Carboranylimine-complexed titanium (IV) organometallics: An investigation of synthesis, structure and catalytic polymerization

Article abstract of DOI:10.1016/j.jorganchem.2012.07.010

The condensation reaction of carboranylmethyl ammonium chloride, 1-(CH ₂NH₃Cl)-1,2-C₂B₁₀H₁₁ (1) with phenyl aldehydes produced phenyl(carboranylmethyl)imine ligands, 1-(CH ₂N = CC₆

Full text of DOI:10.1016/j.jorganchem.2012.07.010

Journal of Organometallic Chemistry 721-722 (2012) 119e123
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Carboranylimine-complexed titanium (IV) organometallics: An investigation of
synthesis, structure and catalytic polymerization
,
a
a
a
a
a
Zhu Yinghuai a , Xiao Shiwei , Venu R. Vangala , Sze Chen Chia , Angie Cheong , Ong Nuan Qin ,
*
Narayan S. Hosmane b
a Institute of Chemical and Engineering Sciences (ICES), 1 Pesek Road, Jurong Island 627833 Singapore, Singapore
b Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL 60115-2862, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
The condensation reaction of carboranylmethyl ammonium chloride, 1-(CH2NH3Cl)-1,2-C2B10H11 (1) with
phenyl aldehydes produced phenyl(carboranylmethyl)imine ligands, 1-(CH2N ¼ CC6H4R-2)-1,2-C2B10H11
(2 R ¼ H; 3 R ¼ OH). Deprotonation of 2 and 3 with n-BuLi followed by metalation with TiCl4 led to the
Received 28 May 2012
Received in revised form
9 July 2012
formation of phenyl(carboranylmethyl)imidotitanium (IV) chlorides, [1-(CH2N
¼
CC6H4R-2)-1,2-
Accepted 9 July 2012
C2B10H10]TiCl3 (4 R ¼ H; 5 R ¼ O). Compounds 4 and 5 were found to catalyze the polymerization of
ethylene in the presence of co-catalyst MAO to produce high molecular weight polyethylene. In addition,
compounds 4 and 5 were also active for copolymerization of ethylene and methyl-10-undecannoate to
generate corresponding copolymers.
Keywords:
Carboranylimine
Metallacarborane
Titanium catalysts
Olefin polymerization
Copolymerization
Crystal structure
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
properties [17e26]. Therefore, the incorporation of a carborane
cage with the 3D-aromaticity by substituting the benzene ring in
A three-dimensional aromatic and highly thermally stable bulky
carborane cage, has been used to construct various metal
complexes [1e3] since the first report on a metalladicarbollide
complex by Hawthorne and co-workers [1]. Subsequently, Group IV
metal complexes derived from functionalized ansa-ligands with
cyclopentadienyl [4,5], pyridinyl [6], phosphino [7], sulfano [8,9],
alkyloxo [10,11] and alkylamino [12e16] moieties, have been
developed and their reasonable activity for olefin polymerization
was demonstrated. On the other hand, the titanium complexes
derived from the phenoxyeimine ligands, popularly named as
TieFI catalysts, have been well recognized as highly active catalysts
the phenoxyeimine ligands should lead to a new class of carbor-
anylimines. Consequently, the metalation of the carboranylimines
with the Group IV metals should produce unique analogues of TieFI
catalysts. Thus, the carboranylimines, synthesized by dehydration
of carboranylaldehyde and anilines were first decapitated and then
metalated to form h1
,
h5(nidoecage)-coordinated constrained-
(C]N)
geometry Group IV complexes [27]. However, neither the exo-
polyhedral metalation of the closo-carboranylimine ligands with
the h1
, s(closoecage)-functionalities to form the corresponding
(C]N)
Group IV metal complexes nor its catalytic activities has been
investigated. Herein, we report the synthesis and crystal structure
of the closo-carboranylimine ligands along with the catalytic
activity of the corresponding titanium complexes.
for a-olefin polymerization [17e26]. Despite the fact that the tita-
nium complexes are recognized as being highly oxophilic and easily
poisoned by a polar monomer, the prototype TieFI catalysts have
demonstrated good activity for copolymerization of ethylene and
unsymmetrical olefins to form functional polymers [24]. None-
theless, the designable phenoxyeimine functionality plays an
important role in catalysis and, ultimately, it alters the polymer
2. Results and discussion
2.1. Ligands
Reaction of the carboranylmethyl ammonium salt with
commercially available phenyl aldehyde in the presence of NaHCO3
ꢀ
and molecular sieve (4 A) followed by purification produced air-
* Corresponding author. Tel.: þ65 67963801; fax: þ65 63166184.
E-mail addresses: zhu_yinghuai@ices.a-star.edu.sg (Z. Yinghuai), hosmane@
niu.edu (N.S. Hosmane).
stable waxy solid, phenyl(carboranylmethyl)imines 2 and 3, 1-
(CH2N ¼ CC6H4R-2)-1,2-C2B10H11 (2 R ¼ H; 3 R ¼ OH) in 53% and
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.07.010

120
Z. Yinghuai et al. / Journal of Organometallic Chemistry 721-722 (2012) 119e123
Table 1
Selected bond lengths, angles (ꢁ) for carbonylimine 2.
ꢀ
Bond lengths (A)
N(1)eC(7)
N(1)eC(8)
C(8)eC(9)
C(9)eC(10)
Angles (ꢁ)
1.265(2)
1.458(2)
1.528(2)
1.643(2)
C(7)eN(1)eC(8)
C(1)eC(7)eN(1)
116.7(1)
123.0(1)
in 5 causes the reverse shift and thus reduced the intra-molecular
strain leading to enhanced electron delocalization. Similar
phenomenon was also observed in the corresponding IR absorp-
tions. In comparison with the nBH of the corresponding precursors,
the red shifts of 27 and 7 cmꢀ1 were observed for the metalation of
2 and 3, respectively. In the 11B NMR spectra, 4 and 5 showed the
splitting patterns of 1:1:1:3:2:2 and 1:1:3:2:3, respectively in
a range of ꢀ3.17eꢀ15.21 ppm. No peaks beyond ꢀ30 ppm were
observed. In far-IR spectra (Fig. 2), compounds 4 and 5 show strong
absorptions in the range of 425e500 cmꢀ1, which are consistent
with the reported nTieCl and nTieO absorptions [28,29]. In compar-
ison with 4, compound 5 shows one more peak that could be due to
the vibration of TieO bond in 5. Neither 2 nor 3 shows such
absorptions (Fig. 2).
Scheme 1. Synthesis of carboranylimine and derived titanium metal complexes.
64% yield, respectively (Scheme 1). Compounds 2 and 3 were
characterized by 1H, 13C, 11B NMR and FTeIR spectroscopy as well as
elemental analyses. The 1H, 13C, and 11B NMR spectra of 2 and 3
appear normal relative to other related structures. In the 11B NMR
spectra, both 2 and 3 showed a splitting model of 1:1:3:2:3. In the
IR spectra, strong absorptions at w2600 cmꢀ1 are attributed to nBH
.
The molecular structure of 2 was characterized by single-crystal
X-ray diffraction as shown in Fig. 1. Fig. 1 reveals that compound 2
exhibits a trans-configuration with a normal C]N bond length. The
CeB and BeB bond lengths are consistent with the literature values
[27]. The angles of the C(1)eC(7)eN(1) and C(8)eN(1)eC(7) are
123.0(1) and 116.7(1), respectively. The selected bond lengths and
angles are summarized in Table 1.
These results clearly indicate the presence of the TieCl and TieO
bonds in 4 and 5, respectively. The MS (ESI) analysis showed
[M ꢀ H]þ peaks further confirming the molecular composition of
the complexes.
2.3. Ethylene and ethylene/methyl-10-undecannoate
polymerization
2.2. Titanium complexes
In situ deprotonation with n-BuLi at ꢀ78 ꢁC in toluene followed
by reaction with TiCl4 led to the formation of the phenyl(-
carboranylmethyl)imido titanium (IV) chlorides 4 and 5, [1-
(CH2N ¼ CC6H4R-2)-1,2-C2B10H10]TiCl3 (4 R ¼ H; 5 R ¼ O), in 49%
and 51% yields, respectively, as illustrated in Scheme 1. Compounds
4 and 5 are highly soluble in polar solvents such as THF, DCM, DMF,
and also in benzene, thus permitting purification by precipitation
from the corresponding benzene solution with n-pentane. In
comparison with their precursors 2 and 3, the 1H chemical shifts of
eCH ¼ N in 4 and 5 were shifted downfield from w0.30 ppm to 8.52
and 8.51 ppm, respectively, indicating significant involvement of
this moiety in coordination to the metal. Similarly, the 13C chemical
The catalytic properties of the complexes 4 and 5 have been
examined for the olefin polymerization processes using commer-
cially available ethylene and methyl-10-undecannoate in toluene
with MAO, trimethylaluminum (MA) and tris(pentafluorophenyl)
borane co-catalysts. Table 2 summarizes the homo- and co-
polymerization results of ethylene with carboranylimine-
coordinated titanium complexes with MAO co-catalyst. It has
been observed that (a) both 4 and 5 are active catalysts for homo-
and co-polymerization of ethylene with an activity of 5.2e57 kg
polymer (molTi)ꢀ1hꢀ1 barꢀ1 The results are comparable with FI
catalyst, bis[N-(3-phenylsalicylidene)-30,50-bis-tert-butylanilinato]
titanium(IV)dichloride showing an activity of 41.6 and 5.1 kg
polymer (molTi)ꢀ1hꢀ1 barꢀ1 for homo- and co-polymerization of
shift (d) of eCH¼N moiety in 2, after metalation, shifted downfield
by 5.5 ppm. In contrast, the dCH¼N in 3 was shifted upfield by
11.6 ppm after metalation. This observation can be rationalized
based on the fact that the formation of a stable six-membered ring
Fig. 1. A perspective view showing the molecular structure of 2, with atom labels and
50% probability displacement ellipsoids for non-H atoms.
Fig. 2. Far-IR spectra of compounds 2e5.

Z. Yinghuai et al. / Journal of Organometallic Chemistry 721-722 (2012) 119e123
121
Table 2
4. Experimental
Results of ethylene and ethylene/methyl-10-undecannoate polymerization by 4 and
5a.
All synthetic procedures were carried out in inert atmosphere
with standard Schlenk techniques or glove box. Tetrahydrofuran,
diethyl ether, toluene, pentane and hexane were heated over
sodium and benzophenone until a blue color was obtained, and
further distilled under argon just before use. The reagents, n-
butyllithium (1.6 M in hexanes), titanium (IV) chloride, benzalde-
hyde, methylaluminoxane (MAO, 1.7 M in toluene), trimethylalu-
minum (MA, 2.0 M in toluene), tris(pentafluorophenyl)borane and
organic solvents, were used as received from Aldrich. The precursor
1-(CH2NH3Cl)-1,2-C2B10H11 (1) was prepared according to the
literature procedure [31]. The 1H, 13C and 11B NMR spectra were
recorded on a Bruker Fourier-Transform multinuclear NMR spec-
trometer at 400, 100.6 and 128.4 MHz, respectively, relative to
external Me4Si (TMS) and BF3$OEt2 standards. Infrared (IR) spectra
were measured using a BIO-RAD spectrophotometer with KBr
pellets technique and presented in the sequence of signal strength
as strong (s), middle (m) and weak (w), and peak model as single
(s), multiple (m) and broad (br). Elemental analyses were deter-
mined by a Perkin Elemer 2400 CHN elemental analyzer. MS (ESI)
analyses were carried out on a Thermo Finnigan MAT XP95
analyzer using ESI model.
Polymer
Cat
Activity
(kg/mol h bar)
Mw (106)
Mw/Mn
(g/mol)b
Polyethylene
4
5
4
5
41
57
5.2
12.3
1.26
1.44
0.54
1.26
4.84
4.63
4.52
3.64
Poly(ethylene/
methyl 10-undecannoate)
a
Polymerization conditions: ratio of catalyst and co-catalyst ([Al]/[Ti]) ¼ 2000,
toluene, temperature 1.5 bar, methyl-10-
50 ꢁC, Pethylene
solvent
¼
¼
¼
undecannoate (1.0 M in toluene, 10 mmol), polymerization time ¼ 2 h.
b
Molecular weight and molecular weight distribution of the polymers were
determined by means of gel-permeation chromatography (GPC: Waters 150) at
145 ꢁC using 1,2,4-trichlorobenezene as a solvent. The weight average molecular
weight and polydispersity index (Mw and Mw/Mn, respectively) were calculated on
the basis of polystyrene standards.
ethylene, respectively [24]. However, with the co-catalysts trime-
thylaluminum and tris(pentafluorophenyl)borane, both 4 and 5
demonstrate low activity (<0.01 kg polymer (molTi)ꢀ1hꢀ1 barꢀ1
)
for ethylene polymerization because of the relatively strong TieCl
bonds; (b) under the same conditions, complex 5 is more active
than the corresponding analogue 4, which may be caused by the
formation of the six-membered ring (Scheme 1) that enhances the
intramolecular electron delocalization and reconstruct the mole-
cule configuration differing from 4, the resulting unique bis(cyclo)-
coordination model may benefit the olefin polymerization proce-
dure [26]; (c) the obtained polymers have a high molecular weight
with reasonable molecular weight distributions (Mw/Mn are in the
range 3.64e4.84) To further elucidate the structure of the obtained
ethylene/methyl-10-undecannoate copolymer, products obtained
from catalyst 5 have been analyzed by 1H and 13C NMR spectra at
110 ꢁC in 1,2-dichlorobenzene-d4. According to the 1H NMR spectra,
an incorporation ratio of 4.7 mol% methyl-10-undecannoate has
been reached in the copolymers; and (d) although the mechanism
for the carboranylimine-complexed titanium(IV)/MAO catalytic
process is not known in control experiments, neither 2 nor 3
produced polymers in the presence of MAO.
4.1. Synthesis of phenyl(carboranylmethyl)imine, 1-(CH2N]
CC6H5)-1,2-C2B10H11, (2)
A mixture of 1-(CH2NH3Cl)-1,2-C2B10H11 (1), (1.5 g, 7.2 mmol),
NaHCO3 (35.0 g, 416.7 mmol), benzaldehyde (3.8 g, 35.1 mmol) and
30.0 g 4 Å MS in 250 mL toluene was heated to reflux for 2 days
under argon. After reaction, the mixture was cooled to room
temperature and filtered. The solid residue was washed with
dichloromethane (50 mL ꢂ 2). The combined organic phase was
reduced under reduced pressure resulting in a yellow sticky residue
which was further washed with pentane to remove unreacted
benzaldehyde to obtain 0.99 g waxy solid (2) in 53% yield. Analytic
data: Calcd. (Found) for C10H19B10N (2): C, 45.95 (46.33); H, 7.33
(7.25); N, 5.36 (5.24). 1H NMR (CDCl3, ppm),
7.66e7.35 (m, 5H, C6H5), 4.10 (s, 2H, CH2eN), 4.05 (s, 1H, HCcage),
2.72e1.48 (m, br, 10H, B10H10). 13C NMR (CDCl3, ppm),
¼ 164.14
d
¼ 8.12 (s, 1H, CH]N),
These results suggest that the catalytic activity is sensitive to
initiator and the titanium cations could be the active species.
Similar to other titanium based FI catalysts [21], the active titanium
cations can be generated in situ by a reaction of MAO with precursor
4 or 5 leading to a metal-ligand bond rupture. On the other hand
the TieCl bond could be broken to form the catalytically active
d
(C]N), 134.80, 131.92, 128.86, 128.58 (C6H5), 73.48 and 63.64
(Ccage), 57.94 (eCH2eN). 11B NMR (CDCl3, ppm),
d
¼ ꢀ2.96 (1B,
1
1JBH
1JBH
¼
152 Hz), ꢀ5.19 (1B, JBH
¼
150 Hz), ꢀ9.07 (3B,
1
¼
150 Hz), ꢀ11.15 (2B, JBH
¼
109 Hz), ꢀ13.07 (3B,
1JBH ¼ 167 Hz). IR (KBr pellet, cmꢀ1), 3649 (w, m), 3278 (w, s), 3069
(s, s), 2880 (m, br), 2604 (vs, s), 2566 (vs, s), 1646 (vs, s), 1445 (m, s),
1386 (m, s), 1335 (m, s), 1016 (s, s), 752 (s, s), 689 (s, s), 526 (w, s),
465 (w, s).
species,
[1-(CH2N¼CC6H4)-1,2-C2B10H10]Ti(IV)Me2
or
[1-
(CH2N¼CC6H4O-2)-1,2-C2B10H10]Ti(IV)Me, upon coordination with
the ethylene or methyl-10-undecannoate monomer. In the
processes, a single-site polymerization mechanism of the conven-
tional “ZieglereNatta” catalysts may be operable [30]. More
detailed mechanistic studies are currently underway in our labo-
ratory, using FTeIR and NMR spectroscopy.
4.2. Single crystal X-ray diffraction of (2)
A suitable quality single crystal of 2 was chosen under a Leica
microscope and placed on a fibre needle which was then mounted
on the goniometer of the X-ray diffractometer. The crystal was
purged with a cooled nitrogen gas stream at 110 K throughout the
data collection. X-ray reflections were collected on a Rigaku Saturn
3. Conclusions
The new carborane-based imine ligands have been synthesized
conveniently and coordinated with titanium to form phenyl(-
carboranylmethyl)imido titanium(IV) chlorides. The resulting tita-
CCD area detector with graphite monochromated Mo-K
a
radiation
ꢀ
(l
¼ 0.71073A). Data were collected and processed using Crystal-
nium complexes were found to be efficient
a-olefin polymerization
Clear (Rigaku) software. Crystal structure was solved by direct
methods and SHELX-TL was used for structure solution and least-
squares refinement. The non-hydrogen atoms were refined aniso-
tropically. Hydrogen atoms were either fixed at idealized positions
or located from the difference Fourier map and allowed to ride on
their parent atoms in the refinement cycles. Data collection and
refinement details are given in Table S-1.
catalysts to produce high molecular weight polyethylene and
poly(ethylene/methyl-10-undecannoate). We expect the catalysts
to find broader applications in both academia and materials
industry. A study of the mechanism of the catalytic process along
with the structural modifications of the catalysts is currently
underway in our laboratories.

122
Z. Yinghuai et al. / Journal of Organometallic Chemistry 721-722 (2012) 119e123
4.3. Synthesis of 1-(CH2N]CC6H4(OH)-2)-1,2-C2B10H11 (3)
4.6. Polymerization procedures
A similar process, adopted for the preparation of (2), was used to
synthesize 1.27 g of (3) in 64% yield from 1.5 g of (7.2 mmol) (1),
9.92 g of (36.0 mmol) salicyladehyde, NaHCO3 (35.0 g, 416.7 mmol)
and 30.0 g of 4 Å MS in 250 mL toluene. Analytic data: Calcd.
(Found) for C10H19B10NO: C, 43.3 (43.50); H, 6.90 (6.89); N, 5.05
The polymerization of ethylene and methyl-10-undecannoate
catalyzed by compounds 4 and 5 were performed for 2 h in
70 mL toluene in the presence of methylaluminoxane (MAO, 1.7 M
in toluene) or trimethylaluminum (MA, 2.0 M in toluene) or tris(-
pentafluorophenyl)borane in Parr reactor. The argon pressure
inside the reactor was reduced by applying vacuum. Monomer
pressure was then applied to the reactor which was adjusted to
constant temperature and pressure. During the polymerization
(4.89). 1H NMR (CDCl3, ppm),
d
¼ 12.06 (s, 1H, ꢀOH), 8.20 (s, 1H,
CH]N), 7.35e6.85 (m, 4H, C6H4), 4.15 (s, 2H, CH2eN), 3.68 (s, 1H,
HCcage), 2.74e1.18 (m, br, 10H, B10H10). 13C NMR (CDCl3, ppm),
d
¼ 168.37 (C]N), 160.79, 133.91, 132.35, 119.41, 117.81, 117.32
process, 3.0
mmol catalyst (4 or 5) based on titanium species and
(C6H4), 72.58 and 63.74 (Ccage), 58.45 (eCH2eN). 11B NMR (CDCl3,
2000 mol MAO or MA were used to give a concentration ratio of
m
ppm),
d
¼
ꢀ2.45 (1B, 1JBH1
¼
150 Hz), ꢀ4.96 (1B,
150 Hz), ꢀ8.96 (3B, JBH ¼ 143 Hz), ꢀ11.31 (2B,
1
[Al]/[Ti] ¼ 2000. For initiator tris(pentafluorophenyl)borane, a mole
ratio of 3 for [B]/[Ti] was used. The co-monomer methyl-10-
undecannoate (1 M in toluene, 10 mmol) was charged with syringe.
The reaction temperature was 50 ꢁC under 1.5 bar pressure. After
polymerization process, the reaction was carefully quenched with
10 mL mixture of 10% HCl solution of MeOH. The polymer was then
precipitated with 150 mL methanol, collected by filtration, washed
with MeOH (4 ꢂ 20 ml) and n-hexane (2 ꢂ 20 ml) in sequence and
dried at 60 ꢁC in high vacuum to a constant weight. Polymerization
results are summarized in Table 2.
1JBH
¼
1JBH ¼ 104 Hz), ꢀ13.05 (3B, JBH ¼ 175 Hz). IR (KBr pellet, cmꢀ1),
3671 (w, br), 3649 (w, m), 3057 (m, s), 2911 (w, br), 2599 (vs, s),
2574 (vs, s), 1948 (w, m), 1626 (vs, s), 1559 (m, s), 1457 (m, s), 1400
(m, s), 1275 (s, s), 1208 (m, s), 1117 (m, s), 1019 (s, m), 935 (w, s), 820
(m, s), 756 (s), s3, 723 (m, s), 639 (w, s), 592 (w, s), 455 (w, s).
4.4. Synthesis of phenyl(carboranylmethyl)imidotitanium (IV)
chloride, [1-(CH2N]CC6H5)-1,2-C2B10H10]TiCl3 (4)
Acknowledgements
A 1.0 g (3.8 mmol) of (2) was dissolved in 120 mL of dry toluene
and the resulting solution was cooled to ꢀ78 ꢁC and to which
2.51 ml (4.02 mmol) of n-BuLi (1.6 M in hexanes) was carefully
added with syringe. After addition, the mixture was kept at that
temperature for 30 min before warming to room temperature for
4 h. The reaction mixture was then allowed to cool to 0 ꢁC and
0.76 g (4.01 mmol) of TiCl4 was added. After 30 min at 0 ꢁC, the
mixture was stirred at room temperature for 2 days. After filtration
and removal of all the solvents under reduced pressure, the ob-
tained residue was precipitated with a mixture of benzene/pentane
(v:v ¼ 1:2) to collect 0.51 g of (4) in 32% yield. MS (ESI) for
C10H18B10Cl3NTi (5): m/z ¼ 413.27 [M ꢀ H]þ. 1H NMR (CD3CN, ppm),
We thank ICES in Singapore for support of the work. We also
acknowledge Dr Chacko Jacob in ICES for help to analyze high
temperature NMR. NSH thanks the support by grants from the
National Science Foundation (CHE-0906179 and CHE-0840504),
Alexander von Humboldt Foundation, and the NIU Inaugural Board
of Trustees Professorship Award.
Appendix A. Supplementary material
CCDC 883306 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
d
¼ 8.52 (s, 1H, CH]N), 7.80e7.42 (m, 5H, C6H5), 4.41 (s, 2H,
CH2eN), 3.12e1.28 (m, br, 10H, B10H10). 13C NMR (CD3CN, ppm),
d
¼ 169.6 (C]N), 131.99, 131.18, 129.80, 129.21 (C6H5), 78.1 and
66.69 (Ccage), 58.0 (eCH2eN). 11B NMR (CD3CN, ppm),
d
¼ ꢀ3.17 (1B,
Appendix B. Supplementary material
1JBH
1JBH
¼
148), ꢀ5.37 (1B, JBH
¼
159 Hz), ꢀ6.73 (1B,
1
1
¼
163 Hz), ꢀ9.99 (3B, JBH
¼
167 Hz), ꢀ12.13 (2B,
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.jorganchem.2012.
07.010.
1JBH ¼ 98 Hz), ꢀ13.22 (2B, JBH ¼ 136.1 Hz). IR (KBr pellet, cmꢀ1),
3397 (s, br), 2593 (s, s), 1632 (s, br), 1457 (m, s), 1339 (m, br), 1209
(m, s), 1167 (m, s), 1089 (w, s), 911 (s, s), 846 (s, br), 759 (m, s), 729
(m, s), 694 (m, s), 490 (m, s).
1
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4.5. Synthesis of [1-(CH2N]CC6H4(O)-2)-1,2-C2B10H10]TiCl2 (5)
A similar process, described above for the preparation of (4), was
used to synthesize 0.73 g of (5) in 51% yield from 1.0 g of (3.6 mmol)
(3), 4.73 mL of (7.57 mmol) n-BuLi (1.6 M in hexanes) and 0.72 g of
(3.80 mmol) TiCl4 in 120 mL dry toluene. MS (ESI) for
C10H17B10Cl2NOTi (5): m/z ¼ 391.28 [M ꢀ 3H]þ. 1H NMR (CD2Cl2,
ppm),
d
¼ 8.51 (s, 1H, CH]N), 7.57e7.01 (m, 4H, C6H4), 4.41 (s, 2H,
CH2eN), 2.90e0.95 (m, br, 10H, B10H10). 13C NMR (CD2Cl2, ppm),
¼ 156.8 (C]N), 155.5, 129.9, 129.3, 124.3, 119.7, 117.1 (C6H4), 74.2
and 68.3 (Ccage), 60.7 (eCH2eN). 11B NMR (CD2Cl2, ppm),
¼ ꢀ4.39
(1B, JBH ¼ 148 Hz), ꢀ7.23 (1B, JBH ¼ 144 Hz), ꢀ11.41 (3B,
d
d
1
1
1JBH
¼ 146 Hz), ꢀ14.09 (2B, JBH ¼ 149 Hz), ꢀ15.21 (3B,
1
1JBH ¼ 154 Hz). IR (KBr pellet, cmꢀ1), 3397 (s, br), 2960 (s, s), 2931 (s,
s), 2581 (s, s), 1610 (s, br), 1553 (s, s), 1447 (m, s), 1401 (m, s), 1288
(m, s), 1234 (m, s), 1125 (w, s), 1034 (w, s), 911 (m, s), 758 (s, s), 729
(s, s), 635 (s, s), 515 (m, s).
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