Novel straightforward access to a 2,2′-bipyridine ligand bearing two (η2-dppe)(η5-C5Me 5)FeC≡C- redox-active substituents by homocoupling of mononuclear organoiron(II) 2-bromopyridyl synthons

Article abstract of DOI:10.1021/om800388j

We report in this contribution the synthesis and characterization of the two organoiron(II) (η²-dppe)(η⁵-C ₅Me₅)FeC≡C-(5,2-C₅H₃N-X) compounds (X = Cl, 6a; X -Br, 6b) bearing a pendant halogenated m-pyridyl group. These new functional metallo-ligands allow for an original, convenient, and rapid synthetic access to the 2,2′-bipyridine (bipy) ligand (3) bearing two redox-active (η²- dppe(η⁵-C₅Me₅)FeC≡ C- organometallic moieties grafted to the 5,5′-positions of bipy via a Pd-catalyzed homocoupling procedure.

Full text of DOI:10.1021/om800388j

4260
Organometallics 2008, 27, 4260–4264
Novel Straightforward Access to a 2,2′-Bipyridine Ligand Bearing
Two “(η2-dppe)(η5-C5Me5)FeCt C-” Redox-Active Substituents by
Homocoupling of Mononuclear Organoiron(II) 2-Bromopyridyl
Synthons
Fre´de´ric Justaud,† Gilles Argouarch,† Safaa Ibn Ghazala,† Loic Toupet,‡ Fre´de´ric Paul,*,†
and Claude Lapinte*,†
UMR CNRS 6226, Sciences Chimiques de Rennes, and UMR CNRS 6251, Institut de Physique, UniVersite´
de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
ReceiVed May 2, 2008
We report in this contribution the synthesis and characterization of the two organoiron(II) (η2-dppe)(η5-
C5Me5)FeCt C-(5,2-C5H3N-X) compounds (X ) Cl, 6a; X ) Br, 6b) bearing a pendant halogenated
m-pyridyl group. These new functional “metallo-ligands” allow for an original, convenient, and rapid
synthetic access to the 2,2′-bipyridine (bipy) ligand (3) bearing two redox-active “(η2-dppe)(η5-C5Me5)FeCt
C-” organometallic moieties grafted to the 5,5′-positions of bipy via a Pd-catalyzed homocoupling
procedure.
Judicious spatial or topologic arrangements of redox-active
in our group.6,7 Although the targeted compound 3 could be
isolated and characterized according to this synthesis, its yield
as an isolated compound proved very poor (e15%) due to its
difficult purification, which was based on a repetitive fractional
recrystallization procedure. Now, the exploration of the coor-
dination chemistry of this fascinating “metallo-ligand” evidently
requires its isolation in good yields. We therefore logically
wondered if an alternative approach based on the catalytic
coupling of organoiron synthons such as 6a,b (Chart 1) might
not provide an easier access to 3. Moreover, such an approach
in which the bipyridine moiety is formed in the last synthetic
step should prevent to some extent any undesired side reaction
that might happen between this chelating site and organoiron
compounds present in the reaction medium.8
end groups can lead to molecular architectures presenting unique
properties for information storage or information processing at
the molecular level.1 On the basis of that statement, we have
previously reported on the synthesis of several ubiquitous
chelating ligands incorporating redox-active “(η2-dppe)(η5-
C5Me5)FeCt C-” fragments such as 1-3 (Chart 1).2,3 Related
alkynyl electron-rich metallo-ligands bearing one redox-active
site connected to a diimine unit have been scarce in the literature
until now.4 Moreover, to the best of our knowledge, with the
exception of 2 and 3, no other polydentate ligand carrying
seVeral such redox-active organometallic end groups has been
reported so far.5
Compound 3 was previously isolated using a bis-Sonogashira
coupling reaction between the known acetylide complex (η2-
dppe)(η5-C5Me5)FeCt CH (4) and 5,5′-dibromo-2,2′-bipyridine
(5),3 following a coupling protocol which had ample precedence
In this contribution, we disclose such a synthetic pathway.
Remarkably, the fact that 3 could be straightforwardly obtained
by extending a known Pd-based homocoupling procedure to the
bromopyridyl compound 6b emphasizes the interest of this class
of functional organometallics as potent building blocks.
* To whom correspondence should be addressed. E-mail: frederic.paul@
univ-rennes1.fr (F.P.); claude.lapinte@univ-rennes1.fr (C.L.). Tel: (33) 02
23 23 64 97. Fax: (33) 02 23 23 52 92.
Results and Discussion
We initially started our investigations with the chloro complex
6a, using a Ni-based protocol.9,10 The synthesis of the required
starting mononuclear precursor 6a was readily achieved fol-
lowing the “so-called” metalla-Sonogashira approach from 4
† UMR CNRS 6226, Sciences Chimiques de Rennes.
‡ UMR CNRS 6251, Institut de Physique.
(1) (a) Balzani, V.; de Silva, A. P. Electron Transfer in Chemistry;
Wiley-VCH: Weinheim, Germany, 2000; Vol. 5. (b) Norgaard, K.;
Bjornholm, T. Chem. Commun. 2005, 1812–1823. (c) Gianneschi, N. C.;
Masar, M. S., III; Mirkin, C. A. Acc. Chem. Res. 2005, 38, 825–837. (d)
Lehn, J.-M. Angew. Chem., Int. Ed. Engl. 1990, 29, 1304–1319. (e) Lehn,
J. M. Supramolecular Chemistry-Concepts and PerspectiVes, VCH: Wein-
heim, Germany, 1995.
(2) Ibn Ghazala, S.; Gauthier, N.; Paul, F.; Toupet, L.; Lapinte, C.
Organometallics 2007, 26, 2308–2317.
(3) Paul, F.; Goeb, S.; Justaud, F.; Argouarch, G.; Toupet, L.; Ziessel,
R. F.; Lapinte, C. Inorg. Chem. 2007, 46, 9036–9038.
(4) (a) Fan, Y.; Zhang, L.-Y.; Dai, F.-R.; Shi, L.-X.; Chen, Z.-N. Inorg.
Chem. 2008, 47, 2811–2819. (b) Cifuentes, M. P.; Humphrey, M. G.;
Koutsantonis, G. A.; Lengkeek, N. A.; Petrie, S.; Sanford, V.; Schauer,
P. A.; Skelton, B. W.; Stranger, R.; White, A. H. Organometallics 2008,
27, 1716–1726. (c) Xu, H.-B.; Zhang, L.-Y.; Xie, Z.-L.; Ma, E.; Chen,
Z.-N. Chem. Commun. 2007, 2744–2746. (d) Wong, C.-Y.; Tong, G. S. M.;
Che, C.-M.; Zhu, N. Angew. Chem., Int. Ed. 2006, 45, 2694–2698. (e)
Yamamoto, Y.; Shiotsuka, M.; Okuno, S.; Onaka, S. Chem. Lett. 2004, 33,
210–211.
(5) Several ferrocene derivatives have been reported, though; see for
instance: (a) Siemeling, U.; Vor der Bru¨ggen, J.; Vorfeld, U.; Neumann,
B.; Stammler, A.; Stammler, H.-G.; Brockhinke, A.; Plessow, R.; Zanello,
P.; Laschi, F.; de Biani, F. F.; Fontani, M.; Steenken, S.; Stapper, M.;
Gurzadayan, G. Chem. Eur. J. 2003, 9, 2819–2833. (b) Siemeling, U.;
Vorfeld, U.; Neumann, B.; Stammler, H.-G.; Zanello, P.; Fabrizi de Biani,
F. Eur. J. Inorg. Chem. 1999, 1–5. (c) Butler, I. R.; McDonalds, S. J.;
Hursthouse, M. B.; Malik, K. M. A. Polyhedron 1995, 14, 529–539. (d)
Constable, E. C.; Edwards, A. J.; Martinez-Manes, R.; Raithby, P. R.;
Thompson, A. M. W. G. J. Chem. Soc., Dalton Trans. 1994, 645–650.
(6) Denis, R.; Weyland, T.; Paul, F.; Lapinte, C. J. Organomet. Chem.
1997, 545/546, 615–618.
(7) Le Stang, S.; Lenz, D.; Paul, F.; Lapinte, C. J. Organomet. Chem.
1998, 572, 189–192.
(8) Ibn Ghazala, S.; Paul, F.; Toupet, L.; Lapinte, C. J. Organomet.
Chem. 2007, 692, 917–920.
10.1021/om800388j CCC: $40.75
2008 American Chemical Society
Publication on Web 08/01/2008

Straightforward Access to a 2,2′-Bipyridine Ligand
Organometallics, Vol. 27, No. 16, 2008 4261
Chart 1. Selected Pyridine-Based Organometallic Complexes
Scheme 1. Synthesis of 6a
(Scheme 1) and the commercially available 2-chloro-5-iodopy-
couplings,12 we feared that the metalla-Sonogashira coupling
reaction between 4 and commercial 2-bromo-5-iodopyridine (7b)
might prove less selective than in the case of 7a. Thus, isolation
of the compound 6b was also attempted from the chloro complex
8 and the preformed organic alkyne 9 following the classic
activation approach (Scheme 2).6,13 By any of these routes, the
desired compound was successfully isolated in more than 70%
yield. In spite of slightly lower yields, the former route to 3
starting from the chloro complex 8 and the 2-bromo-5-
ethynylpyridine 9 (reaction i, Scheme 2) is more easily amenable
to large-scale syntheses than is the catalytic approach starting
from 4 and 7b (reaction ii, Scheme 2), especially when
considering that the organic alkyne 9 can simply be isolated in
good yields from the commercial 2-bromo-5-iodopyridine 7b
(>70%).14 The new compound 6b was characterized, and its
solid-state structure was also solved (Figure 1).
ridine (7a).6,7 This reaction was performed at ambient temper-
ature in order to avoid any undesired coupling at the
carbon-chlorine bond. Good yields of the new compound 6a
were obtained. This key compound was fully characterized, and
its solid-state structure was solved (Figure 1).
The Ni-based homocoupling of 6a was subsequently at-
tempted. However, the desired product 3 could not be isolated
according to the classic procedure (see the Supporting Informa-
tion).10 We then tried a Pd-based homocoupling protocol
recently reported by Lemaire and co-workers for a similar
coupling reaction with organic 2-halopyridines.11 In contrast to
the former reaction, this alternative procedure slowly but
selectively generated the desired complex 3. The desired
complex 3 is formed in a 2:1 ratio along with unreacted starting
compound 6a after ca. 50 h of reaction. However, the separation
of 3 from 6a proved to be quite difficult. At this stage, the next
step in order to improve this homocoupling reaction and to
obtain 3 in good yields was to repeat it with an organometallic
substrate, such as 6b, presenting a more reactive aryl-halogen
bond toward oxidative addition than 6a.
The compound 6b was then tested in the aforementioned Pd-
based homocoupling reaction. As expected, 3 was quantitatively
formed in the medium after 16 h (Scheme 3). Notably, when
this reaction was repeated several times, the known m-pyridyl
compound 10 was formed in low and variable amounts in some
runs.15 However, the desired complex 3 could be conveniently
The synthesis of 6b was therefore undertaken. However,
considering the increased reactivity of the halogen atoms when
appended in positions ortho to nitrogen in heterocycles along
with the high reactivity of bromine-aryl bonds in Sonogashira
(12) (a) Diederich, F.; Stang, P. J. Metal-Catalyzed Cross-Coupling
Reactions; Wiley-VCH: Weinheim, Germany, 1998. (b) Campbell, I. B. In
Organocopper Reagents-A Practical Approach; Taylor, J. K., Ed.; Oxford
University Press: Oxford, U.K., 1994; pp 216-235.
(13) (a) Denis, R.; Toupet, L.; Paul, F.; Lapinte, C. Organometallics
2000, 19, 4240–4251. (b) Connelly, N. G.; Gamasa, M. P.; Gimeno, J.;
Lapinte, C.; Lastra, E.; Maher, J. P.; Le Narvor, N.; Rieger, A. L.; Rieger,
P. H. J. Chem. Soc., Dalton Trans. 1993, 2575–2578.
(9) (a) Fanni, S.; Di Pietro, C.; Serroni, S.; Campagna, S.; Vos, J. G.
Inorg. Chem. Commun. 2000, 3, 42–44. (b) Griffiths, P. M.; Loiseau, F.;
Puntoriero, F.; Serroni, S.; Campagna, S. Chem. Commun. 2000, 2297–
2298.
(10) (a) Ford, A.; Sinn, E.; Woodward, S. J. Chem. Soc., Perkin Trans.
1 1997, 927–934. (b) Colon, I.; Kesley, D. R. J. Org. Chem. 1986, 51,
2627–2637.
(14) Baxter, P. N. W. J. Org. Chem. 2000, 65, 1257–1272.
(15) Le Stang, S.; Paul, F.; Lapinte, C. Inorg. Chim. Acta 1999, 291,
403–425.
(11) Hassan, J.; Penalva, J.; Lavenot, L.; Gozzi, C.; Lemaire, M.
Tetrahedron 1998, 54, 13793–13804.

4262 Organometallics, Vol. 27, No. 16, 2008
Justaud et al.
Figure 1. ORTEP representations of the complexes (a) 6a and (b) 6b with displacement ellipsoids at the 50% probability level. Selected
distances (Å) and angles (deg): 6a, Fe1-(Cp*)centroid ) 1.733, Fe1-P1 ) 2.1748(8), Fe1-P2 ) 2.1808(8), Fe1-C37 ) 1.899(3), C37-C38
) 1.217(4), C38-C39 ) 1.433(4), C39-C40 ) 1.404(4), C40-C41 ) 1.378(4), C41-C42 ) 1.379(4), C39-C43 ) 1.397(4), N1-C42
) 1.315(4), N1-C43 ) 1.347(4), Cl1-C42 ) 1.755(3), P1-Fe1-P2 ) 86.82(3), Fe1-C37-C38 ) 178.1(2), C37-C38-C39 ) 174.4(3),
C43-C39-Fe1-(Cp*)centroid ) -69.7; 6b, Fe1-(Cp*)centroid ) 1.743, Fe1-P1 ) 2.1808(6), Fe1-P2 ) 2.1888(6), Fe1-C37 ) 1.894(2),
C37-C38 ) 1.217(3), C38-C39 ) 1.435(3), C39-C40 ) 1.382(3), C40-C41 ) 1.378(4), C41-C42 ) 1.360(3), C39-C43 ) 1.386(3),
N1-C40 ) 1.343(3), N1-C41 ) 1.306(4), Br1-C41 ) 1.921(2), P1-Fe1-P2 ) 86.68(2), Fe1-C37-C38 ) 179.4(2), C37-C38-C39
) 173.6(2), C43-C39-Fe1-(Cp*)centroid ) 117.3.
Scheme 2. Syntheses of 6ba
a
Isolated yields: reaction i, 70%; reaction ii, 79%.
separated from this side product by exploiting their different
solubilities in organic solvents.
In conclusion, a new, original, and efficient synthetic homo-
coupling procedure involving mononuclear organoiron(II) in-
termediates could be devised, allowing us to isolate 3 in good
yields following a quite straightforward workup. This reaction
opens now the way to the exploration of the coordination
chemistry of this fascinating metallo-ligand. Notably, only scant
examples of such catalyzed couplings occurring in the coordina-
tion sphere of electron-rich metal centers present as substituents
(spectators) on functional (hetero)aryl rings have been reported
so far.9,19 Thus, in line with these recent studies, it seems that
Pd-catalytic procedures involving organometallic building blocks
offer very appealing synthetic alternatives to more classic
approaches, where introduction of the metal centers is usually
performed at the end of the synthetic sequence. With this in
mind, we now intend to explore the coupling chemistry of
functional 2-bromo-5-pyridylacetylide complexes such as 6b in
a more systematic way.
Thus, this new route constitutes a convenient preparative
access to the metallo-ligand 3. Its overall yield over two steps
(Schemes 2 and 3) compares very favorably with that of the
previous synthesis (46% vs 15%). Then, recalling that 4 is itself
isolated in two steps from the chloro complex 8,16 the isolation
of 6b in 70% yield from the same precursor constitutes a very
appealing synthetic approach for obtaining large quantities of
3 via the organometallic precursor 6b.17 Moreover, this synthesis
can be undertaken from commercially available precursors such
as 2-bromo-5-iodopyridine (7b) or (trimethylsilyl)acetylene (11),
in contrast to that previously reported requiring the more
involved preparation of 5.18
(16) Le Narvor, N.; Toupet, L.; Lapinte, C. J. Am. Chem. Soc. 1995,
117, 7129–7138.
(17) The overall yield of 3 obtained from 4 and the noncommercial 5,5′-
dibromo-2,2′-bipyridine 5 when the synthesis of 4 from 8 is taken into
consideration is below 13%, vs 46% for the present route when the synthesis
of 6b is undertaken from 8 and 9.
(18) Note also that the halogenated reactant 7b can be obtained at the
multigram scale in much better yields than 5 according to published
procedures; see for instance: Bouillon, A.; Lancelot, J.-C.; Collot, V.; Bovy,
P. R.; Rault, S. Tetrahedron 2002, 58, 2885–2890.
(19) (a) Ren, T., C. R. Chim.,in press. (b) Zhang, L.; Huang, Z.; Chen,
W.-Z.; Negishi, E.-I.; Fanwick, P. E.; Updegraff, J. B.; Protasiewicz, J. D.;
Ren, T. Organometallics 2007, 6526–6528. (c) Chen, W.-Z.; Ren, T.
Organometallics 2005, 24, 2660–2669. (d) Hurst, S. K.; Cifuentes, M. P.;
Humphrey, M. G. Organometallics 2002, 21, 2353–2355. (e) Courmarcel,
J.; Le Gland, G.; Toupet, L.; Paul, F.; Lapinte, C. J. Organomet. Chem.
2003, 670, 108–122.

Straightforward Access to a 2,2′-Bipyridine Ligand
Organometallics, Vol. 27, No. 16, 2008 4263
Scheme 3. Synthesis of 3 Based on the Pd-Homocoupling Reaction of 6b
NMR (δ, C6D6, 81 MHz): 100.8 (s, dppe). 1H NMR (δ, C6D6, 200
MHz): 8.25 (s, 1H, HPy), 7.85 (m, 4H, HAr), 7.30 (m, 4H, HAr),
7.10-6.94 (m, 13H, HAr+Py), 6.80 (d, 3JHH ) 9 Hz, 1H, HPy), 2.50
(m, 2H, CH2/dppe), 1.77 (m, 2H, CH2/dppe), 1.47 (s, 15 H, C5(CH3)5).
Experimental Section
General Data. All manipulations were carried out under an inert
atmosphere. Solvents and reagents were used as follows: THF, Et2O,
and n-pentane, distilled from Na/benzophenone; CH2Cl2, distilled
from CaH2 and purged with Ar, opened/stored under Ar; DMF
(extra dry, ACROS), distilled. High-field NMR spectra experiments
were performed on a multinuclear Bruker 500, 300, or 200 MHz
instrument (AVANCE 500, AM300WB, and 200DPX). Chemical
shifts are given in parts per million relative to tetramethylsilane
2
13C{1H} NMR (δ, CDCl3, 50 MHz): 151.0 (t, JCP ) 38 Hz,
FeCt C), 151.3 (s, CHPy), 143.9 (s, CPy), 139.5-137.0 (m, CHPy
+ CPy + CAr/dppe), 134.4-123.4 (m, CHAr/dppe + CHPy + CPy), 115.5
(s, FeCt C), 88.2 (s, C5(CH3)5), 31.2 (m, (CH2)dppe), 10.4 (s,
C5(CH3)5). UV-vis (CH2Cl2, λmax/nm [ꢀ/103 dm3 M-1 cm-1]): 372
[12.9]. CV (CH2Cl2, 0.1 M n-Bu4N+PF6-, 20 °C, 0.1 V s-1; E° in
V vs SCE (∆Ep in V, ip,a/ip,c)): -0.07 (0.07, 1.0).
(TMS) for H and 13C NMR spectra and external H3PO4 for 31P
1
NMR spectra. Transmittance-FTIR spectra were recorded using a
Bruker IFS28 spectrometer (400-4000 cm-1). UV-visible spectra
were recorded using a Cary 5000 spectrometer. MS analyses were
performed at the “Centre Regional de Mesures Physiques de
l’Ouest” (CRMPO, University of Rennes) on a high-resolution MS/
MS ZABSpec TOF Micromass spectrometer. Elemental analyses
were performed at the “Centre Regional de Mesures Physiques de
l’Ouest” (CRMPO, University of Rennes). The solid-state structures
(X-ray) were resolved at the “Centre de Diffractome´trie X” (UMR
CNRS 6226, University of Rennes). The complexes (η5-C5Me5)Fe(η2-
dppe)(Ct CH) (4) and [(η5-C5Me5)Fe(η2-dppe)Cl (8) were prepared
according to published procedures.16,20
Compound 6b. Yield: 79%. Crystals were grown by slow
diffusion of pentane in a dichloromethane solution of 6b (layer/
layer). Anal. Calcd for C43H42NBrP2Fe: C, 67.03; H, 5.49; N, 1.82.
Found: C, 66.92; H, 5.64; N, 1.80. MS (positive LSI, CH2Cl2):
m/z 770.1372 [M]+, m/z calcd for [C43H42NBrP2Fe] 770.1404. FT-
IR (ν, CH2Cl2/KBr, cm-1): 2054/2049 (vs, Ct C) and 2025/2022
(sh, Ct C). 31P NMR (δ, C6D6, 81 MHz): 100.7 (s, dppe). 1H NMR
3
(δ, C6D6, 200 MHz): 8.21 (d, JHH ) 2.0 Hz, 1H, HPy), 7.84 (m,
3
4H, Hdppe), 7.40-7.05 (m, 16H, Hdppe), 6.97 (d, JHH ) 8.2 Hz,
1H, HPy), 6.85 (dd, 3JHH ) 8.2 Hz, 3JHH ) 2.0 Hz, 1H, HPy); 2.46
(m, 2H, (CH2)dppe), 1.77 (m, 2H, (CH2)dppe), 1.46 (s, 15H, C5(CH3)5).
UV-vis (CH2Cl2, λmax/nm [ꢀ/103 dm3 M-1 cm-1]): 372 [12.0]. CV
(CH2Cl2, 0.1 M n-Bu4N+PF6-, 20 °C, 0.1 V s-1; E° in V vs SCE
(∆Ep in V, ip,a/ip,c)): -0.06 (0.07, 1.0).
Synthesis of (η2-dppe)(η5-C5Me5)FeCt C-(5,2-C5H3NX) (X
) Cl, 6a; X ) Br, 6b) from (η2-dppe)(η5-C5Me5)FeCt CH (4)
by the Metalla-Sonogashira Approach. In a Schlenk tube, the
complex (η2-dppe)(η5-C5Me5)FeCt CH (4; 0.400 g, 0.65 mmol),
the (PPh3)2PdCl2 catalyst precursor (0.045 g, 0.06 mmol; 10%),
and CuI cocatalyst (0.025 g, 0.13 mmol; 20%) were introduced
under argon. Subsequently, the desired 2-halogeno-5-iodopyridine
7a (X ) Cl; 0.188 g, 0.78 mmol) or 7b (X ) Br; 0.219 g, 0.78
Synthesis of (η2-dppe)(η5-C5Me5)FeCt C-(5,2-C5H3NBr) (6b)
from (η2-dppe)(η5-C5Me5)FeCl (8). In a Schlenk tube, (η2-
dppe)(η5-C5Me5)FeCl (8; 0.625 g, 1.0 mmol) was solubilized in
40 mL of a MeOH/THF (1:1) mixture. 2-Bromo-5-ethynylpyridine
(9; 200 mg, 1.1 mmol) and NH4PF6 (0.180 g, 1,1 mmol) were
subsequently added before stirring the reaction medium for 16 h at
i
t
mmol) was added to 70 mL of a Pr2NH/THF (3:4) mixture or of
25 °C. Then, BuOK (0.134 g; 1.1 mmol) was added and the
i
a Pr2NH/toluene (1:3) mixture, respectively, and the reaction
reaction was stirred for another 5 h. The volatiles were then removed
in vacuo, and the solid residue was extracted with 3 × 30 mL of
diethyl ether. Once the solvent was removed, the orange powder
was washed with 2 × 30 mL of pentane to afford the desired
compound (η2-dppe)(η5-C5Me5)FeCt C-(5,2-C5H3NBr) (6b; 0.540
g, 0.70 mmol; 70%).
medium was stirred for 25 h. The solvents were then cryogenically
trapped, and the dark orange residue was extracted with toluene
and filtered on an alumina/Celite pad. Evaporation of the toluene
and washing with cooled pentane (-40 °C, 2 × 10 mL) yielded
the desired complexes (η2-dppe)(η5-C5Me5)FeCt C-(5,2-C5H3NX)
(6a, X ) Cl, 0.344 g, 0.47 mmol; 6b, X ) Br, 0.393 g, 0.51 mmol)
as orange solids after drying in vacuo.
Compound 6a. Yield: 73%. Crystals were grown by slow
diffusion of pentane in a toluene solution of 6a (layer/layer). Anal.
Calcd for C43H42NClP2Fe: C, 71.13; H, 5.83; N, 1.93. Found: C,
70.76; H, 5.97; N, 1.87. MS (positive LSI, CH2Cl2): m/z 725.1832
[M]+, m/z calcd for [C43H42NClP2Fe] 725.1830. FT-IR (ν, CH2Cl2/
KBr, cm-1): 2048/2051 (s, Ct C) and 2026/2019 (m, Ct C). 31P
Synthesis of 5,5′-[(η2-dppe)(η5-C5Me5)FeCt C]2-[2,2′-(C5H3N)2]
(3). In a Schlenk tube, 6b (0.770 g, 1.0 mmol), K2CO3 (0.138 g,
1.0 mmol), and Pd(OAc)2 (0.022 g, 0.1 mmol) were introduced in
i
5 mL of anhydrous DMF. A 150 µL portion of anhydrous PrOH
(2.0 mmol) was next syringed at once into the Schlenk tube, which
was placed in a preheated oil bath at 110 °C with stirring. A rapid
color change of the mixture from red to black took place. After
16 h, the reaction mixture was cooled back to room temperature
and the solvents evacuated in vacuo. The residue was subsequently
extracted with 3 × 30 mL of toluene, and the extract was evaporated
to dryness. The resulting residue was then washed with 2 × 30
(20) Roger, C.; Hamon, P.; Toupet, L.; Rabaaˆ, H.; Saillard, J.-Y.; Hamon,
J.-R.; Lapinte, C. Organometallics 1991, 10, 1045–1054.

4264 Organometallics, Vol. 27, No. 16, 2008
Justaud et al.
Table 1. Crystal Data, Data Collection, and Refinement Parameters
for 6a,b
per frame, hkl ranges h 0-15, k 0-25; l -20 to +20) and 26 498
(2θmax ) 54°, ω scan frames via 0.7° ω rotation and 10 s per frame,
hkl ranges h 0-15, k 0-24, l -20 to +20) reflections, respectively.
The data reduction with Denzo and Scalepack21 led to 8379
(respectively 8132) independent reflections, from which 6733
(respectively 5091) had I > 2.0σ(I). The structures were solved
with SIR-97, which revealed the non-hydrogen atoms of these
molecules.21 After anisotropic refinement, many hydrogen atoms
could be found by difference Fourier techniques. The entire
structures were subsequently refined with SHELXL97 by full-matrix
least-squares techniques (use of F2 magnitude; x, y, z, ij for Fe, P,
Br, Cl, C, and N atoms, x, y, z in riding mode for H atoms: 434
variables and 6733 observations with I > 2.0σ(I); calcd w )
6a
6b
formula
fw
FeP2NClC43H42
726.02
FeP2NBrC43H42
770.48
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n
11.9115(3)
19.3856(3)
15.7925(3)
90.0
92.1160(10)
90.0
3644.2(1)
4
monoclinic
P21/n
12.0155(5)
19.3821(8)
16.1491(7)
90.0
92.543(3)
90.0
3757.5(3)
4
R (deg)
(deg)
γ (deg)
V (Å3)
Z
2
2
1/[σ2(Fo ) + (0.068P)2 + 4.72P], where P ) (Fo + 2Fc2)/3 for
Dcalcd (g cm-3
)
1.323
1.352
6a and 433 variables and 5091 observations with I > 2.0σ(I); calcd
cryst size (mm)
F(000)
0.35 × 0.15 × 0.12
0.35 × 0.32 × 0.32
2
w ) 1/[σ2(Fo ) + (0.04P)2 + 1.1P], where P ) (Fo2 + 2Fc2)/3 for
1520
1592
6b).23 Atomic scattering factors were taken from ref 24. Ortep views
abs coeff (mm-1
)
0.607
1.581
were realized with PLATON98.25
no. of total/unique rflns
no. of variables
final R
8379/8379
434
0.051
8379/8379
433
0.0312
Acknowledgment. The CNRS is acknowledged for fi-
nancial support.
Rw
0.130
1.075
0.0702
0.909
goodness of fit/F2 (Sw)
Supporting Information Available: CIF files giving crystal-
lographic data for 6a,b and text and figures giving additional
synthesis details and characterization data. This material is available
free of charge via the Internet at http://pubs.acs.org. Final atomic
positional coordinates, with estimated standard deviations, bond
lengths and angles, and anisotropic thermal parameters, have been
deposited at the Cambridge Crystallographic Data Centre and were
allocated the deposition numbers CCDC 221829 and CCDC
607551, respectively.
mL of diethyl ether and 2 × 30 mL of pentane before being
solubilized in 2 mL of THF. This solution was filtered through a
plug compacted with silica gel and eluted with THF/toluene (1:1).
After evacuation of the solvent, the desired bipy complex 5,5′-
[(η2-dppe)(η5-C5Me5)FeCt C]2-[2,2′-(C5H3N)2] (3) was obtained as
an orange-brown powder (473 mg; 0.343 mmol; 68%). Preliminary
characterization data have already been reported for this compound.3
Crystallography. Data collection of crystals of 6a and 6b was
performed on an NONIUS Kappa CCD and on an Oxford
Diffraction Xcalibur Saphir 3 diffractometer at 120 and 295 K,
respectively, with graphite-monochromated Mo KR radiation (Table
1). The cell parameters were obtained with Denzo and Scalepack
with 10 frames (ψ rotation: 1° per frame).21 The data collections22
gave 64 195 (2θmax ) 54°, 298 frames via 1.4° ω rotation and 160 s
OM800388J
(22) Kappa CCD Software; Nonius BV, Delft, The Netherlands, 1999.
CrysAlis/RED, Version 1.171.26pre2 beta ed.; Oxford Diffraction Ltd.,
Oxford, U.K.
(23) Sheldrick, G. M., SHELX97-2: Program for the Refinement of
Crystal Structures; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
(24) International Tables for X-ray Crystallography; Kluwer Academic:
Dordrecht, The Netherlands, 1992; Vol. C.
(21) Otwinowski, Z.; Minor, W. In Methods in Enzymology; Carter,
C. W., Sweet, R. M., Eds.; Academic Press: London, 1997; Vol. 276, pp
307-326.
(25) Spek, A. L. PLATON. A Multipurpose Crystallographic Tool;
Utrecht University, Utrecht, The Netherlands, 1998.