Chiral organometallic chromophores for nonlinear optics derived from (μ-C-CH3)]+ [BF4]-

Article abstract of DOI:10.1016/S0022-328X(02)01415-8

Two series of chiral organometallic Donor-π-Acceptor chromophores derived from [Fe₂(η⁵-C₅H ₅)₂(CO)₂(μ-CO)(μ-C-CH ₃)]⁺ [BF₄]^- have been synthesised. In the first series (S)-(-)-2-methoxymethyl pyrrolidine acts as the chiral donor end group and in the second series 1,1′-binaphthyl acts as the chiral π-bridging unit. The nonlinear optical properties of these compounds were measured by the Kurtz powder technique and by hyper-Raleigh scattering. β-values of up to 964 × 10^-30 esu were obtained for a member of the first series. Single crystal X-ray studies of [Fe₂ (η⁵-C₅H₅)₂(CO) ₂(μ-CO)(μ-C-CH₃)]⁺ [BF₄]^-, [Fe₂(η⁵-C ₅H₄CH₃)₂(CO)₂ (μ-CO)(μ-(E)-C-CH=CH-2 -(5-piperidin-1-yl-thiophene))]⁺ [BF₄]^- and [Fe₂(η⁵- C₅H₄CH₃)₂(CO)₂ (μ-CO)(μ-(E)-C-CH=2-(naphthalene))]⁺ [BF₄] ^- are reported.

Full text of DOI:10.1016/S0022-328X(02)01415-8

Journal of Organometallic Chemistry 655 (2002) 70ꢃ88
/
www.elsevier.com/locate/jorganchem
Chiral organometallic chromophores for nonlinear optics derived
from [Fe2(h5-C5H5)2(CO)2(m-CO)(m-CÃCH3)]ꢀ [BF4]ꢁ
/
Richard D.A. Hudson a, Anthony R. Manning a,*, John F. Gallagher b,*, Marie
Helena Garcia c, Nelson Lopes c, Inge Asselberghs d, Roel Van Boxel d,
Andre´ Persoons d, Alan J. Lough e
a Department of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland
b School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
c Complexo 1, IST, Av. Rovisco Pais, 1049-001 Lisboa Codex, Portugal
d Katholieke Universiteit Leuven, Celestijnenlaan 200D, B3001 Leuven, Belgium
e Department of Chemistry, University of Toronto, Toronto, ON, Canada MS5 3H6
Received 12 March 2002; accepted 20 March 2002
Abstract
Two series of chiral organometallic Donor-p-Acceptor chromophores derived from [Fe2(h5-C5H5)2(CO)2(m-CO)(m-CÃ
[BF4]ꢁ have been synthesised. In the first series (S)-(ꢁ
)-2-methoxymethyl pyrrolidine acts as the chiral donor end group and in the
second series 1,1?-binaphthyl acts as the chiral p-bridging unit. The nonlinear optical properties of these compounds were measured
by the Kurtz powder technique and by hyper-Raleigh scattering. b-values of up to 964ꢂ
10ꢁ30 esu were obtained for a member of
the first series. Single crystal X-ray studies of [Fe2(h5-C5H5)2(CO)2(m-CO)(m-CÃCH3)]ꢀ [BF4]ꢁ, [Fe2(h5-C5H4CH3)2(CO)2(m-
CHÄCH-2-
/
CH3)]ꢀ
/
/
/
CO)(m-(E)-CÃ
/
CHÄ
/
CH-2-(5-piperidin-1-yl-thiophene))]ꢀ [BF4]ꢁ and [Fe2(h5-C5H4CH3)2(CO)2(m-CO)(m-(E)-CÃ
/
/
(naphthalene))]ꢀ [BF4]ꢁ are reported. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Nonlinear optics; Kurtz powder; Hyper-Raleigh scattering; Second harmonic generation; Iron; Crystal structures
1. Introduction
aldehydes to form diiron alkenylidyne complexes [4]
(Scheme 1).
Organometallic groups are receiving considerable
attention in nonlinear optical (NLO) studies due to the
flexible nature of their substitution and oxidation states
[1]. They have been utilised as donors (D) or acceptors
(A) in the well established D-p-A motif, and very high
hyperpolarisabilities (b-values) have been obtained by
the judicious combination of bridging element and end
groups [2]. In this context we are interested in the
A theoretical study has revealed that the cationic m-
carbyne may efficiently accept electron density into the
formally vacant p-orbital from an adjacent donor
throughout rotation about the m-CÃ
/
CÄ
/
CHR single
bond [5]. Research by Green and co-workers has shown
that derivatives of 1 may have potential for 2nd order
NLO studies [6]. We have recently sought to extend this
work by synthesising a number of merocyanine struc-
tures incorporating this acceptor and subsequent mea-
surements by hyper-Raleigh scattering (HRS) [7] have
shown that some of these compounds exhibit extremely
high b-values [8]. HRS is measured in solution and since
b is a vector quantity; in centrosymmetric environments
all of its components disappear. Therefore, for measure-
ments in the solid state, compounds that crystallise in an
acentric space group are desirable [9]. This was well
illustrated in a ground-breaking report by Green et al.,
in which they observed (by the Kurtz powder technique
cationic complex [Fe2(h5-C5H5)2(CO)2(m-CO)(m-CÃ
/
CH3)]ꢀ [BF4]ꢁ (1), (originally synthesised by Rosen-
blum and co-workers [3]), which may function as an
acceptor end group after facile condensation with
* Corresponding authors. Tel.:
7045503.
ꢀ
/
353-1-7045114; fax:
ꢀ/353-1-
E-mail addresses: anthony.manning@ucd.ie (A.R. Manning),
john.gallagher@dcu.ie (J.F. Gallagher).
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 4 1 5 - 8

R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ
/88
71
2.1. Synthesis of the chiral donor-containing
merocyanines 6 and 7
Thiophenes have been used extensively as conduits for
electron transfer in conducting polymers [15] and are
effective spacer elements in NLO active materials
[8,14c,16]; consequently we have included a thienyl
residue in both series of chromophores as part of the
p-bridging systems. Aldehydes 2 were readily synthe-
sised according to the method of Prim et al. [17] and
these compounds were further homologated to the (E)-
vinyl aldehydes 3. Both achiral (2a, 3a) and chiral
versions (2b, 3b) of the chromophores were prepared
Scheme 1. 1; ([Fe2(h5-C5H5)2(CO)2(m-CO)(m-CÃCH3)]ꢀ [BF4]ꢁ).
/
[10]) that (Z)-[1-ferrocenyl-2-(4-nitrophenyl)-ethylene]
exhibits a large second harmonic generation (SHG)
with piperidine and (S)-(ꢁ)-2-methoxymethylpyrroli-
/
powder efficiency (62ꢂurea), whereas the E-isomer is
/
dine functioning as the donor end groups, respectively.
Optical rotation measurements on the chiral adducts 2b
completely inactive in the solid state despite its larger
molecular hyperpolarisability [11]. This was attributed
to the acentric crystal packing of the Z-isomer as
opposed to the presumed centrosymmetric space group,
which the E-isomer resided in. Green’s initial observa-
tion of the p-dimethylaminophenylethenyl derivative of
1 was also made using the Kurtz powder technique [10].
It is thus remarkable that any SHG signal at all was
observed since a crystallographic study of the chromo-
phore reveals that the structure occupies the centrosym-
metric space group P21/n. The powder efficiencies of the
compound (0.77 and 3.6 times that of urea, as their
[BF4]ꢁ and [CF3SO3]ꢁ salts, respectively) were attrib-
uted to either surface effects or to minute crystal-
Hg
546
and 3b show rotations of [a] : ꢁ178 and ꢁ155ꢀ;
respectively. Compound 2a was further homologated by
HornerꢃWittig condensation with diethyl(2-thienyl-
/
methyl)phosphonate [18] to afford 4 (not shown)
followed by formylation to give 5 (Scheme 2).
Condensation of 2 and 3 with 1 in refluxing dichlor-
omethane provided the merocyanines 6 and 7 in reason-
able yields as dark red and blue, air-stable solids,
respectively, which exhibited the expected spectroscopic
and constitutional data. The solids crystallise with
fractional amounts of dichloromethane, which is seen
1
in the H-NMR and X-ray structure of 9, vide infra
(Scheme 3). As 6 and 7 are highly coloured, reliable
optical rotations could not be recorded even at high
dilutions and a variety of wavelengths. Unfortunately, 1
did not undergo a condensation reaction with 5 even
with prolonged reaction times (5 days) or on the
lographically
undetectable
deviations
from
centrosymmetry. It was subsequently recognised that
the planar chirality of 1,2-disubstituted and related
ferrocenes could also be exploited to promote noncen-
trosymmetric crystal packing and several groups have
reported chromophores derived from this motif [12] with
powder efficiencies as high as 220 times that of urea [13].
We have been motivated by these results to introduce
chirality into potential NLO candidates derived from 1
and we report here the synthesis and optical measure-
ments of the first generation of this class of chiral
organometallic chromophores.
addition of HBF4×
/
OEt2. Instead, 1 was deprotonated
to the neutral vinylidene complex 1a (Scheme 4). This
may be attributed to the increasing basicity of the
2. Results and discussion
Two series of chiral compounds were synthesised
which included an aldehyde functionality in the starting
materials for condensation with 1 (Scheme 1) [4]. In the
first series the chirality was achieved by the incorpora-
tion of a chiral donor (derived from the amine (S)-(ꢁ)-
/
Scheme 2. Reagents and conditions: (i) Amine, water, reflux 12 h; (ii)
2-tributylphosphoniumacetaldehyde diethylacetal bromide, THF,
KOt Bu, 12 h; (iii) diethyl(2-thienylmethyl)phosphonate, THF, KOt -
Bu, 12 h; (iv) BuLi, DMF, THF.
2-methoxymethyl pyrrolidine [14]) and in the second it
arises as a consequence of the inclusion of chiral 1,1?-
binaphthyl spacer elements.

72
R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ88
/
as the donor moieties, and where possible, to arrange
the end groups of the chromophores in a 2,3- (the
shortest distance) or 2,6- (the longest distance) relation-
ship about the naphthylene spacer. The 1,1?-binaphthyl
motif incorporating alkoxy donors has been examined in
this latter configuration by other investigators both in
the racemic [19] and resolved forms [20] for NLO
activity.
In order to examine the efficiency of the methoxy
group as a donor in either of these configurations the
model compounds 13ꢃ
readily accessible aldehydes 10ꢃ
1 in a manner analogous to the synthesis of 6 and 7
(Scheme 5). These complexes were obtained as redꢃ
brown solids and exhibited all the expected spectro-
scopic and constitutional data. A single crystal was
grown of 15 and the structure was established by X-ray
diffraction (Fig. 4).
/
15 were synthesised from the
/
12 by condensation with
Scheme 3. Reagents and conditions: (i) CH2Cl2, reflux, 12 h; (ii)
/
HBF4×OEt2, CH2Cl2, reflux, 4 h.
/
Racemic 1,1?-bi-2-naphthol was prepared according
to the literature procedure [21] and resolved according
to the method of Cai et al. [22]. The racemate and
enantiomers were methylated to afford 2,2?-dimethoxy-
1,1?-binaphthyl and formylated by ortho-metallation
followed by a DMF quench. During the course of this
reaction we obtained the ortho-monoaldehydes 16 (R/S
Scheme 4. Formation of the neutral vinylidene complexes 1a and 8.
nitrogen atom as the aldehyde functionality is displaced
away by longer conjugated path lengths. To a lesser
extent this effect was also observed in the condensation
times and IR profiles of the successful reactions which
produced 6 and 7. Compounds 3, having an extra
double bond with respect to 2, took much longer to
condense with 1 and appreciable amounts of 1a were
seen in the IR spectra of the reaction mixtures. This
slowly diminished as complexes 7 were formed. No
evidence of 1a was detected in the reaction of 2 with 1.
Neither 6 nor 7 yielded X-ray quality crystals and in
order to address the relative insolubility of these
compounds and hence their poor crystallisation proper-
ties, condensation of the methylcyclopentadienyl analo-
and racemate; from (R)-1,1?-bi-2-naphthol [a]D: ꢀ
/
101.68; from (S)-1,1?-bi-2-naphthol [a]D: ꢁ100.48) and
/
the dialdehydes 20. Compound 16 was converted [18] to
the monoaldehydes 17 (R/S and racemate: from (R)-
1,1?-bi-2-naphthol [a]D: ꢀ
/
221.18; from (S)-1,1?-bi-2-
naphthol [a]D: ꢁ222.98). Both 16 and 17 condensed
/
with 1 to give 18 (R/S and racemate) and 19 (R/S and
racemate) (Scheme 6). These were isolated as red/brown
and blue solids, respectively, which exhibited all the
expected spectroscopic and constitutional data (Scheme
6).
The dialdehydes 20b (R/S and racemate) were pre-
from
pared
6,6?-dibromo-2,2?-dimethoxy-1,1?-bi-
metal exchange with
naphthalene by double halogenꢃ
/
gue of 1, [Fe2(h5-C5H4Me)2(CO)2(m-CO)(m-CÃ
/
CH3)]ꢀ
n-butyl lithium followed by a DMF quench. Both 20a
(R/S and racemate, see above) and 20b (R/S and
racemate) were condensed with 1 to afford chromo-
phores 21 (R/S and racemate) and 22 (R/S and
racemate) (Scheme 7), which were recovered as brown/
red solids. Unfortunately, both were highly insoluble
and 13C-NMR spectroscopic data could not be re-
corded. However, all the other data required for
unambiguous characterisation were obtained. Chain
extension of both aldehydes in 20b (R/S and racemate)
with the Wittig reagent diethyl(2-thienylmethyl)pho-
sphonate afforded 2,2?-dimethoxy-6,6?-bis(E-2-(2-thio-
phene))ethenyl)-1,1?-binaphthalene, (24) (R/S and
racemate) (not shown) which were formylated to 25
(enriched R/S and racemate). Some scrambling of the
enantiomers occurred in the conversion of 20b to 25
(optical rotation data: from R-1,1?-binaphthyl:
[BF4]ꢁ (8) (Scheme 4), with 2a was attempted. This salt
is much less reactive than 1 towards condensation with
aldehydes and would not react with the relatively
deactivated aldehyde in 2a. However, reaction of 2a
with the neutral species 8 in the presence of HBF4×
/OEt2
afforded 9 from which X-ray quality crystals were
obtained (Fig. 3, vide infra). Condensation of 8 with
chiral 2b was very slow and only decomposition
products were obtained. Representative spectroscopic
data for compounds 6, 7 and 9 are collected in Table 1.
2.2. Synthesis of the naphthyl and chiral 1,1?-binaphthyl-
containing merocyanines 13, 14, 15, 19, 22, 23 and 26
In the case of all of the naphthyl-bridged merocya-
nines described below we chose to use methoxy groups

R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ
/88
73
Table 1
Selected spectroscopic data for compounds 6, 7, 9, 13, 14, 15, 18, 19, 21, 22 and 26
lmax (nm) (o ꢂ103, Mꢁ1 cmꢁ1
)
nCO (cmꢁ1
)
dm13C (ppm)
a
b
c
Entry
Compound
CH2Cl2
CH3CN
DE/kJ Mꢁ1
1
2
3
4
5
6
7
1
ꢃ
/
ꢃ
/
2047, 2016, 1853
1992, 1953, 1790
2013, 1982, 1820
2014, 1981, 1821
2008, 1976, 1816
2009, 1980, 1815
2010, 1983, 1816
499
272
349
350
354
340
340
1a
6a
6b
9
528 (1)
528 (1)
0
4
3
5
4
5
557 (80)
556 (57)
562 (59)
658 (86)
655 (97)
547 (68)
547 (52)
551 (53)
643 (60)
640 (73)
7a
7b
8
9
13
14
15
18
19
21
22
26
467 (27)
458 (49)
511 (61)
460 (23)
608 (62)
441 (26)
448 (58)
481 (49)
451 (22)
566 (58)
15
4
2035, 2002, 1845
2033, 2004, 1843
2034, 2005, 1844
2036, 2005, 1846
2032, 2002, 1841
2034, 1992, 1844
2034, 2007, 1842
2031, 2000, 1840
441
438
432
437
417
10
11
12
13
14
15
14
5
15
4
453 (ꢃ
/
)
523 (52)
446 (ꢃ
/
)
496 (53)
ꢃ/
ꢃ/
13
12
633 (75)
594 (75)
416
a
Measured at 1ꢂ10ꢁ5 mol.
Recorded in CH2Cl2.
Recorded in CD2Cl2.
b
c
Scheme 5. Reagents and conditions: (i) CH2Cl2, reflux, 12 h.
Scheme 7. Reagents and conditions: (i) CH2Cl2, reflux 18 h; (ii)
diethyl(2-thienylmethyl)phosphonate, KOt Bu, THF, 1 h; (iii) BuLi,
THF, ꢁ78 8C, 1 h. DMF, 30 min.
/
[a]D: ꢁ
/
650.28 and from S-1,1?-binaphthyl: [a]D: ꢀ
/
569.18). Compound 25 condensed with 1 giving 26
(enriched R/S and racemate) in good yield as red solids
(Scheme 7). Unfortunately, although 20a (racemate)
reacted with diethyl(2-thienylmethyl)phosphonate, the
product, 23 (racemate), was too insoluble to allow
further study. Representative spectroscopic data for
compounds 13, 14, 15 and racemic 18, 19, 21, 22, and
26 are collected in Table 1.
Scheme 6. Reagents and conditions: (i) Diethyl(2-thienylmethyl)pho-
sphonate, KOt Bu, THF, 1 h; (ii) BuLi, THF, ꢁ
78 8C, 1 h. DMF, 30
min; (iii) CH2Cl2, reflux 18 h.
/

74
R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ88
/
2.3. Linear optical and NMR properties of 6, 7, 9, 13, 14,
15, 18, 19, 21, 22 and 26
Ã
/
CHÄ
/
CHÃ
/
moiety causes rotation about the CÃ
/
naph-
thyl bond and reduces the ppꢃ
/
pp overlap between
aromatic ring and CC double bond. However, it may
be that the methoxy group in this ortho-arrangement is
The spectroscopic data for compounds containing the
six-membered piperidine donor, 6a, 7a and 9, differ little
from those for compounds containing the five-mem-
bered pyrrolidine residue, 6b and 7b (Table 1). Inclusion
of the pendant functionality in 7, in order to induce
asymmetry in the solid state, appears to have no linear
spectroscopic effect in solution. Compounds 6 are dark
simply not acting as donor (so OMeꢄ0.10 [23]).
/
The two level model [24] predicts that the dipole
moment change on excitation is important in SHG and
insight into this process may be gained from the
solvatochromic behaviour of the compounds [25]. Both
series of chromophores exhibit lmax values that are
solvent dependent. For derivatives 6 and 7 this depen-
dency is small with around 4 kJ Mꢁ1 but for some of the
naphthyl-containing merocyanines the energy differ-
ences are more significant. The expected decrease in
energy on excitation of 14 versus 15 commensurate with
the increase in length of the chromophores and the more
red solids and have UVꢃ
nm in dichloromethane. These bands are attributable to
donorꢃacceptor based charge transfer (CT) on photo-
/
vis absorbances at 557 and 556
/
chemical excitation from the ground to excited state.
The position of the CT bands is unfortunate since the
laser frequency used for the Kurtz powder measure-
ments is 1064 nm and so any second harmonic signal at
532 nm would fall directly in this range and be absorbed.
Increasing the p-spacer in a D-p-A chromophore results
in a shift to lower energies of the principle absorption
band and this was the initial motivation for the synthesis
of 5 and its condensation product with 1. As 5 did not
condense, compounds 7 were synthesised and it was
found that the extra double bond was enough to
bathochromically shift the CT band away from the
region of interest at 532 to around 640 nm.
effective donorꢃ
by an increase in solvatochromism with 14 (DEꢄ
Mꢁ1) apparently exhibiting a smaller dipole moment
change than 15 (DEꢄ
14 kJ Mꢁ1). Unsurprisingly a
similar DE value of 4ꢃ
5 kJ Mꢁ1 is observed for both 14
/acceptor arrangement is accompanied
/4 kJ
/
/
and 18 on elaboration of the bridging unit to the 1,1?-
binaphthyl core but this is accompanied by an unex-
pected decrease in extinction coefficient of around
26 000 Mꢁ1 cmꢁ1 (CH2Cl2). Similar solvatochromic
behaviour is manifested between 21 (Dlꢄ
/
4 kJ Mꢁ1
)
Chromophores 13, 14, 15, 18, 19, 21, 22 and 26 are
dark brown to blue solids and have absorbances in the
range 421 (for 13 in acetonitrile) to 633 nm (for 26 in
CH2Cl2). The higher energies of their CT transitions
and 22 (Dlꢄ
/
13 kJ Mꢁ1). These full binary chromo-
phores also appear to suffer a loss in extinction
coefficient in comparison with their naphthyl counter-
parts 14 and 15. They may be expected to exhibit o
values twice that of 14 and 15 but the value obtained for
22 is comparable to 15. The large decrease in excitation
energy and apparent increased dipole moment change
suggest that their donorꢃacceptor interactions are
/
weaker than they are for 6 and 7. This might have
been expected from the Hammett parameters sp
NMe2ꢄ
/
ꢁ
/
0.63 and sp OMeꢄ
/
ꢁ
/
0.28 [23]. Comparison
between 18 (DEꢄ
/
5 kJ Mꢁ1) and 19 (DEꢄ
/
15 kJ Mꢁ1
)
of 13, in which there is no methoxy substituent, with 15
and 22 suggests that in the 2,6-substitution pattern the
methoxy group acts as a moderate donor. The lowering
of the nCO frequencies and the upfield shift of the 13Cm
is probably due to the auxiliary donor effect of the
electron-rich thiophene ring which compensates for the
lack of communication between the putative out-of-
plane acceptor and the poorly donating ortho-methoxy
group.
resonance of the Fe2(h5-C5H5)2(CO)2(m-CO)(m-CÃ
/
) end
group suggests that in the ground state its positive
charge is delocalised onto the methoxy group as well as
the naphthyl spacer. There is a consequent lowering of
the energy of the CT transition in going from 13 to 15.
Its further lowering in 22 suggests that there is some
interaction between the two methoxynaphthyl subunits.
In contrast the presence of an ortho-MeO group
appears to hinder the communication between the
The 13C-NMR chemical shift for the cationic m-
carbyne is indicative of the amount of charge residing
on the diiron moiety. The m-carbyne in 1 has an
extremely low field chemical shift of d 499 and
compounds 6 and 7 have shifts about 150 ppm upfield
of this at around d 350 and 340, respectively (Table 1).
It is informative to compare these values with those
obtained for 1a, which is comparable to the diiron
fragment in the limiting CT resonance forms of 6 and 7
on excitation. Compound 1a exhibits a neutral m-
carbene shift of d 272, which is about 80 ppm upfield
of 6 and 7. This trend also appears in the IR data with
nCO stretches around 30 cmꢁ1 higher for 1 than 6 and 7,
Fe2(h5-C5H5)2(CO)2(m-CO)(m-CÃ
/
) end group and the
naphthyl part of the spacer. This is particularly apparent
in the 13Cm chemical shifts and the energies of the CT
transitions. The former are more downfield for the 2,3-
derivatives than the 2,6- and are not very different from
the values for 13, whilst the latter are of higher energies
for 14, 18 and 21 than for 15 and 22, and are even higher
than for 13. A possible explanation is that steric
interaction between the ortho-methoxy group and the
which indicates increased MÃ
/
CO back donation. These
are in turn around 20 cmꢁ1 above the nCO stretches for
the neutral 1a. The extra double bond in compounds 7
with respect to 6 contributes more resonance canonical

R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ
/88
75
Table 2
Comparison of dimensions of 1 with those of related [Fe2(h -C5H5)2(CO)2(m-CO)(m-CX)] compounds (A and 8)
5
˚
forms to the overall description of the charge-separated
states and so lower m-carbyne and nCO values are
recorded for these complexes. These spectroscopic
findings suggest that the complexes are extensively
delocalised with, in effect, almost two-thirds of the
positive charge residing on the organic ligand.
The ground state structure in 6, 7 and 9 may be
regarded as a mixture of canonical forms, the limiting
forms of which for 6b are shown in Fig. 1. In one, A/B,
the positive charge resides on the bridging carbon atom
of the diiron end group, but in the other A1/B1 it resides
on N and there is an iminium contribution. In the
examples where there is a substituent adjacent to the
nitrogen (6b and 7b) there is the potential to use NMR
spectroscopy to observe restricted rotation about the
number of accessible canonical forms for charge delo-
calisation over the longer bridge. Although rotation
about the CÃ
/
C bonds between vinyl and divinyl linkages
to Cm might also be expected to be restricted, we were
unable to investigate them at the temperatures available
to us (ca. ꢁ
rotational barriers of several cationic diiron m-carbyne
complexes at temperatures as low as ꢁ103 8C as this is
/
30 8C). Casey et al. have studied the
/
often necessary to slow down rotations in alkyl and
alkoxy substituted merocyanines. They concluded that
the barrier to rotation about the carbyne carbon to vinyl
carbon bond is very low and can only be observed when
a good electron donor is attached to the remote vinyl
carbon [5]. For example, in the case of the dimethyla-
minovinyl complex [Fe2(h5-C5H5)2(CO)2(m-CO)(m-CÃ
/
nitrogenÃ
/
thiophene bond since A1 and B1 are different
CHÄ
/
CHÃNMe2)][BF4] the Cm-to-vinyl rotational bar-
/
rier is 19.8 kcal molꢁ1 with coalescence at 93 8C [5].
This is reduced to 10.6 kcal molꢁ1 (observed at
configurational isomers.
Low temperature NMR studies on 6b and 7b show
that the thienyl proton adjacent to the nitrogen-contain-
ing ring has a coalescence temperature of 24 and 7 8C in
6b and 7b, respectively, corresponding to rotational
barriers about the N-thiophene single bond of around
14.3 and 12.4 kcal molꢁ1. As expected, the energy
barrier for 7b is the lower of the two due to the larger
ꢁ
/
73 8C) in [Fe2(h5-C5H5)2(CO)2(m-CO)(m-CÃ
/
CHÄ
NMe2-4)][BF4] (29, Table 2) where a phenyl
group intervenes between the donor and the acceptor;
/
CHÃ
/
C6H4Ã
/
the barrier to rotation about the phenylÃ
/
vinyl bond was
13.0 kcal molꢁ1 [5]. From line width analysis a rate of
exchange for rotation about the carbon nitrogen bond in
the former complex was estimated to be ꢀ22.7 and 10.9
/
kcal molꢁ1 in the latter. In our compounds the amine
donors are separated from the diiron moiety by ethe-
nylthiophene linkages and the barriers to rotation (14.3
and 12.4 kcal molꢁ1, respectively) should be slightly
greater than that observed for [Fe2(h5-C5H5)2(CO)2(m-
CO)(m-CÃ
/
CHÄ
/
CHÃ
/
C6H4Ã
/
NMe2-4)][BF4] (10.9 kcal
molꢁ1) due to the higher resonance energy of benzene
versus thiophene. Conversely they should be much lower
than that observed for [Fe2(h5-C5H5)2(CO)2(m-CO)(m-
CÃ
/
CHÄ
/
CHÃ
/
NMe2)][BF4] (22.7 kcal molꢁ1) as the
nitrogen is separated from the cationic centre by the
extra distance and aromaticity of the intervening
Fig. 1. Limiting canonical forms contributing to the presence of
rotational barriers in 6b.

76
R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ88
/
thiophene. Indeed, the spectroscopic data discussed
above support these assumptions.
Interestingly 1 was found to have crystallised in the
orthorhombic acentric space group P21nb (Table 3)
with two anions and two cations in the asymmetric unit.
An ORTEP view of one of the cations, from molecule B,
is depicted as Fig. 2, and selected bond lengths and
angles are given in Table 2. In 1 the core geometry of the
two independent cations of [Fe2(h5-C5H5)2(CO)2(m-
Compounds 13, 14, 15, 18, 19 and 26 exhibit cationic
m-carbyne resonances much closer to the d 499 shift for
1 indicating less delocalisation of charge throughout the
structures as expected, nonetheless the trends identified
in the UV spectroscopic data are still evident. The 2,3-
substituted series 14 and 18 (Table 1) exhibit shifts at d
438 and 437 (compound 21 was too insoluble to
measure) comparable to 13 at d 441 and these values
decrease to around d 432 in the 2,6-substituted com-
pound 15. For the lengthier 19 and 26 a more upfield
shift to around at d 417 was recorded. No rotational
barriers for any of the compounds in this series could be
observed at the temperatures accessible to us. The IR
data also support these observations with a general
decrease in stretching frequency for this series with
respect to 1 although this is not as marked as in the
more highly delocalised compounds 6, 7 and 9 (Table 1).
CO)(m-CÃ
/
CH3)]ꢀ are essentially identical with FeÃ
/Fe
˚
bond lengths of 2.499(3) and 2.503(3) A for the A and B
molecules, respectively. There is some disorder in the
structure of 1, principally with respect to the [BF4]ꢁ
anions. The four FeÃ
/
COterminal bond lengths are in the
˚
range 1.73(2)ꢃ
/
1.80(2) A and FeÃ
/
CO angles are close to
linearity as expected 177(2)8. The four COterminal dis-
˚
tances are normal and lie in the range 1.11ꢃ1.18(2) A.
/
The bridging m(CÃ
/
CH3) ligand has FeÃ
/
C distances from
CH3 bond lengths of
˚
1.818(18) to 1.862(16) A, with CÃ
/
˚
1.42(3) and 1.45(3) A. This contrasts with the m(CO)
moiety where the FeÃC distances are in the range
1.96(2) A and CÃO bond lengths are 1.14(2)
A. The FeÃCOÃFe bond angles are 79.1(9)/80.1(7)8 in
contrast to 85.3(7)/86.1(8)8 for the bridging CCH3 in
FeÃCCÃFe. The FeÃCObridging angles are in the range
from 138.8(15) to 141.2(19)8 and the FeÃCÃCH3 angle
/
˚
1.93(2)ꢃ
/
/
˚
/
/
2.4. X-ray structures of 1, 9 and 15
/
/
/
There are now several structures for adducts of 1 in
/
/
the literature [4ꢃ/6,26] but there has been no diffraction
is between 136.3(15) and 137.9(15)8, with little difference
between the two sets of angles. The terminal carbonyl
ligands are eclipsed with respect to one another with
study of the paradigm compound 1 despite the fact that
it has been known for over 20 years [3]. Clearly it would
be relevant to have a structure for the parent complex
with which to compare the bond lengths and angles
within the diiron core with those of the more delocalised
vinylogous adducts and we have sought to obtain one.
Compound 1 is insoluble in many common polar
organic solvents and often undergoes deprotonation in
solution rendering it difficult to crystallise in the normal
way (diffusion or layering of ethereal solvents over polar
solutions of the salt) and so we undertook a different
approach. Compound 1 was deliberately deprotonated
to form its conjugate base 1a, which was dissolved in a
small amount of diethyl ether. This was placed in a
narrow test tube and more diethyl ether was carefully
added so two layers were formed. Several drops of
2.2(5)8 for O1AÁ Á ÁFe1AÃ
/
Fe2AÁ Á ÁO2A and ꢁ
/
1.5(5)8 for
O1BÁ Á ÁFe1BÃ
(with
Cg3Á Á ÁFe1BÃ
/
Fe2BÁ Á ÁO2B, likewise the h5-C5H5 rings
Cg1Á Á ÁFe1AÃ
/
Fe2AÁ Á ÁCg(2)ꢄ
/
1.9(7)8
and
/
Fe2BÁ Á ÁCg4ꢄ
/
1.4(8)8) are eclipsed and
cis- with respect to one another (Cg1, Cg2, Cg3, Cg4
are the four cyclopentadienyl ring centroids on mole-
cules A and B). The two tetrafluoroborate anions are
disordered and were both modelled with two different
site orientations and restrained bond length and angle
DFIX controls in the full matrix least-square refine-
ments cycles. There are no classical hydrogen bonds in
the crystal structure although there are numerous CÃ
/
HÁ Á ÁF contacts.
The structure of the ruthenium analogue of 1 has been
determined previously [27]. Unlike 1, this structure
crystallises in a centrosymmetric space group, mono-
clinic P21/n and has been determined to a high degree of
precision. The structure is similar to the two indepen-
HBF4×
/
OEt2 (54% solution in diethyl ether) were intro-
duced into the upper layer and the solution allowed to
stand overnight. An X-ray diffraction study of the poor
quality fine needles formed by this method provided a
structure for 1.
dent molecules A and B in 1. The CÃ/CH3 bond length is
Although the crystals of 1, 9 and 15 only diffracted
relatively poorly (see Table 3 for details of crystal data
and structure refinement) we were able to obtain
sufficient data to allow us to determine the details of
their conformations unequivocally. For the structures of
9 and 15, important information was obtained on
relevant parameters with a reasonable precision. Se-
lected data for 1, 9 and 15 are tabulated in Table 2 along
with some closely related structures for comparative
purposes.
1.462(6) A as compared to 1.42(3) and 1.45(3) A in 1. Of
interest is the fact that these two compounds crystallise
in different space groups. This may be due to steric and
molecular size reasons primarily giving rise to the
inability of the iron dimer to crystallise well using
well-tried solvent systems, unlike the ruthenium analo-
gue.
The IR spectra of 6, 7, 9, 13ꢃ
show that both in solution and in the solid state their
Fe2(h5-C5H5)2(CO)2(m-CO)(m-CÃ
) end groups have a
/
15, 18, 19, 21, 22 and 26
/

R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ
/88
77
Table 3
Crystal data and structure refinement for 1, 9 and 15
Compound
1
9
15
Empirical formula
C
15H13BF4Fe2O3
C27H28BF4Fe2NO3S,
0.49(C4H8O),0.53H2O
694.27
C27H21BF4Fe2O4
Formula weight
Temperature (K)
˚
Wavelength (A)
439.76
123(2)
607.95
294(2)
295(2)
0.71073
0.71073
Orthorhombic
P21nb
0.71073
Monoclinic
P21/c
Crystal system
Space group
Unit cell dimensions
Monoclinic
C2/c
˚
a (A)
12.697(2)
14.998(2)
17.232(3)
20.6105(16)
16.8844(14)
17.759(3)
97.131(9)
6132.4(11)
8
18.239(2)
9.6005(16)
14.635(2)
93.225(7)
2558.7(7)
4
˚
b (A)
˚
c (A)
b (8)
ꢃ/
3
V (A )
˚
3281.5(9)
8
1.780
Z
Dcalc (Mg mꢁ3
)
1.504
1.075
1.578
1.195
Absorption coefficient (mmꢁ1
F(000)
Crystal size (mm)
)
1.821
1760
2856
0.60ꢂ0.17ꢂ0.10
1232
0.48ꢂ0.20ꢂ0.13
0.30ꢂ0.10ꢂ0.05
u Range for data collection (8)
Index ranges
2.5ꢃ
/
25.0
2.5ꢃ
/
26.0
2.2ꢃ26.1
/
ꢁ155h 515, ꢁ175k 517,
ꢁ205l 520
5564
ꢁ255h 51, ꢁ15k 520,
ꢁ215l 521
6997
ꢁ225h 522, 05k 511,
ꢁ185l 50
7926
Reflections collected
Unique reflections
5564
99%
6014
100%
0.900, 0.565
5053
99%
Completeness to 2uꢄ268
Max/min transmission
Data/restraints/parameters
Final R indices [I ꢀ2s(I)]
R indices (all data)
0.91, 0.61
0.86, 0.60
5564/305/481
R1ꢄ0.149, wR2ꢄ0.235
R1ꢄ0.193, wR2ꢄ0.254
1.225
6014/171/514
R1ꢄ0.062, wR2ꢄ0.112
R1ꢄ0.164, wR2ꢄ0.147
1.000
5053/250/482
R1ꢄ0.079, wR2ꢄ0.188
R1ꢄ0.151, wR2ꢄ0.230
1.015
Goodness-of-fit on F2
Largest difference peak and hole 0.77/ꢁ0.87
)
Largest shift and error maximum 0.004
0.38/ꢁ0.29
0.92/ꢁ0.80
ꢁ3
˚
(e A
0.001
0.001
Fig. 3. ORTEP diagram of the major conformation of the iron dimer
cation in 9. Displacement ellipsoids are depicted at the 30% level.
Fig. 2. ORTEP diagram of the major conformation of the iron dimer
cation of molecule B in 1. Displacement ellipsoids are depicted at the
30% level.
of the cation is shown in Fig. 3 with selected bond
lengths and angles listed in Table 2. The methylcyclo-
pentadienyl ligands show some disorder over two sites
cis conformation comparable to that found in 1 (cf. Ref.
[8] for a discussion). This was verified by X-ray
diffraction studies of 9 and 15.
Unlike 1, 9 crystallises in a centrosymmetric space
group (monoclinic, C2/c). A representative ORTEP view
for the methyl substituent. The FeÃ
/
COterminal bond
˚
lengths are 1.726(7), 1.722(9) A and the FeÃ
/CO angles
are close to linearity 179.1(2)/179.2(2)8; the two terminal
˚
CO distances are 1.149(7) and 1.163(8) A. The bridging
m(CÃ
/
CH3) ligand Fe1,2 C distances are 1.877(5) and
Ã
/

78
R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ88
/
˚
1.878(5) A. The suggested highly delocalised ground
state structures of 6 and 7 are further confirmed by
inspection of the crystal structure of 9. There is
essentially complete delocalisation between C1 and C4
˚
C4
with the single bonds C1Ã
/
C2 1.365(6) A and C3Ã
/
2
˚
1.372(6) A similar and shortened from the normal sp Ã
/
2
sp single bond length (1.48 A) [28]. The double bond
˚
˚
C2Ã
/
C3 {1.380(7) A} is lengthened in comparison with a
normal sp2Ä
C7RÃ
length from a typical sp2Ã
/
sp double bond (1.32 A) [28]. Similarly the
2
˚
˚
/
N31 1.330(6) A bond is considerably reduced in
˚
NR2 bond (1.38 A) [28] and is
/
among the shortest known bonds between and amine
and an aromatic carbon [29]. For the thiophene ring an
increased contribution of the quinoid [30] compared
Fig. 4. ORTEP diagram of the major conformation of the iron dimer
cation and tetrafluoroborate anion in 15. Displacement ellipsoids are
depicted at the 30% level.
with the aromatic structure [31] is seen {C4RÃ
1.400(7), C5RÃC6R 1.354(7) and C6RÃC7R 1.416(7)
A}. In comparison the trends along the formal CÃCÄ
CÃC chain in the benzothiophene derivative 28 (Table
2) reported by us previously [8b] are more distinct
/C5R
/
/
˚
/
/
O1TÁ Á ÁFe1Ã
are primarily CÃ
C6RÃH6RÁ Á ÁF(4A) , CÁ Á ÁF 3.380(17) A, CÃ
and C16AÃ
/
Fe2Á Á ÁO2T. The intermolecular interactions
/
/
HÁ Á ÁF and CÃHÁ Á ÁO in nature of which
˚
/
/
i
/
HÁ Á ÁFi 1728
˚
1.416(7)/1.362(7)/1.419(7) A and the benzothiophene
unit itself has no visible quiniodal character, exhibiting
the expected bond lengths and angles for this moiety
˚
/
H16AÁ Á ÁO3B, CÁ Á ÁO 3.341(16) A, CÃ
/
HÁ Á ÁOii 1358 are representative and will not be discussed
further. A representative ORTEP view of the cationic
species in 15 is depicted as Fig. 4, and selected bond
lengths and angles are listed in Table 2.
[31]. The m(CO) moiety has typical distances with the
˚
C bond lengths of 1.902(7) and 1.915(6) A and with
FeÃ
/
˚
a bridging CO bond length of 1.181(6) A. The FeÃ
Fe bond angle is 81.8(3)8 in contrast to the 83.5(2)8 for
the bridging m-CCH(ligand) in FeÃCCÃFe which is
similar to, though not as large as in 1 above. The FeÃ
CObridging angles are 138.2(5)/139.9(5)8 and the FeÃCÃ
CH3 angles are 137.8(4)/138.6(4)8.
/
COÃ
/
The FeÃ
/
COterminal bond lengths are normal, 1.748(7),
˚
1.757(9) A and the FeÃ
/CO angles are close to linearity
/
/
(as expected) 179.3(6)/176.4(7)8; the two terminal CO
/
˚
distances are 1.137(8) and 1.139(9) A. The bridging
m(CÃCH) ligand Fe1,2 C distances are 1.847(6) and
1.843(6) A, with a C1ÃC2 bond length of 1.400(9), C2Ã
C3R 1.330(10), C3ÃC11 1.453(9) A indicating that the
/
/
/
Ã
/
˚
/
/
The m-CCHCHC4H2NC5H10 ligand in 9 lies in a
slightly twisted arrangement with respect to the plane
defined by the two iron atoms and the bridging carbon
˚
/
C1Ã
normal sp2Ã
above): the CÄ
a normal Csp2Ä
/
C2/C3Ã
/
C11 distances do not deviate much from
2
˚
/
sp bond lengths [1.46 A] (c.f. 9 described
atom [dihedral angles Fe1Ã
C2ÃC3RÃC4R 179.3(5)8,
174.1(6)8. This is smaller than the twist observed in the
benzothiophene derivative 28 where they are 161.8(5)/ꢁ
/
C1Ã
/
C2Ã
/
C3R 169.0(5)8, C1Ã
/
˚
/
C bond length of 1.330(10) A is similar to
/
/
C2Ã
/
C3RÃC4RÃC5R
/
/
/
sp2 bond, [however, caution must be
invoked when making comparisons as the e.s.d.’s of
/
these CC bond lengths are rather large]. The m(CO)
178.8(5)/171.3(6)8 (Table 2). This small out-of-plane
twist may be a consequence of crystal packing but
moiety exhibits typical distances with the FeÃ
/
C bond
˚
lengths of 1.924(7) and 1.941(7) A and a CO bond length
rotation of the ligand about the m-CÃ/vinyl bond is not
˚
of 1.162(8) A. The FeÃ
81.0(3)8 compared with the 85.8(3)8 for FeÃ
the bridging m-CCHCHR ligand. The FeÃCÃ
are 140.1(6)/138.9(6)8 and the FeÃCÃCH3 angles are
/
COÃ
/
Fe bond angle at CO is
CCÃFe at
Om angles
expected to diminish electronic communication with the
metal cluster [5]. The pyrrolidine donor, however, does
lie almost co-planar with the thiophene [torsion angles
/
/
/
/
/
/
C5RÃ
/
C6RÃ
/
C7RÃ
/
N31ꢄ
/
178.9(6)8;
N31Ã
/
C7RÃ
/
S1Ã
/
140.1(5)/134.1(5)8, perhaps indicating some asymmetry.
The terminal carbonyl ligands are eclipsed with respect
to one another with a dihedral angle of 1.6(2)8 for
C4Rꢄ
/
ꢁ
/
178.7(5)8] and this reflects the high degree of
positive charge, which must be resident on the nitrogen
atom.
O1TÁ Á ÁFe1ÃFe2Á Á ÁO2T. The ligand lies in a slightly
/
The m(CO) moiety has typical distances with the FeÃ
/
˚
C bond lengths of 1.902(7) and 1.915(6) A and with both
twisted arrangement with respect to the plane defined by
˚
the two iron atoms and the m-carbon [with dihedral
CO bond lengths 1.181(6) A. The FeÃ
/
COÃ
/
Fe bond
angles Fe1Ã
175.1(6)8 and C2Ã
as large as the twist observed in the benzothiophene
derivative, 29, 161.8(5)/ꢁ178.8(5)/171.3(6)8. There are
no classical hydrogen bonds in the crystal structure
although there are some CÃHÁ Á ÁF contacts which will
/
C1Ã
/
C2Ã
/
C3 10.4(11)8, C1Ã
/
C2Ã
/
C3Ã/C11,
angle is 83.5(2)8 in contrast to the 81.8(3)8 for the
bridging m-CCH3 in FeÃCCÃFe. The FeÃCObridging
angles are 138.2(5)/139.9(5)8 and the FeÃCÃCH3 angles
are 137.8(4)/138.6(4)8, with little difference between the
two sets of angles. The terminal carbonyl ligands are
eclipsed with respect to one another with 1.7(2)8 for
/
C3Ã
/
C11ÃC12, 9.3(11)8]. This is not
/
/
/
/
/
/
/
/

R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ
/88
79
not be discussed, as they are rather weak and involve
disordered [BF4]ꢁ residues.
do not absorb at the second harmonic, also gave values
ca. 0 times the urea standard.
In 15 the O1MÃ
/
C19Ã
/
C18 and O1MÃ
/
C19Ã
/
C20
It is important to stress that results obtained with the
Kurtz powder technique [10] are very difficult to
angles are markedly different at 114.4(7) and 125.5(7)8.
This asymmetry is a structural feature of arylethers with
the Cambridge Structural Database giving angles of
115.5 and 124.78 [33,34] and has been the subject of
much discussion in the literature [32,33]. It has been
suggested that conjugation of a lone pair on the O atom
with the aromatic p system causes the methoxy group to
lie in the plane of the aryl group: whilst steric interac-
tions between the methyl CH3 and the phenyl/naphthyl-
H atoms may be responsible for the asymmetry in the
interpret in terms of molecular structureꢃproperty
/
relationships, since they depend not only on the
molecular hyperpolarisability b, but also very strongly
on the crystal packing structure, grain size and phase-
matching properties etc. Efficiencies as high as 100 times
urea have been recorded for a perfectly aligned chiral
ferrocene derivative of nitrobenzene but closely related
compounds gave rise to much lower values ranging from
0 to 20 times urea despite their comparable molecular
hyperpolarisabilities [12b,12c]. Even higher SHG has
been observed by Marder and co-workers for a pyr-
idinium derivative of ferrocene (220 times urea) [13] but
was measured at just over one-third of this value by
Daran and Manoury more recently [35]. Indeed many
recorded attempts to produce chiral organometallic [36]
or organic [37] NLO chromophores result in 0 or
negligible powder efficiencies and these results have
often been explained in terms of unfavourable alignment
of otherwise highly NLO chromophores in the crystal
lattice. Often the molecular hyperpolarisabilities are
unreported for these compounds. The situation is
further complicated by the general unpredictability of
crystal packing from the molecular structure. Minute
changes in peripheral groups or even crystallisation
conditions can have a drastic effect on packing and
ultimately the NLO properties. Unfortunately, we were
unable to grow crystals of the chiral chromophores in
either series in order to assess the packing in our
compounds by examination of the angle between the
molecular CT axis and the polar crystal axis if one is
present.
reported OÃ
/
CÃ/C angles.
In Table 2 we have compared bond lengths and angles
of 1 with those of 9, 15 and some related compounds. It
˚
CO 1.95 A
can be seen that the FeÃ
/
Fe and bridging FeÃ
/
bond lengths (mean) are comparable. However, the
˚
bridging FeÃ
/
CC bond lengths (1.84 A mean) are ca.
˚
0.05ꢃ0.10 A shorter than those in 9, 27 and 29 and
/
similar to those in 15 and the benzothiophene salt 28
reported by us previously [8b]. Although it may not be
valid to compare 1 with the other compounds in Table 2,
due to large vibrational motion in the molecular
structures of the two independent Fe2 cationic systems
in 1, it is valid to compare these others amongst
themselves. It can be seen that the strong donor end
groups cause an increase in the FeÃ
/CC distances but a
decrease in the CCÃC (CmÃC) as the ground state
/
/
structure tends towards the cyanine limit. It implies
that with the more positively charged Cm atoms, there is
more donation of electrons from the iron atoms into the
unhybridised Pz orbital on Cm and greater FeÃ
/
Cm bond
CC distances are even greater,
order. In 30 these FeÃ
/
perhaps due to the tetrahedral nature of Cm.
Although zero bulk responses were obtained in our
study, it does not follow that the molecular hyperpolar-
isabilties of these compounds are intrinsically zero.
Previously we have recorded some extremely high b-
values for organometallic merocyanines which incorpo-
rate the powerfully accepting [(C5H5)2Fe2(CO)2(m-
2.5. NLO properties of 6a, 6b, 7a, 7b, 18, 19, 21, 22 and
26
The efficiency of SHG for 6a, 6b, 7a, 7b, 18, 19, 21, 22
and 26 was assessed using the Kurtz powder method
[10]. The samples were prepared by slow diffusion of
diethyl ether into a CH2Cl2 solution of the salts in order
to form microcrystalline powders that were then mulled
to a fine powder and compacted in the sample holder.
Grain sizes were not standardised. All the measurements
were performed at the Nd:YAG laser fundamental
wavelength (1064 nm). Other details of our experimental
setup have been reported elsewhere [1f]. Unsurprisingly
the values for the shorter chromophores 6a (achiral), 6b
(chiral), 18 (R/S and racemate) 21 (R/S and racemate)
and 22 (R/S and racemate) which exhibit UV absor-
bances around the second harmonic at 532, were all 0
times the urea standard. Unfortunately the longer
chromophores 7a (achiral), 7b (chiral), 19 (R/S and
racemate) and 26 (enriched R/S and racemate), which
CO)(m-CÃ
/
)]ꢀ [BF4]ꢁ residue [8]. The HRS technique
[7] was used to obtain the hyperpolarisability (b) of our
most promising compounds 6 and 7 at 1064 nm using
the external reference method. No fluorescence was
detected at 532 nm, the second harmonic frequency, in
any of the cases but for compounds 6 the principle
absorption band falls at this frequency and so, as
expected, no second harmonic light was observed due
to absorption. For compounds 7 however, b-values
were obtained. In the achiral 7a, bꢄ
and for chiral 7b, bꢄ964ꢂ
10ꢁ30 esu. Generally b-
values for organometallic chromophores fall within 50ꢃ
700ꢂ
10ꢁ30 esu [2] and comparison of our results with
/
826ꢂ
/
10ꢁ30 esu
/
/
/
/
this range demonstrate that chomophores 7, and prob-
ably 6, represent extremely efficient NLO molecules. It

80
R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ88
/
is noteworthy that 7b which incorporates the more
highly strained nitrogen-donor ring affords the higher
b-value.
these findings. The efficiency of SHG was measured
using the Kurtz powder method [10]. Our experimental
setup is described elsewhere [1f]. The filtered second
harmonic signals emitted by a randomly sized sample
placed in the holder were collected at a photomultiplier
and measured with a 2 GS/s digital oscilloscope, which
automatically integrates the signal. This integral is
proportional to the SHG efficiency and a quantitative
value was extracted by comparing it with its correspon-
dent from a reference material (urea or KDP) obtained
under the same experimental conditions.
3. Conclusions
The first examples of chiral D-p-A derivatives of 1
have been prepared. This was achieved by the inclusion
of a chiral donor ((S)-(ꢁ)-2-methoxymethylpyrrolidine)
/
to afford 6b and 7b or the use of the chiral bridging 1,1?-
binaphthyl element to afford 18, 19, 21, 22 and 26 (in
both the racemic and R and S series). X-ray structural
analysis of the paradigm complex 1 is reported for the
first time along with structures for 9 and 15, representa-
tive of the two classes of chromophores. Unfortunately
measurement of the solid state NLO properties by the
Kurtz powder technique [10] afforded zero SHG bulk
efficiencies which may be explained in terms of un-
favourable alignment of the dipoles in the crystal lattice.
Measurement of compounds 6 and 7 by the HRS
technique revealed that this series exhibits very high
4.2. (S)-(ꢁ
/
)-5-(2-Methoxymethyl-pyrrolidin-1-yl)-
thiophene-2-carbaldehyde (2b)
Following the procedure of Prim et al. [17] (S)-(ꢀ)-2-
/
(methoxymethyl)-pyrrolidine (0.345 g, 3.0 mmol) and 5-
bromothiophene-2-carboxaldehyde (0.570 g, 3.0 mmol)
were added to water (10 ml) and heated at reflux for 12
h. The cooled mixture was extracted with Et2O (2ꢂ50
/
ml) and the combined organic extracts were dried over
MgSO4. The solvent was removed in vacuo and the
residue was purified by column chromatography on
molecular hyperpolarisabilities (up to 964ꢂ
10ꢁ30 esu).
/
Work is ongoing to design and synthesise the next
generation of chromophores derived from 1 that will
exhibit both high molecular and bulk SHG.
silica gel with 30:70 Et2OꢃCH2Cl2 as the eluant to
/
afford the title compound as a light brown oil (0.34 g) in
Hg
546
1
50% yield. [a]
ꢁ178ꢀ: H-NMR (300 MHz, CDCl3):
d 9.49 (s, 1H, CHO), 7.47 (d, 1H, Jꢄ
(d, 1H, Jꢄ4.4 Hz, Th), 3.86 (m, 1H, NCH (CH2O-
Me)CH2), 3.24ꢃ3.53 (m, 4H, CH2NCH(CH2O-
/
4.4 Hz, Th), 5.97
/
4. Experimental
/
Me)CH2), 3.36 (s, 3H, OMe), 2.11 (m, 4H,
CH2CH2CH2NCH). 13C-NMR (75 MHz, CDCl3): dC
180.2, 164.6, 140.4, 126.5, 103.8, 72.2, 62.4, 59.5, 29.4,
24.2. IR (CH2Cl2, cmꢁ1): 1633.9 (10, nCO), 1534.6 (4),
1371.8 (2), 1351.8 (1), 1141.4 (1), 1110.4 (2), 1055.8 (5).
IR (KBr, cmꢁ1): 1635.6 (9, nCO), 1534.5 (5), 1490.8 (10),
1397.5 (1), 1370.3 (2), 1350.7 (1), 1264.8 (2), 1249.2 (2),
1139.9 (1), 1109.5 (2), 1054.4 (4), 976.0 (1), 922.1 (1),
4.1. General methods
All reactions were performed under a nitrogen atmo-
sphere. Tetrahydrofuran was freshly distilled from
sodium benzophenone ketyl. [Fe2(h5-C5H5)2(CO)2(m-
CO)(m-CÃ
/
CH3)]ꢀ [BF4]ꢁ, 1, was prepared according
to the literature procedure [3]. All other chemicals and
reagents were used as received without further purifica-
tion. Melting points were recorded on an Electrothermal
digital melting point apparatus and are uncorrected. 1H-
NMR spectra were obtained on a Varian INOVA-300
MHz spectrometer or a Varian INOVA-500 MHz
spectrometer. 13C-NMR spectra were obtained on a
Varian INOVA-300 MHz spectrometer or a Varian
INOVA-500 MHz spectrometer operating at 75 and 126
MHz, respectively. FT-IR spectra were obtained on a
744.2 (1), 660.0 (1). UVꢃ/vis (CH2Cl2): lmax 368 nm;
UVꢃvis (MeCN): lmax 367 nm. Anal. Calc. for
/
C11H15NO2S: C, 58.67; H, 6.67; N, 6.22. Found: C,
58.84; H, 6.58; N, 5.98%.
4.3. Preparation of (Z)-(E)-3-(5-piperidin-1-yl-
thiophen-2-yl)-propenal (3a)
5-Piperidin-1-yl-thiophene-2-carboxaldehyde (0.230
g, 1.20 mmol) and 2-tributylphosphinoacetaldehyde
diethyl acetal bromide (2.00 g, 5.0 mmol) were dissolved
in dry THF (25 ml) and potassium tert-butoxide (1.00 g,
8.9 mmol) was added. The reaction was stirred at room
temperature (r.t.) overnight. The mixture was then
filtered through a plug of alumina in a Hirsch funnel
PerkinꢃElmer Paragon 1000 as either a solution in
/
CH2Cl2 (windows: KBr, path length 0.1 mm) or in a
KBr pellet (relative peak heights are given in parenth-
esis). UVꢃ
spectrometer. Optical rotations were performed on a
PerkinꢃElmer 241 polarimeter at 546 nm, in CH2Cl2 at
cꢄ0.1 g/100 ml in a cell of path length 10 cm.
/vis spectra were obtained on a UnicamUV2
/
/
followed by washing with Et2O (2ꢂ50 ml). The solution
/
Spectroscopic assignments and analytical data are given
for the racemic compounds; where appropriate the data
for the enantiopure compounds are in agreement with
was evaporated to dryness and dissolved in THF (50
ml). Oxalic acid dihydrate (1.5 g, 11.9 mmol) was
dissolved in water (20 ml) and added to the reaction

R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ
/88
81
mixture. There was an immediate colour change to dark
green and the solution was stirred for a further 1 h. The
4.5. Preparation of (E)-1-[5-(2-thiophen-2-yl-vinyl)-
thiophen-2-yl]-piperidine (4)
mixture was extracted with Et2O (1ꢂ
aq. layer was neutralised with K2CO3 before being
extracted again with Et2O (2ꢂ100 ml). The combined
extracts were washed with K2CO3 (10% solution in
water) and water (2ꢂ100 ml) and dried over MgSO4
/
100 ml) and the
5-Piperidin-1-yl-thiophene-2-carboxaldehyde (0.390
g, 2.0 mmol) and diethyl(2-thienylmethyl)phosphonate
[18] (1.0 g, 4.30 mmol) were dissolved in dry THF (25
ml) and potassium tert-butoxide (0.495 g, 4.5 mmol)
was added. The reaction was stirred overnight and
quenched with water (50 ml). The mixture was extracted
/
/
before being evaporated to dryness. Recrystalisation
from C6H14 afforded the title compound as a yellow
crystalline solid (0.252 g) in 95% yield. M.p. 91.0ꢃ
/
with Et2O (50 ml), washed with water (2ꢂ50 ml) and
dried over MgSO4 followed by removal of the solvent.
The residue was purified by column chromatography on
/
1
93.5 8C. H-NMR (270 MHz, CDCl3): d 9.44 (d, 1H,
Jꢄ7.9 Hz, CHO), 7.41 (d, 1H, Jꢄ15.0 Hz, ThCH Ä
CHCHO), 7.10 (d, 1H, Jꢄ4.4 Hz, Th), 6.08 (dd, 1H,
Jꢄ7.9, 15.0 Hz, ThCHÄCHCHO), 6.00 (d, 1H, Jꢄ4.2
Hz, Th), 3.29 (t, 4H, Jꢄ5.13 Hz, CH2NCH2), 1.65 (m,
/
/
/
/
silica gel with 1:1 CH2Cl2ꢃ
to afford the title compound in 84% yield (0.462 g), as a
mixture of isomers in the Z ꢃE ratio 1:3 (by NMR).
Crystallisation from C6H14 afforded the major isomer as
yellow crystals: m.p. 126.5ꢃ
127.5 8C. 1H-NMR (300
MHz, CDCl3): d 7.08 (d, 1H, Jꢄ4.8 Hz, Th), 6.94 (m,
2H, Th), 6.90 (d, 1H, Jꢄ16.0 Hz, ThCH ÄCHTh), 6.71
(d, 1H, Jꢄ3.3 Hz, Th), 6.68 (d, 1H, Jꢄ16.0 Hz,
ThCHÄCHTh), 5.91 (1H, d, Jꢄ3.95 Hz, Th), 3.17 (t,
4H, Jꢄ5.27 Hz, CH2NCH2), 1.71 (m, 4H, piperidine),
/petroleum ether as the eluant
/
/
/
/
/
6H, piperidine). 13C-NMR (75 MHz, CDCl3): d 192.6,
165.0, 146.2, 136.5, 123.4, 121.0, 104.5, 51.4, 25.2, 23.8.
IR (CH2Cl2, cmꢁ1): 1657 (6, nCO), 1600 (10), 1526 (3),
1480 (9), 1383 (1), 1367 (1), 1124 (8), 1067 (5). IR (KBr,
cmꢁ1): 1651 (10, nCO), 1597 (10), 1564 (4), 1525 (5),
1479 (9), 1445 (8), 1386 (3), 1367 (3), 1314 (3), 1240 (5),
1133 (5), 1118 (9), 1068 (7), 1041 (2), 1014 (2), 950 (3),
890 (2), 858 (2), 818 (2), 749 (3), 612 (2), 565 (2), 522 (1).
/
/
/
/
/
/
/
/
/
1.57 (m, 2H, piperidine). 13C-NMR (75 MHz, CDCl3): d
159.3, 143.7, 128.3, 127.7, 127.2, 124.5, 123.1, 123.0,
116.9, 104.3, 52.2, 25.4, 24.0. IR (CH2Cl2, cmꢁ1): 1610
(1), 1541 (2), 1514 (5), 1482 (10), 1385 (2), 1227 (2), 1190
(0.5), 1182 (0.5), 1130 (1), 1061 (1), 1012 (1), 936 (2). IR
(KBr, cmꢁ1): 1577 (10), 1542 (1), 1541 (4), 1483 (6),
1446 (7), 1426 (5), 1384 (3), 1247 (4), 1226 (3), 1190 (1),
1181 (1), 1126 (2), 1062 (2), 1012 (2), 936 (3), 888 (2), 861
UVꢃ
/
vis (CH2Cl2): lmax 424 nm; UVꢃvis (MeCN): lmax
/
418 nm. Anal. Calc. for C12H15NOS: C, 65.12; H, 6.83;
N, 6.33. Found: C, 64.90; H, 6.81; N, 6.30%.
4.4. (S)-(ꢁ)-(E)-3-[5-(2-Methoxymethyl-pyrrolidin-
/
1-yl)-thiophen-2-yl]-propenal (3b)
Following the procedure above 2b (0.200 g, 0.89
mmol), 2-tributylphosphinoacetaldehyde diethyl acetal
bromide (1.40 g, 3.50 mmol) and potassium tert-
butoxide (1.00 g, 8.9 mmol) were dissolved in dry
THF (25 ml) and stirred overnight under nitrogen.
Work-up as above and purification by column chroma-
(1), 833 (2), 756 (2), 699 (3). UVꢃ
/
vis (CH2Cl2): lmax 395
nm; UVꢃvis (MeCN): lmax 390 nm; UVꢃ
/
/vis (C6H14):
lmax 383 nm. Anal. Calc. for C15H17NS2: C, 65.41; H,
6.22; N, 5.09. Found: C, 65.05; H, 5.89; N, 5.03%.
4.6. (E)-5-[2-(5-Piperidin-1-yl-thiophen-2-yl)-vinyl]-
thiophene-2-carbaldehyde (5)
tography on silica gel with 30:70 Et2Oꢃ
/
CH2Cl2 as the
eluant afforded the title compound as a light brown oil
Hg
(0.203 g) in 91% yield. [a]
546
ꢁ155ꢀ: 1H-NMR (300
Compound 4 (0.275 g, 1.0 mmol) was dissolved in dry
MHz, CDCl3): d 9.44 (d, 1H, Jꢄ
1H, Jꢄ14.9 Hz, ThCH ÄCHCHO), 7.10 (d, 1H, Jꢄ
Hz, Th), 6.07 (dd, 1H, Jꢄ7.9, 14.9 Hz, ThCHÄ
CHCHO), 5.89 (d, 1H, Jꢄ4.2 Hz, Th), 3.82 (m, 1H,
NCH(CH2OMe)CH2), 3.13ꢃ3.60 (m, 4H,
CH2NCH(CH2OMe)CH2), 3.49 (s, 3H, OMe), 2.02ꢃ
/
8.1 Hz, CHO), 7.40 (d,
THF (15 ml) and cooled to ꢁ78 8C. BuLi (1.6 ml, 4.0
/
/
/
/4.2
mmol, 2.5 mol. sol. in C6H14) was added dropwise and
the mixture was stirred for 1 h. DMF (0.5 ml, 6.4 mmol)
was introduced and the reaction was allowed to warm to
r.t. The mixture was diluted with Et2O (50 ml) and
quenched with water (100 ml). Extraction with Et2O (50
/
/
/
/
/
2.19 (m, 4H, CH2CH2CH2NCH). 13C-NMR (75 MHz,
CDCl3): d 192.5, 161.0, 146.2, 136.8, 122.7, 120.3, 103.6,
72.6, 62.5, 59.5, 52.0, 29.4, 24.2. IR (CH2Cl2, cmꢁ1):
1655.1 (7, nCO), 1600.9 (9), 1526.0 (5), 1385.2 (1), 1354.1
(2), 1197.4 (1), 1124.5 (10), 1054.7 (4). IR (KBr, cmꢁ1):
1656 (5, nCO), 1599 (5), 1526 (6), 1455 (10), 1386 (1),
1353 (2), 1195 (1), 1124 (7), 1054 (3), 1000 (1), 948 (1),
ml), washing with water (4ꢂ50 ml), drying over MgSO4
/
followed by removal of the solvent afforded a red solid.
Purification by column chromatography on silica gel
with CH2Cl2 as the eluant afforded the title compound
in 96% yield (0.29 g). Recrystallisation from Et2Oꢃ
/
1
C6H14 gave red plates: m.p. 139.5ꢃ
(300 MHz, CDCl3): d 9.78 (s, 1H, CHO), 7.59 (d, 1H,
Jꢄ4.0 Hz, Th), 7.14 (d, 1H, Jꢄ15.6 Hz, ThCH Ä
CHTh), 6.97 (d, 1H, Jꢄ4.0 Hz, Th), 6.85 (d, 1H, Jꢄ
4.2 Hz, Th), 6.60 (d, 1H, Jꢄ15.6 Hz, ThCHÄCHTh),
5.93 (d, 1H, Jꢄ4.0 Hz, Th), 3.22 (t, 4H, Jꢄ5.05 Hz,
/
141.0 8C. H-NMR
817 (1), 753 (1). UVꢃ
/
vis (CH2Cl2): lmax 429 nm; UVꢃ
/vis
/
/
/
(MeCN): lmax 425 nm. Anal. Calc. for C13H17NO2S: C,
62.12; H, 6.82; N, 5.57. Found: C, 61.51; H, 6.71; N,
5.42%.
/
/
/
/
/
/

82
R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ88
/
CH2NCH2), 1.71 (m, 4H, piperidine), 1.57 (m, 2H,
piperidine). 13C-NMR (75 MHz, CDCl3): d 182.4,
161.2, 154.3, 140.1, 137.9, 130.6, 127.6, 126.6, 124.8,
114.8, 104.2, 51.9, 25.4, 24.0. IR (CH2Cl2, cmꢁ1): 1656
(10, nCO), 1600 (6), 1538 (2), 1515 (5), 1489 (5), 1383 (4),
1229 (10), 1130 (1), 1063 (3), 1048 (5), 1021 (1), 1013 (1),
936 (2). IR (KBr, cmꢁ1): 1643 (7, nCO), 1589 (6), 1582
(3), 1516 (5), 1432 (10), 1370 (3), 1352 (2), 1288 (3), 1264
(2), 1229 (5), 1122 (1), 1068 (2), 1045 (4), 1007 (2), 934
(4), 892 (2), 857 (2), 828 (3), 800 (2), 756 (4), 738 (1), 650
4.7.2. (S)-[Fe2(h5-C5H5)2(CO)2(m-CO)(m-(E)-CÃ
CHÄCH-2-(5-(2-methoxymethyl-pyrrolidin-1-yl)-
thiophene))]ꢀ [BF4]ꢁ (6b)
/
/
Experimental procedures and work-up were as de-
scribed above. Experimental details: 2b (0.100 g, 0.44
mmol), 1 (0.100 g, 0.23 mmol). Obtained as a dark red
1
solid. Yield: 0.077 g, 52% based on 1. H-NMR (500
MHz, CD2Cl2): d 8.73 (d, 1H, Jꢄ
mC), 8.09 (bs, 1H, Th), 7.82 (d, 1H, Jꢄ
ThCH ÄCH-mC), 6.69 (bs, 1H, Th), 5.06 (s, 10H, Cp),
4.34 (bs, 1H, NCH(CH2OMe)CH2), 3.50ꢃ3.90 (bm, 4H,
CH2NCH(CH2OMe)CH2), 3.37 (s, 3H, OMe), 2.20ꢃ
/
12.2 Hz, ThCHÄ
/
CH-
/
12.02 Hz,
/
(2), 530 (2). UVꢃ
/
vis (CH2Cl2): lmax 470 nm; UVꢃ
/vis
/
(MeCN): lmax 462 nm; UVꢃ/vis (C6H14): lmax 443 nm.
/
Anal. Calc. for C16H17NOS2: C, 63.33; H, 5.65; N, 4.62.
Found: C, 63.39; H, 5.65; N, 4.53%.
2.30 (bm, 4H, CH2CH2CH2NCH). 13C-NMR (75
MHz, CD2Cl2): dC 350.3 (m-C), 262.9 (m-CO), 209.0
(tCO), 174.2, 152.0, 145.5, 143.7, 126.6, 117.0, 72.6,
64.7, 59.7, 54.0, 29.3, 24.1. IR (CH2Cl2, cmꢁ1): 2014
(10, CO), 1981 (2, CO), 1821 (4, CO), 1605 (3), 1507 (7),
1375 (2), 1218 (2), 1190 (2), 1170 (8), 1113 (3), 1061 (3).
IR (KBr, cmꢁ1): 1998 (9, CO), 1965 (4, CO), 1803 (4,
CO), 1572 (1), 1510 (6), 1439 (10), 1374 (3), 1282 (2),
1246 (4), 1219 (5), 1169 (9), 1104 (4), 1084 (5), 914 (1),
4.7. General procedure for the condensation of [Fe2(h5-
C5H5)2(CO)2(m-CO)(m-CÃ
/
CH3)]ꢀ [BF4]ꢁ (1) with
aldehydes
Following the procedure of Casey et al. [4], 1 (one
equivalent) and the required aldehyde (two equivalents)
were stirred at reflux in CH2Cl2 (5ꢃ
/
10 ml). The reactions
851 (1), 778 (1), 708 (1), 629 (2), 587 (3), 551 (2). UVꢃ
/
vis
were monitored by IR spectroscopy for the disappear-
ance of the nCO bands of the starting material that took
ca. 18 h. The volume of the solvent was reduced in vacuo
to half the original amount and the product was isolated
(CH2Cl2): lmax (o) 556 nm (56 960 Mꢁ1 cmꢁ1); UVꢃ
/
vis
(MeCN): lmax (o) 547 nm (51 830 Mꢁ1 cmꢁ1). Anal.
Calc. for C26H26BF4Fe2NO4S×
/
0.8CH2Cl2: C, 44.97; H,
3.86; N, 1.96. Found: C, 44.95; H, 3.86; N, 1.46%.
by precipitation by the addition of Et2O (50ꢃ100 ml).
/
The precipitate was collected by filtration and redis-
solved in a minimum volume of CH2Cl2 before being
reprecipitated by the addition of Et2O (100 ml). This
was repeated and the solid was dried under high
vacuum.
4.7.3. [Fe2(h5-C5H5)2(CO)2(m-CO)(m-(E)-CÃ
CHÃCHÄ
CH-2-(5-piperidin-1-yl-thiophene))]ꢀ
[BF4]ꢁ (7a)
/
CHÄ
/
/
/
Experimental procedures and work-up were as de-
scribed above. Experimental details: 3a (0.090 g, 0.41
mmol), 1 (0.090 g, 0.20 mmol). Obtained as a dark blue
4.7.1. [Fe2(h5-C5H5)2(CO)2(m-CO)(m-(E)-CÃ
CH-2-(5-piperidin-1-yl-thiophene))]ꢀ [BF4]ꢁ (6a)
/
CHÄ
/
1
solid. Yield: 0.084 g, 67% based on 1. H-NMR (500
Experimental procedures and work-up were as de-
scribed above. Experimental details: 5-piperidin-1-yl-
thiophene-2-carboxaldehyde (0.250 g, 1.28 mmol), 1
(0.220 g, 0.50 mmol). Obtained as a dark red solid.
MHz, CD2Cl2): d 8.67 (d, 1H, Jꢄ
CHÃCHÄCH ÃmC), 7.85 (d, 1H, Jꢄ
CHÃCHÄCHÃmC), 7.76 (bs, 1H, Th), 7.47 (dd, 1H, Jꢄ
2ꢂ10.3 Hz, ThCHÄCH ÃCHÄCHÃmC), 6.72 (bs, 1H,
Th), 6.42 (dd, 1H, Jꢄ2ꢂ10.3 Hz, ThCHÄCHÃCH Ä
CHÃmC), 5.02 (s, 10H, Cp), 4.87 (bs, 4H, CH2NCH2),
1.60ꢃ
1.95 (bm, 6H, piperidine). 13C-NMR (75 MHz,
/
10.0 Hz, ThCHÄ
11.2 Hz, ThCH Ä
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
1
Yield: 0.170 g, 55% based on 1. H-NMR (500 MHz,
/
/
/
/
/
CD2Cl2): d 8.61 (d, 1H, Jꢄ
8.20 (d, 1H, Jꢄ4.9 Hz, Th), 7.74 (d, 1H, Jꢄ
ThCH ÄCH-mC), 6.77 (d, 1H, Jꢄ4.6 Hz, Th), 5.06
(10H, s, Cp), 3.79 (bs, 4H, CH2NCH2), 1.60ꢃ1.90 (bm,
/
12.2 Hz, ThCHÄ
/
CH-mC),
/
/
/
12.2 Hz,
/
/
/
CD2Cl2): dC 339.8 (m-C), 263.6 (m-CO), 209.8 (tCO),
175.8, 154.5, 149.8, 148.4, 147.7, 130.8, 118.9, 115.4,
89.4, 54.3, 26.2, 23.5. IR (CH2Cl2, cmꢁ1): 2009 (7, CO),
1981 (2, CO), 1815 (4, CO), 1586 (1), 1545 (3), 1470 (5),
1385 (3), 1360 (2), 1208 (3), 1191 (2), 1146 (10), 1092 (5),
1086 (5), 1018 (2). IR (KBr, cmꢁ1): 1993 (7, CO), 1959
(3, CO), 1801 (4, CO), 1618 (2), 1549 (4), 1473 (6), 1434
(10), 1384 (4), 1279 (1), 1254 (2), 1152 (9), 1132 (9), 1084
(8), 1015 (4), 886 (1), 852 (1), 732 (2), 614 (2), 494 (2).
/
6H, piperidine). 13C-NMR (75 MHz, CD2Cl2): dC 349.4
(m-C), 262.0 (m-CO), 209 (tCO), 176.7, 152.8, 145.0,
143.7, 125.7, 115.8, 89.8, 50.7, 26.3, 23.3. IR (CH2Cl2,
cmꢁ1): 2013 (10, CO), 1982 (2, CO), 1820 (4, CO), 1515
(6), 1456 (6), 1160 (5), 1137 (1), 1100 (3), 1060 (3). IR
(KBr, cmꢁ1): 1996 (10, CO), 1966 (4, CO), 1805 (5),
1522 (6), 1442 (10), 1245 (6), 1170 (9), 1084 (4), 888 (1),
852 (1), 779 (1), 707 (1), 616 (2), 551 (1), 497 (2). UVꢃ
/
vis
UVꢃ
/
vis (CH2Cl2): lmax (o) 658 nm (86 480 Mꢁ1 cmꢁ1).
vis (MeCN): lmax (o) 643 nm (59 580 Mꢁ1 cmꢁ1).
(CH2Cl2): lmax (o) 557 nm (79 560 Mꢁ1 cmꢁ1); UVꢃ
/
vis
(MeCN): lmax (o) 547 nm (67 770 Mꢁ1 cmꢁ1). Anal.
UVꢃ
/
Anal. Calc. for C26H26BF4Fe2NO3S×/0.75CH2Cl2: C,
Calc. for C25H24BF4Fe2NO3S×
/
0.4CH2Cl2: C, 64.82; H,
46.20; H, 3.95; N, 2.02. Found: C, 46.26; H, 3.93; N,
1.90%.
3.81; N, 2.15. Found: C, 46.75; H, 3.79; N, 1.93%.

R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ
/88
83
4.7.4. (S)-[Fe2(h5-C5H5)2(CO)2(m-CO)(m-(E)-CÃ
CHÄCHÃCHÄCH-2-(5-(2-methoxymethyl-pyrrolidin-
1-yl)-thiophene))]ꢀ [BF4]ꢁ (7b)
/
551 nm (52 680 Mꢁ1 cmꢁ1). Anal. Calc. for
C27H28BF4Fe2NO3S×0.75CH2Cl2: C, 46.98; H, 4.16; N,
1.98. Found: C, 46.93; H, 4.21; N, 1.99%. Structure also
/
/
/
/
Experimental procedures and work-up were as de-
scribed above. Experimental details: 3b (0.100 g, 0.40
mmol), 1 (0.100 g, 0.23 mmol). Obtained as a dark red
established by X-ray analysis.
4.8. 2,2?-Dimethoxy-3-(2-(5-
thiophenecarboxaldehyde))-1,1?-binaphthalene (17)
1
solid. Yield: 0.103 g, 65% based on 1. H-NMR (500
MHz, CD2Cl2): d 8.68 (d, 1H, Jꢄ
CHÃCHÄCH ÃmC), 7.88 (d, 1H, Jꢄ
CHÃCHÄCHÃmC), 7.72 (bs, 1H, Th), 7.50 (dd, 1H, Jꢄ
2ꢂ12.0 Hz, ThCHÄCH ÃCHÄCHÃmC), 6.98 (bs, 1H,
Th), 6.47 (dd, 1H, Jꢄ2ꢂ12.2 Hz, ThCHÄCHÃCH Ä
CHÃmC), 5.03 (s, 10H, Cp), 4.29 (bs, 1H, NCH(CH2O-
Me)CH2), 3.50ꢃ3.90 (bm, 4H, CH2NCH(CH2O-
Me)CH2), 3.36 (s, 3H, OMe), 2.15ꢃ2.30 (bm, 4H,
/
11.2 Hz, ThCHÄ
12.2 Hz, ThCH Ä
/
/
/
/
/
/
/
KOtBu (0.112 g, 1.0 mmol) was added to a solution of
2,2?-dimethoxy-3-carboxaldehyde-1,1?-binaphthalene
(16) (0.130 g, 0.38 mmol) (from (R)-1,1?-bi-2-naphthol
/
/
/
/
/
/
/
/
/
/
/
/
/
[a]D:
ꢀ101.68 from (S)-1,1?-bi-2-naphthol [a]D:
/
/
ꢁ
/
100.48) and diethyl(2-thienylmethyl)phosphonate
/
(0.234 g, 1.0 mmol) in dry THF (25 ml). The mixture
was stirred at r.t. under an inert atmosphere for 1 h. The
solution was then poured into a separating funnel
charged with water (50 ml) and extracted with CH2Cl2
/
CH2CH2CH2NCH). 13C-NMR (75 MHz, CD2Cl2): dC
340.7 (m-C), 263.5 (m-CO), 209.8 (tCO), 173.7, 154.8,
148.7, 148.5, 147.7, 131.6, 119.0, 117.0, 89.4, 73.2, 64.9,
59.5, 54.5, 29.4, 24.2. IR (CH2Cl2, cmꢁ1): 2010 (7, CO),
1983 (3, CO), 1816 (4, CO), 1605 (2), 1588 (1), 1537 (4),
1382 (4), 1348 (4), 1168 (9), 1148 (10), 1108 (10), 1081
(6). IR (KBr, cmꢁ1): 1995 (6, CO), 1963 (3, CO), 1804
(4, CO), 1580 (3), 1538 (3), 1434 (10), 1348 (3), 1167 (7),
1147 (7), 1104 (7), 1084 (7), 988 (2), 914 (1), 850 (1), 733
(2ꢂ/50 ml). The organic extracts were combined,
washed with water (2ꢂ/50 ml) and dried over MgSO4.
After removal of the solvent, the yellow oil was purified
by column chromatography on silica gel with 1:1
CH2Cl2ꢃpetroleum ether as the eluant to afford 2,2?-
/
dimethoxy-3-(E-(2-(2-thienyl)ethene)-1,1?-binaphtha-
lene as a yellow solid (0.120 g, 0.28 mmol) in 74% yield.
(1), 613 (1). UVꢃ
Mꢁ1 cmꢁ1); UVꢃ
Mꢁ1 cmꢁ1). Anal. Calc. for C28H28BF4Fe2NO4S×
/vis (CH2Cl2): lmax (o) 655 nm (97 300
M.p. 216ꢃ
(s, 1H, C4Ã
2H, Jꢄ7.9 Hz, aryl), 7.00ꢃ
/
218 8C. 1H-NMR (300 MHz, CDCl3): d 8.15
/vis (MeCN): lmax (o) 640 nm (72 500
/
H), 8.00 (d, 1H, Jꢄ
/
9.0 Hz, C4?Ã/H), 7.87 (d,
/
/
/7.56 (m, 12H, aryl, alkenyl,
1.34CH2Cl2: C, 44.76; H, 3.89; N, 1.78. Found: C,
44.67; H, 4.01; N, 1.65%.
thienyl), 3.79 (s, 3H, OCH3), 3.42 (s, 3H, OCH3). 13C-
NMR (75 MHz, CDCl3): d 155.2, 154.6, 149.9, 137.9,
134.3, 133.9, 131.2, 130.8, 130.0, 129.4, 128.3, 128.2,
127.9, 126.9, 126.4, 126.3, 126.1, 125.8, 125.5, 125.3,
124.8, 124.3, 123.9, 123.8, 119.4, 113.9, 61.3, 56.8. IR
(CH2Cl2, cmꢁ1): 2940 (1.5), 2840 (1.5), 1623 (4), 1594
(4.5), 1510 (4.5), 1460 (4), 1445 (7), 1357 (4), 1334 (2),
1236 (10), 1149 (4.5), 1103 (3.5), 1080 (5), 1046 (3.5),
1006 (4), 960 (3). IR (KBr, cmꢁ1): 2933 (1.5), 2838 (1),
1622 (4), 1592 (5), 1510 (4), 1496 (3), 1473 (3), 1452 (4),
1431 (3.5), 1405 (4), 1357 (4), 1334 (3.5), 1273 (10), 1262
(5), 1240 (5), 1147 (3.5), 1104 (4), 1080 (7), 1043 (2.5),
1007 (5), 956 (4.5), 933 (1), 910 (1), 893 (1.5), 850 (1.5),
805 (5), 776 (1.5), 763 (4.5), 746 (4), 710 (5), 612 (1.5),
600 (0.5), 493 (1.5). UV lmax (CH2Cl2): 339 nm. Anal.
4.7.5. [Fe2(h5-C5H4CH3)2(CO)2(m-CO)(m-(E)-CÃ
CHÄ
CH-2-(5-piperidin-1-yl-thiophene))]ꢀ [BF4]ꢁ (9)
/
/
Compound 8 (0.100 g, 0.26 mmol), 5-piperidin-1-yl-
thiophene-2-carboxaldehyde (2a), (0.250 g, 1.28 mmol)
and tetraflouroboric acid diethyl etherate (five drops)
were mixed in CH2Cl2 (5 ml) and heated at reflux for 4
h. Work-up by precipitation as above afforded the title
compound as a dark red solid (0.130 g) in 77%.
Crystallisation by diffusion of Et2O into a CH2Cl2
solution of the product produced X-ray quality crystals.
1H-NMR (500 MHz, CDCl3): d 8.65 (d, 1H, Jꢄ
Hz, ThCHÄCH ÃmC), 8.10 (d, 1H, Jꢄ5.3 Hz, Th), 7.79
(d, 1H, Jꢄ12.3 Hz, ThCH ÄCHÃmC), 6.71 (d, 1H, Jꢄ
5.3 Hz, Th), 4.65 (bs, 2H, CpÃHa), 4.53 (bs, 2H, CpÃ
Hb), 3.87 (m, 4H, CH2NCH2), 2.18 (s, 6H, CpÃMe),
/
12.3
/
/
/
/
/
/
/
Calc. for C28H22O2S×
Found: C, 78.36; H, 5.12%. From R-1,1?-binaphthyl
[a]D: ꢀ185.58. From S-1,1?-binaphthyl [a]D: ꢁ184.38.
BuLi (0.2 ml, 0.5 mmol, 2.5 mol. solution in C6H14)
was introduced to a cooled solution (ꢁ78 8C) of 2,2?-
/0.1CH2Cl2: C, 78.33; H, 5.16.
/
/
/
/
/
1.83 (bs, 6H, piperidine). 13C-NMR (75 MHz, CDCl3):
dC 353.6 (m-C), 264.4 (m-CO), 209.5 (tCO), 176.0,
152.8, 144.9, 142.6, 125.4, 115.2, 51.8, 26.1, 23.5, 13.3.
IR (CH2Cl2, cmꢁ1): 2009 (7, CO), 1976 (2, CO), 1816 (4,
CO), 1619 (1), 1514 (5), 1383 (1), 1171 (10), 1160 (4),
1137 (2), 1100 (3), 1090 (3), 1064 (3). IR (KBr, cmꢁ1):
1992 (8, CO), 1962 (3, CO), 1802 (4, CO), 1619 (3), 1518
(7), 1441 (10), 1267 (5), 1246 (7), 1169 (10), 1137 (3),
1126 (3), 1084 (5), 886 (2), 853 (1), 778 (1), 707 (1), 615
/
dimethoxy-3-(E -(2-(2-thienyl)ethene)-1,1?-binaphtha-
lene (0.11 g, 0.26 mmol) in dry THF (25 ml). The
mixture was allowed to warm slowly to 0 8C over 1 h
and DMF (0.5 ml) was added. The solution was stirred
for a further 30 min at r.t. and then quenched by the
addition of dilute HCl (50 ml, 0.1 mol). The mixture was
diluted with CH2Cl2 (50 ml) and washed with water
(1), 582 (1), 551 (1), 498 (1). UVꢃ
/
vis (CH2Cl2): lmax (o)
vis (MeCN): lmax (o)
(4ꢂ
/
50 ml). After drying the organic portion over
562 nm (59 440 Mꢁ1 cmꢁ1); UVꢃ
/
MgSO4 the solvent was removed in vacuo and a brown

84
R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ88
/
oil was obtained. This was purified by column chroma-
tography on silica gel with CH2Cl2 as the eluant to
afford the title compound as a yellow solid (0.109 g, 0.24
binaphthyl[a]D: ꢁ
/
495.38. From S-1,1?-binaphthyl[a]D:
ꢀ
/
486.58.
1
mmol) in 92% yield. M.p. (R-isomer) 187ꢃ
/
190 8C. H-
4.10. 2,2?-Dimethoxy-6,6?-bis(E-2-(2-(5-
thiophenecarboxaldehyde))ethenyl)-1,1?-binaphthalene
(25)
NMR (300 MHz, CDCl3): d 9.86 (s, 1H, CHO), 8.19 (s,
1H, C4ÃH), 8.02 (d, 1H, Jꢄ9.1 Hz, aryl) 7.90 (d, 1H,
Jꢄ3.8 Hz, aryl), 7.87 (d, 1H, Jꢄ3.8 Hz, aryl), 7.67 (d,
1H, Jꢄ3.8 Hz, aryl), 7.65 (d, 1H, Jꢄ19.9 Hz, CHÄ
CH), 7.47 (d, 1H, Jꢄ9.1 Hz, aryl) 7.18ꢃ7.42 (m, 7H,
aryl, thienyl), 7.22 (d, 1H, Jꢄ19.9 Hz, CHÄCH), 7.20
/
/
/
/
/
/
/
According to the procedure in Section 4.6, BuLi (0.25
ml, 0.64 mmol, 2.5 mol. solution in C6H14) was reacted
with 24 (0.100 g, 0.19 mmol) followed addition of DMF
(0.5 ml) and acidic aq. quench to afford the title
compound as a yellow solid (0.082 g, 0.13 mmol) in
/
/
/
/
(m, 1H, aryl), 3.80 (s, 3H, OCH3), 3.42 (s, 3H, OCH3).
13C-NMR (75 MHz, CDCl3): d 182.8 (CO), 155.2,
154.6, 153.4, 141.9, 137.4, 134.5, 134.2, 131.1, 130.2,
129.7, 129.3, 129.1, 128.5, 128.3, 127.2, 127.0, 127.0,
126.8, 126.1, 125.8, 125.6, 125.3, 124.0, 122.8, 119.1,
113.8, 61.4, 56.8. IR (CH2Cl2, cmꢁ1): 1660 (10), 1606
(6), 1510 (1), 1497 (1), 1386 (1), 1358 (2), 1149 (2), 1104
(1), 1080 (2), 1048 (2.5), 1021 (0.5), 1005 (1). IR (KBr,
cmꢁ1): 2931 (1), 2834 (1), 1657 (10), 1620 (4), 1591 (4),
1508 (3), 1495 (2.5), 1456 (7), 1437 (6.5), 1408 (2), 1357
(4), 1332 (3), 1266 (7), 1247 (6), 1220 (7), 1146 (4.5),
1101 (3), 1077 (5), 1045 (5), 1019 (3), 1004 (4.5), 951 (2),
906 (1), 893 (1), 807 (5), 778 (2), 748 (5), 663 (1), 643 (1),
608 (1), 534 (1), 476 (1). UV lmax (CH2Cl2): 239, 378 nm.
68% yield. M.p. (R-isomer) 258ꢃ
/
260 8C; (S-isomer)
253 8C. H-NMR (300 MHz, CDCl3): d 9.84 (s,
2H, CHO), 7.99 (d, 2H, Jꢄ9.0 Hz, aryl), 7.90 (s, 2H,
aryl), 7.64 (d, 2H, Jꢄ4.0 Hz, thienyl), 7.47 (d, 2H, Jꢄ
9.0 Hz), 7.42 (dd, 2H, Jꢄ9.0, 1.3 Hz, aryl), 7.29 (d, 2H,
Jꢄ16.3 Hz, CH ÄCHÃthienyl), 7.19 (d, 2H, Jꢄ16.0
Hz, CHÄCH Ãthienyl), 7.12 (d, 2H, Jꢄ4.1 Hz, thienyl),
7.10 (d, 2H, Jꢄ
9.7 Hz, aryl), 3.79 (s, 6H, OCH3). 13C-
1
252ꢃ
/
/
/
/
/
/
/
/
/
/
/
/
/
NMR (75 MHz, CDCl3): d 182.8, 156.0, 153.1, 141.6,
137.5, 134.4, 133.4, 131.5, 130.3, 129.4, 128.5, 126.6,
126.1, 123.9, 120.4, 119.7, 114.8, 57.0. IR (CH2Cl2,
cmꢁ1): 2842 (1), 1662 (10), 1616 (1.5), 1590 (2), 1384
(0.5), 1353 (1), 1232 (5), 1178 (1), 1096 (1), 1064 (1),
1048 (3), 953 (2). IR (KBr, cmꢁ1): 2832 (1), 2792 (1),
1657 (10), 1604 (4), 1588 (4), 1519 (0.5), 1495 (1), 1482
(1), 1447 (8), 1436 (8), 1351 (1.5), 1268 (6), 1254 (6),
1226 (7), 1166 (3), 1095 (3), 1063 (4), 1045 (5), 950 (2),
872 (1), 813 (3), 790 (2.5), 733 (0.5), 678 (0.5), 654 (0.5),
498 (0.5). UV lmax (CH2Cl2): 392 nm. Anal. Calc. for
Anal. Calc. for C29H22O3S×
Found: C, 76.20; H, 5.00%. From R-1,1?-binaphthyl
[a]D: ꢀ221.18. From S-1,1?-binaphthyl [a]D: ꢁ222.98.
/
0.35H2O: C, 767.27; H, 4.97.
/
/
4.9. 2,2?-Dimethoxy-6,6?-bis(E-2-(2-thienyl)ethene)-
1,1?-binaphthalene (24)
According to the procedure in Section 4.8, diethyl(2-
thienylmethyl)phosphonate [18] (0.468 g, 2.0 mmol) was
reacted with 2,2?-dimethoxy-6,6?-dicarboxaldehyde-1,1?-
binaphthalene (0.200 g, 0.54 mmol) followed by pur-
ification in the same way to afford the title compound as
a yellow solid (0.162 g, 0.31 mmol) in 57% yield. M.p.
C36H26O4S2×
73.08; H, 4.79%. From R-1,1?-binaphthyl [a]D: ꢁ
From S-1,1?-binaphthyl [a]D: ꢀ569.18.
/
1CH2Cl2: C, 72.98; H, 3.97. Found: C,
/
650.28.
/
4.10.1. [2-(CHÄ
/
CH-m-CÃ
/
Fe2(m-CO)(h5-
(R and S isomers) 246.5ꢃ
CDCl3): d 7.95 (d, 2H, Jꢄ
Jꢄ7.0 Hz, aryl), 7.44 (d, 2H, Jꢄ
2H, Jꢄ9.1, 1.9 Hz, aryl), 7.23 (d, 2H, Jꢄ
CH Ãthienyl), 7.17 (bd, 2H, Jꢄ4.8 Hz, thienyl), 7.08 (d,
2H, Jꢄ8.6 Hz, aryl), 7.05 (d, 2H, Jꢄ16.0 Hz, CH Ä
CHÃthienyl), 7.05 (bd, 2H, Jꢄ2.6 Hz, thienyl), 6.99
(dd, 2H, Jꢄ5.0, 3.7 Hz, thienyl), 3.77 (s, 6H, OCH3).
/
248 8C. 1H-NMR (300 MHz,
9.0 Hz, aryl), 7.84 (d, 2H,
9.0 Hz, aryl), 7.31 (dd,
16.0 Hz, CHÄ
C5H5)2(CO)2)naphthalene]ꢀ [BF4]ꢁ (13)
/
According to the procedure in Section 4.7, 1 (0.500 g,
1.15 mmol) was condensed with 10 (0.360 g, 2.3 mmol)
to afford 13 as a red solid (0.370 g, 0.66 mmol) in 57%
/
/
/
/
/
1
/
/
yield. H-NMR (500 MHz, acetone-d6): d 10.41 (d, 1H,
/
/
/
Jꢄ
1H, Jꢄ
aryl), 8.05 (d, 1H, Jꢄ
8.4, 7.0 Hz, aryl), 7.76 dd, 1H, Jꢄ
(s, 10H, C5H5). 13C-NMR (126 MHz, acetone-d6): d
441.0 (m-CCHÄ
CH), 254.8 (m-CO), 209.0 (tCO), 153.0,
/
15.0 Hz, m-CCH Ä
14.9 Hz, m-CCHÄ
8.4 Hz, aryl), 7.77 (dd, 1H, Jꢄ
7.9, 7.0 Hz, aryl), 5.73
/CH), 8.90 (s, 1H, aryl), 8.38 (d,
/
/
/
/
CH), 8.13 (d, 2H, Jꢄ8.7 Hz,
/
/
/
/
13C-NMR (75 MHz, CDCl3): d 155.6, 143.5, 138.0,
133.9, 132.6, 129.9, 128.9, 127.9, 126.9, 126.1, 126.0,
124.4, 124.1, 121.5, 119.9, 114.8, 57.1. IR (CH2Cl2,
cmꢁ1): 1605 (10), 1498 (0.5), 1481 (1), 1339 (1), 1166
(0.5), 1096 (1.5), 1064 (1.5), 1044 (1.5). IR (KBr, cmꢁ1):
2931 (1), 2834 (1), 1621 (1.5), 1589 (5), 1497 (3), 1474
(5), 1459 (4.5), 1438 (2), 1334 (3), 1256 (10), 1023 (2),
1164 (2), 1095 (5), 1063 (5), 1042 (5), 947 (6), 888 (1), 855
(1), 824 (3), 803 (4), 696 (6), 668 (1). UV lmax (CH2Cl2):
346, 360 (sh) nm. Anal. Calc. for C34H26O2S2: C, 76.98;
H, 4.90. Found: C, 77.10; H, 5.17%. From R-1,1?-
/
/
152.8, 138.5, 136.8, 134.6, 133.1, 130.4, 129.1, 128.5,
125.9, 93.2 (C5H5). IR (CH2Cl2, cmꢁ1): 2035 (10), 2002
(2.0), 1845 (4.5), 1545 (9). IR (KBr, cmꢁ1): 2028 (10),
1989 (8), 1854 (7.5), 1543 (9). UV lmax (o/Mꢁ1 cmꢁ1
(CH2Cl2): 468 nm (27 400). UV lmax (o/Mꢁ1 cmꢁ1
)
)
(CH3CN): 441 nm (26 000). Anal. Calc. for
C26H19BF4Fe2O3×H2O: C, 52.41; H, 3.52. Found: C,
52.55; H, 3.60%.
/

R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ
/88
85
4.10.2. [2-Methoxy-3-(CHÄ
/
CH-m-CÃ
/
Fe2(m-CO)(h5-
4.10.4. [2,2?-Dimethoxy-3-(CHÄ
/
CH-m-CÃ
/
Fe2(m-
CO)(h5-C5H5)2(CO)2)-1,1?-binaphthalene]ꢀ [BF4]ꢁ
(18)
C5H5)2(CO)2) naphthalene]ꢀ [BF4]ꢁ (14)
As detailed in the procedure in Section 4.7, 1 (0.350 g,
0.8 mmol) was condensed with 11 (0.300 g, 1.6 mmol) to
afford 14 as a red solid (0.328 g, 0.54 mmol) in 68%
As detailed in the procedure for Section 4.7, 1 (0.114
g, 0.26 mmol) was condensed with 16 (0.20 g, 0.58
mmol) to afford 18 as a red solid (0.142 g, 0.19 mmol) in
1
yield. H-NMR (500 MHz, CD2Cl2): d 10.13 (d, 1H,
1
Jꢄ
1H, Jꢄ
aryl), 7.82 (s, 1H, aryl), 7.66 (dd, 1H, Jꢄ
aryl), 7.48 (dd, 1H, Jꢄ7.8, 7.3 Hz, aryl), 7.31 (s, 1H,
aryl), 5.40 (s, 10H, C5H5), 4.16 (s, 3H, OCH3). 13C-
NMR (126 MHz, CD2Cl2): d 437.7 (m-CCHÄCH),
/
14.6 Hz, m-CCH Ä
/
CH), 8.82 (1H, s, aryl), 8.22 (d,
CH), 8.08 (d, 1H, Jꢄ8.3 Hz,
7.8, 7.3 Hz,
73% yield. H-NMR (500 MHz, CD2Cl2): d 10.25 (d,
/
14.6 Hz, m-CCHÄ
/
/
1H, Jꢄ
(d, 1H, Jꢄ
CCHÄCH), 8.07 (d, 1H, Jꢄ
Jꢄ8.5 Hz, aryl), 7.50 (d, 1H, Jꢄ
(m, 1H, aryl), 7.39 (ddd, 1H, Jꢄ8.2, 6.5, 1.1 Hz, aryl),
7.37 (ddd, 1H, Jꢄ8.7, 6.5, 1.1 Hz, aryl), 7.32 (ddd, 1H,
Jꢄ8.7, 6.5, 1.6 Hz, aryl), 7.19 (d, 1H, Jꢄ8.7 Hz, aryl),
7.13 (d, 1H, Jꢄ8.7 Hz, aryl), 5.40 (s, 5H, C5H5), 5.40 (s,
5H, C5H5), 3.83 (s, 3H, OCH3), 3.50 (s, 3H, OCH3). 13C-
NMR (126 MHz, CD2Cl2): d 437.9 (m-CCHÄCH),
/
15.0 Hz, m-CCH Ä
8.0 Hz, aryl), 8.12 (d, 1H, Jꢄ
9.0 Hz, aryl), 7.91 (d, 1H,
10.0 Hz, aryl), 7.48
/
CH), 9.12 (s, 1H, aryl), 8.28
/
/
/
15.0 Hz, m-
/
/
/
/
/
/
/
253.7 (m-CO), 207.8 (tCO), 157.9, 153.2, 149.9, 138.8,
135.3, 131.1, 130.7, 129.7, 127.6, 126.1, 124.7, 107.7,
92.4 (C5H5), 57.0 (OCH3). IR (CH2Cl2, cmꢁ1): 2033
(10), 2004 (2), 1843 (4), 1625 (1.5), 1597 (1), 1537 (7),
1496 (1), 1468 (1), 1386 (1), 1360 (0.5), 1342 (1), 1226
(3), 1218 (2), 1176 (2), 1152 (1), 1115 (1), 1060 (2.5),
1038 (2), 1017 (1.5). IR (KBr, cmꢁ1): 2025 (10), 1990
(3), 1834 (6), 1624 (3), 1596 (2.5), 1535 (8), 1496 (2),
1432 (2), 1418 (0.5), 1386 (1), 1362 (1), 1342 (1.5), 1328
(1), 1282 (2), 1261 (1), 1224 (3.5), 1176 (3), 1149 (2),
1111 (2.5), 1082 (3.5), 1052 (3.5), 1015 (2), 860 (2), 783
(2), 733 (2.5), 687 (0.5), 660 (1), 637 (1), 515 (2.5). UV
lmax (o/Mꢁ1 cmꢁ1) (CH2Cl2): 458 nm (49 300). UV lmax
(o/Mꢁ1 cmꢁ1) (CH3CN): 441 nm (57 700). Anal. Calc.
/
/
/
/
/
254.0 (m-CO), 207.3 (tCO), 156.2, 155.2, 153.4, 153.0,
148.9, 137.8, 134.4, 134.0, 131.5, 131.2, 130.7, 130.3,
129.4, 128.4, 127.4, 127.0, 126.7, 126.0, 125.1, 124.3,
118.1, 113.7, 92.0 (C5H5), 56.8 (OCH3). IR (CH2Cl2,
cmꢁ1): 2036 (10), 2005 (3), 1846 (4), 1618 (1), 1594 (1),
1570 (1), 1538 (7), 1511 (1), 1496 (2), 1377 (1), 1359 (1),
1221 (3), 1190 (1.5), 1107 (2), 1080 (3), 1056 (3). IR
(KBr, cmꢁ1): 3113 (1), 2028 (10), 1994 (sh, 4), 1842 (5),
1618 (1), 1592 (1), 1538 (8), 1495 (2), 1458 (2), 1412
(2.5), 1358 (2), 1335 (1), 1269 (4), 1220 (4), 1150 (1),
1082 (5), 1047 (4.5), 858 (1), 801 (1), 755 (3), 690 (1), 659
(1), 602 (1), 598 (1), 540 (1), 514 (2). UV lmax (o/Mꢁ1
cmꢁ1) (CH2Cl2): 430 (26 200), 460 nm (24 700). UV lmax
(o/Mꢁ1 cmꢁ1) (CH3CN): 421 (24 300), 451 nm (sh,
for C27H21BF4Fe2O4×
/
0.1CH2Cl2: C, 52.75; H, 3.44.
Found: C, 52.71; H, 3.44%.
4.10.3. [2-Methoxy-6-(CHÄ
/
CH-m-CÃ
/
Fe2(m-CO)(h5-
C5H5)2(CO)2) naphthalene]ꢀ [BF4]ꢁ (15)
22 400). Anal. Calc. for C38H29BF4FeO5×
57.74; H, 3.73. Found: C, 57.83; H, 3.95%.
/0.4CH2Cl2: C,
As described in the procedure for Section 4.7, 1 (0.350
g, 0.8 mmol) was condensed with 12 (0.300 g, 1.6 mmol)
to afford 15 as a red solid (0.295 g, 0.49 mmol) in 63%
4.10.5. [2,2?-Dimethoxy-3-(E-2-(5-(E-2-(CHÄ
CÃ
Fe2(m-CO)(h5-C5H5)2(CO)2))thienyl)ethenyl)-
1,1?-binaphthalene]ꢀ [BF4]ꢁ (19)
/CH-m-
1
yield. H-NMR (500 MHz, CD2Cl2): d 10.13 (d, 1H,
/
Jꢄ
1H, Jꢄ
aryl), 7.82 (d, 1H, Jꢄ
7.8, 7.3 Hz, aryl), 7.48 (d, 1H, Jꢄ
(s, 1H, aryl) 5.40 (s, 10H, C5H5), 4.16 (s, 3H, OCH3).
CH),
/
14.6 Hz, m-CCH Ä
14.6 Hz, m-CCHÄ
7.3 Hz, aryl), 7.66 (dd, 1H, Jꢄ
7.8, 7.3 Hz, aryl), 7.31
/
CH), 8.82 (1H, s, aryl), 8.22 (d,
/
/
CH), 8.08 (1H, d, Jꢄ8.3 Hz,
/
As described for the procedure in Section 4.7, 1 (0.066
g, 0.15 mmol) was condensed with 17 (0.110 g, 0.24
mmol) to afford 19 as a red solid (0.109 g, 0.12 mmol) in
80% yield. 1H-NMR (500 MHz, CD2Cl2): d 9.36 (d, 1H,
/
/
/
13C-NMR (126 MHz, CD2Cl2): d 432.2 (m-CCHÄ
/
Jꢄ
1H, Jꢄ
aryl), 7.94 (d, 1H, Jꢄ
Hz, aryl), 7.85 (m, 1H, aryl), 7.76 (d, 1H, Jꢄ
CHÄCH Ãthienyl), 7.58 (d, 1H, Jꢄ15.9 Hz, CH Ä
thienyl), 7.49 (d, 1H, Jꢄ9.0 Hz, aryl), 7.20ꢃ7.40 (m,
5H, aryl), 7.17 (d, 1H, Jꢄ8.1 Hz, aryl), 7.11 (d, 1H, Jꢄ
/
13.4 Hz, m-CCH Ä
12.7 Hz, m-CCHÄ
14.4 Hz, aryl), 7.90 (d, 1H, Jꢄ
15.9 Hz,
CHÃ
/
CH), 8.26 (s, 1H, aryl), 8.25 (d,
CH), 8.04 (d, 1H, Jꢄ9.3 Hz,
8.1
254.4 (m-CO), 207.9 (tCO), 162.3, 154.9, 151.7, 139.2,
139.1, 132.6, 129.9, 129.9, 129.3, 126.6, 121.0, 107.5,
92.2 (C5H5), 56.5 (OCH3). IR (CH2Cl2, cmꢁ1): 2034 (9),
2005 (2), 1844 (4), 1621 (2), 1534 (10), 1497 (1), 1482 (1),
1397 (1), 1349 (3), 1195 (3), 1171 (7), 1154 (5), 1059 (3).
IR (KBr, cmꢁ1): 2025 (9), 1994 (4.5), 1835 (5), 1620 (3),
1534 (10), 1496 (1), 1482 (1), 1419 (2), 1397 (1), 1349 (3),
1285 (2), 1264 (4), 1235 (2.5), 1194 (2.5), 1171 (8), 1084
(4), 1052 (3.5), 855 (1.5), 796 (1.5), 740 (1.5), 683 (1), 634
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
8.3 Hz, aryl), 5.29 (s, 10H, C5H5), 3.82 (s, 3H, OCH3),
3.45 (s, 3H, OCH3). 13C-NMR (126 MHz, CD2Cl2): d
416.9 (m-CCHÄ
CH), 255.8 (m-CO), 207.4 (tCO), 158.7,
/
(1.5), 589 (1), 517 (1.5). UV lmax (o/Mꢁ1 cmꢁ1
(CH2Cl2): 511 nm (60 700). UV lmax (o/Mꢁ1 cmꢁ1
)
)
155.2, 154.7, 149.5, 146.0, 145.6, 138.9, 134.9, 134.2,
131.5, 131.1, 130.9, 130.3, 129.4, 129.3, 128.9, 128.3,
128.0, 127.4, 127.1, 126.2, 125.8, 125.7, 125.3, 124.0,
123.1, 118.9, 113.8, 91.4 (C5H5), 61.6 (OCH3), 56.8
(OCH3). IR (CH2Cl2, cmꢁ1): 2032 (7), 2002 (2), 1841
(CH3CN): 481 nm (49 300). Anal. Calc. for
C27H21BF4Fe2O4×0.4CH2Cl2: C, 51.21; H, 3.40. Found:
C, 51.22; H, 3.44%.
/

86
R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ88
/
(4), 1583 (1), 1532 (10), 1495 (4), 1382 (3), 1370 (3), 1220
(4), 1176 (6), 1150 (2), 1113 (5), 1078 (4), 1059 (4). IR
(KBr, cmꢁ1): 2021 (8), 1990 (4), 1832 (5), 1594 (1), 1531
(10), 1494 (4.5), 1433(6), 1371 (3), 1333 (2), 1264 (4),
1224 (6), 1176 (7), 1125 (4), 1083 (6), 1053 (5.5), 959 (1),
846 (1), 808 (1), 749 (1), 581 (1), 544 (1), 519 (1). UV
lmax (o/Mꢁ1 cmꢁ1) (CH2Cl2): 608 nm (61 600). UV lmax
(o/Mꢁ1 cmꢁ1) (CH3CN): 566 (58 300) nm. Anal. Calc.
4.10.8. [2,2?-Dimethoxy-6,6?-bis(E-2-(2-(5-(E-2-
Fe2(m-CO)(h5-C5H5)2(CO)2))-
(CHÄ
/
CH-m-CÃ
/
thienyl)ethenyl)-1,1?-binaphthalene]ꢀ ([BF4]ꢁ)2 (26)
As summarised in the detailed procedure in Section
4.7, 1 (1.00 g, 2.27 mmol) was condensed with 25 (0.293
g, 0.50 mmol) to afford 26 as a red solid (0.548 g, 0.39
1
mmol) in 77% yield. H-NMR (500 MHz, CD2Cl2): d
9.45 (d, 2H, Jꢄ
4.2 Hz, thienyl), 8.09 (d, 2H, Jꢄ
2H, Jꢄ13.7 Hz, m-CCHÄCH), 7.57 (d, 1H, Jꢄ
Hz, CHÄCH Ãthienyl), 7.52ꢃ7.55 (m, 4H, aryl), 7.39 (d,
2H, Jꢄ15.9 Hz, CH ÄCHÃthienyl), 7.39 (d, 2H, Jꢄ3.9
Hz, thienyl), 7.13 (d, 2H, Jꢄ9.0 Hz, aryl) 5.33 (20H, s,
Cp), 3.83 (s, 6H, OCH3). 13C-NMR (126 MHz,
CD2Cl2): d 415.8 (m-CCHÄCH), 255.3 (m-CO), 208.0
/
13.9 Hz, m-CCH Ä
/
CH), 8.15 (d, 2H, Jꢄ
8.8 Hz, aryl), 8.07 (d,
16.1
/
/
for C44H33BF4Fe2O5S×
/
2CH2Cl2: C, 52.98; H, 3.55.
/
/
/
Found: C, 53.59; H, 3.72%.
/
/
/
/
/
/
/
/
4.10.6. [2,2?-Dimethoxy-3,3?-bis(E-CHÄ
/
CH-m-CÃ
/
Fe2(m-CO)(h5-C5H5)2(CO)2)-1,1?-binaphthalene]ꢀ
([BF4]ꢁ)2 (21)
/
(tCO), 159.9, 157.1, 149.9, 146.2, 145.6, 139.0, 137.0,
135.3, 131.9, 131.2, 131.0, 130.4, 129.9, 126.7, 124.5,
121.2, 119.9, 115.2, 91.8 (Cp), 57.3 (OCH3). IR
(CH2Cl2, cmꢁ1): 2873 (1), 2031 (6), 2000 (2.5), 1840
(4), 1604 (2.5), 1538 (10), 1492 (3.5), 1384 (3.5), 1231 (5),
1170 (6.5), 1113 (5), 1058 (5). IR (KBr, cmꢁ1): 2019 (7),
1986 (sh, 4), 1830 (4), 1598 (2), 1530 (10), 1493 (4), 1432
(6), 1384 (3.5), 1371 (3.5), 1348 (2), 1339 (2), 1259 (4),
1227 (7), 1170 (8), 1113 (4), 1084 (5), 1054 (6), 950 (2),
844 (1), 798 (1), 639 (0.5), 580 (1), 548 (1), 518 (1.5), 484
(0.5). UV lmax (o/Mꢁ1 cmꢁ1) (CH2Cl2): 633 (75 400)
nm. UV lmax (o/Mꢁ1 cmꢁ1) (CH3CN): 594 (75 400) nm.
As detailed in the procedure in Section 4.7, 1 (1.00 g,
0.227 mmol) was condensed with 20a (0.185 g, 0.50
mmol) to afford 21 as a red solid (0.443 g, 0.38 mmol) in
1
76% yield. H-NMR (300 MHz, CD2Cl2): d 10.26 (bm,
2H, m-CCH Ä
/
CH), 9.26 (s, 2H, aryl), 8.26 (bm, 2H, m-
CCHÄCH), 8.14 (bd, 2H, aryl), 7.25ꢃ
/
/7.60 (bm, 6H,
aryl), 5.51 (s, 20H, C5H5), 3.60 (s, 12H OCH3). IR
(CH2Cl2, cmꢁ1): 2034 (10), 1992 (5), 1844 (4), 1540 (5),
1361 (2), 1098 (4.5), 1080 (5), 1066 (5). IR (KBr, cmꢁ1):
2030 (9), 1993 (4), 1840 (4), 1543 (5), 1493 (1), 1476 (1),
1434 (2), 1414 (2), 1398 (1.5), 1337 (1), 1359 (1), 1300
(1), 1266 (2), 1226 (3), 1187 (1), 1104 (8), 1084 (10), 1071
(9), 1037 (10), 850 (1), 804 (1), 760 (1), 667 (1), 534 (2),
522 (2). UV lmax (CH2Cl2): 453 nm. UV lmax (CH3CN):
Anal. Calc. for C66H48B2F8Fe4O8S2×
/
3CH2Cl2: C, 49.14;
H, 3.20. Found: C, 49.28; H, 3.55%.
446 nm. Anal. Calc. for C54H40B2F4Fe4O8×
/1.5H2O: C,
4.11. Crystal structure data for 1, 9 and 15
52.21; H, 3.46. Found: C, 52.29; H, 3.60%.
The crystalline samples of 1 were of very poor quality
and grew as thin red lathes. Several specimens had the
appearance of plastic shavings. Several attempts were
made to obtain a crystal that diffracted satisfactorily
prior to the selection of the sample reported. A small red
4.10.7. [2,2?-Dimethoxy-6,6?-bis(E-CHÄ
/
CH-m-CÃ
/
Fe2(m-CO)(h5-C5H5)2(CO)2)-1,1?-binaphthalene]ꢀ
([BF4]ꢁ)2 (22)
As detailed in the procedure in Section 4.7, 1 (1.00 g,
2.27 mmol) was condensed with 20b (0.211 g, 0.57
mmol) to afford 22 as a red solid (0.489 g, 0.42 mmol) in
crystal with dimensions 0.30ꢂ
/
0.10ꢂ0.05 mm was
/
finally chosen for data collection between 2.5 and 258
on u at 123 K. The crystal hardly diffracted beyond 188
on u. Compound 1 crystallises in the orthorhombic
system. The space group is P21nb or Pmnb. P21nb was
chosen (nonstandard setting of Pna21) and confirmed
by the crystal structure analysis (repeated attempts to
solve the structure in Pmnb were unsuccessful). An
absorption correction was applied and gave minimum
1
73% yield. H-NMR (500 MHz, CD2Cl2): d 9.99 (bm,
2H, m-CCH Ä
/
CH), 8.89 (bs, 2H, aryl), 8.37 (bm, 2H, m-
CCHÄCH), 8.04 (bm, 4H, aryl), 7.79 (bs, 2H, aryl), 7.31
/
(bs, 2H, aryl), 5.45 (s, 20H, C5H5), 3.92 (s, 12H OCH3).
IR (CH2Cl2, cmꢁ1): 2034 (10), 2007 (sh, 5), 1842 (5),
1606 (7), 1531 (10), 1478 (1), 1380 (1.5), 1353 (2), 1221
(5.5), 1167 (6), 1094 (4), 1063 (5.5). IR (KBr, cmꢁ1):
2025 (9), 1991 (sh, 4.5), 1837 (5.5), 1613 (3), 1534 (10),
1478 (3), 1435 (1), 1381 (2), 1354 (3), 1282 (5), 1224
(6.5), 1169 (7), 1083 (5), 1056 (5), 974 (1), 857 (1), 824
(1), 804 (1), 741 (1), 703 (1), 640 (1.5), 520 (2). UV lmax
(o/Mꢁ1 cmꢁ1) (CH2Cl2): 523 (52 000) nm. UV lmax (o/
and maximum transmission factors in the range 0.61ꢃ
/
0.91. The structure was solved using direct methods in
SHELXS-86 [38] and refined by full-matrix least-square
techniques using SHELXL-97 [39]. The hydrogen atoms
were treated as riding atoms with CÃ
/
H distances in the
˚
range 0.93ꢃ
/
0.98 A [SHELXL-97 defaults]. It was evident
M
ꢁ1 cmꢁ1) (CH3CN): 496 (53 200) nm. Anal. Calc. for
at an intermediate stage of refinement {when R[F2ꢀ
/
2s(F2)] was 0.20} that there were minor components
C54H40B2F4Fe4O8: C, 53.38; H, 3.29. Found: C, 53.59;
H, 3.72%.
of disorder associated with the [BF4]ꢁ anion and a Cp

R.D.A. Hudson et al. / Journal of Organometallic Chemistry 655 (2002) 70ꢃ
/88
87
ring. Coordinates for the minor sites of the [BF4]ꢁ
anion and Cp ring were generated and, for the final
refinement cycles, soft DFIX and DELU/ISOR re-
straints were used in the SHELXL-97 calculations, [39].
The atoms of the major conformations of the [BF4]ꢁ
anion and (h5-C5H5) ring were refined with anisotropic
displacement parameters: the minor with isotropic
displacement parameters to final site occupancies of
0.70(4)/0.30(4):0.87(4)/0.13(4) and 0.71(4)/0.29(4), re-
spectively; disorder in a [BF4]ꢁ anion is relatively
common [40]. The final R-factor is 0.149 for 4218
(GOA 2000/03). J.F.G. thanks Dublin City University
for the purchase of a P4 diffractometer. Elemental
analyses were performed by Anne Connolly at Uni-
versity College Dublin.
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/
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