Syntheses and catalytic activities of Group 4 metal complexes derived from C(cage)-appended cyclohexyloxocarborane trianion

Article abstract of DOI:10.1016/j.jorganchem.2005.01.047

The reaction of Li[closo-1-Me-1,2-C₂B₁₀H ₁₀] with cyclohexene oxide produced closo-1-Me-2-(2′- hydroxycyclohexyl)-1,2-C₂B₁₀H₁₀ (1) in 86% yield. Decapitation of (1) with potassium hydroxide in refluxing ethanol gave the corresponding cage-opened potassium salt of the carborane anion, [nido-1-Me-2-(2′-hydroxycyclohexyl)-1,2-C₂B₉H ₁₀]^- (2) in 82% yield. Deprotonation of (2) with two equivalents of n-butyllithium in THF at -78 °C, followed by its further reaction with anhydrous MCl₄ ? 2THF (M = Ti, Zr) produced the corresponding d⁰-half-sandwich metallacarboranes, closo-1-M(Cl)-2-Me-3-(2′-σ-O-cyclohexyl)-η⁵-2, 3-C₂B₉H₉ (3 M = Zr; 4 M = Ti), in 59% and 51% yields, respectively. Reaction of Li[closo-1,2-C₂B₁₀H ₁₁] with Merrifield's peptide resin (1%) in refluxing THF gave the ortho-carborane-functionalized polymer (5) in 88% yield. The corresponding closo-1-polystyryl-2-(2′-hydroxycyclohexyl)-1,2-C₂B ₁₀H₁₀ (6) was produced in 94% yield by refluxing a mixture of the lithium salt of (5) and cyclohexene oxide in THF for 2 days. Compound (6) was decapitated, deprotonated and then reacted with ZrCl₄ ? 2THF to produce a polymer-supported d⁰-half-sandwich metallacarborane closo-1-Zr(Cl)-2-polystyryl-3-(2′-σ-O-cyclohexyl)- η⁵-2,3-C₂B₉H₉ (7) in 41% yield. Compounds (3) and (7), in the presence of MMAO-7 (13% ISOPAR-E), were found to catalyze the polymerization of ethylene and vinyl chloride in toluene to give high molecular weight PE (9.4 × 10³ (M_w/M _n = 1.8)) and PVC (2.1 × 10³ (M_w/M _n = 1.6)), respectively.

Full text of DOI:10.1016/j.jorganchem.2005.01.047

Journal of Organometallic Chemistry 690 (2005) 2802–2808
www.elsevier.com/locate/jorganchem
Syntheses and catalytic activities of Group 4 metal complexes
derived from C(cage)-appended cyclohexyloxocarborane trianion
a,
a
a
b
Zhu Yinghuai *, Zhong Yulin , Keith Carpenter , John A. Maguire ,
c
Narayan S. Hosmane
a
Institute of Chemical and Engineering Sciences Ltd., 1 Pesek Road, Jurong Island, Singapore 627833, Singapore
b
Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, USA
c
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115-2862, USA
Received 19 October 2004; accepted 28 January 2005
Available online 19 March 2005
Abstract
The reaction of Li[closo-1-Me-1,2-C2B10H10] with cyclohexene oxide produced closo-1-Me-2-(20-hydroxycyclohexyl)-1,2-
C2B10H10 (1) in 86% yield. Decapitation of (1) with potassium hydroxide in refluxing ethanol gave the corresponding cage-opened
potassium salt of the carborane anion, [nido-1-Me-2-(20-hydroxycyclohexyl)-1,2-C2B9H10]ꢀ (2) in 82% yield. Deprotonation of (2)
with two equivalents of n-butyllithium in THF at ꢀ78 ꢀC, followed by its further reaction with anhydrous MCl4 Æ 2THF
(M = Ti, Zr) produced the corresponding d0-half-sandwich metallacarboranes, closo-1-M(Cl)-2-Me-3-(20-r-O-cyclohexyl)-g5-2,3-
C2B9H9 (3 M = Zr; 4 M = Ti), in 59% and 51% yields, respectively. Reaction of Li[closo-1,2-C2B10H11] with Merrifieldꢀs peptide
resin (1%) in refluxing THF gave the ortho-carborane-functionalized polymer (5) in 88% yield. The corresponding closo-1-polysty-
ryl-2-(20-hydroxycyclohexyl)-1,2-C2B10H10 (6) was produced in 94% yield by refluxing a mixture of the lithium salt of (5) and cyclo-
hexene oxide in THF for 2 days. Compound (6) was decapitated, deprotonated and then reacted with ZrCl4 Æ 2THF to produce a
polymer-supported d0-half-sandwich metallacarborane closo-1-Zr(Cl)-2-polystyryl-3-(20-r-O-cyclohexyl)-g5-2,3-C2B9H9 (7) in 41%
yield. Compounds (3) and (7), in the presence of MMAO-7 (13% ISOPAR-E), were found to catalyze the polymerization of ethylene
and vinyl chloride in toluene to give high molecular weight PE (9.4 · 103 (Mw/Mn = 1.8)) and PVC (2.1 · 103 (Mw/Mn = 1.6)),
respectively.
ꢁ 2005 Elsevier B.V. All rights reserved.
Keywords: Half-sandwich metallacarborane; Trianionic ligand; Ligand immobilization; Olefin polymerization; Group 4 metallacarborane; Ziegler–
Natta catalysis
1. Introduction
has been shown to be function of the metal, plus the nat-
ure of the g5-ligand as well as the other ligands [2–4]. Of
particular interest are the so called constrained-geome-
try complexes in which an early transition metal is
bonded to at least one g5-ligand that has tethered to it
a terminal r-bonding group [5–9]. The advantages of
the use of suitably modified metallocenes as ‘‘single site’’
polymerization catalysts include enhanced activities
compared to conventional Ziegler–Natta catalysts and
their ability to produce stereospecific polymers with nar-
row molecular weight distributions [2]. However, the
The identification of new generations of polymeriza-
tion catalysts remains one of the main avenues of cur-
rent polymer research. The range, and success, of such
studies is demonstrated in the area of Ziegler–Natta type
polyolefin catalysis, especially involving the use of met-
allocenes as the active catalyst sites [1]. Catalytic activity
*
Corresponding author. Tel.: +65 68744217; fax: +65 68734805.
E-mail address: zhu_yinghuai@ices.a-star.edu.sg (Z. Yinghuai).
0022-328X/$ - see front matter ꢁ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.01.047

Z. Yinghuai et al. / Journal of Organometallic Chemistry 690 (2005) 2802–2808
2803
homogeneous nature of these catalysts limit their practi-
2. Results and discussion
cal use, prompting investigations of supported catalysts
[10,11]. Although the polymerization of vinyl chloride
catalyzed by half-titanocene/MAO (MAO = methylalu-
minoxine) has been reported [12], the electrophilic nat-
ure of the metals prevents their wide spread use in the
polymerization of monomers with polar groups. There-
fore, conventional free radical polymerization is still
used in industry to produce a wide range of functional-
ized polymers such as polyvinylacetate, polyvinylchlo-
ride (PVC), etc. [13]. However, such methods produce
polymers containing a number of structural defects
and are not conducive to the production of stereospe-
cific polymers having narrow molecular weight distribu-
tions. Therefore, there is a need to generate new types of
metal catalytic systems for the production of functional-
ized polymers or co-polymers that possess narrow
molecular weight distributions.
In addition to the cycolpentadienyl based ligands,
there is another class of 6p electron donors, namely
the dinegative nido-carboranes, [R2C2B4H4]2ꢀ and
[R2C2B9H9]2ꢀ (R@H or a single bonding group) [14].
Both the small and large cage metal complexes have
been shown to catalyze olefin polymerization, but the
results are limited [15,16]. There has been even less infor-
mation as to the possible efficacy of constrained-geome-
try complexes as olefin catalysts; to date, most of the
reports have only described their syntheses or ligand ex-
change reactions [17,18]. Herein we report the synthesis
of C(cage)-appended nido-carborane ligands, each con-
taining an oxide anion in the terminal position of a
hydrocarbyl bridge in the appended unit, along with
their conversion to the corresponding Group 4 metalla-
carboranes. Their use as polymerization catalysts, both
in homogeneous and heterogeneous phases, is also
presented.
The reaction of the lithium salt of the carborane
monoanion, [closo-1-Me-1,2-C2B10H10]ꢀ, with com-
mercially available cyclohexene oxide afforded the
ligand precursor, closo-1-Me-2-(20-hydroxycyclohexyl)-
1,2-C2B10H10 (1), in 86% yield (Scheme 1). The 1H,
13C and 11B NMR spectra of (1) show normal group res-
onances that are consistent with a closo-C2B10H11 cage
with a hydroxycyclohexyl group bonded to one of the
cage carbons, as depicted in Scheme 1 [19]. The IR spec-
trum of (1) shows the absorption band of mBH at the ex-
pected region (2588 cmꢀ1). The monoanion of the
C
(cage)-appended carborane, [nido-7-Me-8-(20-hydroxy-
cyclohexyl)-7,8-C2B9H10]ꢀ (2), was synthesized by the
reaction of (1) with potassium hydroxide in refluxing
ethanol in 82% yield after purification, following the lit-
erature procedures [20]. Compared with its precursor
(1), the d13C of CH–OH in (2) down shifted 4.65 ppm.
The 11B NMR spectrum of (2) is essentially the same
as those obtained for [nido-7-(CH2NH2)-7,8-C2B9H11]ꢀ
[18c] and [nido-7-(CH2OH)-8-Me-7,8-C2B9H10]ꢀ [18b].
1
The H NMR spectrum of (2) showed resonances at d
3.56 and ꢀ2.81 ppm corresponding to the hydroxy
and bridging hydrogens, respectively, and its IR spec-
trum shows peaks at m = 3524 cmꢀ1 and m = 2497 cmꢀ1
that are assigned to the O–H and B–H stretches, respec-
tively. The trianionic carborane ligand (Fig. 1), gener-
ated in situ from (2), was allowed to react with
MCl4 Æ 2THF to produce closo-1-M(Cl)-2-Me-3-[20-r-
O-cyclohexyl]-g5-2,3-C2B9H9 in 59% (3, M = Zr) and
51% (4, M = Ti) yields (see Scheme 1), respectively.
Compounds (3) and (4) could be easily purified by
precipitation of the product in pentane. A comparison
of the 11B NMR spectra of (3) and (4) with their precur-
sor, (2), shows that on metalation the apical boron
HO
HO
K+
H
H
(1) n-BuLi
(1) KOH/EtOH
Me
Me
Me
(2) HCl (aq)
(2) Cyclohexene
oxide
(1)
(2)
Cl
O
M
( 3 M = Zr; 4 M = Ti )
(1) 2 n-BuLi
(2) MCl4 2THF
Me
(
)
= C
= BH
Scheme 1. Synthesis of constrained-geometry Group 4 metallacarboranes.

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Z. Yinghuai et al. / Journal of Organometallic Chemistry 690 (2005) 2802–2808
+Li-X
[K+Li+]
CH2
R
(
)
= C
= BH
(X = O, N(H); R = H, Me)
Fig. 1. Carborane trianionic ligands.
resonance shifts downfield from d ꢀ38.10 ppm in the
precursor to ꢀ27.70 ppm for (3) and ꢀ24.51 ppm for
(4). This is consistent with the withdrawing of electron
density by the bonded metal from the cage, thus deshiel-
1
ding the boron opposite to it [21]. H NMR spectra of
(3) and (4) are consistent with the molecular geometries
shown in Scheme 1.
Fig. 2. TGA curves of Merrifieldꢀs peptide resin (support), closo-
C2B10H12, 5, 6 and 7.
An organic polymer substrate was introduced onto
the closo-1,2-C2B10H10 by reaction of its lithium salt
with Merrifieldꢀs peptide resin (1%) that produced 1-
polystyrenyl-1,2-C2B10H11 (5), in 88% yield. Compound
(5) reacts in situ with n-BuLi and cyclohexene oxide in
THF to give the polymer-supported ligand, closo-1-
polystyryl-2-(20-hydroxycyclohexyl)-1,2-C2B10H10 (6) in
94% yield with the loading amounts up to 1.24 mmol/g
(Merrifieldꢀs peptide resin (1%)) based on lithium chlo-
ride produced (Scheme 2). Decapitation of (6) with
potassium hydroxide in refluxing ethanol, followed by
deprotonation with n-BuLi in THF, produced the trian-
ionic intermediatethatreactsfurtherwithZrCl4 Æ 2THFto
form the corresponding zirconium complex, closo-1-
Zr(Cl)-2-polystyryl-3-(20-r-O-cyclohexyl)-g5-2,3-C2B9H9
(7) with loading amounts of zirconium moiety up
to 0.48 mmol/g (Merrifieldꢀs peptide resin (1%)). The
presence of the mBH absorption bands in the range of
2590–2510 cmꢀ1 in IR spectra of compounds 5–7, cou-
pled with the formation of LiCl, confirms the successful
immobilization of carborane cages to the polymer sup-
port. Further support for successful immobilization of
the carborane was furnished by thermogravimetric anal-
yses of compounds 5–7 (see Fig. 2). The TGA plots
show that, while both the closo-1,2-C2B10H12 and the
Merrifieldꢀs peptide resin precursors have completely re-
acted, or sublimed, by 900 ꢀC, the supported carborane
products (5–7) show mass residues of 8.13%, 15.77%,
and 19.20%, respectively. Unfortunately, the chemical
compositions of the residues could not be determined,
so their masses could not be used for analysis purposes.
HO
H
H
(1) n-BuLi
(1) n-BuLi
Poly
(6)
Poly
H
(2) Merrifield’s
(2) Cyclohexene
oxide
peptide resin
(= Poly)
(5)
Cl
O
HO
Zr
K+
H
(1) 2 n-BuLi
(1) KOH/EtOH
Poly
Poly
(2) HCl (aq)
(2) ZrCl4 2THF
(7)
(
)
= C
= BH
Scheme 2. Synthesis of Merrifieldꢀs peptide resin-supported constrained-geometry zirconacarborane.

Z. Yinghuai et al. / Journal of Organometallic Chemistry 690 (2005) 2802–2808
2805
Table 1
Polymerization results of ethylene and vinyl chloride with 3 and 7
standard decapitation reaction to yield the correspond-
ing nido-carborane ligand that was further reacted with
ZrCl4 Æ 2THF to afford the polymer-supported zircona-
Polymera
Activityb
Mw (·103/mol)c
Mw/Mn
carborane,
closo-1-Zr(Cl)-2-polystyl-3-(20-r-O-cyclo-
Polyethylene
Polyvinyl chloride
53(A) 31(B)
22(A) 14(B)
9.4(A) 3.8(B)
2.1(A) 1.3(B)
1.8(A) 1.3(B)
1.6(A) 1.2(B)
hexyl)-g5-2,3-C2B9H9. Both the supported and the
unsupported zirconacarboranes in the presence of
MMAO-7 were found to be active catalysts for the poly-
merization of ethylene and vinyl chloride.
a
A results are for (3) and B results are for (7), polymerization
conditions: ratio of catalyst and co-catalyst ([Al]/[Zr]) = 2000, sol-
vent = toluene, temperature = 50 ꢀC, pressure = 1.5 bar (polyethylene)
and 1.2 bar (polyvinyl chloride), polymerization time = 4 h.
b
Activity = kg polymer per mol catalyst per h per bar.
c
Molecular weight and molecular weight distribution of the poly-
mers were determined by means of gel-permeation chromatography
(GPC: Waters 150 ꢀC) at 145 ꢀC using 1,2,4-trichlorobene as a solvent.
The weight average molecular weight and polydispersity index (Mw
and Mw/Mn, respectively) were calculated on the basis of polystyrene
standards.
4. Experimental
All syntheses were carried out in an inert atmo-
sphere with standard Schlenk techniques or in a glove
box. Tetrahydrofuran (THF), diethyl ether, toluene,
benzene, pentane and n-hexane were heated over so-
dium and benzophenone until a blue color was ob-
tained, and then distilled under argon just before
use. n-Butyllithium (1.6M in hexanes), zirconium
(IV) chloride tetrahydrofuran complex (1:2), titanium
(IV) chloride tetrahydrofuran complex (1:2), cyclohex-
ene oxide, Merrifieldꢀs peptide resin (1%) (contains
1.97 mmol Clꢀ/g), ethylene, vinyl chloride, and organ-
ic solvents were used as received from Aldrich. Mod-
ified methylaluminoxane 7 (MMAO-7, 13% ISOPAR-E)
was obtained from Akzo Chemicals Inc. 1-Mecloso-
1,2-C2B10H11 and closo-1,2-C2B10H12 were provided
by Katchem Ltd. Proton, carbon-13 and boron-11
NMR spectra were recorded on a Bruker Fourier-
transform multinuclear spectrometer at 400.13,
100.62 and 128.38 MHz, respectively. Chemical shifts
Therefore, the loading amounts of anchored carborane
was determined by titration of the lithium chloride pro-
duced in their formation reactions with standard
AgNO3.
The polymerization reactions of ethylene and vinyl
chloride in the presence of (3) or (7) and MMAO-7
cocatalyst were studied. The catalytic runs were carried
out in toluene with an [Al]/[Zr] = 2000 at 50 ꢀC under
pressures of 1.5 bar of ethylene or 1.2 bar of vinyl chlo-
ride. The polymerization data are presented in Table 1.
As can be seen from the table, both (3) and (7), in the
presence of MMAO-7 are moderately active catalysts
for olefin polymerization affording polymers with nar-
row molecular mass distributions (Mw/Mn = 1.2–1.8).
Even though the activity of the homogeneous olefin
(ethylene) is greater than that of vinyl chloride, the
activity of the latter is sufficiently high to warrant fur-
ther investigations of these systems, including their
mechanisms. Such studies are currently underway in
our laboratories.
1
for H NMR and 13C NMR spectra were referenced
to SiMe4 (0.00 ppm) and measured with respect to
residual protons in the deuterated solvent. Chemical
shift values for 11B NMR spectra were referenced rel-
ative to BF3 Æ OEt2 (0.00 ppm). Infrared (IR) spectra
were measured using a BIO-RAD spectrophotometer
with KBr pellets techniques and presented in a se-
quence of signal strength and peak mode in brackets,
in which s = strong, vs = very strong, m = middle and
w = weak for signal strength and s = single, m = multi-
ple and br = broad for peak model. Elemental analy-
ses were determined by a Perkin–Elemer 2400 CHN
elemental analyzer. The TGA analyses were carried
out on an SDT 2960 Simultaneous DSC-TGA
analyzer.
3. Conclusions
The hydroxycyclohexyl-appended carborane, closo-
1-Me-2-(20-hydroxycyclohexyl)-1,2-C2B10H10 have been
synthesized in high yields, decapitated with alcoholic
KOH and reacted with n-BuLi to give a trianionic
ansa-carborane ligand. The reaction of this ligand
with anhydrous MCl4 Æ 2THF (M = Ti, Zr) afforded
the corresponding d0-half-sandwich metallocarboranes,
closo-1-M(Cl)-2-Me-3-(20-r-O-cyclohexyl)-g5-2,3-C2B9H9
(3, M = Zr; 4, M = Ti) in good yields. The polymer-sup-
ported metallacarborane, closo-1-Zr(Cl)-2-polystyryl-3-
(20-r-O-cyclohexyl)-g5-2,3-C2B9H9 was prepared in a
three-step sequence. First, closo-1,2-C2B10H12 was
immobilized on Merrifieldꢀs peptide resin (1%) and then
reacted with cyclohexene oxide to give closo-1-polysty-
ryl-2-(20-hydroxycyclohexyl)-1,2-C2B10H10. The poly-
4.1. Synthesis of closo-1-Me-2-(20-hydroxycyclohexyl)-
1,2-C2B10H10 (1)
A solution of 1.00 g (6.32 mmol) of 1-Me-1,2-
C2B10H11, dissolved in a mixture of 40 ml diethyl ether
and 20 ml benzene, was cooled to ꢀ78 ꢀC and 4.20 ml
(6.72 mmol) of n-BuLi (1.6 M in n-hexane) was added
with syringe. After addition and half an hour of further
mer-linked carborane was found to undergo
a

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Z. Yinghuai et al. / Journal of Organometallic Chemistry 690 (2005) 2802–2808
stirring, the mixture was allowed to warm to room tem-
perature and stirring was continued for 4 h. After that
time, 0.70 ml (6.78 mmol) of cyclohexene oxide was
added with a syringe at 0 ꢀC and the reaction was con-
tinued at room temperature for another 6 h before
hydrolysis with 10 ml water. The mixture was trans-
ferred to a separatory funnel where the organic phase
was separated and the aqueous phase was extracted with
2 · 25 ml ethyl ether. After drying with MgSO4, the sol-
vent was removed under reduced pressure and the resi-
due was re-crystallized with n-hexane to obtain 1.40 g
sticky residue identified as closo-1-Me-2-(20-hydrox-
ycyclohexyl)-1,2-C2B10H10 (1) in 86% yield. Analytical
data: Calcd. (Found) for C9H24B10O (1): C, 42.16
(42.11); H, 9.44 (9.40). 1H NMR (CDCl3, ppm),
d = 3.40 (m, 1H, CH–O), 2.90–0.63 (m, br, 20H,
B10H10, –CH, 4CH2, OH), 1.80 (s, 3H, Ccage–CH3).
13C NMR (CDCl3, ppm), d = 83.20 and 75.71 (Ccage),
71.64 (–CH–O), 47.03, 35.99, 33.56, 25.62, 23.60, 23.01
(–CH–Ccage, 4CH2, CH3–Ccage). 11B NMR (CDCl3,
4.3. Synthesis of closo-1-Zr(Cl)-2-Me-3-(20-r-O-
cyclohexyl)-g5-2,3-C2B9H9 (3)
A 1.50-g (5.27 mmol) sample of (2) was dissolved in
75 ml of dry tetrahydrofuran, the resulting mixture
was cooled to ꢀ78 ꢀC and 6.60 ml (10.56 mmol) n-
BuLi (1.6 M in hexanes) was carefully added with a
syringe. After addition, the system was kept reacting
at ꢀ78 ꢀC for 30 min before being warmed to room
temperature and stirred for 6 h. The reaction mixture
was cooled to 0 ꢀC and 2.00 g (5.25 mmol)
ZrCl4 Æ 2THF was added to the THF solution under
argon. The colour of the mixture changed from pale
yellow to red-brown during the addition of
ZrCl4 Æ 2THF. After 30 min at 0 ꢀC, the mixture was
then stirred at room temperature for 2 days. After fil-
tration and removal of the solvent under reduced pres-
sure, the residue was re-crystallized from a mixture of
benzene/pentane (v:v = 2:1) to give 1.15 g of closo-1-
Zr(Cl)-2-Me-3-(20-r-O-cyclohexyl)-g5-2,3-C2B9H9 (3)
in 59% yield. Analytical data: Calcd. (Found) for
C9H22B9ClOZr (3): C, 29.20, (29.18); H, 6.00, (5.95).
1H NMR (DMSO-d6, ppm), d = 3.10 (m, 1H, CH–O),
1.90–0.43 (m, br, 18H, B9H9, –CH, 4CH2), 1.66 (s,
ppm),
d = ꢀ3.65
(1B,
1JBH = 160 Hz),
ꢀ5.01
1
(1B, 1JBH = 149 Hz), ꢀ8.52 (2B, JBH = 85 Hz), ꢀ9.11
1
1
(2B, JBH = 103 Hz), ꢀ9.95 (4B, JBH = 150 Hz). IR
(KBr pellet, cmꢀ1), t = 3062(s, s), 2588(vs, s), 1447(m,
s), 1390(m, s), 1229(w, s), 1133(m, s), 1094(m, s),
1017(s, s), 934(m, s), 722(s, s).
3H,
C
cage–CH3). 13C NMR (DMSO-d6, ppm),
d = 69.94, 68.20 (Ccage), 56.18 (–CH–O), 49.63, 32.71,
26.37, 26.32, 23.92, 23.74 (–CH–Ccage
,
4CH2,
4.2. Synthesis of K[nido-7-Me-8-(20-hydroxy-
cyclohexyl)-7,8-C2B9H10] (2)
CH3–Ccage). 11B NMR (C6D6, ppm), d = ꢀ8.31 (2B,
1
1JBH = 113 Hz), ꢀ10.56 (4B, JBH = 128 Hz), ꢀ17.52
1
(2B,1JBH = 139 Hz), ꢀ27.70 (1B, JBH = 117 Hz). IR
A 1.50-g (5.85 mmol) sample of (1) was added to a
clear solution of 2.00 g (32.08 mmol) potassium hydrox-
ide in 50 ml of 95% ethanol with continuous stirring.
After all of the solid dissolved, the mixture was heated
to reflux for 16 h. The vessel was cooled to room tem-
perature, neutralized with aqueous HCl and the solvent
was removed under reduced pressure. The resulting res-
idue was extracted with anhydrous THF. After filtration
and drying in vacuum, 1.36 g of sticky solid, K[nido-7-
Me-8-(20-hydroxycyclohexyl)-7,8-C2B9H10] (2) was ob-
tained in 82% yield. Analytical data: Calcd. (Found)
for C9H24B9KO (2): C, 37.97 (37.93); H, 8.50 (8.48).
1H NMR (DMSO-d6, ppm), d = 3.56 (br, 1H, –OH),
3.18 (m, 1H, CH–O), 2.00–0.95 (m, br, 22H, B9H9,
–CH, 4CH2, Ccage–CH3, OH), ꢀ2.81(br, 1H, BHbridge).
13C NMR (DMSO-d6, ppm), d = 76.29 (–CH–O),
(KBr pellet, cmꢀ1), t = 3413(s, s), 2919(vs, s), 2851(s,
s), 1637(m, s), 1457(s, s), 1305(s, s), 963(m, s),
423(m, s).
4.4. Synthesis of closo-1-Ti(Cl)-2-Me-3-(20-r-O-
cyclohexyl)-g5-2,3-C2B9H9 (4)
A method similar to that described in the prepara-
tion of (3) was used to produce 0.99 g of closo-1-
Ti(Cl)-2-Me-3-(20-r-O-cyclohexyl)-g5-2,3-C2B9H9 (4)
(51% yield) from 1.70 g (5.96 mmol) (2), 7.65 ml
(12.24 mmol) n-BuLi (1.6 M in hexanes) and 2.05 g
(5.95 mmol) TiCl4 Æ 2THF in 70 ml dry THF. Analyti-
cal data: Calcd. (Found) for C9H22B9ClOTi (4): C,
33.07, (33.05); H, 6.78, (6.76). 1H NMR (DMSO-d6,
ppm), d = 3.30 (m, 1H, CH–O), 2.10–0.20 (m, br,
18H, B9H9, –CH, 4CH2), 1.48 (s, 3H, Ccage–CH3).
13C NMR (THF-d8, ppm), d = 70.49, 68.26 (Ccage),
51.81 (–CH–O), 35.50, 33.49, 29.73, 26.80, 26.54,
45.59, 36.90, 33.63, 26.71, 25.21, 24.05 (–CH–Ccage
4CH2, CH3–Ccage). 11B NMR (DMSO-d6, ppm),
,
d = ꢀ8.10
(1B,
1JBH = 147 Hz),
ꢀ11.47
(2B,
1
1JBH = 138 Hz), ꢀ16.32 (1B, JBH = 103 Hz), ꢀ19.52
26.43 (–CH–Ccage
,
4CH2, CH3–Ccage). 11B NMR
1
1
1
(2B, JBH = 124 Hz), ꢀ21.75 (1B, JBH = 120 Hz),
ꢀ34.90 (1B,1JBH = 110 Hz), ꢀ38.10 (1B, 1JBH = 135Hz).
IR (KBr pellet, cmꢀ1), t = 3524(vs, s), 3040(m, s),
2931(s, s), 2857(s, s), 2497(vs, s), 1477(s, s), 1449(s, s),
1388(s, s), 1273(m, s), 1212(m, s), 1036(vs, s), 978(s, s),
860(m, s), 472(m, s).
(C6D6, ppm), d = ꢀ7.42 (2B, JBH = 122 Hz), ꢀ9.10
1
(4B, JBH = unresolved), ꢀ16.48 (2B,1JBH = 126 Hz),
1
ꢀ24.51 (1B, JBH = 131 Hz). IR (KBr pellet, cmꢀ1),
t = 3490(m, s), 3117(s, s), 3039(s, s), 2901(s, s),
2705(vs, s), 1685(s, s), 1528(s, s), 1410(s, s), 1292(m,
br), 959(m, s), 703(s, s), 455(m, s).

Z. Yinghuai et al. / Journal of Organometallic Chemistry 690 (2005) 2802–2808
2807
4.5. Synthesis of Merrifield’s peptide resin supported
ortho-carborane (5)
lid was re-suspended in 60 ml THF with vigorous stir-
ring followed by addition of 0.36 ml (3.49 mmol) of
cyclohexene oxide with a syringe at 0 ꢀC, then the reac-
tion mixture was stirred at room temperature for an-
other 4 h before heating to reflux for 2 days. After
cooling to room temperature and quenching with
4.0 ml mixture of 20% HCl solution of methanol, the
solvent was removed under reduced pressure and the
crude product was washed with de-ionized water
(2 · 10 ml) to remove any trace quantity of LiCl, then
dried in high vacuum for 3 days to collect 2.25 g of a
pale yellow solid, identified as closo-1-polymeryl-2-(20-
hydroxycyclohexyl)-1,2-C2B9H10] (6) in 94% yield. The
collected aqueous solution was combined and concen-
trated to 5.0 ml and subjected to titration with AgNO3
to determine that 0.118 g of LiCl was produced with a
consumption of 27.83 ml AgNO3 standard. The loading
amount of carborane reached to 1.24 mmol (functional-
ized carborane cage)/g (Merrifieldꢀs peptide resin).
IR (KBr, pellet, cmꢀ1): t = 3328(w, br), 3063(w, s),
2938(s, s), 2844(s, s), 2547(vs, s, tBH), 1781(m, s),
1500(m, s), 1453(s, s), 1391(m, s), 1359(m, s), 1047(s,
s), 906(m, s), 875(m, s), 766(s, s), 688 (s, s), 656(s, s),
477(m, s), 438(m, s).
A 0.58-g (4.02 mmol) sample of 1,2-C2B10H12 was ta-
ken in a 250 ml two-necked round-bottom flask equipped
with a magnetic stirring bar to which 100 ml of dry THF
was then added to dissolve the carborane compound pro-
ducing a clear solution. The solution was cooled to
ꢀ78 ꢀC and 2.6 ml (4.16 mmol) n-BuLi (1.6 M in hexane)
was added using a syringe with continuous stirring. After
the addition, the mixture was maintained at that temper-
ature for 30 min followed by warming to room tempera-
ture spontaneously and reacted further for 4 h.
Merrifieldꢀs peptide resin (1%), 2.0 g (3.94 mmol Clꢀ),
was added and the resulting mixture was stirred at room
temperature under argon for 2 days. At the end of the
reaction process, the mixture was heated to reflux for
4 h before cooling down to room temperature and
quenching with 3.0 ml methanol. The solvents were re-
moved under reduced pressure and the crude product
was washed with de-ionized water (2 · 10 ml) and n-hex-
ane (2 · 20 ml) to remove any trace of LiCl and starting
material 1,2-C2B10H12, then dried in high vacuum for
2 days to give 2.39 g of a pale yellow solid of 1-polysty-
ryl-closo-1,2-C2B10H11 in 88% yield. The collected aque-
ous solution was combined and concentrated to 5.0 ml
and titrated with AgNO3 that determined 0.150 g
(3.54 mmol) of LiCl was produced in the reaction. Titra-
tion procedure: The 5.0 ml of concentrated aqueous
washing was pipetted into a 250-ml volumetric flask
and diluted with de-ionized water to 250 ml and titrated
with standard silver nitrate solution (0.1 M in water)
using five drops of 5% potassium chromate as an indica-
tor. Titrant was added until a pinkish yellow color per-
sisted at the end point to consume 35.38 ml of AgNO3.
The loading amount of carborane reached to 1.48 mmol
(carborane cage)/g (Merrifieldꢀs peptide resin).
4.7. Synthesis of closo-1-Zr(Cl)-2-polystyryl-3-
(20-r-O-cyclohexyl)-g5-2,3-C2B9H9 (7)
A 2.33-g (contains 2.89 mmol of carborane) sample of
6 was suspended in a clear solution of 1.10 g (16.66 mmol)
potassium hydroxide in 150 ml 95% ethanol, the mixture
was stirred at room temperature for 30 min before reflux-
ing for 2 days. Then the reaction mixture was cooled to
room temperature, neutralized with aqueous HCl and fil-
tered. The resulting solid was washed with de-ionized
water (3 · 10 ml) to remove any traces of KCl, dried in
high vacuum for 2 days and then suspended in 120 ml
dry THF. The mixture was cooled to ꢀ78 ꢀC and 6.5 ml
(10.40 mmol) n-BuLi in hexanes was added under argon
atmosphere with continuous stirring. After reacting at
ꢀ78 ꢀC for 30 min, the mixture was warmed to room tem-
perature spontaneously and kept stirring for 1 day, the
solvent was then removed under reduced pressure and
the resulting residue was washed with n-hexane
(2 · 15 ml) to remove any traces of unreacted n-BuLi.
The residue was re-suspended in 150 ml THF and 1.10 g
(2.89 mmol) of ZrCl4 Æ 2THF was added at 0 ꢀC. After
the addition, the reaction was continued at room temper-
ature for 2 days, the mixture was filtered and the collected
solid was washed with absolute ethanol (2 · 10 ml) to re-
move lithium chloride followed by drying in high vacuum
for 2 days to collect closo-1-Zr(Cl)-2-polystyryl-3-(20-r-
O-cyclohexyl)-g5-2,3-C2B9H9 (7) as a pale yellow solid
(2.48 g, 41% yield). The collected alcohol solutions were
combined, dried and the resulting residue was dissolved
in 5.0 ml de-ionized water and subjected to titration with
IR (KBr pellet, cmꢀ1): t = 3440(m, br), 3024(s, s),
2920(vs, s), 2583(vs, s, tBH), 1944(m, s), 1802(m, s),
1601(s, s), 1490(s, s), 1420(s, s), 1374(m, s), 1314(m, s),
1265(s, s), 1182(m, s), 1154(m, s), 1111(m, s), 1069(s,
s), 1024(s, s), 907(s, s), 824(s, s), 756(s, s), 698(s, s),
545(s, s).
4.6. Synthesis of closo-1-polystyryl-2-(20-hydroxy-
cyclohexyl)-1,2-C2B10H10 (6)
A 2.00 g of (5) (containing 2.96 mmol carborane) was
suspended in 60 ml of THF. The resulting mixture was
cooled to ꢀ78 ꢀC and 2.50 ml (4.00 mmol) n-BuLi
(1.6 M in hexanes) was added with a syringe carefully.
After addition, the mixture was maintained at that tem-
perature for 30 min, followed by warming to room tem-
perature spontaneously and reacted further for 8 h.
After removal of all volatiles, the residue was washed
with n-hexane to remove any unreacted n-BuLi. The so-

2808
Z. Yinghuai et al. / Journal of Organometallic Chemistry 690 (2005) 2802–2808
AgNO3 to determine that 0.101g of LiCl was produced
with a consumption of 23.82 ml AgNO3 standard. The
loading amount of zirconium moiety reached up to
0.48 mmol (zirconium moiety)/g (Merrifieldꢀs peptide
resin).
IR (KBr pellet, cmꢀ1): t = 3435(w, br), 3026(s, s),
2913(s, s), 2850(m, s), 2515(s, s, tBH), 1630(s, s),
1528(s, s), 1491(m, s), 1410(m, s), 1365(s, s), 1163(m,
s), 1096(w, s), 1015(s, s), 743(s, s), 703(s, s), 527(s, s).
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Acknowledgements
This work was supported by Grants from ICES of
Singapore, the National Science Foundation (CHE-
0241319), the donors of the Petroleum Research Fund,
administered by the American Chemical Society, The
Robert A. Welch Foundation (N-1322 to JAM) and
Northern Illinois University through a Presidential Re-
search Professorship. N.S.H. gratefully acknowledges
the Forschungspreis der Alexander von Humboldt-Stif-
tung and the Gauss Professorship of the Go¨ttingen
Academy of Sciences.
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