in the for-
mation of 1c is that the likely neutral intermediate,
1-substituted cyclopentadiene C5H5CO2Ph, is in this
case rapidly deprotonated by a second molecule of Cp
and not by the concurrently produced phenoxide NaOPh
[cf. pKa(C5H6) ) 151a with pKa(PhOH) ) 10]. The overall
reaction stoichiometry is shown in eq 2.
2NaCp + (PhO)2CO f Na[C5H4CO2Ph] + C5H6 +
NaOPh (2)
1c is a light brown solid, stable in air and water for
short periods and sparingly soluble in THF; it was
characterized by NMR (D2O and pyr-d5) and IR spec-
troscopy as well as by the reaction with FeCl2 that gave
the new ferrocene derivative [Fe{C5H4CO2Ph}2] (2).
Noteworthy, the yield of 1c is strictly dependent on the
reaction time: short reaction times favor higher yields
(3 h, 89%). After 20 h 1c is obtained in about 20% yield,
and after 2 days of stirring the yield drops to zero. This
behavior is due to the instability in solution of 1c: the
pure product totally decomposes after 48 h of stirring
in THF.
The lower nucleophilic character of 1, compared with
the unsubstituted cyclopentadienide, did not allow
further functionalization with dialkyl or diaryl carbon-
ates; therefore the more reactive chloroformates had to
be employed in order to obtain our target disubstituted
molecules. Indeed, by treatment of 1 with the corre-
sponding ROCOCl in a 2:1 molar ratio at room temper-
ature in THF solvent, the disubstituted [C5H3{CO2R}2]-
(3) was obtained in 80-90% yield together with dicy-
clopentadiene dicarboxylic ester [C5H5CO2R]2 (eq 3).
The nature of [Na([18]-crown-6)][C5H3(CO2Et)2-1,2]
(4b) has been unambiguously ascertained by an X-ray
diffraction study. The crystals contain ion pairs orga-
nized around the sodium cation that, although sur-
rounded by the six oxygens of the crown ether, is
exposed to the κ2O,O′-coordination of the more basic
carbonyl oxygens of the anion (Figure 1). Relevant bond
parameters concerning the anion are listed in Table 1.
The anion adopts a conformation of C2v idealized sym-
metry, if the ethyl appendages are ignored. The -C(O)O
groups are almost coplanar with the Cp ring with
dihedral angle for C(6)O(1)O(2) of 5.9(4)° and C(7)O-
(3)O(4) of 4.1(4)°. The C(ring)-C(carboxylate) distances
are 1.430(4) and 1.421(4) Å for C(6) and C(7), respec-
tively. These figures indicate significant double-bond
character, comparable with that present in the Cp ring
[C-C(ring) distances in the range 1.427-1.359(4) Å,
average 1.39 Å]. The above distances can be compared
with those found in HC5(CO2Me)5,8d in which two
adjacent -CO2Me groups “chelating” the proton are
coplanar with the Cp ring and exhibit an average
C(ring)-C(carboxylate) distance of 1.427 Å, while two
such groups almost orthogonal to the Cp ring have an
average C(ring)-C(carboxylate) distance of 1.493 Å.
The flat conformation of the anion allows efficient
charge delocalization on the carbonylic oxygens and
improves their basicity. In fact, these oxygens have a
strong interaction with the sodium cation [average Na-
2Na[C H {CO R}]
R ) Me, Et, Ph
+ ROCOCl f
5
4
2
Na[C5H3{CO2R}2]+ 1/2[C5H5CO2R]2 + NaCl (3)
The 1H NMR spectra in D2O or pyridine-d5 for 3 showed
that the major, 1,2 isomers [R ) Me (3a ), Et (3b), Ph
(3c)] were contamined by the 1,3 form in amounts
varying from ca. 5% (or less) when R ) Ph, to 10% for
R ) Et, to a maximum of 20% for R ) Me; no
dependence was observed on reaction conditions, and
the same ratios were observed carrying out the reaction
at -78 °C. The [C5H3(CO2R)2-1,2]- anion can be re-
garded as a â-dicarbonyl system exhibiting further
stabilization due to an additional fulvenoid mesomeric
(8) (a) Linn, W. J .; Sharkey, W. H. J . Am. Chem. Soc. 1957, 79, 4970.
(b) J ackman, L. M.; Trewella, J . C.; Haddon, R. C. J . Am. Chem. Soc.
1980, 102, 2519. (c) Hartke, K.; Kohl, A.; Kampchen, T. Chem. Ber.
1983, 116, 2653. (d) Bruce, M. I.; Walton, J . K.; Williams, M. L.; Hall,
S. R.; Skelton, B. W.; White, A. H. J . Chem. Soc., Dalton Trans. 1982,
2209. (e) Bruce, M. I.; Humphrey, P. A.; Patrick, J . M.; Skelton, B. W.;
White, A. H.; Williams, M. L. Aust. J . Chem. 1985, 38, 1441. (f) Bruce,
M. I.; Humphrey, P. A.; Skelton, B. W.; White, A. H. J . Organomet.
Chem. 1989, 361, 369.
(9) Cambillau, C.; Bram, G.; Corset, J .; Riche, C. Can. J . Chem.
1982, 60, 2554.

284 Organometallics, Vol. 20, No. 2, 2001
Busetto et al.
F igu r e 2. Molecular structure of [Mn{C5H3(CO2Ph)2-1,2}-
(CO)3] (5c) showing the atomic numbering (thermal el-
lipsoids at 50% probability level).
F igu r e 1. Molecular structure of [Na([18]-crown-6)]-
[C5H3(CO2Et)-1,2] (4b) showing the ionic pair and the
atomic numbering (thermal ellipsoids at 20% probability
level).
Sch em e 1
Ta ble 1. Releva n t Bon d Len gth s [Å] a n d
An gles [d eg] for 4b
Na(1)-O(3)
Na(1)-O(1)
Na(1)-O(5)
Na(1)-O(9)
Na(1)-O(8)
Na(1)-O(10)
Na(1)-O(6)
Na(1)-O(7)
C(1)-C(5)
2.309(3)
2.322(3)
2.504(4)
2.582(4)
2.693(5)
2.719(6)
2.736(5)
2.915(8)
1.408(4)
1.421(4)
1.427(4)
1.387(4)
C(2)-C(6)
C(3)-C(4)
C(4)-C(5)
C(6)-O(1)
C(6)-O(2)
C(7)-O(3)
C(7)-O(4)
C(8)-C(91)
C(8)-O(4)
C(8)-C(92)
C(10)-C(11)
C(10)-O(2)
1.430(4)
1.381(5)
1.359(5)
1.202(3)
1.340(4)
1.198(4)
1.346(4)
1.407(9)
1.429(5)
1.442(9)
1.350(6)
1.472(5)
C(1)-C(7)
cyclopentadienide in the formation of transition metal
complexes, we examined the reactions of [Na([18]-crown-
6)][C5H3(CO2Et)-1,2] (4b) and Na[C5H3(CO2Ph)-1,2] (3c)
with MBr(CO)5 [M ) Mn, Re] and [RuCl2(CO)3]2 (Scheme
1). Due to the small amount of 1,3 isomer present in 3c
(see above) and the ease of crystallization of the related
manganese complex (see next paragraph), it was used
without treating it with a crown ether.
The reactions with MnBr(CO)5 produced [Mn{η5-
C5H3(CO2R)2-1,2}(CO)3] [R ) Et (5b); R ) Ph (5c)] in
ca. 80% yields as a yellow oil (R ) Et) and yellow
crystals (R ) Ph). The infrared spectra of 5b [5c] in CH2-
Cl2 show ν(CO) terminal absorptions at 2037 [2040] and
1959 [1963] cm-1. These values are, as expected, higher
than those reported for [Mn{η5-C5H4(CO2Et}(CO)3] [IR-
(CH2Cl2) 2031, 1948]3d but unexpectedly significantly
higher than those in [Mn{C5(CO2Me)5}(CO)3] [IR (CH2-
Cl2) 2020, 1940], which are identical to those found for
the unsubstituted complex [Mn(C5H5)(CO)3].10 This fact
can be related to a significant charge delocalization on
the two vicinal -CO2R groups in 5.
The solid state structure of the neutral molecule [Mn-
{C5H3(CO2Ph)2-1,2}(CO)3] (5c) is shown in Figure 2, and
its bond parameters are listed in Table 2. Its main
stereochemical feature is the regular η5-coordination of
the anion to the Mn(CO)3 fragment. It is to be noted
that, although a mirror plane of the C3v Mn(CO)3
fragment approximately matches a vertical plane of the
Cp ring, the -CO2Ph substituents do not conform to this
potential symmetry and the molecule is asymmetric in
C(1)-C(2)
C(2)-C(3)
C(5)-C(1)-C(7)
C(5)-C(1)-C(2)
C(7)-C(1)-C(2)
C(3)-C(2)-C(1)
C(3)-C(2)-C(6)
C(1)-C(2)-C(6)
C(4)-C(3)-C(2)
C(5)-C(4)-C(3)
C(4)-C(5)-C(1)
O(1)-C(6)-O(2)
124.1(3)
1106.6(3)
129.3(3)
106.4(3)
124.2(3)
129.3(3)
109.6(3)
108.3(3)
109.1(3)
117.4(3)
O(1)-C(6)-C(2)
O(2)-C(6)-C(2)
O(3)-C(7)-O(4)
O(3)-C(7)-C(1)
O(4)-C(7)-C(1)
C(91)-C(8)-O(4)
O(4)-C(8)-C(92)
C(11)-C(10)-O(2)
C(6)-O(2)-C(10)
C(7)-O(4)-C(8)
129.2(3)
113.3(3)
117.9(3)
129.7(3)
112.4(3)
119.1(9)
121.0(10)
111.3(5)
117.2(3)
118.0(4)
O(carbonyl) distance 2.32 Å], to be compared with the
Na-O(crown ether) ones, found in the range 2.504-
2.914(4) Å. The just described geometry of the anion
surely optimizes the total energy but at the cost of some
intraligand tension, as demonstrated by the short O‚‚‚
O(carbonyl) contact [2.774(3) Å] (van der Waals radius
ca. 1.5 Å) and by the wider inner C(carbonyl)-C(ring)-
C(ring) angles [average 129.30°] with respect to the
outer ones [average 124.17°]. Also the displacement of
the carbonyl oxygens out of the Cp ring plane are not
concerted rotations around the C(ring)-C(carboxyl)
axes, but actually consist in a rotation around the C(1)-
C(7) axis [distances from the ring plane O(4) +0.093(6)
and O(3) -0.063(6) Å] and an out-of-plane tilting of the
whole C(6)O(1)O(2) group [distances from the Cp plane
C(6) +0.061(4), O(1) +0.124(6), and O(2) +0.133(6) Å].
In light of these facts one can hypothesize that the
stable anion conformation, in the absence of a κ2O,O′-
chelation, should not be a flat one (see below).
Syn th esis a n d Ch a r a cter iza tion of Meta l Com -
p lexes. To asses the synthetic utiliy of the disubstituted
(10) Arsenault, C.; Bougeard, P.; Sayer, B. G.; Yeroushalmi, S.;
McGlinchey, M. J . J . Organomet. Chem. 1984, 265, 283.

Cyclopentadienyl Ester-Disubstituted Ligands
Organometallics, Vol. 20, No. 2, 2001 285
Ta ble 2. Releva n t Bon d Len gth s [Å] a n d
An gles [d eg] for 5c
2.138, C-C(ring) 1.407, Mn-C(carbonyl) 1.793, C-O(car-
bonyl) 1.144 Å. They are in good agreement with the
corresponding values in 5c.
Mn(1)-C(20)
Mn(1)-C(21)
Mn(1)-C(22)
Mn(1)-C(1)
Mn(1)-C(5)
Mn(1)-C(2)
Mn(1)-C(4)
Mn(1)-C(3)
O(5)-C(20)
O(6)-C(21)
O(7)-C(22)
O(1)-C(6)
1.777(3)
1.789(3)
1.794(3)
2.133(2)
2.137(2)
2.141(2)
2.158(2)
2.162(2)
1.160(3)
1.150(3)
1.141(3)
1.179(3)
O(2)-C(6)
O(2)-C(8)
O(3)-C(7)
O(4)-C(7)
O(4)-C(14)
C(1)-C(5)
C(1)-C(2)
C(1)-C(7)
C(2)-C(3)
C(2)-C(6)
C(3)-C(4)
C(4)-C(5)
1.330(2)
1.417(3)
1.191(2)
1.358(2)
1.417(2)
1.434(3)
1.436(3)
1.472(3)
1.413(3)
1.489(3)
1.410(3)
1.410(3)
The ester carbonyl stretching frequency (THF), which
occurs at 1680 cm-1 (4b) and 1706 cm-1 (3c) in the
starting ligands, exhibits a ca. 40 cm-1 shift to higher
frequency on complex formation 1722 [1742] cm-1 for
the corresponding manganese derivatives 5b [and 5c]
in agreement with the η5 coordination of the ligand.12
1
The H NMR in CDCl3 of 5b shows for the C5H3 unit
resonances at δ 5.60 (2H), 4.87 (1 H), at significantly
higher field compared with the sodium salt 4b. All the
peaks are broad due to the presence of the quadrupolar
55Mn, and lowering the temperature results only in
further broadening. The same trend is observed in the
13C spectra, where the corresponding resonances for the
C5H3 unit are at δ 91.2 (ipso-C), 87.7(CH), 80.0 (CH).
C(5)-C(1)-C(2)
C(5)-C(1)-C(7)
C(2)-C(1)-C(7)
C(3)-C(2)-C(1)
C(3)-C(2)-C(6)
C(1)-C(2)-C(6)
O(1)-C(6)-O(2)
O(1)-C(6)-C(2)
O(2)-C(6)-C(2)
106.5(2)
125.5(2)
127.7(2)
108.4(2)
122.3(2)
129.2(2)
123.8(2)
122.8(2)
113.3(2)
O(3)-C(7)-O(4)
O(3)-C(7)-C(1)
O(4)-C(7)-C(1)
C(6)-O(2)-C(8)
C(7)-O(4)-C(14)
O(5)-C(20)-Mn(1)
O(6)-C(21)-Mn(1)
O(7)-C(22)-Mn(1)
123.8(2)
126.2(2)
109.9(2)
118.0(2)
117.2(1)
179.6(3)
178.9(3)
177.5(2)
The reaction of 4b with ReBr(CO)5 afforded the com-
plex 6b, which exhibits the same spectroscopic features
as the manganese analogue. However, no comparison
could be done with the pentasubstituted complex, as the
reaction of Tl[C5(CO2Me)5] with [ReCl(CO)4]2 in aceto-
nitrile was reported to give the [C5(CO2Me)5]- salt of
the cation [Re(CO)3(NCMe)3]+ as the only product.4
the crystal. The Mn-C(ring) distances are in the range
2.133-2.162(2) Å, average 2.15 Å. The small but sig-
nificant differences in bond distances do not show any
relation to the chemical nonequivalence of the carbon
atoms and should be considered packing effects. Also
the ring is quite regular [C-C distances in the range
1.410-1.436(3) Å, average 1.42 Å]. The average C-C-
(ring) bond length can be compared with that reported
above in 4b [average 1.39 Å]: a 0.03 Å elongation is a
small but measurable effect of the ring-metal interac-
tion.
The η5 coordination ability of the disubstituted ligand
has been confirmed by the formation of the diruthenium
complex [Ru{η5-C5H3(CO2Et)2-1,2}(CO)2]2 (7b) obtained
by reaction of 4b with [RuCl2(CO)3]2. The reaction occurs
with an excess of 4b in refluxing THF for about 16 h,
and 7b has been isolated as a dark yellow oil in >70%
yield. The IR spectrum (Etp) of 7b features the expected
ν(CtO) bands at 2032, 2024, 1992, 1964, 1812 cm-1 (cf.
with IR (heptane) of [Ru(C5H5)(CO)2]2: 2020, 2010,
1973, 1944, 1794),13 while the ν(CdO) for the ester
carbonyl is at 1726 cm-1. The 1H NMR in CDCl3 at room
temperature shows for the C5H3 unit one set of signals
at δ 5.82 (2H) and 5.35 (1H), while the 13C NMR shows
only one peak at δ 210.2 for the M-CO and peaks at δ
96.9 (ipso-C), 92.1 (CH), 89.8 (CH) for the cyclopenta-
A major structural difference between the present η5-
coordinated and the κ2O,O′-chelated anion is found for
the -CO2R substituents that are equivalent under C2v
idealized symmetry in 4b and related by a quasi 5-fold
rotation in 5c (the C5 ring axis). The conformation of
[C5H3(CO2Ph)2-1,2]- is deprived of symmetry, and the
intramolecular tension found in 4b is partially allevi-
ated [O(2)‚‚‚O(3) contact 2.841(2) Å, inner and outer
C(carboxyl)-C(ring)-C(ring) average angles 128.4° and
123.9°, respectively]. The -C(O)O groups are signifi-
cantly rotated around their C(ring)-C(carboxylate) bond
[21.5° around C(1)-C(7) and 35.6° around C(2)-C(6)],
and some ring-carboxylate conjugation has been lost.
Consistently, the C(ring)-C(carboxylate) distances [C(1)-
C(7) 1.472 and C(2)-C(6) 1.489(3) Å, average 1.48 Å]
are 0.06 Å longer than in 4b, and the longer C(2)-C(6)
distance corresponds to the higher torsion angle. The
observed correlation between ring-carboxylate dihedral
angles and C(ring)-C(carboxylate) bond distances shows
that the π electron delocalization in the anion is reduced
but not extinguished, in accord with the spectroscopic
evidence.
1
dienyl ring. A more detailed H NMR study of complex
7b in CD2Cl2 has shown a temperature dependence
(-90 °C, +20 °C) of the chemical shift of the ring
protons, without line broadening [H(2), H(4) δ 5.76 (+20
°C), 5.69 (-90 °C), ∆δ ) -0.07 ppm; H(3) δ 5.24 (+20
°C), 5.36 (-90 °C), ∆δ ) +0.12 ppm]. A similar behavior,
involving the signals of the protons of complexes con-
taining a cyclopentadienyl ring substituted with electron-
withdrawing groups, has already been reported and was
attributed to the loss of the symmetric η5-delocalized
bonding and adoption of a (η3 + η2) localized structure.14
Concerning the Mn(CO)3 moiety, the average Mn-C
and C-O distances are 1.79 and 1.15 Å, respectively.
The structural parameters of 5c should be compared
with those in the unsubstituted Mn(C5H5)(CO)3, the
structure of which has been repeatedly reported with
an increasing level of accuracy.11a-c The most recent low-
temperature results11c are as follows: Mn-C(ring)
(12) As a rule chelation with the carbonyl oxygens is accompanied
by noticeable shifts of the ν(CdO) IR bands to lower wavenumbers.
Lappert, M. F. J . Chem. Soc. 1961, 817. Komiya, S.; Ito, T.; Cowie,
M.; Yamamoto, A.; Ibers, J . J . Am. Chem. Soc. 1976, 98, 3874. Bruce,
M. I.; Humphrey, P. A.; Miyamae, H.; Skelton, B. W.; White, A. H. J .
Organomet. Chem. 1992, 429, 187. Bodensieck, U.; Santiago, J .;
Stoeckli-Evans, H.; Suss-Fink, G. J . Organomet. Chem. 1992, 433, 141.
Bohle, D. S.; Christensen, A. N.; Goodson, P. A. Inorg. Chem. 1933,
32, 4173. Suzuki, H.; Omori, H.; Lee, D. H.; Yoshida, Y.; Fukushima,
M.; Tanaka, M.; Moro-oka, Y. Organometallics 1994, 13, 1129. Chi,
Y.; Wu, H.-L.; Peng, S.-M.; Lee, G.-H. J . Chem. Soc., Dalton Trans.
1997, 1931. Siemling, U. Coord. Chem. Rev. 2000, 100, 1495.
(13) Cotton, F. A.; Yagupsky, G. Inorg. Chem. 1967, 6, 15. McArdle,
P.; Manning, A. R. J . Chem. Soc. 1970, 2128.
(11) (a) Berndt, A. F.; Marsh, R. E. Acta Crystallogr. 1963, 16, 118.
(b) Fitzpatrick, P. J .; Le Page, Y.; Sedman, J .; Butler, I. S. Inorg. Chem.
1981, 20, 285. (c) Cowie, J .; Hamilton, E. J . M.; Laurie, J . C. V.; Welch,
A. J . J . Organomet. Chem. 1990, 394, 1.

286 Organometallics, Vol. 20, No. 2, 2001
Busetto et al.
The reagents Na[C5H4CO2R] (R ) Me, Et)3a,b and MBr(CO)5
(M ) Mn, Re)16 were prepared according to literature proce-
dures; [18]-crown-6 (Aldrich) was crystallized from acetonitrile,
and the adduct was kept under vacuum at 40 °C for 4 h and
recrystallized from hexane; diphenyl carbonate (Aldrich) was
crystallized from petrolum ether; [Ru(CO)3Cl2]2 (Strem) and
FeCl2 (Aldrich) were used as purchased; and the chlorofor-
mates ROCOCl (Aldrich) were kept under argon on molecular
sieves. Petroleum ether (Etp) refers to a fraction of bp 60-80
°C. Silica gel was heated at about 200 °C while a slow stream
of a dry nitrogen was passed through it.17 Melting points were
taken in sealed capillaries and were uncorrected.
Complexes 5b,c, 6b, and 7b are stable to air and heat;
for example the oils 5b and 6b can be distilled under
vacuum (p ) 0.1 mmHg) at 100 °C without decomposi-
tion.
Con clu sion s
The cyclopentadienyl ester-disubstituted ligands [C5H3-
(CO2R)2-1,2]- 3a -c have been obtained from NaCp in
a two-step sequence together with variable amounts of
the 1,3 form. The 3b derivative has been prepared free
from the contaminating 1,3 isomer by addition of an
equimolar amount of [18]-crown-6. The resulting crys-
talline salt, [Na([18]-crown-6)][C5H3(CO2Et)2-1,2] (4b),
was structurally characterized by X-ray diffraction. The
new Na[C5H3(CO2Ph)2-1,2] (3c) was less contamined by
the 1,3 isomer, and therefore no treatment with the
crown ether was necessary. Unlike the direct reaction
between NaCp and ROCOCl,7 our method was more
reproducibile and not dependent on reaction conditions
such as temperature and reaction time.
4b and 3c have been reacted with Mn, Re, and Ru
carbonyl complexes. The η5 derivatives [M{C5H3(CO2R)2-
1,2}(CO)3] [R ) Et, M ) Mn (5b) or Re (6b); R ) Ph, M
) Mn (5c)] and [Ru{C5H3(CO2Et)2-1,2}(CO)]2 (7b) have
been prepared and the complex 5c has been structurally
characterized by X-ray diffraction. The IR comparison
between the manganese adducts 5b, 5c, and [Mn-
{C5(CO2Me)5}(CO)3] revealed that the disubstituted-
ester ligands are more effective than the pentasubsti-
tuted ones in delocalizing the Cp ring charge.
Na [C5H4CO2P h ] (1c). To a solution of NaCp (7.2 g, 81.7
mmol) in THF (150 mL) was added solid (PhO)2CO (8.7 g, 40.9
mmol). After a few minutes the formation of a light brown
precipitate was observed, the mixture was stirred at room
temperature for 3 h, and then a large amount of Et2O (200
mL) was added. The solid was filtered and further washed with
diethyl ether to give 7.6 g (89%) of 1c as a light brown solid.
1H NMR (D2O): δ 7.53-7.15 (m, 5H, Ph), 6.68 (m, 2H), 6.17
1
(m, 2H). H NMR (Pyr-d5): δ 7.51 (m, 2H, Cp), 7.28-7.07 (m,
5H, Ph), 6.72 (m, 2H). 13C{1H} NMR (pyr): δ 166.5 (CdO),
154.4 (ipso-C, Ph), 129.3 (o-Ph), 123.8 (p-Ph) 123.2 (m-Ph),
114.3 (CH, Cp), 112.8 (CH, Cp), 108.4 (ipso-C, Cp). IR (THF,
cm-1): ν(CdO) 1691 s, 1665 s, 1635 s. Anal. Calcd for C12H9-
NaO2: C, 69.2; H, 4.33. Found: C, 69.6; H, 4.60. The filtrate
was dried in vacuo: GC-MS analysis of the volatiles showed
1
the presence of cyclopentadiene, while the IR and H and 13C
NMR spectra of the solid residue showed the presence of
NaOPh.18
[F e(C5H4CO2P h )2] (2). To a suspension of 1c (0.59 g, 2.84
mmol) in THF (20 mL) was added solid FeCl2 (0.180 g, 1.42
mmol). The suspension was stirred at room temperature for 4
h. After concentration to a small volume the crude material
was chromatographed on silica gel and eluted with a mixture
of THF/CH3CN in a 4:6 ratio to give 0.45 g (87%) of a dark
orange product that can be crystallized from a double layer of
CH2Cl2/Etp at -20 °C. 1H NMR (CDCl3): δ 7.28-7.14 (m, 10H,
Ph), 5.05 (m, 2H), 4.60 (m, 2H). 13C{1H} NMR (CDCl3): δ 169.1
(CdO), 150.6 (ipso-C), 129.4 (o-Ph), 125.7 (p-Ph) 121.7 (m-Ph),
73.3 (CH, Cp), 72.3 (CH, Cp), the ipso-C Cp carbon is hidden
Studies on the reactivity of 3 toward the more
oxophilic lanthanide triflates Ln(OTf)3 or group 4 metal
halides MX4 are in progress, and preliminary results
indicate that a κ2O,O′-chelation with the carbonyl
oxygen atoms is favored, as found in the structurally
characterized sodium salt 4b.15 Moreover the reported
metal 5, 6, and 7 derivatives could be used as metallo-
ligands in which the ortho ester act as (O,O′) coordinat-
ing groups toward oxophilic transition metals.
under the signals of the deuterated chloroform. IR (THF, cm-1):
12
ν(CdO) 1738 s. EIMS for
C
1H1856Fe16O4 (m/z, %): 426
24
([M]+, 100), 333 ([M]+ - OPh, 87). Mp: 143 °C. Anal. Calcd
Exp er im en ta l Section
for C24H18O4Fe: C, 67.6; H, 4.22. Found: C, 67.6; H, 4.23.
Ma ter ia ls a n d P r oced u r es. All reactions with organome-
tallic reagents or substrates were carried out under argon
using standard Schlenk techniques. Solvents were dried and
distilled under nitrogen prior to use. The prepared derivatives
were characterized by elemental analysis and spectroscopic
methods. The IR spectra were recorded with a FT-IR spec-
trometer Perkin-Elmer Spectrum 2000. The routine NMR
spectra (1H, 13C, DEPT) were always recorded using a Varian
Gemini 300 instrument (1H, 300.1; 13C, 75.5 MHz), while the
two-dimensional spectra (COSY and gHSQC experiments)
were recorded using a Varian Mercury-VX 400 (1H, 399.8; 13C,
100.5 MHz) instrument. The spectra were referenced inter-
nally to residual solvent resonances and were recorded at 298
K for characterization purposes. Electron impact mass spectra
were taken using a VG 7070E mass spectrometer; GC-MS
analyses were performed using a Hewlett-Packard Model HP
5890B GC interfaced to a HP 5970 MSD.
Na [C5H3(CO2Me)2] (3a ). To a solution of Na[C5H4(CO2Me)]
(20.3 g, 139 mmol) in THF was added dropwise MeOCOCl (37
mL, 69.5 mmol) in 10 mL of THF at room temperature. After
stirring for 2 h the dark red suspension was filtered on a Celite
pad and the solvent was removed in vacuo, and after keeping
the solid under vacuum at ca. 80 °C for 4 h, the residue was
thoroughly washed with diethyl ether to give 11.8 g (83%) of
1
3
a light brown solid. H NMR (D2O): δ 6.75 (d, J ) 3.6, 2H),
3
1
5.95 (t, J ) 3.6, 1H), 3.75 (s, 6H). H NMR (Pyr-d5): δ 7.66
(d, J ) 3.6, 2H), 6.49 (t, J ) 3.6, 1H), 3.56 (s, 6H). 13C{1H}
3
3
NMR (Pyr-d5): δ 168.2 (CdO), 124.3 (CH), 112.2 (ipso-C, Cp),
1
111.1 (CH), 50.1 (OCH3). The H NMR (Pyr) spectrum showed
the presence of the 1,3 isomer (up to a maximum of 20%
4
4
observed): δ 8.26 (t, J ) 2.1, 1H), 7.33 (d, J ) 2.1, 1H), 3.56
(s, 6H). IR (THF): ν(CdO) 1687 s. IR (KBr, cm-1): ν(CdO)
1663 vs, ν(C-O) 1284 s, ν(C-OCH2) 1082 s. Anal. Calcd. for
C9H9NaO4: C, 52.9; H, 4.41. Found: C, 52.6; H, 4.80. The NMR,
GC-MS, and EIMS analysis (m/z, %): 124 (1/2[M]+), of the
(14) Arthurs, M.; Nelson, S. M.; Drew, M. G. B. J . Chem. Soc., Dalton
1977, 779. Arthurs, M.; Karodia, H.; Sedgwick, M.; Morton-Blake, D.
A.; Cardin, C. J . J . Organomet. Chem. 1985, 291, 231. Arthurs, M.
Bickerton, C. J .; Kirkley, M.; Palin, J .; Piper, C. J . Organomet. Chem.
1992, 429, 245. Costa, M.; Dias, F. S.; Chiusoli, G. P.; Gazzola, G. L.
J . Organomet. Chem. 1995, 488, 47.
(16) Herrmann, W. A. In Synthetic Methods of Organometallics and
Inorganic Chemistry; Herrmann, W. A., Ed.; Georg Thieme Verlag:
Stuttgart, Germany, 1997; Vol. 7.
(15) Busetto, L.; Cassani, M. C. Proceedings of XIIIth FECHEM
Conference on Organometallic Chemistry; Lisboa, Portugal, 1999; p 113.
(17) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals, 2nd ed.; Pergamon Press: New York, 1980.

Cyclopentadienyl Ester-Disubstituted Ligands
Organometallics, Vol. 20, No. 2, 2001 287
ether washings showed the presence of dicyclopentadiene
dicarboxylic ester (C5H5CO2Me)2.5,19
on silica gel using 1Etp/1CH2Cl2 as eluent to give 2.11 g (81%)
of 5b as an air- and moisture-stable yellow oil. 1H NMR
(CDCl3): δ 5.33 (br, 2H), 4.70 (br, 1H), 4.30 (br, 4H), 1.34 (br,
6H). 13C{1H} NMR (CDCl3): δ 222.3 (CtO), 164.0 (CdO), 91.2
(ipso-C, Cp), 87.7 (CH, Cp), 80.0 (CH, Cp), 61.9 (OCH2CH3),
14.0 (OCH2CH3). IR (THF, cm-1): ν(CtO) 2034 s, 1953 vs, ν-
(CdO) 1727 m. IR (CH2Cl2 cm-1): ν(CtO) 2037 s, 1959 vs,
ν(CdO) 1722 m. IR(neat, CsI, cm-1): ν(CtO) 2033 s, 1954 vs,
Na [C5H3(CO2Et)2] (3b). To a solution of Na[C5H4(CO2Et)]
(11.6 g, 72 mmol) in THF was added dropwise EtOCOCl (3.5
mL, 3.76 mmol) in 10 mL of THF at room temperature. After
stirring for 2 h the dark red suspension was filtered on a Celite
pad and the solvent was removed in vacuo, and after keeping
the solid under vacuum at ca. 80 °C for 4 h the residue was
thoroughly washed with diethyl ether to give 7.15 g (85%) of
ν(CdO) 1726 s, ν(C-O) 1259 s, ν(C-OCH2) 1078. EIMS for
12
C
1H1355Mn16O7 (m/z, %): 348 ([M]+, 21), 264 ([M]+ - 3CO,
1
3
a light brown solid. H NMR (D2O): δ 6.78 (d, J ) 3.6, 2H),
14
92), 220 ([Mn{C5H3(CO2Et)2}]+ - CO2, 100), 176 ([Mn{C5H3(CO2-
3
3
3
5.97 (t, J ) 3.6, 1H), 4.25 (q, J ) 7.2, 4H), 1.32 (t, J ) 7.2,
Et)2}]+ - 2CO2, 86), 119 ([MnCp]+, 58). Anal. Calcd for C14H13
-
1
3
3
6H). H NMR (Pyr-d5): δ 7.69 (d, J ) 3.6, 2H), 6.50 (t, J )
3.6, 1H), 4.11 (q, J ) 7.2, 4H), 1.11 (t, J ) 7.2, 6H). 13C{1H}
NMR (Pyr): δ 167.8 (CdO), 124.3 (CH), 112.5 (ipso-C, Cp),
110.8 (CH), 58.2 (OCH2CH3), 15.0 (OCH2CH3). The 1H NMR
(Pyr-d5) spectrum showed the presence of the 1,3 isomer (up
to a maximum of 10% observed): δ 8.21 (t, 4J ) 2.1, 1H), 7.33
3
3
MnO7: C, 48.3; H, 3.75. Found: C, 48.5; H, 3.79.
[Mn {C5H3(CO2P h )2-1,2}(CO)3] (5c). To a solution of MnBr-
(CO)5 (0.25 g, 1.1 mmol) in ca. 30 mL of THF was added Na-
[C5H3(CO2Ph)2] as a solid (0.35 g, 1.1 mmol). After refluxing
the mixture for 4 h the solvent was removed in vacuo and CH2-
Cl2 was added. The suspension was filtered on a Celite pad,
and the resulting yellow solution was concentrated to a small
volume and layered with Etp. After 3 days at -20 °C, 0.44 g
(93%) of yellow crystals of 5c were obtained. 1H NMR
(CDCl3): δ 7.41-7.16 (m, 10H, Ph), 5.61 (br, 2H), 4.89 (br, 1H).
13C{1H} NMR (CDCl3): δ 221.8 (CtO), 162.6 (CdO), 150.3
(ipso-C, Ph), 129.5 (o-Ph), 126.3 (p-Ph), 121.4 (m-Ph), 89.9
(ipso-C, Cp), 88.9 (CH, Cp), 81.0 (CH, Cp). IR (THF, cm-1):
ν(CtO) 2036 s, 1957 vs, ν(CdO) 1747 m. IR (CH2Cl2, cm-1):
2040 s, 1962 vs, 1742 m. IR (KBr, cm-1): ν(CtO) 2040 s, 1972
4
3
3
(d, J ) 2.1, 1H), 4.31 (q, J ) 7.2, 4H), 1.19 (t, J ) 7.2, 6H).
IR (THF, cm-1): ν(CdO) 1680 s. IR (KBr, cm-1): ν(CdO) 1663
vs, ν(C-O) 1284 s, ν(C-OCH2) 1082 s. Anal. Calcd. for C11H13
-
NaO4: C, 56.9; H, 5.60. Found: C, 57.3; H, 4.57. The NMR,
GC-MS, and EIMS analysis (m/z, %): 138 (1/2[M]+), of the
ether washings showed the presence of dicyclopentadiene
dicarboxylic ester (C5H5CO2Et)2.
Na [C5H 3(CO2P h )2-1,2] (3c). To a suspension of Na-
[C5H4(CO2Ph)] (7.0 g, 33.6 mmol) in THF was added dropwise
PhOCOCl (2.1 mL, 16.8 mmol) in 10 mL of THF at room
temperature. After stirring for 2 h the volatiles were removed
under reduced pressure; the dark red solid was kept under
vacuum at 80 °C for 4 h and then thoroughly washed with
diethyl ether (3 × 50 mL). The ether of the combined washings
was removed in vacuo: the resulting sticky crude material was
found to contain the desired product 3c contamined with the
dimer (C5H5CO2Ph)2. The final purification was accomplished
by redissolving the oily mixture in a small volume of ether
and adding Etp: the resulting precipitate was triturated for
vs, 1942 vs, ν(CdO) 1739 s, ν(C-O) 1259 s, ν(C-OCH2) 1078
12
m. EIMS for
C
1H1355Mn16O7 (m/z, %): 444 ([M]+, 8), 360
22
([M]+ - 3CO, 55), 119 ([MnCp]+, 100). Mp: 112 °C. Anal. Calcd
for C22H13MnO7: C, 59.5; H, 2.93. Found: C, 59.5; H, 2.94.
The complex was also characterized by an X-ray diffraction
study.
[Re{C5H3(CO2Et)2-1,2}(CO)3] (6b). To a solution of ReBr-
(CO)5 (0.51 g, 1.26 mmol) in ca. 30 mL of THF was added [Na-
([18]-crown-6)][C5H3(CO2Et)2-1,2] as a solid (0.625 g, 1.26
mmol). The mixture was refluxed for 8 h and then chromato-
graphed on silica gel (eluting mixture 1Etp/1CH2Cl2) to give
0.47 g (70%) of 6b as a light yellow oil. 1H NMR (CDCl3): δ
1
one night to give 4.45 g (81%) of a light brown solid. H NMR
of 3c (pyr): δ 7.95 (d, 3J ) 3.6, 2H), 7.32-7.14 (m, 10 H), 6.59
(t, 3J ) 3.6, 1H). 13C{1H} NMR (pyr): δ 165.7 (CdO), 153.6
(ipso-Ph), 129.4 (o-Ph), 127.3 (CH, Cp) 124.6 (p-Ph), 123.5 (m-
Ph), 112.7 (CH, Cp), 111.5 (ipso-C, Cp); a poorly resolved triplet
at δ 8.55 was assigned to the 1,3 isomer (5% or less of the
total product). IR (THF, cm-1): ν(CO) 1706 s. Anal. Calcd. for
3
3
3
5.85 (d, J ) 3.0, 2H), 5.29 (t, J ) 3.0, 1H), 4.31 (q, J ) 7.2,
4H), 1.33 (t, 3J ) 7.2, 6H). 13C{1H} NMR (CDCl3): δ 191.3
(CtO), 162.6 (CdO), 94.7 (ipso-C, Cp), 88.8 (CH, Cp), 82.5
(CH, Cp), 62.2 (OCH2CH3), 13.9 (OCH2CH3). IR (THF, cm-1):
ν(CtO) 2034 s, 1941 vs, ν(CdO) 1730 m. IR (CH2Cl2, cm-1):
ν(CtO) 2037 s, 1947 vs, ν(CdO) 1724 m. IR (neat, CsI, cm-1):
C
19H13NaO4: C, 69.5; H, 3.96. Found: C, 69.8; H, 4.00. The
dimer (C5H5CO2Ph)2 was characterized by NMR, GC-MS, and
EIMS analysis (m/z, %): 186 (1/2[M]+).
ν(CtO) 2033 s, 1941 vs, ν(CdO) 1733 s, ν(C-O) 1259 s,
12
[Na ([18]-cr ow n -6)][C5H3(CO2Et)2-1,2] (4b). To a solution
of 3b (3.7 g, 16 mmol) in THF (20 mL) was added [18]-crown-
6 (4.1 g, 15.5 mmol). After 30 min the slightly turbid suspen-
sion was filtered and the solution concentrated to a small
volume in vacuo. A large quantity of Et2O was added, and the
solution was cooled at -20 °C, yielding buff-colored crystals
of 4b (three crops, 5.6 g, 70%). 1H NMR (CDCl3): δ 6.92 (d, 3J
ν(C-OCH2) 1082 m. EIMS for
C 1H1316O7187Re (m/z, %):
14
480 ([M]+, 100), 396 ([M]+ - 3CO, 25), 324 ([Re{C5H3CO2Et}]+,
38). Anal. Calcd for C14H13O7Re: C, 35.0; H, 2.71. Found: C,
35.4; H, 2.75.
[Ru {C5H3(CO2Et)2-1,2}(CO)]2 (7b). To a solution of [Ru-
(CO)3Cl2]2 (0.41 g, 0.81 mmol) in ca. 30 mL of THF was added
[Na([18]-crown-6)][C5H3(CO2Et)2-1,2] (2.18 g, 4.40 mmol). The
solution was refluxed, and the progress of the reaction was
monitored by infrared spectroscopy. After 15 h, when the
absorption at 2128 cm-1 due to a carbonyl stretching of [RuCl2-
(CO)3]2 had disappeared, the reaction mixture was cooled to
room temperature. The solvent was removed under vacuum
and the solid washed three times with ether. The combined
washings were concentrated to a small volume and then
cromatographed on silica gel. The ruthenium complex was
eluted with acetonitrile, and evaporation of the solvent pro-
duced 0.46 g (77%) of 7b as a dark yellow-orange oil. 1H NMR
3
3
) 3.6, 2H), 5.91 (t, J ) 3.6, 1H), 4.16 (q, J ) 7.2, 4H), 3.64
(s, 24H), 1.28 (t, 3J ) 7.2, 6H). 13C{1H} NMR (CDCl3): δ 167.2
(CdO), 122.2 (CH, Cp), 111.5 (ipso-C, Cp), 109.8 (CH, Cp), 69.5
([18]-crown-6), 57.9 (OCH2CH3), 14.9 (OCH2CH3). IR (THF,
cm-1): ν(CO) 1680 s. IR(KBr, cm-1): ν(CdO) 1695 s, ν(C-O)
1258 s, ν(C-OCH2) 1108 vs, 1058 s. Mp: 144 °C (dec). Anal.
Calcd for C23H37NaO10: C, 55.6; H, 7.46. Found: C, 55.5; H,
7.45. The complex was also characterized by an X-ray diffrac-
tion study.
[Mn {C5H3(CO2Et)2-1,2}(CO)3] (5b). To a solution of MnBr-
(CO)5 (1.80 g, 6.55 mmol) in ca. 30 mL of THF was added [Na-
([18]-crown-6)][C5H3(CO2Et)2-1,2] as a solid (3.25 g, 6.72 mmol).
The mixture was refluxed for 4 h and then chromatographed
3
3
(CDCl3): δ 5.76 (d, J ) 3.0, 2H), 5.25 (t, J ) 3.0, 1H), 4.29
(q, 3J ) 7.2, 4H), 1.32 (t, 3J ) 7.2, 6H). 13C{1H} NMR (CDCl3):
δ 210.2 (CtO), 162.9 (CdO), 96.9 (ipso-C, Cp), 92.1 (CH), 89.8
(CH), 62.0 (OCH2CH3), 14.0 (OCH2CH3). IR (THF, cm-1): ν-
(CO) 2018 s, 1985 s, 1959 s, 1805 s, 1726 s. IR (neat, CsI, cm-1):
ν(CtO) 2018 s, 1985 s, 1961 s, 1802 s, ν(CdO) 1717 s, ν(C-
O) 1286 s, 1253 s, ν(C-OCH2) 1072 m. Anal. Calcd for
(18) Kunert, M.; Dinjus, E.; Nauck, M.; Sieler, J . Chem. Ber./ Recl.
1997, 130, 1461.
(19) Peters, D. J . Chem. Soc. 1959, 1761. Guyon, C.; Boule, P.;
Lemaire, J . Tetrahedron Lett. 1982, 23, 1581. Top, S.; Lehn, J .-S.;
Morel, P.; J aouen, G. J . Organomet. Chem. 1999, 583, 63.
C
26H26O12Ru2: C, 42.5; H, 3.54. Found: C, 42.6; H, 3.58.

288 Organometallics, Vol. 20, No. 2, 2001
Busetto et al.
Ta ble 3. Cr ysta l Da ta a n d Deta ils of Str u ctu r e
Refin em en t for Com p lexes 4b a n d 5c
K, trying to overcome the weak diffraction power of the
samples. All the structure models showed high thermal motion
of the crown-ether counterion. None of the different experi-
ments improved thermal motion information significantly, so
that we concluded that this was an intrinsic crystal charac-
teristic probably due to the quite loose encapsulation of the
sodium ion in the [18]-crown-6. Therefore, the set of data with
the highest number of observed reflections was used for
structure solving and refinement.
Both structures were solved by direct methods and refined
on F2 by full matrix least-squares calculations using the
SHELXTL/PC package.20 Thermal vibrations were treated
anisotropically; H atoms were geometrically positioned [C-H
0.96 Å] and refined “riding” on their corresponding carbon
atoms. For 4b, one of the two ethyl appendages was found
affected by positional disorder over two orientations for the
methyl C(9) group. Refinement of the relative contribution to
each orientation converged to an occupancy factor ratio of
approximately 70:30.
4b
5c
empirical formula
fw
C
23H37NaO10
C22H13MnO7
444.02
496.52
temp (K)
293
293
wavelength (Å)
cryst syst
space group
unit cell dimens
0.71069
monoclinic
P21/n
a ) 12.619(2) Å
b ) 14.620(3) Å
c ) 14.805(3) Å
â ) 91.96(3)°
2729.8
0.71069
monoclinic
P21/n
a ) 10.133(2) Å
b ) 10.415(2) Å
c ) 18.864(4) Å
â ) 103.94(3)°
1932.2
volume (Å3)
Z
4
4
F(000)
1064
904.0
cryst size (mm)
max θ for data collection
no. of reflns collected
no. of obsd ind reflns
no. of params
0.53 × 0.55 × 0.42 0.25 × 0.31 × 0.28
33.5°
27 159
1917
322
36.5°
22 564
3027
271
goodness-of-fit on F2
1.03
0.97
Refinement converged at a final R ) 0.085, wR2 ) 0.24, S
) 1.03 for 4b, R ) 0.052, wR2 ) 0.14, S ) 0.974 for 5c.
Molecular graphics were prepared using ORTEP3 for
WindowsNT.21
final R indices [I > 2σ(I)] 0.085
0.053
0.16
R indices (all data)
0.26
largest diff peak and
0.26, -0.15
0.54, -0.30
hole (e Å-3
)
Ack n ow led gm en t. The authors thank the Minis-
tero dell’Universita´ e della Ricerca Scientifica e Tecno-
logica (MURST) and the University of Bologna for
financial support.
X-r a y Cr ysta llogr a p h y. Crystals of 4b and 5c suitable for
the X-ray single-crystal studies were precipitated from THF/
diethyl ether for 4b and CH2Cl2/Etp for 5c. Diffraction intensi-
ties were collected at room temperature on a Bruker 2K
SMART-CCD diffractometer using graphite monochromated
Mo KR radiation. The data were collected using 0.3° wide ω
scans with a crystal-to-detector distance of 5.0 cm and cor-
rected for absorption empirically using the SADABS routine.
Crystal data and details of structure refinement are reported
in Table 3.
Su p p or tin g In for m a tion Ava ila ble: A listing of atomic
coordinates, bond lengths and angles, and anisotropic thermal
parameters. Crystallographic files, in CIF format, for both
complexes 4b and 5c. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM000662X
Data collections nominally covered a full sphere of reciprocal
space for both complexes with 30 and 20 s exposure time per
frame for 4b and 5c, respectively. Five independent data
collections were performed for 4b on crystals from different
crystallization batches both at room temperature and at 223
(20) Siemens. SHELXTLplus Version 5.1 (Windows NT version)
Structure Determination Package; Siemens Analytical X-ray Instru-
ments Inc.: Madison, W1, 1998.
(21) Farrugia, L. J . J . Appl. Crystallogr. 1997, 565.