Stereoelectronic effects of the arenophile (η5-Cp*) Ru+ in electron-rich σ-arylacetylide iron complexes including redox-driven haptotropic rearrangement: An approach toward readable binary molecular memory components

Article abstract of DOI:10.1021/om060575q

The organoiron vinylidene derivatives [(η²-dppe) (η⁵-Cp*)Fe=C=CH-(1-naphthyl)][X] (Cp* = C ₅-Me₅; dppe = 1,2-bis(diphenylphosphino)ethane; X = BPh₄, 3[BPh₄]; X = PF₆, 3[PF₆]) were synthesized from (η²-dppe)(η⁵-Cp*)FeCl and 1-naphthyl acetylene in the presence of NaBPh₄ or NaPF₆, respectively. The daughter organometallic acetylide complex, (η²-dppe)(η⁵-Cp*)Fe-C≡C-(1-naphthyl), 4, was obtained, in 81% yield, upon deprotonation of the vinylidene precursor, 3[BPh₄], by t-BuOK in a MeOH/THF mixture at room temperature. One new dicationic heterobimetallic vinylidene Fe(II)-Ru(II) complex, 5[PF ₆]₂, was obtained, in 74% yield, upon reaction of the 1-naphthyl vinylidene precursor 3[PF₆], with [(η⁵- Cp*)Ru(CH₃CN)₃][PF₆]. Binuclear acetylides were prepared via η⁶ complexation of the (η⁵-Cp*)-Ru⁺ arenophile onto either the substituted or the free naphthyl ring of 1-naphthyl acetylide derivative 4, and both of these haptotropomers, 6A[PF₆]·and 6B[PF₆], were isolated. A third bimetallic model compound, 2[PF₆], was prepared in 69% yield via (η⁵-Cp*Ru) coordination of the ethynyl phenyl ring of the known complex (η²-dppe) (η⁵-Cp*)Fe-C≡C-Ph (1). All three complexations are regioselective, occurring only on the acetylenic aryl moiety instead of the competing dppe phenyls. The thermally stable Fe^III counterparts, 2[PF₆]₂, 4[PF₆], and 6B[PF₆] ₂, were obtained (70-86% isolated yield) upon oxidation, in THF at -60°C, with ferrocenium hexafluorophosphate. All the new compounds were thoroughly authenticated using analytical and spectroscopic methods. In the heterobimetallic species, the aromaticity of the acetylide aryl linker is changed in situ via (i) the complexation of the (η⁵-Cp*) Ru⁺ arenophile and (ii) for the case of the 1-naphthyl substituent, by the η⁶-η⁶ inter-ring haptotropic migration of this group between naphthyl rings. The upshot is that these compounds exhibit significantly different degrees of electronic communication between the two organometallic termini across the length of the ethynediylaryl segment as a function of arenophile location: either (i) collinear to the Fe-C≡C wire-like segment (2[PF₆] and 6A[PF₆]) or (ii) on the free ring of the 1-naphthyl moiety (6B[PF₆]). To establish the degree of electron transfer within the novel compounds reported herein, their physical properties are compared using NMR, UV-vis, IR, Moessbauer, and electron spin resonance (ESR) spectroscopies, as well as cyclic voltammetry and X-ray crystallography. Accordingly, the solid-state structures of all seven novel, electronrich organometallic acetylides are described, including both haptotropomers 6A[PF₆] and 6B[PF₆], Finally, the first redox-driven inter-ring haptotropic rearrangement of (η⁵- Cp*)Ru^- between naphthyl rings was shown to occur.

Full text of DOI:10.1021/om060575q

Organometallics 2006, 25, 5311-5325
5311
Stereoelectronic Effects of the Arenophile (η5-Cp*)Ru+ in
Electron-Rich σ-Arylacetylide Iron Complexes Including
Redox-Driven Haptotropic Rearrangement: An Approach toward
Readable Binary Molecular Memory Components
Jennifer A. Shaw-Taberlet,† Sourisak Sinbandhit,‡ Thierry Roisnel,†
Jean-Rene´ Hamon,*,† and Claude Lapinte*,†
UMR 6226 Sciences Chimiques de Rennes, CNRS-UniVersite´ de Rennes 1, Campus de Beaulieu, 35042
Rennes Cedex, France, and Centre Re´gional de Mesures Physiques de l’Ouest, UniVersite´ de Rennes 1,
Campus de Beaulieu, 35042 Rennes Cedex, France
ReceiVed June 29, 2006
The organoiron vinylidene derivatives [(η2-dppe)(η5-Cp*)FedCdCH-(1-naphthyl)][X] (Cp* ) C5-
Me5; dppe ) 1,2-bis(diphenylphosphino)ethane; X ) BPh4, 3[BPh4]; X ) PF6, 3[PF6]) were synthesized
from (η2-dppe)(η5-Cp*)FeCl and 1-naphthyl acetylene in the presence of NaBPh4 or NaPF6, respectively.
The daughter organometallic acetylide complex, (η2-dppe)(η5-Cp*)Fe-CtC-(1-naphthyl), 4, was
obtained, in 81% yield, upon deprotonation of the vinylidene precursor, 3[BPh4], by t-BuOK in a MeOH/
THF mixture at room temperature. One new dicationic heterobimetallic vinylidene Fe(II)-Ru(II) complex,
5[PF6]2, was obtained, in 74% yield, upon reaction of the 1-naphthyl vinylidene precursor 3[PF6], with
[(η5-Cp*)Ru(CH3CN)3][PF6]. Binuclear acetylides were prepared via η6 complexation of the (η5-Cp*)-
Ru+ arenophile onto either the substituted or the free naphthyl ring of 1-naphthyl acetylide derivative 4,
and both of these haptotropomers, 6A[PF6] and 6B[PF6], were isolated. A third bimetallic model
compound, 2[PF6], was prepared in 69% yield via (η5-Cp*Ru) coordination of the ethynyl phenyl ring
of the known complex (η2-dppe)(η5-Cp*)Fe-CtC-Ph (1). All three complexations are regioselective,
occurring only on the acetylenic aryl moiety instead of the competing dppe phenyls. The thermally stable
FeIII counterparts, 2[PF6]2, 4[PF6], and 6B[PF6]2, were obtained (70-86% isolated yield) upon oxidation,
in THF at -60 °C, with ferrocenium hexafluorophosphate. All the new compounds were thoroughly
authenticated using analytical and spectroscopic methods. In the heterobimetallic species, the aromaticity
of the acetylide aryl linker is changed in situ via (i) the complexation of the (η5-Cp*)Ru+ arenophile and
(ii) for the case of the 1-naphthyl substituent, by the η6-η6 inter-ring haptotropic migration of this group
between naphthyl rings. The upshot is that these compounds exhibit significantly different degrees of
electronic communication between the two organometallic termini across the length of the ethynediyl-
aryl segment as a function of arenophile location: either (i) collinear to the Fe-CtC wire-like segment
(2[PF6] and 6A[PF6]) or (ii) on the free ring of the 1-naphthyl moiety (6B[PF6]). To establish the degree
of electron transfer within the novel compounds reported herein, their physical properties are compared
using NMR, UV-vis, IR, Mo¨ssbauer, and electron spin resonance (ESR) spectroscopies, as well as cyclic
voltammetry and X-ray crystallography. Accordingly, the solid-state structures of all seven novel, electron-
rich organometallic acetylides are described, including both haptotropomers 6A[PF6] and 6B[PF6]. Finally,
the first redox-driven inter-ring haptotropic rearrangement of (η5-Cp*)Ru+ between naphthyl rings was
shown to occur.
a nanoconnect or via the indirect methods employed here and
elsewhere, electronic properties5 of nanodevices are being
increasingly published and compared. In order for a molecule
to serve as a unit of binary computational memory, it must
undergo a fast, solid-state transformation between two distinct
states that are macroscopically distinguishable. Such a trans-
formation could be made electronically, magnetically, or opti-
cally; however, a solution-state, chemical transformation would
be poorly suited to application within a nanodevice. Finally,
Introduction
The vast potential for the future use of molecules as building
blocks of nanoscaled devices has inspired chemists to design
and characterize compounds capable of performing useful
functions within an as-yet hypothetical nanodevice. Specifically,
in the fields of molecular and nanoelectronics,1 nanodevices such
as molecular wires2 and switches3 are described and occasionally
attributed with information storage and processing potentials.4
While the characterization of nanodevices remains a difficult
problem, whether it takes place upon a single molecule within
(1) (a) Robertson, N.; Mc. Gowan, G. A. Chem. Soc. ReV. 2003, 32,
96-103. (b) Caroll, R. L.; Gorman, C. B. Angew. Chem., Int. Ed. 2002,
41, 4379-4400. (c) Tour, J. M. Acc. Chem. Res. 2000, 33, 791-803. (d)
Paul, F.; Lapinte, C. Coord. Chem. ReV. 1998, 178/180, 427-505. (e) Paul,
F.; Lapinte, C. In Unusual Structures and Physical Properties in Organo-
metallic Chemistry; Gielen, M., Willem, R., Wrackmeyer, B., Eds.; Wiley:
San Francisco, 2002; pp 219-295.
* To whom correspondence should be addressed. E-mail: jean-
rene.hamon@univ-rennes1.fr. Fax: +33
2 23 23 56 37. E-mail:
claude.lapinte@univ-rennes1.fr. Fax: +33 2 23 23 59 63.
† UMR 6226.
‡ CRMPO.
10.1021/om060575q CCC: $33.50 © 2006 American Chemical Society
Publication on Web 09/21/2006

5312 Organometallics, Vol. 25, No. 22, 2006
Shaw-Taberlet et al.
Scheme 1. Definition of Type I Compounds and Selected
Resonance Forms for Fe(II) and Fe(III) Species
distinctions between binary states should arise from spectro-
scopic or electronic data.
Inter-ring haptotropic rearrangement in which a metal mi-
grates along a polyaromatic system has culminated in the design
of organometallic switches. For instance, a recent study by Do¨tz
and co-workers reported that the η6-η6 solution-state inter-ring
haptotropic rearrangement of the Cr(CO)3 arenophile on sub-
stituted naphthyl ligands proceeds photochemically in one
direction and thermally in the other.6 Other examples of
irreversible7 and chemically reversible switches8 using solution-
state haptotropic rearrangement of Cr(CO)3 have also been
reported. In addition, Benn and co-workers reported on the intra-
ring haptotropic rearrangements of nickel complexes of naph-
thalene, which occur spontaneously in the solid state, as
observed by NMR.9
In both theoretical10 and experimental11 discoveries published
within recent years, mononuclear organoiron complexes in
which a [(η2-dppe)(η5-Cp*)Fe] (dppe ) 1,2-bis(diphenylphos-
phino)ethane; Cp* ) C5Me5) redox-active terminus is σ-bonded
to a para-substituted phenylethynyl spacer have served particu-
larly well as molecular wire models (Scheme 1). For similar
complexes, electron transfer and exchange processes have been
determined to depend on the aromaticity of the conducting
ligand.12 In simple terms, the less aromatic the ligand, the more
conductive the segment. To explain this empirical discovery, a
resonance argument, summarized in Scheme 1, has been
employed. Upon oxidation to Fe(III), a quinoidal, cumulenic
mesomer IV contributes a 19-electron Fe(I). However, this
structure perturbs the aromatic stabilization present in the aryl
moiety. In conclusion, complexes containing fewer aromatic
ligands, by favoring the quinoidal form, II and IV, exhibit better
electronic transfer and exchange between termini.
In the current study, we document the novel syntheses of the
series of compounds shown in Scheme 2. Furthermore, we
compare their differing capacities to conduct an electron across
the length of the iron-ethynyl-aryl segment using multinuclear
NMR, UV-vis, IR, Mo¨ssbauer, and electron spin resonance
(ESR) spectroscopies, as well as cyclic voltammetry and X-ray
crystallography. In addition, we endeavored to vary the aro-
maticity of the ligand in situ via the η6 complexation of the
12-electron (η5-Cp*)Ru+ arenophile.13 The Ru precursor was
[(η5-Cp*)Ru(CH3CN)3][PF6],14 and complexation took place
onto either naphthyl ring A (for complexation onto the acetylide,
4) or ring B (for coordination onto the vinylidene, 3[PF6],
followed by reversible deprotonation), thus yielding both
regioisomers of interest, 6A[PF6] and 6B[PF6] (Scheme 3). The
difference in electron transfer properties between the resulting
heterobinuclear species is macroscopically readable and identi-
fies the binary states, A and B. Unfortunately, it was not possible
to isolate more than a few crystals of haptotropomer 6A[PF6]
in pure form (see Experimental Section). Therefore, the
completely characterized model compound 2[PF6] is often
compared to 6B[PF6] in place of 6A[PF6] in this proof of
concept. Finally, chemically and redox-induced haptotropic
rearrangements of the (η5-Cp*)Ru+ arenophile were shown to
(2) For studies in carbon-rich organometallic wires, see: (a) Rigaut, S.;
Touchard, D.; Dixneuf, P. H. Coord. Chem. ReV. 2004, 248, 1585-1601.
(b) Bruce, M. I.; Low, P. J. AdV. Organomet. Chem. 2004, 50, 179-444.
(c) Szafert, S.; Gladysz, J. A. Chem. ReV. 2003, 103, 4175-4205. (d) Yam,
V. W.-W. Acc. Chem. Res. 2002, 35, 555-563. (e) Powell, C. E.; Humphrey,
M. G. Coord. Chem. ReV. 2004, 248, 725-756. For a recent review on
organic molecular wires, see: (f) James, D. K.; Tour, J. M. Top. Curr.
Chem. 2005, 257, 33-62.
(3) For some recent reviews, see: (a) Moussa, N. O.; Molnar, G.;
Bonhommeau, S.; Zwick, A.; Mouri, S.; Tanaka, K.; Real, J. A.; Bousseksou,
A. Phys. ReV. Lett. 2005, 94, 107205-107209. (b) Mendes, P. M.; Flood,
A. H.; Stoddart, J. F. Appl. Phys. A: Mater. Sci. Process. 2005, 80, 1197-
1209. (c) Benniston, A. C. Chem. Soc. ReV. 2004, 33, 573-578. (d)
Bousseksou, A.; Molnar, G.; Matouzenko, G. Eur. J. Inorg. Chem. 2004,
4353-4369.
(4) See for instance: (a) Cifuentes, M. P.; Humphrey, M. G.; Morall, J.
P.; Samoc, M.; Paul, F.; Roisnel, T.; Lapinte, C. Organometallics 2005,
24, 4280-4288. (b) Hu, Q. Y.; Lu, W. X.; Tang, H. D.; Sung, H. H. Y.;
Wen, T. B.; Williams, I. D.; Wong, G. K. L.; Lin, Z.; Jia, G. Organome-
tallics 2005, 24, 3966-3973. (c) Fillaut, J.-L.; Perruchon, J.; Blanchard,
P.; Roncali, J.; Gohlen, S.; Allain, M.; Migalska-Zalas, A.; Kityk, I. V.;
Sahraoui, B. Organometallics 2005, 24, 687-695. (d) Venkatesan, K.;
Blacque, O.; Fox, T.; Alfonso, M.; Schmalle, H. W.; Berke, H. Organo-
metallics 2004, 23, 1183-1186. (e) Jiao, J.; Long, G. J.; Grandjean, F.;
Beatty, A. M.; Fehlner, T. P. J. Am. Chem. Soc. 2003, 125, 7522-7523.
(f) Wong, K. M.-C.; Lam, S. C.-F.; Ko, C.-C.; Zhu, N.; Yam, V. W.-W.;
Roue, S.; Lapinte, C.; Fathallah, S.; Costuas, K.; Kahlal, S.; Halet, J.-F.
Inorg. Chem. 2003, 42, 7086-7097. (g) Powell, C. E.; Humphrey, M. G.;
Cifuentes, M. P.; Morall, J. P.; Samoc, M.; Luther-Davies, B. J. Phys. Chem.
A 2003, 107, 11264-11266. (h) Naklicki, M. L.; White, C. A.; Plante, L.
L.; Evans, C. E. B.; Crutchley, R. J. Inorg. Chem. 1998, 37, 1880-1885.
(5) For one recent review of direct conduction measurements, see: (a)
James, D. K.; Tour, J. M. Chem. Mater. 2004, 16, 4423-4435. For electron
transfer studies, see: (b) Benniston, A. C.; Harriman, A. Chem. Soc. ReV.
2006, 35, 169-179. (c) Ren, T. Organometallics 2005, 24, 4854-4870.
(d) Crutchley, R. J. AdV. Inorg. Chem. 1994, 41, 273-325. (e) Schwab, P.
F. H.; Levin, M. D.; Michl, J. Chem. ReV. 1999, 99, 1863-1933. (f) Schwab,
P. F. H.; Smith, J. R.; Michl, J. Chem. ReV. 2005, 105, 1197-1279. (g) Qi,
H.; Gupta, A.; Noll, B. C.; Snider, G. L.; Lu, Y.; Lent, S. S.; Fehlner, T.
P. J. Am. Chem. Soc. 2005, 127, 15218-15227. (h) Blum, A. S.; Ren, T.;
Parish, D. A.; Trammell, S. A.; Moore, M. H.; Kushmerick, J. G.; Xu,
G.-L.; Deschamps, J. R.; Polack, S. K.; Shashidar, R. J. Am. Chem. Soc.
2005, 127, 10010-10011. (i) Xu, G.-L.; Crutchley, R. J.; DeRosa, M. C.;
Pan, Q.-J.; Zhang, H.-X.; Wang, X.; Ren, T. J. Am. Chem. Soc. 2005, 127,
13354-13365. (j) Schull, T. L.; Kushmerick, J. G.; Patterson, C. H.; George,
C.; Moore, M. H.; Pollack, S. K.; Shashidhar, R. J. Am. Chem. Soc. 2003,
125, 3202-3203. (k) Astruc, D. Electron Transfer and Radical Processes
in Transition-Metal Chemistry; VCH: New York, 1995.
(6) (a) Jahr, H. C.; Nieger, M.; Do¨tz, K. H. Chem. Commun. 2003, 2866-
2867. (b) Do¨tz, K. H.; Jahr, H. C. Chem. Rec. 2004, 4, 61-71. (c) Jahr, H.
C.; Nieger, M.; Do¨tz, K. H. Chem. Eur. J. 2005, 11, 5333-5342. (d) Do¨tz,
K. H.; Wenzel, B.; Jahr, H. C. Top. Curr. Chem. 2004, 248, 63-103.
(7) (a) Pan, J.; Wang, J.; Nanaszak, M. M.; Kampf, J. W.; Ashe, A. J.,
III. Organometallics 2006, 25, 3463-3467, see also references therein. (b)
Oprunenko, Y. F. Russ. Chem. ReV. 2000, 69, 683-704.
(11) (a) Denis, R.; Toupet, L.; Paul, F.; Lapinte, C. Organometallics
2000, 19, 4240-4251. (b) Paul, F.; Mevellec, J.-Y.; Lapinte, C. Dalton
Trans. 2002, 1783-1790. (c) Paul, F.; Toupet, L.; Thepot, J.-Y.; Costuas,
K.; Halet, J.-F.; Lapinte, C. Organometallics 2005, 24, 5464-5478.
(12) (a) de Montigny, F.; Argouarch, G.; Costuas, K.; Halet, J.-F.;
Roisnel, T.; Toupet, L.; Lapinte, C. Organometallics 2005, 24, 4558-4572.
(b) Ibn-Ghazala, S.; Paul, F.; Toupet, L.; Roisnel, T.; Hapiot, P.; Lapinte,
C. J. Am. Chem. Soc. 2006, 128, 2463-2476. (c) Shaw-Taberlet, J. A.;
Hamon, J.-R.; Lapinte, C. Unpublished work.
(13) Fagan, P. J.; Ward, M. D.; Calabrese, J. C. J. Am. Chem. Soc. 1989,
111, 1698-1719.
(14) Mbaye, M. D.; Demerseman, B.; Renaud, J.-L.; Toupet, L.; Bruneau,
C. AdV. Synth. Catal. 2004, 346, 835-841.
(8) Pan, J.; Kampf, J. W.; Ashe, A. J., III. Organometallics 2006, 25,
197-202.
(9) Benn, R.; Mynott, R.; Topalovic, I.; Scott, F. Organometallics 1989,
8, 2299-2305.
(10) Costuas, K.; Paul, F.; Toupet, L.; Halet, J.-F.; Lapinte, C. Orga-
nometallics 2004, 23, 2053-2068.

Stereoelectronic Effects of the Arenophile (η5-Cp*Ru)
Organometallics, Vol. 25, No. 22, 2006 5313
Scheme 2. Novel Iron Ethynyl and Vinylidene Complexes Described Herein
Scheme 3. Definitions of Regioisomers A and B
The yellow heterobinuclear vinylidene 1-naphthyl derivative
5B[PF6]2 was synthesized in 74% isolated yield, via an
1
analogous procedure (Scheme 6). H NMR showed that the
crude mixture included regioisomers A and B (Scheme 3).
However, the small yield (8%) of isomer A was easily removed
along with excess starting material by partial precipitation of a
dichloromethane solution of the mixture in pentane followed
by multiple washings with a 50:1 mixture of THF and
dichloromethane until the rinses were colorless. Once again,
side-complexation onto dppe phenyls was ruled out by careful
characterization (see Experimental Section). The daughter
bimetallic acetylides, 6A[PF6] and 6B[PF6], were made via two
routes, the former giving rise to a mixture of isomers A and B,
and the latter affording only regioisomer B. These two modus
operandi are shown in Scheme 6. The first procedure yields a
47:53 ratio of regioisomers 6A[PF6]:6B[PF6], determined by
1H NMR spectroscopy before purification. Due to the differing
solubilities of the isomers, partial precipitation, a common
method of purification, artificially changes this fraction. Thus,
a few orange crystals of 6A[PF6] were isolated after slow
diffusion of pentane into a THF solution of the mixture of
regioisomers. In contrast, analytically pure isomer 6B[PF6] was
prepared as a very dark powder in 80% isolated yield upon
deprotonation of the dicationic bimetallic vinylidene derivative
5B[PF6]2 with 1.3 equiv of t-BuOK, in methanol at room
temperature for 2 h. Dry samples of the above-described
heterobimetallic species 6A[PF6] and 6B[PF6] display good
thermal stability in air.
In agreement with the two previous reactions (syntheses of
2[PF6] and 5B[PF6]2), the complexations in Scheme 6 never
involve the dppe phenyls unless an excess of the ruthenium
precursor is used. Given the body of work relating the consistent
preference of arenophiles for phenyl rings versus naphthyl ones,
this result is certainly interesting. For example, in a seminal
study, Nolan, Fagan, and co-workers established the enthalpies
of the complexations of (η5-Cp*)Ru+ onto naphthalene and
various substituted benzenes and found that the naphthalene
complex was formed the least favorably (∆H ) -1.7 kcal/mol)
and that complexation onto substituted benzenes became more
and more favorable the more electron-donating the substitu-
ents.16 Furthermore, Fagan et al.13 reported the facile complex-
ation of the (η5-Cp*)Ru+ arenophile onto all four phenyl rings
of tetraphenyl methane. Given the fact that the tetrahedral dppe
site provides an analogous steric and electronic environment, it
occur at room temperature to a limited extent between the two
naphthyl rings upon in situ variation of the electronic and steric
environment.
Results and Discussion
Syntheses of the Mononuclear Iron(II) Complexes. To
obtain the novel organoiron vinylidenes, 3[BPh4] and 3[PF6],
1-naphthyl acetylene was reacted, in a methanol/THF mixture,
with (η2-dppe)(η5-Cp*)FeCl in the presence of either NaBPh4
or NaPF6, as shown in Scheme 4. Both vinylidene syntheses
are comparable in terms of yield and facility of purification.
The two salts were isolated in 94 and 83% yield, respectively,
as brown solids. These are stable for long periods at room
temperature under argon, and dry samples display air-stability
for short periods.
The daughter acetylide complex, (η2-dppe)(η5-Cp*)Fe-Ct
C-(1-naphthyl), 4, was obtained upon deprotonation of the
vinylidene precursor, 3[BPh4], by an excess (1.2 equiv) of
potassium tert-butoxide in a MeOH/THF mixture at room
temperature. Complex 4 was isolated in 81% yield as an air-
and moisture-sensitive orange powder. This derivative can also
be prepared (70% overall yield) via the one-pot route in which
the two steps shown in Scheme 4 are combined.
Syntheses of the Heterobinuclear Fe(II)/Ru(II) Complexes.
In general, the heterobimetallic complexes were obtained upon
η6 complexation of the arylvinylidene or arylethynyl iron(II)
by [(η5-Cp*)Ru(CH3CN)3][PF6]. For example, novel binuclear
complex 2[PF6] was prepared in 69% yield and isolated as a
red powder, from the known ethynylphenyl derivative (η2-dppe)-
(η5-Cp*)Fe-CtC-Ph, 1,11,15 as shown in Scheme 5. Given
stoichiometric conditions, this reaction is regioselective; com-
plexation occurs only on the acetylenic phenyl moiety, never
on the competing dppe phenyls.
(15) 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.
(16) Nolan, S. P.; Martin, K. L.; Stevens, E. D.; Fagan, P. J. Organo-
metallics 1992, 11, 3947-3953.

5314 Organometallics, Vol. 25, No. 22, 2006
Shaw-Taberlet et al.
Scheme 4. Syntheses of the Vinylidenes, 3[BPh4] and 3[PF6], and the Corresponding Acetylide 4a
a Key reagents: (a) NaBPh4 or NaPF6, 20 °C, MeOH/THF, 16 h; (b) KBuOt, 20 °C, MeOH, THF, 2 h.
Scheme 5. Regioselective Synthesis of 2[PF6]
Scheme 7. Syntheses of the Mono- and Binuclear Fe(III)
and Fe(III)-Ru(II) Complexesa
(a) R ) (η5-C5Me5)Ru[η6-(phenyl)]; (b) R ) 1-naphthyl; (c) R )
(η5-C5Me5)Ru[η6-(naphthyl)].
Scheme 6. Synthesis of 6A[PF6] (top) and Regioselective
Synthesis of 6B[PF6] (bottom)
Syntheses of the Mono- and Binuclear Fe(III) and Fe-
(III)-Ru(II) Complexes. Chemical oxidation, in THF at -60
°C, of the iron(II) products 2[PF6], 4, and 6B[PF6] gave the
corresponding, thermally stable paramagnetic iron(III) coun-
terparts, 2[PF6]2, 4[PF6], and 6B[PF6]2, respectively, in the
presence of ferrocenium hexafluorophosphate (Scheme 7). In
all cases, good to high yields (70-86%) were consistently
obtained, and purification by partial precipitation using common
organic solvents provided spectroscopically pure material (see
Experimental Section).
All of these new complexes were structurally characterized
1
by the usual spectroscopies (FT-IR, UV-vis, H, 13C, and 31P
NMR), ESI high-resolution mass spectrometry, and cyclic
voltammetry. Furthermore, the crystal structures of all of the
organometallic acetylide complexes were resolved. While
satisfactory elemental analyses were obtained in most cases,
all compounds were found to be spectroscopically pure.
Moreover, the paramagnetic iron(III) derivatives were character-
ized by electron spin resonance (ESR) and Mo¨ssbauer spec-
trometry.
is quite surprising, but interesting, that our reactions are
regiospecific in preference of the naphthalene. Another example
of arenophile preference for a fused ring moiety in the presence
of phenyl groups has previously been reported for [(η5-Cp*)-
Ru(η6-rubrene)][O3SCF3] (rubrene ) 5,6,11,12-tetraphenyl-
naphthacene).17 In this work, the (η5-Cp*)Ru+ unit was bound
to the outermost ring of the naphthacene functionality under
certain conditions.
Interestingly, preliminary results show that complexation by
the arenophile (η5-Cp*)Ru+ onto the dppe phenyls of (η2-dppe)-
(η5-Cp*)Fe-R does occur in some cases. Two such cases were
observed within our group and will be published in detail in a
following paper.12c The first such dppe phenyl complexation
took place on a common precursor, (η2-dppe)(η5-Cp*)FeCl, a
compound in which no other aromatic rings were available.
Another was observed in bimetallic species when all other
aromatic rings were quite sterically encumbered, and the dppe
groups were attached to very electron-rich sites linked by a 1,4-
bisethynylaryl spacer.
1
NMR Spectroscopy. The relevant H, 13C, and 31P NMR
data of the mononuclear complexes agree well with those of
previously described, related compounds in the (η2-dppe)(η5-
Cp*)Fe series.11,18 Thus, the vinylidene precursors 3[BPh4] and
3[PF6] exhibited the characteristic features of the iron-
vinylidene core, FedCRdCâH-, with the triplets assigned to
the vinylidene protons at δ ) 5.79 and 5.76 ppm, respectively,
4
1
with a coupling constant JH-P ) 4.0 Hz, in their H NMR
spectra, and the downfield triplet resonance of the CR nucleus
at 356.7 ppm with a 2JC-P of 33 Hz in the 13C NMR spectrum
of 3[BPh4]. In addition, the NMR spectra of 18- and 17-electron
ethynyl-1-naphthyl iron molecules, 4 and 4[PF6] (the latter being
paramagnetic, no 13C spectrum is reported herein), Very closely
resemble those of related compounds 1 and 1[PF6], as ex-
pected.11,15 In the 31P NMR spectrum of 4, the single signal
observed at 101.0 ppm is characteristic of an acetylide iron(II)
(17) Fagan, P. J.; Ward, M. D.; Calabrese, J. C.; Caspar, J. V.; Krusic,
P. J. J. Am. Chem. Soc. 1988, 110, 2981-2983.

Stereoelectronic Effects of the Arenophile (η5-Cp*Ru)
Organometallics, Vol. 25, No. 22, 2006 5315
complex, and the 13C NMR spectrum shows the triplet (2JC-P
) 39.2 Hz) and singlet signatures for the acetylide linkage at δ
) 145.1 and 119.7 ppm, respectively. The 31P NMR signal of
the dppe groups of paramagnetic 4[PF6] was possibly found at
315 ppm (br s, w1/2 ) 21 200 Hz), making this one of the rare
iron(III) compounds studied in our laboratory for which the dppe
signal was observed.19
1
Upon complexation to (η5-Cp*)Ru+, H and 13C chemical
shifts attributed to the complexed aromatic ring of 2[PF6], 6A-
[PF6], and 6B[PF6] undergo an upfield shift, as usual for η6-
arene metal complexes.20 In addition, the arenophile of these
four compounds is observed via the presence of one and two
sharp singlets in the 1H and 13C{1H} NMR spectra, respectively
(see Experimental Section). The two regioisomers 6A[PF6] and
1
6B[PF6] are easily distinguishable using room-temperature H
NMR by their resolved upfield signals (6.54 < δ < 5.58 and
6.55 < δ < 6.08) of cumulative relative intensities 3H and 4H
that correspond to the complexed ring protons. Furthermore,
the dppe phosphorus nuclei are split as in an AB system in the
31P NMR spectra of 5B[PF6]2, 6A[PF6], and 6B[PF6], whereas
the corresponding organoiron precursors, 3[PF6] and 4, are each
characterized by a singlet (see above). The AB system doublet
is further split into a smaller doublet, because the heterobinuclear
species are planar chiral. Therefore, the enantiotopic phosphorus
atom of each enantiomer within the racemic mixtures is
distinguishable by between 15 and 30 Hz.
The bulky arenophile also introduces coalescence into the
spectra, giving rise to the temperature dependence of certain
peaks in the 1H and 31P spectra and resulting in the decreasing
of the intensity and broadening of dppe signals (both in 1H and
31P spectra) and (η5-Cp*)Fe signals (both in 1H and13C spectra).
This coalescence is surely due to steric strain, observed in the
crystal structures of all novel heterobinuclear species described
herein (vide infra). It is noteworthy that both NMR and X-ray
crystallography show a larger degree of strain between the dppe
ligand and (η5-Cp*)Ru+ group for compound 6A[PF6], whereas
strain between the two Cp* entities is greater for compound
6B[PF6].
Figure 1. Aromatic region of the high-field 1H NMR spectra (500
MHz) of 6A[PF6] at various temperatures in acetone-d6. The singlet
(a) is due to the crystallization solvent.
Table 1. IR νCtC Bond Stretchinga
compd
Fe(II)
Fe(III)
∆νCtC
ref
1[PF6]n
2[PF6]n
4[PF6]n
6B[PF6]n
2053b
2021, 1988c
2042d
-32, -65
+14, +60
-62, -122
0, -22
7a
2028, 1982c
2040b
this work
this work
this work
1988, 1918c
2026, 1978d
2026c
a In Nujol, cm-1
.
b n ) 0. c n ) 1. d n ) 2.
to observe the beginning and end of the coalescence phenom-
enon. For the first regioisomer, between 193 and 243 K, the
31P spectrum showed no coalescence, and the signal is split into
a sharp, well-defined doublet of doublets. With increasing
temperature, the doublets converge and broaden and their
intensities decrease. To explain the spectral data, we conclude
that rotation about the carbon bridge between the two organo-
metallic termini is sterically restricted by the bulky, terminal
dppe and Cp* ligands. At low temperatures, well-resolved
spectra of one rotamer is possible, but as the temperature rises,
molecular motion creates a poorly defined average due to the
restrained wagging of the terminal moieties. Heating up to 343
K in THF was not adequate to give rise to a different, spectrally
unique, rotamer, and the spectra remained identical.
From variable-temperature 1H NMR experiments of this same
compound, 6A[PF6], another very interesting observation arose
(Figure 1). At low temperatures, the three shielded, aromatic
protons of the complexed naphthyl ring, sounding off between
6.5 and 5.4 ppm, are joined by an additional doublet integrating
at 2 protons. In contrast, all other noncomplexed aromatic signals
remain at much lower field, between 8.1 and 7.0 ppm. As the
temperature rises, this errant doublet, witness to a dynamic
process, traverses the void between complexed and free aromatic
regions of the spectrum. This signal can be attributed to two
ortho protons of the dppe phenyl groups, due to their proximity
to the ruthenium atom, as observed in the crystal structure (see
Figure 2g).
Variable-temperature NMR spectra were taken of crystals of
both 6A[PF6] and 6B[PF6] dissolved in acetone-d6 in attempts
(18) (a) Roue, S.; Lapinte, C. J. Organomet. Chem. 2005, 690, 594-
604. (b) Bruce, M. I.; Costuas, K.; Davin, T.; Ellis, B. G.; Halet, J.-F.;
Lapinte, C.; Low, P. J.; Smith, M. E.; Skelton, B. W.; Toupet, L.; White,
A. H. Organometallics 2005, 24, 3864-3881. (c) Paul, F.; Ellis, B. G.;
Bruce, M. I.; Toupet, L.; Roisnel, T.; Costuas, K.; Halet, J.-F.; Lapinte, C.
Organometallics 2006, 25, 649-665. (d) Bruce, M. I.; Low, P. J.; Hartl,
F.; Humphrey, P. A.; de Montigny, F.; Jevric, M.; Lapinte, C.; Perkins, G.
J.; Roberts, R. L.; Skelton, B. W.; White, A. H. Organometallics 2005, 24,
5241-5255. (e) Bruce, M. I.; De Montigny, F.; Jevric, M.; Lapinte, C.;
Skelton, B. W.; Smith, M. E.; White, A. H. J. Organomet. Chem. 2004,
689, 2860-2871. (f) Bruce, M. I.; Ellis, B. G.; Gaudio, M.; Lapinte, C.;
Melino, G.; Paul, F.; Skelton, B. W.; Smith, M. E.; Toupet, L.; White, A.
H. Dalton Trans. 2004, 1601-1609. (g) Roue, S.; Lapinte, C.; Bataille, T.
Organometallics 2004, 23, 2558-2567. (h) Costuas, K.; Paul, F.; Toupet,
L.; Halet, J.-F.; Lapinte, C. Organometallics 2004, 23, 2053-2068. (i) Coat,
F.; Paul, F.; Lapinte, C.; Toupet, L.; Costuas, K.; Halet, J.-F. J. Organomet.
Chem. 2003, 683, 368-378. (j) Roue, S.; Le Stang, S.; Toupet, L.; Lapinte,
C. C. R. Chimie 2003, 6, 353-366. (k) Jiao, H.; Costuas, K.; Gladysz, J.
A.; Halet, J.-F.; Guillemot, M.; Toupet, L.; Paul, F.; Lapinte, C. J. Am.
Chem. Soc. 2003, 125, 9511-9522. (l) Argouarch, G.; Thominot, P.; Paul,
F.; Toupet, L.; Lapinte, C. C. R. Chimie 2003, 6, 209-222. (m) Courmarcel,
J.; Le Gland, G.; Toupet, L.; Paul, F.; Lapinte, C. J. Organomet. Chem.
2003, 670, 108-122.
(19) (a) Guillaume, V.; Mahias, V.; Mari, A.; Lapinte, C. Organometallics
2000, 19, 1422-1426. (b) Fettinger, J. C.; Mattamana, S. P.; Poli, R.;
Rogers, R. D. Organometallics 1996, 15, 4211-4222. (c) Weyland, T.;
Costuas, K.; Mari, A.; Halet, J.-F.; Lapinte, C. Organometallics 1998, 17,
5569-5579.
(20) Hubig, S. M.; Lindeman, S. V.; Kochi, J. K. Coord. Chem. ReV.
2000, 200-202, 831-873.
As for the other regioisomer, while the aromatic signals in
1
the H spectrum do travel as a function of temperature, the
signals attributed to the complexed ring in 6B[PF6] remain the

5316 Organometallics, Vol. 25, No. 22, 2006
Shaw-Taberlet et al.
Figure 2. ORTEP diagram at 50% probability level for (a) 2[PF6]; (b) 2[PF6]2; (c) 4; (d) 4[PF6]; (e) 6B[PF6]; (f) 6B[PF6]2; (g) 6A[PF6].
only ones to appear between 5.7 and 6.7 ppm at all temperatures.
In other words, the dppe phenyl rings seem to remain outside
of the shielding cone of the ruthenium atom. In conclusion,
rotation about the Fe-C37 and C38-C39 (see Figure 2 for the
labeling scheme) bonds is hindered in 6A[PF6] and 6B[PF6],
probably due to steric constraints.
Infrared Spectroscopy. Table 1 reports IR absorption bands
due to the CtC stretching mode of the novel organometallic
acetylides and the related 1[PF6]n (n ) 0, 1).11a For iron(II)
cases in which a degree of contribution from mesomer II, shown
in Scheme 1, becomes favored, a decrease in IR stretching
frequency is expected. In other words, as the delocalization of
electron density from iron to the carbon-rich ligand increases,
the frequency of the IR stretch decreases, as has been re-
ported.11,15 Such delocalization in type I compounds, however,
comes at a cost due to the loss in aromatic stabilization upon
perturbation of the (4n+2) aromatic electron count. Therefore,
it is not surprising that the IR stretch is lower for the naphthyl

Stereoelectronic Effects of the Arenophile (η5-Cp*Ru)
Organometallics, Vol. 25, No. 22, 2006 5317
Table 2. Crystal Data, Collection, and Refinement Parameters
2[PF6]
2[PF6]2
4
4[PF6]
6A[PF6]
6B[PF6]
6B[PF6]2
formula
C
54H59F6P3FeRu‚ 3C54H59F12FeP4Ru‚
C
48H46P2Fe
C48H46 F6P3Fe
C58H61P3FeF6Ru‚
CH2Cl2
1206.82
293(2)
triclinic
P1h
13. 113(5)
16.069(5)
16.817(5)
117.596(5)
92.541(5)
105.820(5)
2960(2)
2
C
58H61P3FeF6Ru‚
C
58H61F12FeP4Ru‚
CH2Cl2 4CH2Cl2
5171.25
CH2Cl2
CH3CN
fw
1142.74
293(2)
monoclinic
C2/c
31.623(5)
19.517(5)
20.576(5)
90
125.645(5)
90
740.64
100(2)
triclinic
P1h
8.5490(4)
11.9143(6)
19.4745(9)
91.627(2)
100.166(3)
103.780(2)
1891(0.2)
2
885.61
100(2)
monoclinic
P21/a
12.1157(4)
30.6594(10)
12.1468(4)
90
107.230(2)
90
1206.82
293(2)
triclinic
P1h
12.611(5)
15.465(5)
15.726(5)
73.519(5)
79.923(5)
72.445(5)
2791(2)
2
1307.92
293(2)
monoclinic
P21/c
16.9349(4)
14.5532(3)
22.8752(5)
90
96.1740(10)
90
temp (K)
cryst syst
space group
a (Å)
b (Å)
c (Å)
100(2)
monoclinic
P21/n
31.5094(18)
12.6356(7)
45.491(3)
90
92.890(3)
90
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
10320(4)
8
1.471
18089(2)
12
1.341
4310(0.2)
4
1.365
5605(0.2)
4
1.55
D
calc (g cm-3
)
1.301
1.282
1.436
cryst size (mm)
F(000)
0.7 × 0.5 × 0.4
0.4 × 0.2 × 0.02
0.3 × 0.25 × 0.1 0.28 × 0.15 × 0.04 0.5 × 0.4 × 0.3
0.5 × 0.4 × 0.3
0.8 × 0.4 × 0.1
4688
7452
780
1836
1170
1240
2676
abs coeff, µ (mm-1
θ range (deg)
hkl range
)
0.828
0.666
0.517
0.521
0.636
0.77
0.723
0.998-27.485
-41 to +40,
-25 to +25,
-25 to +26
10 840
0.77-27.50
-40 to +40,
-14 to +16,
-58 to +58
41 218
1.07-27.57
-11 to +11,
-15 to +15,
-21 to +25
29 196
1.76-27.50
-14 to +15,
-39 to +38,
-15 to +15
36 332
3.51-30.06
-15 to +17,
-22 to +22,
-23 to +23
14 252
1.36-34.93
-19 to +20,
-24 to +24,
-24 to +24
21 521
2.66-27.50
-21 to +21,
-18 to +17,
-29 to +29
23 838
total no. of reflns
no. of unique reflns
no. of restrs/params
a, b for wa
R1
6775
0/614
0.0305, 85.5961
0.048
15 406
0/1885
0.0893, 0
0.0884
8489
0/461
0.0600, 0.7368
0.0426
9863
0/532
0.0661, 9.3346
0.0708
7898
0/703
0.0871, 8.6493
0.0619
14 935
0/649
0.1151, 1.2884
0.0565
12 819
0/714
0.0655, 10.4225
0.0679
Rw
0.1034
0.2070
0.1062
0.1611
0.1508
0.1669
0.158
R1 (all data)
0.1082
0.1985
0.0612
0.1261
0.1410
0.0845
0.1177
R
w (all data)
0.1454
1.145
1.182, -0.746
0.2375
0.986
1.588, -1.774
0.1201
1.117
1.015, -0.465
0.1814
1.039
1.047, -0.629
0.2097
1.044
0.953, -0.874
0.1941
1.026
3.139, -0.734
0.1832
1.059
0.702, -0.527
goodness of fit/F2
refine diff density
max., min. (e Å-3
)
iron(II) derivative 4 than for the phenyl one 1, because the
naphthyl ring is less aromatic than the phenyl one.21
contribution from cumulenic resonance structure II (Scheme 1)
is larger in the iron(II) compound than in mesomer IV for the
iron(III) derivative. This phenomenon can be rationalized using
two arguments. First, the connection of the electron-rich iron-
(II) arylalkynyl moiety with (η5-Cp*)Ru+, a cationic electron-
withdrawing group, naturally explains the importance of me-
somer II. The mesomer resulting from π donation from the
iron(II) atom toward the complexed arene would result in a
cumulenic structure (Scheme 8) that would support complex-
ation by the arenophile on the five exterior phenyl carbons.
Evidence of the importance of this mesomer for a related
compound was given by Matsuzaka et al. (Scheme 9).23 This
group obtained a crystal structure that clearly showed unequal
Ru-C bond lengths about a flat benzenoid ring, which was part
of a fused-ring polyaromatic metallocycle. Furthermore, the
decrease of the CtC bond stretch induced by the coordination
of the (η5-Cp*)Ru+ fragment onto the phenyl ring is relatively
large (25 < ∆νCtC < 71 cm-1). These values are larger than
those for strongly electron-withdrawing groups such as NO2,
which favor a strong reorganization of the π-electron system
from the metal to the heteroatoms. In addition, after oxidation
of the iron center the inversion of the polarization of the
π-electron system observed for type I complexes does not occur.
Indeed, the π-electrons of the aromatic ring engaged in the
complexation with the Ru atom are not available to allow a
stabilization of the FeIII center, and the charge-delocalized
mesomer II (Scheme 8) includes a high-energy vinylic cation.
From these data, it cannot be concluded that the Ru terminus is
a stronger π acceptor than the nitro group, but the electron-
withdrawing character and the impact of its coordination on
the aryl ring taken as a whole make the (η5-Cp*)Ru+ fragment
more efficient than the nitro group at weakening the electron
density on the (η2-dppe)(η5-Cp*)Fe end-group.
Alternately, a contribution from cumulenic mesomer IV
(Scheme 1) can occur upon the oxidation of the iron atom, as
electron density is transferred across the ethynyl linker toward
the 17-electron iron. For example, the IR stretching frequency
decreases for both the phenyl 1[PF6] and naphthyl 4[PF6] iron-
(III) acetylides versus their iron(II) precursors. The comparison
between oxidation states enables us to report that the phenyl
and naphthyl aromatic rings act as better electron donors than
acceptors. Delocalization across the CtC bond occurs more
readily from the aromatic ring toward an electron-deficient iron
than from an electron-rich iron toward the aromatic ring.
Furthermore, the difference in frequency between the iron(II)
and iron(III) species is larger for the naphthyl species, which
is, once again, explained by its lower aromaticity relative to
the phenyl product. The important conclusion to be drawn is
that the significant reduction of the value of this IR stretch
implies good conduction of electron density along the acetylene
carbons. Despite the relative simplicity of these data, it should
be remembered that the frequency of the stretching mode
depends not only on the CtC bond order but also on the masses
of the termini.22 This size effect also plays a role in stretching
frequency reductions observed between 1 and 2[PF6] and
between 4 and 6B[PF6].
Interestingly, compounds 2[PF6] and 2[PF6]2 display a
relationship opposite that previously observed among the
plethora of known compounds of type I.11a These unique
products result in IR stretching frequencies for the iron(III)
compounds that are significantly larger than those for the
corresponding iron(II) species, in agreement with the shortening
of the C-C bond length of ca. 0.01 Å upon oxidation of 2-
[PF6] to 2[PF6]2 (see Table 3). These data suggest that the
(22) Schrader, B. Infrared and Raman Spectroscopy. Methods and
Applications; VCH: Weinheim, 1995.
(21) Randic, M. Chem. ReV. 2003, 103, 3449-3606.

5318 Organometallics, Vol. 25, No. 22, 2006
Shaw-Taberlet et al.
Table 3. Bond Lengths (Å) and Angles (deg)
a
2[PF6]
2[PF6]2
4
4[PF6]
6A[PF6]
6B[PF6]
6B[PF6]2
Bond Lengths
2.1689(6)
Fe-P1
2.1870(13)
2.1779(13)
1.889(5)
1.230(6)
1.424(6)
1.433(7)
1.405(7)
1.419(8)
1.393(8)
1.433(7)b
1.416(7)
2.256(2)
2.259(3)
2.277(2)
2.276(3)
2.283(2)
2.271(3)
1.900(8)
1.886(9)
2.2911(12)
2.1795(15)
2.1933(9)
2.2050(9)
1.880(3)
1.225(4)
1.427(4)
1.367(4)
1.416(4)
1.365(5)
1.438(5)
1.438(4)c
1.447(4)
2.2787(14)
Fe-P2
2.1608(6)
1.895(2)
1.223(3)
1.440(3)
1.378(3)
1.409(4)
1.384(4)
1.403(4)
1.432(3)c
1.427(3)
2.2436(11)
1.888(5)
1.253(7)
1.424(7)
1.399(7)
1.375(7)
1.345(7)
1.410(6)
1.439(7)c
1.434(6)
2.1783(17)
1.890(5)
1.216(7)
1.433(8)
1.422(8)
1.424(9)
1.399(10)
1.408(9)
1.445(8)‡
1.432(8)
2.3105(14)
1.905(5)
1.214(7)
1.429(7)
1.360(7)
1.424(8)
1.340(10)
1.419(9)
1.444(7)c
1.446(7)
Fe-C37
1.884(8)
C37-C38
C38-C39
C39-C40
C40-C41
C41-C42
C42-C43
C39-C44b or C48c
C43-C44b or C48c
1.211(10)
1.223(11)
1.214(10)
1.421(11)
1.419(11)
1.425(11)
1.400(12)
1.463(11)
1.438(10)
1.450(12)
1.425(11)
1.436(12)
1.404(13)
1.411(10)
1.366(13)
1.356(13)
1.406(11)
1.415(13)
1.445(11)
1.410(10)
1.423(11)
1.429(12)
1.413(11)
1.412(12)
C47-C48
C46-C47
C45-C46
C44-C45
C43-C44
Fe-Cp*centroid
1.417(3)
1.364(4)
1.403(4)
1.360(4)
1.423(4)
1.737
1.404(6)
1.343(7)
1.374(8)
1.365(7)
1.438(7)
1.779
1.436(9)
1.351(9)
1.385(11)
1.340(11)
1.438(10)
1.757
1.454(4)
1.404(4)
1.408(5)
1.387(5)
1.425
1.430(7)
1.396(7)
1.398(8)
1.399(9)
1.420(8)
1.801
1.748
1.809
1.655
1.790
1.774
1.785
1.817
1.813
1.805
1.718
1.700
1.712
1.746
Ru-Cp*centroid
Ru-Arcentroid
1.798
1.739
1.797
1.731
1.807
1.731
Bond Angles
85.37(2)
P1-Fe-P2
85.72(5)
88.69(13)
86.75(14)
172.0(4)
172.9(5)
117.2(4)b
119.2(4)
84.55(9)
84.76(9)
85.57(9)
84.4(2)
81.8(2)
80.6(3))
94.1(3)
84.10(4)
99.37(14)
79.50(13)
164.3(4)
176.5(5)
118.8(4)c
120.0(5)
85.64(6)
86.63(16)
84.83(15)
177.9(4)
166.3(6)
116.6(5)c
120.8(6)
86.60(4)
87.56(8)
81.12(8)
177.4(2)
171.8(3)
117.6(2)c
119.7(3)
84.71(5)
91.59(15)
84.03(15)
173.1(5)
173.1(6)
117.7(5)c
121.0(6)
P1-Fe-C37
85.22(7)
82.93(7)
175.4(2)
174.4(3)
118.6(2)c
119.2(2)
P2-Fe-C37
92.5(2)
94.6(3)
Fe-C37-C38
C37-C38-C39
C40-C39-C44b or 48c
C41-C42-C43
171.6(7)
175.7(7)
169.0(7)
171.2(9)
171.1(9)
176.3(8)
117.2(8)
117.2(8)
118.1(7)
122.3(10)
122.8(8)
120.6(10)
C48-C47-C46
119.9(2)
122.2(3)
121.8(5)
121.0(5)
119.7(6)
120.6(7)
179.1
120.6(3)
120.9(3)
179.1
120.8(5)
121.6(5)
178.8
C43-C44-C45
Arcentroid-Ru-Cp*centroid
177.4
118.3
179.0
177.9
178.7
119.7
121.4
120.2
Cp*centroid-Fe-C37
119.7
117.7
121.0
121.3
121.2
a There are three molecules and four disordered dichloromethane molecules in the asymmetric unit. b Data refer to phenyl bridging carbon, C44. c Data
refer to naphthyl bridging carbon, C48

Stereoelectronic Effects of the Arenophile (η5-Cp*Ru)
Organometallics, Vol. 25, No. 22, 2006 5319
Scheme 8. Cumulenic, Charge-Separated Mesomer of (I)
2[PF6] and (II) 2[PF6]2 Resulting from Donor-Acceptor
Interactions
activity, indicating that both enantiomers crystallized in equal
proportions within one crystal.
For complex 2[PF6], the bond distances between the Ru atom
and the carbon atoms of the phenyl ring are very similar. They
range from 2.203 to 2.214 Å (average 2.220 Å) with a Ru-
Cipso distance being slightly longer (2.270 Å). In the Fe(III)
derivative, 2[PF6]2, the coordination of the Ru atom is very
similar (average bond distances 2.216 Å, Ru-Cipso 2.288 Å).
The 2-3% lengthening of the Ru-Cipso bond lengths versus
Ru-CAr average lengths is not associated with a deformation
of the phenyl ring, which remains planar in both cases, clearly
indicating that the (η5-Cp*)Ru+ entity is firmly η6-coordinated.
This evidence of the π-accepting nature of the arenophile is in
agreement with the IR data reported above and the structural
data found by Matsuzaka et al. (Scheme 9).23 The X-ray analysis
reveals that the π donation from the electron-rich iron terminus
to the electron-withdrawing arenophile is not associated with a
partial decoordination of the Ru atom.
It is noteworthy that the complexation of the arenophile, (η5-
Cp*)Ru+, in 2[PF6] (Figure 2a) engenders some interesting
changes in molecular geometry with respect to the reference
molecule and precursor, 1.11a Upon complexation, the dppe
ligand retreats from the iron atom, while the Cp* ligand
undergoes no displacement. The retreat of the dppe ligand
suggests reduced Fe back-bonding due to the electron-withdraw-
ing nature of the arenophile. The Fe-C37 bond shortens slightly,
by 0.005 Å, a value that is within the error of the measurement,
and the C37-C38 triple bond lengthens by 0.020 Å with respect
to 1. This is in agreement with a reduction in C37-C38 bond
order as shown by the decrease in IR stretching frequency upon
complexation (see above and Table 1). However, the coordina-
tion of the arenophile seems to limit the structural reorganization
of the alkynyl fragment. The contribution of the mesomer II
(Scheme 1) is much smaller in 2[PF6] than in 1.
Finally the large degree of steric encumbrance is obvious from
the structural data. For example, the angle formed between the
Ru ligand centroids and the focal Ru atom (177.4°) slightly
deviates from linearity probably due to steric hindrance from
the ligated iron terminus. These steric constraints are also nicely
illustrated in Figure 2a with the curvature of the Fe‚‚‚C39
segment (Fe-C37-C38 ) 172.0(4)° and C37-C38-C39 )
172.9(5)°).
Oxidation of 2[PF6] to give 2[PF6]2 (Figure 2b) results in
the retreat of all ligands from the iron atom, while the Ru-
Caryl-centroid distance increases from 1.655 Å to ca. 1.710 Å.
Meanwhile, the average Ru-Caryl distance is almost unchanged
and the Cp*Ru unit is weakly displaced away from the iron
center, indicating that the steric constraints probably increase
upon oxidation of the iron center.
Scheme 9. Inter-ring Haptotropic Rearrangement of
(η5-Cp*)Ru+ Observed by Matsuzaka et al.23
Upon complexation to the arenophile, the iron(II) naphthyl
derivative IR stretch also decreases (4 vs 6B[PF6], ∆νCtC )
14 cm-1), a fact that may be attributed to a small increase of
the weight of mesomer B in the description of the electronic
structure. Upon oxidation, the peaks of both 4[PF6] and 6B-
[PF6]2 are split in two, as commonly occurs for type I
compounds.11a The frequency of the CtC stretch of organoiron,
4, decreases much more (62 < ∆νCtC < 122 cm-1) than that
of the binuclear daughter complex, 6B[PF6] (0 < ∆νCtC < 22
cm-1). This indicates that a cumulenic, quinoidal mesomer
(Schemes 1 and 8) plays a larger role in the description of the
electronic structure of oxidized organoiron, 4[PF6], than for its
ruthenium-containing homologue, due to the electronic proper-
ties of the (η5-Cp*)Ru+ arenophile.
X-ray Crystal Structures. Monocrystals of 2[PF6], 2[PF6]2,
4, 4[PF6], 6A[PF6], 6B[PF6], and 6B[PF6]2 were grown by the
slow diffusion of a nonsolvent into a concentrated solution of
the product (see Experimental Section). The diffractometric
parameters are given in Table 2, and interesting bond lengths
and angles are given in Table 3. The resulting structures
(excluding hydrogen atoms, counterions, and solvent molecules)
are shown in the ORTEP diagrams in Figures 2a-g. The
numbering of the phenyl and naphthyl rings is C39-44 and
C39-48, respectively, following the exteriors of the rings,
starting from the substituted carbon, C39. The salt 2[PF6]2
crystallizes in the monoclinic space group P21/n, and three
nonequivalent molecules were found in the unit cell. As a
consequence, the structural parameters are less accurate for this
heterobimetallic complex. Since the heterobimetallic naphthyl
derivatives 6A[PF6], 6B[PF6], and 6B[PF6]2 exhibit planar
chirality, attention was paid to whether these compounds
crystallized into a non-centrosymmetric space group, as such a
result may indicate the crystallization of a single enantiomer.
Optical polarimetry was conducted on crystals of 6B[PF6]2,
which was the only one to have a non-centrosymmetric space
group (P21/c). Unfortunately, the crystals showed no optical
Between the mononuclear iron(II) and iron(III) compounds,
4 and 4[PF6] (Figure 2), respectively, the molecular geometry
is perturbed in such a fashion that is in agreement with previous
findings for compounds of type I (Scheme 1).11a In brief, the
Fe-Cp*centroid and Fe-P bonds are lengthened upon oxidation,
whereas the Fe-C37 bond is slightly shortened. Furthermore,
the C37tC38 triple bond length significantly increases (see
Table 3). In addition, the marked general lengthening of the
C-C aromatic bonds of the naphthalene fragment points toward
the importance of the IV mesomer upon oxidation (Scheme 1).
Finally, the amplitude of bond length alternation around the
naphthyl rings is exaggerated in the case of 4[PF6] as compared
to 4 (Table 3). This fact points to a decrease in aromaticity upon
(23) Takemoto, S.; Oshio, S.; Shiromoto, T.; Matsuzaka, H. Organo-
metallics 2005, 24, 801-804.

5320 Organometallics, Vol. 25, No. 22, 2006
Shaw-Taberlet et al.
Table 4. UV-Vis Absorption Data in CH2Cl2
the loss of electron density. This is in accord with the prediction
of Hu¨ckel’s rule requiring a (2n+2)π integral electron count
for aromatic rings. Finally, one can note that the Fe(II)-C37t
C38 fragment of 4 mildly deviates from linearity (175.4(2)°),
as has been reported for other compounds of type I,11a and this
bending occurs to a greater extent (164.2(4)°) upon oxidation
to Fe(III), 4[PF6].
compd
absorption γ/nm (103 e/dm3 mol-1 cm-1
)
17a
277 (sh, 14,5); 350 (6.6)
261 (sh, 32.6); 280 (sh, 27.4); 301 (sh, 18.8);
1[PF6]7c
342 (sh, 5.9); 379 (sh, 3.6); 575 (sh, 2.3); 662 (3.1)
161 (sh, 11.3); 402 (9.1)
422 (3.9); 515 (3.5)
2[PF6]
2[PF6]2
4
433 (12.8)
A further iron(II)-iron(III) structural contrast can be made
between 6B[PF6] and 6B[PF6]2. The iron(II) species crystallizes
into the rotational conformer in which (η5-Cp*)Fe and (η5-Cp*)-
Ru+ fragments are cofacial with respect to the naphthyl plane
(Figure 2e), while the opposite conformer is chosen for the iron-
(III) species (Figure 2f). All iron(III) ligands retreat from the
metal with respect to the iron(II) product (see Table 3), whereas
the Fe-C37 bond weakly shortens upon oxidation in the case
of the mononuclear precursor, 4. In agreement with the results
for 4/4[PF6], the bending of the Fe-C37tC38 fragment also
increases (by 4°) upon oxidation of 6B[PF6] to 6B[PF6]2.
Comparison of the variation of the bond distances in the
coordination sphere of the iron atom upon oxidation to form
complexes 4[PF6] and 6B[PF6]2 suggests that the presence of
the (η5-Cp*)Ru+ fragment on cycle B does not significantly
affect the reorganization of the coordination sphere of iron upon
electron transfer. However, one notes that ring A geometry is
less perturbed by oxidation of the iron center in the case of
6B[PF6] (av difference in bond length, 0.01067 Å) than in that
of 4 (0.04183 Å). In both cases, the average C-C naphthalene
bond length decreases upon oxidation.
4[PF6]
6B[PF6]
6B[PF6]2
496 (2.9); 772 (2.8)
329 (sh, 11.5); 569 (7.9)
354 (6.6); 415 (6.6); 508 (4.2); 791 (1.3)
while complexed rings display increased aromaticity. Such a
change in aromaticity largely accounts for the difference in
electron transfer and exchange properties within this series.
UV-Visible Spectroscopy. UV-visible spectra for this
novel family of ethynyl compounds are compared in Table 4.
The data resemble spectra for previously studied type I
compounds, for which the principle absorptions above 270 nm
were attributed to MLCT (iron(II) and iron(III) complexes) or
LMCT (iron(III) complexes) bands.11 Complexation of the
arenophile results in a red shift of the MLCT band observed
for iron(II) species. For example, compared to that of their
respective precursors 1 and 4, this band undergoes a large
bathochromic shift of 52 nm in the case of 2[PF6] and of 136
nm for 6B[PF6]. Such a bathochromic shift indicates a decrease
in the HOMO-LUMO gap upon complexation. The reduction
in the HOMO-LUMO gap for the latter provides evidence that
the metal-centered HOMO electrons are more polarizable when
the arenophile resides on the B ring. In comparison with type
I compounds (Scheme 1), the UV-vis data indicate that the
electron-withdrawing effect of the (η5-Cp*Ru) arenophile falls
between those of the nitro and cyano groups.11c
It is of interest to contrast the molecular geometries of the
naphthyl acetylide iron(II) species before (4) and after com-
plexation (6A[PF6] and 6B[PF6]). Both 6A[PF6] (Figure 2g)
and 6B[PF6] (Figure 2e) crystallize as the conformer in which
(η5-Cp*)Fe and (η5-Cp*)Ru+ are on the same face of the
naphthyl plane. For both regioisomers, Fe-Cp* and Fe-P bonds
lengthen upon complexation of the arenophile (Table 3).
However, the increase of the Fe-P bond distances is much
larger in 6B[PF6] than in 6A[PF6], indicating that the arenophile
modifies the electronic properties of the iron center more
efficiently when it is coordinated on the side cycle (cycle B) of
the naphthalene fragment than on the cycle A linked onto the
metal alkynyl. This confirms that the coordination of the
arenophile on cycle B favors the electronic delocalization and
increases the weight of the cumulenic mesomer like mesomer
II (Scheme 1), whereas complexation of the (η5-Cp*)Ru on cycle
A has a limited effect (see mesomer II, Scheme 8) due to the
reinforcement of the aromaticity of cycle A.
Moreover, the LMCT band, the lowest energy absorption
observed for the iron(III) species, is even more sensitive to the
position of the arenophile (ring A or ring B). For example, the
phenyl ethynyl organoiron(III), 1[PF6], absorbs at 662 nm,
whereas the dinuclear Fe(III)/Ru(II) complex undergoes the
LMCT transition at 515 nm. The large hypsochromic shift of
the LMCT band upon A-ring complexation amounts to nearly
150 nm for the phenyl series. In other words, the energy of the
ligand-centered orbital, HOMO-n, should decrease much more
upon complexation than does the energy of the HOMO. This
suggests that the LMCT transition comes from the aryl-centered
orbitals. The large blue shift of this transition provides strong
evidence that the phenyl electrons of 2[PF6] are much less
polarizable than those of 1. Therefore, the arenophile increases
hardness of both the iron (HOMO) electrons and aryl (HOMO-
n) electrons in the phenyl series. On the other hand, the naphthyl
iron(III) series is characterized by a small bathochromic shift
of the LMCT band upon (η5-Cp*)Ru+ complexation (19 nm).
Similarly, this indicates that the aryl electrons are more
polarizable after complexation onto the B ring of 4. These UV-
vis spectroscopic data provide further examples, along with IR
data, of the opposite effects that A-ring and B-ring complexation
have on the electronic communication across the ethynyl linker.
Cyclic Voltammetry. Table 5 reports the reversible
An in-depth analysis of the degree of perturbation of
naphthalene aromaticity upon arenophile complexation can be
obtained by comparing the naphthyl geometries before and after
complexation. In general, for both naphthyl rings of both
regioisomers 6A[PF6] and 6B[PF6], bonds within the complexed
ring in both cases incorporate less overall bond length deviation
and a smaller and less regular amplitude of bond length
alternation than for the corresponding ring in 4.20 For noncom-
plexed naphthalene rings in 6A[PF6] and 6B[PF6], the overall
deviation in bond length and the amplitude of bond length
alternation are greater than for 4. The reduction in bond length
alternation observed for both regioisomers 6A[PF6] and 6B-
[PF6] for the complexed rings suggests that the π-bonding
electrons of such a ring can be described as being more
delocalized, more equally shared among the six aromatic carbon
bonds. In contrast, the noncomplexed ring in both regioisomers
exhibits exaggerated bond alternation. In conclusion, the areno-
phile complexation reduces the aromaticity of adjacent rings,
a
c
(ip /ip ) 1.0), one-electron standard redox potentials for the
iron(II)-iron(III) couples from the cyclic voltamograms. The
reversibility of the oxidation reveals that the iron(III) species
are stable at the electrode. Compounds 111a and 4 exhibit similar
peak potentials, with the naphthyl acetylide adduct, 4, being
shifted anodically by 0.014 V, in accordance with a decrease
(13 cm-1) of the C-C infrared absorption (see above). The
relative facility of oxidation of 4 is attributed to the lower
aromaticity of the substituted naphthalene ring, which facilitates

Stereoelectronic Effects of the Arenophile (η5-Cp*Ru)
Organometallics, Vol. 25, No. 22, 2006 5321
Table 5. Standard Redox Potentials Measured by Cyclic
Voltammetry
Table 7. Electron Spin Resonance Spectroscopic Data
b
compd
g1
g2
g3
giso
∆g
giso
ref
compd
E0(FeII-FeIII),a V
ref
1[PF6]
2[PF6]2
4[PF6]
2.464 2.033 1.975 2.157 0.489
2.506 2.031 1.972 2.170 0.534
2.465 2.028 1.973 2.155 0.492 2.013 this work
14
this work
1
-0.15
0.090
-0.136
0.055
7a
2[PF6]
4
6B[PF6]
this work
this work
this work
6B[PF6]2 2.503 2.026 1.971 2.167 0.532 2.010 this work
a At 77 K in CH2Cl2/C2H4Cl2 (1:1) glass unless otherwise noted. b At
298 K.
a Conditions: 0.1 M tetra-n-butylammonium hexafluorophosphate in
CH2Cl2; scan rate ) 0.1 V/s, Pt electrodes, V vs SCE (cf. ferrocene/
ferrocenium 0.460 V vs SCE).
77 and, when electronic relaxation proved sufficiently rapid, at
298 K. Table 7 summarizes the results. The spectra of 1[PF6]
and 4[PF6] nearly appear superimposable at 77 K. However,
whereas the complex 1[PF6] is not ESR active at 298 K, the
complex with the naphthyl substituent displays a well-resolved
sharp signal allowing the determination of the giso value at 298
K. Upon warming, the giso shifts from 2.155 to 2.013. These
data taken as a whole suggest that SOMOs are very similar in
both complexes, but upon warming reorganization takes place
in the case of 4[PF6] and the ligand character of the radical
increases.
Upon complexation of the (η5-Cp*)Ru+ arenophile, the g1
tensor increases for both the phenyl ethynyl, 2[PF6]2, and
1-naphthyl acetylide, 6B[PF6]2, whereas g2 and g3 remain almost
unchanged. As a consequence, the presence of the arenophile
increases both the isotropy (giso) and anisotropy (∆g) tensors.
This is in line with previous observations for Fe(III) type I
complexes for which the giso and ∆g values increase with the
electron-withdrawing character of the substituents on the phenyl
ring.11c It has been assumed that ESR anisotropy arises
essentially from spin-orbit coupling. The more the unpaired
electron is ligand centered, the less anisotropic the ESR signal
will be. In addition, its giso value becomes concomitantly closer
and closer to the ge value (ge ) 2.0023). On the basis of this
simple reasoning, we can conclude that the (η5-Cp*)Ru+
arenophile increases the iron character of the odd electron, by
decreasing the contribution from a cumulenic mesomer of type
II (Scheme 8).
Table 6. Least-Squares-Fitted Mo1ssbauer Spectroscopic
Data
compd
ISa(QS), mm s-1
FeII or FeIII
ref
1
0.27 (2.02)
0.25 (0.9)
II
14
14
1[PF6]
2[PF6]2
4
4[PF6]
6B[PF6]
6B[PF6]2
III
III
II
III
II
0.21 (0.74)
0.26 (2.00)
0.28 (0.97)
0.27 (2.05)
0.28 (0.95)
this work
this work
this work
this work
this work
III
iron(III) stabilization through the contribution of mesomer IV
(Scheme 1b). Similar aromaticity arguments have been made
to describe the electrochemical behavior of related phenyl and
anthracenyl acetylide iron compounds.12a,b
Complexation of organoirons 1 and 4 by the Cp*Ru+
arenophile to give 2[PF6] and 6B[PF6], respectively, results in
a large anodic shift in redox potential. Specifically, this
difference amounts to 0.240 V for the phenyl adduct (2[PF6])
and 0.191 V for the naphthyl one (6B[PF6]) (Table 5). The
increased difficulty of oxidation of the iron(II) results from three
factors. First, the fact that the bimetallic compounds are already
cationic in the iron(II) state plays a role. Second, the electron-
withdrawing nature of the arenophile perturbs the electronic
environment of the electron-rich iron(II) center. Finally, the
trapping of the aromatic π-electrons via coordination to the
arenophile affects the formation of the cumulenic/quinoidal
mesomer (Scheme 8). The latter two factors play a larger role
for 2[PF6] than for 6B[PF6], which explains the much larger
anodic shift of the former, in agreement with the spectroscopic
data.
Inter-ring Haptotropic Rearrangements. As stated in the
Introduction, arene chromium tricarbonyl derivatives have
frequently been employed to study inter-ring haptotropic migra-
tion focusing on η6-η6 metal shifts.6-8 Such transformations
have been observed in sandwich compounds as well. For
instance, the (η5-Cp*)Ru+ arenophile was shown to undergo
inter-ring haptotropic rearrangement in the metallocyclic fused-
ring system shown in Scheme 9.23 Another example, the inter-
ring migration of the isolobal dicationic (η5-Cp*)Ir2+ group, was
reported in the reaction of [(η5-Cp*)Ir(OdCMe2)3][BF4]2 with
1,2,5,6-tetramethylcorannulene (C20H6Me4).26 In both cases, the
shifts of the arenophile are likely solvent assisted. In contrast,
the absence of residual coordinating solvent to facilitate
isomerization may explain the very slow, or nonexistent,
migration of the (η5-Cp*)Ru+ group generated in situ from [(η5-
Cp*)Ru(µ3-Cl)]4 and an AgX salt in CD3NO2, with C20H6Me4.27
Mo1ssbauer Spectral Studies. These spectral data are sum-
marized in Table 6. The results point to the high degree of purity
of all products, only one doublet being seen in each spectrum.24
All compounds, excepting 2[PF6]2, behave like classical type I
compounds in both oxidation states.11a Surprisingly, 2[PF6]2,
an iron(III) complex, exhibits much lower isomer shift (IS )
0.21 mm/s) and quadrupole splitting (QS ) 0.74 mm/s) values.
The IS parameter is known to be very sensitive to the electronic
density about the iron nucleus. It is possible that the positive
charge around the Ru center is sensed by the iron nucleus both
through bonding and, considering the small Fe-Ru distance,
through space. The QS value for 2[PF6]2 is exceptionally small.
It is significantly lower than for the iron(III) type I compound
substituted with NO2. This observation is consistent with a lower
Fe-CR bond order18L,25 within 2[PF6]2, in agreement with the
IR data (see above). The (η5-Cp*)Ru+ arenophile both serves
as a strong electron acceptor and effectively prevents the
formation of cumulenic mesomer D (Scheme 1).
1
In related studies, variable-temperature H NMR spectroscopy
has ruled out intramolecular migration (∆G > 20 kcal/mol) of
the (η5-Cp*)Ru+ unit on the corannulene or acecorannulene
surface.28 On the other hand, Wheeler and co-workers have
Electron Spin Resonance Spectroscopy. The spectra for all
paramagnetic compounds reported herein were taken both at
(26) Alvarez, C. M.; Angelici, R. J.; Sygula, A.; Sygula, R.; Rabideau,
P. W. Organometallics 2003, 22, 624-626.
(27) Vecchi, P. A.; Alvarez, C. M.; Ellern, A.; Angelici, R. J.; Sygula,
A.; Sygula, R.; Rabideau, P. W. Organometallics 2005, 24, 4543-4552.
(28) (a) Seiders, T. J.; Baldridge, K. K.; O’Connor, J. M.; Siegel, J. S.
J. Am. Chem. Soc. 1997, 119, 4781-4782. (b) Seiders, T. J.; Baldridge, K.
K.; O’Connor, J. M.; Siegel, J. S. Chem. Commun. 2004, 950-951.
(24) (a) Greenwood, N. N. Mo¨ssbauer Spectroscopy; Chapman and
Hall: London, 1971. (b) Varret, F.; Mariot, J.-P.; Hamon, J.-R.; Astruc, D.
Hyperfine Interact. 1988, 39, 67-81.
(25) Guillaume, V.; Thominot, P.; Coat, F.; Mari, A.; Lapinte, C. J.
Organomet. Chem. 1998, 565, 75-80.

5322 Organometallics, Vol. 25, No. 22, 2006
Shaw-Taberlet et al.
shown29 that the regioselectivity of (η5-Cp*)Ru+ complexation
onto monosubstituted naphthalenes favors more electron-rich
rings and that, in some instances, sterics plays a role even more
important than that played by electronics. We found the same
to be true for inter-ring haptotropic migration, as detailed below.
Among the reactions described in the present study, two were
expected to give rise to chemically and redox induced inter-
ring haptotropic rearrangements of the (η5-Cp*)Ru+ arenophile
on the basis of steric and electronic arguments. As previously
reported,8 we expected to see a switch from the B haptotropomer
to the A one (Scheme 3) upon the deprotonation of 5B[PF6]2.
Upon deprotonation, the steric encumbrance of the A ring was
expected to be reduced to a larger extent than for the B ring.
Furthermore, the strongly electron-donating organoiron sub-
stituent loses its positive charge upon deprotonation, and full
conjugation is restored along the ethynyl linker. All three of
these factors were expected to favor inter-ring slippage of the
arenophile onto the substituted naphthyl ring. In agreement with
the above arguments, the deprotonation of 5B[PF6]2 yielded
some of the A haptotropomer, 6A[PF6], along with the major
product, 6B[PF6], in a 1:11 spectroscopic ratio (8 mol %
underwent inter-ring haptotropic rearrangement, while 92% did
not) in MeOH/THF solution at room temperature.
among the complexes were roundly revealed to change as a
function of whether the arenophile was collinear with the ligated
iron (as in 2[PF6] and 6A[PF6]) or found on the unsubstituted
naphthyl ring (6B[PF6]). In addition, this work represents the
first thorough study of the changing electronic and steric
environments of an arenophile on both the substituted and
unsubstituted naphthyl rings between which it moves. The
electron-withdrawing character, specifically the trapping of the
aromatic π electrons, renders the (η5-Cp*)Ru+ fragment more
efficient than the nitro group at reducing the electron density
on the redox-active (η2-dppe)(η5-Cp*)Fe end-group.
Finally, a small degree of haptotropic rearrangement of the
(η5-Cp*)Ru+ arenophile was shown to occur at room temper-
ature between the two naphthyl rings upon in situ variation of
the electronic and steric environments. The low overall degree
of inter-ring haptotropic rearrangement is accounted for by the
steric encumbrance in both haptotropomers. A significant
decrease in total steric strain might solve the above-mentioned
problems and give rise to better yields of inter-ring haptotropic
rearrangements upon deprotonation, oxidation, and reduction.
In this vein, syntheses incorporating a less bulky arenophile are
currently under way.
More interestingly, based on X-ray data, we thought that an
oxidation state dependent contraction/elongation of the Fe-C39
segment might work in conjunction with electronics in favor
of a redox-initiated inter-ring haptotropic rearrangement of the
arenophile. Therefore, a regiopure sample of 6B[PF6], which
is thermally stable and does not interconvert into 6A[PF6], was
subjected to chemical oxidation and reduction cycles. The
oxidation was carried out as described in the Experimental
Section. Upon treatment of the resulting solution with cobal-
tocene at ambient temperature, the ratio 6A[PF6]:6B[PF6] was
determined to be 6:94 by NMR. We were curious to see whether
the percentage to undergo inter-ring migration can be cumula-
tive. Therefore, we subjected a regiopure sample of 6B[PF6] to
two successive chemical redox cycles. After the second cycle,
about 12% of the product had been converted to regioisomer
A. The small degree of haptotropic rearrangement induced
during the oxidation/reduction cycle was not accompanied by
decomplexation of the arenophile. The low overall degree of
both above-mentioned inter-ring haptotropic rearrangements is
accounted for by the steric encumbrance in both haptotropomers
in both oxidation states.
Experimental Section
General Procedures. Manipulations of air-sensitive compounds
were performed under an argon atmosphere using standard Schlenk
techniques or in an argon-filled Jacomex 532 drybox. Tetrahydro-
furan (THF), diethyl ether, toluene, and pentane were dried and
deoxygenated by distillation from sodium/benzophenone ketyl.
Acetone was distilled from P2O5. Dichloromethane and dichloro-
ethane were distilled under argon from P2O5 and then from Na2-
CO3. Methanol was distilled over dried magnesium turnings. The
following compounds were prepared following published proce-
dures: 1-ethynylnaphthalene,30 ferrocenium hexafluorophosphate
[Fe(η5-Cp)2][PF6](FcPF6),31 (η2-dppe)(η5-Cp*)Fe-Cl,32 (η2-dppe)-
(η5-Cp*)Fe-CtC-Ph (1),11a and [(η5-Cp*)Ru(CH3CN)3][PF6].13,14
Potassium tert-butoxide (ACROS) was used without further puri-
fication. Infrared spectra were obtained as Nujol mulls or as films
between KBr windows with a Bruker IFS28 FTIR infrared
spectrophotometer (4000-400 cm-1). UV-visible spectra were
1
recorded on a UVIKON XL spectrometer. H, 13C, and 31P NMR
spectra were recorded on a Bruker DPX200, Avance 300, or Avance
500 NMR multinuclear spectrometer at ambient temperature, unless
otherwise noted. Chemical shifts are reported in parts per million
(δ) relative to tetramethylsilane (TMS), using the residual solvent
resonances as internal references. Coupling constants (J) are
reported in hertz (Hz), and integrations are reported as numbers of
protons. The following abbreviations are used to describe peak
patterns: br ) broad, s ) singlet, d ) doublet, dd ) double doublet,
Conclusions
In this contribution, we have detailed the efficient syntheses
and complete spectroscopic and structural characterizations of
a novel family of mono- and heterobinuclear acetylide com-
plexes. These complexes feature an electron-rich (η2-dppe)(η5-
Cp*)Fe end-group and another end-group of variable aromaticity
as well as steric and electronic environment, sometimes includ-
ing a cationic ruthenium sandwich complex. These syntheses
are noteworthy in that they exhibit regioselective complexation
of the (η5-Cp*)Ru+ arenophile onto either a phenyl, 2[PF6], or
a naphthyl, 5B[PF6]2, 6A[PF6], and 6B[PF6], ring in the
presence of four free and electron-rich phenyl rings. This
preference is explained by both the steric encumbrance of the
dppe phenyl rings and the excellent overlap between the
electron-rich iron acetylide substituent and the ethynyl phenyl
and naphthyl rings. Furthermore, the electron transfer properties
1
t ) triplet, h ) heptet, m ) multiplet. H and 13C NMR peak
assignments are supported by the use of COSY, HMQC, and HMBC
experiments. High-resolution mass spectra (HRMS) were recorded
on a high-resolution ZabSpec TOF VG analytical spectrometer
operating in the ESI+ mode, at the Centre Re´gional de Mesures
Physiques de l’Ouest (CRMPO), Rennes. Poly(ethylene glycol)
(PEG) was used as internal reference, and dichloromethane was
used as solvent. EPR spectra were recorded on a Bruker EMX-8/
2.7 (X-band) spectrometer. The 57Fe Mo¨ssbauer spectra were
recorded with a 2.5 × 10-2 C (9.25 × 108 Bq) 57Co source using
a symmetric triangular sweep mode. Computer fitting of the
Mo¨ssbauer data to Lorentzian line shapes was carried out with a
(30) John, J. A.; Tour, J. M. Tetrahedron 1997, 53, 15515-15534.
(31) Connelly, N. G.; Geiger, W. E. Chem. ReV. 1996, 96, 877-910.
(32) Roger, C.; Hamon, P.; Toupet, L.; Rabaa, H.; Saillard, J.-Y.; Hamon,
J.-R.; Lapinte, C. Organometallics 1991, 10, 1045-1054.
(29) Wheeler, D. E.; Hill, S. T.; Carey, J. M. Inorg. Chim. Acta 1996,
249, 157-161.

Stereoelectronic Effects of the Arenophile (η5-Cp*Ru)
Organometallics, Vol. 25, No. 22, 2006 5323
previously reported computer program.33 The isomer shift values
are reported relative to iron foil at 298 K. Elemental analyses were
conducted on a Thermo-Finnigan Flash EA 1112 CHNS/O analyzer
by the Microanalytical Service of the CRMPO at the University of
Rennes 1, France, and by Ilse Beetz Microanalytisches Laborato-
rium, Kronach, Germany.
C48H47P256Fe (C+), 741.2502; found, 741.2502. FT-IR (Nujol,
1
cm-1): 1623, 1606 (d, CdC). H NMR (200 MHz, CDCl3): δ
7.88-6.56 (m, 47H, Ar/dppe, Ar/BPh4, and Ar/napht); 5.76 (t, 4JH-P
) 4.0 Hz, 1H, Hvin); 2.90 (m, 2H, CH2/dppe); 2.32 (m, 2H, CH2/
dppe); 1.57 (s, 15H, Fe-Cp*). 13C{1H} NMR (75.5 MHz,
2
CDCl3): δ 356.70 (t, JP-C ) 33 Hz, CR); 137.0-122.5 (m, Ar/
[(η2-dppe)(η5-Cp*)Fe-CtC-{(η6-phenyl)Ru(η5-Cp*)}]-
[PF6] (2[PF6]). The previously described product, 1 (0.260 g, 0.377
mmol), and [(η5-Cp*)Ru(CH3CN)3][PF6] (0.1715 g, 0.377 mmol,
1 equiv) were combined with 10 mL of CH2Cl2. This red solution
was stirred overnight at RT, protected from light, and then filtered
into a new Schlenk flask. The filtrate was partially precipitated with
diethyl ether. The product isolated by filtration was washed twice
with 2 mL portions of diethyl ether and dried in vacuo to yield
0.270 g (0.252 mmol) of red powder (69% yield), which was
crystallized by slow diffusion of diethyl ether into a concentrated
dichloromethane solution of the product. HRMS ESI+: m/z calcd
for C54H5956FeP2102Ru (C+), 927.24849; found, 927.2504. 1H NMR
(200 MHz, CDCl3): δ 7.68 (m, 4H, o-Ar dppe); 7.43 (m, 8H, 4m-
Ar dppe and 4p-Ar dppe); 7.32 (t, 3JH-H ) 6.8 Hz, 4H, m-Ar dppe);
7.21 (t, 3JH-H ) 7.6 Hz, 4H, o-Ar dppe); 5.53 (t, 3JH-H ) 5.6 Hz,
2H, m-C6H5); 5.45 (d, 3JH-H ) 5.2 Hz, 1H, p-C6H5); 5.06 (d, 3JH-H
) 5.8 Hz, 2H, o-C6H5); 2.46 (m, 2H, CH2/dppe); 2.02 (m, 2H,
CH2/dppe); 1.75 (s, 15H, Ru-Cp*); 1.34 (s, 15H, Fe-Cp*). 13C-
{1H} NMR (50 MHz, acetone-d6): δ 137.15 (br s, CR); 133.91 (s,
o-Ar/dppe); 133.60 (s, o-Ar/dppe); 129.64 and 129.53 (s, p-Ar/dppe);
127.65 (s, m-Ar/dppe); 95.01 (s, Ru-Cp*); 93.10 (s, o-C6H5); 88.80
(br s, Fe-Cp*); 86.27 (s, m-C6H5); 84.17 (s, p-C6H5); 84.1 (s, ipso-
C6H5); 29.85 (m, CH2/dppe); 10.37 (s, Ru-Cp*); 10.22 (s, Fe-
Cp*). 31P NMR (81 MHz, acetone-d6): δ 98.85 (s, dppe); -143.0
BPh4, Ar/napht, and Ar/dppe); 122.0 (s, Câ); 100.60 (s, Fe-Cp*);
30.15 (m, CH2/dppe); 10.78 (s, Fe-Cp*). 31P NMR (81 MHz,
CDCl3): δ 88.74 (s, dppe). Anal. Calcd for C72H67BP2Fe: C, 81.51;
H, 6.37. Found: C, 81.65; H, 6.53.
[(η2-dppe)(η5-Cp*)FedCdCH-1-Naphthyl][PF6] (3[PF6]). An
excess of freshly deprotected 1-naphthyl acetylene (1.09 equiv,
0.250 g, 1.64 mmol) was combined with NaPF6 (1.2 equiv, 0.3023
g, 1.800 mmol) and stirred in MeOH (20 mL) for 30 min before a
THF solution of (η2-dppe)(η5-Cp*)FeCl (0.921 g, 1.47 mmol) was
added via cannula. The reaction was stirred overnight at room
temperature in the absence of light. The solvents were then
evaporated and the solid was extracted with CH2Cl2 and partially
precipitated from pentane to yield a brown, gluey paste. After one
pentane washing (10 mL) and vacuum-drying, a brown powder was
obtained at a yield of 1.303 g (1.214 mmol, 83%). HRMS (ESI+):
m/z calcd for C48H47P256Fe (C+), 741.25024; found, 741.2482. FT-
IR (Nujol, cm-1): 1588 and 1510 s. 1H NMR (200 MHz, acetone-
4
d6): δ 7.94-6.73 (m, 27H, Ar/dppe, Ar/napht); 5.79 (t, JH-P
)
4.4 Hz, 1H, Hvin); 3.29 (m, 2H, CH2/dppe); 2.77 (m, 2H, CH2/
dppe); 1.74 (s, 15H, Fe-Cp*). 31P NMR (81 MHz, acetone-d6): δ
1
88.95 (s, dppe); -143.0 (h, JP-F ) 708 Hz, PF6).
[(η2-dppe)(η5-Cp*)Fe-CtC-1-Naphthyl] (4). To 1.002 g
(1.057 mmol) of 3[BPh4]) was added 1.2 equiv of t-BuOK (142
mg) along with 10 mL of MeOH and 5 mL of THF. The mixture
was stirred at room temperature for 2 h, after which the solvents
were evaporated under vacuum, and the remaining solid was
extracted in THF and partially precipitated from methanol. The
resulting precipitate was washed three times with pentane and
vacuum-dried to yield 0.630 g of orange powder (0.85 mmol, 81%),
from which crystals were obtained via the slow diffusion of
methanol into a concentrated dichloromethane solution of the
product. HRMS (ESI+): m/z calcd for C48H46P256Fe (C+), 740.2424;
found, 740.2419. 1H NMR (CDCl3, 200 MHz): δ 8.09 (t, 4H, 3JH-H
) 7.8 Hz, HAr/dppe); 8.02 (d, 1H, 3JH-H ) 9.6 Hz, HAr); 7.86 (d,
1
(h, JP-F ) 708 Hz, PF6).
[(η2-dppe)(η5-Cp*)Fe-CtC-{(η6-phenyl)Ru(η5-Cp*)}]-
[PF6]2 (2[PF6]2). A 180 mg (0.168 mol) quantity of the Fe(II)
complex 2[PF6] and 1 equiv (0.056 g, 0.168 mmol) of FcPF6 were
combined and cooled to -60 °C under inert atmosphere before
being dissolved in cold THF (-60 °C) and allowed to warm to
room temperature overnight with stirring. The following morning,
a reddish solid was visible in the solution. Enough dichloromethane
(30 °C) was added to dissolve the solid, and the product was
precipitated from cold diethyl ether. Removal by cannula filter of
the supernatant, one diethyl ether washing, and repetition of the
partial precipitation yielded 0.175 g (86%) of dark product upon
vacuum-drying. Orange, platelike crystals were obtained upon the
slow diffusion of pentane into a concentrated dichloromethane
solution of product at -20 °C. HRMS (ESI+): m/z calcd for
C54H5956FeP2102Ru (C2+), 463.6242; found, 463.6253. 1H NMR (200
MHz, acetone-d6): δ 15.5 (br s, 2H, ArH); 7.9 (br s, 3H, ArH);
7.6 (br s, 6H, ArH); 6.1 (br s, 3H, ArH); 3.5 (br s, 5H, ArH); 2.8
(s, 3H, ArH); 2.75 (m, 2H CH2/dppe); 2.7 (s, 15H, Ru-Cp*); 0.8
(m, 2H, CH2/dppe); -3.9 (br s, 1H, ArH); -9.7 (br s, 2H, ArH);
-11.7 (br s, 15H, Fe-Cp*).
[(η2-dppe)(η5-Cp*)FedCdCH-1-Naphthyl][BPh4] (3[BPh4]).
To an excess of freshly made 1-naphthyl acetylene (0.304 g, 2.0
mmol) was added 0.704 g (1.13 mmol) of (η2-dppe)(η5-Cp*)FeCl
along with 10 mL of MeOH and 3 mL of THF under inert
atmosphere. The mixture was stirred at room temperature for 30
min, at which point, 0.386 g (1.13 mmol) of NaBPh4 in THF was
added via cannula, and the reaction was stirred overnight at room
temperature in the absence of light. The solvents were then
evaporated and the solid was extracted with CH2Cl2 and partially
precipitated from pentane. After one pentane washing (10 mL), the
brown, gluey paste was dried under vacuum to yield 1.002 g of
brown powder (1.057 mmol, 94%). HRMS (ESI+): m/z calcd for
3
3
1H, JH-H ) 8.0 Hz); 7.6-7.3 (m, 19H, HAr); 7.20 (t, 1H, JH-H
3
) 7.2 Hz, HAr); 7.1 (d, 1H, JH-H ) 7.2 Hz, HAr); 2.77 (m, 2H,
dppe) 2.05 (m, 2H, dppe); 1.54 (s, 15H, FeCp*). 13C{1H} NMR
2
(CDCl3, 50.3 MHz): δ 145.07 (t, JP-C ) 39.2 Hz, FeCtC);
139.8-122.1 (m, Ar/napt and Ar/dppe); 119.7 (s, FeCtC); 87.83
(s, FeCp*); 30.79 (m, CH2/dppe); 10.28 (s, FeCp*). 31P NMR
(CDCl3, 81 MHz): δ 101 (s, dppe). Anal. Calcd for C48H46-
FeP2‚CH3OH (crystallization solvent): C, 76.16; H, 6.52. Found:
C, 75.80; H, 6.28.
[(η2-dppe)(η5-Cp*)Fe-CtC-1-Naphthyl][PF6] (4[PF6]). The
Fe(II) complex, 4 (0.260 g, 0.232 mmol), and 0.92 equiv (0.073 g,
0.213 mmol) of FcPF6 were combined and cooled to -60 °C under
inert atmosphere before being dissolved in cold THF (-60 °C) and
allowed to warm to room temperature overnight with stirring. The
following morning, the solution was concentrated and the product
precipitated from a 4:1 mixture of cold ether/pentane. Removal by
cannula filter of the supernatant and vacuum-drying yielded 0.206
g (70%) of a very dark powder, which formed orange, platelike
crystals by slow diffusion of pentane into a concentrated dichlo-
romethane solution of the product. HRMS (ESI+): m/z calcd for
C48H4656FeP2 (C+), 740.2424; found, 740.2415. 1H NMR (300 MHz,
acetone-d6): δ 33.06 (s, 1H, ArH); 16.74 (br s, 1H, ArH); 16.37
(s, 1H, ArH); 6.94 (s, 4H, ArH); 6.67 (s, 1H, ArH); 6.50 (s, 1H,
ArH); 3.82 (s, 5H) 2.08 (br s, 2H, CH2/dppe); -2.60 (s, 1H, ArH);
-2.91 (br s, 2H, CH2/dppe); -4.91 (s, 1H, ArH); -10.46 (br s,
15H, Fe-Cp*); -52.68 (br s, 1H, ArH); -63.78 (br s, 1H, ArH).
31P NMR (δ,121.5 MHz, acetone-d6): δ 315 (br s, w1/2 ) 21200
(33) (a) Boinnard, D.; Boussekssou, A.; Dworkin, A.; Savariault, J.-M.;
Varret, F.; Tuchagues, J.-P. Inorg. Chem. 1994, 33, 271-281. (b) Varret,
F. International Conference on Mo¨ssbauer Effects Applications; Jaipur,
India, 1981; Varret, F., Ed.; Indian Science Academy: New Delhi, 1982.

5324 Organometallics, Vol. 25, No. 22, 2006
Shaw-Taberlet et al.
1
Hz, dppe); -143.6 (h, JP-F ) 708 Hz, PF6). Anal. Calcd for
87.4 (s, Napht C-3); 82.4 (s, Napht C-4); 30.0 (m, CH2/dppe); 9.94
(s, Fe-Cp*); 8.71 (s, Ru-Cp*). 31P NMR (121.5 MHz, acetone-
d6, 193 K): δ 97.77 (dd, 2JP-P ) 16.3 Hz, dppe); -143.0 (h, 2JP-F
) 708 Hz, PF6). Anal. Calcd for C58H61F6FeP3Ru: C, 62.09; H,
5.48. Found: C, 61.49; H, 5.67.
C48H46F6FeP3: C, 65.10; H, 5.24. Found: C, 65.21; H, 5.58.
[(η2-dppe)(η5-Cp*)FedCdCH-1-{(η6-naphthyl)Ru(η5-Cp*)}]-
[PF6]2 (5B[PF6]2). The iron vinylidene, 3[PF6] (1.072 g, 1.21
mmol), and [(η5-Cp*)Ru(CH3CN)3][PF6] (0.5456 g, 0.9 equiv) were
cooled to 0 °C under inert atmosphere and combined with 30 mL
of CH2Cl2. This reddish-orange solution was stirred for 1 h at 0
°C, after which all insoluble ruthenium starting material had been
consumed. This solution was then filtered via cannula under argon,
and the filtrate was concentrated and partially precipitated with
diethyl ether. The brown, gluey paste isolated by filtration was
washed multiple times with a mixture of mostly THF and a few
drops of dichloromethane until the filtrate was colorless. The
product was then dried in vacuo to yield 1.020 g of yellow powder
(0.804 mmol, 74% yield), which crystallized into long, yellow fibers
by slow diffusion of pentane into a solution of the product in
dichloromethane. While the major, isolated, product contained only
the B regioisomer, the THF washings rinsed away vinylidene
starting material as well as a small quantity of the B regioisomer
and all of the present A regioisomer. HRMS (ESI+): m/z calcd for
C58H62P256Fe102Ru (C2+), 489.1360; found, 489.1368. 1H NMR (200
MHz, acetone-d6): δ 7.83-7.63 (m, 12H, ArH); 7.49-7.21 (m, 10H,
ArH); 7.35 (d, napht H-2); 7.20 (t, napht H-3) {the two above peaks
are attributable by the use of COSY, HMBC, and HMQC
experiments; the determinations of J, integration, and precise δ are
rendered impossible by the dominance of dppe Ar peaks in the
[(η2-dppe)(η5-Cp*)Fe-CtC-1-{(η6-naphthyl)Ru(η5-Cp*)}]-
[PF6] (6B[PF6]). A 0.700 g (0.552 mmol) quantity of 5B[PF6]2
was combined with 0.0804 g (1.3 equiv) of potassium tert-butoxide
and dissolved in methanol. The solution underwent an immediate
color change to purple. After 2 h, the solvent was evaporated and
the product extracted with dichloromethane. This solution was
concentrated, and the product was precipitated from pentane and
dried under vacuum, yielding 0.550 g (0.446 mmol, 80%) of a very
dark powder. HRMS (ESI+): calcd for C58H6156FeP2102Ru (C+),
1
977.26414; found, 977.2667. H NMR (200 MHz, acetone-d6): δ
8.0-7.0 (m, 23H, ArH); 6.55 (d, 3JH-H ) 5.6 Hz, 1H, Napht H-5);
6.27 (d, 3JH-H ) 6.2 Hz, 1H, Napht H-8); 5.82 (t, 3JH-H ) 6.0 Hz,
3
1H, Napht H-6); 6.08 (t, JH-H ) 5.6 Hz, 1H, Napht H-7); 2.69
(m, 2H, CH2/dppe); 2.65 (m, 2H, CH2/dppe); 1.69 (s, 15H, Ru-
Cp*); 1.51 (br s, 15H, Fe-Cp*). 13C{1H} NMR (δ,75.5 MHz,
CDCl3): δ 135.3-127.0 (m, Ar); 96.21 (s, Napht C-10); 93.1 (s,
Ru-Cp*); 89.5 (s, Fe-Cp*); 87.77 (s, napht C-7); 87.65 (s, napht
C-6); 85.40 (s, napht C-5); 84.75 (s, napht C-8); 30.0 (m, CH2/
dppe); 9.71 (br s, Fe-Cp*); 8.99 (br s, Ru-Cp*). 31P NMR (121
MHz, acetone-d6): δ 98.90 (dd, 2JP-P ) 412.5 Hz, dppe); -143.0
1
(h, JP-F ) 708 Hz, PF6). Anal. Calcd for C58H61F6FeP3Ru‚CH2-
3
3
Cl2 (solvate observed in crystal structure): C, 58.72; H, 5.26.
Found: C, 58.80; H, 5.47.
region}; 6.85 (d, JH-H ) 7.0 Hz, 1H, Napht H-2); 6.72 (d, JH-H
3
) 6.0 Hz, 1H, napht H-5); 6.28 (t, JH-H ) 5.8 Hz, 1H, napht
3
3
[(η2-dppe)(η5-Cp*)Fe-CtC-1-{(η6-naphthyl)Ru(η5-Cp*)}]-
[PF6]2 (6B[PF6]2). A 0.420 g (0.375 mmol) quantity of the Fe(II)
complex, 6B[PF6], and 0.94 equiv (0.1202 g, 0.352 mmol) of FcPF6
were combined and cooled to -60 °C before being dissolved in
cold THF (-60 °C) and allowed to warm to room temperature
overnight with stirring. The following morning, a solid was visible
in the brown solution. Dichloromethane was added to dissolve the
solid, and the product was precipitated twice from cold diethyl ether.
The brown, gluey paste obtained was washed with diethyl ether
and then with THF until the filtrate was colorless, yielding 0.350
g (78%) of pure product upon vacuum-drying. Crystals were
obtained via the slow diffusion of diethyl ether into a dichlo-
romethane solution of the product at -4 °C. HRMS (ESI+): calcd
for C58H61F656FeP3102Ru [(C2+PF6-)+], 1122.2302; found, 1122.2306.
1H NMR (300 MHz, acetone-d6): δ 29.78 (s, 1H, ArH); 13.94 (br
s, 1H, ArH); 8.46 (s, 1H, ArH); 7.77 (s, 2H, ArH); 7.58 (s, 1H,
ArH); 7.44 (s, 1H, ArH); 6.98 (s, 2H, ArH); 6.38 (s, 1H, ArH);
5.94 (s, 1H, ArH); 4.78 (s, 1H, ArH); 3.61 (s, 2H, ArH); 3.51 (s,
2H, CH2/dppe); 2.91 (s, 3H, ArH); 2.64 (s, 1H, ArH); 2.39 (s, 1H,
ArH); 2.05 (s, 15H, Ru-Cp*); 1.34 (s, 1H, ArH); 1.30 (s, 1H, ArH);
0.47 (br s, 2H, CH2/dppe); -0.26 (br s, 2H, ArH); -6.37 (s, 1H,
ArH); -11.34 (s, 15H, Fe-Cp*); -14.06 (br s, 1H, ArH); -40.03
(br s, 1H, ArH); -57.78 (br s, 1H, ArH). 31P NMR (121 MHz,
acetone-d6): δ 340 (br s, w1/2 ) 21258 Hz, dppe); -143.8 (h, 1JP-F
) 708 Hz, PF6). Anal. Calcd for C58H61F12FeP4Ru.CH3OH (crystal-
lization solvent): C, 54.55; H, 5.04. Found: C, 54.15; H, 5.13.
H-6); 6.16 (t, JH-H ) 5.6 Hz, 1H, napht H-7); 6.01 (d, JH-H
)
4
6.2 Hz, 1H, napht H-8); 5.14 (t, JH-P ) 4.6, 1H, Hvin); 3.30 (m,
2H, CH2/dppe); 2.73 (m, 2H, CH2/dppe); 1.77 (br s, 15H, Fe-
Cp*); 1.70 (s, 15H, Ru-Cp*). 13C{1H} NMR (75.5 MHz, acetone-
d6): δ 353.4 (t, 2JP-C ) 34 Hz, CR); 134.0-125.0 (m, CAr); 130.8
(s, Napht C-2); 126.1 (s, Napht C-1); 125.2 (s, Napht C-3); 119.5
(s, Câ); 101.3 (s, Fe-Cp*); 97.80 (s, Napht C-9); 93.9 (s, Napht
C-10); 93.93 (s, Ru-Cp*); 93.46 (s, Napht C-4); 88.47 (s, Napht
C-6); 88.23 (s, Napht C-7); 85.57 (s, Napht C-5); 81.82 (s, Napht
C-8); 29.85 (m, CH2/dppe); 9.82 (s, Fe-Cp*); 8.95 (s, Ru-Cp*).
31P NMR (81 MHz, acetone-d6): δ 86.42 (dd, 2JP-P ) 91 Hz, dppe);
1
-143.0 (h, JP-F ) 707 Hz, PF6). Anal. Calcd for C58H62F12P4-
FeRu‚CH2Cl2 (crystallization solvent): C, 52.38; H, 4.77. Found:
C, 52.75; H, 4.83.
[(η2-dppe)(η5-Cp*)Fe-CtC-1-{(η6-naphthyl)Ru(η5-Cp*)}]-
[PF6] (6A[PF6]). Compound 4 (0.300 g, 0.405 mmol) and [(η5-
Cp*)Ru(CH3CN)3][PF6] (0.203 g, 0.405 mmol) were combined with
10 mL of CH2Cl2 in a Schlenk flask. This red solution was stirred
for a minimum of 4 h at RT, protected from light. The solution
was then filtered into another Schlenk flask, and the filtrate was
partially precipitated with a diethyl ether/pentane solution (4:1).
The product isolated by filtration was washed twice with 2 mL
portions of diethyl ether and dried in vacuo to yield 0.318 g (0.284
mmol, 70% yield) of deep red powder. This procedure results in a
mixture of regioisomers 6A[PF6] and 6B[PF6] in the ratio a:b )
47:53 (1H NMR), from which platelike, orange crystals of 6A[PF6]
were formed by slow diffusion of pentane into a THF solution of
the mixture. HRMS (ESI+): calcd for C58H6156FeP2102Ru (C+),
977.26414; found, 977.2662. 1H NMR (300 MHz, acetone-d6, 193
K): δ 8.05 (t, 3JH-H ) 7.9 Hz, 2H, ArH); 7.80 (t, 3JH-H ) 6.9 Hz,
2H, ArH); 7.70-7.45 (m, 13H, ArH); 7.35 (t, 3JH-H ) 6.8 Hz, 2H,
ArH); 7.16 (t, 3JH-H ) 7.4 Hz, 1H, ArH); 7.08 (t, 3JH-H ) 6.9 Hz,
X-ray Crystal Structure Determinations. Single crystals suit-
able for X-ray crystallography of compounds 2[PF6], 2[PF6]2, 4,
4[PF6], 6A[PF6], 6B[PF6], and 6B[PF6]2 were obtained as described
above and were mounted with epoxy cement on the tip of a glass
fiber. Crystal, data collection, and refinement parameters are given
in Table 2. All the compounds were studied on a Kappa-CCD Enraf-
Nonius FR590 diffractometer equipped with a bidimensional CCD
detector employing graphite-monochromated Mo KR radiation (λ
) 0.71073 Å). The cell parameters were obtained with Denzo and
Scalepack with 10 frames (psi rotation: 1° per frame).34 The data
collection provided reflections for the seven compounds (Table 2).35
Subsequent data reduction with Denzo and Scalepack34 gave the
independent reflections (Table 2). The space groups were chosen
3
3
2H, ArH); 6.70 (d, JH-H ) 8.8 Hz, 1H, ArH); 6.54 (d, JH-H
)
5.9 Hz, 1H, Napht H-4); 6.08 (t, 3JH-H ) 5.4 Hz, 1H, Napht H-3);
5.58 (d, 3JH-H ) 5.8 Hz, 1H, Napht H-2); 2.28 (m, 2H, CH2/dppe);
1.86 (m, 2H, CH2/dppe); 1.58 (s, 15H, Ru-Cp*); 1.48 (br s, 15H,
Fe-Cp*). 13C{1H} NMR (75.5 MHz, CDCl3): δ 135.3-127.0 (m,
ArC); 97.64 (s, Napht C-9); 96.87 (s, Napht C-10); 93.53 (s, Napht
C-1); 91.7 (s, Ru-Cp*); 90.9 (s, Napht C-2); 88.6 (br s, Fe-Cp*);

Stereoelectronic Effects of the Arenophile (η5-Cp*Ru)
Organometallics, Vol. 25, No. 22, 2006 5325
based on the systematic absences in the diffraction data. In the
crystal lattice of 2[PF6]2, four molecules of dichloromethane per
asymmetric unit were present in a severely disordered form. They
were treated as a diffuse contribution using the program SQUEEZE.
All structures were solved with SIR-97, which revealed the non-
hydrogen atoms.36 After anisotropic refinement, the remaining atoms
were found in Fourier difference maps. The complete structures
were then refined with SHELXL97 by the full-matrix least-squares
procedures on reflection intensities (F2).37 The absorption was not
corrected. In all cases the non-hydrogen atoms were refined with
anisotropic displacement coefficients, and all hydrogen atoms were
treated as idealized contributions. Atomic scattering factors were
taken from the literature.38 ORTEP views of the compounds were
generated with ORTEP-3 for Windows.39
Acknowledgment. The authors would like extend hearty
thanks to Dr. B. Demerseman (Rennes) for a generous gift of
[(η5-Cp*)Ru(CH3CN)3][PF6]. Dr. F. Paul is gratefuly acknowl-
edged for stimulating discussions. Prof. M. Tilset (Oslo,
Norway) is acknowledged for his help in acquiring elemental
analyses. Thanks are also expressed to J.-Y. The´pot and F.
Justaud (Rennes), A. Mari (Toulouse), and Drs. P. Jehan and
P. Gue´not (CRMPO, Rennes) for skillful assistance in recording
ESR, Mo¨ssbauer, and high-resolution mass spectra, respectively.
The Ministe`re de l’Education Nationale de l’Enseignement
Supe´rieur et de la Recherche (MENESR, grant for J.S.-T.) is
gratefully acknowledged.
(34) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data
Collected in Oscillation Mode. In Methods in Enzymology, Macromolecular
Crystallography, Part A; Carter, C. W., Sweet, R. M., Eds.; Academic
Press: London, 1997; Vol. 276, p 307.
(35) Nonius. KappaCCD Software; Nonius B. V.: Delft, The Nether-
lands, 1999.
(36) (a) Altomare, M. C.; Burla, M.; Camalli, G.; Cascarano, C.;
Giacovazzo, A.; Guagliardi, A. G. G.; Moliterni, G.; Polidori, R.; Spagna,
R. Sir97: a new tool for crystal structure determination and refinement. J.
Appl. Crystallogr. 1998, 31, 74-77. (b) Van der Sluis, P.; Spek, A. L.
Acta Crystallogr. 1990, A46, 194-201. (c) Spek, A. L. J. Appl. Crystallogr.
2003, 36, 7.
Supporting Information Available: Crystallographic files in
CIF format for the seven reported X-ray crystal structures are
available free of charge via the Internet at http://pubs.acs.org.
OM060575Q
(38) International Tables for X-ray Crystallography; Wilson, A. J. C.,
Ed.; Kluwer Academic Publishers: Dordrecht, The Netherlands, 1992; Vol.
C.
(37) Sheldrick, G. M. SHELX97. Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(39) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.