Preparation of (η5-Alkoxyfluorenyl)(η6-p- Cymene)-Sandwich Ruthenium(II) Complexes

Article abstract of DOI:10.1021/om900350n

Diazoalkane complexes [RuCl(N₂CAr lAr2)(η⁶-p- cymene)P]BPh₄ [Ar1 = Ph; Ar2 = Ph or p-tolyl; P = PPh(OEt) ₂ or P(OEt)₃] were prepared by allowing p-cymene complexes RuCl₂(η⁶-p-cym

Full text of DOI:10.1021/om900350n

Organometallics 2009, 28, 4475–4479 4475
DOI: 10.1021/om900350n
Preparation of (η5-Alkoxyfluorenyl)(η6-p-Cymene)-Sandwich
Ruthenium(II) Complexes
,†
Gabriele Albertin,* Stefano Antoniutti, Fabio Callegaro, and Jesus Castro
†
†
‡
ꢀ
†
ꢁ
Dipartimento di Chimica, Universita Ca’ Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy, and
Departamento de Quımica Inorganica, Universidade de Vigo, Facultade de Quımica, Edificio de Ciencias
‡
´
ꢀ
´
Experimentais, 36310 Vigo (Galicia), Spain
Received May 4, 2009
Diazoalkane complexes [RuCl(N2CAr1Ar2)(η6-p-cymene)P]BPh4 [Ar1=Ph; Ar2=Ph or p-tolyl;
P=PPh(OEt)2 or P(OEt)3] were prepared by allowing p-cymene complexes RuCl2(η6-p-cymene)P to
react with diaryldiazoalkane Ar1Ar2CN2. Treatment of the triisopropylphosphine complex
RuCl2(η6-p-cymene)(PiPr3) with 9-diazofluorene yielded the (η5-alkoxyfluorenyl)(η6-p-cymene)-
sandwich derivative [Ru(η5-RO-fluorenyl)(η6-p-cymene)]BPh4 (R=Me, Et). The complexes were
characterized spectroscopically (IR and 1H, 13C, 31P NMR) and by X-ray crystal structure
determination of the [Ru(η5-EtO-fluorenyl)(η6-p-cymene)]BPh4 derivative.
Introduction
Interest in this area stems not only from study of the
factors influencing the coordination mode and the reactivity
of the R1R2CN2 species but also from the importance of
diazoalkane complexes as models in the chemistry of N2
fixation.3,6,7
We are interested in the chemistry of diazo complexes and
have reported the synthesis and reactivity of aryldiazenido,
aryldiazene, and hydrazine derivatives of the iron triad8 and
diazoalkane complexes of osmium.9 We have now extended
the study on diazoalkane to half-sandwich complexes and
found a novel reaction of one diazoalkane, the 9-diazofluor-
ene C12H8CN2, toward a transition metal compound, allow-
ing the synthesis of unprecedented sandwich complexes10
Diazoalkanes R1R2CN2 are reported to react with transi-
tion metal complexes to give metallacarbene derivatives1,2
after loss of N2. In some cases, the reaction proceeds with
coordination of the diazoalkane to the metal center through
the dinitrogen atoms, giving stable and isolable complexes in
which the R1R2CN2 ligand displays a variety of coordina-
tion modes (Chart 1).2,3
In mononuclear complexes, either η1-, end-on (type I), or
η2-N,N, side-on (type II) coordination modes have commonly
been observed,4 whereas the two bridging modes III and IV
have been reported in dinuclear derivatives.5
*Corresponding author. Fax: þ39 041 234 8917. E-mail: albertin@
unive.it.
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knowledge, no sandwich complex containing η5-fluorenyl and η6-arene
ligands has yet been reported. For recent papers on η5-fluorenyl com-
plexes see: (a) Kirillov, E.; Kahlal, S.; Roisnel, T.; Georgelin, T.;
Saillard, J.-Y.; Carpentier, J.-F. Organometallics 2008, 27, 387–393.
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r
2009 American Chemical Society
Published on Web 07/02/2009
pubs.acs.org/Organometallics

4476 Organometallics, Vol. 28, No. 15, 2009
Albertin et al.
Chart 1
0.4 mmol of the appropriate complex RuCl2(η6-p-cymene)P, an
excess of diazoalkane (1.2 mmol), an excess of NaBPh4
(0.6 mmol, 0.20 g), and 10 mL of ethanol. The reaction mixture
was stirred at room temperature for 24 h, and then the solid that
formed was filtered and crystallized from CH2Cl2 and ethanol;
yield g75%.
1
1a: IR (KBr) cm-1: νCdN = N 1925 (s). H NMR (CD2Cl2,
25 °C) δ: 7.75-6.88 (m, 35H, Ph), 5.67, 5.58, 5.37 (d, 4H, Ph
p-cym), 3.82, 3.70, 3.53 (m, 4H, CH2), 2.48 (m, 1H, CH), 1.85
(s, 3H, p-CH3), 1.14, 1.12 (d, 6H, CH3 iPr), 1.11 (t, 6H, CH3
phos). 31P{1H} NMR (CD2Cl2, 25 °C) δ: A spin system, 139.4 s.
Anal. Calcd for C57H59BClN2O2PRu: C, 69.69; H, 6.05; Cl,
3.68; N, 2.90. Found: C, 69.53; H, 6.13; Cl, 3.47; N, 2.78. ΛM=
56.3 Ω-1 mol-1 cm2.
2a: IR (KBr) cm-1: νCdNdN 1938 (s). 1H NMR (CD2Cl2, 25
°C) δ: 7.69-6.87 (m, 34H, Ph), 5.66, 5.58, 5.39 (d, 4H, Ph
p-cym), 3.82, 3.73, 3.55 (m, 4H, CH2), 2.43 (s, 3H, p-CH3
alkane), 2.40 (m, 1H, CH), 1.85 (s, 3H, p-CH3 p-cym), 1.13,
1.10 (d, 6H, CH3 iPr), 1.16, 1.10 (t, 6H, CH3 phos). 31P{1H}
NMR (CD2Cl2, 25 °C) δ: A spin system, 139.4 s. 13C{1H} NMR
(CD2Cl2, 25 °C) δ: 160-120 (m, Ph), 105.6, 98.9, 88.6, 80.9 (s, Ph
p-cym), 64.9 (d, CH2), 30.8 (s, CH), 24.2 (s, CH3 iPr), 21.9 (s, p-
CH3 alkane), 17.8 (s, p-CH3 p-cym), 16.4 (d, CH3 phos). Anal.
Calcd for C58H61BClN2O2PRu: C, 69.91; H, 6.17; Cl, 3.56; N,
2.81. Found: C, 69.78; H, 6.11; Cl, 3.40; N, 2.72. ΛM=52.8 Ω-1
mol-1 cm2.
containing both η5-alkoxyfluorenyl and η6-p-cymene as
ligands.
The results of these studies, which include the synthesis of
new diazoalkane complexes of ruthenium and of a novel
sandwich derivative, are reported here.
Experimental Section
2b: IR (KBr) cm-1: νCdNdN 1920 (s). 1H NMR (CD2Cl2, 25
°C) δ: 7.49-6.87 (m, 29H, Ph), 5.89, 5.49 (d, 4H, Ph p-cym),
4.19, 4.08 (qnt, 6H, CH2), 2.72 (m, 1H, CH), 2.43 (s, 3H, p-CH3
alkane), 2.09 (s, 3H, p-CH3 p-cym), 1.26, 1.24 (d, 6H, CH3 iPr),
1.14 (t, 9H, CH3 phos). 31P{1H} NMR (CD2Cl2, 25 °C) δ: A spin
system, 112.3 s. Anal. Calcd for C54H61BClN2O3PRu: C, 67.25;
H, 6.38; Cl, 3.68; N, 2.90. Found: C, 67.11; H, 6.47; Cl, 3.50; N,
2.78. ΛM=56.1 Ω-1 mol-1 cm2.
General Comments. All synthetic work was carried out in an
appropriate atmosphere (Ar) using standard Schlenk techniques
or an inert atmosphere drybox. Once isolated, the complexes
were found to be relatively stable in air, but were stored under
nitrogen at -25 °C. All solvents were dried over appropriate
drying agents, degassed on a vacuum line, and distilled into
vacuum-tight storage flasks. RuCl3 3H2O was a Pressure Che-
3
mical Co. (USA) product, used as received. Phosphite PPh
(OEt)2 was prepared by the method of Rabinowitz and Pellon,11
while P(OEt)3 was an Aldrich product purified by distillation
under nitrogen. Diaryldiazoalkanes (Ar1Ar2CN2) and 9-diazo-
fluorene (C12H8CN2) were prepared according to literature
procedures.12 Other reagents were purchased from commercial
sources in the highest available purity and used as received.
Infrared spectra were recorded on a Perkin-Elmer Spectrum-
One FT-IR spectrophotometer. NMR spectra (1H, 31P, 13C)
were obtained on AC200 or AVANCE 300 Bruker spectro-
meters at temperatures between -90 and þ30 °C, unless other-
wise noted. 1H and 13C spectra are referred to internal
tetramethylsilane, and 31P{1H} chemical shifts are reported with
respect to 85% H3PO4 with downfield shifts considered positive.
COSY, HMQC, and HMBC NMR experiments were per-
formed with standard programs. The SwaN-MR and iNMR
software packages13 were used to treat NMR data. The con-
ductivity of 10-3 mol dm-3 solutions of the complexes in
CH3NO2 at 25 °C was measured on a Radiometer CDM 83.
Elemental analyses were determined in the Microanalytical
Laboratory of the Dipartimento di Scienze Farmaceutiche,
University of Padova (Italy).
[Ru(η5-EtO-fluorenyl)(η6-p-cymene)]BPh4 (3a). In a 25 mL
three-necked round-bottomed flask were placed 300 mg
(0.64 mmol) of solid RuCl2(η6-p-cymene)(PiPr3), an excess of 9-
diazofluorene (C12H8CN2) (2.0 mmol, 0.38 g), an excess of
NaBPh4 (1.0 mmol, 0.34 g), and 10 mL of ethanol. The reaction
mixture was stirred for 24 h, and then the brown solid formed was
filteredandcrystallizedfrom CH2Cl2 and ethanol. Orange crystals
of the complex were obtained by diffusion of ethanol into an
acetone solution of the crystallized compound; yield g55%.
1H NMR (CD2Cl2, 25 °C) δ: 8.18-6.88 (m, 28H, Phþfluor-
enyl), 5.06, 4.95 (d, 4H, Ph p-cym), 4.32 (q, 2H, OCH2), 1.93 (m,
1H, CH), 1.60 (s, 3H, p-CH3), 1.51 (t, 3H, CH3 OEt), 1.10 (d, 6H,
CH3 iPr). 13C{1H} NMR (CD2Cl2, 25 °C) δ: 165-120 (m,
Phþfluorenyl), 108.1, 97.6, 88.05, 84.6 (s, Ph p-cym), 71.7 (s,
OCH2), 30.2 (s, CH), 22.3 (s, CH3 iPr), 16.7 (s, p-CH3), 15.9 (s,
CH3 OEt). Anal. Calcd for C49H47BORu: C, 77.05; H, 6.20.
Found: C, 77.17; H, 6.14. ΛM=55.3 Ω-1 mol-1 cm2.
[Ru(η5-MeO-fluorenyl)(η6-p-cymene)]BPh4 (3b). This com-
plex was prepared exactly like the related ethoxyfluorenyl 3a,
but using methanol as a solvent; yield g60%.
1H NMR (CD2Cl2, 25 °C) δ: 8.20-6.86 (m, 28H, Phþfluor-
enyl), 5.07, 4.95 (d, 4H, Ph p-cym), 4.11 (s, 3H, OCH3), 1.87 (m,
1H, CH), 1.54 (s, 3H, p-CH3), 1.07 (d, 6H, CH3 iPr). 13C{1H}
NMR (CD2Cl2, 25 °C) δ: 165-122 (m, Phþfluorenyl), 107.97,
87.0, 84.4 (s, Ph p-cym), 62.4 (s, OCH3), 30.0 (s, CH), 22.2 (s, CH3
iPr), 16.6 (s, p-CH3). Anal. Calcd for C48H45BORu: C, 76.89; H,
6.05. Found: C, 76.75; H 6.12. ΛM=49.8 Ω-1 mol-1 cm2.
Crystal Structure Determination of [Ru(η5-EtO-fluorenyl)(η6-
p-cymene)]BPh4 (3a). Intensity data sets were collected using a
Bruker SMART APEX 2 CCD diffractometer at RIAIDT-CAC-
TUS (Universidade de Santiago de Compostela) using graphite-
monochromated Mo KR radiation (λ = 0.71073 A) at 293 K
and were corrected for Lorentz and polarization effects. The
software APEX215 was used for collecting frames of data, indexing
Synthesis of Complexes. The compounds RuCl2(η6-p-cymene)
P [P=P(OEt)3, PPh(OEt)2, PiPr3] were prepared following the
method previously described.14
[RuCl(N2CAr1Ar2)(η6-p-cymene)P]BPh4 (1, 2) [Ar1=Ar2=
Ph (1); Ar1=Ph, Ar2=p-tolyl (2); P=PPh(OEt)2 (a), P(OEt)3
(b)]. In a 25 mL three-necked round-bottomed flask were placed
(11) Rabinowitz, R.; Pellon, J. J. Org. Chem. 1961, 26, 4623–4626.
(12) (a) Smith, L. I.; Howard, K. L. Organic Syntheses; Wiley:
New York, 1955; Vol. III, p 351. (b) Miller, J. B. J. Org. Chem. 1959, 24,
560. (c) Baltzly, R.; Mehta, N. B.; Russell, P. B.; Brooks, R. E.; Grivsky,
E. M.; Steinberg, A. M. J. Org. Chem. 1961, 26, 3669.
(13) Balacco, G. J. Chem. Inf. Comput. Sci. 1994, 34, 1235–1241http://
www.inmr.net/.
(14) Albertin, G.; Antoniutti, S.; Castro, J.; Paganelli, S. Manuscript
in preparation.
(15) APEX2, v2.0-1; Bruker AXS Inc.: Madison, WI, 2005.

Article
Table 1. Crystal Data and Structure Refinement for 3a
Organometallics, Vol. 28, No. 15, 2009 4477
Scheme 1a
empirical formula
fw
temperature
wavelength
cryst syst
C98H94B2O2Ru2
1527.49
296(2) K
0.71073 A
triclinic
P-1
a =12.0598(5) A
b =14.7273(8) A
c =21.7163(11) A
R = 82.678(3)°
β = 80.261(2)°
γ = 88.684(3)°
3770.4(3) A3
space group
unit cell dimens
a Ar1=Ar2=Ph (1); Ar1=Ph, Ar2=p-tolyl (2); P=PPh(OEt)2 (a), P
(OEt)3 (b).
Scheme 2
volume
Z
density (calcd)
absorp coeff
F(000)
2
1.345 Mg/m3
0.453 mm-1
1592
cryst size
θ range for data collection
index ranges
0.19 ꢀ 0.12 ꢀ 0.09 mm
0.96 to 26.41°
-15 e h e 15; -18 e k e 18;
-26 e l e 27
reflns collected
indep reflns
reflns obsd (>2σ)
data completeness
absorp corr
max. and min transmn
refinement method
data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
largest diff peak and hole
52 260
15 348 [R(int) = 0.0867]
9689
0.991
semiempirical from equivalents
1.000 and 0.821
full-matrix least-squares on F2
15 348/0/945
2.43 ppm for both 2a and 2b of the p-tolyl substituents of the
diazoalkane; the 31P{1H} NMR spectra appear as a sharp
singlet, fitting the proposed formulation for the complexes.
Diazoalkane complexes of ruthenium are1-5 rare and,
apart from Ru(CO)2(N2R)(PPh3)2 (N2R=N2C5Cl4, 9-dia-
zofluorene),4d which contains an (η2-N,N) side-on coordina-
tion mode of the diazo group, they are all di- or polynuclear
complexes with bridging diazo ligands.2,5d-5f The use of half-
sandwich p-cymene complexes with one phosphite as a
supporting ligand allowed the preparation of new Ru dia-
zoalkane derivatives with the-for this metal-unprece-
dented (η1-N) end-on coordination mode.
0.989
R1 = 0.0492 wR2 = 0.0823
R1 = 0.0982 wR2 = 0.0974
0.552 and -0.539 e A-3
reflections, determination of lattice parameters, integration of
intensity of reflections, and scaling, and SADABS16 for empirical
absorption correction. The crystal structure was solved and refined
with the Oscail program17 by Patterson methods and refined by
full-matrix least-squares based on F2.18 Non-hydrogen atoms were
refined with anisotropic displacement parameters. Hydrogen
atoms were included in idealized positions and refined with
isotropic displacement parameters. Details of crystal data and
structural refinement are given in Table 1.
The reaction of the p-cymene complexes RuCl2(η6-p-cym-
ene)P was also extended to the 9-diazofluorene C12H8CN2,
but, in this case, no stable diazoalkane complex was ob-
tained. Surprisingly, the half-sandwich complex RuCl2(η6-p-
cymene)(PiPr3), containing triisopropylphosphine instead of
phosphite, reacted with 9-diazofluorene20 to give an orange
solid, which was characterized as the (η5-ethoxyfluorenyl)
(η6-p-cymene)-sandwich derivative [Ru(η5-EtO-fluorenyl)
(η6-p-cymene)]BPh4 (3a) (Scheme 2).
The formation of this novel sandwich complex was un-
expected, but may be explained as due to the initial coordi-
nation of 9-diazofluorene to the ruthenium center to give a
diazoalkane complex [A] (Scheme 3) like those obtained with
phosphites 1 and 2.
The coordinated 9-diazofluorene is probably unstable in
[A] and, after presumed rearrangement to a C-bonded
diazoalkane [B]21 and subsequent loss of N2, can yield the
carbene intermediate [C]. The carbene carbon atom in com-
plex [C] probably has such an electrophilic character that it
undergoes nucleophilic attack by the oxygen atom of etha-
nol, giving the ethoxyfluorenyl anion C12H8COEt- after
deprotonation. The η5-coordination of this anion is prob-
ably easy in the hypothesized η1-fluorenyl intermediate [D]
Results and Discussion
Half-sandwich p-cymene complexes RuCl2(η6-p-cymene)
P (P=phosphite)14 react with diaryldiazoalkanes Ar1Ar2-
CN2 to give diazoalkane complexes [RuCl(N2CAr1Ar2)-
(η6-p-cymene)P]BPh4 (1, 2), which were isolated in good
yields and characterized (Scheme 1).
Crucial for successful synthesis is the use of ethanol as solvent,
containing 1 equiv of NaBPh4. The presence of the sodium salt
probably favors the substitution of chloride by diazolkane and
allows the separation of complexes as BPh-4 salts.
Good analytical data were obtained for diazoalkane com-
plexes 1 and 2, which are reddish-brown stable solids and
soluble in polar organic solvents, in which they behave as 1:1
electrolytes.19 The IR spectra show a medium-intensity band
at 1920-1938 cm-1, attributed to νCdNdN of the diazoalk-
ane ligand. These values also suggest2,4c,4e,5a singly bent
geometry (I) for the Ar1Ar2CN2 group.
Apart from the signals characteristic of the p-cymene and
1
phosphite ligands, the H NMR spectra show a singlet at
(20) The reaction of the triisopropylphosphine complex RuCl2(η6-p-
cymene)(PiPr3) was also studied with Ar1Ar2CN2 (Ar1=Ar2=Ph or
Ar1=Ph, Ar2=p-tolyl), but in this case neither a stable diazoalkane
complex nor a carbene derivative was isolated. An oily product contain-
ing a mixture of unidentified species was separated from the reaction.
(21) As suggested by a reviewer, N2 loss does not occur from N-
coordinated diazoalkane, and probable rearrangement of [A] to a C-
bonded diazoalkane [B] precedes N2 loss.
(16) Sheldrick, G. M. SADABS, An empirical absorption correction
€
program for area detector data; University of Gottingen: Germany, 1996.
(17) McArdle, P. J. Appl. Crystallogr. 1995, 28, 65–65.
(18) Sheldrick, G. M. SHELX-97, Program for the solution and
€
refinement of crystal structures; University of Gottingen: Germany, 1997.
(19) Geary, W. J. Coord. Chem. Rev. 1971, 7, 81–122.

4478 Organometallics, Vol. 28, No. 15, 2009
Albertin et al.
Scheme 3a
a P = PiPr3; R = Et (a), Me (b).
a
˚
Table 2. Selected Bond Lengths [A] and Angles [deg] for 3a
molecule 1 molecule 2
Ru(1)-C(11)
2.219(4)
2.200(4)
2.195(4)
2.224(3)
2.214(4)
2.188(4)
1.6937(3)
2.184(3)
2.245(4)
2.209(4)
2.238(3)
2.215(3)
1.8473(3)
179.24(2)
Ru(2)-C(31)
2.213(3)
2.213(3)
2.205(4)
2.232(4)
2.224(4)
2.179(3)
1.8541(3)
2.217(3)
2.256(3)
2.210(3)
2.229(3)
2.201(3)
1.7008(3)
177.67(2)
Ru(1)-C(12)
Ru(1)-C(13)
Ru(1)-C(14)
Ru(1)-C(15)
Ru(1)-C(16)
Ru(1)-Ct11
Ru(2)-C(32)
Ru(2)-C(33)
Ru(2)-C(34)
Ru(2)-C(35)
Ru(2)-C(36)
Ru(2)-Ct21
Ru(1)-C(29)
Ru(1)-C(210)
Ru(1)-C(211)
Ru(1)-C(212)
Ru(1)-C(213)
Ru(1)-Ct12
Ru(2)-C(49)
Ru(2)-C(410)
Ru(2)-C(411)
Ru(2)-C(412)
Ru(2)-C(413)
Ru(2)-Ct22
Ct11-Ru(1)-Ct12
Ct21-Ru(2)-Ct22
a Ct11 and Ct21 locate the centroid of the p-cymene ligand. Ct12 and
Ct22 locate the centroid of the fluorenyl ligand pentagon.
Solution of the crystalline structure gives two cations and
two anions in the asymmetric unit. The perspective view of
one of the two cations is shown in Figure 1. The compound
crystallized in the triclinic space group P1, and any attempt
to find more symmetry in order to reduce the molecules in the
asymmetric unit was unsuccessful, as both cations show
slight differences in the conformation of the ethoxy group.
Other metrical parameters of two cations were identical
within the range of experimental errors of the diffraction
experiments.
The geometry of the molecule is a typical, regular sand-
wich with a nearly linear Centroid-Ru-Centroid angle of
average 178.45(2)°. Both planar ligands are almost parallel,
with a dihedral plane of 0.8(2)° and 4.4 (2)°. The Ru-C
distances (A) (see Table 2) are between the values 2.179(3)
and 2.256(3) A.
The coordination of the ethoxy-fluorenyl ligand to the
ruthenium atom is clearly η5, with C-Ru bond distances
ranging between 2.184(3) and 2.256(3) A and also showing a
small range of only 0.07 A. The average distance from the
metal atom to the centroid of the pentagon is 1.8507(3) A,
and that from the metal atom to the best plane formed by the
five carbon atoms is also 1.851(2) A. The fluorenyl ligand is
planar, with a maximum deviation of 0.093(3) A for C(29)
and 0.071(3) A for C(49), showing that it is slightly folded
around this carbon bridge, with dihedral angles between
benzene planes of 6.3(2)° and 4.5(2)° in both molecules.
The 1H and 13C NMR spectra are diagnostic for the
presence of both the alkoxyfluorenyl and p-cymene rings.
Figure 1. One of the cations of the asymmetric unit of 3a drawn
at the 50% probability level.
and involves substitution of both phosphine and chloride to
afford the final η5-ethoxyfluorenyl sandwich complex 3a.
Besides the well-known precedents of intermediates [A]
and [C], support for this reaction path22 came from the use of
methanol as solvent, which yielded (η5-methoxyfluorenyl)-
(η6-p-cymene)-sandwich complex [Ru(η5-MeO-fluorenyl)-
(η6-p-cymene)]BPh4 (3b).
Sandwich complexes with the η5-fluorenyl ligand are
rather rare10 and often contain η5- cyclopentadienyl as a
supporting ligand. The reaction of 9-diazofluorene with the
half-sandwich η6-p-cymene complexes RuCl2(η6-p-cymene)-
(PiPr3) allows preparation of a new type of cationic sandwich
complexes with alkoxyfluorenyl and p-cymene as ligands.
Complexes 3 were isolated as yellow-orange microcrystal-
line solids and were characterized spectroscopically (IR, 1H,
13C NMR) and by X-ray crystal structure determination of
[Ru(η5-EtO-fluorenyl)(η6-p-cymene)]BPh4 (3a).
(22) 9-Diazofluorene has been reported to react with manganese
carbonyl complexes to give polynuclear derivatives containing an
appended (fluorenyl)Mn(CO)3 unit, forming as a result of a C-C
coupling reaction. A complex like [C] has been involved as an inter-
mediate in the proposed mechanism: Michon, C.; Djukic, J.-P.;
Ratkovic, Z.; Collin, J.-P.; Pfeffer, M.; de Cian, A.; Fischer, J.; Heiser,
€
D.; Dotz, K. H.; Nieger, M. Organometallics 2002, 21, 3519–3535.

Article
Organometallics, Vol. 28, No. 15, 2009 4479
In the high-frequency region of the proton spectra of 3a and
3b, a multiplet of the fluorenyl hydrogen atoms appears
between 8.20 and 7.80 ppm, and the signals of the alkoxy
substituents were found at 4.32 (q) and 1.51 (t) ppm for
C2H5O (3a) and at 4.11 (s) for CH3O (3b). The characteristic
signals of the p-cymene ligand were also observed in both 1H
and 13C spectra. In addition, the fluorenyl carbon resonances
of 3a and 3b appear as multiplets between 165 and 145 ppm
in the 13C NMR spectra, whereas the alkoxy substituents
are singlets at 71.7 (OCH2) and 15.9 ppm (CH3) for 3a
and at 62.4 ppm (CH3O) for 3b, matching the proposed
formulation.
Acknowledgment. The financial support of MIUR
(Rome)-PRIN 2008 is gratefully acknowledged. We
ꢁ
thank Mrs. Daniela Baldan, from the Universita Ca’
Foscari Venezia (Italy), for her technical assistance.
ꢀ
Dr. J. Romero and Dr. J. A. Garcıa-Vazquez, from the
´
University of Santiago de Compostela (Spain), are grate-
fully acknowledged for their help in the crystallographic
data collection.
Supporting Information Available: Crystallographic data for
compound 3a: CIF and Figures S1 and S2 (pdf). This material is
available free of charge via the Internet at http://pubs.acs.org.