Synthesis of carbosilane dendrimers containing peripheral (cyclopentadienyl)(aryloxy)titanium(IV) units

Article abstract of DOI:10.1021/om0010114

Treatment of [Ti(C₅H₅)Cl₃] with 4-allyl-2,6-dimethoxyphenol (II) gave the corresponding aryloxy complex [Ti(C₅H₅){OC₆H₂(OMe)₂ (C₃H₅)}Cl₂] (2), while hydrosilylation reactions of the allyl group of 4-allyl-2-methoxyphenol (eugenol; I) or 4-allyl-2,6-dimethoxyphenol (II) with HSiEt₃ and subsequent reaction with [Ti(C₅H₅)Cl₃] led to the mononuclear compounds [Ti(C₅H₅){OC₆H_4-n(OMe)_n (C₃H₆SiEt₃)}Cl₂] (n = 1 (3), 2 (4)) in high yield. This synthetic procedure has been used as a model for the preparation of new peripheral carbosilane metallodendrimers. Series of carbosilane dendrimer generations G1, G2, and G4, with 4, 8, and 32 end groups, respectively, have been functionalized with these phenol groups on the surface. The divergent synthesis was accomplished via hydrosilylation of the olefinic group of the phenols with the corresponding silicon hydride terminated dendrimers, giving 4G-[(CH₂)₃{C₆H₃(OMe)} OH]₃₂ (9), 1G-[(CH₂)₃{C₆ H₂(OMe)₂}OH]₄ (10), 2G-[(CH₂)₃{C₆H₂ (OMe)₂}-OH]₈ (11), and 4G-[(CH₂)₃{C₆H₂ (OMe)₂}OH]₃₂ (12) as oils in high yield. Reaction of 9-12 with [Ti(C₅H₅)Cl₃] afforded corresponding metallodendrimers containing (cyclopentadienyl)(aryloxy)titanium units at their periphery 4G-[(CH₂)₃[{C₆H₃(OMe)}O] Ti(C₅H₅)Cl₂]₃₂ (15), 1G-[(CH₂)₃[{C₆H₂(OMe)₂}O] Ti(C₅H₅)Cl₂]₄ (16), 2G-[(CH₂)₃[{C₆H₂(OMe)₂}O] Ti(C₅H₅)Cl₂]₈ (17), and 4G-[(CH₂)₃[{C₆H₂ (OMe)₂}O]Ti(C₅H₅)Cl₂]₃₂ (18). The compounds have been characterized by ¹H, ¹³C, and ²⁹Si NMR spectroscopy and elemental analysis and, up to the second generation of phenol-terminated dendrimers, by MALDI-TOF mass spectrometry. Gel permeation chromatography was used for all phenolic dendrimers, showing good linear relationships between calculated molecular weight and retention time.

Full text of DOI:10.1021/om0010114

Organometallics 2001, 20, 2583-2592
2583
Syn th esis of Ca r bosila n e Den d r im er s Con ta in in g
P er ip h er a l (Cyclop en ta d ien yl)(a r yloxy)tita n iu m (IV)
Un its
Silvia Are´valo, Ernesto de J esu´s, F. J avier de la Mata,* J uan C. Flores, and
Rafael Go´mez*
Departamento de Quı´mica Inorga´nica, Universidad de Alcala´, Campus Universitario,
E-28871 Alcala´ de Henares, Spain
Received November 27, 2000
Treatment of [Ti(C5H5)Cl3] with 4-allyl-2,6-dimethoxyphenol (II) gave the corresponding
aryloxy complex [Ti(C5H5){OC6H2(OMe)2(C3H5)}Cl2] (2), while hydrosilylation reactions of
the allyl group of 4-allyl-2-methoxyphenol (eugenol; I) or 4-allyl-2,6-dimethoxyphenol (II)
with HSiEt3 and subsequent reaction with [Ti(C5H5)Cl3] led to the mononuclear compounds
[Ti(C5H5){OC6H4-n(OMe)n(C3H6SiEt3)}Cl2] (n ) 1 (3), 2 (4)) in high yield. This synthetic
procedure has been used as a model for the preparation of new peripheral carbosilane
metallodendrimers. Series of carbosilane dendrimer generations G1, G2, and G4, with 4, 8,
and 32 end groups, respectively, have been functionalized with these phenol groups on the
surface. The divergent synthesis was accomplished via hydrosilylation of the olefinic group
of the phenols with the corresponding silicon hydride terminated dendrimers, giving 4G-
[(CH2)3{C6H3(OMe)}OH]32 (9), 1G-[(CH2)3{C6H2(OMe)2}OH]4 (10), 2G-[(CH2)3{C6H2(OMe)2}-
OH]8 (11), and 4G-[(CH2)3{C6H2(OMe)2}OH]32 (12) as oils in high yield. Reaction of 9-12
with [Ti(C5H5)Cl3] afforded corresponding metallodendrimers containing (cyclopentadienyl)-
(aryloxy)titanium units at their periphery 4G-[(CH2)3[{C6H3(OMe)}O]Ti(C5H5)Cl2]32 (15), 1G-
[(CH2)3[{C6H2(OMe)2}O]Ti(C5H5)Cl2]4 (16), 2G-[(CH2)3[{C6H2(OMe)2}O]Ti(C5H5)Cl2]8 (17), and
4G-[(CH2)3[{C6H2(OMe)2}O]Ti(C5H5)Cl2]32 (18). The compounds have been characterized by
1H, 13C, and 29Si NMR spectroscopy and elemental analysis and, up to the second generation
of phenol-terminated dendrimers, by MALDI-TOF mass spectrometry. Gel permeation
chromatography was used for all phenolic dendrimers, showing good linear relationships
between calculated molecular weight and retention time.
In tr od u ction
immobilization of metallocene catalysts.2c,5 All these
procedures of heterogenization have proven to be very
successful for the commercial-scale production of poly-
olefins. However, transition-metal complexes anchored
to these supports are difficult to study at the molecular
level for several reasons, which include an inaccurate
control of the number and location of the active sites.
In search of models that could elucidate a structure-
activity relationship of the active sites, several authors
have studied different strategies such as the synthesis
of group 4 metal silsesquioxane precursors,6 as mimics
for silica-grafted catalysts. Another approach to this
might consist of the use of dendrimers,7 which are
highly branched monodisperse, polyfunctionalized mac-
romolecules. Two general strategies for the construction
of dendritic molecules containing transition metals have
The immobilization of well-defined, homogeneous
olefin polymerization catalysts on solid supports com-
bines the advantages of both heterogeneous and homo-
geneous processes, such as the morphological control of
the resulting polymer and the presence of single active
sites.1 Group 4 metallocenes are examples that must
be heterogenized for some industrial applications.2
Several approaches have been used for this purpose,
such as the use of organic support materials such as
cross-linked polystyrene,3 inorganic materials widely
used for Ziegler-Natta and Phillips catalysts (silica,
alumina, magnesium chloride, etc.),4 or the self-
(1) Hungenberg, K. D.; Kerth, J .; Langhauser, F.; Marczinke, B.;
Schlund, R. In Ziegler Catalysts; Fink, G., Mu¨lhaupt, R., Brintzinger,
H. H., Eds.; Springer-Verlag: New York, 1995; pp 363-386.
(2) (a) Abbenhuis, H. C. L. Angew. Chem., Int. Ed. 1999, 38, 1058
and references therein. (b) Alt, H. G.; Schertl, P.; Ko¨ppl, A. J .
Organomet. Chem. 1998, 568, 263. (c) Alt, H. G. J . Chem. Soc., Dalton
Trans. 1999, 1703. (d) Hlatky, G. G. Coord. Chem. Rev. 1999, 181,
243.
(3) For example see: (a) Grubbs, R. H.; Gibbons, C.; Kroll, L. C.;
Bonds, W. D., J r.; Brubaker, C. H., J r. J . Am. Chem. Soc. 1973, 95,
2373. (b) Sun. L.; Hsu, C. C.; Bacon, D. W. J . Polym. Sci., Part A 1994,
32, 2127. (c) Roscoe, S. B.; Fre´chet, J . M.; Walzer, J . F.; Dias, A. J .
Science 1998, 280, 270.
(5) Peifer, B.; Milius, W.; Alt. H. G. J . Organomet. Chem. 1998, 553,
205.
(6) (a) Crocker, M.; Herold, R. H. M.; Orpen, A. G.; Overgaag, M. T.
A. J . Chem. Soc., Dalton Trans. 1999, 3791 and references therein.
(b) Duchateau, R.; Abbenhuis, H. C. L.; van Santen, R. A.; Thiele, S.
K. H.; van Tol, M. F. H. Organometallics 1998, 17, 5222. (c) Duchateau,
R.; van Santen, R. A.; Yap, G. P. A. Organometallics 2000, 19, 809.
(7) (a) Issberner, J .; Moors, R.; Vo¨gtle, F. Angew. Chem., Int. Ed.
Engl. 1994, 33, 2413. (b) Lothian-Tomalia, M. K.; Hedstrand, D. M.;
Tomalia, D. A.; Padias, A. B.; Hall, H. K., J r. Tetrahedron 1997, 53,
15495. (c) Fischer, M.; Vo¨gtle, F. Angew. Chem., Int. Ed. 1999, 38, 884.
(d) Majoral, J . P.; Caminade, A. M. Chem. Rev. 1999, 99, 845. (e)
Hearshaw, M. A.; Moss, J . R. Chem. Commun. 1999, 1.
(4) For example see: (a) Kaminsky, W. Macromol. Chem. Phys.
1996, 197, 3907. (b) Soga, K.; Kaminaga, M. Makromol. Chem. Phys.
1994, 195, 1369. (c) Tudor, J .; O’Hare, Chem. Commun. 1997, 603.
10.1021/om0010114 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 05/17/2001

2584 Organometallics, Vol. 20, No. 12, 2001
Are´valo et al.
Sch em e 1
been applied. The first one entails the formation of one
or more catalytic sites in the core of the dendrimer,8
while the second one involves the attachment of mul-
tiple sites at the periphery of the dendritic macromol-
ecules.9,10 Both types of metallodendrimers represent
nanoscopic materials with physical characteristics such
as size, solubility, and dispersity of catalytic sites, very
precisely defined. All this could afford advantageous
properties for physical separation and catalyst recycling
while all the characteristics found in the analogous
mononuclear model are retained. With respect to the
second strategy, although an increasing number of
reports have been published about peripheral late-
transition-metal dendrimers,9 titanium and other early
transition metals have been scarcely represented.10
We are interested in the development of peripheral
group 4 metallodendrimers based on a chemically inert
carbosilane framework.11 Furthermore, as a part of
our current research, we are involved in the synthesis
of mono(cyclopentadienyl)(aryloxy)titanium complexes
which are very attractive for polymerization processes.12
We have previously reported that the reaction of 4-allyl-
2-methoxyphenol (I; commonly called eugenol) with
[Ti(C5H5)Cl3] cleanly produced the mononuclear com-
pound [Ti(C5H5){OC6H3(OMe)(C3H5)}Cl2] (1).13 Eugenol,
complex 1 itself, or other related derivatives containing
pendant allyl groups are suitable systems for their
introduction on the surface of organosilicon dendrimers
containing Si-H bonds11d via hydrosilylation reactions.
We report here the synthesis and characterization of
carbosilane dendrimers with peripheral phenolic func-
tionalities and their reaction with [Ti(C5H5)Cl3]. A
preliminary account of part of this work has been
published.10e
(8) (a) Oosterom, G. E.; van Hareen, R. J .; Reek, J . N. H.; Kamer,
P. C. J .; van Leeuwen, P. W. N. M. Chem. Commun. 1999, 1119 and
references therein. (b) Maraval, V.; Laurent, R.; Caminade, A. M.;
Majoral, J . P. Organometallics 2000, 19, 4025.
(9) (a) Newkome, G. R.; He, E.; Moorefield, C. N. Chem. Rev. 1999,
99, 1689 and references therein. Selected references on the synthesis
of periphery-metalated carbosilane dendrimers are: (b) Knapen, J . W.
J .; van der Made, A. W.; de Wilde, J . C.; van Leeuwen, P. W. N. M.;
Wijkens, P.; Grove, D. M.; van Koten, G. Nature 1994, 372, 659. (c)
Hoare, J . L.; Lorentz, K.; Hovestad, N. J .; Smeets, W. J . J . H.; Spek,
A. L.; Canty, A. J .; Frey, H.; van Koten, G. Organometallics 1997, 16,
4167. (d) Kleij, A. W.; Kleijn, H.; J astrzebski, J . T. B. H.; Smeets, W.
J . J .; Spek, A. L.; van Koten, G. Organometallics 1999, 18, 268. (e)
Hovestad, N. J .; Hoare, J . L.; J astrzebski, J . T. B. H.; Canty, A. J .;
Smeets, W. J . J .; Spek, A. L.; van Koten, G. Organometallics 1999,
18, 2970. (f) Alonso, B.; Cuadrado, I.; Mora´n, M.; Losada, J . J . Chem.
Soc., Chem. Commun. 1994, 2575. (g) Lobete, F.; Cuadrado, I.; Casado,
C. M.; Alonso, B.; Mora´n, M.; Losada, J . J . Organomet. Chem. 1996,
509, 109. (h) Casado, C. M.; Cuadrado, I.; Alonso, B.; Mora´n, M.;
Losada, J . J . Electroanal. Chem. 1999, 463, 87. (i) Seyferth, D.; Kugita,
T.; Rheingold, A. L.; Yap, G. P. A. Organometallics 1995, 14, 5362. (j)
Benito, M.; Rossell, O.; Seco, M.; Segale´s, G. Organometallics 1999,
18, 5191. (k) Kim, C.; J ung, I. J . Organomet. Chem. 1999, 588, 9. (l)
de Groot, D.; Eggeling, E. B.; de Wilde, J . C.; Kooijmann, H.; van
Haaren, R. J .; van der Made, A. W.; Spek, A. L.; Vogt, D.; Reek, J . N.
H.; Kamer, P. C. J .; van Leeuwen, P. W. N. M. Chem. Commun. 1999,
1623.
(10) (a) Cadierno, V.; Igau, A.; Donnadieu, B.; Caminade, A. M.;
Majoral, J . P. Organometallics 1999, 18, 1580. (b) Bru¨ning, K.; Lang,
H. J . Organomet. Chem. 1999, 575, 153. (c) Sellner, H.; Seebach, D.
Angew. Chem., Int. Ed. 1999, 38, 1918. (d) Rheiner, P. B.; Seebach, D.
Chem. Eur. J . 1999, 5, 3221. (e) Arevalo, 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. (f) Seyferth, D.; Wryrwa, R.; Franz, U. W.; Becke, S.
PCT Int. Appl. WO 97/32908, 1997; Chem. Abstr. 1997, 127, 263179p.
(g) Reetz, M. T.; Giebel, D. Angew. Chem., Int. Ed. 2000, 39, 2498.
(11) (a) van der Made, A. W.; van Leeuwen, P. W. N. M. J . Chem.
Soc., Chem. Commun. 1992, 1400. (b) van der Made, A. W.; van
Leeuwen, P. W. N. M.; de Wilde, J . C.; Brandes, R. A. C. Adv. Mater.
1993, 5, 466. (c) Zhou, L. L.; Roovers, J . Macromolecules 1993, 26, 963.
(d) Seyferth, D.; Son, D. Y.; Rheingold, A. L.; Ostrander, R. L.
Organometallics 1994, 13, 2682. (e) 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: Greenwich,
CT, 1996; Vol. 3, pp 151-191. (f) Kim, C.; Son, S. J . Organomet. Chem.
2000, 599, 123 and references therein.
Resu lts a n d Discu ssion
Syn th esis of Mon on u clea r Mod els. In a synthetic
method similar to that previously reported for the
aryloxy complex [Ti(C5H5){OC6H3(OMe)(C3H5)}Cl2] (1),13
the reaction of [Ti(C5H5)Cl3] with 1 equiv of 4-allyl-2,6-
dimethoxyphenol (II) in toluene at 80 °C gave the
analogous compound [Ti(C5H5){OC6H2(OMe)2(C3H5)}-
Cl2] (2) as red microcrystals in 85% yield (Scheme 1).
Hydrosilylation of compounds 1 and 2 with triethyl-
silane (HSiEt3) were studied using the Karstedt catalyst
(platinum divinyltetramethyldisiloxane).14 The reactions
proceeded in toluene at 60-70 °C, affording [Ti(C5H5)-
{OC6H4-n(OMe)n(C3H6SiEt3)}Cl2] (n ) 1 (3), 2 (4)) as
the main products, resulting from anti-Markovnikov
addition (â-isomer) of HSiEt3. The complexes obtained
by this method were always contaminated with com-
pounds resulting from the isomerization of the allyl
group to propenyl [Ti(C5H5){OC6H4-n(OMe)n(CHd
CHCH3)}Cl2] (n ) 1, 2) as indicated by their 1H NMR
spectra.15 Attempts to separate these derivatives failed.
However, the Markovnikov R-isomer units -CH2CH-
(SiEt3)CH3 were not observed in any cases.
A more suitable procedure for the synthesis of 3 and
4 involved the prior hydrosilylation of the organic pre-
cursors and the subsequent reaction with [Ti(C5H5)Cl3].
Hence, treatment of 4-allyl-2-methoxyphenol (I) or
4-allyl-2,6-dimethoxyphenol (II) with an excess of
HSiEt3 (using Karstedt catalyst) in neat silane or THF,
respectively, at 70 °C, produced the â-addition deriva-
(12) (a) Skupinski, W.; Wasilewski. A. J . Organomet. Chem. 1981,
220, 39. (b) Skupinski, W.; Wasilewski. A. J . Organomet. Chem. 1985,
282, 69. (c) Nomura, K.; Naga, N.; Miki, M.; Yanagi, K.; Imai. A.
Organometallics 1998, 17, 2152. (d) Vilardo, J . S.; Thorn, M. G.;
Fanwick, P. E.; Rothwell. I. P. Chem. Commun. 1998, 2425. (e)
Doherty, S.; Errington, R. J .; J arvis, A. P.; Collins, S.; Clegg, W.;
Elsegood, M. R. J . Organometallics 1998, 17, 3408. (f) Nomura, K.;
Naga, N.; Miki, M.; Yanagi, K. Macromolecules 1998, 31, 7588.
(13) Arevalo, 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.
(14) Karstedt, B. D. U.S. Patent 3,775,452, 1973.
(15) Selected 1H NMR data in CDCl3 for [Ti(C5H5){OC6H4-n
-
(OMe)n(CHdCHCH3)}Cl2] (n ) 1, 2): δ 6.70 (s, 5H, C5H5), 6.25 (m,
1H, CHdCHCH3), 6.18 (m, 1H, CHdCHCH3), 3.85 (s, 3H or 6H, OMe),
1.88 (m, 3H, CHdCHCH3).

Carbosilane Dendrimers Containing Ti(IV) Units
Organometallics, Vol. 20, No. 12, 2001 2585
The 1H NMR spectrum of complex 2 shows one singlet
for the cyclopentadienyl ligand at δ 6.71 and one
resonance located at δ 121.1 for the corresponding
carbon atoms in the 13C NMR spectrum, both in the
same position as those found in the NMR spectra of
compound 1.13 For compounds 3 and 4, the cyclopentan-
dienyl ligand affords chemical shifts identical with those
shown for complexes 1 and 2. Thus, it can be assumed
that hydrosilylation of the allyl fragment does not
produce significant changes on the electron density of
Sch em e 2
1
the metal center. In the case of derivatives 3-6, the H
NMR data show the presence of the -CH2CH2CH2SiEt3
grouping as the result of an anti-Markovnikov addition.
For the R-addition grouping -CH2CH(SiEt3)CH3, the
expected doublets are not observed and, therefore,
â-addition products occur exclusively.
The synthetic procedures described for these mono-
nuclear compounds along with their spectroscopic char-
acterization provided a useful basis for the synthesis of
their peripheral carbosilane dendrimer analogues.
tives {HOC6H4-n(OMe)n(C3H6SiEt3)} (n ) 1 (5), 2 (6))
in 85-75% yield, along with certain amounts (less than
10-15%) of the propenyl isomers of I (trans-2-methoxy-
4-propenylphenol) or II (trans-2,6-dimethoxy-4-pro-
penylphenol), respectively,16 and other products (5-
10%) resulting from O-silylation (Scheme 2). The latter
impurities were the result of competitive reaction of the
Si-H groups with the phenolic hydroxy group.17 The
formation of siloxy derivatives Et3Si-O-Ph was de-
tected by 1H NMR spectroscopy, as the m-methoxy
substituent of the phenyl ring is sensitive to the
presence of a hydroxy (δ 3.86) or siloxy group (δ 3.76).18
For the former side products and under these reaction
conditions, the hydrosilylation was found to compete
with the isomerization of the allyl to propenyl groups
induced by the platinum catalyst used. To improve the
chemoselectivity for hydrosilylation vs isomerization,
and the C-silylation vs O-silylation, higher concentra-
tions of catalyst were used. Interestingly, hydrosilyl-
ation of the commercially available 2,6-dimethoxy-4-
propenylphenol (isoeugenol) under analogous conditions
led very slowly to the formation of 6 in low yield as the
sole reaction product, showing that no hydrosilylation
occurred at the internal double bond. Derivatives 5 and
6 could be purified from the unwanted materials by
chromatography, giving spectroscopically pure oils in
40% overall yield.
Syn th esis of Den d r im er s a n d Meta llod en d r im -
er s. The syntheses of dendrimers containing phenols
or titanium metal centers at their periphery have been
studied. For this purpose, allylsilane-terminated den-
drimers of first, second, and fourth generation were
synthesized according to previously reported methods.11
Typically, we used tetraallylsilane as the initiator core,
dichloromethylsilane in the hydrosilylation step, and
allylmagnesium bromide in the allylation step. The
first-, second-, and fourth-generation chlorodimethyl-
silyl-terminated dendrimers were obtained by a hy-
drosilylation reaction, adding HSiMe2Cl to allyl-termi-
nated dendrimers in the presence of a platinum catalyst
(Karstedt catalyst). Finally, these dendrimers contain-
ing peripheral Si-Cl bonds were converted into the well-
known Si-H analogues 1G-H4, 2G-H8, and 4G-H32 by
reduction with LiAlH4.11d The H-Si-terminated den-
drimers were the starting materials for the preparation
of new dendrimers via hydrosilylation reactions of the
organic monomers I and II.
The synthesis of the new dendrimers was carried out
by the same routes as those described for model
compounds 5 and 6. Furthermore, we have recently
published10e that reaction of I with 1G-H4 or 2G-H8
afforded the corresponding dendrimers 1G-[(CH2)3-
{C6H3(OMe)}OH]4 (7) and 2G-[(CH2)3{C6H3(OMe)}OH]8
(8) in high yields. To increase the number of generations
and to modify the environment around the metal center
for catalytic purposes, a fourth generation has been
synthesized and first, second, and fourth generations,
using the more encumbered end group 4-allyl-2,6-
dimethoxyphenol (II), were prepared as well. Then,
hydrosilylation reactions of eugenol (I) with 4G-H32 or
the phenol ligand II with 1G-H4, 2G-H8, or 4G-H32
performed in THF at 70 °C and using the Karstedt
catalyst afforded the corresponding dendrimers 4G-
[(CH2)3{C6H3(OMe)}OH]32 (9), 1G-[(CH2)3{C6H2(OMe)2}-
OH]4 (10), 2G-[(CH2)3{C6H2(OMe)2}OH]8 (11), and 4G-
[(CH2)3{C6H2(OMe)2}OH]32 (12) containing terminal
Treatment of 5 and 6 with 1 molar equiv of [Ti-
(C5H5)Cl3] in toluene at 80 °C gave 3 and 4, respectively,
which were obtained as red oils in high yields. No
reaction was observed when the mixture was stirred
overnight at room temperature. Derivatives 2-6 were
soluble in all common organic solvents, and the or-
ganometallic complexes 2-4 are thermally stable but
moisture sensitive. The structures proposed for 2-6 are
shown in Scheme 1, and their spectroscopic and analyti-
cal data are collected in the Experimental Section.
(16) Selected 1H NMR data in CDCl3 for trans-2-methoxy-4-pro-
penylphenol or trans-2,6-dimethoxy-4-propenylphenol: δ 6.31 (dc, 1H),
6.06 (dc, 1H), 3.87 (s, OMe), 1.84 (dd, CH3).
(17) Zhang, C.; Laine, R. M. J . Am. Chem. Soc. 2000, 122, 6979 and
references therein.
(18) Protection of eugenol (I) or 4-allyl-2,6-methoxyphenol (II) with
SiMe3Cl afforded [Me3SiOC6H4-n(OMe)n(CH2CHdCH2)} (n ) 1, 2).
Selected 1H NMR data in CDCl3: δ 5.96 (m, 1H, CHdCHCH3), 5.10
(m, 1H, CHdCHCH3), 3.76 (s, 3H or 6H, OMe), 3.30 (m, 3H,
CHdCHCH3), 0.19 (s, 9H, SiMe3). When the (aryloxy)trimethylsilane
was used in the hydrosilylation instead of the phenol, the reaction
proceeded exclusively via C-silylation and formation of small amounts
of the isomers [Me3SiOC6H4-n(OMe)n(CHdCHCH3)} (n ) 1, 2).
1
phenol groups (Scheme 3). H NMR spectroscopy was
used for following the progress of the reactions by
monitoring the loss of the Si-H resonance.
As in the preparation of compounds 3-6, only â-
addition derivatives were formed. Again, certain amounts

2586 Organometallics, Vol. 20, No. 12, 2001
Are´valo et al.
ing to the 1H NMR spectra. Most likely, steric congestion
on the silicon atom hindered the completion of the
reactions.
Sch em e 3
The incorporation of titanium centers on the carbo-
silane dendrimer surface containing phenol end groups
was carried out by reaction with a Ti-Cl bond of
[Ti(C5H5)Cl3] using a procedure similar to that described
for the monomeric models 3 and 4 and used recently in
the treatment with 7 or 8 to give 1G-[(CH2)3[{C6H3-
(OMe)}O]Ti(C5H5)Cl2]4 (13) or 2G-[(CH2)3[{C6H3-
(OMe)}O]Ti(C5H5)Cl2]8 (14),10e respectively. Reaction of
dendrimers 9-12 with the appropriate amounts of
[Ti(C5H5)Cl3] in toluene at 80 °C led quantitatively to
the formation of organotitanium dendrimers 4G-
[(CH2)3[{C6H3(OMe)}O]Ti(C5H5)Cl2]32 (15), 1G-[(CH2)3-
[{C6H2(OMe)2}O]Ti(C5H5)Cl2]4 (16), 2G-[(CH2)3[{C6H2-
(OMe)2}O]Ti(C5H5)Cl2]8 (17), and 4G-[(CH2)3[{C6H2-
(OMe)2}O]Ti(C5H5)Cl2]32 (18) with concomitant evolu-
tion of HCl (Schemes 3 and 4). In the case of the fourth-
generation metallodendrimers 15 and 18, complete
conversion was achieved by adding a drop of a Lewis
base such as NEt3 to the toluene solution before isola-
tion. The alternative procedure consisting of the hy-
drosilylation of complexes 1 and 2 with hydride-
terminated dendrimers to prepare the organometallic
dendrimers gave only low yields.
of O-silylated byproducts (between 5 and 10%)18 and the
internal olefinic isomers of I or II (between 10 and
15%)16 were detected in the 1H NMR spectra of the
crude products. The competitive reaction of the den-
drimeric terminal Si-H groups with the phenolic hy-
droxy group, resulting in O-silylation, should form
species of higher molecular weight. In this case, the allyl
phenols serve as bifunctional units that are able to
cross-link different dendrimeric molecules.17 The un-
wanted materials were readily removed by washing the
crude products with hexane (olefinic isomers of I or II)
and then by chromatographing the residue (mainly
higher molecular weight components), giving in 70-75%
yield spectroscopically and analytically pure oils of
increasing viscosity on going from the first to the fourth
generation. All these dendrimers are soluble in THF,
diethyl ether, and chlorinated and aromatic solvents but
insoluble in aliphatic hydrocarbons and water. Dendritic
carbosilanes containing aliphatic hydroxy groups on
their periphery have been reported recently.19 Deriva-
tives 7-12 are amphiphilic carbosilane dendrimers, and
to our knowledge, they represent the first examples
containing phenolic ligands as amphiphilic groups at-
tached to the terminal branches of hydrophobic carbo-
silane backbones. Slow aggregation processes have
been detected in such amphiphilic materials, but they
can be stopped by storing them in THF or CH2Cl2
solutions.19
The dendritic organometallic systems are red oils,
thermally stable but moisture sensitive. In the presence
of water they afforded the starting phenol-terminated
dendrimers and oxotitanium derivatives.20 Therefore,
the addition of an excess of water to diethyl ether
solutions of the dendritic organotitanium derivatives
13-18 allows recovering the phenolic dendrimers al-
most quantitatively.
The NMR spectroscopic and analytical data of com-
plexes 7-18 are consistent with their proposed struc-
1
tures shown in Schemes 3 and 4 and Figure 1. The H
NMR spectra of the carbosilane framework for dendrim-
ers 7-12 have almost identical chemical shifts for
analogous nuclei in different generations, although
broader and unstructured resonances are present for the
fourth generations. These features have been ascribed
to both a polymer-like structure with slightly different
chemical environments for nuclei in different genera-
tions and restricted mobility of the respective protons
in the outer shells.19a Four sets of signals attributed to
the methylene groups have been observed with the
expected integration ratio. Those for the SiCH2CH2CH2-
Ph fragments appear at the same position as those
detected for the monomers 3-6. For the branches
SiCH2CH2CH2Si, the middle methylenes are located at
δ 1.28, while the methylene groups bonded directly to
silicon atoms are centered at δ 0.53 and overlap the
analogous groups in the SiCH2CH2CH2Ph branches. The
13C NMR spectra of these groups show three resonances
located at δ 39.7, 26.4, and 15.3 for the outer branches
SiCH2CH2CH2Ph, and for the inner branches SiCH2-
CH2CH2Si signals in the range δ 20.0-17.5 are ob-
served. For the methyl groups, the corresponding sig-
nals for the 1H and 13C NMR spectra are detected,
although only in the first and second generations can
Attempts to prepare macromolecules containing more
than one peripheral phenol group on the outer silicon
atoms, i.e., 1G-[(CH2)3{C6H2(OMe)2}OH]8 from dihy-
dride terminated carbosilane dendrimer 1G-H811 under
the same conditions as those described above, were
unsuccessful, resulting in incomplete reactions accord-
(19) (a) Lorenz, K.; Mu¨lhaupt, R.; Frey, H.; Rapp, U.; Mayer-Posner,
F. J . Macromolecules 1995, 28, 6657. (b) Sheiko, S. S.; Muzafarov, A.
M.; Winkler, R. G.; Getmanova, E. V.; Eckert, G.; Reineker, P.
Langmuir 1997, 13, 4172. (c) Krska, S. W.; Seyferth, D. J . Am. Chem.
Soc. 1998, 120, 3604. (d) Kim, C.; Son, S.; Kim, B. J . Organomet. Chem.
1999, 588, 1.
(20) (a) Thewalt, U.; Schomburg, D. J . Organomet. Chem. 1977, 127,
169. (b) Gowik, P.; Klapo¨tke, T.; Pickardt, J . J . Organomet. Chem. 1990,
393, 343.

Carbosilane Dendrimers Containing Ti(IV) Units
Organometallics, Vol. 20, No. 12, 2001 2587
Sch em e 4
-SiMe2- and -SiMe- fragments be distinguished. In
the cases of the higher generations overlapping occurs
due to the broadening mentioned above. The 1H and 13C
NMR spectra also show an unchanged resonance for the
methoxy groups of 7-12 along with the corresponding
signals of the aromatic rings in the expected regions.
The hydroxy groups appear at δ 5.46 for the eugenol
derivatives and δ 5.36 for the 2,6-dimethoxyphenol

2588 Organometallics, Vol. 20, No. 12, 2001
Are´valo et al.
F igu r e 1. Molecular representation of the fourth-generation organotitanium dendrimer 4G-[(CH2)3[{C6H3(OMe)}O]-
Ti(C5H5)Cl2]32 (15).
compounds, typically shifted upfield again, as a conse-
quence of the presence of a second m-methoxy substitu-
ent (see Figure 2 for 1H and 13C NMR of 12). The 29Si
NMR spectra of the first generations show two singlets
at δ 1.02 and 1.98, whereas for the second and fourth
generations only the two outer silicon atoms could be
detected.
In addition, the air-stable titanium-free dendrimers
have been studied by MALDI-TOF MS using 1,8,9-
trihydroxyanthracene (dithranol) as a suitable matrix.
In all compounds of the first and second generations
MNa+, MK+, and MH+ give the most intense peaks.
However, the molecular peaks were not observed for the
fourth generations, as described for many of the high-
molecular-weight dendrimers.9k,11e,21 Mass spectral stud-
ies are also useful for the identification of branching
defects. This information is important not only as a
proof of purity but also as an indicator of building-up
reactions that tend to be incomplete if they are not
handled carefully. Defects are only found in a small
fraction of molecules which contain no more than one
error, as expected for a statistical distribution. The most
frequent defects are those related to hydrosilylations,
which could be minimized if they are monitored by NMR
in order to ensure their completion. Complexes 7-12
have also been studied by gel permeation chromatog-
raphy (GPC). As expected, the elution time of the six
compounds increases from fourth to first generations.
(21) (a) Veith, M.; Elsa¨sser, R.; Kru¨ger, R. P. Organometallics
1999, 18, 656. (b) Kim, C.; J ung, I. J . Organomet. Chem. 2000, 599,
208.

F igu r e 2. 1H NMR (300 MHz, CDCl3) (A and B) and, 13C{1H} NMR (75.43 MHz, CDCl3) (C and D) spectra of 4G-X32 species 12 (A and C) and 18 (B and D). Solvent peaks
are indicated by asterisks.

2590 Organometallics, Vol. 20, No. 12, 2001
Are´valo et al.
Syn th esis of [Ti(C5H5)Cl2{O[C6H2(OMe)2(CH2CHd
CH2)]}] (2). A solution of 4-allyl-2,6-dimethoxyphenol (0.88
g, 4.56 mmol) in toluene (20 mL) was slowly added to a solution
of [Ti(C5H5)Cl3] (1.00 g, 4.56 mmol) in toluene (40 mL). The
mixture was heated to 80 °C for 6 h and subsequently stirred
overnight at room temperature. The solvent was removed
under vacuum to obtain an oily red solid. The product was
washed with hexane at -78 °C to give 1 as red microcrystals
(1.46 g, 85% yield). 1H NMR (CDCl3): δ 6.71 (s, 5H, C5H5),
6.37 (s, 2H, C6H2), 5.92 (m, 1H, -CH2CHdCH2), 5.08 (m, 2H,
CH2CHdCH2), 3.84 (s, 6H, OMe), 3.32 (m, 2H, CH2CHdCH2).
13C{1H} NMR (CDCl3): δ 150.8 (Cipso bonded to -OMe), 148.7
(Cipso bonded to -OTi), 136.8 (Cipso bonded to -C3H5), 136.1
(CH2CHdCH2), 121.1 (C5H5), 116.3 (CH2CHdCH2), 105.8
A good linear relationship is shown between theoretical
molecular weight and elution time on GPC traces.21a, 22
The 1H and 13C NMR spectra of the new metallo-
dendrimers 15-18 (see Figure 2 for 1H and 13C NMR
of 18) exhibit resonances identical with those observed
in their counterparts 7-12 for the carbosilane frame-
work and phenoxide group. In addition, the proton and
carbon atoms of the cyclopentadienyl ring of the deriva-
tives 15-18 appear at the same positions (δ 6.73 and
121.0, respectively) and compare well with the previ-
ously reported metallodendrimers 13 and 1410e and the
mononuclear complexes 113 and 2. All these spectro-
scopic data suggest that the differences in size and
length of the dendritic species, as well as substitution
of the eugenolate moiety for the 2,6-dimethoxyphenoxide
fragment, are not extended to the metal microenviron-
ment. Attempts to carry out MALDI-TOF MS of all the
titanium-containing dendrimers failed, probably due to
the use of unsuitable matrices, usually organic acids or
alcohols. Analogous results have been reported for other
metallodendrimers.9j,k, 23
(C6H2), 56.8 (OMe), 40.5 (CH2CHdCH2). Anal. Calcd for C16H18
-
Cl2O3Ti: C, 50.96; H, 4.81. Found: C, 50.93; H, 4.83.
Syn t h esis of [Ti(C5H5)Cl2{O[C6H3(OMe)(CH2CH2CH2-
SiEt3)]}] (3). A solution of [HO{C6H3(OMe)(CH2CH2CH2-
SiEt3)}] (5) (see preparation below; 0.40 g, 1.43 mmol) in
toluene (20 mL) was slowly added to a solution of [Ti(C5H5)-
Cl3] (0.31 g, 1.43 mmol) in toluene (40 mL). The mixture was
heated to 80 °C for 6 h, and then, the solvent was removed
1
under vacuum to obtain 3 as a red oil (0.66 g, 100% yield). H
NMR (CDCl3): δ 6.91 (m, 1H, C6H3), 6.74 (s, 5H, C5H5), 6.73
(m, 1H, C6H3), 6.63 (m, 1H, C6H3), 3.87 (s, 3H, OMe), 2.57 (m,
2H, CH2CH2CH2Ph), 1.58 (m, 2H, CH2CH2CH2Ph), 0.90 (t, 9H,
SiCH2CH3), 0.50 (m, 8H, SiCH2CH3 and SiCH2CH2CH2Ph
overlapping). 13C{1H} NMR (CDCl3): δ 157.3 (Cipso bonded to
-OTi), 149.8 (Cipso bonded to -OMe), 140.0 (Cipso bonded to
-CH2), 121.0 (C5H5), 120.4, 118.9, 113.1 (C6H3), 56.4 (OMe),
40.1 (CH2CH2CH2Ph), 26.0 (CH2CH2CH2Ph), 11.2 (CH2CH2-
CH2Ph), 7.5 (SiCH2CH3), 3.3 (SiCH2CH3). Anal. Calcd for
In summary, a synthetic strategy has been developed
for the preparation of new peripheral carbosilane den-
drimers containing phenols or titanium metal centers.
It consists of the hydrosilylation of phenols having
pendant allyl groups with well-known hydride termi-
nated dendrimers and the subsequent alcoholysis reac-
tion of [Ti(C5H5)Cl3]. This procedure has been shown to
be suitable for the growing of high generations. In
addition, the hydrosilylation step using the Karstedt
catalyst proceeds with both C-silylation and O-silylation
in the ratio 9:1. An additional isomerization reaction of
the allyl phenols was also observed. Investigations of
the catalytic activity of the metallodendrimers prepared
in this work for olefin polymerization are in progress.
C
21H32Cl2O2SiTi: C, 54.44; H, 6.96. Found: C, 54.23; H, 6.81.
Syn th esis of [Ti(C5H5)Cl2{O[C6H2(OMe)2(CH2CH2CH2-
SiEt3)]}] (4). A solution of [HO{C6H2(OMe)2(CH2CH2CH2-
SiEt3)}] (6) (see preparation below; 0.40 g, 1.29 mmol) in
toluene (20 mL) was slowly added to a solution of [Ti(C5H5)-
Cl3] (0.28 g, 1.29 mmol) in toluene (40 mL). The mixture was
heated to 80 °C for 6 h, and then, the solvent was removed
1
under vacuum to obtain 4 as a red oil (0.63 g, 100% yield). H
Exp er im en ta l Section
NMR (CDCl3): δ 6.71 (s, 5H, C5H5), 6.35 (s, 2H, C6H2), 3.84
(s, 6H, OMe), 2.54 (m, 2H, CH2CH2CH2Ph), 1.55 (m, 2H,
CH2CH2CH2Ph), 0.90 (t, 9H, SiCH2CH3), 0.50 (m, 8H, SiCH2CH3
and SiCH2CH2CH2Ph overlapping). 13C{1H} NMR (CDCl3): δ
150.6 (Cipso bonded to -OMe), 148.5 (Cipso bonded to -OTi),
139.0 (Cipso bonded to -CH2), 121.1 (C5H5), 105.7 (C6H2), 56.8
(OMe), 40.6 (CH2CH2CH2Ph), 25.9 (CH2CH2CH2Ph), 11.2
(CH2CH2CH2Ph), 7.5 (SiCH2CH3), 3.3 (SiCH2CH3). Anal. Calcd
for C22H34Cl2O3SiTi: C, 53.56; H, 6.95. Found: C, 53.78; H,
6.87.
Syn th esis of [HO{C6H3(OMe)(CH2CH2CH2SiEt3)}] (5).
Two drops of the poly(dimethylsiloxane) solution of the Karstedt
catalyst (3-3.5% Pt) were slowly added to a solution of 4-allyl-
2-methoxyphenol (1.00 g, 6.1 mmol) in neat HSiEt3 (2.0 mL,
12.6 mmol). The resulting mixture was stirred for 9 h at 70
°C and subsequently at room temperature overnight. The
solvent was removed at reduced pressure, and the product was
purified by chromatography on a silica gel column (35-70
mesh) with hexane as eluent to give 5 as a pale yellow oil (0.68
g, 40% yield). 1H NMR (CDCl3): δ 6.81 (m, 1H, C6H3), 6.66
(m, 2H, C6H3), 5.44 (s, 1H, OH), 3.86 (s, 3H, OMe), 2.53 (m,
2H, CH2CH2CH2Ph), 1.58 (m, 2H, CH2CH2CH2Ph), 0.90 (t, 9H,
SiCH2CH3), 0.50 (m, 8H, SiCH2CH3 and SiCH2CH2CH2Ph
overlapping). 13C{1H} NMR (CDCl3): δ 146.3 (Cipso bonded to
-OMe), 143.5 (Cipso bonded to -OH), 134.7 (Cipso bonded to
-CH2), 121.0, 114.1, 111.0 (C6H3), 55.5 (OMe), 39.8 (CH2CH2-
CH2Ph), 26.2 (CH2CH2CH2Ph), 11.2 (CH2CH2CH2Ph), 7.4
(SiCH2CH3), 3.3 (SiCH2CH3). Anal. Calcd for C16H28O2Si: C,
68.52; H, 10.06. Found: C, 68.31; H, 9.87.
Gen er a l P r oced u r es. All manipulations of oxygen- or
water-sensitive compounds were carried out under an atmo-
sphere of argon by using standard Schlenk techniques or an
argon-filled glovebox equipped with a -40 °C freezer. 1H, 13C,
and 29Si NMR spectra were recorded on a Variant Unity VXR-
300 or Variant 500 Plus instruments. Chemical shifts (δ, ppm)
1
were measured relative to residual H and 13C resonances for
chloroform-d used as solvent. The 29Si chemical shifts were
referenced to external SiMe4 (0.00 ppm). C, H, and N analyses
were carried out with a Perkin-Elmer 240 C microanalyzer.
MALDI-TOF MS samples were prepared in a 1,8,9-trihydroxy-
anthracene (dithranol) matrix, and spectra were recorded on
a Bruker Reflex II spectrometer equipped with a nitrogen laser
emitting at 337 nm and operated in the reflector mode at an
accelerating voltage in the range 23 000-25 000 V. Thin-layer
chromatography was accomplished using 0.25 mm silica gel
plates from ALUGRAM, and chromatography was performed
on silica gel (35-70 mesh).
Ma ter ia ls. Solvents were dried prior to use and freshly
distilled under argon: tetrahydrofuran and diethyl ether from
sodium benzophenone ketyl, toluene from sodium, hexane from
sodium-potassium alloy, and methylene chloride over P4O10
.
Unless otherwise stated, reagents were obtained from com-
mercial sources and used as received. [Ti(C5H5)Cl3]24 and GnH
dendrimers11d,e were prepared according to reported methods.
(22) Morikawa, A.; Kakimoto, M.; Imai, Y. Macromolecules 1992,
25, 3247.
(23) Liao, Y.-H.; Moss, J . R. Organometallics 1995, 14, 2130.
(24) Cardoso, A. M.; Clark, R. J . H.; Moorhouse, S. J . Chem. Soc.,
Dalton Trans. 1980, 1156.
Syn th esis of [HO{C6H2(OMe)2(CH2CH2CH2SiEt3)}] (6).
HSiEt3 (2 mL, 12.6 mmol) and 2 drops of the poly(dimethyl-

Carbosilane Dendrimers Containing Ti(IV) Units
Organometallics, Vol. 20, No. 12, 2001 2591
siloxane) solution of the Karstedt catalyst (3-3.5% Pt) were
slowly added to a solution of 4-allyl-2,6-dimethoxyphenol (1.00
g, 5.15 mmol) in THF (2 mL). The resulting mixture was
stirred for 9 h at 70 °C and subsequently at room temperature
overnight. Then, the solvent and the silane in excess were
removed at reduced pressure, and the product was purified
by chromatography (silica gel column (35-70 mesh)/hexane)
to give 6 as a pale yellow oil (0.70 g, 44% yield). 1H NMR
(CDCl3): δ 6.37 (s, 2H, C6H2), 5.34 (s, 1H, OH), 3.86 (s, 6H,
OMe), 2.53 (m, 2H, CH2CH2CH2Ph), 1.56 (m, 2H, CH2CH2CH2-
Ph), 0.90 (t, 9H, SiCH2CH3), 0.50 (m, 8H, SiCH2CH3 and
SiCH2CH2CH2Ph overlapping). 13C{1H} NMR (CDCl3): δ 146.8
(Cipso bonded to -OMe), 133.8 (Cipso bonded to -OH), 132.7
(Cipso bonded to -CH2), 105.0 (C6H2), 56.2 (OMe), 40.3
(CH2CH2CH2Ph), 26.2 (CH2CH2CH2Ph), 11.2 (CH2CH2CH2Ph),
7.4 (SiCH2CH3), 3.3 (SiCH2CH3). Anal. Calcd for C17H30O3Si:
C, 65.76; H, 9.74. Found: C, 65.53; H, 9.38.
(CDCl3): δ 6.36 (s, 4H, C6H2), 5.35 (s, 2H, OH), 3.84 (s, 12H,
OMe), 2.51(m, 4H, CH2CH2CH2Ph), 1.59 (m, 4H, CH2CH2CH2-
Ph), 1.29 (m, 6H, SiCH2CH2CH2Si), 0.53 (m, 16H, SiCH2-
CH2CH2Si and CH2CH2CH2Ph overlapping), -0.07 (s, 12H,
SiMe2), -0.10 (s, 3H, SiMe). 13C{1H} NMR (CDCl3): δ 146.8
(Cipso bonded to -OMe), 133.8 (Cipso bonded to -OH), 132.7
(Cipso bonded to -CH2), 105.0 (C6H2), 56.2 (OMe), 40.2 (CH2-
CH2CH2Ph), 26.3 (CH2CH2CH2Ph), 15.3 (CH2CH2CH2Ph), 20.1,
18.8, 18.5 and overlapped signals of (Si(CH2)3Si), -3.3 (SiMe2),
-5.0 (SiMe). 29Si{1H} NMR (CDCl3): δ 1.86 (G2-Si), 1.19 (G1-
Si), not observed (G0-Si). MALDI-TOF-MS: m/z 2752.7 [M +
Na]+ (calcd 2752.5). Anal. Calcd for C144H252O24Si13: C, 63.29;
H, 9.29. Found: C, 62.52; H, 9.47.
Syn th esis of 4G-[(CH2)3{C6H2(OMe)2}OH]32 (12). This
dendrimer was prepared by a method similar to that described
for 10, starting from 4G-H32 (0.44 g, 0.078 mmol) and 4-allyl-
2,6-dimethoxyphenol (0.51 g, 2.62 mmol). The product was
purified as in the procedure described above for 10, giving 12
as a pale yellow, thick oil (0.63 g, 68% yield). 1H NMR
(CDCl3): δ 6.34 (s, 16H, C6H2), 5.36 (s, 8H, OH), 3.82 (s, 48H,
OMe), 2.50 (m, 16H, CH2CH2CH2Ph), 1.54 (m, 16H, CH2CH2-
CH2Ph), 1.28 (m, 30H, SiCH2CH2CH2Si), 0.52 (m, 76H, SiCH2-
CH2CH2Si and CH2CH2CH2Ph overlapping), -0.07 (s, 48H,
SiMe2), -0.11 (s broad, 21H, SiMe). 13C{1H} NMR (CDCl3): δ
146.8 (Cipso bonded to -OMe), 133.7 (Cipso bonded to -OH),
132.7 (Cipso bonded to -CH2), 105.0 (C6H2), 56.2 (OMe), 40.2
(CH2CH2CH2Ph), 26.3 (CH2CH2CH2Ph), 15.3 (CH2CH2CH2Ph),
20.1, 18.8, 18.5 and overlapped signals (Si(CH2)3Si), - 3.2
(SiMe2), -5.0 (s broad, SiMe). 29Si{1H} NMR (CDCl3): δ 1.91
(G4-Si), 1.28 (G3-Si), the rest were not observed (G1-Si, G0-
Syn t h esis of 4G-[(CH2)3{C6H3(OMe)}OH]32 (9). This
fourth-generation dendrimer was prepared from 4G-H32 (0.49
g, 0.087 mmol) and 4-allyl-2-methoxyphenol (0.48 g, 2.92
mmol) using 2 drops of the poly(dimethylsiloxane) solution of
the Karstedt catalyst (3-3.5% Pt). The resulting mixture was
stirred for 9 h at 70 °C and subsequently at room temperature
overnight. The solvent was removed at reduced pressure, and
the product was washed twice with hexane to eliminate mainly
the olefinic isomer of I and then purified by chromatography
(10 cm column of silica gel; CH2Cl2 for higher weight compo-
nents and then 10% ethyl acetate in CH2Cl2)18 to give 9 as a
1
pale yellow, thick oil (0.66 g, 70% yield). H NMR (CDCl3): δ
6.79 (m, 8H, C6H3), 6.62 (m, 16H, C6H3), 5.46 (s, 8H, OH), 3.81
(s, 24H, OMe), 2.50 (m, 16H, CH2CH2CH2Ph), 1.53 (m, 16H,
CH2CH2CH2Ph), 1.28 (m, 30H, SiCH2CH2CH2Si), 0.52 (m, 76H,
SiCH2CH2CH2Si and CH2CH2CH2Ph overlapping), -0.08 (s,
48H, SiMe2), -0.11 (broad, 21H, SiMe). 13C{1H} NMR
(CDCl3): δ 146.2 (Cipso bonded to -OMe), 143.5 (Cipso bonded
to -OH), 134.6 (Cipso bonded to -CH2), 120.9, 114.1, and 111.0
(C6H3), 55.8 (OMe), 39.7 (CH2CH2CH2Ph), 26.4 (CH2CH2CH2-
Ph), 15.3 (CH2CH2CH2Ph), 20.1, 18.8, 18.5, and overlapped
signals (Si(CH2)3Si), -3.2 (SiMe2), -4.9, -5.0, and -5.1 (SiMe).
29Si{1H} NMR (CDCl3): δ 2.06 (G4-Si), 1.46 (G3-Si), the rest
were not observed. Anal. Calcd for C592H1052O64Si61: C, 65.19;
H, 9.72. Found: C, 64.31; H, 9.67.
Si). Anal. Calcd for C624H1116O96Si61
Found: C, 64.15; H, 9.10.
: C, 63.15; H, 9.48.
Syn th esis of 4G-[(CH2)3[{C6H3(OMe)}O]Ti(C5H5)Cl2]32
(15). A solution of [Ti(C5H5)Cl3] (0.26 g, 1.18 mmol) in toluene
(20 mL) was added to another solution containing 9 (0.40 g,
0.037 mmol) in toluene (10 mL). The mixture was heated at
80 °C for 6 h and subsequently stirred overnight at room
temperature. Afterward, 1 drop of NEt3 was added. Then, after
filtration, the solvent was removed at reduced pressure to give
15 as a red oil in quantitative yield (0.61 g). 1H NMR (CDCl3):
δ 6.89 (m, 8H, C6H3), 6.72 (s, 40 H, C5H5), 6.64 (m, 16H, C6H3),
3.84 (s, 24H, OMe), 2.54 (m, 16H, CH2CH2CH2Ph), 1.55 (m,
16H, CH2CH2CH2Ph), 1.29 (m, 30H, SiCH2CH2CH2Si), 0.53 (m,
76H, SiCH2CH2CH2Si and CH2CH2CH2Ph overlapping), -0.06
(s, 48H, SiMe2), -0.09 (s broad, 21H, SiMe). 13C{1H} NMR
(CDCl3): δ 157.2 (Cipso bonded to -OTi), 149.8 (Cipso bonded to
-OMe), 139.9 (Cipso bonded to -CH2), 121.1 (C5H5), 120.2,
118.9, 113.0 (C6H3), 56.3 (OMe), 39.9 (CH2CH2CH2Ph), 26.1
(CH2CH2CH2Ph), 15.4 (CH2CH2CH2Ph), 20.1, 18.8, 18.5 and
overlapped signals (Si(CH2)3Si), -3.2 (SiMe2), -4.8 (SiMe).
29Si{1H} NMR (CDCl3): δ 1.94 (G4-Si), 1.31 (G3-Si), the rest
were not observed. Anal. Calcd for C752H1180Cl64O64Si61Ti32: C,
53.89; H, 7.10. Found: C, 53.46; H, 7.17.
Syn th esis of 1G-[(CH2)3[{C6H2(OMe)2}O]Ti(C5H5)Cl2]4
(16). A solution of [Ti(C5H5)Cl3] (0.33 g, 1.52 mmol) in toluene
(20 mL) was added to a solution of 10 (0.46 g, 0.38 mmol) in
toluene (10 mL). The mixture was heated at 80 °C for 6 h and
subsequently stirred overnight at room temperature. Then, the
solvent was removed at reduced pressure to obtain 16 as a
red oil in quantitative yield (0.74 g). 1H NMR (CDCl3): δ 6.71
(s, 5H, C5H5), 6.34 (s, 2H, C6H2), 3.84 (s, 6H, OMe), 2.53 (m,
2H, CH2CH2CH2Ph), 1.59 (m, 2H, CH2CH2CH2Ph), 1.29 (m,
2H, SiCH2CH2CH2Si), 0.53 (m, 6H, SiCH2CH2CH2Si and
CH2CH2CH2Ph overlapping), -0.06 (s, 6H, SiMe2). 13C{1H}
NMR (CDCl3): δ 150.7 (Cipso bonded to -OMe), 148.5 (Cipso
bonded to -OTi), 138.9 (Cipso bonded to -CH2), 121.1 (C5H5),
105.7 (C6H2), 56.8 (-OMe), 40.4 (CH2CH2CH2Ph), 26.0 (CH2CH2-
CH2Ph), 15.4 (CH2CH2CH2Ph), 20.3, 18.6, 17.6 (Si(CH2)3Si),
-3.3 (SiMe2). 29Si{1H} NMR (CDCl3): δ 1.97 (G1-Si), 0.89 (G0-
Si). Anal. Calcd for C84H124Cl8O12Si5Ti4: C, 51.97; H, 6.44.
Found: C, 51.57; H, 6.43.
Syn th esis of 1G-[(CH2)3{C6H2(OMe)2}OH]4 (10). 4-Allyl-
2,6-dimethoxyphenol (1.00 g, 5.12 mmol) and 2 drops of the
poly(dimethylsiloxane) solution of the Karstedt catalyst (3-
3.5% Pt) were added to a THF (3 mL) solution of 1G-H4 (0.53
g, 1.22 mmol). The resulting mixture was stirred for 9 h at 70
°C and subsequently at room temperature overnight. The
solvent was removed at reduced pressure, and the product was
washed with hexane twice to eliminate mainly the olefinic
isomer of II and then purified by chromatography (10 cm
column of silica gel; CH2Cl2 for higher weight components and
then 10% ethyl acetate in CH2Cl2)18 to give 10 as a pale yellow,
1
thick oil (1.04 g, 70% yield). H NMR (CDCl3): δ 6.36 (s, 2H,
C6H2), 5,34 (s, 1H, OH), 3.84 (s, 6H, OMe), 2.51 (m, 2H, CH2-
CH2CH2Ph), 1.57 (m, 2H, CH2CH2CH2Ph), 1.27 (m, 2H,
SiCH2CH2CH2Si), 0.53 (m, 6H, SiCH2CH2CH2Si and CH2CH2-
CH2Ph overlapping), -0.07 (s, 6H, SiMe2). 13C{1H} NMR
(CDCl3): δ 146.8 (Cipso bonded to -OMe), 133.8 (Cipso bonded
to -OH), 132.7 (Cipso bonded to -CH2), 105.0 (C6H2), 56.2
(OMe), 40.2 (CH2CH2CH2Ph), 26.4 (CH2CH2CH2Ph), 15.4
(CH2CH2CH2Ph), 20.3, 18.6, 17.6 (Si(CH2)3Si), -3.3 (SiMe2).
29Si{1H} NMR (CDCl3): δ 1.98 (G1-Si), 1.02 (G0-Si). MALDI-
TOF-MS: m/z 1209.5 [M + H]+ (calcd 1209.7). Anal. Calcd for
C
64H108O12Si5: C, 63.53; H, 9.00. Found: C, 63.60; H, 9.37.
Syn th esis of 2G-[(CH2)3{C6H2(OMe)2}OH]8 (11). This
dendrimer was prepared by a method similar to that described
for 10, starting from 2G-H8 (0.50 g, 0.42 mmol) and 4-allyl-
2,6-dimethoxyphenol (0.68 g, 3.53 mmol). The product was
purified as in the procedure for the preparation of 10, giving
11 as a pale yellow, thick oil (0.83 g, 72% yield). 1H NMR

2592 Organometallics, Vol. 20, No. 12, 2001
Are´valo et al.
Syn th esis of 2G-[(CH2)3[{C6H2(OMe)2}O]Ti(C5H5)Cl2]8
(17). This metallodendrimer was prepared by a method similar
to that described for 16, starting from [Ti(C5H5)Cl3] (0.32 g,
1.46 mmol) and 11 (0.50 g, 0.18 mmol), to give 17 as a red oil
in quantitative yield (0.76 g). 1H NMR (CDCl3): δ 6.70 (s, 10H,
C5H5), 6.33 (s, 4H, C6H2), 3.83 (s, 12H, OMe), 2.53 (m, 4H,
CH2CH2CH2Ph), 1.56 (m, 4H, CH2CH2CH2Ph), 1.27 (m, 6H,
SiCH2CH2CH2Si), 0.52 (m, 16H, SiCH2CH2CH2Si and CH2CH2-
CH2Ph overlapping), -0.06 (s, 12H, SiMe2), -0.09 (s, 3H,
SiMe). 13C{1H} NMR (CDCl3): δ 150.7 (Cipso bonded to -OMe),
148.5 (Cipso bonded to -OTi), 138.9 (Cipso bonded to -CH2),
121.0 (C5H5), 105.7 (C6H2), 56.8 (OMe), 40.4 (CH2CH2CH2Ph),
26.0 (CH2CH2CH2Ph), 15.4 (CH2CH2CH2Ph), 20.1, 18.8, 18.5
and overlapped signals (Si(CH2)3Si), -3.2 (SiMe2), -4.9 (SiMe).
29Si{1H} NMR (CDCl3): δ 1.89 (G2-Si), 1.20 (G1-Si), not
observed (G0-Si). Anal. Calcd for C184H284Cl16O24Si13Ti8: C,
52.67; H, 6.82. Found: C, 52.43, H; 6.51.
Syn th esis of 4G-[(CH2)3[{C6H2(OMe)2}O]Ti(C5H5)Cl2]32
(18). A solution of [Ti(C5H5)Cl3] (0.18 g, 0.81 mmol) in toluene
(20 mL) was added to another solution containing 12 (0.30 g,
0.025 mmol) in toluene (10 mL). The mixture was heated to
80 °C for 6 h and subsequently stirred overnight at room
temperature. Afterward, 1 drop of NEt3 was added. Then, after
filtration, the solvent was removed at reduced pressure to give
18 as a red oil in quantitative yield (0.44 g). 1H NMR (CDCl3):
δ 6.68 (s, 40 H, C5H5), 6.32 (s, 16H, C6H2), 3.81 (s, 48H, OMe),
2.52 (m, 16H, CH2CH2CH2Ph), 1.55 (m, 16H, CH2CH2CH2Ph),
1.28 (m, 30H, SiCH2CH2CH2Si), 0.52 (m, 76H, SiCH2CH2CH2-
Si and CH2CH2CH2Ph overlapping), -0.07 (s, 48H, SiMe2),
0.10 (broad, 21H, SiMe). 13C{1H} NMR (CDCl3): δ 150.6 (Cipso
bonded to -OMe), 148.4 (Cipso bonded to -OTi), 138.8 (Cipso
bonded to -CH2), 121.1 (C5H5), 105.6 (C6H2), 56.7 (OMe), 40.4
(CH2CH2CH2Ph), 26.0 (CH2CH2CH2Ph), 15.4 (CH2CH2CH2Ph),
20.2, 18.8, 18.5 and overlapped signals (Si(CH2)3Si), -3.2
(SiMe2), -4.9 (SiMe). 29Si{1H} NMR (CDCl3): δ 2.08 (G4-Si),
1.46 (G3-Si), the rest were not observed. Anal. Calcd for
C
784H1244Cl64O96Si61Ti32: C, 53.14; H, 7.08. Found: C, 52.68;
H, 7.27.
Ack n ow led gm en t. We acknowledge the DGESIC-
Ministerio de Educacio´n y Cultura (Project PB97-0765),
the University of Alcala´ (project E023/2000), and The
Royal Society of Chemistry of the U.K. for financial
support. S.A. is grateful to the University of Alcala´ for
providing a fellowship. We thank the reviewers for their
comments, suggestion, and proofreading.
1
Su p p or tin g In for m a tion Ava ila ble: Selected data as H
and 13C NMR and MALDI-TOF spectra of derivatives 10 and
11, 29Si NMR spectra of 4G dendrimer generation 9, 12, 15,
and 18, and GPC traces of derivatives 10-12. This material
is available free of charge via the Internet at http://pubs.acs.org.
OM0010114