Coupling of pentacarbonyl[(cyclopropyl)methoxymethylene]molybdenum complex with ferrocenyl alkynes: Synthesis of ferrocenyl-substituted cycloheptadienones and cycloheptenediones

Article abstract of DOI:10.1016/j.jorganchem.2006.12.008

Pentacarbonyl[(cyclopropyl)methoxymethylene]molybdenum complex reacts with ferrocenyl alkynes to afford ferrocenyl-substituted 2,4-cycloheptadienones as major products, accompanied by varying amounts of 2-cycloheptene-1,4-diones and/or 2-cyclobutenones. 2-Cycloheptene-1,4-diones are secondary reaction products and result from initially formed 2,4-cycloheptadienones via hydrolysis. In one reaction, a hydroxy-substituted 2,4-cycloheptadienone derivative was isolated, which was not observed previously from similar reactions.

Full text of DOI:10.1016/j.jorganchem.2006.12.008

Journal of Organometallic Chemistry 692 (2007) 1571–1578
www.elsevier.com/locate/jorganchem
Coupling of pentacarbonyl[(cyclopropyl)methoxymethylene]-
molybdenum complex with ferrocenylalkynes: Synthesis of
ferrocenyl-substituted cycloheptadienones and cycloheptenediones
a,
a
c,1
Metin Zora *, Canet Ac¸ıkgoz , Mustafa Odabasog˘lu b,1, Orhan Buyukgungor
¨
ß
¨ ¨
¨
¨
a
Department of Chemistry, Faculty of Arts and Sciences, Middle East Technical University, 06531 Ankara, Turkey
Department of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayıs University, 55139 Kurupelit Samsun, Turkey
b
c
Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, 55139 Kurupelit Samsun, Turkey
Received 18 November 2006; received in revised form 12 December 2006; accepted 12 December 2006
Available online 20 December 2006
Abstract
Pentacarbonyl[(cyclopropyl)methoxymethylene]molybdenum complex reacts with ferrocenyl alkynes to afford ferrocenyl-substituted 2,4-
cycloheptadienones as major products, accompanied by varying amounts of 2-cycloheptene-1,4-diones and/or 2-cyclobutenones.
2-Cycloheptene-1,4-diones are secondary reaction products and result from initially formed 2,4-cycloheptadienones via hydrolysis. In one
reaction, a hydroxy-substituted 2,4-cycloheptadienone derivative was isolated, which was not observed previously from similar reactions.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Fischer metal carbene; Molybdenum carbene complex; Ferrocene; Ferrocenyl alkynes; Carbocyclic seven-membered rings; Cycloheptadie-
nones; Cycloheptenediones; Cyclobutenones; Coupling
1. Introduction
C6H4-O-CH2-CH2-NMe2], a ferrocenyl analog of hydroxy-
tamoxifen which is a drug currently used in the treatment
of hormone-dependent breast cancer lines [8]. The replace-
ment of the phenyl ring by a ferrocenyl (Fc) moiety has
brought about novel pharmacological properties for
hydroxyferrocifen since it is active against both hormone-
dependent and hormone-independent breast cancer cells
whereas its phenyl counterpart, hydroxytamoxifen, is active
only against hormone-dependent cancer cells [7,8]. Due to
its unique structure, different membrane-permeation proper-
ties and anomalous metabolism, ferrocene is often incorpo-
rated into a compound in order to get unexpected or
enhanced biological activities [9]. Surprisingly, seven-mem-
bered ring carbocycles bearing a ferrocenyl moiety are very
rare. The development of a general synthetic entry to such
compounds is therefore of considerable interest since it
could lead to a new source of biologically active compounds.
These ring systems are typically constructed by ring
expansion reactions, cyclization reactions, cycloaddition
reactions and synthetic modifications of other seven-
membered rings [10]. Recently, Fischer type metal carbene
Carbocyclic seven-membered rings are present in a vari-
ety of biologically-important molecules, including phorbol
esters [1], colchicine derivatives [2], guaiazulenes [3], guai-
anolides [3] and pseudoguiainolides [3,4], the latest having
more than 1000 varieties [4]. Some of them exhibit high
biological activities such as antitumor, antiulcer, antisistos-
omal, anthelmintic, cardiotonic, contraceptive, immuno-
modulation, root-growth stimulatory, root-growth and
germination inhibitory activities, as well as preventive or
curative activities for crop diseases [5]. Recent studies have
suggested that the integration of a ferrocenyl group into
such structures may enhance their biological activities or
generate new medicinal properties [6,7]. A typical example
is hydroxyferrocifen [7], (Z)-[(Et)(Fc)C@C(p-C6H4-OH)p-
*
Corresponding author. Tel.: +90 312 2103213; fax: +90 312 2103200.
E-mail address: zora@metu.edu.tr (M. Zora).
Authors to whom inquiries concerning the X-ray analysis should be
1
directed.
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.12.008

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M. Zora et al. / Journal of Organometallic Chemistry 692 (2007) 1571–1578
Fe
Fe
Fe
Fe
O
O
O
Mo(CO)
5
R
THF
O
+
+
+
+
Fe
OH
R
OCH
3
o
65 C, 5 h
OCH
R
R
3
R
1
2
OCH
O
OCH
3
3
3
4
5
6
Scheme 1. Reaction of carbene complex 2 with ferrocenyl alkynes 1. For definition of R group for compounds 1 and 3–6, see Table 1.
complexes have emerged as valuable reagents for organic
synthesis [11]. An ever continuing aspect of these studies
has been the use of a structurally diverse set of Fischer
carbene complexes to afford a diverse array of compounds.
In this regard, as shown by the Herndon research group
[12,13], the reaction between alkynes and pentacarbonyl-
[(cyclopropyl)methoxymethylene]metal complexes represent
a very rapid entry to the corresponding 2,4-cycloheptadie-
nones. This methodology, however, has not been utilized
for the synthesis of 2-ferrocenyl-2,4-cycloheptadienones,
presumably due to the scarce availability of the starting
ferrocenyl alkynes. As part of our general interest in ferro-
cene [14,15] and metal carbene chemistry [13,16], as well
as small and medium-size ring systems [17], we have inves-
tigated the reaction between ferrocenyl alkynes 1 and
pentacarbonyl[(cyclopropyl)methoxymethylene]molybdenum
complex 2 to afford ferrocenyl-substituted cycloheptadie-
nones 3 (Scheme 1) [18]. We herein report the results of
this study.
Table 1
Reaction of carbene complex 2 with ferrocenyl alkynes 1
Entrya
Alkyne
R
Products (isolated yield, %)
A
B
C
D
a
1A
1B
1C
1D
CH3
CH2Ph
Ph
3A (47) + 4A (12) + 5Ab (12)
3B (70) + 4B (13)
3C (72) + 4C (10)
3D (15) + 6D (8)
Fc (ferrocenyl)
Entry letters define R group for compounds 1 and 3–6.
Relative stereochemistry of substituents at carbons 6 and 7 was not
b
determined.
Scheme 1 and Table 1. The reactions were carried out
under optimal conditions, which involve heating a 1:1.5
mole ratio of carbene complex 2 and alkyne 1, respectively,
in THF at 65 ꢁC. Initially, the reaction between propynyl-
ferrocene (1A) and carbene complex 2 was examined,
which afforded the expected cycloheptadienone (3A) as
the major product of the reaction, along with the varying
amounts of cycloheptenedione (4A) and hydroxy-substi-
tuted cycloheptadienone (5A) (entry A). The coupling of
carbene complex 2 with benzylferrocenylacetylene (1B)
produced two products, cycloheptadienone (3B) and cyclo-
heptenedione (4B), with 3B the major product of the reac-
tion (entry B). A similar trend was observed in the reaction
of 2 with (phenylethynyl)ferrocene (1C), where cyclohepta-
dienone (3C) and cycloheptenedione (4C) were obtained,
the former being the major product (entry C). On the other
hand, the reaction between diferrocenylacetylene (1D) and
carbene complex 2 revealed a complex reaction mixture;
only cycloheptadienone (3D) and cyclobutenone (6D)
could be isolated (entry D). Triphenylphosphine is often
used to improve the yields of products in metal carbene
reactions [13]. Triphenylphosphine could displace carbon
monoxide at early stage of the reaction, which could then
be replaced by the alkyne. When the same reactions, how-
ever, were carried out in the presence of triphenylphos-
phine, low yields of products were obtained in contrast to
previous studies [13a], which may be attributed to the prob-
able steric effect caused by triphenylphosphine and ferro-
cene moieties. That is why; all reactions in this study
were performed without using triphenylphosphine.
2. Results and discussion
2.1. Synthesis of starting materials
The synthesis of ferrocenyl alkynes were achieved from
ethynylferrocene [19] according to known or modified liter-
ature procedures [20–22]. Treatment of ethynylferrocene
with n-butyllithium produced in situ lithioethynylferrocene
that was further reacted with methyl iodide and benzyl bro-
mide to yield propynylferrocene (1A) and (3-phenylpropy-
nyl)ferrocene (1B), respectively [20]. On the other hand, the
reaction of ethynylferrocene and iodobenzene in the pres-
ence of copper iodide, triphenylphosphine and potassium
carbonate in refluxing DMF produced (phenylethynyl)fer-
rocene (1C) [21]. Diferrocenylethyne (1D) was synthesized
by the metathesis of propynylferrocene in the presence of
molybdenum hexacarbonyl and 2-fluorophenol in refluxing
chlorobenzene [22]. Pentacarbonyl[(cyclopropyl)meth-
oxymethylene]molybdenum complex 2 was prepared from
cyclopropyl bromide and molybdenum hexacarbonyl
according to a standard protocol [13b].
As noted in Table 1, cycloheptadienones (3) have been
obtained as the major products from the reactions between
molybdenum carbene complex 2 and ferrocenyl alkynes (1).
In the light of previous studies [13,23], the proposed mecha-
nism for their formation is outlined in Scheme 2. The loss of
a carbon monoxide ligand from complex 2 and coordination
2.2. Coupling of pentacarbonyl [(cyclopropyl)methoxy-
methylene]molybdenum complex 2 with ferrocenyl alkynes 1
We next investigated the reaction of carbene complex 2
with ferrocenyl alkynes 1. The results are summarized in

M. Zora et al. / Journal of Organometallic Chemistry 692 (2007) 1571–1578
1573
Fc
regiochemistry of the reaction is set up in the formation of
metallacyclobutene (8) and/or vinyl carbene complex 9
(Scheme 2), where the larger Fc group ends up a to the
molybdenum in order to minimize steric interactions. Fol-
lowing this substituent through the mechanism in Scheme
2, it is predicted that Fc group will be a to the carbonyl
group in the final products.
Fc
R
Mo(CO)
(CO) Mo
5
Δ, −CO
4
(CO) Mo
4
R
OCH
3
Fc
R
OCH
3
OCH
3
1
2
8
7
Cycloheptenediones (4) were also resulted from these
reactions (Table 1) but in low yields. In fact, cyclohepten-
ediones (4) are secondary product of the reactions and
result from the initially formed cycloheptadienones (3)
via hydrolysis of enol ether functionality. Note that when
subjected to acidic hydrolysis, cycloheptadienones (3) pro-
vides cycloheptenediones (4) in very high yields. That is
why; if the crude reaction mixture is hydrolyzed under
acidic conditions before chromatography, 2- or 3-ferroce-
nyl-substituted 2-cycloheptene-1,4-diones (4) can be
obtained as the major products of the reactions.
Interestingly, from the reaction with propynylferrocene
(1A) (Table 1, entry A), a new product was isolated and
assigned as a 7-hydroxy-2,4-cycloheptadienone derivative,
5A. To the best of our knowledge, such product was not
observed previously from similar reactions. It should be
noted that, at relatively higher temperatures, 4-methoxy-
2,4-cycloheptadienone derivatives are well known to con-
vert to thermodynamically more stable 5-methoxy-2,4-
cycloheptadienones by two consecutive 1,5-H shifts
[12,13]. Although, at present, we do not speculate the
mechanism for the formation of this product, which
requires further study, it is apparent that, during the rear-
rangement of the initially formed cycloheptadienone 3A to
5A, water addition occurs somehow. Interestingly, in 5A,
hydroxy substituent ends up a to the ferrocenyl group. This
might be attributed to the developing radical or positive
charge at that carbon during the course of the reaction,
which is well stabilized, although it is also a to the car-
bonyl, since the ferrocenyl group is very effective at stabiliz-
ing an a radical or carbocation [14d,27]. In addition, the
ferrocenyl group is a much better radical and carbocation
stabilizing group than the phenyl group.
The reaction with diferrocenylacetylene (1D) afforded
the products in relatively low yields (Table 1, entry D), as
compared to that with diphenylacetylene [13]. Low yields
of these products might be due to the steric effect caused
by two ferrocenyl groups of 1D during the course of the
reaction. In this reaction, cyclobutenone derivative 6D
was also formed. Cyclobutenones are often observed in
the reaction of metal carbenes with alkynes [28]. Cyclobute-
none (6D) could arise via two possible pathways as depicted
in Scheme 3. Metallacyclobutene (8D) first gives CO inser-
tion to afford internally-coordinated metallacyclopente-
none (14D), which produces cyclobutenone (6D) upon
reductive elimination Alternatively, vinylcarbene complex
9D experiences CO insertion and yields vinylketene com-
plex 15D, which furnishes cyclobutenone (6D) after electro-
cyclic ring closure followed by decomplexation. Note that
metallacyclobutene (8D) and vinyl carbene complex 9D
O
(CO)
Mo
(CO)
4
3
(CO) Mo
Fc
R
Fc
4
Mo
Fc
R
CO Ins.
R
OCH
3
OCH
3
OCH
3
11
10
9
-Mo(CO)
CO Ins.
3
O
O
O
C
Fc
R
Fc
R
Fc
R
-Mo(CO)
3
Mo(CO)
3
CH O Mo(CO)
3
3
OCH
CH O
3
3
3
13
12
Scheme 2. Proposed mechanism for the formation of cycloheptadienones
(3).
of alkyne 1 produces alkyne-carbene complex 7, which
undergoes a [2+2] cycloaddition reaction to afford metalla-
cyclobutene (8). Electrocyclic ring opening then occurs to
yield internally-coordinated vinyl carbene complex 9. The
involvement of metallacyclobutenes in these processes has
recently been questioned by Hofmann and found to be unfa-
vorable on the basis of theoretical calculations [24]. Thus,
complex 9 could be directly formed from 7 via alkyne inser-
tion without formation of metallacyclobutene (8). After-
wards, complex 9 undergoes a 1,5-alkyl shift to give
metallacycloheptadiene (10). CO insertion then occurs to
afford metallacyclooctadienone (11), which upon reductive
elimination yields cycloheptadienones (3). Alternatively,
CO insertion in 9 produces vinylketene complex 12. Cyclo-
propane ring of 12 then opens by a 1,5-alkyl shift to generate
metallacycloheptadienone (13), which upon decomplex-
ation affords cycloheptadienones (3). As noted by Herndon
[13b] using similar reactions, two variations (9 ! 10 !
11 ! 3 vs. 9 ! 12 ! 13 ! 3) in this mechanism can be
envisaged, which differ in their timing of CO insertion versus
cyclopropane ring opening step (Scheme 2). The former
pathway is the currently-favored mechanism since there is
evidence that cyclopropane ring opening reactions can arise
from (2-cyclopropylvinyl)carbene complexes [25]. Con-
versely, (2-cyclopropylvinyl)ketenes obtained from ther-
molysis of 4-cyclopropyl-2-cyclobutenones do not produce
cycloheptadienones [13b,26]. Thus the later mechanism
can only be operative if vinylketene-metal complexes are
very different in their reactivity.
In all products, the larger group of the alkyne (i.e. Fc
group) has ended up a to the carbonyl, which is the regio-
chemistry observed in such reactions [12,13,23]. In fact, the

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M. Zora et al. / Journal of Organometallic Chemistry 692 (2007) 1571–1578
O
Fc
Fc
Fc
Fc
(CO) Mo
4
(CO) Mo
3
−Mo(CO)
3
OCH
3
OCH
3
8D
14D
Fc
Fc
O
OCH
3
O
(CO) Mo
4
Fc
Fc
C
Fc
Fc
6D
−Mo(CO)
3
Mo(CO)
OCH
CH O
3
3
3
9D
15D
Scheme 3. Proposed mechanism for the formation of cyclobutenone (6D).
are interconvertible and their formation has been shown in
Scheme 2.
Fig. 1. ORTEP diagram of 3-benzyl-2-ferrocenyl-4-methoxy-2,4-cyclo-
heptadienone (3B). Ellipsoids are drawn at 30% probability.
On the other hand, the reaction of metal carbene com-
plex 2 with ethynylferrocene (a terminal alkyne) or 3-ferr-
ocenylpropynal (an electron-deficient alkyne) failed,
presumably due to the polymerization or electron-defi-
ciency of the alkyne system, a result consistent with the
findings of previous investigators using similar systems [13].
In the reactions between molybdenum complex 2 and
conventional alkynes, furanone formation was reported
to be a major competing pathway [13]. Furanone forma-
tion, however, was not a problem when diphenylacetylene
is the alkyne or when phosphine ligands such as triphenyl-
phosphine are used as an additive. On the other hand, in
our reaction conditions, even in the absence of triphenyl-
phosphine, furanones were not observed. Apparently, the
presence of ferrocenyl moiety electronically and/or steri-
cally prevents the formation furanone type products.
Table 2
Crystallographic data and structure refinement parameters for 3B
Empirical formula
Formula weight
Crystal size (mm)
Crystal shape
Temperature (K)
Crystal system
Space group
C25H24FeO2
412.29
0.390 · 0.300 · 0.180
Prism
296(2)
Triclinic
ꢀ
P1
˚
a (A)
7.7443(5)
11.3769(7)
11.5864(7)
76.372(5)
80.118(5)
89.386(5)
976.90(11)
2
1.402
0.790
Mo Ka/0.71073
0.7651, 0.8892
26
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Dx (g cmꢀ3
)
l (Mo Ka) (mmꢀ1
)
2.3. Crystal structure of 3-benzyl-2-ferrocenyl-4-methoxy-
2,4-cycloheptadienone (3B)
˚
Radiation/wavelength (A)
Transmission factors (Tmin, Tmax
hmax (ꢁ)
Index range (hkl)
Reflections measured
)
The structure of cycloheptadienone (3B) was determined
by X-ray crystal analysis. ORTEP diagram of 3B is shown
in Fig. 1. Details of cell data, X-ray data collection, struc-
ture solution and refinement are given in Table 2. Selected
bond distances and angles are denoted in Table 3. A com-
plete list of atomic coordinates, bond distances and angles,
anisotropic thermal parameters, hydrogen atom coordi-
nates have been deposited and are available upon request,
Supplementary data.
ꢀ9/8, ꢀ14/14, ꢀ14/14
21080
Independent reflections (Rint
Reflections with I > 2r(I)
Number of parameters
Number of restraints
R[F2 > 2r(F2)]
)
3839 (0.0387)
3249
254
0
0.0257
0.0648
1.030
0.198, ꢀ0.286
wR(F2)
Goodness-of-fit (F2)
Maximum, minimum Dq (e/A )
3
˚
In the solid state, seven-membered ring adopts a boat-
like conformation and, as a result, conjugation between
double bonds is largely interrupted as shown by the C12–
C11–C17–O1 and C11–C12–C13–C14 torsion angles of
107.41(18)ꢁ and 42.2(2)ꢁ, respectively. C15 and C16 meth-
ylene carbons in the ring exist in a staggered gauche con-
formation and the related torsion angle (C14–C15–C16–
C17) is 50.7(2)ꢁ. O1–C17, C11–C12 and C13–C14 bond
the average C–Cgs–Cgas–C torsion angle of ꢀ14.11(9)ꢁ,
where Cgs and Cgas are the substituted and unsubstituted
Cp ring centroids, respectively. The centroids of Cp rings
are almost equidistant from Fe atom as indicated by the
Fe–Cgs and Fe–Cgas distances of 1.648(17) and 1.657(17)
˚
A, respectively, and the Cgs–Fe–Cgas angle is 177.48(11)ꢁ.
Cp rings of ferrocenyl group are almost parallel since the
˚
distances are 1.211(2), 1.344(2) and 1.327(2) A, respec-
tively, and all are as expected. Ferrocenyl group is in a
slightly distorted eclipsed conformation as concluded from
angle between Cp ring planes is 3.67(12)ꢁ. The C–C bond
˚
distances in Cp rings alter from 1.382(3) to 1.435(2) A,

M. Zora et al. / Journal of Organometallic Chemistry 692 (2007) 1571–1578
1575
Table 3
Selected bond distances (A), bond angles (ꢁ) and torsion angles (ꢁ) for 3B
interactions (Fig. 2). There is a single type of intermolecu-
˚
lar hydrogen bond, [C9–H9. . .O1i: H. . .O = 2.59 A,
˚
˚
C1–C2
1.435(2)
1.469(2)
2.0697(15)
1.407(2)
1.402(3)
2.0361(18)
1.382(3)
1.387(3)
1.414(3)
2.0342(19)
2.0460(19)
1.344(2)
1.516(2)
C12–C13
C12–C19
C13–C14
C13–O2
C14–C15
C15–C16
C16–C17
C17–O1
C18–O2
C19–C20
C20–C21
C21–C22
C22–C23
1.486(2)
1.512(2)
1.327(2)
1.3736(19)
1.499(2)
1.513(3)
1.493(2)
1.211(2)
1.4260(19)
1.511(2)
1.381(2)
1.387(3)
1.369(4)
C. . .O = 3.511(2) A, C–H. . .O = 171ꢁ, (i) ꢀx, 1 ꢀ y,
C1–C11
C1–Fe1
C2–C3
1 ꢀ z], linking the molecules and generate cyclic centrosym-
metric R22(14) dimers which ring centroid at (1,1/2,1/2) [29].
Centrosymmetric dimers are linked through C15–
C3–C4
C4–Fe1
C6–C7
C6–C10
C7–C8
ii
H15a. . .Cgas [Cgas is the centroid of the C6. . .C10 ring;
˚
˚
H15a. . .Cg = 2.975 A,
C15. . .Cg = 3.736(2) A,
C15–
H15a. . .Cg = 136.20ꢁ, (ii) 1 ꢀ x, 1 ꢀ y, 1 ꢀ z] and C14ꢀ
H14 . . . Cgipii [Cgp is the centroid of the C20. . .C25 ring;
C8–Fe1
C10–Fe1
C11–C12
C11–C17
˚
˚
H14. . .Cg = 2.903 A, C4. . .Cg = 3.783(2) A, C14–H14. . .
Cg = 158.35ꢁ (iii) 1 ꢀ x, 1 ꢀ y, ꢀz] interactions.
3. Conclusion
C5–C1–C2
106.21(14)
126.93(10)
117.80(13)
120.66(13)
124.87(14)
124.10(14)
O2–C13–C12
O1–C17–C16
O1–C17–C11
C20–C19–C12
C21–C20–C19
C10–Fe1–C1
110.33(13)
121.82(15)
118.59(15)
114.45(13)
119.92(15)
111.47(7)
C11–C1–Fe1
C12–C11–C17
C11–C12–C13
C11–C12–C19
C14–C13–C12
In summary, we have investigated the reaction between
pentacarbonyl[(cyclopropyl)methoxymethylene]molybdenum
complex 2 and ferrocenyl alkynes 1, affording ferrocenyl-
substituted 2,4-cycloheptadienones (3) as the major
products, along with the minor amounts of 2-cyclohep-
tene-1,4-diones (4) and/or 2-cyclobutenones (6). The reac-
tion is regioselective and general for internal alkynes
unless the alkyne is electron-deficient. The hydrolysis of
2,4-cycloheptadienones (3) under acidic conditions provides
2-cycloheptene-1,4-diones (4) in very high yields. In the case
of diferrocenylacetylene (1D), steric effects are more pro-
nounced, lowering the yields of products. In conclusion,
our study has shown that, under appropriate conditions,
C5–C1–C11–C12
ꢀ154.60(16) C15–C16–C17–C11 31.5(2)
18.2(2) C12–C11–C17–O1 107.41(18)
C11–C12–C19–C20 ꢀ114.66(16)
ꢀ140.06(14) C12–C19–C20–C21 ꢀ133.55(16)
C12–C13–C14–C15 ꢀ3.6(3) C12–C13–O2–C18 ꢀ179.21(13)
C5–C1–C11–C17
C17–C11–C12–C13 11.9(2)
C11–C12–C13–O2
while Fe–C bond lengths vary between 2.029(19) and
2.070(15) A, all of which are as expected [21a].
Crystals of cycloheptadienone (3B) are stabilized by
C–H. . .O intermolecular hydrogen bond and C–H. . .p
˚
Fig. 2. A packing diagram for 3B, showing the C–H. . .O, C–H. . .np interactions represented as dashed lines. H atoms not involved in hydrogen bonds
have been omitted for clarity. [Symmetry codes: (i) ꢀx, 1 ꢀ y, 1 ꢀ z; (ii) 1 ꢀ x, 1 ꢀ y, 1 ꢀ z; (iii) 1 ꢀ x, 1 ꢀ y, ꢀz].

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M. Zora et al. / Journal of Organometallic Chemistry 692 (2007) 1571–1578
ferrocenyl alkynes follow the reactivity patterns of conven-
tional alkynes upon reaction with metal carbene complexes.
9:1 hexane–ethyl acetate afforded the products given in
Table 1 with the indicated yields.
4. Experimental
4.3. Spectral data for products
4.1. General consideration
4.3.1. 2-Ferrocenyl-4-methoxy-3-methyl-2,4-
cycloheptadienone (3A)
Nuclear Magnetic Resonance (1H and 13C) spectra were
recorded on a Bruker Spectrospin Avance DPX400 Ultra-
shield (400 MHz) spectrometer. Chemical shifts are
reported in parts per million (d) downfield from an internal
tetramethylsilane reference. Coupling constants (J values)
are reported in hertz (Hz), and spin multiplicities are indi-
cated by the following symbols: s (singlet), d (doublet), t
(triplet), q (quartet), m (multiplet). DEPT 13C NMR infor-
mation is given in parenthesis as C, CH, CH2 and CH3.
Infrared spectra were recorded on a Perkin Elmer 1600 Ser-
ies FT-IR spectrometer. Band positions are reported in
reciprocal centimeters (cmꢀ1). Band intensities are reported
relative to the most intense band and are listed as: br
(broad), vs (very strong), s (strong), m (medium), w (weak),
vw (very weak). Mass spectra (MS) were obtained on a
Finnigan MAT 95 spectrometer, using electron impact
(EI) at 70 eV; m/z values are reported. High resolution
mass spectra (HRMS) were obtained on a Finnigan
MAT 95 spectrometer by preselected-ion peak matching
at R ꢁ 10000 to be within 3 ppm of the exact masses.
Flash chromatography was performed using thick-walled
glass columns and ‘flash grade’ silica (Merck 230-400
mesh). Routine thin layer chromatography (TLC) was
effected by using precoated 0.25 mm silica gel plates pur-
chased from Merck. The relative proportion of solvents
in mixed chromatography solvents refers to the vol-
ume:volume ratio. Ferrocenyl alkynes 1A–D [19–22] and
pentacarbonyl[(cyclopropyl)methoxymethylene]molybde-
num complex 2 [13b] were synthesized according to the well
known literature procedures. All other commercially avail-
able reagents and reactants were obtained in reagent grade
and used without purification. All reaction solvents were
distilled for purity. Diethyl ether, THF and dioxane were
distilled from sodium/benzophenone ketyl. The inert atmo-
sphere was created by slight positive pressure (ca. 0.1 psi)
of argon.
1H NMR (CDCl3): d 5.13 (t, 1H, J = 7.3 Hz), 4.41 (s,
2H), 4.28 (s, 2H), 4.08 (s, 5H), 3.49 (s, 3H), 2.86 (pseudo
t, 2H, J = 6.4 Hz), 2.36 (pseudo q, 2H, J = 6.8), 1.93 (s,
3H); 13C NMR (CDCl3): d 206.1 (C), 158.1 (C), 137.7
(C), 132.2 (C), 98.5 (CH), 79.3 (C), 69.9 (CH), 69.6 (CH),
68.9 (CH), 54.6 (CH3), 51.6 (CH2), 20.1 (CH2), 16.5
(CH3); IR (CH2Cl2): 3052 (s) 1683 (s), 1629 (m), 1422
(m), 1362 (m), 1272 (vs), 1258 (vs), 1203 (m), 1130 (m),
1105 (m) cmꢀ1; MS (EI): 336.2 (M+), 334.2, 308.2, 293.1,
255.0, 227.0, 199.1, 186.0, 153.1, 129.1, 121.0, 115.1;
HRMS (EI): calcd. for C19H20FeO2: 336.0813. Found:
336.0816.
4.3.2. 3-Benzyl-2-ferrocenyl-4-methoxy-2,4-
cycloheptadienone (3B)
1H NMR (CDCl3): d 7.34–7.28 (m, 3H), 7.19 (m, 2H),
5.13 (t, 1H, J = 7.3 Hz), 4.41 (t, 2H, J = 1.8 Hz), 4.25 (t,
2H, J = 1.8 Hz), 4.08 (s, 5H), 3.80 (s, 2H), 3.36 (s, 3H),
2.98 (pseudo t, 2H, J = 6.7 Hz), 2.45 (pseudo q, 2H,
J = 7.0 Hz); 13C NMR (CDCl3): d 205.7 (C), 157.1 (C),
139.8 (C), 139.5 (C), 133.5 (C), 128.4 (CH), 128.1 (CH),
125.9 (CH), 99.8 (CH), 78.3 (C), 69.6 (CH), 69.3 (CH),
69.1 (CH), 54.6 (CH3), 51.7 (CH2), 35.2 (CH2), 20.3
(CH2); IR (CH2Cl2): 3056 (vs), 2981 (m), 2682 (w), 2301
(m), 1688 (s), 1627 (m), 1424 (vs), 1260 (vs), 1049 (m),
902 (s) cmꢀ1; MS (EI): 412.2 (M+), 398.2, 384.2, 370.2,
331.1, 318.1, 303.1, 275.1, 253.1, 217.1, 213.0, 186.1,
151.2, 137.1, 121.0; HRMS (EI): calcd. for C25H24FeO2:
412.1126. Found: 412.1130.
4.3.3. 2-Ferrocenyl-4-methoxy-3-phenyl-2,4-
cycloheptadienone (3C)
1H NMR (acetone-d6): d 7.25 (m, 3H), 7.05 (m, 2H),
5.46 (t, 3H, J = 7.3 Hz), 4.16 (t, 2H, J = 1.8 Hz), 4.09 (s,
5H), 3.87 (t, 2H, J = 1.8 Hz), 3.38 (s, 3H), 3.03 (pseudo t,
2H, J = 6.5 Hz), 2.64 (pseudo q, 2H, J = 6.5 Hz); 13C
NMR (acetone-d6): d 204.6 (C), 157.6 (C), 139.1 (C),
138.7 (C), 133.7 (C), 129.5 (CH), 127.9 (CH), 127.1 (CH),
100.4 (CH), 77.5 (C), 69.3 (CH), 69.2 (CH), 69.0 (CH),
54.1 (CH3), 51.5 (CH2), 20.4 (CH2); IR (CH2Cl2): 3049
(vs), 2988 (s), 2680 (m), 2521 (w), 2407 (w), 2298 (s),
4.2. General procedure for the reaction of pentacarbonyl-
[(cyclopropyl)methoxymethylene]molybdenum complex 2
with ferrocenyl alkynes 1 (Table 1)
A
solution of molybdenum carbene complex
2
1682 (s), 1418 (m), 1259 (vs), 1158 (w), 900 (vs) cmꢀ1
;
(0.50 mmol) and ferrocenyl alkyne 1 (0.75 mmol) in THF
(30 mL) was refluxed under argon until all carbene com-
plex was consumed. The progress of the reaction was mon-
itored by routine TLC for the disappearance of carbene
complex. The mixture was then cooled to 25 ꢁC, and the
solvent was removed on a rotary evaporator. Final purifi-
cation was achieved by flash chromatography on silica
gel. Eluting with 19:1 hexane–ethyl acetate followed by
MS (EI): 398.2 (M+), 370.2, 339.2, 317.1, 303.1, 261.1,
226.1, 202.1, 186.1, 165.1, 127.2, 119.1; HRMS (EI): calcd.
for C24H22FeO2: 398.0969. Found: 398.0972.
4.3.4. 2,3-Diferrocenyl-4-methoxy-2,4-cycloheptadienone
(3D)
1H NMR (CDCl3): d 5.09 (t, 1H, J = 7.4 Hz), 4.21 (s,
2H), 4.17 (s, 2H), 4.12 (s, 2H), 4.11 (s, 5H), 4.08 (s, 5H),

M. Zora et al. / Journal of Organometallic Chemistry 692 (2007) 1571–1578
1577
3.98 (s, 2H), 3.64 (s, 3H), 2.91 (pseudo t, 2H, J = 6.4 Hz),
2.44 (q, 2H, J = 6.9 Hz); IR (CH2Cl2): 3054 (vs), 2989 (s),
2682 (m), 2406 (w), 2304 (m), 1700 (s), 1418 (s), 1266 (vs),
1102 (w), 897 (s) cmꢀ1; MS (EI): 506.2 (M+), 438.1, 394.1,
362.2, 308.1, 242.1, 186.0, 113.1; HRMS (EI): calcd. for
C28H26Fe2O2: 506.0632. Found: 506.0635.
186.1, 139.1, 121.0, 115.1; HRMS (EI): calcd. for
C19H20FeO3: 352.0762. Found: 352.0759.
4.3.9. 2,3-Diferrocenyl-4-cyclopropyl-4-methoxy-2-
cyclobutenone (6D)
1H NMR (CDCl3): d 5.02 (s, 1H), 4.92 (s, 1H), 4.89 (s,
1H), 4.64 (s, 1H), 4.62 (s, 1H), 4.40 (s, 1H), 4.39 (s, 1H),
4.30 (s, 5H), 4.18 (s, 5H), 4.06 (s, 1H), 3.28 (s, 3H), 1.44
(m, 1H), 0.85 (m, 1H), 0.71 (m, 1H), 0.63 (m, 1H), 0.39
(m, 1H); IR (CH2Cl2): 3054 (m), 1743 (s), 1695 (m), 1606
(m), 1483 (m), 1261 (vs), 1103 (m), 916 (m), 821 (m), 755
(vs) cmꢀ1; MS (EI): 506.1 (M+), 478.2, 464.1, 394.1,
328.0, 273.1, 215.1, 197.0, 186.0, 149.0; HRMS (EI): calcd
for C28H26Fe2O2: 506.0632. Found 506.0634.
4.3.5. 2-Ferrocenyl-3-methyl-2-cycloheptene-1,4-dione (4A)
1H NMR (CDCl3): d 4.49 (s, 2H), 4.43 (s, 2H), 4.16 (s,
5H), 2.83 (t, 2H, J = 6.8 Hz), 2.61 (pseudo t, 2H,
J = 6.0 Hz), 2.04 (pseudo p, 2H, J = 6.3 Hz), 2.01 (s,
3H); 13C NMR (CDCl3): d 204.2 (C), 203.4 (C), 148.6
(C), 134.8 (C), 77.3 (C), 70.7 (CH), 70.4 (CH), 69.7 (CH),
43.3 (CH2), 41.7 (CH2), 17.2 (CH2), 16.4 (CH3); IR
(CH2Cl2): 3052 (s), 2985 (m), 1696 (s), 1663 (s), 1420 (m),
1272 (vs), 1260 (vs) 1108 (w), 895 (m) cmꢀ1; MS (EI):
322.1 (M+), 320.1, 294.1, 277.1, 258.0, 257.0, 229.0,
199.0, 167.1, 149.1, 121.0; HRMS (EI): calcd. for
C18H18FeO2: 322.0656. Found: 322.0659.
Acknowledgements
The authors thank the Scientific and Technical Research
Council of Turkey (104T202) and the Research Board of
Middle East Technical University (BAP-2005-07-02-00-
57) for financial support of this research, Dr. Holm Frau-
endorf (University of Go¨ttingen) for obtaining MS and
HRMS spectra, and the Faculty of Arts and Sciences, Ond-
okuz Mayıs University, for the use of Stoe IPDS II diffrac-
tometer (purchased under Grant F.279 of the University
Research Fund).
4.3.6. 2-Benzyl-3-ferrocenyl-2-cycloheptene-1,4-dione (4B)
1H NMR (CDCl3): d 7.25 (t, J = 7.2 Hz, 2H), 7.19–7.10
(m, 3H), 4.47 (s, 2H), 4.38 (s, 2H), 4.17 (s, 5H), 3.94 (s, 2H),
2.81 (t, 2H, J = 5.8 Hz), 2.49 (pseudo t, 2H, J = 5.3 Hz),
2.06 (pseudo p, 2H, J = 5.3 Hz); IR (neat): 3104 (w),
2937 (w), 1696 (vs), 1664 (vs), 1578 (m), 1497 (w), 1259
(m), 1213 (s), 1107 (m), 1053 (m), 1004 (m) cmꢀ1; MS
(EI): 398.2 (M+), 370.2, 333.1, 305.1, 275.1, 248.1, 234.1,
191.1, 178.1, 165.1, 121.0; HRMS (EI): calcd. for
C24H22FeO2: 398.0969. Found: 398.0966.
Appendix A. Supplementary material
CCDC 621658 contains the supplementary crystallo-
graphic data for 3B. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk. Supplemen-
tary data associated with this article can be found, in the
online version, at doi:10.1016/j. jorganchem. 2006.12.008.
4.3.7. 2-Ferrocenyl-3-phenyl-2-cycloheptene-1,4-dione (4C)
1H NMR (CDCl3): d 7.36–7.29 (m, 3H), 7.02 (dd, 2H,
J = 7.8, 1.3 Hz), 4.19 (t, 2H, J = 1.8 Hz), 4.08 (s, 5H),
3.80 (t, 3H, J = 1.8 Hz), 2.90 (t, 2H, J = 6.0 Hz), 2.58
(pseudo t, 2H, J = 6.6 Hz), 2.15 (pseudo p, 2H,
J = 6.4 Hz); 13C NMR (CDCl3): d 197.6 (C), 156.3 (C),
137.8 (C), 135.3 (C), 130.2 (CH), 128.3 (CH), 127.1 (CH),
81.7 (C), 70.5 (CH), 70.2 (CH), 69.6 (CH), 38.2 (CH2),
30.7 (CH2), 22.7 (CH2); IR (CH2Cl2): 3048 (vs), 2985 (s),
2680 (w), 2305 (m), 1650 (s), 1578 (m), 1422 (s), 1358
(m), 1265 (vs), 1175 (m), 891 (s) cmꢀ1; MS (EI): 384.2
(M+), 357.2, 356.2, 300.2, 291.1, 263.1, 235.1, 202.1,
178.1, 165.1, 152.1, 112.0; HRMS (EI): calcd. for
C23H20FeO2: 384.0813. Found: 384.0816.
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