Synthesis, Characterisation of (Arene)tricarbonylchromium Complexes Linked to Cationic Fe and Ru Derivatives and Studies of First Hyperpolarisabilities by Hyper-Rayleigh Scattering

Article abstract of DOI:10.1002/ejic.200300190

In order to investigate the non-linear optical properties, in particular second-order effects of binuclear organometallic complexes, a series of new cationic binuclear [MCp-(DPPE)N≡C-(spacer)-C≡C-C₆H ₅Cr(CO)₃]⁺[

Full text of DOI:10.1002/ejic.200300190

FULL PAPER
Synthesis, Characterisation of (Arene)tricarbonylchromium Complexes Linked
to Cationic Fe and Ru Derivatives and Studies of First Hyperpolarisabilities by
Hyper-Rayleigh Scattering
Maria Helena Garcia,*[a,b] Sophie Royer, Maria Paula Robalo,*
[b]
[b,c]
[b]
Alberto Rom a˜ o Dias,
[d]
[d]
[d]
[d]
Jean-Philippe Tranchier, Ren e´ Chavignon, Damien Prim, Audrey Auffrant,
[d]
[d]
[e]
[f]
Fran c¸ oise Rose-Munch, Eric Rose,* Jacqueline Vaissermann, Andr e´ Persoons, and
Inge Asselberghs[
f]
Keywords: Chromium / Iron / Ruthenium / Non-linear optics / Arene ligands / Carbonyl ligands / Hyperpolarisability
In order to investigate the non-linear optical properties, in
particular second-order effects of binuclear organometallic
to the π-electron resonance, found on the solid state structure
of the mononuclear complex [NϵC−C H −CϵC−(η -
6 5
6
complexes,
a
series of new cationic binuclear [MCp-
C
6
H
5
)Cr(CO)
3
] (1Cr) determined by X-ray diffraction [mono-
+
−
˚
(DPPE)NϵC−(spacer)−CϵC−C
6
H
5
Cr(CO)
3
] [PF
6
]
com- clinic system, P2
1
/c space group, with a = 10.326(2) A, b =
˚
˚
pounds and mononuclear precursors [NϵC−(spacer)−Cϵ
C−C Cr(CO)
] have been synthesised [where M = FeII or
Ru ; Cp = η -C and spacer = phenyl ring (C ), thi-
ophene, (C S), or bithiophene (C S)
ganometallic π-donor fragments were linked by an extended
π system to the acceptor Cr(CO) fragment. The effect of π
13.209(5) A, c = 11.799(2) A and Z = 4] emphasises the elec-
tronic effect of this building block. The significant values of
first hyperpolarisability β determined by hyper-Rayleigh
6
H
5
3
II
5
5
H
5
6 4
H
4
H
2
4
H
2
2
]. The Fe or Ru or- scattering (HRS) indicate that the Fe containing compounds
were more efficient on second-order non-linear optical prop-
erties than the ruthenium analogues and the parent mononu-
clear chromium compounds.
3
back-donation involving the second Fe or Ru metal centre
and the π* orbitals of the NϵC-coordinated group, was
probed by the ν(NϵC) stretching bands on the IR spectra and
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
also by NMR spectroscopic data. The planarity, largely due Germany, 2003)
Introduction
states and large transition dipole moments.[1] Using this
molecular criteria, organometallic and coordination chem-
Over the past decade a pattern has emerged for the design ists have synthesised compounds possessing very intense
of organometallic materials with large second-order optical metal-to-ligand and ligand-to-metal charge transfer bands
non-linearities, in which the molecules have important in the UV/Visible spectrum, which showed very large mo-
[
2]
changes of dipole moments between ground and excited lecular hyperpolarisabilities. The use of organometallic
polarising groups in dipole structures has been of growing
[
a]
interest in the search for new molecular materials for non-
linear optics, and various binuclear compounds have been
published in the literature presenting significant values of
first hyperpolarisabilities β. Representative examples are the
ferrocenyl derivatives where the best reported β values are
Faculdade de Ci eˆ ncias da Universidade de Lisboa,
Ed. C8, Campo Grande, 1749-016 Lisboa, Portugal
Centro de Qu ´ı mica Estrutural, Instituto Superior T e´ cnico,
Av. Rovisco Pais 1049-001 Lisboa codex, Portugal
Fax: (internat.) ϩ 351-21/8464455
[
b]
E-mail: lena.garcia@ist.utl.pt
[
[
c]
Departamento de Engenharia Qu ´ı mica, Instituto Superior de
Engenharia de Lisboa,
5
found for bimetallic compounds possessing an (η -thio-
[
3]
[4]
7
Rua Conselheiro Em ´ı dio Navarro, 1, 1949-014 Lisboa, Portugal phene)Mn(CO)3, a group 6 pentacarbonyl, or an η -
d]
Laboratoire de Synth e` se Organique et Organometallique, UMR
CNRS 7611,
[5]
cycloheptatrienyltricarbonylchromium
as the acceptor
moieties. Also indenyl or cyclopentadienylruthenium()
donor moieties and group 6 pentacarbonyl or pentamina-
ruthenium() acceptor partners have been used successfully
as building blocks for the synthesis of bimetallic non-linear
Tour 44-4, Place Jussieu, 75252 Paris, Cedex 05, France
E-mail: rose@ccr.jussieu.fr
[
[
e]
f]
Laboratoire de Chimie Inorganique et Mat e´ riaux Mol e´ culaires,
UMR CNRS 7071
Leuven, Belgium
Laboratory of Chemical and Biological Dynamics, Center for
Research on Molecular Electronics and Photonics, University
of Leuven,
[6]
optical (NLO) active systems.
Our approach to the synthesis of bimetallic molecules for
NLO purposes, was based on the use of the fragment
Leuven, Belgium
Eur. J. Inorg. Chem. 2003, 3895Ϫ3904
DOI: 10.1002/ejic.200300190
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3895

M. H. Garcia, M. P. Robalo, E. Rose et al.
FULL PAPER
M(η -C H )(P-P)] (M ϭ FeII or RuII and P-P ϭ diphos- Preparation of the Bimetallic Iron/Chromium and
5
ϩ
[
5 5
phane) as a π-donor building block, bridged through a π- Ruthenium/Chromium Derivatives
6
delocalised system to the auxochrome [η -(benzene)-
6
[
FeCp(DPPE){NϵCϪ(spacer)ϪCϵCϪη -C H }Cr-
6
5
Cr(CO) ]. The amphoteric nature has been studied in
monometallic compounds. The π-donor ability of the
5
3
(
(
CO) ][PF ] [Cp ϭ η -C H ; spacer ϭ C H : 1FeCr, C H S
3 6 5 5 6 4 4 2
[7]
thiophene): 2FeCr, and (C H S) (bithiophene): 3FeCr]
were prepared following the general procedure of iodide ab-
straction of the parent compound [FeCp(DPPE)I] by the
use of TlPF , in the presence of a slight excess of the corre-
4
2
2
II
II
Ru /Fe fragments and the high values found for the quad-
ratic hyperpolarisabilities of some monometallic molecules
based on these moieties, have been explained on the basis
of π back-donation towards the π* empty orbitals of
ϪNϵCϪ and ϪCϵCϪ functional groups.[
6
[13]
sponding chromophores,
which in the present case were
8,9]
the mononuclear chromium complexes 1Cr, 2Cr, and 3Cr
described above. The reactions were carried out in dichloro-
methane by stirring at room temperature for several hours,
and were followed by thin layer chromatography (TLC).
After workup, orange reddish crystalline compounds were
5
The interest surrounding the use of these [M(η -C H )(P-
5
5
ϩ
P)] fragments as building blocks also comes from their
cationic nature, where the contribution for the alignment of
the chromophores in the solid state can be of potential
interest for macroscopic NLO properties, as found for
Fe(η -C H ){(R)-prophos}(p-NCC H NO )][PF ] (β
obtained in a yield of ca. 90%.
[
5
[
5
ϭ
6
5
Ϫ30
5
6
4
2
6
RuCp(DPPE){NϵCϪ(spacer)ϪCϵCϪη -C H }Cr-
6
5
[10]
45·10
esu)
.
(
CO) ][PF ] [DPPE ϭ 1,2-diphenylphosphanyl ethane; with
the spacer as C H : 1RuCr, C H S (thiophene): 2RuCr, and
C H S) (bithiophene): 3RuCr], were prepared following
the same general procedure of halide abstraction, by pre-
cipitation of TlCl from the parent compound
3 6
In the present work based on donorϪspacerϪacceptor
structures, besides the exploitation of two donor fragments
based on Ru and Fe centres, we have studied different
spacers, using conjugated π systems containing the benzene
ring and alternatively one or two thiophene rings.
6
4
4
2
(
4 2 2
II
II
[
RuCp(DPPE)Cl], with TlPF in the presence of a slight
6
excess of the corresponding chromophores [{NϵCϪ
6
(
spacer)ϪCϵCϪη -C H }Cr(CO) ] (compounds 1Cr, 2Cr,
6
5
3
[
14]
and 3Cr) in dichloromethane.
Depending on the chro-
Results and Discussion
mium derivative, the reactions were carried out at room
temperature or refluxed for several hours. The evolution of
the reactions was followed by TLC, as in the case of the
iron analogues. After workup orange crystalline com-
pounds were obtained in a yield of ca. 70%.
Preparation of the Mononuclear Chromium
6
[
{NϵC؊(spacer)؊CϵC؊η -C H }Cr(CO) ] Complexes
6
5
3
1Cr, 2Cr, and 3Cr
Mononuclear chromium complexes of the general for-
6
Characterisation of the New Mono 1Cr, 2Cr, and 3Cr and
Binuclear 1FeCr؊3FeCr and 1RuCr؊3RuCr Compounds
mula [{NϵCϪ(spacer)ϪCϵCϪη -C H }Cr(CO) ], where
6
5
3
the spacer is a phenyl ring ϪC H (1Cr), a thiophene ring
6
4
ϪC H S (2Cr) or two thiophene rings (C H S) (3Cr) were
4
2
4
2
2
All the new compounds are fairly stable towards oxi-
dation in air and to moisture, but the ruthenium bithio-
phene derivative [RuCp(DPPE){NϵCϪ2-(5-C H S) ϪCϵ
[
11]
obtained
coupling reaction
by a Sonogashira palladium-catalysed cross-
[
12]
6
between the (η -phenyl)ethynyltricar-
4
2
2
bonylchromium complex and various bromo, iodo arenes
substituted by a nitrile group, 1-CN, 2-CN, and 3-CN as
depicted in Scheme 1. The free ligands 1Ϫ3 were syn-
thesised analogously by the palladium copper catalysed
coupling of iodonitrile aromatics 1-CN, 2-CN, and 3-CN
and phenylacetylene, see Experim. Section.
6
CϪη -C H }Cr(CO) ][PF ] (3RuCr) turned out to be light-
6
5
3
6
1
31
sensitive. Analytical data, IR spectroscopy, and H, P, and
C NMR spectroscopy support the formulations. For the
13
cationic binuclear complexes, the molar conductivities of
Ϫ3
1
Ω
0
 solutions in acetone, in the range 101Ϫ115
Ϫ1
2
Ϫ1
·cm ·mol , are consistent with values reported for 1:1
[
15]
electrolytes.
IR Spectroscopic Studies
Two well resolved CO stretching modes in accordance
with the symmetry C3v are observed from IR measurements
on solutions of chromium tricarbonyl arene complexes. The
wavenumber of the CO modes is known to reflect the effect
of a substituent on the coordinated aromatic ring. For ex-
ample the complex of anisole presents two bands at 1978.9
and 1908.9 in isooctane whereas the complex of methylben-
zoate shows two bands at 1992.5 and 1929.2, which have
to be compared with the values of 1984.3 and 1916.5 for
[
16a]
[
C H Cr(CO) ].
Thus an electron donating group signif-
6
6
3
icantly decreases the IR resonance. The two bands relative
Ϫ1
Scheme 1. Sonogashira-coupling reactions
to the ν(CϵO) are in the range 1985Ϫ1898 cm for the
3896
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Eur. J. Inorg. Chem. 2003, 3895Ϫ3904

(Arene)tricarbonylchromium Complexes Linked to Cationic Fe and Ru Derivatives
FULL PAPER
mononuclear complexes and in the range 1969Ϫ1888 cmϪ1 Table 2. H NMR spectroscopic data of ligand 1 derivatives
1
for the dinuclear complexes. Coordination of 1Cr with Fe
and Ru give the dinuclear complexes 1FeCr and 1RuCr
which present resonances at lower frequencies: up to Ϫ17
Ϫ1
cm is in good agreement with π back-bonding from the
other metal. This effect is also observed for complexes
2FeCr and 2RuCr. As for complexes 3FeCr and 3RuCr, the
spectra exhibit a small decrease of the E mode but an unex-
pected although small increase of the A1 mode, Table 1.
H2,6 H3,5 H4 H10,14 H11,13
7.45 7.28 7.28 7.52 7.49
C
H
5
δ(H
) Ϫ δ(H
) x %
5
3
2
Table 1. Selected IR data (KBr)
1
Ϫ
Ϫ
Ϫ0.17
Ϫ0.21
Ϫ
ν CN (cmϪ1
)
ν CO (cmϪ1
)
1Cr
5.55 5.34 5.34 7.57 7.63[
38
41
41
a]
1
FeCr 5.49 5.34 5.34 7.62 6.45 4.48 Ϫ0.15
1RuCr 5.49 5.33 5.33 7.53 6.52[ 4.83 Ϫ0.16
b]
1
1
1
1
2
2
2
2
3
3
3
3
2218
2222
2216
2227
2220
2214
2197
2216
2220
2212
2197
2212
Ϫ
Cr
FeCr
RuCr
1985Ϫ1902
1969Ϫ1900
1968Ϫ1890
Ϫ
1972Ϫ1915
1969Ϫ1890
1969Ϫ1892
Ϫ
[a]
1Cr Ϫ δ1FeCr ϭ 1.18 ppm. [b]
δ
δ1Cr Ϫ δ1RuCr ϭ 1.11 ppm.
1
Table 3. H NMR spectroscopic data of ligand 2 derivatives
Cr
FeCr
RuCr
Cr
FeCr
RuCr
1957Ϫ1898
1965Ϫ1888
1966Ϫ1889
The ν(NϵC) IR analysis of mononuclear complexes 1Cr,
2
Cr, 3Cr shows the presence of the characteristic nitrile
H2,6 H3,5 H4 H10 H11
7.44 7.30 7.30 7.10 7.40
C
H
5
δ(H
) Ϫ δ(H
) x %
Ϫ1
5
3
2
band in the range 2212 to 2222 cm . For the binuclear
derivatives, typical IR bands confirm the presence of the
cyclopentadienyl ligand (ഠ 3060 cm ), the [PF6] anion 2Cr
2
Ϫ
Ϫ
Ϫ0.14
Ϫ0.18
Ϫ
Ϫ1
Ϫ
5.52 5.34 5.34 7.23 7.51
40
41
41
840 and 545 cmϪ1), the characteristic band of the coordi- 2FeCr 5.48 5.32 5.32 6.94[ 6.65 4.46 Ϫ0.16
[a]
[b]
(
c] [d]
Ϫ1
2 RuCr 5.51 5.35 5.35 7.00 6.79 4.84 Ϫ0.16
nated nitrile ν(NϵC) in the range 2197 to 2227 cm . Com-
parison of ν(NϵC) upon coordination of the chromium
mononuclear complexes to iron or ruthenium centres, re-
[a]
[b]
2Cr Ϫ δ2FeCr ϭ 0.86 ppm. [c]
δ
2Cr Ϫ δ2FeCr ϭ 0.29 ppm.
Ϫ δ2RuCr ϭ 0.23 ppm.
δ
δ
2Cr
[d]
δ2Cr Ϫ δ2RuCr ϭ 0.72 ppm.
Ϫ1
veals a negative shift Ϫ6 to Ϫ17 cm for the iron binuclear
compounds indicating the existence of π back-bonding
from the metal to the NϵC group, Table 1. The unexpected
1
RuCrϪ3RuCr complexes in Tables 2, 3, and 4. The com-
plexation of the benzene ring to the chromiumtricarbonyl
moiety in complexes 1Cr, 2Cr, 3Cr was easily identified due
to the characteristic upfield shift to the region
Ϫ1
Ϫ1
slight positive shifts, ϩ5 cm
for 1RuCr, ϩ2 cm
for
2RuCr, and no shift for 3RuCr, observed for the corre-
sponding ruthenium atom which are less effective π donors
than the iron derivatives, can also be correlated with a
weaker π back-donation effect, since normal σ coordination
leads to significant positive shifts on ν(NϵC) (up to ϩ80
[16b]
5.3Ϫ5.6 ppm.
The protons of the free arene give rise
to different sets of signals and multiplicity in the region
.2Ϫ7.5 ppm. We took into account that in the case of di-
7
2
6
phenyl acetylene, the protons H and H resonated at the
highest frequency and the protons H , H , and H res-
onated almost at the same frequency (increment Hortho
ϩ0.19, increment Hmeta ϭ ϩ0.02 and increment Hpara
Ϫ1
cm ). The present results for terminal nitrile coordination
3
5
4
are in good agreement with our earlier reports dealing with
ϭ
ϭ
[
13,14]
iron and ruthenium related monometallic compounds.
ϩ0.00). It is worth noting that in the case of tricarbonylch-
romiumarene complexes, the differences in the chemical
3
NMR Spectroscopic Studies
shifts between the meta and the ortho protons: δ(H ) Ϫ
2
δ(H ) can give an idea as to the effect of the substituent
1H NMR spectroscopic data of arenetricarbonylchrom- and about the conformation of the tripod in solution with
[
17aϪ17g]
ium complexes 1Cr, 2Cr, 3Cr are presented together with respect to the arene ring.
By using the classical
3
2
[17g]
the corresponding data for the free aromatic ligands and equation δ(H ) Ϫ δ(H ) ϭ (2x Ϫ 1)·∆δ
we calculated
max
the binuclear iron 1FeCrϪ3FeCr and ruthenium the percentage of the conformation eclipsing the substituted
Eur. J. Inorg. Chem. 2003, 3895Ϫ3904
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M. H. Garcia, M. P. Robalo, E. Rose et al.
FULL PAPER
1
Table 4. H NMR spectroscopic data of ligand 3 derivatives
1CrϪ3Cr, the anisotropy of the Cp and the phenyl groups
of the phosphane ligand being unable to interfere at this
distance. This indicated a weak electron donating ability of
the ϪCCϪC H ϪCNFeCp(DPPE) residue; indeed, it is
6
4
well reported that the protons of C H RϪCr(CO) (R ϭ
6
5
3
electron donating group) resonate at lower frequencies than
[
16b]
the protons of C H ϪCr(CO) .
6
6
3
In a similar manner the analysis of Tables 3 and 4, for
compounds containing one and two thiophene units, re-
veals a shielding of 0.86 ppm (δ2 Ϫ δ2FeCr) and 0.72 ppm
Cr
(δ2Cr Ϫ δ2RuCr) for protons H11 (ortho to the NC group)
with respect to the mononuclear complex 2Cr and smaller
shieldings for the adjacent H10 protons. Similar shielding
H2,6 H3,5 H4
H10
H11
H14
H15
C
5
H
5
δ(H
3
) Ϫ δ(H
2
)
x %
3
3
3
3
7.40 7.28 7.28 7.08 7.11 7.05
5.53 5.28 5.28 7.16 7.16 7.22
7.43
7.52
6.65
6.75
Ϫ
Ϫ
4.45
4.80
Ϫ0.12
Ϫ0.25
Ϫ0.19
Ϫ0.19
Ϫ
Cr
36
39
39
14
[
a]
[b]
[d]
values were also found for the equivalent protons H and
FeCr 5.50 5.31 5.31 7.15 7.01 6.87
RuCr 5.51 5.32 5.32 7.20 7.03 6.90[
c]
15
H
of the bithiophene containing compounds. Neverthe-
11
less this shift effect is barely felt on the H proton of the
second thiophene ring where only the small shielding values
[
a]
[b]
δ δ
3Cr Ϫ δ3FeCr ϭ 0.87 ppm. [c]
3Cr
δ
3Cr Ϫ δ3FeCr ϭ 0.35 ppm.
Ϫ δ3RuCr ϭ 0.32 ppm.
[d]
δ3Cr Ϫ δ3RuCr ϭ 0.77 ppm.
11
of ca. 0.15 ppm were observed for H . The chemical shifts
of the H2 protons of complexes 2FeCr,3FeCr and
,6
aromatic carbons. Thus we obtained populations x of 38,
0, and 36% for complexes 1Cr, 2Cr, and 3Cr respectively,
Tables 2Ϫ4, in good agreement with the almost staggered
conformation found in the solid state, Figure 1.
Analysis of the H NMR spectroscopic data of the iron
2RuCr,3RuCr resonate at lower frequencies with respect to
4
the mononuclear complexes 2Cr,3Cr but the shielding is
small.
Selected 13C NMR spectroscopic data of mononuclear
complexes are reported in Table 5. The carbon resonances
1
6
binuclear complex [FeCp(DPPE)(NϵCϪC H ϪCϵCϪη -
6
4
1
4
of the C to C atoms (complexed phenyl rings of 1Cr, 2Cr,
C H )Cr(CO) ][PF ] (1FeCr), and its ruthenium analogue
6
5
3
6
6
[
RuCp(DPPE)(NϵCϪC H ϪCϵCϪη -
6
4
C H )Cr(CO) ][PF ] (1RuCr), Table 2, shows a shielding
6
5
3
6
Table 5. Selected 13C NMR spectroscopic data of complexes 1, 2,
3-Cr: and complexing chemical shifts (CCS)
δ1Cr Ϫ δ1FeCr ϭ 1.18 and δ1Cr Ϫ δ1RuCr ϭ 1.11 ppm, respec-
tively, for protons H11,13, placed at the ortho position rela-
tive to the NϵC functional group with respect to the
mononuclear complex 1Cr. Such shielding could be in good
agreement with the π back-donation from the other metal
already suggested by the ∆ν(NϵC) found for both com-
pounds, and also with the results earlier reported for other
C1 [a]
C2
C3
C4
C7
C8
1
1
121.1
88.3
32.9
120.5
87.3
33.2
121.3
88.8
32.5
130.7
95.0
35.7
130.6
95.1
35.5
130.4
94.7
35.7
127.5
91.3
36.2
127.5
91.1
36.4
127.5
91.0
36.5
128.1
91.3
36.8
128.4
91.6
36.8
127.9
91.2
36.7
92.7
89.6
3.1
95.7
91.9
3.8
94.5
90.5
.0
86.7
87.6
Ϫ0.9
79.5
80.5
Ϫ1.0
81.1
82.0
Ϫ0.9
Cr
[b]
b]
CCS
2
monocyclopentadienylruthenium/iron mononuclear com- 2Cr
pounds containing benzonitrile ligands as chromoph- CCS[
[
13,14]
3
3
ores.
This is better proved by the fact that the H2,6
Cr
protons even farther from the Fe and the Ru residues res-
onate at slightly lower frequencies for 1FeCrϪ3FeCr and
[b]
CCS
[a]
CDCl
3
. [b] CCS ϭ Complexing Chemical Shift.
1RuCrϪ3RuCr with respect to the mononuclear complex
Figure 1. ORTEP diagram and atomic numbering scheme of the molecular structure of complex 1Cr including a view along the Cr-ring
axis. Thermal ellipsoids are presented at the 30% probability level
3898
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Eur. J. Inorg. Chem. 2003, 3895Ϫ3904

(Arene)tricarbonylchromium Complexes Linked to Cationic Fe and Ru Derivatives
FULL PAPER
3Cr) are assigned by CH correlation spectroscopy. They are
shifted to lower frequency in the region 88Ϫ96 ppm. It is
worth calculating the complexing chemical shifts
[
18,19]
(CCS)
of these carbons. Indeed the shifts due to the
complexation are characteristic of each carbon, this is also
7
true for the resonances of the alkyne carbon atoms C and
Figure 2. Complexes A[18] and B[19]
8
1
C . Thus the quaternary carbon
C
is shifted by
2.8Ϯ0.4 ppm, the carbons C , C , and C are shielded by
5.6Ϯ0.1, 36.3Ϯ0.3, and 36.7Ϯ0.1 ppm, respectively. The
carbon C is shielded by 3.5Ϯ0.5 ppm whereas the carbon
C is deshielded by 1.0Ϯ0.1 ppm. The carbonyl carbon res-
onances of complexes 1Cr, 2Cr, and 3Cr appeared almost
at the same frequency δ ϭ 231.8 ppm for 1Cr and 2Cr, δ ϭ
2
3
4
3
3
˚
7
8
[18]
shown in Figure 2. 1.167 A for C ϵC in complex A,
7
˚
[19]
1
.188(5) A for complex B. The slight elongation observed
8
7
8
for the C ϵC
triple bond in our compound
6
[
(NϵCϪC H ϪCϵCϪη -C H )Cr(CO) ] when compared
6
4
6
5
3
with complex B [with two Cr(CO) tripods attached to the
phenyl rings] shows that the effect of the NϵC group can
3
231.9 ppm for 3Cr.
The 13C NMR spectra of the binuclear compounds reveal
a deshielding of up to ca. 7.5 ppm of the carbon atom of
the NC group, as expected. The P NMR spectra of the
Fe/Cr and Ru/Cr binuclear compounds display one singlet
relative to the dppe coligand at δ ഠ 97 ppm for the Fe de-
rivatives and at δ ഠ 79 ppm for the Ru analogues, at about
the same chemical shifts found for other related com-
be compared with the effect of the Cr(CO) acceptor group.
3
15
˚
The C ϪN bond length of 1.113 A in 1Cr should be
3
1
˚
compared with a similar value of 1.114 A described in the
case of a nitrile coordinated to a cationic Ru(Cp)(PPh3)2
fragment: [CpFeC H ϪCHϭCHϪp-C H ϪCNϪRu(Cp)-
5
4
6
4
[
2c]
(
PPh ) ].
These values seem similar but with the nature
3
2
of the phosphanes being different it is hard to compare the
back-donation of the metal in these mono and dinuclear
complexes.
[
14]
Ϫ
pounds.
The signal relative to the PF6 counterion is
placed for all the compounds at δ ഠ Ϫ143 ppm as a septet.
The deviation from co-planarity of the complexed and
uncomplexed phenyl rings in 1Cr is small (10°) whereas the
corresponding dihedral angle in complex A is 50.9° (in com-
X-ray Structural Determination of
6
[
(NϵC؊C H ؊CϵC؊η -C H )Cr(CO) ]
6
4
6
5
3
6
Information on [(NϵCϪC H ϪCϵCϪη -C H )Cr- plex B this deviation is small: 3°). It would be interesting to
6
4
6
5
(
CO) ] (1Cr) and conformation of the solid state could be evaluate the preservation of the planarity in the spacer in
3
obtained from the X-ray crystal analysis, Table 6. Suitable the binuclear compounds. Nevertheless, attempts of grow-
crystals were obtained by crystallisation of complex 1Cr in ing suitable single crystals for this purpose have been unsuc-
a mixture of diethyl ether and petroleum ether. The struc- cessful so far.
ture represented in Figure 1 shows an almost staggered con-
formation of the Cr(CO) tripod with respect to the carbon UV/Visible Studies
3
2
1
atoms of the aromatic ring, with the CrϪC bond rotating
The UV/Vis electronic spectra of the aromatic free li-
gands 1Ϫ3, the new monometallic 1CrϪ3Cr and the bimet-
allic 1FeCrϪ3FeCr and 1RuCrϪ3RuCr compounds were
studied in acetone and chloroform solutions, in order to
characterise the absorption bands and to obtain some idea
of their hyperpolarisabilities, Table 7.
The spectra of the aromatic free ligands 1Ϫ3 displayed
one intense π-π* intraligand absorption band (ILCT) in the
region 317 to 370 nm.
2
3° away from the alkynyl substituent.
7
8
˚
The C ϵC triple bond: 1.196(3) A is slightly longer than
those observed in two relevant examples in the literature
˚
Table 6. Selected interatomic distances (A) for 1Cr
1Cr
C1ϪC2
C2ϪC3
C3ϪC4
C4ϪC5
C5ϪC6
C6ϪC1
C7ϪC8
C1ϪC7
C8ϪC9
C15ϪN
C12ϪC15
CrϪC1
CrϪC2
CrϪC3
CrϪC4
CrϪC5
CrϪC6
1.398(4)
1.406(3)
1.391(4)
1.407(4)
1.397(3)
1.427(3)
1.196(3)
1.431(3)
1.430(3)
1.133(4)
1.447(4)
2.216(2)
2.220(2)
2.211(2)
2.215(2)
2.220(2)
2.216(2)
The spectra of the monometallic complexes 1Cr؊3Cr in
chloroform solutions, were characterised by two bands, one
at ca. 425 nm and the other one in the region 300Ϫ360 nm.
The first band was assigned to a metal-to-ligand charge
transfer (MLCT) transition originating due to the charge
transition from the chromium centre to the π- and σ-bound
ligands. Although spectroscopic and theoretical stud-
[20,21]
ies
predict the existence of two bands for the dominant
6
excitations d -to-2π*(CO) and d -to-π*(arene) in [(η -
π
π
C
6
H
)Cr(CO)
] related compounds, only one band was
6
3
clearly observed in the present studies. A similar situation
was also reported by other authors for related complexes,
namely alkynyl and the alkenyltricarbonylchromium deriva-
[
7c]
tive. The second and more intense absorption band, pre-
dicted for the π-π* intraligand transitions (ILCT),[ was
20]
Eur. J. Inorg. Chem. 2003, 3895Ϫ3904
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3899

M. H. Garcia, M. P. Robalo, E. Rose et al.
FULL PAPER
Table 7. UV/Vis spectroscopic data for compounds [MCp-
(
DPPE)NϵC(arene)CϵCC
6
H
4
Cr (CO)
3 6
][PF ] measured in solu-
Ϫ4
II
II
tions ഠ10
 of acetone and chloroform (M ϭ Fe and Ru .
Compound[a] Acetone
Chloroform
λ
max
ε
max
λ
max
max
ε )
(molϪ1·L·cmϪ1
) )
(nm) (mol ·L·cmϪ1
Ϫ1
(nm)
1
FeCr
FeCr
Ϫ[b]
Ϫ
317
348
429
307
374
444
398[
19500
14750
12000
30120
12820
12690
26840
3
66
13500
13850
Ϫ
430
[
b]
2
Ϫ
3
4
85[c]
43
Ϫ
15920
29760
27920
Ϫ
d]
3
FeCr
RuCr
365
Figure 3. UV/Vis. Electronic spectra of 2FeCr, showing a weak
MLCT band, and 2Cr
3
Ϫ
92
[
b]
1
317
Ϫ
Ϫ
30690
Ϫ
Ϫ
3
3
38(sh) ഠ 26540
76(sh) ഠ 12530
Interestingly, the 3FeCr showed only one very broad and
intense band (chloroform solution), centred at 398 nm, with
the shape suggesting the overlap of the observed bands for
2
3
1
2
3
RuCr
RuCr
Cr
352
14
362
20990
11150
31980
16650
Ϫ
4550
Ϫ
5290
28860
8070
Ϫ
330
414
364
426
325
422
305
430
355
424
317
349
370
38070
16420
32130
17110
13090
4720
27110
5490
29640
9010
17680
7170
10010
4
1FeCr and 2FeCr. The complexity of this band was corrob-
4
Ϫ
26
[
b]
orated by the optical spectrum of this compound in ace-
tone, where two peaks seem to emerge clearly from that
broad band.
4
Ϫ
16
[
b]
Cr
4
24
351
24
The general characteristic of the electronic spectra of the
studied set of binuclear complexes was a comparative in-
crease of the intensity of the MLCT (Cr centred) and ILCT
absorption to the corresponding mononuclear chromium
derivatives. This effect was more pronounced on the ILCT
band and particularly for ruthenium derivatives. In ad-
dition, the existence of a new MLCT, centred on the second
metal, clearly observed in the binuclear iron derivatives and
located in the same direction of the strengthened ILCT
Cr
4
1
2
3
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
[
a]
6
[
H
Fe] ϭ FeCp(DPPE)Ϫ, [Ru] ϭ RuCp(DPPE)Ϫ, [Cr] ϭ Cr(η -
[
b]
[c]
[d]
C
6
5
)(CO)
3
.
Obscured by the solvent signal. Broad band.
Very broad and intense band.
found in the range 300Ϫ360 nm, in agreement with the elec- transition, might be the origin of the higher hyperpolarisa-
tronic spectra of the aromatic free ligands 1Ϫ3.
bilities found for the binuclear derivatives, discussed below.
The spectra of the bimetallic compounds (chloroform
solution) showed the expected MLCT (at ca. 430 nm) and Nonlinear Optical Studies
ILCT (in the range 320Ϫ400 nm) bands attributed to the
The dynamic first hyperpolarisabilities β of the new com-
6
monometallic parent [{NϵCϪ(spacer)ϪCϵCϪη -C H}-
6
plexes were measured in chloroform using the HRS
Cr(CO) ] complexes. The MLCT band was found to be in-
[23Ϫ25]
3
technique
with a 1064 nm Nd:YAG laser funda-
sensitive to the polarity of the solvent, when chloroform
was replaced by acetone, suggesting that there is no signifi-
cant variation of polarity between the fundamental and the
excited states, while the ILCT band showed some solvoch-
romicity. In addition to these bands, a third band emerged
in the electronic spectra of some of the binuclear complexes,
namely 1FeCr (348 nm) and 2FeCr (374 nm), and it was at-
mental. Results are presented in Table 8. The applicability
of the two-level model to these types of chromium tricar-
[20]
bonyl arene derivatives has been questioned.
For the
push-pull extended organic π-system chromophores func-
Table 8. Experimental first hyperpolarisability β determined by
hyper-Rayleigh scattering of mono Cr complexes and the corre-
tributed to a new metal-to-ligand charge transfer band in- sponding Fe and Ru binuclear derivatives
volving the iron centre. The characterisation of this new
band as a MLCT transition centred at the iron fragment, Compound
β(10Ϫ30esu)
was supported by our previous studies in other related
1
2
FeCr
FeCr
94
mononuclear iron compounds and explained by π back-do-
170
197
42
83
143
28
[8,22]
nation involving d -π*(NϵC) orbitals.
π
3FeCr
In Figure 3, the electronic spectrum of the binuclear com- 1RuCr
pound 2FeCr is compared with the spectrum of the parent 2RuCr
mononuclear compound 2Cr in chloroform. The arrow in
the figure points indicates this new Fe centred MLCT band,
clearly absent in the spectrum of the mononuclear parent
compound.
3
1
2
3
RuCr
Cr
Cr
59
88
Cr
3900
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2003, 3895Ϫ3904

(Arene)tricarbonylchromium Complexes Linked to Cationic Fe and Ru Derivatives
FULL PAPER
tionalised with the Cr(CO) group, this model has been ap- the direction of the ILCT transition is reversed when the
3
plied based on the assumption that the major contribution binuclear compounds are formed. In fact, the NϵC ending
to the hyperpolarisabilities arises from the ILCT transition group, in the chromium mononuclear compounds
[
7c]
6
occurring along the chromophore molecular axis.
The [{NϵCϪ(spacer)ϪCϵCϪη -C H}Cr(CO) ], plays the role
6
3
II
additional MLCT band centred at the second metal (Fe
or Ru ) fragment due to an enhanced back-donation to the acts as the donor group (see Figure 4, a). However, the co-
of acceptor while the chromiumtricarbonylarene fragment
II
π* nitrile group, found clearly for the iron binuclear deriva- ordination of this NϵC group to a second metal (Fe/Ru)
1
tives, and the evidence found in the IR and H NMR spec- makes it behave as a π* acceptor relatively to this new metal
troscopic data, for its existence in the ruthenium analogues, centre. Thus, in the binuclear complexes, the new ending
ϩ
strongly suggests that the two-level approximation should group [MCp(DPPE)(NϵC)Ϫ] acts as a π donor while the
not be applied in this case and therefore the corresponding chromiumtricarbonyl fragment now behaves as an acceptor
static hyperpolarisabilities β were not calculated. More- (see Figure 4, b). These results are in good agreement with
0
over, the similarity in the positions of the charge-transfer the electronically amphoteric character reported for the
bands would result in approximately identical resonance en- chromium tricarbonyl arene fragment in analogous com-
6
hancement for all the complexes.
pounds of general structure [{RϪ(spacer)ϪCϵCϪη -
The β values found for compounds [{NϵCϪ(spacer)Ϫ C H}Cr(CO) ] where R is the donor NMe or the ac-
6
3
[7c]
2
6
Ϫ30
CϵCϪη -C H }Cr(CO) ] (28Ϫ88 ϫ10
esu), where ceptor NO2.
6
5
3
NϵCϪ is an acceptor group, are similar to those reported
in the literature for compounds of the same general for-
6
mula,
namely
[Cr(η -C H R)(CO) ]
with
Rϭ
6
5
3
ϪCϵCϪC H RЈ or ϪC(H)ϭC(H)ϪC H RЈ (RЈ ϭ NMe ,
6
4
6
4
2
NO ), corroborating that the chromium tricarbonyl arene
2
fragment is amphoteric with respect to its electronic behav-
[
7]
iour. Indeed, electron donating or electron withdrawing
behaviour in NLO chromophores depends on the electronic
nature of the far end group of the chromophore.[ In ad-
dition, the substitution of the phenyl spacer 1Cr by a thio-
phene spacer 2Cr causes a twofold increase in the β value,
probably due to the reduced aromaticity of the thiophene.
The introduction of the second thiophene unity 3Cr also
enhances the hyperpolarisability, as expected due to the in-
crease of the conjugation length.
7c]
The experimental β values measured for all the binuclear
compounds studied (Table 8) showed that the best values of
β were obtained for the Fe binuclear derivatives 2FeCr and
Ϫ30
3FeCr, 170 and 197 ϫ10
esu, respectively. These values
are relatively higher than those of the precursor mononu- Figure 4. Ground state dipole vectors of chromium mononuclear
clear compounds 2Cr (59·10Ϫ30 esu) and 3Cr (88·10Ϫ30
complexes compared with the corresponding binuclear complexes.
The direction of the ILCT contribution in the binuclear complexes
esu). The ruthenium series 1RuCr, 2RuCr, and 3RuCr is reversed, due to the role of the new ending group
ϩ
[MCp(DPPE)(NϵCϪ)]
showed lower β values relative to the iron series, as would
[
8]
be expected from our previous studies on similar systems
and in accordance with the better donor role of the iron
fragment. Comparison of the different spacers follow the
same trend observed for the corresponding mononuclear Conclusion
chromium complexes. The β values obtained can be com-
6
pared with other β values of organometallic congeners de-
The synthesis of nitrile ligands linked to tricarbonyl (η -
scribed in the literature[
1b,2i,5,7c]
and with the 31·10
Ϫ30
esu arene)chromium complexes [{NϵCϪ(spacer)ϪCϵCϪη -
6
β value in the case of the prototypical ‘‘push-pull’’ chromo- C H }Cr(CO) ] by conjugated spacers is performed by re-
6
5
3
phore (Z)-1-ferrocenyl-2-(4-nitrophenyl)ethylene com- acting aromatic bromo or iodo nitrile derivatives with
[
2m]
plex
which has an SHG efficiency 62 times that of urea. tricarbonyl chromium complexed phenylacetylene using the
The comparison of the β values of mono and binuclear Sonogashira-coupling reaction. Characterisation of these
compounds studied in the present work show relatively mononuclear complexes obtained and the corresponding
6
higher values for the binuclear derivatives. These results dinuclear [M{NϵCϪ(spacer)ϪCϵCϪη -C H }Cr(CO) ]
6
5
3
might be expected by the higher intensity of the ILCT tran- complexes M ϭ Fe(dppe)Cp, Ru(dppe)Cp has been studied
1
13
sitions observed in the optical spectra of the binuclear com- using H, C, IR, and UV/Vis spectroscopy and in the case
pounds and the existence of a second MLCT band (iron/ of one of them by X-ray crystallography. Measurements of
ruthenium centred) in the axis of the chromophore, due to the dynamic first hyperpolarisabilities (β) by HRS, showed
dπ-π*(NϵC) π back-donation. It is important to note that significant higher values for the binuclear derivatives when
Eur. J. Inorg. Chem. 2003, 3895Ϫ3904
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3901

M. H. Garcia, M. P. Robalo, E. Rose et al.
FULL PAPER
compared with the corresponding monometallic parent [{NϵC؊(C
compounds. This enhancement of β observed upon coordi-
nation of the [{NϵCϪ(spacer)ϪCϵCϪη -C H }Cr(CO) ]
ligand complex to a second iron() or ruthenium() metal
centre can be explained by the significant enhancement ob-
served for the molar absorptivity of the ILCT band relative
to the nitrile chromophore and the synergic effect of a new
MLCT band originating due to π back-bonding from the
second metal towards the nitrile functional group.
6
6
6
H
4
)؊CϵC؊η -C
6
H
5
}Cr(CO)
3
]
(1Cr): (η -Phenyl)-
ethynyltricarbonylchromium complex (171 mg, 0.71 mmol),
[PdCl (PPh ) ] (25 mg, 0.035 mmol), CuI (7 mg, 0.035 mmol), and
6
2
3 2
6
5
3
p-iodobenzonitrile (158 mg, 0.69 mmol) were placed in a bicol un-
der unit atmosphere and dried in vacuo for 30 min. NEt (5 mL)
3
and anhydrous THF (10 mL) were then added and the mixture was
immediately heated to reflux for 3 h. After cooling at room tem-
perature, the suspension was filtered, washed with Et
2
O (3 ϫ
2
0 mL) and the solvents were removed under reduced pressure. The
residue was chromatographed on silica gel (diethyl ether/ petroleum
ether 96:4 to 80:20) to afford 1Cr (210 mg) in 87% yield as an
1
orange solid. m.p. 168 °C (dec). IR: see Table 1. H NMR: see
1
3
9
10 14
Experimental Section
Table 2. C NMR: see Table 5 and 126.8 (C ), 132.2 (C ,C ),
1
1
13
12
15
1
32.5 (C ,C ), 112.4 (C ), 118.4 (C ), 231.6 (CO) ppm.
General Procedures: All the experiments were carried out under
C H CrNO (339.3): calcd. C 63.72, H 2.65, N 4.13; found C
1
8
9
3
vacuum or nitrogen atmosphere using standard Schlenk techniques,
63.13, H 2.84, N 3.96.
[26]
6
and solvents were dried following published methods.
[Cr(η -
6
6
] was easily prepared as reported recently.[
18]
[{NϵC؊2-(5-C H S)؊CϵC؊η -C H }Cr(CO) ] (2Cr): (η -Phe-
4
2
6
5
3
C
6
H
5
ϪCϵCH)(CO)
3
nyl)ethynyltricarbonylchromium complex (119 mg, 5 mmol),
[PdCl (PPh ) ] (175 mg, 0.25 mmol), 2-bromocyanothiophene
Chlorobenzene tricarbonylchromium complex was prepared ac-
cording to literature procedures.[
27]
The halo nitrile aromatics 1-
2
3 2
(
3
6.05 g, 25 mmol), and NEt (30 mL) were added together in a bicol
CNϪ3-CN are commercially available or prepared using standard
[
28]
under N . The mixture was heated for 3 h. By using the same pro-
literature procedures. The synthesis of some new chromium de-
2
[
11]
cedures complex 2Cr was obtained in 81% (1.38 g) as an orange
rivatives was recently published in a preliminary communication.
1
5
[22]
5
[29,30]
solid. m.p. 140 °C (dec). IR (KBr): see Table 1. H NMR: see
Fe(η -C
5
H
5
)(dppe)(I)]
and [Ru(η -C
5
H
5
)(dppe)(Cl)]
were
1
3
9
10
Table 3. C NMR: see Table 5 and 129.2 (C ), 132.9 (C ), 137.4
prepared according to the procedures described in the literature.
1
1
12
13
(
7 3
C ), 111.1 (C ), 113.6 (C ), 231.8 (CO) ppm. C16H CrNO S:
IR spectra were recorded in KBr pellets on a PerkinϪElmer 683
1
13
calcd. C 55.65, H 2.02, N 4.05; found C 55.43, H 2.21, N 3.92.
spectrophotometer; only significant bands are cited. H, C, and
31
P NMR spectra were recorded in CDCl
3
on a Varian Unity 300
6
(3Cr):[11] 81%
13
[
{NϵC؊2-(5-C
4
H
2
S)
2
؊CϵC؊η -C
6
H
5
}Cr(CO)
3
]
spectrometer at probe temperature. The UV/Vis spectra were taken
on a PerkinϪElmer λ9 UV/Vis/Nir spectrophotometer. Elemental
analysis of mononuclear compounds were performed by ‘‘le service
de Microanalyses’’ (Universit e´ Pierre et Marie Curie). Binuclear
compounds were analysed at Laborat o´ rio de An a´ lises, Instituto Su-
perior T e´ cnico, using a Fisons Instruments EA1108 system. Data
acquisition, integration, and handling were performed using a PC
with the software package Eager-200 (Carlo Erba Instruments).
Melting points were obtained on a Reichert Thermovar. The molar
1
yield; m.p. 141 °C (dec). IR: see Table 1. H NMR: see Table 4.
C
9
10
11
NMR: see Table 5, and 134.2 (C ), 125.9 (C ), 132.7 (C ), 143.4
12
13
14
15
16
17
(
2
C ), 123.1 (C ), 124.2 (C ), 138.4 (C ), 112.2 (C ), 114.2 (C ),
31.9 (CO) ppm.
General Procedure for the Synthesis of the Bimetallic Iron/Chro-
mium Derivatives
[
FeCp(dppe){NϵC؊(spacer)؊CϵC؊C
slight excess of the adequate amount of chromium chromophore
[{NϵCϪ(arene)ϪCϵCϪC H }Cr(CO) ] (1.1 mmol) and TlPF
6
6
H
5
}Cr(CO)
3
][PF
6
]:
A
Ϫ3
Ϫ1
condutivities of 10 mol·L solutions of the complexes in ace-
1
tone were recorded with a Schott CGB55 Konduktometer. The H
6
5
3
[D]chloroform) and 1 C ([D]chloroform) chemical shifts are re-
ported in parts per million downfield from internal Me Si and the
P NMR spectra are reported downfield from external 85% H PO
[D]chloroform). Spectral assignments follow the numbering
3
(1.1 mmol) was added to a solution of the [CpFe(dppe)(I)]
(
(
1 mmol) in dichloromethane (25 ml) followed by stirring, at room
4
6
31
6 4
temperature, for 3 h in the case of [{NϵCϪ(C H )ϪCϵCϪη -
C H }Cr(CO) ] and 18 h for the thiophene derivatives. The evol-
6 5 3
3
4
(
ution of these reactions was followed by TLC (thin layer chroma-
tography). A colour change was observed from brown to red with
simultaneous precipitation of thallium iodide.
scheme shown in Tables 2Ϫ4.
Synthesis of the Free Ligands 1, 2, and 3: The free ligands were
synthesised in a similar manner to the chromium complexes (see
below) by the palladium copper catalysed coupling of the aromatic
iodonitriles 1-CN, 2-CN, and 3-CN and phenylacetylene.
After filtration, the solution was evaporated under vacuum to dry-
ness and washed several times with diethyl ether to remove the
excess of chromium [{NϵCϪ(arene)ϪCϵCϪC H }Cr(CO) ]
6 5 3
starting material. The residue was recrystallised from dichloro-
methane/ diethyl ether.
NϵC؊(C
6
H
4
)؊CϵC؊C
6
H
5
(1): 54% yield. IR: see Table 1. 1H
13
9
NMR: see Table 2. C NMR: see Table 5 and 127.2 (C ), 131.0
10
14
11 13
12
15
(
C ,C ), 131.0 (C ,C ), 110.4 (C ), 117.5 (C ), (UV/Vis, see
Table 7).
[FeCp(dppe)(NϵC؊C H ؊CϵC؊C H )Cr(CO) ][PF ] (1FeCr):
6
4
6
5
3
6
1
9
0% yield, red-orange, m.p. 128Ϫ130 °C. IR: see Table 1. H NMR:
NϵC؊2-(5-C
4
H
2
S)؊CϵC؊C
6
H
5
(2): 49% yield. IR: see Table 1.
13 5 1 2 6
5 5
see Table 2. C NMR: δ ϭ 79.8 (η -C H ), 88.3 (C ), 95.1 (C ,C ),
9
1
1
13
9
H NMR: see Table 3. C NMR: see Table 5 and 129.7 (C ), 130.4
3
4
5
7
8
9
10 14
1.3 (C ,C ,C ), 90.1 (C ), 87.6 (C ), 126.5 (C ), 132.7 (C ,C ),
10
11
12
13
(C ), 136.2 (C ), 108.8 (C ), 112.6 (C ).
1
1
13
12
15
31
31.6 (C ,C ), 112.0 (C ), 110.9 (C ), 231.9 (CO) ppm.
P
NϵC؊2-(5-C
4
H
2
S)
2
؊CϵC؊C
6
H
5
(3): 33% yield. IR: see Table 1. NMR:
δ
ϭ
97.59 (s, dppe), Ϫ143.69 (hept, PF
6
) ppm.
1
13
9
H NMR: see Table 4. C NMR: see Table 5 and 134.7 (C ), 124.8
C ), 131.8 (C ), 149.7 (C ), 123.8 (C ), 123.8 (C ), 137.3 (C ), found C 59.8, H 3.70, N 1.47. Molar conductance: 113.7
C
49
H
38CrF
6
FeNO ·1/2(C O: calcd. C 58.64, H 3.80, N 1.39;
3
P
3
2 5 2
H )
10
11
12
13
14
15
(
16
17
Ϫ1
Ϫ1 Ϫ1
1
09.7 (C ), 113.0 (C ).
cm ·mol ·Ω
.
General Procedure for the Synthesis of Chromium Mononuclear
Complexes
[FeCp(dppe){NϵC؊2-(5-C
4
H
2
S)؊CϵC؊C
6 5 3 6
H }Cr(CO) ][PF ]
(2FeCr): 86% yield, red, m.p. 130Ϫ132 °C. IR: see Table 1. 1H
3902
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2003, 3895Ϫ3904

(
Arene)tricarbonylchromium Complexes Linked to Cationic Fe and Ru Derivatives
FULL PAPER
1
3
5
1
31P NMR: δ ϭ 79.66 (s, dppe), Ϫ143.61 (hept, PF
NMR: see Table 3. C NMR: δ ϭ 80.2 (η -C
5
8
H
5
), 87.0 (C ), 95.0
6
) ppm. * Located
2
6
3
4
5
7
9
(
(
C ,C ), 91.0 (C ,C ,C ), 91.4 (C ), 80.8 (C ), 129.3 (C ), 132.6 under a broad signal.
10
11
12
13
31
C ), 138.6 (C ), 110.4 (C ), 108.8 (C ), 231.6 (CO) ppm.
97.43 (s, dppe), Ϫ143.53 (hept, PF ppm.
FeNO S: calcd. C 55.90, H 3.57, N 1.38, S 3.18;
found C 55.8, H 3.52, N 1.31, S 3.0. Molar conductance: 109.4
P
3 9
Crystal Structure of 1Cr: [(CO) Cr(C15H N)], M ϭ 339.27, µ ϭ
NMR:
C
δ
ϭ
6
)
Ϫ1
Ϫ3
0
.735 mm , ρ ϭ 1.46 g·cm , monoclinic, P2
1
/c, Z ϭ 4, a ϭ
47
H
36CrF
6
3 3
P
˚
1
0.326(2), b ϭ 13.209(5), c ϭ 11.799(2) A, β ϭ 106.61(2)°, V ϭ
˚
3
Ϫ1
Ϫ1 Ϫ1
1542.3(7) A , from 25 reflections (27.6°Ͻ 2θ Ͻ 28.4°). Cell dimen-
cm ·mol ·Ω
.
sions and intensities were measured at 295 K on a Nonius CAD4
diffractometer with graphite-monochromated Mo-K
α
radiation
[
(
CpFe(dppe){NϵC؊2-(5-C
4
H
2
S)
2 6 5 3 6
؊CϵC؊C H }Cr(CO) ][PF ]
˚
(
λ ϭ 0.71069 A). ω/2θ scans, two standard reflections measured
3FeCr): 91% yield, orange reddish, m.p. 127Ϫ129 °C. IR: see
1
13
5
every hour showed no significant variation.1° Ͻ θ Ͻ 28° (0 Ͻ h Ͻ
13, 0 Ͻ k Ͻ 17, Ϫ15 Ͻ l Ͻ 14), 4085 measured reflections, 3715
5 5
Table 1. H NMR: see Table 4. C NMR: δ ϭ 80.0 (η -C H ), 88.9
(
(
1
δ
C
1
2
6
3
4
5
7
8
C ), 94.8 (C , C ), 91.3 (C , C , C ), 91.1 (C ), 82.0 (C ), 134.3
2
2
9
10
11
12
13
14
unique reflections of which 2590 were observed [Fo Ͼ 3σ(F )];
C ), 132.6 (C ), 131.1 (C ), 143.2 (C ), 122.9 (C ), 130.7 (C ),
o
15
16
17
31
Rintϭ 0.03 for equivalent reflections. Data were corrected for Lor-
39.6 (C ), 124.2 (C ), 106.9 (C ); 231.9 (CO) ppm. P NMR:
entz and polarisation effects. The structure was solved by direct
ϭ
97.48 (s, dppe), Ϫ143.63 (hept, PF
6
)
ppm.
[
31]
methods using SHELXS,
all other calculations used CRYS-
51
H
38CrF FeNO ·2(CH CH O: calcd. C 57.14, H 4.70, N
6
3
P
3
S
2
3
2 2
)
TALS.[
32]
Atomic scattering factors and anomalous dispersion
terms were taken from the literature.
1
.10, S 5.17; found C 57.13, H 4.73, N 0.90, S 5.14. Molar conduc-
[33]
Ϫ1
Ϫ1 Ϫ1
Full-matrix least-squares
tance: 101.2 cm ·mol ·Ω
.
refinement based on F and a Chebychev weighting scheme gave
final values R ϭ 0.0399, wRϭ 0.0508, and s ϭ 1.05 for 209 vari-
ables and 2590 contributing reflections. The maximum shift/esd on
the last cycle was 1.75. Non-hydrogen atoms were anisotropically
refined. Hydrogen atoms were located on a difference Fourier map;
they were allocated an overall isotropic thermal parameter. The
final difference electron density map showed a maximum of 0.42
General Procedure for the Synthesis of the Bimetallic Ruthenium/
Chromium Derivatives
[
RuCp(DPPE){NϵC؊(spacer)؊CϵC؊C
1RuCr؊3RuCr): The corresponding chromium complex
)Cr(CO) ] (1.1 mmol) was added to a
solution of the [RuCp(dppe)Cl] (1 mmol) in dichloromethane
25 mL) followed by addition of TlPF (1.1 mmol) at room tem-
perature. The mixture was refluxed for 12 h in the case of
(NCϪC ϪCCϪC )Cr(CO) ] and 48 h for [{NϵCϪ2-(5-
S)ϪCϵCϪC }Cr(CO) ]. In the case of the bithiophene de-
rivative the reaction was carried out at room temperature for 14 h. of 23·10
The evolution of these reactions was followed by TLC. A colour
culate the hyperpolarisability of the compounds by the external
change was observed from red to orange with the simultaneous reference method. Solutions for measurements until 10  de-
precipitation of thallium chloride. After filtration, the solution was
pending on the nature of the complex under study, the low concen-
evaporated under vacuum to dryness and washed several times with tration being necessary to minimise absorptive losses. One-dimen-
6 5 3 6
H }Cr(CO) ][PF ]
(
[(NϵCϪ(arene)ϪCϵCC
6
H
5
3
˚
Ϫ3
and a minimum of Ϫ0.30 e·A
.
(
6
Hyper-Rayleigh Scattering: Details of the HRS experiment have
been discussed previously.[ A Q-switched Nd: YAG laser emitting
at 1064 nm was used to obtain the incident light. A reference value
20]
[
6
H
4
6
H
5
3
C
4
H
2
6
H
5
3
Ϫ30
[23]
esu for 4-nitroaniline in chloroform was used to cal-
Ϫ4
diethyl ether to remove the excess of the chromium chromophores
{NϵCϪ(arene)ϪCϵCϪC }Cr(CO) ]. The residue was recrys-
tallised from dichloromethane/diethyl ether.
sional hyperpolarisability is assumed, i.e. β1064 ϭ β333, and a rela-
tive error of Ϯ10% is estimated.
[
6
H
5
3
Supplementary Material: Crystallographic data for the structural
6
analysis of compound [Cr(η -C
6
H
5
ϪCϵCϪC
6
H
4
CϵN)(CO)
3
] (ex-
[
7
CpRu(dppe)(NϵC؊C
6 4 6 5 3 6
H ؊CϵC؊C H )Cr(CO) ][PF ] (1RuCr):
1
cluding structure factors) have been deposited in the Cambridge
data base. CCDC-147256 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the
Cambridge Crystallographic Data Centre, 12, Union Road, Cam-
bridge CB2 1EZ, UK; Fax: (internat.) ϩ44-1223-336-033; E-mail:
deposit@ccdc.cam.ac.uk].
0% yield, red-orange, m.p. 125Ϫ128 °C. IR: see Table 1. H
13
13
5
NMR:see Table 2. C NMR: δ ϭ C NMR: δ ϭ 82.2 (η -C
8
(
2
PF
4
1
5
H
5
),
1
2
6
3
4
5
7
8
8.3 (C ), 95.1 (C ,C ), 91.3 (C ,C ,C ), 90.1 (C ), 87.7 (C ), 126.7
9
10 14
11 13
12
15
C ), 133.0 (C ,C ), 131.7 (C ,C ), 112.0 (C ), 110.4 (C ),
3
1
31.8 (CO) ppm. P NMR: δ ϭ 79.85 (s, dppe), Ϫ143.73 (hept,
) ppm. C49 38CrF NO Ru·2(CH CH O: calcd. C 57.19, H
.8, N 1.20; found: C 57.10, H 4.10, N 1.29. Molar conductance:
6
H
6
3
P
3
3
2 2
)
Ϫ1
Ϫ1 Ϫ1
14.8 cm ·mol ·Ω
.
Acknowledgments
Financial support for this work was provided by the TMR ‘‘Or-
[
(
RuCp(dppe)(NϵC؊2-(5-C
4 2 6 5 3 6
H S)؊CϵC؊C H )Cr(CO) ][PF ]
1
2RuCr): 71% yield, orange, m.p. 133Ϫ135 °C. IR: see Table 1. H
13
5
1
5 5
NMR: see Table 3. C NMR: δ ϭ 82.5 (η -C H ), 87.0(C ), 95.0
(
(
NMR: δ ϭ 79.59 (s, dppe), Ϫ143.71 (hept, PF
NO
H 3.41, N 1.33, S 2.90. Molar conductance: 115.2 cm ·mol ·Ω
ganometallic
dipoles
with
NLO
properties’’
contract
2
6
3
4
5
7
8
9
C , C ), 91.1 (C , C , C ), 91.6(C ), 80.2 (C ), 129.3 (C ), 132.9
ERBFMRXCTCT980166, by COST D14 and partly by Funda c¸ a˜ o
para a Ci eˆ ncia e Tecnologia PRAXIS PCEX/C/QUI/96/96 and
CNRS.
10
11
12
13
31
C ), 138.9 (C ), 109.0 (C ), 108.0 (C ), 231.7 (CO) ppm.
) ppm. C47 36CrF
RuS: calcd. C 53.51, H 3.42, N 1.32, S 3.04; found: C 53.50,
P
6
H
6
3 3
P
Ϫ1
Ϫ1 Ϫ1
.
[
1] [1a]
T. MeyerFriedrichsen, H. Wong, M. H. Prosenc, J. Heck,
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4
H
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H
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Eur. J. Inorg. Chem. 2003, 3895Ϫ3904
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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