Synthesis and structure of half-sandwich zincocenes

Article abstract of DOI:10.1002/zaac.200700201

Half-sandwich zinc complexes (η⁵-C₅Me ₅)ZnR have been prepared for R= Me, 2; Et, 3; Mes, 4 and Ph, 5, by the conproportionation reaction of Zn(C₅Me₅)₂ and the corresponding ZnR₂

Full text of DOI:10.1002/zaac.200700201

DOI: 10.1002/zaac.200700201
Synthesis and Structure of Half-Sandwich Zincocenes
´
Irene Resa, Eleuterio Alvarez, and Ernesto Carmona*
´
´
´
Sevilla/Spain, Instituto de Investigaciones Quımicas-Departamento de Quımica Inorganica, Consejo Superior de Investigaciones
´
Cientıficas-Universidad de Sevilla
Received April 23rd, 2007.
˜
Dedicated to Professor Alfonso Castaneiras on the Occasion of his 65th Birthday
Abstract. Half-sandwich zinc complexes (η5-C5Me5)ZnR have been
prepared for Rϭ Me, 2; Et, 3; Mes, 4 and Ph, 5, by the conpropor-
tionation reaction of Zn(C5Me5)2 and the corresponding ZnR2 re-
agent. The new compounds have been fully characterized by spec-
troscopy and in the cases of 2 and 4 by X-ray crystallography. Since
the reaction of Zn(C5Me5)2 and ZnEt2 yields 3, together with the
known dizincocene Zn2(η5-C5Me5)2, the rearrangements of the
related zincocenes ZnCp2Ј and ZnEt2 were investigated, with the
result that only the half-sandwich (η5-CpЈ)ZnEt derivatives (CpЈϭ
C5Me4SiMe3 (6); C5Me4CMe3 (7) and C5Me4H (8)) were produced.
Keywords: Zinc; Metallocenes; Sandwich complexes; Solid-state
structure
Introduction
It appears that only the latter compound has been
characterized by diffraction methods. In the crystal it is a
polymer consisting of a puckered chain of zinc atoms [8]
each bound to a terminal methyl group and to two bridging
cyclopentadienyl units, with coordination between η2 and
η3. The compound is monomeric in benzene and also in
the gas phase [9], with a relatively strong ZnϪMe bond of
Organozinc reagents are an important family of organo-
metallic compounds that find numerous applications in syn-
thesis [1Ϫ3]. Alkyl and aryl zinc derivatives, in addition to
possessing a distinguished history [4], are widely used as
hydrocarbyl transfer reagents in a variety of transmetall-
ation reactions [1]. Related derivatives containing cyclopen-
tadienyl ligands, namely zincocenes ZnCp2Ј (CpЈ stands as
a general representation for C5H5 or any substituted cyclo-
pentadienyl group) exhibit interesting structural features
since they contain almost parallel cyclopentadienyl groups
with one η5- and one η1-CpЈ rings, in the so-called slipped
sandwich geometry [5]. It is therefore somewhat surprising
that information on the corresponding half-sandwich struc-
tures (η5-CpЈ)ZnR is sparse and dates back to about twenty
to forty five years ago. Thus, the ethyl and phenyl deriva-
tives were prepared in 1960 by the reaction of ZnCl2 with
Mg(C2H5)Br and C5H6 [6] (an alternative, high-yield syn-
thesis of (η5-C5H5)Zn(C2H5), consisting in the conpro-
portionation of Zn(C5H5)2 and Zn(C2H5)2, was later
provided [7]), while the related methyl compound (η5-
C5H5)ZnCH3 was obtained from Zn(CH3)I and NaC5H5
[8].
5
˚
1.903(12) A and weaker Zn-η -C5H5 interactions of ca
˚
2.28 A.
Following previous studies on the structural properties
of zincocenes containing the bulky C5Me4CMe3, and
C5Me4SiMe3 ligands [10] we set out to prepare half-sand-
wich complexes of type (η5-CpЈ)ZnR for different cyclopen-
tadienyl groups. As discussed in detail somewhere else [11],
attempts to obtain (η5-C5Me5)Zn(C2H5) led unexpectedly
to a mixture of this product and Zn2(η5-C5Me5)2, the first
compound with a ZnϪZn bond. Here we wish to report the
synthesis and structural characterization of half-sandwich
compounds (η5-CpЈ)ZnR for various combinations
of the cyclopentadienyl ligand (C5Me5, C5Me4SiMe3,
C5Me4CMe3 and C5Me4H) and of the hydrocarbyl group
R (Me, Et, Ph, Mes).
Results and Discussion
As mentioned briefly in the Introduction, a 1:1 mixture of
Zn(C5H5)2 and ZnEt2 reacts at 60 °C to give almost pure
(η5-C5H5)ZnEt in quantitative yield [7]. In agreement with
this result, the room temperature reaction of Zn(C5Me5)2
(1a), with ZnMe2 in Et2O as the solvent proceeds in accord
with Eq. (1), to give the expected complex (η5-
C5Me5)ZnMe (2), in almost quantitative yield (by 1H
NMR). At variance with this result, the analogous reaction
* Prof. E. Carmona
´
´
Instituto de Investigaciones Quımicas-Departamento de Quımica
´
Inorganica
´
Consejo Superior de Investigaciones Cientıficas-Universidad de
Sevilla
´
Americo Vespucio 49
E-41092, Sevilla / Spain
Fax: (ϩ)0034 954460565
E-mail: guzman@us.es
Z. Anorg. Allg. Chem. 2007, 633, 1827Ϫ1831
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1827

´
I. Resa, E. Alvarez, E. Carmona
All new compounds are colourless or pale-yellow crystalline
solids, very reactive toward oxygen and water, both in solu-
tion and in the solid state. They are soluble in common
ether and hydrocarbon solvents and are fairly volatile. Thus,
the methyl derivative 2 sublimes readily at 40 °C and
0.1 mbar, while the bulkier mesityl species 4 requires
heating at 120 °C under high vacuum for sublimation
(10Ϫ4 mbar).
Scheme 1 Reaction of 1a with ZnR2 in Et2O which leads to a
mixture of two compounds.
1
Spectroscopic characterization of 2 ؊ 8 relies on H and
13C{1H} 1D and 2D NMR experiments. NMR spectra are
simple and allow unequivocal solution characterization,
complemented by X-ray studies on single crystals of 2 and
of 1a with ZnEt2, which is also fast at room temperature,
yields a mixture of two compounds, the expected half-sand-
wich derivative (η5-C5Me5)ZnEt (3) and the unforeseen [11]
dizincocene Zn2(η5-C5Me5)2 (Scheme 1). The bis(mesityl)
complex ZnMes2 (Mes ϭ 2,4,6-C6H2Me3) behaves like
ZnMe2 and provides only the half-sandwich compound 4,
as shown in Eq. 1. However Zn(C6H5)2 has behaviour akin
to ZnEt2 and provides also a mixture of the half-sandwich
product 5 and the dizincocene Zn2(η5-C5Me5)2 (Scheme 1).
1
4 (see below). Thus, the H NMR spectrum of 2 recorded
in C6D6 shows signals at δ 1.96 and Ϫ0.65, with intensity
ratio 5:1, due respectively to the cyclopentadienyl and zinc-
bound methyl protons. Corresponding 13C{1H} resonances
appear at δ 9.8 and Ϫ25.8, and are complemented by an-
other resonance at δ 107.8 which arises from the ring car-
bon nuclei. This is a very characteristic value, that can be
taken as diagnostic for (η5-C5Me5)Zn coordination. Indeed
the ethyl complex analogue 3 exhibits identical chemical
shift while the corresponding resonance for the aryl deriva-
tives 4 and 5 centres around 108.5 ppm (see Experimental
Section). The NMR spectra of the ethyl derivatives 6-8 are
also simple. For example, compound 6, with a C5Me4SiMe3
ligand, exhibits (1H NMR) the expected quartet at δ 0.37
(Zn-CH2CH3) and triplet at 1.19 ppm (Zn-CH2CH3;
3JHHϭ 8.1 Hz) for the zinc-bonded ethyl group, together
with singlets at δ 0.34, 1.90 and 2.12 (relative intensity
3:2:2) due to the ϪSiMe3 and ϪMe substituents of the ring.
13C{1H} resonances for the ring carbon atoms at δ 98.2 (C-
SiMe3) and 115.1 and 117.6 can be taken as a clear indi-
cation of (η5-C5Me4SiMe3) coordination to zinc.
As mentioned above, confirmation of the proposed struc-
tures for 2 Ϫ 8 has been obtained by solid-state X-ray stud-
ies carried out with compounds 2 and 4. The structure of
the mesityl derivative 4 exhibits disorder of the C5Me5 ring
over two sets of positions with refined occupancies of 0.67
and 0.33 (see Experimental Part). Since there are no rel-
evant features in this structure it is not further discussed.
Instead we concentrate on the structure of 2 (Figure 1) and
in the comparison of the structural parameters of this com-
plex with those of the parent (η5-C5H5)ZnMe (Figure 2),
as obtained from gas electron diffraction [9].
Zn(C5Me5)2 ϩ ZnR2 Ǟ 2 (η5-C5Me5)ZnR
(1)
1a
2 R ϭ Me
4 R ϭ Mes
As discussed elsewhere [11], generation of the metal-
metal bonded zincocene in the reactions of 1a with ZnEt2
and ZnPh2 is competitive with formation of the respective
half-sandwich products 3 and 5, when ether solvents are
employed. However, hydrocarbon solvents prevent forma-
tion of Zn2(η5-C5Me5)2 and direct the syntheses towards
the half-sandwich compounds 3 and 5. Thus, 1a and ZnEt2
combine in pentane at Ϫ60 °C to afford 3 as the exclusive
reaction product. It is likely that the route leading to 2Ϫ5
involves the intermediacy of binuclear species similar to
those that participate in Schlenk-type equilibria (Scheme 2).
To complete these studies the analogous reactions of
Zn(C5Me4SiMe3)2 (1b), Zn(C5Me4CMe3)2 (1c) and
Zn(C5Me4H)2 (1d) with ZnEt2, have been investigated (Eq.
(2)). Originally, these reactions were intended to ascertain
if generation of dimetallocenes Zn2(η5-C5Me4R)2 derived
from the above cyclopentadienyl ligands could be possible,
but as shown in Eq. 2 only the half-sandwich products
(η5-C5Me4R)ZnEt were observed (C5Me4SiMe3ZnEt, 6;
C5Me4CMe3ZnEt, 7; C5Me4HZnEt, 8).
The molecules of 2 feature in the solid state the expected
Pentane
Zn(C5Me4R)2 ϩ ZnEt2
1bϪ1d
2 (η5-C Me R)ZnEt
(2)
Ǟ
(η5-C5Me5)ZnMe structure, characterized by ZnϪCp*centr.
5
4
Ϫ10 °C
˚
and ZnϪCH3 distances of 1.90 and 1.94 A, respectively,
6 R ϭ SiMe3
7 R ϭ CMe3
8 R ϭ H
and by a linear Cp*centr.ϪZnϪMe arrangement (177.4°).
The ZnϪC distances to the ring carbon atoms concentrate
Scheme 2 Possible mechanism for the formation of compounds 2Ϫ5.
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 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2007, 1827Ϫ1831

Synthesis and Structure of Half-Sandwich Zincocenes
tution of the hydrogen atoms of C5H5 by Me groups does
not alter significantly the strength of the ZnϪC(η5) bonds.
The same conclusion stems from the comparison of the
˚
ZnϪCpЈcentr. distances of 1.93(C5H5) and 1.90 A (C5Me5).
The difference in both the ZnϪC(η5) and the ZnϪCpЈcentr.
distances just discussed, although too small to allow any
conclusions to be drawn, point into the same direction, na-
mely, somewhat stronger (η5-CpЈ)ϪZn interaction for the
better electron-donor C5Me5 ring. ZnϪCH3 distances in the
˚
two compounds differ by 0.04 A, being longer for com-
pound 2 of the permethylated cyclopentadienyl ligand. This
might indicate somewhat higher trans influence of C5Me5
as compared with C5H5.
Experimental Part
Figure 1 ORTEP drawing of compound 2. Thermal ellipsoids are
drawn at the 50 % probability level. Hydrogen atoms are omitted
for clarity.
General methods and instrumentation
All preparations and manipulations were carried out under oxygen-
free argon using conventional Schlenk [13] and glovebox tech-
niques. Solvents were rigorously dried and degassed before use [14].
Zn(C5Me5)2, [5c] ZnPh2 [15] and ZnMes2 [16] were prepared
following the procedures described in the literature while
Zn(C5Me4SiMe3)2, Zn(C5Me4But)2 and Zn(C5Me4H)2 were ob-
tained as described [17]. Microanalyses were obtained at the Micro-
´
analytical Service of the Instituto de Investigaciones Quımicas
(Sevilla). NMR spectra were recorded on Bruker DPX-300, DRX-
400 and DRX-500 spectrometers. The 1H and 13C resonances of
the solvent were used as the internal standard, and the chemical
shifts are reported relative to TMS.
Figure 2 Comparison between structures of (C5H5)ZnMe (a) de-
termined by GED and (C5Me5)ZnMe (b) determined by XRD.
Syntheses
˚
within the very narrow range of 2.24-2.27 A, in marked
Although all new compounds have been isolated as crystalline or
microcrystalline solids of spectroscopic purity, due to their high
reactivity toward oxygen and water obtaining sufficiently accurate
microanalytical data has proved difficult in some instances. How-
ever, as discussed in the text, characterization by NMR is complete
and furthermore, the structures of two of the new compounds (2
and 4) have been authenticated by X-ray crystallography.
contrast with corresponding ZnϪC(η5) distances to the η5-
ring of the slipped-sandwich (η5-CpЈ)Zn(η1-CpЈ) structures
of known zincocenes [5]. For the latter complexes there are
remarkable irregularities, as found for example in
Zn(C5Pr4 H)2, where ZnϪC distances vary between 1.99
and 2.51 A [5d] and to a lesser extent in Zn(C5Me4Ph)2
i
˚
˚
(2.09 to 2.30 A) [5c]. Even in Zn(C5Me4SiMe3)2, where the
(C5Me5)ZnMe (2): Over a solution of 500 mg (1.5 mmol) of
Zn(C5Me5)2 in pentane (20 mL) 0.75 mL (1.5 mmol) of a 2.0 M
solution of ZnMe2 in toluene were added. The mixture was stirred
at room temperature for 1 hour and the solvent was removed under
vacuum to yield a white solid which can be purified by sublimation
(10Ϫ1 mbar, 40 °C) yielding colourless crystals (325 mg; 50 %). El-
emental analysis: C11H18Zn (215.6); C 60.8 (calc. 61.3); H 8.5
(8.4) %.
Zn(η5-C5Me4SiMe3) coordination is fairly regular, ZnϪC
˚
distances vary between 2.15 and 2.32 A [10].
With respect to the ZnϪMe moiety of compound 2 its
length of 1.94 A is comparable to that found in ZnMe2
˚
˚
˚
(1.930(2) A by gas electron diffraction [9]; 1.945 A, com-
puted value from DFT calculations [12]). This bond length
is significantly shorter than the ZnϪC distance to the η1-
ring of the slip-sandwich structures of zincocenes (formally
this geometry may be considered as a half-sandwich struc-
ture), with the exception of Zn(C5Me4SiMe3)2. The latter
compound has a geometry close to η5/η1(σ) and it is
1H NMR (300 MHz, C6D6, 25 °C, ppm): Ϫ0.65 (s, 3H, ZnCH3), 1.96 (s,
15H, C5Me5). 13C{1H} NMR (75 MHz, C6D6, 25 °C, ppm): Ϫ25.8 (ZnCH3),
9.8 (C5Me5), 107.8 (C5Me5).
(C5Me5)ZnEt (3): Over
a solution of 335 mg (1 mmol) of
˚
characterized by a Zn-C distance of 1.953(3) A, somewhat
Zn(C5Me5)2 in pentane (20 mL) 1 mL (1 mmol) of a 1.0 M solution
of ZnEt2 in hexane were added. The mixture was stirred at Ϫ10 °C
for 1 hour and the solvent was removed under vacuum to yield a
colourless solid with spectroscopical purity (138 mg; 60 %).
1H NMR (300 MHz, C6D6, 25 °C, ppm): 0.38 (q, 2H, JHH
ZnCH2CH3), 1.19 (t, 3H, JHH ϭ 8 Hz, ZnCH2CH3), 1.98 (s, 15H, C5Me5).
13C{1H} NMR (75 MHz, C6D6, 25 °C, ppm): Ϫ8.2 (ZnCH2CH3), 9.8
(C5Me5), 12.9 (ZnCH2CH3), 107.8 (C5Me5).
shorter than the ZnϪC separations to the η1-ring found in
i
˚
the slip-sandwich structures of Zn(C5Pr4 H)2 (1.99 A, [5d]
˚
and Zn(C5Me4Ph)2 (2.09 A, [5c]).
As shown in Figure 2 the ZnϪC(η5) bond lengths
have comparable values in (η5-C5H5)ZnMe and (η5-
C5Me5)ZnMe, indicating that in these complexes substi-
ϭ 8 Hz,
Z. Anorg. Allg. Chem. 2007, 1827Ϫ1831
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1829

´
I. Resa, E. Alvarez, E. Carmona
˚
Table 1 Selected bond distances /A and angles /° for 2.
ZnϪCpЈcentr
ZnϪC1
ZnϪC2
ZnϪC3
ZnϪC4
ZnϪC5
ZnϪC11
1.904(4)
2.262(4)
2.245(4)
2.243(4)
2.274(4)
2.276(4)
1.943(5)
C1ϪC2
C2ϪC3
C3ϪC4
C4ϪC5
C5ϪC1
CpЈcentrϪZnϪC11
1.438(5)
1.429(5)
1.424(5)
1.433(5)
1.433(5)
177.40(2)
(C5Me5)ZnMes (4): 200 mg (0.6 mmol) of Zn(C5Me5)2 and 182 mg
(0.6 mmol) of ZnMes2 were dissolved in diethyl ether (20 mL). The
mixture was stirred at room temperature for 3 hours and the sol-
vent was removed under vacuum to yield a white solid which can
be purified by sublimation (10Ϫ4 mbar, 120 °C) yielding colourless
crystals (171 mg; 80 %). Elemental analysis: C19H26Zn (277.72); C
71.3 (calc. 71.4); H 8.2 (8.2) %.
1H NMR (500 MHz, C6D6, 25 °C, ppm): 1.99 (s, 15H, C5Me5), 2.18 (s, 3H,
ArCH3,para), 2,20(s, 6H, ArCH3,ortho), 6.8(s, 2H, ArHmeta). 13C{1H} NMR
(125 MHz, C6D6, 25 °C, ppm): 10.2 (C5Me5), 21.2 (ArCH3,para), 28.7 (Ar-
CH3,ortho), 108.2 (C5Me5), 126.0 (CHmeta), 137.0 (CH3,ipso), 141.5 (CH3,para),
145.8 (CH3,meta).
(C5Me5)ZnPh (5): 620 mg (1.85 mmol) of Zn(C5Me5)2 and 406 mg
(1.85 mmol) of ZnPh2 were dissolved in toluene (10 mL). The mix-
ture was stirred at Ϫ20 °C for 2 hours and the solvent was removed
under vacuum to yield compound 5 as a yellow solid (410 mg;
40 %).
1H NMR (300 MHz, C6D6, 25 °C, ppm): 1.98 (s, 15H, C5Me5), 7.12Ϫ7.15
(3H, Haryl), 7.30-7.34 (2H, Haryl). 13C{1H} NMR (75 MHz, C6D6, 25 °C,
ppm): 10.9 (C5Me5), 108.6 (C5Me5), 127.5 (Cortho), 127.9 (Cmeta), 140.2
(Cpara).
Figure 3 ORTEP drawing for compound 4. Thermal ellipsoids are
drawn at the 50 % probability level. Hydrogen atoms are omitted
for clarity. The η5-C5Me5 ring was observed disordered in two posi-
tions with refined occupancy factors of 0.67 and 0.33, where the
CpЈ rings are rotated 36°; one of them is also omitted for clarity.
(C5Me4R)ZnEt (6 - 8): To a solution of Zn(C5Me4R)2 in pentane,
a 1.0 M solution of ZnEt2 in hexane was added to afford a 1:1
mixture of the reagents. The mixture was stirred at Ϫ10 °C for 2Ϫ4
hours and the solvent was removed under vacuum to yield the cor-
responding compound.
6: 119 mg (0.26 mmol) of Zn(C5Me4SiMe3)2 in 10 mL of pentane
and 0.26 mL (0.26 mmol) of ZnEt2 (45 mg; 58 %).
˚
Table 2 Selected bond distances /A and angles /° for compound 4.
1H NMR (400 MHz, C6D6, 25 °C, ppm): 0.34 (s, 9H, SiMe3), 0.37 (q, 2H,
JHH ϭ 8.1 Hz, ZnCH2CH3), 1.19 (t, 3H, JHH ϭ 8.1 Hz, ZnCH2CH3), 1.90
(s, 6H, 2CpCH3), 2.12 (s, 6H, 2CpCH3). 13C{1H} NMR (125 MHz, C6D6,
25 °C, ppm): Ϫ8.3 (ZnCH2CH3), 1.4 (SiMe3), 10.0 (2CpCH3), 12.9 (2CpCH3
and ZnCH2CH3), 98.2 (CqSiMe3), 115.1 (CqCH3), 117.6 (CqCH3).
ZnϪCpЈcentr
ZnϪC1A
ZnϪC2A
ZnϪC3A
ZnϪC4A
ZnϪC5A
ZnϪC11
1.896(3)
C1AϪC2A
C2AϪC3A
C3AϪC4A
C4AϪC5A
C5AϪC1A
CpЈcentrϪZnϪC11
1.4159(2)
1.4159(2)
1.4159(2)
1.4158(2)
1.4159(2)
155.63(4)
2.2387(2)
2.2519(2)
2.2571(2)
2.2470(2)
2.2356(2)
1.933(3)
7: 96 mg (0.23 mmol) of Zn(C5Me4CMe3)2 in 10 mL of pentane
and 0.23 mL (0.23 mmol) of ZnEt2 (40 mg; 65 %). Elemental analy-
sis: C19H26Zn (215.67); C 61.4 (calc. 61.3); H 8.5 (8.4) %.
1H NMR (500 MHz, C6D6, 25 °C, ppm): 0.40 (q, 2H, JHH ϭ 8.1 Hz,
ZnCH2CH3), 1.23 (t, 3H, JHH ϭ 8.1 Hz, ZnCH2CH3), 1.42 (s, 9H, CCH3),
1.95 (s, 6H, 2CpCH3), 2.18 (s, 6H, 2CpCH3). 13C{1H} NMR (125 MHz,
C6D6, 25 °C, ppm): Ϫ8.4 (ZnCH2CH3), 10.1 (2CpCH3), 12.9 (2CpCH3), 13.6
(ZnCH2CH3), 32.2 (CMe3), 107.0 (CqCH3), 110.2(CqCH3), 119.8 (CqBut).
mation, coated with dry perfluoropolyether was mounted on a
glass fiber and fixed in a cold nitrogen stream, 100(2) K, to the
goniometer head. Monoclinic, space group P21/c (no.14), a ϭ
˚
˚
˚
12.0761(9) A, b ϭ 14.3625(9) A, c ϭ 12.4260(9) A, β ϭ 90.636(2)°,
3
V ϭ 2155.1(3) A , Z ϭ 8, ρcalcd ϭ 1.329 gcmϪ3, λ(Mo Kα1) ϭ
˚
8: 30 mg (0.1 mmol) of Zn(C5Me4H)2 in 5 mL of pentane and
0.1 mL (0.1 mmol) of ZnEt2 (13 mg; 60 %).
0.71073 A, F(000) ϭ 912, µ ϭ 2.226 mmϪ1. 21767 Reflections were
˚
collected from a Bruker-Nonius X8Apex-II CCD diffractometer in
the range 3.38<2θ<61.86° and 6437 independent reflections
[R(int) ϭ 0.0514] were used in the structural analysis. The data
were reduced (SAINT) and corrected for Lorentz polarisation ef-
fects and absorption by multiscan method applied by SADABS [18,
19]. The structure was solved by direct methods (SIR-2002) [20]
and refined against all F2 data by full-matrix least-squares tech-
niques (SHELXL97) [21] converged to final R1 ϭ 0.0535 [I > 2σ(I)],
and wR2 ϭ 0.2457 for all data, with a Goodness-of-fit on F2, S ϭ
1H NMR (500 MHz, C6D6, 25 °C, ppm): Ϫ0.30 (q, 2H, JHH ϭ 8 Hz,
ZnCH2CH3), 1.19 (t, 3H, JHH ϭ 8 Hz, ZnCH2CH3), 1.95 (s, 6H, 2CpCH3),
1.99 (s, 6H, 2CpCH3), 5.50 (s, 1H, Cp-H). 13C{1H} NMR (125 MHz, C6D6,
25 °C, ppm): Ϫ8.3 (ZnCH2CH3), 9.8 (2CpCH3), 11.7 (2CpCH3), 12.9
(ZnCH2CH3), 95.9 (Cp-H), 108.6 (CqCH3), 112.5 (CqCH3).
Structure Determination
Crystal data for 2: C11H18Zn, Mw ϭ 215.62, a single crystal of
suitable size, colourless prism (0.31 x 0.27 x 0.25 mm3) from subli-
1.059 and 229 parameters. Crystal data for 4: C19H26Zn, Mw ϭ
1830
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Z. Anorg. Allg. Chem. 2007, 1827Ϫ1831

Synthesis and Structure of Half-Sandwich Zincocenes
319.77, a single crystal of suitable size, colourless prism (0.28 x 0.26
x 0.12 mm3) from sublimation, coated with dry perfluoropolyether
was mounted on a glass fiber and fixed in a cold nitrogen stream,
100(2) K, to the goniometer head. Monoclinic, space group P21/c
zelaar, B. Fischer, A. Haaland, H. V. Volden, J. Weidlein, Acta
Chem. Scan. 1986, A40, 113. (c) B. Fischer, P. Wijkens, J.
Boersma, G. van Koten, W. J. J. Smeets, A. L. Spek, P. H. M.
Budzelaar, J. Organomet. Chem. 1989, 376, 223. (d) D. J.
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˚
˚
˚
(no.14), a ϭ 15.2130(7) A, b ϭ 8.5525(4) A, c ϭ 13.3227(6) A, β ϭ
3
97.439(2)°, V ϭ 1718.82(14) A , Z ϭ 4, ρcalcd ϭ 1.236 gcmϪ3, λ(Mo
˚
Kα1) ϭ 0.71073 A, F(000) ϭ 680, µ ϭ 1.418 mmϪ1. 13378 Reflec-
˚
tions were collected from a Bruker-Nonius X8Apex-II CCD dif-
fractometer in the range 6.12 < 2θ < 57.58° and 4163 independent
reflections [R(int) ϭ 0.0257] were used in the structural analysis.
Data reduction, solving and refinement was performed likewise for
2 converged to final R1 ϭ 0.0467 [I > 2σ(I)], and to wR2 ϭ 0.1240
for all data, with a Goodness-of-fit on F2, S ϭ 1.057 and 232 par-
ameters. As discussed in the text, the structure of 4 is disordered
(see Fig. 3 and table 2 that contains selected bond distances and
angles). Crystallographic data for the structures have been de-
posited with the Cambridge Crystallographic Data Centre no.
CCDC 643972 and 643973. Copies of the data can be obtained free
of charge on application to The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: (44) 01223 336033; e-mail
for inquiry: fileserv@ccdc.cam.ac.uk; e-mail for deposition:
deposit@ccdc.cam.ac.uk).
´
[10] R. Fernandez, I. Resa, D. del Rıo, E. Carmona, E. Gutierrez-
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 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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