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

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 NaBPh₄or 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 η⁶complexation 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

Fe^IIIcounterparts, 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-η⁶inter-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 properties⁵of 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,¹nanodevices such

as molecular wires²and switches³are 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.

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-η⁶solution-state inter-ring

haptotropic rearrangement of the Cr(CO)₃arenophile on sub-

stituted naphthyl ligands proceeds photochemically in one

direction and thermally in the other.⁶Other examples of

irreversible⁷and chemically reversible switches⁸using solution-

state haptotropic rearrangement of Cr(CO)₃have 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 theoretical¹⁰and experimental¹¹discoveries 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.¹²In 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 η⁶complexation of the

12-electron (η⁵-Cp*)Ru⁺arenophile.¹³The Ru precursor was

[(η⁵-Cp*)Ru(CH₃CN)₃][PF₆],¹⁴and 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

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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]₂was 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]₂with 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.¹⁶Furthermore, Fagan et al.¹³reported 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

η⁶complexation 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,^11,15as 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 4^a

^aKey reagents: (a) NaBPh₄or NaPF₆, 20 °C, MeOH/THF, 16 h; (b) KBuO^t, 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) Complexes^a

(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).¹⁷In 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.^12cThe 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.^11,18Thus, the vinylidene precursors 3[BPh₄] and

3[PF₆] exhibited the characteristic features of the iron-

vinylidene core, FedC_RdC_âH-, with the triplets assigned to

the vinylidene protons at δ ) 5.79 and 5.76 ppm, respectively,

4

1

with a coupling constant J_H-P) 4.0 Hz, in their H NMR

spectra, and the downfield triplet resonance of the C_Rnucleus

at 356.7 ppm with a ²J_C-Pof 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.^11,15In 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 (²J_C-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, w_1/2) 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.²⁰In 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 Stretching^a

compd

Fe(II)

Fe(III)

∆ν_CtC

ref

1[PF₆]_n

2[PF₆]_n

4[PF₆]_n

6B[PF₆]_n

2053^b

2021, 1988^c

2042^d

-32, -65

+14, +60

-62, -122

0, -22

7a

2028, 1982^c

2040^b

this work

1988, 1918^c

2026, 1978^d

2026^c

^aIn Nujol, cm^-1

.

^bn ) 0. ^cn ) 1. ^dn ) 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-d₆in 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).^11aFor 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.^11,15Such 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

C₄₈H₄₆F₆P₃Fe

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‚

CH₂Cl₂4CH₂Cl₂

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 w^a

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

R_w

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).²³This

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 < ∆ν_CtC < 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 Fe^IIIcenter, 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.²²This 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]₂display a

relationship opposite that previously observed among the

plethora of known compounds of type I.^11aThese 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-C44^bor C48^c

C43-C44^bor C48^c

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-Ar_centroid

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-C44^bor 48^c

C41-C42-C43

171.6(7)

175.7(7)

169.0(7)

171.2(9)

171.1(9)

176.3(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

Ar_centroid-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

^aThere are three molecules and four disordered dichloromethane molecules in the asymmetric unit. ^bData refer to phenyl bridging carbon, C44. ^cData

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]₂Resulting 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-

C_ipsodistance 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-C_ipso2.288 Å).

The 2-3% lengthening of the Ru-C_ipsobond lengths versus

Ru-C_Araverage 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).²³The 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.^11aUpon 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-

C_{aryl-centroid}distance increases from 1.655 Å to ca. 1.710 Å.

Meanwhile, the average Ru-C_aryldistance 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], ∆ν_CtC )

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]₂are split in two, as commonly occurs for type I

compounds.^11aThe frequency of the CtC stretch of organoiron,

4, decreases much more (62 < ∆ν_CtC< 122 cm^-1) than that

of the binuclear daughter complex, 6B[PF₆] (0 < ∆ν_CtC< 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]₂were 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]₂exhibit 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).^11aIn brief, the

Fe-Cp*_centroidand 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,^11aand this

bending occurs to a greater extent (164.2(4)°) upon oxidation

to Fe(III), 4[PF₆].

compd

absorption γ/nm (10³e/dm³mol^-1cm^-1

)

1^7a

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]₂suggests 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.¹¹Complexation 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 4.²⁰For 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

(i_p/i_p) 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 1^11aand 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

g_iso

∆g

g_iso

ref

compd

E₀(Fe^II-Fe^III),^aV

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

6B[PF₆]₂2.503 2.026 1.971 2.167 0.532 2.010 this work

^aAt 77 K in CH₂Cl₂/C₂H₄Cl₂(1:1) glass unless otherwise noted. ^bAt

298 K.

^aConditions: 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 g_isovalue at 298

K. Upon warming, the g_isoshifts 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 g₂and g₃remain almost

unchanged. As a consequence, the presence of the arenophile

increases both the isotropy (g_iso) and anisotropy (∆g) tensors.

This is in line with previous observations for Fe(III) type I

complexes for which the g_isoand ∆g values increase with the

electron-withdrawing character of the substituents on the phenyl

ring.^11cIt 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 g_isovalue becomes concomitantly closer

and closer to the g_evalue (g_e) 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

IS^a(QS), mm s^-1

Fe^IIor Fe^III

ref

1

0.27 (2.02)

0.25 (0.9)

II

14

1[PF₆]

2[PF₆]₂

4

4[PF₆]

6B[PF₆]

6B[PF₆]₂

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

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-η⁶metal shifts.^6-8Such 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 9.²³Another 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]₂with

1,2,5,6-tetramethylcorannulene (C₂₀H₆Me₄).²⁶In 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)]₄and 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.^11aSurprisingly, 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]₂is 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-C_Rbond order^18L,25within 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.²⁸On 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.

shown²⁹that 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,⁸we 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]₂yielded

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 P₂O₅and then from Na₂-

CO₃. Methanol was distilled over dried magnesium turnings. The

following compounds were prepared following published proce-

dures: 1-ethynylnaphthalene,³⁰ferrocenium hexafluorophosphate

[Fe(η⁵-Cp)₂][PF₆](FcPF₆),³¹(η²-dppe)(η⁵-Cp*)Fe-Cl,³²(η²-dppe)-

(η⁵-Cp*)Fe-CtC-Ph (1),^11aand [(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^-2C (9.25 × 10⁸Bq) 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.³³The 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, ⁴J_H-P

) 4.0 Hz, 1H, H_vin); 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, J_P-C) 33 Hz, C_R); 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, ³J_H-H) 6.8 Hz, 4H, m-Ar dppe);

7.21 (t, ³J_H-H) 7.6 Hz, 4H, o-Ar dppe); 5.53 (t, ³J_H-H) 5.6 Hz,

2H, m-C₆H₅); 5.45 (d, ³J_H-H) 5.2 Hz, 1H, p-C₆H₅); 5.06 (d, ³J_H-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, C_R); 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, C_â); 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 CH₂Cl₂and 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, J_H-P

)

4.4 Hz, 1H, H_vin); 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, J_P-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, ³J_H-H

) 7.8 Hz, HAr/dppe); 8.02 (d, 1H, ³J_H-H) 9.6 Hz, HAr); 7.86 (d,

1

(h, J_P-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 FcPF₆were

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 NaBPh₄in 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 CH₂Cl₂and 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

1H, J_H-H) 8.0 Hz); 7.6-7.3 (m, 19H, HAr); 7.20 (t, 1H, J_H-H

3

) 7.2 Hz, HAr); 7.1 (d, 1H, J_H-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, J_P-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 FcPF₆were 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, w_1/2) 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, J_P-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, ²J_P-P) 16.3 Hz, dppe); -143.0 (h, ²J_P-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, ³J_H-H) 5.6 Hz, 1H, Napht H-5);

6.27 (d, ³J_H-H) 6.2 Hz, 1H, Napht H-8); 5.82 (t, ³J_H-H) 6.0 Hz,

3

1H, Napht H-6); 6.08 (t, J_H-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, ²J_P-P) 412.5 Hz, dppe); -143.0

1

(h, J_P-F) 708 Hz, PF₆). Anal. Calcd for C₅₈H₆₁F₆FeP₃Ru‚CH₂-

3

Cl₂(solvate observed in crystal structure): C, 58.72; H, 5.26.

Found: C, 58.80; H, 5.47.

region}; 6.85 (d, J_H-H) 7.0 Hz, 1H, Napht H-2); 6.72 (d, J_H-H

3

) 6.0 Hz, 1H, napht H-5); 6.28 (t, J_H-H) 5.8 Hz, 1H, napht

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, w_1/2) 21258 Hz, dppe); -143.8 (h, ¹J_P-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, J_H-H) 5.6 Hz, 1H, napht H-7); 6.01 (d, J_H-H

)

4

6.2 Hz, 1H, napht H-8); 5.14 (t, J_H-P) 4.6, 1H, H_vin); 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, ²J_P-C) 34 Hz, C_R); 134.0-125.0 (m, C_Ar); 130.8

(s, Napht C-2); 126.1 (s, Napht C-1); 125.2 (s, Napht C-3); 119.5

(s, C_â); 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, ²J_P-P) 91 Hz, dppe);

1

-143.0 (h, J_P-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 CH₂Cl₂in 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, ³J_H-H) 7.9 Hz, 2H, ArH); 7.80 (t, ³J_H-H) 6.9 Hz,

2H, ArH); 7.70-7.45 (m, 13H, ArH); 7.35 (t, ³J_H-H) 6.8 Hz, 2H,

ArH); 7.16 (t, ³J_H-H) 7.4 Hz, 1H, ArH); 7.08 (t, ³J_H-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]₂were 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).³⁴The data

collection provided reflections for the seven compounds (Table 2).³⁵

Subsequent data reduction with Denzo and Scalepack³⁴gave the

independent reflections (Table 2). The space groups were chosen

3

2H, ArH); 6.70 (d, J_H-H) 8.8 Hz, 1H, ArH); 6.54 (d, J_H-H

)

5.9 Hz, 1H, Napht H-4); 6.08 (t, ³J_H-H) 5.4 Hz, 1H, Napht H-3);

5.58 (d, ³J_H-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.³⁶After 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).³⁷The 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.³⁸ORTEP 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.

Article Doi

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

DOI: 10.1021/om060575q

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Full text of DOI:10.1021/om060575q

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