Synthesis of Aryloxo Cyclopentadienyl Group 4 Metal-Containing Dendrimers

Article abstract of DOI:10.1021/om034042i

A quantitative procedure for the hydrosilylation of allylic-SiMe ₃ protected phenols with Et₃SiH and Si-H terminated carbosilane dendrimers of first, second, and fourth generation was discussed. It was found that solvent polarity was not affecting the selectivity and a high concentration of reagents favored the C-silylation versus the two side reaction. It is observed that the organometallic unit retained the spectroscopic and chemical properties of the mononuclear counterparts. The analysis showed that the dendritic framework was inert and spectroscopically invariable to the changes produced in the periphery.

Full text of DOI:10.1021/om034042i

Organometallics 2003, 22, 5109-5113
5109
Syn th esis of Ar yloxo Cyclop en ta d ien yl Gr ou p 4
Meta l-Con ta in in g Den d r im er s
Silvia Are´valo, Ernesto de J esu´s, F. J avier de la Mata,* J uan C. Flores,
Rafael Go´mez,* Ma. Pilar Go´mez-Sal, Paula Ortega, and Susana Vigo
Departamento de Qu´ımica Inorga´nica, Universidad de Alcala´, Campus Universitario,
E-28871 Alcala´ de Henares, Spain
Received J uly 16, 2003
A quantitative procedure for the hydrosilylation of allylic -SiMe3 protected phenols with
Et3SiH and Si-H terminated carbosilane dendrimers of first, second, and fourth generations
have been performed to give nG-[(CH2)3{C6H4-r(OMe)r}OH]m. The subsequent treatment with
[Ti(C5Me5)Cl2Me], [Ti(C5Me5)Me3], or [M(C5H5)2ClX] (M ) Ti, X ) Cl; M ) Zr, X ) H) afforded
the corresponding organometallic metallodendrimers.
In tr od u ction
also explained by some observations about their cata-
lytic activities.6 However, the selectivity of the key
reaction affording the phenol-functionalized dendrimers,
i.e., the hydrosilylation of allylphenols with the terminal
Si-H units of carbosilane dendrimers, was limited and
an additional study was needed.
An area of growing interest is the synthesis of metal-
lodendrimers in which the metal has been attached to
the surface for generating new inorganic/organic hybrid
macromolecules with interesting advantages over both
homogeneous and heterogeneous catalysis.1 On the
other hand, Ziegler-Natta polymerization of R-olefins
by homogeneous catalysts has been the subject of both
fundamental and applied studies, and the development
of new “single-site” group 4 catalyst precursors for
optimizing polymerization catalysis is one of the most
striking subjects in the field of organometallic chemis-
try.2 The combination of these two areas affords cyclo-
pentadienyl group 4 metal derivatives as a family of
attractive candidates for the attachment over a dendritic
surface, providing in this way model systems for het-
erogenization of such complexes on, for example, silica
supports. A few examples have been reported so far,3,4
consisting of bis(cyclopentadienyl) group 4 metals, in
which the metallocene units were linked to a carbosilane
dendritic skeleton through the ancillary cyclopentadi-
enyl ring.
Resu lts a n d Discu ssion
We have reported5 that treatment of 4-allyl-2-meth-
oxyphenol (Ia ; eugenol) or 4-allyl-2,6-dimethoxyphenol
(Ib) with Et3SiH or Si-H terminated dendrimers using
Karstedt’s catalyst7 in THF produced the C-silylated
derivatives (hydrosilylation of the olefin fragment)
together with variable amounts of the O-silylated
products (silylation of the phenol functionality) along
with the 2-propenyl isomers of I, as a result of competi-
tive isomerization reactions (see Scheme 1). The undes-
ired products (O-silylated and 2-propenyl isomers) could
be easily removed using chromatographic techniques.
Nevertheless, the overall yield of the reaction was
significantly diminished.
To increase the selectivity of the hydrosilylation
reaction, we have conducted sets of experiments in
which Et3SiH, 1G-H4, 2G-H8, and 4G-H32 have been
used in the hydrosilylation reaction of Ia ,b: (i) varying
the solvent (THF or toluene), (ii) changing reactant
concentrations, (iii) using different catalyst concentra-
tions, and (iv) repeating these experiments while pro-
tecting the phenolic function of I with the -SiMe3 group.
The percentage of C- and O-silylation was determined
by 1H NMR spectroscopy, as the o-methoxy substituent
of the phenyl ring is sensitive to the presence of a
hydroxy (δ 3.86) or siloxy group (δ 3.78). In a prelimi-
nary set of experiments, we observed that solvent
polarity does not have an appreciable effect on selectiv-
ity and a high concentration of reagents favors the
C-silylation versus the two side reactions. In the absence
of solvent, the silane dendrimers form a gel and the
reaction does not proceed. Thus, unless otherwise
We have recently reported the synthesis of carbosilane
dendrimers with peripheral phenol functionalities that
have proved to be useful supports for [Ti(C5H5)Cl3].5 The
extension reported here of this methodology to other
cyclopentadienyl titanium and zirconium complexes is
* To whom correspondence should be addressed. Tel: 34-1-8854654.
Fax: 34-1-8854683. E-mail: rafael.gomez@uah.es (R.G.), javier.
delamata@uah.es (F.J .d.l.M.).
(1) (a) Tomalia, D. A.; Brothers, H. M., II; Pielher, L. T.; Hsu, Y.
Polym. Mater. Sci. Eng. 1995, 73, 75. (b) Ardoin, N.; Astruc, D. Bull.
Soc. Chim. Fr. 1995, 132, 875. (c) Zeng, F.; Zimmerman, S. Chem. Rev.
1997, 97, 1681. (d) Hearshaw, M. A.; Moss, J . R. Chem. Commun. 1999,
1. (e) Astruc, D.; Chardac, F. Chem. Rev. 2001, 101, 2991. (f) Oosterom,
G. E.; Reek, J . N. H.; Kamer, P. C. J .; van Leeuwen, P. W. N. M. Angew.
Chem., Int. Ed. 2001, 40, 1828.
(2) Cornils, B., Herrmann, W. A., Eds. Applied Homogeneous
Catalysis with Organometallic Compounds; VCH: Weinheim, Ger-
many, 1996.
(3) Seyferth, D.; Wryrwa, R.; Franz, U. W.; Becke, S. PCT Int. Appl.
WO 97/32908, 1997; Chem. Abstr. 1997, 127, 263179p.
(4) Bru¨ning, K.; Lang, H. J . Organomet. Chem. 1999, 575, 153.
(5) (a) Are´valo, S.; Benito, J . M.; de J esu´s, E.; de la Mata, F. J .;
Flores, J . C.; Go´mez, R. J . Organomet. Chem. 2000, 602, 208. (b)
Are´valo, S.; de J esu´s, E.; de la Mata, F. J .; Flores, J . C.; Go´mez, R.
Organometallics 2001, 20, 2583.
(6) de J esu´s, E.; Andre´s, R.; Are´valo, S.; Benito, J . M.; de la Mata,
F. J .; Flores, J . C.; Go´mez, R. Polym. Mater. Sci. Eng. 2001, 84, 1027.
(7) Karstedt, B. D. U.S. Patent 3,775,452, 1973.
10.1021/om034042i CCC: $25.00 © 2003 American Chemical Society
Publication on Web 10/25/2003

5110 Organometallics, Vol. 22, No. 24, 2003
Are´valo et al.
Sch em e 1
tional Et3SiH. A similar result was observed by Laine
et al. using silsesquioxane silanes.8
With the intermediates described above, we carried
out the hydrosilylation reactions using -SiMe3 protect-
ed phenols IIa ,b, which were easily prepared by addi-
tion of SiMe3Cl to the corresponding alcohol in the pre-
sence of NEt3, and a Karstedt catalyst concentration of
2.6 mM (Scheme 2). As expected, no O-silylation prod-
ucts were found. For Et3SiH, a dramatic decrease of
isomerization reactions occurred, affording IIIa ,b in
high yields. For dendritic silanes, 1G-H4, 2G-H8, and
4G-H32, isomerization products were not observed and
dendrimers V-VII were quantitatively obtained.9 The
subsequent treatment of these siloxy derivatives with
aqueous HCl afforded the previously reported5 phenol-
terminated carbosilane dendrimers VIII-X in 90-95%
overall yield after purification by column chromato-
graphy.5b
Titanium centers have been successfully incorporated
at the surface of the carbosilane dendrimer containing
phenol end groups via alcoholysis of a Ti-Cl bond in
[Ti(C5H5)Cl3].5 However, this approach is not appropri-
ate for the synthesis of analogous dendrimers containing
pentamethylcyclopentadienyl titanium units because of
the enhanced stability of the Ti-Cl bond in [Ti(C5Me5)-
Cl3] toward alcoholysis. We have also reported10 the
synthesis in good yield of mononuclear pentamethylcy-
clopentadienyl aryloxo titanium complexes via reaction
of [Ti(C5Me5)Cl3] with the dilithium salt of different
hydroquinones or the lithium salt of eugenol. This
second approach may be convenient for early-generation
dendrimers but seems to be unsuitable for higher
generations because the selectivity of lithiation de-
creases when the number of phenol groups increases.
Here, we describe appropriate synthetic procedures for
anchoring chloro and methyl pentamethylcyclopenta-
dienyl titanium fragments to the periphery of phenol-
ended dendrimers via reaction of such systems with
[Ti(C5Me5)Cl2Me] or [Ti(C5Me5)Me3] or bis(cyclopenta-
dienyl) titanium or zirconium units by using [Ti(C5H5)2-
Cl2] or [Zr(C5H5)2HCl], respectively.
a
[Pt] ) Karstedt’s catalyst (0.85 mM).
stated, the hydrosilylation reactions were carried out
in a minimum amount of THF with Karstedt’s catalyst
(0.8 mM), under an argon atmosphere at 70 °C for 9 h
and then at room temperature for 12 h. Under these
conditions, Et3SiH afforded O-silylated products (10-
15% for Ia and <5% for Ib) and 40-50% of isomerized
compounds, whereas negligible amounts of O-silylation
and a lower percentage of isomerization (15-25%) were
found for dendrimers 1G-H4, 2G-H8, and 4G-H32. With
regard to the catalyst concentration, when it is increased
2- or 3-fold (2.6 mM), the amounts employed above gave
an increase of the O-silylation products in the cases of
all the silane reagents used and a decrease of the
isomerization products, which were negligible for the
dendritic silanes. From these results we cannot make
a proposal about the nature of the active species in the
catalytic cycle, but it seems clear that the polyfunctional
nature of the dendrimers strongly favors C-silylation
versus O-silylation and isomerization, hence inferring
a different mechanism with respect to the monofunc-
The reaction of monophenolic derivatives I and IV
with [Ti(C5Me5)Cl2Me] in toluene at room temperature
Sch em e 2

Synthesis of Aryloxo Dendrimers
Organometallics, Vol. 22, No. 24, 2003 5111
Sch em e 3
proceeds with evolution of methane to form the corre-
sponding aryloxo complexes 1-4 (see Scheme 3) as red
solids in quantitative yields. The same procedure has
been used for the synthesis of the corresponding den-
drimers. Metathetical replacement of a methyl group
by an aryloxo unit is readily achieved when phenol-
ended dendrimers VIIIa -Xa react with 1 equiv (per
phenol group) of [Ti(C5Me5)Cl2Me] in toluene overnight,
leading to the new organometallic dendrimers 5-7 (see
Scheme 3). These metallodendrimers are obtained as
red, moisture-sensitive oils, soluble in aromatic solvents
and insoluble in aliphatic solvents.
drimers requires different synthetic procedures for
titanium and zirconium. Reaction of phenols Ia , IVa ,
VIIIa , and IXa with [Ti(C5H5)2Cl2] in the presence of
NEt3 affords monosubstituted aryloxides 15-18 (see
Scheme 4). No disubstitution has been observed in any
of these reactions, possibly due to steric hindrance at
the titanium center relative to zirconium (see below).
For the synthesis of mononuclear complexes a light
excess of the phenol derivative can be used in order to
ensure completion of the reaction. However, in the case
of titanium dendrimers an accurate stoichiometry must
be used in order to avoid the presence of unsubstituted
phenol groups.
Aryloxo methyl derivatives have been prepared by
reaction of phenol derivatives I and IV or phenol-ended
dendrimers VIIIa -Xa with 1 equiv (per phenol group)
of [Ti(C5Me5)Me3]. In this case, the reaction is carried
out in hexane and is complete after 2 h at room
temperature, giving the complexes 810 and 9-14 (see
Scheme 3). These methyl complexes are soluble in
aromatic solvents and in saturated hydrocarbons. They
are soluble in chlorinated solvents, but in these solvents
Ti-Me bonds are transformed into Ti-Cl bonds. As
reported for other aryloxo pentamethylcyclopentadienyl
titanium derivatives,11 these methyl derivatives cannot
be prepared by methylation of chloro derivatives 1-7,
because methylating reagents such as AlMe3 and Mg-
ClMe react with the Ti-aryloxo bonds of complexes 1-7
to give a mixture of [Ti(C5Me5)MeCl2], [Ti(C5Me5)Me3],
and aryloxo aluminum or magnesium derivatives.12
Phenol-functionalized dendrimers have also been used
to support bis(cyclopentadienyl) group 4 complexes at
their surface. The preparation of these supported den-
In contrast, the reaction of Ia with 1 equiv of [Zr-
(C5H5)2Cl2] in the presence of 1 equiv of NEt3 affords a
mixture of the starting zirconium precursor together
with the mono- and disubstitution aryloxo derivatives,
whereas the reaction of [Zr(C5H5)2Cl2] with 2 equiv of
eugenol in the presence of 2 equiv of NEt3 affords
quantitatively the bis(aryloxide) compound 19. This
behavior can be attributed to the larger size of the
(8) Zhang, C.; Laine, R. M. J . Am. Chem. Soc. 2000, 122, 6979.
(9) For spectroscopic data see the Supporting Information.
(10) Are´valo, S.; Benito, J . M.; de J esu´s, E.; de la Mata, F. J .; Flores,
J . C.; Go´mez, R. J . Organomet. Chem. 1999, 592, 265.
(11) Nomura, K.; Naga, N.; Miki, M.; Yanagi, K.; Imao, A. Organo-
metallics 1998, 17, 2152.
(12) For instance, the reaction of Ib with AlMe3 allowed the isolation
of an aryloxo aluminium derivative, {(AlMe2)2[µ-{O[C6H2(OMe)2-
(C3H5)]}]2}. 1H NMR (CDCl3): δ 6.37 (s, 4H, C6H2), 5.70 (m, 2H,
CH2CHdCH2), 5.06 (m, 4H, CH2CHdCH2), 3.80 (s, 12H, OMe), 3.30
(m, 4H, CH2CHdCH2), -0.83 (s, 12H, Al-CH3). 13C{1H} NMR
(CDCl3): δ 147.4 (Cipso bonded to -OMe), 137.4 (CH2CHdCH2), 131.9
(Cipso bonded to -C3H5), 115.9 (CH2CHdCH2), 104.4 (C6H2), 56.4 (OMe),
40.3 (CH2CHdCH2), -9.2 (Al-CH3).

5112 Organometallics, Vol. 22, No. 24, 2003
Are´valo et al.
Sch em e 4a
F igu r e 1. ORTEP (50% thermal ellipsoids) view of [Ti(C5-
Me5)Cl2{O[C6H2(OMe)2(CH2CHdCH2)]}] (2). Selected bond
lengths (Å) and angles (deg): Ti(1)-O(1) ) 1.770(3), Ti-
(1)-Cl(1) ) 2.2661(18), Ti(1)-Cp(1) ) 2.026; Cp(1)-Ti(1)-
O(1) ) 118.9, Ti(1)-O(1)-C(21) ) 163.1(3).
these data it could be assumed that substitution of the
eugenolate moiety for the 2,6-dimethoxyphenoxide frag-
ment or hydrosilylation of the allyl fragment does not
produce significant changes on the electronic density at
the metal center.
For complexes 1, 2, 8, 9, 15, 19, and 20, the allyl group
resonances were unambiguously assigned. The 1H NMR
data of the dendritic complexes show, in contrast, the
presence of the SiCH2CH2CH2-Ph fragment as the
result of an anti-Markovnikov addition of a Si-H bond
to the allyl fragment. The resonance patterns for these
methylene protons and for the methylene protons of the
branches -SiCH2CH2CH2Si- present in the dendrimers
are in agreement with the proposed formulation (full
details of the assignment of these signals is given in
the Experimental Section and the Supporting Informa-
tion, and a more detailed discussion of this assignment
can be found in ref 5b). The carbosilane fragments do
not present significant changes, due to the nature and
number of the cyclopentadienyl rings or to the presence
of a titanium or zirconium metal center. In agreement
with this, the 29Si NMR data show no significant
changes from the organic dendritic precursors or the
metallodendrimers containing [Ti(C5H5)Cl2] units, as
was expected.
Single crystals of 2 suitable for X-ray diffraction
studies were obtained from a mixture of Et2O and
hexane cooled to -20 °C. An ORTEP drawing of the
molecular structure is shown in Figure 1. The Ti-O
bond (1.76 Å) and Ti-O-C angle (163.0°) are almost
identical with those of other similar monometallic
complexes such as {Ti(C5Me5)[O(2,6-Me2C6H3)]Cl2}16 or
an analogue containing the unsubstituted cyclopenta-
dienyl ligand, {Ti(C5H5)[O(2,6-iPr2C6H3)]Cl2}.11,17
In summary,we have developed a synthetic strategy
to obtain selectively the C-silylation products of phenols
having pendant allyl groups with Si-H terminated
dendrimers and allowing the synthesis of phenol-ended
carbosilane dendrimers in almost quantitative yields.
These dendrimers can be used to anchor different mono-
and bis(cyclopentadienyl) complexes of titanium and
zirconium through the use of suitable organometallic
a
Conditions: M ) Ti, X ) Cl, toluene as solvent, NEt3 must
be added; M ) Zr, X ) H, THF as solvent.
zirconium center that allows the entry of a second
aryloxo ligand to its coordination sphere.13
Nevertheless, we have been able to obtain monosub-
stituted aryloxo derivatives of zirconium by reaction of
phenols Ia , IVa , VIIIa , and IXa with 1 equiv of [Zr-
(C5H5)2HCl] (per phenol group) to give 20-23 in quan-
titative yield with evolution of dihydrogen (see Scheme
4).
These bis(cyclopentadienyl) titanium and zirconium
derivatives are moisture sensitive and in the presence
of air decompose, giving the µ-oxo complexes [{M(C5H5)2-
Cl}2(µ-O)] (M ) Ti,14 Zr15), although they can be stored
under an inert atmosphere for long time periods. All of
them are soluble in chlorinated and aromatic solvents
and completely insoluble in saturated hydrocarbons.
The organometallic compounds have been character-
ized using 1H, 13C, and 29Si NMR spectroscopy and
elemental analysis (full details are given in the Sup-
porting Information). For complex 2 the solid-state
structure has been determined by X-ray diffraction
methods.
The 1H NMR spectra of some metallodendrimers have
shown small peaks of impurities (less than 2%) due to
hydrolysis processes or solvent molecules, which were
difficult to separate. The NMR spectra of all complexes
1-23 show singlets corresponding to the pentamethyl-
cyclopentadienyl or cyclopentadienyl ligands in the
expected region (see the Supporting Information). Meth-
yl groups bonded to titanium appear as singlets in 1H
NMR (0.40 ppm) and in 13C NMR (53.6 ppm). From
(13) Firth, A. V.; Stewart, J . C.; Hoskin, A. J .; Stephan, D. W. J .
Organomet. Chem. 1999, 591, 185.
(14) Wailes, P. C.; Couts, R. S. P.; Weigold, H. In Organometallic
Chemistry of Titanium, Zirconium and Hafnium; Academic: New York,
1974.
(15) Cardin, D. J .; Lappert, M. F.; Raston, C. L. Chemistry of
Organozirconium and Hafnium Compounds; Ellis Horwood: Chich-
ester, England, 1986.
(16) Go´mez-Sal, P.; Mart´ın, A.; Mena, M.; Royo, P.; Serrano, R. J .
Organomet. Chem. 1991, 419, 77.
(17) Nomura, K.; Naga, N.; Miki, M.; Yanagi, K. Macromolecules
1998, 31, 7588.

Synthesis of Aryloxo Dendrimers
Organometallics, Vol. 22, No. 24, 2003 5113
Syn th esis of 4G-[(CH2)3{[C6H3(OMe)]O}Ti(C5Me5)Me2]32
(14). A solution of 4G-{(CH2)3[C6H3(OMe)]OH}32 (0.30 g, 2.75
× 10-2 mmol) in Et2O (10 mL) was slowly added to a solution
of [Ti(C5Me5)Me3] (0.20 g, 0.88 mmol) in Et2O (5 mL). The
reaction mixture was stirred for 2 h at room temperature. The
solvent was removed at reduced pressure to obtain 14 as a
brown-yellow oil in quantitative yield (0.48 g). Selected data
precursors. In all cases, the dendritic framework seems
to be chemically inert and spectroscopically invariable
to the changes produced in the periphery, while the
organometallic unit retains the spectroscopic, and hence
chemical, properties of the mononuclear counterparts.
1
are as follows. H NMR (CDCl3): δ 0.38 (s, 48H, TiMe2). 13C
Exp er im en ta l Section
NMR (CDCl3): δ 152.3 (Cipso bonded to -OTi), 53.8 (TiMe2).
The rest of the data are almost invariable with respect to
compound 7; see the Supporting Information. 29Si{1H} NMR
(CDCl3): δ 1.94 (G4-Si), 1.31 (G3-Si); the rest were not
observed. Anal. Calcd for C976H1692O64Si61Ti32: C, 66.24; H,
9.64. Found: C, 65.02; H, 9.40.
Gen er a l P r oced u r es. All manipulations were performed
under an inert atmosphere of argon using standard Schlenk
techniques or a drybox. Solvents used were previously dried
and freshly distilled under argon: tetrahydrofuran from
sodium benzophenone ketyl, toluene from sodium, hexane from
sodium-potassium, and methylene chloride over P4O10. Unless
otherwise stated, reagents were obtained from commercial
sources and used as received. [Ti(C5Me5)Cl3],18 [[Ti(C5Me5)Cl2-
Me],19 [Ti(C5Me5)Me3],20 and Gn-H dendrimers21 were prepared
according to reported methods.
Syn th esis of 2G-[(CH2)3{[C6H3(OMe)]O}Ti(C5H5)2Cl]8
(18). A solution of 2G-{(CH2)3[C6H3(OMe)]OH}8 (0.10 g, 0.04
mmol) in toluene (10 mL) was slowly added to a solution of
[Ti(C5H5)2Cl2] (0.08 g, 0.32 mmol) in toluene (50 mL). To this
mixture was added a slight excess of NEt3 (50 µL, 0.36 mmol).
The reaction mixture was stirred for 12 h and then filtered
through Celite to remove NEt3‚HCl. The resulting red solution
was evaporated under reduced pressure to give 18 as a red
1H, 13C, and 29Si NMR spectra were recorded on Varian
Unity VXR-300 and Varian 500 Plus instruments. Chemical
1
shifts (δ, ppm) were measured relative to residual H and 13C
microcrystalline solid (0.127 g, 79%). 1H NMR (CDCl3):
δ
resonances for chloroform-d and benzene-d6 used as solvents,
and 29Si chemical shifts were referenced to external SiMe4 (0.00
ppm). The integral values of the signals in the 1H NMR spectra
of dendrimer complexes represent only one-fourth of the total
amount of hydrogen atoms. C, H analyses were carried out
with a Perkin-Elmer 240 C microanalyzer. Thin-layer chro-
matography was accomplished using 0.25 mm silica gel plates
from Alugram, and chromatography was performed on silica
gel (35-70 mesh) for the organic dendrimers.
6.67-6.60 (m, 6H, C6H3), 6.32 (s, 20H, C5H5), 3.76 (s, 6H,
OMe), 2.51 (m, 4H, SiCH2CH2CH2Ph), 1.54 (m, 4H, SiCH2CH2-
CH2Ph), 1.29 (m, 6H, SiCH2CH2CH2Si), 0.50 (m, 16H, SiCH2-
CH2CH2Ph and SiCH2CH2CH2Si overlapping), -0.07 (s, 12H,
SiMe2), -0.09 (s, 3H, SiMe). 13C NMR (CDCl3): δ 159.1 (Cipso
bonded to -OTi), 145.8 (Cipso bonded to -OMe), 134.9 (Cipso
bonded to -CH2), 125.1, 120.5, and 111.8 (C6H3), 117.4 (C5H5),
55.9 (OCH3), 39.9 (SiCH2CH2CH2Ph), 26.4 (SiCH2CH2CH2Ph),
15.6 (SiCH2CH2CH2Ph), 22.7, 19.1, 18.7, and overlapped
signals (Si(CH2)3Si), -2.9 (SiMe2), -4.6 (SiMe). 29Si{1H} NMR
(CDCl3): δ 1.87 (G2-Si), 1.19 (G1-Si), 0.77 (G0-Si). Anal. Calcd
for C216H308Cl8O16Si13Ti8: C, 61,88; H, 7,40. Found: C, 61.52;
H, 7.46.
Syn th esis of 2G-[(CH2)3{[C6H3(OMe)]O}Zr (C5H5)2Cl]8
(23). A solution of 2G-{(CH2)3[C6H3(OMe)]OH}8 (0.05 g, 0.02
mmol) in THF (5 mL) was slowly added to a suspension of
[Zr(C5H5)2HCl] (0.04 g, 0.17 mmol) in THF (5 mL). The reaction
mixture was stirred for 15 min. After hydrogen evolution
ceased, the resulting yellow solution was evaporated under
reduced pressure, affording quantitatively 23 as a yellow oil
(0.088 g). Selected data are as follows. 1H NMR (CDCl3): δ
6.33 (s, 20H, C5H5). 13C NMR (CDCl3): δ 152.6 (Cipso bonded
to -OZr), 114.4 (C5H5). The rest of the data are almost
invariable with respect to those of compound 18; see the
Supporting Information. 29Si{1H} NMR (CDCl3): δ 1.86 (G2-
A selection of synthetic procedures and data are shown; for
the rest, see the Supporting Information.
Syn th esis of 4G-[(CH2)3{[C6H3(OMe)]O}Ti(C5Me5)Cl2]32
(7). A solution of 4G-{(CH2)3[C6H3(OMe)]OH}32 (0.30 g, 2.75
× 10-2 mmol) in CH2Cl2 (10 mL) was slowly added to a solution
of [Ti(C5Me5)Cl2Me] (0.24 g, 0.88 mmol) in CH2Cl2 (5 mL). The
mixture was stirred overnight. The solvent was removed at
reduced pressure, to obtain a foamy red solid. The product was
washed with Et2O (2 × 2 mL) to give 7 as a red foamy solid
(0.39 g, 75% yield). 1H NMR (CDCl3): δ 6.84 (m, 8H, C6H3),
6.60 (m, 16H, C6H3), 3.77 (s, 24H, OMe), 2.52 (m, 16H, SiCH2-
CH2CH2Ph), 2.16 (s, 120H, C5Me5), 1.54 (m, 16H, SiCH2CH2-
CH2Ph), 1.24 (m, 30H, SiCH2CH2CH2Si), 0.52 (m br, 76H,
SiCH2CH2CH2Si and SiCH2CH2CH2Ph overlapping), -0.07 (m
br, 69 H, SiMe2 and SiMe overlapping). 13C NMR (CDCl3); δ
153.4 (Cipso bonded to -OTi), 149.9 (Cipso bonded to -OMe),
138.6 (Cipso bonded to -CH2), 132.7 (C5Me5), 120.6, 120.1, and
113.0 (C6H3), 56.3 (OMe), 39.9 (SiCH2CH2CH2Ph), 26.1
(SiCH2CH2CH2Ph), 15.3 (SiCH2CH2CH2Ph), 20.2, 18.9, 18.5,
and overlapped signals (Si(CH2)3Si), 12.8 (C5Me5), -3.2 (SiMe2),
-4.9 (SiMe). 29Si{1H} NMR (CDCl3): δ 1.91 (G4-Si), 1.28 (G3-
Si); the rest were not observed. Anal. Calcd for C912H1500Cl64O64-
Si61Ti32: C, 57.64; H, 7.95. Found: C, 56.82; H, 7.70.
Si), 1.19 (G1-Si), 0.77 (G0-Si). Anal. Calcd for C216H308Cl8O16
-
Si13Zr8: C, 57.18; H, 6.79. Found: C, 56.92; H, 6.56.
Ack n ow led gm en t. We acknowledge the Ministerio
de Ciencia y Tecnolog´ıa of Spain (Grant No. BQU2001-
1160) and Consejer´ıa de Educacio´n-Comunidad de
Madrid (Grant No. 07N/0078/2001) for financial support.
(18) (a) Hidalgo, G.; Mena, M.; Palacios, F.; Royo, P.; Serrano, R. In
Synthetic Methods of Organometallic and Inorganic Chemistry; Her-
rmann, W. A., Salzer, A., Eds.; Thieme Verlag: Stuttgart, Germany,
1996; Vol. 1, p 95. (b) Hidalgo, G.; Mena, M.; Palacios, F.; Royo, P.;
Serrano, R. J . Organomet. Chem. 1998, 340, 37.
(19) Mart´ın, A.; Mena, M.; Pellinghelli, M. A.; Royo, P.; Serrano,
R.; Tiripicchio, A. J . Chem. Soc., Dalton Trans. 1993, 2117.
(20) Mena, M.; Pellinghelli, M. A.; Royo, P.; Serrano, R.; Tiripicchio,
A. Organometallics 1989, 8, 476.
(21) (a) Seyferth, D.; Son, D. Y.; Rheingold, A. L.; Ostrander, R. L.
Organometallics 1994, 13, 2682. (b) Cuadrado, I.; Mora´n, M.; Losada,
J .; Casado, C. M.; Pascual, C.; Alonso, B.; Lobete, F. In Advances in
Dendritic Macromolecules; Newkome, G. R., Ed.; J AI Press: Green-
wich, CT, 1996; Vol. 3, pp 151-191.
Su p p or tin g In for m a tion Ava ila ble: Text giving experi-
mental procedures and NMR and analytical data of all the
complexes, figures giving a selection of 1H, 13C, and 29Si NMR
spectra of titanium and zirconium mononuclear complexes and
dendrimers, and tables of crystal and data collection param-
eters, atomic coordinates, bond lengths, bond angles, and
thermal displacement parameters of compound 2; X-ray crystal
data are also available as CIF files. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM034042I