Synthesis of seven-membered cyclic allenes, 1-zirconacyclohepta-2,3,6- trienes, from alkynes and 1-en-3-ynes

Article abstract of DOI:10.1016/j.jorganchem.2013.05.023

Seven-membered metallacyclic allene compounds, 1-zirconacyclohepta-2,3,6- trienes, were synthesized by intermolecular coupling between alkynes and 1-en-3-ynes on a zirconium atom. X-ray diffraction studies and NMR spectroscopic observation indicated their seven-membered structures, although the contribution from 2-alkynyl-1-zirconacyclopent-4-ene might be considered. Benzyne, an unstable alkyne, also coupled with 1-en-3-ynes on zirconium and titanium.

Full text of DOI:10.1016/j.jorganchem.2013.05.023

Journal of Organometallic Chemistry 741-742 (2013) 91e96
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of seven-membered cyclic allenes, 1-zirconacyclohepta-
2,3,6-trienes, from alkynes and 1-en-3-ynes
*
Noriyuki Suzuki , Takashi Tsuchiya, Yoshiro Masuyama
Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Seven-membered metallacyclic allene compounds, 1-zirconacyclohepta-2,3,6-trienes, were synthesized
by intermolecular coupling between alkynes and 1-en-3-ynes on a zirconium atom. X-ray diffraction
studies and NMR spectroscopic observation indicated their seven-membered structures, although the
contribution from 2-alkynyl-1-zirconacyclopent-4-ene might be considered. Benzyne, an unstable
alkyne, also coupled with 1-en-3-ynes on zirconium and titanium.
Received 5 April 2013
Received in revised form
19 May 2013
Accepted 20 May 2013
Ó 2013 Elsevier B.V. All rights reserved.
Keywords:
Cyclic allene
Zirconium
Titanium
Benzyne
1-En-3-yne
1. Introduction
l
II
(1)
Small cyclic allene compounds are normally labile and difficult
to isolate. Five-membered cyclic allenes, cyclopenta-1,2-dienes
have been reported, although these were extremely reactive and
were trapped by [2 þ 2] cycloaddition [1]. For six-membered cy-
clic allenes, more than two of the six ring members must be
replaced by silicon or phosphorus atoms to make them stable
enough to isolate [2]. Recently Erker’s group and we indepen-
dently reported the synthesis of stable five-membered cyclic
allene compounds, 1-metallacyclopenta-2,3-dienes, that contain
one transition metal in the ring structure and unambiguously
determined their molecular structures (Fig. 1) [3]. These com-
plexes were synthesized by 1,1-hydroboration of bisalkynylme-
tallocene or transformation of 1-zirconacyclopent-3-yne derived
from a [5] cumulene derivative.
As well as known synthetic protocols for five-membered un-
saturated metallacyclic compounds such as 1-metallacyclopent-3-
ene [4], 1-metallacyclopenta-2,3,4-triene [5], and 1-metallacy
clopent-3-yne [6], 1-zirconacyclopenta-2,3-diene complexes have
also been prepared from low-valent zirconocene and 1-en-3-yne
compounds (Eq. (1)) [7].
l
Five-membered azametallacyclic allenes, 1-aza-2-zirconacyclo
penta-3,4-dienes, have been reported by Rosenthal [8], and Erk-
er’s group and we reported alternative methodologies to synthesize
them [9]. During our recent study on the reactivity of five-
membered metallacyclic allene we found that insertion of C]O
and C^N groups into the ZreC bond took place and that the cor-
responding alcohols and ketones were obtained after hydrolysis
(Scheme 1). We suggested seven-membered cyclic allene in-
termediates 1 and 2. Spectroscopic data supported the formation of
1 and 2 although these were not structurally characterized. Xi and
coworkers have reported 1-aza-2-zirconacyclohepta-3,4,7-triene 3
by a different approach from silane compounds and determined its
structure (Fig. 2) [10].
Buchwald and coworkers reported that dimeric coupling of a
1,3-diyne on zirconium gave 1-zirconacyclohepta-2,4,5,6-tetraene
4, which has a cyclic [3] cumulene structure [11].
Erker and coworkers recently reported that seven-membered
metallacyclic allenes
5 and 6 were formed from the five-
membered cyclic allene compound (Scheme 2) [7b]. Two mole-
cules of 7 coupled on the zirconium atom to afford 5, while nitrile
insertion resulted in the formation of 6. These were very interesting
* Corresponding author. Tel./fax: þ81 3 3238 3452.
E-mail address: norisuzuki@sophia.ac.jp (N. Suzuki).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.05.023

92
N. Suzuki et al. / Journal of Organometallic Chemistry 741-742 (2013) 91e96
Fig. 2. Examples of seven-membered zirconacyclic cumulenes.
Fig. 1. Stable five-membered metallacyclic allenes.
10a took place on the zirconium metal. Six carbon atoms and zir-
conium form the seven-membered framework. The C1eC2 distance
compounds from the view of the chemistry of small cyclic allenes.
However, only these examples have been reported to date. They
also reported that insertion of oct-4-yne into the five-membered
metallacyclic allene produced 3-alkenyl-1-zirconacyclopenta-2,4-
diene 8 instead of the seven-membered ring.
ꢀ
ꢀ
(1.261(4) A) is significantly shorter than C2eC3 (1.366(5) A), and
C1eC2eC3 is bent from a linear alignment. The bond distances
ꢀ
between Zr and C1, C2 and C3 are in the range of 2.4e2.5 A. The
dihedral angle between the planes formed by the three atoms
We recently reported seven-membered metallacyclic alkyne
compounds that were synthesized by coupling between alkynes
and [3] cumulene derivatives on the metal (Eq. (2)) [12].
located at the termini of the “allene” moiety [pl(ZreC1eSi) and
pl(C4eC3eH3)] was 87.4ꢀ. These data suggested
a seven-
membered cyclic allene structure for the molecule, but the
contribution from 2-alkynyl-1-zirconacyclopent-4-ene 11a0 cannot
be ruled out (vide infra) (Fig. 4). The structural features are
fundamentally similar to those of 5 reported by Erker and
coworkers.
(2)
Quaternary carbon atoms appeared at 113.3 and 134.9 ppm in
the 13C NMR spectrum, and coupling with 29Si was observed by 1JSie
¼ 71 Hz for the former. A methine signal was observed at
C
These prompted us to study coupling reactions between alkynes
and 1-en-3-ynes on the metal atom that would give the corre-
sponding seven-membered cyclic allene compounds. If normal al-
kynes can be employed for the formation of seven-membered
cyclic allenes, it will allow us to obtain a variety of analogous
compounds. Thus, it is of interest to develop a methodology for the
synthesis of cyclic allene compounds from alkynes and 1-en-3-
ynes. We herein report the synthesis of seven-membered metal-
lacyclic allene compounds, 1-zirconacylohepta-2,3,6-trienes.
75.8 ppm. These signals were assignable to allene carbons. The
geminal protons of methylene appeared inequivalent at 3.07 and
3.33 ppm being coupled to each other by 15.5 Hz. The methine
proton was observed at 5.05 ppm, indicating its sp2 character.
Inequivalent Cp signals were observed at 5.27 and 5.65 ppm. Hy-
drolysis of 11a with various proton sources gave a complex mixture
of hydrolyzed products on the basis of gas chromatography. The
reaction with 4-phenylbut-1-en-3-yne (10b) gave 11b in 55% yield
by 1H NMR spectroscopy. Complex 11b was structurally character-
ized although the result of X-ray analysis was unsatisfactory (see
the Supplementary material). When we started from the zircono-
cene(1-trimethylsilylprop-1-yne) complex instead of the dipheny-
lacetylene complex 9, the reaction with 10b (R ¼ Ph) gave a mixture
of isomeric products. This was in sharp contrast to the formation of
seven-membered alkynes in which the zirconocene(1-
trimethylsilylprop-1-yne) complex gave single isomer in the reac-
tion with 1,4-bis(trimethylsilyl)buta-1,2,3-triene [12]. Next, we
examined benzyne, which is known to be an unstable alkyne. Re-
actions of 10 with the zirconoceneebenzyne complex derived from
diphenylzirconocene 15 [13] afforded the corresponding 1-
metallacyclohepta-2,3,6-trienes 16 in moderate yields (Scheme
4). The molecular structure of 16a was confirmed by an X-ray
2. Results and discussion
We added 4-trimethylsilylbut-1-en-3-yne (10a) to a tetrahy-
drofuran (THF) solution of zirconoceneediphenylacetylene phos-
phine adduct 9, which was prepared from Negishi reagent and
diphenylacetylene in the presence of PMe3. After stirring for 1 h at
80 ꢀC, NMR observation of the reaction solution showed the
quantitative formation of 1-zirconacyclohepta-2,3,6-triene com-
pound 11a (Scheme 3). Interestingly, 11a was the only product, and
possible isomers such as 12, 13 and 14 were not observed on the
basis of the NMR spectra. Recrystallization from toluene solution
gave colorless crystals of 11a that were suited for X-ray diffraction
analysis.
The molecular structure of 11a is shown in Fig. 3. It shows that
intermolecular coupling of diphenylacetylene and the 1-en-3-yne
Scheme 1. Formation of seven-membered zirconacyclic allenes.
Scheme 2. Alkyne and nitrile insertion into 1-zirconacyclopenta-2,3-diene.

N. Suzuki et al. / Journal of Organometallic Chemistry 741-742 (2013) 91e96
93
Fig. 4. Possible canonical structures of 11a.
2-alkynyl-1-zirconacyclopent-4-ene structure 11a0 to some extent.
It is noteworthy that the coupling between benzyne and 1,4-
bis(trimethylsilyl)but-1-en-3-yne (10c) on the zirconium metal
resulted in the formation of 3-alkenyl-1-zirconacyclopenta-2,4-
diene compound 19 (Scheme 5). In the 1H NMR spectroscopy two
doublets were observed at 5.52 and 5.68 ppm, being coupled with
each other by 3.4 Hz. The corresponding methylene carbon
appeared at 125.9 ppm. These obviously indicated a different
structure from the cyclic allene complexes 16. This result reminded
us of complex 8 reported by Erker and coworkers.
Scheme 3. Formation of 1-zirconacyclohepta-2,3,6-trienes.
diffraction study, although the analysis was again unsatisfactory
(see the Supplementary material). These results showed that un-
stable alkynes such as benzyne also were suitable for the reaction. It
is interesting that the titanoceneebenzyne complex formed from
diphenyltitanocene 17 reacted with 10a and 10b to give titanacyclic
allene complexes 18a and 18b, respectively. These are the first ex-
amples of seven-membered titanacyclic allene compounds.
A plausible mechanism for formation of the 1-metallacyclohepta-
2,3,6-triene is illustrated in Scheme 6. An alkyne and a 1-en-3-yne
coordinate to the metal in h
2-fashion to afford bisealkyne complex
A first. Then [2 þ 2 þ 1] cycloaddition resulted in the five-membered
compound 21, which corresponds to 8 and 19. This is a commonly
observed reactionpattern in organozirconium chemistry [14]. On the
other hand, [4 þ 2 þ 1] cycloaddition would give a seven-membered
compound 20 that corresponds to 11,16 and 18. It is also possible that
alkyneeene coupling on the metal (C) once formed 2-alkynyl-1-
metallacyclopent-4-ene 22 and then it isomerized into 20, but it
seems unlikely taking into account the stronger coordination ability
of a triple bond. Discussion of the factors that determine the diver-
gence in the reaction products must await further investigations.
Chemical shifts of 11,16 and 18 in the NMR spectra are compared
with reported compounds in Table 1. The H3 protons appeared at
4.4e5.6 ppm, showing their sp2 character. The chemical shifts of the
C2 atoms were in the range of 118e137 ppm, and these are at a high
field compared with 5 and 6. The C3 atoms of 11 and 16 also
appeared upfield. These results suggest the seven-membered cyclic
allene structure of compounds 11, 16 and 18 although the contri-
bution of a 2-alkynyl-1-zirconacyclopent-4-ene structure cannot
be ruled out. Bond lengths and angles are summarized in Table 2.
The ZreC3 bond distance is significantly shorter in 11a than those
in 6 and 3. The C1eC2 bond was significantly shorter than the C2e
C3 bond in 11a, and it showed a much greater short/long difference
between C1eC2/C2eC3 compared with those in 6 and 3. The C1e
C2eC3 angles also showed the corresponding feature. It was more
bent in 11a, whereas the angles were 173e176ꢀ in 6 and 3. In
particular, nitrogen-containing compounds 6 and 3 clearly show
seven-membered cyclic allene structures. Compound 11a, on the
other hand, might be better thought of the contribution from
3. Conclusion
In summary, we found that zirconium- and titaniumealkyne
complexes reacted with 1-en-3-ynes to afford seven-membered
metallacyclic allene compounds, 1-metallalcyclohepta-2,3,6-trie
nes. X-ray diffraction studies and NMR spectroscopy indicated
that the compounds have a seven-membered structure, although
the contribution from a five-membered metallacycle cannot be
ruled out.
Fig. 3. Molecular structure of 11a. Top view (left) and front view (right). Drawn with 50% probability. Most hydrogen atoms are omitted for clarity.

94
N. Suzuki et al. / Journal of Organometallic Chemistry 741-742 (2013) 91e96
Table 2
ꢀ
ꢀ
Selected bond lengths (A) and angles ( ) of seven-membered zirconacyclic allenes.
11a
5a
6a
3b
Scheme 4. Coupling of benzyne and 1-en-3-ynes.
ZreC1
ZreC2
ZreC3
ZreC6
C1eC2
C2eC3
2.449(4)
2.397(4)
2.496(4)
2.427(3)
1.261(4)
1.366(5)
2.373(2)
2.419(2)
2.697
2.396(2)
1.268(3)
1.355(3)
2.257(2)
2.471(2)
3.174
2.166(2)
1.284(3)
1.342(3)
2.38(1)
2.829
3.688
2.03(1)
1.33(2)
1.37(2)
4. Experimental section
4.1. General
C1eC2eC3
154.5(4)
158.7(2)
173.0(2)
176(1)
a
Ref. [7b].
Ref. [10].
Manipulations that involved organometallic species were car-
ried out under an inert atmosphere using the standard Schlenk
technique or in a glove-box. Tetrahydrofuran (THF) was purchased
from Kanto Chemical Co., Inc. (dehydrated grade) and purified us-
ing a Glass-Contour Solvent SystemsÔ (SG Water USA) prior to use.
Anhydrous hexane was purchased from Kanto Chemical Co., Inc.
b
this solution was added n-butyllithium (1.6 M hexane solution,
1.05 mmol) dropwise at ꢁ78 ꢀC and the mixture was stirred for 1 h.
Trimethylphosphine (48 mg, 0.63 mmol) and diphenylacetylene
(94 mg, 0.52 mmol) was added and the mixture was warmed up to
rt. After stirring for 1 h at rt, it was stirred for additional 1 h at 50 ꢀC.
The zirconoceneediphenylacetylene complex trimethylphosphine
adduct 9 was formed quantitatively in this stage [17]. Then 4-
trimethylsilylbut-1-en-3-yne (10a) (65 mg, 0.52 mmol) was
added and the mixture was stirred for 1 h at 80 ꢀC. 1H NMR
observation indicated the formation of 11a in 99%. The volatiles
were removed in vacuo and the residue was dissolved in toluene.
The solution was filtered and the filtrate was concentrated and kept
at ꢁ30 ꢀC. Complex 11a was obtained as colorless crystals (178 mg,
and degassed prior to use. Dichlorobis(
h
5-cyclopentadienyl)zirco-
nium, dichlorobis(
h
5-cyclopentadienyl)titanium and vinyl bromide
(1 M in THF solution) were purchased from SigmaeAldrich Co. Ltd.
and used as received. Diphenylacetylene, ethylmagnesium bromide
(0.89 M THF solution), phenyllithium (1.05 M cyclohexaneediethyl
ether solution) and n-butyllithium (1.6 M hexane solution) were
purchased from Kanto Chemical Co., Inc. Trimethylphosphine was
purchased from Strem Chemicals, Inc. and used as received. 4-
Phenylbut-1-en-3-yne and 4-trimethylsilylbut-1-en-3-yne were
prepared from the corresponding terminal alkyne and vinyl bro-
mide [15]. 2,4-Bis(trimethylsilyl)but-1-en-3-yne was prepared ac-
cording to the literature [16]. Infrared spectra were recorded on a
Shimadzu FTIR-8300. 1H and 13C NMR spectra were recorded on
JEOL ECX 300 and ECA 500 spectrometers. 1H NMR yields were
determined using pyrene or toluene as an internal standard.
68%). 1H NMR (500 MHz, C6D6, Me4Si)
d 0.27 (s, 9H), 3.07 (dd,
J ¼ 15.5, 10.3 Hz, 9H), 3.33 (dd, J ¼ 15.5, 5.7 Hz, 1H), 5.05 (dd,
J ¼ 10.3, 5.7 Hz,1H), 5.27 (s, 5H), 5.65 (s, 5H), 6.88e7.16 (m, 10H). 13C
NMR (125 MHz, C6D6, Me4Si) d 1.38, 41.72, 75.78,106.81 (Cp),107.93
(Cp), 113.31 (q, JSieC ¼ 71 Hz), 122.99, 125.20, 127.67, 127.71, 127.90,
128.29, 134.86 (q), 143.46 (q), 153.78 (q), 155.55 (q). IR (KBr):
n
¼ 698, 797, 849, 1018, 1246, 1389, 1439, 1481, 1589, 1921, 2839,
4.2. Preparation of 1-zirconacylohepta-2,3,6-triene (11)
2901, 3055 (cmꢁ1). Elemental analysis gave unsatisfactory results
despite repeated recrystallization presumably because the com-
pound was sensitive toward air and moistures, although we
handled under an inert atmosphere.
Typical procedure is as follows. In a thoroughly dried 20 mL
Schlenk tube filled with argon, dichlorobis(h
5-cyclopentadienyl)
zirconium(IV) (149 mg, 0.5 mmol) was dissolved in THF (3 mL). To
Table 1
Chemical shifts in 1H and 13C NMR for the compounds.
Complex metal
11a
11b
16a
16b
18a
18b
5a
6a
Zr
Zr
Zr
Zr
Ti
Ti
Zr
Zr
H3
H4
H40
C1
C2
C3
C4
5.05
3.07
3.33
5.63
3.14
3.45
4.70
2.96
3.25
5.39
3.17
3.37
4.36
3.27
3.29
5.59
3.22
3.30
e
e
2.52
2.95
e
e
113.3
134.6
113.1
125.0
99.3
126.4
115.3
143.5
94.5
137.1
157.6
115.3
e
134.9
75.8
41.7
128.4
86.1
41.9
137.2
77.3
40.1
131.6
88.3
40.7
118.9
66.6
41.8
118.2
95.4
40.4
49.3
a
Ref. [15].

N. Suzuki et al. / Journal of Organometallic Chemistry 741-742 (2013) 91e96
95
(125 MHz, C6D6, Me4Si)
d
1.30, 40.15, 77.28, 105.94 (Cp), 108.16 (Cp),
113.07 (q), 123.59, 123.63, 124.38, 137.19 (q), 164.15 (q), 175.01(q).
16b: The title compound was prepared similarly to 16a using 4-
phenylbut-1-en-3-yne (10b) (95 mg, 0.74 mmol) in 60% yield by 1H
NMR. Volatile was removed in vacuo and the residue was dissolved
in benzene-d6 for NMR spectroscopy. 1H NMR (500 MHz, C6D6,
Me4Si)
5.39 (dd, J ¼ 11.4, 5.2 Hz, 1H), 5.40 (s, 5H), 5.44 (s, 5H), 7.11e7.61 (m,
9H). 13C NMR (125 MHz, C6D6, Me4Si)
40.65, 88.34, 105.87 (Cp),
d
3.17 (dd, J ¼ 14.9,11.4 Hz,1H), 3.37 (dd, J ¼ 14.9, 5.2 Hz,1H),
d
108.17 (Cp), 123.82, 124.09, 124.22, 124.99 (q), 127.74, 128.89, 131.58
(q), 132.25, 134.81(q), 142.77, 163.89 (q), 174.08 (q).
4.4. Preparation of 19
Scheme 5. Formation of 3-alkenyl-1-zirconacyclopenta-2,4-diene.
The title compound was prepared in a similar manner to that
of 16a with 2,4-bis(trimethylsilyl)but-1-en-3-yne (10c) (122 mg,
0.62 mmol). 1H NMR spectroscopy revealed the formation of 19 in
11b: The title compound was prepared in a similar manner to
11a using an excess amount of 4-phenylbut-1-en-3-yne (10b)
(120 mg, 0.93 mmol). 1H NMR spectroscopy of the reaction mixture
showed the formation of 11b in 55% yield. Recrystallization from
toluene solution gave colorless crystals in 48% yield. 1H NMR
55% yield. 1H NMR (500 MHz, C6D6, Me4Si)
d
0.04(s, 9H), 0.24 (s,
9H), 5.52 (d, J ¼ 3.4 Hz, 1H), 5.68 (d, J ¼ 3.4 Hz,1H), 5.94 (s, 5H), 6.05
(s, 5H), 6.55e7.20 (m, 4H). 13C NMR (125 MHz, C6D6, Me4Si)
0.59,
d
3.76, 112.36 (Cp), 112.38 (Cp), 124.80, 124.93, 125.94 (CH2), 126.36,
136.56, 144.95 (q), 158.92(q, CeSi), 162.44 (q, JCeSi ¼ 60 Hz), 187.22
(q), 199.22 (q, JCeSi ¼ 53 Hz).
(500 MHz, C6D6, Me4Si)
J ¼ 15.5, 5.2 Hz, 1H), 5.29 (s, 5H), 5.63 (dd, J ¼ 10.9, 5.2 Hz, 1H), 5.70
(s, 5H), 6.93e7.51 (m,15H). 13C NMR (125 MHz, C6D6, Me4Si)
41.93,
d
3.14 (dd, J ¼ 15.5, 10.9 Hz, 1H), 3.45 (dd,
d
86.06, 106.72 (Cp), 107.96 (Cp), 123.11, 124.43 (q), 125.37, 127.77,
127.85, 127.96, 128.29, 128.39 (q), 128.92, 129.15, 132.32, 134.63 (q),
4.5. Preparation of the titanium complex with benzyne 18
Dichlorobis(h
5-cyclopentadienyl)titanium (125 mg, 0.5 mmol)
143.61 (q), 153.69 (q), 155.36 (q), 178.49 (q). IR (KBr):
n
¼ 629, 698,
756, 922, 1018, 1072, 1258, 1439, 1489, 1593, 1894, 2824, 2889, 3016
(cmꢁ1). Elemental analysis, calcd. for C34H28Zr: C 77.37, H 5.35;
found C 77.16, H 5.35.
was dissolved in toluene (4 mL), phenyllithium (1.05 M in cyclo-
hexaneediethyl ether, 1.0 mL, 1.05 mmol) was added dropwise
at ꢁ78 ꢀC. The mixture was stirred for 1 h, and then warmed up to
room temperature. 4-trimethylsilylbut-1-en-3-yne (10a) (76 mg,
0.61 mmol) was added and the mixture was stirred at 100 ꢀC for 3 h.
The formation of 18a was observed by NMR spectra (55% by 1H
4.3. Preparation of 16a and 16b
16a: To a solution of dichlorobis(
h
5-cyclopentadienyl)zirconiu-
NMR). 1H NMR (500 MHz, C6D6, Me4Si)
d 0.22 (s, 9H), 3.27 (dd,
m(IV) (149 mg, 0.5 mmol) in THF (5 mL) was added phenyllithium
(1.05 M in cyclohexaneediethyl ether, 1.05 mmol) dropwise
at ꢁ78 ꢀC. After stirring for 1 h, 4-trimethlsilylbut-1-en-3-yne (10a)
(90 mg, 0.72 mmol) was added and the mixture was warmed to rt.
The solution was stirred at 100 ꢀC for 3 h. The formation of 16a was
observed by 1H NMR spectroscopy (67% yield). Volatile was removed
in vacuo and the residue was dissolved in benzene-d6 for NMR
J ¼ 15.5, 6.3 Hz, 1H), 3.29 (dd, J ¼ 15.5, 11.4 Hz,1H), 4.36 (dd, J ¼ 11.4,
6.3 Hz, 1H), 5.46 (s, 5H), 5.52 (s, 5H), 6.59e7.02 (m, 4H). 13C NMR
(125 MHz, C6D6, Me4Si)
111.05 (Cp), 112.28 (Cp), 118.84 (q), 123.56, 125.22, 126.04, 138.27,
154.08 (q), 183.72 (q).
d
1.20, 41.84, 66.61, 99.33 (q, JCeSi ¼ 84 Hz),
18b: The title compound was prepared similarly to 18a using
10b (64% by 1H NMR). 1H NMR (500 MHz, C6D6, Me4Si)
d 3.22 (dd,
spectroscopy.1H NMR (500 MHz, C6D6, Me4Si)
d
0.15 (s, 9H), 2.96 (dd,
J ¼ 14.3, 11.4 Hz,1H), 3.30 (dd, J ¼ 14.3, 5.7 Hz,1H), 5.59 (dd, J ¼ 11.4,
J ¼ 14.9,11.4 Hz,1H), 3.25 (dd, J ¼ 14.9, 5.2 Hz,1H), 4.70 (dd, J ¼ 11.4,
5.7 Hz, 1H), 5.17 (s, 5H), 5.26 (s, 5H), 7.01e7.47 (m, 9H). 13C NMR
5.2 Hz, 1H), 5.30 (s, 5H), 5.32 (s, 5H), 6.99e7.51 (m, 4H). 13C NMR
(125 MHz, C6D6, Me4Si)
d 40.38, 95.43, 105.95 (Cp), 108.76 (Cp),
Scheme 6. Plausible mechanism for formation of the seven-membered metallacyclic allenes.

96
N. Suzuki et al. / Journal of Organometallic Chemistry 741-742 (2013) 91e96
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structure was solved by direct methods [18] and expanded using
Fourier techniques. The non-hydrogen atoms were refined aniso-
tropically. Some hydrogen atoms were refined isotropically and the
rest were refined using the riding model. The final cycle of full-
matrix least-squares refinement on F2 was based on 5631
observed reflections and 310 variable parameters. All calculations
were performed using the CrystalStructure [19] crystallographic
software package except for refinement, which was performed
using SHELXL-97 [20]. Crystallographic data are summarized in
Table S1.
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N. Suzuki, S. Yuasa, K. Hagimori, S. Inoue, T. Asada, T. Takemoto, Y. Masuyama,
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Acknowledgment
[10] S. Zhang, W.-X. Zhang, J. Zhao, Z. Xi, J. Am. Chem. Soc. 132 (2010) 14042e
14045.
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[12] (a) N. Suzuki, N. Aihara, M. Iwasaki, M. Saburi, T. Chihara, Organometallics 24
(2005) 791e793;
We thank Ms. S. Machishima (Sophia Univ.) and Ms. K. Yamada
(RIKEN) for assistance in elemental analysis. We acknowledge Ms.
E. Okano (Sophia Univ.) for assistance in NMR measurement. This
work was financially supported by JSPS KAKENHI Grant Number (B)
22350022.
(b) N. Suzuki, T. Tsuchiya, N. Aihara, M. Iwasaki, M. Saburi, Eur. J. Inorg. Chem.
2013 (2013) 347e356.
Appendix A. Supplementary material
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(b) E.-i. Negishi, Dalton Trans. (2005) 827e848;
CCDC 929905 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
(c) U. Rosenthal, V.V. Burlakov, M.A. Bach, T. Beweries, Chem. Soc. Rev. 36
(2007) 719e728;
(d) L. Zhou, M. Yamanaka, K.-I. Kanno, T. Takahashi, Heterocycles 76 (2008)
923e947;
(e) N. Suzuki, D. Hashizume, Coord. Chem. Rev. 254 (2010) 1307e1326.
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Appendix B. Supplementary material
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Ber. 122 (1989) 1035e1042.
Supplementary data related to this article can be found online at
http://dx.doi.org/10.1016/j.jorganchem.2013.05.023.
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