Synthesis, structures and properties of platinum(II) complexes of oligothiophene-functionalized ferrocenylacetylene

Article abstract of DOI:10.1039/b105016h

A series of rigid-rod alkynylferrocenyl precursors with oligothiophene (from thiophene to terthiophene) linkage units in the backbone,[(η⁵-C₅H₅)Fe(η ⁵-C₅H₄)C≡C(C₄H ₂S)_mBr] 2a-2c, [(η⁵-C₅H₅)Fe(η⁵-C ₅H₄)C≡C(C₄H₂S) _mC≡CSiMe₃] 3a-3c and [(η⁵-C₅H₅)Fe(η⁵-C ₅H₄)C≡C(C₄H₂S) _mC≡CH] 4a-4c (m = 1-3), have been prepared in moderate to good yields. The ferrocenylacetylene complexes 4a-4c can be used to form a range of stable platinum(II) alkynyl and bis(alkynyl) compounds trans-[(η⁵-C₅H₅)Fe(η⁵-C ₅H₄)C≡C(C₄H₂S) _mC≡CPt(PEt₃)₂Ph] 5a-5c and trans-[(η⁵-C₅H₅)-Fe(η⁵-C ₅H₄)C≡C(C₄H₂S) _mC≡CPt(PBu₃)₂C≡C(C₄H ₂S)_mC≡C(η⁵-C₅H ₄)Fe(η⁵-C₅H₅)] 6a-6c (m = 1-3). All these new compounds have been fully characterized by analytical and spectroscopic methods and the molecular structures of the bithienyl-linked complexes [(η⁵-C₅H₅)Fe(η⁵-C ₅H₄)C≡C(C₄H₂S) ₂C≡C(η⁵-C₅H₄)Fe(η ⁵-C₅H₅)], 2b, 4b, 5b and 6b have been established by X-ray crystallography. Structural analysis of 6b confirms its rigid-rod structural motif, featuring coplanar bithienyl rings and a trans arrangement of the two bithiophene groups. An iron-iron through-space distance of ca. 32 A is observed in 6b. Although there is no significant metallocene-metallocene interaction through the alkynyl-platinum-oligothiophene bridge, a slight negative shift of the ferrocene-ferrocenium redox potential in the platinum-containing species indicates some degree of electron delocalization into the platinum segment, in line with the results from theoretical studies. Oxidation of the thiophene units is facilitated by the presence of the platinum centre and increased conjugation in the chain.

Full text of DOI:10.1039/b105016h

View Article Online / Journal Homepage / Table of Contents for this issue
Synthesis, structures and properties of platinum(II) complexes of
oligothiophene-functionalized ferrocenylacetylene
Wai-Yeung Wong,*a Guo-Liang Lu,a Ka-Fai Ng,a Ka-Ho Choia and Zhenyang Linb
a Department of Chemistry, Hong Kong Baptist University, Waterloo Road, Kowloon Tong,
Hong Kong, P.R. China. E-mail: rwywong@hkbu.edu.hk
b Department of Chemistry, The Hong Kong University of Science and Technology,
Clearwater Bay, Hong Kong, P.R. China
Received 6th June 2001, Accepted 10th September 2001
First published as an Advance Article on the web 1st November 2001
A series of rigid-rod alkynylferrocenyl precursors with oligothiophene (from thiophene to terthiophene) linkage
5
5
5
5
᎐
᎐
᎐
᎐
m
units in the backbone, [(η -C H )Fe(η -C H )C᎐C(C H S) Br] 2a–2c, [(η -C H )Fe(η -C H )C᎐C(C H S) C᎐CSiMe ]
᎐
᎐
5
5
5
4
4
2
m
5
5
5
4
4
2
3
5
5
᎐
᎐
3a–3c and [(η -C H )Fe(η -C H )C᎐C(C H S) C᎐CH] 4a–4c (m = 1–3), have been prepared in moderate to good
᎐
᎐
5
5
5
4
4
2
m
yields. The ferrocenylacetylene complexes 4a–4c can be used to form a range of stable platinum() alkynyl and
5
5
5
᎐
᎐
᎐
m
᎐
bis(alkynyl) compounds trans-[(η -C H )Fe(η -C H )C᎐C(C H S) C᎐CPt(PEt ) Ph] 5a–5c and trans-[(η -C H )-
᎐
᎐
5
5
5
4
4
5
2
m
3
2
5
5
5
5
᎐
᎐
᎐
Fe(η -C H )C᎐C(C H S) C᎐CPt(PBu ) C᎐C(C H S) C᎐C(η -C H )Fe(η -C H )] 6a–6c (m = 1–3). All these new
᎐
᎐
᎐
5
4
4
2
m
3
2
4
2
5
4
5
5
compounds have been fully characterized by analytical and spectroscopic methods and the molecular structures of
5
5
5
5
᎐
᎐
the bithienyl-linked complexes [(η -C H )Fe(η -C H )C᎐C(C H S) C᎐C(η -C H )Fe(η -C H )], 2b, 4b, 5b and 6b
᎐
᎐
5
5
5
4
4
2
2
5
4
5
5
have been established by X-ray crystallography. Structural analysis of 6b confirms its rigid-rod structural motif,
featuring coplanar bithienyl rings and a trans arrangement of the two bithiophene groups. An iron–iron through-
space distance of ca. 32 Å is observed in 6b. Although there is no significant metallocene–metallocene interaction
through the alkynyl–platinum–oligothiophene bridge, a slight negative shift of the ferrocene–ferrocenium redox
potential in the platinum-containing species indicates some degree of electron delocalization into the platinum
segment, in line with the results from theoretical studies. Oxidation of the thiophene units is facilitated by the
presence of the platinum centre and increased conjugation in the chain.
electrophores and their derivatives offers fascinating perspec-
tives for the design and realization of such molecular wires, due
to its stability in both the neutral and oxidized forms. Tremen-
dous efforts have been devoted to the synthesis of ferrocene-
based materials with π-conjugation.2a,12h,i,13 Although the 1,4-
Introduction
There is a flurry of research interest in the development of
carbon-rich organometallics containing rigid, π-conjugated
chains due to their widespread applications in the syntheses
of unsaturated organic species,1 organometallic polymers,2 and
π-conjugated bi- or multi-metallic systems.3 These organo-
metallic assemblies are important design targets for the investi-
gation of electron-transfer processes,4 the formation of liquid
crystalline materials,5 the construction of molecular devices,6
and the generation of conjugated dendrimers.7 In particular, the
᎐
᎐
diethynylbenzene –C᎐CC H C᎐C– unit has been extensively
᎐
᎐
6
4
used as the π-spacer in organic and homo- and hetero-metallic
oligomers and polymers,14 increasing attention is currently
being paid to materials based on oligothiophenes and poly-
thiophenes because of their remarkable electronic and opto-
electronic properties.15 The ease of modification and knowledge
of the structure–property relationship of poly-thiophenes
continue to make the synthesis of oligo- and poly-thiophenes
a critical subject in the development of new advanced
materials.15,16 Especially, π-conjugation of organometallic
moieties into the oligothiophene chain should provide interest-
ing models that possess unique properties which are not access-
ible in the classical organic counterparts.2,17 Insertion of these
metal groups may promote or inhibit electron delocalization in
such conjugated systems. Evidence indicates that metal acetyl-
ide polymers containing oligothienyl bridges may be good
candidates for conducting materials.15b,18 Following our recent
reports of the synthesis and optical properties of dimeric and
polymeric platinum acetylide compounds with oligothienyl
bridges,19 we have expanded this system to the alkynylferrocenyl
complexes in the quest for new ferrocene-containing materials.
We describe here the chemistry of a series of platinum() com-
plexes of oligothiophene-functionalized ferrocenylacetylene.
᎐
᎐
polyynyls [L M–(C᎐C) –R] and polyyndiyls [L M–(C᎐C) –
᎐
᎐
n
m
n
m
MЈLn] (m = 1, 2, . . .; M = MЈ, M ≠ MЈ) are attractive candidates
for use in the preparation of molecular wires and in the
assembly of nano-scale electronic devices, by virtue of the
possible charge delocalization along the entire conjugated
backbone.8 Molecular wires comprising mixed-valence bi-
metallic fragments or remote redox-active organometallic
building blocks assembled with all-carbon chains could be used
in molecular electronics, optoelectronic devices and chemical
sensing applicances.6b,9 Since the first report of diferrocenyl-
acetylene,10 the interest in these metal-capped linear polycarbon
chains as models for materially useful compounds has dramat-
ically increased.11 Two models are commonly employed to
evaluate the capability of electronic communication between
two terminal metal centres “M1” made possible by an organic
spacer “M1–spacer–M1”, and the influence of an organo-
metallic fragment “M2” in a conjugated organic chain “M1–
spacer–M2–spacer–M1”.11a,12 In several cases, redox active sites
are strongly coupled electronically through the polyynyl frag-
ments.12 It has also been demonstrated that
bis(acetylide) unit allows a significant ground-state interaction
between terminal redox-active groups in some multimetallic
systems.12h,i
a metal
Results and discussion
Synthesis
Scheme 1 summarizes the reaction steps leading to the new ferro-
cenylcompoundsinthisstudy. 2-Bromo-5-(2-ferrocenylethynyl)-
Within this research framework, the use of ferrocenyl
3250
J. Chem. Soc., Dalton Trans., 2001, 3250–3260
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b105016h

View Article Online
i
i
᎐
Scheme 1 Reagents and conditions: (i) NHPr 2, Pd(OAc)2, PPh3, CuI; (ii) Me3SiC᎐CH, NHPr 2, Pd(OAc)2, PPh3, CuI; (iii) K2CO3, MeOH;
᎐
(iv) trans-[Pt(PEt3)2PhCl], NHPri2, CuI; (v) trans-[Pt(PBu3)2Cl2], NHPri2, CuI.
thiophene 2a, 5Ј-bromo-5-(2-ferrocenylethynyl)[2,2Ј]bithio-
Spectroscopic and structural characterization
phene 2b and 5Љ-bromo-5-(2-ferrocenylethynyl)[2,2Ј : 5Ј,2Љ]-
terthiophene 2c were prepared in good yields as orange solids
by the Sonogashira coupling reactions of ethynylferrocene with
an excess of the corresponding dibromothiophenes.13b,20 The
previously reported diferrocenyl bis(alkynyl) complexes 1a–1c
were also formed as minor products in these preparations
and can hardly be avoided.13b We were able to circumvent
the formation of 1,4-diferrocenylbutadiyne under strictly
anaerobic conditions.13b,21 Analogous Pd()/CuI-catalyzed
cross-coupling reactions of 2a–2c with trimethylsilylacetylene
readily afforded the Me3Si-substituted ferrocenyl species 3a–3c
in reasonable yields.19a,20 Removal of the Me3Si groups in 3a–3c
to form 4a–4c was accomplished by treatment with K2CO3 in
MeOH20c and these complexes with the free alkyne group can
be used as key starting products for access to the hetero-
bimetallic and trimetallic systems. The classical dehydrohalo-
genation reactions between 4a–4c and trans-[Pt(PEt3)2PhCl] or
trans-[Pt(PBu3)2Cl2] under the CuI–NHPri2 conditions provided
the alkynyl and bis(alkynyl) platinum() complexes trans-
All the compounds show weak IR stretching vibrations for the
Ϫ1
᎐
C᎐C groups in the range 2077–2229 cm and a characteristic
᎐
᎐
C᎐C–H stretching mode is apparent as an intense peak around
᎐
3270 cmϪ1 for 4a–4c. Essentially, two νC᎐C bands are observed in
᎐
the spectra for 3–6. Those at the higher frequencies appear at
similar energies for the whole series, and the lower frequency
νC᎐C bands are lower in energy for 5 and 6 than the correspond-
ing absorptions for 3 and 4, demonstrating the effect of back-
bonding of the Pt() centre to the acetylide. The proton signals
due to the heteroaromatic and other organic groups were
1
clearly evident from the H NMR spectra. In most cases, the
expected ferrocenyl spectral pattern can be observed where
the unsubstituted C5H5 ring resonates as a strong singlet and
the monosubstituted C5H4 ring gives an unsymmetrical pair
of ‘pseudo’ triplets corresponding to the A2B2 spectrum with
J(adjacent) ≅ J(cross). For 6a–6c, the symmetrical arrangement
of the central platinum bis(acetylide) fragment was noted. The
room-temperature 31P NMR signal of the platinum-containing
species is observed as a sharp singlet accompanied by platinum
satellites in each case. This is consistent with a trans configur-
ation of the coordinated phosphine units around the platinum
centre, which was further confirmed by X-ray structural
determinations for 5b and 6b (vide infra). The 1JP–Pt values range
from 2622–2626 Hz for 5a–5c and 2316–2325 Hz for 6a–6c, as
expected for related trans-PtP2 systems.19,22 The formulae of
these new compounds were also established by the appearance
of intense molecular ion peaks in the respective positive FAB
mass spectra.
5
5
᎐
᎐
[(η -C H )Fe(η -C H )C᎐C(C H S) C᎐CPt(PEt ) Ph]
5a–5c
᎐
᎐
5
5
5
4
4
2
m
᎐
3 2
᎐
5
5
and trans-[(η -C H )Fe(η -C H )C᎐C(C H S) C᎐CPt(PBu ) -
᎐
᎐
5
5
5
5
4
5
4
2
m
3 2
᎐
᎐
C᎐C(C H S) C᎐C(η -C H )Fe(η -C H )] 6a–6c (m
= 1–3),
᎐
᎐
4
2
m
5
4
5
5
respectively,19,22 and they were isolated as air-stable red
crystalline solids in high yields. In all cases, the desired
products were purified by preparative TLC on silica using a
mixture of hexane and CH2Cl2 as eluent and obtained as
solids in high purity. They exhibit moderate to good solu-
bilities in common chlorinated solvents such as CH2Cl2
and CHCl3. Satisfactory analytical and spectroscopic (FTIR,
NMR and MS) data readily establish the exact identity of each
compound and the molecular structures of selected complexes
have been determined unequivocally by single-crystal X-ray
analyses.
Although compound 1b is known in the literature,13b its
structural characterization is not yet reported. The molecular
structures of the bithienyl derivatives 1b, 2b, 4b, 5b and 6b were
determined and are illustrated in Figs. 1–5, respectively, and
J. Chem. Soc., Dalton Trans., 2001, 3250–3260
3251

View Article Online
pertinent bond parameters along with dihedral angles are
collected in Tables 1–5. For 1b, two halves of the molecules are
related by the centre of symmetry at the midpoint of the C(16)–
C(16A) bond. Reminiscent of other transition metal oligo-
geometry with respect to the two thiophene groups. The C(11)–
C(12) bonds are 1.177(3) and 1.197(3) Å, respectively, and the
᎐
free alkyne C᎐C bond distance is 1.169(4) Å in 4b with the bond
᎐
angle C(20)–C(21)–C(22) (179.3(3)Њ) close to linearity. In all the
above three cases, the cyclopentadienyl rings of the ferrocenyl
group are essentially planar and the tilt angles lie within the
narrow range 0.8–1.4Њ. The ferrocenyl moieties have nearly
staggered conformations for the five-membered rings with
an angle deviation of ca. 3.0Њ in each case. The substituted
cyclopentadienyl rings are more or less coplanar with the
2,5-disubstituted bithiophene nucleus and the complete list
of dihedral angles between the planes passing through the
thiophene and the C5H4 rings are tabulated in Tables 1–3.
thienyl acetylide complexes reported such as trans-[Ph(Et3P)2-
19a
᎐
᎐
᎐
PtC᎐CRC᎐CPt(PEt ) Ph]
and trans-[Ru(dppm) (C᎐CR) ]
᎐
᎐
᎐
3
2
2 2
(R = terthiophenediyl),23 the two thiophene rings display a trans
arrangement in order to minimize steric repulsions between the
lone pairs on both sulfur atoms. The iron–iron through-space
distance is estimated to be ca. 17 Å in 1b. The ethynyl bond is
fairly typical at 1.189(3) Å and the linear rigid-rod nature of
the molecule was shown by the C(10)–C(11)–C(12) bond angle
of 174.3(3)Њ. The structures of 2b and 4b both reveal a trans
Fig. 1 A perspective drawing of compound 1b.
Fig. 2 A perspective drawing of compound 2b.
Fig. 3 A perspective drawing of compound 4b.
Fig. 4 A perspective drawing of compound 5b.
3252
J. Chem. Soc., Dalton Trans., 2001, 3250–3260

View Article Online
Fig. 5 A perspective drawing of compound 6b.
Table 1 Selected bond lengths (Å) and angles (Њ) for complex 1b Table 4 Selected bond lengths (Å) and angles (Њ) for complex 5b
Fe(1)–Cp
C(10)–C(11)
C(12)–C(13)
1.6556
1.427(3)
1.423(3)
Fe(1)–C5H4
C(11)–C(12)
C(16)–C(16A)
1.6536
1.189(3)
1.448(4)
Fe(1)–Cp
1.6456
Fe(1)–C5H4
C(11)–C(12)
C(16)–C(17)
C(21)–C(22)
Pt(1)–P(1)
1.6429
C(10)–C(11)
C(12)–C(13)
C(20)–C(21)
Pt(1)–C(22)
Pt(1)–P(2)
1.425(6)
1.412(6)
1.424(5)
2.014(4)
2.291(1)
1.195(6)
1.460(5)
1.197(6)
2.288(1)
2.074(4)
C(10)–C(11)–C(12)
174.3(3)
C(11)–C(12)–C(13)
176.1(2)
Pt(1)–C(35)
Dihedral angles (Њ) between planesa
A and B 0.8 A and C
a Planes: A, defined by C(1)–C(2)–C(3)–C(4)–C(5); B, C(6)–C(7)–C(8)–
C(9)–C(10); C, S(1)–C(13)–C(14)–C(15)–C(16).
C(10)–C(11)–C(12)
C(20)–C(21)–C(22)
C(22)–Pt(1)–C(35)
C(22)–Pt(1)–P(2)
176.9(5)
174.6(5)
175.9(2)
92.6(1)
C(11)–C(12)–C(13)
Pt(1)–C(22)–C(21)
C(22)–Pt(1)–P(1)
178.6(5)
174.7(4)
87.1(1)
6.0
B and C
5.8
Dihedral angles (Њ) between planesa
A and B
A and E
B and E
D and E
0.1
44.4
44.6
52.2
A and C
B and C
C and D
10.7
10.6
3.3
A and D
B and D
C and E
11.4
11.3
53.6
Table 2 Selected bond lengths (Å) and angles (Њ) for complex 2b
Fe(1)–Cp
1.6480
Fe(1)–C5H4
C(11)–C(12)
C(16)–C(17)
1.6463
1.177(3)
1.453(3)
C(10)–C(11)
C(12)–C(13)
Br(1)–C(20)
1.426(3)
1.436(3)
1.870(2)
a Planes: A, defined by C(1)–C(2)–C(3)–C(4)–C(5); B, C(6)–C(7)–C(8)–
C(9)–C(10); C, S(1)–C(13)–C(14)–C(15)–C(16); D, S(2)–C(17)–C(18)–
C(19)–C(20); E, C(35)–C(36)–C(37)–C(38)–C(39)–C(40).
C(10)–C(11)–C(12)
Br(1)–C(20)–S(2)
176.0(3)
120.2(2)
C(11)–C(12)–C(13)
176.6(3)
Table 5 Selected bond lengths (Å) and angles (Њ) for complex 6b
Dihedral angles (Њ) between planesa
A and B
B and C
1.4
14.5
A and C
B and D
15.9
10.4
A and D
C and D
11.8
4.6
Fe(1)–Cp
Fe(2)–Cp
1.6204
1.7031
1.40(1)
1.47(2)
1.44(1)
2.07(1)
2.282(4)
1.30(2)
1.42(1)
1.24(2)
Fe(1)–C5H4
Fe(2)–C5H4
C(11)–C(12)
C(16)–C(17)
C(21)–C(22)
Pt(1)–P(1)
Pt(1)–C(23)
C(24)–C(25)
C(32)–C(33)
C(34)–C(35)
1.6706
1.5897
1.19(2)
1.54(2)
1.15(2)
2.325(3)
1.92(1)
1.51(2)
1.43(2)
1.48(2)
a Planes: A, defined by C(1)–C(2)–C(3)–C(4)–C(5); B, C(6)–C(7)–C(8)–
C(9)–C(10); C, S(1)–C(13)–C(14)–C(15)–C(16); D, S(2)–C(17)–C(18)–
C(19)–C(20).
C(10)–C(11)
C(12)–C(13)
C(20)–C(21)
Pt(1)–C(22)
Pt(1)–P(2)
C(23)–C(24)
C(28)–C(29)
C(33)–C(34)
Table 3 Selected bond lengths (Å) and angles (Њ) for complex 4b
Fe(1)–Cp
1.6525
Fe(1)–C5H4
C(11)–C(12)
C(16)–C(17)
C(21)–C(22)
1.6492
C(10)–C(11)
C(12)–C(13)
C(20)–C(21)
1.433(3)
1.421(3)
1.421(3)
1.197(3)
1.454(3)
1.169(4)
C(10)–C(11)–C(12)
C(20)–C(21)–C(22)
C(22)–Pt(1)–P(1)
C(22)–Pt(1)–C(23)
C(23)–C(24)–C(25)
C(33)–C(34)–C(35)
168(1)
158(1)
93.4(3)
178.3(6)
162(1)
173(1)
C(11)–C(12)–C(13)
Pt(1)–C(22)–C(21)
C(22)–Pt(1)–P(2)
Pt(1)–C(23)–C(24)
C(32)–C(33)–C(34)
159(1)
173(1)
86.2(3)
174(1)
159(1)
C(10)–C(11)–C(12)
C(20)–C(21)–C(22)
176.2(2)
179.3(3)
C(11)–C(12)–C(13)
177.1(2)
Dihedral angles (Њ) between planesa
Dihedral angles (Њ) between planesa
A and B
B and C
1.3
15.5
A and C
B and D
16.8
12.5
A and D
C and D
13.8
3.9
A and B
A and E
A and H
B and E
B and H
C and F
D and E
D and H
E and H
G and H
1.3
5.8
8.9
6.3
7.6
5.5
5.8
15.8
11.2
4.1
A and C
A and F
B and C
B and F
C and D
C and G
D and F
E and F
F and G
9.9
15.2
10.5
15.9
1.6
10.6
4.0
A and D
A and G
B and D
B and G
C and E
C and H
D and G
E and G
F and H
11.5
7.3
12.1
6.3
a Planes: A, defined by C(1)–C(2)–C(3)–C(4)–C(5); B, C(6)–C(7)–C(8)–
C(9)–C(10); C, S(1)–C(13)–C(14)–C(15)–C(16); D, S(2)–C(17)–C(18)–
C(19)–C(20).
4.1
14.6
11.7
7.5
9.6
15.6
19.7
For 5b, the bithiophenediyl-spaced bis(alkynyl) ligand links
a ferrocenyl unit at one end and a Pt(PEt3)2Ph unit at the
other extreme. The two PEt3 groups adopt a trans geometry at
the platinum centre with unexceptional coordination dis-
tances. Unlike the free precursor 4b, the two sulfur atoms in the
bithiophene fragment are arranged on the same side in 5b,
presumably due to solid-state packing effects. An almost stag-
gered conformation is observed for the cyclopentadienyl rings
in 5b with a twist angle of 2.0Њ. All four five-membered
rings within the molecule are nearly coplanar (dihedral angles
0.1–11.4Њ) and the phenyl ring is inclined by ca. 52Њ to the S(2)
a Planes: A, defined by C(1)–C(2)–C(3)–C(4)–C(5); B, C(6)–C(7)–C(8)–
C(9)–C(10); C, S(1)–C(13)–C(14)–C(15)–C(16); D, S(2)–C(17)–C(18)–
C(19)–C(20); E, S(3)–C(25)–C(26)–C(27)–C(28); F, S(4)–C(29)–C(30)–
C(31)–C(32); G, C(35)–C(36)–C(37)–C(38)–C(39); H, C(40)–C(41)–
C(42)–C(43)–C(44).
thienyl mean plane. The alkynyl bond distances C(11)–C(12)
and C(21)–C(22) are 1.195(6) and 1.197(6) Å, respectively,
and do not differ significantly from those seen in, for example,
J. Chem. Soc., Dalton Trans., 2001, 3250–3260
3253

View Article Online
5
5
᎐
᎐
᎐
trans-[Ph(Et P) PtC᎐C(η -C H )Fe(η -C H )C᎐CPt(PEt ) Ph]
᎐
3
2
5
4
5
4
3 2
(1.203(7) Å),22f trans-[Ph(Et P) PtC᎐C{(η -C H )Fe(η -C H ) -
5
5
᎐
᎐
3
2
5
4
5
4 2
Fe(η -C H )}C᎐CPt(PEt ) Ph] (1.21(1) Å),22f trans-[{(η5-C5H5)-
5
᎐
᎐
5
4
3 2
5
᎐
᎐
Fe(η -C H )C᎐C} C H {C᎐CRu(dppm) Cl}] (1.20(2) and
᎐
᎐
5
4
2
6
3
2
1.21(2) Å),24 trans-[Ph(Et P) PtC᎐CRC᎐CPt(PEt ) Ph] (R =
᎐
᎐
᎐
᎐
3
2
3 2
fluorene-2,7-diyl) (1.17(2) and 1.18(2) Å),25 trans-[Ph(Et3P)2-
᎐
᎐
PtC᎐CRC᎐CPt(PEt ) Ph] (R = 9-ferrocenylmethylenefluorene-
᎐
᎐
3
2
2,7-diyl) (1.22(2) and 1.21(2) Å)25 and trans-[{(η5-C5H5)-
Fe(η -C H )C᎐C} Ru(dppm) ] (1.184(8) Å).12h,i The bond
5
᎐
᎐
5
4
2
2
angles C(10)–C(11)–C(12) (176.9(5)Њ) and Pt(1)–C(22)–C(21)
(174.7(4)Њ) are close to 180Њ for the alkynyl fragments.
For 6b, the crystal structure shows a diferrocenyl end-capped
molecule in which the two acetylide linkages are bonded to the
central platinum centre in a trans orientation with normal bond
parameters. The platinum atom is surrounded by four ligands in
a square planar geometry. Within each ferrocenyl subunit, the
cyclopentadienyl rings have a slightly staggered (ca. 6.4–6.9Њ)
conformation, the rings being almost parallel to within 1.3–
4.1Њ. On steric grounds, the bithienyl systems exhibit a trans
conformation for the sulfur atoms and do not deviate signifi-
cantly from planarity (mean deviation of ca. 0.019–0.035 Å). A
slight lengthening of the alkynyl bond lengths (mean distance =
Fig. 6 Absorption spectra of compounds 6a–6c.
1.22(2) Å) suggests π-conjugation along the main chain. The
᎐
rigidity of the complex is confirmed with four C᎐C bonds and
᎐
four thienyl rings connecting the organometallic entities to
afford an iron–iron through-space separation of ca. 32 Å. The
average through-space Fe–Pt distance is 16 Å. However, there
are no intermolecular interactions of note.
Absorption properties
The electronic absorption spectra of all new complexes were
measured in CH2Cl2 solutions and the data are collected in
Table 6. In general, the absorption spectra of the ferrocenyl
precursor complexes 1–4 show intense, relatively high-energy
bands in the near UV and visible region, which arise from the
π–π* transition of the oligothienyl fragments.12c,13b,19,26 This
assignment is in agreement with the fact that an increase in the
extent of π-conjugation with additional thienyl units from one
to three results in a bathochromic shift of the π–π* transition
and a notable increase in the molar absorption coefficients
(Fig. 6).13b Increasing the number of thienyl units in the main
chain stabilizes the lowest unoccupied molecular orbitals of the
oligothiophene linkage. The electronic spectra of the platinum-
containing complexes 5 and 6 are also dominated by the struc-
tureless π–π* transition bands of the corresponding oligothio-
phene bridges.19 The effect of attachment of the platinum()
moiety is found to lower the transition energies and to increase
the absorption intensity, indicating an enhancement in the
degree of π-delocalization through the platinum conjugated
system. These observations also provide evidence for the add-
itional charge-transfer character due to the platinum centre,27
which was further supported by molecular orbital calculations
(vide infra). Again, increasing conjugation through more thienyl
units leads to a decreased transition energy fo 5a–5c as well as
6a–6c. Thus, a red shift of ca. 61 nm is observed from 5a to 5c,
whereas the shift is 57 nm from 6a to 6c (Fig. 6). We note that
λmax decreases according to the sequence 6 > 5 > 1 > 3 > 4 > 2.
However, the extent of bathochromic shifts induced by the end
substitution of organometallic groups is less pronounced with
increasing number of thienyl rings. This substituent effect
diminishes progressively as more thienyl units are added and
there would be little benefit in increasing the number of thio-
phene units above 5 or 6. Such chain length dependence of the
optical properties can be rationalized from the plot of ∆λ
against n (Fig. 7) where ∆λ corresponds to the red shift in wave-
length between the organometallic end-substituted complexes
1, 5 and 6 and the free alkynes 4 in the absence of metal groups,
and n is the number of thiophene units per ferrocenyl end group
in the main chain. From the plot, it is obvious that the shift is
Fig. 7 Bathochromic shifts of the absorption maximum induced by
the end ferrocenyl substitution (ꢀ), end –Pt(PEt3)2Ph substitution (᭿)
and end –Pt(PBu3)2– substitution (᭹), relative to the number of
thiophene units of the chain; the optical data for 1a–1c are taken from
ref. 13b.
the largest for the bis(alkynyl) platinum() complexes 6a–6c at
the same value of n.
Electrochemistry
The electrochemical behaviour of our complexes were studied
by cyclic voltammetry in CH2Cl2 at room temperature and the
results are given in Table 6. In each case, the cyclic voltam-
mogram is characterized by a single quasi-reversible oxid-
ation wave due to the ferrocenyl electrophore that is present in
the complex. An anodic shift of the ferrocene–ferrocenium
couple with respect to the ferrocene standard is in line with the
unsaturation of the ethynyl bridge which makes the removal
of electrons more difficult than for pure ferrocene.28 Clearly, a
small negative shift of the ferrocenyl redox potential occurs
upon progressive insertion of thienyl rings because of the
increased electron density in the ferrocene vicinity induced
by the electron-rich thiophene groups. When the conjugation
length is increased, oxidation is favoured by the delocalization
of charge along the system which renders the ferrocenyl oxid-
ation easier. Likewise, the slight but notable cathodic shift of
the Fe()/Fe() couple for 5 and 6 can be attributed to the
electron delocalization into the platinum segment through a
dπ
pπ interaction.12c It was also found that the first oxid-
ation wave for each of the diferrocenyl compounds 6a–6c
corresponds to a single-step two-electron oxidation involving
the concomitant oxidation of the two terminal ferrocenyl
moieties.13b,29 Analogous to 1b, these two ferrocenyl end groups
only exhibit sparse electronic communication in 6a–6c.13b It has
also been reported that there is very little electronic interaction
between the redox-active iron cores through the metal ethynyl
3254
J. Chem. Soc., Dalton Trans., 2001, 3250–3260

View Article Online
Table 6 Electronic absorption and redox data for ferrocenyl compounds
a
Compound
λmax/nm (ε × 10Ϫ3/MϪ1 cmϪ1
)
Optical gapb/eV
Eox (∆Ep)c
2a
2b
2c
3a
3b
3c
4a
4b
4c
5a
5b
5c
6a
6b
6c
1a
1b
1c
311 (5.0), 445 sh (0.3)
355 (14.4), 460 sh (1.2)
394 (43.3)
327 (17.1), 442 sh (1.0)
374 (30.1)
405 (39.3)
319 (7.1), 429 sh (0.6)
369 (29.0)
404 (40.7)
368 (24.3), 421 (1.4)
405 (32.9)
429 (35.9)
383 (71.3)
3.12
3.03
2.74
3.04
2.90
2.63
2.99
2.92
2.64
2.93
2.75
2.49
2.90
2.57
2.44
2.91
2.72
2.46
0.15 (119)
0.12 (119)
0.11 (119), 0.82d
0.16 (160)
0.11 (139)
0.10 (80), 0.80d
0.16 (139)
0.11 (99)
0.08 (119), 0.72d
0.12 (99), 0.67d
0.10 (119), 0.53d
0.06 (119), 0.38,d 0.70d
0.07 (99), 0.65d
0.04 (116), 0.51d
421 (89.4)
440 (101.5)
0.02 (120), 0.35,d 0.61d
340 (26.7), 445 sh (3.4)e
385 (32.4)e
e
e
e
412 (44.7)e
a All absorption spectra were recorded in CH2Cl2 at 293 K. b Estimated from the absorption edge. c All the potential values are with reference to the
external ferrocene standard. Eox = (Epc ϩ Epa)/2 for reversible oxidation, and peak potential is reported for irreversible oxidation (in volts). ∆Ep in mV.
Scan rate = 100 mV sϪ1 d Irreversible wave. e Ref. 13b.
.
bridge in a series of complexes of the type trans-[(η5-C5H5)-
5
5
5
30
᎐
᎐
Fe(η -C H )C᎐CPt(PR ) C᎐C-(η -C H )Fe(η -C H )]
and
᎐
᎐
5
4
3
2
5
4
5
5
5
5
11a
᎐
᎐
trans-[Pd(PBu ) {C᎐CC H C᎐C(η -C H )Fe(η -C H )} ].
᎐
᎐
3
2
6
4
5
4
5
5
2
Another redox event was also observed at higher positive
potentials in several compounds due to the oxidation of the
thienyl fragments. No such anodic wave was associated with
compounds 2a, 2b, 3a, 3b, 4a and 4b with one or two thiophene
units but without Pt() functionality. However, complexes 2c,
3c and 4c with an increased oligothienyl chain length were
found to undergo an irreversible thienyl oxidation peaking at
0.82, 0.80 and 0.72 V, respectively, which agrees with the com-
mon phenomenon that formation of the heteroaromatic cation
radicals is favoured by the presence of electron-donating end
groups31 and increased in the conjugation in the chain.26b It is
well-documented that electrooxidation of oligothiophenes is
often an irreversible process because the electrogenerated
radical cations readily undergo rapid coupling reactions leading
to higher oligomers or polymers. The stability of these radical
cations increases when the oligomeric chain becomes longer.26b
Insertion of platinum() moieties in 5 and 6 also tends to facili-
tate the oxidation processes of the thienyl core. For complexes
5a–5c or 6a–6c, each of them displays an irreversible thienyl
oxidation wave within 0.38–0.67 V for 5 and 0.35–0.65 V for 6,
and a second irreversible oxidation of the thiophene moiety
also occurs at 0.70 and 0.61 V for 5c and 6c, respectively (Fig. 8).
The waves become more reversible at higher scan rates (>100
mV sϪ1). Lowering of the redox potential of the thiophene units
on increasing the chain length can be verified for 5a–5c as well
as 6a–6c, which is a manifestation of a more π delocalized
system in the terthienyl congeners. As observed for some
thienylenevinylene oligomers, it is likely that the first thienyl
oxidation step is generally followed by chemical reactions or the
formation of a polymer.16c
Fig. 8 Cyclic voltammetric traces of compounds 5a–5c measured in
CH2Cl2 solution (scan rate 100 mV sϪ1).
structural unit(s). To better understand this common feature,
we plot a correlation diagram, depicted in Fig. 9, showing the
frontier molecular orbitals for 5,5Ј-diethynyl[2,2Ј]bithiophene
and compound 4b.33 From Fig. 9, we can see clearly the com-
mon feature that the HOMO and LUMO correspond to π and
π* of the bithiophene aromatic unit. The HOMO–LUMO gap
for 4b is smaller in comparison to the parent bithiophene with-
out the terminal ferrocenyl moiety. This is consistent with the
presence of the metal coordination which enhances the delocal-
ization in the conjugated structural backbone. The main con-
tribution to the second and third HOMOs is mainly from the Fe
2
centre, corresponding to the dxy and dx
Ϫ
y2
orbitals of Fe, if
we define the Cp–Fe–Cp axis as the z-axis of the Cartesian
system (Fig. 9).
Theoretical studies
Fig. 10 shows the molecular orbitals in the frontier region for
all five complexes studied. For each of them, the HOMO–
LUMO transition is related to the π–π* excitation within the
bithiophene structural unit(s). There are two Fe d orbitals
immediately below the HOMO which may give rise to a high-
energy Fe(d)-to-ligand(π*) charge-transfer transition. For
complexes 5b and 6b containing square-planar Pt() coordin-
ation, the energy levels are complicated because of the presence
of Pt–L(σ*) components and the Pt’s empty p orbital in the
LUMO region. We expect that ligand(π)-to-Pt charge transfer is
also accessible in the UV/VIS spectra at high energies. The
To study the electronic structures of these newly synthesized
ferrocenyl complexes, we have carried out molecular orbital
calculations at the B3LYP level of density functional theory for
1b, 2b, 4b, 5b and 6b based on their experimental geometries
obtained from the crystallographic studies.32 For theoretical
simplicity, PH3 was used to replace the phosphines bonded to
the Pt() centre in the calculations. Examining the character-
istics of the highest occupied (HOMO) and lowest unoccupied
(LUMO) molecular orbitals for these complexes, we found that
they are commonly related to π and π* of the bithiophene
J. Chem. Soc., Dalton Trans., 2001, 3250–3260
3255

View Article Online
with the use of standard Schlenk techniques, but no special
precautions were taken to exclude oxygen during work-up.
Solvents were predried and distilled from appropriate drying
agents. All chemicals, unless otherwise stated, were obtained
from commercial sources and used as received. Preparative
TLC was performed on 0.7 mm silica plates (Merck Kieselgel
60 GF254) prepared in our laboratory. The starting materials
ethynylferrocene,34 trans-[Pt(PEt3)2PhCl]35 and trans-[Pt(PBu3)2-
Cl2]36 were prepared by the literature methods. IR spectra were
recorded in CH2Cl2 using a Perkin-Elmer Paragon 1000 PC or
Nicolet Magna 550 Series II FTIR spectrometer. NMR spectra
were measured in appropriate solvents on a JEOL EX270 or a
Varian INOVA 400 MHz FT-NMR spectrometer, with 1H
NMR chemical shifts quoted relative to SiMe4 and 31P chemical
shifts relative to an 85% H3PO4 external standard. Fast atom
bombardment (FAB) mass spectra were recorded on a Finnigan
MAT SSQ710 mass spectrometer. Electronic absorption
spectra were obtained with a Hewlett-Packard 8453 UV-vis
spectrometer. Cyclic voltammetry experiments were done with
a Princeton Applied Research (PAR) model 273A potentiostat.
A conventional three-electrode configuration consisting of a
glassy-carbon working electrode, a Pt-wire counter electrode
and a Ag/AgNO3 reference electrode (0.1 M in acetonitrile) was
used. The solvent in all measurements was deoxygenated
CH2Cl2 and the supporting electrolyte was 0.1 M [Bu4N]BF4.
Ferrocene was added as a calibrant after each set of measure-
ments and all potentials reported were quoted with reference to
the ferrocene–ferrocenium couple. The number of electrons
transferred for compounds 6a–6c was estimated by comparing
the peak height of the respective ferrocene oxidation wave with
an equal concentration of the ferrocene standard added in the
same system, in which one-electron oxidation was assumed. For
density functional calculations at the B3LYP level, the basis set
used for C and H atoms was 6-31G while effective core poten-
tials with a LanL2DZ basis set were employed for P, S, Br, Fe
and Pt atoms. Polarization functions were added for P, S and Br
atoms (ξd(P) = 0.340, ξd(S) = 0.421 and ξd(Br) = 0.389).
Fig. 9 The frontier molecular orbitals for compound 4b and the
parent 5,5Ј-diethynyl[2,2Ј]bithiophene.
HOMO–LUMO gaps shown in Fig. 10 are closely correlated to
the extent of delocalization in the π-conjugation for the com-
plexes. The increase of the π-delocalization by extending the
conjugation system or introducing the metal coordination
results in a smaller optical gap. The calculated relative HOMO–
LUMO gaps are consistent with the experimental energy gap
order 2b > 4b > 5b > 1b > 6b (Table 6) and complex 6b absorbs
at the longest wavelength among the homologous bithiophene
family.
Synthetic procedures
2-Bromo-5-(2-ferrocenylethynyl)thiophene 2a. 2,5-Dibromo-
thiophene (0.11 cm3, 1.00 mmol), ethynylferrocene (105 mg,
0.50 mmol) and NHPri2 (10 cm3) were mixed under N2 with
catalytic amounts of Pd(OAc)2 (1 mg), CuI (1 mg) and PPh3
(2 mg). The mixture was stirred under reflux for 17 h, after
which all volatile components were removed under reduced
pressure. The residue was dissolved in CH2Cl2 and the red solu-
tion filtered through a short silica column. The filtrate was con-
centrated and subjected to preparative TLC separation on silica
using hexane–CH2Cl2 (6 : 1, v/v) as eluent. The orange product
2a (Rf = 0.53) was obtained in 60% yield (111 mg), accompanied
by 15% of the known compound 2,5-bis(ferrocenylethynyl)-
thiophene 1a (Rf = 0.23). (Found: C, 51.50; H, 2.86. C16H11-
BrFeS requires C, 51.79; H, 2.99%). IR (CH2Cl2): 2207 cmϪ1
(νC᎐C). 1H NMR (CDCl3): δ 6.94 (d, JH–H = 4.0 Hz, 1H, thienyl),
6.9᎐1 (d, JH–H = 4.0 Hz, 1H, thienyl), 4.48 (t, JH–H = 1.9 Hz, 2H,
C5H4), 4.25 (t, JH–H = 1.9 Hz, 2H, C5H4) and 4.24 (s, 5H, Cp).
MS (FAB): m/z 371 (calc. Mϩ 371).
Concluding remarks
In summary, a new series of soluble oligothiophene-substituted
alkynylferrocene complexes have been prepared in good yields
and their use in the generation of novel rigid-rod platinum()
complexes has been pursued. Electronic absorption and electro-
chemical studies of these hetero-bimetallic and trimetallic
complexes have been investigated as a function of the oligo-
thienyl chain length. Addition of Pt() decreases the energy of
the π–π* transition in the oligothienyl bridges which is consist-
ent with the theoretical calculations, and increases the absorp-
tion intensity. Electrochemical oxidation of the thiophene
moiety can be facilitated and stabilized by increased conju-
gation length and incorporation of a Pt centre. It is likely that
the redox behaviour of this class of materials can be modulated
and improved by using 3,4-disubstituted thiophene segments
that can exert a stabilizing effect induced by the substituents
on the ionized states. Work in this direction and in extending
this synthetic protocol to design other conjugated ferrocenyl
heterometallic systems incorporating different spacer units or
organometallic fragments is in progress.
5Ј-Bromo-5-(2-ferrocenylethynyl)[2,2Ј]bithiophene 2b. Com-
pound 2b was prepared using the conditions described above
for 2a but 5,5Ј-dibromo[2,2Ј]bithiophene (324 mg, 1.00 mmol)
and ethynylferrocene (105 mg, 0.50 mmol) were used instead to
afford an orange powder of 2b (Rf = 0.30) in 45% yield (102 mg)
along with 5,5Ј-bis(ferrocenylethynyl)[2,2Ј]bithiophene 1b (Rf =
0.15, 14%) after silica TLC purification using hexane–CH2Cl2
(9 : 1, v/v) as eluent. (Found: C, 52.80; H, 2.81. C20H13BrFeS2
Experimental
requires C, 53.01; H, 2.89%). IR (CH2Cl2): 2202 cmϪ1 (νC᎐C). 1H
᎐
General
NMR (CDCl3): δ 7.08 (d, JH–H = 3.8 Hz, 1H, thienyl), 6.97 (d,
All reactions were carried out under a nitrogen atmosphere
JH–H = 3.8 Hz, 1H, thienyl), 6.96 (d, JH–H = 3.8 Hz, 1H, thienyl),
3256
J. Chem. Soc., Dalton Trans., 2001, 3250–3260

View Article Online
Fig. 10 Bonding characteristics of the frontier molecular orbitals for the bithienyl-linked ferrocenyl compounds.
6.91 (d, JH–H = 3.8 Hz, 1H, thienyl), 4.50 (t, JH–H = 2.0 Hz, 2H,
C5H4), 4.27 (t, JH–H = 2.0 Hz, 2H, C5H4) and 4.25 (s, 5H, Cp).
MS (FAB): m/z 453 (calc. Mϩ 453).
= 1.9 Hz, 2H, C5H4) and 4.25 (s, 5H, Cp). MS (FAB): m/z 535
(calc. Mϩ 535).
2-Trimethylsilylethynyl-5-(2-ferrocenylethynyl)thiophene 3a.
3
᎐
5Љ-Bromo-5-(2-ferrocenylethynyl)[2,2Ј : 5Ј,2Љ]terthiophene 2c.
Compound 2c was synthesized similarly from 5,5Љ-dibromo[2,2Ј
: 5Ј,2Љ]terthiophene (406 mg, 1.00 mmol) and ethynylferrocene
(105 mg, 0.50 mmol) and isolated as an orange solid in 35%
yield (94 mg) by TLC on silica (Rf = 0.48) eluting with hexane–
CH2Cl2 (4 : 1, v/v). The diferrocenyl complex 1c was also
formed as a minor orange band (Rf = 0.25, yield 12%). (Found:
C, 53.65; H, 2.71. C24H15BrFeS3 requires C, 53.85; H, 2.82%).
A mixture of 2a (111 mg, 0.30 mmol), Me SiC᎐CH (0.42 cm ,
᎐
3
3.00 mmol) and NHPri2 (10 cm3) combined with catalytic quan-
tities of Pd(OAc)2 (1 mg), CuI (1 mg) and PPh3 (2 mg) were
allowed to reflux for 17 h. The red solid obtained by removing
the solvent in vacuo was redissolved in CH2Cl2. Upon filtration
through a short silica pad, the filtrate was concentrated and
purified by preparative TLC (Rf = 0.35) using hexane–CH2Cl2
(24 : 1, v/v) as eluent. An analytically pure sample of 3a was
collected as an orange solid in an isolated yield of 95% (110
mg). (Found: C, 64.78; H, 5.07. C21H20FeSiS requires C, 64.94;
IR (CH2Cl2): 2199 cmϪ1 (νC᎐C). 1H NMR (CDCl3): δ 7.10 (d, JH–H
᎐
= 3.8 Hz, 1H, thienyl), 7.06 (d, JH–H = 3.8 Hz, 1H, thienyl), 7.02
(d, JH–H = 3.8 Hz, 1H, thienyl), 7.00 (d, JH–H = 3.8 Hz, 1H,
thienyl), 6.97 (d, JH–H = 3.8 Hz, 1H, thienyl), 6.91 (d, JH–H = 3.8
Hz, 1H, thienyl), 4.50 (t, JH–H = 1.9 Hz, 2H, C5H4), 4.26 (t, JH–H
1
H, 5.19%). IR (CH2Cl2): 2210 and 2145 cmϪ1 (νC᎐C). H NMR
᎐
(CDCl3): δ 7.08 (d, JH–H = 4.0 Hz, 1H, thienyl), 7.02 (d, JH–H
=
4.0 Hz, 1H, thienyl), 4.50 (t, JH–H = 1.8 Hz, 2H, C5H4), 4.27 (t,
J. Chem. Soc., Dalton Trans., 2001, 3250–3260
3257

View Article Online
JH–H = 1.8 Hz, 2H, C5H4), 4.25 (s, 5H, Cp) and 0.25 (s, 9H,
SiMe3). MS (FAB): m/z 388 (calc. Mϩ 388).
mixture (10 cm3, 1 : 1, v/v) was added CuI (1 mg). The solution
was stirred at room temperature over 18 h. Evaporation of the
volatile components left behind a reddish residue, purification
of which was accomplished by preparative TLC using hexane–
CH2Cl2 (6 : 1 (5a); 4 : 1, v/v (5b and 5c)) as eluent. Subsequent
removal of the solvent and recrystallization of the product
from the same solvent system led to pure 5a–5c as red-orange
solids.
5a: Yield 60% (30 mg). (Found: C, 52.30; H, 5.61. C36H46-
FeP2PtS requires C, 52.49; H, 5.63%). IR (CH2Cl2): 2201 and
2081 cmϪ1 (νC᎐C). 1H NMR (CDCl3): δ 7.31 (d, JH–H = 6.8 Hz, 2H,
Hortho of Ph), ᎐6.99–6.95 (m, 3H, thienyl ϩ Hmeta of Ph), 6.81 (t,
JH–H = 7.4, 1H, Hpara of Ph), 6.70 (d, JH–H = 3.6 Hz, 1H, thienyl),
4.47 (t, JH–H = 2.0 Hz, 2H, C5H4), 4.24 (m, 7H, Cp ϩ C5H4),
1.78–1.58 (m, 12H, CH2) and 1.13–1.02 (m, 18H, CH3). 31P
NMR (CDCl3): δ 11.04 (1JP–Pt = 2624 Hz). MS (FAB): m/z 824
(calc. Mϩ 824).
5Ј-Trimethylsilylethynyl-5-(2-ferrocenylethynyl)[2,2Ј]bithio-
phene 3b. Compound 3b was prepared in 70% yield (82 mg) by
following a procedure similar to that described for 3a using 2b
(113 mg, 0.25 mmol). (Found: C, 63.75; H, 4.64. C25H22FeSiS2
requires C, 63.82; H, 4.71%). IR (CH2Cl2): 2200 and 2140 cmϪ1
(νC᎐C). 1H NMR (CDCl3): δ 7.11 (d, JH–H = 3.8 Hz, 1H, thienyl),
7.0᎐8 (d, JH–H = 3.8 Hz, 1H, thienyl), 7.02 (d, JH–H = 3.8 Hz, 1H,
thienyl), 7.00 (d, JH–H = 3.8 Hz, 1H, thienyl), 4.50 (t, JH–H
=
1.9 Hz, 2H, C5H4), 4.26 (t, JH–H = 1.9 Hz, 2H, C5H4), 4.25
(s, 5H, Cp) and 0.25 (s, 9H, SiMe3). MS (FAB): m/z 470
(calc. Mϩ 470).
5Љ-Trimethylsilylethynyl-5-(2-ferrocenylethynyl)[2,2Ј:5Ј,2Љ]-
terthiophene 3c. From 2c (107 mg, 0.20 mmol), this procedure
provided the title compound 3c in moderate yield (46%, 51 mg).
(Found: C, 62.85; H, 4.30. C29H24FeSiS3 requires C, 63.03; H,
5b: Yield 74% (40 mg). (Found: C, 52.89; H, 5.21. C40H48-
FeP2PtS2 requires C, 53.04; H, 5.34%). IR (CH2Cl2): 2201 and
4.38%). IR (CH2Cl2): 2229 and 2139 cmϪ1 (νC᎐C). 1H NMR
2080 cmϪ1 (νC᎐C). 1H NMR (CDCl3): δ 7.31 (d, JH–H = 7.2 Hz, 2H,
᎐
᎐
(CDCl3): δ 7.14 (d, JH–H = 4.0 Hz, 1H, thienyl), 7.11 (d, JH–H
=
Hortho of Ph), 7.06 (d, JH–H = 3.6 Hz, 1H, thienyl), 6.99–6.94 (m,
4H, thienyl ϩ Hmeta of Ph), 6.81 (t, JH–H = 7.4, 1H, Hpara of Ph),
6.74 (d, JH–H = 3.6 Hz, 1H, thienyl), 4.49 (t, JH–H = 1.8 Hz, 2H,
C5H4), 4.26 (t, JH–H = 1.8 Hz, 2H, C5H4), 4.25 (s, 5H, Cp), 1.77–
1.70 (m, 12H, CH2) and 1.14–1.06 (m, 18H, CH3). 31P NMR
(CDCl3): δ 11.10 (1JP–Pt = 2626 Hz). MS (FAB): m/z 906 (calc.
Mϩ 906).
4.0 Hz, 1H, thienyl), 7.08 (m, 2H, thienyl), 7.04 (d, JH–H = 4.0
Hz, 1H, thienyl), 7.01 (d, JH–H = 4.0 Hz, 1H, thienyl), 4.51 (t,
JH–H =2.0Hz, 2H, C5H4), 4.27(t, JH–H =2.0Hz, 2H, C5H4), 4.26(s,
5H, Cp) and 0.26 (s, 9H, SiMe3). MS (FAB): m/z 552 (calc. Mϩ
552).
2-Ethynyl-5-(2-ferrocenylethynyl)thiophene 4a. To a solution
of the silylated complex 3a (93 mg, 0.24 mmol) in Et2O (15 cm3)
was added K2CO3 (17 mg, 0.12 mmol) in MeOH (20 cm3). The
mixture was stirred for 24 h at room temperature. After evapor-
ation of the solvent the crude material was dissolved in CH2Cl2
and purified via silica TLC using hexane–CH2Cl2 (5 : 1, v/v) as
eluent to afford a major orange solid (Rf = 0.48) in 93% yield
(71 mg). (Found: C, 68.27; H, 3.71. C18H12FeS requires C,
5c: Yield 86% (51 mg). (Found: C, 53.25; H, 5.01. C44H50-
FeP2PtS3 requires C, 53.49; H, 5.10%). IR (CH2Cl2): 2197 and
2086 cmϪ1 (νC᎐C). 1H NMR (CDCl3): δ 7.31 (d, JH–H = 6.8 Hz, 2H,
᎐
Hortho of Ph), 7.10 (d, JH–H = 3.6 Hz, 1H, thienyl), 7.05 (d, JH–H
=
3.6 Hz, 1H, thienyl), 7.01–6.96 (m, 5H, thienyl ϩ Hmeta of Ph),
6.81 (t, JH–H = 7.0 Hz, 1H, Hpara of Ph), 6.76 (d, JH–H = 3.6 Hz,
1H, thienyl), 4.51 (t, JH–H = 1.8 Hz, 2H, C5H4), 4.27 (t, JH–H
=
1.8 Hz, 2H, C5H4), 4.26 (s, 5H, Cp), 1.78–1.71 (m, 12H, CH2)
and 1.14–1.00 (m, 18H, CH3). 31P NMR (CDCl3): δ 11.09 (1JP–Pt
= 2622 Hz). MS (FAB): m/z 988 (calc. Mϩ 988).
68.37; H, 3.83%). IR (CH2Cl2): 3272 (ν᎐CH), 2201 and 2101 cmϪ1
᎐
(νC᎐C). 1H NMR (CDCl3): δ 7.13 (d, JH–H = 3.6 Hz, 1H, thienyl),
7.0᎐4 (d, JH–H = 3.6 Hz, 1H, thienyl), 4.50 (t, JH–H = 1.6 Hz, 2H,
C5H4), 4.27 (t, JH–H = 1.6 Hz, 2H, C5H4), 4.25 (s, 5H, Cp) and
General procedures for the synthesis of platinum(II)-bridged
diferrocenyl complexes 6a–6c. The compound trans-[Pt(PBu3)2-
Cl2] (20 mg, 0.03 mmol) and two molar equivalents of 4a–4c
(0.06 mmol) were charged in a reaction flask containing a CuI–
NHPri2–CH2Cl2 mixture under a N2 atmosphere and stirred for
18 h under ambient conditions. In each case, the solvent was
then expelled to result in a deep orange product. It was sub-
sequently purified on preparative TLC plates on silica using a
hexane–CH2Cl2 mixture (3 : 1 (6a); 2 : 1 (6b); 4 : 1, v/v (6c))
to give good yields of air-stable reddish orange solids after
recrystallization from the same solvents.
ϩ
᎐
3.36 (s, 1H, C᎐CH). MS (FAB): m/z 316 (calc. M 316).
᎐
5Ј-Ethynyl-5-(2-ferrocenylethynyl)[2,2Ј]bithiophene 4b. The
same desilylation method was employed to give 4b from 3b and
the compound was isolated as an orange powdery solid in 84%
yield by TLC (hexane–CH2Cl2, 3 : 1, v/v, Rf = 0.55). (Found: C,
66.35; H, 3.44. C22H14FeS2 requires C, 66.34; H, 3.54%). IR
1
(CH2Cl2): 3274 (ν᎐CH), 2192 and 2098 cmϪ1 (νC᎐C). H NMR
(CDCl3): δ 7.17 (d᎐, JH–H = 3.7 Hz, 1H, thienyl), 7.10 (d, JH–H
=
᎐
3.7 Hz, 1H, thienyl), 7.05 (d, JH–H = 3.7 Hz, 1H, thienyl), 7.02
(d, JH–H = 3.7 Hz, 1H, thienyl), 4.51 (t, JH–H = 1.9 Hz, 2H, C5H4),
4.27 (t, JH–H = 1.9 Hz, 2H, C5H4), 4.26 (s, 5H, Cp) and 3.42 (s,
6a: Yield 63% (23 mg). (Found: C, 58.35; H, 6.12. C60H76-
Fe2P2PtS2 requires C, 58.59; H, 6.23%). IR (CH2Cl2): 2204 and
ϩ
1
1H, C᎐CH). MS (FAB): m/z 398 (calc. M 398).
2094 cmϪ1 (νC᎐C). H NMR (CDCl3): δ 6.98 (d, JH–H = 4.0 Hz,
᎐
᎐
᎐
2H, thienyl), 6.68 (d, JH–H = 4.0 Hz, 2H, thienyl), 4.48 (t, JH–H
=
5Љ-Ethynyl-5-(2-ferrocenylethynyl)[2,2Ј : 5Ј,2Љ]terthiophene 4c.
Compound 4c was prepared in a similar manner to 3c and the
usual work-up by TLC on silica (hexane–CH2Cl2 7 : 1, v/v) gave
the desired product as an orange solid (Rf = 0.25) in 86% yield.
(Found: C, 64.85; H, 3.44. C26H16FeS3: C, 65.00; H, 3.36%). IR
1.8 Hz, 4H, C5H4), 4.24 (m, 14H, Cp ϩ C5H4), 2.09 (m, 12H,
PCH2), 1.57 (m, 12H, PCH2CH2), 1.48 (m, 12H, CH2CH3) and
0.94 (t, JH–H = 7.6 Hz, 18H, CH3). 31P NMR (CDCl3): δ 4.51
(1JP–Pt = 2322 Hz). MS (FAB): m/z 1230 (calc. Mϩ 1230).
6b: Yield 90% (38 mg). (Found: C, 58.35; H, 5.82. C68H80-
Fe2P2PtS4 requires C, 58.58; H, 5.78%). IR (CH2Cl2): 2199 and
2079 cmϪ1 (νC᎐C). 1H NMR (CDCl3): δ 7.07 (d, JH–H = 3.9 Hz, 2H,
thienyl), 6.96᎐(d, JH–H = 3.9 Hz, 2H, thienyl), 6.94 (d, JH–H = 3.9
Hz, 2H, thienyl), 6.73 (d, JH–H = 3.9 Hz, 2H, thienyl), 4.50 (t,
JH–H = 2.0 Hz, 4H, C5H4), 4.25 (m, 14H, Cp ϩ C5H4), 2.11 (m,
12H, PCH2), 1.60 (m, 12H, PCH2CH2), 1.49 (m, 12H, CH2CH3)
and 0.95 (t, JH–H = 7.6 Hz, 18H, CH3). 31P NMR (CDCl3): δ 4.49
(1JP–Pt = 2325 Hz). MS (FAB): m/z 1394 (calc. Mϩ 1394).
1
(CH2Cl2): 3272 (ν᎐CH), 2201 and 2098 cmϪ1 (νC᎐C). H NMR
(CDCl3): δ 7.18 (d᎐, JH–H = 4.0 Hz, 1H, thienyl), 7.11 (d, JH–H
=
᎐
4.0 Hz, 1H, thienyl), 7.09 (d, JH–H = 4.0 Hz, 1H, thienyl), 7.08
(d, JH–H = 4.0 Hz, 1H, thienyl), 7.04 (d, JH–H = 4.0 Hz, 1H,
thienyl), 7.03 (d, JH–H = 4.0 Hz, 1H, thienyl), 4.51 (t, JH–H
=
1.8 Hz, 2H, C5H4), 4.27 (t, JH–H = 1.8 Hz, 2H, C5H4), 4.25
᎐
(s, 5H, Cp) and 3.43 (s, 1H, C᎐CH). MS (FAB): m/z 480 (calc.
᎐
Mϩ 480).
6c: Yield 70% (33 mg). (Found: C, 58.32; H, 5.22. C76H84-
Fe2P2PtS6 requires C, 58.57; H, 5.43%). IR (CH2Cl2): 2202 and
2077 cmϪ1 (νC᎐C). 1H NMR (CDCl3): δ 7.10 (d, JH–H = 3.9 Hz, 2H,
General procedures for the synthesis of platinum(II) complexes
5a–5c. To a mixture of trans-[Pt(PEt3)2PhCl] (33 mg, 0.06
mmol) and 4a–4c (0.06 mmol) in deoxygenated CH2Cl2–NHPri2
thienyl), 7.05᎐(d, JH–H = 3.9 Hz, 2H, thienyl), 7.01 (d, JH–H
=
3258
J. Chem. Soc., Dalton Trans., 2001, 3250–3260

View Article Online
Table 7 Crystal data for complexes 1b, 2b, 4b, 5b and 6b
1b
2b
4b
5b
6b
Empirical formula
M
C32H22Fe2S2
582.32
C20H13BrFeS2
453.18
C22H14FeS2
398.30
C40H48FeP2PtS2
905.78
C68H80Fe2P2PtS4
1394.29
Crystal system
Space group
Monoclinic
P21/n
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/n
Triclinic
P1
T /K
a/Å
b/Å
c/Å
α/Њ
β/Њ
293(2)
293(2)
293(2)
293(2)
293(2)
5.9211(4)
18.602(1)
11.2551(8)
5.8596(4)
27.334(2)
10.7396(7)
5.8487(4)
28.156(2)
10.7594(7)
10.9280(6)
14.6387(8)
24.620(2)
10.271(1)
11.198(2)
14.226(2)
95.844(3)
101.305(2)
93.949(3)
1589.5(4)
1
101.799(1)
96.729(1)
97.990(1)
96.225(1)
γ/Њ
U/Å3
1213.5(2)
2
1.389
1708.2(2)
4
3.464
1754.6(2)
4
1.098
3915.2(4)
4
4.154
Z
µ(Mo-Kα)/mmϪ1
2.866
No. reflections collected
7112
2747 (0.0231)
2747
R1 = 0.0281
wR2 = 0.0704
R1 = 0.0397
wR2 = 0.0794
9988
3852 (0.0220)
3852
R1 = 0.0289
wR2 = 0.0723
R1 = 0.0361
wR2 = 0.0808
10265
3953 (0.0220)
3953
R1 = 0.0283
wR2 = 0.0736
R1 = 0.0371
wR2 = 0.0866
22570
8725 (0.0200)
8725
R1 = 0.0320
wR2 = 0.0950
R1 = 0.0418
wR2 = 0.0995
9617
8227 (0.0312)
8227
R1 = 0.0563
wR2 = 0.1253
R1 = 0.1010
wR2 = 0.1544
Unique reflections (Rint
)
Observed reflections [I > 2σ(I )]
R indicesa
[I > 2σ(I )]
R indices
(all data)
2
a R1 = Σ Fo| Ϫ |Fc /Σ|Fo|. wR2 = {Σ[w(Fo2 Ϫ Fc2)2]/Σ[w(Fo )2]}1/2
.
3.9 Hz, 2H, thienyl), 6.99 (d, JH–H = 3.9 Hz, 2H, thienyl), 6.96
(d, JH–H = 3.9 Hz, 2H, thienyl), 6.74 (d, JH–H = 3.9 Hz, 2H,
thienyl), 4.51 (t, JH–H = 1.8 Hz, 4H, C5H4), 4.27 (t, JH–H = 1.8 Hz,
4H, C5H4), 4.26 (s, 10H, Cp), 2.11 (m, 12H, PCH2), 1.59 (m,
Acknowledgements
Financial support from the Hong Kong Baptist University
(FRG/00-01/II-57) is gratefully acknowledged.
12H, PCH2CH2), 1.49 (m, 12H, CH2CH3) and 0.96 (t, JH–H
=
7.0 Hz, 18H, CH3). 31P NMR (CDCl3): δ 4.46 (1JP–Pt = 2316 Hz).
MS (FAB): m/z 1559 (calc. Mϩ 1559).
References
1 U. H. F. Bunz, Angew. Chem., Int. Ed. Engl., 1994, 33, 1073;
F. Diederich, Modern Acetylene Chemistry, P. J. Stang and
F. Diederich, ed., VCH Publishers, Weinheim, Germany, 1995,
p. 443; U. H. F. Bunz, Y. Rubin and Y. Tobe, Chem. Soc. Rev., 1999,
28, 107.
2 (a) I. Manners, Angew. Chem., Int. Ed. Engl., 1996, 35, 1602; (b) R. P.
Kingsborough and T. M. Swager, Prog. Inorg. Chem., 1999, 48, 123.
3 N. Le Narvor, L. Toupet and C. Lapinte, J. Am. Chem. Soc., 1995,
117, 7129; W. Weng, T. Bartik and J. A. Gladysz, Angew. Chem.,
Int. Ed. Engl., 1994, 33, 2199; M. C. B. Colbert, J. Lewis, N. J. Long,
P. R. Raithby, M. Younus, A. J. P. White, D. J. Williams, N. N. Payne,
L. Yellowlees, D. Beljonne, N. Chawdhury and R. H. Friend,
Organometallics, 1998, 17, 3034; U. H. F. Bunz and J. E. C.
Wiegelmann-Kreiter, Chem. Ber., 1996, 129, 785 and references
therein; M. I. Bruce, J.-F. Halet, S. Kahal, P. J. Low, B. W. Skelton
and A. H. White, J. Organomet. Chem., 1999, 578, 155.
Crystallography
Yellow crystals of 1b, 2b, 4b, 5b and 6b suitable for X-ray dif-
fraction studies were grown by slow evaporation of their
respective solutions in hexane–CH2Cl2 at room temperature.
Geometric and intensity data were collected using graphite-
monochromated Mo-Kα radiation (λ = 0.71073 Å) on a
Bruker AXS SMART 1000 CCD area-detector. Cell param-
eters and orientation matrices for all crystal samples were
obtained from the least-squares refinement of reflections meas-
ured in three different sets of 15 frames each. The collected
frames were processed with the software SAINT37a and an
absorption correction was applied (SADABS)37b to the
collected reflections.
4 V. Grosshenny, A. Harriman and R. Ziessel, Angew. Chem., Int. Ed.
Engl., 1995, 34, 1100.
The space groups of each crystal were determined from the
systematic absences and Laue symmetry check and confirmed
by successful refinement of the structure. The structures of
these molecules were solved by direct methods (SHELXTL)38
in conjunction with standard difference Fourier techniques and
subsequently refined by full-matrix least-squares analyses on
F 2. Except for 5b and 6b, all non-hydrogen atoms were assigned
with anisotropic displacement parameters. For 6b, only the
heavy atoms were refined anisotropically and constraints were
placed on the C–C bond distances of the ferrocenyl moieties.
For 5b, all ethyl groups were refined isotropically and those
attached to the P(2) atom showed positional disorder in which
a two-sites model with occupancy factors of 0.5 each was
applied. The resulting model was refined to convergence and
yielded reasonable bond lengths and angles. Hence, no hydro-
gen atoms were included for these disordered ethyl groups in the
Fc calculations. In all other cases, the hydrogen atoms were
generated in their idealized positions and allowed to ride on the
respective carbon atoms. Crystal data and other experimental
details are summarized in Table 7.
5 M. Altmann and U. H. F. Bunz, Angew. Chem., Int. Ed. Engl., 1995,
34, 569; L. Oriol and J. L. Serrano, Adv. Mater., 1995, 7, 348.
6 (a) J.-M. Lehn, Supramolecular Chemistry: Concepts and
Perspectives, VCH Publishers, Weinheim, Germany, 1995; (b) M. D.
Ward, Chem. Soc. Rev., 1995, 121; (c) J. M. Tour, Chem. Rev., 1996,
96, 537.
7 S. Campagna, G. Denti, S. Serroni, A. Juris, M. Venturi, V. Riceunto
and V. Balzani, Chem. Eur. J., 1995, 1, 211; R. Faust, F. Diederich,
V. Gramlich and P. Seiler, Chem. Eur. J., 1995, 1, 111; A. J. Amoroso,
A. M. W. Cargill-Thompson, J. P. Maher, J. A. McCleverty
and M. D. Ward, Inorg. Chem., 1995, 34, 4828; S. Achar and
R. Puddephatt, Angew. Chem., Int. Ed. Engl., 1994, 33, 847.
8 M. D. Ward, Chem. Ind., 1996, 568; U. H. F. Bunz, Angew. Chem.,
Int. Ed. Engl., 1996, 35, 969; H. Lang, Angew. Chem., Int. Ed. Engl.,
1994, 33, 547; W. Beck, B. Niemer and M. Wieser, Angew. Chem.,
Int. Ed. Engl., 1993, 32, 923 and references therein; R. D. Markwell,
I. S. Butler, A. K. Kakkar, M. S. Khan, Z. H. Al-Zakwani and
J. Lewis, Organometallics, 1996, 15, 2331.
9 J. A. McCleverty and M. D. Ward, Acc. Chem. Res., 1998, 31, 842.
10 C. Le Vanda and D. O. Cowan, J. Am. Chem. Soc., 1974, 96, 6728.
11 (a) O. Lavastre, J. Plass, P. Bachmann, A. Salaheddine, C. Moinet
and P. H. Dixneuf, Organometallics, 1997, 16, 184; (b) M. Brady,
W. Weng, Y. Zhou, J. W. Seyler, A. J. Amoroso, A. M. Arif,
M. Böhme, G. Frenking and J. A. Gladysz, J. Am. Chem. Soc., 1997,
119, 775; (c) H. Schimanke and R. Gleiter, Organometallics, 1998,
17, 275.
CCDC reference numbers 165361–165365.
See http://www.rsc.org/suppdata/dt/b1/b105016h/ for crystal-
lographic data in CIF or other electronic format.
J. Chem. Soc., Dalton Trans., 2001, 3250–3260
3259

View Article Online
12 (a) Z. Yuan, G. Stringer, I. R. Jobe, D. Kreller, K. Scott, L. Koch,
N. J. Taylor and T. B. Marder, J. Organomet. Chem., 1993, 452, 115;
(b) H. Schimanke and R. Gleiter, Organometallics, 1998, 17, 275;
(c) K. R. Justin Thomas, J. T. Lin and K.-J. Lin, Organometallics,
1999, 18, 5285; (d ) A. Hradsky, B. Bildstein, N. Schuler,
H. Schottenberger, P. Jaitner, K.-H. Ongania, K. Wurst and
J.-P. Launay, Organometallics, 1997, 16, 392; (e) S. L. Stang, F. Paul
and C. Lapinte, Organometallics, 2000, 19, 1035; ( f ) M. Brady,
W. Weng and J. A. Gladysz, J. Chem. Soc., Chem. Commun., 1994,
2655; (g) K. R. Justin Thomas, J. T. Lin and Y. S. Wen, J. Organomet.
Chem., 1999, 575, 301; (h) N. D. Jones, M. O. Wolf and D. M.
Giaquinta, Organometallics, 1997, 16, 1352; (i) M. C. B. Colbert,
J. Lewis, N. J. Long, P. R. Raithby, A. J. P. White and D. J. Williams,
J. Chem. Soc., Dalton Trans., 1997, 99; (j) V. Grosshenny,
A. Harriman, M. Hissler and R. Ziessel, J. Chem. Soc., Faraday
Trans., 1996, 92, 2223; (k) J. A. Thomas, C. J. Jones, J. A.
McCleverty and M. G. Hutchings, Polyhedron, 1996, 15, 1409.
13 (a) N. J. Long, Metallocenes: An Introduction to Sandwich
Complexes, Blackwell Science, Oxford, UK, 1998; (b) K. R. Justin
Thomas, J. T. Lin and Y. S. Wen, Organometallics, 2000, 19, 1008;
(c) M. C. B. Colbert, A. J. Edwards, J. Lewis, N. J. Long, N. A. Page,
D. G. Parker and P. R. Raithby, J. Chem. Soc., Dalton Trans., 1994,
2589; (d ) M. C. B. Colbert, D. Hodgson, J. Lewis, P. R. Raithby and
N. J. Long, Polyhedron, 1995, 14, 2759; (e) S.-M. Lee, M. Marcaccio,
J. A. McCleverty and M. D. Ward, Chem. Mater., 1998, 10, 3272.
14 K. Sonogashira, K. Ohga, S. Takahashi and N. Hagihara,
J. Organomet. Chem., 1980, 188, 237; S. Takahashi, K. Sonogashira,
H. Morimoto, E. Murata, S. Kataoka and N. Hagihara, J. Polym.
Sci., Polym. Chem. Educ., 1982, 20, 565; O. Lavastre, M. Even,
P. H. Dixneuf, A. Pacreau and J. P. Vairon, Organometallics, 1996,
15, 1530.
20 (a) K. Sonogashira, Y. Tohda and N. Hagihara, Tetrahedron Lett.,
1975, 4467; (b) M. S. Khan, A. K. Kakkar, N. J. Long, J. Lewis,
P. R. Raithby, P. Nguyen, T. B. Marder, F. Wittmann and R. H.
Friend, J. Mater. Chem., 1994, 4, 1227; (c) S. Takahashi,
Y. Kuroyama, K. Sonogashira and N. Hagihara, Synthesis, 1980,
627.
21 Z. Yuan, G. Stringer, I. R. Jobe, D. Kreller, K. Scott, L. Koch,
N. J. Taylor and T. B. Marder, J. Organomet. Chem., 1993, 452, 115;
J.-G. Rodriguez, A. Oñate, R. M. Martin-Villamil and I. Fonseca,
J. Organomet. Chem., 1996, 513, 71; H. Fink, N. J. Long, A. J.
Martin, G. Opromolla, A. J. P. White, D. J. Williams and P. Zanello,
Organometallics, 1997, 16, 2646.
22 (a) K. Sonogashira, Y. Fujikura, T. Yatake, N. Toyoshima,
S. Takahashi and N. Hagihara, J. Organomet. Chem., 1978, 145, 101;
(b) K. Sonogashira, S. Kataoka, S. Takahashi and N. Hagihara,
J. Organomet. Chem., 1978, 160, 319; (c) J. Lewis, P. R. Raithby and
W.-Y. Wong, J. Organomet. Chem., 1998, 556, 219; (d ) W.-Y. Wong,
S.-M. Chan, K.-H. Choi, K.-W. Cheah and W.-K. Chan, Macromol.
Rapid Commun., 2000, 21, 453; (e) H. Zhang, A. W. M. Lee, W.-Y.
Wong and M. S. M. Yuen, J. Chem. Soc., Dalton Trans., 2000, 3675;
( f ) N. J. Long, A. J. Martin, R. Vilar, A. J. P. White, D. J. Williams
and M. Younus, Organometallics, 1999, 18, 4261; (g) W.-Y. Wong,
K.-H. Choi, G.-L. Lu and J.-X. Shi, Macromol. Rapid Commun.,
2001, 22, 461.
23 Y. Zhu, D. B. Millet, M. O. Wolf and S. J. Rettig, Organometallics,
1999, 18, 1930.
24 N. J. Long, A. J. Martin, A. J. P. White, D. J. Williams, M. Fontani,
F. Laschi and P. Zanello, J. Chem. Soc., Dalton Trans., 2000, 3387.
25 W.-Y. Wong, W.-K. Wong and P. R. Raithby, J. Chem. Soc., Dalton
Trans., 1998, 2761.
26 (a) J. W. Sease and L. Zechmeister, J. Am. Chem. Soc., 1947, 69, 270;
(b) P. Garcia, J. M. Pernaut, P. Hapiot, V. Wintgens, P. Valat,
F. Garnier and D. Delabouglise, J. Phys. Chem., 1993, 97, 513.
27 C. Lopez and J. Granell, J. Organomet. Chem., 1998, 555, 211;
J. Burdeniuk and D. Milstein, J. Organomet. Chem., 1993, 451, 213.
28 M. Sato, E. Mogi and S. Kamakura, Organometallics, 1995, 14,
3157; H. Lang, K. Köhler and S. Blau, Coord. Chem. Rev., 1995,
143, 113; S. Back, G. Rheinwald and H. Lang, Organometallics,
1999, 18, 4119.
15 (a) R. D. McCullough, Adv. Mater., 1998, 10, 93 and references cited
therein; (b) Handbook of Conducting Polymers, T. A. Skotheim,
ed., Marcel Dekker, New York, 1986; (c) J. Roncali, Chem. Rev.,
1997, 97, 173; (d ) A. Kraft, A. C. Grimsdale and A. B. Holmes,
Angew. Chem., Int. Ed., 1998, 37, 402.
16 (a) W.-L. Yu, H. Meng, J. Pei, Y.-H. Lai, S.-J. Chua and W. Huang,
Chem. Commun., 1998, 1957; (b) H. Nakanishi, N. Sumi, A. Yoshio
and T. Otsubo, J. Org. Chem., 1998, 63, 8632; (c) I. Jestin, P. Frère,
N. Mercier, E. Levillain, D. Stievenard and J. Roncali, J. Am. Chem.
Soc., 1998, 120, 8150; (d ) D. D. Graf and K. R. Mann, Inorg. Chem.,
1997, 36, 150; (e) D. D. Graf, R. G. Duan, J. P. Campbell,
L. L. Miller and K. R. Mann, J. Am. Chem. Soc., 1997, 119, 5888;
( f ) U. Mitschke, E. Mena Osteritz, T. Debaerdemaeker,
M. Sokolowski and P. Bäuerle, Chem. Eur. J., 1998, 4, 2211.
17 T. P. Pollagi, T. C. Stoner, R. F. Dallinger, T. M. Gilbert and
M. D. Hopkins, J. Am. Chem. Soc., 1991, 113, 703; J. C. Calabrese,
L.-T. Cheng, J. C. Green, S. R. Marder and W. Tam, J. Am. Chem.
Soc., 1991, 113, 7227; L. K. Meyers, C. Langhoff and M. E.
Thompson, J. Am. Chem. Soc., 1992, 114, 7560; D. L. Lichtenberger,
S. K. Renshaw and R. M. Bullock, J. Am. Chem. Soc., 1993, 115,
3276.
18 H. E. Katz, J. Mater. Chem., 1997, 7, 369; N. J. Long, Angew. Chem.,
Int. Ed. Engl., 1995, 34, 21; B. Servet, G. Horowitz, S. Ries,
O. Lagorsse, P. Alnot, A. Yassar, F. Deloffre, P. Srivastava,
R. Hajlaoui, P. Lang and F. Garnier, Chem. Mater., 1994, 6, 1809.
19 (a) J. Lewis, N. J. Long, P. R. Raithby, G. P. Shields, W.-Y. Wong
and M. Younus, J. Chem. Soc., Dalton Trans., 1997, 4283;
(b) N. Chawdhury, A. Köhler, R. H. Friend, W.-Y. Wong, J. Lewis,
M. Younus, P. R. Raithby, T. C. Corcoran, M. R. A. Al-Mandhary
and M. S. Khan, J. Chem. Phys., 1999, 110, 4963.
29 W.-Y. Wong, G.-L. Lu, K.-F. Ng, C.-K. Wong and K.-H. Choi,
J. Organomet. Chem., in press.
30 D. Osella, L. Milone, C. Nervi and M. Ravera, J. Organomet. Chem.,
1995, 488, 1; D. Osella, R. Gobetto, C. Nervi, M. Ravera,
R. D’Amato and M. V. Russo, Inorg. Chem. Commun., 1998, 1,
239.
31 P. Bäuerle, Adv. Mater., 1992, 4, 102.
32 A. D. Becke, J. Chem. Phys., 1993, 98, 5648; B. Miehlich, A. Savin,
H. Stoll and H. Preuss, Chem. Phys. Lett., 1989, 157, 200; C. Lee,
W. Yang and G. Parr, Phys. Rev. B, 1988, 37, 785.
33 G. Schaftenaar, Molden v3.5, CAOS/CAMM Center Nijmegen,
Toernooiveld, Nijmegen, The Netherlands, 1999.
34 M. Rosenblum, N. Brawn, J. Papenmeier and M. Applebaum,
J. Organomet. Chem., 1966, 6, 173.
35 J. Chatt and B. L. Shaw, J. Chem. Soc., 1960, 4020.
36 J. Chatt and R. G. Hayter, J. Chem. Soc., Dalton Trans., 1961,
896.
37 (a) SAINT, Reference manual, Siemens Energy and Automation,
Madison, WI, 1994–1996; (b) G. M. Sheldrick, SADABS, Empirical
Absorption Correction Program, University of Göttingen, 1997.
38 G. M. Sheldrick, SHELXTL, Reference manual, v5.1, Madison,
WI, 1997.
3260
J. Chem. Soc., Dalton Trans., 2001, 3250–3260