Syntheses and NLO Properties of Chromium Carbonyl Arene Complexes with Conjugated Side Chains: The Amphoteric Nature of Chromium Carbonyl Complexation in Push-Pull Chromophores

Article abstract of DOI:10.1021/om9904551

Donor- and acceptor-substituted alkynylated chromium carbonyl arene complexes Cr(CO)₂L-(η⁶-R¹-C₆H ₄)(C≡C)_nR² (1, n = 1, L = CO, PPh₃, R¹ = H, o-formyl, R

Full text of DOI:10.1021/om9904551

5066
Organometallics 1999, 18, 5066-5074
Syn th eses a n d NLO P r op er ties of Ch r om iu m Ca r bon yl
Ar en e Com p lexes w ith Con ju ga ted Sid e Ch a in s: Th e
Am p h oter ic Na tu r e of Ch r om iu m Ca r bon yl
Com p lexa tion in P u sh -P u ll Ch r om op h or es
Thomas J . J . Mu¨ller,* Astrid Netz, and Markus Ansorge
Institut fu¨r Organische Chemie, Ludwig-Maximilians-Universita¨t Mu¨nchen,
Butenandtstrasse 5-13 (Haus F), D-81377 Mu¨nchen, Germany
Elmar Schma¨lzlin, Christoph Bra¨uchle, and Klaus Meerholz
Institut fu¨r Physikalische Chemie, Ludwig-Maximilians-Universita¨t Mu¨nchen,
Butenandtstrasse 5-13 (Haus E), D-81377 Mu¨nchen, Germany
Received September 8, 1999
Donor- and acceptor-substituted alkynylated chromium carbonyl arene complexes Cr(CO)2L-
(η6-R1-C6H4)(CtC)nR2 (1, n ) 1, L ) CO, PPh3, R1 ) H, o-formyl, R2 ) p-C6H4-NMe2, p-C6H4-
NO2, ferrocenyl; 3, n ) 2, L ) CO, R1 ) H, R2 ) p-C6H4-NMe2, p-C6H4-NO2, ferrocenyl) are
easily accessible by Sonogashira alkynylations of chloroarene complexes and Cadiot-
Chodkiewicz couplings of bromoalkynes with the complexed phenyl acetylene 1a (n ) 1, L
) CO, R1 ) R2 ) H), respectively. The Horner-Emmons-Wadsworth olefinations of the
Cr(CO)3-complexed benzylphosphonate and (hetero)aromatic aldehydes give rise to numerous
alkenylated chromium carbonyl arene complexes (E)n-Cr(CO)3(η6-C6H5)(CHdCH)nR1 (6, n
) 1-3, R1 ) p-C6H4-NMe2, p-C6H4-NO2, 2-(4-nitrothienyl)). The linear (UV/vis spectra) and
the nonlinear optical properties (hyper Rayleigh scattering measurements) of the complexes
1, 3, and 6 reveal that the chromium carbonyl arene fragment behaves electronically
amphoteric, i.e., as an electron donor or electron acceptor depending on the substituent on
the far end of the conjugating bridge. The first hyperpolarizability â-values (â0333 ) (8-41)
× 10-30 esu) are found to be similar to those of related ferrocenyl compounds.
In tr od u ction
structure consists of an electron-donating group, a
conjugated π-bridge (alkyne, alkene or (hetero)arene),
and an electron-accepting group, generally referred to
as a push-pull system. Typically, these push-pull
chromophores are structurally prerequisite for designing
NLO systems with large second-order hyperpolarizabili-
ties â0 (>10 × 10-30 esu). Especially, extended conju-
gated π-systems such as donor-acceptor R,ω-diaryl
polyenes and polyynes are classes of organic molecules
that display considerable NLO responses.3 Many transi-
tion-metal π-complexes are also highly polarizable. The
facile excitation of metal-to-ligand transitions upon
irradiation with visible light and the formation of stable
specimens of higher oxidation states has made π-com-
plexes attractive and advantageous for the construction
of organometallic NLO chromophores with extended
π-conjugation.1a,d,2a,b In particular, due to its high polar-
ity, its amphoteric electronic nature, and its rich
chemistry4 the (arene)chromium carbonyl fragment
could be a promising auxochrome for novel organo-
The rapidly increasing demand for novel chromo-
phores suitable for photonic applications such as fre-
quency doubling and the electrooptical effect1 has initi-
ated an eager search for highly polarizable organo-
metallic chromophores and auxochromes.2 Since non-
linear optical (NLO) properties of quite a number of
organic chromophores have been thoroughly studied,
both experimentally and theoretically, some common
structural features could be deduced such that the lead
(1) For recent reviews on NLO materials see, e.g.: (a) Long, N. J .
Angew. Chem. 1995, 107, 37; Angew. Chem., Int. Ed. Engl. 1995, 34,
6. (b) Marder, S. R.; Perry, J . W. Adv. Mater. 1993, 5, 804. (c) Nie, W.
Adv. Mater. 1993, 5, 520. (d) Kanis, D. R.; Ratner, M. A.; Marks, T. J .
Chem. Rev. 1994, 94, 195. (e) Marks, T. J .; Ratner, M. A. Angew. Chem.
1995, 107, 167; Angew. Chem., Int. Ed. Engl. 1995, 34, 155.
(2) For excellent reviews on organometallic NLO chromophores see,
e.g. (a) Whittall, I. R.; McDonagh, A. M.; Humphrey, M. G.; Samoc,
M. Adv. Organomet. Chem. 1998, 42, 291. (b) Whittall, I. R.; McDonagh,
A. M.; Humphrey, M. G.; Samoc, M. Adv. Organomet. Chem. 1998,
43, 349. For representative novel organometallic NLO chromophores
see, e.g.: (c) Behrens, U.; Brussaard, H.; Hagenau, U.; Heck, J .;
Hendrickx, E.; Ko¨rnich, J .; van der Linden, J . G. M.; Persoons, A.; Spek,
A. L.; Veldman, N.; Voss, B.; Wong, H. Chem. Eur. J . 1996, 2, 98. (d)
Dhenaut, C.; Ledoux, I.; Samuel, I. D. W.; Zyss, J .; Bourgault, M.; Le
Bozec, H. Nature 1995, 374, 339. (e) Tamm, M.; Grzegorzeweski, A.;
Steiner, T.; J entzsch, T.; Werncke, W. Organometallics 1996, 15, 4984.
(f) Whittall, I. R.; Humphrey, M. G.; Houbrechts, S.; Persoons, A.;
Hockless, D. C. R. Organometallics 1996, 15, 5738. (g) Whittall, I. R.;
Cifuentes, M. P.; Humphrey, M. G.; Luther-Davies, B.; Samoc, M.;
Houbrechts, S.; Persoons, A.; Heath, G. A.; Hockless, D. C. R. J .
Organomet. Chem. 1997, 549, 127.
(3) (a) Nguyen, P.; Lesley, G.; Marder, T. B.; Ledoux, I.; Zyss, J .
Chem. Mater. 1997, 9, 406. (b) Cheng, L.-T.; Tam, W.; Marder, S. R.;
Steigman, A. E.; Rikken, G.; Spangler, C. W. J . Phys. Chem. 1991, 95,
10643. (c) Cheng, L.-T.; Tam, W.; Stevenson, S. H.; Meredith, G. R.;
Rikken, G.; Marder, S. R. J . Phys. Chem. 1991, 95, 10631. (d) Steigman,
A. E.; Graham, E.; Perry, K. J .; Khundkar, L. R.; Cheng, L.-T.; Perry,
P. J . J . Am. Chem. Soc. 1991, 113, 7658. (e) Oudar, J . L. J . Chem.
Phys. 1977, 67, 446. (f) Oudar, J . L.; Chemla, D. S. J . Chem. Phys.
1977, 66, 2664.
10.1021/om9904551 CCC: $18.00 © 1999 American Chemical Society
Publication on Web 11/03/1999

Chromium Complexes with Conjugated Side Chains
Organometallics, Vol. 18, No. 24, 1999 5067
Ch a r t 1
metallic NLO systems, either electron donating or
withdrawing depending on the attached electronic en-
vironment. Interestingly, there have been extensive
calculations1d,5 on the NLO properties of alkenylated
chromium arene complexes, but only one synthetic
approach has been reported6 so far, which unfortunately
gives no details on the optical nonlinearities of those
systems. Here, we describe the synthesis and structures
as well as our first findings on the linear and nonlinear
optical properties of alkynylated and alkenylated donor-
and acceptor-substituted chromium-complexed arenes.
Resu lts a n d Discu ssion
Syn th eses. Gen er a l Con sid er a tion s. Since the
direct complexation of the free hydrocarbon ligand is
either unselective or inefficient, we have transposed
olefination7 and palladium-catalyzed alkynylation8 meth-
odologies to the synthesis of conjugated side chains on
the η6-coordinated arene ligand. In particular, this
approach has been shown to be successful in the con-
struction of [(cyclobutadienylcobalt)ethynylene(arylene)-
ethynylene] copolymers with liquid crystalline proper-
ties.9 Prior to this work the Wittig reaction of Cr(CO)3-
complexed benzaldehydes and aryl phosphonium salts
has already been successfully applied to the construction
of ethenyl bridges on the organometallic template.6,10
However, due to the low stereoselectivity (E vs Z
configuration of the double bond) in these cases and the
tedious preparation of allyl phosphonium salts for
extended π-systems, we sought more general and even
more straightforward strategies of alkenylation and
alkynylation starting from easily accessible chromium
carbonyl arene complexes. Chemically, the Cr(CO)3
complexation activates chloroarenes considerably to-
ward the oxidative addition11 and thus has opened the
possibility of palladium-catalyzed alkynylations.8,12 Fur-
thermore, Cr(CO)3-complexed benzylphosphonates can
be easily condensed with aldehydes in the sense of a
Horner-Emmons-Wadsworth olefination.7
Syn th eses of Alkyn ylated (Ar en e)ch r om iu m Car -
bon yl Com p lexes. Chlorobenzene-Cr(CO)3 complexes
are by far more reactive in palladium-catalyzed cross-
coupling reactions than uncomplexed iodobenzenes.11,12a
Recently, we synthesized the alkynylated complexes 1
upon coupling the corresponding chlorobenzene chro-
mium carbonyl complexes with terminal alkynes under
Sonogashira conditions13 in good to excellent yields
(Chart 1).8b,f
The Cr(CO)3-complexed phenylacetylene8a 1a reacts
in a Cadiot-Chodkiewicz coupling14 with bromoalkynes
2 to give the dumbbell-shaped rigid-rod homologous
butadiynylated complexes 3 in excellent yields (Scheme
1). Characteristically, the appearance of four quaternary
alkynyl carbon resonances in the 13C NMR spectra and
the significant alkynyl stretching vibrations in the IR
spectra at 2200 cm-1 unambiguously support the struc-
ture of these novel unsymmetrically substituted or-
(4) (a) For side chain activation see, e.g.: Davies, S. G.; McCarthy,
T. D. In Comprehensive Organometallic Chemistry II; Abel, E. W.,
Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford, U.K., 1995;
Vol. 12, p 1039. (b) For application in asymmetric syntheses see, e.g.:
Uemura, M. In Advances in Metal-Organic Chemistry; Liebeskind, L.
S., Ed.; J AI Press: London, 1991; Vol. 2, p 195. (c) For nucleophilic
additions see, e.g.: Semmelhack, M. F. In Comprehensive Organo-
metallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.;
Pergamon: Oxford, U.K., 1995; Vol. 12, p 979. (d) For ring lithiations
see, e.g.: Semmelhack, M. F. In Comprehensive Organometallic
Chemistry II, Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.;
Pergamon: Oxford, U.K., 1995; Vol. 12, p 1017. (e) For stabilization
of benzylic carbanions see, e.g.: Davies, S. G.; Coote, S. J .; Goodfellow,
C. L. In Advances in Metal-Organic Chemistry; Liebeskind, L. S., Ed.;
J AI Press: London, 1991; Vol. 2, p 1. (f) For stabilization of benzylic
carbocations see, e.g.: Davies, S. G.; Donohoe, T. J . Synlett 1993, 323.
(5) Kanis, D. R.; Ratner, M. A.; Marks, T. J . J . Am. Chem. Soc. 1992,
114, 10338.
ganometallic diynes. The carbonyl resonances in the 13
C
NMR spectra appear in the expected region between δ
232.8 and 233.3, displaying only a small substituent
influence.
(6) Gilbert, T. M.; Hadley, F. J .; Bauer, C. B.; Rogers, R. D.
Organometallics 1994, 13, 2024.
(7) (a) Mu¨ller, T. J . J . Tetrahedron Lett. 1997, 38, 1025. (b) Mu¨ller,
T. J . J . J . Organomet. Chem. 1999, 578, 95.
(8) (a) Mu¨ller, T. J . J .; Lindner, H. J . Chem. Ber. 1996, 129, 607. (b)
Mu¨ller, T. J . J .; Ansorge, M.; Lindner, H. J . Chem. Ber. 1996, 129,
1433. (c) Mu¨ller, T. J . J .; Ansorge, M. Chem. Ber./ Recl. 1997, 130, 1135.
(d) Mu¨ller, T. J . J .; Ansorge, M. Tetrahedron 1998, 54, 1457. (e) Mu¨ller,
T. J . J .; Ansorge, M.; Polborn, K. J . Organomet. Chem. 1999, 578, 252.
(f) Ansorge, M.; Mu¨ller, T. J . J . J . Organomet. Chem., in press.
(9) (a) Altmann, M.; Bunz, U. H. F. Angew. Chem. 1995, 107, 603;
Angew. Chem., Int. Ed. Engl. 1995, 34, 569. (b) Bunz, U. H. F. Pure
Appl. Chem. 1996, 68, 309.
(10) (a) Drefahl, G.; Ho¨rhold, H.-H.; Ku¨hne, K. Chem. Ber. 1965,
98, 1826. (b) Bitterwolf, T. E.; Dai, X. J . Organomet. Chem. 1992, 440,
103.
(11) For a review on palladium-catalyzed reactions with (haloarene)-
chromium carbonyl complexes, see, e.g.: Carpentier, J . F.; Petit, F.;
Morteux, A.; Dufaud, V.; Basset, J .-M.; Thivolle-Cazat, J . J . Mol. Catal.
1993, 81, 1.
Syn th eses of Alken ylated (Ar en e)ch r om iu m Car -
bon yl Com p lexes. Benzylic anions are efficiently
stabilized by chromium carbonyl complexation.4e Thus,
the Cr(CO)3-complexed benzylphosphonate 47b is suc-
cessfully applied in Horner-Emmons-Wadsworth ole-
(12) (a) Wright, M. E. Organometallics 1989, 8, 407. (b) Wright, M.
E. Macromolecules 1989, 22, 3256.
(13) (a) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara,
N. Synthesis 1980, 627. (b) Sonogashira, K. In Metal Catalyzed Cross
Coupling Reactions; Stang, P. J ., Diederich, F., Eds.; Wiley-VCH:
Weinheim, Germany, 1998; p 203.
(14) (a) Cadiot, P.; Chodkiewicz, W. In Chemistry of Acetylenes;
Viehe, H. G., Ed.; Marcel Dekker: New York, 1969; p 597. (b) Scott,
L. T.; Cooney, M. J . In Modern Acetylene Chemistry; Stang, P. J .,
Diederich, F., Eds.; VCH: Weinheim, Germany, 1995; p 321. (c)
Brandsma, L. Preparative Acetylene Chemistry, 2nd ed.; Elsevier:
Amsterdam, Oxford, New York, Tokyo, 1988; p 212.

5068 Organometallics, Vol. 18, No. 24, 1999
Mu¨ller et al.
Sch em e 1
Sch em e 2
finations7 with p-dimethylamino- and p-nitro-substitut-
ed aromatic and heteroaryl aldehydes 5 to furnish the
alkenylated (arene)Cr(CO)3 complexes 6 as orange to
deep red crystalline solids in good yields (Scheme 2).
The carbonyl resonances in the 13C NMR spectra
appear in the expected region between δ 234.0 and
234.7, displaying only a small substituent influence. In
the proton and carbon NMR spectra the characteristic
high-field shift of the complexed arene carbon and
proton resonances not only facilitates the unambiguous
assignment of the arene signals but also clearly indi-
cates that in the case of the donor-substituted systems
a shift of the chromium carbonyl tripod to the more
electron-rich arene rings can definitely be excluded.
According to the vicinal coupling constants (3J ) 15.3-
16.5 Hz) the E configuration of newly formed double
bonds supports the highly stereoselective olefination. In
the case of the conjugated dienes (6b and 6f) and triene
(6d ) the additional vicinal coupling constants (3J ) 9.7-
10.3 Hz) establish the preferred s-trans conformation
of the conjugated side chains.
bonds are trans-configured. The chromium-centroid
distances (1.70 and 1.71 Å) are in the expected range.16
Lin ea r Op tica l P r op er ties of th e Com p lexes 1,
3, a n d 6 (Electr on ic Sp ectr a a n d Solvoch r om icity).
In the UV/vis spectra of the alkynylated (1 and 3) and
the alkenylated complexes (6) recorded in chloroform,
the appearance of the intense longest wavelength
absorption band between 378 (1f) and 488 nm (6g) can
be assigned to the metal-to-ligand charge-transfer
(MLCT) band arising from a charge transition from the
chromium center to the π- and σ-bound ligands.5,17 The
next band between 309 (1b) and 383 nm (6f) is the most
intense absorption and arises from intraligand (IL)
According to X-ray crystal structure analyses15 of two
alkenyl-bridged representatives, the deep red stilbazole
complex 6a (Figure 1, Table 1) and the orange dimethyl-
amino-substituted stilbene complex 6e (Figure 2, Table
1), the chromium arene fragments, the olefin bridges,
and the arene substituents are almost coplanar. There-
fore, an ideal overlap of the π-system and a strong
electronic coupling can be assumed in the solid state.
This is consistent with previously published structural
details on several complexed stilbenes.6 In both cases,
as already supported by NMR spectroscopy, the double
(15) Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publication
Nos. CCDC-127408 (6a ) and CCDC-127407 (6e). Copies of the data
can be obtained free of charge on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, U.K. (Fax, + 44-1223/336-033; e-mail, deposit@
ccdc.cam.ac.uk).
(16) Davis, R.; Kane-Maguire, L. A. P. In Comprehensive Organo-
metallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.;
Pergamon: Oxford, U.K., 1982; Vol. 3, p 953.
(17) (a) Lundquist, R. T.; Cais, M. J . Org. Chem. 1962, 27, 1167. (b)
Carroll, D. G.; McGlynn, S. P. Inorg. Chem. 1968, 7, 1285.

Chromium Complexes with Conjugated Side Chains
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t Deta ils for 6a a n d 6e15
6a 6e
Organometallics, Vol. 18, No. 24, 1999 5069
empirical formula
color, form
fw
C
16H11CrNO3
C19H17CrNO3
orange sticks
359.37
red sticks
317.28
temp, K
294(2)
297(2)
wavelength (Å), radiation
cryst syst
space group
0.710 69 (Mo KR)
monoclinic
P21/c
0.710 93 (Mo KR)
monoclinic
P21/c
unit cell dimens
a, Å
7.930(21)
11.424(2)
b, Å
13.164(3)
8.995(1)
c, Å
13.388(2)
18.660(3)
R, deg
90
96.37(2)
90
90
91.32(1)
90
â, deg
γ, deg
V, Å3
1389.0(5)
1725.2(5)
Z
4
4
density (calcd), g/cm3
abs coeff, mm-1
F(000)
1.517
0.81
648
1.384
0.66
744
cryst size, mm
θ range for data collecn, deg
index ranges
0.4 × 0.225 × 0.225
0.65 × 0.35 × 0.075
2.18-22.97
1.78-22.97
-8 e h e 1, 0 e k e 14,
-14 e l e 14
2093
1929 (R(int) ) 0.0410)
empirical from ψ-scans
0.995 and 0.586
full-matrix least-squares on F2
1927/3/208
-12 e h e 10, 0 e k e 8,
-20 e l e 20
4646
2397 (R(int) ) 0.0422)
empirical from ψ-scans
0.838 and 0.717
full-matrix least-squares on F2
2397/8/302
no. of rflns collected
no. of indep rflns
abs cor
max and min transmissn
refinement method
no. of data/restraints/params
goodness of fit on F2
final R indices (I > 2σ(I))
R1
1.063
1.058
0.0561
0.1469
0.0418
0.1057
wR2
R indices (all data)
R1
0.0663
0.0609
wR2
0.1650
0.961 and -0.652
0.1192
0.376 and -0.341
largest diff peak and hole, e/Å3
F igu r e 2. X-ray crystal structure of 6e. Selected bond
lengths (Å) and torsional angles (deg): Cr-arene centroid,
1.703; C(6)-C(10A), 1.510(3); C(10A)-C(11A), 1.308(12);
C(11A)-C(12), 1.499(9); C(15)-N(1), 1.367(4); N(1)-C(18),
1.435(5); N(1)-C(18), 1.440(5); C(5)-C(6)-C(10A)-C(11A),
17.7(8); C(10A)-C(11A)-C(12)-C(13), 177.8(5); C(14)-
C(15)-N(1)-C(19), -8.2(5); C(16)-C(15)-N(1)-C(18), 7.4(5).
F igu r e 1. X-ray crystal structure of 6a . Selected bond
lengths (Å) and torsional angles (deg): Cr-arene centroid,
1.714; C(9)-C(10A), 1.553(13); C(10A)-C(11A), 1.307(13);
C(11A)-C(12),1.480(11);C(4)-C(9)-C(10A)-C(11A),-4.3(13);
C(10A)-C(11A)-C(12)-C(16), 2.1(13); C(10A)-C(11A)-
C(12)-C(13), -177.3(7).
to the dominant µz-dipole vector component directed
from the arene to the chromium carbonyl tripod (Figure
3).5
transitions with high oscillator strength, to the most
extent from π-π* transitions.5 This rationale is also
supported by the inspection of the solvochromicities of
these complexes. In all cases the MLCT band dis-
plays a small to moderate negative solvochromicity,
indicating that the electronic ground state is more polar
than the first excited state, and therefore an increase
in solvent polarity causes a hypsochromic shift.18 This
is also in agreement with the highly polar nature of
chromium carbonyl complexes, which can be attributed
Interestingly, the π-π* transitions directed along the
µx-dipole axis display a different solvochromic behavior.
For most of the alkynyl-bridged chromophores this band
shows a negative solvochromicity. However, for alkenyl-
bridged chromophores this intraligand charge-transfer
(ILCT) band is shifted bathochromically upon the
increase of solvent polarity. Clearly, there seems to be
a strong dependence on the hybridization of the conju-
gated π-bridge. In contrast to alkynes the canonical
resonance structures of alkenes still retain a double
(18) (a) McRae, E. G. J . Phys. Chem. 1957, 61, 562. (b) Paley, M.
S.; Harris, J . M. J . Org. Chem. 1989, 54, 3774.

5070 Organometallics, Vol. 18, No. 24, 1999
Mu¨ller et al.
F igu r e 3. Additive nature of ground-state dipole vectors of chromium carbonyl complexed arenes with conjugated side
chains.
Sch em e 3. Reson a n ce Hybr id s of Alk en yl- (Top ) a n d Alk yn yl-Br id ged (Bottom ) Don or - a n d
Accep tor -Su bstitu ted Ch r om iu m Ca r bon yl Ar en e Com p lexes
bond alternation without adopting unfavorable cumu-
logous resonance hybrids as with alkynes (Scheme 3).
Since the solvochromicity reflects the polarizability of
a chromophore, large solvochromicities can hint to the
magnitude of expected optical nonlinearities.18b In all
cases the relevant bands for the polarizability are the
ILCT bands. The dipole moment of the MLCT bands is
perpendicular (µz) and does not coincide with that of the
principal ILCT direction (µx).5 Therefore, the largest
solvochromicities for the π-π* transitions are found
expectedly for long acceptor substituted alkenylated
complexes 6c,d and, surprisingly, also for long donor
substituted alkynylated complexes 3b and the short
acceptor substituted alkynylated chromium dicarbonyl
phosphane complex 1e.
fluorescence around 750 nm, fluorescence enhancement
at the second-harmonic frequency can be excluded.
The extrapolation of the dynamic hyperpolarizabilities
1500nm
333
â
to their static counterparts â0333 is accomplished
by using the two-level model.3f Since there might be a
contribution of MLCT components to the nonlinear
optical response of the chromium carbonyl arene com-
plexes, the applicability of the two-level model, which
is only valid for rodlike chromophores with a CT along
the molecule axis, must be questioned.5 However, the
â-value of the unsubstituted chromium tricarbonyl
benzene π-complex is negligibly small (-0.8 × 10-30 esu
at 1910 nm in toluene).1d,5,22 Furthermore, the inspec-
tion of the solvochromicities (vide supra) has clearly
shown that the major contribution of the polarizability
and ultimately the hyperpolarizability arises from ILCT
terms in the absorption band. For these reasons, the
assumption of rodlike geometry is justified and the two-
level model should still be applicable to the correspond-
ing π-π* absorption bands.
Non lin ea r Op tica l P r op er ties of th e Com p lexes
1, 3, a n d 6 (F ir st Hyp er p ola r iza bilities). The first
hyperpolarizablities â of the complexes 1, 3, and 6 were
measured by hyper Rayleigh scattering (HRS).19 Unlike
the more common electric-field-induced second-harmonic-
generation (EFISHG) method,20 HRS allows us to
determine â without the knowledge of the dipole mo-
ment. However, according to eq 2 (see Experimental
Section), HRS does not allow us to determine the sign
of â and, therefore, the â-values given in this paper are
only absolute values. The HRS experiments were car-
ried out in chloroform solutions of the complexes at 1500
nm fundamental wavelength. Conducting HRS experi-
ments in a far off-resonant regime is a safeguard against
resonance enhancement and multiphoton-induced fluo-
rescence, which may lead to unphysically high â-val-
ues.21 Since all investigated complexes display no
Our results reveal that the magnitude of the â-values
of chromium carbonyl arene complexes with conjugated
substituents are comparable to those of related ferro-
cenyl systems.2a Some important structure-property
relationships can already be derived from the dynamic
and static â-values of the complexes 1, 3, and 6 (Table
2). As expected, the increase in conjugation length by n
multiple bonds results in an approximately n-fold
enhancement of the â0333-values and the efficiency of
hyperpolarization depends on the hybridization of the
side chain.1a,d As already stated for the solvochromici-
(21) (a) Stadler, S.; Bourhill, G.; Bra¨uchle, C. J . Phys. Chem. 1996,
100, 6927. (b) Flipse, M. C.; de J onge, R.; Woudenberg, R. H.; Marsman,
A. W.; van Walree, C. A.; J enneskens, L. W. Chem. Phys. Lett. 1995,
245, 297.
(22) Cheng, L.-T.; Tam, W.; Meredith, G. R.; Marder, S. R. Mol.
Cryst. Liq. Cryst. 1990, 189, 137.
(19) Hendrickx, E.; Clays, K.; Persoons, A.; Dehu, C.; Bre´das, J . L.
J . Am. Chem. Soc. 1995, 117, 3547.
(20) Levine, B. F.; Bethea, C. G. J . Chem. Phys. 1974, 60, 3856.

Chromium Complexes with Conjugated Side Chains
Ta ble 2. Absor p tion Ma xim a , Solvoch r om icities, a n d Hyp er p ola r iza bilitiesa of th e Com p lexes 1, 3, a n d 6
acceptor-substituted complex donor-substituted complex
Organometallics, Vol. 18, No. 24, 1999 5071
d
d
MLCT
λCHCl λDMSO
ILCT
â333
1500
MLCT
λCHCl λDMSO
ILCT
â333
1500
∆ν˜
(nm) (nm) (cm-1
λCHCl λDMSO
∆ν˜
∆ν˜
(nm) (nm) (cm-1
λCHCl λDMSO
∆ν˜
3
3
3
3
)
(nm) (nm) (cm-1
)
nm
0
)
(nm) (nm) (cm-1
)
nm
0
DMAZb
1b
3a
6b
6c
6d
6g
1e
384
35
10
18
15
33
44
30
52
24 DMAZb
384
35
11
34
20
38
9
24
9
26
14
27
7
435
437
455
457
453
488
481
433c
434
451
451
448
485
472
-106
309
322
317
339
377
356
318
308c
320
321
351
384
358
310
-105
8
1c
405
414
418
438
387
419
378
400c
410
413
428
395c
411
-309
338
342
360
383
328
324
344
336c
347
362
388
327c
322
-176
-158
-195
-291
-246
-127
-396
-194
393
14 3b
12 6e
25 6f
31 1d
22 3c
41 1f
-235
-290
-533
-523
-465
421
153
1008
484
157
336
-188
-191
11
52
9
39
-812
a
Measured by the hyper Raleigh scattering (HRS) technique at a fundamental wavelength of 1500 nm in a chloroform solution.
Reference chromophore p-dimethylamino cinnamic aldehyde (DMAZ).33 c Measured in acetonitrile. All â-values are given in 10-30 esu
b
d
(10-30 esu ≡ 0.37 × 10-50 cm3 V-2); the â0333 -values were calculated by applying the two-level model on the π-π* absorption band.
Ta ble 3. Com p a r ison of Exp er im en ta l â0333-Va lu es,
ties, alkenes tend to be more hyperpolarizable than
alkynes. In addition, the substitution of the phenylene
ZINDO-Der ived Molecu la r Hyp er p ola r iza bilities1d ,5
a lon g th e ILCT Dip ole Axis âvec, a n d Tota l
bridge (6b) by a thienylene bridge (6g) causes a 2-fold
increase in the â-value due to the reduced aromaticity
of thiophene.1a Interestingly, comparable donor- and
acceptor-substituted series of both alkynylated and
In tr in sic Hyp er p ola r iza bilities1d ,5 âtot a t a
F u n d a m en ta l of 1900 n m a
alkenylated complexes display almost similar â3033
-
values, and ferrocene as a donor in these systems (1d
and 3c) is not efficient. All this strongly supports the
view that the chromium carbonyl arene fragment be-
haves electronically amphoteric, i.e., electron donating
or electron withdrawing in NLO chromophores depend-
ing on the electronic nature of the attached auxochrome
at the far end of the chromophore. Furthermore, the
trend of the homologous series of alkenylated p-nitro-
phenyl-substituted complexes is reproduced correctly by
ZINDO calculations5 based upon a three-level model
(Table 3). Due to the pseudo-centrosymmetric electronic
environment around the pseudo-octahedral ligand field
of the chromium center these types of complexes inher-
ently cannot display their higher total intrinsic hyper-
polarizabilities.5
Therefore, the crucial question arises how the â-val-
ues can be enhanced for this kind of organometallic
chromophores. One possibility is the additive enhance-
ment of the push-pull character. The introduction of
an electron-withdrawing ortho substituent on the com-
plexed arene moiety of an alkynylated donor substituted
complex (1f) not only causes a 4-fold enhancement of
the â-value compared to the system 1c but also opens a
facile access to planar-chiral complexes. Especially, the
introduction of chirality can be favorable for potential
solid-state applications due to crystallization in non-
centrosymmetric space groups.
a
All â-values are given in 10-30 esu (10-30 esu ≡ 0.37 × 10-50
cm3 V-2).
Another option is the exchange of the carbonyl ligands
on the metal. The exchange by phosphanes not only
renders the chromium carbonyl center more electron
rich in the sense of enhancing the push-pull character
of acceptor-substituted complexes (1e) but also causes
a break in the centrosymmetric electronic environment
around the pseudo-octahedral ligand field, giving rise
to a 5-fold increase in the â-values compared to the tri-
carbonylchromium complex 1b. Most interestingly, com-
putations on hypothetical triamminechromium arene
complexes with short side chains such as 7 and 8 predict
very large hyperpolarizabilities at a fundamental of
1900 nm (Table 3).1d,5 Although the synthesis of these
structures involves quite some difficulty, we expect
comparable effects for phosphane-complexed systems
simultaneously allowing extensive electronic fine-tuning
on the metal. Further studies directed at optimizing the
NLO properties of alkynyl- and alkenyl-bridged chro-
mium carbonyl arene complexes are currently under-
way.
Con clu sion
Chromium carbonyl arene complexes with conjugated
side chains are easily accessible by palladium/copper-
catalyzed alkynylations of chloroarene complexes,
Cadiot-Chodkiewicz couplings of bromoalkynes with a

5072 Organometallics, Vol. 18, No. 24, 1999
Mu¨ller et al.
mg (1.60 mmol) of the complexed o-chlorobenzaldehyde29 and
250 mg (1.72 mmol) of (p-(dimethylamino)phenyl)acetylene30
gave after chromatography on silica gel (diethyl ether/pentane
1:1) 440 mg (71%) of pure 1f as a red-orange solid. Mp: 110-
complexed phenylacetylene, and Horner-Emmons-
Wadsworth olefinations of a complexed benzylphosphon-
ate and aromatic aldehydes. This approach of side chain
construction on the metal template not only proceeds
in good yields but also circumvents the regioselectivity
problems of the direct complexation of the corresponding
free ligands. The linear (electronic spectra and the
solvochromicities) as well as the nonlinear optical
properties (â-values from HRS measurements) of the
alkynylated and alkenylated complexes reveal that
chromium arene auxochromes at the R-terminus behave
electronically amphoteric, i.e., as electron donors or
electron acceptors depending on the counterpart at the
ω-terminus, with a medium-sized magnitude of the
â-values similar to those of ferrocenyl structures. Two
possible strategies for optimizing the nonlinearities of
chromium carbonyl complexes arise from these inves-
tigations: the organic synthetic approach would em-
phasize the additive enhancement of the push-pull
character of the π-ligand and the organometallic strat-
egy would be to disturb the electronic pseudosymmetry
about the metal center by CO-phosphane exchange.
1
111 °C. H NMR (CDCl3, 300 MHz): δ 3.01 (s, 6 H), 5.20 (dd,
J ) 6.2, 6.5 Hz, 1 H), 5.38 (d, J ) 6.5 Hz, 1 H), 5.73 (dd, J )
6.3, 6.6 Hz, 1 H), 6.12 (d, J ) 6.6 Hz, 1 H), 6.64 (m, AA′BB′, J
) 8.7 Hz, 2 H), 7.40 (m, AA′BB′, J ) 8.6 Hz, 2 H), 10.14 (s,
1H). 13C NMR (CDCl3, 75 MHz): δ 40.05 (CH3), 79.67 (Cquat),
87.20 (CH), 91.29 (CH), 91.58 (CH), 93.75 (Cquat), 94.44 (CH),
97.69 (Cquat), 98.59 (Cquat), 107.10 (Cquat), 111.63 (CH), 133.31
(CH), 150.99 (Cquat), 188.28 (CH), 230.20 (Cquat, CO). MS (EI,
70 eV; m/z (%)): 335 (M+ - C4H2, 15), 249 (M+ - Cr(CO)3, 8),
235 (M+ - Cr(CO)3 - CH2, 33), 134 (C9H12N+, 100), 120
(C8H10N+, 75), 91 (C7H7+, 52), 77 (C6H5+, 30), 52 (Cr+, 8). IR
(KBr): ν˜ 2923, 2207, 1964, 1889, 1687, 1604, 1519, 1363, 945,
818, 661, 624 cm-1. UV/vis (CHCl3): λmax (ꢀ) 344 (28 200), 378
(19 300) nm. Anal. Calcd for C20H15CrNO4 (385.34): C, 62.34;
H, 3.92; N, 3.63. Found: C, 61.89; H, 4.04; N, 3.49.31
Gen er a l P r oced u r e (GP 1) for th e Ca d iot-Ch od k ie-
w icz Cou p lin g of Tr ica r bon yl(η6-eth yn ylben zen e)ch r o-
m iu m (0) (1a ) w ith Br om oa lk yn es 2. A 0.150 g (0.63 mmol)
portion of 1a and 5 mg (70 µmol) of hydroxylamine hydrochlo-
ride were suspended in 20 mL of degassed methanol. To this
mixture was added a solution of 4 mg (40 µmol) of copper(I)
chloride in 3 mL of ethylamine under argon at room temper-
ature. Then 0.63 mmol of the corresponding bromoalkyne 2
dissolved in 2 mL of N,N-dimethylformamide was added
dropwise at room temperature to this suspension over a period
of 2 min. This reaction mixture was stirred at room temper-
ature under argon overnight. To the suspension was then
added 20 mL of diethyl ether and 15 mL of water. The organic
phase was separated, and the aqueous layer was extracted
twice with 20 mL portions of ether. The combined organic
phases were washed twice with 20 mL of brine. After these
phases were dried over magnesium sulfate and filtered, the
solvents were removed in a rotary evaporator to give the pure
and crystalline butadiynes 3 (TLC). Further purification was
achieved by recrystallization.
Cr (CO)3(η6-C6H5)CtCCtC(p-C6H4)NO2 (3a ). According
to GP 1 the reaction was carried out with 0.142 g (0.60 mmol)
of bromo(4-nitrophenyl)acetylene (2a ) to give 0.204 g (90%) of
pure 3a as orange-red crystals, mp 140 °C dec (dichloro-
methane/pentane). 1H NMR ([D6]DMSO, 300 MHz): δ 5.77 (dd,
J ) 6.1 Hz, 2 H), 5.86 (t, J ) 6.0 Hz, 1 H), 6.14 (d, J ) 6.1 Hz,
2 H), 7.92 (d, J ) 8.3 Hz, 2 H), 8.28 (d, J ) 8.3 Hz, 2 H). 13C
NMR ([D6]DMSO, 75 MHz): δ 72.14 (Cquat), 77.12 (Cquat), 80.19
(Cquat), 81.03 (Cquat), 86.54 (Cquat), 93.30 (CH), 95.29 (CH), 98.46
(CH), 124.16 (CH), 126.85 (Cquat), 134.15 (CH), 147.93 (Cquat),
232.80 (Cquat, CO). MS (EI, 70 eV; m/z (%)): 383 (M+, 8), 327
(M+ - 2 CO, 5), 299 (M+ - 3 CO, 13), 247 (M+ - Cr(CO)3, 60),
200 (M+ -Cr(CO)3 - HNO2, 29), 52 (Cr+, 100). IR (KBr): ν˜
2214, 1976, 1898, 1592, 1522, 1343, 852, 748, 667, 649, 614,
531 cm-1. UV/vis (DMSO): λmax (ꢀ) 320 (27 700), 434 (6650)
nm. Anal. Calcd for C19H9CrNO5 (383.28): C, 59.54; H, 2.37;
N, 3.65. Found: C, 59.08; H, 2.47; N, 4.09.31
Exp er im en ta l Section
All reactions involving tricarbonylchromium complexes were
carried out in flame-dried Schlenk flasks under nitrogen by
using septum and syringe techniques. Solvents were dried and
distilled according to standard procedures.23 Column chroma-
tography: silica gel 60 (0.063-0.2 mm/70-230 mesh, Firma
Merck). TLC: silica gel plates (60 F254 Merck, Darmstadt,
Germany). Melting points (uncorrected values): Reichert-J ung
Thermovar. The alkynylated chromium carbonyl arene com-
plexes 18a,b,f and the chromium tricarbonyl complexed ben-
zylphosphonate 47 were prepared according to our previously
published protocols. The bromoalkyne 2a 24 was prepared by
literature methods, and the bromoalkynes 2b,c were prepared
by lithiation (n-BuLi) and subsequent NBS bromination in
THF at -78 °C of the corresponding terminal alkynes.25 The
aromatic aldehydes 5a ,b,e,g, sodium hydride (95%), hydroxyl-
amine hydrochloride, copper(I) chloride, and aqueous ethyl-
amine (70%) were purchased from Merck, Aldrich, or Fluka
and used without further purification; the aldehydes 5c,26 5d ,27
and 5f28 were prepared according to literature methods. 1H
and 13C NMR spectra: Bruker ARX 300, Varian VXR 400S,
Bruker WM 300, and Bruker AC 300 spectrometers, [D6]-
DMSO or CDCl3. IR: Perkin-Elmer FT-IR Paragon 1000 PC,
samples were pressed into KBr pellets. UV/vis: Beckman DK-
2-A, Beckman UV 5240, and Perkin-Elmer Lambda 16 instru-
ments. MS: Finnigan MAT 311-A/100MS, Finnigan MAT 90,
and MAT 95 Q spectrometers. The structure was solved by
direct methods and refined anisotropically on F2 (programs
SHELXS-86 and SHELXL-93 by G. M. Sheldrick, University
of Go¨ttingen). Elemental analyses were carried out in the
Microanalytical Laboratories of the Institut fu¨r Organische
Chemie, Technische Universita¨t Darmstadt, and the Institut
fu¨r Organische Chemie, Ludwig-Maximilians-Universita¨t
Mu¨nchen.
Cr (CO)3(η6-C6H5)CtCCtC(p-C6H4)N(CH3)2 (3b). Accord-
ing to GP1 the reaction was carried out with 0.146 g (0.65
mmol) of (4-(dimethylamino)phenyl)bromoacetylene (2b) to
give 0.238 g (96%) of pure 3b as yellow platelets, mp 160 °C
1
dec (diethyl ether/pentane). H NMR ([D6]DMSO, 300 MHz):
Cr (CO)3[η6-o-OHC(C6H4)]CtC(p-C6H4)N(CH3)2 (1f). Ac-
cording to our previously published standard procedure, 440
(29) Maiorana, S. Tetrahedron 1990, 46, 7823.
(30) In analogy to ref 13a in boiling piperidine and subsequent base-
mediated desilylation.
(23) Organikum, 14th ed.; VEB Deutscher Verlag der Wissen-
schaften: Berlin, 1993.
(31) The deviation (-0.5 to 1%) of the calculated from the found
percentages of carbon in the combustion analyses can be attributed to
a small content (< 5%) of dichloromethane (solvent used for recrys-
tallization) that cannot be removed even after 24 h of drying under
dynamic vacuum (∼10-4 mbar). In the proton NMR spectra a tiny peak
at δ 5.3 is found. This seems to be reasonable also on the basis of an
X-ray structure of a related complex where trichloromethane was
incorporated nonstoichiometrically in the crystal lattice.8a
(24) Bestmann, H. J .; Frey, H. Liebigs Ann.Chem. 1980, 2061.
(25) Brandsma, L. Preparative Acetylene Chemistry, 2nd ed.; Elsevi-
er: Amsterdam, Oxford, New York, Tokyo, 1988; p 143.
(26) Waley, S. G. J . Chem. Soc. London 1948, 2010.
(27) Cresp, T.; Sargent, V.; Vogel, P. J . Chem. Soc., Perkin Trans. 1
1974, 37.
(28) Ko¨nig, W.; Schramek, W.; Ro¨sch, G. Chem. Ber. 1928, 61, 2078.

Chromium Complexes with Conjugated Side Chains
Organometallics, Vol. 18, No. 24, 1999 5073
Ta ble 4. Exp er im en ta l Deta ils on Syn th esis of Alk en yla ted Ar en e Com p lexes 6
amt of
complexed
amt of
benzylphosphonate
4, mg (mmol)
amt of NaH,
mg (mmol)
aldehyde 5,
mg (mmol)
amt of
THF, mL
reacn
time, h
yield of 6,
mg (%)
504 (1.50)
336 (1.00)
336 (1.00)
337 (1.00)
504 (1.50)
1001 (3.00)
840 (2.50)
40 (1.6)
26 (1.0)
40 (1.6)
40 (1.6)
40 (1.6)
80 (3.2)
65 (2.6)
161 (1.50), 5a
151 (1.00), 5b
177 (1.00), 5c
208 (1.02), 5d
201 (1.49), 5e
530 (3.02), 5f
393 (2.50), 5g
15
10
25
25
15
20
25
14
14
19
22
15
8
400 (84),a 6a
220 (61), 6b
343 (89), 6c
279 (68), 6d
482 (90), 6e
1000 (86), 6f
750 (85),b 6g
8
a
b
Recrystallized from THF/pentane. Recrystallized from diethyl ether/pentane.
δ 2.99 (s, 6 H), 5.77 (m, 3 H), 6.04 (m, 2 H), 6.72 (m, 2 H), 7.44
(m, 2 H). 13C NMR ([D6]DMSO, 75 MHz): δ 39.74 (CH3), 71.58
(Cquat), 74.17 (Cquat), 77.75 (Cquat), 85.06 (Cquat), 89.20 (Cquat),
93.75 (CH), 94.55 (CH), 97.94 (CH), 105.08 (Cquat), 111.99 (CH),
134.09 (CH), 151.20 (Cquat), 233.25 (Cquat, CO). MS (EI, 70 eV;
m/z (%)): 381 (M+, 21), 325 (M+ - 2 CO, 17), 297 (M+ - 3 CO,
100), 245 (M+ - Cr(CO)3, 19), 80 (Cr(CO)+, 5), 52 (Cr+, 21). IR
(KBr): ν˜ 2205, 1963, 1896, 1878, 1602, 1518, 1447, 1367, 1182,
1151, 813, 671, 654, 627, 614, 533 cm-1. UV/vis (DMSO): λmax
(ꢀ) 278 (12 600), 333 (28 800 sh), 347 (33 400), 410 (13 600 sh)
nm. Anal. Calcd for C21H15CrNO3 (381.35): C, 66.14; H, 3.96;
N, 3.67. Found: C, 66.01; H, 4.28; N, 3.54.
(E)-Cr (CO)3(η6-C6H5)CHdCH(p-C6H4)NO2 (6b). Mp: 180
°C dec. 1H NMR ([D6]DMSO, 300 MHz): δ 5.75 (t, J ) 6.2 Hz,
1 H), 5.88 (dd, J ) 6.2, 6.4 Hz, 2 H), 6.13 (d, J ) 6.4 Hz, 2 H),
7.21 (d, J ) 16.4 Hz, 1 H), 7.43 (d, J ) 16.4 Hz, 1 H), 7.83 (m,
AA′BB′, J ) 8.6 Hz, 2 H), 8.26 (m, AA′BB′, J ) 8.6 Hz, 2 H).
13C NMR ([D6]DMSO, 75 MHz): δ 93.67 (CH), 94.44 (CH),
95.19 (CH), 105.89 (Cquat), 124.32 (CH), 127.83 (CH), 128.64
(CH), 130.09 (CH), 142.83 (Cquat), 146.86 (Cquat), 234.04 (Cquat
,
CO). MS (CI, 70 eV; m/z (%)): 361 (M+, 17), 305 (M+ - 2 CO,
9), 277 (M+ - 3 CO, 28), 225 (M+ - Cr(CO)3, 75), 52 (Cr+, 100).
IR (KBr): ν˜ 1978, 1897, 1865, 1593, 1509, 1340, 873, 848, 837,
750, 669, 658, 626 cm-1. UV/vis (DMSO): λmax (ꢀ) 321 nm
(25 300), 451 (7200) nm. UV/vis (CHCl3): λmax 317, 455 nm.
Anal. Calcd for C17H11CrNO5 (361.28): C, 56.52; H, 3.07; N,
3.88. Found: C, 56.22; H, 2.98; N, 3.85.
Cr (CO)3(η6-C6H5)CtCCtC(η5-C5H4)F e(η5-C5H5) (3c). Ac-
cording to GP1 the reaction was carried out with 0.182 g (0.63
mmol) of bromoethynylferrocene (2c) to give 0.272 g (97%) of
pure 3c as orange platelets, mp 171 °C dec (dichloromethane/
pentane). 1H NMR ([D6]DMSO, 300 MHz): δ 4.28 (s, 5 H), 4.41
(m, 2 H), 4.66 (m, 2 H), 5.75 (m, 3 H), 6.03 (m, 2 H). 13C NMR
([D6]DMSO, 75 MHz): δ 61.17 (Cquat), 69.37 (Cquat), 70.27
(Cquat), 70.32 (CH), 72.51 (CH), 74.03 (Cquat), 75.64 (Cquat), 84.03
(Cquat), 88.82 (Cquat), 93.69 (CH), 94.68 (CH), 98.05 (CH), 233.11
(E,E)-Cr (CO)3(η6-C6H5)CHdCHCHdCH(p-C6H4)NO2 (6c).
1
Mp: 166 °C dec. H NMR ([D6]DMSO, 300 MHz): δ 5.69 (m,
1 H), 5.79 (m, 2 H), 6.03 (d, J ) 5.8 Hz, 2 H), 6.50 (d, J ) 15.3
Hz, 1 H), 6.86 (d, J ) 15.4 Hz, 1 H), 7.12 (m, 1 H), 7.27 (m, 1
H), 7.76 (m, AA′BB′, J ) 8.1 Hz, 2 H), 8.18 (m, AA′BB′, J )
8.1 Hz, 2 H). 13C NMR ([D6]DMSO, 75 MHz): δ 93.49 (CH),
94.30 (CH), 95.14 (CH), 106.51 (Cquat), 124.21 (CH), 127.59
(CH), 131.27 (CH), 131.92 (CH), 132.29 (CH), 133.11 (CH),
143.63 (Cquat), 146.50 (Cquat), 234.16 (Cquat, CO). MS (CI, 70 eV;
m/z (%)): 387 (M+, 11), 331 (M+ - 2 CO, 6), 303 (M+ - 3 CO,
14), 251 (M+ - Cr(CO)3, 100), 52 (Cr+, 56). IR (KBr): ν˜ 1969,
(Cquat, CO). MS (EI, 70 eV; m/z (%)): 446 (M+, 25), 362 (M+
-
3 CO, 100), 310 (M+ -Cr(CO)3, 16), 306 (M+ - 3 CO - Fe, 5),
189 (M+ - Cr(CO)3 - FeCp, 6), 121 (FeCp+, 10), 80 (Cr(CO)+,
13), 52 (Cr+, 69). IR (KBr): ν˜ 2220, 1963, 1880, 1106, 1001,
823, 671, 654, 619, 532 cm-1. UV/vis (DMSO): λmax (ꢀ) 305
(15 200 sh), 322 (16 900), 411 (6800) nm. Anal. Calcd for
1885, 1859, 1589, 1515, 1336, 989, 856, 747, 659, 630 cm-1
.
C
23H14CrFeO3 (446.21): C, 61.91; H, 3.16. Found: C, 61.50;
H, 3.02.31
Hor n er -Em m on s-Wa d sw or th Olefin a tion s of P h os-
UV/vis (DMSO): λmax (ꢀ) 290 (sh, 16 200), 351 (26 200), 451
(11 100) nm. UV/vis (CHCl3): λmax 339, 457 nm. Anal. Calcd
for C19H13CrNO5 (387.32): C, 58.92; H, 3.38; N, 3.62. Found:
C, 58.90; H, 3.30; N, 3.63.
p h on a te Com p lexes (Gen er a l P r oced u r e, GP 2). To a
degassed solution of 1 equiv of phosphonate complex 1 in THF
was added 1.1 equiv of sodium hydride (95%) under argon.
After the mixture was stirred for 10 min at room temperature,
a solution of 1 equiv of the corresponding aldehyde in 2 mL of
THF was added dropwise to the suspension. The reaction
mixture was heated to reflux temperature for 12 h. After it
was cooled, the reaction mixture was diluted with 20 mL of
ether and filtered through a short plug of silica gel. The
solvents were removed in vacuo to give the crude alkenylated
arene complexes 2 as orange to deep red crystalline solids.
Further purification was achieved by chromatography on silica
gel (diethyl ether/pentane) and/or by recrystallization from
dichloromethane/pentane. The experimental details and yields
are summarized in Table 4.
(E ,E ,E )-Cr (CO)3(η6-C6H 5)CH dCH CH dCH CH dCH (p -
C6H4)NO2 (6d ). Mp: 168 °C dec. 1H NMR ([D6]DMSO, 300
MHz): δ 5.66 (t, J ) 6.3 Hz, 1 H), 5.80 (dd, J ) 6.2, 6.4 Hz, 2
H), 5.99 (d, J ) 6.5 Hz, 2 H), 6.40 (d, J ) 15.5 Hz, 1 H), 6.65
(m, J ) 15.3, 9.6 Hz, 2 H), 6.84 (d, J ) 15.6 Hz, 1 H), 7.07 (m,
J ) 15.4, 9.6 Hz, 1 H), 7.30 (m, J ) 15.2, 9.7 Hz, 1 H), 7.73
(m, AA′BB′, J ) 8.6 Hz, 2 H), 8.18 (m, AA′BB′, J ) 8.6 Hz, 2
H). 13C NMR ([D6]DMSO, 75 MHz): δ 93.20 (CH), 93.97 (CH),
95.39 (CH), 107.29 (Cquat), 124.24 (CH), 127.43 (CH), 130.36
(CH), 131.45 (CH), 131.60 (CH), 133.92 (CH), 135.17 (CH),
135.48 (CH), 144.01 (Cquat), 146.30 (Cquat), 234.66 (Cquat, CO).
MS (CI, 70 eV; m/z (%)): 413 (M+, 5), 357 (M+ - 2 CO, 1), 329
(M+ - 3 CO, 4), 277 (M+ - Cr(CO)3, 100), 52 (Cr+, 36). IR
(KBr): ν˜ 1957, 1918, 1889, 1865, 1581, 1514, 1336, 999, 867,
825, 747, 657, 630 cm-1. UV/vis (DMSO): λmax (ꢀ) 312 (19 600
sh), 384 (33 600), 448 (20 100 sh) nm. UV/vis (CHCl3): λmax
377, 453 nm. Anal. Calcd for C21H15CrNO5 (413.35): C, 61.02;
H, 3.66; N, 3.39. Found: C, 60.67; H, 3.72; N, 3.34.31
(E)-Cr (CO)3(η6-C6H5)CHdCH(4-C5H4N) (6a ). Mp: 170-
171 °C dec. 1H NMR ([D6]DMSO, 300 MHz): δ 5.75 (t, J ) 6.1
Hz, 1 H), 5.84 (dd, J ) 6.2, 6.3 Hz, 2 H), 6.11 (d, J ) 6.4 Hz,
2 H), 7.22 (d, J ) 16.5 Hz, 1 H), 7.29 (d, J ) 16.5 Hz, 1 H),
7.52 (m, AA′BB′, J ) 5.3 Hz, 2 H), 8.52 (m, AA′BB′, J ) 5.3
Hz, 2 H). 13C NMR ([D6]DMSO, 75 MHz): δ 93.63 (CH), 94.43
(CH), 95.23 (CH), 105.83 (Cquat), 121.19 (CH), 128.38 (CH),
129.99 (CH), 143.23 (Cquat), 150.39 (CH), 234.04 (Cquat, CO).
MS (CI, 70 eV; m/z (%)): 317 (M+, 9), 261 (M+ - 2 CO, 4), 233
(M+ - 3 CO, 66), 181 (M+ - Cr(CO)3, 10), 80 (CrCO+, 8), 52
(Cr+, 100). Anal. Calcd for C16H11CrNO3 (317.27): C, 60.57;
H, 3.49; N, 4.41. Found: C, 59.53; H, 3.50; N, 4.34.31
(E)-Cr (CO)3(η6-C6H 5)CH dCH (p -C6H 4)N(CH 3)2
(6e).
1
Mp: 172 °C dec. H NMR ([D6]DMSO, 300 MHz): δ 2.94 (s, 6
H), 5.58 (t, J ) 6.2 Hz, 1 H), 5.85 (dd, J ) 6.2, 6.4 Hz, 2 H),
5.98 (d, J ) 6.4 Hz, 2 H), 6.61 (d, J ) 16.3 Hz, 1 H), 6.72 (m,
AA′BB′, J ) 8.6 Hz, 2 H), 7.16 (d, J ) 16.3 Hz, 1 H), 7.39 (m,
AA′BB′, J ) 8.6 Hz, 2 H). 13C NMR ([D6]DMSO, 75 MHz): δ
40.04 (CH3), 92.07 (CH), 92.83 (CH), 96.17 (CH), 110.65 (Cquat),
112.25 (CH), 119.26 (CH), 123.65 (Cquat), 128.30 (CH), 132.04

5074 Organometallics, Vol. 18, No. 24, 1999
Mu¨ller et al.
(CH), 150.73 (Cquat), 234.73 (Cquat, CO). MS (CI, 70 eV; m/z
(%)): 359 (M+, 17), 303 (M+ - 2 CO, 10), 275 (M+ - 3 CO,
100), 223 (M+ - Cr(CO)3, 19), 52 (Cr+, 37). IR (KBr): ν˜ 1956,
1899, 1603, 1529, 1364, 963, 811, 674, 660, 631 cm-1. UV/vis
(DMSO): λmax (ꢀ) 337 (25 300 sh), 362 (26 700), 413 (13 000
sh) nm. UV/vis (CHCl3) :λmax 360, 418 nm. Anal. Calcd for
nm.32 To determine the â-values, the external reference method
was used. Here, the intensity of the second harmonic I(2ω) is
measured for a dilution series of the chromophore under
investigation and for a reference chromophore with a known
hyperpolarizability in the same solvent. Both are plotted as a
function of chromophore number density N and, in the absence
of absorption, the ratio of the two slopes is directly proportional
to ratio of the orientational averages of the square of the first
hyperpolarizabilities:
C
19H17CrNO3 (359.35): C, 63.51; H, 4.77; N, 3.90. Found: C,
63.27; H, 4.88; N, 3.90.
(E ,E )-C r (C O )3 (η6 -C 6 H 5 )C H dC H C H dC H (p -C 6 H 4 )N -
(CH3)2 (6f). Mp: 174 °C dec. 1H NMR ([D6]DMSO, 300 MHz):
δ 2.92 (s, 6 H), 5.60 (m, 1 H), 5.80 (m, 2 H), 5.94 (m, 2 H), 6.21
(d, J ) 15.2 Hz, 1 H), 6.69 (m, J ) 10.3, 15.4 Hz, AA′BB′, J )
7.9 Hz, 4 H), 7.03 (dd, J ) 10.3, 15.2 Hz, 1 H), 7.34 (m, AA′BB′,
J ) 7.9 Hz, 2 H). 13C NMR ([D6]DMSO, 75 MHz): δ 39.98
(CH3), 92.48 (CH), 93.31 (CH), 95.77 (CH), 109.32 (Cquat),
112.33 (CH), 123.56 (CH), 124.53 (Cquat), 125.50 (CH), 128.04
slopesample
dI(2ω)sample/dNsample
â2HRS
â2HRS
sample
)
)
(1)
slopereference
dI(2ω)reference/dNreference
reference
Chromophores with a CT along the molecule axis can be
assumed to be rodlike, and all â tensor elements except â333
can be neglected. In this case the relation between â333 and
the orientational averages is given by eq 2:
(CH), 133.29 (CH), 135.91 (CH), 150.45 (Cquat), 234.57 (Cquat
,
CO). MS (CI, 70 eV; m/z (%)): 385 (M+, 26), 329 (M+ - 2 CO,
4), 301 (M+ - 3 CO, 100), 249 (M+ - Cr(CO)3, 50), 52 (Cr+,
50). IR (KBr): ν˜ 1959, 1885, 1601, 1521, 1359, 987, 833, 752,
693, 673, 659, 631 cm-1. UV/vis (DMSO): λmax (ꢀ) ) 337 nm
(15 900 sh), 388 (29 300), 428 (22 300 sh). UV/vis (CHCl3) λmax
383, 438 nm. Anal. Calcd for C21H19CrNO3 (385.35): C, 65.45;
H, 4.97; N, 3.63. Found: C, 65.79; H, 4.97; N, 3.58.
6
35
â2HRS
)
â2333
(2)
As a reference chromophore, p-dimethylamino cinnamic alde-
hyde (â333 ) 35 × 10-30 esu at 1500 nm in chloroform) was
used.33 A more detailed description of the HRS experiment and
the data evaluation can be found in ref 31.
Ack n ow led gm en t. The financial support of the
Fonds der Chemischen Industrie, Deutsche Forschungs-
gemeinschaft, FORMAT, and the Dr.-Otto-Ro¨hm
Geda¨chtnisstiftung is gratefully acknowledged. We wish
to express our appreciation to Prof. H. Mayr for his
generous support. We heartily thank Ms. Brigitte J an-
ker for recording the fluorescence spectra, Ms. S. Foro
and Prof. Dr. H. J . Lindner, Technical University of
Darmstadt, for performing the X-ray crystal structure
analyses, and Ms. Diana Angebrandt for experimental
assistance.
(E)-Cr (CO)3(η6-C6H 5)CH dCH [2-(5-C4H 2S)NO2]
(6g).
Mp: 158-159 °C dec. 1H NMR ([D6]DMSO, 300 MHz): δ 5.79
(t, J ) 6.0 Hz, 1 H), 5.86 (dd, J ) 6.0, 6.6 Hz, 2 H), 6.11 (d, J
) 6.6 Hz, 2 H), 7.10 (d, J ) 16.2 Hz, 1 H), 7.35 (d, J ) 3.9 Hz,
1 H), 7.53 (d, J ) 16.2 Hz, 1 H), 8.10 (d, J ) 3.9 Hz, 1 H). 13C
NMR ([D6]DMSO, 75 MHz): δ 89.69 (Cquat), 93.57 (CH), 94.44
(CH), 94.69 (CH), 122.32 (CH), 126.83 (CH), 130.40 (CH),
131.65 (Cquat), 131.20 (CH), 148.80 (Cquat), 234.02 (Cquat, CO).
MS (CI, 70 eV; m/z (%)): 367 (M+, 51), 311 (M+ - 2 CO, 20),
283 (M+ - 3 CO, 20), 235 (M+ - 3 CO - SO, 47), 231 (M+
-
Cr(CO)3, 15), 198 (C5H2Cr(CO)3+, 100), 52 (Cr+, 93). IR (KBr):
ν˜ 1967, 1889, 1866, 1624, 1491, 1427, 1329, 945, 812, 733, 656,
629 cm-1. UV/vis (DMSO): λmax (ꢀ) 357 (22 900), 485 (8600)
nm. UV/vis (CHCl3): λmax 356, 488 nm. Anal. Calcd for C15H9-
CrNO5S (367.29): C, 49.05; H, 2.47; N, 3.81; S, 8.71. Found:
C, 48.03; H, 2.60; N, 3.66; S, 8.74.31
Su p p or tin g In for m a tion Ava ila ble: Tables of data col-
lection parameters, bond lengths and angles, positional and
thermal parameters, and least-squares planes for 6a ,e. This
material is available free of charge via the Internet at
http://pubs.acs.org.
HRS Mea su r em en ts of th e Hyp er p ola r iza bilities of
th e Com p lexes 1, 3, a n d 6. The HRS experiments were
carried out in chloroform. The HRS cell consisted of a 12 cm
glass tube of 1 cm diameter filled with the solution under
investigation. A tuneable optical parametric oscillator (OPO)
based HRS apparatus was used for the measurements at 1500
OM9904551
(32) (a) Stadler, S.; Dietrich, R.; Bourhill, G.; Bra¨uchle, C. Opt. Lett.
1996, 21, 251. (b) Lequan, M.; Branger, C.; Simon, J .; Thami, T.;
Chauchard, E.; Persoons, A. Chem. Phys. Lett. 1994, 229, 101.
(33) Schma¨lzlin, E.; Meerholz, K.; Stadler, S.; Bra¨uchle, C.; Patzelt,
H.; Oesterhelt, D. Chem. Phys. Lett. 1997, 280, 551.