The synthesis and characterisation of 1′-ethynyl-2,5-dimethylazaferrocene and derivatives

Article abstract of DOI:10.1016/j.jorganchem.2006.05.043

The synthesis of 1′-ethynyl-2,5-dimethylazaferrocene is reported along with its cyclic voltammetry measurements and the X-ray structure determination of its W(CO)₅-complex. Basic coordination and organic chemistry of 1′-ethynyl-2,5-dimethylazaf

Full text of DOI:10.1016/j.jorganchem.2006.05.043

Journal of Organometallic Chemistry 691 (2006) 3902–3908
www.elsevier.com/locate/jorganchem
The synthesis and characterisation of
10-ethynyl-2,5-dimethylazaferrocene and derivatives
a,b,
a
b,
*
Konrad Kowalski
Sławomir Domagała , Andrew J.P. White
*, Janusz Zakrzewski , Nicholas J. Long
,
c
b
a
Department of Organic Chemistry, Institute of Chemistry, University of Ło´dz´, Narutowicza 68, 90-136 Ło´dz´, Poland
b
Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, UK
Department of General and Inorganic Chemistry, Institute of Chemistry, University of Ło´dz´, Narutowicza 68, 90-136 Ło´dz´, Poland
c
Received 4 May 2006; received in revised form 19 May 2006; accepted 19 May 2006
Available online 3 June 2006
Abstract
The synthesis of 10-ethynyl-2,5-dimethylazaferrocene is reported along with its cyclic voltammetry measurements and the X-ray struc-
ture determination of its W(CO)5-complex. Basic coordination and organic chemistry of 10-ethynyl-2,5-dimethylazaferrocene is also
presented via derivatives incorporating cis-Pt(dppe) and Si(Et)3 units.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Azaferrocenes; Alkynes; Cyclic voltammetry
1. Introduction
[4a,4b,4c]. Ethynylferrocene (1) exhibits a very rich coordi-
nation chemistry towards metals and metalloids i.e. com-
plexes with Pt [5], Mn [6], Ru [6,7a,7b,7c], Os [6,7b], Ti
[8a,8b], Co [9], Ni [8b,10] Si [8a,9] have been reported.
Additionally, 1 has been described as a building block in
more structurally sophisticated complexes [11] i.e. via
metal-catalysed cross-coupling reactions and the synthesis
of 1,3,5-tris(ferrocenyl)benzene [12]. The third order non-
linear optical properties of alkynes and polyynes contain-
ing 1 have been reported [13] and ethynylferrocene (1)
modified estrogens have been demonstrated as possessing
an estrogenic effect in vitro [14] and as substrates for the
synthesis of its 99(m)Tc(CO)3 derivatives [15]. In contrast,
progress in the synthetic chemistry of azaferrocene and
its more stable derivative 2,5-dimethylazaferrocene – the
closest heteroanalogues of ferrocene – has been limited
due to its instability and the lack of efficient functionalisa-
tion methods. In recent years however, the chemistry of
azaferrocenes has been revitalised. Lateral lithiation opens
access to wide variety of derivatives [16a,16b,16c], and the
classical Friedel–Crafts reaction has also recently been
reported for azaferrocenes some 40 years after its discovery
Conjugated molecules linked to redox active ferrocene
fragments represent promising candidates for the design
of ‘molecular wires’, carbon rich compounds, nonlinear
optical materials or biochemically useful compounds.
Ethynylferrocene (1) (Fig. 1) is an important example of
a redox active molecule successfully used as a building
block in materials and coordination chemistry. Electro-
chemical study of diferrocenylacetylene has been reported
[1] and reveals a mixed-valence state of its monocation.
Detailed spectroscopic and diffraction studies have been
reported featuring ethynylferrocene (1) linked to a (g6-
arene)tricarbonylmanganese fragment [2]. 1 has also been
built into redox active polymers, oligomers and highly con-
ductive molecular wires [3a,3b,3c], organometallic dehy-
droannulenes and other carbon rich compounds
*
Corresponding authors. Tel.: +44 20 75945781; fax: +44 20 75945804
(N.J. Long); tel.: +48 426355755; fax: +48 426786583 (K. Kowalski).
E-mail addresses: kondor15@wp.pl (K. Kowalski), n.long@imperial.
ac.uk (N.J. Long).
0022-328X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.05.043

K. Kowalski et al. / Journal of Organometallic Chemistry 691 (2006) 3902–3908
3903
starting aldehyde 4 was also isolated. It should be noted
that isolation of 2 via column chromatography and the
removal of some organic impurities suffers from difficulties.
We assume that the low product yield in this experiment is
due to the complex character of the reaction mixture that
can trigger decomposition of the rather unstable 10-form-
ylo-2,5-dimethyloazaferrocene (4) or the product 2.
Another factor that should be considered is the electron
rich character of the formyl group in 4 that deactivates
aldehydes towards reaction with moderately nucleophilic
reagents generated during the course of the reaction from
dimethyl-1-diazo-2-oxopropylphosphonate 3.
In a second attempt we applied diazotransfer reaction to
the synthesis of dimethyl-1-diazo-2-oxopropylphosphonate
3 according to the procedure reported by Vanderwalle et al.
[24]. According to the procedure, the crude reaction
mixture was filtered through a Celite pad and the solvent
evaporated. 1H and 31P NMR examination of this material
revealed its very high level of purity. The 31P NMR
spectrum exhibited only signals at 22.98 ppm and
14.71 ppm. The first signal was attributed to dimethyl-2-
oxopropylphosphonate (the starting material in the synthe-
sis of 3) and the second signal was assigned to 3. The ratio
of signals was 1:8.5, so an enhanced amount of 3 was
clearly achieved. We decided to use this mixture as the
reactant in the next experiment.
N
Fe
Fe
H
1
2
H
Fig. 1. The structures of compounds 1 and 2.
[17]. Some azaferrocene derivatives show moderate anti-
cancer activity [18] and interesting electrochemical behav-
iour for aryl capped ethenylazaferrocenes have been
recently described [19]. Application of azaferrocenes in
catalysis [20a,20b] and as a redox active nitrogen ligand
enabling novel photoinduced redox processes of metallo-
porphyrins and metallophthalocyanines [21] are known.
In this paper, we report the synthesis and electrochemis-
try of 10-ethynyl-2,5-dimethylazaferrocene (2) (Fig. 1), a
direct nitrogen heteroanalogue of 1. We also report here
the crystallographic structure of W(CO)5-2 complex and
synthesis of Pt and Si derivatives of 2. Progress in coordi-
nation and materials chemistry strongly demands the
design and synthesis of new ligands and building blocks,
and in this respect we believe that 2 has a real role to play.
To a suspension of 4 and K2CO3 in methanol, a THF
solution of reactant was added and allowed to react over-
night (Scheme 1). After simple workup, product 2 was
isolated by column chromatography as an air-stable orange
oil in analytically pure form. The procedure was repeated
several times, with differing amounts of reactant, and it
was found that even when an increased amount of reactant
(see Section 4) was used, traces of starting material 4 were
still isolated. However, using a mixture of dimethyl-2-
oxopropylphosphonate and dimethyl-1-diazo-2-oxopropyl-
phosphonate in place of the one-pot method previously
applied gave an excellent yield of 75%. Our method is oper-
ationally simple (it is not necessary to isolate 3 in pure
form) and gave a pure product, easily separable by chroma-
tography in reproducible yields. The 1H NMR spectrum of
2 shows a singlet (4.36 ppm) for b-pyrrolyl protons, two
two-proton triplets (4.34 and 4.19 ppm) from the substi-
tuted cyclopentadienyl ligand, a singlet (2.82 ppm) from
the ethynyl group and a singlet (2.24 ppm) from the two
a-pyrrolyl methyl groups. Accumulated for comparison
2. Results and discussion
2.1. Synthesis of 2
High yielding syntheses of ethynylferrocene (1) have
been described [22a,22b]. However, to synthesise 2 we
adopted
methods
based
on
dimethyl-1-diazo-2-
oxopropylphosphonate 3 (Fig. 2), a reagent that trans-
forms a variety of aliphatic, aromatic and organometallic
aldehydes into terminal alkynes under mild conditions
[23a,23b]. Utilisation of 3 in ferrocenyl alkyne synthesis
has also been described [4a,4b]. In a first attempt to make
2 we followed a one-pot procedure described by Bestmann
et al. [23a]. Dimethyl-1-diazo-2-oxopropylphosphonate 3
was generated in situ by addition of dimethyl-2-
oxopropylphosphonate to a suspension of K2CO3 and
p-toluenesulfonylazide and was then reacted with 10-form-
ylo-2,5-dimethyloazaferrocene (4) at room temperature for
6 h. After workup and purification by column chromatog-
raphy 2 was isolated as an orange oil in 6% yield. A trace of
1
(on the same 270 MHz spectrometer) the H NMR spec-
trum of ethynylferrocene (1) shows a singlet corresponding
to the ethynyl proton at 2.71 ppm. The 13C NMR spectrum
of 2 shows signals for ethynyl group carbons at 80.8 ppm
(C„CH) and 75.0 ppm (C„CH). Analogous signals for
the ethynyl group of 1 are present at 82.5 ppm (C„CH)
and 73.5 ppm (C„CH). The IR spectrum of 2 shows char-
acteristic ethynyl absorption bands at 2109 cmꢀ1
(2103 cmꢀ1 for 1). The high resolution mass spectrum
(HRMS, EI, 70 eV) of 2 indicates a peak at m/e 239.0403
with the calculated value for C13H13NFe being 239.0397.
O
O
P
O
O
N+
N-
Fig. 2. The structure of compound 3.

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K. Kowalski et al. / Journal of Organometallic Chemistry 691 (2006) 3902–3908
"
"
O
O
P
O
O
N
N
N+
N-
Fe
Fe
O
K2CO3 / MeOH / THF
H
2
4
H
Scheme 1. The formation of compound 2.
80.0
2.2. Cyclic voltammetry of 2
60.0
40.0
20.0
0.0
The measurements were carried out in dichlorometh-
ane solutions at room temperature on a standard three-
electrode system (platinum working electrode, saturated
calomel electrode as a reference and platinum gauze
counter electrode) using 0.1 M Bu4NClO4/CH2Cl2 as sup-
porting electrolyte. All potentials were recalculated and
2
1
6
given vs. FeCpþ=FeCp2 redox couple. Electrochemical
2
data are given in Table 1. Ethynylferrocene (1), ferrocene
(5), 2,5-dimethylazaferrocene (6) were also investigated as
reference compounds. Compounds 2 and 6 displayed
(Fig. 3) a single partially chemically reversible and elec-
trochemically irreversible oxidation process. The ratio
ipc/ipa ꢁ 0.5 for 2,5-dimethylazaferrocene and ꢁ 0.3 for
2, indicates the lower stability (i.e. a higher reactivity)
of the radical cation of the latter compound. The instabil-
ity of the azaferrocenium cation was attributed to the
localisation of the unpaired electron on nitrogen rather
than at iron [25]. The higher reactivity of the ethynyl-
substituted azaferrocenium cation is in keeping with the
higher oxidation potential of 2 in comparison with 2,5-
dimethylazaferrocene (2+Å is therefore a stronger oxidant
than the 2,5-dimethylazaferrocenium ion). Under the
same conditions, ferrocene and ethynylferrocene dis-
played chemically reversible oxidation processes (ipc/
ipa = 0.95–0.96). Comparison of the data in Table 1
shows that introduction of the ethynyl group to ferrocene
and to 2,5-dimethylazaferrocene brings about approxi-
mately the same anodic shift of the E1/2 values (0.16 V).
This contrasts with the effect of the styryl group which
behaves as an electron withdrawing group in styrylferro-
cene and as an electron donating group in 10-styryl-2,5-
dimethylazaferrocene [19]. Apparently, further compara-
-20.0
-40.0
-0.6
-0.4
-0.2
0.0
0.2
E [V]
0.4
0.6
0.8
1.0
Fig. 3. Cyclic voltammograms of 1, 2 and 6 in CH2Cl2 with 0.1 M
Bu4NClO4 on Pt vs. 5+/5, scan rate: 0.1 V sꢀ1
.
tive studies are needed to understand differences in elec-
tronic properties of these metallocenes.
2.3. X-ray structure of W(CO)5-2
In pure isolated form 2 is an air-stable, orange oil. The
oily character, which is common for 2,5-dimethylazaferro-
cene and its derivatives at room temperatures, makes it
impossible for any crystallographic measurements for this
class of molecules. To overcome these difficulties, oily 2
can be transformed via reaction with photochemically gen-
erated W(CO)5-THF into its W(CO)5-2 crystalline deriva-
1
tive. Compound W(CO)5-2 was characterised by IR, H
NMR spectroscopy, mass spectrometry, elemental analysis
and X-ray crystallography. X-ray quality crystals of
W(CO)5-2 were grown from n-pentane. The structure
revealed the 2,5-dimethylazaferrocene unit to have an
eclipsed conformation (ca. 3° stagger, rings inclined by
ca. 3°) with the alkynyl substituent lying directly under-
neath the C(11) methyl group (Fig. 4), a conformation sta-
bilised by a C–Hꢂ ꢂ ꢂp contact from one of the methyl
protons to the centre of the C(13)„C(14) triple bond
Table 1
Electrochemical data on 1, 2, 6 and 5
Compound
E1/2/V
DE/V
ipc/ipa
2
6
1
5
0.400
0.240
0.160
0
0.230
0.160
0.230
0.090
0.31
0.69
0.96
0.95
˚
[Hꢂ ꢂ ꢂp 2.93 A, C–Hꢂ ꢂ ꢂp 129°, Hꢂ ꢂ ꢂp vector inclined by
ca. 82° to the C(13)„C(14) bond]. The geometry of the
The reported ipc/ipa ratios have been calculated at scan rate: 0.1 V sꢀ1
.
coordination of the tungsten-pentacarbonyl unit to the

K. Kowalski et al. / Journal of Organometallic Chemistry 691 (2006) 3902–3908
3905
from the O(18) carbonyl oxygen atom in a Ci-related mol-
˚
ecule at ca. 3.34 A [the C–Oꢂ ꢂ ꢂp angle is ca. 123°].
2.4. Reactivity of 2 – the synthesis of 7, 8, 9
We examined the chemical properties of 2 towards
lithiation, silylation and coordination to Pt centres via
the cis-[Pt(dppe)Cl2] complex. 10-Ethynyl-2,5-dimethylaza-
ferrocene (2) was treated with n-BuLi in THF at ꢀ78 °C
for 1 h and then chlorotriethylsilane in THF was added
(Scheme 2). After 1 h, the reaction was quenched by
addition of water. The separation of 10-(triethylsilyl)ethy-
nyl-2,5-dimethylazaferrocene (7) was easily achieved via
column chromatography on silica and the product was iso-
lated as an air stable red-orange oil. Substitution of the
hydrogen atom of the ethynyl group is confirmed by the
1H NMR spectrum of 7. The ethynyl proton signal is not
present but the characteristic nine protons triplet
(1.04 ppm) and six proton quartet (0.66 ppm) of the ethyl
groups are present. In the 13C NMR spectrum signals of
the ethynyl carbons are shifted downfield (103.2 ppm and
89.5 ppm) in comparison to 2 (80.8 ppm and 75.0 ppm).
The IR spectrum of 7 shows ethynyl absorption bands at
2149 cmꢀ1. The high resolution mass spectrum (HRMS,
EI, 70 eV) of 7 indicates a peak at m/e 353.1246 with the
calculated value for C19H27NSiFe being 353.1262.
For the synthesis of the bis(10-ethynyl-2,5-dimethylo-
azaferrocenyl) complex of platinum (II) 8, a literature
procedure was followed (Scheme 3) [27]. 10-Ethynyl-2,5-
dimethylazaferrocene (2) was reacted overnight at room
temperature with cis-[Pt(dppe)Cl2] in the presence of a
catalytic amount of copper iodide in the solvent mixture
diisopropylamine and methylene chloride. Product 8 was
isolated as an orange-red highly viscous oil via column
chromatography on neutral alumina. Compound 8 was
characterised by IR, 1H, 13C, 31P NMR spectroscopy
and mass spectrometry. The cis-geometry of complex 8
was confirmed by comparison of 13C and 31P NMR spec-
tra with those previously reported for the analogous cis-
ethynylferrocene platinum (II) complex [5a]. Carbon 1
(directly linked to the Pt centre) generates a doublet of
doublets pattern of signals due to large (152 Hz)
trans-2JPC and small (15 Hz) cis-2JPC coupling constants.
For the cis-ethynylferrocene analogue of 8 such coupling
constants were reported as 145 and 13 Hz [5a]. The dou-
blet assigned to carbon 2 has trans-3JPC coupling con-
stants equal to 35 Hz but the cis- signals were not
detected. This same doublet in the cis-ethynylferrocene
counterpart was reported to be 33 Hz but the cis-coupling
constant was also not detected. The 31P NMR spectrum
of 8 shows a single phosphorus signal with the plati-
num-phosphorus coupling constant equal to 2283 Hz (cf.
2281 Hz reported for the cis-ethynylferrocene analogue).
Again, the oily 8 was transformed by formation of the
crystalline W(CO)5-8 species. The structure of W(CO)5-8
was confirmed by IR, 1H, 13C, 31P NMR spectroscopy
and elemental analysis.
Fig. 4. The molecular structure of W(CO)5-2.
nitrogen of the aza-ferrocenyl moiety is very similar to
those seen previously in related structures [16b,17,26].
The tungsten centre has a distorted octahedral geometry
with cis angles in the range 86.42(9)–93.52(7)°, and trans
angles between 174.36(9)° and 179.20(7)° (Table 2). The
˚
W–CO bond trans to the nitrogen [1.966(2) A] is noticeably
shorter than the others [which range between 2.039(2) and
2.044(2) A] reflecting the relative donor abilities of car-
bonyl and pyrrole. The coordination of the tungsten to
the pyrrole ring is markedly distorted, the metal lying ca.
˚
˚
0.27 A out of the C4N plane. The W(CO)5 moiety adopts
a staggered conformation with respect to the pyrrole ring,
the {W,C(15),C(17),C(19),N(1)} and {W,C(15),C(16),
C(18),N(1)} planes being inclined by ca. 44° and 42°,
respectively to the plane of the pyrrole ring. Adjacent mol-
ecules are linked by a C–Hꢂ ꢂ ꢂp interaction between a pro-
ton on the pyrrole ring in one molecule and the
cyclopentadienyl ring in a screw-related counterpart with
˚
an Hꢂ ꢂ ꢂp separation of ca. 2.73 A and a C–Hꢂ ꢂ ꢂp angle
of ca. 143° [the Hꢂ ꢂ ꢂp vector is inclined by ca. 81° to the
ring plane] forming a chain of molecules along the crystal-
lographic b axis direction (see Fig. S2 in the supporting
information). The closest approach to the pyrrole ring is
Table 2
˚
Selected bond lengths (A) and bond angles (°) for W(CO)5-2
W–N(1)
2.2870(16)
2.044(2)
2.039(2)
1.184(3)
W–C(15)
W–C(17)
W–C(19)
1.966(2)
2.042(2)
2.039(2)
W–C(16)
W–C(18)
C(13)–C(14)
N(1)–W–C(15)
N(1)–W–C(17)
N(1)–W–C(19)
C(15)–W–C(17)
C(15)–W–C(19)
C(16)–W–C(18)
C(17)–W–C(18)
C(18)–W–C(19)
179.20(7)
N(1)–W–C(16)
N(1)–W–C(18)
C(15)–W–C(16)
C(15)–W–C(18)
C(16)–W–C(17)
C(16)–W–C(19)
C(17)–W–C(19)
C(10)–C(13)–C(14)
91.13(7)
92.50(8)
88.07(9)
88.31(9)
90.95(9)
89.27(9)
174.36(9)
177.4(3)
92.10(8)
93.52(7)
87.96(10)
86.42(9)
176.21(8)
87.84(10)
91.59(9)

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K. Kowalski et al. / Journal of Organometallic Chemistry 691 (2006) 3902–3908
N
1.n-BuLi / THF/ -780C
N
2. ClSi(C2H5)3
Fe
Fe
7
Si
2
H
Scheme 2. The formation of compound 7.
N
N
N
cis-[Pt(dppe)Cl2] / CuI
iPr2NH-CH2Cl2
2
Fe
Fe
Fe
2
1
H
2
Pt
Ph
Ph
Ph
Ph
P
P
Ph
P
Ph
Ph
P
dppe =
8
Ph
Scheme 3. The formation of compound 8.
3. Conclusions
Bruker AV500 spectrometers. Chemical shifts are reported
in d (ppm) using CDCl3 (1H d 7.26 ppm), or external 85%
aqueous H3PO4 (31P) as the reference solvents. Mass spec-
tra were recorded using positive FAB and EI methods on a
micromass Autospec Q spectrometer. Infrared spectra were
recorded as KBr disks on a Perkin–Elmer Spectrum RX
FTIR spectrometer. Microanalyses were carried out by
Mr. S Boyer at SACS (Scientific Analysis and Consultancy
Services) at the University of North London. 2,5-Dimethy-
lazaferrocene [28], 10-formylo-2,5-dimethylazaferrocene
[16b], p-toluenesulfonylazide [29] and cis-[Pt(dppe)Cl2]
[30] were prepared according to literature methods. All
other chemicals were purchased from the Aldrich Chemical
Co. The cyclic voltammetry measurements of 1–4, 2,5-
dimethylazaferrocene and ferrocene derivatives were car-
ried out in CH2Cl2 with 0.1 M Bu4NClO4 under an Ar
atmosphere on AUTOLAB (Eco Chemie BV) in three elec-
trode system, where the working electrode was Pt (/
= 1.5 mm), the reference was a saturated calomel electrode,
and the counter electrode was cylindrical platinum gauze.
All potentials were recalculated and given vs.
10-Ethynyl-2,5-dimethylazaferrocene (2), a new air-sta-
ble heterometallocene has been prepared and characterised.
Spectroscopy of 2 (IR, H, 13C NMR) indicates a similar
1
triple bond character compared to ethynylferrocene (1).
Cyclic voltammetry of 2 reveals an anodic shift of the oxi-
dation potential in comparison to the parent 2,5-dimethy-
lazaferrocene. The W(CO)5-2 crystal structure indicates
intramolecular hydrogen contacts between the a-methyl
groups of the pyrrolyl ring and triple bond. The synthetic
potential of 2 was explored in a preliminary fashion via
the synthesis of two Si and Pt derivatives. These results,
in our opinion, support further study into the organic
and coordination chemistry of 2 as a new potential heter-
ometallocene building block in coordination, materials
and medicinal chemistry. The advantage that 2 offers is in
the tuning of electrochemical or optical properties by nitro-
gen atom protonation, methylation or coordination of
additional metal centres.
4. Experimental
FeCpþ=FeCp2 redox couple.
2
4.1. General remarks
4.1.1. Synthesis of 2
To a stirred suspension of 10-formyl-2,5-dimethylazafer-
rocene (115 mg, 0.47 mmol) and finely powdered K2CO3
(194 mg, 1.4 mmol) in dry methanol (4 ml), a mixture of
dimethyl-1-diazo-2-oxopropylphosphonate and dimethyl-
2-oxopropylphosphonate (540 mg, 8.5:1 by 31P NMR) in
dry THF (1 ml) were added. The mixture was allowed to
react overnight at room temperature and protected against
All preparations were carried out using standard
Schlenk techniques. All solvents were distilled over stan-
dard drying agents under nitrogen directly before use,
and all reactions were carried out under an atmosphere
of nitrogen. NMR spectra were recorded using a Delta
upgrade on JEOL EX270 MHz, Bruker DRX400 MHz,

K. Kowalski et al. / Journal of Organometallic Chemistry 691 (2006) 3902–3908
3907
light. A water saturated solution of NaHCO3 was added
and the mixture was extracted with chloroform. The com-
bined organic layers were dried over MgSO4 and the sol-
vent was evaporated. The resultant oily, orange residue
was subjected to column chromatography (SiO2, eluent:
chloroform). The second (orange) fraction was collected
and after evaporation of solvent furnished 2 as an orange
m/e = 353.1246 (Calc. for C19H27NSiFe: 353.1262) IR
(KBr, cmꢀ1): mC„CH 2149. Anal. Calc. for C19H27NSiFe:
C, 64.58; H, 7.70; N, 3.96. Found: C, 64.68; H, 7.78; N,
3.89%.
4.1.4. Synthesis of 8
A mixture of 2 (110 mg, 0.5 mmol) and cis-[Pt(dppe)Cl2]
1
i
oil in 75% yield (84 mg). H NMR d (CDCl3) 270 MHz:
(166 mg, 0.25 mmol) in a 1:2 volume ratio in Pr2NH–
4.36 (s, 2H, b-pyrrolyl), 4.34 (t, J = 1.7 Hz, 2H, C5H4),
CH2Cl2 (5 ml:10 ml) was allowed to react in the presence
of CuI (4 mg) at room temperature overnight. The result-
ing solution was evaporated to dryness. The residue was
re-dissolved in chloroform and the solution was subjected
to column chromatography on neutral Al2O3 (eluent:chlo-
roform). One orange fraction was eluted and after removal
of the solvent, 8 was isolated as an orange-red high viscos-
ity oil. Yield 232 mg (43%). 1H NMR d (CDCl3) 400 MHz:
8.03–7.98 (m, 8H, meta-Ph), 7.46–7.44 (m, 12H, ortho and
para-Ph), 4.06 (t, J = 1.7 Hz, 2H, C5H4), 4.04 (s, 2H,
b-pyrrolyl), 3.97 (t, J = 1.7 Hz, 2H, C5H4), 2.44–2.34 (m,
4H, –CH2CH2–), 2.09 (s, 6H, CH3-pyrrolyl). 13C
{1H}NMR d (CDCl3) 125 MHz: 134.0–133.2 (m, meta-
4.19 (t, J = 1.7 Hz, 2H, C5H4), 2.82 (s, 1H, C„CH), 2.24
(s, 6H, CH3-pyrrolyl). 13C {1H}NMR
d
(CDCl3)
100 MHz: 102.7 (a-pyrrolyl), 80.8 (C„CH), 75.0 (C„CH
), 72.7 (C5H4), 72.2 (b-pyrrolyl), 70.9 (C5H4), 65.6 (ipso-
C5H4), 14.7 (CH3 groups). MS (EI, 70 eV) m/e = 239
[M+], 89 [C5H4C„CH+] HRMS: m/e = 239.0403 (Calc.
for C13H13NFe: 239.0397). IR (KBr, cmꢀ1): mC„CH 2109.
Anal. Calc. for C13H13NFe: C, 65.30; H, 5.48; N, 5.86.
Found: C, 65.24; H, 5.42; N, 5.86%.
4.1.2. Synthesis of W(CO)5-2
W(CO)5 (211 mg, 0.6 mmol) dissolved in THF (40 ml)
was photolysed with a 400 W high-pressure mercury lamp
for 25 min. The photolyte was treated with 2 (136 mg,
0.56 mmol) and the resulting solution was protected
against light and stirred at room temperature for 5 h.
Removal of solvent, followed by column chromatography
(SiO2, eluent:chloroform:n-hexane 1:1) and evaporation
of solvents gave W(CO)5-2 as orange crystals. Yield
252 mg (80%). 1H NMR d (CDCl3) 270 MHz: 4.62 (s,
2H, b-pyrrolyl), 4.38 (m, 4H, C5H4), 2.93 (s, 1H, C„CH),
2.59 (s, 6H, CH3-pyrrolyl) MS (EI, 70 eV) m/e = 563 [M+],
479 [M+–3CO], 423 [M+–5CO], 239 [M+–W(CO)5] IR
(KBr, cmꢀ1): mC„CH 2068, mC„O 1905, 1862. Anal. Calc.
for C18H13NO5WFe: C, 38.40; H, 2.33; N, 2.49. Found:
C, 38.46; H, 2.21; N, 2.46%.
1
Ph), 131.2 (s, para-Ph), 129.7 (d, JPC = 54 Hz, ipso-Ph),
3
128.7–128.5 (m, ortho-Ph), 106.4 (d, JPC = 35 Hz Pt–
2
C„C), 101.7 (s, a-pyrrolyl), 101.2 (dd, JPC(trans) =
2
152 Hz, JPC(cis) = 15 Hz, Pt–C„C), 73.2 (s, b-pyrrolyl),
72.6 (s, ipso-C5H4), 71.6 (s, a or b C5H4), 69.8 (s, a or b
C5H4), 28.7–28.2 (m, –CH2CH2–), 15.3 (s, CH3-pyrrolyl).
31P {1H}NMR d (CDCl3) 162 MHz: 40.75 (1JPtP
=
2283 Hz). IR (KBr, cmꢀ1): 2122; 2107; 533 FAB MS
(+ve): m/e = 1070 [M + H]+, 975 [M + H–C6H9N]+, 832
[M + H–C13H12NFe]+.
4.1.5. Synthesis of W(CO)5-8
W(CO)5 (140 mg, 0.4 mmol) dissolved in THF (40 ml)
was photolysed with a 400 W high-pressure mercury lamp
for 25 min. The photolyte was treated with 8 (154 mg,
0.14 mmol) and the resulting solution was stirred at room
temperature for 6 h. Removal of the solvent, followed by
column chromatography (neutral Al2O3, eluent:chloro-
form:n-pentane 1:1) and evaporation of the solvents gave
W(CO)5-8 as an orange crystalline solid. Yield 167 mg
4.1.3. Synthesis of 7
n-BuLi (1.6 M in hexane, 0.3 ml, 0.45 mmol) was added
to a nitrogen-saturated solution of 10-ethynyl-2,5-dimeth-
yloazaferrocene (2) (100 mg, 0.41 mmol) in THF (10 ml)
at ꢀ78 °C. The orange solution darkened and the mixture
was stirred for 1 h at ꢀ78 °C. Chlorotriethylsilane (50 ll,
0.3 mmol) in 1 ml of THF was added and the stirring was
continued for 1 h. The reaction was then quenched by
water, extracted with chloroform, dried over MgSO4
and the solvent evaporated to give a dark brown-orange
oil which was subjected to column chromatography
(SiO2, eluent:ethyl acetate). After evaporation of the
solvent, 7 was isolated as a red-orange oil. Yield 67 mg
1
(70%). H NMR d (CDCl3) 270 MHz: 8.05–7.95 (m, 8H,
meta-Ph), 7.59–7.46 (m, 12H, ortho and para-Ph), 4.17
(s, 2H, b-pyrrolyl), 4.12 (s, 4H, C5H4), 2.42–2.34 (m,
4H, –CH2CH2–), 2.34 (s, 6H, CH3-pyrrolyl). 13C
{1H}NMR d (CDCl3) 125 MHz: 198.6 trans-CO, 191.1
cis-CO, 134.0–133.0 (m, meta-Ph), 131.6 (s, para-Ph),
129.8–128.2 (m, ipso-Ph and ortho-Ph), 105.31 (d,
3JPC = 35 Hz Pt–C„C), 105.0 (s, a-pyrrolyl), 103.7 (dd,
1
2
(46%). H NMR d (CDCl3) 400 MHz: 4.36 (s, 2H, b-pyrr-
2JPC(trans) = 145 Hz, JPC(cis) = 15 Hz, Pt–C„C), 75.9
olyl), 4.33 (s, 2H, C5H4), 4.19 (s, 2H, C5H4), 2.25 (s, 6H,
(s, b-pyrrolyl), 73.6 (s, ipso-C5H4), 73.5 (s, a or b
CH3-pyrrolyl), 1.04 (t, J = 7.8 Hz, CH2CH3), 0.66 (q,
C5H4), 71.7 (s, a or b C5H4), 29.3–28.7 (m, –CH2CH2–),
J = 7.8 Hz, CH2CH3) 13C {1H}NMR
d
(CDCl3)
18.8 (s, CH3-pyrrolyl). 31P {1H}NMR
d (CDCl3)
100 MHz: 103.2 (C„C ), 102.5 (a-pyrrolyl), 89.5 (C„
C), 72.5 (C5H4), 72.3 (b-pyrrolyl), 70.9 (C5H4), 67.1
(ipso-C5H4), 14.6 (a-CH3 pyrrolyl groups), 7.4 (C2H5),
4.4 (C2H5) MS (EI, 70 eV) m/e = 353 [M+], HRMS:
109 MHz: 41.70 (1JPtP = 2294 Hz) IR (KBr, cmꢀ1): 2065,
1907, 532. Anal. Calc. for C62H48N2P2O10PtW2Fe2: C,
43.36; H, 2.82; N, 1.63. Found: C, 43.27; H, 2.82; N,
1.63%.

3908
K. Kowalski et al. / Journal of Organometallic Chemistry 691 (2006) 3902–3908
[7] (a) T. Ren, Organometallics 24 (2005) 4854;
4.2. Crystallography
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Crystal data for [W(CO)5-2]: C18H13FeNO5W,
M = 562.99, monoclinic, P21/c (no. 14), a = 9.4161(12) A,
˚
˚
˚
b = 12.345(3) A, c = 16.1457(15) A, b = 100.786(9)°, V =
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1843.6(5) A , Z = 4, Dc = 2.028 g cmꢀ3
, l(Mo Ka) =
3
˚
7.049 mmꢀ1, T = 173 K, orange/brown blocks, Oxford
Diffraction Xcalibur 3 diffractometer; 6061 independent
measured reflections, F2 refinement, R1 = 0.022, wR2 =
0.054, 4758 independent observed absorption-corrected
reflections [|Fo| > 4r(|Fo|), 2hmax = 64°], 238 parameters.
CCDC 603274.
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1046;
Acknowledgements
We acknowledge financial support from the Polish Min-
istry of Education and Science (grant PBZ-KBN-118/T09/
12) and Imperial College London.
Appendix A. Supplementary data
(b) K. Kowalski, J. Zakrzewski, L. Jerzykiewicz, J. Organomet.
Chem. 690 (2005) 764;
(c) C.T. Fukuda, K. Imazato, M. Iwao, Tetrahedron Lett. 44 (2003)
7503.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.
2006.05.043.
[17] K. Kowalski, J. Zakrzewski, L. Jerzykiewicz, J. Organomet. Chem.
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