2-Ferrocenyl-substituted pyrylium ions from coupling of ethynylferrocene with cyclomanganated chalcones

Article abstract of DOI:10.1016/j.jorganchem.2010.05.006

2-Ferrocenyl-substituted pyrylium salts are produced when orthomanganated chalcones are reacted with ethynylferrocene in CCl₄. When the reaction is carried out in benzene, intermediate ferrocenyl-substituted (η⁵-pyranyl)Mn(CO)₃ species can be isolated which give the pyrylium cations on oxidation. The electrochemistry of the 2-ferrocenyl-pyrylium cations shows both oxidation (of the ferrocenyl) and reduction (of the pyrylium) processes, and the UV-visible spectra show a broad band at ca 680 nm which can be assigned to an intramolecular charge transfer transition. 2-Ferrocenyl pyrylium salts have been prepared from cyclomanganated chalcones and ferrocenylethyne.

Full text of DOI:10.1016/j.jorganchem.2010.05.006

Journal of Organometallic Chemistry 695 (2010) 1961e1965
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Journal of Organometallic Chemistry
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2-Ferrocenyl-substituted pyrylium ions from coupling of ethynylferrocene with
cyclomanganated chalcones
,
a
,
b
Narendra Prasad a, Lyndsay Main a , Brian K. Nicholson , C. John McAdam
*
*
a Chemistry Department, University of Waikato, Private Bag 3105, Hamilton, New Zealand
b Chemistry Department, University of Otago, PO Box 56, Dunedin, New Zealand
a r t i c l e i n f o
a b s t r a c t
Article history:
2-Ferrocenyl-substituted pyrylium salts are produced when orthomanganated chalcones are reacted
with ethynylferrocene in CCl4. When the reaction is carried out in benzene, intermediate ferrocenyl-
Received 11 March 2010
Received in revised form
27 April 2010
Accepted 6 May 2010
Available online 31 May 2010
substituted (h
5-pyranyl)Mn(CO)3 species can be isolated which give the pyrylium cations on oxidation.
The electrochemistry of the 2-ferrocenyl-pyrylium cations shows both oxidation (of the ferrocenyl) and
reduction (of the pyrylium) processes, and the UVevisible spectra show a broad band at ca 680 nm which
can be assigned to an intramolecular charge transfer transition.
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
Pyrylium salts
Ferrocenyl
Pyranyl complex
Electrochemistry
1. Introduction
alkynes [7]. The present report uses this method to provide 2-fer-
rocenyl-pyrylium compounds and describes spectroscopic and
Pyrylium cations are aromatic species formally related to
benzene by replacement of a CH by an Oþ ion. They are less aromatic
than benzene or pyridine, so are more reactive and find wide
application in organic synthesis [1]. They have uses ranging from
dyes and photosensitisers to corrosion-inhibitors and have a well
developed oxidation-reduction chemistry [2]. Balaban et al. have
reviewed the many syntheses of pyrylium salts containing different
organic substituents [1]. However there appear to be relatively few
pyrylium cations incorporating organometallic substituents. Russian
workers have briefly reported examples of ferrocenyl-substituted
pyrylium perchlorates, and showed these were readily transformed
into the corresponding pyridines, but gave few physical data [3].
Caro’s group have investigated the synthesis, structures and some
reactions of pyrylium cations substituted by an acetylenic-CO2(CO)6
electrochemical properties.
2. Results and discussion
2.1. Reaction of ferrocenylethyne with cyclomanganated chalcones
Reactions carried out with the parent chalcone and the trime-
thoxy-substituted analogue are summarized in Scheme 1.
When FcCCH (Fc ¼ ferrocenyl) was reacted with the cyclo-
manganated chalcone 1a in refluxing CCl4 a green powder precip-
itated. This was identified as being the ferrocenyl-substituted
pyrylium cation 2a with [FeCl4]ꢀ as the counterion, this assignment
supported by microanalytical data and by high resolution ESI-MS
peaks found for the cation and anion in the þve and ꢀve ion modes
respectively. NMR spectra were not obtainable because of the
paramagnetism of the [FeCl4]ꢀ anion. The green colour is also
strongly indicative of a ferrocenyl-pyrylium species by comparison
with the colour reported for analogues isolated as ClOꢀ4 salts in
earlier work [3]. The positioning of the ferrocenyl group on the ring
adjacent to the oxygen atom has precedent from earlier studies
where the bulky group of the alkyne ends up in this position [7].
In contrast, when the reaction between 1a and FcCCH was
carried out in refluxing benzene (or acetonitrile) the resulting
solution was intensely red. Chromatography separated two main
moiety, or by (
h
5-C5H4)M(CO)3 (M ¼ Mn, Re), (
h
6-C6H5)Cr(CO)3 or 4-
ferrocenyl groups [4], as well as bispyrylium salts incorporating
ferrocenyl methylene substituents [5]. Shaw et al. have reported
pyrylium cations directly s-bonded to Mn(CO)5 or Fe(CO)2Cp groups,
and investigated their electrochemistry [6].
We have previously established a new synthesis of pyrylium
cations, via the reaction of cyclomanganated chalcones with
* Corresponding authors. Fax: þ64 7 838 4219.
E-mail addresses: l.main@waikato.ac.nz (L. Main), b.nicholson@waikato.ac.nz
(B.K. Nicholson), mcadamj@chemistry.otago.ac.nz (C.J. McAdam).
products. The first of these was an
h
5-(ferrocenyl)pyranyl-
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.05.006

1962
N. Prasad et al. / Journal of Organometallic Chemistry 695 (2010) 1961e1965
and orthomanganated chalcones [7]. In the first step, the alkyne
inserts into the MneC bond of the cyclomanganated chalcone with
the bulkier substituent adjacent to the manganese. This seven-
membered ring extrudes the Mn(CO)n group as the CeO bond
forms to give a six-membered ring, with the Mn retained on the
R
R
R
R
O
PhCH2Mn(CO)5
R
Mn
(CO)4
face of the ring by coordination in an h
5-fashion, giving the isolated
O
H
species 3a. In benzene this compound is essentially stable under
the reaction conditions, although a small amount of protio-deme-
tallation to generate 4a occurs, presumably induced by small
amounts of adventitious water. In CCl4 the same initial processes
take place, but now the species 3a undergoes oxidation in situ to
eliminate the manganese and generate the pyrylium cation 2a.
Decomposition of some of the ferrocenyl groups by the CCl4 must
provide the counterion [FeCl4]ꢀ. It is well-established [10] that
solutions of ferrocene in CCl4 undergo an efficient photolytic/
radical conversion to [Cp2Fe]þ[FeCl4]ꢀ, so presumably this is
occurring in our system, with the ferricenium cation providing the
oxidizing agent for converting 3a to 2a. The yields of 2a$[FeCl4] are
reasonable so formation is obviously efficient even with thermal
conditions under normal laboratory lighting.
Exactly the same types of products were characterized in the
corresponding reactions of the substituted cyclomanganated chal-
cone 1b, giving 2b, 3b, 4b with similar yields.
For further characterization, the pyrylium cations 2a or 2b were
converted in to the corresponding pyridines 5a or 5b using the
known reaction with aqueous NH3 [3,4]. Ferrocenyl-substituted
pyridines have been used recently to prepare ruthenium complexes
with anticancer activities [11].
R
(1a R = H)
(1b R = OMe)
FcCCH
FcCCH
benzene
CCl4
or acetonitrile
R
R
R
O
I2/CCl4
R
R
O
(OC)3Mn
X-
+
Fe
R
(3a R = H)
(3b R = OMe)
Fe
(2a R = H)
(2b R = OMe)
X = [FeCl4]- or I3
-
R
R
R
O
NH3
H
R
Fe
2.2. Crystal structure of (4,6-diphenylpyranyltricarbonyl
manganese, 3a
R
N
(4a R = H)
(4b R = OMe)
R
The X-ray crystal structure of the
h
5-pyranyl-manganese
(5a R = H)
(5b R = OMe)
Fe
complex 3a was determined. Fig. 1 shows the overall geometry. The
structure has a Mn(CO)3 group attached to the five carbon atoms of
the pyranyl ring with the oxygen displaced from the plane of the
ring, away from the side attached to the manganese. The C(1)eC(5)
atoms are coplanar to within ꢁ0.03 Å, with the Mn 1.696(1) Å from
the plane. The individual MneC distances vary from 2.095(2) [to C
(3)] to 2.275(2) Å [to C(1)]. The ferrocenyl group is attached to C(1)
and is orientated so that the Fe is on the opposite side of the rings to
the Mn, no doubt for steric reasons. The two phenyl rings are
attached at C(3) and C(5), with their planes twisted by 22.5ꢂ and
Scheme 1.
manganese tricarbonyl, 3a, corresponding to the major product
reported from reactions of other alkynes with cyclomanganated
chalcones [7,8]. This was fully characterized by elemental analysis,
and by an X-ray crystal structure determination (see below), with
further validation provided by 1H and 13C NMR spectra. The ESI-MS
gave a single peak assignable to [MeMn(CO)3]þ suggesting very
ready oxidation and loss of the manganese carbonyl group to
generate the very stable pyrylium cation in the source of the mass
spectrometer. As expected [7], oxidation of 3a by I2 also cleaved the
manganese carbonyl group to generate the pyrylium cation 2a,
isolated as the Iꢀ3 salt, a reaction distinguished by a dramatic colour
change from deep red to intense green. Interestingly, during the
chromatographic separation the red band from which 3a was iso-
lated was tailed by a faint green streak which suggests oxidation of
the pyranyl-manganese to form the pyrylium salt was taking place
on the silica.
The second product from the reaction in benzene was orange
and was characterized as the substituted pyran 4a, arising
presumably from protio-demetallation of the pyranyl-manganese
species 3a. This was identified by elemental analysis and by 1H and
13C NMR spectra. In particular a distinctive doublet proton reso-
nance at
d 6.20 was assigned to the additional hydrogen on the
Fig. 1. The structure of (2-ferrocenyl-4,6-diphenylpyranyl-h
5)tricarbonylmanganese
pyran C2. For this example ESI-MS gave a main peak assignable to
[M]þ, presumably through oxidation of the ferrocene to ferricinium
in the source, a process that has precedent [9].
The formation of the various products can be accounted for by
analogy with our earlier proposals for reactions between alkynes
(3a). Selected distances (Å) Mn(1)eC(1) 2.275(2), Mn(1)eC(2) 2.124(2), Mn(1)eC(3)
2.095(2) Mn(1)eC(4) 2.098(2) Mn(1)eC(5) 2.190(2), C(1)eO(1) 1.397(2), C(5)eO(1)
1.411(2), C(1)eC(2) 1.365(2), C(2)eC(3) 1.410(2), C(3)eC(4) 1.411(2), C(4)eC(5) 1.381
(2), Mn(1)eplane of [C(1)eC(5)] 1.696(1), Fe(1)eplane of [C(11)eC(15)] 1.636(1), Fe
(1)eplane of [C(21)eC(25)] 1.635(1).

N. Prasad et al. / Journal of Organometallic Chemistry 695 (2010) 1961e1965
1963
24.8ꢂ respectively from being coplanar with the C(1)eC(5) plane.
3
μ
I /
A
The Cp rings of the ferrocenyl group are 8ꢂ from the eclipsed
conformation, with equal Fe/ring-plane distances [1.635(1) Å].
The plane of the C(11)eC(15) ring is only 10.3ꢂ from the C(1)eC(5)
2
1
0
one which should allow some p-electron communication between
the two rings, perhaps explaining why the C(11)eC(1) distance
[1.431(2) Å] is significantly shorter than the C(3)eC(31) and C(5)eC
(51) ones [av. 1.464(2) Å] even though they are all formally sp2esp2
CeC bonds. There are two previous structures reported for h5
-
-1
-2
-3
pyranyl-manganese compounds, with 1-methyl-3,5-diphenyl or
with 1-styryl-3,5-diphenyl substituents; these have slightly longer
Mn/ring distances (1.715 and 1.742 Å respectively), but are
otherwise very similar [7].
E / V
2.3. Electrochemistry of the pyrylium salts
-1.2 -1 -0.8 -0.6 -0.4 -0.2
0
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6
Fig. 2. Cyclic voltammogram of 2a$[FeCl4] (CH2Cl2, [Bu4N][BF4], GCE, 100 mV sꢀ1).
Electrochemical data for pyrylium cations are given in Table 1
and the cyclic voltammogram of 2a is shown in Fig. 2. Electro-
chemistry of triarylpyrylium salts (P) has been well-studied and
generally shows two cathodic processes associated with reduction
first to the radical P$ then the anion Pꢀ [2,6]. Pyrylium salts can also
be oxidised [13]. For triphenylpyrylium the reduction processes
occur at ꢀ0.22 and ꢀ1.40 V (CH2Cl2, [Fc*]þ/0 ¼ 0.0 V). In MeCN the
radical formed from the first reduction can undergo a dimerisation
reaction, the bipyrane product generating an anodic feature
(w0.7 V) on the reverse scan [2]. This signal was not observed in
dichloromethane.
For 2a the first pyrylium reduction occurs at ꢀ0.40 V, the
observed cathodic shift is as predicted due to the electron
donating ability of the attached ferrocenyl group. An ia/ic of 0.7 for
this process and new broad feature occurring at w0.6 V on the
anodic sweep is consistent with a chemical reaction of the radical
species that may be dimerisation of the radical to the bipyrane.
The effect of the trimethoxybenzene group in 2b on the redox
potentials is minor. It would appear however that this group sta-
bilises the radical species formed at ꢀ0.41 V with respect to the
chemical reaction that generates the feature at 0.7 V. The second
pyrylium reduction of both 2a and 2b is electrochemically irre-
versible and cathodically shifted to a similar extent from that of
triphenylpyrylium to ca. ꢀ1.5 V. The ferrocenyl [Fc]þ/0 redox
couple occurs at 0.92 and 0.89 V for 2a and 2b respectively,
consistent with the attachment of a strongly electron withdrawing
group to the Fc unit [12].
from the pyrylium group. These are readily assigned from pub-
lished data [1, 2, 16]. More interesting is a weak, broad band at
around 694 nm in benzene, with small shifts to 669 and 692 nm in
acetone and dichloromethane respectively. This absorption can be
attributed to an intramolecular charge transfer transition from the
ferrocenyl centre to the pyrylium ring, promoted by the combina-
tion of a readily-oxidised and a readily-reduced group in the same
species. The counter anion in 2a and 2b, tetrachloroferrate con-
taining the d5 Fe(III) ion, is pale yellow and does not contribute to
any significant UVevisible absorption. There is no sign of the low
energy band in the
expected.
h
5-pyranyl nor the pyran species 3 or 4, as
Triphenylpyrylium tetrafluoroborate in dichloromethane
displays strong fluorescent emission at 461 nm, but this is
quenched for the 2a/2b salts.
2.5. Conclusion
A new synthesis of 2-ferrocenyl-substituted pyrylium salts has
been established, which allows more ready variation of substitu-
ents than the previous routes [3]. It also avoids the strongly acid
conditions used in the usual syntheses [1] which may be an
advantage for some substituents. By varying the solvent, interme-
diate species can be isolated. The 2-ferrocenyl-pyrylium cations
incorporate both a reducible and an oxidisable centre and both
redox processes are clearly seen in the electrochemical measure-
ments. The UVevisible spectra show a broad band at ca 680 nm
which arises from an internal charge transfer from the ferrocenyl
moiety to the pyrylium ring.
Both of the ferrocenyl-pyrylium salts contain the electrochem-
ically non-innocent tetrachloroferrate counter anion. This ion
undergoes a reversible [FeCl4]ꢀ/2ꢀ reduction at 0.08 V. A sample of
tetrabutylammonium tetrachloroferrate displayed the same
reduction feature at 0.08 V (cf. [15]).
3. Experimental
2.4. UVevisible spectra of the pyrylium salts
3.1. General
The UVevisible spectra of the pyrylium salts 2a and 2b show
strong bands in the 200e300 nm range which can be attributed
mainly to the ferrocenyl moiety, and in the 350e450 nm region
Petroleum spirit (b.p. 60e80 ꢂC) and all other solvents in
preparative and chromatographic work were of analytical grade.
Other commercial reagents were used without purification. Coupling
reactions with the alkyne were carried out under a nitrogen atmo-
sphere, other reactions required no precautions. P.l.c refers to
preparative layer chromatography on silica (Merck Kieselgel
60PF254: 200 ꢃ 200 ꢃ 2 mm). Infrared spectra were recorded on
a Digilab FTS-45 FTIR instrument, NMR spectra on a Bruker AC300
instrument in CDCl3, and UVevisible spectra on a Varian Cary 100
instrument. Low resolution electrospray mass spectrometry (ESI-
MS) was carried out on VG Platform II and high resolution ESI-MS on
a Bruker MicrOTOF, with MeOH as mobile phase.
Table 1
Half wave potentials for pyrylium salts in dichloromethane solution.
Eꢂ/Va
P./ꢀ
P0/.
FeClꢀ4 /2ꢀ
Fcþ/0
Triphenylpyrylium.BFꢀ4 [cf 2,6]
2a$FeClꢀ4
ꢀ1.40
ꢀ0.22
ꢀ0.40
ꢀ0.41
ꢀ1.52 (Epc)
ꢀ1.59 (Epc)
0.08
0.07
0.08
0.92
0.89
2b$FeClꢀ4
Bu4Nþ$FeClꢀ4
a
1 ꢃ 10ꢀ3 M in CH2Cl2, 0.1 M [Bu4N][BF4], GCE, referenced to [Fc*]þ/0 ¼ 0.0 V [14].

1964
N. Prasad et al. / Journal of Organometallic Chemistry 695 (2010) 1961e1965
Electrochemical measurements of the pyrylium salts were
(CDCl3) d 137.4 (Ph i), 137.0 (Ph i’), 129.2 (Ph m), 128.7 (Ph m’), 128.5
carried out in a standard cell with glassy carbon (working), Pt
(Ph p), 128.5 (Ph p’), 127.5 (Ph o), 122.7 (Ph o’), 111.1 (pyr C2), 96.8
(pyr C4), 93.4 (pyr C6), 85.0 (pyr C3), 80.6 (pyr C5), 78.3 (Fc i), 69.9
(auxiliary) and Ag/AgCl (reference) electrodes on 1 ꢃ 10ꢀ3
M
solutions of the analyte with 0.1 M Bu4Nþ$BF4ꢀ supporting elec-
trolyte in CH2Cl2. Potentials were referenced to [Fc*]þ/0 ¼ 0.0 V [14].
The sample of tetrabutylammonium tetrachloroferrate was
prepared by a literature method [17]. Cyclomanganated chalcones
were synthesised as reported by Tully et al. [18] using PhCH2Mn
(CO)5 prepared by the standard method [19]. Ferrocenylethyne was
generously provided by Professor M. I. Bruce, University of
Adelaide.
(Fc C5H5), 67.4 (Fc a), 64.7 (Fc b).
ESI-MS m/z 417 [M-Mn(CO)3]þ. This compound was further
characterized by an X-ray crystal structure determination, see
below.
Band 2, orange, Rf 0.2 was 2-ferrocenyl-4,6-diphenylpyran, 4a,
(10 mg, 8%), as orange crystals from ether/pentane. Found: C, 77.52;
H, 5.30%, calc for C27H22OFe: C, 76.83; H, 5.32%.
1H NMR (CDCl3)
d
7.86 (d, J ¼ 21.0 Hz, 1H, pyr H3), 7.32 (m, 10H,
Ph-H), 6.78 (s, 1H, pyr H5), 6.20 (d, J ¼ 21.0 Hz, 1H, pyr H2), 4.75 (dd,
J ¼ 1.6 Hz, 2H, Fc ), 4.71 (dd, J ¼ 1.6 Hz, 2H, Fc ), 4.11 (s, 5H, Fc
C5H5). 13C NMR (CDCl3),
151.3 (pyr C6), 148.3 (Ph i), 142.3 (pyr C4),
3.1.1. Reaction of cyclomanganated chalcone 1a with FcCCH in CCl4
The manganese complex 1a (106 mg, 0.28 mmol) and FcCCH
(119 mg, 0.56 mmol) were dissolved in CCl4 (20 mL), and heated
under reflux for 1 h. The mixture turned from yellow to green, and
IR monitoring showed all nCO bands of 1 had disappeared. On
cooling, a green powder formed which was collected by filtration
and shown to be 2-ferrocenyl-4,6-diphenylpyrylium tetra-
chloroferrate (2a$[FeCl4]) (82 mg, 47%). Found: C 51.34 H 3.93%; calc
for C27H21Fe2OCl4: C 52.73; H 3.44%. ESI-MS positive ion: m/z
417.096, calc for [C27H21FeO]þ 417.094; negative ion: m/z 195.807,
calc for [FeCl4]ꢀ 195.809.
a
b
d
123.6 (pyr C3) 120.5 (pyr C5),120.0e128.0 (Ph-C), 77.0 (pyr C2), 69.6
(Fc C5H5), 69.2, 66.9, 66.7 (Fc C5H4). ESI-MS m/z 418.125 [M]þ, calc
for C27H22OFe 418.122.
3.1.4. Reaction of cyclomanganated chalcone 1b with FcCCH in
benzene
Similarly,1b (120 mg, 0.23 mmol) and FcCCH (65 mg, 0.31 mmol)
were refluxed in benzene for 2.5 h to give a red solution. Chroma-
tography (1:1 CH2Cl2/hexane) gave two major products.
The first was [2-ferrocenyl-4-(3,4,5-trimethoxyphenyl)-6-phe-
3.1.2. Reaction of cyclomanganated chalcone 1b with FcCCH in CCl4
In exactly the same fashion 2-ferrocenyl-4-(3,4,5-trimethox-
yphenyl)-6-phenylpyrylium tetrachloroferrate (2b$[FeCl4]) was
prepared in 58% yield from 1b (106 mg, 0.28 mmol) and FcCCH
(119 mg, 0.57 mmol) as a green powder, identified spectroscopi-
cally. ESI-MS positive ion: m/z 507.129, calc for [C30H27FeO4]þ
507.129; negative ion: m/z 195.813, calc for [FeCl4]ꢀ 195.809.
nylpyranyl-
crystals after crystallisation from ether/pentane. Found: C, 60.41; H,
4.20%, calc for C33H27FeMnO7: C, 60.39; H, 4.15%. IR: (nCO, cmꢀ1
h
5]tricarbonylmanganese, 3b, (56 mg, 40%) as red
)
2012vs, 1951m, 1931m. ESMS: (MeOH), (positive ion) m/z 507
(100%, [M ꢀ Mn(CO)3]þ.
1H NMR (CDCl3)
d
7.50 (d, 2H, J ¼ 8.6 Hz, Ph o’), 7.28e7.58 (m, 3H,
Ph-H), 7.13 (s, 2H, Ph o), 5.63 (s,1H, pyr H3), 5.32 (s,1H, pyr H5), 4.80
(dd, J ¼ 1.6 Hz, 2H, Fc ), 4.43 (dd, J ¼ 1.6 Hz, 2H, Fc ), 4.19 (s, 5H, Fc
C5H5), 4.03 (s, 3H, p OMe), 3.97 (s, 6H, m OMe). 13C NMR (CDCl3)
142.3 (Ph i), 137.0 (Ph i’), 131.3 (Ph m), 128.9 (Ph m’), 128.6 (Ph p),
a
b
3.1.3. Reaction of cyclomanganated chalcone 1a with FcCCH in
benzene
d
Cyclomanganated chalcone 1a (106 mg, 0.28 mmol) and ferro-
cenylethyne (119 mg, 0.32 mmol) were heated under reflux in
benzene (20 mL) for 2.5 h. The reaction mixture turned from yellow
to red, and nCO bands of 1a were absent. The solvent was removed
under vacuum, and the residue chromatographed [p.l.c., CH2Cl2/
hexane 1:1) to give two major bands.
126.5 (Ph o),123.0 (Ph o’),110.7 (pyr C2), 96.8 (pyr C4), 93.4 (pyr C6),
85.0 (pyr C3), 80.9 (pyr C5), 78.2 (Fc i), 69.9 (Fc C5H5), 67.4, 64.7
(C5H4), 60.4 (m OMe), 56.5 (p OMe).
The second product was (2-ferrocenyl-4-(3,4,5-trimethox-
yphenyl)-6-phenyl)pyran, 4b, (31 mg, 24%) as orange crystals from
ether/pentane. Found: C, 70.29; H 6.81%, calc for C30H28O4Fe: C,
70.88; H, 5.55%. ESI-MS m/z 508.137 [Mþ], calc 508.133.
Band 1, red, Rf 0.8 was (2-ferrocenyl-4,6-diphenylpyranyl-h5
)
tricarbonylmanganese, 3a, (47 mg, 26%) as red crystals after crys-
tallisation from ether/pentane. Found: C, 64.80; H, 3.81%, calc for
C30H21FeMnO4: C, 64.78; H, 3.81%. IR: (nCO, cmꢀ1) 2012vs, 1951m,
1931m.
1H NMR (CDCl3)
d
7.32 (m, 5H, Ph-H), 7.12 (d, J ¼ 21.0 Hz, 1H, pyr
H3), 6.74 (s, 1H, pyr H5), 6.68 (s, 2H, Ph o), 6.10 (d, J ¼ 21.0 Hz, 1H,
pyr H2), 4.80 (dd, J ¼ 1.6 Hz, 2H, Fc ), 4.45 (dd, J ¼ 1.6 Hz, 2H, Fc ),
4.27 (s, 5H, C5H5), 3.94 (s, 3H, p OMe), 3.85 (s, 6H, m OMe). 13C NMR
(CDCl3) 153.7 (pyr C6), 151.3 (Ph i), 148.4 (pyr C4), 123.6 (pyr C3),
a
b
d
120.6 (pyr C5), 77.4 (pyr C2), 120.0e128.0 (Ph-C), 69.6, (Fc C5H5),
66.9, 66.7, 66.2, (Fc C5H4), 56.2 (p OMe), 60.9 (m OMe).
p'
m'
R
3.1.5. Preparation of 2-ferrocenyl-4,6-diphenylpyrylium triiodide,
(2a$I3)
o'
i'
6
5
The pyranyl complex 3a (50 mg, 0.09 mmol) and iodine (46 mg,
0.36 mmol) were stirred in CCl4 for 1 h. The solution changed from
yellow to green and all of 4 had been consumed (IR). Solvent was
removed under vacuum to leave a green oil, which solidified to
a green solid when mixed with diethyl ether, tentatively identified
as 2a$I3, (40 mg, 51%) from ESI-MS measurements. Attempts to
purify the solid by recrystallisation were unsuccessful. Further
characterisation was by conversion to the corresponding pyridine
derivative 5a (see below).
R
O
p
4
i
2
o
m
3
i
α
R
(OC)3Mn
β
(3a R = H)
(3b R = OMe)
Fe
Numbering system for NMR of 3a/b. The numbering of other
compounds follows the same convention.
3.1.6. Reaction of 2-ferrocenyl-4,6-diphenylpyrylium
tetrachloroferrate with ammonia
The solid pyrylium salt 2a$[FeCl4] (40 mg, 0.05 mmol) was
treated with a few drops of 30% aqueous ammonia. The resulting
1H NMR (CDCl3)
d
7.50 (d, J ¼ 8.6 Hz, 2H, Ph o’), 7.28e7.58 (m, 8H,
Ph-H), 5.72 (s, 1H, pyr H3), 5.71 (s, 1H, pyr H5), 4.80 (dd, J ¼ 1.6 Hz,
2H, Fc
), 4.43 (dd, J ¼ 1.6 Hz, 2H, Fc
), 4.19 (s, 5H, Fc C5H5). 13C NMR
a
b

N. Prasad et al. / Journal of Organometallic Chemistry 695 (2010) 1961e1965
1965
mixture was chromatographed (p.l.c., ethyl acetate/hexane 1:2) to
Appendix A. Supplementary material
afford one major yellow band, Rf 0.8. Removal gave a yellow oil of
2-ferrocenyl-4,6-diphenylpyridine (12 mg, 57%), 5a, which did not
crystallize. ESI-MS: m/z 415.105 [M]þ, calc for C27H21NFe 415.102;
m/z 416.110 [M þ H]þ, calc for C27H22NFe 416.110; m/z 438.095
[M þ Na]þ, calc for C27H21NFeNa 438.092.
Full details of the structure determination of 2b have been
deposited with the Cambridge Crystallographic Data Centre as
CCDC 767138, which contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.
uk/data_request/cif.
1H NMR (CDCl3)
d
7.28e8.21 (m, 10H, Ph-H), 6.91 (s, 2ꢃ 1H, pyr
), 4.45 (dd, 2H, J ¼ 2.4 Hz, Fc ),
4.11 (s, 5H, Fc C5H5). 13C NMR (CDCl3)
127.0e130.0 (Ph-C), 159.5
(pyr C6), 149.2 (pyr C4), 139.8 (Ph i), 139.3 (pyr C2), 139.1 (Ph i’),
116.5 (pyr C3), 115.6 (pyr C5), 84.0 (Fc i), 69.9 (Fc ), 69.7 (Fc C5H5),
67.1 (Fc ).
H3, H5), 5.10 (dd, J ¼ 2.4 Hz, 2H, Fc
a
b
d
a
References
b
[1] A.T. Balaban, A. Dinculescu, G.N. Dorofeenko, G.W. Fischer, A.V. Koblik,
V.V. Mezheritskii, W. Schroth, Pyrylium salts: synthesis, reactions and
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3.1.7. Reaction of 2-ferrocenyl-4-(3,4,5-trimethoxyphenyl)-6-
phenylpyrylium tetrachloroferrate with ammonia
Similarly the pyrylium salt 2b$[FeCl4] (40 mg, 0.05 mmol)
treated with a few drops of 30% ammonia afforded a yellow band, Rf
0.8. Removal and crystallisation from CH2Cl2/pentane gave yellow
crystals of 2-ferrocenyl-4-(3,4,5-trimethoxyphenyl)-6-phenyl-
pyridine (19 mg, 56%), 5b. Found: C, 70.79; H, 5.71; N, 2.77%. Calc for
C30H27NFeO3: C, 71.30; H, 5.38; N, 2.77%. ESI-MS: m/z 506 [M þ H]þ.
G.N. Dorofeenko, V.V. Krasnikov, Zh. Org. Khim. 8 (1972) 2620.
[4] K.L. Malisza, S. Top, J. Vaissermann, B. Caro, M.C. Sénéchal-Tocquer,
D. Sénéchal, J.Y. Saillard, C. Triuki., S. Kahlal, J.F. Britten, M.J. McGlinchey,
G. Jaouen, Organometallics 14 (1995) 5273;
1H NMR (CDCl3)
d
7.28e8.21 (m, 10H, Ph-H), 6.91 (s, 2ꢃ 1H, pyr
H3, H5), 5.10 (dd, J ¼ 2.4 Hz, 2H, Fc
4.11 (s, 5H, Fc C5H5), 4.00 (s, 3H, p OMe), 3.97 (s, 6H, m OMe). 13
NMR (CDCl3)
139.8 (Ph i), 139.6 (pyr C2), 139.1 (Ph i’), 116.5 (pyr C3), 115.6 (pyr
a
), 4.45 (dd, 2H, J ¼ 2.4 Hz, Fc
b
),
C
B. Caro, F.R. Guen, M.C. Sénéchal-Tocquer, V. Prat, J. Vaissermann, J. Organo-
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B. Caro, Bioconjugate Chem. 5 (1994) 655;
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M. Salmain, B. Caro, F. Le Guen-Robin, J.C. Blais, G. Jaouen, ChemBioChem 5
(2004) 99.
d
127.0e130.0 (Ph-C), 157.0 (pyr C6), 153.8 (pyr C4),
C5), 84.0 (Fc i), 69.9 (Fc
60.4 (m OMe).
a), 69.7 (Fc C5H5), 67.1 (Fc b), 56.5 (p OMe),
[5] F. Ba, N. Cabon, F. Robin-Le Guen, P. Le Poul, N. Le Poul, Y. Le Mest, S. Golhen,
B. Caro, Organometallics 27 (2008) 6396.
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[9] W. Henderson, J.S. McIndoe, Mass spectrometry of inorganic, coordination
and organometallic compounds; tools, techniques, tips. Wiley, Chichester,
2005.
3.2. X-ray crystal structure determination of (2-ferrocenyl-4,6-
diphenylpyranyl-
5)-tricarbonylmanganese (3a)
h
Crystal data: C30H21FeMnO4, Mr 556.26, monoclinic, space group
P21/c, a ¼ 7.417(2), b ¼ 14.716(4), c ¼ 21.750(6) Å,
b
¼ 94.39(2)ꢂ,
V
¼
2366.8(12) Å3, Dcalc
¼
1.56
g
cmꢀ3
,
Z
¼
4, m(Mo
Ka
)
¼
1.183 mmꢀ1
,
red crystals from CH2Cl2/pentane, size
[10] L.A. Pena, A.J. Seidl, L.R. Cohen, P.E. Hoggard, Transition Met. Chem. 34 (2009)
135;
1.08 ꢃ 0.32 ꢃ 0.20 mm3, F(000) ¼ 1136, T ¼ 93(2) K. Total data
S.L. Phan, P.E. Hoggard, Inorg. React. Mech. 1 (1998) 17;
O. Traverso, R. Rossi, V. Carassiti, Synth. React. Inorg. Met-Org. Chem. 4 (1974)
309;
34245, unique data 5435 (Rint 0.029), 2ꢂ
< q
< 27.5ꢂ, Tmax,min 1.00,
0.671, R1 ¼ 0.0254, [4871 data with I > 2
s(I)], wR2 (all data) 0.0653,
GoF 1.069, residual
D
e ꢄ j0.38j e Åꢀ3. The structure was solved by
D.M. Papsun, J.K. Thomas, J.A. Labinger, J. Organomet. Chem. 208 (1981) C36.
ꢀ
ꢀ
ꢀ
[11] M. Auzias, B. Therrien, G. Süss-Fink, P. Stepnicka, W.H. Ang, P.J. Dyson, Inorg.
Chem. 47 (2008) 578.
direct methods and developed and refined routinely using the
SHELX-97 programmes [20] running under WinGX [21] with
hydrogen atoms included in calculated positions.
[12] C.J. McAdam, B.H. Robinson, J. Simpson, Acta Cryst E59 (2003) m687.
[13] M.R. Detty, J.M. McKelvey, H.R. Luss, Organometallics 7 (1988) 1131.
[14] F. Barrière, W.E. Geiger, J. Am. Chem. Soc. 128 (2006) 3980.
[15] M. Yamagata, N. Tachikawa, Y. Katayama, T. Miura, Electrochim. Acta 52
(2007) 3317;
L.J. Sacks, Anal. Chem. 35 (1963) 1299.
[16] Y.S. Sohn, D.N. Hendrickson, H.B. Gray, J. Am. Chem. Soc. 93 (1971) 3603.
[17] M.T. Hay, S.J. Geib, Acta Cryst. E61 (2005) m190.
Acknowledgement
[18] W. Tully, L. Main, B.K. Nicholson, J. Organomet. Chem. 503 (1995) 75.
[19] L. Main, B.K. Nicholson, Adv. Metal-Org. Chem. 3 (1994) 1.
[20] G.M. Sheldrick, SHELX97 Programs for the solution and refinement of crystal
structures. University of Göttingen, Germany, 1997.
[21] L.J. Farrugia, WinGX, Version 1.70.01, University of Glasgow, UK. L.J. Farrugia,
J. Appl. Cryst. 32 (1999) 837.
We thank Dr Jan Wikaira, University of Canterbury, for collection
of X-ray intensity data. Professor M I Bruce and G. Perkins,
University of Adelaide, are thanked for
ferrocenylethyne.
a generous gift of