A study of ortho- and para-siloxyanilines for the synthesis of mono-, bi-, and tetra-nuclear early transition metal-imido complexes

Article abstract of DOI:10.1016/S0022-328X(00)00391-0

The siloxyanilines o-Me₃SiOC₆H₄NH₂ (1) and p-RMe₂SiOC₆H₄NH₂ (R = H (2); R = Me (3)), and their N-silylated derivatives p-Me₃SiOC₆H₄NHS

Full text of DOI:10.1016/S0022-328X(00)00391-0

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Journal of Organometallic Chemistry 610 (2000) 42–48
A study of ortho- and para-siloxyanilines for the synthesis of
mono-, bi-, and tetra-nuclear early transition metal–imido
complexes
J.M. Benito, Silvia Are´valo, E. de Jesu´s *1, F.J. de la Mata, J.C. Flores *2, R. Go´mez
Departamento de Qu´ımica Inorga´nica, Uni6ersidad de Alcala´, Campus Uni6ersitario, ES-28871 Alcala´ de Henares, Madrid, Spain
Received 17 April 2000; accepted 27 June 2000
Abstract
The siloxyanilines o-Me3SiOC6H4NH2 (1) and p-RMe2SiOC6H4NH2 (R=H (2); R=Me (3)), and their N-silylated derivatives
p-Me3SiOC6H4NHSiMe3 (4) and p-Me3SiOC6H4N(SiMe3)2 (5) have been prepared from ortho- or para-aminophenol and used in
the synthesis of imido complexes. Thus, binuclear [{Ti(h5-C5H5)Cl}{m-NC6H4(p-OSiMe3)}]2 (6) and mononuclear
[TiCl2{NC6H4(p-OSiMe3)}(py)3] (7) imido complexes have been obtained from the reaction of 3 and [Ti(h5-C5H5)Cl3] or
t
[TiCl2(NtBu)(py)3], respectively. In contrast, the reaction of 1 with TiCl4 and Bupy affords the titanocycle [TiCl2{OC6H4(o-
NH)ꢀN,O}(tBupy)2] (8). Compound 5 has also been used to prepare the niobium imide complex [NbCl3{NC6H4(p-
OSiMe3)}(MeCN)2] (9), by its reaction with NbCl5 in CH3CN. These findings have been applied to the synthesis of polynuclear
systems. Thus, chlorocarbosilane Si[CH2CH2CH2Si(Me)2Cl]4 (CS–Cl) has been functionalized with the ortho- and para-
aminophenoxy groups to give 10 and 11, respectively. The use of 11 has allowed the formation of the tetranuclear compound 12.
t
Attempts to synthesize terminal imido titanium complexes from 10 and TiCl4 in the presence of Bupy and Et3N, give complex
8 and carbosilane CS–Cl. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Imido complexes; Cyclopentadienyl complexes; Transition metal dendrimers; Titanium; Niobium
1. Introduction
Here, we present work carried out on the synthesis of
imido complexes of titanium and niobium containing
siloxy-substituted phenylimido ligands. The siloxyani-
line p-Me3SiOC6H4NH2 (3) and its N-silyl substituted
p-Me3SiOC6H4N(SiMe3)2 (5) have been useful as pre-
cursors for the synthesis of terminal and bridging imido
complexes. In the last part of this article we describe
the synthesis of the tetranuclear titanium complex 12, a
non-branched model of a dendrimer.
Due to the relevance of imido complexes in transition
metal chemistry, a large variety of synthetic methodolo-
gies have been developed [1a,2]. Among the main fea-
tures of the imido ligand are its electronic flexibility,
which allows a chemical behavior ranging from remark-
able stability to extreme reactivity, its variety of coordi-
nation modes, and its capability to stabilize high
oxidation states [1,2]. We are looking for NR com-
plexes of early transition metals in which the R group is
linked to a silyl group. Our interest in such imido
ligands is because their synthesis might be extended to
support transition metal complexes on carbosilane den-
drimers through imido links [3]. For instance, reports
published up to date on titanium dendrimers are limited
to alkoxo or cyclopentadienyl anchoring ligands [4,5].
2. Results and discussion
NMR and analytical data for 1–12 are given in
Section 4. Only selected data will be presented for this
discussion.
The lithium aminophenoxides Ia–b (Scheme 1) have
been obtained by deprotonation of the hydroxyl group
in ortho- or para-aminophenol with one equivalent of
LinBu in THF. They can be isolated as white solids,
1 *Corresponding author.
2 *Corresponding author. Tel.: +34-91-8854654; fax: +34-91-
8854683; e-mail: jcflores@inorg.alcala.es
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00391-0

J.M. Benito et al. / Journal of Organometallic Chemistry 610 (2000) 42–48
43
cleaved by nucleophiles, the effect of two equivalents of
butyllithium on compounds 3 and 4 must be the forma-
tion of p-LiOC6H4N(H)Li and p-LiOC6H4N(SiMe3)Li,
respectively. Thereafter, the addition of SiMe3Cl must
proceed with silylation back on the oxygen atom and
silylation on the nitrogen as well, leading to the target
compounds 4 and 5. Both compounds are oils and have
been found to be moisture sensitive, as samples exposed
to air slowly undergo hydrolysis of the NꢀSi bonds to
produce compound 3 (1H-NMR evidence).
although they have been used in situ through this work.
Reaction of I and one equivalent of SiMe2RCl (R=H,
Me) has allowed the synthesis of the oily siloxyanilines
o-Me3SiOC6H4NH2 (1), p-HMe2SiOC6H4NH2 (2), and
p-Me3SiOC6H4NH2 (3) in good yields (\80% relative
to aminophenol).
The regioselectivity of the silylation process on the
oxygen of aminophenols must be understood as a result
of the much higher Bro¨nsted acidity of the hydroxy
compared with the amino group (pKaꢀ10 and ꢀ27
for phenol and aniline, respectively [6]). Thus, any
eventual lithium amide formation during the course of
the deprotonation reaction must shift the proton trans-
fer equilibrium from HOC6H4NHLi to the side of
LiOC6H4NH2 (Keqꢀ1017). Moreover, in an experiment
carried out in a NMR-tube scale, the mixture of p-
Me3SiOC6H4NHSiMe3 (4, vide infra) with p-
HOC6H4NH2, one to one in THF, followed by
replacement of the solvent by CDCl3, gives 4-
Me3SiOC6H4NH2 (3) as the only product detected by
1H-NMR (Scheme 1)
Stepwise reaction of 3 through the sequence (i) one
equivalent of LinBu (ii) one equivalent of SiMe3Cl in
THF, has led to mixtures of p-Me3SiOC6H4NHSiMe3
(4) and the starting material 3 (Scheme 1). Instead, 4 is
readily synthesized free of 3 by addition of two equiva-
lents of LinBu and SiMe3Cl to p-aminophenol. Simi-
larly, further N-silylation of compound 4 in THF with
only one equivalent of LinBu and SiMe3Cl has given
The 1H-NMR spectra of 1–5 show resonances due to
the aromatic ring consistent with the AA%BB% (para) or
ABCD (ortho) spin systems. In addition, a broad sin-
glet (l 3.2–3.9) is recorded for the NHx protons in 1–4,
and a heptet (l 4.88) for the SiMe2H proton in 2. Also,
a SiMe resonance for 1–3 and two for 4–5 are ob-
1
1
served in H- and 29Si-NMR; H integration confirms
the progressive proton substitution by SiMe3 groups at
the nitrogen atom, on going from 3 to 5.
Many procedures have been described for the synthe-
sis of early transition metal–imido complexes [1a,2].
Among them, deprotonation of primary amines and
exchange reactions of alkylimido ligands and aryl-
amines have been found to be straightforward synthetic
methods [7]. Siloxyanilines 1 and 3 have been tested as
potential precursors of TiN compounds using both
methods.
The reaction of 3 with [Ti(h5-C5H5)Cl3] in CH2Cl2, in
the presence of two equivalents of Et3N as an auxiliary
base, yields the imido binuclear complex [{Ti(h5-
C5H5)Cl}{m-NC6H4(p-OSiMe3)}]2 (6) (Scheme 2). This
compound is obtained as a dark violet solid moderately
moisture stable, although it readily decomposes into
wet solvents. Due to the high oxophilic character of
Ti(IV) species, the high yield of its preparation (ca.
90%) reveals an effective oxygen-protection by the
SiMe3 group in compound 3. The NMR data of com-
plex 6 show equivalent cyclopentadienyl, phenyl and
mixtures of p-Me3SiOC6H4N(SiMe3)2 (5) and
4
(Scheme 1). Although both compounds are separated
by fractional distillation, pure compound 5 has been
obtained by reaction of 4 with two equivalents of LinBu
and SiMe3Cl. The different results using one or two
equivalents of LinBu/SiMe3Cl for the synthesis of 4 and
5, are most likely due to nucleophilic attack of LinBu to
the SiꢀO bond competing with deprotonation of the
amino group. Since trimethylsilyl ethers are easily
Scheme 1.

44
J.M. Benito et al. / Journal of Organometallic Chemistry 610 (2000) 42–48
The synthesis of imido derivatives from the ortho
substituted arylamine 1 was unsuccessful under the
same conditions. Thus, the reaction of 1 with TiCl4 in
the presence of two equivalents of tBupy and two
equivalents of Et3N in CH2Cl2, gives the titanocycle
[TiCl2{OC6H4(o-NH)ꢀN,O}(tBupy)2] (8), obtained as a
moisture sensitive dark violet microcrystalline solid.
The presence of the amido group is confirmed by a low
field resonance (l 11.16) in the 1H-NMR spectrum.
t
Both Bupy ligands are equivalent suggesting a trans
arrangement in the octahedral titanium environment.
The fairly similar compound [TiCl2{OC6H4(o-
NH)ꢀN,O}(py)2] is detected by 1H-NMR [10] in the
reaction of 1 and [TiCl2(NtBu)(py)3], although attempts
to isolated pure samples failed. During the course of
these reactions, the ortho position of the trimethylsiloxy
group clearly facilitates the SiꢀO bond cleavage, most
likely assisted by SiMe3Cl elimination. This finding
suggests that reaction of siloxyanilines and TiCl4 pro-
ceeds through amido intermediates that evolve to the
imido compound 7 or to the titanocycle 8, depending
on the para or ortho position of the OSiMe3 group.
Cleavage of NꢀSi bond in N-silylamines or N-silyl-
anilines, accompanied by formation of strong Siꢀhalide
bond, has also been reported as an effective synthetic
method for introducing imido ligands in early transition
metal complexes [1b,11]. Accordingly, compound 5 re-
acts with NbCl5 in CH3CN at room temperature af-
fording the siloxyarylimide [NbCl3{NC6H4(p-OSi-
Me3)}(MeCN)2] (9), which is isolated as a moisture
sensitive orange–red solid (Scheme 2). Analytical and
spectroscopic data are consistent with the structure
proposed for 9 and show the presence of two equivalent
CH3CN ligands coordinated to the metal center in an
octahedral environment, suggesting a trans arrange-
ment of them and therefore mer of the chlorides. When
Scheme 2.
SiMe3 groups, quite in agreement with either a
mononuclear or a symmetric binuclear structure. A
binuclear arrangement with imido bridges is assumed
by comparison with the proposed or determined struc-
tures for other analogues [8], such as [Ti(h5-
C5H5)Cl]2(m-NPh)2] [8a], and accordingly with the
observation of a MS peak corresponding to a dimeric
molecule (see Section 4). On the other hand, cyclopen-
tadienyl mononuclear compounds with terminal imido
groups have only been observed in complexes of gen-
eral formula [TiCp(NR)ClL] (Cp=generic cyclopenta-
dienyl
ring,
L=py,
tBupy;
py=pyridine,
tBupy=4-tert-butylpyridine), which contain coordi-
nated pyridine ligands [9]. Our attempts to obtain
mononuclear complexes adding py or Bupy in the
t
synthetic procedure of complex 6 were unsuccessful as
no other organometallic compound than 6, free of any
L ligand, was detected. This result is in agreement with
the observed tendency of mono- or non-substituted
cyclopentadienyl complexes [TiCp(NR)ClL] to lose the
L ligand affording dimers [9b].
Complex 7 has been obtained as a very moisture
sensitive brownish–yellow solid by exchange of the
tert-butylimido group in [TiCl2(NtBu)(py)3] by the
siloxyaniline 3 or, alternatively, by deprotonation of 3
with TiCl4, pyridine and two equivalents of Et3N in
CH2Cl2 (Scheme 2). Pure 7 can be isolated by simple
1
the H-NMR spectrum of 9 is registered in CD3CN,
only free CH3CN is observed, indicating exchange be-
tween free and coordinated acetonitrile.
The reactions described above for the synthesis of
terminal-imido complexes can be useful for the synthe-
sis of periphery-metallated carbosilane structures start-
ing from aniline-functionalized cores as 10 or 11
(Scheme 3). These are easily prepared as yellow oils by
reaction of the chloro terminated derivative CS–Cl [12]
with phenoxides Ia or Ib, respectively. Both compounds
have been characterized by 1H- and 13C{1H}-NMR,
and 11 by 29Si{1H}-NMR, elemental analysis and
MALDI-TOF MS as well (see Section 4). Chemical
shifts observed for the ꢀSiMe2OC6H4NH2 moieties in
10 and 11 are similar to those for 1 and 3, respectively.
Attemps to synthesize terminal arylimido titanium
complexes from 10 and 11 have yielded comparable
results with those described above for 1 and 3. Thus,
t
removal of the solvent and of the BuNH2 byproduct in
the first case, whereas attempts to isolate neat samples
from the deprotonation reaction failed. The pyridine
1
ligands appear in the H-NMR spectrum of 7 as two
groups of resonances in a 2:1 ratio, with those of the
single pyridine ligand occurring at higher fields and
being somewhat broadened. This is the same spectro-
scopic behavior found in other [TiCl2(NR)(py)3] com-
plexes [7a] and corresponds to a trans arrangement of
the chloride and mer of the pyridine ligands with a
labile py trans to the imido group.
t
the reaction of 10 with TiCl4 in the presence of Bupy

J.M. Benito et al. / Journal of Organometallic Chemistry 610 (2000) 42–48
45
3. Conclusions
and Et3N in CH2Cl2, gives complex 8 (Scheme 3),
together with the recovery of the chlorocarbosilane
CS–Cl. Again, the ortho position of the siloxy group
facilitates the SiꢀO bond cleavage to afford the metallo-
cycle 8. Instead, the tetranuclear titanium compound 12
can be prepared from the para-substituted isomer 11
(Scheme 3). Although complex 12 is obtained from the
reaction of 11 with either, four equivalents of
[TiCl2(NtBu)(py)3] in CH2Cl2 at room temperature, or a
mixture of TiCl4, pyridine and Et3N in CH2Cl2, the
former procedure is cleaner, as observed in the related
synthesis of 7 from 3. The product is isolated as a
moisture sensitive dark-brown solid. Interestingly, its
NMR data show free and coordinated pyridine ligands
(ratio 1:2) in solution even after several washings of the
solid in pentane. However, analytical and spectroscopic
data of samples dried in vacuo at 50°C for several
hours are consistent with the presence of only two py
ligands per titanium, cis to the imido group and trans
each other (see Section 4). Five-coordinated titanium
complexes of this type (i.e. [TiCl2(NR)(py)2]) have been
reported by Mountford and co-workers [9], and their
formation explained as a consequence of the trans-labi-
lizing ability of the imido group. Therefore, it is most
likely that the crude solid obtained in the preparation
of 12 holds a titanium environment with a loosely
coordinated trans-py, which remains after washings
with pentane. This pyridine ligand must be readily
liberated in solution or removed upon warming under
vacuum due to a marked trans-labilitation effect in
compound 12.
ortho- and para-Siloxyanilines 1 and 3, and the N-
disilylated derivative of the latter (5) have been studied
as potential ligands for the synthesis of early transition
metal–imido complexes. The para compounds are use-
ful in this regard (e.g. compounds 7 and 9), while the
ortho one undergoes desilylation of the oxygen leading
to the formation of the metallocycle 8. Similar results
are observed in attempts toward the synthesis of
polynuclear arylimido–titanium complexes using ani-
line derivatives as anchoring ligands. Thus, the aniline-
functionalized carbosilane 11 has allowed the isolation
of tetranuclear titanium compound 12, in which the
metal moieties are linked to the framework by terminal
imido ligands.
As stated in the introduction, the work initiated here
is directed toward the support of early transition metal
moieties to the periphery of carbosilane dendrimers
through imido ligands. However, several issues must be
worked out first such as poor moisture stability and low
yield found for compound 12. As a future work, a
study comprising para-silylanilines, instead of
siloxyanilines, is underway.
4. Experimental
4.1. General methods
All operations were performed under an argon atmo-
sphere using Schlenk or dry-box techniques. Unless
Scheme 3.

46
J.M. Benito et al. / Journal of Organometallic Chemistry 610 (2000) 42–48
otherwise stated, reagents were obtained from commer-
cial sources and used as received. Solvents were previ-
ously dried and purified as described elsewhere [13].
[Ti(h5-C5H5)Cl3] [14], [TiCl2(NtBu)(py)3] [7a] and car-
bosilane Si[CH2CH2CH2Si(Me)2Cl]4 (CS–Cl, see
Scheme 3) [12] were prepared according to literature
procedures. NMR spectra were recorded on Varian
Unity 500+, Varian Unity VR-300 or Varian Unity
200 NMR spectrometers. Chemical shifts (l) are re-
4.3. Preparation of p-Me3SiOC6H4NHSiMe3 (4)
LinBu (34.4 ml, 1.6 M in hexane, 55.0 mmol) was
slowly added, from a funnel equipped with a bubbler,
to a solution of 4-HOC6H4NH2 (3.00 g, 27.5 mmol).
After stirring for 4 h in THF (50 ml) at r.t., SiMe3Cl
(7.0 ml, 55.3 mmol) in THF (50 ml) was added at
−78°C, and the reaction mixture was allowed to warm
up to r.t. Then, the solvent was removed under vac-
uum, and the residue extracted into hexane. Compound
4 (5.00 g, 72%) was obtained as a yellow–orange oil by
evaporation of the hexane solution to dryness. Anal.
Calc. for C12H23NOSi2: C, 56.86; H, 9.15; N, 5.53.
Found: C, 56.21; H, 9.11; N, 5.78%. 1H-NMR (CDCl3):
l 6.63 and 6.50 (AA% and BB% parts of an AA%BB% spin
system, 4H, C6H4), 3.19 (br s, 1H, NH), 0.23 (s, 9H,
SiMe3), 0.21 (s, 9H, SiMe3). 13C{1H}-NMR (CDCl3): l
146.8 (ipso-C6H4), 141.5 (ipso-C6H4), 120.7 (C6H4),
116.8 (C6H4), 0.2 (SiMe3), 0.1 (SiMe3). 29Si{1H}-NMR
(CDCl3): l 15.0 (OSiMe3), 2.2 (NSiMe3).
1
ported in ppm referenced to TMS for H, 13C and 29Si.
Elemental analyses were performed by the Microanalyt-
ical Laboratories of the Universidad de Alcala´ on a
Heraeus CHN-O-Rapid mycroanalyzer, and MALDI-
TOF MS were performed by the Analytical Services of
the Universidad Auto´noma de Madrid.
4.2. Preparation of siloxyanilines RMe2SiOC6H4NH2
(1–3)
The synthesis of the siloxyanilines (1–3) and interme-
diates (Ia and Ib) are exemplified by the preparation of
p-Me3SiOC6H4NH2 (3).
4.4. Preparation of p-Me3SiOC6H4N(SiMe3)2 (5)
LinBu (28.7 ml, 1.6 M in hexane, 45.9 mmol) was
slowly added, from a funnel equipped with a bubbler,
to a solution of p-HOC6H4NH2 (5.00 g, 45.8 mmol) in
THF (50 ml) at room temperature (r.t.). After the
addition was completed, the reaction mixture was
stirred for 4 h. Then, the solvent was removed under
reduced pressure and the remaining solid washed with
hexane (2×30 ml) to afford the lithium phenoxide
derivative Ib as a white powder. SiMe3Cl (5.8 ml, 45.9
mmol) was added to a solution of Ib in THF (50 ml) at
r.t. and the mixture was stirred overnight. The volatile
products were removed in vacuo and the residue ex-
tracted into CH2Cl2. Compound 3 (6.84 g, 82%) was
isolated as an orange oil by evaporation of the filtrates
in vacuo to dryness.
Compound 4 was prepared as described above from
p-HOC6H4NH2 (3.00 g, 27.5 mmol) and reacted in situ
with two additional equivalents of LinBu (34.4 ml, 1.6
M in hexane, 55.0 mmol) in THF for 4 h. Then,
SiMe3Cl (7.0 ml, 55.0 mmol) was syringed to the reac-
tion mixture at 0°C, and the yellow solution with white
precipitate stirred overnight at r.t. The volatile products
were removed under reduced pressure and the residue
extracted into pentane. Compound 5 was obtained
spectroscopically pure as a dark orange oil by evapora-
tion of the solvent. Fractional distillation of this crude
oil (60–65°C, 10–3 mmHg) afforded analytically pure 5
as a pale-yellow oil (7.92 g, 88%). Anal. Calc. for
C15H31NOSi3: C, 55.32; H, 9.59; N, 4.30. Found: C,
1: Anal. Calc. for C9H15NOSi: C, 59.62; H, 8.34; N,
1
55.16; H, 9.45; N, 4.37%. H-NMR (CDCl3): l 6.72
1
7.73. Found: C, 58.81; H, 8.64; N, 7.42%. H-NMR
and 6.65 (AA% and BB% parts of an AA%BB% spin system,
4H, C6H4), 0.23 (s, 9H, OSiMe3), 0.03 (s, 18H,
NSiMe3). 13C{1H}-NMR (CDCl3): l 151.3 (ipso-C6H4),
141.3 (ipso-C6H4), 130.8 (C6H4), 119.8 (C6H4), 2.0
(NSiMe3), 0.2 (OSiMe3). 29Si{1H}-NMR (CDCl3): l
19.4 (OSiMe3), 4.7 (NSiMe3).
(CDCl3): l 6.8–6.6 (m, 4H, C6H4), 3.89 (br s, 2H,
NH2), 0.30 (s, 9H, SiMe3). 13C{1H}-NMR (CDCl3): l
142.8 (ipso-C6H4), 138.0 (ipso-C6H4), 121.9 (C6H4),
118.5 (C6H4, two resonances overlapping), 115.7
(C6H4), 0.4 (SiMe3). 29Si{1H}-NMR (CDCl3): l 16.7.
1
2: H-NMR (CDCl3): l 6.71 and 6.57 (AA% and BB%
parts of an AA%BB% spin system, 4H, C6H4), 4.88 (sept,
1H, J=18 Hz, SiH), 3.42 (br s, 2H, NH2), 0.31 (d, 6H,
J=18 Hz, SiMe2). 13C{1H}-NMR (CDCl3): l 147.8
(ipso-C6H4), 140.6 (ipso-C6H4), 119.9 (C6H4), 116.2
(C6H4), −1.5 (SiMe2).
4.5. Preparation of
[{Ti(p5-C5H5)Cl}{v-NC6H4(p-OSiMe3)}]2 (6)
A solution of 3 (0.50 g, 2.8 mmol) in CH2Cl2 (20 ml)
was added dropwise to a mixture of Ti(h5-C5H5)Cl3
(0.60 g, 2.7 mmol), pyridine (py) (0.23 ml, 2.8 mmol)
and Et3N (0.77 ml, 5.5 mmol) in CH2Cl2 (20 ml) at r.t.
The solution turned to dark violet and was stirred for
24 h. Then, the volatile products were evaporated under
vacuum and the residue was extracted into toluene
(2×20 ml). The solution was filtered to remove the
3: Anal. Calc. for C9H15NOSi: C, 59.62; H, 8.34; N,
1
7.73. Found: C, 60.22; H, 8.16; N, 7.87%. H-NMR
(CDCl3): l 6.65 and 6.58 (AA% and BB% parts of an
AA%BB% spin system, 4H, C6H4), 3.77 (br s, 2H, NH2),
0.20 (s, 9H, SiMe3). 13C{1H}-NMR (CDCl3): l 147.8
(ipso-C6H4), 139.9 (ipso-C6H4), 120.6 (C6H4), 116.5
(C6H4), 0.0 (SiMe3). 29Si{1H}-NMR (CDCl3): l 15.4.

J.M. Benito et al. / Journal of Organometallic Chemistry 610 (2000) 42–48
47
Et3NHCl byproduct and evaporated to dryness. The
resulting solid was recrystallized from toluene leading
to complex 6 (0.80 g, 89%) as a microcrystalline dark
violet solid. Anal. Calc. for C28H36Cl2N2O2Si2Ti2: C,
51.31; H, 5.54; N, 4.27. Found: C, 50.89; H, 5.44; N,
164.4 (ipso-tBupy), 156.4 (ipso-C6H4), 149.1 (tBupy),
147.6 (ipso-C6H4), 123.9 (C6H4), 123.8 (C6H4), 121.7
(tBupy), 111.7 (C6H4), 111.4 (C6H4) , 35.3 (tBupy-qua-
ternary), 30.3 (tBupy), ipso-C6H4 not observed.
1
3.86%. H-NMR (CDCl3): l 6.68 and 6.55 (AA% and
4.8. Preparation of
BB% parts of an AA%BB% spin system, 4H, C6H4), 6.27 (s,
5H, C5H5), 0.25 (s, 9H, SiMe3). 13C{1H}-NMR
(CDCl3): l 152.9 (ipso-C6H4), 149.3 (ipso-C6H4), 122.8
(C6H4), 119.8 (C6H4), 117.6 (C5H5), 0.2 (SiMe3).
29Si{1H}-NMR (CDCl3): l 12.2 (SiMe3). MS (70 eV,
EI): m/z: 654 [M+].
[NbCl3{NC6H4(p-OSiMe3)}(MeCN)2] (9)
A solution of NbCl5 (1.012 g, 3.75 mmol) in acetoni-
trile (20 ml) was added to 5 (1.22 g, 3.75 mmol) in
acetonitrile (20 ml) at r.t. The solution quickly changed
to a red color and was stirred for 24 h. Evaporation of
the solvent afforded crude material as a foamy red
solid, which was washed with hexane (2×20 ml), and
dried under vacuum to give 9 (1.51 g, 87%). Anal. Calc.
for C13H19 Cl3N3NbOSi: C, 33.90; H, 4.16; N, 9.12
Found: C, 33.80; H, 4.04; N, 8.71%. 1H-NMR (CDCl3):
l 7.26 and 6.71 (AA% and BB% parts of an AA%BB% spin
system, 4H, C6H4), 2.15 (br s, 6H, MeCN), 0.23 (s, 9H,
SiMe3). 13C{1H}-NMR (CD3CN): l 155.4 (ipso-C6H4,
other C-ipso not observed), 127.5 (C6H4), 120.8 (C6H4),
1.6 (CH3CN, signal for quaternary carbon of coordi-
nated CH3CN obscured by CD3CN at 118.20 ppm), 0.0
(SiMe3).
4.6. Preparation of [TiCl2{NC6H4(p-OSiMe3)}(py)3] (7)
A solution of 3 (1.37 g, 7.56 mmol) in CH2Cl2 (25 ml)
was added to another solution of [TiCl2(NtBu)(py)3]
(3.22 g, 7.56 mmol) in CH2Cl2 (25 ml) at r.t. The
solution turned to a darker red color and was stirred
overnight. After removal of the volatile products, the
resulting solid was washed with hexane (2×25 ml) and
dried in vacuo. Complex 7 (3.12 g, 77%) was thus
obtained as a brown–yellow powder. Anal. Calc. for
C24H28N4OSiCl2Ti: C, 53.84; H, 5.27; N, 10.46. Found:
C, 53.46; H, 5.32; N, 10.52%. 1H-NMR (CDCl3): l 9.07
(d, 4H, ortho-H of cis-py), 8.75 (br s, 2H, ortho-H of
trans-py), 7.76 (t, 2H, para-H of cis-py), 7.65 (br t, 1H,
para-H of trans-py), 7.31 (t, 4H, meta-H of cis-py),
7.19 (br t, 2H, meta-H of trans-py), 6.80 and 6.45 (AA%
and BB% parts of an AA%BB% spin system, 4H, C6H4),
0.15 (s, 9H, SiMe3). 13C{1H}-NMR (CDCl3): l 151.4
(ortho-C of cis-py), 150.6 (ortho-C of trans-py), 138.6
(para-C of cis-py), 136.8 (para-C of -trans-py), 124.7
(C6H4), 124.2 (meta-C of cis-py), 123.7 (meta-C of
trans-py), 119.2 (C6H4), 0.2 (SiMe3). 29Si{1H}-NMR
(CDCl3): SiMe3 not observed after 72 h at 99 Hz.
4.9. Preparation of
[Si{CH2CH2CH2SiMe2OC6H4(o-NH2)}4] (10)
The same procedure described below for 11 was
followed to synthesize the ortho-substituted 10, starting
from Ia (13.7 mmol) and CS–Cl (1.96 g, 3.43 mmol).
Compound 10 (1.90 g, 64%) was obtained as a spectro-
scopically pure yellow oil, but satisfactory microanaly-
1
sis failed likely due to residual LiCl. H-NMR (CDCl3):
l 6.8–6.5 (m, 4H, C6H4), 3.62 (br s, 2H, NH2), 1.40 (m,
2H, CH2CH2CH2), 0.81 (m, 2H, outermost SiCH2),
0.56 (m, 2H, innermost SiCH2), 0.23 (s, 6H, SiMe2).
13C{1H}-NMR (CDCl3): l 142.7 (ipso-C6H4), 138.1
(ipso-C6H4), 121.9 (C6H4), 118.4 (C6H4), 118.3 (C6H4),
115.6 (C6H4), 21.7 (CH2), 17.8 (CH2), 17.0 (CH2), −1.1
(SiMe2).
4.7. Preparation of
[TiCl2{OC6H4(o-NH)ꢀN,O}(tBupy)2] (8)
TiCl4 (0.6 ml, 5.5 mmol) was added to a mixture of 1
(1.00 g, 5.5 mmol), Et3N (1.6 ml, 11.5 mmol), and
4-tert-butylpyridine (tBupy) (1.7 ml, 11.5 mmol) in
CH2Cl2 (30 ml) at r.t. With the addition, the solution
warmed and changed to a dark violet color. Then, the
stirring was kept 48 h, the volatile products were re-
moved under reduced pressure and the residue was
washed with diethyl ether (20 ml) and extracted into
toluene. After partial solvent evaporation, complex 8
(2.05 g, 75%) precipitated at −20°C as a shiny dark
violet microcrystalline solid. Anal. Calc. for
C24H31N3OCl2Ti: C, 58.08; H, 6.30; N, 8.47. Found: C,
4.10. Preparation of
[Si{CH2CH2CH2SiMe2OC6H4(p-NH2)}4] (11)
Lithium phenoxide derivative Ib (16.8 mmol) was
prepared as described above and reacted in situ with
chlorocarbosilane CS–Cl (2.40 g, 4.20 mmol) in THF
(50 ml) at r.t. The resulting yellow solution was stirred
overnight, the solvent removed under vacuum, and the
residue extracted into CH2Cl2 (2×25 ml). Compound
11 (3.28 g, 91%) was obtained as a pale yellow oil by
evaporation of the solvent in vacuo to dryness. Anal.
Calc. for C44H72N4O4Si5: C, 61.34; H, 8.42; N, 6.50.
Found: C, 60.98; H, 8.88; N, 5.90%. MS (MADI-TOF):
1
57.45; H, 6.43; N, 7.97%. H-NMR (CDCl3): l 11.16
t
(br s, 1H, NH), 9.15 (d, 4H, Bupy), 7.50 (d, 4H,
tBupy), 6.60, 6.50, 6.17, and 5.78 (ABCD system, 4 H,
C6H4), 1.35 (s, 18 H, tBupy). 13C{1H}-NMR (CDCl3): l
m/z 883.3, Calc. [MNa+]: 883.4. H-NMR (CDCl3): l
1

48
J.M. Benito et al. / Journal of Organometallic Chemistry 610 (2000) 42–48
6.64 and 6.55 (AA% and BB% parts of an AA%BB% spin
system, 4H, C6H4), 3.42 (br s, 2H, NH2), 1.39 (m, 2H,
CH2CH2CH2), 0.76 (m, 2H, outermost SiCH2), 0.59 (m,
2H, innermost SiCH2), 0.19 (s, 6H, SiMe2). 13C{1H}-
NMR (CDCl3): l 147.2 (ipso-C6H4), 140.3 (ipso-C6H4),
120.3 (C6H4), 116.0 (C6H4), 21.1 (CH2), 17.5 (CH2),
16.7 (CH2), −1.5 (SiMe2). 29Si{1H}-NMR (CDCl3): l
14.9 (SiMe2), 1.0 (Si-core).
References
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4.11. Preparation of
[Si{CH2CH2CH2SiMe2OC6H4[p-NTiCl2(py)2]}4] (12)
A solution of 11 (0.82 g, 0.95 mmol) in CH2Cl2 (15
ml) was added to another solution of TiCl2(NtBu)(py)3
(1.62 g, 3.80 mmol) in CH2Cl2 (15 ml) at r.t. The
solution turned to a darker red color and was stirred
overnight. After removal of the volatile products, the
resulting solid was washed with pentane (2×15 ml),
dried in vacuo at 50°C, and extracted into toluene.
After partial solvent evaporation, compound 12 (1.07 g,
51%) precipitated at −20°C as a dark brown solid.
Anal. Calc. for C84H104N12O4Si5Cl8Ti4: C, 51.44; H,
5.34; N, 8.57. Found: C, 50.97; H, 5.68; N, 8.93%.
1H-NMR (CDCl3): l 9.07 (br s, 2H, ortho-py), 7.65 (t,
2H, para-py), 7.31 (m, 1H, meta-py), 6.79 and 6.44
(AA% and BB% parts of an AA%BB% spin system, 4H,
C6H4), 1.38 (m, 2H, CH2CH2CH2), 0.70 (m, 2H,
SiCH2), 0.54 (m, 2H, SiCH2), 0.11 (s, 6H, SiMe2).
13C{1H}-NMR (CDCl3): l 151.3 (ortho-py), 138.8
(para-py), 124.7 (C6H4), 124.2 (meta-py), 119.3 (C6H4),
21.4 (CH2), 17.7 (CH2), 17.0 (CH2), −1.3 (SiMe2),
ipso-C6H4 not observed.
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[10] [TiCl2{OC6H4(2-NH)-N,O}(py)2] 1H-NMR (CDCl3):
l 11.22
(br s, 1 H, NH), 9.29 (d, 4H, ortho-H of py), 7.94 (t, 2H,
para-H of py), 7.54 (t, 4H, meta-H of py), 6.53 (2 t overlap-
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We gratefully acknowledge financial support from
the Direccio´n General de Ensen˜anza Superior e Inves-
tigacio´n Cient´ıfica del Ministerio de Educacio´n y Cul-
tura (ref. PB97-0765), the University of Alcala´ (ref. no.
E020/98 and E040/99) and The Royal Society of Chem-
istry of UK (ref. SSL/vca).
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.