Polar cofacially fixed sandwich complexes: Do they demonstrate second harmonic generation (SHG)?

Article abstract of DOI:10.1002/ejic.200500812

For the purpose of possible second harmonic generation (SHG) a cationic and a neutral sandwich unit were cofacially arranged in a three-step synthesis starting from 1,8-diiodonaphthalene. First, 1-cyclopentadienyl-8-iodonaphthalene (2) was formed, then the neutral ferrocenyl substituent was fixed in the 8-position by a Negishi cross-coupling reaction. The deprotonation of the cyclopentadienyl substituent, and the subsequent coordination of the half-sandwich fragments ML = [Fe(η⁵-C₅Me ₅)]⁺, [Rh(η⁵-C₅Me ₅)]²⁺, [Ir(η⁵-C₅Me ₅)]²⁺, [Ru(η⁶-C₆H ₆)]²⁺ to the cyclopentadienyl anion revealed the desired dinuclear complexes 1-[(η⁵-cyclopentadienediyl)- (η⁵-pentamethylcyclopentadienyl)iron(II)]-8- ferrocenylnaphthalene (5), 1-[(η⁵-cyclopentadienediyl) (η⁵-pentamethylcyclopentadienyl)rhodium(III)]-8- ferrocenylnaphthalene hexafluorophosphate (6PF₆), 1-[(η⁵-cyclopentadienediyl)(η⁵- pentamethylcyclopentadienyl)iridium(III)]-8-ferrocenylnaphthalene hexafluorophosphate (7PF₆), and 1-[(η⁶-benzene) (η⁵-cyclopentadienediyl)ruthenium(II)]-8-ferrocenylnaphthalene hexafluorophosphate (8PF₆). The neutral complex 5 was oxidized to the paramagnetic cation 1-[(η⁵-cyclopentadienediyl)- (η⁵-pentamethylcyclopentadienyl)iron(III)]-8- ferrocenylnaphthalene hexafluorophosphate (5PF₆). Compounds 3, 5PF₆, 6PF₆, and 7PF₆ were characterized by X-ray structure determination; the neutral compound 3 crystallizes in the space group P2₁/c, whereas all of the cationic dinuclear complexes crystallize in the chiral space group C222₁. A cyclic voltammetry study points to a predominant through-space interaction between the cationic sandwich unit and the neutral ferrocene substituent. The compounds 5PF₆, 6PF₆, 7PF₆, and 8PF₆ were subjected to hyper-Rayleigh scattering (HRS) and Kurtz-powder measurements. In both studies no SHG intensity could be observed. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200500812

FULL PAPER
DOI: 10.1002/ejic.200500812
Polar Cofacially Fixed Sandwich Complexes: Do They Demonstrate Second
Harmonic Generation (SHG)?
Maik Malessa,[a] Jürgen Heck,*[a] Jürgen Kopf,[a] and M. Helena Garcia[b]
Dedicated to Prof. Dr. Wittko Francke on the occasion of his 65th birthday
Keywords: Heterometallic complexes / Sandwich complexes / Donor–acceptor systems / Nonlinear optics / Through-space
interaction
For the purpose of possible second harmonic generation
(SHG) a cationic and a neutral sandwich unit were cofacially
arranged in a three-step synthesis starting from 1,8-diiodo-
naphthalene. First, 1-cyclopentadienyl-8-iodonaphthalene
(2) was formed, then the neutral ferrocenyl substituent was
fixed in the 8-position by a Negishi cross-coupling reaction.
The deprotonation of the cyclopentadienyl substituent, and
the subsequent coordination of the half-sandwich fragments
cyclopentadienediyl)ruthenium(II)]-8-ferrocenylnaphthalene
hexafluorophosphate (8PF6). The neutral complex 5 was oxi-
dized to the paramagnetic cation 1-[(η5-cyclopentadienediyl)-
(η5-pentamethylcyclopentadienyl)iron(III)]-8-ferrocenylnaph-
thalene hexafluorophosphate (5PF6). Compounds 3, 5PF6,
6PF6, and 7PF6 were characterized by X-ray structure deter-
mination; the neutral compound 3 crystallizes in the space
group P21/c, whereas all of the cationic dinuclear complexes
crystallize in the chiral space group C2221. A cyclic voltam-
metry study points to a predominant “through-space” inter-
action between the cationic sandwich unit and the neutral
ferrocene substituent. The compounds 5PF6, 6PF6, 7PF6, and
ML = [Fe(η5-C5Me5)]+, [Rh(η5-C5Me5)]2+, [Ir(η5-C5Me5)]2+
,
[Ru(η6-C6H6)]2+ to the cyclopentadienyl anion revealed the
desired dinuclear complexes 1-[(η5-cyclopentadienediyl)-
(η5-pentamethylcyclopentadienyl)iron(II)]-8-ferrocenylnaph-
thalene (5), 1-[(η5-cyclopentadienediyl)(η5-pentamethylcy- 8PF6 were subjected to hyper-Rayleigh scattering (HRS) and
clopentadienyl)rhodium(III)]-8-ferrocenylnaphthalene hexa-
fluorophosphate (6PF6),
Kurtz-powder measurements. In both studies no SHG inten-
sity could be observed.
1-[(η5-cyclopentadienediyl)(η5-
pentamethylcyclopentadienyl)iridium(III)]-8-ferrocenylnaph-
thalene hexafluorophosphate (7PF6), and 1-[(η6-benzene)(η5-
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
Introduction
Cofacially stacked arrays of organic and organometallic
π-systems are of increasing interest for chemists and physi-
cists, because of novel electrical,[1,2] optical,[2] and mag-
netic[3] properties. Just recently, theoretical[4] and experi-
mental[5] work has demonstrated that stacked donor–ac-
ceptor arrangements of π-systems are suitable for second
harmonic generation (SHG) effected by through-space (hy-
per)polarization (Figure 1).
Conventional types of compounds revealing nonlinear
optical (NLO) properties, i.e. SHG, are composed of donor
and acceptor units linked by conjugated π-bonds, which
very often suffer from absorbance in the region of the SHG,
and are thus not suitable for practical applications. In con-
trast, π-stacked donor-acceptor combinations seem to pro-
Figure 1. Cofacially stacked arrangement of donor(D)–acceptor(A)
π-systems for second harmonic generation (SHG) due to polar
“through-space” interaction.
vide a better optical transparency.[6] Our approach to
stacked organometallic π-complexes with donor–acceptor
combinations, which may call forth SHG, is based on Ro-
senblum’s concept of 1,8-disubstituted naphthalene deriva-
tives containing two sandwich complexes in the peri posi-
tion. Whereas the Rosenblum naphthalene derivatives are
symmetrically constructed with the same sandwich com-
plexes in the peri position,[7,8] our desired target molecules
should contain different sandwich complexes,[9] one of
which is a cation, generating an overall dipole moment,
which is a possible prerequisite for SHG (Figure 2).
[a] Institut für Anorganische und Angewandte Chemie, Universität
Hamburg,
Martin-Luther-King-Platz 6, 20146 Hamburg
[b] Faculdade de Ciências da Universidade de Lisboa, Ed. C8,
Campo Grande, 1749-016 Lisboa, Portugal
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857

M. Malessa, J. Heck, J. Kopf, M. H. Garcia
FULL PAPER
protonation by sodium bis(trimethylsilyl)amide to yield 4,
and a consecutive coordination reaction with the proper
half-sandwich complexes (Scheme 1). For Rh, Ir, and Ru
complexes 6PF6, 7PF6, and 8PF6, the deprotonated com-
plex 4 was treated with thallium chloride in acetonitrile to
replace the counterion Na+ with Tl+.[13] This cation ex-
change is necessary to obtain good yields of the desired
dinuclear cationic complexes with Ru, Rh and Ir. In order
to achieve the polar structure of the diiron derivative, com-
pound 5 was oxidized to the paramagnetic monocation
5PF6 by addition of a stoichiometric amount of ferrocen-
ium hexafluorophosphate (Scheme 2), and a dark red-
brown crystalline material was obtained. All compounds
were fully characterized by elemental analyses, spectro-
scopic methods and cyclic voltammetry. For compound 3a,
5PF6, 6PF6 and 7PF6 X-ray structure analyses were deter-
mined.
Figure 2. Unsymmetrically 1,8-disandwich-substituted naphthalene
derivatives.
Results and Discussion
Synthesis
The assembly of different sandwich complexes in peri po-
sition of naphthalene requires a stepwise synthesis. Starting
with a cross-coupling reaction of 1,8-diiodonaphthalene (1)
[10]
with cyclopentadienylzinc chloride[7a,9a] (Scheme 1), re-
sults in the formation of 1-cyclopentadienyl-8-iodonaph-
thalene (2). For the second step, a Pd-catalyzed Negishi
cross-coupling reaction with ferrocenylzinc chloride[11,12]
was performed, revealing complex 3, which is composed of
the two different isomers 3a and 3b (see Exp. Sect.). In or-
der to synthesize the unsymmetrical disandwich-substituted
naphthalene derivatives, complex 3 was subjected to a de-
Scheme 2. Oxidation of 5 with ferrocenium hexafluorophosphate.
Crystal Structures
The solid-state structures of 3a, 5PF6, 6PF6 and 7PF6 are
displayed in Figures 3, 4, 5 and 6. The mononuclear com-
plex 3a crystallizes in the monoclinic space group P21/c,
whereas the space group for the dinuclear monocationic
species is found to be orthorhombic and chiral with C2221.
Not surprisingly, the structural data of the sandwich units
are very similar to those of published data for correspond-
ing prototype sandwich complexes (Table 1).[14–17]
Scheme 1. Synthesis of polar cofacially fixed sandwich complexes.
Figure 3. Molecular structure of 3a (50% ellipsoids).
858
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Polar Cofacially Fixed Sandwich Complexes
FULL PAPER
Figure 4. Molecular structure of 5PF6 (50% ellipsoids, hydrogen atoms and counterion are omitted for clarity).
Table 1. Selected bond lengths [pm] of the metallocene units in 3a,
5PF6, 6PF6, 7PF6.
3a
5PF6
6PF6
7PF6
Fe(1)–C(9)
207.8(3) 206(1)
204.8(3) 205(1)
203.7(4) 203(1)
204.0(4) 204(1)
204.5(3) 206(1)
164.47(18) 165(1)
203.8(4) 204(2)
203.9(4) 202(2)
205.3(4) 205(2)
204.8(3) 204(1)
204.7(4) 205(1)
165.0(2) 166(1)
208(1)
206(1)
205(1)
204(1)
203(1)
166(1)
206(1)
204(1)
204(1)
205(2)
204(1)
165(1)
224(1)
221(1)
215(1)
214(1)
218(1)
181(1)
219(1)
217(1)
215(1)
217(1)
221(1)
181(1)
144(1)
143(2)
140(2)
140(2)
144(2)
143(2)
143(2)
141(2)
144(2)
143(2)
208(2)
204(3)
201(3)
201(2)
204(2)
165(1)
206(3)
210(2)
203(3)
208(2)
203(3)
168(1)
219(2)
217(3)
219(2)
217(2)
220(2)
183(1)
215(3)
224(3)
220(3)
218(2)
220(3)
182(1)
139(3)
146(4)
133(3)
145(3)
143(3)
148(4)
146(5)
139(4)
144(4)
141(5)
Fe(1)–C(10)
Fe(1)–C(11)
Fe(1)–C(12)
Fe(1)–C(13)
Fe(1)–Cent[C(9)–C(13)]
Fe(1)–C(14)
Fe(1)–C(15)
Fe(1)–C(16)
Fe(1)–C(17)
Fe(1)–C(18)
Fe(1)–Cent[C(14)–C(18)]
M–C(19)
M–C(20)
M–C(21)
M–C(22)
M–C(23)
M–Cent[C(19)–C(23)]
M–C(24)
M–C(25)
M–C(26)
M–C(27)
M–C(28)
[a]
[a]
Figure 5. Molecular structure of 6PF6 (50% ellipsoids, hydrogen
atoms and counterion are omitted for clarity).
–
–
–
–
–
–
–
–
–
–
–
–
215(1)
207(2)
206(2)
205(1)
210(1)
171(1)
210(2)
210(2)
202(2)
207(2)
217(2)
170(1)
[a]
[a]
M–Cent[C(24)–C(28)]
C(19)–C(20)
C(20)–C(21)
C(21)–C(22)
C(22)–C(23)
C(23)–C(19)
C(24)–C(25)
C(25)–C(26)
C(26)–C(27)
C(27)–C(28)
C(28)–C(24)
141.9(6) 144(2)
148.1(7) 139(2)
142.0(8) 140(2)
141.4(7) 142(2)
140.7(6) 137(2)
–
–
–
–
–
147(3)
137(2)
139(2)
145(2)
143(2)
Figure 6. Molecular structure of 7PF6 (50% ellipsoids, hydrogen
atoms and counterion are omitted for clarity).
[a] Cent: centroid of the corresponding cyclopentadienyl rings.
The most eye-catching feature of all structures under
study is the distortion of the compound entities (Figure 7, membered naphthalene rings varies from 45.6(6)° (5PF6) to
Table 2); a common occurrence for naphthalene derivatives 77.9(8)° (6PF6) (Table 2). For the less crowded example 3a,
disubstituted in the 1,8-positions by aromatic moieties.[8,18] with only one sandwich unit, intermediate tilt angles of
The tilt angle between the best plane of the naphthalene- 53.5(2)° and 53.0(2)° are found. Remarkably, the permethyl-
bound Cp ligands and the best planes of the connected six- ation of one of the distal Cp ligands in the cationic species
Eur. J. Inorg. Chem. 2006, 857–867
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859

M. Malessa, J. Heck, J. Kopf, M. H. Garcia
FULL PAPER
Figure 7. Cofacial arrangement of metallocene fragments in 5PF6; left: showing the interplanar distortion between the naphthalene moiety
and the sandwich units; right: view along the metallocene axes; (50% ellipsoids, hydrogen atoms and counterion are omitted for clarity).
Table 2. Selected interplanar und torsion angles [°], bond lengths and interatomic distances [pm] between the naphthalene und metallocene
units.
[8b]
3a
5PF6
20.5(8)
45.6(6)
48.4(7)
31.3
6PF6
19.7(6)
77.9(8)
60.5(8)
28.9
7PF6
19.1(15)
45.6(12)
48.6(12)
29.4
9BF4
CpC(9)–C(13)–CpC(19)–C(23)
CpC(9)–C(13)–naphthalene[a]
CpC(19)–C(23)–naphthalene[a]
C(19)–C(1)–C(8)–C(9)
22.3(2)
53.5(2)
53.0(2)
23.3
17.5
58.0
60.8
25.2
C(1)–C(19)
C(8)–C(9)
C(1)–C(8)
C(9)–C(19)
Fe(1)–M
CentC(9)–C(13)–CentC(14)–C(18)
CentC(19)–C(23)–CentC(24)–C(28)
CentC(9)–C(13)–CentC(19)–C(23)
148.0(5)
148.3(5)
255.6(5)
291.4(5)
–
330.5(3)
–
147(2)
148(2)
149(3)
148.4
148.9
254.1
286.9
651.3
329.6
343.5
317.9
151(2)
254(2)
291(2)
651.9
331.0(9)
341(1)
323.1(9)
150(2)
257(2)
288(1)
153(3)
258(2)
290(2)
658.6
657.9
[b]
330.8(8)
362.5(8)
318.6(7)
332(2)
365(2)
319(2)
[b]
[b]
330.4(3)
[a] Best plane of the adjacent six-membered naphthalene ring. [b] Cent: centroid of the corresponding Cp ligand.
does not cause tilt angles that deviate distinctly from those the symmetrical diferrocenyl-substituted naphthalene con-
obtained for other comparable naphthalene derivatives,[8,18] gener 9[8] was studied. The H NMR signals of the sand-
1
which points out that the distortion is not a consequence wich units are found in the typical range for the corre-
of the steric hindrance between the positions C2 and C7, sponding unsubstituted derivatives. The deviations are diffi-
and the distal Cp ligands, but rather a result of the steric cult to explain, because they are small and probably
repulsion of the two-faced Cp units in the peri position strongly dominated by the anisotropy effects of the neigh-
(compare also data in Table 2). Despite the distortion of the boring sandwich complex. The 13C NMR shifts, which are
entire peri-disubstituted naphthalene derivatives, a projec- less influenced by anisotropy effects compared to the over-
tion along the molecular axis of the sandwich complexes all shift range, illustrate a slight but distinct low-field shift
still shows an almost complete face-to-face arrangement of for the signals of the unsubstituted Cp ligand as well as of
the sandwich units (Figure 7). This nicely demonstrates the the carbon nuclei in 2,5- and 3,4-positions of the naphtha-
clamp function of the naphthalene backbone for the pur- lene-bound Cp ligand of the ferrocenyl substituent in the
pose of stacking the sandwich units.
order 5 Ͻ 9 Ͻ 3 < 8PF6 Ͻ 6PF6 Ͻ 7PF6. The order may
reflect a subtle decrease of the electron repulsion between
the ferrocenyl substituent and the neighboring sandwich
complex (Table 3).
Spectroscopic Properties
The NMR signals of the complexes 3, 5, 6PF6, 7PF6 and
UV/Vis spectroscopy is a well-tried tool for obtaining ini-
8PF6 have been assigned by means of 1H, 13C, 1H1H COSY, tial information about potential nonlinear optical (NLO)
HMQC, ATP and 1H1H NOESY spectra. For comparison, behavior in virtue of the solvatochromism of dipolar com-
Table 3. NMR spectroscopic data of the ferrocenyl substituents in 3a, 5, 6PF6, 7PF6, 8PF6 and 9.
ML
δ(C5H5)
δ(H-2ЈЈ,5ЈЈ)
δ(H-3ЈЈ,4ЈЈ)
δ(C5H5)
δ(C-2ЈЈ,5ЈЈ)
δ(C-3ЈЈ,4ЈЈ)
δ(C-1ЈЈ)
3a
5
6PF6
7PF6
8PF6
9
–
3.96
3.83
3.98
3.99
3.98
3.86
4.30
4.12
4.31
4.35
4.32
4.11
4.03
3.86
4.10
4.14
4.11
3.84
69.9
69.4
70.5
71.0
69.9
69.5
72.1/70.7
70.5
72.2
72.7
71.8
67.2/66,7
66.4
68.3
68.7
67.6
n.d.[a]
87.5
92.5
[FeCp*]
[RhCp*]+
[IrCp*]+
[Ru(C6H6)]+
[FeCp]
92.8
n.d.[a]
91.3
70.9
66.5
[a] n.d.: not detectable.
860
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Polar Cofacially Fixed Sandwich Complexes
FULL PAPER
Table 4. UV/Vis data of the complexes 3a, 5, 5PF6, 6PF6, 7PF6 and 8PF6.
[a]
[a]
λmax (ε)[b]
λmax (ε)[b]
[c]
[c]
ν
ν
˜
max
˜
max
ML
MeOH
CH2Cl2
MeOH
CH2Cl2
3a
–
296 (6000)
33784
296 (13000)
33794
304 (24780)
32895
293 (19170)
34130
289 (5271)
34602
286 (3758)
34965
458 (290)
21834
456 (540)
21930
[d]
[d]
[d]
[d]
[d]
[d]
5
[FeCp*]
[FeCp*]+
[RhCp*]+
[IrCp*]+
477 (1355)
20964
481 (1930)
20790
5PF6
6PF6
7PF6
8PF6
428 (3712, sh)[e]
23364
433 (2850, sh)[e]
23095
[f]
[f]
450 (220)
22222
461 (190)
21602
454 (780)
22026
463 (960)
21598
[Ru(C6H6)]+
[a] In nm. [b] In –1·cm–1. [c] In cm–1. [d] Beyond solvent range. [e] Shoulder. [f] Shoulder, not resolved.
pounds. If the dipole moments of the ground and an excited was additionally investigated. As expected, all complexes re-
state are different, a variation of the solvent polarity will veal an electrochemically reversible one-electron oxidation
stabilize the two states differently, resulting in a batho- in the range of ferrocene itself (Table 5, Figure 8), and can
chromic or hypsochromic shift of the absorption maxi- thus be assigned to the oxidation of the ferrocenyl substitu-
mum.[19,20] Therefore, the UV/Vis spectra of the complexes ent. The peak-to-peak separations found (∆Ep = Epc – Epa)
3, 5, 5PF6, 6PF6, 7PF6 and 8PF6 were recorded in dichloro- are generally larger than the ideal value of 60 mV for a fully
methane and methanol (Table 4). For both solvents, weak reversible one-electron process, which is probably due to the
absorption bands can be detected in the region at λ Ϸ 300 uncompensated solution resistance.
and 450 nm because of d–d transitions typical for ferro-
The cyclic voltammograms of the diiron complexes 5 and
cenes.[21,22] The high-energy d–d transition is superimposed 9 contain an additional reversible one-electron redox wave
by a strong π–π* transition at λ Ͻ 300 nm, and is thus only due to the oxidation of the second ferrocenyl unit. The per-
observable as a shoulder. The dependence of the absorption methylation of one of the cyclopentadienyl ligands causes a
maxima on the polarity of the solvent is minor: only a small more pronounced cathodic shift of the first oxidation step
hypsochromic shift is observed for the low-energy d–d tran- for 5 relative to 9. The rhodium and ruthenium congeners
sition. 5PF6 and 9PF6 demonstrate additional absorption display an irreversible reduction beyond –2000 mV vs. fer-
bands at λmax = 813 nm (ε = 649 –1 cm–1) and at about rocene/ferrocenium, which is caused by the reduction of the
840 nm (ε = 800 –1 cm–1),[8a] respectively, which are typical cationic sandwich unit;[24,25] for the iridium derivative 7PF6
for ferrocenium derivatives, as well as very broad absorp- a corresponding reduction was not observed within the ac-
tion bands at λmax = 1284 nm (ν = 7788 cm–1) and λ
=
cessible range, which seems reasonable, as the reduction po-
˜
max
1500 nm[8a] (ν = 6667 cm–1) (∆ν
Ͼ 4000 cm–1, ε Ͻ tential for the cationic sandwich complex [CpIr(C5Me5)]+ is
˜
˜
1/2
100 –1 cm–1, respectively. The NIR bands are indicative of about 500 mV more negatively shifted than for the corre-
mixed-valence charge-transfer (MVCT) transitions in sponding rhodium complex.[25] A reduction of the aromatic
mixed-valence compounds of class II.[9a,9b,23a,23b]
π-system of the naphthalene unit is not expected within the
scan range, because naphthalene reveals a reduction be-
yond –3 V vs. ferrocene/ferrocenium.[26]
Redox Properties
When the oxidation potentials of the ferrocene units of
Cyclic voltammograms were obtained for all of the naph- all the monocationic species under study are compared, an
thalene derivatives in this study. For comparison, the redox increase is observed in the order 5PF6 Ͻ 3 Ͻ 7PF6 Ͻ 6PF6
behavior of the 1,8-diferrocenyl-substituted naphthalene 9 Ͻ 8PF6 Ͻ 9PF6. It is still under discussion whether the
Table 5. Redox potentials[a] of the complexes 3a, 5PF6, 6PF6, 7PF6, 8PF6 and 9PF6.
E1/2 (1)[b]
∆Ep (1)[c]
E1/2 (2)[b]
∆Ep (2)[c]
Epc
∆E
[d]
ML
3a
–
–0.036
0.102
–
–
–
–
–
5PF6
6PF6
7PF6
8PF6
9PF6
[FeCp*]+
[RhCp*]+
[IrCp*]+
[Ru(C6H6)]+
[FeCp]+
–0.042
0.041
0.036
0.053
0.106
0.097
0.073
0.084
0.070
0.069
–0.532
–
–
–
0.107
–
–
–
0.490[e]
–2.157[d]
2.198[f]
–
–
–2.345[d]
2.398[f]
0.204[e]
–0.098
0.84
–
[a] In CH2Cl2 at room temperature, [nBu4N]PF6 (0.4 ) as supporting electrolyte, Ag/AgPF6 as standard elektrode referenced vs.
E1/2(ferrocene/ferrocenium) = 0 V, scan rate 100 mV/s. [b] Potentials E 0.005 V. [c] ∆Ep = |Epc – Epa|. [d] Peak potential Epc of the
irreversible reduction. [e] ∆E = |E1/2(1) – E1/2(2)|. [f] ∆E = | E1/2(1) – Epc|.
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M. Malessa, J. Heck, J. Kopf, M. H. Garcia
FULL PAPER
Figure 8. Cyclic voltammograms of 3 (a), 8PF6 (b), 6PF6 (c), 7PF6 (d), 5PF6 (e), 9 (f) (for more details see Table 5).
oxidation potentials are mainly influenced by a direct bond and can thus adopt a coplanar conformation of the
“through-space” interaction of the sandwich units, which ferrocene and benzene π-systems suitable for a proper π-
are in an almost perfect face-to-face arrangement, or by interaction.[27,28] In contrast to this and in accordance with
a “through-bond” interaction facilitated by the π-bonding others,[8] a difference in the oxidation potentials of about
system of the naphthalene core. However, some arguments 200 mV was found for 9. The interpretation of an important
point to a predominant contribution of the “through- “through-space” interaction in face-to-face stacked sand-
space” interaction: (i) the almost perpendicular conforma- wich complexes is also in harmony with the explanation
tion of the sandwich substituents with respect to the naph- of an antiferromagnetic coupling between two para-
thalene plane hampers the interaction between the sand- magnetic trovacene complexes in peri position of naphtha-
wich and naphthalene π-bonding systems and (ii) the 1,8- lene.[18]
disubstitution of the aromatic naphthalene system dis-
favours the π-interaction between the substituents. This has
been demonstrated by 1,3-diferrocenylated benzene deriva-
tives, which may be regarded electronically similar to the
Measurements Concerning Second Harmonic Generation
1,8-diferrocenylated naphthalene species; the benzene com-
In order to elucidate the NLO activity of the stacked
pounds reveal a difference in the oxidation potentials for sandwich compounds with respect to second harmonic gen-
the ferrocene units of less than 100 mV, although the ferro- eration (SHG), hyper-Rayleigh scattering (HRS) measure-
cene substituents rotate around the benzene–ferrocene σ- ments were performed for liquid solution samples of 5PF6,
862
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Polar Cofacially Fixed Sandwich Complexes
FULL PAPER
6PF6, 7PF6, 8PF6, and 9PF6 with a pulsed Nd:YAG laser stacked sandwich entities may raise some doubts about the
at λ = 1064 and 1500 nm. The measurements were carried applicability for SHG in stacked π-systems. To obtain a
out as described in the literature.[29,30] Dichloromethane deeper insight into the “through-space” interaction con-
and acetonitrile were used as solvents. In addition, the cerning NLO effects it would be worthwhile to extend the
Kurtz-powder method[31] was applied for crystalline sam- amount of face-to-face stacked sandwich complexes in a
ples of 5PF6, 6PF6 and 7PF6, because they crystallize in the polar fashion to make the π-electronic system more polariz-
chiral space group C2221. However, no method could detect able, which is subject of current work.
a measurable intensity of a frequency-doubled light. One
explanation for the lack of SHG of the liquid solution sam-
ples is the weak polarizability and thus hyperpolarizability
of the polar complexes, which can already be suggested
from small solvatochromism. Even for the mixed-valence
diferrocenyl species 5PF6 and 9PF6, which illustrate broad
absorption bands in the NIR region (vide supra), no fre-
quency-doubled signal could be detected, although SHG
Experimental Section
General: Manipulations were carried out under dry nitrogen using
standard Schlenk technique. Solvents were saturated with nitrogen.
Diethyl ether (Et2O), tetrahydrofuran (THF), n-hexane and toluene
were freshly distilled from the appropriate alkali metal or metal
alloy. Dichloromethane (CH2Cl2) and nitromethane (MeNO2) were
has been observed for species containing two ferrocene ter-
mini, which are separated by a cumulenium bridge.[32] The
considerable absorption of 5PF6 and 9PF6 at λ Ͻ 800 nm
may hamper the recognition of the second harmonic signal
by absorption of light over a long range in the visible re-
gion. The lack of a SHG of the crystalline phase may be
due to the orthorhombic crystal space group C2221, which
is a less effective space group for second harmonic genera-
tion.[33]
dried with calcium hydride. NMR: Varian Gemini 200 BB; Bruker
AM 360; measured at 295 K rel. to TMS. UV/Vis: Perkin–Elmer
Model 554. IR: KBr pellets; FT-IR Perkin–Elmer Model 325. MS:
Finnigan MAT 311 A (EI-MS). Elemental analyses: CHN-O-Ra-
pid, Fa. Heraeus, Zentrale Elementanalytik, Fachbereich Chemie,
Universität Hamburg. 1,8-Diiodonaphthalene,[10] di-µ-chloro-
bis[chloro(η5-pentamethylcyclopentadienyl)rhodium()]
[Cp*RhCl2]2,[34] di-µ-chlorobis[chloro(η5-pentamethylcyclopen-
tadienyl)iridium()] [Cp*IrCl2]2,[34] di-µ-chlorobis[chloro(η6-ben-
zene)ruthenium()] [(C6H6)RuCl2]2,[35] ferrocenium hexafluoro-
phosphate [FcH]PF6,[36] chloro-(η5-pentamethylcyclopentadienyl)-
(tetramethylethylenediamine)iron() [Cp*Fe(tmeda)Cl][37] were
synthesized according to literature procedures. Zinc chloride was
dried by stirring in thionyl chloride unter reflux for several hours.
[Pd(PPh3)4] was purchased commercially.
Conclusions
In order to create second harmonic generation by
“through-space” hyperpolarization in two face-to-face, but
polar arranged sandwich complexes, four novel disandwich
complexes have been synthesized, wherein a ferrocene and
a cationic sandwich complex are combined and held to-
gether by a naphthalene clamp. The synthesis was per-
formed by two consecutively conducted cross-coupling re-
actions of cyclopentadienylzinc chloride and ferrocenylzinc
chloride, respectively, with 1,8-diiodonaphthalene as start-
ing material. After deprotonation of the free cyclopen-
tadienyl substituent, the coordination of different half-
sandwich units revealed the desired dinuclear complexes. In
addition, the neutral, but unsymmetrical diferrocenyl deriv-
ative 5, was oxidized to the monocationic dipolar com-
pound 5PF6. For compounds 3, 5PF6, 6PF6, 7PF6 the mol-
ecular structures have been determined by X-ray structure
analysis. Complex 3 crystallizes in the space group P21/c,
whereas the dinuclear species crystallize in the chiral space
group C2221. The fixation of the sandwich entities in the
peri position of the naphthalene backbone causes severe
distortion of the entire complex, but warrants an almost
linear face-to-face alignment of the two sandwich units. The
redox properties of all of these complexes turned out a
“through-space” polar interaction, which influences the
oxidation potential of the ferrocene unit in 5PF6, 6PF6,
7PF6 and 8PF6. However, no SHG effect could be detected
by means of HRS measurements. Having in mind the chi-
rality of the crystalline material of 5PF6, 6PF6 and 7PF6,
the Kurtz-powder method has been applied, but again, no
1-Cyclopentadienyl-8-iodonaphthalene (2): The synthesis was carried
out similar to the reaction described in the literature.[7c] Cyclopen-
tadienyllithium (1.82 g, 25.25 mmol) and anhydrous zinc chloride
(7.35 g, 53.95 mmol) were stirred in THF (70 mL) at 0 °C for
45 min. 1,8-Diiodonaphthalene (1) (4.97 g, 13.08 mmol) was added,
the reaction mixture was warmed to room temperature and was
stirred for 50 h. The reaction mixture was hydrolyzed with satu-
rated NH4Cl solution (150 mL), and the products were extracted
with Et2O (total amount 450 mL). The organic layer was dried with
MgSO4 and the solvents were evaporated to dryness. Extraction
with hexane revealed 1-cyclopentadienyl-8-iodnaphthalene (2) as a
yellow oil composed of three different isomers (3.55 g, 85.2%).
1
M.p. ca. –10 °C. H NMR (360 MHz, CDCl3, rel. to TMS, room
temp.): δ = 8.21 (dd, 3J6,7 = 7.2, 4J5,7 = 3.6 Hz, 1 H, 7-H), 7.86 (dd,
3J5,6 = 7.2, 4J5,7 = 3.6 Hz, 1 H, 5-H), 7.75–7.79 (m, 1 H, 3-H), 7.44
3
3
(d, J2,3 = 5 Hz, 1 H, 2-H), 7.42 (d, J3,4 = 5 Hz, 1 H, 4-H), 7.07
3
(“t”, J6,7
=
3J5,6 = 7.2 Hz, 1 H), 6.62–6.70 (m, 3 H, Cp-Hvinyl),
3.12–3.14 (m, 1 H, sp3-CpH) ppm. IR (KBr): ν = 3049, 2960, 2927,
˜
2908, 2846, 1927, 1802, 1719, 1595, 1571, 1536, 1498 1437, 1419,
1362, 1352, 1321, 1250, 1221, 1194, 1175, 1139, 1106, 1037, 1001,
950, 928, 890, 860, 826; 815, 764, 726, 681, 641, 606, 581, 557, 522,
505, 466, 419 cm–1.
Monolithioferrocene: Monolithioferrrocene was prepared similar to
the procedure described in the literature.[11] A pentane solution of
tBuLi (1.48 , 35 mL, 51.63 mmol) was added dropwise to a solu-
tion of ferrocene (10.0 g, 5.37 mmol) in THF (25 mL) at room tem-
perature. After 15 min of stirring, the solution was cooled to
–15 °C. The addition of n-hexane led to the precipitation of the
lithiated products, which contain the monolithiated ferrocene as the
main product (3.50 g, 34%). The orange solid material is extremely
SHG effect could be observed. The lack of SHG in the oxygen- and moisture-sensitive.
Eur. J. Inorg. Chem. 2006, 857–867
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863

M. Malessa, J. Heck, J. Kopf, M. H. Garcia
FULL PAPER
1-Cyclopentadienyl-8-ferrocenylnaphthalene (3): Anhydrous zinc
chloride (2.21 g, 16.2 mmol) was added to a solution of monolith-
ioferrocene (2.317 g, 12,07 mmol) in THF (30 mL) at 0 °C. After
124.0 (C-3), 91.2 (C-1Ј), 87.5 (C-1ЈЈ), 79.7 (C5Me5), 72.8 (C-2Ј,5Ј),
71.5 (C-3Ј,4Ј), 70.5 (C-2ЈЈ,5ЈЈ), 69.4 (C5H5), 66,40 (C-3ЈЈ,4ЈЈ), 10,81
(C Me ) ppm. IR (KBr):ν = 3089, 3054, 2943, 2900, 2853, 1636,
˜
5
5
stirring for 1 h, the red solution was added to a solution of 1-cyclo- 1571, 1506, 1476, 1448, 1425, 1414, 1377, 1365, 1314, 1266, 1182,
pentadienyl-8-iodonaphthalene (2) (2.57 g, 8.08 mmol) and tetrakis-
(triphenylphosphane)palladium(0) (0.55 g, 0.48 mmol, 6 mol-%) in
THF (10 mL). The reaction mixture was stirred at room tempera-
ture for 4 h and poured into a solution of saturated ammonium
chloride (200 mL). The mixture was vigorously stirred and ex-
tracted with Et2O. The orange-red organic layer was dried with
MgSO4. The volume of the solution was reduced to a minimum
amount, dissolved in hexane/Et2O (10:1), filtered through a column
of alumina (5% water), and subjected to column chromatography
on basic alumina [5% water, hexane/Et2O (1:0 to 10:1)]. Unreacted
ferrocene could be separated first. The second fraction contained
the desired compound 3 as an orange-red solid material, consisting
of two isomers: 1-(cyclopentadien-1Ј-yl)-8-(ferrocen-1ЈЈ-yl)naph-
thalene (3a) and 1-(cyclopentadien-2Ј-yl)-8-(ferrocen-1ЈЈ-yl)naph-
thalene (3b) (1.90 g, 63%). C25H20Fe (376.28): calcd. C 79.80, H
5.36; found C 79.74, H 5.80. M.p. 122–125 °C; ref.[7c] 134–140 °C.
1H NMR (200 MHz, CDCl3, rel. to TMS, room temp.): δ = 8.18
1137, 1105, 1066, 1032, 999, 935, 912, 881, 843, 825, 811, 788, 772,
692, 661, 640, 602, 587, 533, 521, 510, 494, 483, 460, 432, 423, 414,
408 cm–1. MS (EI): m/z (%) = 566 (100) [M+], 501 (24) [M – Cp]+,
431 (12) [M – Cp*]+, 445 (6) [M – Cp]+, 375 (3) [M – FeCp*]+, 310
(46) [M – CpFeCp*]+, 254 (6) [C10 H6 (C5H4)2]+, 189 (6)
[C10H5(C5H4)]+, 121 (5) [FeCp]+. UV/Vis (CH2Cl2): λmax (ε) = 298
(18240), 391 (2390, sh), 481 (1932 –1 cm–1) nm; (MeOH): λmax (ε)
= 296 (ca. 13000), 398 (ca. 1600, sh), 477 (ca. 1355 –1 cm–1) nm.
Figure 9. Numbering scheme for the assignment of the NMR sig-
nals.
3
3
(d, J6,7 = 8 Hz, 1 H, 7-H), 7.79 (m, 2 H, H-2, 5-H), 7.50 (t, J6,7
3
= J5,6 = 7.5 Hz, 1 H, 6-H), 7.32–7.42 (m, 2 H, H-3, 4-H), 5.88–
6.30 (m, 3 H, Cp-Hvinyl), 4.30, 4.26 (br. t, 2 H, Fc-H2,5, isomer 3a
and 3b), 4.03 (br. t, Fc-H3,4, 1.2 H, isomer 3b), 3.96 (br. s, 5.8 H,
Fc-H, isomer 3a and 3b, Fc-H3,4 isomer 3a), 2.89 (br. s, 0.6 H, sp3-
CpH, isomer 3b), 2.68 (br. s, 0.4 H, sp3-CpH, isomer 3a) ppm. 13C
NMR (50 MHz, CDCl3, rel. to TMS, room temp.): δ = 137.4, 136.3
(C-1, C-8); 133.2, 132.6, 132.1, 131.9, 129.5, 129.5, 129.20, 128.7,
128.2, 127.8, 125.5, 125.1, 72.1, 70.7 (C-2ЈЈ,5ЈЈ); 69.9 (C5H5), 67.2,
1-[(η5-Cyclopentadienediyl)(η5-pentamethylcyclopentadienyl)iron-
(
III)]-8-ferrocenylnaphthalene Hexafluorophosphate (5PF6): 1-[(η5-
Cyclopentadienediyl)(η5-pentamethylcyclopentadienyl)iron()]-8-
ferrocenylnaphthalene (5) (0.314 g, 0.55 mmol) was dissolved in
CH2Cl2 (30 mL). Ferrocenium hexafluorophosphate (0.166 g,
0.50 mmol) was added, whereupon the color of the reaction mix-
ture changed form orange-red to dark brown. After stirring at
room temperature for 80 min, n-hexane (60 mL) was layered on the
CH2Cl2 solution, and the reaction flask was stored at –30 °C for
2 d. The precipitated crystals were filtered off and dried in vacuo.
1-[(η5-Cyclopentadienediyl)(η5-pentamethylcyclopentadienyl)-
iron()]-8-ferrocenylnaphthalene hexafluorophosphate (5PF6) was
obtained in dark red-brown crystals (0.32 g, 0.45 mmol, 82%).
C35H34Fe2PF6·(CH2Cl2)0.66 (767.94): calcd. C 55.78, H 4.64; found
66.7 (C-3ЈЈ,4ЈЈ), 44.7, 41.7 (sp3C-C H ) ppm. IR (KBr): ν = 3076,
˜
5
5
3046, 2916, 2897, 2871, 1637, 1591, 1570, 1500, 1478, 1422, 1365,
1105, 1052, 1032, 1022, 999, 952, 894, 824, 810, 773, 673, 485 cm–1.
MS (EI): m/z (%) = 376.3 (100) [M+], 310.3 (59) [M – C5H6]+, 254
(23) [C10H6(C5H4)2+], 189 (16) [C10H5(C5H4)+], 121 (16) [FeCp+].
UV/Vis (CH2Cl2): λmax (ε) = 382 (1420, sh), 456 (536 –1 cm–1) nm;
(MeOH): λmax (ε) = 295 (ca. 6000), 378 (ca. 800), 458 (ca.
300 –1 cm–1) nm.
1
C 55.98, H 4.70. M.p. 189 °C (dec). H NMR (360 MHz, [D6]ace-
tone, rel. to TMS, room temp.): δ = 34.2 (2Ј,5Ј-H), 24.9 (2ЈЈ,5ЈЈ-H),
22.5 (3ЈЈ,4ЈЈH), 18.5 (3Ј,4Ј-H), 10.9 (C5H5), 1.87 (4-H, 5-H), –2.22
(6-H), –10.81 (7-H), –25.26 (3-H), –36.55 (C5Me5), –55.84 (2-H).
1-[(η5-Cyclopentadienediyl)(η5-pentamethylcyclopentadienyl)iron-
(
II)]-8-ferrocenylnaphthalene (5): 1-Cyclopentadienyl-8-ferrocenyl-
naphthalene (3) (0.182 g, 0.48 mmol) was dissolved in THF
(10 mL), treated with an Na[N(SiMe3)2] solution in THF (1 ,
0.5 mL, 0.5 mmol) at 0 °C and stirred for 90 min. To this solution,
which was cooled to –78 °C, [Cp*Fe(tmeda)Cl] (0.412 g, 1.2 mmol)
was added. After stirring overnight and warming to room tempera-
ture, the reaction mixture was concentrated to dryness. The residue
was dissolved in a minimum amount of toluene and filtered
through alumina (neutral, 5% water) and the filtrate was purified
by column chromatography on alumina (neutral, 5% water). As
eluent n-hexane/toluene (10:1) was used. The eluate was concen-
trated to dryness, to yield 1-[(η5-cyclopentadienediyl)(η5-penta-
methylcyclopentadienyl)iron()]-8-ferrocenylnaphthalene (5)
(0.18 g, 65 %) as an orange crystalline material (Figure 9).
C35H34Fe2 (566.35): calcd. C 74.23, H 6.05; found C 73.99, H 6.59.
IR (KBr): ν = 3121, 3051, 2963, 2916, 1631, 1587, 1502, 1474, 1448,
˜
1423, 1412, 1389, 1314, 1268, 1185, 1133, 1105, 1070, 1032, 1000,
935, 919, 846, 837, 775, 732, 699, 692, 638, 598, 557, 533, 521, 510,
494, 483, 460, 432, 423, 414, 408 cm–1. MS (FAB): m/z (%) = 566
(100) [M+], 501 (8) [M – Cp]+, 445 (12) [M – FeCp]+, 431 (20) [M –
Cp*]+, 310 (44) [M – CpFeCp*]+. UV/Vis (CH2Cl2): λmax (ε) = 433
(2850, sh), 813 (649), 1284 (122 –1 cm–1) nm; MeOH: λmax (ε) =
304 (24780), 428 (3712, sh), 801 (953 –1 cm–1) nm.
1-[(η5-Cyclopentadienediyl)(η5-pentamethylcyclopentadienyl)-
rhodium(III)]-8-ferrocenylnaphthalene Hexafluorophosphate (6PF6):
1-Cyclopentadienyl-8-ferrocenylnaphthalene (3) (0.29 g,
0.77 mmol) was dissolved in THF (15 mL), and treated with a solu-
tion of Na[N(SiMe3)2] in THF (1 M, 0.75 mL, 0.75 mmol) at 0 °C.
M.p. 150 °C. 1H NMR (200 MHz, CDCl3 rel. to TMS, room After stirring for 80 min, the solvent was stripped off in vacuo,
3
4
temp.): δ = 8.06 (dd, J6,7 = 7.5, J5,7 = 2 Hz, 1 H, 7-H), 7.93 (d,
and the residue was redissolved in acetonitrile (50 mL), whereupon
3J2,3 = 6.5 Hz, 1 H, 2-H), 7.74 (dt, 2 H, H-4, 5-H), 7.48 (t, J6,7
=
thallium() chloride (0.185 g, 0,77 mmol) was added. The reaction
3
3J5,6 = 7.5 Hz, 1 H, 6-H), 7.45 (t, J3,4 = 3J2,3 = 6.5 Hz, 1 H, 3-H), mixture was stirred at room temperature for 3 h and at 40 °C for
3
3
3
4.12 (t, J = 2 Hz, 2 H, 2ЈЈ,5ЈЈ-H), 3.86 (t, J = 2 Hz, 2 H, 3ЈЈ,4ЈЈ-
18 h. [Cp*RhCl2]2 (0.236 g, 0.38 mmol) was added and the mixture
stirred at 45 °C for 3 h and at room temperature for 20 h. The reac-
3
H), 3.83 (s, 5 H, C5H5), 3.64 (t, J = 2 Hz, 2 H, 2Ј,5Ј-H), 3.38 (t,
3J = 2 Hz, 2 H, 3Ј,4Ј-H), 1.60 (s, 15 H, C5Me5) ppm. 13C NMR tion solution was filtered through Celite, and the filtrate was con-
(50 MHz, CDCl3 rel. to TMS, room temp.): δ = 136.9 (C-8), 135.3 centrated to dryness. The solid red residue was dissolved in water
(C-1), 131.2 (C-7), 130.5 (C-2), 126.6, 126.1 (C-4,5), 124.2 (C-6), (60 mL) and, after filtration, NH4PF6 (0.150 g, 1.03 mmol), dis-
864
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Eur. J. Inorg. Chem. 2006, 857–867

Polar Cofacially Fixed Sandwich Complexes
FULL PAPER
solved in water (5 mL), was added to the filtrate. An orange, volu-
minous precipitate formed, which was collected on a filter frit,
washed with water and Et2O and dried in vacuo. For recrystalli-
zation the orange-red powder of 6PF6 (0.425 g, 0.57 mmol, 74%)
was redissolved in CH2 Cl2 and overlayered with Et2 O.
C35H34FeRhPF6 (758.37): calcd. C 55.43, H 4.52; found C 56.48,
H 4.87. M.p. 172 °C (dec). 1H NMR (200 MHz, [D6]acetone, rel.
Yi e l d : 0 . 2 2 g ( 3 7 % ) o f o r a n g e - r e d p ow d e r o f 8 P F 6 .
C31H25FeRuPF6·(C6H5CH3)0.66 (760.85): calcd. C 56.30, H 4.02;
found C 57.00, H 4.07. M.p. 318 °C (dec.). 1H NMR (200 MHz,
3
[D6]acetone, rel. to TMS, room temp.): δ = 8.33 (dd, J2,3 = 7.5,
4J2,4 = 1.5 Hz, 1 H, 2-H), 7.99–7.90 (m, 3 H, 4-H, 5-H, 7-H), 7.62
3
3
3
(t, J3,4 = 7.5 Hz, 1 H, 3-H), 7.50 (t, J6,7 = J5,6 = 7.5 Hz, 1 H, 6-
3
H), 6.13 (s, 6 H, C6H6), 5.49 (t, J = 2 Hz, 2 H, 2Ј,5Ј-H), 5.18 (t,
3
4
3
to TMS, room temp.): δ = 8.33 (dd, J2,3 = 7.5, J2,4 = 1,5 Hz, 1
3J = 2 Hz, 2 H, 3Ј,4Ј-H), 4.32 (t, J = 2 Hz, 2 H, 2ЈЈ,5ЈЈ-H), 4.11
3
3
H, 2-H), 8.03 (dd, 3J6,7 = 8, 4J5,7 = 2 Hz, 1 H, 7-H), 7.94 (dd, J3,4
(t, J = 2 Hz, 2 H, 3ЈЈ,4ЈЈ-H), 3.98 (s, 5 H, C5H5) ppm. 13C NMR
4
= 8, J2,4 = 1.5 Hz, 1 H, 4-H), 7.74–7.61 (m, 3 H, 3-H, 5-H, 6-H), (50 MHz, [D6]acetone, rel. to TMS, room temp.): δ = 133.6 (C-2),
3
3
5.62 (t, 2 H, J = 2 Hz, 2Ј,5Ј-H), 5.38 (t, J = 2 Hz, 2 H, 3Ј,4Ј-H), 133.5 (C-7), 130.3 (C-4), 129.0 (C-4a or 8a), 127.9 (C-5), 125.8 (C-
3
3
4.31 (t, J = 2 Hz, 2 H, 2ЈЈ,5ЈЈ-H), 4.10 (t, J = 2 Hz, 2 H, 3Ј,4Ј-
H), 3.98 (s, 5 H, C5H5), 1.94 (s, 15 H, C5Me5) ppm. 13C NMR
(50 MHz, [D6]acetone, rel. to TMS, room temp.): δ = 136.4 (C-1),
135.9 (C-8), 133.7 (C-2), 131.9 (C-8a), 130.8 (C-7), 128.2 (C-4),
128.0 (C-4a), 126.3, 125.5 (C-5,6), 113.7 (C-1Ј), 101.6 [d,
3), 125.0 (C-6), 87.3 (C6H6), 82.0 (C-2Ј,5Ј), 78.4 (C-3Ј,4Ј), 71.8 (C-
2ЈЈ,5ЈЈ), 69.9 (C H ), 67.6 (C-3ЈЈ,4ЈЈ) ppm. IR (KBr): ν = 3090,
˜
5
5
1629, 1509, 1480, 1441, 1395, 1365, 1187, 1146, 1106, 1067, 1028,
1002, 879, 841, 775, 739, 691, 558, 510, 484 cm–1. MS (EI): m/z (%)
= 555 (65) [M+], 490 (5) [M – Cp]+, 477 (15) [M – C6H6]+, 376 (16)
[M – C6H6Ru]+, 311 (18) [M – C6H6RuCp]+. UV/Vis (CH2Cl2):
λmax (ε) = 463 (960 –1 cm–1) nm; (MeOH): λmax (ε) = 286 (3758),
1J(13C103Rh) = 8 Hz, C5Me5], 92.5 (C-1ЈЈ), 88.4 [d, J(13C103Rh) =
1
6 Hz C-2Ј, 5Ј], 87.7 [d, 1J(13C103Rh) = 7.5 Hz, C-3Ј,4Ј], 72.2 (C-
2ЈЈ,5ЈЈ), 70.5 (C5H5), 68.3 (C-3ЈЈ,4ЈЈ), 10.1 (C5Me5) ppm. IR (KBr): 461 (190 –1 cm–1) nm.
ν = 3093, 2919, 1626, 1500, 1476, 1455, 1425, 1389, 1314, 1266,
˜
Cyclic Voltammetry: Measurements were performed in CH2Cl2
with 0.4  [nBu4N]PF6 as supporting electrolyte. An Amel 5000
system was used with a Pt wire as working electrode and a Pt plate
(0.6 cm2) as auxiliary electrode. The potentials were measured
against Ag/AgPF6 and were referenced to E1/2(ferrocene/ferrocen-
ium) = 0 V.
1185, 1133, 1106, 1068, 1028, 1001, 841, 773, 740, 692, 558,
481 cm–1. MS (FAB): m/z (%) = 613 (100) [M+], 548 (10) [M –
Cp]+,492 (13) [M – FeCp]+,478 (18) [M – Cp*]+, 375 (22) [M –
RhCp*]+, 357 (47) [M – Cp*-FeCp]+. UV/Vis (MeOH): λmax (ε) =
293 (19170 –1 cm–1) nm.
1-[(η5-Cyclopentadienediyl)(η5-pentamethylcyclopentadienyl)-
iridium(III)]-8-ferrocenylnaphthalene Hexafluorophosphate (7PF6):
The synthesis of 7PF6 was carried out in the same manner as for
6PF6 with additional washing of the precipitate with toluene and
hexane. Used quantities: 1-cyclopentadienyl-8-ferrocenylnaph-
thalene (3) (0.27 g, 0.72 mmol), THF (15 mL), Na[N(SiMe3)2] in
THF (1 , 0.72 mL, 0.72 mmol), thallium() chloride (0.225 g,
0.94 mmol), [Cp*IrCl2]2 (0.28 g, 0.35 mmol), water (60 mL), solu-
tion of NH4PF6 (0.150 g, 1.03 mmol) in water (5 mL). Yield:
0.373 g (61%) of orange-red powder of 6PF6, prior to recrystalli-
zation from CH2Cl2/Et2O. C35H34FeIrPF6·(C6H5CH3) (939.83):
calcd. C 53.68, H 4.50; found C 54.11, H 4.58. M.p. 167 °C (dec).
1H NMR (200 MHz, [D6]acetone, rel. to TMS, room temp.): δ =
8.34 (dd, 3J2,3 = 7, 4J2,4 = 2 Hz, 1 H, 2-H), 8.00 (dd, 3J6,7 = 7, 4J5,7
X-ray Structure Determination: Crystals of compound 3, 5PF6,
6PF6 and 7PF6 suitable for an X-ray structure determination were
obtained for compound 3 by careful evaporation of the solvent,
and for 5PF6, 6PF6 and 7PF6 by slow diffusion of Et2O into a
CH2Cl2 solution of the complexes at –30 °C. The data were col-
lected with a four-circle diffractometer by Hilger and Watts, Mo-
Kα, λ = 0.71073 Å (Table 6). The structures were solved by direct
methods (SHELXS-86)[38a] and the refinements on F2 were carried
out by full-matrix least-squares techniques (SHELXL-97).[38b] All
non-hydrogen atoms were refined with anisotropic thermal param-
eters. The hydrogen atoms were refined with a fixed isotropic ther-
mal parameter related by a factor of 1.2 to the value of the equiva-
lent isotropic parameter of their carrier atoms. Weights were opti-
mized in the final refinement cycles. Residual electron density was
observed for crystals of 5PF6, 6PF6, and 7PF6 pointing out diffuse
incorporation of solvent molecules.[39] CCDC-279705 (3), -279702
(5PF6), -279703 (6PF6), and -279704 (7PF6) contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
3
4
= 2 Hz, 1 H, 7-H), 7.93 (dd, J3,4 = 7, J2,4 = 2 Hz, 1 H, 4-H),
3
7.69 –7.60 (m, 3 H, H-3, 5-H, 6-H), 5.70 (t, 2 H, J = 2 Hz, 2Ј,5Ј-
H), 5.37 (t, 2 H, 3J = 2 Hz, 3Ј,4Ј-H), 4.35 (t, 3J = 2 Hz, 2 H, 2ЈЈ,5ЈЈ-
3
H), 4.14 (t, J = 2 Hz, 2 H, 3ЈЈ,4ЈЈ-H), 3.99 (s, 5 H, C5H5), 2.02 (s,
15 H, C5Me5) ppm. 13C NMR (50 MHz, [D6]aceton/TMS, room
temp.): δ = 137.0 (C-1), 136.6 (C-8), 134.5 (C-2), 133.5 (C-3), 132.6
(C-8a), 131.5 (C-7), 128.9 (C-4), 128.3 (C-4a), 126.9 (C-5), 126.2
(C-6), 107.8 (C-1Ј), 95.6 (C5Me5), 92.8 (C-1ЈЈ), 82.4 (C-2Ј,5Ј), 80.9
(C-3Ј,4Ј), 72.7 (C-2ЈЈ,5ЈЈ), 71.0 (C5H5), 68.7 (C-3ЈЈ,4ЈЈ), 10.0
SHG Measurements: The efficiency of SHG of the crystalline mate-
rials are measured with our experimental setup[40] for the Kurtz
powder method.[31] The measurements were performed at 1064 nm
laser pulses produced by the Nd:YAG laser at low power (50 mJ
per pulse); this laser produces 40-ns pulses with a repetition rate
of 10 Hz. The procedure for the measurements is as follows: for
crystalline samples, the grain size was not standardized. For this
reason signals between individual measurements were seen to vary
in some cases by as much as 20%. The material to be measured
was ground to a fine powder and compacted in a mount and in-
stalled in the sample holder. In order to compare the new samples
with the reference urea, the measurements were averaged over se-
veral laser cycles. The voltage from the photomultiplier was mea-
(C Me ) ppm. IR (KBr): ν = 3093, 2917, 1626, 1475, 1389, 1314,
˜
5
5
1264, 1184, 1106, 1035, 1002, 843, 773, 692, 558, 483 cm–1. MS
(EI): m/z (%) = 703 (100) [M+], 581 (14) [M – CpFe]+, 568 (8) [M –
Cp*]+, 447 (15) [M – Cp* – FeCp]+, 376 (52) [M – Cp*Ir]+. UV/
Vis (CH2Cl2): λmax (ε) = 454 (780 –1 cm–1) nm; (MeOH): λmax (ε)
= 289 (5271), 450 (220 –1 cm–1) nm.
1-[(η6-Benzene)(η5-cyclopentadienediyl)ruthenium(II)]-8-ferrocenyl-
naphthalene Hexafluorophosphate (8PF6): The synthesis of 8PF6
was carried out in the same mannere as for 6PF6 with additional
washing of the precipitate with toluene and hexane. Used quanti-
ties: 1-cyclopentadienyl-8-ferrocenylnaphthalene (3) (0.33 g,
0.86 mmol), THF (20 mL), Na[N(SiMe3)2] in THF (1 , 0.85 mL, sured by an oscilloscope which was triggered by the signal itself.
0.85 mmol), MeCN (50 mL), thallium() chloride (0.208 g,
0.87 mmol), [C6H6RuCl2]2 (0.205 g, 0.41 mmol), water (60 mL),
The photomultiplier voltage and the neutral density filter area were
optimized to obtain a good signal-to-noise ratio and to prevent the
solution of NH4PF6 (0,18 g, 1.07 mmol) in water (5 mL). saturation of the photomultiplier. The oscilloscope measures the
Eur. J. Inorg. Chem. 2006, 857–867
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
865

M. Malessa, J. Heck, J. Kopf, M. H. Garcia
FULL PAPER
Table 6. Crystallographic data of 3a, 5PF6, 6PF6 und 7PF6.
3a
5PF6
6PF6
7PF6
Empirical formula
Mr [g/mol]
T [K]
C25H20Fe
376.25
153(2)
C35H34Fe2PF6
711.29
153(2)
C35H34FeRhPF6
758.35
153(2)
C35H34FeIrPF6
847.64
153(2)
λ [pm]
71.073
71.073
71.073
71.073
Crystal system
Space group
a [pm]
b [pm]
c [pm]
monoclinic
P21/c
orthorhombic
C2221
1239.8(3)
2377.0(5)
2271.4(5)
orthorhombic
C2221
1231.3(11)
2408.3(18)
2277.8(18)
orthorhombic
C2221
1234.1(8)
2405.1(9)
2279.0(18)
1142.3(7)
985.1(6)
1903.2(10)
123.71(4)
1781.5(18)
4
1.403
0.851
784
β [°]
V [106 pm3]
Z
6694(3)
8
1.412
0.971
6754.1(9)
8
1.492
1.021
3072
6764(7)
8
1.665
4.463
ρcalcd. [Mg/m3]
µ [mm–1]
F(000)
2920
3328
Crystal size [mm]
θmin,max
Index range
0.50×0.50×0.20
2.26–27.45
–5 Յ h Յ 14
–12 Յ k Յ 2
–24 Յ l Յ 22
6429
0.30×0.40×0.50
2.48–25.08
–1 Յ h Յ 14
–1 Յ k Յ 28
–1 Յ k Յ 26
4059
0.80×0.15×0.10
2.46–27.56
–16 Յ h Յ 1
–1 Յ k Յ 31
–1 Յ l Յ 29
5115
0.50×0.20×0.50
2.46–25.06
–7 Յ h Յ 14
–9 Յ k Յ 28
–27 Յ l Յ 2
3421
Reflections total
Reflections independent
Rint
4068
0.0342
3809
0.0424
4827
0.0349
3314
0.0498
Reflections [I Ͼ 4σ(I)]
Parameters
3022
253
1.033
0.0503/0.1158
0.0802/0.1307
–0.523/0.736
1996
436
0.846
0.0745/0.1548
0.1464/0.1842
–0.398/0.905
3880
437
1.086
0.0641/0.1733
0.0834/0.1891
–0.913/1.684
2431
402
1.029
0.0612/0.1371
0.0963/0.1534
–1.681/1.564
GOF[a]
[b]
R1/wR2[b] [I Ͼ 2σ(I)]
R1/wR2 (all data)
Min./max. residue [e·Å3]
2 2
[a] GOF = “Goodness-of-fit” = {Σ[w(Fo2 – Fc ) ]/(n – p)}1/2 (n = number of reflections, p = number of parameters). [b] R1 = Σ||Fo| – |Fc||;
wR2 = {Σ[w(Fo – Fc ) ]/Σ[w(Fo2)]}1/2
.
2
2 2
time integral of the photomultiplier voltage automatically, which is
proportional to the SHG efficiency. The oscilloscope also performs
the average over several shots automatically. The SHG efficiency
measurement for the reference sample was performed under the
same experimental conditions as that of the test samples. The SHG
efficiency for liquid solutions of the polar compounds was deter-
mined by means of hyper-Rayleigh scattering (HRS).[41] The HRS
measurements were performed with a pulsed Nd:YAG laser at a
wavelength of λ = 1064 and 1500 nm. For the experimental setup
for HRS1064nm, see ref.[28] Solutions of the complexes in dichloro-
methane and acetonitrile with concentrations in the range of 10–4
to 10–6  were used with p-nitroaniline as a reference [β(CH2Cl2)
Acknowledgments
This work was supported by the Deutsche Forschungsgemeinschaft
(DFG, HE 1309/3), by the DAAD (Deutsch-Portugiesicher Wissen-
schaftleraustausch INIDA) and by the European Community
(COST D14, TMR FMRX-CT98-0166). We thank the DEGUSSA
AG for a donation of RuCl3, the Sartorius GmbH for a donation
of microfilters, and Nelson Lopes, GoLP, Centro de Física de
Plasmas, Instituto Superior Técnico, Lisboa, Portugal, for per-
forming the Kurtz powder measurements. M. H. G. thanks for fin-
ancial support by Fundação para a Ciência e Tecnologia, project
POCTI/QUI/48443/2002.
= 21.6·10–30 esu; β(MeCN)1064 = 29.2·10–30 esu].[42] The mea-
1064
surements at 1500 nm wavelength were carried out similar to the
setup described in ref.[43] Instead of the third harmonic (355 nm),
generated from an Nd:YAG laser with a wavelenghth of 1064 nm,
the optical parametric oscillator (OPO)[44] in use was pumped with
the second harmonic (532 nm). The signal intensity at 824 nm and
the fundamental at 532 nm were removed from the idler by using
dichroic mirrors (HR 650–850 and HR 532), a green light and a
silicon filter (transparent Ͼ 1000 nm). An additional Glan–Taylor
polarizer ensured the vertical polarization of the beam into the
measurement cell. Measurements were performed with ca. 10–4–
10–6  solutions of 5, 7 and 8 in CH2Cl2. Disperse Red 1 (DR1)
was used as an external standard with a value of β1500 (DR1) =
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866
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Eur. J. Inorg. Chem. 2006, 857–867

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Received: September 14, 2005
Published Online: December 22, 2005
Eur. J. Inorg. Chem. 2006, 857–867
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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