Alkaline earth metallocenes coordinated with ester pendants: Synthesis, structural characterization, and application in metathesis reactions

Article abstract of DOI:10.1002/chem.201301618

A variety of ester-substituted cyclopentadiene derivatives have been synthesized by one-pot reactions of 1,4-dilithio-1,3-butadienes, CO, and acid chlorides. Direct deprotonation of the ester-substituted cyclopentadienes with Ae[N(SiMe₃)₂]₂ (Ae=Ca, Sr, Ba) efficiently generated members of a new class of heavier alkaline earth (Ca, Sr, Ba) metallocenes in good to excellent yields. Single-crystal X-ray structural analysis demonstrated that these heavier alkaline earth metallocenes incorporated two intramolecularly coordinated ester pendants and multiply-substituted cyclopentadienyl ligands. The corresponding transition metal metallocenes, such as ferrocene derivatives and half-sandwich cyclopentadienyl tricarbonylrhenium complexes, could be generated highly efficiently by metathesis reactions. The multiply-substituted cyclopentadiene ligands bearing an ester pendant, and the corresponding heavier alkaline earth and transition-metal metallocenes, may have further applications in coordination chemistry, organometallic chemistry, and organic synthesis. Alkaline earth metallocenes: Heavier alkaline earth (Ca, Sr, Ba) metallocenes containing two intramolecularly coordinated ester pendants and bearing multiply substituted cyclopentadienyl ligands (see scheme) can be prepared efficiently. These metallocenes can undergo metathesis reactions to form the transition-metal metallocenes. Copyright

Full text of DOI:10.1002/chem.201301618

FULL PAPER
DOI: 10.1002/chem.201301618
Alkaline Earth Metallocenes Coordinated with Ester Pendants: Synthesis,
Structural Characterization, and Application in Metathesis Reactions
Heng Li,[a] Wen-Xiong Zhang,[a] and Zhenfeng Xi*[a, b]
Abstract: A variety of ester-substituted
cyclopentadiene derivatives have been
synthesized by one-pot reactions of 1,4-
dilithio-1,3-butadienes, CO, and acid
chlorides. Direct deprotonation of the
ester-substituted cyclopentadienes with
er alkaline earth metallocenes incorpo-
rated two intramolecularly coordinated
ester pendants and multiply-substituted
cyclopentadienyl ligands. The corre-
sponding transition metal metallocenes,
such as ferrocene derivatives and half-
sandwich cyclopentadienyl tricarbonyl-
ACHTUNGTRENNrUNG henium complexes, could be generated
highly efficiently by metathesis reac-
tions. The multiply-substituted cyclo-
pentadiene ligands bearing an ester
pendant, and the corresponding heavi-
er alkaline earth and transition-metal
metallocenes, may have further appli-
cations in coordination chemistry, orga-
nometallic chemistry, and organic syn-
thesis.
Ae[NACHTUNGTRENNUNG(SiMe3)2]2 (Ae=Ca, Sr, Ba) effi-
ciently generated members of a new
class of heavier alkaline earth (Ca, Sr,
Ba) metallocenes in good to excellent
yields. Single-crystal X-ray structural
analysis demonstrated that these heavi-
Keywords: alkaline earth metals ·
cyclopentadienyl esters · metallo-
cenes · metathesis · pendant ligands
Introduction
Recent years have witnessed a significant growth in the syn-
thesis, structural characterization, and catalytic application
of heavier alkaline earth (Ca, Sr, Ba) complexes.[1–4] Howev-
er, their high reactivity (instability), which can lead to intra-
molecular ligand rearrangement, and poor solubility in
many common solvents significantly hamper their further
application.[5,6] As a consequence, considerable effort has
been directed towards the search for suitable ligands that
are capable of stabilizing such complexes and increasing
their solubility. In this context, multiply-substituted cyclo-
pentadienyl ligands bearing pendant groups have attracted
considerable interest[7] because the pendant groups may co-
ordinate intramolecularly to the metal center, compensating
for its electron deficiency and stabilizing the corresponding
p complex.
As shown in Scheme 1, cyclopentadienyl ligands bearing
donor-functionalized pendants, such as amine and pyridyl (1,
2),[8a,b] methoxy (3, 4, 5),[8b–d] and alkenyl (6)[8e] groups, have
Scheme 1. Alkaline earth metallocenes incorporating pendants.
[a] H. Li, Prof. Dr. W.-X. Zhang, Prof. Dr. Z. Xi
Beijing National Laboratory for Molecular Sciences (BNLMS)
Key Laboratory of Bioorganic Chemistry and
Molecular Engineering of Ministry of Education
College of Chemistry, Peking University, Beijing 100871 (P.R. China)
Fax : (+86)10-62751708
been successfully applied for the synthesis of heavier alka-
line earth (Ca, Sr, Ba) complexes. Intramolecular coordina-
tion of the pendant groups to the metal centers has been
confirmed by single-crystal X-ray structural analysis.[8b,d,e]
However, although some progress has been made by using
the above-mentioned ligands, diversity among the cyclopen-
tadienyl ligands and their pendant groups remains very lim-
ited. Since the properties of metallocenes are significantly
influenced by the substitution pattern on the cyclopenta-
E-mail: zfxi@pku.edu.cn
[b] Prof. Dr. Z. Xi
State Key Laboratory of Organometallic Chemistry
Shanghai Institute of Organic Chemistry
CAS, Shanghai 200032 (P.R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201301618.
Chem. Eur. J. 2013, 19, 12859 – 12866
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
12859

dienyl ligands,[9] we initiated a study to
apply our own ester-substituted cyclopen-
tadienes (Scheme 1) for the synthesis of
heavier alkaline earth (Ca, Sr, Ba) metal-
locenes.
Table 1. Formation of multiply-substituted cyclopentadienyl ester derivatives
reactions of 1,4-dilithio-1,3-butadienes (7), CO, and acid chlorides.
9
by one-pot
In this work, we first prepared various
ester-substituted cyclopentadiene deriva-
tives by the one-pot reaction of 1,4-di-
Entry
7
RCOCl
Product 9
Yield
[%][a]
ACHTUNGTRENNUNGlithio-1,3-butadienes, CO, and acid chlor-
ides. The ester-substituted cyclopenta-
diene derivatives were then treated with
Ae[NACHTUNGTRENNUNG(SiMe3)2]2 (Ae=Ca, Sr, Ba), afford-
1
tBuCOCl
79
70
51
53
ing a new type of heavier alkaline earth
(Ca, Sr, Ba) metallocene in good to ex-
cellent yields by direct deprotonation.
Single-crystal X-ray structural analysis
demonstrated that these heavier alkaline
earth metallocenes were intramolecularly
coordinated by the ester pendants. In
general, ester-substituted metallocenes
are difficult to synthesize,[10] because the
electrophilic ester groups may be sensi-
tive to nucleophiles. The calcium and
strontium metallocenes thus generated
were found to be air-stable, but the
barium metallocenes were air-sensitive.
Furthermore, the barium metallocenes
displayed high reactivity and could be ap-
plied highly efficiently for the prepara-
tion of the corresponding transition metal
metallocenes by metathesis reactions.
2
3
4
AdCOCl
tBuCOCl
AdCOCl
5
6
7
MeCOCl
tBuCOCl
AdCOCl
61
68
65
Results and Discussion
One-pot synthesis of ester-substituted
cyclopentadienes: In 2009, we reported
the isolation of oxy-cyclopentadienyl di-
ACHTUNGTRENNUNGanions 8 from the reaction between 1,4-
dilithio-1,3-butadienes
7
and
CO
(Table 1).[11] The dilithio reagents 7 could
be readily generated from the corre-
sponding 1,4-diiodobutadienes and tBuLi.
When the tetraethyl-substituted dianion
8a was treated with one equivalent of
tBuCOCl, an O-acylation reaction took
place, affording the tetraethyl ester cyclo-
pentadiene derivatives 9a and 9a’ as
8
57
double-bond positional isomers in 79%
combined yield.[11] Cyclopentadiene de-
rivatives of this type cannot be readily
prepared by conventional methods, and
[a] Yields of the isolated products (Ad=adamantyl).
we anticipated that they might show
unique properties as ligands with an ester pendant in the
context of metallocenes. In this work, we first investigated
the scope of the above synthetic method for the generation
of more diverse ester-substituted cyclopentadienes. Thus, as
indicated in Table 1, a variety of ester-substituted cyclopen-
tadiene derivatives 9 and their double-bond positional iso-
mers 9’ were synthesized in one-pot reactions from the
requisite 1,4-dilithio-1,3-butadienes, CO, and bulky acid
12860
www.chemeurj.org
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 12859 – 12866

A New Class of Alkaline Earth Metallocenes
FULL PAPER
chlorides such as tBuCOCl or AdCOCl. It should be men-
tioned that when less bulky acid chlorides such as PhCOCl
or BuCOCl were used, acylation took place at both the O
and the C3 sites to afford doubly-acylated cyclopenta-
dienes.[11] Because of a similar steric effect, in the case of
tert-butyl-substituted dilithio reagent 7c, relatively small
MeCOCl was needed to generate the cyclopentadienyl ester
9e. Moreover, the unsymmetrical 1,4-dilithio-1,3-butadienes
7d,e and bulky 2,4,6-trichlorobenzoyl chloride could also be
employed. This reaction provides an efficient method for
obtaining such ester-substituted cyclopentadiene derivatives.
(Scheme 3). X-ray single-crystal structural analyses of com-
plexes 10d·THF, 10e·THF, and 10 f·Et2O revealed nine-coor-
dinated metal centers, involving two ester-substituted side
chains, two cyclopentadienyl ligands, and one solvent mole-
cule (Figures 1–3).[13] The solvent molecules THF or Et2O
Synthesis and structural characterization of alkaline earth
metallocenes: As shown in Scheme 2, the ester-substituted
cyclopentadienes 9 (and their double-bond positional iso-
Scheme 3. The transformation of 10 into the corresponding solvent-coor-
dinated 10·L.
can be considered as “loose” ligands coordinated to the
heavier alkaline earth centers, dissociation of which from
the metal center can occur under vacuum (Scheme 3). To
the best of our knowledge, these are the first well-defined
ester-substituted alkaline earth metallocenes. They adopt
similar structures with approximate C2 symmetry. The
Cp(centroid)-Ae-Cp(centroid) angles range from 141.088 to 145.238,
indicating bent structures, in agreement with the reported
heavier alkaline earth metallocenes 2 and 4–6 shown in
Scheme 1. The respective dihedral angles between the two
Cp rings are 36.298 for 10d·THF, 35.778 for 10e·THF, and
À
40.208 for 10 f·Et2O. The Ae CpACTHNUTRGNEUGN(centroid) distances become
larger in the order Ca<Sr<Ba, which may be attributed to
the ionic radii of these heavier alkaline earth metals.[14]
À
For the calcium metallocene 10d·THF, the Ca O(C
tances (2.436 and 2.454 ꢁ) were found to be similar to the
dis-
=
O)
Scheme 2. Synthesis of metallocenes 10 and 11 from cyclopentadienyl
ester derivatives and Ae[NACHTUNGRTNEUNG(SiMe3)2]2 (Ae=Ca, Sr, Ba).
mers 9’) could be directly deprotonated by Ae[NACHTUNGTRNEG(UN SiMe3)2]2
(Ae=Ca, Sr, Ba) in THF at room temperature[8b] to afford
the corresponding alkaline earth metallocenes 10 and 11 in
excellent yields. Complexes 10 proved to be readily soluble
in hexane and aromatic solvents such as benzene, whereas
complexes 11 dissolved in more polar solvents such as Et2O.
Notably, in a similar manner to some cyclopentadienyl Ae
complexes synthesized by Sitzmann,[12] these ester-substitut-
ed cyclopentadienyl calcium and strontium complexes
(10a,b,d,e) were stable in dry air for about 12 h without de-
composition,[12] although they decomposed slowly in mois-
ture. In contrast, the barium complexes (10c,f, 11a,b) were
found to be air-sensitive.
Figure 1. ORTEP drawing of complex 10d·THF with thermal ellipsoids
at the 30% probability level. Hydrogen atoms are omitted for clarity. Se-
À
À
lected bond lengths [ꢁ] and angles [8]: Ca1 O1 2.436(4), Ca1 O3
Recrystallization of 10d,e from hexane/THF and of 10 f
from hexane/Et2O at room temperature afforded suitable
single crystals of 10d·THF, 10e·THF, and 10 f·Et2O
À
À
À
2.454(4), Ca1 O5 2.439(4), C14 O1 1.208(7), C38 O3 1.223(6),
À
Ca1 Cp(centroid) 2.470(7) and 2.494(7); O1-Ca1-O3 154.84, O1-Ca1-O5
75.75, O3-Ca1-O5 79.12, Cp(centroid)-Ca1-Cp(centroid) 142.99.
Chem. Eur. J. 2013, 19, 12859 – 12866
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
12861

Z. Xi et al.
À
For the strontium metallocene 10e·THF, the Sr O(THF)
distance (2.570 ꢁ) corresponds to the value determined for
a seven-coordinated [{1,2,4-(Me3C)3C5H2}2SrACTHNUTRGENUGN(THF)] complex
À
(2.587 ꢁ). The Sr Cp(centroid) distances in 10e·THF (2.612
and 2.619 ꢁ) were found to be similar to that in the complex
[{1,2,4-(Me3C)3C5H2}2SrACHTUNGTRNEUNG
(THF)] (2.61 ꢁ).[12c]
À
For the barium metallocene 10 f·Et2O, both the Ba O-
À
AHCTUNGTRENNUNG
ACTHNUTRGNEUNG
ordinated [(Cp3i)Ba(THF)2] (Cp3i =triisopropylcyclopenta-
À
dienyl) complex, in which the Ba O(THF) distance is 2.771 ꢁ
and the Ba Cp(centroid) distance is 2.79 ꢁ.[16]
À
Application of alkaline earth metallocenes for the synthesis
of ester-substituted ferrocene: The metathesis reaction be-
tween a heavier alkaline earth metallocene and a transition-
metal salt has been reported to be an effective means of
preparing the corresponding transition-metal metallocene.[17]
Thus, as shown in Scheme 4, in a first attempt the calcocene
Figure 2. ORTEP drawing of complex 10e·THF with thermal ellipsoids at
the 30% probability level. Hydrogen atoms are omitted for clarity. Se-
À
À
lected bond lengths [ꢁ] and angles [8]: Sr1 O3 2.567(2), Sr1 O1
À
À
À
2.597(2), Sr1 O5 2.570(3), C30 O3 1.222(4), C6 O2 1.222(4),
À
Sr1 Cp(centroid) 2.612(3) and 2.619(4); O1-Sr1-O3 174.29, O3-Sr1-O5 83.58,
O1-Sr1-O5 91.00, Cp(centroid)-Sr1-Cp(centroid) 145.23.
Figure 3. ORTEP drawing of complex 10 f·Et2O with thermal ellipsoids at
the 30% probability level. Hydrogen atoms are omitted for clarity. Se-
Scheme 4. Synthesis of ester-substituted ferrocene 12 by metathesis reac-
tion between 10c and FeCl2.
À
À
lected bond lengths [ꢁ] and angles [8]: Ba1 O4 2.749(4), Ba1 O1
À
À
À
2.742(4), Ba1 O5 2.797(5), C38 O4 1.210(7), C14 O1 1.212(7),
À
Ba1 Cp(centroid) 2.779(6) and 2.774(6); O4-Ba1-O1 177.10, O4-Ba1-O5
95.80, O1-Ba1-O5 81.31, Cp(centroid)-Ba1-Cp(centroid) 141.08.
10a was treated with FeCl2, but no reaction was observed
after heating the reaction mixture in THF at 808C for 24 h.
To our delight, however, when the barium metallocene 10c
was used, the expected metathesis reaction proceeded
smoothly, generating the ester-substituted ferrocene deriva-
tive 12 in 82% yield.[17b,c,e] The driving force for this reaction
is assumed to be the precipitation of BaCl2.
Recrystallization of 12 from hexane afforded single crys-
tals suitable for X-ray structural analysis (Figure 4). The fer-
rocene derivative 12 was found to be oriented about a C2
axis, and consequently showed perfect C2 symmetry with a
Cp(centroid)-Fe-Cp(centroid) angle of 1808. Unlike in the previous-
ly described ester-substituted alkaline earth metallocenes 10
and 11, in complex 12 the two ester-substituted side chains
are directed away from the metal center, resulting in an 18-
electron ferrocene complex.[18] Additionally, the 13C NMR
signal of the carbonyl group in 12 in C6D6 appears at a
À
À
Ca O(THF) distance (2.439 ꢁ). These Ca O distances are
slightly longer than those in the reported eight-coordinated
calcium metallocenes 4 (2.412 and 2.401 ꢁ) and 5 (2.400 and
2.417 ꢁ)[8b,d] and about 0.1 ꢁ longer than that in the six-co-
ordinated [{(Cp4i)Ca
A
(THF)}2] (Cp4i =tetraisopropyl-
ACHTUNGTRENNUNG
À
Ca Cp(centroid) distances in the reported calcium metallocenes
5 (2.382 and 2.379 ꢁ) and 6 (2.382 and 2.412 ꢁ),[8d,e] the cor-
responding distances in 10d·THF are also longer (2.470 and
2.494 ꢁ), which may be explained in terms of the steric and
electronic effects of the substituents attached to the Cp
rings. As a consequence, the complex 10d·THF has a larger
coordination sphere, and can easily be coordinated by an ad-
ditional polar solvent molecule such as THF or Et2O.
12862
www.chemeurj.org
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 12859 – 12866

A New Class of Alkaline Earth Metallocenes
FULL PAPER
83% yields, respectively. Recrystallization of 14 from
hexane/Et2O yielded a yellow crystalline compound suitable
for X-ray structure analysis (Figure 5). X-ray structure anal-
Figure 4. ORTEP drawing of ester-substituted ferrocene 12 with thermal
ellipsoids at the 30% probability level. Hydrogen atoms are omitted for
À
À
clarity. Selected bond lengths [ꢁ]: C1 C2 1.417(2), C1 C5 1.418(2),
À
À
À
À
C2 C3 1.433(2), C3 C4 1.437(2), C4 C5 1.435(2), C1 O1 1.406(2),
À
À
À
C6 O2 1.195(9), C6 O1 1.353(2), Fe1 Cp(centroid) 1.647(2).
Figure 5. ORTEP drawing of ester-substituted cyclopentadienyltricarbo-
nylrhenium complex 14 with thermal ellipsoids at the 30% probability
level. Hydrogen atoms are omitted for clarity. Selected bond lengths [ꢁ]:
À
À
À
À
C1 C2 1.426(7), C1 C5 1.425(7), C2 C3 1.432(8), C3 C4 1.439(7),
chemical shift of d=177.8 ppm, similar to those of cyclopen-
tadienyl ester derivatives 9a (176.53 ppm) and 9a’
(177.19 ppm). In contrast, the corresponding chemical shifts
of the alkaline earth metallocenes 10a (190.8 ppm), 10b
(190.2 ppm), and 10c (189.0 ppm) in C6D6 are significantly
shifted to lower field, consistent with the corresponding
X-ray structures, again demonstrating that the C=O bonds
in 10a–c are coordinated to the alkaline earth metal center
in solution.
À
À
À
À
C4 C5 1.441(7), C27 Re1 1.921(6), C28 Re1 1.922(6), C29 Re1
À
À
À
À
1.915(6), C27 O3 1.145(7), C28 O4 1.146(7), C29 O5 1.157(7), C1 O1
1.400(6), C10 O2 1.194(7), C10 O1 1.369(7), Re1 Cp(centroid) 1.964(6).
À
À
À
ysis of 14 showed it to be a half-sandwich cyclopentadienyl
tricarbonylrhenium complex with the expected three-legged
piano-stool configuration. As in ferrocene derivative 12, the
ester unit attached to the Cp ring is directed away from the
À
Re center. The Cp(centroid) Re distance (1.964 ꢁ) is similar to
that in a previously reported cyclopentadienyltricarbonylr-
Application of alkaline earth metallocenes for the synthesis
of ester-substituted cyclopentadienyl tricarbonylrhenium
complexes: The metathesis reaction was also successfully ap-
plied for the preparation of some corresponding Re com-
plexes. Thus, as shown in Scheme 5, when [Re(CO)5Cl] was
treated with the barium metallocenes 10 f or 11a, the corre-
sponding ester-substituted cyclopentadienyl half-sandwich
Re(CO)3 complexes 13 and 14 were obtained in 81% and
henium species.[19]
Conclusion
We have reported an efficient one-pot synthesis of cyclopen-
tadienyl ester derivatives. Through a direct deprotonation
process with Ae[NACTHNUTRGNEUNG(SiMe3)2]2 (Ae=Ca, Sr, Ba), examples of
a new type of heavier alkaline earth (Ca, Sr, Ba) metallo-
cenes have been efficiently synthesized and structurally
characterized. These metallocenes feature two intramolecu-
larly coordinated ester pendants and multiply-substituted cy-
clopentadienyl ligands. The corresponding transition-metal
metallocenes, such as ferrocene derivatives and half-sand-
wich cyclopentadienyl tricarbonylrhenium complexes, could
be efficiently generated by metathesis reactions. These
unique multiply-substituted cyclopentadienyl ester ligands
and their corresponding metallocenes are expected to have
further applications in organometallic chemistry and organic
synthesis.
Experimental Section
General methods: All reactions were carried out under a slightly positive
pressure of dry and oxygen-free nitrogen by using standard Schlenk-line
techniques or under a nitrogen atmosphere in a Mikrouna Super (1220/
Scheme 5. Synthesis of ester-substituted cyclopentadienyl tricarbonyl-
ACHTUNGTRENNUNGrhenium complexes 13 and 14 by metathesis reactions.
Chem. Eur. J. 2013, 19, 12859 – 12866
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
12863

Z. Xi et al.
750) glovebox. The nitrogen in the glovebox was constantly circulated
through a copper/molecular sieves catalyst unit. The oxygen and moisture
concentrations in the glovebox atmosphere were monitored by an O2/
H2O Combi-Analyzer to ensure that both were always below 1 ppm.
Unless otherwise noted, all starting materials were commercially availa-
ble and were used without further purification. Solvents were purified by
means of an MBraun SPS-800 solvent purification system and dried over
2H; CH2), 2.76–2.81 (m, 1H; CH2), 3.34 (dd, J=12.5, 5.9 Hz, 1H; CH),
7.14–7.18 (m, 1H; CH), 7.23–7.36 (m, 7H; CH), 7.43–7.45 ppm (m, 2H;
CH); 13C NMR (100 MHz, CDCl3, SiMe4): d=25.48, 26.85, 27.09, 29.13,
33.08, 38.65, 49.23, 126.09, 126.93, 127.17, 127.99, 128.28, 129.24, 130.62,
133.50 (2C), 133.59, 146.59, 146.60, 175.56 ppm; IR (neat): n˜ =1750 cmÀ1
(C=O); HRMS: m/z calcd for C26H29O2: 373.2162 [M+H]+; found:
373.2167.
freshly cut Na chips in the glovebox. Ca[N
ACHTUTGNERNNUG(SiMe3)2]2CAHTUNGTERN(NGUN THF)2, Sr[N-
Cyclopentadienyl ester 9d: White solid; yield of the isolated product:
120 mg (53%); 1H NMR (400 MHz, CDCl3, SiMe4): d=0.83–0.89 (m,
1H; CH2), 0.95–1.06 (m, 1H; CH2), 1.20–1.24 (m, 1H; CH2), 1.52–1.57
(m, 1H; CH2), 1.61–1.70 (m, 6H; CH2), 1.76–1.77 (m, 6H; CH2), 1.83–
1.88 (m, 1H; CH2), 1.95–1.96 (m, 3H; CH), 2.24–2.39 (m, 2H; CH2),
2.77–2.82 (m, 1H; CH2), 3.33 (dd, J=12.6, 5.8 Hz, 1H; CH), 7.15–7.18
(m, 1H; CH), 7.26–7.37 (m, 7H; CH), 7.43–7.45 ppm (m, 2H; CH);
13C NMR (100 MHz, CDCl3, SiMe4): d=25.52, 26.89, 27.86, 29.16, 33.14,
36.38, 38.67, 40.62, 49.25, 126.05, 126.91, 127.18, 127.99, 128.29, 129.26,
130.58, 133.51, 133.55, 133.62, 146.59, 146.64, 174.74 ppm; IR (neat): n˜ =
1756 cmÀ1 (C=O); HRMS: m/z calcd for C32H35O2: 451.2632 [M+H]+;
found: 451.2640.
A
R
CHTUNGTRENNUNG
ature methods.[5a,20] All 1,4-diiodo-1,3-butadienes were synthesized ac-
cording to a reported procedure.[21] 1,4-Dilithio-1,3-butadienes were syn-
thesized by lithium–halogen exchange reactions. Organometallic samples
for NMR spectroscopic measurements were prepared in the glovebox
employing J. Young valve NMR tubes (Wilmad 528-JY). 1H and
13C NMR spectra were recorded on a Bruker-400 spectrometer (FT,
400 MHz for 1H; 100 MHz for 13C) or a JEOL-AL300 spectrometer (FT,
1
300 MHz for H; 75 MHz for 13C) at room temperature, unless otherwise
noted. Infrared spectra (IR) were recorded on a Thermo Nicolet Avatar
330 FTIR spectrometer. High-resolution mass spectra (HRMS) were re-
corded on a Bruker Apex IV FTMS mass spectrometer using electro-
spray ionization (ESI). Micro elemental analyses were performed on a
Vario EL elemental analyzer.
Cyclopentadienyl ester 9e: Yellow liquid; yield of the isolated product:
1
88 mg (61%); H NMR (400 MHz, CDCl3, SiMe4): d=0.97 (s, 9H; CH3),
1.21 (s, 9H; CH3), 1.41–1.52 (m, 2H; CH2), 1.75–1.85 (m, 2H; CH2), 2.12
(s, 3H; CH3), 2.18–2.24 (m, 1H; CH2), 2.29–2.37 (m, 2H; CH2), 2.45–2.50
(m, 1H; CH2), 2.85 ppm (s, 1H; CH); 13C NMR (100 MHz, CDCl3,
SiMe4): d=21.53, 23.10, 23.60, 27.32, 28.42, 28.76, 30.53, 33.49, 33.89,
60.06, 136.30, 136.53, 137.34, 147.67, 170.84 ppm; IR (neat): n˜ =1752 cmÀ1
(C=O); HRMS: m/z calcd for C19H31O2: 291.2319 [M+H]+; found:
291.2325.
Synthesis of 1,4-diiodo-1,3-butadiene derivatives: Typical procedure for
the preparation of 1,2,3,4-tetraethyl-1,4-diiodo-1,3-butadiene: A solution
of nBuLi (3.0 mL, 1.6m, 4.8 mmol) was added dropwise by means of a sy-
ringe to a solution of [Cp2ZrCl2] (700 mg, 2.4 mmol) in THF (10 mL) at
À788C. After the addition was completed, the reaction mixture was stir-
red at À788C for 1 h. 3-Hexyne (328 mg, 4.0 mmol) was then added, and
the reaction mixture was warmed to 258C and stirred at this temperature
for 3 h. The mixture was then cooled to 08C, whereupon CuCl (198 mg,
2.0 mmol) and I2 (1.016 g, 4.0 mmol) were added. The solution was
warmed to 258C and kept at this temperature for 1 h. The reaction was
then quenched with 3n HCl and the resulting mixture was extracted
three times with diethyl ether. The combined extracts were washed se-
quentially with NaHCO3(aq), Na2S2O3(aq), and brine, and then dried over
anhydrous MgSO4. Evaporation of the solvent in vacuo left a yellow oil,
which was subjected to column chromatography on SiO2 eluting with
hexane.
Cyclopentadienyl ester 9 f: Yellow liquid; yield of the isolated product:
138 mg (68%); 1H NMR (400 MHz, CDCl3, SiMe4): d=0.14 (s, 9H;
CH3), 1.20 (s, 9H; CH3), 2.05 (s, 3H; CH3), 3.79 (s, 1H; CH), 6.95–7.01
(m, 4H; CH), 7.11–7.14 ppm (m, 6H; CH); 13C NMR (75 MHz, CDCl3,
SiMe4): d=À1.95, 15.31, 27.30, 39.02, 51.86, 126.04, 126.27, 127.49,
127.62, 129.40, 129.85, 133.18, 133.95, 136.30, 136.32, 137.70, 148.99,
177.59 ppm; IR (neat): n˜ =1744 cmÀ1 (C=O); HRMS: m/z calcd for
C26H32O2Si: 405.2244 [M+H]+; found: 405.2244.
Cyclopentadienyl ester 9g: White solid; yield of the isolated product:
157 mg (65%); 1H NMR (300 MHz, CDCl3, SiMe4): d=À0.14 (s, 9H;
CH3), 1.55 (brs, 6H; CH2), 1.77 (brs, 6H; CH2), 1.85 (brs, 3H; CH), 1.90
(s, 3H; CH3), 3.66 (s, 1H; CH), 6.81–6.86 (m, 4H; CH), 6.97–7.07 ppm
(m, 6H; CH); 13C NMR (75 MHz, CDCl3, SiMe4): d=À1.94, 15.33, 27.85,
36.35, 38.84, 40.95, 51.92, 126.00, 126.21, 127.43, 127.60, 129.42, 129.84,
133.13, 133.88, 136.27, 136.27, 137.64, 148.93, 176.70 ppm; IR (neat): n˜ =
1727 cmÀ1 (C=O); HRMS: m/z calcd for C32H39O2Si: 483.2714; [M+H]+
found: 483.2724.
Synthesis of cyclopentadienyl ester derivatives: tBuLi (2.0 mmol;
4 equiv) was added to a solution of the requisite 1,4-diiodo-1,3-butadiene
(0.5 mmol) in Et2O (10 mL) at À788C. After stirring at À788C for 1 h,
CO was bubbled into the reaction mixture for 0.5 h. The resulting mix-
ture was stirred for a further 0.5 h under a CO atmosphere. The requisite
acid chloride (0.5 mmol) was then added and the reaction mixture was al-
lowed to warm to room temperature. After 1 h, the reaction was
quenched by adding water. The aqueous layer of the quenched mixture
was extracted with several portions of Et2O and the combined organic
layers were washed with brine. The solvent was evaporated and the resi-
due was subjected to column chromatography on SiO2 eluting with
hexane/Et2O (10:1).
Cyclopentadienyl ester 9h: Yellow liquid; yield of the isolated product:
135 mg (57%); 1H NMR (300 MHz, CDCl3, SiMe4): d=0.00 (s, 9H;
CH3), 0.89 (t, J=7.2 Hz, 3H; CH3), 1.25–1.48 (m, 4H; CH2), 1.55–1.66
(m, 2H; CH2), 1.74–1.85 (m, 2H; CH2), 2.21–2.42 (m, 6H; CH2), 3.21 (s,
1H; CH), 7.39 ppm (s, 2H; CH); 13C NMR (75 MHz, CDCl3, SiMe4): d=
À2.22, 13.96, 22.96, 22.98, 23.14, 23.26, 24.11, 26.16, 31.49, 47.74, 128.20,
130.82, 132.01, 132.68, 133.91, 135.10, 136.24, 146.13, 163.10 ppm; IR
(neat): n˜ =1756 cmÀ1 (C=O); HRMS: m/z calcd for C23H30Cl3O2Si:
471.1075 [M+H]+; found: 471.1089.
Cyclopentadienyl esters 9b and 9b’: Colorless liquid; yield of the isolated
product: 125 mg (70%); ratio (9b/9b’)=2:1 (determined by 1H and
13C NMR spectroscopy). 1H NMR (300 MHz, CDCl3, SiMe4): d=0.47–
0.62 (m, 3H; CH3), 0.80–1.08 (m, 9H; CH3), 1.21–1.31 (m, 2H; CH2),
1.51–1.61 (m, 2H; CH2), 1.73–1.76 (m, 6H; CH2), 1.89–1.98 (m, 3H;
CH), 2.01–2.06 (m, 6H; CH2), 2.16–2.39 (m, 4H; CH2), 3.01 (t, J=7.2 Hz,
0.66H; CH), 3.06 ppm (t, J=7.2 Hz, 0.30H; CH). 9b: 13C NMR
(75 MHz, CDCl3, SiMe4): d=7.24, 13.86, 14.56, 15.30, 17.79, 18.18, 19.48,
20.07, 27.98, 36.50, 38.93, 40.92, 48.20, 130.76, 136.49, 141.80, 145.47,
175.72 ppm; 9b’: 13C NMR (75 MHz, CDCl3, SiMe4): d=8.05, 13.92,
14.60, 15.35, 15.48, 17.42, 18.70, 19.27, 27.98, 36.50, 38.93, 40.99, 48.58,
131.11, 137.98, 138.81, 149.26, 176.40 ppm; IR (neat): n˜ =1746 cmÀ1
Synthesis of ester-substituted alkaline earth metallocenes 10 and 11:
Ae[NACTHNURTGENNUG(SiMe3)2]2ACHTUNGTRNEN(NGU thf)x (Ae=Ca, Sr, Ba) (0.25 mmol) was added to a solu-
tion of the appropriate cyclopentadienyl ester derivative 9 (0.5 mmol) in
THF (10 mL) at room temperature. The reaction mixture was stirred
overnight. An insoluble precipitate was then filtered off and the filtrate
was concentrated to dryness in vacuo. The resulting powder was identi-
fied as the ester-substituted alkaline earth metallocene 10 or 11. For
10a–c, the resulting powders were sufficiently pure for NMR analysis.
For 10d–f and 11, the obtained powders had to be rinsed with hexane.
ACHTUNGTRENNUNG
(C=O); HRMS: m/z calcd for C24H37O2: 357.2788 [M+H]+; found:
357.2791.
Ester-substituted alkaline earth metallocene 10a: Yellow solid; yield of
the isolated product: 138 mg (93%); 1H NMR (300 MHz, C6D6): d=1.14
(s, 18H; CH3), 1.20 (t, J=7.2 Hz, 12H; CH3), 1.26 (t, J=7.2 Hz, 12H;
CH3), 2.15–2.22 (m, 4H; CH2), 2.46–2.60 ppm (m, 12H; CH2); 13C NMR
(75 MHz, C6D6): d=17.17, 17.93, 18.74, 19.17, 26.97, 38.76, 107.89, 113.78,
Cyclopentadienyl ester 9c: White solid; yield of the isolated product:
95 mg (51%); H NMR (400 MHz, CDCl3, SiMe4): d=0.99–1.06 (m, 1H;
CH2), 1.09 (s, 9H; CH3), 1.19–1.26 (m, 1H; CH2), 1.49–1.59 (m, 1H;
CH2), 1.79–1.82 (m, 1H; CH2), 1.92–1.95 (m, 1H; CH2), 2.23–2.39 (m,
1
12864
www.chemeurj.org
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 12859 – 12866

A New Class of Alkaline Earth Metallocenes
FULL PAPER
132.57, 190.78 ppm; elemental analysis calcd (%) for C36H58O4Ca: C
72.68, H 9.83; found: C 73.26, H 10.34.
112.08, 177.80 ppm; elemental analysis calcd (%) for C36H58O4Fe: C
70.80, H 9.57; found: C 70.83, H 9.58. Recrystallization of 12 from
hexane at room temperature afforded single crystals suitable for X-ray
analysis.
Ester-substituted alkaline earth metallocene 10b: Yellow solid; yield of
the isolated product: 159 mg (99%); 1H NMR (300 MHz, C6D6): d=
1.16–1.31 (m, 42H; CH3), 2.20–2.27 (m, 4H; CH2), 2.43–2.50 (m, 4H;
CH2), 2.58 ppm (q, J=7.2 Hz, 8H; CH2); 13C NMR (75 MHz, C6D6): d=
17.09, 17.86, 18.95, 19.14, 27.07, 38.88, 108.00, 113.73, 133.36, 190.10 ppm.
Synthesis of ester-substituted cyclopentadienyl tricarbonylrhenium com-
plexes 13 and 14 by a metathesis reaction: The barium metallocene 10 f/
11a (0.25 mmol) was added to
a solution of [Re(CO)5Cl] (181 mg,
0.5 mmol) in THF (5 mL) at room temperature. The reaction mixture
was heated at 808C for 12 h. The BaCl2 produced was then filtered off
and the filtrate was concentrated to dryness in vacuo. For 13, the result-
ing liquid was sufficiently pure for NMR analysis. For 14, the resulting
powder had to be rinsed with hexane to afford the pure ester-substituted
cyclopentadienyl tricarbonylrhenium complex.
Ester-substituted alkaline earth metallocene 10c: Yellow solid; yield of
the isolated product: 156 mg (90%); 1H NMR (300 MHz, C6D6): d=
1.17–1.24 (m, 30H; CH3), 1.30 (t, J=7.2 Hz, 12H; CH3), 2.16–2.29 (m,
4H; CH2), 2.37–2.62 ppm (m, 12H; CH2); 13C NMR (75 MHz, C6D6): d=
16.84, 17.94, 18.64, 19.06, 27.20, 38.95, 109.09, 114.77, 135.40, 188.97 ppm.
Ester-substituted alkaline earth metallocene 10d: White solid; yield of
the isolated product: 133 mg (71%); 1H NMR (300 MHz, C6D6): d=
1.29–1.34 (m, 24H; CH3), 1.44–1.53 (m, 12H; CH2), 1.75–1.82 (m, 6H;
CH), 1.97–2.09 (m, 12H; CH2), 2.26–2.33 (m, 4H; CH2), 2.58–2.66 ppm
(m, 12H; CH2); 13C NMR (75 MHz, C6D6): d=17.34, 18.01, 18.82, 19.26,
27.98, 36.30, 39.05, 40.99, 107.95, 113.79, 132.49, 189.72 ppm; elemental
analysis calcd (%) for C48H70O4Ca: C 76.75, H 9.39; found: C 76.85, H
9.47. Recrystallization of 10d from THF/hexane at room temperature af-
forded single crystals of 10d·THF suitable for X-ray analysis.
Ester-substituted cyclopentadienyl tricarbonylrhenium 13: Yellow liquid;
yield of the isolated product: 254 mg (81%); 1H NMR (400 MHz, C6D6):
d=0.87 (t, J=7.6 Hz, 6H; CH3), 1.05 (t, J=7.6 Hz, 6H; CH3), 1.50 (brs,
6H; CH2), 1.79 (brs, 3H; CH), 1.95–1.96 (m, 6H; CH2), 2.00–2.26 ppm
(m, 8H; CH2); 13C NMR (100 MHz, C6D6): d=17.52, 17.55, 17.86, 18.80,
28.08, 36.39, 39.07, 41.30, 97.31, 101.13, 125.66, 175.75, 197.00 ppm.
Ester-substituted cyclopentadienyl tricarbonylrhenium 14: Yellow solid;
yield of the isolated product: 266 mg (83%); 1H NMR (400 MHz,
C4D8O): d=0.88 (s, 9H; CH3), 1.74–1.78 (m, 4H; CH2), 2.65–2.69 (m,
2H; CH2), 2.87–2.91 (m, 2H; CH2), 7.29–7.36 (m, 6H; CH), 7.42–
7.44 ppm (m, 4H; CH); 13C NMR (100 MHz, C4D8O): d=23.30, 23.48,
26.92, 39.31, 96.14, 100.89, 127.79, 129.01, 129.15, 130.61, 132.50, 176.53,
196.68 ppm; elemental analysis calcd (%) for C29H27O5Re: C 54.28, H
4.24; found: C 54.21, H 4.33. Recrystallization of 14 from hexane at
room temperature afforded single crystals suitable for X-ray analysis.
Ester-substituted alkaline earth metallocene 10e: White solid; yield of
the isolated product: 162 mg (81%); 1H NMR (300 MHz, C6D6): d=1.27
(t, J=7.2 Hz, 12H; CH3), 1.32 (t, J=7.2 Hz, 12H; CH3), 1.46–1.54 (m,
12H; CH2), 1.77–1.83 (m, 6H; CH), 1.98–2.05 (m, 12H; CH2), 2.30–2.37
(m, 4H; CH2), 2.52–2.68 ppm (m, 12H; CH2); 13C NMR (75 MHz, C6D6):
d=17.13, 17.88, 18.96, 19.19, 28.06, 36.37, 39.14, 41.13, 108.19, 113.88,
133.49, 189.33 ppm; elemental analysis calcd (%) for C48H70O4Sr: C
72.18, H 8.83; found: C 72.02, H 8.98. Recrystallization of 10e from
THF/hexane at room temperature afforded single crystals of 10e·THF
suitable for X-ray analysis.
X-ray crystallographic studies: Single crystals of 10d·THF, 10e·THF,
10 f·Et2O, 12, and 14 suitable for X-ray analysis were grown as described
above. The crystals of 10 f·Et2O were manipulated under a nitrogen at-
mosphere and were sealed in a thin-walled glass capillary. Data collec-
tions for 10e·THF, 10 f·Et2O, 12, and 14 were performed at À1008C on a
Rigaku CCD SATURN 724 diffractometer, using graphite-monochromat-
ed MoKa radiation (l=0.71073 ꢁ). The data collection for 10d·THF was
performed at À1508C on a Rigaku RAXIS RAPID IP diffractometer,
also using graphite-monochromated MoKa radiation (l=0.71073 ꢁ). De-
termination of crystal type and unit-cell parameters was carried out by
means of the Crystal Clear (Rigaku Inc., 2007) program package for
10e·THF, 10 f·Et2O, 12, and 14 or the Rapid-AUTO (Rigaku 2000) pro-
gram package for 10d·THF. The raw frame data were processed using
Crystal Clear (Rigaku Inc., 2007) for 10e·THF, 10 f·Et2O, 12, and 14 or
Crystal Structure (Rigaku/MSC 2000) for 10d·THF to yield the reflection
data file. The structures of 10d·THF, 10e·THF, 10 f·Et2O, 12, and 14 were
solved using the SHELXTL program. The structures were refined aniso-
tropically against F2 for all non-hydrogen atoms by the full-matrix least-
squares method. Hydrogen atoms were placed in calculated positions and
were included in the structure calculation without further refinement of
the parameters. CCDC-920755 (10d·THF), 920756 (10e·THF), 920757
(10 f·Et2O), 920758 (12), and 920759 (14) contain the supplementary crys-
tallographic data (excluding structure factors) 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
Ester-substituted alkaline earth metallocene 10 f: White solid; yield of
the isolated product: 153 mg (72%); 1H NMR (300 MHz, C6D6): d=1.24
(t, J=7.2 Hz, 12H; CH3), 1.32 (t, J=7.2 Hz, 12H; CH3), 1.48–1.58 (m,
12H; CH2), 1.80–1.86 (m, 6H; CH), 1.99–2.08 (m, 12H; CH2), 2.30–2.38
(m, 4H; CH2), 2.48–2.55 (m, 4H; CH2), 2.63 ppm (q, J=7.5 Hz, 8H;
CH2); 13C NMR (75 MHz, C6D6): d=16.75, 17.88, 18.89, 19.09, 28.14,
36.45, 39.23, 41.20, 109.38, 114.97, 135.62, 188.47 ppm; elemental analysis
calcd (%) for C48H70O4Ba: C 67.95, H 8.32; found: C 67.69, H 8.42. Re-
crystallization of 10 f from Et2O/hexane at room temperature afforded
single crystals of 10 f·THF suitable for X-ray analysis.
Ester-substituted alkaline earth metallocene 11a: Yellow solid; yield of
the isolated product: 202 mg (92%); 1H NMR (400 MHz, C4D8O): d=
1.34 (s, 18H; CH3), 1.50–1.59 (m, 8H; CH2), 2.36–2.40 (m, 4H; CH2),
2.63–2.66 (m, 4H; CH2), 6.91–6.94 (m, 4H; CH), 7.11–7.15 ppm (m, 16H;
CH); 13C NMR (100 MHz, C4D8O): d=25.52, 25.89, 27.63, 39.66, 110.91,
114.65, 123.86, 128.06, 128.69, 133.98, 137.56, 188.60 ppm; elemental anal-
ysis calcd (%) for C52H54O4Ba: C 70.95, H 6.18; found: C 71.13, H 6.32.
Ester-substituted alkaline earth metallocene 11b: Yellow solid; yield of
the isolated product: 249 mg (96%); 1H NMR (400 MHz, C4D8O): d=
1.52–1.61 (m, 8H; CH2), 1.80 (brs, 12H; CH2), 1.95–2.00 (m, 6H; CH),
2.06 (brs, 12H; CH2), 2.37–2.42 (m, 4H; CH2), 2.59–2.64 (m, 4H; CH2),
6.91–6.95 (m, 4H; CH), 7.14–7.15 ppm (m, 16H; CH); 13C NMR
(100 MHz, C4D8O): d=25.51, 25.94, 29.07, 37.22, 39.89, 41.37, 110.88,
114.65, 123.81, 128.01, 128.68, 133.96, 137.55, 187.53 ppm; elemental anal-
ysis calcd (%) for C64H66O4Ba: C 74.16, H 6.42; found: C 74.38, H 6.46.
Synthesis of ester-substituted ferrocene 12 by a metathesis reaction: The
barium metallocene 10c (0.25 mmol) was added to a solution of FeCl2
(32 mg, 0.25 mmol) in THF (5 mL) at room temperature. The reaction
mixture was then heated at 808C for 12 h. The BaCl2 produced was then
filtered off and the filtrate was concentrated to dryness in vacuo. The re-
sulting powder was rinsed with hexane to afford pure ester-substituted
ferrocene 12.
Acknowledgements
This work was supported by the Natural Science Foundation of China
and the Major State Basic Research Development Program
(2011CB808705).
Ester-substituted ferrocene 12: Yellow solid; yield of the isolated prod-
uct: 125 mg (82%); 1H NMR (400 MHz, C6D6): d=1.12–1.20 (m, 24H;
CH3), 1.30 (s, 18H; CH3), 2.14–2.28 ppm (m, 16H; CH2); 13C NMR
(100 MHz, C6D6): d=15.61, 17.16, 18.00, 18.90, 27.47, 39.21, 80.07, 81.73,
[1] a) T. P. Hanusa, Polyhedron 1990, 9, 1345–1362; b) T. P. Hanusa,
Chem. Rev. 1993, 93, 1023–1036; c) D. J. Burkey, T. P. Hanusa, Com-
ments Inorg. Chem. 1995, 17, 41–77; d) M. Westerhausen, Trends
Organomet. Chem. 1997, 2, 89–105; e) M. Westerhausen, Coord.
Chem. Eur. J. 2013, 19, 12859 – 12866
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
12865

Z. Xi et al.
Chem. Rev. 1998, 176, 157–210; f) T. P. Hanusa, Coord. Chem. Rev.
2000, 210, 329–367; g) T. P. Hanusa, Organometallics 2002, 21,
2559–2571; h) M. Westerhausen, Z. Anorg. Allg. Chem. 2009, 635,
13–32.
Angew. Chem. 2011, 123, 11136–11140; Angew. Chem. Int. Ed. 2011,
50, 10944–10948.
[11] a) L. Liu, W.-X. Zhang, C. Wang, C. Y. Wang, Z. Xi, Angew. Chem.
2009, 121, 8255–8258; Angew. Chem. Int. Ed. 2009, 48, 8111–8114;
b) H. Li, L. Liu, Z. Wang, F. Zhao, S. Zhang, W.-X. Zhang, Z. Xi,
Chem. Eur. J. 2011, 17, 7399–7403.
[2] a) M. Westerhausen, M. Gꢂrtner, R. Fischer, J. Langer, L. Yu, M.
Reiher, Chem. Eur. J. 2007, 13, 6292–6306; b) M. Westerhausen, M.
Gꢂrtner, R. Fischer, J. Langer, Angew. Chem. 2007, 119, 1994–2001;
Angew. Chem. Int. Ed. 2007, 46, 1950–1956; c) M. Westerhausen,
Coord. Chem. Rev. 2008, 252, 1516–1531.
[3] a) A. G. M. Barrett, M. R. Crimmin, M. S. Hill, P. A. Procopiou,
Proc. R. Soc. A 2010, 466, 927–963; b) S. Harder, Chem. Rev. 2010,
110, 3852–3876.
[12] a) R. A. Williams, K. F. Tesh, T. P. Hanusa, J. Am. Chem. Soc. 1991,
113, 4843–4851; b) H. Sitzmann, T. Dezember, M. Ruck, Angew.
Chem. 1998, 110, 3293–3296; Angew. Chem. Int. Ed. 1998, 37, 3113–
3116; c) F. Weber, H. Sitzmann, M. Schultz, C. D. Sofield, R. A. An-
dersen, Organometallics 2002, 21, 3139–3146; d) H. Sitzmann, F.
Weber, M. D. Walter, G. Wolmershꢂuser, Organometallics 2003, 22,
1931–1936; e) M. D. Walter, G. Wolmershꢂuser, H. Sitzmann, J.
Am. Chem. Soc. 2005, 127, 17494–17503.
[13] a) S. Harder, M. Lutz, A. W. G. Straub, Organometallics 1997, 16,
107–113; b) N. Leyser, K. Schmidt, H.-H. Brintzinger, Organometal-
lics 1998, 17, 2155–2161; c) K. D. Demadis, J. D. Sallis, R. G. Raptis,
P. Baran, J. Am. Chem. Soc. 2001, 123, 10129–10130; d) T. Hatan-
pꢂꢂ, M. Vehkamꢂki, I. Mutikainen, J. Kansikas, M. Ritala, M. Le-
skelꢂ, Dalton Trans. 2004, 1181–1188; e) K. Fichtel, U. Behrens, Z.
Anorg. Allg. Chem. 2005, 631, 2508–2516; f) K. Fichtel, S. Hçxter,
U. Behrens, Z. Anorg. Allg. Chem. 2006, 632, 2003–2009; g) R.
Fischer, J. Langer, S. Krieck, H. Gçrls, M. Westerhausen, Organo-
metallics 2011, 30, 1359–1365; h) D. P. Daniels, G. B. Deacon, D.
Harakat, F. Jaroschik, P. C. Junk, Dalton Trans. 2012, 41, 267–277.
[14] R. D. Shannon, Acta Crystallogr. Sect. A 1976, 32, 751–767.
[15] D. J. Burkey, E. K. Alexander, T. P. Hanusa, Organometallics 1994,
13, 2773–2786.
[4] a) D. J. Burkey, T. P. Hanusa, Organometallics 1996, 15, 4971–4976;
b) P.-J. Sinnema, P. J. Shapiro, B. Hçhn, T. E. Bitterwolf, B. Twamley,
Organometallics 2001, 20, 2883–2888; c) A. G. Avent, M. R. Crim-
min, M. S. Hill, P. B. Hitchcock, J. Organomet. Chem. 2006, 691,
1242–1250; d) T. Hatanpꢂꢂ, M. Ritala, M. Leskelꢂ, J. Organomet.
Chem. 2007, 692, 5256–5262; e) E. D. Brady, S. C. Chmely, K. C.
Jayaratne, T. P. Hanusa, V. G. Young, Organometallics 2008, 27,
1612–1616; f) G. B. Deacon, C. M. Forsyth, F. Jaroschik, P. C. Junk,
D. L. Kay, T. Maschmeyer, A. F. Masters, J. Wang, L. D. Field, Orga-
nometallics 2008, 27, 4772–4778; g) P. Jochmann, S. Maslek, T. P.
Spaniol, J. Okuda, Organometallics 2011, 30, 1991–1997; h) X. Li, S.
Huo, Y. Zeng, Z. Sun, S. Zheng, L. Meng, Organometallics 2013, 32,
1060–1066; i) Y. J. Park, S. A. Cook, N. S. Sickerman, Y. Sano, J. W.
Ziller, A. S. Borovik, Chem. Sci. 2013, 4, 717–726.
[5] a) D. C. Bradley, M. B. Hursthouse, A. A. Ibrahim, K. M. Abdul Ma-
lik, M. Motevalli, R. Mçseler, H. Powell, J. D. Runnacles, A. C. Sul-
livan, Polyhedron 1990, 9, 2959–2964; b) J. S. Alexander, K. Ruh-
landt-Senge, Angew. Chem. 2001, 113, 2732–2734; Angew. Chem.
Int. Ed. 2001, 40, 2658–2660; c) J. S. Alexander, K. Ruhlandt-Senge,
H. Hope, Organometallics 2003, 22, 4933–4937.
[6] R. Zerger, G. Stucky, J. Organomet. Chem. 1974, 80, 7–17.
[7] a) A. L. McKnight, R. M. Waymouth, Chem. Rev. 1998, 98, 2587–
2598; b) T. Cuenca, P. Royo, Coord. Chem. Rev. 1999, 193–195,
447–498; c) U. Siemeling, Chem. Rev. 2000, 100, 1495–1526; d) H.
Butenschçn, Chem. Rev. 2000, 100, 1527–1564; e) S. Arndt, J.
Okuda, Chem. Rev. 2002, 102, 1953–1976; f) Z. Xie, Acc. Chem.
Res. 2003, 36, 1–9; g) G. Erker, Coord. Chem. Rev. 2006, 250, 1056–
1070; h) H. Braunschweig, F. M. Breitling, Coord. Chem. Rev. 2006,
250, 2691–2720.
[8] a) P. Jutzi, J. Dahlhaus, M. O. Kristen, J. Organomet. Chem. 1993,
450, C1–C3; b) M. L. Hays, T. P. Hanusa, T. A. Nile, J. Organomet.
Chem. 1996, 514, 73–79; c) W. S. Rees, U. W. Lay, K. A. Dippel, J.
Organomet. Chem. 1994, 483, 27–31; d) G. A. Molander, H. Schu-
mann, E. C. E. Rosenthal, J. Demtschuk, Organometallics 1996, 15,
3817–3824; e) H. Schumann, S. Schutte, H.-J. Kroth, D. Lentz,
Angew. Chem. 2004, 116, 6335–6338; Angew. Chem. Int. Ed. 2004,
43, 6208–6211.
[16] D. J. Burkey, R. A. Williams, T. P. Hanusa, Organometallics 1993, 12,
1331–1337.
[17] a) P. S. Tanner, D. J. Burkey, T. P. Hanusa, Polyhedron 1995, 14,
331–333; b) M. Westerhausen, M. Hartmann, W. Schwarz, J. Orga-
nomet. Chem. 1995, 501, 359–367; c) K. M. Kane, P. J. Shapiro, A.
Vij, R. Cubbon, A. L. Rheingold, Organometallics 1997, 16, 4567–
4571; d) M. Westerhausen, M. Hartmann, N. Makropoulos, B. Wie-
neke, M. Wieneke, W. Schwarz, D. Stalke, Z. Naturforsch. B 1998,
53, 117–125; e) P. J. Shapiro, K. M. Kane, A. Vij, D. Stelck, G. J.
Matare, R. L. Hubbard, B. Caron, Organometallics 1999, 18, 3468–
3473; f) C. J. Matare, D. M. Foo, K. M. Kane, R. Zehnder, M. Wage-
ner, P. J. Shapiro, T. Concolino, A. L. Rheingold, Organometallics
2000, 19, 1534–1539; g) I. L. Fedushkin, T. V. Petrovskaya, M. N.
Bochkarev, S. Dechert, H. Schumann, Angew. Chem. 2001, 113,
2540–2543; Angew. Chem. Int. Ed. 2001, 40, 2474–2477.
[18] a) R. E. Benson, R. V. Lindsey, J. Am. Chem. Soc. 1957, 79, 5471–
5474; b) M. Vogel, M. Rausch, H. Rosenberg, J. Org. Chem. 1957,
22, 1016–1018; c) A. N. Nesmeyanov, V. A. Sazonova, V. N. Drozd,
Tetrahedron Lett. 1959, 1, 13–15; d) M. Sato, Y. P. Lam, I. Motoya-
ma, K. Hata, Bull. Chem. Soc. Jpn. 1971, 44, 808–812; e) S. Aka-
bori, T. Kumagai, T. Shirahige, S. Sato, K. Kawazoe, C. Tamura, M.
Sato, Organometallics 1987, 6, 2105–2109; f) M. Herberhold, H.-D.
Brendel, A. Hofmann, B. Hofmann, W. Milius, J. Organomet. Chem.
1998, 556, 173–187; g) R. C. J. Atkinson, V. C. Gibson, N. J. Long,
A. J. P. White, D. J. Williams, Organometallics 2004, 23, 2744–2751;
h) J. Niemeyer, G. Kehr, R. Frçhlich, G. Erker, Chem. Eur. J. 2008,
14, 9499–9502.
[19] a) F. Minutolo, J. A. Katzenellenbogen, J. Am. Chem. Soc. 1998,
120, 4514–4515; b) F. Minutolo, J. A. Katzenellenbogen, Organome-
tallics 1999, 18, 2519–2530; c) F. Minutolo, J. A. Katzenellenbogen,
Angew. Chem. 1999, 111, 1730–1732; Angew. Chem. Int. Ed. 1999,
38, 1617–1620; d) T. Cautivo, H. Klahn, F. Godoy, C. Lꢄpez, M.
Font-Bardꢅa, T. Calvet, E. Gutierrez-Puebla, A. Monge, Organome-
tallics 2011, 30, 5578–5589.
[20] T. M. Cameron, C. Xu, A. G. Dipasquale, A. L. Rheingold, Organo-
metallics 2008, 27, 1596–1604.
[21] C. Xi, S. Huo, T. H. Afifi, R. Hara, T. Takahashi, Tetrahedron Lett.
1997, 38, 4099–4102.
[9] a) R. L. Halterman, Chem. Rev. 1992, 92, 965–994; b) D. L. Lichten-
berger, Y. Elkadi, N. E. Gruhn, Organometallics 1997, 16, 5209–
5217; c) J. A. Pool, E. Lobkovsky, P. J. Chirik, J. Am. Chem. Soc.
ˇ
ˇ
˘
ˇ
ˇ
2003, 125, 2241–2251; d) M. Horꢃcek, P. Stepnicka, J. Kubista, K.
Fejfarova, R. Gyepes, K. Mach, Organometallics 2003, 22, 861–869;
e) U. Rosenthal, V. V. Burlakov, P. Arndt, W. Baumann, A. Span-
nenberg, V. B. Shur, Eur. J. Inorg. Chem. 2004, 4739–4749; f) J. A.
Pool, E. Lobkovsky, P. J. Chirik, Nature 2004, 427, 527–530; g) U.
Rosenthal, V. V. Burlakov, M. A. Bach, T. Beweries, Chem. Soc.
Rev. 2007, 36, 719–728; h) T. Wondimagegn, D. Wang, A. Razavi, T.
Ziegler, Organometallics 2009, 28, 1383–1390; i) W. Geng, W.-X.
Zhang, W. Hao, Z. Xi, J. Am. Chem. Soc. 2012, 134, 20230–20233;
j) L. Becker, V. V. Burlakov, P. Arndt, A. Spannenberg, W. Bau-
mann, H. Jiao, U. Rosenthal, Chem. Eur. J. 2013, 19, 4230–4237;
k) W. Geng, C. Wang, J. Guang, W. Hao, W.-X. Zhang, Z. Xi, Chem.
Eur. J. 2013, 19, 8657–8664.
[10] a) U. Siemeling, I. Scheppelmann, J. Heinze, B. Neumann, A.
Stammler, H.-G. Stammler, Chem. Eur. J. 2004, 10, 5661–5670;
b) D. Mavrynsky, R. Sillanpꢂꢂ, R. Leino, Organometallics 2009, 28,
598–605; c) H. Kim, Y. K. Choi, J. Lee, E. Lee, J. Park, M.-J. Kim,
Received: April 27, 2013
Revised: May 29, 2013
Published online: August 9, 2013
12866
www.chemeurj.org
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 12859 – 12866