Reactivity of vinyl and alkynyl zirconium complexes with the di-ansa-[1,1′,2,2′-bis(dimethylsilanediyl) dicyclopentadienyl] ligand

Article abstract of DOI:10.1016/S0022-328X(99)00633-6

Vinylation of the chloro-ethyl and dichloro zirconium complexes [Zr(CpSi₂Cp)ClX] (CpSi₂Cp=1,1′,2,2′-(SiMe₂)₂(η⁵-C₅H₃)₂; X=Et, Cl) with one or two equivalents of Mg(CH=CH₂)Cl gave the new zirconacyclopentane [Zr(CpSi₂Cp){η²-CH₂-(CH₂)₂-CH₂}] and (η⁴-butadiene)zirconium [Zr(CpSi₂Cp){η⁴-(butadiene)}] complexes, respectively. Addition of a toluene solution of PhC?CPh to the zirconacyclopentane compound afforded the zirconacyclopentadiene derivative [Zr(CpSi₂Cp){η²-(CPh=CPh-CPh=CPh)}]. Reaction of the chloro-ethyl zirconium complex with LiC?CPh afforded the alkynyl compound [Zr(CpSi₂Cp)Et(C?CPh)] which reacted with CN(2,6-Me₂C₆H₃) to give the insertion product [Zr(CpSi₂Cp)(C?CPh){η²-C(Et)=N(2,6-Me₂C₆H₃)}]. Reactions of the chloro-ethyl [Zr(CpSi₂Cp)EtCl] and alkynyl-ethyl [Zr(CpSi₂Cp)Et(C?CPh)] complexes with the Lewis acid B(C₆F₅)₃ yielding various cationic species have been monitored by ¹H-NMR spectroscopy. The new complexes reported and their intermediates have been identified by IR and ¹H- and ¹³C-NMR spectroscopy.

Full text of DOI:10.1016/S0022-328X(99)00633-6

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 593–594 (2000) 147–153
Reactivity of vinyl and alkynyl zirconium complexes with the
di-ansa-[1,1%,2,2%-bis(dimethylsilanediyl) dicyclopentadienyl] ligand
Francisco J. Ferna´ndez, Mikhail V. Galakhov, Pascual Royo *
Departamento de Qu´ımica Inorga´nica, Facultad de Ciencias, Campus Uni6ersitario, Edificio de Farmacia, Uni6ersidad de Alcala´ de Henares,
E-28871 Alcala´ de Henares, Spain
Received 28 May 1999; accepted 22 October 1999
Abstract
Vinylation of the chloro–ethyl and dichloro zirconium complexes [Zr(CpSi2Cp)ClX] (CpSi2Cp=1,1%,2,2%-(SiMe2)2(h5-C5H3)2;
X=Et, Cl) with one or two equivalents of Mg(CHꢀCH2)Cl gave the new zirconacyclopentane [Zr(CpSi2Cp){h2-
CH2ꢁ(CH2)2ꢁCH2}] and (h4-butadiene)zirconium [Zr(CpSi2Cp){h4-(butadiene)}] complexes, respectively. Addition of a toluene
solution of PhCꢂCPh to the zirconacyclopentane compound afforded the zirconacyclopentadiene derivative [Zr(CpSi2Cp){h2-
(CPhꢀCPhꢁCPhꢀCPh)}]. Reaction of the chloro–ethyl zirconium complex with LiCꢂCPh afforded the alkynyl compound
[Zr(CpSi2Cp)Et(CꢂCPh)] which reacted with CN(2,6-Me2C6H3) to give the insertion product [Zr(CpSi2Cp)(CꢂCPh){h2-
C(Et)ꢀN(2,6-Me2C6H3)}]. Reactions of the chloro–ethyl [Zr(CpSi2Cp)EtCl] and alkynyl-ethyl [Zr(CpSi2Cp)Et(CꢂCPh)] complexes
with the Lewis acid B(C6F5)3 yielding various cationic species have been monitored by 1H-NMR spectroscopy. The new complexes
1
reported and their intermediates have been identified by IR and H- and 13C-NMR spectroscopy. © 2000 Elsevier Science S.A.
All rights reserved.
Keywords: Zirconium; Alkenyl; Alkynyl; Alkylzirconacycles
Dicyclopentadienyl–zirconacyclopentane compounds
have been prepared by reaction of different alkenes
1. Introduction
with ‘Cp2Zr(alkene)’ generated in situ [6] and by alkyla-
Bridged dicyclopentadienyl Group 4 metal complexes
tion of Cp2ZrCl2 with 1,4-dilithiobutane and
are particularly interesting systems, used extensively as
BrMg(CH2)4MgBr [7]. These reactive compounds read-
active and stereoselective catalysts for olefin polymer-
ily undergo reductive decoupling reactions by CbꢁCb%
ization processes [1]. Their activity is increased [2] when
bond cleavage in the presence of phosphine ligands to
silyl-substituted rings are used, and for this reason
give the zirconium(II) species Cp2Zr(CH2ꢀCH2)L [7a]
many studies on the synthesis and reactivity of ansa
and react with different alkenes and alkynes to give new
metallocenes of Group 4 metals with one [3] or two [4]
zirconacyclopentane, -pentene and -pentadiene com-
dimethylsilyl bridges have been reported in recent years.
plexes [6] which have been studied particularly as
Most of the studies concerning applications in olefin
stereoselective reagents for many catalytic [6,8] and
polymerization have focused on alkyl derivatives with-
stoichiometric carbon–carbon bond-forming reactions
out b-hydrogen-containing alkyl groups, because of
[9].
their higher stability. We recently reported [5] the syn-
thesis and structure of b-hydrogen containing alkyl
dicyclopentadienyl zirconium complexes and some as-
Vinyl derivatives are interesting and reactive species
which provide new synthetic pathways to many related
compounds. Divinyl species may rearrange to form
pects of their reactivity.
zirconacyclopent-1-enes through b-hydrogen elimina-
tion [10] and give butadiene derivatives [11,12] by CꢁC
coupling. The structure of such butadiene compounds
* Corresponding author. Tel.: +34-91-8854765; fax: +34-91-
8854683.
E-mail address: proyo@inorg.alcala.es (P. Royo)
has been extensively explored and their behaviour as
h4-diene or s2-p-zirconacyclopent-2-ene species with a
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00633-6

148
F.J. Ferna´ndez et al. / Journal of Organometallic Chemistry 593–594 (2000) 147–153
Scheme 1.
significant p-bonding contribution from the central
CꢁC double bond has been discussed [13,14]. Because
of its known higher stability, we chose the bis(dimethyl-
silanediyl)dicyclopentadienyl (CpSi2Cp) ligand to study
the behaviour of various mixed dialkyl zirconium com-
plexes, to attempt to isolate or characterize intermedi-
ates formed during their thermal decomposition by
NMR spectroscopy, and to characterize cationic species
generated from their reactions with strong Lewis acids,
such as B(C6F5)3.
Complex 1 was isolated as an extremely air and
moisture sensitive yellow solid. The H-NMR spectrum
1
of 1 showed two multiplets for the a- and b-CH2
groups and one ABB% spin system for two equivalent
C5H3 rings resulting from a fast interconversion of the
zirconacyclopentane. The 13C-NMR spectrum showed
two triplets at l 34.8 (1JCꢁH=124.1 Hz) and l 23.0
(1JCꢁH=125.5 Hz) typical for the sp3-carbons of the
zirconacyclic system and consistent with this
formulation.
When the 1H- and 13C-NMR spectra of 1 were
recorded in wet C6D6 the oxo-butyl complex
[Zr(CpSi2Cp)Bu]2(m-O), formed by hydrolytic opening
of the zirconacycle, was observed1. However this com-
pound could not be isolated because the reaction at a
preparative level gave an unresolvable mixture of reac-
tion products.
2. Results and discussion
2.1. Reactions with Mg(CHꢀCH2)Cl
We reported [5] the isolation and thermal transfor-
mation of the b-hydrogen containing zirconium diethyl
[Zr(CpSi2Cp)Et2] derivative of the di-ansa-dicyclopen-
tadienyl [1,1%,2,2%-(SiMe2)2(h5-C5H3)2]ꢀ[CpSi2Cp] lig-
and. This transformation proceeds via activation of the
carbon bonded b-hydrogen with elimination of ethane
to give the ethylene bridged zirconium complex
[Zr(CpSi2Cp)Et]2(m-CH2ꢀCH2). Hydrogen elimination
from sp2 carbon centres is less favourable and therefore
the use of mixed ethyl and alkenyl compounds opens
new reaction pathways. When a THF solution of the
chloro–ethyl complex [Zr(CpSi2Cp)ClEt] reacted with
Mg(CHꢀCH2)Cl the expected mixed alkyl–alkenyl
complex was not observed even at −78°C, and the
The di-olefin character of complex 1 (see Scheme 1)
was demonstrated from its reaction in toluene with
PhCꢂCPh, which displaces the olefin to give the more
stable zirconacyclopentadiene derivative [Zr(CpSi2Cp)-
{h2-(CPhꢀCPhꢁCPhꢀCPh)}] (2). The formation of the
zirconacyclopentene [Zr(CpSi2Cp){h2-(CPhꢀCPhꢁCH2ꢁ
1
CH2)}] intermediate was observed by H-NMR spec-
troscopy as a minor component in a sample of the
solution taken after refluxing for 2 h. Complex 2 was
isolated, after refluxing for 15 h, as a crystalline yellow
solid and characterized by elemental analysis and NMR
spectroscopy (see Section 4).
zirconacyclopentane
derivative
[Zr(CpSi2Cp){h2-
(CH2)4}] (1) was immediately and quantitatively formed
(see Scheme 1). Formation of 1 can be explained as
resulting from a concerted ethyl b-hydrogen transfer to
the a-carbon of the vinyl group located in a plane
perpendicular to the equatorial metallocene plane to
give the bis-ethylene complex, followed by oxidative
coupling to afford the final zirconacyclopentane
complex.
1 NMR spectra of the major component observed when solutions
of 1 were recorded in wet C6D6. 1H-NMR (C6D6, 300 MHz, d ppm):
d 6.78 (m, 4H, C5H3), 6.51 (m, 4H, C5H3), 6.09 (m, 4H, C5H3), 1.82,
1.16, 1.20, 0.89 (4m, 9H, Bu), 0.76 (s, 6H, SiMe2), 0.60 (s, 6H,
SiMe2), 0.52 (s, 6H, SiMe2), 0.27 (s, 6H, SiMe2). 13C-NMR (C6D6, 75
MHz, d ppm): d 132.0 (C5H3), 129.8 (C5H3), 120.4 (C5H3 Cipso), 111.7
(C5H3 Cipso), 109.8 (C5H3), 42.0 (Ca, Bu), 37.6 (Cb, Bu), 30.9 (Cg,
Bu), 14.4 (Cd, Bu), 2.7 (SiMe2), 2.4 (SiMe2), −2.7 (SiMe2), −4.7
(SiMe2).

F.J. Ferna´ndez et al. / Journal of Organometallic Chemistry 593–594 (2000) 147–153
149
The reaction of [Zr(CpSi2Cp)Cl2] [4b] with two
narrow CpꢁMꢁCp angles (ca. 119°, average from six
Zr(CpSi2Cp) structures) [14]. This formulation is con-
sistent with the 13C-NMR spectrum, which shows six
resonances for the ring carbons, two resonances for the
Ca and Cb of the butene ligand and two resonances for
the silicon–methyl groups.
equivalents of Mg(CHꢀCH2)Cl in a sealed tube was
1
monitored by H-NMR spectroscopy in THF-d8. No
reaction was observed at −78°C but the divinyl com-
plex [Zr(CpSi2Cp)(CHꢀCH2)2}] was quantitatively
formed after 5 min at −50°C, as evidenced by the
1H-NMR spectrum of this solution which showed two
singlets for the exo and endo silicon–methyl groups, the
expected ABB% spin system for the cyclopentadienyl
ring protons, and an ABX spin system for both equiva-
2.2. Reaction with LiCꢂCPh
Reaction
of
the
chloro–ethyl
complex
3
2
lent vinyl groups (3Jtrans=21.2, Jcis=15.4 and J=2.6
Hz). The 13C{1H} spectrum showed the Ca signal at l
184.7 (see Section 4). This divinyl complex was further
transformed when the solution was heated to −10°C
and after 30 min at room temperature (r.t.) gave the
(h4-butadiene) zirconium complex [Zr(CpSi2Cp){h4-
(butadiene)}] (3) in 30% yield, together with a mixture
of unidentified products. This is the transformation
expected for reductive elimination [12], although the
presence of other reaction products reveals that this is
[Zr(CpSi2Cp)EtCl] with one equivalent of LiCꢂCPh in
THF afforded the mixed alkyl–alkynyl complex
[Zr(CpSi2Cp)Et(CꢂCPh)] (4), which was isolated as a
crystalline yellow solid in 60% yield after recrystalliza-
tion from pentane. b-Hydrogen elimination was not
observed in a THF solution at r.t. and complex 4 was
stable for short periods under these conditions. The
w(CꢂC) IR absorption at 2078 cm−1 and characteristic
resonances in its 1H-NMR spectrum confirmed the
presence of phenylalkynyl and ethyl ligands located in
the equatorial plane, making the four silicon–methyl
groups inequivalent, whereas an ABC spin system was
observed for two equivalent cyclopentadienyl rings.
This formulation is also consistent with the 13C-NMR
data (see Section 4).
Complex 4 reacted in toluene with one equivalent of
CN(2,6-Me2C6H3) which selectively inserted into the
zirconium–ethyl bond to give the iminoacyl complex
[Zr(CpSi2Cp)(CꢂCPh){h2-C(Et)ꢀN(2,6-Me2C6H3}] (5)
(Scheme 3) , isolated as a white solid in 90% yield. The
IR w(CꢂC) and w(CꢀN) absorptions were observed at
1
not a selective reaction. The r.t. H-NMR spectrum of
complex 3 shows inequivalent cyclopentadienyl rings
due to a high energy barrier for the transformation
shown in Scheme 2 and three multiplets for the 1,4-s-
h2-2-butene ligand, one of them clearly shifted to high
field (l −0.80) corresponding to the butadiene Hanti
protons. This behaviour is consistent with the pro-
nounced s2,p-metallacyclopentene character reported
for related compounds. The high inversion barrier has
been related to the stronger bonding of the butadiene
internal carbon atoms for metallocenes which have
Scheme 2.
Scheme 3.

150
F.J. Ferna´ndez et al. / Journal of Organometallic Chemistry 593–594 (2000) 147–153
Table 1
1H- and 13C-NMR data for the ring CꢁH and SiꢁMe groups of intermediate species observed in the reactions of [Zr(CpSi2Cp)EtX] (X=Cl,
CꢂCPh) with B(C6F5)3 in a 1:1 molar ratio (CD2Cl2, 500 MHz, l ppm)
Complex
C5H3
C5H3
SiꢁCH3
SiꢁCH3
2.0; 1.9
1.5; 1.3
−3.4; −3.5
−5.3; −5.4
[Zr(CpSi2Cp)Cl(m-Cl)
7.01 (m, 2H)
6.92 (m, 2H)
6.61 (m, 2H)
6.56 (m, 4H)
6.50 (m, 2H)
141.8, 141.0
134.8; 132.6
120.8 (ipso); 118.1 (ipso)
117.6; 116.6 (ipso)
115.4; 111.5 (ipso)
0.99 (s, 3H); 0.97 (s, 3H)
0.82 (s, 3H); 0.77 (s, 3H)
0.76 (s, 3H); 0.42 (s, 3H)
0.40 (s, 3H); 0.26 (s, 3H)
Zr(CpSi2Cp)Et]+
[Zr(CpSi2Cp)Cl(m-Cl)
7.01 (m, 4H)
6.71 (m, 4H)
6.63 (m, 4H)
135.3; 134.8
132.7; 116.9 (ipso)
110.9 (ipso)
1.02 (s, 6H); 0.99 (s, 6H)
0.45 (s, 6H); 0.43 (s, 6H)
1.7; 1.6
−4.5; −4.6
Zr(CpSi2Cp)Cl]+
[{Zr(CpSi2Cp)(CꢂCPh)}2
(m-Et)]+
6.65 (m, 4H)
6.57 (m, 4H)
5.77 (m, 4H)
0.94 (s, 6H); 0.84 (s, 6H)
0.77 (s, 6H); −0.14 (s, 6H)
1
2086 and 1592 cm−1, respectively. The H-NMR spec-
trum of 5 showed the expected ABC spin system for
two equivalent cyclopentadienyl rings, four singlets for
the silicon-bonded methyl groups and characteristic
resonances for the aryl and ethyl groups. The character-
istic resonance due to the h2-iminoacyl carbon was
observed in the 13C{1H}-NMR spectrum at l 241.0 [15]
(see Section 4).
presence of 1/2 equivalent excess of B(C6F5)3. The
presence of the zirconium-bound ethyl group was confi-
rmed by the observation of an A2B3 spin system in the
1H spectrum (l 1.09 t, 3H, J=7.5 Hz) and two signals
at l 16.2 and l 61.5 in the 13C-NMR spectrum.
When the temperature was raised to −10°C for 30
min the 1H- and 13C-NMR spectra of the resulting
solution showed three proton and five carbon reso-
nances corresponding to one ABC spin system due to
four equivalent C5H3 rings, and four proton and car-
bon singlets for the silicon-bound methyl groups of a
dinuclear cation which does not contain ethyl groups.
This behaviour is consistent with the presence of
[Zr(CpSi2Cp)Cl(m-Cl)Zr(CpSi2Cp)Cl]+ formed by the
irreversible reaction of the previous cation with the
chlorinated CD2Cl2 solvent [17].
This cationic species exhibited reversible dynamic
behaviour between −70 and 20°C, consistent with an
anti–syn transformation through a transition state
formed by three chlorine bridges and characterized by
DG‡263 K=13 kcal mol−1 at coalescence temperature
(see Scheme 4). Finally a quantitative transformation
led to the dichloro complex [Zr(CpSi2Cp)Cl2] when the
solution was heated to r.t. for 24 h.
2.3. Reactions with B(C6F5)3
All the reactions with B(C6F5)3, carried out in
CD2Cl2 solutions in sealed NMR tubes and monitored
by 1H-NMR spectroscopy, finally gave the neutral
dichloro complex [Zr(CpSi2Cp)Cl2] resulting from chlo-
rination by the CD2Cl2 solvent. Formation of different
1
intermediate cationic species was detected from the H-
and 13C-NMR spectra recorded at different
temperatures.
Addition of B(C6F5)3 to a CD2Cl2 solution of the
chloro–ethyl complex [Zr(CpSi2Cp)ClEt] at −78°C in
a 1:1 molar ratio caused the ethyl group to be elimi-
nated to give the free anion [B(C6F5)3Et]−, as evidenced
by its H-, 13C- and 19F-NMR spectra [16]. The inter-
1
mediate 14-electron cationic species [Zr(CpSi2Cp)Cl]+
initially formed was not observed and the solution
remained reversibly unaltered between −70 and −
10°C. As shown in Table 1 the 1H- and 13C-NMR
spectra showed six ring-proton (two overlapping) and
ten ring-carbon resonances due to two ABC spin sys-
tems for the C5H3 rings and eight proton and carbon
resonances for the silicon-bound methyl groups. This
behaviour is consistent with the presence of a dinuclear
cation containing two bridged non-equivalent metal
fragments, as expected for the m-chloro bridged dinu-
clear species [Zr(CpSi2Cp)Cl(m-Cl)Zr(CpSi2Cp)Et]+,
formed by coordination of one molecule of the starting
chloro–ethyl complex to the initially generated chloro
zirconium cation, which remained unaltered even in the
A similar study was carried out adding one equiva-
lent of B(C6F5)3 to one equivalent of the ethyl alkynyl
complex [Zr(CpSi2Cp)Et(CꢂCPh)] (4) at −78°C in
CD2Cl2. Formation of the [B(C6F5)3Et]− borate anion
was also observed along with a series of different
1
cationic complexes (Scheme 4). The H-NMR spectrum
at −50°C showed one multiplet at l −1.65 (2H)
corresponding to a CH2ꢁCH3 bridging group, an ABC
spin system for four equivalent C5H3 rings and four
singlets for the methyl–silicon protons (see Table 1).
This is consistent with the presence of the cationic
dimer [{Zr(CpSi2Cp)(CꢂCPh}2(m-CH2CH3)]+. Between
−50 and −20°C a mixture of compounds was ob-
served, which after 1 h at −20°C contained two major
components which could not be identified. A slow

F.J. Ferna´ndez et al. / Journal of Organometallic Chemistry 593–594 (2000) 147–153
151
Scheme 4.
transformation took place finally when the solution was
heated at r.t. for more than 24 h to give the dichloro
derivative [Zr(CpSi2Cp)Cl2].
oxygenated agents: tetrahydrofuran (sodium/benzo-
phenone), toluene (sodium) and hexane (sodium/potas-
sium alloy). [Zr(CpSi2Cp)Cl(CH2ꢁCH3)] [5], [Zr(Cp-
Si2Cp)Cl2] [4b] and B(C6F5)3 [18] were prepared
according to literature procedures. Mg(CHꢀCH2)Cl
(Aldrich), PhCꢂCPh (Aldrich), HCꢂCPh (Aldrich),
were purchased from commercial sources and used
3. Conclusions
1
Easy b-hydrogen elimination from the ethyl group of
[Zr(CpSi2Cp)EtCl] when it is vinylated is an appropri-
ate method to synthesize the zirconacyclopentane
derivative and the related zirconacyclopentadiene from
its reaction with phenylacetylene. In contrast, the
alkynyl compound [Zr(CpSi2Cp)Et(CꢂCPh)] is ther-
mally stable and can insert isocyanide into its Zrꢁethyl
bond. Thermal transformation of the divinyl derivative
[Zr(CpSi2Cp)(CHꢀCH2)2], which can be isolated in so-
lution between −50 and −10°C, leads to the corre-
sponding (h4-butadiene) zirconium complex [Zr(Cp-
Si2Cp){h4-(butadiene)}]. Reactions of the chloro–ethyl
and alkynyl–ethyl compounds with B(C6F5)3 in sealed
NMR tubes allow new dinuclear cationic species to be
identified.
without further purification. H- and 13C-NMR spectra
were recorded on Unity-300 and Unity 500 Plus spec-
1
trometers. H and 13C chemical shifts are reported in l
units measured with respect to the solvent signals. Mass
spectra were recorded on a Hewlett–Packard 5890
spectrometer. Elemental C and H analyses were per-
formed with a Perkin–Elmer 240B microanalyzer.
4.2. [Zr{(p5-C5H3)2[Si(CH3)2]2}-
{p2-[CH2ꢁ(CH2)2ꢁCH2]}] (1)
A 1 M THF solution of Mg(CHꢀCH2)Cl (2.51 ml,
2.51 mmol) was added to a toluene solution (25 ml) of
[Zr(CpSi2Cp)(CH2ꢁCH3)Cl] (1.00 g, 2.51 mmol) at 0°C.
The mixture was stirred for 2 h to give a red solution
which after the solvent was removed and the residue
extracted into hexane afforded complex 1, as a yellow
solid. Yield, 0.79 g, 80%. Anal. Calc. for C18H26Si2Zr:
C, 55.46; H, 6.72. Found: C, 54.92; H, 6.40%. 1H-NMR
(C6D6, 500 MHz): l 6.64 (d, 4H, C5H3), 6.60 (t, 2H,
C5H3), 1.80 (m, 4H, ꢁCH2ꢁCH2), 1.10 (m, 4H,
ZrꢁCH2), 0.47 (s, 6H, SiMe2), −0.05 (s, 6H, SiMe2);
13C-NMR (C6D6, 125 MHz): l 128.4 (C5H3), 114.9
(C5H3), 110.9 (C5H3 Cipso), 34.8 (t, 1JCH=124.1 Hz,
ZrꢁCH2ꢁ), 23.0 (t, 1JCH=125.5 Hz, CH2ꢁCH2), 2.0
(SiMe2), −4.1 (SiMe2).
4. Experimental
4.1. General
All operations were performed under an inert atmo-
sphere of argon using Schlenk and vacuum-line tech-
niques or a VAC glovebox Model HE-63-P. The
,
following solvents were pre-dried by standing over 4 A
molecular sieves and purified by distillation under ar-
gon before use by employing the appropriate drying/de-

152
F.J. Ferna´ndez et al. / Journal of Organometallic Chemistry 593–594 (2000) 147–153
4.3. [Zr{(p5-C5H3)2[Si(CH3)2]2-
{p2(CPhꢀCPhꢁCPhꢀCPh)}] (2)
(SiMe2), −4.1 (SiMe2). After 30 min at 20°C, reso-
nances of complex 3 started to appear and after 12 h at
r.t. complex 3 was the major component in the solution,
together with other unidentified complexes.
A THF solution of 1 prepared as described above
from Mg(CHꢀCH2)Cl (2.51 ml, 2.51 mmol) and
[Zr(CpSi2Cp)(CH2ꢁCH3)Cl] (0.99 g, 2.49 mmol) was
evaporated and the residue was treated with a toluene
solution (30 ml) of PhCꢂCPh (0.89 g, 5.20 mmol) and
4.4.2. Preparati6e scale
A 1 M THF solution of Mg(CHꢀCH2)Cl (5 ml, 5
mmol) was added to a toluene solution (50 ml) of
[Zr(CpSi2Cp)Cl2] (1.00 g, 2.47 mmol) at r.t. and stirred
for 12 h to give a red–brown solution. The solution was
filtered and the solvent was removed under vacuum to
give a red oil. Recrystallization from hexane afforded
the zirconacyclo-3-pentene complex [Zr(Cp-Si2Cp){h2-
(CH2ꢁCHꢀCHꢁCH2)}] (3) as a red solid. Yield 0.29 g,
30%. Anal. Calc. for C18H24Si2Zr: C, 55.75; H, 6.24.
1
then refluxed for 2 h. The H-NMR spectrum of this
solution showed that the intermediate complex
[Zr(CpSi2Cp){h2-(PhCꢀCPhꢁCH2ꢁCH2)}] was present
1
as a minor component. H-NMR (C6D6, 300 MHz, l
ppm): l 7.10–6.80 (m, 10H, C6H5 and 2H, C5H3), 6.72
(m, 2H, C5H3), 6.47 (m, 2H, C5H3), 2.98 (t, 2H, JHH
=
6.6 Hz, ꢁCH2ꢁCH2ꢁ), 1.47 (t, 2H, JHH=6.6 Hz,
ZrꢁCH2ꢁ), 0.52 (s, 3H, SiMe2), 0.45 (s, 3H, SiMe2), 0.01
(s, 3H, SiMe2), −0.40 (s, 3H, SiMe2). After refluxing
for 15 h the solution was filtered and the solvent was
removed under vacuum. The solid residue was washed
with hexane (15 ml), to give a yellow solid which was
characterized by NMR spectroscopy and elemental
analysis as compound 2. Yield 1.03 g, 60%. Anal. Calc.
for C42H38Si2Zr: C, 73.09; H, 5.55. Found: C, 73.42; H,
5.68%. Mass spectrum (EI): m/z 689 [M+, 2.7], 511
[M+−PhCꢂCPh, 2], 333 [M+−2PhCꢂCPh, 64.7], 178
1
Found: C, 55.54; H, 6.31%. H-NMR (C6D6, 300 MHz,
l ppm): l 6.52 (d, 2H, C5H3), 5.25 (d, 2H, C5H3), 5.05
(t, 1H, C5H3), 4.64 (m, 2H, ꢁCHꢀ), 4.14 (t, 1H, C5H3),
3.28 (m, 2H, ꢁCH2-syn), 0.71 (s, 6H, SiMe2), 0.42 (s,
6H, SiMe2), −0.80 (m, 2H, ꢁCH2-anti ). 13C-NMR
(C6D6, 125 MHz, l ppm): l 129.8 (C5H3 Cipso), 126.7
(C5H3 Cipso), 124.1 (C5H3), 112.5 (C5H3), 110.7 (ꢁCHꢀ),
110.1 (C5H3), 102.4 (C5H3), 49.8 (dd, 1JCH=158.7,
1JCH=132.0 Hz, ꢁCH2ꢁ), 2.2 (SiMe2), −3.1 (SiMe2).
1
[PhCꢂCPh, 100]. H-NMR (C6D6, 300 MHz, l ppm): l
4.5. [Zr{(p5-C5H3)2[Si(CH3)2]2}(CꢂCPh)(CH2ꢁCH3)]
(4)
7.10–7.04 (m, 6H, C6H5), 6.96 (t, 2H, C5H3), 6.90–6.82
(m, 8H, C6H5), 6.77–6.74 (m, 4H, C6H5), 6.80 (d, 4H,
C5H3), 6.60–6.55 (m, 2H, C6H5), 0.48 (s, 6H, SiMe2),
−0.36 (s, 6H, SiMe2); 13C-NMR (C6D6, 75 MHz, l
ppm): l 193.2 (ZrꢁCPhꢀ), 150.7 (PhCꢀCPh), 141.9
(C6H5 Cipso), 132.4, 130.2, 126.8, 124.9, 123.1 (C6H5),
135.5 (C5H3 Cipso), 127.9 (C5H3), 116.5 (C5H3), 2.60
(SiMe2), −5.06 (SiMe2).
A THF (25 ml) solution of LiCꢂCPh (0.11 g, 1.00
mmol) was added to a THF solution (25 ml) of
[Zr(CpSi2Cp)Cl(CH2CH3)] (0.40 g, 1.00 mmol) at 0°C.
The mixture was stirred for 3 h to give a dark red
solution, the solvent was removed in vacuo and the
residue was extracted into hexane to give complex 4,
which was recrystallized from pentane as yellow crys-
tals. Yield 0.30 g, 64%. Anal. Calc. for C24H28Si2Zr: C,
62.14; H, 6.08. Found: C, 61.87; H, 6.01%. IR: (Nujol)
2078 cm−1 [w(CꢂC)]. 1H-NMR (C6D6, 300 MHz, l
ppm): l 7.53 (m, 2H, C6H5), 7.18 (m, 2H, C5H3),
6.96–7.01 (m, 3H, C6H5), 6.51 (m, 2H, C5H3), 6.32 (m,
4.4. Reaction of [Zr{(p5-C5H3)2[Si(CH3)2]2}Cl2] with
two equi6alents of Mg(CHꢀCH2)Cl
4.4.1. NMR tube scale
An NMR tube containing
a mixture of the
3
dichlorozirconocene (0.05 g, 0.12 mmol) and a 1 M
THF solution of Mg(CHꢀCH2)Cl (0.24 ml) in 0.75 ml of
THF-d8 was sealed under vacuum at −78°C. The
reaction was monitored by 1H- and 13C-NMR spec-
troscopy. After 5 min at −50°C all of the starting
complex had been transformed into [Zr(CpSi2Cp)-
(CHꢀCH2)2], which was the only organometallic com-
pound present in the solution (NMR yield, ca. 100%).
1H-NMR (THF-d8, −50°C, 500 MHz, l ppm): l 7.47
(dd, 2H, 3Jtrans=21.2, 3Jcis=15.4 Hz, ZrꢁCHꢀ), 6.43 (d,
4H, J=2.8 Hz, C5H3), 6.22 (t, 2H, J=2.8 Hz, C5H3),
5.87 (dd, 2H, 3Jcis=15.4, 2J=2.6 Hz, ꢀCH2ꢁ), 5.35 (dd,
2H, 3Jtrans=21.2, 2J=2.6 Hz, ꢀCH2), 0.65 (s, 6H,
SiMe2), 0.37 (s, 6H, SiMe2). 13C-NMR (THF-d8, −
50°C, 125 MHz, l ppm): l 184.7 (ꢁCHꢀ), 131.5 (C5H3),
126.8 (ꢀCH2), 113.6 (C5H3), 110.1 (C5H3 Cipso), 2.4
2H, C5H3), 1.33 (t, 3H, JHH=8 Hz, ꢁCH2ꢁCH3), 0.72
3
(q, 2H, JHH=8 Hz, ꢁCH2ꢁCH3), 0.54 (s, 3H, SiMe2),
0.51 (s, 3H, SiMe2), 0.50 (s, 3H, SiMe2), 0.12 (s, 3H,
SiMe2). 13C-NMR (C6D6, 75 MHz, l ppm): l 135.6
(ZrꢁCꢂ), 131.5 (C5H3), 129.2 (C5H3), 127.1 (C6H5),
126.0 (C6H5), 119.0 (ꢂCPh), 113.1 (C5H3), 111.8 (C5H3
Cipso), 109.2 (C5H3 Cipso), 49.5 (t, JCH=115.5 Hz,
CH2ꢁCH3), 13.1 (q, JCH=123.2 Hz, CH2ꢁCH3), 2.42
(SiMe2), 2.40 (SiMe2), −3.72 (SiMe2), −3.62 (SiMe2).
4.6. [Zr{(p5-C5H3)2[Si(CH3)2]2}(CꢂCPh){p2-
[C(Et)N[2,6-(CH3)2C6H3]]}] (5)
A toluene (25 ml) solution of 2,6-dimethylphenyliso-
cyanide (0.25 g, 1.90 mmol) was added to a toluene (25
ml) solution of [Zr(CpSi2Cp)Et(CꢂCPh)] (4) (0.90 g,

F.J. Ferna´ndez et al. / Journal of Organometallic Chemistry 593–594 (2000) 147–153
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1.90 mmol) at 20°C. The mixture was stirred for 12 h to
give a red dark solution. Solvent was removed in vacuo
and the residue extracted into hexane to yield complex
5 after evaporation. Yield 1.02 g, 90%. Anal. Calc. for
C33H37NSi2Zr: C, 66.61; H, 6.27; N, 2.35. Found: C,
66.42; H, 6.04; N, 2.34%. IR: (Nujol) 2086 [w(CꢂC)],
1592 cm−1 [w(CꢀN)]. 1H-NMR (C6D6, 300 MHz, l
ppm): l 7.50 (m, 2H, C6H5), 7.30 (m, 2H, C6H5), 7.05
(t, 1H, C6H5), 6.94 (m, 3H, Me2C6H3), 6.90 (m, 2H,
C5H3), 6.59 (m, 2H, C5H3), 5.36 (m, 2H, C5H3), 2.40 (q,
2H, JHH=7.5 Hz, ꢁCH2ꢁCH3), 1.84 (s, 6H, Me2C6H3),
1.11 (s, 3H, SiMe2), 0.73 (t, 3H, JHH=7.5 Hz,
ꢁCH2ꢁCH3), 0.72 (s, 3H, SiMe2), 0.69 (s, 3H, SiMe2), l
0.56 (s, 3H, SiMe2). 13C-NMR (C6D6, 75 MHz, l ppm):
l 241.0 (CꢀN), 145.0 (ZrꢁCꢂ), 134.8 (C5H3), 131.4 (Ph),
129.4 (Ph), 125.6 (Ph), 125.3 (Ph), 122.1 (C5H3), 118.0
(ꢂCPh), 109.4 (C5H3 Cipso), 107.8 (C5H3), 107.3 (C5H3
Cipso), 31.7 (t, JCH=123.8 Hz, CH2ꢁCH3), 19.0 (q,
JCH=125.7 Hz, Me2C6H3), 10.1 (q, JCH=127.5 Hz,
CH2ꢁCH3), 3.2 (SiMe2), 3.1 (SiMe2), −3.50 (SiMe2),
−3.9 (SiMe2).
4.7. Reaction of
[Zr{(p5-C5H3)2[Si(CH3)2]2}(CH2CH3)Cl] with B(C6F5)3
An NMR tube containing a mixture of the zirconium
complex (0.05 g, 0.12 mmol) and B(C6F5)3 (0.065 g,
0.12 mmol) in 0.75 ml of CD2Cl2 was sealed under
vacuum at −78°C and the reaction was monitored by
1H- and 13C-NMR spectroscopy.
4.8. Reaction of [Zr{(p5-C5H3)2[Si(CH3)2]2}Et(CꢂCPh)]
(4) with B(C6F5)3
An NMR tube containing a mixture of complex 4
(0.04 g, 0.08 mmol) and B(C6F5)3 (0.041 g, 0.08 mmol)
in 0.75 ml of CD2Cl2 was sealed under vacuum at
−78°C. The reaction was monitored by 1H-NMR
spectroscopy.
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Acknowledgements
Support from DGESEIC (Project PB-97-0776) is
gratefully acknowledged. F.J.F. acknowledges MEC-
FPI for the award of Fellowship.
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