Hydrozirconation of first-generation allyl-functionalized dendrimers and dendrimer model compounds

Article abstract of DOI:10.1016/j.jorganchem.2004.03.010

Several allyl-functionalized dendrimers and mono-functional model compounds have been prepared. These have been hydrozirconated using [Cp₂ZrHCl]_x to give zirconocene terminated dendrimers. These dendrimers have been characterized usi

Full text of DOI:10.1016/j.jorganchem.2004.03.010

Journal of Organometallic Chemistry 689 (2004) 1876–1881
www.elsevier.com/locate/jorganchem
Hydrozirconation of first-generation allyl-functionalized
dendrimers and dendrimer model compounds
a,
a
b
Reinout Meijboom a,*,1, John R. Moss *, Alan T. Hutton , Tracy-Ann Makaluza ,
b
b
Selwyn F. Mapolie , Fazlin Waggie , Mark R. Domingo
c
a
Department of Chemistry, University of Cape Town, South Africa
b
Department of Chemistry, University of the Western Cape, South Africa
c
Sasol Polymers, P.O. Box 2525, Randburg 2125, South Africa
Received 20 February 2004; accepted 11 March 2004
Abstract
Several allyl-functionalized dendrimers and mono-functional model compounds have been prepared. These have been hydro-
zirconated using [Cp2ZrHCl]x to give zirconocene terminated dendrimers. These dendrimers have been characterized using spec-
troscopic techniques, particularly NMR.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Dendrimer; Schwartz’s reagent; Hydrozirconation; Zirconium
1. Introduction
to employ reactions that have a quantitative yield in
order to prevent imperfections and by-products in the
dendrimer build-up [5,6].
The rising demand for materials with improved and
novel properties has shifted the emphasis in polymer
research from traditional linear polymers, via cross-
linked and branched polymers, to hyperbranched or
dendritic polymers. This new class of highly branched
three-dimensional molecules has intrigued researchers
and numerous review articles have been published in
recent years [1,2]. Many applications for dendrimers
have been found, one of the most exciting applications
being the use of dendrimers as an immobilisation phase
for homogeneous catalysts [3]. From our ongoing re-
search into dendrimers and their applications in orga-
nometallic chemistry [2,4], it has become clear that the
number of synthetic routes available to attach an or-
ganometallic moiety to the branches of a dendrimer is
limited. This limitation is mainly due to the requirement
Schwartz’s reagent is a well-known and convenient
reagent in organic chemistry for the functionalization of
alkenes [7]. In our search towards new organometallic
dendrimers [2,4] we have utilized Schwartz’s reagent to
functionalize a series of organic dendrimers. We have
also hydrozirconated some mono-functional model
compounds in order to compare the reactions of these
compounds with those of the dendrimers with Sch-
wartz’s reagent. The poly-zirconium species reported
here are valuable reactants for the functionalization of
easily-obtained poly-alkene functionalized dendrimers.
For example the hydrozirconation reaction has been
used to build up organogermanium dendrimers in the
past [8]. Only a few other examples of zirconocene
functionalized dendrimers have been reported [9] up to
date.
* Corresponding authors. Tel.: +27-11-4892363; fax: +27-11-
4892819.
E-mail addresses: Reinout@science.uct.ac.za (R. Meijboom),
jrm@science.uct.ac.za (J.R. Moss).
2. Results and discussion
1
Present address: Department of Chemistry and Biochemistry, Rand
Afrikaans University, P.O. Box 524, Auckland Park 2006, South
Africa.
The allyl terminated dendrimer (entry 9, Table 1) was
prepared according to Scheme 1. Allylbromide was
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.03.010

R. Meijboom et al. / Journal of Organometallic Chemistry 689 (2004) 1876–1881
1877
Table 1
Hydrozirconation of poly-alkenes
Entry
Alkene starting material
Product
Appearance
1
2
Me3SiCH2CH@CH2
PhCH2CH2CH@CH2
PhOCH2CH@CH2
PhOCH2C6H3-3,5-(OCH2CH@CH2)2
PhC(CH2CH@CH2)3
1,2,4,5-C6H2(CH2CH2CH@CH2)4
Si(CH2CH@CH2)4
1,4-C6H4[C(CH2CH@CH2)3]2
CH3C[C6H4-4-OCH2C6H3-3,5-(OCH2CH@CH2)2]3
Si[(CH2)3Si(CH2CH@CH2)3]4
Me3Si(CH2)3(Cp2ZrCl)
Ph(CH2)4(Cp2ZrCl)
Yellow oil
Yellow solid
Red oil
3
PhO(CH2)3(Cp2ZrCl)
PhOCH2C6H3-3,5-[O(CH2)3(Cp2ZrCl)]2
PhC[(CH2)3(Cp2ZrCl)]3
4
Yellow oil
Yellow solid
Yellow solid
Yellow solid
Yellow oil
Yellow oil
Yellow oil
5
6
1,2,4,5-C6H2[(CH2)3(Cp2ZrCl)]4
Si[(CH2)3(Cp2ZrCl)]4
7
8
1,4-C6H4{C[(CH2)3(Cp2ZrCl)]3}
CH3C{C6H4-4-OCH2C6H3-3,5-[O(CH2)3(Cp2ZrCl)]2}3
Si{(CH2)3Si[(CH2)3(Cp2ZrCl)]3}4
9
10
O
O
HO
OH
O
O
allylbromide
K CO
18-crown-6
acetone
CBr
PPh
4
2
3
3
Br
OH
OH
OH
OH
K CO
2
3
18-crown-6
acetone
OH
O
O
O
O
O
O
O
O
O
Scheme 1. Synthesis of allyl-functionalized dendrimer (entry 9, Table 1).
reacted with 3,5-dihydroxybenzylalcohol to give 3,5-
diallyloxybenzylalcohol in acetone in the presence of
base in good yields after chromatographic purification.
The alcohol functionality was subsequently converted to
a bromide by using PPh3/CBr4. The resulting 3,5-dial-
lyloxybenzylbromide was used to react with both phenol
and the dendrimer core CH3C(C6H4OH)3. All com-
pounds were isolated in good yields after chromato-
graphic purification.
scopic data is provided. The products were purified by
extraction into pentane, leaving the pure R(CH2)3-
(Cp2ZrCl) (R ¼ SiMe3, CH2Ph, OPh) after evaporation
of the pentane. The products are thermally stable and
can be stored for a long period (several months) under
an inert atmosphere at room temperature without ap-
parent decomposition (1H NMR spectroscopy). Hy-
drozirconation of allyltrimethylsilane was also
performed in benzene, THF, and CH2Cl2. This resulted
in the same product, as was concluded from 1H and 13
C
2.1. Hydrozirconations of mono-allyl species
NMR spectroscopy, and by chemical derivation. The
products of hydrozirconation were identified as the ex-
pected hydrometallation complexes R(CH2)3(Cp2ZrCl)
(R ¼ SiMe3, CH2Ph, OPh). The hydrozirconation reac-
tion in THF was faster than the reaction in benzene, due
to the more polar character of the solvent, as observed
by consumption of the insoluble zirconocene hydride
reagent. This resulted in enhanced solubility of the re-
active Cp2Zr(H)Cl monomer because of solvent co-or-
dination. Reaction in CH2Cl2 was even faster; but a
The product of hydrozirconation reactions of allyl
functionalized silanes (see Scheme 2) and alkanes in
toluene resulted in yellow oils or solids, which were very
soluble in common organic solvents. These species were
highly oxygen- and moisture-sensitive, which interfered
with analytical techniques such as elemental analysis
and mass spectrometry. Due to the sensitive nature of
the hydrozirconation products, only NMR spectro-

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R. Meijboom et al. / Journal of Organometallic Chemistry 689 (2004) 1876–1881
(Cp2ZrCl)
Si
+ 1/n (Cp ZrClH)
Si
Si
(Cp ZrCl)
2
n
2
(Cp2ZrCl)
(Cp2ZrCl)
Scheme 2. Hydrozirconation of allyltrimethylsilane (entry 1, Table 1).
Si
+ 4/n [Cp2 ZrClH]n
(Cp Zr
)
Cl
2
Scheme 3. Hydrozirconation of tetraallysilane (entry 7, Table 1).
competitive reaction of zirconocene hydrochloride with
dichloromethane to form zirconocene dichloride also
occurred in this solvent (1H NMR) [10] resulting in a
lower yield.
3. Conclusion
The hydrozirconation of several allyl-functionalized
alkanes, carbosilane and hydrocarbon dendrimers was
successful as shown by NMR spectroscopy. In the
process, several new dendrimers were synthesized and
characterized. All hydrozirconation products gave the
expected spectroscopic characteristics. In addition se-
lected hydrozirconated polyalkenes were reacted with
H2O and I2 to show that hydrozirconation is a feasible
and successful route to functionalize dendrimers.
2.2. Hydrozirconations of polyalkenes
The reaction of [Cp2Zr(H)Cl]n with R(CH2-
CH@CH2)4, (R ¼ Si, C6H2(CH2)4) resulted in the tet-
rakis-insertion product R[(CH2)3(Cp2ZrCl)]4, as was
concluded from 1H and 13C NMR spectroscopy (see
Table 1). During the reactions, a solvent effect was once
again observed. The reaction of these compounds in
THF took about 2 h to reach completion, whereas the
same reaction in benzene took 48 h. This made it pos-
sible to monitor the reaction of [Cp2Zr(H)Cl]n with
tetraallylsilane in benzene. Thus it was possible to
identify all four possible insertion products by 1H
NMR. However, upon reaction of 1 equivalent of tet-
raallylsilane with 1 equivalent of [Cp2Zr(H)Cl]n in ben-
zene, a statistical mixture of insertion products was
obtained – and not just the mononuclear organometallic
4. Experimental
4.1. General
Manipulations of sensitive compounds were carried
out under purified nitrogen using glovebox (MBraun
Unilab) or standard Schlenk line techniques under pu-
rified argon [12]. Solvents (diethyl ether, pentane, THF,
toluene) were pre-dried by passage through a column
containing alumina (neutral, Brockmann grade I) fol-
lowed by distillation from sodium/benzophenone ketyl/
tetraglyme [13] prior to use. Acetone was distilled
from Drierite prior to use. CDCl3 was dried over
CaH2 and C6D6 was dried over NaK and both were
distilled prior to use. Allylbromide, allyltrimethyl-silane,
allyloxy-benzene, carbontetrabromide, 18-crown-6,
5-hydroxymethylbenzene-1,3-diol, K2CO3, phenol,
4-phenyl-1-butene, triphenylphosphine, tetraallylsi-
lane and 1,1,1-tris(4-hydroxyphenyl)ethane were pur-
chased from Sigma Aldrich and used as received.
[Cp2ZrHCl]n [10], Si[CH2CH2CH2Si(CH2CH@CH2)3]4
[14], 1,3-bisallyloxy-5-bromomethyl benzene [15], (1,1-
diallylbut-3-enyl)-benzene [16] and 1,4-bis-(1,1-diallyl-
but-3-enyl)-benzene [16] were prepared according to
literature procedures. NMR spectra were recorded on
either a Varian Unity-400 (1H: 400 MHz; 13C: 100.6
MHz) spectrometer, a Varian Mercury-300 (1H: 300
MHz; 13C: 75.5 MHz) spectrometer or a Varian Gemini
2000 (1H: 200 MHz, 13C: 50.3 MHz) at ambient tem-
perature. NMR spectra were referenced relative to TMS
using either the residual protonated impurities in the
solvent (1H NMR: CDCl3: d 7.27; C6D6: d 7.16) or the
solvent resonances (13C NMR: CDCl3: d 77.0; C6D6: d
128.0). Infrared spectra were recorded neat between
NaCl disks on a Perkin–Elmer Paragon 1000 FTIR
1
complex. From the H NMR spectrum of the reaction
mixture obtained by using a 1:1 mole ratio of starting
materials, it can be concluded that the products do not
undergo b-H elimination. It can also be concluded that a
fast ligand redistribution reaction, as reported for
Cp2ZrXY [11] (X, Y ¼ F, Cl, Br, I), is not likely to oc-
cur. The tetrazirconium species Si[(CH2)3(Cp2ZrCl)]4
could be isolated as a yellow, crystalline solid (see
Scheme 3). However, no crystals suitable for X-ray
crystallography could be obtained. This was mainly due
to the increased reactive nature of the tetrazirconium
species towards oxygen and moisture. This increased
reactivity (as compared to normal alkyl-zirconocene
compounds [5]) precluded the normal analytical analy-
ses such as elemental analysis and mass spectrometry. In
order to additionally confirm the existence of the poly-
zirconated species, some of the compounds (entry 5, 6
and 8) were reacted with H2O to give the alkane and
[Cp2ZrCl]2O, as was concluded from NMR spectros-
copy. In addition entries 1, 5 and 6 were treated with I2.
The compound Me3Si(CH2)3(Cp2ZrCl) (entry 1) reacted
with I2 to completely decompose. This is presumably
because I2 also cleaves the Me3Si group in addition to
the Zr–C bond. In the reaction of the other compounds
with I2 the appropriate alkyliodide was found and an-
alyzed. The identity of these products was confirmed by
NMR spectroscopy.

R. Meijboom et al. / Journal of Organometallic Chemistry 689 (2004) 1876–1881
1879
spectrometer. Mass spectra were recorded on a Finnigan
MAT GCQ GC/MS. Elemental analyses were per-
formed using a Carlo Erba EA1108 elemental analyzer
in the microanalytical laboratory of the University of
Cape Town.
7.00 (d, 6H, 3J(H,H) ¼ Hz, ArHcore) 6.87 (d, 6H,
3J(H,H) ¼ Hz, ArHcore), 6.59 (d, 6H, 4J(H,H) ¼ Hz,
4
ArH), 6.42 (t, 3H, J(H,H) ¼ Hz, ArH), 6.18–5.96 (m,
6H, 6CH@), 5.44–5.22 (m, 12H, 6CH2@), 4.96 (s, 6H,
3ArCH2O), 4.50 (d, 12H, 3J(H,H) ¼ Hz, 6CH2O);
dCfHg(50.3 MHz, CDCl3): d 157.9 (ArC), 154.8 (ArC-
core), 140.1 (ArCcore), 137.5 (ArC), 131.1 (CH@), 126.7
(ArCcore), 115.8 (CH2@), 112.0 (ArCcore), 104.2
(ArC), 99.3 (ArC), 67.9 (ArCH2O), 66.9 (CH2O), 40
(CH3); m=z (FAB): 912 (Mþ–H), 503 (C30H31Oþ7 ), 105
(C7H5Oþ), 91 (C7H7þ), 57 (C3H5Oþ). Anal. Calc. for
CHO: C, 77.61; H, 6.62. Found: C, 77.52; H, 6.65%.
4.2. Synthesis of polyalkenes
4.2.1. Synthesis of 3,5-(H2C@CHCH2O)2C6H3CH2OH
((3,5-bisallyloxy-phenyl)-methanol)
A different synthesis for this compound has been re-
ported [15]. Allylbromide (0.34 g, 2.8 mmol) was added
to a mixture of 3,5-dihydroxybenzylalcohol (0.21 g, 1.47
mmol), K2CO3 (0.51 g, 3.70 mmol) and 18-crown-6
(0.15 g, 0.57 mmol) in acetone (20 ml). The mixture was
heated under reflux for 72 h. The solids were filtered off
and the volatiles removed in vacuo. The compound was
dissolved in CH2Cl2 (30 ml) and washed with water (30
ml), dried over MgSO4, filtered and the solvent was
evaporated in vacuo to give a yellow oil. Column
chromatography over silica, eluting with 10% CH2Cl2 in
hexane followed by 50% CH2Cl2 in hexane and finally
CH2Cl2 gave 0.36 g (90%) of 3,5-di(allyloxy)benzylal-
cohol as a yellow oil. Analytical data were in agreement
with literature [15].
4.2.4. Synthesis of tetrakis-1,2,4,5-(4-butenyl)benzene
a
To
suspension of tetrakis-1,2,4,5-(bromom-
ethyl)benzene (1.11 g, 2.46 mmol) in diethyl ether (20
ml) was added over 5 min a solution of allylmagnesium
bromide in diethyl ether (1.0 M, 10 ml, 10 mmol). The
resulting clear yellow solution was heated under reflux
for 4 h and subsequently stirred at ambient temperature
for 20 h. The reaction was quenched with aqueous
NH4Cl solution (1.0 M, 20 ml), the organic layer sepa-
rated, dried over MgSO4, filtered and the volatiles were
removed from the filtrate in vacuo to give tetrakis-
1,2,4,5-(4-butenyl)benzene as a colorless oil, 0.70 g
(96%). dH(200 MHz, CDCl3): 6.99 (s, 2H, ArH), 5.99–
5.82 (m, 4H, 4CH@), 5.15–4.99 (m, 8H, 4CH2@), 2.78–
2.66 (m, 8H, CH2CH2Ar), 2.46–2.30 (m, 8H, 4CH2Ar).
dCfHg(50.3 MHz, CDCl3): 138.4, 137.1, 130.0 (ArC),
116.8, 114.7 (C@C).
4.2.2. Synthesis of 3,5-(H2C@CHCH2O)2C6H3CH2OPh
Acetone (40 ml) was added to a mixture of 3,5-
(H2C@CHCH2O)2C6H3CH2Br (0.33 g, 1.16 mmol),
phenol (0.11 g, 1.16 mmol), K2CO3 (0.4 g, 2.91 mmol)
and 18-crown-6 (0.62 g, 0.23 mmol) and the resulting
mixture was heated under reflux for 72 h. The salts were
filtered off and the volatiles removed in vacuo to give an
orange oil. Column chromatography over silica, eluting
with 20% CH2Cl2 in hexane gave a colorless oil, 0.22 g
(65%) of 3,5-(H2C@CHCH2O)2C6H3CH2Ph. dH(200
MHz, CDCl3): d 7.34–7.22 (m, 2H, ArH), 7.01–6.92 (m,
3H, ArH), 6.61–6.12 (m, 2H, ArH), 6.46–6.43 (m, 1H,
ArH), 6.18–5.97 (m, 2H, CH@), 5.46–5.24 (m, 4H,
CH2@), 5.0 (s, 2H, ArCH2O), 4.53–4.51 (m, 4H,
ArOCH2); dCfHg(50.3 MHz, CDCl3): d 159.9, 158.7,
139.5, 133.1, 129.4, 121.0 (ArC), 117.7, 114.9 (C@C),
106.3 (ArCH2), 69.8, 68.9 (CH2).
4.3. Hydrozirconations
All hydrozirconations were performed using similar
procedures. A representative example is given for the
synthesis of Cp2ZrCl(CH2)3SiMe3.
4.3.1. Cp2ZrCl(CH2)3SiMe3
Schwartz’s reagent (0.158 g, 0.61 mmol) and allyltri-
methylsilane (198 mm3, 1.25 mmol) were mixed in tol-
uene (1.6 cm3) at room temperature and stirred for 1 h.
A clear yellow solution was obtained. The volatiles were
removed in vacuo and the yellow oil was stripped with
pentane (2 ꢀ 1.0 cm3). The product was extracted into
pentane (3 ꢀ 2.0 cm3) and the volatiles were removed in
vacuo to give a yellow oil Cp2ZrCl(CH2)3Si(CH3)3 (0.23
g, 68%). dH(C6D6, 400 MHz): 5.78 (10H, 2C5H5), 1.70
4.2.3. Synthesis of {4-[3,5-(H2C@CHCH2O)2C6H3-
CH2O]C6H4}3CCH3
K2CO3 (0.17 g, 1.2 mmol), 18-crown-6 (0.08 g, 0.32
mmol) and 1,1,1-tris(4-hydroxyphenyl)ethane (0.1 g,
0.32 mmol) were added to a solution of 3,5-diallyloxy-
phenylmethylbromide (0.28 g, 0.98 mmol) in acetone (15
ml) and heated under reflux for 78 h. The suspension
was filtered and the volatiles removed in vacuo. Column
chromatography over silica, eluting with 20% CH2Cl2 in
hexane, followed by 50% CH2Cl2 and CH2Cl2 gave
0.54 g (61%) of {4-[3,5-(H2C@CHCH2O)2C6H3CH2O]-
C6H4}3CCH3 as a yellow oil. dH(200 MHz, CDCl3): d
3
(2H, m, CH2CH2CH2), 1.17 (2H, m, J(H,H) ¼ 8 Hz,
ZrCH2), 0.62 (2H, m, 3J(H,H) ¼ 8 Hz, SiCH2), 0.09 (9H,
s, 3CH3); dCfHg(C6D6, 50.3 MHz): 112.20 (10C, 2C5H5),
60.16 (1C, ZrCH2), 28.79 (1C, CH2CH2CH2), 24.18 (1C,
CH2Si), )1.04 (3C, 3 CH3).
4.3.2. Cp2ZrCl(CH2)4Ph
dH(200 MHz, CDCl3): 7.36–7.17 (m, 5H, ArH), 6.32
(s, 10H, 2Cp), 2.64–2.57 (m, 2H, CH2Ar), 1.67–1.55 (m,

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R. Meijboom et al. / Journal of Organometallic Chemistry 689 (2004) 1876–1881
2H, CH2CH2Ar), 1.44–1.3 (m, 2H, CH2CH2Zr), 0.98–
0.95 (m, 2H, CH2Zr); dH(400 MHz, C6D6): 7.20–7.16
CH2CH2Ar), 1.46–1.41 (m, 2H, CH2CH2Zr), 1.08–0.90
(m, 2H, CH2Zr); dCfHg(50.3 MHz, CDCl3): 137.7, 130.0
(ArC), 116.0 (Cp), 56.2 (CH2Zr), 37.5 (CH2CH2Zr),
34.3 (CH2CH2Ar).
3
(m, 5H, ArH), 5.72 (s, 10H, 2Cp), 2.59 (t, 2H, J ¼ Hz
CH2Ar), 1.57 (m, 4H, CH2CH2CH2Ar), 1.09 (t, 2H,
3J ¼ Hz CH2Zr); dCfHg(50.3 MHz, CDCl3): 136.4, 121.8,
121.75 (ArC), 105.5 (Cp), 47.6 (CH2Zr), 31.0
(CH2CH2Zr), 28.8 (CH2CH2Ar), 26.8 (CH2Ar);
dCfHg(100 MHz, C6D6): 143.3, 128.6, 125.8 (ArC), 112.3
(Cp), 54.5 (CH2Zr), 37.8, 35.7, 33.6.
4.3.9. {3,5-[(Cp2ZrCl)(CH2)3O]2C6H3CH2OC6H4}3
CCH3
dH(200 MHz, CDCl3): 7.19–6.80 (br m, ArH), 6.31 (s,
60H, 12Cp), 4.99 (s, 6H, 3ArCH2), 3.74–3.70 (m, 12H,
CH2O), 2.08–2.01 (m, 12H, CH2CH2O), 1.28 (s, 3H,
CH3), 1.05–0.90 (m, 12H, CH2Zr); dH(200 MHz, C6D6):
7.15–6.90 (br m, ArH), 5.73 (s, 60H, 12Cp), 4.98 (s, 6H,
3ArCH2), 3.83–3.78 (m, 12H, CH2O), 2.04–1.99 (m,
12H, CH2CH2O), 1.25 (s, 3H, CH3), 1.01–0.90 (m, 12H,
CH2Zr).
4.3.3. PhO(CH2)3(Cp2ZrCl)
dH(200 MHz, CDCl3): 7.26–7.22 (m, 2H, ArH), 6.99–
6.88 (m, 3H, ArH), 6.39 (s, 10H, 2Cp), 3.93–3.91 (m,
2H, CH2O), 1.85–1.76 (m, 2H, CH2CH2O), 1.04–1.03
(m, 2H, CH2Zr); dH(200 MHz, C6D6): 7.15–7.02 (m,
5H, ArH), 5.72 (s, 10H, 2Cp), 3.68–3.65 (m, 2H, CH2O),
2.02–1.90 (m, 2H, CH2CH2O), 1.12–0.97 (m, 2H,
CH2Zr); dCfHg(50.3 MHz, CDCl3): 127.41, 127.38, 118.5
(ArC), 114.0 (Cp), 67.4 (CH2Zr), 20.6 (CH2CH2O), 8.54
(CH2O).
4.4. Reactions of polyalkylzirconium species
4.4.1. Reaction of PhC[(CH2)3(Cp2ZrCl)]3 with H2O
To a suspension of [Cp2Zr(H)Cl]n (0.1 g, 0.39 mmol)
in toluene (5 ml) was added a solution of C6H5–
C(CH2CH@CH2)3 (0.028 g, 0.13 mmol) in toluene (5
ml). The solution was stirred overnight at room tem-
perature giving a clear yellow solution. The reaction
mixture was filtered and the solvent removed in vacuo. A
yellow solid was obtained which was dissolved in diethyl
ether (5 ml). H2O (1 ml) was added and the mixture
stirred for 30 min. The solution decolorized and a white
precipitate formed. The white solid was filtered off. The
organic layer was separated from the aqueous layer,
dried over MgSO4, filtered and the volatiles evaporated
in vacuo to give C6H5C(CH2CH2CH3)3 (0.020 g, 67%) as
a colorless oil dH(200 MHz, CDCl3): 7.00 (br d, 2H,
C6H5), 7.19 (br t, 1H, C6H5), 7.55 (br t, 2H, C6H5), 1.53
(t, 6H, C(CH2CH2)3), 1.30 (m, 6H, 3CH2CH2CH3), 0.83
(t, 9H, 3CH3); dCfHg(50.3 MHz, CDCl3): 160.71, 128.43,
125.78 (ArC), 42.81 (PhC), 40.25 (C(CH2)3), 20.06
(CH2CH2CH3), 14.92 (CH3).
4.3.4. 3,5-[(Cp2ZrCl)(CH2)3O]2C6H3CH2OPh
dH(200 MHz, CDCl3): 7.37–7.25 (m, 3H, ArH), 6.99–
6.95 (m, 3H, ArH), 6.62–6.59 (m, 2H, ArH), 6.37 (s,
20H, 4Cp), 4.99 (s, 2H, ArCH2), 3.72–3.69 (m, 4H,
2CH2O), 1.9–2.09 (CH2CH2O), 1.18–0.90 (m, 4H,
CH2Zr); dCfHg(50.3 MHz, CDCl3): 160.0, 129.4, 121.1
(ArC), 114.1 (Cp), 106.1 (CH2Ar), 69.7 (CH2Zr), 22.4
(CH2CH2O), 10.0 (CH2O).
4.3.5. PhC[(CH2)3(Cp2ZrCl)]3
dH(200 MHz, CDCl3): 7.22–7.10 (br m, 5H, C6H5),
6.09 (s, 30H, 6Cp), 1.46–1.40 (br m, 12H,
3
(CH2)2CH2Zr), 0.95 (br t, 6H, 3CH2Zr); dCfHg(50.3
MHz, CDCl3): 145.1, (ArC), 133.41 (ArC), 115.00 (Cp),
56.81 (ZrCH2), 43.88 (C6H5–C), 40.91 (ZrCH2CH2),
28.31 (ArCH2CH2).
4.3.6. C6H4{C[(CH2)3(Cp2ZrCl)]3}2
dH(200 MHz, CDCl3): 7.23, (s, 4H, C6H4), 6.12 (s,
60H, 6Cp), 1.45 (br m, 24H, 6 (CH2)2CH2Zr), 0.97 (br t,
12H, 6CH2Zr); dCfHg(50.3 MHz, CDCl3): 144.39 (ArC),
135.34 (ArC), 116.00 (Cp), 57.36 (ZrCH2), 44.18 (C6H5–
C), 41.80 (ZrCH2CH2), 27.61 (ZrCH2CH2CH2).
4.4.2. 1,2,4,5-C6H2[(CH2)3CH3]4
Reaction performed in a similar way to the above.
dH(200 MHz, CDCl3): 6.90 (s, 2H, C6H2), 2.54 (t, 8H,
4CH2CH2CH2CH3), 1.41 (m, 16H, 4CH2CH2CH2CH3),
0.94 (t, 12H, 4CH3); dCfHg(50.3 MHz, CDCl3): 137.64,
129.85 (ArC), 33.64 (ArCH2), 32.05 (CH2CH2CH3),
22.92 (CH2CH3), 14.02 (CH3).
4.3.7. Si[(CH2)3(Cp2ZrCl)]4
dH(C6D6, 400 MHz): 5.95 (40H, s, 8C5H5), 2.00 (8H,
m, 4CH2CH2CH2), 1.41 (8H, m, 3J(H,H) ¼ 8 Hz,
ZrCH2), 0.98 (8H, m, 3J(H,H) ¼ 8 Hz, SiCH2);
dCfHg(C6D6, 50.3 MHz): 112.20 (10C, 2C5H5), 60.16
(1C, ZrCH2), 28.79 (1C, CH2CH2CH2), 24.18 (1C,
CH2Si).
4.4.3. 1,4-C6H4{C[(CH2)2CH3]3}2
Reaction performed in a similar way to the above.
dH(200 MHz, CDCl3): 7.10 (br s, 4H, C6H4), 1.53 (br t,
12H, 2C–(CH2)3), 1.27 (m, 12H, 6CH2CH2CH3), 0.83
(t, 18H, 6CH3); dCfHg(50.3 MHz, CDCl3): 144.45,
125.78 (ArC), 42.81 (Ph–C), 40.28 (C(CH2)3), 20.12
(CH2CH3), 14.92 (CH3).
4.3.8. 1,2,4,5-C6H2[(CH2)4(CpZrCl)]4
dH(200 MHz, CDCl3): 6.9 (s, 2H, ArH), 5.96 (s, 10H,
2Cp), 2.52–2.49 (m, 2H, CH2Ar), 1.65–1.55 (m, 2H,

R. Meijboom et al. / Journal of Organometallic Chemistry 689 (2004) 1876–1881
1881
4.4.4. Reaction of PhC[(CH2)3(Cp2ZrCl)]3 with I2
The zirconium alkyl was prepared as described pre-
viously. To the toluene solution of the compound was
added solid I2 (0.1 g, 0.39 mmol). The mixture was
stirred overnight at room temperature. The resultant
precipitate was filtered off and the filtrate washed with a
1 M solution of sodium thiosulphate (3 ꢀ 20 ml). The
organic layer was dried over MgSO4, filtered and the
solvent removed in vacuo leaving a pale yellow solid.
dH(200 MHz, CDCl3): 7.23 (m, 2H), 7.15 (m, 1H), 7.10
(m, 2H, Ar), 2.97 (br t, 6H, 3CH2I), 1.66 (br t, 6H,
C(CH2)3), 1.49 (br t, 6H, 3CH2–CH2CH2); dCfHg(50.3
MHz, CDCl3): 128.21, 128.21, 125.55, 122.95 (ArC),
40.99 (Ph–C), 38.89 (Ph–C(CH2)3), 30.45 (CH2CH2I),
6.05 (CH2I).
[3] (a) J.W.J. Knapen, A.W. van der Made, J.C. de Wilde, P.W.N.M.
van Leeuwen, P. Wijkens, D.M. Grove, G. Van Koten, Nature
372 (1994) 659;
(b) G.E. Oosterom, J.N.H. Reek, P.C.J. Kamer, P.W.N.M. van
Leeuwen, Angew. Chem. Int. Ed. Engl. 40 (2001) 1828.
[4] (a) Y.-H. Liao, J.R. Moss, J. Chem. Soc., Chem. Commun. (1993)
1774;
(b) Y.-H. Liao, J.R. Moss, Organometallics 14 (1995) 2130;
(c) Y.-H. Liao, J.R. Moss, Organometallics 15 (1996) 4307;
(d) I.J. Mavunkal, J.R. Moss, J. Bacsa, J. Organomet. Chem. 593
(2000) 361;
(e) R. Meijboom, A.T. Hutton, J.R. Moss, Organometallics 22
(2003) 1811;
(f) R. Meijboom, M.J. Overett, J.R. Moss, J. Organomet. Chem.
689 (2004) 987;
(g) S. Harder, R. Meijboom, J.R. Moss, J. Organomet. Chem., in
press;
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Chim. Acta, J. Organomet. Chem. 689 (2004) 1095.
[5] The composition of dendrimers formed in a reaction of the arms
with a less than 100% yield can be calculated from the yield of the
4.4.5. 1,2,4,5-C6H2[(CH2)3I]4
À
Á
Reaction performed in a similar way to the above.
dH(200 MHz, CDCl3): 6.76 (s, 2H, Ar), 3.12 (br t, 8H,
CH2I), 2.46 (br t, 8H, 4PhCH2), 1.74 (br m, 16H,
N!
n!m!
specific reaction using the following formula: P ¼
Y n
m
ð1 ꢁ Y Þ ; where P ¼ mole fraction of product; N ¼ n þ m ¼ total
number of reactive groups; n ¼ number of reacted groups;
m ¼ number of unreacted groups and Y ¼ reaction yield. For
example a reaction with a yield of 95% on a dendrimer with 4 arms
4CH2CH2CH2);
125.55 (ArC), 32.90 (PhCH2CH2), 32.80 (CH2CH2I),
32.40 (PhCH2), 6.70 (CH2I).
dCfHg(50.3 MHz, CDCl3): 134.34,
4
0
gives a mole fraction of P ¼ ð4!=4!0!Þð0:95Þ ð0:05Þ ¼ 0:815 of
pure product. The other 18.5% are impure dendrimers with one or
more branches unreacted.
[6] R. Meijboom, Ph.D Thesis, University of Cape Town, 2001.
[7] (a) See for example: P.C. Wailes, H. Weigold, J. Organomet.
Chem. 24 (1970) 405;
Acknowledgements
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We would like the thank Sasol Polymers, the Uni-
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Cape, THRIP and the NRF for financial support.
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