Synthesis, Characterization and Reactivity of Formal 20 Electron Zirconocene-Pentafulvene Complexes

Article abstract of DOI:10.1021/acs.organomet.7b00213

The reaction of low-valent zirconocene reagents formed either from the Negishi reagent Cp₂Zr(n-butyl)₂ or from the reduction of Cp₂ZrCl₂ with Mg with various pentafulvenes yielded the first zirconocene-pentafulv

Full text of DOI:10.1021/acs.organomet.7b00213

Article
pubs.acs.org/Organometallics
Synthesis, Characterization and Reactivity of Formal 20 Electron
Zirconocene-Pentafulvene Complexes
Florian Jaroschik,* Manfred Penkhues, Bernard Bahlmann, Emmanuel Nicolas, Malte Fischer,‡
,
†
‡
‡
§,⊥
†
†
†
‡
Fabien Massicot, Agathe Martinez, Dominique Harakat, Marc Schmidtmann,
Radhakrishnan Kokkuvayil Vasu, Jean-Luc Vasse, and Rudiger Beckhaus*
̈
∥
†
,‡
†
‡
§
∥
Institut de Chimie Molec
Institut fur Chemie, Carl von Ossietzky Universitat
Laboratoire Heteroelements et Coordination, Ecole Polytechnique and CNRS, 91128 Palaiseau, France
National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Industrial Estate, P.O. Trivandrum 19, Kerala, India
S Supporting Information
́
ulaire de Reims, CNRS UMR 7312, Universite
́
de Reims, 51687 Reims Cedex 2, France
̈
̈
Oldenburg, D-26111 Oldenburg, Federal Republic of Germany
́
́
́
́
*
ABSTRACT: The reaction of low-valent zirconocene reagents formed
either from the Negishi reagent Cp Zr(n-butyl) or from the reduction of
2
2
Cp ZrCl2 with Mg with various pentafulvenes yielded the first
2
zirconocene−pentafulvene complexes, Cp ZrFv (Fv = 6,6-di(aryl),
2
6
,6′-adamantylidene, and 6-tert-butylfulvene), which are formal 20-
electron complexes. In addition to NMR spectroscopic analysis and DFT
calculations, three complexes were characterized by X-ray crystallog-
raphy, showing a η :η dianionic binding mode of the fulvene to the
5
1
metal. The obtained complexes react with carbonyl compounds
(
aldehydes and ketones) to unexpectedly afford double-insertion
products, as shown by NMR spectroscopy and X-ray studies. In the
case of aldehydes these diolate complexes were obtained as single
diastereoisomers. The reaction of Cp ZrFv with internal alkynes did not
2
result in the formation of insertion products but release of the
coordinated fulvene and reductive dimerization of the alkynes to the corresponding zirconacyclopentadienes.
4
,5
INTRODUCTION
fashion, as in complexes C and D, respectively. The most
widely used synthetic pathway to early-transition-metal and f-
element pentafulvene complexes is the heat- or light-induced
deprotonation of alkyl-substituted cyclopentadienyl ligands
■
Transition-metal pentafulvene complexes exhibit a wide range of
structural and reactivity patterns. With late transition metals
bonding to one or two double bonds of the fulvene skeleton has
been observed: e.g., complexes A and B (Figure 1). However,
1
6
containing protons in the α position. Another method consists
of the displacement of neutral ligands from the metal center by
the fulvene fragment. In group 4 chemistry, an important
breakthrough was achieved when Ti(IV), Zr(IV), and Ti(III)
precursors were reduced by sodium or magnesium in the
presence of sterically encumbered pentafulvenes (Fv), yielding a
range of new mixed Cp/Fv or bis-Fv complexes. These
complexes gave rise to numerous transformations, including
insertion of electrophiles, small-molecule activation, hydro-
amination and hydroaminoalkylation reactions, including C−H
2
,3
6
7
most metals bind in a η manner, either with a neutral fulvene
2
2
2
5
1
fragment bound in a η :η :η fashion or in a dianion-like η :η
8
bond activation reactions.
8c,9
With very few exceptions,
the reactive part of early-
transition-metal−pentafulvene complexes is the bond between
the metal and the exocyclic fulvene carbon (C6). Many insertion
reactions have been described using carbonyl groups, nitriles,
isonitriles, alkynes, or sulfur-containing compounds as electro-
6
,8,10
philes to gain access to new metallocene complexes.
With
Figure 1. Selected examples of metal−pentafulvene complexes showing
different binding modes.
Received: March 21, 2017
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.7b00213
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5
,8
boranes cationic metal complexes could be obtained through
complexes.
These reactions were carried out at room
11
carbon−boron bond formation.
temperature in THF for 15 h and afforded the corresponding
To date, all metal−pentafulvene complexes contain either one
or no cyclopentadienyl-type ligand. To the best of our
knowledge, no metallocene−pentafulvene complex has been
Cp ZrFv complexes 2b−e in good to very good isolated yields
(Scheme 1b). This approach was successfully employed on a
multigram scale.
2
6
described. In the case of group 4 metals, η coordination of a
Characterization of Zirconocene−Pentafulvene Com-
plexes. The obtained yellow to orange solids 2a−e are stable
under an inert atmosphere for weeks at room temperature but
decompose quickly upon heating above 100 °C. They are well
soluble in ethereal and aromatic solvents, show poor solubility in
alkanes, and decompose in chlorinated solvents. The complexes
were fully characterized by multinuclear NMR spectroscopy,
single-crystal X-ray diffraction studies, and electron-impact mass
spectrometry. Correct elemental analysis could only be obtained
in the case of 2e; in all other cases the analyses showed
systematically low values for carbon.
fulvene moiety to the 14-electron metallocene part would lead to
formal 20-electron complexes, a class of compounds which has
attracted considerable interest of both experimental and
12
theoretical chemists. For example, Cp MX complexes (X =
3
H, Me, Cl, Cp) show different binding modes in the triad Ti, Zr,
5
1
Hf: i.e., Ti and Hf mainly bind the Cp ligands in a 2η :1η fashion,
5
whereas Zr generally adopts a 3η mode. The analysis of the
electronic configuration in such 20-electron complexes revealed
the presence of one ligand-centered molecular orbital which does
not interact with the metal, hence reducing the formal 20
12c,e
electrons down to 18 electrons.
1
NMR Spectroscopy. The H NMR spectra of the 6,6-
We herein report the synthesis and characterization of the first
zirconocene−pentafulvene complexes and their unexpected
reaction behavior toward carbonyl compounds and alkynes.
disubstituted complexes 2b−e are very similar (some selected
data are summarized in Table 1). They show one signal for the
Cp protons between 5.03 and 5.23 ppm and two signals in the
ranges 3.85−4.50 and 5.44−5.52 ppm for the fulvene ring
protons. In comparison to the free fulvenes, this corresponds to a
significant high-field shift, especially for the protons in the 1,4-
positions. These signals indicate a symmetrical arrangement of
RESULTS AND DISCUSSION
■
Synthesis of Zirconocene−Pentafulvene Complexes.
Negishi Reagent. Low-valent zirconocene(II) equivalents are
known to bind well to alkenes, alkynes, and dienes. It was
therefore anticipated that the unsaturated fulvene system may
readily coordinate onto the metallocene(II) species. The Negishi
reagent was chosen for this purpose, as the Zr-bound alkene
moiety formed during the warming of Cp Zr(n-butyl) to room
temperature is readily displaced by dienes or alkynes. Indeed,
warming this complex from −60 °C to room temperature in the
presence of differently substituted pentafulvenes 1a−c led to the
formation of the first zirconocene−pentafulvene complexes
Cp ZrFv (2a−c), which were isolated in good to moderate yields
after workup (Scheme 1a). It should be noted that with fulvenes
6
1
3
the complex, which is in good agreement with a dianionic η
coordination of the fulvene to the metal. For the monosub-
stituted complex 2a two signals for the Cp ligand and four signals
for the fulvene ring protons are observed. Interestingly, the
exocyclic proton in 2a is shifted upfield to 3.14 ppm with respect
to the free fulvene (6.18 ppm): however, at considerably lower
field than the corresponding proton in the Cp*(6-tert-
butylfulvene)TiCl complex (1.68 ppm). The C NMR spectra
of 2a−e indicate a high-field shift for all carbons of the fulvene
skeleton with respect to the free fulvenes. Especially, the signals
for C6 are shifted up to 60 ppm, confirming important electron
donation from the metal to the carbon center. The signals for the
fulvene ring are in the vicinity of the Cp signals, in agreement
with the formation of a Cp-type ligand upon coordination. The
2
2
14
8a
13
2
1
a,c the reaction was complete after 6 h, whereas the bulky
adamantylidene fulvene 1b required 15 h reaction time.
Bimetallic Approach. Alternatively, we also investigated the
reduction of Cp ZrCl with Mg in the presence of pentafulvenes
1
13
H and C spectra of 2c correspond well to the previously
reported spectra for complex D.
2
2
5
1
b−e, in analogy to previous reports on Ti and Zr fulvene
X-ray Diffraction Studies. Complexes 2c−e were further
characterized by single-crystal X-ray diffraction studies. Selected
bond lengths and angles of these complexes and of free fulvene
Scheme 1. Synthesis of Zirconocene−Pentafulvene
Complexes Cp Zr(Fv) (2a−e)
2
1
c for comparison reasons are summarized in Table 2, and the
5
1
structures are shown in Figure 2. The structures confirm the η :η
coordination of the fulvene moiety to zirconium. As in other
metal−pentafulvene complexes, this coordination leads to a
bending of the exocyclic C5−C6 bond out of the fulvene plane
toward the metal by 28.4−29.2°, slightly more than in complex
D. The zirconium is in a distorted-trigonal-pyramidal coordina-
tion environment, as indicated by the sum of angles around Zr,
close to 360°. The metal lies just above the plane defined by the
three centroids of the Cp and fulvene ligands (0.20 Å for 2c, 0.18
Å for 2d,e) as in other Cp ZrX complexes, e.g. 0.20 Å in
3
12d
Cp ZrH.
In the fulvene moiety, the coordination to the
3
metallocene fragment leads to the loss of the alternating single-
bond-double bond pattern of the free fulvene as shown by the
narrow range of the C−C bond lengths (1.390−1.442 Å). The
most significant change occurs in the exocyclic bond which is, for
example, elongated by 0.08 Å in 2c compared to 1c. A slight
influence of the para-substituents on the phenyl groups of the
fulvene can be observed on the Zr−C6 and the C5−C6 bond
B
DOI: 10.1021/acs.organomet.7b00213
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1
13
Table 1. Selected H and C NMR Data of Fulvenes 1a−c, Complexes 2a−c, and Complex D in C D at Room Temperature
6
6
a
1
a
1b
1c
2a
2b
2c
D
H1
6.18
6.39
6.57
6.69
6.18
6.62
6.67
6.67
6.62
6.58
6.66
6.66
6.58
3.58
5.52
5.45
4.25
3.14
3.85
5.52
5.52
3.85
4.50
5.49
5.49
4.50
4.17
4.39
5.72
6.43
H2
H3
H4
H6
H(Cp)
C1
5.21, 5.39
111.4
5.23
5.13
120.2
120.5
124.8
108.2
109.8
92.2
C2
134.5
129.0
129.0
143.4
152.8
131.6
131.6
120.5
137.1
167.3
132.4
132.4
124.8
144.3
152.1
105.1
106.2
106.2
108.2
117.7
106.5
106.7
108.8
108.8
109.8
117.6
103.8
109.1
99.1
102.6
114.7
129.2
103.4
C3
111.8
C4
111.9
C5
114.9
C6
94.6
C(Cp)
106.4, 106.5
a
See ref 5.
a
Table 2. Selected X-ray Data of Fulvene 1c, Complexes 2c−e, and Complex D
b
c
1
c
2c
2d
2e
D
C1−C2
C2−C3
C3−C4
C4−C5
C5−C1
C5−C6
Zr−C1
Zr−C2
Zr−C3
Zr−C4
Zr−C5
Zr−C6
Ct(Fv)−Zr
Ct(Cp)−Zr
Ct(Cp)−Zr−Ct(Cp)
Ct(Fv)−Zr−Ct
1.340(3)
1.445(3)
1.344(3)
1.458(3)
1.465(2)
1.359(2)
1.390(9)
1.419(9)
1.402(8)
1.434(7)
1.432(8)
1.440(7)
2.474(5)
2.597(6)
2.623(5)
2.464(5)
2.332(5)
2.602(6)
2.191
1.409(3)
1.397(4)
1.398(4)
1.442(3)
1.439(3)
1.455(3)
2.485(2)
2.636(4)
2.617(2)
2.473(2)
2.330(2)
2.574(2)
2.203
1.402(3)
1.400(3)
1.397(3)
1.428(3)
1.436(3)
1.462(2)
2.4907(18)
2.631(2)
2.637(2)
2.4840(19)
2.3321(17)
2.5623(17)
2.213
1.412(2), 1.414(2)
1.401(3), 1.403(2)
1.415(3), 1.407(2)
1.443(2), 1.443(2)
1.446(2), 1.444(2)
1.443(2), 1.450(2)
2.4109(16), 2.4316(16)
2.5278(17), 2.5273(17)
2.5322(17), 2.5637(17)
2.4058(17), 2.3867(16)
2.3266(16), 2.3266(16)
2.7084(17), 2.7007(16)
2.121, 2.129
2.304, 2.325
117.8
2.336, 2.319
117.6
2.315, 2.332
117.7
133.9
121.4, 118.5
357.7
121.9, 118.4
357.7
120.8, 119.6
358.1
∑
θ
(angles around Zr)
28.4
29.2
29.2
26.9
Δ
0.310
0.335
0.340
0.236, 0.262
a
b
c
Bond lengths are given in Å and angles in deg. See ref 8b. See ref 5.
lengths, which are shorter/longer in the case of the hydrogen or
fluorine substituents in 2d,e compared to the methyl group in 2c.
EI Mass Spectrometry. For all complexes 2a-e, the molecular
complexes were clearly identified, namely CpZrFv, Cp Zr and
2
the free fulvenes.
DFT Calculations. In order to obtain further insights into the
bonding situation of the new complexes, DFT calculations were
carried out. Complexes 2a−c were optimized in the gas phase,
ion peak corresponding to Cp ZrFv was observed by EI-MS,
2
albeit in low intensity. Furthermore, relevant fragments of the
C
DOI: 10.1021/acs.organomet.7b00213
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Figure 3. Evolution of NBO charges upon coordination of fulvene 1a to
Cp Zr.
2
performed with the ADF software indicates a clear shift toward a
single bond for the C −C bond: in the free fulvenes the bond
5
6
orders are 1.56 for the 6-tert-butylfulvene, 1.54 for the 6,6-
adamantylidene, and 1.47 for the 6,6-bis-p-tolylfulvene, which
shift to 1.09, 1.16, and 1.15 for 2a−c, respectively, upon
coordination. This analysis further shows an increased
interaction in the Zr−C bond (HOMO; see Figure 4) and a
6
similar bond order for Zr−C(Cp) and Zr−C(fulvene ring).
Figure 2. Molecular structures of complexes 2c−e, with 50% probability
ellipsoids. Hydrogen atoms and solvent molecules are omitted.
with the B3PW91 functional, Def2-QZVP basis set for Zr and 6-
31G(d) for all other atoms (see the Supporting Information for
details), and the results are shown in Table 3. A good agreement
between the crystal structure of 2c and the optimized calculated
structure was obtained. Next, the evolution of NBO charges
upon coordination of Zr to the pentafulvene was examined. An
important decrease in the charge on the exocyclic carbon is
observed, ranging from 0.26 to 0.39 e, which indicates a strong
reorganization of the electron density (Figure 3). A comparison
of the NICS(0) values between free and coordinated fulvenes
shows a strong increase in aromaticity, displaying values of
Figure 4. HOMO of complex 2a.
All of this information (NBO charges, aromaticity, bond
distances, bond orders) points toward the formation of a formal
Cp ZrX type complex. However, the one-bond link between the
3
Cp moiety and the X ligand in the fulvene prevents a true Cp ZrX
3
complex from forming. The Zr−C bond is thus not completely
6
formed, and the C −C is not a true single bond but still contains
1
6
−
15.5, −15.6, and −15.1 ppm for 2a−c, respectively, close to
a slight double-bond character. The highest negative charge was
15
that of Cp ligands. Finally, a Mayer bond order analysis
found on the exocyclic fulvene carbon in complexes 2a−c, in
a
Table 3. Selected Structural Parameters, NBO Charges, NICS(0) Values, and Mayer Bond Orders for Cp ZrFv complexes
2
2
a
2b
2c
C −C bond (Å)
1.48 (1.35)
−0.42 (−0.10)
−15.5 (−0.9)
1.09 (1.56)
0.22
1.44 (1.36)
−0.18 (0.11)
−15.6 (−1.7)
1.16 (1.54)
0.22
1.45 (1.37)
−0.21 (0.06)
−15.1 (−0.7)
1.15 (1.47)
0.24
5
6
NBO charge C (e)
6
NICS(0) C −C ring
1
5
Mayer bond order C −C
av Mayer bond order for Zr−C(Cp)
5
6
av Mayer bond order for Zr−C(fulvene ring)
0.27
0.27
0.26
a
Values for free fulvenes are given in parentheses.
D
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1
13
agreement with other early-transition-metal pentafulvene
complexes. It was therefore interesting to study the influence
of an “excess” of electrons on the reactivity of these complexes.
Reactivity Studies. Carbonyl Compounds. It has been well
established that the coordination of pentafulvenes to group 4
metals inverts the polarity of the exocyclic carbon atom. This
makes insertion of electrophilic reagents into the metal−carbon
bond possible. We started our investigations with the addition of
Table 4. Selected H and C NMR Data of Complexes 3a−e
in C D at Room Temperature
6
6
1
equiv of p-bromobenzaldehyde to a C D solution of 2c. This
6 6
led to the transformation of half the amount of 2c to a new
product, while half of the starting material remained, as shown by
1
H NMR. Further addition of 1 equiv of p-bromobenzaldehyde
led to the complete conversion of 2c to complex 3b (Scheme 2).
The same results were observed in the case of benzaldehyde and
p-anisaldehyde, resulting in the formation of complexes 3a,c,
respectively.
3a
5.94
3b
5.96
3c
6.03
3d
5.70
3e
5.34
H1
H2
H3
H4
3.52
6.27
6.81
5.50
5.37
3.42
6.17
6.83
5.40
5.22
3.55
6.35
6.84
5.52
5.40
2.84
6.31
6.77
2.92
6.31
7.09
Scheme 2. Reaction of Cp ZrFv Complex 2c with Carbonyl
2
Compounds
H21
H28
H(Cp)
C2
5.97, 6.06 5.95, 6.09 6.03, 6.11 6.00, 6.20 6.05, 6.26
62.0
63.0
93.0
61.6
62.7
92.1
82.6
62.3
62.9
92.4
83.1
62.7
64.8
87.3
80.9
57.8
64.3
92.2
86.5
C6
C21
C24/26/28 83.4
shown by NMR analysis and X-ray studies. The generation of two
adjacent quaternary carbon centers (C6 and C21) increases the
steric crowding of the complexes. This has some influence on the
1
H NMR shifts of the cyclopentadiene ring protons, especially
H2, and leads to a spreading apart of the signals of the Cp rings
(
Table 4).
X-ray Diffraction Studies. Complex 3b was formed as a single
diastereoisomer and the solid-state structure confirmed the
above description based on NMR spectroscopy (Scheme 2 and
Table 4). Some major differences were observed in the solid state
structures of 3b in comparison to 3d,e (Figure 5 and Table 5).
First, in the case of 3d,e the nine-membered ring shows
considerable strain, as indicated by the long C6−C21 bond
lengths (1.634(4) and 1.625(2) Å), which are in contrast only
slightly elongated in the case of 3b (1.595(5) Å). Second, other
interesting features are the large Zr−O1−C21 and Zr−O2−
C24/C26 angles in 3d,e ranging from 168.42(19) to 171.69(9)°,
which are only 151.4(2) and 155.7(3)° in 3b. A consequence of
these angles is that the C24/C26−O2−Zr−O1−C21 system in
3d,e is quasi-planar: e.g. the tilt angles C21−O1−Zr−O2 and
O1−Zr−O2−C26 have values of only 1.35 and 3.06°,
respectively, in 3e. In contrast, in 3b an up-and-down
arrangement is observed; here the corresponding tilt angles are
56.5 and 73.0°, respectively. In the literature, two nine-
membered zirconocene−diolate complexes have been described.
The sterically strained cumulene complex E has features between
those of complexes 3b and 3d,e: e.g. Zr−O−C1 and Zr−O−C2
One- and two-dimensional NMR analysis of the newly formed
complexes 3a−c revealed their identity, and additional stereo-
chemical information was obtained by NOE experiments (Table
4
). The structure of 3b was further corroborated by X-ray
1
diffraction studies (see below). The H NMR spectra of
complexes 3a−c show one set of signals, in agreement with a
highly diastereoselective reaction. Two peaks are observed for
the Cp protons, which are shifted downfield with respect to those
for 2c. The signal for H2 is between 3.42 and 3.55 ppm, in the
range of cyclopentadienes, whereas the other protons of the
former fulvene ring are found in the alkene region (5.94−6.84
ppm). The C NMR spectra reveal a drastic shift for the C2 and
C6 carbons, going, for example, from 108.8 and 117.6 ppm in 2c
to 62.0 and 63.0 ppm in 3a, in good agreement with the loss of
the aromatic character of the fulvene moiety.
16
angles of 165.88(10) and 151.12(10)°, respectively. On the
other hand, the strain-free phosphonium complex F ressembles
complex 2b, with Zr−O−C1 and Zr−O−C2 angles of 142.3(2)
13
17
and 141.9(2)°, respectively (Figure 6).
Mechanistic Considerations. The diolate complexes 3a−e
constitute the first examples of endo- and exocyclic reactivity of
metal−fulvene complexes. There is only one other report of a
double incorporation of an aldehyde into a metal−fulvene
complex, Cp*Fv*Ti; however, in that case both insertions took
We next studied the reaction behavior of 2c toward ketones.
The reaction with acetone or 3-pentanone was successful,
yielding again the double-insertion products 3d,e, respectively, as
E
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a
Table 5. Selected X-ray Data of Complexes 3b,d,e
3
b
3d
3e
C1−C2
C2−C3
C3−C4
C4−C5
C5−C1
C5−C6
C6−C21
C2−C24/26/28
Zr−O1
Zr−O2
O1−C7
O2−C24/26/28
Ct−Zr
Ct−Zr−Ct
O1−Zr−O2
Zr−O1−C21
Zr−O2−C24/26/28
C21−C6−C1
1.498(6)
1.497(6)
1.335(6)
1.487(5)
1.346(6)
1.517(5)
1.595(5)
1.573(6)
1.979(3)
1.971(3)
1.408(4)
1.403(5)
2.269, 2.271
127.0
1.490(4)
1.493(5)
1.323(5)
1.483(4)
1.344(4)
1.522(4)
1.634(4)
1.555(4)
1.959(2)
1.9374(19)
1.408(4)
1.401(3)
2.261, 2.287
124.1
1.5072(19)
1.496(2)
1.331(2)
1.4849(19)
1.338(2)
1.5358(19)
1.625(2)
1.566(2)
1.9582(10)
1.9332(10)
1.4268(17)
1.4047(18)
2.272, 2.302
123.0
103.70(11)
101.77(8)
168.42(19)
169.4(2)
106.2(2)
101.74(4)
170.17(9)
171.69(9)
106.43(11)
155.7(3)
151.4(2)
1
03.4(3)
a
Bond lengths are given in Å and angles in deg.
16,17
Figure 6. Other nine-membered zirconocene−diolate complexes.
Scheme 3. Mechanistic Proposal for the Double Insertion of
Carbonyl Compounds into Zirconocene−Fulvene Complexes
Figure 5. Molecular structures of complexes 3b,d,e with 50% probability
ellipsoids. Hydrogen atoms and solvent molecules are omitted.
9
place at the endocyclic positions. A proposed mechanistic
pathway for the formation of our double-insertion products is
shown in Scheme 3 (stereochemical indications have been
neglected for clarity). As the 20-electron complex does not have
any available coordination site for the carbonyl group, an electron4
shift has to occur in 2, leading presumably to a dienic η
13b
coordination mode of zirconium to the fulvene moiety. The
first insertion of the carbonyl group then leads to a zirconium
allyl species, which further reacts with a second equivalent of
F
DOI: 10.1021/acs.organomet.7b00213
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
carbonyl compound to yield the observed complexes 3. Under
the conditions described above, the monoinsertion product
could not be observed and the reaction goes straight to the bis-
insertion product.
mechanism of the double insertion and the scope of reactivity of
this new class of metal−fulvene complexes is currently underway.
EXPERIMENTAL SECTION
■
Reactivity toward Alkynes. In 2008, Mach reported the
insertion of internal alkynes into the Ti−C6 bond of a Cp*FvTi
General Considerations. All reactions were conducted under an
atmosphere of argon with rigorous exclusion of oxygen and moisture
using standard glovebox and Schlenk techniques. Solvents were freshly
distilled over sodium/benzophenone ketyl or collected from a
PURSOLV MD-3 (Innovative Technologies Inc.) solvent purification
unit. C D was stored over activated 4 Å molecular sieves. Zirconocene
1
0a
complex. In analogy, we have investigated the reaction of
complex 2c with 1 equiv of diphenylacetylene in C D . After 1 h,
6
6
the solution had turned from pale yellow to pale orange and the
1
H NMR spectrum indicated the presence of a new singlet peak
6
6
dichloride was purchased from Strem Chemicals. Aldehydes and n-
butyllithium (2.5 M solution in hexanes) were purchased from Aldrich
and used as received. Fulvenes were prepared according to literature
at 6.0 ppm as well as the appearance of signals corresponding to
the free fulvene in addition to remaining starting complex.
Addition of another 1 equiv of diphenylacetylene led to full
conversion of 2c and only the peak at 6.0 ppm remained as a
signal for the Cp ligands, which can be attributed to the
2
0
1
13
procedures. H and C NMR spectra were recorded in C D on a 500
6
6
MHz Bruker Avance III spectrometer equipped with a BBFO+ probe.
Chemical shifts are reported in delta (δ) units, expressed in parts per
million (ppm) and referenced to residual protons of the solvent.
Elemental analyses were carried out on a EuroEA 3000 Elemental
Analyzer. High-resolution ESI-MS spectra were recorded on a hybrid
tandem quadrupole/time-of-flight (Q-TOF) instrument, equipped with
a pneumatically assisted electrospray (Z-spray) ion source (Micromass,
Manchester, U.K.) operated in positive mode. Low-resolution EI-MS
spectra were obtained by direct introduction on a GCT Premier mass
spectrometer with orthogonal acceleration time-of-flight detector using
an electron impact source (Micromass, Manchester, U.K.) or on a
Finnigan-MAT 95 spectrometer using the LIFDI method.
1
4b
zirconacyclopentadiene 4a,
dimerization of the alkyne at the low-valent zirconium center.
arising from the reductive
18
Quenching the reaction mixture with HCl and analysis of the
obtained solution indicated the formation of 1,2,3,4-tetraphenyl-
1,3-butadiene (Scheme 4). The same reaction outcome was
observed when 2 equiv of 3-hexyne was reacted with 2c to form
19
zirconacyclopentadiene 4b.
Scheme 4. Reductive Dimerization of Alkynes with Complex
2
c
Single crystals were coated in Paratone-N oil and mounted on a loop.
Data were collected at 150.0(1) K on a Nonius Kappa CCD or a Stoe
IPDS diffractometer using a Mo Kα (λ= 0.71070 Å) X-ray source and a
graphite monochromator. All data were measured using ψ and ω scans.
The crystal structures were solved using SIR 97 and refined using Shelx
2
1,22
2
014.
General Procedure (GP-1) for the Synthesis of Cp ZrFv
2
Complexes 2 Using the Negishi Reagent. In a Schlenk tube
under argon, a solution of zirconocene dichloride (292 mg, 1.0 mmol) in
THF (8 mL) was reacted at −78 °C with n-butyllithium (2.5 M in
hexanes, 0.8 mL, 2.0 mmol) for 30 min. A solution of fulvene (1 mmol)
in THF (2 mL) was added to the reaction mixture at −60 °C, and the
solution was slowly warmed to room temperature over 2 h. The reaction
was further stirred at this temperature for the given time to result in a
dark orange-red solution. THF was evaporated under vacuum, and
toluene (10 mL) was added to the resulting yellow-orange solid. The
white precipitate of LiCl was removed by centrifugation. Then toluene
was evaporated under vacuum and the solid washed with hexanes (10
mL). Further drying of the solid under vacuum yielded complexes 2.
Despite the supposedly strong coordination of the fulvene
moiety to the zirconocene fragment, which we have described as
dianionic according to NMR and X-ray studies, the fulvene keeps
some triene character and can therefore be displaced from the
metal center by more strongly π-complexating ligands. The
synthetic potential of complexes 2 as new isolable Zr(II)
equivalents needs to be investigated further.
General Procedure (GP-2) for the Synthesis of Cp ZrFv
2
Complexes Using the Bimetallic Approach. In a Schlenk tube
under argon was prepared a mixture of zirconocene dichloride (1 equiv)
and Mg (1 equiv). A solution of fulvene (1 equiv) in THF (100 mL) was
added at room temperature, and the reaction mixture was stirred for 12
h. THF was evaporated under vacuum, and toluene (70 mL) was added
onto the resulting yellow-orange solid. After filtration, toluene was
evaporated under vacuum and the solid washed with small amounts of
hexanes. Further drying of the solid under vacuum yielded complexes 2.
CONCLUSION
■
In this work we have described the synthesis of the first
metallocene−pentafulvene type complexes using either the
Negishi reagent or the bimetallic system Cp ZrCl /Mg with a
2
2
Cp Zr(6-tert-butylfulvene) (2a). According to GP-1, 6-tert-
2
variety of pentafulvenes. These formal 20-electron complexes
were characterized in the solid state by X-ray diffraction studies
and in solution by NMR spectroscopy, showing in both cases a
butylfulvene (134 mg, 1.0 mmol) was reacted for 6 h to give complex
1
2
a as a yellow solid in 73% yield (260 mg, 0.7 mmol). H NMR (500
MHz, C D ): δ 5.52 (s, 1H, H2), 5.46 (s, 1H, H3), 5.39 (s, 5H, Cp), 5.21
6
6
5
1
η :η binding mode of the fulvene to the zirconium metal. DFT
studies confirmed this description as well as the inversion of
polarity at the exocyclic fulvene carbon upon complexation. The
reactivity of these new complexes was explored toward carbonyl
compounds and alkynes. In the former case, a new double-
insertion reaction was observed, leading to zirconocene−diolate
complexes with excellent diastereoselectivity in the case of
aldehydes. With alkynes, fulvene displacement occurred with
concomitant reductive dimerization to yield the corresponding
zirconacyclopentadienes. Further work to elucidate the reaction
(s, 5H, Cp), 4.25 (s, 1H, H4), 3.58 (s, 1H, H1), 3.17 (s, 1H, H6), 1.42 (s,
9H, tBu). 13C NMR (125 MHz, C
): δ 114.9 (C), 111.9 (CH), 111.8
CH), 111.4(CH), 106.5(CH), 106.4(CH), 105.1(CH), 94.6(CH),
D
6
6
(
+
3
8
1
5.8(C), 34.1(CH ). LR-MS (EI, m/z, relative intensity): 354 ([M ],
3
+
+
+
), 289 ([M − Cp], 7), 220 ([M − Fv], 12), 134 ([M − Cp Zr], 25),
19 ([Fv − CH ], 100). No correct elemental analysis of the bulk
2
+
3
product was obtained, despite several attempts.
Cp Zr(6,6-adamantylidenefulvene) (2b). According to GP-1,
2
6
,6-adamantylidenefulvene (198 mg, 1.0 mmol) was reacted for 15 h to
1
give complex 2b as a yellow solid in 72% yield (290 mg, 0.7 mmol). H
NMR (600 MHz, C D ): δ 5.52 (t, J = 2.6 Hz, 2H, H2 + H3), 5.23 (s,
6
6
G
DOI: 10.1021/acs.organomet.7b00213
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1
0H, Cp), 3.85 (t, J = 2.6 Hz, 2H, H1 + H4), 2.38 2.32 (m, 2H,
126.9 (CH), 125.6 (CH), 112.0 (CH), 111.6 (CH), 93.0 (CH), 83.4
CH (Ad)), 2.32 2.26 (m, 3H, CH + CH(Ad)), 2.21 2.14 (m, 3H, CH
(CH), 63.0 (C), 62.0 (CH), 21.0 (CH ), 20.9 (CH ). LR-MS (EI, m/z,
2
2
2
3
3
13
+
+
+
CH(Ad)), 2.08 2.03 (m, 2H, CH (Ad)), 1.82 (m, 2H, 2CH(Ad)). C
relative intensity (%)): 690 ([M ], 7), 584 ([M − C H CHO], 4), 478
2
6
5
+
+
NMR (151 MHz, C D ): δ 117.7 (C), 108.2 (CH), 106.7 (CH), 106.5
([M − 2{C H CHO}], 19), 413 ([M − 2{C H CHO} − Cp], 7), 326
6
6
6
5
6
5
+
+
+
(
2
5
C), 106.2 (CH), 44.3 (CH ), 39.0 (CH ), 38.8 (CH ), 36.9 (CH),
([M − {C H CHO} − Fv], 100), 258 ([Fv ], 39), 220 ([Cp Zr ], 98),
2
2
2
6
5
2
+
+
9.6(CH), 29.1 (CH). LR-MS (EI, m/z, relative intensity): 418 ([M ],
91 ([C H -CH ], 91).
6 4 3
+
+
+
), 353 ([M − Cp], 3), 220 ([M − Fv], 15), 198 ([M − Cp Zr], 100).
Cp Zr[OCH(p-Br-Ph)C(p-tolyl) C H CH(p-Br-Ph)O] (3b; NMR
2
2
2
5
3
No correct elemental analysis of the bulk product was obtained, despite
several attempts.
Experiment). To a C D solution of complex 2c (20 mg, 0.04
6 6
mmol) was added p-bromobenzaldehyde (15 mg, 0.08 mmol) and after
1
Cp Zr(6,6-di-p-tolylfulvene) (2c). According to GP-1, 6,6-di-p-
stirring for 30 min H NMR confirmed full conversion to complex 3a.
2
1
tolylfulvene (258 mg, 1.0 mmol) was reacted for 4 h to give complex 2c
H NMR (500 MHz, C D ): δ 7.81 (d, J = 8.3 Hz, 2H, m-CH, Ar), 7.46
6 6
1
as an orange-yellow powder in 50% yield (240 mg, 0.5 mmol). H NMR
(d, J = 8.4 Hz, 2H, m-CH, Ar), 7.28 (d, J = 8.5 Hz, 2H, m-CH, p-tol), 7.20
(d, J = 8.3 Hz, 2H, m-CH, p-tol), 7.17 (d, J = 8.2 Hz, 2H, o-CH, Ar), 7.06
(d, J = 8.5, 3.0 Hz, 2H, o-CH, Ar), 7.06 (d, J = 8.5, 3.0 Hz, 2H, o-CH, p-
tol), 6.92 (d, J = 8.1 Hz, 2H, o-CH, p-tol), 6.83 (d, J = 5.3 Hz, 1H, H4),
6.22−6.17 (m, 1H, H3), 6.09 (s, 5H, Cp), 5.96 (s, 6H, Cp + H1), 5.40 (s,
1H, H21), 5.22 (s, 1H, H28), 3.42 (s, 1H, H ), 2.28 (s, 3H, CH ), 2.16
(
4
500 MHz, C D ): δ 7.79 (d, J = 8.2 Hz, 4H, o-CH), 7.03 (d, J = 7.9 Hz,
6 6
H, m-CH), 5.49 (t, J = 2.6 Hz, 2H, H2 + H3), 5.13 (s, 10H, Cp), 4.50 (t,
13
J = 2.6 Hz, 2H, H1 + H4), 2.17 (s, 6H, CH3). C NMR (126 MHz,
C D ): δ 146.3 (C), 134.1 (C), 129.8 (CH), 128.7 (CH), 117.5 (C),
6
6
1
09.8 (CH), 109.1 (CH), 108.8 (CH), 103.8 (C), 21.0 (CH ). LR-MS
3
2
3
+
+
13
(
EI, m/z, relative intensity (%)): 478 ([M ], 26), 258 ([M − Cp Zr],
00), 220 ([M − Fv], 76). No correct elemental analysis of the bulk
(s, 3H, CH ). C NMR (125 MHz, C D ) δ152.7 (C), 146.5 (C), 143.7
2
3
6
6
+
1
(C), 142.3 (C), 140.4 (C), 136.5 (CH), 136.2 (C), 136.1 (CH), 135.9
(C), 133.5 (CH), 132.0 (CH), 131.9 (CH), 131.7 (CH), 131.6 (CH),
131.0 (CH), 128.3 (CH), 127.8 (CH), 127.3 (CH), 121.3 (C), 120.6
(C), 112.0 (CH), 111.6 (CH), 92.1 (CH), 82.6 (CH), 62.7 (C), 61.6
product was obtained, despite several attempts. Crystals of complex 2c
suitable for X-ray studies were grown from a concentrated C D6
6
solution.
+
Cp Zr(6,6-diphenylfulvene) (2d). According to GP-2, Cp ZrCl
(CH), 21.0 (CH ), 20.9 (CH ). ESI-MS for [C H O Br ZrK] : calcd
2
2
2
3
3
44 38
2
2
(
(
2.34 g, 8.0 mmol), Mg (0.19 g, 8.0 mmol), and 6,6-diphenylfulvene
884.9923, found 884.9913. Crystals suitable for X-ray studies were
1.84 g, 8.0 mmol) were reacted to give complex 2d as an orange-yellow
grown from a concentrated C D solution.
6
6
1
powder in 65% yield (2.35 g, 5.2 mmol). H NMR (500 MHz, C D ): δ
7
Cp Zr[OCH(p-MeO-Ph)C(p-tolyl) C H CH(p-MeO-Ph)O] (3c;
6
6
2
2
5
3
3
.83 (m, 4H, phenyl), 6.94−7.20 (m, 6H, phenyl), 5.45 (t, J = 2.6 Hz,
H, H2 + H3), 5.08 (s, 10H, Cp), 4.44 (t, J = 2.6 Hz, 2H, H1 + H4).
NMR Experiment). To a C D solution of complex 2c (20 mg, 0.04
6 6
HH
3
2
mmol) was added p-anisaldehyde (11 mg, 0.08 mmol), and after stirring
HH
1
3
1
1
C NMR (126 MHz, C D ): δ 148.9 (C), 129.8 (CH), 128.5 (CH),
for 30 min H NMR confirmed full conversion to complex 3c. H NMR
6
6
(
500 MHz, C D ): δ 7.89 (d, J = 8.3 Hz, 2H, o-CH, p-tol), 7.30 (d, J = 8.3
1
(
25.0 (CH), 117.2 (C), 109.8 (CH), 109.1 (CH), 108.9 (CH), 103.9
6
6
+
+
Hz, 2H, o-CH, p-tol), 7.29 (d, J = 8.6 Hz, 2H, o-CH, anisyl) 7.26 (d, J =
.7 Hz, 2H, o-CH, anisyl), 7.17 (d, J = 8.3 Hz, 2H, m-CH, p-tol), 6.94 (d,
C). LR-MS (EI, m/z, relative intensity (%)): 450 ([M ], 16), 385 ([M
+
+
8
−
Cp], 7), 230 ([M − Cp Zr], 100), 220 (([M − Fv], 69). No correct
2
J = 8.6 Hz, 2H, m-CH, anisyl), 6.92 (d, J = 8.2 Hz, 2H, m-CH, p-tol), 6.84
(d, J = 5.1 Hz, 1H, H4), 6.74 (d, J = 8.7 Hz, 2H, m-CH, anisyl), 6.35 (d, J
elemental analysis of the bulk product was obtained, despite several
attempts. Crystals of complex 2d suitable for X-ray studies were grown
from a toluene solution at −15 °C. The compound crystallizes with 0.5
equiv of toluene.
=
5.4 Hz, 1H, H3), 6.11 (s, 5H, Cp), 6.03 (s, 6H, Cp + H1), 5.52 (s, 1H,
H21), 5.40 (s, 1H, H28), 3.55 (s, 1H, H2), 3.43 (s, 3H, OMe), 3.28 (s,
13
Cp Zr(6,6-di-p-fluorophenylfulvene) (2e). According to GP-2,
3H, OMe), 2.23 (s, 3H, CH
), 2.10 (s, 3H, CH ). C NMR (125 MHz,
3 3
2
Cp ZrCl (2.00 g, 6.84 mmol), Mg (0.17 g, 6.84 mmol), and 6,6-di-p-
C D
6 6
): δ 159.1 (C), 159.0 (C), 153.0 (C), 142.9 (C), 141.0 (C), 139.8
2
2
fluorophenylfulvene (1.82 g, 6.84 mmol) were reacted to give complex
(C), 136.9 (C), 136.4 (CH), 136.2 (CH), 135.9 (C), 135.6 (C), 133.9
(CH), 132.2 (CH), 131.9 (CH), 131.3 (CH), 128.3 (CH), 127.7 (CH),
126.7 (CH), 114.0 (CH), 113.5 (CH), 112.0 (CH), 111.5 (CH), 92.4
1
2
e as an orange-yellow powder in 72% yield (2.41 g, 4.92 mmol). H
3
4
NMR (500 MHz, C D ): δ 7.50 (m, J = 8.5 Hz, J = 5.6 Hz, 4H, o-
CH), 6.83 (m, J = 8.5 Hz, J = 9.0 Hz, 4H, m-CH), 5.44 (t, J =
6
6
HH
HF
3
3
3
(CH), 83.1 (CH), 62.9 (C), 62.3 (CH), 54.9 (CH
), 54.7 (CH
), 21.1
H O ZrNa] : calcd 773.2184,
44 4
HH
HF
HH
3
3
3
+
2
.6 Hz, 2H, H2 + H3), 5.03 (s, 10H, Cp), 4.26 (t, J = 2.6 Hz, 2H, H1
(CH
found 773.2195.
Cp Zr[OCMe
3
), 20.9 (CH
3
). ESI-MS for [C46
C(p-tolyl) CMe O] (3d). According to GP-3,
2
HH
1
+
(
H4). 13C NMR (126 MHz, C D ): δ 160.8 ( J = 244 Hz, C), 144.9
6 6 CF
4J = 3.0 Hz, C), 129.8 ( J = 7.0 Hz, CH), 117.2 (C), 114.7 ( J
3
2
=
F
C
2
H
5
CF
CF
CF
2
2
3
19
2
1.0 Hz, CH), 109.7 (CH), 109.1 (CH), 109.0 (CH), 101.1 (C).
complex 2c (0.89 g, 1.81 mmol) was reacted with acetone (0.21 g, 0.27
NMR (300 MHz, C D ): δ −118.1. LR-MS (EI, m/z, relative intensity
mL, 3.62 mmol) in toluene (70 mL) for 2 h to give complex 3d as a white
6
6
+
+
+
1
(
%)): 486 ([M ], 13), 421 ([M − Cp], 2), 220 ([M − Fv], 100). Anal.
solid in 75% yield (0.83 g, 1.40 mmol). H NMR (500 MHz, C
D
6
6
): δ
Calcd for C3 H F Zr: C, 70.88; H, 4.91. Found: C, 70.72; H, 5.14.
7.04−7.52 (m, 8H, p-tol), 6.77 (m, 1H, H4), 6.31 (m, 1H, H3), 6.20 (s,
5H, Cp), 6.00 (s, 5H, Cp), 5.70 (s, 1H, H1), 2.84 (s, 1H, H ), 2.18 (s,
3H, CH ), 2.14 (s, 3H, CH ), 1.66 (s, 3H, CH ), 1.47 (s, 3H, CH ), 1.22
(s, 3H, CH ), 1.19 (s, 3H, CH ). C NMR (125 MHz, C ): δ 151.6
1.5
26 2
Crystals of complex 2e suitable for X-ray studies were grown from a
toluene solution at 4 °C. The compound crystallizes with 0.5 equiv of
toluene.
2
3
3
3
3
13
D
6 6
3
3
General Procedure (GP-3) for Reaction of Cp ZrFv Complex
(C), 144.9 (C), 142.6 (C), 137.8 (CH), 136.8 (CH), 135.7 (C), 135.4
(C), 133.5 (CH), 131.7 (CH), 128.8 (CH), 127.1 (CH), 111.7 (CH),
2
2
c with Carbonyl Compounds (Bulk Reaction). To a solution of
111.4 (CH), 87.3 (C), 80.9 (C), 64.8 (C), 62.7 (CH), 32.2 (CH ), 31.7
3
(CH ), 31.4 (CH ), 30.9 (CH ), 21.0 (CH ), 20.9 (CH ). LR-MS (EI,
3
3
3
3
3
+
+
m/z, relative intensity (%)): 594 ([M ], 1), 536 ([M − acetone], 4),
+
+
478 ([M − 2 acetone], 25), 413 ([M − 2 acetone − Cp], 35), 278
+
+
+
3
([M − acetone − Fv], 87), 220 ([Cp Zr ], 67), 91 ([C H -CH ],
2
6
4
100). No correct elemental analysis of the bulk product was obtained,
despite several attempts. Crystals suitable for X-ray studies were grown
from a hexane/toluene solution at −15 °C.
Cp Zr[OCEt C(p-tolyl) C H CEt O] (3e). According to GP-3,
2
2
2
5
3
2
C D ): δ 6.85−7.84 (m, 18H, p-tolyl and phenyl), 6.81 (d, J = 5.3 Hz,
complex 2c (0.47 g, 0.98 mmol) was reacted with 3-pentanone (0.17
g, 0.21 mL, 1.96 mmol) in toluene (60 mL) for 12 h to give complex 3e
as a white solid in 67% yield (0.43 g, 0.66 mmol). H NMR (500 MHz,
6
6
1
1
3
1
1
H, H4), 6.27 (m, 1H, H3), 6.06 (s, 5H, Cp), 5.97 (s, 5H, Cp), 5.94 (m,
1
H, H1), 5.50, (s, 1H, H21), 5.37 (s, 1H, H28), 3.52 (s, 1H, H ), 2.19 (s,
2
13
H, CH ), 2.08 (s, 3H, CH ). C NMR (125 MHz, C D ): δ 152.9 (C),
C D ): δ 6.94−7.81 (m, 8H, p-tol), 7.09 (m, 1H, H4), 6.31 (m, 1H, H3),
3
3
6
6
6
6
47.7 (C), 144.9 (C), 142.8 (C), 140.8 (C), 136.7 (CH), 136.1 (CH),
35.9 (C), 135.5 (C), 133.8 (CH), 132.2 (CH), 131.9 (CH), 130.3
6.26 (s, 5H, Cp), 6.05 (s, 5H, Cp), 5.34 (s, 1H, H1), 2.92 (s, 1H, H ),
2
2.32 (m, 1H, CH2CH3, 2.66 (m, 1H, CH CH ), 2.17 (s, 3H, CH ), 2.12
2
3
3
(
CH), 128.5 (CH), 128.3 (CH), 127.9 (CH), 127.7 (CH), 127.2 (CH),
(s, 3H, CH ), 2.03 (m, 1H, CH CH ), 1.83 (m, 1H, CH CH ), 1.64 (m,
3 2 3 2 3
H
DOI: 10.1021/acs.organomet.7b00213
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1
H, CH CH ), 1.40−1−56 (m, 3H, CH CH ), 0.98 (t, 3H, CH CH ),
BMBF (Bundesminsiterium fu
BB, 03C0276G4).
̈
r Bildung und Forschung, MP,
2
3
2
3
2
3
0
.75 (t, 3H, CH CH ), 0.57 (t, 3H, CH CH ), 0.27 (t, 3H, CH CH ).
2
3
2
3
2
3
1
3
C NMR (125 MHz, C D ): δ 152.3 (C), 145.1 (C), 142.1 (C), 138.4
6
6
(
CH), 137.8 (CH), 136.0 (C), 135.3 (C), 133.1 (CH), 128.3 (CH),
REFERENCES
■
1
5
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(
4
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2
2
2
2
(
CH ), 20.9 (CH ), 11.6 (CH ), 9.5 (CH ), 9.0 (CH ), 7.6 (CH ). LR-
3 3 3 3 3 3
+
+
MS (EI, m/z, relative intensity (%)): 650 ([M ], 5), 621 ([M − C H ],
1
C H ], 47), 499 ([M − {(C H ) CO} − Cp], 36), 413 ([M −
2
5
+
+
0), 564 ([M − (C H ) CO], 35), 535 ([M − {(C H ) CO} −
2
5
2
2
5 2
+
+
2
5
2
5 2
+
2
{(C H ) CO} − Cp], 22), 305 ([M − {(C H ) CO} − Fv], 100) 258
2
5
2
2
5 2
+
(
[Fv ], 32). Crystals suitable for X-ray studies were grown from a
benzene solution at room temperature. The compound crystallizes with
.5 molecules of C D .
(
(
2
(
1
6
6
General Procedure for Reaction of Cp ZrFv Complex 2c with
2
Alkynes (NMR Experiments). To a solution of complex 2c (15 mg,
0
mmol) in C D (0.2 mL). After the mixture was stirred for 12 h at room
temperature, the disappearance of complex 2c was observed in the H
NMR spectrum with concomitant formation of free fulvene 1c and the
corresponding zirconacyclopentadiene 4. The H NMR data of 4a,b
were in agreement with literature reports.
.03 mmol) in C D (0.5 mL) was added a solution of alkyne (0.06
6
6
1
440−1452.
6
6
1
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ASSOCIATED CONTENT
■
*
S
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.7b00213.
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can be obtained free of charge via www.ccdc.cam.ac.uk/
data_request/cif, or by emailing data_request@ccdc.cam.ac.uk,
or by contacting The Cambridge Crystallographic Data Centre,
1
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Lauterbach, N.; Dorfler, J.; Schmidtmann, M.; Saak, W.; Doye, S.;
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AUTHOR INFORMATION
■
̌
va, I.; Horac k, M.; Kubista,
́
́
e
̌
̌
Corresponding Authors
*
E-mail for F.J.: florian.jaroschik@univ-reims.fr.
Email for R.B.: ruediger.beckhaus@uni-oldenburg.de.
(
*
̌
A. J. Am. Chem. Soc. 1997, 119, 5132−5143. (b) Varga, V.; Sindelar
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Eisenblatter, T.; Erker, G.; Frohlich, R.; Meyer, O.; Bergander, K.
́ ̌
, P.;
ORCID
̌
́
́
e
̌
̌
2
(
1
Florian Jaroschik: 0000-0003-0201-568X
Radhakrishnan Kokkuvayil Vasu: 0000-0001-8909-3175
̈
hlich, R. Organometallics 1997,
̈
Rudiger Beckhaus: 0000-0003-3697-0378
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Present Address
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F.; Lachicotte, R. J.; Jones, W. D. Organometallics 1999, 18, 3170−3177.
⊥
́
NIMBE, CEA, CNRS, Universite Paris-Saclay, CEA Saclay,
1191 Gif sur Yvette Cedex, France.
9
(
(
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The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
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de Reims Champagne-
Ardenne for financial support. This work was supported by the
analytical platform PlAneT at the Universite de Reims
Champagne-Ardennne (financial support by CNRS, Conseil
Regional Champagne Ardenne, Conseil General de la Marne,
Ministry of Higher Education and Research (MESR), and EU-
programme FEDER). This work was supported also by the
(
1
́
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DOI: 10.1021/acs.organomet.7b00213
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