Reactions of a phosphido-bridged unsymmetrical diiron complex (η5-C5Me5)Fe2 (CO)4(μ-CO)(μ-PPh2) with various alkynes

Article abstract of DOI:10.1016/j.jorganchem.2004.01.013

A phosphido-bridged unsymmetrical diiron complex (η⁵-C₅Me₅)Fe₂ (CO)₄(μ-CO)(μ-PPh₂) (1) was synthesized by a new convenient method; photo-dissociation of a CO ligand from (η⁵-C₅Me₅)Fe₂ (CO)₆(μ-PPh₂) (2) that was prepared by the reaction of Li[Fe(CO)₄PPh₂] with (η⁵-C₅Me₅)Fe(CO)₂I. The reactivity of 1 toward various alkynes was studied. The reaction of 1 with ^tBuC≡CH gave a 1:1 mixture of two isomeric complexes (η⁵-C₅Me₅)Fe₂ (CO)₃(μ-PPh₂)[μ-CH≡C(^tBu) C(O)] (3) containing a ketoalkenyl ligand. The reactions of 1 with other terminal alkynes RC≡CH (R=H, CO₂Me, Ph) afforded complexes incorporating one or two molecules of alkynes and a carbonyl group. The principal products were dinuclear complexes bridged by a new phosphinoketoalkenyl ligand, (η⁵-C₅ Me₅)Fe₂(CO)₃(μ-CO)[μ- CR¹=CR²C(O)PPh₂] (4a: R¹=H, R²=H; 4b: R¹=CO₂Me, R²=H; 4c: R¹=H, R²=Ph). In the cases of alkynes RC=CH (R=H, CO₂Me), dinuclear complexes having a new ligand composed of two molecules of alkynes, a carbonyl group, and a phosphido group; i.e. (η⁵-C₅Me₅) Fe₂(CO)₃[μ-CRCHCHCRC(O)PPh₂] (5a: R=H; 5b: R=CO₂Me), were also obtained. In all cases, mononuclear complexes, (η⁵-C₅Me₅) Fe(CO)[CR¹=CR²C(O)PPh₂] (6a: R¹=H, R²=H; 6b: R¹=H, R²=CO₂Me; 6c: R¹=H, R²=Ph) were isolated in low yields. The structures of 1, 4c, 5b, and 6a were confirmed by X-ray crystallography. The detailed structures of the products and plausible reaction mechanisms are discussed.

Full text of DOI:10.1016/j.jorganchem.2004.01.013

Journal of Organometallic Chemistry 689 (2004) 1481–1495
www.elsevier.com/locate/jorganchem
Reactions of a phosphido-bridged unsymmetrical diiron complex
(g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2) with various alkynes
a,
a
a,
b
Hisako Hashimoto *, Kazuyoshi Kurashima , Hiromi Tobita *, Hiroshi Ogino
a
Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Aramaki, Aoba, Sendai 980-8578, Japan
b
Miyagi Study Center, The University of the Air, Sendai 980-8577, Japan
Received 2 December 2003; accepted 8 January 2004
Abstract
A phosphido-bridged unsymmetrical diiron complex (g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2) (1) was synthesized by a new con-
venient method; photo-dissociation of a CO ligand from (g5-C5Me5)Fe2(CO)6(l-PPh2) (2) that was prepared by the reaction of
Li[Fe(CO)4PPh2] with (g5-C5Me5)Fe(CO)2I. The reactivity of 1 toward various alkynes was studied. The reaction of 1 with
tBuCBCH gave a 1:1 mixture of two isomeric complexes (g5-C5Me5)Fe2(CO)3(l-PPh2)[l-CH@C(tBu)C(O)] (3) containing a ke-
toalkenyl ligand. The reactions of 1 with other terminal alkynes RCBCH (R ¼ H, CO2Me, Ph) afforded complexes incorporating
one or two molecules of alkynes and a carbonyl group. The principal products were dinuclear complexes bridged by a new
phosphinoketoalkenyl ligand, (g5-C5Me5)Fe2(CO)3(l-CO)[l-CR1@CR2C(O)PPh2] (4a: R1 ¼ H, R2 ¼ H; 4b: R1 ¼ CO2Me, R2 ¼ H;
4c: R1 ¼ H, R2 ¼ Ph). In the cases of alkynes RCBCH (R ¼ H, CO2Me), dinuclear complexes having a new ligand composed of two
molecules of alkynes, a carbonyl group, and a phosphido group; i.e. (g5-C5Me5)Fe2(CO)3[l-CRCHCHCRC(O)PPh2] (5a: R ¼ H;
5b: R ¼ CO2Me), were also obtained. In all cases, mononuclear complexes, (g5-C5Me5)Fe(CO)[CR1@CR2C(O)PPh2] (6a: R1 ¼ H,
R2 ¼ H; 6b: R1 ¼ H, R2 ¼ CO2Me; 6c: R1 ¼ H, R2 ¼ Ph) were isolated in low yields. The structures of 1, 4c, 5b, and 6a were
confirmed by X-ray crystallography. The detailed structures of the products and plausible reaction mechanisms are discussed.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Iron complex; Phosphido-bridged complex; Alkyne insertion; C–C bond formation; P–C bond formation; X-ray structure analysis
1. Introduction
spotlight the difference of the effects of ligands bound to
the neighboring metals during bimetallic activation.
We previously reported the synthesis of a phosphido-
The chemistry of dinuclear transition-metal com-
plexes continues to attract considerable interests owing
to its unique activation of substrates, so-called ‘‘bime-
tallic activation’’, which cannot be expected to mono-
nuclear complexes [1]. Multisite interactions between the
metal aggregates and substrate molecules followed by
their activation are often believed to operate during
chemical transformations, but not fully understood. In
relation to this, we have been interested in homometallic
but unsymmetrical dinuclear complexes where each
metal has the different supporting ligands. This type of
complexes are much less studied among a large number
of dinuclear complexes, and are expected to be suited to
bridged
unsymmetrical
diiron
complex
(g5-
C5Me5)Fe2(CO)4(l-CO)(l-PPh2) (1) [2]. Complex 1
shows a unique reactivity toward hydrosilanes to cause
the stoichiometric redistribution of dihydrosilane to
produce monohydrosilane and a monohydrosilylene-
bridged diiron complex [3a], and the catalytic redistri-
bution of trihydrosilane to produce dihydrosilane and
tetrahydrosilane [3b]. In these reactions, the steric dif-
ference of the ligands between two metal atoms seems to
play an important role to control the route of reaction.
For our continuous interests about reactivity of this type
of unsymmetrical complexes, we studied the reactions of
1 with various alkynes and found that one or two al-
kynes and a carbonyl group inserted into one of the Fe–
P bonds of the bridging phophido ligand regioselectively
to produce new complexes having a ligand with a
* Corresponding authors. Tel.: +81222176540; fax: +81222176543.
E-mail address: hhashimoto@mail.tains.tohoku.ac.jp (H. Hashim-
oto).
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.01.013

1482
H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
–P–C(O)– CR0@CR– or –P–C(O)CR0@CRCR@CR0-
linkage dependent on the substituents on the alkynes.
There are now an increasing number of reports for al-
kyne and/or CO insertion into the bond between the
metal and the bridging phosphido ligand in dinuclear
complexes [4–8]. For example, Werner et al. [8] reported
an insertion of Me2OOCCBCCO2Me into the Co–P
bond in (g5-C5H5)2Co2(l-PMe2)2 to produce a dinu-
clear complex with an alkenylphosphine ligand. Mays
et al. [5] reported that the ring expansion underwent
by the reactions of Co2(CO)6(l-PPh2) with alkynes to
afford complexes bearing a ligand such as l-PPh2CR@
CR0C(O) and l-PPh2CR@CR0C(O)CR00@CR000. Yama-
zaki et al. [6] and Dixneuf et al. [7] also reported
the alkyne-insertion reactions by using heterometallic
phosphido-bridged complexes. These examples well
demonstrated the existence of the new methodology of
the P–C bond formation using dinuclear complexes,
though the detailed mechanisms and the controlling
factors of the product formation have not been clarified
yet.
in Scheme 1. Thus, the deprotonation of hydrophos-
phine iron complex Fe(CO)4(PPh2H) with n-BuLi pro-
duced the anionic complex Li[Fe(CO)4PPh2], which was
then treated with (g5-C5Me5)Fe(CO)2I to give (g5-
C5Me5)Fe2(CO)6(l-PPh2) (2) in 97% yield. Subsequent
photochemical CO dissociation from 2 produced 1 in
76% yield. The 31P NMR signal of 2 appears at 90.8
ppm (in C6D6), which lies much higher in field com-
pared with that of 1 (169.9 ppm). These data and
comparison of them with the previous examples suggest
that 2 does not have a metal–metal bond whereas 1 has a
metal–metal bond [11]. For example, the 31P NMR
signals of (g5-C5H5)Fe(CO)2(l-PPh2)W(CO)5 (with no
metal–metal bond) and (g5-C5H5)Fe(CO)(l-CO)(l-
PPh2)W(CO)4 (with a metal–metal bond) are reported
to appear at 0.1 and 160.8 ppm (in THF), respectively
[12a]. Complex 1 is inert to UV light, but thermally
decomposes above 90 °C to produce (g5-
C5Me5)2Fe2(CO)4 and Fe2(CO)6(l-PPh2)2 quantita-
tively as described in the following equation
O
C
We report here the new convenient preparation, the
X-ray structure, and the details of the reactions of 1 with
various alkynes and propose the reaction mechanisms
for our system.
O
C
Ph2
OC
P
90˚C
2
(OC)3Fe
Ph
Fe
CO
Ph
Fe
Fe
+
(OC)3Fe
Fe(CO)3
CO
P
Ph2
P
C
O
1
ð1Þ
Although the crystal structures of several unsym-
2. Results and discussion
metrical monophosphido-bridged dinuclear complexes
with one cyclopentadienyl group have been determined
[11–14], those of (g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2)
(1) and its g5-C5H5 analog have not been determined.
Therefore, we performed the X-ray crystal structure
determination of 1. Black needle-like crystals of 1 suit-
able for X-ray analysis were obtained by layering a
toluene solution of 1 with hexane at )15 °C. Two in-
dependent molecules (A and B) were found in the unit
cell. The molecular structures of them are illustrated in
Fig. 1, and crystal data and structure refinement infor-
mation are presented in Table 1. The selected inter-
atomic distances and bond angles are given in Table 2
together with the mean values. The two molecules differ
in the orientation of the phenyl groups on the phosphido
ligand with marginally different bonding parameters,
2.1. A new preparation and X-ray structure determination
of (g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2) (1)
Complex 1 was first synthesized by us by the reaction
of a tetramethylfulvene-bridged diiron complex (g1:g5-
CH2C5Me4)Fe2(CO)6 with diphenylphosphine [2]. As
this method needed several steps from the starting pen-
tamethylcyclopentadiene, we started to search a simpler
synthetic method by referring to those of other related
complexes. The cyclopentadienyl analog of 1, (g5-
C5H5)Fe2(CO)4(l-CO)(l-PPh2), has previously been
synthesized by three methods. Haines and co-workers [9]
reported that the reaction of Na-[(g5-C5H5)Fe(CO)2]
with Fe(CO)4(PPh2Cl) gave (g5-C5H5)Fe2(CO)6(l-
PPh2), which then underwent photochemical CO disso-
ciation to produce the cyclopentadienyl analog of 1. They
also reported that the complex (g5-C5H5)Fe2(CO)6(l-
PPh2) was obtained by the reaction of Fe2(CO)9 with (g5-
C5H5)Fe(CO)2(PPh2) in 80% yield [9]. Yasufuku and
Yamazaki prepared the same complex (g5-C5H5)-
Fe2(CO)6(l-PPh2) in 40% yield from the reaction of
(g5-C5H5)Fe(CO)2Cl with Fe(CO)4(PPh2H) in the pres-
ence of HNEt2. It was then converted to (g5-C5H5)-
Fe2(CO)4(l-CO)(l-PPh2) in 70% yield in a similar
photochemical method [10].
CpFe(CO)2I
n-BuLi
Fe( CO) 4PPh2H
Li[ Fe(CO) 4PPh2]
- n-BuH
O
C
hv
(OC)4Fe
Fe
P
(OC)3Fe
Ph
Fe
CO
CO
- CO
CO
P
Ph Ph
Ph
2
1
As modification of these methods, we newly devel-
oped a convenient method to prepare 1, which is shown
Scheme 1.

H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
1483
ꢀ
PPhH)2 [15], and av. 2.610(3) A for Fe2(CO)6(l-
PPh2)(l-SPh) [16]. Both of the bridging phosphido and
carbonyl ligands are almost symmetrically coordinated
ꢀ
to the two iron atoms (av. 2.208(3) A for Fe(1)–P, av.
ꢀ
2.207(3) A for Fe(2)–P; and av. 1.969(9) A for Fe(1)–
ꢀ
ꢀ
C(O), av. 1.944(11) A for Fe(2)–C(O)), despite differ-
ences in adjacent ligands and oxidation numbers [+2 for
Fe(1), 0 for Fe(2)] between the two metals. The Fe–P
bond distances and the angle Fe(1)–P–Fe(2) (av.
73.54(9)°) of 1 are comparable with the corresponding
values of other related complexes: the Fe–P bond
ꢀ
lengths, 2.233(3) A for Fe2(CO)6(l-PPh2)2 [15], av.
5
ꢀ
2.203(3) and 2.184(3) A for (g -C5H5)Fe2(CO)4(l-
ꢀ
CO)(l-PMe2) [14b], av. 2.212(1) A for Fe2(CO)6(l-
PPhH)2 [15]; the Fe–P–Fe bond angles, 72.0(1)°
for Fe2(CO)6(l-PPh2)2 [15], av. 73.6(1)° for (g5-
C5H5)Fe2(CO)4(l-CO)(l-PMe2) [14b], 74.0(1)° for
Fe2(CO)6(l-PPhH)2 [15]. These structural features are
almost identical to those of (g5-C5H5)Fe2(CO)4(l-
CO)(l-PMe2), but there is a significant steric repulsion
between a bulky g5-C5Me5 group and a phenyl group
on the bridging phosphido ligand in 1: e.g. the distances
of C(9)ꢀ ꢀ ꢀC(22) and C(9)ꢀ ꢀ ꢀC(23) in molecule A are
ꢀ
3.52(2) and 3.53(2) A, respectively, which are shorter
than the sum of the effective van der Waals radii of a
methyl group and a half-thickness of the p-cloud of a
ꢀ
phenyl group (3.7 A). Similar steric repulsions are also
observed in molecule B: the short distances between a
methyl carbon of the g5-C5Me5 ring and some of the
ꢀ
phenyl carbon atoms are 3.32(1) A for C(9)ꢀ ꢀ ꢀC(16),
ꢀ
ꢀ
for
3.56(1)
A
for C(9)ꢀ ꢀ ꢀC(21), and 3.61(1)
A
C(10)ꢀ ꢀ ꢀC(21), respectively.
2.2. Reactions of 1 with alkynes and characterizations of
the products
The phosphido-bridged diiron complex 1 reacted with
tBuCBCH at 35 °C to give (g5-C5Me5)Fe2(CO)3(l-
PPh2)[l-CH@C(tBu)C(O)] (3) containing a new keto-
alkenyl ligand in 59% yield (Eq. (2)). Although we have
not succeeded in growing crystals of 3 suitable for X-ray
diffraction study, 3 was characterized spectroscopically
(Table 3) [17]. All spectral data suggest that there are
two isomeric complexes for 3, which are in equilibrium
in solution (see experimental section). Knox et al. [18]
also reported that their isomeric complexes having
Fig. 1. ORTEP drawing of (g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2) (1),
showing 50% thermal ellipsoids. Hydrogen atoms were omitted for
clarity.
but the whole features are essentially equal to each
other. Therefore, the mean values of the two molecules
are used in the following discussion. The two iron atoms
are bridged by a phosphido and a carbonyl group. The
Fe(1) atom adopts an almost four-legged piano-stool
structure and the Fe(2) atom adopts a distorted octa-
hedral structure. The average Fe–Fe bond distance is
a
similar
l-ketoalkenyl
ligand,
Fe2(CO)5{l-
CR1@CR2C(O)}(l-dppm) (R1 ¼ H, R2 ¼ Me; R1 ¼ H,
R2 ¼ Ph) are in equilibrium in solution. Therefore, we
suggest that the two isomers have the syn- and anti-
configurations with respect to the mutual positions of
the g5-C5Me5 ligand and the carbonyl group of the
ketoalkenyl ligand as displayed in Chart 1. In the 31P
NMR spectrum, two sets of signals for 3 appear at very
low field, 257.6 and 265.3 ppm, which suggests that both
5
ꢀ
2.643(2) A, which is slightly longer than that in (g -
ꢀ
C5H5)Fe2(CO)4(l-CO)(l-PMe2) (av. 2.627(2) A) [14b],
but in the range of normal single bond lengths found in
ꢀ
other phosphido-bridged complexes; e.g. 2.623(3) A for
ꢀ
Fe2(CO)6(l-PPh2)2 [15], 2.662(1) A for Fe2(CO)6(l-

1484
H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
Table 1
Crystallographic data for complexes 1, 4c, 5b, and 6a
Entry
1
4c
5b
6a
Formula
C27H25Fe2O5P
C35H31Fe2O5Pꢀ3/
2C7H8
812.51
C34H33Fe2O8P
C26H27FeO2P
Fw
Crystal system
572.17
Triclinic
712.3
458.3
Triclinic
Monoclinic
A2=n (No. 15)
36.102(6)
Monoclinic
P1=a (No. 14)
25.148(4)
10.841(2)
11.683(2)
ꢁ
ꢁ
Space group
ꢀ
P1 (No. 2)
P1 (No. 2)
a (A)
15.205(2)
19.863(5)
19.863(5)
109.44(2)
99.71(2)
76.29(2)
2598(1)
4
14.501(2)
18.825(4)
8.666(1)
100.93(2)
91.54(1)
78.68(2)
2277.4(6)
4
ꢀ
b (A)
11.865(1)
17.960(4)
ꢀ
c (A)
a (°)
b (°)
c (°)
94.13(1)
100.09(1)
3
ꢀ
V (A )
7673(2)
3135.6(9)
Z
8
1.41
4
1.51
qcalcd (g cmꢁ3
)
1.46
6.20
1.34
7.71
l (Mo Ka) (cmꢁ1
Crystal size (mm)
Radiation
)
4.20
0.40 ꢂ 0.30 ꢂ 0.35
10.55
0.30 ꢂ 0.15 ꢂ 0.25
0.14 ꢂ 0.25 ꢂ 0.40
0.52 ꢂ 0.38 ꢂ 0.10
Mo Ka (l ¼ 0:71073 Mo Ka (l ¼ 0:71073 Mo Ka (l ¼ 0:71073 Mo Ka (l ¼ 0:71073
ꢀ
A)
ꢀ
A)
ꢀ
A)
ꢀ
A)
Monochromator
T (°C)
Reflections measured
Graphite
18
Graphite
18
Graphite
20
Graphite
20
ꢃh; ꢃk; l
3–53
ꢃh; k; l
3–55
ꢃh; k; l
ꢃh; ꢃk; l
3–50
2h range (°)
scan mode
3–50
x
x-2h
x
x-2h
x-scan width (°)
No. of unique data
No. of data used
No. of parameters refined
Ra
1:1 þ 0:35 tan h
1:2 þ 0:35 tan h
1:1 þ 0:35 tan h
1:1 þ 0:35 tan h
10746
12740
5843
8016
6186 ðjFoj > 3rðjFojÞÞ 3165 ðjFoj > 6rðjFojÞÞ 3337 ðjFoj > 3rðjFojÞÞ 5388 ðjFoj > 3rðjFojÞÞ
417
499
415
542
0.069
0.076
1.28
0.86
0.057
0.071
1.39
0.50
0.068
A0.089
1.36
0.075
0.092
1.66
0.73
b
Rw
Quality of fit indicatorc
Maximum residual electron density (e A
ꢁ3
ꢀ
)
0.79
a R ¼ RjjFoj ꢁ jFcjj=RjFoj.
2
2 1=2
b Rw ¼ ½RwðjFoj ꢁ jFcjÞ =RwjFoj ꢄ ; w ¼ ½r2ðjFojÞ þ aF 2ꢄꢁ1, where a ¼ 0:001 for complexes 1 and 6a, and a ¼ 0:003 for complexes 4c and 5b.
o
2
1=2
c [RðjFoj ꢁ jFcjÞ =ðNobservations ꢁ NparametersÞꢄ
.
of them have a phosphido ligand bridging across the
metal–metal bond [11]. The mass spectrum (FAB) of
the mixture shows the Mþ + 1 at m=z ¼ 627 along with
the fragment peaks corresponding to the successive loss
of four carbonyls. A proton resonance for the l-CH
portion of each of two isomers appears at very low field
[10.72 ppm (3JPH ¼ 0:7 Hz) and 11.14 ppm (3JPH ¼ 1:2
Hz)] that is characteristic of the bridging carbene pro-
ton. In accord with this, two sets of the 13C NMR sig-
nals for l-CH carbons of the isomers appear at 185.1
ppm (2JPC ¼ 4:2 Hz) and 189.3 ppm (2JPC ¼ 3:4 Hz),
which are in the typical region of the bridging carbene
carbons. Two resonances at 70.8 ppm (3JPC ¼ 2:6 Hz)
and 77.8 ppm (3JPC ¼ 2:6 Hz) can be assigned to two
sets of alkenyl carbon signals for the @C(tBu)C(O)A
moiety. There are eight doublets in a carbonyl region for
two isomers. Two of them must come from the inserted
carbonyls in the new bridging ligands, though the exact
assignments of them are difficult. A clear evidence for
the existence of the inserted carbonyls comes from the
IR spectrum (KBr pellet). In addition to the mCO bands
for the terminal carbonyls, several mCO bands appear
around 1700 cmꢁ1, which is typical of a ketoalkenyl
carbon, assigned to the inserted carbonyl groups. The
Table 2
5
ꢀ
Selected bond distances (A) and angles (°) for (g -C5Me5)Fe2(CO)4(l-
CO)(l-PPh2) (1)
Molecule A Molecule B Average
(X ¼ A)
(X ¼ B)
Bond distances
Fe(1X)–Fe(2X)
Fe(1X)–P(X)
2.643(2)
2.224(2)
2.210(2)
1.990(9)
1.932(7)
1.740(10)
2.651(2)
2.191(3)
2.203(3)
1.948(9)
1.956(11)
1.759(10)
2.643(2)
2.208(3)
2.207(3)
1.969(9)
1.944(11)
1.750(10)
Fe(2X)–P(X)
Fe(1X)–C(11X)
Fe(2X)–C(11X)
Fe(1X)–C(12X)
Bond angles
Fe(1X)–Fe(2X)–P(X)
Fe(2X)–Fe(1X)–P(X)
Fe(1X)–P(X)–Fe(2X)
53.82(6)
53.30(6)
72.88(7)
53.10(7)
52.69(6)
74.20(9)
47.4(3)
47.1(3)
85.5(5)
53.5(7)
53.0(6)
73.54(9)
48.1(3)
47.0(3)
85.0(5)
Fe(1X)–Fe(2X)–C(11X) 48.8(2)
Fe(2X)–Fe(1X)–C(11X) 46.9(3)
Fe(1X)–C(11X)–Fe(2X) 84.4(3)

Table 3
1H NMR, 31P NMR, and IR spectral data for complexes 3–6
m(CO)d
a
b
Complex
dH
dP
3, (g5-C5Me5)Fe2(CO)3
1.20 (s, 15H, C5Me5), 1.30 (s, 15H, C5Me5) 1.27 (s, 9H, tBu), 1.31 (s, 9H, tBu), 6.9-8.2 (m, 10H, Ph), 257.6c, 265.3c, 1983vs, 1959vs, 1950vs,
3
3
(l-PPh2)@[l-CH@C(tBu)C(O)]
(a mixture of two isomers)
4a, (g5-C5Me5)Fe2(CO)3
10.72 (d, JPH ¼ 0:7 Hz, l-CH), 11.14 (d, JPH ¼ 1:2 Hz, l-CH)
1907vs, 1732s, 1699m,
1686s
3
3
(1.25 s, 15H, C5Me5), 4.24 (dd, JPH ¼ 31:8 Hz, JHH ¼ 4:8 Hz, 1H, –CHC(O)–), 6.8–8.2 (m, 10H, 75.3
2015vs, 1942vs, 1924s,
1843m, 1635m, 1624m
2040vs, 2017s, 1975vs,
1900m, 1869s, 1682m,
1624s
3
3
(l-CO) @ [l-CH@CHC(O)PPh2]
Ph), 9.92 (dd, JPH ¼ 2:4 Hz, JHH ¼ 4:8 Hz, 1H, l-CH),
4b, (g5-C5Me5)Fe2(CO)3
1.38 (s, 15H, C5Me5) 3.73 (s, 3H, CO2Me), 4.18 (d, 3JPH ¼ 34:7 Hz, 1H, CCH), 6.8–8.3 (m, 10H, Ph) 56.4,
(l-CO) @ [l-C(CO2Me)@CHC(O)PPh2]
4c, (g5-C5Me5)Fe2(CO)3
(l-CO) @ [l-CH@CPhC(O)PPh2]
5a, (g5-C5Me5)Fe2(CO)3@[l-CH-
CHCHCH–C(O)PPh2]
1.34 (s, 15H, C5Me5), 6.5–8.2 (m, 15H, Ph), 10.81 (d, JPH ¼ 2:0 Hz, 1H, CH)
81.5,
2013vs, 1959vs, 1936vs,
1924vs, 1857m, 1589m
2013s, 1942vs, 1925s,
1832m, 1635m
3
1.34 (s, 15H, C5Me5), 4.01 (br, t, 3JHH ¼ 8:4 Hz, 1H, CH), 4.93 (dd, 3JHH ¼ 8:4 Hz, 3JPH ¼ 23:6 Hz, 57.5
1H, –CHC(O)), 5.02 (br, t, 3JHH ¼ 8:4 Hz, 1H, CH), 6.8–7.7 (m, 10H, Ph), 8.79 (br, d, 3JHH ¼ 8:4 Hz,
1H, l-CH)
5b, (g5-C5Me5)Fe2(CO)3@[l-C(CO2-
Me)CHCHCC(CO2Me)C(O)PPh2]
(C6D6): 0.96 (s, 15H, C5Me5), 3.43 (s, 3H, CO2Me), 3.63 (dd, JHH ¼ 4:0 Hz, JPH ¼ 2:1 Hz, 1H,
CH), 3.77 (s, 3H, CO2Me), 6.27 (dd, JHH ¼ 4:0 Hz, JPH ¼ 1:5 Hz, 1H, CH), 6.8-8.2 (m, 10H, Ph)
(C6D6) 75.9,
2037vs, 1969vs, 1711m,
1693s, 1687s, 1647m,
1637w
3
3
3
3
3
3
(CD2Cl2): 1.31 (s, 15H, C5Me5), 3.45 (s, 3H, CO2Me), 3.48 (dd, JHH ¼ 4:0 Hz, JPH ¼ 2:2 Hz, 1H, (CD2Cl2) 79.0
3
3
CH), 4.05 (s, 3H, CO2Me), 6.20 (dd, JHH ¼ 4:0 Hz, JPH ¼ 1:6 Hz, 1H, CH), 7.4-8.0 (m, 10H, Ph)
6a, (g5-C5Me5)Fe(CO)[CH@CHC(O)PPh2]
1.34 (d, 4JPH ¼ 0:5 Hz, 15H, C5Me5), 6.8-8.3 (m, 10H, Ph), 7.63 (dd, 3JHH ¼ 7:7 Hz, 3JPH ¼ 35:0 Hz, 83.2
1919vs, 1720s, 1637w
3
3
1H, @CHC(O)–), 10.82 (dd, JHH ¼ 7:7 Hz, JPH ¼ 2:5 Hz, 1H, FeACH@)
6b, (g5-C5Me5)Fe(CO)–
[CH@C(CO2Me)C(O)PPh2]
1.29 (s, 15H, C5Me5), 3.60 (s, 3H, CO2Me), 6.7–8.2 (m, 10H, Ph), 12.81 (d, 3JPH ¼ 0:5 Hz, 1H, CH) 88.6
1942vs, 1720m, 1691w,
1625m
1925vs, 1639s
6c, (g5-C5Me5)Fe(CO)–[CH@CPhC(O)PPh2] 1.37 (s, 15H, C5Me5), 6.8-8.3 (m, 15H, Ph), 11.39 (d, JPH ¼ 2:1 Hz, 1H, l-CH)
87.1
107.0
3
6d, (g5-C5Me5)Fe(CO)–
1.41 (s, 15H, C5Me5), 3.04 (s, 3H, CO2Me), 3.45 (s, 3H, CO2Me), 6.8–8.3 (m, 10H, Ph),
1923vs, 1909vs, 1734vs,
1718s, 1593m, 1585m
[C(CO2Me)@C(CO2Me)C(O)PPh2]
a In C6D6 at 300 MHz.
b In C6D6 at 36.3 MHz, referenced to aqueous H3PO4 (external).
c KBr pellet, cmꢁ1
d In C6D6 at 121.5 MHz, referenced to aqueous H3PO4 (external).
.

1486
H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
tBu
C
CO
Cp*
4c with the structure of I. On the other hand, complex 4b
tBu
C C
OC
OC
OC
H
has the structure of II (vide infra). For the double
alkyne-insertion product 5b, four regioisomers are
possible: a head-to-tail insertion leads to two isomers
with a ligand having a ACR@CHACR@CHA or
ACH@CRACH@CRA linkage, and a head-to-head
H
C
OC
OC
Cp*
CO
CO
P
P
Ph
Ph
Ph
Ph
insertion leads to two isomers containing
a
syn-3
anti-3
ACR@CHACH@CRA or ACH@CRACR@CHA
linkage. The obtained 5b has a ACR@CHACH@CRA
linkage formed via one of the head-to-head insertion
mode. There is no evidence for other isomers. Similarly,
although there are two possible regioisomers for the
mononuclear complex 6, only complexes having a
ACH@CRC(O)PPh2A linkage were obtained. All
products 4, 5, and 6 are fairly stable in solution com-
pared with 1.
Chart 1.
observation of more than two bands in that region may
be attributed to the packing effect of the crystals.
tBu
H
O
+ tBuC≡CH
1
OC
Fe
Ph
Fe
ð2Þ
- CO
35 ˚C,
40 h
OC
CO
Ph
RC≡CH
P
1
40 ˚C ,
3 ~ 20 h
R = H, CO2 Me, Ph
3 (59%)
R2
O
C
When complex 1 was treated with other terminal al-
R1
Fe
R1
R1
(OC)3Fe
R2
Fe
R1
Fe
P
(OC)3Fe
R2
kynes RCꢅCH (R ¼ H, CO2Me, Ph), complexes incor-
porating up to two molecules of alkynes were obtained
(Eq. (3)). In every case, the principal product was a di-
nuclear complex incorporating one alkyne molecule in
which the two iron atoms are bridged by a new phos-
+
+
CO
R2
P
Ph
Ph
P
Ph
Ph
Ph
Ph
O
O
O
4a (R1 = H, R2 = H, 24%)
5a (R1 = H, R2 = H, 7%)
4b (R1 = CO2Me, R2 = H, 54%) 5b (R1 = H, R2 = CO2Me, 38%) 6b (R1 = H, R2 = CO2Me, 2%)
4c (R1 = H, R2 = Ph, 67%) 6c (R1 = H, R2 = Ph, 5%)
6a (R1 = H, R2 = H, 24%)
phinoketoalkenyl
ligand,
(g5-C5Me5)Fe2(CO)3(l-
ð3Þ
CO)[l-CR1@CR2C(O)PPh2] (4a: R1 ¼ H, R2 ¼ H; 4b:
R1 ¼ CO2Me, R2 ¼ H; 4c: R1 ¼ H, R2 ¼ Ph). For
RCBCH (R ¼ CO2Me, H), dinuclear complexes having
a new ligand composed of two molecules of alkynes, a
Dark brown crystals of 4c suitable for X-ray crystal
structure analysis were obtained by layering a toluene
solution of 4c with hexane at room temperature. Crystal
data and structure refinement information of 4c are
presented in Table 1. The ORTEP drawing of 4c is il-
lustrated in Fig. 2 and selected bond distances and bond
angles are given in Table 4. The X-ray structure analysis
carbonyl group, and
a
phosphido group, (g5-
(5a:
C5Me5)Fe2(CO)3[l-CR2CR1CR1CR2C(O)PPh2]
R1 ¼ H, R2 ¼ H; 5b: R1 ¼ H, R2 ¼ CO2Me), were also
obtained. In all cases, mononuclear complexes, (g5-
C5Me5)Fe(CO)2[CR1@CR2C(O)PPh2] (6a: R1 ¼ H,
R2 ¼ H; 6b: R1 ¼ H, R2 ¼ CO2Me; 6c: R1 ¼ H, R2 ¼ Ph)
were isolated in low yields. The structures of 4c, 5b, and
6a were confirmed by X-ray crystal structure analysis.
Other complexes were fully characterized by comparing
their spectral data with those of complexes 4c, 5b, and
6a. Two regioisomers I and II depicted in Chart 2 are
candidates for complexes 4b and 4c, but the repeated
clearly shows that 4c has
a
bridging phos-
phinoketoalkenyl ligand [l-CH@CPhC(O)PPh2] and a
semi-bridging carbonyl ligand. The new ligand is coor-
dinated to the Fe(1) atom by a phosphorus atom and the
alkenyl carbon atom C(30) to make a five-membered
Fe(1)–P–C(35)–C(29)–C(30) chelate ring. The double
bond [C(29)–C(30) bond] of the chelate ring is bound to
the Fe(2) atom in an g2-fashion. The coordinated
ꢀ
1
C(29)–C(30) bond length (1.433(17) A) is typical for
monitoring of the reaction of 1 with PhCBCH by H
NMR spectroscopy indicated the selective formation of
olefin-metal complexes with relatively strong back-do-
nation [19]. The P–C(35)–C(29)–C(30) moiety is almost
planar. The Fe(1) atom is slightly out of this plane. The
geometry around the Fe(1) atom can be regarded as a
distorted four-legged piano-stool when a metal–metal
bond is included as one of four legs. The Fe(2) has
bonding contacts with seven atoms and the geometry is
close to a capped octahedron. The Fe–Fe bond length
O
C
O
C
(OC)3Fe
H
Fe
P
(OC)3Fe
R
Fe
P
R
H
Ph
Ph
Ph
Ph
ꢀ
ꢀ
(2.636(3) A) is comparable with that (av. 2.643(2) A)
found in the parent complex 1. The Fe(1)–C(30) bond
ꢀ
length (1.926(11) A) is considerably shorter than those
O
O
I
II
Chart 2.
of Fe(2)–C bonds involving p-bonded carbon atoms

H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
1487
more electron rich than the Fe(1) atom and would tend
to reduce the electron density by donating it from a filled
dp orbital of the Fe(2) atom to the pꢆ orbital of the CO
group attached to the Fe(1) atom. As a result, the
bridging carbonyl ligand adopts a semi-bridging geom-
etry. Another explanation would stem from a possible
dative bond character of the metal–metal bond in 4c.
This is closely related to the explanation for the semi-
bridging structure of one of the carbonyl ligands in
Fe2(CO)5(l-CO)[l-CMe@CMeACMe@CMe]
[21].
Thus, we can count 18 electrons for the Fe(1) atom and
16 electrons for the Fe(2) atom when we ignore the
metal–metal bond and the semi-bridging interaction
between the Fe(2) atom and the carbonyl C(34)–O(4). In
order to attain an 18-electron valence shell for each
metal atom, the Fe–Fe bond must be considered as a
dative bond from Fe(1) to Fe(2). The semi-bridging
structure might serve to mitigate the resulting charge
separation by the electron donation from Fe(2) to the pꢆ
orbital of the CO group.
Fig. 2. ORTEP drawing of (g5-C5Me5)Fe2(CO)3(l-CO)[l-
CH@CPhC(O)PPh2]ꢀ3/2C6H5CH3 (4cꢀ3/2C6H5CH3), showing 50%
thermal ellipsoids. Hydrogen atoms except H(30) were omitted for
clarity.
The spectral data of 4c indicate that the crystal
structure of 4c is maintained in solution. Characteristic
1
spectral features for 4c are as follows: The H NMR
signal of the l-CH in 4c appears at 10.81 ppm as a
3
doublet with a coupling constant JPH ¼ 2:0 Hz. This
Table 4
5
ꢀ
Selected bond distances (A) and angles (°) for (g -C5Me5)Fe2(CO)3(l-
CO)[l-CH@CPhC(O)PPh2] ꢀ 3/2C6H5CH3 (4c ꢀ 3/2C6H5CH3)
Bond distances
low-field shift is attributable to the bridging-carbene-like
situation of the methylene moiety, and is comparable to
those of the l-CH in the complexes having an analogous
five-membered metallacyclic ring, e.g. RuCo[l-
CH@C(SiMe3)C(O)PPh2](l-CO)(CO)5 (8.65 ppm, d,
3JPH ¼ 1:3 Hz) [7]. The l-CH carbon signal appears at
Fe(1)–Fe(2)
Fe(1)–C(30)
Fe(2) –C(30)
Fe(2)–C(34)
C(29)–C(35)
2.636(3)
Fe(1)-P
2.181(3)
2.158(8)
1.793(11)
1.433(17)
1.894(15)
1.926(11)
1.997(12)
2.259(11)
1.443(12)
Fe(2)–C(29)
Fe(1)–C(34)
C(29)–C(30)
P–C(35)
2
168.1 ppm (d, JPC ¼ 21:1 Hz), which is a typical
chemical shift for a bridging carbene carbon. The 13C
Bond angles
2
signals at 81.7 ppm (d, JPC ¼ 77:7 Hz) and 199.7 ppm
Fe(2)–Fe(1)–P
Fe(1)–C(30)–Fe(2)
Fe(1)–Fe(2)–C(29)
P–C(35)–C(29)
123.1(1)
84.4(3)
75.5(2)
106.3(9)
Fe(1)–Fe(2)–C(30)
Fe(2)–Fe(1)–C(30)
Fe(1)–P–C(35)
46.7(3)
49.0(3)
101.6(5)
2
(d, JPC ¼ 38:3 Hz) are assigned to the carbons for CPh
moiety and the inserted carbonyl group [AC(O)PPh2],
respectively. A sharp singlet at 213.7 ppm suggests that
the three terminal carbonyl ligands are mutually ex-
changing rapidly. A low-field resonance at 239.2 ppm (d,
2JPC ¼ 25:9 Hz) is corresponding to the carbon of the
semi-bridging carbonyl ligand. In the IR spectrum,
broad CO stretching bands at 1857 and 1589 cmꢁ1 are
assigned to the semi-bridging carbonyl and an inserted
carbonyl in the [l-CH@CPhC(O)PPh2] ligand, respec-
tively. The position of the latter is comparable with the
corresponding bands (1600–1625 cmꢁ1) for the related
ꢀ
ꢀ
[Fe(2)–C(29) 2.158(8) A, Fe(2)–C(30) 1.997(12) A], re-
flecting the r-bond character of the Fe(1)–C(30) bond.
The existence of semi-bridging carbonyl ligand is dem-
onstrated by the large difference between two Fe–C–O
bond angles [153.1(12)°, 126.2(10)°] and two Fe–CO
ꢀ
ꢀ
bond distances [1.739(11) A, 2.259(11) A] for the
bridging carbonyl group.
According to the literature [20], a semi-bridging
structure of a carbonyl ligand is often observed for
multinuclear complexes in which the electron richness of
metal atoms are not equal or the metal atoms are in
sterically crowded situation. As there is no close contact
between the bridging carbonyl ligand and the other li-
gands on two metals in 4c, the net difference of electron
richness between two metals in 4 must cause the semi-
bridging structure. Since the oxidation numbers are 0
for Fe(2) and +2 for Fe(1), the Fe(2) atom could be
complexes,
e.g.,
RuCo[l-CR1@CR2C(O)PPh2](l-
CO)(CO)5 (R1, R2 ¼ Ph, Ph; Ph, H; Bu, H; H, SiMe3,
etc.) [7]. Other spectral data of 4c are consistent with the
X-ray structure shown in Fig. 2. The spectral data of 4b
suggests that 4b has a structure analogous to 4c except
for the reverse orientation of the inserted alkyne.
The signal of the CH proton in the [l-
C(CO2Me)@CHC(O)PPh2] ligand in 4b was observed at
4.18 ppm, which is much higher in field compared with
that (10.81 ppm) of 4c, with a large coupling constant
t

1488
H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
3JPH ¼ 34:7 Hz. This strongly suggests that 4b differs
from 4c in the orientation of the inserted alkyne. The
structure of 4a was also determined as shown in Eq. (3)
on the basis of the close similarities of spectral data
among 4a, 4b, and 4c.
Violet crystals of 5b were obtained by layering a
CH2Cl2 solution of 5b with hexane at room temperature
and used for the X-ray crystal structure analysis. Crystal
data and structure refinement information of 5b are
presented in Table 1. The ORTEP drawing of 5b is il-
lustrated in Fig. 3 and selected bond distances and bond
angles are given in Table 5. Fig. 3 clearly shows that two
iron atoms in 5b are bridged by a new chelate ligand [l-
C(CO2Me)@CHACH@C(CO2Me)C(O)PPh2] to form a
seven-membered metallacyclic ring. Consequently, 5b
has a structure in which the second MeO2CCBCH is
coupled with the l-CH carbon in a hypothetical regio-
isomer
of
4c,
(g5-C5Me5)Fe2(CO)3(l-CO)[l-
CH@C(CO2Me)C(O)PPh2] (4c0), via head-to-head cou-
ꢀ
pling. The Fe–Fe bond length (2.759(2) A) is consistent
with a single Fe–Fe bond, but significantly longer than
ꢀ
ꢀ
those found in 1 (av. 2.643(2) A) and 3a (2.636(3) A).
The elongation of the Fe–Fe bond in 5b may be ex-
plained by the dative bond character. According to the
electron counting rule, the Fe(1) atom and the Fe(2)
atom have 18 and 16 valence electrons, respectively, if
the Fe–Fe bond is ignored: The new ligand is coordi-
nated to the Fe(1) atom by the phosphorus atom and the
C(16)–C(17)–C(18) moiety in a p-allyl fashion, and to
the Fe(2) atom by two carbon atoms [C(15) and C(18)]
in a r-bonding fashion. Thus, to fulfill the 18 electron
rule, the Fe(1) atom must donate two electrons to the
Fe(2) atom. Then the oxidation numbers of both iron
atoms in 5b are +2. It should be noted that Mays et al.
reported
a
dicobalt
complex,
Co2(CO)4[l-
PPh2CMe@CHC(O)CH@CHPPh2]. The bridging li-
gand in this complex is similar to the bridging ligand in
5b but is different in the linkage [5c].
The 1H, 13C{1H },13C–1H COSY, 31P, and IR spectra
of 5b are all consistent with the solid state structure.
Some characteristic spectral features of 5b can be sum-
marized as follows. The two CH proton signals appear
3
3
at 3.48 ppm (dd, JHH ¼ 4:0 Hz, JPH ¼ 2:2 Hz) and
3
3
1
6.20 ppm (dd, JHH ¼ 4:0 Hz, JPH ¼ 1:6 Hz) in the H
NMR spectrum that can be assigned to coordinated
olefin protons. Correspondingly, the two CH carbons
appear at 62.8 ppm (JPC ¼ 5:0 Hz) and 128.6 ppm
(JPC ¼ 9:1 Hz), respectively, which have been confirmed
by the 13C–1H COSY NMR spectroscopy. Three dou-
blets at 75.8 ppm (2JPC ¼ 86:3 Hz), 171.9 ppm
(2JPC ¼ 34:7 Hz), and 183.3 ppm (1JPC ¼ 43:8 Hz) in the
13C{1H} NMR spectrum are assigned to the two car-
bons attached to CO2Me groups, C(15) and C(18), and
the inserted carbonyl carbon, C(14), respectively. The
31P NMR signal of 5b appears at 75.9 ppm, which is
comparable to those of 4a–c. Similarly, based on the
spectral data, complex 5a is suggested to have a struc-
ture similar to 5b.
The crystal structure of 6a was determined as the
representative of complexes 6a–c. Orange plate-like
crystals of 6a were obtained by layering a toluene so-
lution of 6a with hexane at )30 °C and used for the X-
ray study. Crystal data and structure refinement infor-
mation of 6a are presented in Table 1. Two independent
molecules (A and B) were found in the unit cell. As there
is no significant difference between the two molecules,
the ORTEP drawing of molecule A is illustrated in
Fig. 4. Selected bond distances and bond angles for
molecule A are given in Table 6. Fig. 4 clearly shows
Fig. 3. ORTEP drawing of (g5-C5Me5)Fe2(CO)3(l-CO)[l-
C(CO2Me)CHCHC(CO2Me)C(O)PPh2] (5b), showing 50% thermal
ellipsoids. Hydrogen atoms except H(C16) and H(C17) were omitted
for clarity.
Table 5
5
ꢀ
Selected bond distances (A) and angles (°) for (g -C5Me5)Fe2(CO)3(l-
CO)[l-C(CO2Me)CHCHCHC(CO2Me)C(O)PPh2] (5b)
Bond distances
Fe(1)–Fe(2)
Fe(2)ꢀ ꢀ ꢀP
2.759(2)
2.985(3)
2.065(12)
2.163(9)
1.894(15)
1.498(12)
1.413(11)
Fe(1)–P
2.242(2)
Fe(1)–C(16)
Fe(1)–C(18)
Fe(2)–C(18)
C(14)–C(15)
C(16)–C(17)
C(14)–O(4)
2.152(11)
2.083(10)
1.948(8)
Fe(1)–C(17)
Fe(2)–C(15)
P–C(14)
1.461(13)
1.388(12)
1.225(10)
C(15)–C(16)
C(17)–C(18)
Bond angles
Fe(2)–Fe(1)–P
72.46(7)
69.6(3)
70.7(3)
86.3(4)
Fe(1)–Fe(2)–C(15)
Fe(1)–Fe(2)–C(18)
Fe(2)–Fe(1)–C(18)
Fe(1)–P–C(14)
59.6(3)
93.0(3)
44.8(3)
105.2(4)
Fe(2)–Fe(1)–C(16)
Fe(2)–Fe(1)–C(17)
Fe(1)–C(18)–Fe(2)

H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
1489
H
H
+
Fe
CO
Fe
P
CO
R
R
P
Ph
Ph
Ph
Ph
O
-
O
A
B
Chart 3.
also appears at very low field, 231.3 ppm (2JPC ¼ 25:3 Hz,
1JCH ¼ 136:6 Hz), which is also in accord with the large
contribution of form B. In addition, the carbon signals for
the CPh@ moiety, the C(O)P moiety, and a terminal
carbonyl ligand of 6c appear at 155.5 ppm (2JPC ¼ 71:1
Hz), 206.5 ppm (2JPC ¼ 27:0 Hz,3JCH ¼ 15:6 Hz), and
218.8 ppm (2JPC ¼ 27:0 Hz), respectively, which have
1
been confirmed by the 13C NMR measurement in a H
non-decoupling mode. The corresponding signals for
complexes 6a and 6b appear in similar regions. There are
some mononuclear complexes related to 6 but all of them
have a ligand consisting of a carbonyl-alkene-phosphido
linkage instead of an alkene-carbonyl-phosphido linkage:
Fig. 4. ORTEP drawing of (g5-C5Me5)Fe(CO)[CH@CHC(O)PPh2]
(6a), showing 50% thermal ellipsoids (Molecule A). Hydrogen atoms
except H(C23A) and H(C24A) were omitted for clarity.
i.e.
(g5-C5H5)Fe(CO)[C(O)CR1@CR2PPh2]
(R1@
CO2Me; R2@H, CO2Me) [24] and (g5-C5H5)M(CO)3-
[C(O)CR1@CR2PPh2] (M ¼ Mo, W; R1 ¼ H, R2 ¼ Ph,
CO2Me; R1 ¼ R2 ¼ CO2Me, CO2Me) [25]. These com-
plexes have been prepared by the reaction of the corre-
sponding metallophosphines with alkynes.
Table 6
Selected bond distances (A) and angles (°) for (g5-
C5Me5)Fe(CO)[CHCHC(O)PPh2] (6a) (Molecule A)
ꢀ
Bond distances
FeA–PA
2.180(2)
1.355(12)
1.219(11)
1.715(8)
FeA–C(23A)
C(24A)–C(25A)
PA–C(25A)
1.943(8)
1.424(11)
1.917(9)
C(23A)–C(24A)
C(25A)–O(1A)
FeA–C(26A)
Although terminal alkynes easily reacted with 1 under
mild conditions, inner alkynes such as diphenyl or di-p-
tolyl acetylene did not react with 1 even at 80 °C. Only
MeO2CCBCCO2Me reacted with 1 to give a mononu-
clear iron complex (g5-C5Me5)Fe(CO)[C(CO2Me)@
C(CO2Me)C(O)PPh2] (6d) as an isolable complex in
30% yield (Eq. (4)). The patterns of all NMR spectra of
6d are very similar to those of 6a, 6b, and 6c. The
comparison of the carbon chemical shifts for the Fe–
CR@ moiety among complexes 6a–d shows that 6d has
the strongest character of the above-mentioned terminal
carbene complex (resonance form B in Chart 3): 6d
(MeO2CCBCCO2Me): 258.6 ppm, 6b (MeO2CCBCH):
253.3 ppm, 6c (PhCBCH): 231.3 ppm, 6a (HCBCH):
230.8 ppm. This is well explained by the electronic effect
of the substituents on the inserted alkyne moiety: the
strong electron-withdrawing group on the alkenyl moi-
ety induces the strong p-back donation from the metal
and results in giving the high double-bond character on
the Fe–C carbon.
Bond angles
PA–FeA–C(23A)
C(23A)–FeA–
C(26A)
81.3(2)
87.3(3)
PA–FeA–C(26A)
FeA–C(23A)–
C(24A)
90.8(3)
127.0(6)
C(23A)–C(24A)–
C(25A)
PA–C(25A)–O(1A) 122.8(6)
117.3(7)
C(24A)–C(25A)–
C(24A)
FeA–PA–C(25A)
130.2(8)
102.5(3)
that complex 6c is a mononuclear complex having a
chelate [CH@CHC(O)PPh2] ligand. The Fe atom adopts
a three-legged piano-stool structure. The Fe–P distance
ꢀ
(2.180(2) A) is typical of the Fe–P dative bond. The
ꢀ
C(23)–C(24) distance (1.355(12) A) corresponds with a
ꢀ
double bond. The Fe–C(23) distance (1.943(8) A) is
within a normal Fe–C r-bond length.
There are some characteristic features in the spectral
data of complex 6. The proton of the FeACH@ moiety
shows a resonance at very low field (6c: 11.39 ppm, 6b:
12.81 ppm, 6a: 10.82 ppm) in the 1H NMR spectrum. This
is surprising because the corresponding signals of the
related complexes such as those of a-CH of (g5-
C5Me5)Fe(CO)2(g1-CH@CH2) [22] and the b-CH of
cyclopentenone [23] appear around 7–8 ppm. This
anomaly can be rationalized by a large contribution of the
canonical form B as a terminal carbene complex shown in
Chart 3. The carbon signal for the Fe–CH@ moiety of 6c
MeO2C
MeO2CC≡CCO2Me
Fe
P
1
CO
45 ˚C,
12 h
MeO2C
Ph
Ph
O
6d (30%)
ð4Þ

1490
H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
2.3. A plausible reaction mechanism
insertion of another alkyne into a C–Fe bond of 4 ac-
companied by a CO dissociation gives 5. The other
path includes an initial insertion of another alkyne into
a C–Fe bond of E accompanied by a CO dissociation
to give intermediate F. Then, the insertion of the
phosphido ligand into the Fe–C(O) bond in F accom-
panied by rearrangement occurs to afford 5. Interme-
diate F might also be formed from the reaction of 3
with an alkyne. Complex 5b may be formed from a
hypothetical regioisomer of 4b, (g5- C5Me5)Fe2(CO)4-
[l-CH@C(CO2Me)C(O)PPh2] (4b0), and MeO2CCBCH
via head-to-head coupling. The bridging moiety of 4b0
are less hindered and could react with another alkyne
to produce 5b. In fact, more hindered 4b did not react
with another molecule of MeO2CCBCH. We found
that 4a reacted with HCBCH, but produced only a
trace of 5a. Therefore, this reaction may proceed
mainly through F. Mononuclear complex 6 can form by
the thermal decomposition of 4 with liberation of a
Fe(CO)3 fragment. This is consistent with the fact that
prolonged heating of the solution of 4a or 4c leads
to the principal formation of 6a or 6c, respectively
A plausible mechanism for the reaction of 1 with
alkynes is illustrated in Scheme 2. The first step is most
probably the coordination of the alkyne to the iron
atom without a bulky g5-C5Me5 ligand with either
metal–metal bond cleavage or CO loss to give inter-
mediates C or D. Then, the coupling of a carbonyl
group and the alkyne in C or D affords 3 or the in-
termediate E, respectively. An intermediate related to E
involving
a
five-membered M–CR@CR0AC(O)AM
metallacyclic ring has been previously proposed in the
reaction of Co2(l-HCBCH)(CO)6 with P2Ph4 to give
Co2[l-HX@CHC(O)PPh2](l-PPh2)](CO)4 [26]. A CO
loss from E leads to the formation of 3 in the case of
tBuCBCH. Without a CO loss, the insertion of the
phosphido ligand into the Fe–C(O) bond in E produces
4 in the case of RCBCR0 (R ¼ H, R0 ¼ CO2Me, Ph).
There are some examples for insertion of the phosphido
ligand into the M–C(O)R bond [27]. There are two
paths to be considered for the formation of 5 from the
proposed intermediate E. One is the path via 4: an
O
C
Cp*
Cp* =
(OC)3Fe
Ph
Fe
Ph
CO
P
1
+ RC≡CR'
RC≡CR'
+ RC≡CR' - CO
O
C
Cp*
OC
RC≡CR'
R
Cp*
Cp*
CO
CO
Fe
Fe
OC Fe
OC
OC Fe
OC
Fe
CO
Ph
R'
P
CO
P
P
O
Ph
Ph Ph
Ph Ph
C
D
6
- Fe(CO)3
R'
R
R'
O
O
O
C
Cp*
Fe
R
Cp*
CO
Cp*
OC
(OC)3Fe
R'
Fe Fe
(OC)3Fe
Fe
CO
R
OC
- CO
P
P
Ph
P
Ph Ph
Ph
Ph Ph
O
3
4
E
+ RC≡CR'
+ RC≡CR'
- CO
R'
- CO
+ RC≡CR'
R
R'
R'
Cp*
Ph
O
Fe Cp*
R
Fe
R
P
(OC)3Fe
R'
(OC)3Fe
R
P
Ph Ph
Ph
O
F
5
Scheme 2.

H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
1491
(Eq. (5)). The regiochemistry of the products 3–6 seems
O
R1
C
to be controlled at the step of the alkyne insertion
(from C or D to E) by minimizing the steric interaction
between the bulky g5-C5Me5 group on the other metal
and the substituent on the alkyne, though electronic
factors cannot be ignored.
(OC)3Fe
R2
Fe
R1
40 ~ 60 ˚C
-F e(CO)3
Fe
P
CO
P
R2
Ph
Ph
Ph
Ph
O
O
4a (R1 =H , R2 =H )
6a (R1 =H , R2 =H )
6c (R1 =H , R2 =P h)
4c (R1 =H , R2 =P h)
ð5Þ
2.4. Summary
A plausible reaction mechanism for the formation of
these products was suggested. The key steps are (1)
initial coordination of an alkyne, (2) coupling of the
coordinated alkyne with a carbonyl ligand, and (3)
formation of an alkyne-carbonyl-phosphido linkage.
The regiochemistry of the products 3–6 seems to be
controlled mainly at the step after the coupling of the
coordinated alkyne with a carbonyl ligand on a metal by
minimizing the steric interaction between the bulky g5-
C5Me5 group on the other metal and the substituent on
the alkyne. When the substituent on a terminal alkyne is
small or electron-withdrawing (H, CO2Me), the second
alkyne can insert into a C–Fe bond to produce dinu-
clear complexes having a [l-CRCHCHCRC(O)PPh2]
ligand.
Complex (g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2) (1)
was prepared in high yield by a new method, i.e., the
coupling between the anionic phosphido iron complex
Li[Fe(CO)4PPh2] with (g5-C5Me5)Fe(CO)2I followed
by photolysis. The X-ray crystal structure analysis of
1 revealed that the two bridging ligands, phosphido
and carbonyl, are both almost symmetrically coordi-
nated to two metals, despite the differences in ligands
and oxidation numbers between the two metal frag-
ments. The large steric repulsion between a bulky g5-
C5Me5 group and a phenyl group on the bridging
phosphido ligand is notable. The reactions of 1 with
various terminal alkynes produced complexes incor-
porating one or two molecules of alkynes and a car-
bonyl group as a result of C–C bond and P-C bond
formation. The structures of three types of products
except for 3 have been determined by X-ray crystal
3. Experimental details
t
structure analysis. The reaction of 1 with BuCBCH,
a terminal alkyne with a bulky group, gave a mixture
of two isomeric complexes (g5-C5Me5)Fe2(CO)3(l-
PPh2)(l-CH@C(tBu)C(O)) (3) containing a ketoalke-
nyl ligand [17]. For the terminal alkynes with a less
hindered and/or electron-withdrawing group, the
principal products were dinuclear complexes bridged
3.1. General procedure
All manipulations were carried out under a dry ni-
trogen or argon atmosphere using standard Schlenk
techniques. Hexane, benzene, toluene, ether, and THF
were distilled from sodium/benzophenone before use.
by
a
new phosphinoketoalkenyl ligand, (g5-
(4a:
Fe(CO)4PPh2H
[28],
t
(g5-C5Me5)Fe(CO)2I
[29],
C5Me5)Fe2(CO)3(l-CO)[l-CR1@CR2C(O)PPh2]
PhCBCH [30], and BuCBCH [31] were prepared ac-
cording to the literature methods. MeO2CCBCH and
MeO2CCBCCO2Me were purchased and dried over
molecular sieves 4A before use. 1H and 13C NMR
spectra were recorded on Bruker ARX-300 and Varian
XL-200 instruments. 31P NMR spectra were recorded
on JEOL FX-90Q and Bruker ARX-300 spectrometers
referenced to external 85% H3PO4. IR spectra were
obtained with a Horiba FT-200 spectrophotometer, and
mass spectra were obtained on Hitachi M-2500S and
JEOL JMS HX-110 spectrometers. Irradiation was
carried out using a 450-W medium-pressure Hg arc
lamp (Ushio UV-450).
R1 ¼ H, R2 ¼ H; 4b: R1 ¼ CO2Me, R2 ¼ H; 4c: R1 ¼ H,
R2 ¼ Ph). In the cases of alkynes RCBCH
(R ¼ CO2Me, H), double insertion of alkynes into a
metal–phosphido bond accompanied by CO insertion
also occurred to produce dinuclear complexes (g5-
C5Me5)Fe2(CO)3[l-CRCHCHCRC(O)PPh2] (5a: R ¼
H; 5b: R ¼ CO2Me). In all cases, mononuclear com-
plexes, (g5-C5Me5)Fe(CO)[CR1 ¼ CR2C(O)PPh2] (6a:
R1 ¼ H, R2 ¼ H; 6b: R1 ¼ H, R2 ¼ CO2Me; 6c: R1 ¼ H,
R2 ¼ Ph) were isolated in low yields. Most of inner
alkynes did not react with 1 even at high tempera-
tures, but highly electron deficient MeO2CCBC-
CO2Me reacted with 1 to give a mononuclear iron
complex (g5-C5Me5)Fe(CO)[C(CO2Me)@C(CO2Me)-
C(O)PPh2] (6d) as only an isolable complex in low
yield. According to the spectroscopic data, these di-
nuclear complexes have a nature of the carbene-
bridged dinuclear complexes and mononuclear com-
plexes have a strong character of the terminal carbene
complex (canonical form B in Chart 3).
3.2. Preparation of (g5-C5Me5)Fe2(CO)4(l-CO)(l-
PPh2) (1) (a new method)
To a solution of Fe(CO)4PPh2H (1.00 g, 2.83 mmol)
in THF (20 ml) was added 2.0 ml (3.4 mmol) of n-bu-
tyllithium (1.63 M in hexane) at 0 °C. The color of the

1492
H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
solution changed to dark red. A solution of (g5-
C5Me5)Fe(CO)2I (1.06 g, 2.82 mmol) in THF (20 ml)
was added within 10 min to the above solution and the
resulting solution was stirred overnight. After filtration
of the reaction mixture with alumina (activated with a
microwave oven for 3 minutes), removal of solvent from
the filtrate under reduced pressure gave crude (g5-
C5Me5)Fe2(CO)6(l-PPh2) (2) in 97% yield (1.65 g, 2.74
mmol). A benzene (280 ml) solution of 2 (0.610 g, 1.02
mmol) was irradiated with a 450-W medium-pressure
Hg lamp for 7 h. After removal of the solvent under
reduced pressure, the residue was chromatographed on
an alumina column (300 mesh, i.d. 2.3 cm ꢂ 7 cm; eluent:
hexane/benzene ¼ 2/1). Concentration of a black fraction
gave (g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2) (1) in 76%
yield (0.446 g, 0.779 mmol). 2: 1H NMR (300
MHz,C6D6) d 1.39 (s, 15H, Me), 6.8–8.4 (m, 10H, Ph),
31P NMR (36.3 MHz, C6D6) d 90.8. IR (KBr) mCO 1998
(vs), 1948 (vs), 1930 (sh, vs), 1871 (s), 1851 (vs), 1840 (vs)
m-nitrobenzyl alcohol matrix) m/z 627 (Mþ + 1, 54.4),
598 (Mþ ) CO, 10.5), 570 (Mþ ) 2CO, 100), 542 (Mþ-
3CO, 58.3), 514 (Mþ ) 4CO, 70.7), 376 ((C5Me5)Fe-
PPh2, 88.5). Exact mass calcd for C32H35Fe2O4P:
626.0972. Found: 626.0974.
3.4. Reaction of (g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2)
(1) with HCBCH
Acetylene gas was bubbled through a solution of 1
(100 mg, 0.175 mmol) in benzene (20 ml) for 3 h at 40
°C. After removal of volatiles, the residue was chro-
matographed on a silica gel flash column (silica gel 30 g,
1.5 ꢂ 18 cm). Elution with CH2Cl2/hexane (3/1) gave
unidentified brown products, orange crystals of (g5-
C5Me5)Fe(CO)[CH@CHC(O)PPh2] (6a) in 24% yield
(19 mg, 0.041 mmol), and then brown crystals of (g5-
C5Me5)Fe2(CO)3[l-CHCHCHCHC(O)PPh2] (5a) in 7%
yield (7 mg, 0.01 mmol). Finally elution with CH2Cl2
gave olive crystals of (g5-C5Me5)Fe2(CO)3(l-CO)[l-
CH@CHC(O)PPh2] (4a) in 24% yield (18 mg, 0.030
cmꢁ1
.
3.3. Reaction of (g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2)
mmol). The H and 31P NMR, and IR spectral data for
1
t
(1) with BuCBCH
4a, 5a, and 6a are listed in Table 3. 4a: 13C NMR (75.5
MHz, C6D6) d 9.1 (C5Me5), 66.2 (d, 2JPC ¼ 82:6 Hz, –C
A solution of 1 (400 mg, 0.699 mmol) and tBuCBCH
(GC 86% pure, 100 mg, 1.05 mmol) in benzene (20 ml)
was stirred for 40 h at 35 °C. After removal of solvent,
the residue was chromatographed on a silica gel flash
column (silica gel 35 g, 1.8 ꢂ 16 cm). Elution with
CH2Cl2/hexane (5/1) gave a brown fraction, which
contained several unidentified products, and a dark
green fraction. The eluent was then changed to CH2Cl2
to collect a brown fraction. The color of both dark green
and brown fractions changed to greenish brown even
during elution. Concentration of each of the last two
fractions afforded the same isomeric mixture of (g5-
C5Me5)Fe2(CO)3(l-PPh2)[l-CH@C(tBu)C(O)] (3a and
3b) in 59% total yield (259 mg, 0.414 mmol). The 1H and
31P NMR, and IR spectral data for a mixture of 3a and
3b are listed in Table 3. 3a and 3b: 13C NMR (75.5 MHz,
C6D6) d 9.4 (C5Me5), 9.9 (C5Me5), 28.8 (CMe3), 29.2
HC(O)–), 85.9 (d, JPC ¼ 0:9 Hz, C5Me5), 127-129 (m,
3
PPh2), 130.1 (d, JPC ¼ 2:9 Hz, PPh2), 131.0 (d, JPC ¼ 2:3
Hz, PPh2), 132.75 (d, JPC ¼ 9:0 Hz, PPh2), 132.81 (d,
JPC ¼ 39:5 Hz, PPh2), 134.3 (d, JPC ¼ 7:6 Hz, PPh2),
2
1
168.9 (d, JPC ¼ 19:7 Hz, l-CH), 206.7 (d, JPC ¼ 31:9
2
Hz, –C(O)PPh2–), 213.9 (s, CO), 239.6 (d, JPC ¼ 26:2
Hz, l-CO). Mass (FAB, Xe, m-nitrobenzyl alcohol
matrix) m/z 599 (Mþ+1, 32.4), 571 (Mþ ) CO+1, 9.6),
542 (Mþ ) 2CO, 68.3), 514 (Mþ ) 3CO, 100), 486
(Mþ ) 4CO, 53.5), 458 (Mþ ) 5CO, 65.2), 402
(Mþ ) 5CO–Fe, 66.9), 376 ((C5Me5)FePPh2, 97.0).
Anal. Calcd for C29H27Fe2O5P: C, 58.23; H, 4.55.
Found: C, 58.05; H, 4.70. 5a: 13C NMR (75.5 MHz,
2
C6D6)
d
9.1 (C5Me5), 67.3 (d, JPC ¼ 59:2 Hz,
2
¼ CHC(O)-), 87.3 (C5Me5), 89.0 (d, JPC ¼ 3:3 Hz,
2
CH), 110.2 (d, JPC ¼ 10:2 Hz, CH), 127-129 (PPh2),
129.9 (d, JPC ¼ 2:7 Hz, PPh2), 130.0 (d, JPC ¼ 2:6 Hz,
PPh2), 133.9 (d, JPC ¼ 7:7 Hz, PPh2), 134.5 (d, JPC ¼ 8:6
Hz, PPh2), 130-134 (m, PPh2), 161.5 (d, 2JPC ¼ 24:5 Hz,
4
(CMe3), 33.2 (d, JPC ¼ 0:9 Hz, CMe3), 34.0 (d,
3
4JPC ¼ 0:8 Hz, CMe3), 70.8 (d, JPC ¼ 2:6 Hz, CBut),
3
2
77.8 (d, JPC ¼ 2:6 Hz, CBut), 96.5 (C5Me5), 97.3
l-CH), 190.3 (d, JPC ¼ 18:1 Hz, –C(O)PPh2–). Mass
(C5Me5), 129.15 (d, JPC ¼ 2:1 Hz, PPh2), 129.24 (d,
JPC ¼ 2:1 Hz, PPh2), 129.5 (d, JPC ¼ 3:4 Hz, PPh2),
130.2 (d, JPC ¼ 3:4 Hz, PPh2), 133.3 (d, JPC ¼ 8:3 Hz,
PPh2), 134.5, 134.63, 134.66, 134.8, 135.3, 135.5 (PPh2),
139.8 (d, JPC ¼ 43 Hz, PPh2), 142.3 (d, JPC ¼ 18 Hz,
PPh2), 143.3 (d, JPC ¼ 26 Hz, PPh2), 144.9 (d, JPC ¼ 36
(FAB, Xe, m-nitrobenzyl alcohol matrix) m/z 597
(Mþ+1, 2.3), 568 (Mþ-CO, 14.0), 540 (Mþ-2CO, 9.3),
512 (Mþ-3CO, 54.0), 484 (Mþ-4CO, 100). 6a: 13C NMR
(75.5 MHz, C6D6, d) 9.6 (C5Me5), 93.3 (C5Me5), 127.-
129 (PPh2), 129.5 (d, JPC ¼ 2:3 Hz, PPh2), 130.9 (d,
JPC ¼ 2:3 Hz, PPh2), 131.2 (d, JPC ¼ 32:5 Hz, PPh2),
132.6 (d, JPC ¼ 9:1 Hz, PPh2), 135.5 (d, JPC ¼ 28:7 Hz,
PPh2), 136.0 (d, JPC ¼ 9:8 Hz, PPh2), 146.0 (ddd (1H
2
Hz, PPh2), 185.1 (d, JPC ¼ 4:2 Hz, CH), 189.3 (d,
2JPC ¼ 3:4 Hz, CH), 209.7 (d, 2JPC ¼ 1:3 Hz, CO), 212.2
2
2
2
1
(d, JPC ¼ 3:9 Hz, CO), 213.9 (d, JPC ¼ 14 Hz, CO),
nondecoupling mode), JPC ¼ 74:7 Hz, JCH ¼ 160:9
2
2
3
1
214.3 (d, JPC ¼ 17 Hz, CO), 220.5 (d, JPC ¼ 11 Hz,
Hz, JCH ¼ 1:7 Hz, @CHC(O)A), 209.3 (d, JPC ¼ 26:3
2
2
2
CO), 221.0 (d, JPC ¼ 10 Hz, CO), 227.8 (d, JPC ¼ 8:5
Hz, AC(O)PPh2), 219.4 (d, JPC ¼ 26:8 Hz, CO), 230.8
2
Hz, CO), 228.1 (d, JPC ¼ 12 Hz, CO). Mass (FAB, Xe,
(dd, 2JPC ¼ 22:3 Hz, 1JCH ¼ 139:3 Hz, FeACH@). Mass

H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
1493
(FAB, Xe, m-nitrobenzyl alcohol matrix) m/z 459
(Mþ+1, 54.3), 431 (Mþ-CO+1, 32.2), 402 (Mþ-2CO,
91.9), 376 ((C5Me5)FePPh2, 100). Exact mass calcd for
C26H27FeO2P: 458.1098. Found: 458.1098.
3JPC ¼ 3:9 Hz, CO). Mass (FAB, Xe, m-nitrobenzyl al-
cohol matrix) m / z 713 (Mþ+1, 12.7), 628 (Mþ-
HCCCO2Me, 22.6), 392 (Fe2(CO)4(HCCCO2Me), 100).
Anal. Calcd for C34H33Fe2O8P: C, 57.33; H, 4.67.
Found: C, 57.03; H, 4.80. 6b: 13C NMR (75.5 MHz,
C6D6) d 9.5 (C5Me5), 50.8 (CO2Me), 94.7 (C5Me5),
127.3 (PPh2), 127.3 (PPh2), 129.9 (d, JPC ¼ 2:3 Hz,
PPh2), 130.4, 130.9 (PPh2), 131.2 (d, JPC ¼ 2:3 Hz,
PPh2), 132.3 (d, JPC ¼ 8:3 Hz, PPh2), 134.4 (d,
JPC ¼ 29:8 Hz, PPh2), 136.1 (d, JPC ¼ 9:8 Hz, PPh2),
3.5. Reaction of (g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2)
(1) with MeO2CCBCH
A
solution of 1 (252 mg, 0.440 mmol) and
MeO2CCBCH (55 mg, 0.66 mmol) in benzene (15 ml)
was stirred for 20 h at 40 °C. After removal of solvent,
the residue was dissolved in a minimum amount of
CH2Cl2, absorbed with Celite, and solvent removed,
and the remaining Celite with the sample was placed on
the top of a column (silica gel 35 g, 2.3 ꢂ 9 cm). The first
brown fraction was eluted with CH2Cl2/ether (5 / 1),
which contained some products. The second fraction
was eluted with ether and removal of solvent gave violet
crystals of (g5-C5Me5)Fe2(CO)3[l-C(CO2Me)CHCHC-
(CO2Me)C(O)PPh2] (5b) (89 mg). The first brown frac-
tion was chromatographed again on alumina (300 mech,
1.5 ꢂ 10 cm) and elution with CH2Cl2/ether (1/1) gave
(g5-C5Me5)Fe2(CO)3(l-CO)[l-C(CO2Me)@CHC(O)PPh2]
(4b) as a dark brown solid in 54% yield (119 mg, 0.240
mmol) and (g5-C5Me5)Fe(CO)[CH@C(CO2Me)C(O)-
PPh2] (6b) as an orange solid in 2% yield (4.0 mg, 0.008
mmol). Finally, another 30 mg of 5b was obtained from
the eluate with EtOH. The total yield of 5b was 38%
2
147.0 (d, JPC ¼ 76:3 Hz, CCO2Me), 150.0 (d,
2
JPC ¼ 59:0 Hz, PPh2), 162.2 (d, JPC ¼ 20:8 Hz, PPh2),
1
203.1 (d, JPC ¼ 32:6 Hz, C(O)PPh2), 204.3 (d,
2
3JPC ¼ 1:4 Hz, CO2Me), 218.0 (d, JPC ¼ 26:4 Hz, CO),
2
253.3 (d, JPC ¼ 24:0 Hz, CH). Mass (FAB, Xe, m-ni-
trobenzyl alcohol matrix) m/z 517 (Mþ+1, 40.2), 485
(Mþ-OMe, 68.5), 460 (Mþ-2CO, 93.8), 401 (Mþ-2
CO-CO2Me, 50.2), 376 ((C5Me5)FePPh2, 100). Exact
mass calcd for C28H29FeO4P: 516.1143. Found:
516.1150.
3.6. Reaction of (g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2)
(1) with PhCBCH
A solution of 1 (62 mg, 0.11 mmol) and PhCBCH
(95% purity by GC, 13 ll, 0.13 mmol) in benzene (10 ml)
was stirred for 9 h at 40 °C. The resulting solution was
filtered through a Celite pad (activated in an oven at 180
°C for several days) and the filtrate was evaporated to
dryness under reduced pressure. The black residue was
layered with pentane and kept at room temperature for
5 days. Black crystals of (g5-C5Me5)Fe2(CO)3(l-CO)[l-
CH@CPhC(O)PPh2] (4c) (45 mg) was isolated from the
solution. The mother liquor was again kept at room
temperature to afford 4 mg of 4c. The total yield of 4c
was 67% (49 mg, 0.073 mmol). The mother liquor was
then cooled to 5 °C to give orange crystals of (g5-
C5Me5)Fe(CO)[CH@CPhC(O)PPh2] (6c) in 5% yield (3
mg, 0.006 mmol).
1
(119 mg, 0.167 mmol). The H and 31P NMR, and IR
spectral data for 4b, 5b, and 6b are listed in Table 3. 4b:
13C NMR (75.5 MHz, C6D6)d 8.7 (C5Me5), 51.6
(CO2Me), 73.8 (d, JPC ¼ 82:8 Hz, CH), 95.2 (C5Me5),
128.4 (d, JPC ¼ 6:8 Hz, PPh2), 128.7 (d, JPC ¼ 9:8 Hz,
PPh2), 130.3 (d, JPC ¼ 2:8 Hz, PPh2), 130.9 (d, JPC ¼ 2:7
Hz, PPh2), 131.7 (d, JPC ¼ 8:3 Hz, PPh2), 134.9 (d,
JPC ¼ 6:8 Hz, PPh2), 134.9 (d, JPC ¼ 36:0 Hz, PPh2),
3
145.8 (d, JPC ¼ 17:3 Hz, CCO2Me), 178.8 (CO2Me),
1
200.3 (d, JPC ¼ 25:5 Hz, –C(O)PPh2–), 211 (br, CO),
230.5 (CO). Mass (FAB, Xe, m-nitrobenzyl alcohol
matrix) m/z 657 (Mþ+1, 100.0), 628 (Mþ ) CO, 15.0),
600 (Mþ ) 2CO, 10.5), 572 (Mþ-3CO, 59.9), 544
(Mþ ) 4CO or Mþ ) HCCCO2Me, 89.5), 516
(Mþ ) 5CO or Mþ ) CO–HCCCO2Me, 38.0). 488
(Mþ ) 2CO–HCCCO2Me, 63.3). Anal. Calcd for
C31H29Fe2O7P: C, 56.74; H, 4.45. Found: C, 57.01; H,
4.53. 5b: 13C NMR (50 MHz, CD2Cl2, d) 9.4 (C5Me5),
The reaction of 1 with PhCBCH was monitored by
1H and 31P NMR spectroscopy. A benzene-d6 solution
of 1 and PhCBCH in an NMR tube was heated at 40
1
°C. After 12 h, the H NMR spectrum showed only the
signals of 4c and excess PhCBCH. The temperature was
raised to 60 °C and the heating was continued. After 1
day, the H NMR spectrum showed the signals of 4c
1
2
50.9 (CO2Me), 51.9 (CO2Me), 62.8 (d, JPC ¼ 7:5 Hz,
and (g5-C5Me5)2Fe2(CO)4 as major products, together
CH), 75.8 (d, 2JPC ¼ 86:3 Hz, ¼ C(CO2Me)C(O)-), 93.4
(C5Me5), 103.7 (CH), 128.6 (d, JPC ¼ 9:1 Hz, PPh2),
130.3 (d, JPC ¼ 2:3 Hz, PPh2), 130.6 (d, JPC ¼ 3:0 Hz,
PPh2), 134.6 (d, JPC ¼ 8:3 Hz, PPh2), 136.8 (d, JPC ¼ 9:1
Hz, PPh2), 137.0 (d, JPC ¼ 25:7 Hz, PPh2), 138.4 (d,
JPC ¼ 43:0 Hz, PPh2), 160.2 (CO2Me), 171.9 (d,
2JPC ¼ 34:7 Hz, l-C(CO2Me) ¼ ), 178.2 (CO2Me), 183.3
with signals arising from some unidentified minor
1
products. The H and 31P NMR, and IR spectral data
for 4c and 6c are listed in Table 3. 4c: 13C NMR (75.5
2
MHz, C6D6) d 9.2 (C5Me5), 81.7 (d, JPC ¼ 77:7 Hz,
CCPh), 96.2 (C5Me5), 127.2 (Ph), 128.9 (Ph), 130.2 (br,
PPh2), 131.0 (Ph), 132.6 (d, JPC ¼ 8:9 Hz, PPh2), 132.8
(Ph), 134.5 (d, JPC ¼ 7:5 Hz, PPh2), 142.5 (d, JPC ¼ 10:7
2
3
2
(d, JPC ¼ 43:8 Hz, -C(O)PPh2-), 207.3 (d, JPC ¼ 5:5
Hz, PPh2), 168.1 (d, JPC ¼ 21:2 Hz, l-CH), 199.7 (d,
3
Hz, CO), 210.5 (d, JPC ¼ 1:7 Hz, CO), 210.8 (d,
1JPC ¼ 38:3 Hz, –C(O)PPh2–), 213.7 (CO), 239.2 (d,

1494
H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
1
2JPC ¼ 25:9 Hz, l-CO). Mass (FAB, Xe, m-nitrobenzyl
alcohol matrix) m/z 675 (Mþ+1, 50.0), 646 (Mþ ) CO,
4.8), 618 (Mþ ) 2CO, 100), 590 (Mþ ) 3CO, 81.4), 562
(Mþ ) 4CO, 33.0), 534 (Mþ ) 5CO, 69.5). Anal. Calcd
for C35H31Fe2O5P: C, 62.34; H, 4.63. Found: C, 61.83;
H, 4.61. 6c: 13C NMR (75.5 MHz, C6D6) d 9.6 (C5Me5),
93.8 (C5Me5), 126.6 (Ph), 126.7 (d, JPC ¼ 0:8 Hz, PPh2),
127.9, 128.1, 128.4, 128.5 (Ph or PPh2), 129.6 (d,
JPC ¼ 2:5 Hz, PPh2), 131.1 (d, JPC ¼ 2:4 Hz, PPh2),
131.2, 131.7 (Ph), 132.5 (d, JPC ¼ 8:4 Hz, PPh2), 135.6
(d, JPC ¼ 30:3 Hz, PPh2), 136.2 (d, JPC ¼ 10:0 Hz,
PPh2), 155.5 (d, JPC ¼ 71:1 Hz, CPh), 206.5 (dd (1H
5a, which were confirmed by the TLC and H NMR
spectroscopy.
3.9. Thermal decomposition of 4a or 4c
A solution of 4a (5.0 mg, 8.4 ꢂ 10ꢁ3 mmol) in C6D6
(0.5 ml) in a sealed NMR tube was heated at 60 °C for 3
days. The H NMR spectrum of the resulting solution
showed the signals of 6a as a main product. Similarly,
heating of a C6D6solution of 4c at 60 °C gave 6c as a
main product after several days.
1
2
3
nondecoupling mode), JPC ¼ 70:8 Hz, JCH ¼ 15:6 Hz
2
–C(O)PPh2–), 218.8 (d, JPC ¼ 27:0 Hz, CO), 231.3 (dd
3.10. X-ray crystal structure analysis
(1H
nondecoupling
mode),
2JPC ¼ 25:3
Hz,
1JCH ¼ 136:6 Hz, CH). Mass (FAB, Xe, m-nitrobenzyl
alcohol matrix) m/z 534 (Mþ+1, 36.4), 506 (Mþ ) CO,
10.7), 478 (Mþ ) 2CO, 43.9), 404 (Mþ ) CO–HCCPh,
29.0), 376 ((C5Me5)FePPh2, 100).
Each of the crystals of 1, 4c, 5b, and 6a for X-ray
diffraction study was cut down to the suitable size and
mounted on a glass rod. Intensity data were collected
by a Rigaku AFC-6A four-circle diffractometer with
graphite-monochromated Mo Ka radiation at 18 °C.
Diffraction data were collected in the x-2h or x scan
mode. The structures of 1, 4c, and 6a were solved by
direct methods (program MALTAN 71 [32] for 1, pro-
gram RANTAN 81 [32] for 4c and 6a) and refined by the
block-diagonal least-squares method with individual
anisotropic thermal parameters for non-hydrogen at-
oms. The positions of hydrogen atoms on the phenyl
groups for 1 and 4c were calculated and added to the
structure factor calculations without refinement. The
positions of hydrogen atoms for methine and phenyl
groups for 6a were calculated and added to the struc-
ture factor calculations without refinement. The struc-
ture of 5b was solved by the heavy-atom method. The
positions of two iron atoms and a phosphorus atom
were deduced from Patterson syntheses and the re-
maining non-hydrogen atoms were found by sub-
sequent difference Fourier syntheses and refined by the
block-diagonal least-squares method with individual
anisotropic thermal parameters. The positions of two
hydrogen atoms for methine groups were found by
difference Fourier syntheses and refined with isotropic
thermal parameters. The positions of hydrogen atoms
on the phenyl groups were calculated and added to the
structure factor calculations without refinement. All the
calculations were performed on a Nippon Electric Co.
ACOS-2000 computer system at the Computer Center
of Tohoku University with the Universal Program
System UNICS III [33]. Crystallographic data for 1, 4c,
5b, and 6a are summarized in Table 3. Crystallographic
Information has been deposited with the Cambridge
Crystallographic Data Centre (CCDC Nos. 211274 (1),
211275 (4c), 211276 (5b), and 211277 (6a)). The data
can be obtained free of charge via www.ccdc.cam.ac.uk
(or from the Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB21EZ, UK; fax:
(+44)1223-336-033; or deposit@ccdc.cam.ac.uk).
3.7. Reaction of (g5-C5Me5)Fe2(CO)4(l-CO)(l-PPh2)
(1) with MeO2CCBCCO2Me
A
solution of
1
(80 mg, 0.14 mmol) and
MeO2CCBCCO2Me (40 mg, 0.28 mmol) in benzene (20
ml) was stirred for 12 h at 50 °C. The solution was fil-
tered through a Celite pad. After removal of volatiles,
the brown residue was dissolved in a minimum amount
of benzene. The solution was layered with hexane and
kept at
5
°C for several days to give (g5-
C5Me5)Fe(CO)[C(CO2Me)@C(CO2Me)C(O)PPh2] (6d)
as orange crystals in 30% yield (24 mg, 0.042 mmol). The
1H and 31P NMR, and IR spectral data for 6d are listed
in Table 3. 6d: 13C NMR (75.5 MHz, C6D6) d 9.3
(C5Me5), 51.69 (CO2Me), 51.72 (CO2Me), 95.1 (d,
JPC ¼ 1:1 Hz, C5Me5), 130.3 (d, JPC ¼ 2:2 Hz, PPh2),
130.6 (d, JPC ¼ 46:3 Hz, PPh2), 131.4 (d, JPC ¼ 2:3 Hz,
PPh2), 132.4 (d, JPC ¼ 13:2 Hz, PPh2), 132.9 (d,
JPC ¼ 36:9 Hz, PPh2), 135.3 (d, JPC ¼ 11:8 Hz, PPh2),
145.5 (d, JPC ¼ 28:7 Hz, C(O)PPh2), 165.7 (d, JPC ¼ 1:2
Hz, CO2Me), 166.5 (d, JPC ¼ 14:2 Hz, C(CO2Me)),
2
166.9 (d, JPC ¼ 3:6 Hz, CO2Me), 219.3 (d, JPC ¼ 26:1
2
Hz, CO), 258.6 (d, JPC ¼ 12:8 Hz, Fe ¼ C(CO2Me)).
Mass (FAB, Xe, m-nitrobenzyl alcohol matrix) m/z
575 (Mþ+1, 70.9), 518 (Mþ ) 2CO, 100), 459
(Mþ ) 2CO–CO2Me, 57.8), 376 ((C5Me5)FePPh2, 46.9).
Exact mass calcd. for C30H31FeO6P: 574.1208. Found:
574.1200.
3.8. Reaction of (g5-C5Me5)Fe2(CO)4(l-CO)[l-
CH@CHC(O)PPh2] (4a) with HCBCH
Acetylene gas was bubbled through a solution of 4a
(100 mg, 0.175 mmol) in benzene (10 ml) for 3 h at
40 °C. The resulting solution contained unreacted 4a
and 6a in a 1:1 ratio together with trace amount of

H. Hashimoto et al. / Journal of Organometallic Chemistry 689 (2004) 1481–1495
1495
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