Ligand control in multihaptotropic o-indenyl rhenium systems. experimental and theoretical study

Article abstract of DOI:10.1021/om900417t

The synthesis of a novel class of alcohol- and ether-functionalized indenyl ligands, focusing on the haptotropic rearrangements of the hybrid O-indenyl rhenium species, is herein described. η¹-Ind_x ^OMeRe(CO)₅ (1

Full text of DOI:10.1021/om900417t

5382 Organometallics 2009, 28, 5382–5394
DOI: 10.1021/om900417t
Ligand Control in Multihaptotropic O-Indenyl Rhenium
Systems. Experimental and Theoretical Study
Silvia Bordoni,* Stefano Cerini, Riccardo Tarroni, Stefano Zacchini, and Luigi Busetto
ꢀ
Dipartimento di Chimica Fisica ed Inorganica, Universita di Bologna, Viale Risorgimento,
4 I-40136 Bologna, Italy
Received May 20, 2009
The synthesis of a novel class of alcohol- and ether-functionalized indenyl ligands, focusing on the
haptotropic rearrangements of the hybrid O-indenyl rhenium species, is herein described. η1-
IndxOMeRe(CO)5 (12x) and η3-IndxOMeRe(CO)4 (13x, x = a, d) [IndaOMe = C9H6CH2CH(Me)OMe,
1a; InddOMe = C9H6CH(CH2)3CHOMe, 1da] are examples of σ and allylic intermediates in the Cp
substitution. The tuning of stereoelectronic effects of the functionalized alkyl chain or the coordinat-
ing solvent (MeCN, THF) allows the study of the relative stabilities of the intercepted solvento
species η5-IndbOMeRe(CO)2(NCMe), 14b, η5-IndcOMeRe(CO)2(THF), 15c, or the chelate [η5:k1-O-
Indb,cORe(CO)2], 16b,c {IndbOMe = [C9H6CH2CH(Ph)OMe]-, 4b; IndcOMe = [C9H6CH(Ph)CH2OMe]-,
4c}. DFT calculations reported on some of the IndO systems have been compared with those of smaller
(CpO) 5a or larger (FluaO) 10a congeners, confirming the experimental findings. As peculiar examples of the
underrepresented low-valent rhenium alkoxy species, the isolation of k1-O-HIndxORe(CO)5 [x = a, b] is
also reported.
Introduction
of these versatile systems depends on the hemilabile donor
atom’s chelating aptitude and on their haptotropic flexibil-
ity.3 Particular efforts have been dedicated to exploiting
features of amino- or phosphino-alkyl ligands4 in early (Ti,
Zr)5 or mid-late (Mo, Fe, Ru, Rh)6 transition metal com-
plexes. Although nucleophilic epoxide ring-opening consti-
tutes an efficient method to associate oxygen functions to
polyene systems,7 few examples are reported on the oxygen-
functionalized Cp-like rhenium complexes.8
A great deal of attention has been devoted in the past
decade1 to hybrid ligands having polyene π-extended rings
such as indenyl (Ind-) or fluorenyl (Flu-) with peripheral
heteroatom-alkyl pendants, focusing on the excellent cata-
lytic performances of their coordinated early transition
metal in polymerization reactions.2 The increased efficiency
*Corresponding author. E-mail: silvia.bordoni@unibo.it.
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A1, 2004. (b) Kim, E.-I.; Choi, S. D. U.S. Pat. Appl. USXXCO US
2004054207 A1, 2004. (c) Esteb, J. J.; Chien, J. C. W.; Rausch, M. D. J.
Organomet. Chem. 2003, 688, 153. (d) Graf, D. D.; Soto, J. PCT Int. Appl.
WO 2003078483 A1, 2003. (e) Mihan, S.; Lilge, D.; De Lange, P.; Schweier,
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Published on Web 08/26/2009
2009 American Chemical Society

Article
Organometallics, Vol. 28, No. 18, 2009 5383
Chart 1a
a Abbreviations and reaction conditions: Nu = C5H5 Cp; C9H7 Ind; C13H9 Flu. aR1 =H, R2 =Me; bR1 =H, R2 =Ph; cR1 =Ph, R2 = H;dR1 =R2 =
-(CH2)3-;(i) rtfor1a,d;refluxfor1b,c;(ii) rt;(iii) -78 °Ctort;(iv) NH4Cl(aq) for2a-d,8a-d; (v) toluene, MeOTf, -78 °C to rt; (vi) LiMe or LiBu, THF, -78 °C.
Herein we describe the syntheses of several indenyl hybrid
ligands, IndO, with a two-carbon alkyl linker such as
and tested in the reaction with rhenium carbonyl species of
the type [Re(CO)5-n(Solv)nBr] (n = 0, 2; Solv = NCMe,
THF). Only the main features of the selected ligands are
reported in the discussion, while a full detailed account
appears in the Experimental Section. As a general method,
room-temperature addition of the appropriate oxide
[CHR1CHR2]O (see Chart 1, path i) to a THF solution
of sodium indenide10 promptly gives brick-red mixtures of
the corresponding sodium salts [C9H6CHR1CHR2O]Na,
HIndxONa, 1x, which are characterized by their NMR data.
In the case of propylene oxide, the 1H single olefin resonance
at δ 6.26 and for CHO methyne moiety at 4.30 ppm indicates
the formation of sodium 1-(3H-inden-3-yl)propan-2-olate,
[C9H6CH2CH(Me)O]Na, HIndaONa, 1a, as the unique anio-
nic species. Modification of the reaction conditions such as
thermal treatment, counterion, and solvent does not alter the
regioselective attack, which is exclusively directed to the less
impeded carbon atom in this case. Water quenching gives the
corresponding alcohol C9H6[CH2CH(Me)OH], 2a (Chart 1,
path iv), which confirms the occurrence of a [H1-3] proto-
tropic shift. The heterocorrelated spectra assign the acciden-
tally isochronous 13C NMR resonances found at δ 38.5 to the
methylene group of the fused-Cp ring (3.45 ppm) and of the
side chain (2.80 ppm), respectively.
2-methyl, IndaOMe = [C9H6CH2CH(Me)OMe]-, 1a; 2-phen-
OMe
yl, Indb
OMe
Indc
= [C9H6CH2CH(Ph)OMe]-, 1b; 1-phenyl,
= [C9H6CH(Ph)CH2OMe]-, 1c, and cyclopentyl,
InddOMe = [C9H6CH(CH2)3CHOMe]-, 1d. The reactivity of
this class of ligands toward rhenium carbonyl complexes is
reported and compared with that shown by the smaller
congener cyclopentadienyl [C5H4CH2CH(Me)OH]-, 5a,
CpaOH, and with the π-extended fluorenyl system [C13H8-
CH2CH(Me)OMe]-, 10a, FluaOMe. The coordination of
functionalized indenyl ligands shows a facile haptotropic
behavior,9 and the reaction with Re(CO)5Br allows the
characterization of η1-Inda,dOMeRe(CO)5 (12a,d) and η3-
Inda,dOMeRe(CO)4 (13a,d) species. Steric requirements favor
the monohapto species, whereas re-aromatization of the
benzo-condensed ring is crucial in stabilizing the allylic
coordination. DFT calculations support the experimental
findings and clarify the lack of isolation of the η5 expected
species. This goal is achieved only by reacting the solvento
Re(CO)3(NCMe)2Br compound, although a strong asym-
metrical π-coordination is observed in π-Indb,cOMeRe(CO)3
(14b,c) complexes. Finally, the bulkiness of methyl or the
electron-withdrawal phenyl 2-substituent is responsible for
trapping the unstable alkoxide derivatives κ1-Ο-Inda,bORe-
It is known that counterion and solvent nature both drive
the selectivity in the nucleophilic addition.8 Indeed, the
reaction with lithium indenide in a THF-hexane (∼85:15)
solution, upon neutralization, gives rise to an analogous
mixture of isomers, whose nature has been determined
by 1H NMR data. The H2 and H3 NMR multiplets,
(CO) , 11a,b, reported as rare examples of the class of low-
valent rhenium alkoxy species.
5
Results and Discussion
Ligand Preparation. In Chart 1 are collected the classes of
novel five-electron donor ligands, which have been prepared
(10) For selected patents see: (a) Hauck, F. P.; Reid, J.; Narayanan,
V. L.; Cimarusti, C. M.; Haugwitz, R. D.; Sundenn, J. E. (E.R. Squibb &
Sons, Inc.) Patent Appl. N. US1976000649116, 1977. (b) Hauck, F. P.;
Sundenn, J. E.; Reid, J. (E.R. Squibb & Sons, Inc.) Patent Appl. N.
US1977000820290, 1979. (c) Hauck, F. P.; Sundenn, J. E.; Reid, J. (E.R.
Squibb & Sons, Inc.) Patent Appl. N. US1978000928483, 1979.
(9) (a) Casey, C. P.; O’Connor, J. M. Organometallics 1985, 4, 384–
388. (b) Casey, C. P.; Vos, T. E.; Brady, J. T.; Hayashi, R. K. Organometallics
2003, 22, 1183–1195.

5384 Organometallics, Vol. 28, No. 18, 2009
Bordoni et al.
acceptor toward two different vicinal molecules. The three
fused rings in the fluorene system are almost planar. As
expected for these classes of compounds, the bonding para-
meters are in agreement with the different hybridizations of
the C-atoms.
Conversely, lithium fluorenyl addition on the styrene
oxide forms a nearly equimolar hydroxyl-anion mixture
O
of Flub [C13H9CH(Ph)CH2OH]- (7b) and the isomeric
O
form Fluc [C13H9CH2CH(Ph)OH]- (7c). The withdraw-
ing phenyl substituent quantitatively promotes proton
O-migration (Chart 1, path iii), preventing the alcoholate
isolation.
Like the indenide, the addition of NaCp as nucleo-
phile yields regioselectively the shiftamer cyclopentadienyl-
OH
propan-2-ol12 Na[C5H4CH2CH(Me)OH], NaCpa
, 5a
(Chart 1, path ii). The 1H NMR spectra of the anion show
a single hydroxy group at δ 2.2 and a downfield-shifted
resonance at δ 3.7 for the methyne moiety, ruling out the
occurrence of 1-cyclopenta-1,4-dienylpropan-2-ol,8 formed
by the alternative epoxide ring-opening. No appreciable
dimerization has been detected in the substituted cyclopen-
tadiene HCpOH tetrahydrofuran solution, although it has
been found to occur in similar polar solvents.7d Under-
standably, the selective O-alkylation of 1a-d (Chart 1, path
v) is largely critical, since it depends on the counterion
nature, solvent polarity, and microenvironment heterogene-
ity of the alkylating mixture.13 It is worth mentioning that
the addition of methyl iodide in low-polar solvents partially
gives ring alkylation (30-40%). This supports our choice of
using methyl triflate instead. However, a sequenced depro-
tonation/alkylation tandem reaction is required to transform
Figure 1. 1H NMR spectra in CDCl3. Olefin region of the 2a,
HIndaOH, isomeric mixture.
upfield-shifted respectively in the ranges δ 6.52-6.64 and
6.76-6.82, indicate the prevalence of 1-substituted indenyl
diastereomers (∼66%) and a minor amount of 3-substituted
2a (∼33%) (see Figure 1).
The reaction with lithium fluorenide (Chart 1, path iii)
forms an almost equimolar mixture of lithium 1-(9H-fluo-
ren-9-yl)propan-2-olate, [C13H9CH2CH(Me)O]Li (6a) and
(lithium-9-fluorenyl)propan-2-ol, [C13H8CH2CH(Me)OH]Li
(7a). The 13C NMR upfield-shifted resonance at δ 40.6 is
attributed to the tetrahedral C9H moiety and ascertains the
nature of 6a, whereas the related signal at δ 134.6 is diagnostic
for the alcoholic shiftamer 7a. Water neutralization (Chart 1,
path iv) gives yellow needles of 1-(9H-fluoren-9-yl)-propan-2-
quantitatively the alcoholic forms (IndxOH, 2x (x=a-d), and
OMe
FluaOH, 8a) to the corresponding ether derivatives (Indx
,
3x, and FluaOMe, 9a). Finally, deprotonation of type 3x (x =
a-d) and 9a affords the anionic derivatives 4x (x = a-d) and
10a, which are readily suitable for rhenium coordination.
1
ol (8a). Variable-temperature H NMR experiments on the
progressively dilute solutions of 8a suggest H-binding involve-
ment, exhibiting a scarce temperature dependence for the
hydroxy signal at δ 2.00. In the NOESY 1D experiments, the
irradiation of the benzo-fused ring ortho-proton (H1, 7.57
ppm) causes a major enhancement in the methyne signal,
whereas saturation of the corresponding benzo proton H8
(7.68 ppm) markedly affects the closest proton of the methylene
(see A in Figure 2).
The reduced steric repulsions and the optimized hydroxyl
hydrogen interactions both favor a flanked conformation
(see Figure 2, structure A).11 The minimum energy config-
uration in solution is retained in the solid state, as inferred by
X-ray diffraction data (B) and also confirmed by DFT
calculations in vacuo (C). An analogous synthesis of
HFluaOH, 8a, has been run with the enantiopure S-propylene
oxide, and the molecular structure of the latter, determined
by X-ray crystal diffraction, is reported in Figure 3, while
selected bond lengths and angles are listed in Table 1. The
asymmetric unit of the orthorhombic cell contains two
independent molecules with identical connectivities, an ab-
solute S configuration at the quaternary asymmetric carbons
[C(2) and C(22), respectively], and very similar bonding
parameters. The H-atoms bonded to O-atoms in both in-
dependent molecules were located in the Fourier map. Ex-
tensive H-bonding exists within the crystal, since the OH
group of each molecule acts at the same time as donor and
ONa
Coordination Chemistry. Treatment of alcoholates HIndx
,
1x (x = a, b), with Re(CO)5Br forms the corresponding alkoxy
species of the type κ1O-HIndxORe(CO)5, 11x, which were
isolated as powdered solids and characterized without any
further purification, in order to prevent the decomposition
observed during the chromatography (on alumina, silica, or
Celite gel). No remarkably shifted NMR signals of the adduct,
with respect to the alcholate 1a,b, suggests a strongly polarized
Re(I)-O bond. The nonstabilizing effect of the metal-oxygen
lone pair interaction14 is responsible for the scarcity of mono-
meric rhenium low-valent carbonyl species. Metal coordination
affects mainly the CHO methyne NMR signals, which appear
remarkably deshielded at δ 1H 4.06 and13C 66.9 ppm in the case
of 11a. DFT calculations and subsequent Mulliken analysis on
the latter confirm the large charge separation between the
O-alcoholate (-0.74) moiety and the Re(I) (þ0.80) atoms
(Figure 4).
The occurrence of four distinct IR absorptions (ν, KBr
2021 m, 1914 s, 1903 s, 1895 s) is due to restricted rotation
of the tether chiral O-pendant.13 Re(CO)5 fragment dimer-
ization and trihydride15 Re3(μ-H)3(CO)12 or hydroxyl
(12) Tantillo, D. J.; Hoffmann, R. Acc. Chem. Res. 2006, 39, 477–486.
(13) Oltmanns, M.; Mews, R. Z. Naturforsch. 1980, 35b, 1324.
(14) Turova, N. Y.; Turevskaya, E. P.; Kessler, V. G.; Yanovskaya,
M. I. The Chemistry of Metal Alkoxydes; Kluwer: Dordrecht, 2002.
(15) (a) Andrews, M. A.; Kirtley, S. W.; Kaesz, H. D.; Cooper, C. B.
Inorg. Synth. 1977, 17, 66. (b) Ciani, G.; Sironi, A.; D'Alfonso, G.; Romiti,
P.; Freni, M. J. Organomet. Chem. 1983, 254, C37.
(11) Price, C. J.; Zeits, P. D.; Reibenspies, J. H.; Miller, S. A.
Organometallics 2008, 27, 3722–3727.

Article
Organometallics, Vol. 28, No. 18, 2009 5385
Figure 2. HFluaOH, 8a, structures: (A) 1D 1H NOESY interactions in CDCl3. The numbers over the arrows indicate the percentage
increase of the signal relative to the saturation of H1 and H8. (B) X-ray structure. (C) DFT calculations.
Table 1. Crystal Data and Experimental Details for HFluaOH, 8a
formula
C16H16O
fw
T, K
λ, A
cryst syst
224.29
291(2)
0.71073
orthorhombic
Pna21
1.9507(7)
11.9175(10)
26.323(2)
2494.2(4)
8
1.195
0.073
960
˚
space group
˚
a, A
˚
b, A
˚
c, A
3
˚
cell volume, A
Z
Dc, g cm-3
μ, mm-1
F(000)
Figure 3. Molecular structure of HFluaOH, 8a. Thermal ellip-
soids are drawn at the 30% probability level. Only one of the two
cryst size, mm
θ limits, deg
index ranges
0.31 ꢁ 0.18 ꢁ 0.16
1.55-27.99
-10 e h e 10
-15 e k e 15
-34 e l e 34
26 611
3055 [Rint = 0.0271]
99.3%
3055/3/315
1.106
0.0462
independent molecules present within the asymmetric unit is
˚
represented. [O(1)-H(1o) 0.836(19) A; H(1o) O(2)#1 2.02(2)
3 3 3
˚
˚
A; O(1) O(2)#1 2.837(2) A; O(1)-H(1o)-O(2)#1 166(4)° for
3 3 3
the first independent molecule acting as a donor; O(2)-H(2o)
reflns collected
indep reflns
completeness to θmax
data/restraints/params
goodness on fit on F2
R1 (I > 2σ(I))
˚
0.84(2) A; H(2o) O(1)#2 1.90(2) A; O(2) O(1)#2 2.721(2)
˚
3 3 3
3 3 3
˚
A; O(2)-H(2o)-O(1)#2 166(4)° for the second independent
molecule]. Mean deviations from the least-squares planes are
˚
0.0475 and 0.0561 A for the two independent molecules, respec-
tively.
wR2 (all data)
largest diff peak and hole, e A
0.1235
0.323/-0.374
-3
˚
tetrarhenium9a [Re(CO)3OH]4 formation are observed as
common degradation paths.
13C NMR resonance (δ 38.5) exhibited by the second frac-
tion is diagnostic for the aliphatic character19 of the C1H-Re
moiety in η1-[C9H6CH2CH(Me)OMe]Re(CO)5, 12a. At
room temperature, the haptomers 12x (x = a, d) convert
quantitatively to 13x (x = a, d) in polar solvents (CH2Cl2,
MeCN). Differently from the similar η1-[C9H6(C6F5)]Re-
(CO)5,20 distinct carbonyl patterns have been observed in
both the 13C NMR and IR spectra. This inequivalence is
caused by the hindered rotation of the chiral side arm, whose
presence precludes H1-3 migration.19 No isolation of η5-
coordinated species, but only degradation21 to [Re2(μ-
OMe)3(CO)6]- or [Re2(μ-OH)3(CO)6]- is detected by ther-
mal treatment of 12x or 13x (at room temperature and at
refluxing THF). This observation prompted us to study the
free energy profile by DFT calculations, which reveal a very
small stability for the η5-haptamer 14a, compared to the
kinetic mono-hapto species 12a (Figure 5). Such a limited
The reaction of ether indenide [C9H6CH(R1)CH(R2)OMe]Li
[R1 = H, R2 = Me; R1 = R2 = -(CH2)3-], 4x (x = a, d),
derivatives with Re(CO)5Br promptly yields a nearly equimolar
mixture of η1-[C9H6(CH2CH(Me)OMe]Re(CO)5, 12a, and η3-
[C9H6(CH2CH(Me)OMe]Re(CO)4, 13a (Scheme 1), which are
characterized by their NMR data, after separation by column
chromatography.
As observed for analogous systems,17 the downfield-
shifted NMR signals (13C δ 142.7 and 1H δ 8.4), attributed
to the olefin C2H moiety, strongly support that the first
eluted band is the allylic-coordinated18 η3-[C9H6CH2CH-
(Me)OMe]Re(CO)4, 13a, species. Conversely, the shielded
(16) Pannarello, A. P.; Vassylyev, O.; Khinast, J. G. Synlett 2005, 5,
797–800.
(17) (a) Trost, B. H.; Vidal, B.; Thommen, M. Chem.;Eur. J. 1999, 5,
1055. (b) Stoll, M. E.; Belanzoni, P.; Calhorda, M. J.; Drew, M. G. B.; Felix,
V.; Geiger, W. E.; Gamelas, C. A.; Goncalves, I. S.; Romao, C. C.; Veiros, L.
F. J. Am. Chem. Soc. 2001, 123, 10595, and references therein.
(18) (a) Brisdon, B. J.; Edwards, D. A.; White, J. W. J. Organomet.
Chem. 1979, 175, 113. (b) Aechter, B.; Polborn, K.; Beck, W. Z. Anorg.
Allg. Chem. 2001, 627, 43. (c) Beattie, I. R.; Emsley, J. W.; Lindon, J. C.;
Sabine, R. M. J. Chem. Soc., Dalton Trans. 1975, 1264. (d) Lippmann, E.;
Robl, C.; Berke, H.; Kaesz, H. D.; Beck, W. Chem. Ber. 1993, 126, 933. (e)
Moll, M.; Behrens, H.; Seibold, H. J.; Merbac, P. J. Organomet. Chem. 1983,
(19) Herrmann, W. A.; Kuhn, F. E.; Romao, C. C. J. Organomet.
Chem. 1995, 489, C56.
(20) Deck, P. A.; Fronczek, F. R. Organometallics 2000, 19, 327.
(21) (a) Roger, A.; Egli, A.; Ulrich, A.; Hegetschweiler, K.; Gramlich,
V.; Schubiger, P. A. J. Chem. Soc., Dalton Trans. 1994, 19, 2815. (b)
Jiang, C. H.; Wen, Y. S.; Liu, L.-K.; Hor, T. S. A.; Yan, Y. K. Organometallics
1998, 17, 173. (c) Jiang, C.; Hor, T. S. A.; Yan, Y. K.; Henderson, W.;
McCaffrey, L. J. J. Chem. Soc., Dalton Trans. 2000, 3197–3203.
~
248 329. (f) Ascenso, J. R.; Gonc-alves, I. S.; Herdtweck, E.; Romao, C. C. J.
Organomet. Chem. 1996, 508, 169.

5386 Organometallics, Vol. 28, No. 18, 2009
Bordoni et al.
˚
(C1) A] (see Figure 6) indicate an asymmetric charge dis-
tribution. Upon standing at -20 °C in acetonitrile solution,
the latter gives the solvento η5-IndbOMeRe(CO)2(NCMe),
15b, showing a similar bond description of the type η2 þ (η2 þ
1
˚
η ), as inferred by DFT calculation [Re-C bond lengths (A):
2.590 (C5); 2.551 (C4) þ 2.415 (C2); 2.374 (C3) þ 2.487 (C1)].
The IR ligand absorptions at lower frequencies (ν 2224 w,
CN; 2035 m, 1937 m, CO) and the NMR signals relative to
the bound MeCN (IR; 1H δ 5.1 MeCN, 13C 121.3; MeCN)
both support the nature of species 15b, which in turn gives a
reddish precipitate at room temperature upon addition of
chlorinated solvent. The nature of the resulting κ1O:η5-
IndbOMeRe(CO)2, 16b (see Scheme 2), has been assigned by
1
the upfield-shifted H NMR signal at δ 1.19 for the bound
methoxy moiety. After dissolution in acetonitrile, the chelate
species 16b reproduces the solvento species 15b.
Figure 4. DFT calculations on the rhenium alkoxide 11a. Only
relevant Mulliken charges have been indicated.
Furthermore, assuming that more accessible space around
the metal site may favor intermediate interception, we in-
vestigated the pendant chelate coordination of the less
congested η5-IndcOMeRe(CO)3, 14c, bearing the side-arm
phenyl substituent in the 1-position (see Scheme 3). Unfor-
tunately, in acetonitrile, degradation prevails. However, by
using a milder coordinating solvent such as THF, prompt
decarbonilation occurs by forming η5-IndcOMeRe(CO)2-
(THF), 15c.
stability is the plausible reason for the lack of its isolation, as
the degradation products are thermodynamically favored.
According to Calhorda and Veiros’s pioneering work,22 the
Re-C bond lenghs, indicating two short bonds [2.472 (C2),
˚
˚
2.439 (C3) A] and a much longer one [3.160 (C1) A], together
with the 13C NMR upfield-shifted ring junction signals,
falling at δ 138.1, 138.8, both indicate [η2 þ η1] as a better
description for the allylic-coordinated 13a.
The H NMR spectrum of IndcOMeRe(CO)2(THF), 15b,
1
showing the NMR resonances at δ 4.25 and 3.36 for H2 and
H3, respectively, indicates a stronger electron density per-
turbation due to 1-phenyl effects (δ CHPh 4.12, see
Scheme 3), compared with the 2-phenyl MeCN-adduct 15b
(1H NMR δ 4.2 H2; 4.4 H3). In addition DFT calculations
evidence the skewed (η2 þ η3) bonding description [Re-C
The reaction with cyclopentylmethoxy indenide [C9H6-
CH(CH2)3CHOMe]Li, LiInddOMe, 4d, analogously yields a
mixture of η3-InddOMeRe(CO)4 (13d) and the σ-coordinated
(12d) haptomers. The highly deshielded NMR signals,17b
found at δ 142.3 (13C) and 8.5 (1H) for the C2H moiety
and at δ 146.4 and 145.2 for the junction carbon atoms,
ascertain the nature of 13d. The four distinct IR carbonyl
absorptions of 12d (ν, KBr 2088 w, 2037 m, 1996 vs, 1893 m)
and its upfield-shifted 1H NMR triplet (δ 1H 2.83), attributed
to the σ-bound CH(Re) group, support its structure as
η1-[C9H6CH(CH2)3CHOMe]Re(CO)5.
˚
bond distances (A): 2.560 (C5); 2.573 (C4) þ 2.360 (C2); 2.375
(C3); 2.359 (C1)]. The presence of broad signals at δ 1.73 and
3.58, attributed to the ligated THF, validates the proposed
structure. Dichloromethane addition promotes THF displa-
cement by methoxy assistance, causing precipitation of the
red k1-O:η5-IndcOMeRe(CO)2, 16c. The 13C NMR ring junc-
tion signals (δ 144.6, 147.4) exhibit low-shifted values,
indicating electron density perturbation. Accordingly with
The isolation of η5-coordinated species has been accom-
plished only by reacting the phenyl-substituted ether inde-
nides [C9H6CH(R1)CH(R2)OMe]Li [R1=H, R2=Ph; R1=
Ph, R2 = H], 4x (x = b, c), with the labile Re(CO)3(NC-
Me)2Br,23 yielding the desired 14b,c complexes, which have
been characterized by their spectroscopic features. In parti-
cular, η5-[C9H6CH2CH(Ph)OMe]Re(CO)3, 14b, has been
assigned by the peculiar C3 (δ 83.8) and C2 (δ 120.0) 13C
NMR signals. The marked downfield shift for the latter is
likely due to the combined effect24 of the substitution and the
electron charge distribution.25
˚
the calculated Re-OMe interaction (2.424 A), the presence
of a chelate structure is also supported by the upfield-shifted
NMR resonances (1H δ 1.11; 13C δ 22.7) of the metal-bound
methoxy function,19 However, dissolution of complex 16c by
donor media promptly causes chelate release, which con-
firms its hemilabile nature (Scheme 3).
No allylic solvento intermediates but only penthapto
derivatives could be intercepted by monitoring the formation
of the chelate κ1O:η5-IndOMeb,cRe(CO)2, 16b,c, likely due to
the low basicity of THF, MeCN, or the side-arm methoxy
ligand, according to Basolo’s kinetic investigations26 on the
SN2 substitution of IndMn(CO)3 by basic phosphines. The
calculated more stable conformer of 14c maximizes the
nonbonding electronic interactions between the carbonyl
The DFT-calculated Re-C distances of the complex 14b
[η2: 2.555 (C4); 2.561 (C5) þ η3: 2.412 (C2); 2.420 (C3) þ 2.456
(22) (a) Veiros, L. F. Organometallics 2000, 19, 3127–3136. (b)
Calhorda, M. J.; Gamelas, C. A.; Romao, C. C.; Veiros, L. F. Eur. J. Inorg.
Chem. 2000, 331–320. (c) Veiros, L. F. Organometallics 2006, 25, 2266–
2273. (d) Bradley, C. A.; Lobkovsky, E.; Chirik, P. J. J. Am. Chem. Soc.
2003, 125, 8110–8111. (e) Bradley, C. A.; Lobkovsky, E.; Keresztes, I.;
Chirik, P. J. J. Am. Chem. Soc. 2005, 127, 10291–10304. (f) Veiros, L. F.
Organometallics 2006, 25, 4698–4701.
(23) Farona, M. F.; Kraus, K. F. Inorg. Chem. 1970, 9, 1700.
~
(24) Ascenso, J. R.; Gonc-alves, I. S.; Herdtweck, E.; Romao, C. C. J.
Organomet. Chem. 1996, 508, 169.
(25) (a) Marder, T. D.; Calabrese, J. C.; Roe, D. C.; Tulip, T. H.
Organometallics 1987, 6, 2012. (b) Calhorda, M. J.; Felix, V.; Veiros, L.F.
Coord. Chem. Rev. 2002, 230, 49. (c) Calhorda, M. J.; Veiros, L.F. Coord.
Chem. Rev. 1999, 185-186, 37–51.
ligands and the alkyl chain (methoxy, CO H-CH2O,
3 3 3
˚
˚
3.24 A, and methylene, CO H-CH, 3.31 A), reducing at
3 3 3
the same time the steric repulsions.
The higher stability (∼13 kcal mol-1), shown by the
MeCN intermediate η5-Indb,cOMeRe(CO)2(MeCN), 15b,
with respect to the analogous THF derivative 15c is in
agreement with the symbiotic soft-soft interaction between
(26) Ji, L.-N.; Rerek, M. E.; Basolo, F. Organometallics 1984, 3, 740–
745.

Article
Organometallics, Vol. 28, No. 18, 2009 5387
Scheme 1a
a a R1 = H, R2 = Me; d R1 = R2 = CH(CH2)3CH. Reaction conditions: (i) THF, -78 °C to rt; (ii) CH2Cl2 or MeCN, rt, 24 h.
Scheme 2. Synthesis and Haptotropic Rearrangement of IndbOMe Re-Coordinated Speciesa
a Reaction conditions: (i) THF, -78 C, 2 h; (ii) -20 C, 12 h; (iii) rt, 16 h.
Re(I) and NΑtCMe, predicted by the hard-soft acid-base
(HSAB) theory and supported by the calculated frontier
orbitals. Indeed, acetonitrile participates as a σ-donor as well
as a π-acceptor in the bonding description and globally
contributes to lowering the energetics of the MeCN
with respect to the THF intermediate complexes (see DFT
frontier orbitals for 15b,c, Figure S4, S5). Finally, in spite
of the comparable Re-O enthalpic contribution and
the favorable entropic factor, the metallacycle strain is likely
to be responsible for the instability of the resulting chelate
κ1O:η5-Indb,cOMeRe(CO)2, 16b,c. As alternative synthetic
route,27 photochemical reaction of Re(CO)5Br with
the neutral C9H7CH2CH(Me)OH, 2a, leads to the exclu-
sive isolation of the tetrahydroxy Re4(CO)12(OH)4 com-
pound.9a
Analogous reactions of the smaller [C5H4CH2CH-
(Me)OH]Na, CpaOH, 5a, and of the larger [C13H8CH2CH-
(Me)OH]Li, LiFluaOMe, 10a, five-electron-donor congeners
permit a comparative study with the above-described In-
daOMe, 4a. In the reaction of 5a with Re(CO)5Br, degradation
to [Re2(μ-OH)3(CO)6]- prevails, although DFT calculations
indicate a lower energy (∼-15 kcal mol-1) for the penthapto
CpaOHRe(CO)5 species (Figure 8) . However, from the
solvento derivative Re(CO)3(THF)2Br it has been possible
to isolate the title η5-CpOHRe(CO)3, 17a. Chiral side-arm-
impeded rotation on the NMR time scale is detected by
the distinct 13C ring resonances at δ 84.5, 84.6, 84.9, 85.3,
and 107.4. Such inequivalence, which is commonly observed in
the much more hindered π-systems,28 is ascribed to hydroxyl
interactions, since the 1H NMR OH signal at δ 4.05 appears
markedly downfield-shifted, compared to the corresponding
signal (δ 2.03) of the neutral HCpOH species. Analogously
LiFluaOMe, 10a, gives a purple solution, showing a five-absorp-
tion IR pattern (2078w, 2031w, 1995s, 1977vs, and 1953m
cm-1). The ESIþ mass data [(m/z, %: 571 [M þ H]þ (25), 515
[M - 2CO]þ (100)] and the 13C NMR signal at δ 83.4,
indicating the presence of the σ-coordinated Re-C9 moiety,
are consistent with the formulation of the metathesis adduct29
η1-FluaOMeRe(CO)5, 18a. Thermolytic decarbonylation does
not promote the formation of the expected penta-hapto
derivative, as reported by other authors,30 but only degrada-
tion to [Re2(μ-OMe)3(CO)6]-. In light of the experimental
path, DFT calculations on the fluorenyl complexes’ energetics
(Figure 8) show that the monohapto coordinating mode is the
(28) Le Bideau, F.; Henique, J.; Pigeon, P.; Joerger, J. M.; Top, S.;
Jaouen, G. J. Organomet. Chem. 2003, 668, 140.
(29) Drago, D.; Pregosin, P. S.; Razavi, A. Organometallics 2000, 19,
1802.
(27) (a) Zhou, Y.; Dewey, M. A.; Gladysz, J. A. Organometallics
1993, 12, 3918. (b) Miguel, D.; Steffan, U.; Stone, F. G. A. Polyhedron 1988,
7, 443. (c) Khayatpoor, R.; Shapley, J. R. Organometallics 2000, 19, 2382.
(30) (a) Young, K. M.; Miller, T. M.; Wrighton, M. S. J. Am. Chem.
Soc. 1990, 112, 1529–1537. (b) Mejdrich, A. L.; Hanks, T. W. Synth. React.
Inorg. Met. -Org. Chem 1998, 28, 953–973.

5388 Organometallics, Vol. 28, No. 18, 2009
Bordoni et al.
Figure 5. DFT-optimized structures for compounds 12a, 13a, and 14a and free energy profile (kcal mol-1). In red is reported the relative
energy of the less stable conformer. Alterations of the calculated free energies upon the inclusion of solvent effects (MeCN, ε = 37.5) are
shown in blue.
Figure 6. DFT-optimized structures and free energy calculations (kcal mol-1) of the lowest and the highest conformations for η5-
IndbOMeRe(CO)3, 14b; η5-IndcOMeRe(CO)2(MeCN), 15b; and κ1O:η5-IndbOMeRe(CO)2, 16b, species. The relative energy of the less
stable conformer is reported in red. The effect of the inclusion of the solvent (MeCN, ε = 37.5) on the free energy is shown in blue.
preferred one, allowing the benzo-condensed rings to retain
their aromatic character.
[C9H5CH2CH(Me)OMe]Li, IndaOMe, the reaction with Re-
(CO)5Br permits isolation and characterization of both the
monohapto- and trihapto-Re carbonyl species. However, the
expected transformation to η5-coordinated species has never
been observed, even under thermal treatment, leading in-
stead to degradation products. The DFT free energy profile
confirms that the penthapto coordination is essentially iso-
energetic with respect to the monohapto one, with the
entropic contributions playing a crucial role. Only by using
Conclusions
This report constitutes a contribution to the synthesis of
the new O-functionalized indenyl (IndO), cyclopentadienyl
(CpO), and fluorenyl (FluO) ligands and to the chemistry of
their rhenium carbonyl complexes. In the case of 4a,

Article
Organometallics, Vol. 28, No. 18, 2009 5389
Figure 7. DFT-optimized structures and free energy calculations (kcal mol-1) of the lowest and the highest conformations for η5-
IndcOMeRe(CO)3, 14c; η5-IndcOMeRe(CO)2(THF), 15c; and κ1O:η5-IndcOMeRe(CO)2, 16c, structures. The relative energy of the less
stable conformer is reported in red. The effect of the inclusion of the solvent (THF, ε = 7.58) on the free energy is shown in blue. The η5-
coordination in 15c is better described as the sum of the distinct hapticities (η2 þ η3).
Figure 8. DFT-optimized structures and free energy calculations (kcal mol-1) of the lowest and the highest conformations for
haptomers of the type (a) η5-CpaOHRe(CO)5, 17a, and (b) η1-FluOMeRe(CO)5, 18a, and the corresponding η1 and η5 unobserved parent
structures. The relative energy of the less stable conformer is shown in red.
Scheme 3a
a Reaction condition: (i) THF, -20 C, 6 h; (ii) THF, rt, 6 h.

5390 Organometallics, Vol. 28, No. 18, 2009
Bordoni et al.
Re(CO)3(Solv)2Br (Solv = MeCN, THF) as precursor does
the interception of π-coordinated solvento η5-Indb,cOMeRe-
Experimental Section
All manipulations were carried out under an argon atmo-
sphere and by using standard Schlenk techniques. Anhy-
drous solvents were dried and distilled under nitrogen prior
to use and saturated with nitrogen.33 Glassware was heated
under vacuum prior to use. The prepared derivatives were
characterized by elemental analysis and spectroscopic meth-
ods. The IR spectra were recorded with a Perkin-Elmer
Spectrum 2000 FT-IR spectrometer. The routine NMR
spectra (1H, 13C, DEPT) were recorded using a Varian
Gemini 300 instrument (1H, 300.1; 13C, 75.5 MHz), while
the two-dimensional heterocorrelated (1H-13C gHSQC,
gHMBC experiments) spectra were recorded using a Varian
Mercury-VX 400 (1H, 399.8; 13C, 100.6 MHz) or Unity
Inova-600 (1H, 600.0; 13C, 150.9 MHz). The spectra were
referenced internally to the residual solvent resonances and
generally recorded at room temperature (298 K), unless
otherwise reported. Solutions of the compound 8a at con-
centrations of 0.5-40 mM were used for NMR H-bond
analyses. One-dimensional 1H NMR spectra for determining
temperature coefficients were obtained at 203-300 K in
increments of 10 K. Electron impact mass spectra were taken
on a VG 7070E mass spectrometer. Electrospray mass spec-
tra were recorded on a Waters ZQ-4000 spectrometer. Ele-
mental analyses were performed only on the air-stable salts
or neutral species by using a CHNSO CE Instruments
FLASH EA 1112 series. The composition of the reaction
mixture is evaluated by mixture aliquots, detected by GC
analyses and comparatively by GC-MS. Gas chromatogra-
phy and GC-MS were performed on a HP6890 equipped with
a 30 m ꢁ 0.2 mm Agilent DB-5 capillary column. General
temperature program: 40 °C for 3 min, then 15 °C/min to
260 °C, which was maintained for 10 min. The general
temperature program was able to separate all compounds.
The reagent Re(CO)5Br was prepared according to the lit-
erature procedure.34 Pretreated γ-alumina (3% in H2O w/w)
and silica (230-400 mesh) gel (Aldrich) were heated under
vacuum and cooled under nitrogen to room temperature.
Column chromatography was performed under slight posi-
tive pressure. Solvent ratios are described as volumes before
mixing. Cyclopentadiene (CpH) is from Aldrich Chemical
Co. and was used without further purification. Indene
(IndH) was purified by filtration over silica gel. Fluorene
(FluH) was recrystallized from dichloromethane.
(CO) (Solv) (Solv = MeCN, THF), 15b,c, species and of the
2
chelate η5-Indb,cOMeRe(CO)2, 16b,c, become possible. This
takes place by promotion of a large excess of the solvent as
reactant, in spite of the unfavorable energies predicted by
DFT calculations. The introduction of the solvent effects
into the DFT theoretical approach, through a simple con-
tinuum dielectric model, always plays only a marginal role
and does not change significantly the free energy profiles.
Another effect that has been fully evidenced is the relevant
bonding asymmetry shown by the tri- and penta-hapto
complexes, which in all cases are better described as (η2 þ
η1) or (η2 þ η3), respectively. The tuning of the ligand
stereoelectronic requirements and the nature of the solvent
both play a relevant role in choosing the preferred hapticity.
The donor side arm, such as methyl or cyclopentyl substit-
uents, promote η1- and η3-coordinating modes as 12a,d and
13a,d, whereas the phenyl electron-withdrawing effect causes
the stabilization of the penthapto derivatives 14b,c, 15b,c, and
16b,c. As important features, the carbonyl substitution by the
π-extended O-functionalized cycloolefin (IndO and FluO) is
sensitive to both size and basicity of the pendant chain
substituents and to the solvent nature. Therefore, the intro-
duction of an O-side arm seems to alter dramatically the
stability of the resulting Cp-like rhenium species. The calcu-
lations confirm relevant shift of the electron density in all the
η5-coordinating modes. The reduced hapticities observed in
the indenyl and fluorenyl rhenium carbonyl derivatives favor
(a) the re-aromatization of the benzo-condensed ring(s) in
both π-extended polyenes, (b) a smaller hindrance for the
side-arm rotation, by reduction of steric repulsion, and (c)
the maximization of nonbonding interactions between car-
bonyl ligands and alkyl-chain moieties in the preferably
adopted conformations.
Computational Details
Ab initio DFT calculations have been performed by using the
ADF 2007.01 quantum chemistry package and through the
built-in TZP basis and the BLYP functional.31a,31b Inner orbi-
tals (1s for carbon and oxygen and 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p,
and 4d for rhenium atom) have been kept frozen; this corre-
sponds to the “small core” option in the definition of the basis
set for the ADF code. Geometry optimizations, without sym-
metry constraints, were carried out in Cartesian coordinates
using default convergence criteria (10-3 au for energies and 10-2
The aromatic alkaline salts NaCp,35 NaInd,19 and LiFlu5e
were prepared as reported in the literature. The epoxides (a
propylene, b styrene, c cyclopentene, oxides) are from Aldrich
Chemical Co. and were used without further purification. The
syntheses of ligands have been performed at the temperature
specified in each case, until the disappearance of the starting
material (checked by GC). The attribution of 1H NMR signals
relative to the side-chain diasterotopic CHaHb methylene group
may be inverted. Abbreviations: THF, tetrahydrofuran; Me-
CN, acetonitrile; Pr, isopropyl; Ep, petroleum ether; GC, gas
chromatography; GC-MS, gas chromatography-mass spec-
troscopy.
X-ray Crystallographic Study. Crystal data and collection
details for HFluaOH, 8a, are reported in Table 1. The diffraction
experiments were carried out on a Bruker APEX II diffracto-
meter equipped with a CCD detector using Mo KR radiation.
Data were corrected for Lorentz polarization and absorption
-1
˚
au A
for gradients). Free energy calculations have been
performed using standard statistical mechanics formulas,31c
starting from the calculated harmonic frequencies and assuming
ideal gas behavior. Free energy variations correspond to differ-
ences of the free energies in vacuo of the shown structures,
increased or diminished by the free energies of the exiting
(-X, X = CO, MeCN, THF) or entering (þX, X = MeCN,
i
THF) species, respectively. Solvent effects for 12a, 13a,b,c, 14a,b,c
,
and 15b,c species have been taken into account according to the
COSMO31d solvation model. The package has been implemen-
ted in ADF 2007.1, by using for MeCN ε = 37.5 as dielectric
ꢁ
˚
constant and 2.76 A as solvent radius, or ε = 7.58 as dielectric
ꢁ
˚
constant and a solvent radius of 3.18 A for THF.
(32) (a) Becke, A. D. Phys. Rev. A 1988, 38, 3098–3100. (b) Lee, T.;
Yang, W. T.; Parr, R. G. Phys. Rev. B 1988, 37, 785–789.
(33) Perrin D. D.; Armarego W. L. F.; Perrin D. R. Purification of
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Fonseca Guerra, C.; Baerends, E. J.; Snijders, J. G.; Ziegler, T. J.
Comput. Chem. 2001, 22, 931–967. (b) ADF2008.01, SCM, Theoretical
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2003, 22, 877.

Article
Organometallics, Vol. 28, No. 18, 2009 5391
Chart 2. Numbering of the Carbon Atoms of Indenyl and Fluorenyl Ligands and Metal Complexes
effects (empirical absorption correction with SADABS).36
Structures were solved by direct methods and refined by full-
matrix least-squares based on all data using F2.37 The asym-
metric unit contains two independent molecules with identical
connectivities, absolute S configuration at the quaternary asym-
metric carbons [C(2) and C(22), respectively], and very similar
bonding parameters. Hydrogen atoms bonded to carbon atoms
were fixed at calculated positions and refined by a riding model.
The H-atoms bonded to O-atoms in both the independent
molecules were located in the Fourier map and refined isotro-
1H, CH-O), 6.19 (s, 1H, H2), 7.0-7.4 (m, 4H). 13C{1H} NMR
(75.44 MHz, CDCl3, δ): 19.7 (Me), 35.0 (CH2), 38.1 (CH2 ring),
56.4 (OMe), 76.1 (CHO), 119.3 (C5), 124.0 (C6), 124.8 (C7),
126.3 (C8), 130.2 (C2), 141.5 (C3), 144.6 (C9), 145.7 (C4).
3b, HIndbOMe: yield 75%. Anal. Calcd for C18H18O: C, 86.35;
H, 7.25. Found: C, 86.30; H, 7.28. 1H NMR (300 MHz, CDCl3,
δ): 2.9-3.3 (m, 2H, CH2), 3.356 (s, 3H, OMe), 3.401 (s, 2H, CH2
ring), 4.65 (dd, 1H, CH-O), 6.31 (s, 1H, H2), 7.2-7.8 (m, 10H).
13C{1H} NMR (75.54 MHz, CDCl3, δ): 37.4, 38.4 (CH2), 57.2
(OMe), 83.2 (CHO), 119.5 (C5), 124.2 (C6), 125.0 (C7), 126.5
(C8), 127.2 (meta-C Ph), 128.1 (para-C Ph), 128.9 (ortho-C Ph),
130.7 (C2), 141.2 (C3), 142.6 (C9) 144.7 (ipso-C Ph), 145.9 (C4).
3c, HIndcOMe: yield 25%. Anal. Calcd for C18H18O: C, 86.35;
H, 7.25. Found: C, 86.29; H, 7.29. 1H NMR (300 MHz, CDCl3,
δ): 3.358 (s, 3H, OMe), 3.504 (s, 2H, CH2 ring), 3.96 (m, 1H,
CHaHb), 4.10 (m, 1H, CHaHb), 4.44 (m, 1H, CHO), 6.31 (s, 1H,
H2), 7.2-7.8 (m, PhþInd 9H). 13C{1H} NMR (75.44 MHz,
CDCl3, δ): 38.4 (CH2 ring), 45.3 (CHPh), 59.2 (OMe), 76.4
(CH2O), 120.3 (C5), 124.1 (C6), 125.1 (C7), 126.4 (C8), 127.1
(meta-C Ph), 128.8 (para-C Ph), 128.9 (ortho-C Ph)), 129.3 (C2),
141.2 (C3), 144.5 (C9) 144.7 (ipso-C Ph), 145.2 (C4).
˚
pically with restrained O-H distances [0.84 A, SE 0.02].
General Procedure for the Synthesis of Indenyl Alcoholate
Derivatives 1x (x = a-d), HIndxO. Epoxides a,b,c (10 mmol)
were added at room temperature to freshly IndNa (10 mmol) in
THF (50 mL). The resulting solution was stirred for 7 h in the
case of propylene oxide a, for 7 h at reflux in the case of styrene
oxide b, and for 24 h in the case of cyclopentene oxide c until the
disappearance of starting material (monitored by GC). All
volatiles were removed in vacuo to yield a red-brown air-
sensitive powder containing alcoholate derivatives.
1a, HIndaO: yield 98%. 1H NMR (300 MHz, THF-d8, δ): 1.20
(d, 3H, JHH = 6.9 Hz; Me), 2.51 (m, br, 1H, CHaHb), 2.8 (m br,
1H, CHaHb) 3.35 (s, 2H, CH2 ring), 4.30 (m br, 1H, CH-O-),
6.26 (s, 1H, H2), 7.1-7.6 (m, 4H). 13C{1H} NMR (75.44 MHz,
THF-d8, δ): 27.6 (Me), 39.5 (CH2 ring), 44.5 (CH2), 69.4 (CHO),
121.2 (C5), 125.3 (C6), 126.0 (C7), 127.6 (C8), 129.8 (C2), 146.5
(C3), 146.5 (C9), 148.5 (C4).
3d, HInddOMe: yield 78%. Anal. Calcd for C15H18O: C, 84.06;
H, 8.47. Found: C, 84.08; H, 8.49. 1H NMR (300 MHz, CDCl3,
δ): 1.70-1.89 (m, 6H, C30H2 þ C40H2 þ C50H2), 2.17 (m, 1H,
C20H), 3.35 (s, 3H, OMe), 3.9 (s, 2H, CH2 ring), 4.35 (m, 1H,
C10HHO), 6.20 (s, 1H, H2), 7.17-7.49 (m, 4H). 13C{1H} NMR
(75.44 MHz, CDCl3, δ): 23.9 (C40H2), 30.8 (C30H2), 31.9
(C50H2), 38.3 (CH2 ring), 45.3 (C20H), 57.5 (OMe), 87.5
(C10HO), 120.3 (C5), 124.4 (C6), 125.2 (C7), 126.6 (C8), 127.2
(C2), 145.3 (C3), 145.8 (C9), 147.5 (C4).
1b, HIndbO: yield 75%. 1H NMR (300 MHz, THF-d8, δ):
2.871 (m, br, 1H, CHaHb), 3.207 (m, br, 1H, CHaHb), 3.264 (s,
2H, CH2 ring), 5.334 (s, br, 1H, CH-O), 6.027 (s, 1H, H2),
7.20-7.60 (m, 10H). 13C{1H} NMR (75.44 MHz, THF-d8, δ):
39.5 (CH2), 46.3 (CH2 ring), 78.0 (CHO), 121.1(C5), 125.2 (C6),
125.8 (C7), 127.1 (C8), 127.4 (para-CH Ph), 128.3 (meta-CH
Ph), 129.0 (ortho-CH Ph), 130.9 (C2), 145.3 (C3), 146.3 (C9),
148.4 (C4), 154.7 (ipso-C Ph).
General Procedure for the Synthesis of Indenyl Ether 4a-d
,
OMe
LiIndx
(x = a-d). A THF (40 mL) solution of the appro-
priate indene ether derivative 3a-d (3.9 mmol) was cooled to
-78 °C and n-BuLi (4.3 mmol, 1.1 equiv) added dropwise.
The mixture was stirred for 1 h until room temperature
was reached. The solution turned immediately from yellow to
purple. The solvent was removed in vacuo, giving a red-brown
solid.
OMe
General Procedure for the Synthesis of Indene Ether HIndx
(x = a-d). A 10 mL amount of methyl trifluoromethane-
sulfonate (1.13 mL, 10 mmol) in toluene solution was added,
at -78 °C via cannula, to relative alcoholate derivatives 1a-d
(10 mmol) in toluene (50 mL). The resulting reaction mixture
was stirred at -78 °C for 30 min and then warmed to room
temperature until the parent alcoholate disappearance was
detected by GC-MS. The yellow slurry was washed with aqu-
eous NH4Cl and the organic phase dried on MgSO4. After
solvent removal the crude product was purified by column silica
gel chromatography (70-230 mesh, grade 60) with Ep/Et2O
(95:5) to yield a pale yellow oil.
4b, LiIndbOMe: 1H NMR (300 MHz, THF-d8, δ): 3.09 (s, 3H,
OMe), 3.22-3.52 (m, 2H, CHaHb), 4.98 (d, 1H, JHH = 8.7 Hz,
CH-O), 6.08 (s, 1H, H2), 6.46 (s, 1H, H3), 6.63 (m, 4H, H5, H6,
H7, H8), 7.20-7.90 (m, 5H, Ph). 13C{1H} NMR (75.44 MHz,
THF-d8, δ): 41.3 (CH2), 57.4 (OMe), 87.1 (CHO), 93.1 (C3),
114.8 (C5), 115.2 (C2), 117.1 (C6), 118.6 (C7), 121.2 (C8), 127.1,
128.3 (C4, C9), 128.7 (meta-C Ph), 129.4 (para-C Ph), 130.4
(ortho-C Ph), 132.8 (C3), 144.8 (ipso-C Ph).
General Procedure for the Synthesis of Sodium Cyclopentadie-
nyl Alcohol Derivatives NaCpxOH (x = a-d). Epoxide (A, B, 10
mmol) was added, via syringe, to a stirred solution of NaCp
(0.88 g, 10 mmol) in THF (120 mL) The deep purple mixture was
stirred at room temperature until the disappearance of starting
material (monitored by TLC). The reaction color turned red
brick in 4 h for 5a and 17 h for 5b,c. The filtered solid was washed
with diethyl ether (3 ꢁ 30 mL) to give a red-brown air-sensitive
powder.
3a, HIndaOMe: yield 98%. Anal. Calcd for C13H16O: C, 82.93;
H, 8.57. Found: C, 82.90; H, 8.58. GC-MS (m/z (%)): 188 (10)
[M]þ, 156 (24) [M - (MeOH)]þ, 141 (12) [IndCHCH2]þ, 128
(100) [IndCH2]þ, 115 (19) [Ind]þ. 1H NMR (300 MHz, CDCl3,
δ): 1.14 (d, 3H, JHH = 6 Hz, Me), 2.5 (m, 1H, CHaHb), 2.8 (m,
1H, CHaHb), 3.24 (s, 2H, CH2 ring), 3.30 (s,3H, OMe), 3.63 (m,
(36) Sheldrick, G. M. SADABS, Program for Empirical Absorption
€
5a, NaCpaOH: C8H11NaO. 1H NMR (400 MHz, pyridine-d5):
1.32 (s, br, 3H, Me) 2.70 (m, br 1H, CHaHb), 3.06 (m, br, 1H,
CHaHb), 4.11 (m, br, 1H, CH-OH), 6.16 (s, br, 2H, H2, H5 Cp),
Correction; University of Gottingen: Germany, 1996.
(37) Sheldrick, G. M. SHELX97, Program for Crystal Structure
€
Determination; University of Gottingen: Germany, 1997.

5392 Organometallics, Vol. 28, No. 18, 2009
Bordoni et al.
6.30 (s, br, 2H, H3, H4 Cp). 13C{1H} NMR (100.59 MHz,
pyridine-d5): 24.7 (Me), 41.7 (CH2), 70.0 (CHOH), 103.6, 105.0
(CHCp), 116.7 (ipso-C).
5 h, until the parent alcoholate disappearance was detected by
GC. The resulting yellow suspension was washed with aqueous
NH4Cl and the organic phase dried on MgSO4. After solvent
removal under reduced pressure, the crude product was purified
by silica gel chromatography with Ep-Et2O (95:5) to yield a
pale yellow oil.
5b, NaCpbOH: 1H NMR (400 MHz, pyridine-d5): 3.07 (m, 1H,
CHaHb), 3.36 (m, 1H, CHaHb), 5.22 (m, 1H, CH-OH), 6.37 (s,
br, 1H, H2 or H5 Cp), 6.43 (s, br, 2H, H3 þ H4 Cp), 6.56 (s, br,
1H, H2 or H5 Cp), 7.22 (m, 1H, para-CH Ph), 7.33 (m, 2H,
ortho-CH Ph), 7.64 (m, 2H, meta-CH Ph). 13C{1H} NMR
(100.59 MHz, pyridine-d5): 43.3 (CH2), 76.8 (CHOH), 104.4
(C2, C5), 104.7 (C3, C4), 117.5 (ipso-Cp), 126.7 (para-C Ph),
126.9 (meta-C Ph), 128.7 (ortho-C Ph), 148.15 (ipso-C Ph).
5c, NaCpcOH: 1H NMR (400 MHz, pyridine-d5): 3.6 (m, 1H,
CHPh), 4.3 (m, 2H, CH2O), 6.3- 6.5 (m, br, 4H, Cp), 7.16 (s, 1H,
para-CH Ph), 7.33 (m, 2H, ortho-CH Ph), 7.06 (m, 2H, meta-CH
Ph). 13C{1H} NMR (100.59 MHz, pyridine-d5): 52.5 (CHPh),
70.3 (CH2O), 104.3 (CH Cp), 116.3 (ipso-C Cp), 125.6 (para-C
Ph), 126.8 (meta-C Ph), 129.4 (ortho-C Ph), 147.0 (ipso-C Ph).
5d, NaCpdOH: 1H NMR (600 MHz, THF-d8, δ):0δ 6.72 (s, 2H,
CH3,4Cp), 6.14 (s, 2H, CH2,5Cp), 4.55 (m, 1H, C1 H-OH), 2.79
9a, HFluaOMe: yield 94%. Anal. Calcd for C17H18O: C, 85.67;
H, 7.62. Found: C, 85.62; H, 7.69. GC-MS (m/z (%)): 238 (7)
[M]þ, 206 (92) [M - MeOH]þ, 191 (100) [FluCH2CH]þ, 178 (36)
1
[FluCH2]þ, 165 (71) [Flu]þ. H NMR (400 MHz, CDCl3, δ):
1.09 (d, 3H, JHH = 6 Hz, Me), 1.66 (m, 1H, CHaHb), 2.26 (m,
1H, CHaHb), 3.29 (s, 3H, OMe), 3.57 (m, 1H, CH-O), 4.11 (m,
1H, CHR), 7.20-7.80 (m, 8H). 13C{1H} NMR (100.59 MHz,
CDCl3, δ): 20.1 (Me), 41.8 (CH2), 45.0 (CHR), 56.4 (OMe), 75.2
(CHO), 120.4, 120.5 (C1, C8), 125.0, 125.6 (C3, C6), 127.3,
127.4, 127.5 (C2, C4, C5, C7), 141.3, 141.6 (C10, C13), 148.0,
148.6 (C11, C12).
Synthesis of LiFluaOMe, 10a. The synthetic procedure was the
same as described for 4a starting from fluorene derivative 9a.
10a, LiFluaOMe: 1H NMR (400 MHz, THF-d8, δ): 1.38 (d, 3H,
(m, 1H, C2 H-Cp), 2.21, 1.67 (m, 6H, CH2). 13C{1H} NMR
0
(150.9 MHz, THF-d8, 298 K): δ 126.45 (ipso-Cp), 113.2, 111.9,
J
HH = 6 Hz, Me), 3.22 (m, 1H, CHaHb), 3.55 (s, 3H, OMe), 3.63
(m, 1H, CHaHb), 4.02 (m, 1H, CHO), 6.67 (dd, 2H, JHH = 7.0
Hz, JHH = 6.8 Hz, H3, H6), 7.11 (dd, 2H, JHH = 8.0 Hz JHH
6.8 Hz, H2, H7), 7.55 (d, 2H, JHH = 8 Hz, H1, H8), 8.13 (d, 2H,
HH = 7.6 Hz, H4, H5). 13C{1H} NMR (100.59 MHz, THF-d8,
0
0
109.7 (CHCp), 78.43 (C1 H-OH), 37.15 (C2 H-Cp), 31.34,
29.16, 21.23 (CH2).
=
Reaction of Lithium Fluorenide with Propylene Oxide. Race-
mic or enantiopure S-propylene oxide (10 mmol) was added at
-78 °C to a stirred solution in THF (50 mL) of FluLi (10 mmol).
The resulting reaction mixture was stirred at -78 °C for 30 min
and then warmed to room temperature for 22 h, until disap-
pearance of the fluorene (detected by GC-MS). The anionic
orange mixture obtained consisted of a equimolar mixture of
fluorene-propanolate 6a and fluorenyl-propanol 7a evaluated by
NMR.
J
δ): 21.5 (Me), 35.6 (CH2), 57.1 (OMe), 81.2 (CHO), 89.3 (C9),
109.6 (C3, C6), 115.2 (C1, C8), 120.3 (C2, C7), 120.9 (C4, C5),
123.6 (C11, C12), 136.8 (C10, C13).
Synthesis of Rhenium Alkoxide Derivatives 11a,b, HInda,bORe-
(CO) . A THF (20 mL) solution of Re(CO)5X (4.0 mmol) was
5
added via syringe to a THF solution (25 mL) of the indene
alcoholate (1a,b) (4.2 mmol). The reaction mixture was stirred at
room temperature for 2 h before being warmed to reflux
temperature. The course of the reaction was monitored by IR
spectroscopy until Re(CO)5X disappeared. The obtained solid
was washed with ethyl ether to extract the NaX (X=Cl, Br). No
further workup was made to prevent decomposition of the
desired products. Synthesis of 11a (X=Cl) requires 5 h, while
30 min was needed in the case of 11b (X=Br).
11a, HIndaORe(CO)5: yield 1.898 g, 95%. Anal. Calcd for
C17H13O6Re: C, 40.80; H, 2.62. Found: C, 40.87; H, 2.59. IR
(νCO THF): 2021 m, 1914 s, 1903 s, 1895 s cm-1. 1H NMR (300
MHz, CDCl3, δ): 1.17 (d, 3H, JHH = 6 Hz, Me), 2.61 (m, br, 2H,
CHaHb), 3.22 (s, 2H, CH2 ring), 4.06 (m, 1H, CHORe), 6.20 (s,
1H, H2), 7.05-7.40 (m, 4H). 13C{1H} NMR (75.44 MHz,
CDCl3, δ): 23.5 (Me), 38.1, 38.2 (CH2), 66.9 (CHO), 119.4
(C5), 124.2 (C6), 125.1 (C7), 126.4 (C8), 130.8 (C2), 141.4
(C3), 144.7 (C9), 145.5 (C4), 193.5, 197.0 (CO).
11b, HIndbORe(CO)5: yield 2.224 g, 99%. Anal. Calcd for
C22H15O6Re: C, 46.97; H, 2.69. Found: C, 47.01; H, 2.72. IR
(νCO THF): 1999 m, 1885 vs. IR (νCO, KBr): 2109 w, 2018 s,
1979 m, 1900 vs cm-1. 1H NMR (600 MHz, THF-d8, δ): 2.8 (m,
br, 1H, CHaHb), 3.2 (m, br, 1H, CHaHb), 3.37 (s, 2H, CH2 ring),
5.33 (s, br, 1H, CHO), 6.033 (s, 1H, H2), 7.10-7.70 (m, 10H).
13C{1H} NMR (75.44 MHz, THF-d8, δ): 38.9 (CH2 ring), 38.9
(CH2), 73.8 (CHO), 120.4 (C5), 124.8 (C6), 125.6 (C7), 127.1
(para-C Ph), 127.3 (meta-C Ph), 128.1 (C8), 129.2 (ortho-C Ph),
131.6 (C2), 142.8 (C3), 145.7 (C9), 147.0 (C4), 154.5 (ipso-C Ph),
180.3, 187.7, 188.8, 199.8, 201.3 (CO).
Synthesis of 12a,d and 13a,d Derivatives. The appropriate
ligand (3a,d) (2.4 mmol) was dissolved in THF (10 mL) and
deprotonated by dropwise addition of n-BuLi (2.5 mmol) at
-78 °C. This solution was stirred for 1 h at room temperature.
The resulting purple anion (4a,d) solution was cooled to -78 °C
and added via syringe to a THF solution (25 mL) of Re(CO)5Br
(0.8318 g, 2.05 mmol). The reaction mixture was stirred at
-78 °C for 30 min, before being warmed to room temperature.
The reaction was monitored by IR in solution (THF). The
reaction was stopped when the IR indicated the disappearance
of Re(CO)5Br (6 h for 4a, 3 h for 4d). Solvent was removed in
6a, HFLuaOLi: 1H NMR (400 MHz, THF-d8, δ): 1.19 (d, 3H,
JHH = 6 Hz, Me), 1.85 (m, 1H, CHaHb), 2.23 (m, 1H, CHaHb),
4.16 (m, 1H, CH-O), 4.18 (m, 1H, CHR), 7.33-7.72 (m, 8H,
arom). 13C{1H} NMR (100.59 MHz, THF-d8, δ): 26.9 (Me),
40.6 (CHR), 46.1 (CH2), 66.9 (CHO), 119.4, 119.7 (C1, C8),
123.4 (C5), 124.2 (C4), 126.8, 126.9 (C3, C6), 127.0, 127.1 (C2,
C7), 141.4, 141.7 (C10, C13), 147.2, 147.9 (C11, C12).
7a, LiFLuaOH: 1H NMR (400 MHz, THF-d8, δ): 1.34 (d, 3H,
JHH = 6 Hz, Me), 2.43 (m, 1H, CHaHb), 2.56 (m, 1H, CHaHb),
2.80 (s, br, 1H, OH), 4.83 (m, 1H, CHO), 6.85-8.52 (m, 8H,
arom). 13C{1H} NMR (100.59 MHz, THF-d8, δ): 23.5 (Me),
37.3 (CH2), 69.7 (CHO), 90.2 (C9), 110.8 (C3, C6), 118.4 (C1,
C8), 122.4 (C2, C7), 122.8 (C4, C5), 124.7 (C11, C12), 135.9
(C10, C13).
Neutralization of 6a and 7a to Fluorene Alcohol Derivatives.
An ethereal solution containing 7a and 8a was washed with
NH4Cl(aq) (10 mL) and the organic phase dried overnight over
MgSO4. The solvent was removed in vacuo, yielding 9a as a waxy
orange oil.
8a, HFluaOH: yield 95%. Anal. Calcd for C16H16O: C, 85.67;
H, 7.14. Found: C, 85.34; H, 7.19. GC-MS (m/z (%)): 224 (14)
[M]þ, 206 (57) [M - OH]þ, 191 (78) [FluCH2CH]þ, 178 (100)
1
[FluCH2]þ, 165 (85) [Flu]þ. H NMR (600 MHz, CDCl3, δ):
1.24 (d, 3H, JHH = 6.6 Hz, Me), 1.90 (m, 1H, CHaHb), 1.99 (d,
1H, JHH = 3.6 Hz, OH), 2.31 (m, 1H, CHaHb), 4.11 (m, 1H,
CH-O), 4.22 (m, 1H, CHR), 7.38 (m, 2H, H3 þ H6), 7.45 (t br,
2H, JHH = 7.8 Hz, H2 þ H7), 7.57 (d, 1H, JHH = 7.8 Hz, H5),
7.68 (d, 1H, JHH = 7.8 Hz, H4), 7.84 (m, 2H, JHH = 7.2 Hz, H1
þ H8). 13C{1H} NMR (100.59 MHz, CDCl3, δ): 24.8 (Me), 43.3
(CH2), 45.2 (C9HR), 66.4 (CHO), 120.5, 120.6 (C1, C8), 124.9
(C5), 125.6 (C4), 127.2, 127.3 (C3, C6), 127.4, 127.5 (C2, C7),
141.3, 141.5 (C10, C13), 147.5, 148.0 (C11, C12).
Synthesis of HFluaOMe, 9a. Ligand 8a (10 mmol) was dissolved
in Et2O (70 mL). This solution was cooled to -30 °C and treated
with n-BuLi (11 mmol). This solution was stirred at 0 °C for 2 h
and added via cannula to a toluene solution (30 mL) of methyl
trifluoromethanesulfonate (1.13 mL, 10 mmol) at -78 °C. The
resulting reaction mixture was warmed to room temperature for

Article
Organometallics, Vol. 28, No. 18, 2009 5393
vacuo, and the resulting orange powder was extracted with
diethyl ether (2 ꢁ 40 mL) and then chromatographed on silica
gel (70-230 mesh, grade 60). Chromatography with Ep-Et2O
(1:1) gave a pale yellow fraction, namely, 13a or 13d followed by
a yellow fraction corresponding to 12a or 12d by eluting with
THF-Et2O (1:1).
(IR and NMR) reveal its transformation to 15b. Dissolution of
15b by CH2Cl2 caused prompt precipitation of a brown powder,
which was extracted with toluene (3 ꢁ 10 mL). The residue was
characterized by NMR spectroscopy, affording 16b (0.366 g,
34% yield calculated for 14b).
14b, η5-IndbOMeRe(CO)3: yield 1.134 g, 90%. Anal. Calcd for
C21H17O4Re: C, 48.45; H, 3.29. Found: C, 48.50; H, 3.22. IR
(νCO, KBr): 2020 s, 1899 vs, 1845 sh cm-1. 1H NMR (300 MHz,
C6D6, δ): 3.19 (s, br, 3H, OMe), 3.28 (s, br, 2H, CH2), 3.99 (m,
br, 1H, CHO), 4.43 (m, 1H, H2), 4.56 (m, br, 1H, H3), 7.00-7.80
(m, 9H). 13C{1H} NMR (75.44 MHz, C6D6, δ): 37.7 (CH2), 57.1
(OMe), 79.6 (CHO), 83.8 (C3), 120.0 (C2), 124.6, 125.5, 126.9
131.2 (CH Ind), 127.7, 129.2, 129.3 (CH Ph), 141.6, 142.9, 145.1
(ipso-C), 146.4 (ipso-C Ph), 192.6, 193.4, 193.8 (CO).
15b, η5-IndbOMeRe(CO)2(NCMe): yield 0.442, 38%. Anal.
Calcd for C22H20NO3Re: C, 49.52; H, 3. 78, N 2.63. Found:
C, 49.48; H, 3.74, N 2.69. IR (νCO, toluene): 2036 m, 1908 vs
cm-1. IR (νCO, KBr): 2224 w (νCN), 2035 m, 1937 m, sh cm-1. 1H
NMR (300 MHz, CD3CN, δ): 1.92 (s, br, 3H, MeCN),
3.06-3.08 (m, br, 2H, CH2), 3.24 (s, br, 3H, OMe), 4.0 (s, br,
1H, CHO), 4.2 (m, 1H, H2), 4.4 (m, br, 1H, H3), 7.0-7.80 (m,
9H). 13C{1H} NMR (75.44 MHz, CD3CN, δ): 5.1 (MeCN), 37.2
(CH2), 57.2 (OMe), 81.9 (CHO), 84.0 (C3), 121.3 (MeCN), 122.9
(C2), 127.2, 127.4, 128.6, 129.1 (CH Ind), 129.3, 129.5, 129.75
(CH Ph), 142.8, 143.5, 144.5 (ipso-C), 146.9 (ipso-C Ph), 199.7,
201.0 (CO).
12a, η1-IndaOMeRe(CO)5: yield 0.372 g, 35%. Anal. Calcd for
C18H15O6Re: C, 42.02; H, 2.94. Found: C, 42.05; H, 2.92. IR
(νCO, CHCl3): 2129 w, 2015 s, 1991 vs, 1979 vs, 1920 m cm-1. 1H
NMR (300 MHz, CDCl3, δ): 1.87 (d, 3H, JHH = 6 Hz, Me), 2.6
(m, 1H, CHaHb), 2.9 (m, 1H, CHaHb), 3.2 (m, 1H, CHRe), 3.37
(s, 3H, OMe), 3.7 (m, 1H, CHO), 6.26 (s, 1H, H2), 7.0-7.6 (m,
4H, arom). 13C{1H} NMR (75.44 MHz, CDCl3, δ): 20.0 (Me),
35.4 (CH2), 38.5 (CHRe), 56.8 (OMe), 76.5 (CHO), 119.6 (C5),
124.3 (C6), 125.1 (C7), 126.6 (C8), 130.6 (C2), 141.8 (C3), 144.9
(C9), 146.1 (C4), 187.2 (CO eq), 186.5 (CO ax).
12b, η1-InddOMeRe(CO)5: yield 0.476 g, 45%. Anal. Calcd for
C20H17O6Re: C, 44.44; H, 3.17. Found: C, 44.35; H, 3.21. IR
1
(νCO, KBr): 2088 w, 2037 m, 1996 vs, 1893 m cm-1. H NMR
(300 MHz, CD3CN, δ): 1.20-1.50 (m, 6H, [CH2]3), 2.12 [m, 1H,
C(E)H], 2.83 (t, 1H, CHRe), 3.27 (s, 3H, OMe), 4.28 (m, 1H,
CHO), 5.16 (s, br, 1H, H2), 7.10-7.50 (m, 4H, arom). 13C{1H}
NMR (75.44 MHz, CD3CN, δ): 22.0, 29.4, 34.2 (CH2), 37.3
(CHRe), 44.4 (CHR), 56.2 (OMe), 86.6 (CHO), 119.6 (C5),
123.6 (C6), 124.4 (C7), 125.8 (C8), 126.6 (C2), 144.6 (C3), 145.2
(C9), 146.4 (C4), 178.5, 185.2, 189.7, 190.0, 196.7 (CO).
13a, η3-IndaOMeRe(CO)4: yield 0.401 g, 40%. Anal. Calcd for
C17H15O5Re: C, 41.97; H, 3.11. Found: C, 41.88; H, 3.15. IR
(νCO, CDCl3): 2091 w, 1993 s, 1922 s, 1893 m cm-1. 1H NMR
(300 MHz, CDCl3, δ): 1.25 (d, 3H, JHH = 6 Hz, Me), 2.7 (m, 1H,
CHaHb), 2.8 (m, 1H, CHaHb), 3.41 (s, 3H, OMe), 3.8 (m, 1H,
CHO), 6.7 (s, 1H, H3), 7.2-7.4 (m, 4H), 8.4 (d, 1H, JHH = 6.3
Hz, H2). 13C{1H} NMR (75.44 MHz, CDCl3, δ): 20.1 (Me), 35.0
(CH2), 56.5 (OMe), 69.1 (CHO), 118.5 (C5), 125.4 (C6), 126.0
(C7), 126.2 (C8), 132.4 (C3), 133.4 (C1), 144.9, 146.1 (C4, C9),
142.7 (C2), 185.0, 191.9, 192.6, 196.7 (CO).
13d, η3-InddOMeRe(CO)4: yield 0.424 g, 38%. Anal. Calcd for
C19H17O5Re: C, 44.53; H, 3.35. Found: C, 44.48; H, 3.39. IR
(νCO, KBr): 2140 w, 1985 vs, 1915 s, 1856 m, sh cm-1. 1H NMR
(300 MHz, CD3CN, δ): 1.2-1.5 (m, 6H, [CH2]3), 2.7 [m, 1H,
C(E)H], 3.31 (s, 3H, OMe), 3.93 (m, br, 1H, CHO), 6.69 (s, br,
1H, H3), 7.1-7.5 (m, 4H, arom), 8.5 (m, 1H, H2). 13C{1H}
NMR (75.44 MHz, CD3CN, δ): 22.2, 26.0, 30.8 (CH2), 44.3
[C(E)H], 56.3 (OMe), 87.1 (CHO), 119.5 (C5), 124.0 (C6), 124.5
(C7), 124.8 (C8), 127.2, 129.1 (C1, C3), 133.2, 136.82 (C4, C9),
142.3 (C2), 178.8 187.5 188.0 200.8 (CO). 13C{1H} NMR (75.44
MHz,C6D6, δ): 196.6, 193.7, 189.1, 179.0 (CO).
16b, κ1O:η5-IndbOMeRe(CO)2: yield 0.366 g, 90%. Anal. Calcd
for C20H17O3Re: C, 48.77; H, 3.48. Found: C, 48.81; H, 3.44. IR
(νCO, KBr): 2014 m, 1895 vs cm-1. IR (νCO, toluene): 2021 m,
1945 m cm-1. 1H NMR (300 MHz, CD3CN, δ): 1.19 (s, br, 3H,
OMe), 2.20 (s, br, 1H, CHO), 2.78 (s, br, 2H, CH2), 3.7 (m, br,
1H, H2 þ H3), 6.8-7.80 (m, 9H). 13C{1H} NMR (75.44 MHz,
CD3CN, δ): 21.7 (OMe), 56.8 (CHO), 59.5 (CH2), 72.1 (C3),
119.5 (C2), 127.7, 127.9, 128.1, 128.3 (CH Ind), 126.5, 129.4,
130.1 (CH Ph), 141.0, 142.2, 143.8(ipso-C), 146.7 (ipso-C Ph),
192.3, 197.3 (CO).
Synthesis and Chelation of η5-IndcOMeRe(CO)3, 14c. A THF
solution of Re(CO)3(MeCN)2Br (0.7321 g, 2.51 mmol) was
reacted with LiIndcOMe (4c) prepared in situ (-78 °C) by addition
of an equimolar amount of n-BuLi to derivative 3c (3.12 mmol,
1.24 equiv). Upon warming to room temperature the reaction
went to completion in 4 h. Solvent was removed in vacuo, giving
an orange-red solid, and the crude product was extracted with
diethyl ether (2 ꢁ 40 mL) to give an orange powder of 14c. The
rearrangement reaction was detected upon addition of THF at
1
-20 C for 6 h, by H NMR monitoring. Solvent evaporation,
filtering on a Celite pad, and washing with petroleum ether gave
the oily 15c, which was characterized directly by spectroscopic
means (IR, H NMR). Dissolution of 15c by CH2Cl2 caused
Degradation of 12a,d, 13a,d to Re3(μ-H)3(CO)12: white micro-
crystalline solid. Anal. Calcd for C12H3O12Re3: C, 16.01; H,
0.33. Found: C, 15.99; H, 0.39. ESI-MS (MeCN, m/z (%)): 898
1
prompt precipitation of a brown-yellow powder, which was
extracted by Et2O. The residue was characterized by NMR
spectroscopy, affording 16c (0.70 g, 60% yield calculated on
14c). Due to its low stability in solution, no 13C spectra could be
recorded.
[M þ H]þ (100). IR (νCO, Et2O): 2046 s, 1984 m cm-1. IR (νCO
,
KBr): 2154 w, 2063 s, 2033 vs, 1971 s, 1959 vs cm-1. 1H NMR
(300 MHz, acetone-d6): -17.0 s. 13C{1H} NMR (75.44 MHz,
acetone-d6): 181.0, 205.2 (CO).
14c η5-IndcOMeRe(CO)3: yield 1.210 g, 93%. Anal. Calcd for
C21H17O4Re: C, 48.45; H, 3.29. Found: C, 48.43; H, 3.32. IR
(νCO, THF): 2021 s, 1913 s, 1986 vs cm-1. 1H NMR (300 MHz,
benzene-d6, δ): 3.26 (s, br, 3H, OMe), 3.38 (s, br, 2H, CH2), 4.12
(m, br, 1H, CHPh), 4.38 (m, 1H, H2), 4.63 (m, br, 1H, H3),
6.90-7.85 (m, 9H). 13C{1H} NMR (75.44 MHz, benzene-d6, δ):
44.4 (CHPh), 56.9 (OMe), 75.8 (CH2), 84.0 (C3), 120.5 (C2),
124.4, 125.9, 127.2, 131.7 (CH Ind), 127.9, 129.5, 129.6 (CH Ph),
142.0, 143.1, 145.8 (ipso-C), 146.9 (ipso-C Ph), 187.3, 191.2,
192.4 (CO).
Synthesis of 14b and Haptotropic Rearrangement to 16b. To a
THF (10 mL) solution of 3b (0.608 g, 2.43 mmol) cooled to
-78 °C was added dropwise n-BuLi (1.0 mL of a 2.5 M solution
in hexanes, 2.5 mmol, 1.04 equiv), and the mixture was stirred
for 1 h until room temperature. The resulting purple solution
was added to a THF solution (30 mL) of Re(CO)3(MeCN)2Br
(0.7321 g, 2.024 mmol). The course of the reaction was mon-
itored by IR spectroscopy until IR measurements indicated the
disappearance of Re(CO)3(MeCN)2Br. Solvent was removed in
vacuo, giving an orange-red solid. The crude product was
extracted with diethyl ether (2 ꢁ 40 mL) to give an orange
powder of 14b. During crystallization attempts of a MeCN/Et2O
mixture (-20 °C, 16 h) the color of the solution turned a deeper
orange. The oily compound was treated with several extractions
with toluene and filtered on a Celite pad. Solvent evaporation
gave a waxy reddish compound. Spectroscopic measurements
15c, η5-IndcOMeRe(CO)2(THF): deep-orange oil. IR (νCO
,
THF): 2009 s, 1883 vs cm-1. IR (νCO, cm-1, KBr): 2017 s,
1904 vs. 1H NMR (300 MHz, THF-d8, δ): 1.73 (s, br, 4H, THF),
3.26 (m, br, 1H, CHPh), 3.28 (s, br, 3H, OMe), 3.36 (s, br, 1H,
H3), 3.58 (s, br, 4H, THF), 3.8-3.9 (m, br, 2H, CH2), 4.25 (m,
br, 1H, H2), 6.8-7.5 (m, 9H).

5394 Organometallics, Vol. 28, No. 18, 2009
Bordoni et al.
16c, κ1O:η5-IndcOMeRe(CO)2: ochre waxy solid. Anal. Calcd
for C20H17O3Re: C, 48.77; H, 3.48. Found: C, 48.75; H, 3.51. IR
(νCO, THF): 2021 s, 1915 s cm-1. 1H NMR (300 MHz, CD2Cl2,
δ): 1.11 (s, 3H, OMe), 2.75 (s, 1H, H2), 3.7 (m, 1H, CHPh), 3.4
(m, br, 3H, H3 þ CH2), 6.9-7.5 (m, 9H). 13C{1H} NMR (75.44
MHz, CD2Cl2, δ): 22.7 (OMe), 44.1 (CHPh), 58.9 (CH2), 75.7
(C3), 119.8 (C2), 124.0, 124.4, 125.5, 126.4 (CH Ind), 127.5,
128.5, 128.9 (CH Ph), 144.5 (ipso-C Ph), 140.0, 144.6, 147.4
(ipso-C), 193.5, 196.2 (CO).
stirred for 1 h until room temperature. The resulting purple 10a
solution was then stirred with a THF solution (30 mL) of
Re(CO)5Br (0.518 g, 1.28 mmol) at -78 °C. The course of the
reaction was monitored by IR spectroscopy, until disappear-
ance of the starting carbonyl complex (20 h). Extraction of the
crude product with diethyl ether (2 ꢁ 40 mL) indicated the
formation of 19a as an orange-red powder. Thermal treatment
of 18a gave rise to fast degradation to trimethoxy Na[Re2(μ-
OMe)3(CO)6], determined by comparison of its spectroscopic
Reaction of 5a with Re(CO)5Br. Excess (4.0 mL, 4.6 mmol) 5a
was added at rt via syringe to a THF solution (30 mL) of
Re(CO)5Br (0.513 g, 1.26 mmol) and stirred for 4 h. The crude
product was extracted with Et2O and dried under reduced pres-
sure to give a white powder, identified as the known trihydroxy
Na[Re2(μ-OH)3(CO)6] complex. Yield: 0.224 g., 30%. Anal.
Calcd for C6H3O9Re2: C, 12.14; H, 0.51. Found: C, 12.19; H,
data. IR (νCO, CH2Cl2): 1989 s, 1872 vs cm-1
.
18a, η1-FluaOMeRe(CO)5: yield 0.670 g, 92%. Anal. Calcd for
C22H17O6Re: C, 46.80; H, 3.04. Found: C, 46.86; H, 3.09. IR
(νCO, THF): 2078 w, 2031 w, 1995 s, 1977 vs, 1953 m cm-1. ESI-
MS (MeOH; m/z (%)): 571 [M þ H]þ (25), 515 [M - 2CO]þ
(100). 1H NMR (600 MHz, CDCl3, δ): 1.53 (d, 3H, JHH = 5.4
Hz, Me), 2.82-2.84 (dt ABX, 2H, JHH = 4.2 Hz, JHH = 3.0 Hz,
CHaHb), 4.15 (s, 3H, OMe), 4.69 (m, 1H, CHO), 7.30-8.0 (m,
8H, arom). 13C{1H} NMR (150.59 MHz, CDCl3, δ): 19.5 (Me),
41.6 (CH2), 56.4 (OMe), 82.9 (C9), 92.9 (CHO), 120.5, 120.7,
121.7, 123.0, 123.6, 128.4, 128.9, 130.0 (CH C1-C4, C5-C8),
138.7, 140.1, 141.4, 141.6 (ipso-C C11, C12, C10, C13), 185.0,
186.2 (CO).
0.62. IR (νCO, THF): 2004 vw, 1991 m, 1874 vs cm-1
.
Synthesis of 17a, CpaOHRe(CO)3. As alternative procedure,
1.5 equiv of anhydrous solid Me3NO was added to the rhenium
carbonyl bromide (0.506 g, 1.25 mmol) dissolved in 30 mL of
THF. The mixture color turned in 1 h from bright violet to
opalescent brown, while decarbonylation went to completion
and Re(CO)3(THF)2Br complex was formed in situ. A 2-fold
excess of anionic ligand 5a was then added, and the reaction was
monitored by IR spectroscopy for 2 h. The obtained brown
solution after filtration over a Celite pad and extraction with
diethyl ether was then chromatographed on an Al3O2 column.
By elution with CH2Cl2/Ep the collected fraction gave after
solvent evaporation a yellow microcrystalline solid, which was
identified as 17a.
Acknowledgment. We thank the University of Bologna
and the MIUR for supporting this work.
Supporting Information Available: 1H NMR of 12a (Figure
S1). 1H NMR spectra of 10a (Figure S2). 13C NMR spectra of
10a (Figure S3). Sample input for the ADF program (Table S1).
X,Y,Z coordinates relative to DFT structure calculations in
vacuo of the selected reported conformations, showing highest
and lowest energy (Table S2). DFT frontier orbitals for 15b
(Figure S4). DFT frontier orbitals for 15c (Figure S5). Experi-
mental details on quenching of indenyl alcoholate derivatives 1x
(x = a-d), HIndxO, to indenyl alcohol derivatives 2x (x = a-d),
HIndxOH. Reaction of lithium indenide and propylene oxide.
Reaction of lithium fluorenide with styrene oxide. Synthesis of
HFludOLi, 6d. Neutralization of fluorene derivatives. Selected
bond lengths and angles for HFluaOH, 8a (Table S2). This
material is available free of charge via the Internet at http://
pubs.acs.org.
17a, CpaOHRe(CO)3: yield 0.297 g, 60%. Anal. Calcd for
C11H11O4Re: C, 33.50; H, 2.81. Found: C, 33.56; H, 2.78. IR
(νCO, CH2Cl2): 2006 m, 1887s cm-1 1H NMR (400 MHz,
.
CDCl3, δ): 1.12 (d, 3H, JHH = 6 Hz, Me), 2.45-2.60 (m, 2H,
CH2), 4.05 (s br, 1H, OH), 4.38 (m, 1H, CHO), 5.27 (s, br, 2H,
CHCp), 5.31 (s, br, 2H, CHCp). 13C NMR (100.59 MHz): 23.7
(Me), 38.4 (CH2), 69.9 (CHO), 84.5, 84.6, 84.9, 85.3 (CH Cp),
107.4 (ipso-C), 195.1 (CO).
Synthesis of 18a, η1-FluaOMeRe(CO)5. A THF (10 mL) solu-
tion of methoxy-propyl fluorene derivative 9a (0.357 g, 1.5
mmol) was added dropwise at -78 °C to a hexane solution of
n-BuLi (0.66 mL of a 2.5 M solution, 1.65 mmol, 1.1 equiv) and