Synthesis and reactivity of [(amidosilyl)cyclopentadienyl]titanium and -zirconium complexes. X-ray molecular structure of [Zr{η5:η1-C5H4SiMe 2(μ-O)}Cl2{H2N(CHMe)Ph}]2

Article abstract of DOI:10.1021/om960606p

New half-sandwich (amidosilyl)cyclopentadienyl complexes of titanium(IV) and zirconium-(IV) were synthesized from the chlorosilyl-substituted cyclopentadienyl precursors [M(η⁵-C₅H₄SiMe₂Cl)Cl ₃] (M = Ti (1a), Zr (1b)). The reaction of [Ti(η⁵-C₅H₄SiMe₂Cl)Cl ₃] (1a) with LiNHR in the presence of NEt₃ gives the [Ti(η⁵:η¹-C₅H₄SiMe ₂NR)Cl₂] (R = ^tBu (2a), (±)-CH(Me)Ph (3a)) complexes. Similarly, the addition of 2 equiv of LiN(SiMe₃)₂ to complex 1a affords the diamido derivative [Ti(η⁵-C₅H₄SiMe ₂Cl)Cl{N(SiMe₃)₂}₂] (4a). The amidotitanium complex [Ti(η⁵:η¹-C₅H₄SiMe ₂NH^tBu)Cl₂(NH^tBu)] (5a) is prepared, in low yield, by reacting 1a with NH₂^tBu in a 1:3 molar ratio. In this reaction, the presence of 2a is also detected. The same complexes 2a and 3a may also be obtained by reaction of the trichloro compound 1a with NH₂R and NEt₃ in a 1:1:2 molar ratio. The reaction of 2a with Tl(C₅H₅) gives the mixed-dicyclopentadienyl derivative [Ti(η⁵:η¹-C₅H₄SiMe ₂N^tBu)(η⁵-C₅H₅)Cl] (6a). The dialkyl derivatives [Ti(η⁵:η¹-C₅H₄SiMe ₂NR)R′₂] (R = ^tBu, R′ = CH₃ (7a), CH₂Ph (8a); R = CH(Me)-Ph, R′ = CH₃ (9a), CH₂Ph (10a)) have been isolated by reaction of 2 equiv of MgClMe or 1 equiv of Mg(CH₂Ph)₂·2THF with the dichlorides 2a and 3a. The analogous reaction of 2a with 1 equiv of MgCl(CH₂Ph) affords the chloro alkyl derivative [Ti(η⁵:η¹-C₅H₄SiMe ₂N^tBu)-(CH₂Ph)Cl] (11a). The reaction of complexes 2a and 3a with CO₂ leads to their conversion into the reported oxo derivative [Ti(μ-(η⁵:η¹-C₅H ₄SiMe₂O)}Cl₂]₂ with elimination of alkyl isocyanate O=C=NR (R = ^tBu, (±)-CH(Me)Ph) as the unique organic product. Addition of 1 equiv of LiN(SiMe₃)₂ to a diethyl ether solution of [Zr(η⁵:η¹-C₅H₄SiMe ₂Cl)Cl₃] (1b) gives the monoamido derivative [Zr(η⁵:η¹-C₅H₄SiMe ₂Cl)Cl₂{N(SiMe₃)₂}] (2b). The related reaction of the zirconium derivative 1b with LiNH^tBu in the presence of NEt₃ produces a mixture of two compounds, [Zr(η⁵:η¹-C₅H₄SiMe ₂N^tBu)Cl₂] (3b) and [Zr(η⁵-C₅H₄SiMe₂NH ^tBu)Cl₃(NEt₃)] (4b). Pure 3b can be isolated by recrystallization of this mixture, but attempts to isolate the pure compound 4b were unsuccessful. The analogous reaction of 1b with 1 equiv of LiNHCH-(Me)Ph in the presence of NEt₃ gives the related zirconium compound [Zr{η⁵:η¹-C₅H₄SiMe ₂-[NH(CHMe)Ph]}Cl₃(NEt₃)] (5b), which cannot be obtained as an analytically pure solid and is identified by ¹H NMR spectroscopy. When water-saturated toluene is used to prepare 5b, the oxo-zirconium derivative [Zr{η⁵:η¹-C₅H₄SiMe ₂(μ-O)}Cl₂{H₂N(CHMe)Ph}]₂ (6b) is obtained by slow precipitation. Compound 6b has been characterized by X-ray crystallography.

Full text of DOI:10.1021/om960606p

Organometallics 1996, 15, 5577-5585
5577
Syn th esis a n d Rea ctivity of
[(Am id osilyl)cyclop en ta d ien yl]tita n iu m a n d -zir con iu m
Com p lexes. X-r a y Molecu la r Str u ctu r e of
†
[Zr {η5:η1-C5H4SiMe2(µ-O)}Cl2{H2N(CHMe)P h }]2
Santiago Ciruelos, Toma´s Cuenca, Rafael Go´mez, Pilar Go´mez-Sal,‡
Antonio Manzanero,‡ and Pascual Royo*
Departamento de Quı´mica Inorga´nica, Universidad de Alcala´, Campus Universitario,
28871 Alcala´ de Henares, Spain
Received J uly 22, 1996X
New half-sandwich (amidosilyl)cyclopentadienyl complexes of titanium(IV) and zirconium-
(IV) were synthesized from the chlorosilyl-substituted cyclopentadienyl precursors [M(η5-
C5H4SiMe2Cl)Cl3] (M ) Ti (1a ), Zr (1b)). The reaction of [Ti(η5-C5H4SiMe2Cl)Cl3] (1a ) with
t
LiNHR in the presence of NEt3 gives the [Ti(η5:η1-C5H4SiMe2NR)Cl2] (R ) Bu (2a ), (()-
CH(Me)Ph (3a )) complexes. Similarly, the addition of 2 equiv of LiN(SiMe3)2 to complex 1a
affords the diamido derivative [Ti(η5-C5H4SiMe2Cl)Cl{N(SiMe3)2}2] (4a ). The amidotitanium
complex [Ti(η5:η1-C5H4SiMe2NHtBu)Cl2(NHtBu)] (5a ) is prepared, in low yield, by reacting
t
1a with NH2 Bu in a 1:3 molar ratio. In this reaction, the presence of 2a is also detected.
The same complexes 2a and 3a may also be obtained by reaction of the trichloro compound
1a with NH2R and NEt3 in a 1:1:2 molar ratio. The reaction of 2a with Tl(C5H5) gives the
mixed-dicyclopentadienyl derivative [Ti(η5:η1-C5H4SiMe2NtBu)(η5-C5H5)Cl] (6a ). The dialkyl
t
derivatives [Ti(η5:η1-C5H4SiMe2NR)R′2] (R ) Bu, R′ ) CH3 (7a ), CH2Ph (8a ); R ) CH(Me)-
Ph, R′ ) CH3 (9a ), CH2Ph (10a )) have been isolated by reaction of 2 equiv of MgClMe or 1
equiv of Mg(CH2Ph)2‚2THF with the dichlorides 2a and 3a . The analogous reaction of 2a
with 1 equiv of MgCl(CH2Ph) affords the chloro alkyl derivative [Ti(η5:η1-C5H4SiMe2NtBu)-
(CH2Ph)Cl] (11a ). The reaction of complexes 2a and 3a with CO2 leads to their conversion
into the reported oxo derivative [Ti{µ-(η5-C5H4SiMe2O)}Cl2]2 with elimination of alkyl
t
isocyanate OdCdNR (R ) Bu, (()-CH(Me)Ph) as the unique organic product. Addition of
1 equiv of LiN(SiMe3)2 to a diethyl ether solution of [Zr(η5-C5H4SiMe2Cl)Cl3] (1b) gives the
monoamido derivative [Zr(η5-C5H4SiMe2Cl)Cl2{N(SiMe3)2}] (2b). The related reaction of the
zirconium derivative 1b with LiNHtBu in the presence of NEt3 produces a mixture of two
compounds, [Zr(η5:η1-C5H4SiMe2NtBu)Cl2] (3b) and [Zr(η5-C5H4SiMe2NHtBu)Cl3(NEt3)] (4b).
Pure 3b can be isolated by recrystallization of this mixture, but attempts to isolate the pure
compound 4b were unsuccessful. The analogous reaction of 1b with 1 equiv of LiNHCH-
(Me)Ph in the presence of NEt3 gives the related zirconium compound [Zr{η5-C5H4SiMe2-
[NH(CHMe)Ph]}Cl3(NEt3)] (5b), which cannot be obtained as an analytically pure solid and
1
is identified by H NMR spectroscopy. When water-saturated toluene is used to prepare
5b, the oxo-zirconium derivative [Zr{η5:η1-C5H4SiMe2(µ-O)}Cl2{H2N(CHMe)Ph}]2 (6b) is
obtained by slow precipitation. Compound 6b has been characterized by X-ray crystal-
lography.
In tr od u ction
effects on the metal centers.2 In addition to the ansa
complexes particular efforts have been made to synthe-
size cyclopentadienyl rings with a pendant donor group
acting as a bidentate ligand bonded to the metal center,3
where one three-electron amido group occupies the site
of one of the cyclopentadienyl rings of the ansa complex.
The so-called half-sandwich metallocenes of constrained
geometry catalysts (CGC), as alternatives to Kaminsky
and Brintzinger type catalysts, are highly active sys-
tems producing R-olefin polymers and ethylene/R-olefin
copolymers with remarkable properties.4 While mono-
and dicyclopentadienyl type derivatives are easily ac-
cessible by various standard methods,5 constrained-
geometry complexes of group 4 transition metals have
Since the report of a new generation of group 4 bent
metallocenes containing bridged cyclopentadienyl ligands,
suitable as olefin polymerization catalysts to produce
high-density polyethylenes and isotactic and syndiotac-
tic polyolefins, there has been increasing interest in the
development of the chemistry of such ansa-metallocene-
based systems.1 Replacement of cyclopentadienyl ring
hydrogens by various substituents has been shown to
result in significant changes in both steric and electronic
† Dedicated to Professor Rafael Uso´n on the ocassion of his 70
birthday.
‡ X-ray diffraction studies.
X Abstract published in Advance ACS Abstracts, November 15, 1996.
(1) (a) Brintzinger, H. H.; Fisher, D.; Mu¨lhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (b)
Bochmann, M. J . Chem. Soc., Dalton Trans. 1996, 225.
(2) Mo¨hring, P. C.; Coville, N. J . J . Organomet. Chem. 1994, 479, 1.
(3) J utzi, P. J . Organomet. Chem. 1995, 500, 175 and references cited
therein.
S0276-7333(96)00606-1 CCC: $12.00 © 1996 American Chemical Society

5578 Organometallics, Vol. 15, No. 26, 1996
Ciruelos et al.
Sch em e 1
different behavior observed for the analogous zirconium
derivatives is also described. Interestingly, the methods
reported here allow the introduction of chiral fragments
into the amido group using titanium and zirconium as
metal centers and give rise to a potentially useful series
of C1-symmetrical complexes of group IV elements.9
Resu lts a n d Discu ssion
Tita n iu m Der iva tives. Reaction of [Ti(η5-C5H4-
SiMe2Cl)Cl3] (1a ) with LiNHR in the presence of NEt3
in a 1:1:1 molar ratio, in hexane at -60 °C, led to [Ti-
(η5:η1-C5H4SiMe2NR)Cl2] (R ) tBu (2a ), CH(Me)Ph
(3a )9e) compounds which contain the bidentate η1-
(amidosilyl)-η5-cyclopentadienyl ligand and which were
isolated as orange microcrystalline solids in about 70%
yield. In a similar reaction the addition of 1 or 2 equiv
of LiN(SiMe3)2 to [Ti(η5-C5H4SiMe2Cl)Cl3] (1a ) in hex-
ane at room temperature gives respectively the previ-
ously reported8 monoamido species and the new diamido
titanium compound with a (chlorodimethylsilyl)cyclo-
pentadienyl ring, [Ti(η5-C5H4SiMe2Cl)Cl{N(SiMe3)2}2]
(4a ), obtained as orange crystals in 66% yield (Scheme
2). The isolation of 4a suggests that both Ti-Cl bonds
are more reactive than the Si-Cl bond toward polar
LiNR2 reagents.
rarely been described.4,6 The strategies employed to
develop efficient synthetic procedures for such com-
pounds are based on a metathetical reaction using the
dilithium salt of the [(C5R4)SiMe2NR′]2- dianions (Scheme
1, method A) to afford the dichloro derivatives of the
type M[(C5R4)SiMe2NR′]Cl2 (M ) Ti, Zr, Hf)6c-f and the
reaction of homoleptic metal amides M(NR2)4 with the
bifunctional [(C5R4H)SiMe2NHR′] ligand via amine
elimination (Scheme 1, method B) to produce the
diamido M[(C5R4)SiMe2NR′](NR2)26g-k,7 (M ) Ti, Zr, Hf)
compounds almost quantitatively. Method A leads to
very poor yields6k with unsubstituted cyclopentadienyl
rings but seems to be a convenient method for substi-
tuted cyclopentadienyl ligands.6d-f Method B repre-
sents an excellent general synthetic method for the
diamido half-sandwich derivatives, but subsequent re-
actions with HCl or NEt3‚HCl are required to obtain
the corresponding dichlorides6h,k,7 and may lead to the
formation of mixtures or amine adducts where the
amine ligand, which makes them undesirable for cata-
lytic purposes, has to be removed by addition of Lewis
acids. Recently, Petersen and co-workers have used
SiMe3Cl as an alternative strategy to the protic re-
agents, providing a suitable quantitative route to the
dichloro complexes.6k
For this reason we propose that the reaction of 1a
with LiNHR (molar ratio 1:1) proceeds with the forma-
tion of the amidotitanium derivative [Ti(η5-C5H4SiMe2-
Cl)Cl2(NHR)] as an intermediate species, which is
further transformed by subsequent elimination of HCl
from the silicon-bonded chlorine in the presence of NEt3
with precipitation of NEt3‚HCl and formation of com-
pounds 2a and 3a . However, reactions with less polar
reagents such as water8 take place at both Si-Cl and
Ti-Cl bonds, which are simultaneously hydrolyzed.
Similar behavior is also observed in the reaction of 1a
with primary amines (NH2R), the final product depend-
ing on the nature of the amine used to neutralize the
HCl evolved in the aminolysis. In the first step the
aminolysis of the Si-Cl or Ti-Cl bond can take place
and compound 1a reacts with 1 equiv of NH2R to give
[Ti(η5-C5H4SiMe2NHR)Cl3] (A) or [Ti(η5-C5H4SiMe2Cl)-
Cl2NHR] (B) intermediate species (Scheme 3). In the
presence of NEt3, A and B are transformed via an
intramolecular elimination of HCl involving the second
chlorine atom from the Ti-Cl (A) or Si-Cl (B) bond,
with precipitation of Et3N‚HCl and formation of the
constrained derivatives 2a and 3a . When the amine in
In this paper, we report efficient synthetic routes to
constrained-geometry complexes of titanium from a
suitable chlorodimethylsilyl-substituted monocyclopen-
tadienyltitanium complex as starting material.8 The
(4) (a) Stevens, J . C.; Timmers, F. J .; Wilson, D. R.; Schmidt, G. F.;
Nickias, P. N.; Rose, R. K.; Kinight, G. W.; Lai, S. Eur. Pat. Appl. EP-
416-815-A2, 1991. (b) Canich, J . M. Eur. Pat. Appl. EP-420-436-A1,
1991. (c) Canich, J . M.; Hlatky, G. G.; Turner, H. W. U.S. Pat. Appl.
542-236, 1990.
t
excess is the primary amine NH2 Bu (1:3 molar ratio),
there is a competitive reaction pathway. Species A and
B may react in the same way, with precipitation of
tBuH2N‚HCl to give 2a , or alternatively, the Ti-Cl from
A or the Si-Cl from B may react with a second NH2-
(5) Comprehensive Organometallic Chemistry II; Wilkinson, G.,
Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, U.K., 1994.
(6) (a) Shapiro, P. J .; Bunel, E.; Schaefer, W. P.; Bercaw, J . E.
Organometallics 1990, 9, 867. (b) Shapiro, P. J .; Cotter, W. D.; Schaefer,
W. P.; Labinger, J . A.; Bercaw, J . E. J . Am. Chem. Soc. 1994, 116,
4623. (c) Bo¨hme, U.; Thiele, K. H. J . Organomet. Chem. 1994, 472, 39.
(d) Okuda, L.; Schattenmann, F. J .; Wocadlo, S.; Massa, W. Organo-
metallics 1995, 14, 789. (e) Plooy, K. E. D.; Moll, U.; Wocadlo, S.; Massa,
W.; Okuda, J . Organometallics 1995, 14, 3129. (f) Spence, R. E. v. H.;
Piers, W. E. Organometallics 1995, 14, 4617. (g) Hughes, A. K.;
Meetsma, A.; Teuben, J . H. Organometallics 1993, 12, 1936. (h)
Herrmann, W. A.; Morawietz, M. J . A. J . Organomet. Chem. 1994, 482,
169. (i) Herrmann, W. A.; Morawietz, M. J . A.; Priermeier, T. Angew.
Chem., Int. Ed. Engl. 1994, 33, 1946. (j) Herrmann, W. A.; Morawietz,
M. J . A.; Priermeier, T.; Mashima, K. J . Organomet. Chem. 1995, 486,
291. (k) Carpenetti, D. W.; Kloppenburg, L.; Kupec, J . T.; Petersen, J .
L. Organometallics 1996, 15, 1572.
t
tBu molecule, with precipitation of BuH2N‚HCl and
formation of 5a . In the latter case, the participation of
a second Ti-Cl bond cannot be ruled out and the final
product obtained is a mixture of 2a , 5a , and other
unidentified substances, from which only 5a can be
isolated in low yield (16%) after recrystallization from
toluene/hexane at -40° C.
(9) (a) Conticello, V. P.; Brard, L.; Giardello, M. A.; Tsuji, Y.; Sabat,
M.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc. 1992, 114, 2761. (b)
Giardello, M. A.; Eisen, M. S.; Stern, C. L.; Marks, T. J . J . Am. Chem.
Soc. 1993, 115, 3326. (c) Duthaler, R. O.; Hafner, A. Chem. Rev. 1992,
92, 807. (d) Halterman, R. L. Chem. Rev. 1992, 92, 965. (e) Enantio-
merically pure forms of 3a and the X-ray crystal structure of (S)-(-)-
3a have been simultaneously studied by J . Okuda (personal commu-
nication).
(7) Mu, Y.; Piers, W. E.; Macgillivray, L. R.; Zaworotko, M. J .
Polyhedron 1995, 14, 1.
(8) Ciruelos, S.; Cuenca, T.; Go´mez-Sal, P.; Manzanero, A.; Royo,
P. Organometallics 1995, 14, 177.

(Amidosilyl)cyclopentadienyl Complexes of Ti and Zr
Organometallics, Vol. 15, No. 26, 1996 5579
Sch em e 2
Sch em e 3
The results observed in these reactions allow us to
conclude that the Ti-Cl bonds in compound 1a react
selectively with LiNR2 or LiNHR, whereas the reactivity
of both Si-Cl and Ti-Cl bonds with NH2R is very
similar. Therefore, the selective aminolysis of either
bond is not possible, with similar behavior observed for
the reactions with water.8
The 1H NMR spectra of complexes 2a , 4a , 5a , 7a , and
8a show an AA′BB′ spin system (two resonances) for
the C5H4 ring protons and one singlet for the SiMe2
group, as expected from the symmetry of these com-
pounds.10 However, compounds 6a and 11a display a
chiral titanium center and complexes 3a , 9a , and 10a
have a chiral carbon atom at the alkylamido pendant
1
group in the molecule. For this reason, their H NMR
The spectroscopic and analytical data for the new
compounds reported in this paper are collected in the
Experimental Section and will not be discussed, except
where appropriate.
spectra show an ABCD spin system (four resonances)
for the C5H4 ring protons and two singlets for the
diastereotopic methylsilyl groups.11 This is also ob-
served in the 13C{1H} NMR spectra. Three different
resonances corresponding to the distal and proximal
Cipso carbon atoms of the cyclopentadienyl ring and one
resonance for the SiMe2 group are found for complexes
2a , 4a , 5a , 7a , and 8a , whereas the expected five
resonances are observed in complexes 3a , 6a , and 9a -
11a . The chemical shift of the cyclopentadienyl Cipso
atom is typically shifted upfield from the other C5H4
The reactions of 2a and 3a with alkylating agents
have been studied. Treatment of [Ti(η5:η1-C5H4SiMe2N-
tBu)Cl2] (2a ) with Tl(C5H5) in toluene at 100 °C gave
the mixed-dicyclopentadienyl derivative [Ti(η5:η1-C5H4-
SiMe2NtBu)(η5-C5H5)Cl] (6a ) as red crystals in 71%
yield. The addition of 1 equiv of Mg(CH2Ph)2‚2THF or
2 equiv of MgClMe to a cooled (-78 °C) hexane solution
of 2a and 3a led to the 14-electron dialkyltitanium
(10) Go´mez, R.; Cuenca, T.; Royo, P.; Hovestreydt, E. Organome-
tallics 1991, 10, 2516.
t
complexes [Ti(η5:η1-C5H4SiMe2NR)R′2] (R ) Bu, R′ )
CH3 (7a ), CH2Ph (8a ); R ) CHMePh, R′ ) CH3 (9a ),
CH2Ph (10a )), isolated as red or yellow crystals in high
yield. The reaction of [Ti(η5:η1-C5H4SiMe2NtBu)Cl2]
with 1 equiv of MgCl(CH2Ph) gave the chloro alkyl
derivative [Ti(η5:η1-C5H4SiMe2NtBu)(CH2Ph)Cl] (11a )
as a red solid in 42% yield (Scheme 4).
(11) (a) Moise, C.; Leblanc, J . C.; Tirouflet, J . J . Am. Chem. Soc.
1975, 97, 6272. (b) Dormont, A.; Moise, C.; Dahchour, A.; Tirouflet, J .
J . Organomet. Chem. 1979, 177, 181. (c) Cesarotti, E.; Kagan, H. B.;
Goddard, K.; Kru¨ger, C. J . Organomet. Chem. 1978, 162, 297. (d)
Mislowi, K.; Siegel, J . J . Am. Chem. Soc. 1984, 106, 3319. (e) Erker,
G.; Nolte, R.; Tsay, Y. H.; Kru¨ger, C. Angew. Chem., Int. Ed. Engl.
1989, 28, 628. (f) Herrmann, G. S.; Alt, H. G.; Rausch, M. D. J .
Organomet. Chem. 1991, 401, C5.

5580 Organometallics, Vol. 15, No. 26, 1996
Ciruelos et al.
Sch em e 4
Sch em e 5
ring carbon resonances and therefore is diagnostic of
the chelation of the appended amido group in these
constrained-geometry complexes. The only exception is
compound 6a , which shows the usual behavior observed
for most of the mononuclear ansa-metallocene dichlo-
rides of the type [M{(η5:η5-C5H4)2SiMe2}Cl2].12 In con-
trast, the opposite situation is observed in the 13C{1H}
NMR spectra of complexes without any constrained
geometry.8,13
Another important feature is that in compounds 7a -
10a the titanium atom is a prochiral center and, as we
have discussed above, compound 11a has a chiral ligand
arrangement around the titanium atom. These disposi-
tions imply diastereotopic NMR behavior for the CH2
protons of the benzyl group14,15 in complexes 8a and 11a ,
1
whose H NMR spectra show the presence of two sets
of doublets, whereas the diastereotopic CH2 protons of
the benzyl group in complex 10a appear as four dou-
blets, in accordance with the presence of one additional
chiral center in the molecule (N-C*H(Me)Ph). The
chemical shifts of the methylene carbons in the benzyl
complexes 8a , 10a , and 11a (see Experimental Section)
are indicative of a normal disposition of the benzyl
ligand in solution, although it is well-documented that
12-electron benzyl complexes of titanium are often
distorted in order to reduce their electronic unsaturation
through interactions of the benzyl ligand with the metal
center,16 whereas 16-electron dibenzylmetallocene com-
plexes adopt a η1-benzyl bonding mode due to both
electronic and steric factors.17 The NMR data suggest
that the constrained-geometry titanium benzyl com-
plexes are more similar to the corresponding dicyclo-
pentadienyl complexes than to the monocyclopentadi-
enyl titanium analogs. The IR spectrum of complex 5a
shows two bands at 3388 and 3306 cm-1, in accordance
with the two different N-H bonds present, and the mass
spectra of all new compounds agree with their mono-
meric formulations.
We have also studied the reactivity of complexes 2a
and 3a with CO2. It is well-known that carbonyl organic
compounds and various titanium complexes can ex-
change oxygen and methylene groups. This olefination
process involves the exchange reaction between a
[Ti]dCH2 unit and the CdO group to give [Ti]dO and
CdCH2.18 An analogous reaction may occur when the
isolobal [Ti]dNR unit reacts with a CdO unit in an
imination reaction affording [Ti]dO and the imine
derivative CdNR.19 Stephan and co-workers20 have
recently reported that terminal zirconium phosphinidine
complexes ZrCp2(PR)(PMe3) react with ketones or al-
dehydes to produce phosphaalkenes CdPR. Prelimi-
nary results show that constrained-geometry derivatives
of titanium containing a linked amidocyclopentadienyl
ligand can be effective reagents for similar reactions.
An NMR-scale reaction of [Ti(η5:η1-C5H4SiMe2NR)Cl2]
(12) (a) Bajgur, C. S.; Tikkanen, W. R.; Petersen, J . L. Inorg. Chem.
1985, 24, 2539. (b) Go´mez, R.; Cuenca, T.; Royo, P.; Herrmann, W. A.;
Herdtweck, E. J . Organomet. Chem. 1990, 382, 103.
(13) Cuenca, T.; Flores, J . C.; Go´mez, R.; Go´mez-Sal, P.; Parra-Hake,
M.; Royo, P. Inorg. Chem. 1993, 32, 3608.
(14) (a) Go´mez, R. Duchateau, R.; Chernega, A. N.; Meetsma, A.;
Edelmann, F. T.; Teuben, J . H.; Green, M. L. H. J . Chem. Soc., Dalton
Trans. 1995, 217. (b) Cuenca, T.; Flores, J . C.; Royo, P.; Larsonneur,
A. M.; Choukroun, R.; Dahan, F. Organometallics 1992, 11, 777.
(15) J ordan, R. F.; LaPointe, R. E.; Baenziger, N.; Hinch, G. D.
Organometallics 1990, 9, 1539.
(16) (a) Mena, M.; Pellinghelli, M. A.; Royo, P.; Serrano, R.;
Tiripicchio, A. J . Chem. Soc., Chem. Commun. 1986, 1118. (b) Alvaro,
L. M.; Cuenca, T.; Flores, J . C.; Royo, P.; Pellinghelli, M. A.; Tiripicchio,
A. Organometallics 1992, 11, 3301.
(R ) tBu (2a ), (()-CH(Me)Ph )3a )) with dry CO2 led to
8
the formation of [Ti{µ-(OSiMe2-η5-C5H4)}Cl2]2 as the
major organometallic compound and OdCdNR (R )
tBu, (()-CH(Me)Ph) as the unique organic product
(Scheme 5). The characterization of the isocyanate
products was confirmed by comparison with analytically
pure samples purchased from Aldrich. Analogous re-
(18) Hughes, D. L.; Payack, J . F.; Cai, D.; Verhoeven, T. R.; Reider,
P. Organometallics 1996, 15, 664.
(17) (a) Alelyunas, Y. W.; J ordan, R. F.; Echols, S. F.; Borkowsky,
S. L.; Bradley, P. K. Organometallics 1991, 10, 1406. (b) Crowther, D.
J .; Borkowsky, S. L.; Swenson, D.; Meyer, T. Y.; J ordan, R.F. Orga-
nometallics 1993, 12, 2897.
(19) Walsh, P. J .; Hollander, F. J .; Bergman, R. G. Organometallics
1993, 12, 3705.
(20) Breen, T. L.; Stephan, D. W. J . Am. Chem. Soc. 1995, 117,
11914.

(Amidosilyl)cyclopentadienyl Complexes of Ti and Zr
Organometallics, Vol. 15, No. 26, 1996 5581
Sch em e 6
sults have recently been reported by Petersen et al.,22a
showing the facile conversion of an appended zirconium
silylamido compound into a silyloxy derivative via
isocyanate elimination.
amount of NEt3‚HCl formed in the course of the reac-
tion, which is always less than expected for a stoichio-
metric reaction. Similar behavior of half-sandwich
zirconium complexes has been observed by other
authors.6g,7 The same behavior was observed when the
complex [Zr(η5-C5H4SiMe2Cl)Cl3] (1b) was treated with
1 equiv of the chiral lithium salt LiNHCH(Me)Ph in the
presence of NEt3, in toluene at -78 °C. After the
solution was warmed to room temperature, a yellow
solution was obtained, in which the adduct [Zr{η5-C5H4-
SiMe2[NH(CHMe)Ph]}Cl3(NEt3)] (5b) was identified by
1H NMR, although it could not be isolated as a pure
solid. The related compound analogous to 3b could not
be detected.
The procedure used to prepare 5b, but carried out
using water-saturated toluene, resulted in the slow
precipitation of the oxozirconium derivative [Zr{η5-C5H4-
SiMe2(µ-O)}Cl2{H2N(CHMe)Ph}]2 (6b) as white crystals
suitable for X-ray diffraction studies (Scheme 6).
The formation of 6b results from the hydrolysis of the
Si-N bond of 5b, with elimination of the amine NH2-
CH(Me)Ph coordinated to the metal, and the simulta-
neous hydrolysis of one Zr-Cl bond to give HCl,
eliminated as the corresponding ammonium salt NEt3‚-
HCl.
Zir con iu m Der iva tives. The zirconium trichloro
complex [Zr(η5-C5H4SiMe2Cl)Cl3] (1b) reacts with 1
equiv of LiN(SiMe3)2, at -78 °C, in a diethyl ether
solution to give, after the mixture was warmed to room
temperature, the monoamido derivative [Zr(η5-C5H4-
SiMe2Cl)Cl2{N(SiMe3)2}] (2b), isolated as pale yellow
crystals in 83% yield. The use of a more polar solvent
such as THF leads to the decomposition of 2b via SiMe3-
Cl elimination. Complex 2b is easily hydrolyzed and
thermally stable, although limited decomposition giving
unidentified products can be observed by heating above
80 °C. This selective reactivity of the Zr-Cl bond
toward the highly polar lithium amide is similar to that
observed for the titanium derivative 1a , although only
one chlorine can be substituted even when using an
excess of the amide. However, the reaction of [Zr(η5-
C5H4SiMe2Cl)Cl3] (1b) with 1 equiv of LiNHtBu in the
presence of NEt3 afforded a mixture of two compounds,
the previously reported [Zr(η5-C5H4SiMe2NtBu)Cl2] (3b)
containing the bidentate η1-(amidosilyl)-η5-cyclopenta-
dienyl ligand4a and the triethylamine adduct [Zr(η5-
C5H4SiMe2NHtBu)Cl3(NEt3)] (4b). Pure samples of 3b
could be isolated as white crystals in 15% yield by
recrystallization of this mixture from toluene at -40 °C,
but attempts to isolate pure 4b were unsuccessful, the
latter being characterized by NMR and IR spectroscopy.
This behavior indicates that a less polar amide does not
react with the Zr-Cl bond but instead preferential
aminolysis of the Si-Cl bond takes place and the
resulting product is only partially transformed by in-
tramolecular elimination of HCl, as demonstrated by the
Descr ip tion of th e Cr ysta l Str u ctu r e of {Zr [η5-
C5H4SiMe2(µ-O)]Cl2[H2NCH(Me)P h ]}2 (6b). Crys-
tals of 6b suitable for X-ray diffraction were obtained
by slow evaporation of a toluene solution. The molec-
ular structure of 6b obtained by X-ray diffraction is
shown in Figure 1. Selected bond distances and bond
angles are given in Table 1.
The molecular structure shows a dimer with two Zr-
[η5-C5H4 SiMe2(O)]Cl2[NH2(CHMe)Ph] units bonded by
two oxygen atoms which are simultaneously bridging
two zirconium atoms and one silicon atom, the two
fragments being related by an inversion center. If the
centroid of the silyl-substituted ring is considered as a
(21) Cardin, D. J .; Lappert, M. F.; Raston, C. L. Chemistry of
Organozirconium and Hafnium Compounds; Horwood: London, 1986.

5582 Organometallics, Vol. 15, No. 26, 1996
Ciruelos et al.
but chemically equivalent molecules (data for the second
molecule are given in brackets).
The geometry about each Zr atom is a distorted
octahedron. The equatorial plane is defined by two
chlorine atoms, one oxygen atom, and one nitrogen
atom, with the apical positions occupied by the Cp
centroid and the other oxygen atom. Angles between
ligands in the ecuatorial plane ranged from 78.4(2)° for
N(1)-Zr(1)-Cl(1) to 96.9(1)° for O(1a)-Zr(1)-Cl(2). Zr
is located 0.476(1) [0.485] Å above the equatorial plane
and the apical oxygen atom 1.707(5) [1.709] Å below.
The angle between this plane and the Cp ring plane is
only 8.5° [8.5°].
The triply bridging oxygen lies in the equatorial plane.
The Zr(1)-O(1)-Zr(1a) angle is 110.0(2)° and the Si-
(1)-O(1a)-Zr(1) and Si(1)-O(1a)-Zr(1a) angles are
108.2 and 141.6°, respectively. The distances from
oxygen to the Zr atoms in compound 6b are very
similar: 2.207(5) [2.188(5)] and 2.185(4) [2.215(5)] Å,
corresponding to single Zr-O bonds (average single
bond distance is 2.2 Å).21 The Si-O distance of 1.662-
(5) [1.661(5)] Å seems not to be affected by the loss of π
interaction of the Zr-O bonds, with a C(13)-Si(1)-
O(1a) angle of 93.7° [94.5°].
It is interesting to remark that this disposition
involves an only slightly asymmetric oxygen bridge, in
contrast with the observed disposition in [Zr(η5-C5Me4-
SiMe2O)(η2-O2CMe)(µ-O2CMe)]2,22a where there is a
greater difference (2.257(1) and 2.126(1) Å). Several
other structures with an oxygen bonded to two zirco-
nium atoms exhibiting both short and long zirconium-
oxygen bond distances have been reported.22b
The central core of the dimeric structure can be
considered as two lateral Zr-Cp-Si-O “oxazircona-
cycle” rings connected by a central Zr-O-Zr-O ring.
When these three rings are viewed together, an eight-
membered cycle is observed. A similar ring is present
in the titanium compound [Ti{µ-(OSiMe2-η5-C5H4)}Cl2]2.8
However, in contrast to the titanium structure, in which
this eight-membered cycle shows a “chair conformation”,
in the zirconium derivative 6b a planar disposition is
observed. The angle between the planes formed by any
lateral Zr-Cp-Si-O ring and the central Zr-O-Zr-O
ring is 2.5°. The metallic environment has a direct
influence in the difference between both structures.
Whereas the coordination around the titanium atom is
a pseudotetrahedron, the zirconium atom in 6b is in a
pseudooctahedral environment with the Zr-O and Zr-
Cp bond axes located in the same Zr2O2 core plane.
F igu r e 1. ORTEP drawing of the molecular structure of
compound 6b together with the atomic labeling scheme.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p ou n d 6b
Zr(1)-O(1a)
Zr(1)-O(1)
Zr(1)-N(1)
Zr(1)-Cl(1)
Zr(1)-Cl(2)
Zr(1)-C(11)
Zr(1)-C(12)
Zr(1)-C(13)
Zr(1)-C(14)
Zr(1)-C(15)
N(1)-C(111)
Si(1)-C(121)
Si(1)-C(122)
Si(1)-O(1a)
Si(1)-C(13)
Zr(1)-Cp(1)a
2.185(5)
2.207(5)
2.377(6)
2.486(2)
2.500(2)
2.565(8)
2.512(7)
2.476(7)
2.493(7)
2.546(8)
1.50(1)
1.836(1)
1.83(1)
1.662(5)
1.852(9)
2.216
Zr(2)-O(2a)
Zr(2)-O(2)
Zr(2)-N(2)
Zr(2)-Cl(3)
Zr(2)-Cl(4)
Zr(2)-C(21)
Zr(2)-C(22)
Zr(2)-C(23)
Zr(2)-C(24)
Zr(2)-C(25)
N(2)-C(131)
Si(2)-C(141)
Si(2)-C(142)
Si(2)-O(2)
2.215(5)
2.188(5)
2.376(6)
2.508(2)
2.493(2)
2.493(7)
2.564(8)
2.569(8)
2.509(7)
2.480(7)
1.50(1)
1.84(1)
1.83(1)
1.661(5)
1.856(9)
2.222
Si(2)-C(25)
Zr(2)-Cp(2)b
O(1)-Zr(1)-O(1a)
O(1a)-Zr(1)-N(1)
O(1)-Zr(1)-N(1)
O(1a)-Zr(1)-Cl(1)
O(1)-Zr(1)-Cl(1)
N(1)-Zr(1)-Cl(1)
O(1a)-Zr(1)-Cl(2)
O(1)-Zr(1)-Cl(2)
Cl(1)-Zr(1)-Cl(2)
N(1)-Zr(1)-Cl(2)
Cp(1)-Zr(1)-Cl(1)
Cp(1)-Zr(1)-Cl(2)
Cp(1)-Zr(1)-N(1)
Cp(1)-Zr(1)-O(1a)
Cp(1)-Zr(1)-O(1)
70.0(2) O(2a)-Zr(2)-O(2)
86.4(2) O(2a)-Zr(2)-N(2)
75.3(2) O(2)-Zr(2)-N(2)
154.9(1) O(2a)-Zr(2)-Cl(3)
86.7(1) O(2)-Zr(2)-Cl(3)
78.4(2) N(2)-Zr(2)-Cl(3)
96.9(1) O(2a)-Zr(2)-Cl(4)
82.0(1) O(2)-Zr(2)-Cl(4)
88.80(8) Cl(4)-Zr(2)-Cl(3)
154.4(2) N(2)-Zr(2)-Cl(3)
70.2(2)
75.3(2)
88.1(2)
81.8(1)
94.2(1)
154.7(2)
86.1(1)
155.3(1)
88.84(9)
154.7(2)
102.6
106.6
102.1
102.7
96.1
Cp(2)-Zr(2)-Cl(3)
Cp(2)-Zr(2)-Cl(4)
Cp(2)-Zr(2)-O(2)
Cp(2)-Zr(2)-O(2)
106.6
96.6
96.6
165.9
Cp(2)-Zr(2)-O(2a) 166.4
C(111)-N(1)-Zr(1) 126.6(5) C(131)-N(2)-Zr(2) 127.2(5)
O(1a)-Si(1)-C(122) 112.8(4) O(2)-Si(2)-C(142)
O(1a)-Si(1)-C(121) 111.7(4) O(2)-Si(2)-C(141)
112.0(4)
111.6(4)
Con clu sion s
C(122)-Si(1)-C(121) 112.1(5) C(142)-Si(2)-C(141) 113.1(5)
The work described in this paper represents a new
approach to the synthesis of constrained-geometry
catalyst precursors by reactions carried out at the Si-
Cl bond of chlorodimethylsilyl-substituted cyclopenta-
dienyl compounds. The highly polar Li[N(SiMe3)2]
selectively attacks the Ti-Cl and Zr-Cl bonds, leading
to the formation of metal amides. Less polar Li[NHR]
also selectively attacks the Ti-Cl bonds, whereas
preferential aminolysis of the Si-Cl bonds takes place
for the zirconium derivatives. Reactions with water and
amines are preferentially directed to the Si-Cl bonds,
particularly in the case of the zirconium complexes,
O(1a)-Si(1)-C(13)
93.7(3) O(2)-Si(2)-C(25)
94.5(3)
C(122)-Si(1)-C(13) 114.1(5) C(142)-Si(2)-C(25) 113.0(5)
C(121)-Si(1)-C(13) 111.2(5) C(141)-Si(2)-C(25) 111.3(5)
Si(1)-O(1a)-Zr(1a) 141.6(3) Si(2)-O(2)-Zr(2)
Si(1)-O(1a)-Zr(1) 108.2(3) Si(2)-O(2a)-Zr(2)
Zr(1)-O(1a)-Zr(1a) 110.0(2) Zr(2)-O(2a)-Zr(2)
142.5(3)
107.6(3)
109.8(2)
a
b
Cp(1) is the centroid of C(11), ..., C(15). Cp(2) is the centroid
of C(21), ..., (C25).
single coordination site bonded to Zr, the structure
shows a four-membered ring (Cp-Si-O-Zr), instead of
the eight-membered ring observed for the related tita-
nium complex.8
(22) (a) Kloppenburg, L.; Petersen, J . L. Organometallics 1996, 15,
7. (b) Procopio, L. J .; Carroll, P. J .; Berry, D. H. Organometallics 1993,
12, 3087 and references cited therein.
In the asymmetric unit of the unit cell two moieties
are found that make up two different crystallographic

(Amidosilyl)cyclopentadienyl Complexes of Ti and Zr
Organometallics, Vol. 15, No. 26, 1996 5583
mother liquor (1 g, 2.78 mmol, 69% yield). Anal. Calcd for
which can coordinate the amine instead of eliminate
HCl. On this basis, reactions of complexes that contain
Ti-Cl and Si-Cl bonds with different lithium amides
LiNHR, or alternatively with primary amines in the
presence of NEt3, are convenient routes to constrained
complexes of the type [Ti(C5H4SiMe2NR′)Cl2].
C
15H19NCl2SiTi: C, 50.02; H, 5.32; N, 3.89. Found: C, 49.79;
H, 5.20; N, 4.08. 1H NMR (benzene-d6): δ -0.48 (s, 3H, SiMe);
0.09 (s, 3H, SiMe); 1.50 (d, J ) 6.8 Hz, 3H, CMe); 5.99 (m,
1H, C5H4); 6.04 (m, 1H, C5H4); 6.48 (m, 1H, C5H4); 6.49 (m,
1H, C5H4); 6.51 (q, J ) 6.8 Hz, 1H, CH); 7.01-7.27 (m, 5H,
Ph). 1H NMR (chloroform-d): δ -0.29 (s, 3H, SiMe); 0.46 (s,
3H, SiMe); 1.59 (d, J ) 6.8 Hz, 3H, CMe); 6.38 (m, 1H, C5H4);
6.41 (q, J ) 6.8 Hz, 1H, CH); 6.44 (m, 1H, C5H4); 7.00 (m, 2H,
C5H4); 7.23-7.33 (m, 5H, Ph). 13C{1H} NMR (chloroform-d):
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations were per-
formed under argon using Schlenk and high-vacuum-line
techniques or a Model HE-63-Pedetrol glovebox. Solvents were
purified by distillation under argon from an appropriate drying
agent (sodium for toluene, sodium-potassium amalgam for
hexane, and sodium-benzophenone for diethyl ether). NEt3
δ -2.0 (SiMe); 0.6 (SiMe); 20.0 (CMe); 65.4 (CMe); 110.6 (Cipso
,
C5H4); 125.1, 125.4, 127.2 (C2-5, C5H4); 127.9, 128.9, 129.6 (Ph);
144.6 (Cipso, Ph). MS: m/ z [assignment, relative intensity (%)]
359 [M+, 2]; 344 [(M - CH3)+, 100].
By the procedure described above using [Ti(η5-C5H4SiMe2-
Cl)Cl3] (1a ) (1.73 g, 5.55 mmol), (()-NH2(CHMe)Ph (0.72 mL,
5.55 mmol), and NEt3 (1.55 mL, 11.12 mmol), 3a was again
obtained (1 g, 2.78 mmol, 50% yield).
t
(Fluka) and NH2 Bu and (()-NH2[CH(Me)Ph] (Aldrich) were
distilled before use and stored over 4 Å molecular sieves.
MgClMe and MgCl(CH2Ph) were purchased from Aldrich as 3
M and 2 M tetrahydrofuran solutions. LiNHtBu and LiNH-
(CHMe)Ph were prepared in hexane (in almost quantitative
Syn th esis of [Ti(η5-C5H4SiMe2Cl)Cl{N(SiMe3)2}2] (4a ).
A mixture of [Ti(η5-C5H4SiMe2Cl)Cl3] (1a ; 0.84 g, 2.69 mmol)
and LiN(SiMe3)2 (0.90 g, 5.40 mmol) in 50 mL of hexane was
stirred at room temperature for 10 h and then filtered. The
filtrate was concentrated under reduced pressure and cooled
to -40 °C to give orange crystals, which were characterized
as 4a (1 g, 1.78 mmol, 66% yield). Anal. Calcd for
t
yield) as solvent-free solids from NH2 Bu and (()-NH2[CH(Me)-
Ph] and n-butyllithium (Aldrich, 1.6 M in hexane). [Ti(η5-C5H4-
23
SiMe2Cl)Cl3] (1a),8 [Zr(η5-C5H4SiMe2Cl])Cl3] (1b),8 LiN(SiMe3)2,
Mg(CH2Ph)2‚2THF,24 and Tl(C5H5)25 were prepared by known
procedures. CO2 was purchased from SEO. C, H, and N
microanalyses were performed on a Perkin-Elmer 240B and/
or Heraeus CHN-O-Rapid microanalyzer. Electron impact (EI)
mass spectra were recorded at 70 eV on a Hewlett-Packard
5988 spectrometer, and IR spectra were taken on a Perkin-
Elmer 883 spectrophotometer using KBr pellets; only selected
MS and IR data are reported. NMR spectra, measured at 25
°C, were recorded on a Varian Unity FT-300 (1H NMR at 300
MHz, 13C NMR at 75 MHz) spectrometer, and chemical shifts
are referenced to residual protons or carbons of the solvents.
Syn th esis of [Ti(η5:η1-C5H4SiMe2NtBu )Cl2] (2a ). A solu-
tion of LiNHtBu (0.34 g, 4.26 mmol) and NEt3 (0.59 mL, 4.26
mmol) in 30 mL of hexane was quickly added to a cooled (-60
°C) suspension of [Ti(η5-C5H4SiMe2Cl)Cl3] (1a ; 1.33 g, 4.26
mmol) in 30 mL of hexane. The reaction mixture was slowly
warmed to room temperature and stirred for 10 h, resulting
in an orange solution and a white residue. After filtration,
the solution was cooled to -30 °C to give orange crystals.
Concentration of the mother liquor (10 mL) and subsequent
cooling to -30 °C gave a second crop of product, which was
characterized as 2a (1 g, 3.20 mmol, 75% yield). Anal. Calcd
for C11H19NCl2SiTi: C, 42.33; H, 6.14; N, 4.49. Found: C,
42.67; H, 6.22; N, 4.78. 1H NMR (benzene-d6): δ 0.18 (s, 6H,
C
19H46N2Cl2Si5Ti: C, 40.62; H, 8.25; N, 4.99. Found: C, 40.38;
H, 8.57; N, 4.68. 1H NMR (chloroform-d): δ 0.36 (s, 36H,
N(SiMe3)2); 0.81 (s, 6H, SiMe2); 6.63-6.67 (m, 4H, C5H4). 1H
NMR (benzene-d6): δ 0.37 (s, 36H, N(SiMe3)2); 0.83 (s, 6H,
SiMe2); 6.46 (m, 2H, C5H4); 6.62 (m, 2H, C5H4). 13C{1H} NMR
(chloroform-d): δ 2.5 (SiMe2); 7.2 (SiMe3); 117.8, 119.8 (C2-5
,
C5H4); 131.6 (Cipso, C5H4).
Syn th esis of [Ti(η5-C5H4SiMe2NHtBu )Cl2(NHtBu )] (5a ).
t
A solution of NH2 Bu (2.73 mL, 26.00 mmol) in 25 mL of
toluene was slowly added to a cooled (-60 °C) solution of [Ti-
(η5-C5H4SiMe2Cl)Cl3] (1a ; 2.70 g, 8.66 mmol) in 75 mL of
toluene. The reaction mixture was warmed to room temper-
ature and then stirred overnight, resulting in an orange
solution together with a white residue. Subsequent filtration
and removal of the solvent under reduced pressure afforded
an orange solid as a mixture of 5a , 2a , and other unidentified
products. Repeated recrystallization of the mixture from
toluene/hexane at -40 °C gave 5a as an analytically pure
sample (0.53 g, 1.38 mmol, 16% yield). Anal. Calcd for
C
15H30N2Cl2SiTi: C, 46.76; H, 7.85; N, 7.27. Found: C, 47.21;
H, 7.53; N, 7.34. 1H NMR (benzene-d6): δ 0.38 (s, 6H, SiMe2);
t
t
1.04 (s, 9H, Bu); 1.36 (s, 9H, Bu); 6.16 (m, 2H, C5H4); 6.47
(m, 2H, C5H4); 10.5 (s br, 2H, NH). 13C{1H} NMR (benzene-
t
SiMe2); 1.37 (s, 9H, Bu); 6.07 (m, 2H, C5H4); 6.60 (m, 2H,
d6): δ 2.3 (SiMe2); 33.3 (CH3, tBu); 34.3 (CH3, tBu); 58.2 (Cipso
,
,
C5H4). 1H NMR (chloroform-d): δ 0.60 (s, 6H, SiMe2); 1.44 (s,
9H, tBu); 6.45 (m, 2H, C5H4); 7.06 (m, 2H, C5H4). 13C{1H} NMR
(benzene-d6): δ -0.2 (SiMe2); 32.2 (CH3, tBu); 63.7 (Cipso, tBu);
110.0 (Cipso, C5H4); 125.7, 126.3 (C2-5, C5H4).4,6k MS: m/ z
[assignment, relative intensity (%)]: 311 [M+, 1]; 296 [(M -
CH3),+ 100].
tBu); 60.1 (Cipso, Bu); 116.2, 118.1 (C2-5, C5H4); 125.9 (Cipso
t
C5H4). IR (KBr, cm-1): ν(N-H) 3388, 3306. MS: m/ z
[assignment, relative intensity (%)] 369 [(M - CH3)+, 1]; 334
t
[(M-CH3-Cl)+, 2]; 296 [(M - CH3 - NH2 Bu)+, 42].
Syn th esis of [Ti(η5:η1-C5H4SiMe2NtBu )(η5-C5H5)Cl] (6a ).
A mixture of [Ti(η5:η1-C5H4SiMe2NtBu)Cl2] (2a ; 1.29 g, 4.13
mmol) and Tl(C5H5) (1.11 g, 4.13 mmol) in 60 mL of toluene
was stirred at 100 °C overnight and then filtered. The filtrate
was concentrated under reduced pressure and cooled to -30
°C to give a red solid. Recrystallization from hexane gave a
microcrystalline solid that was characterized as 6a (1 g, 2.93
mmol, 71% yield). Anal. Calcd for C16H24NClSiTi: C, 56.22;
H, 7.08; N, 4.10. Found: C, 56.01; H, 6.87; N, 4.39. 1H NMR
(benzene-d6): δ 0.15 (s, 3H, SiMe); 0.54 (s, 3H, SiMe); 1.32 (s,
By the procedure described above using [Ti(η5-C5H4SiMe2-
t
Cl)Cl3] (1a ) (1.59 g, 5.10 mmol), NH2 Bu (0.53 mL, 5.10 mmol),
and NEt3 (1.41 mL, 10.20 mmol), 2a was again obtained (1 g,
3.20 mmol, 63% yield).
Syn th esis of [Ti(η5:η1-C5H4SiMe2){N(CHMe)P h }Cl2] (3a).
A suspension of LiNH(CHMe)Ph (0.51 g, 4.02 mmol) and NEt3
(0.56 mL, 4.02 mmol) in 30 mL of hexane was added to a cooled
(-60 °C) suspension of [Ti(η5-C5H4SiMe2Cl)Cl3] (1a ) (1.25 g,
4.02 mmol) in 30 mL of hexane. The reaction mixture was
stirred at room temperature for 15 h, over which time the color
of the solution changed to brown. After filtration, the solution
was cooled to -30 °C to give orange-brown crystals. A second
crop of product 3a was obtained after concentration of the
t
9H, Bu); 5.23 (m, 1H, C5H4); 5.87 (m, 1H, C5H4); 5.87 (s, 5H,
C5H5); 6.30 (m, 1H, C5H4); 7.07 (m, 1H, C5H4). 1H NMR
(chloroform-d): δ 0.31 (s, 3H, SiMe); 0.59 (s, 3H, SiMe); 1.37
t
(s, 9H, Bu); 5.73 (m, 1H, C5H4); 6.20 (s, 5H, C5H5); 6.40 (m,
1H, C5H4); 6.66 (m, 1H, C5H4); 6.89 (m, 1H, C5H4). 13C{1H}
NMR (chloroform-d): δ 1.2 (SiMe); 4.7 (SiMe); 34.2 (CH3,
t
tBu); 65.7 (Cipso, Bu); 113.6 (C5H5); 109.8, 121.8, 122.0, 130.1
(23) Amonoo-Neizer, E. H.; Shaw, R. A.; Skovlin, D. O.; Smith, B.
C. Inorg. Synth. 1966, 8, 19.
(24) Schrock, R. R. J . Organomet. Chem. 1976, 122, 209.
(25) Brauer, H. G. Handbuch der Praparativen Anorganischen
Chemie; F. Euke Verlag: Stuttgart, Germany, 1981; Vol. III.
(C2-5, C5H4); 113.2 (Cipso of C5H4). 13C{1H} NMR (benzene-
t
t
d6): δ 1.3 (SiMe); 4.8 (SiMe); 34.2 (CH3, Bu); 65.1 (Cipso, Bu);
113.8 (C5H5); 110.2, 121.4, 122.8, 130.0 (C2-5, C5H4) (Cipso of

5584 Organometallics, Vol. 15, No. 26, 1996
Ciruelos et al.
C5H4 not observed). MS: m/ z [assignment, relative intensity
(%) 341 [M+, 2]; 326 [(M - CH3)+, 100].
NMR (benzene-d6): δ -1.0 (SiMe); 0.2 (SiMe); 25.4 (CMe); 62.2
(CMe); 81.1 (TiCH2); 82.5 (TiCH2); 105.4 (Cipso, C5H4); 122.0,
122.1, 123.8, 123.9 (C2-5, C5H4); 125.0, 125.3, 125.7, 126.0,
127.5, 128.5, 128.6, 128.7 (Ph, one peak obscured by solvent
peak); 146.5, 148.9, 149.1 (Cipso, Ph). MS: m/ z [assignment,
relative intensity (%)] 380 [(M - C7H7)+, 4]; 289 [(M - 2C7H7)+,
16]; 91 [(C7H7)+, 100].
Syn th esis of [Ti(η5:η1-C5H4SiMe2NtBu )Me2] (7a ). A 3 M
solution of MgClMe in tetrahydrofuran (3.08 mL, 9.24 mmol)
was added to a cooled (-78 °C) suspension of [Ti(η5:η1-C5H4-
SiMe2NtBu)Cl2] (2a ; 1.44 g, 4.61 mmol) in 50 mL of hexane.
After the temperature was raised to 0 °C over 1 h, a yellow
solution with a white precipitate was formed. At this tem-
perature the reaction mixture was filtered and the solution
was concentrated to 5 mL. Cooling to -40 °C gave yellow
crystals of the product, which was characterized as 7a (1 g,
3.69 mmol, 80% yield). Anal. Calcd for C13H25NSiTi: C, 57.55;
H, 9.29; N, 5.16. Found: C, 57.05; H, 9.12; N, 4.95. 1H NMR
(benzene-d6): δ 0.25 (s, 6H, SiMe2); 0.64 (s, 6H, TiMe2); 1.52
Syn th esis of [Ti(η5:η1-C5H4SiMe2NtBu )(CH2P h )Cl] (11a).
A 3 M solution of MgCl(CH2Ph) in tetrahydrofuran (2.16 mL,
6.47 mmol) was added to a cooled (-78 °C) suspension of [Ti-
(η5:η1-C5H4SiMe2NtBu)Cl2] (2a ; 2.02 g, 6.47 mmol) in 50 mL
of diethyl ether. After warming up to room temperature, the
reaction mixture was allowed to stand for 2 h. The MgCl2
formed was removed by filtration, and the volume of the
filtrate was reduced in vacuo to 15 mL and cooled to -40 °C
to give a dark red solid. Recrystallization from hexane at -40
°C gave a microcrystalline solid that was characterized as 11a
(1 g, 2.72 mmol, 42% yield). Anal. Calcd for C18H26NClSiTi:
C, 58.78; H, 7.12; N, 3.81. Found: C, 58.95; H, 6.74; N, 3.76.
1H NMR (benzene-d6): δ 0.16 (s, 3H, SiMe); 0.22 (s, 3H, SiMe);
t
(s, 9H, Bu); 5.82 (m, 2H, C5H4); 6.74 (m, 2H, C5H4). 1H NMR
(chloroform-d): δ 0.34 (s, 6H, SiMe2); 0.35 (s, 6H, TiMe2); 1.55
t
(s, 9H, Bu); 5.96 (m, 2H, C5H4); 7.03 (m, 2H, C5H4). 13C{1H}
NMR (benzene-d6): δ 1.0 (SiMe2); 34.4 (CH3, tBu); 51.0 (TiMe2);
t
58.7 (Cipso, Bu); 103.9 (Cipso, C5H4); 121.2, 122.1 (C2-5, C5H4).
Syn th esis of [Ti(η5:η1-C5H4SiMe2NtBu )(CH2P h )2] (8a ).
A solution of Mg(CH2Ph)2‚2THF (1.06 g, 3.03 mmol) in 15 mL
of diethyl ether was added to a cooled (-78 °C) suspension of
[Ti(η5:η1-C5H4SiMe2NtBu)Cl2] (2a ; 0.94 g, 3.03 mmol) in 30 mL
of hexane. The mixture was warmed to room temperature for
2 h, resulting in a deep red solution with a gray precipitate.
After filtration the solution was concentrated to 5 mL. Cooling
to -40 °C gave dark red crystals of the product, which was
characterized as 8a (1 g, 2.36 mmol, 78% yield). Anal. Calcd
for C25H33NSiTi: C, 70.90; H, 7.85; N, 3.31. Found: C, 70.57;
H, 7.81; N, 2.95. 1H NMR (benzene-d6): δ 0.16 (s, 6H, SiMe2);
t
1.48 (s, 9H, Bu); 2.71 (d, J ) 9.2 Hz, 1H, TiCH2); 3.22 (d, J )
9.2 Hz, 1H, TiCH2); 5.56 (m, 1H, C5H4); 5.83 (m, 1H, C5H4);
6.11 (m, 1H, C5H4); 6.49 (m, 1H, C5H4); 6.89-7.15 (m, 5H, Ph).
13C{1H} NMR (benzene-d6): δ 0.7 (SiMe); 1.1 (SiMe); 35.2 (CH3,
t
tBu); 60.0 (Cipso, Bu); 83.0 (TiCH2); 107.7 (Cipso, C5H4); 121.7,
122.0, 125.2, 125.6 (C2-5, C5H4); 122.9, 126.3, 128.5 (Ph); 149.0
(Cipso, Ph).
NMR-Sca le Rea ction s of 2a a n d 3a w ith CO2. (A) An
NMR tube was charged with [Ti(η5:η1-C5H4SiMe2NtBu)Cl2] (2a ;
45 mg, 0.14 mmol) in benzene-d6 (0.7 mL). After the solution
had been cooled to -196 °C, the argon atmosphere was
replaced by CO2, and the NMR tube was immediately sealed.
The reaction was followed by 1H NMR. After 38 h at room
t
1.50 (s, 9H, Bu); 2.28 (d, J ) 9.5 Hz, 2H, TiCH2); 2.87 (d, J )
9.5 Hz, 2H, TiCH2) 5.44 (m, 2H, C5H4); 6.36 (m, 2H, C5H4);
6.77-7.15 (m, 10H, Ph). 1H NMR (chloroform-d): δ 0.34 (s,
t
1
6H, SiMe2); 1.73 (s, 9H, Bu); 2.24 (d, J ) 9.5 Hz, 2H, TiCH2);
temperature, no reaction occurred. After 5 h at 70 °C, the H
2.85 (d, J ) 9.5 Hz, 2H, TiCH2); 5.47 (m, 2H, C5H4); 6.41 (m,
NMR spectrum showed that all of 2a had been converted into
2H, C5H4); 6.75-7.13 (m, 10H, Ph). 13C{1H} NMR (benzene-
[Ti{µ-(OSiMe2-η5-C5H4)}Cl2]2 as the major organometallic com-
d6): δ 0.8 (SiMe2); 34.5 (CH3, tBu); 60.3 (Cipso
,
tBu); 81.6
pound and BuNdCdO. 1H NMR (benzene-d6): δ 0.91 (s, 9H,
t
(TiCH2); 106.4 (Cipso, C5H4); 125.2, 125.6 (C2-5, C5H4); 122.0,
125.8, 128.5 (Ph); 149.8 (Cipso, Ph). 13C{1H} NMR (chloroform-
d): δ 0.8 (SiMe2); 34.5 (CH3, tBu); 60.5 (Cipso, tBu); 80.8 (TiCH2);
105.9 (Cipso, C5H4); 121.4, 124.8 (C2-5, C5H4); 125.2, 125.3, 128.1
(Ph); 149.5 (Cipso, Ph). MS: m/ z [assignment, relative inten-
sity (%)] 332 [(M - C7H7)+, 90]; 317 [(M - C7H7 - CH3)+, 80];
91 [(C7H7)+, 100].
tBu). The same δ value was obtained from an analytically pure
sample (97%) of tBuNdCdO obtained commercially from
Aldrich. (B) The same procedure was used for [Ti{η5:η1-C5H4-
SiMe2[N(CHMe)Ph]}Cl2 (3a ; 45 mg, 0.12 mmol). After only
10 h at room temperature, all of 3a had been converted into
[Ti{µ-(OSiMe2-η5-C5H4)}Cl2]2 as the major organometallic com-
1
pound and (()-[Ph(Me)HC]NdCdO H NMR (benzene-d6): δ
Syn th esis of [Ti{η5:η1-C5H4SiMe2[N(CHMe)P h ]}Me2]
(9a ). The procedure described for the preparation of complex
[Ti(η5:η1-C5H4SiMe2NtBu)Me2] (7a ) using [Ti{η5:η1-C5H4SiMe2-
[N(CHMe)Ph]}Cl2] (3a ; 1.46 g, 4.07 mmol) and a 3 M solution
of MgClMe in tetrahydrofuran (2.72 mL, 8.16 mmol) gave 9a
as yellow crystals (1 g, 3.13 mmol, 77%). Anal. Calcd for
1.06 (d, J ) 6.9 Hz, 3H, CMe); 4.06 (q, J ) 6.9 Hz, 1H, CH);
6.94-7.05 (m, 5H, Ph). The same δ and J values were
obtained from analytically pure sample (99%) of (+)-[Ph(Me)-
HC]NdCdO purchased from Aldrich.
Syn th esis of [Zr (η5-C5H4SiMe2Cl)Cl2{N(SiMe3)2}] (2b).
A solution of LiN(SiMe3)2 (0.23 g, 1.41 mmol) in 20 mL of
diethyl ether was added to a solution of [Zr(η5-C5H4SiMe2Cl)-
Cl3] (1b; 0.50 g, 1.41 mmol) in 30 mL of diethyl ether at -78
°C. The reaction mixture was warmed to room temperature
and then stirred for 12 h, resulting in a pale yellow solution
along with a white residue. The mixture was filtered and the
solvent was removed under reduced pressure to give 2b as a
pale crystalline solid. Recrystallization of 2b from diethyl
ether at -40 °C gave an analytically pure sample (0.56 g, 1.17
mmol, 83% yield). Anal. Calcd for C13H28NCl3Si3Zr: C, 32.52;
H, 5.83; N, 2.92. Found: C, 32.43; H, 5.60; N, 2.86. 1H NMR
(benzene-d6): δ 0.19 (s, 18H, N(SiMe3)2); 0.68 (s, 6H, SiMe2);
6.27 (m, 2H, C5H4); 6.53 (m, 2H, C5H4). 13C{1H} NMR
C
17H25NSiTi: C, 63.93; H, 7.89; N, 4.39. Found: C, 63.88; H,
8.23; N, 4.73. 1H NMR (benzene-d6): δ -0.20 (s, 3H, SiMe);
0.06 (s, 3H, SiMe); 0.67 (s, 3H, TiMe); 0.68 (s, 3H, TiMe); 1.75
(d, J ) 6.6 Hz, 3H, CMe); 5.80 (m, 1H, C5H4); 5.85 (m, 1H,
C5H4); 5.89 (q, J ) 6.6 Hz, 1H, CH); 6.70 (m, 2H, C5H4); 7.08-
7.29 (m, 5H, Ph).13C{1H} NMR (benzene-d6): δ -1.9 (SiMe);
-0.1 (SiMe); 24.5 (CMe); 51.0 (TiMe); 51.2 (TiMe); 60.9 (CMe);
103.3 (Cipso, C5H4); 119.5, 119.6, 122.5, 122.6 (C2-5, C5H4);
127.0, 128.4 (Ph, one peak obscured by solvent peak); 146.9
(Cipso, Ph).
Syn t h esis
of
[Ti{η5:η1-C5H 4SiMe2[N(CH Me)P h ]}-
(CH2P h )2] (10a ). The procedure described to prepare [Ti(η5:
η1-C5H4SiMe2NtBu)(CH2Ph)2], 8a using [Ti{η5:η1-C5H4SiMe2-
[N(CHMe)Ph]}Cl2] (3a ; 1.08 g, 2.99 mmol) and Mg(CH2Ph)2‚
2THF (1.05 g, 2.99 mmol) gave 10a as dark red crystals (1 g,
2.12 mmol, 71% yield). Anal. Calcd for C29H33NSiTi: C, 73.86;
H, 7.05; N, 2.97. Found: C, 73.68; H, 7.33; N, 2.92. 1H NMR
(benzene-d6): δ -0.07 (s, 3H, SiMe); 0.10 (s, 3H, SiMe); 1.61
(d, J ) 6.6 Hz, 3H, CMe); 2.23 (d, J ) 9.5 Hz, 1H, TiCH2);
2.33 (d, J ) 9.9 Hz, 1H, TiCH2); 2.61 (d, J ) 9.9 Hz, 1H,
TiCH2); 2.74 (d, J ) 9.5 Hz, 1H, TiCH2); 5.44 (m, 1H, C5H4);
5.57 (m, 1H, C5H4); 5.82 (q, J ) 6.6 Hz, 1H, CH); 6.37 (m, 1H,
C5H4); 6.39 (m, 1H, C5H4); 6.61-7.29 (m, 15H, Ph). 13C{1H}
(chloroform-d): δ 2.5 (SiMe2); 5.0 (SiMe3); 118.1, 123.8 (C2-5
,
C5H4); 125.4 (Cipso, C5H4).
Syn th esis of th e Mixtu r e [Zr (η5:η1-C5H4SiMe2NtBu )Cl2]
(3b) a n d [Zr (η5-C5H4SiMe2NHtBu )Cl3(NEt3)] (4b). A solu-
tion of LiNHtBu (0.22 g, 2.82 mmol) in 20 mL of toluene was
slowly added to a solution of [Zr(η5-C5H4SiMe2Cl)Cl3] (1b; 1.00
g, 2.82 mmol) and NEt3 (0.39 mL, 2.82 mmol) in 30 mL of
toluene at -78 °C. The reaction mixture was warmed to room
temperature and then stirred for 12 h, resulting in a pale
yellow solution. Subsequent filtration and removal of the
solvent under reduced pressure afforded a sticky solid, a

(Amidosilyl)cyclopentadienyl Complexes of Ti and Zr
Organometallics, Vol. 15, No. 26, 1996 5585
recrystallization of the mixture were unsuccessful. 1H NMR
(benzene-d6): δ 0.40 (s, 3H, SiMe); 0.52 (s, 3H, SiMe); 0.68 (t,
9H, NCH2CH3); 1.31 (d, J ) 6.6 Hz, 3H, CMe); 2.36 (q, 6H,
NCH2CH3); 4.05 (q, J ) 6.6 Hz, 1H, CH); 4.70 (m, 1H, N-H);
6.74 (m, 2H, C5H4); 6.77 (m, 1H, C5H4); 6.84 (m, 1H, C5H4);
7.00-7.10 (m, 5H, Ph).
Syn th esis of [Zr {η5:η1-C5H4SiMe2(µ_O)}Cl2{H2N(CHMe)-
P h }]2 (6b). A solution of 5b in 20 mL of toluene, prepared
from [Zr(η5-C5H4SiMe2Cl)Cl3] (1b; 0.50 g, 1.41 mmol) as
described above, was treated with wet toluene without stirring.
This resulted in a slow precipitation of 6b as white crystals,
which were suitable for X-ray analysis (0.17 g, 0.20 mmol, 28%
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
Deta ils for Com p ou n d 6b
empirical formula
fw
C30H40Cl4N2O2Si2Zr2
841.06
temp
293(2) K
wavelength
cryst syst
0.710 73 Å
triclinic
space group
unit cel dimens
P1h
a ) 10.301(3) Å
b ) 10.398(2) Å
c ) 19.391(3) Å
R ) 88.69(2)°
â ) 78.97(2)°
γ ) 63.18(2)°
1814.5(7) Å3
2
yield based on compound 1b ).
Anal.
Calcd for
V
Z
C30H42N2Cl4O2Si2Zr2: C, 42.73; H, 4.98; N, 1.66. Found: C,
42.70; H, 5.03; N, 1.51. 1H NMR (chloroform-d): δ 0.47 (s,
3H, SiMe); 0.72 (s, 3H, SiMe); 1.46 (d, J ) 6.6 Hz, 3H, CMe);
4.33 (q, 1H, CH); 5.86 (m, 1H, C5H4); 6.69 (m, 1H, C5H4); 6.75
(m, 1H, C5H4); 7.00 (m, 1H, C5H4); 7.20-7.60 (m, 5H, Ph).
density (calcd)
abs coeff
1.539 g/cm3
9.64 cm-1
F(000)
852
cryst size
θ range for data collection
index ranges
0.2 × 0.2 × 0.3 mm
2-25
0 < h < 12, -12 < k < +12,
-12 < l < +22
6661
6089 (Rint ) 0.1396)
full-matrix least squares on F2
6084/0/379
Cr ysta l Str u ctu r e Deter m in a tion of 6b. A suitably sized
white crystal of 6b was obtained by crystallization from
toluene. The crystal was mounted in an Enraf-Nonius Cad-4
automatic four-circle diffractometer with graphite-monochro-
mated Mo KR radiation (λ ) 0.710 73 Å). Crystallographic and
experimental details are summarized in Table 2. Data were
collected at room temperature. Intensities were corrected for
Lorentz and polarization effects in the usual manner. No
absorption or extinction corrections were made. The structure
was solved by direct methods (SHELXS 90)26 and refined by
least squares against F2 (SHELXL 93).27 All non-hydrogen
atoms were refined anisotropically, and the hydrogen atoms
were introduced from geometrical calculations and refined
using a riding model with thermal parameters equivalent to
those of the atoms to which they are bonded. Calculations
were carried out on an ALPHA AXP (digital) workstation.
no. of rflns collected
no. of indep rflns
refinement method
no. of data/restraints/
params
goodness of fit on F2
final R indices (I > 2σ(I))a
R indices (all data)
weighting scheme
1.127
R1 ) 0.0597, wR2 ) 0.1557
R1 ) 0.1100, wR2 ) 0.1874
calcd w ) 1/[σ2(Fo2) +
(0.0846P)2 + 10.1458P],
2
where P ) (Fo + 2Fc2)/3
largest diff peak and hole
+0.851 and -1.109 e/Å3
a
R1 ) ∑||Fo| - |Fc|/∑|Fo|; wR2 ) {[∑w((Fo2 - Fc2]/[∑w(Fo2)2]}1/2
.
mixture of 3b and 4b. Recrystallization of the mixture from
toluene at -40 °C gave 3b 4a (0.15 g, 0.42 mmol, 15% yield) as
white crystals, but attempts to isolate pure 4b were unsuc-
cessful. 1H NMR (benzene-d6) for 4b: δ 0.62 (s, 6H, SiMe2);
Ack n ow led gm en t. We are grateful to the DGICYT
(Project PB-92-0178-C) and the University of Alcala´ for
financial support of this research. S.C. acknowledges
the MEC for providing a fellowship. A.M. is grateful to
Consejer´ıa Educacio´n (CAM) for a fellowship.
t
0.80 (t, 9H, NCH2CH3); 1.08 (s, 9H, Bu); 2.56 (q, 6H, NCH2-
CH3); 6.05 (br, 1H, NH); 6.85 (m, 2H, C5H4); 6.90 (m, 2H, C5H4).
13C{1H} NMR (benzene-d6): δ 2.7 (SiMe2); 8.8 (NCH2CH3); 33.9
(CH3, tBu); 47.1 (NCH2CH3); 49.9 (Cipso, tBu); 124.3, 127.3 (C2-5
,
C5H4) (Cipso of C5H4 not observed). IR (KBr, cm-1): ν(N-H)
3365.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, all bond distances and angles, and anisotropic
thermal factors for 6b (5 pages). Ordering information is given
on any current masthead page.
Syn th esis of [Zr {η5-C5H4SiMe2[NH(CHMe)P h ]}Cl3(NEt3)]
(5b). A suspension of LiNH(CHMe)Ph (0.36 g, 2.82 mmol) in
20 mL of toluene was slowly added to a solution of [Zr(η5-C5H4-
SiMe2Cl)Cl3] (1b; 1.00 g, 2.82 mmol) and NEt3 (0.39 mL, 2.82
mmol) in 30 mL of toluene at -78 °C. The reaction mixture
was warmed to room temperature and then stirred for 12 h,
resulting in a pale yellow solution. Subsequent filtration and
removal of the solvent under reduced pressure afforded 5b as
an impure sticky pale yellow solid. Attempts to isolate 5b by
OM960606P
(26) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(27) Sheldrick, G. M. SHELXL 93; University of Go¨ttingen, Go¨ttin-
gen, Germany,1993.