Modification of titanium isopropoxide with aromatic aldoximes

Article abstract of DOI:10.1002/ejic.201000881

Dimeric [Ti(OiPr)₂(benzaldoximate)₂]₂ was obtained upon reaction of titanium isopropoxide with two molar equivalents of benzaldehyde (E)- or (Z)-oxime or m-anisaldoxime. Two isomers were formed differing by the mutual orientation of the oximate ligands. Reaction with perillaldoxime or trans-cinnamaldoxime resulted in the corresponding derivatives with functional ligands. The degree of substitution was higher when o- or p-anisaldoxime were employed in the same molar ratio, and dimeric Ti ₂(OiPr)₃(o-anisaldoximate)₅ with a bridging oximate ligand and monomeric Ti(oximate)₄ (oximate = o-anisaldoximate or p-anisaldoximate) were obtained. Dissolution of the p-anisaldoximate derivative upon heating in [D₆]DMSO led to deoximation reactions.

Full text of DOI:10.1002/ejic.201000881

FULL PAPER
DOI: 10.1002/ejic.201000881
Modification of Titanium Isopropoxide with Aromatic Aldoximes
Stefan O. Baumann,[a] Maria Bendova,[a] Michael Puchberger,[a] and Ulrich Schubert*[a]
Keywords: Titanium / O ligands / Metal alkoxides / Bridging ligands
Dimeric [Ti(OiPr)2(benzaldoximate)2]2 was obtained upon re-
action of titanium isopropoxide with two molar equivalents
of benzaldehyde (E)- or (Z)-oxime or m-anisaldoxime. Two
isomers were formed differing by the mutual orientation of
the oximate ligands. Reaction with perillaldoxime or trans-
cinnamaldoxime resulted in the corresponding derivatives
with functional ligands. The degree of substitution was
higher when o- or p-anisaldoxime were employed in the
same molar ratio, and dimeric Ti2(OiPr)3(o-anisaldoximate)5
with a bridging oximate ligand and monomeric Ti(oximate)4
(oximate = o-anisaldoximate or p-anisaldoximate) were ob-
tained. Dissolution of the p-anisaldoximate derivative upon
heating in [D6]DMSO led to deoximation reactions.
mer 1” the oximate ligands are mirror-symmetric with re-
gard to the Ti2O2 plane. The N–Ti–N angle in this isomer
with an idealized C2h symmetry is 162–164°, and the Ti–
Ooximate bonds are nearly perpendicular to each other. The
Ci symmetric “isomer 2”-type compounds have a nearly lin-
ear N–Ti–Ooximate arrangement.
Introduction
The use of oximes as ligands for the complexation of
late transition metals has been investigated intensively. Less
attention, however, has been paid to oximate derivatives of
earlier transition metals. Addition products of oximes to
titanium halides were described in early literature, viz. TiF4-
(Me2C=NOH)2 formed by coordination of acetone oxime
to TiF4.[1] The dimethylglyoxime (dmgH2) adduct to TiCl4,
TiCl4(dmgH2)n, was converted into the oximate derivative
TiCl3(dmgH) by moderate heating.[2] Several alkoxide de-
rivatives Ti(OR)4–x(ON=CRЈRЈЈ)x (x = 1–4) have been re-
ported, but they were only characterized by infrared spec-
troscopy and elemental analysis.[3] The first structural
analysis of a titanium oximate derivative, with side-on coor-
dinated oximate ligand, was carried out by Thewalt et al.
for [Cp2Ti(H2O)(ON=CRЈRЈЈ)]+.[4] More recently, reaction
of Ti(OiPr)4 with salicylaldoxime resulted in a trinuclear
complex in which the oximate groups, as dianionic ligands,
bridge the three titanium centers.[5] In the same work, dinu-
clear complexes with side-on coordinated oximate ligands,
[Ti(μ-OiPr)(OiPr)(ON=CHRЈ)2]2, were obtained from the
reaction of Ti(OiPr)4 with pyridine-2-aldoxime. The latter
compounds are part of the structural family of oximate de-
rivatives described below.
Figure 1. Schematic structures of isomeric [Ti(OiPr)2(oximate)2]2
derivatives: “isomer 1” (left) and “isomer 2” (right).
Oximates are powerful ligands for the modification of
metal alkoxides. They are easily prepared, show versatile
coordination behavior, and, most notably, allow organic
functionalities in inorganic–organic hybrid materials to be
introduced. We have recently shown that sol–gel processing
of acetaldoximate-modified titanium alkoxides in the pres-
ence of the nonionic surfactants results in mesoporous ana-
tase with superior properties.[7] A simple example of “or-
ganic functionalization” is the use of long-chain oximate
derivatives with surfactant properties.[8]
We reported recently the synthesis and structures of di-
meric oximate derivatives with aliphatic ketoximate ligands,
[Ti(OiPr)2(oximate)2]2.[6] Disubstituted derivatives (two oxi-
mate ligands per titanium atom) were found even if a 1:1
ratio of Ti(OR)4 and oxime was employed. Two isomers
were observed (Figure 1), which differ by the mutual orien-
tation of the side-on coordinated oximate ligands. In “iso-
In this article we will show that derivatives Ti(OiPr)4–x
-
(oximate)x with xՆ2 can be isolated for reactions with aro-
matic aldoximes and that aromatic oximes allow easy intro-
duction of unsaturated organic groups. The ligands used in
this work are shown in Figure 2.
[a] Institute of Materials Chemistry,
Vienna University of Technology
Getreidemarkt 9, 1060 Wien, Austria
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S. O. Baumann, M. Bendova, M. Puchberger, U. Schubert
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Figure 2. Anisaldoxime (left), trans-cinnamaldoxime (center), and
perillaldoxime (right).
Results and Discussion
Reaction of Ti(OiPr)4 with benzaldehyde-(Z)-oxime
(2 equiv.) in CH2Cl2 at room temperature resulted in the
formation of
dimeric
[Ti(OiPr)2{benzaldehyde-(Z)-
oximate}2]2 (1). The molecular structure of 1 is of the “iso-
mer 1”-type (Figure 3). In contrast, “isomer 2”-type
[Ti(OiPr)2{benzaldehyde-(E)-oximate}2]2 (2) was obtained
from Ti(OiPr)4 and (E)-benzaldoxime (Figure 4). Only one
isomer crystallized exclusively in either case. As for the reac-
tions with aliphatic oximes,[6] there is no apparent corre-
lation of the formed isomer with the properties of the ap-
plied oxime. As the isomers interconvert in solution (see
below) the preferred crystallization of one isomer is obvi-
ously a crystal packing effect. The Ti–O and Ti–N bond
lengths of 1 and 2 (Table 1) are in the same range as that
of derivatives with aliphatic oximate ligands.[6] The alkoxido
bridges are asymmetric; the bridging Ti–O bond lengths
differ by up to 13 pm (in 1; see Table 1) with the longer Ti–
O distance trans to the terminal OiPr ligand. In all struc-
tures discussed in this article, the phenyl rings are coplanar
with the C=N–O groups, and oximate ligands bonded to
the same titanium atom are nearly coplanar with each
other.
Figure 4. Molecular structure of [Ti(OiPr)2{benzaldehyde-(E)-
oximate}2]2 (2).
tigated by NMR spectroscopy and serves as an example for
the other derivatives. As also observed for [Ti(OiPr)2-
(ON=C6H10)2]2,[6] signals corresponding to exchange of the
OiPr groups (δCH = 4.58 and 4.06 ppm) were present in the
EXSY spectrum (Figure 6). Furthermore, the oximate li-
gands are dynamic in solution; this can possibly be ex-
plained by interconversion of the two isomers (Figure 1).
Equilibria between derivatives with different degrees of sub-
stitution (see below) may also play a role. Such exchange
reactions were also observed for titanium alkoxides modi-
fied with other organic ligands, for example, amino alcohol-
ates[9] or β-diketonates.[10]
1H NMR spectroscopic experiments were performed be-
tween –80 and 80 °C to study the solution behavior and the
exchange of the ligands in 3 at different temperatures. As
shown in Figure 7, the signals of the OiPr and oximate li-
gands merge upon heating of the solution. For instance, the
room temperature signals of the OiPr methyl groups at δCH
3
= 0.98, 1.29, and 1.54 ppm coincide with a signal at δCH
=
3
1.26 ppm at 80 °C, whereas the signal corresponding to the
methine groups at δCH = 3.51 ppm sharpens upon heating
due to faster exchange reactions. In contrast, cooling leads
to splitting of the signals. Three sets of signals are present
for the methine protons of the isopropoxido ligands at tem-
peratures below 0 °C. This means that at low temperatures
the exchange of the ligands is blocked and each ligand can
be detected individually.
Figure 3. Molecular structure of [Ti(OiPr)2{benzaldehyde-(Z)-
oximate}2]2 (1).
Similar observations were made for amine adducts of ti-
1
tanium alkoxides.[11] The methine H NMR signal of di-
The same structure as that of 2 was found for crystalline meric [Ti(OiPr)4(NH2CH2Ph)]2 is averaged at room tem-
[Ti(OiPr)2(m-anisaldoximate)2]2 (3) obtained by the same perature. It splits into four signals when cooled to –80 °C,
reaction (Figure 5). The behavior of 3 in solution was inves- corresponding to the Ci symmetry of the complex.
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Modification of Titanium Isopropoxide with Aromatic Aldoximes
Table 1. Comparison of the Ti–O and Ti–N distances [pm] and N–Ti–O and N–Ti–N bond angles [°] in derivatives 1–4, 7, and 8 (atoms
with an asterisk are inversion related).
1
2
3
4
7
8
Ti1–O1
Ti1–O2
Ti1–O4
Ti1–O4*
Ti2–O4
197.2(3)
197.8(3)
210.6(7)
197.7(8)
197.43(13)
196.53(13)
207.37(12)
200.65(12)
197.7(2)
194.9(2)
206.6(2)
197.7(2)
196.7(3)
195.2(2)
200.7(2)
194.8(5)
197.3(5)
179.6(4)
208.8(4)
196.2(2)
195.5(2)
179.3(2)
205.9(2)
205.3(2)
Ti1–O5
Ti2–O5
209.7(2)
204.1(2)
Ti2–O6
Ti2–O7
195.4(3)
194.2(2)
Ti1–N1
Ti1–N2
208.6(3)
208.7(4)
206.45(14)
210.96(15)
206.2(2)
222.4(2)
206.3(3)
215.7(3)
217.6(5)
206.7(6)
208.0(3)
208.9(3)
Ti2–N4
Ti2–N5
209.7(3)
210.3(3)
O2–Ti1–N1
O1–Ti1–N2
O6–Ti2–N5
O7–Ti2–N4
N1–Ti1–N2
N4–Ti2–N5
124.93(14)
125.21(14)
94.51(6)
171.86(5)
90.10(8)
166.08(8)
91.94(11)
169.21(11)
124.90(11)
124.66(11)
130.67(12)
163.96(12)
167.24(19)
91.3(2)
125.41(11)
125.39(11)
163.59(15)
133.49(6)
127.86(8)
129.2(2)
164.24(12)
Figure 6. EXSY spectrum of 3 in [D8]toluene at room temperature.
Solvent signals are marked by asterisks.
Figure 5. Molecular structure of [Ti(OiPr)2(m-anisaldoximate)2]2
(3).
titanium atoms are not bridged by the NO group, but in-
stead only by the oxygen atom of the oximate. Another
Contrary to the reaction of Ti(OiPr)4 with m-anisaldox- noteworthy difference to the structures of 1–3 is that the
ime, where only 3 was isolated, compounds with a higher mutual orientation of the side-on coordinated oximate li-
degree of substitution were observed when o-anisaldoxime gands in the two halves of the compound are different.
was employed in the same molar ratio (Ti/oxime = 1:2). Whereas the angles around Ti1 are 169.2(1)° for O1–Ti1–
Due to the low solubility of o-anisaldoxime in CH2Cl2 an N2 and 91.9(1)° for O2–Ti1–N1, corresponding to “iso-
alternative solvent was used, viz. 1,2-dichloroethane. This mer 2”, Ti2 is coordinated as in the “isomer 1”-type com-
allowed higher reaction temperatures. Ti2(OiPr)3(o-anis- pounds with a N4–Ti2–N5 angle of 164.0(1)°. The Ti–O
aldoximate)5 (4, Figure 8) crystallized from a concentrated distances in the Ti2O2 ring are again asymmetric, the longer
solution. The increased temperature can be taken into ac- distances being trans to the terminal OiPr groups.
count for the higher degree of substitution.
Complete substitution of the OiPr ligands of Ti(OiPr)4
Compound 4 is formally derived from disubstituted com- against oximates was observed upon reaction with o- or p-
pounds 1–3 by replacing one of the bridging OiPr ligands anisaldoxime in dichloromethane. Because of its low solu-
with an oximate ligand. Different to Ti6O6(OiPr)6- bility in CH2Cl2 compared to that of the m- and p-isomers,
(ON=CR2)6 (CR2=CMe2 or C5H8),[6] for example, the two o-anisaldoxime was treated at elevated temperatures. For-
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S. O. Baumann, M. Bendova, M. Puchberger, U. Schubert
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be crystallized after minor modifications of the preparation
protocol.
In tetrasubstituted derivatives Ti(o-anisaldoximate)4 (5)
and Ti(p-anisaldoximate)4 (6), the titanium atoms are coor-
dinated by four oximate ligands (Figure 9), with the Ti–O
and Ti–N bond length in the same range as that in 1–4.
The oximate ligands are pairwise nearly coplanar with each
other, as in the structures discussed before, with a N1–Ti1–
O3 angle of 172.96(3)° (in 6, similar values in 5). The two
planes containing two oximate ligands each are nearly per-
pendicular to each other. The core of the complexes re-
sembles that of Ti(ONMe2)4 in contrast to S4-symmetric
Ti(ONEt2)4.[12,13]
Figure 7. Temperature-dependent 1H NMR spectra of 3 in [D8]tol-
uene from 80 °C (top) to –80 °C (bottom). Solvent signals are
marked by asterisks.
Figure 9. Molecular structure of Ti(p-anisaldoximate)4 (6). The two
molecules in the asymmetric unit of 5 have approximately the same
geometry. Ti1–O1 195.98(8), Ti1–O3 197.95(8), Ti1–N1 208.34(10),
Ti1–N2 205.61(10) pm; N1–Ti1–N1* 93.59(5), N2–Ti1–N2*
120.97(5), N1–Ti1–N2 89.13(4), N1–Ti1–N2* 133.60(4)°.
Because of the low solubility of the tetrasubstituted com-
pound 6 in common solvents at room temperature, the com-
pound was dissolved in [D6]DMSO at elevated tempera-
tures. Surprisingly, in the NMR spectra of the [D6]DMSO
solution (δ = 147.5 ppm for the carbon bearing the oximate
group) signals corresponding to the deoximation product
anisaldehyde and p-methoxybenzonitrile (Figure 10) were
observed in addition to the expected signals of the coordi-
nated oximate ligands; for example, 13C NMR resonances
at δ = 191.1 ppm for the carbonyl carbon of the aldehyde
and δ = 102.7 ppm for the nitrile carbon. The ratio of ox-
Figure 8. Molecular structure of Ti2(OiPr)3(o-anisaldoximate)5 (4).
mation of Ti(o-anisaldoximate)4 (5) was also observed in ime/aldehyde/nitrile was 2:1:1, as indicated by the corre-
1
1,2-dichloroethane solution, instead of 4, when the reaction sponding intensities in the H NMR spectrum. This ratio
solution was not concentrated before crystallization. This resembles almost exactly that reported for the photooxidat-
shows that compound 4 is just an intermediate stage on ive deoximation products when p-anisaldehyde oxime was
the way to the fully substituted derivatives and can only irradiated in the presence of quinone sensitizers.[14]
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Modification of Titanium Isopropoxide with Aromatic Aldoximes
box techniques. Ti(OiPr)4 (Acros, 98+%), (Z)-benzaldoxime (Ald-
rich, 97%), (E)-benzaldoxime (Aldrich, 97%), o-anisaldehyde
(ABCR, 98%), m-anisaldehyde (Aldrich, 98%), p-anisaldehyde (Al-
drich, 98%), trans-cinnamaldehyde (ABCR, 98%), and (S)-(–)-per-
illaldehyde (Aldrich, 92%) were used as received. All solvents were
dried and purified by standard methods.[15] The solvents for NMR
spectroscopy (Eurisotop) were degassed prior to use and stored
1
over molecular sieves. H and 13C solution NMR spectra were re-
corded with a Bruker Avance 250 (250.13 MHz {1H}, 62.86 MHz
{13C}) and a Bruker DPX 300 spectrometer (300.13 MHz {1H},
75.47 MHz {13C}, 30.38 MHz {15N}) equipped with a 5-mm in-
verse-broadband probe head and a z-gradient unit. 2D NMR spec-
tra were measured with Bruker standard pulse programs COSY
(correlation spectroscopy), TOCSY (total correlation spec-
troscopy), EXSY (exchange spectroscopy, tmix = 1 s), HSQC (het-
eronuclear single quantum correlation), and HMBC (heteronuclear
multiple-bond correlation). Solid-state 13C and 15N NMR spectra
of 6 were recorded with a Bruker Avance 300 [75.40 MHz (13C),
30.38 MHz (15N), δN(NH4Cl) = 0 ppm] equipped with a 4-mm
broadband MAS probe head. 13C NMR spectra were recorded with
ramped CP/MAS spectra (cross-polarization and magic angle spin-
ning) with a rotor spinning speed of 6–8 kHz. The numeric labels
of the carbon atoms refer to the phenyl groups, where C1 is the
ipso carbon atom. Due to the tendency of the complexes to hy-
drolyze, reliable elemental analysis could not be obtained for 1–4,
7, and 8.
Figure 10. HMBC spectrum of the [D]6DMSO solution of 6 heated
to 100 °C. The signals referring to p-anisaldoxime are marked with
full circles, those corresponding to the decomposition products are
marked with open circles (p-anisaldehyde) and squares (4-methoxy-
benzonitrile).
One of the advantages of using oximes for the modifica-
tion of metal alkoxides is that derivatives with functional
groups are easily accessible. The latter are required for the
preparation of inorganic–organic hybrid materials by sol–
gel processing. As examples, Ti(OiPr)4 was treated with the
oximes of two ligands bearing double bonds, viz. perill-
aldoxime and trans-cinnamaldoxime (Figure 2). Both
[Ti(OiPr)2(perillaldoximate)2]2 (7) and [Ti(OiPr)2(trans-
cinnamaldoximate)2]2 (8) were obtained as crystalline sol-
Synthesis of the Anisaldoximes: Anisaldehyde oximes were synthe-
sized as (E)-isomers from the corresponding aldehydes and hydrox-
ylamine hydrochloride by modification of the procedure described
by Bousquet.[16] In a typical synthesis, NH2OH·HCl (7.14 g,
102.7 mmol) was dissolved in H2O (12 mL) and cooled to 5 °C; p-
anisaldehyde (10.0 mL, 82.2 mmol) was then added while stirring.
A solution of Na2CO3 (5.44 g, 51.4 mmol) in deionized water
(20 mL) was added dropwise while the reaction mixture was stirred
ids. The solid-state structures are of “isomer 2”-type for 7 in an ice/water mixture. After stirring overnight at room tempera-
ture, the product was extracted with several portions of CHCl3.
The combined CHCl3 solutions were dried with Na2SO4. Evapora-
tion of the solvent yielded p-anisaldoxime (11.2 g, 73.9 mmol,
90%).
and “isomer 1”-type for 8.
Conclusions
[Ti(OiPr)2{benzaldehyde-(Z)-oximate}2]2 (1): To a solution of benz-
aldehyde-(Z)-oxime (420 mg, 3.47 mmol) in CH2Cl2 (0.40 mL) at
room temperature was dropwise added Ti(OiPr)4 (490 mg,
1.72 mmol). The reaction mixture was stirred for 10 min. Colorless
crystals of 1 (535 mg, 81%) were obtained from the yellow solution
after 2 h. They were recrystallized from CH2Cl2, washed with sev-
eral portions of n-pentane at –20 °C, and dried in vacuo. 1H NMR
(250 MHz, CDCl3): δ = 1.18 [m, 6 H, CH(CH3)2], 3.96/4.51 (m, 1
H, CHMe2), 7.28 (m, 3 H, C3–5H), 7.54/7.70 (d, J = 6.7 Hz, 2 H,
The room-temperature reactions of Ti(OiPr)4 with dif-
ferent stereoisomers of benzaldoximes yielded dimeric com-
plexes [Ti(OiPr)2(benzaldoximate)2]2. There is no apparent
correlation between the formed isomer and the oxime. Solu-
tion NMR spectroscopy revealed ligand exchange, which
can be explained by equilibration of the two isomeric forms.
Higher reaction temperatures led to the formation of
more highly substituted titanium alkoxide derivatives, as in-
vestigated by using anisaldoximes for the modification.
Products with substitution degrees ranging from 2 over 2.5
to 4 were obtained depending on the position of the meth-
oxy group at the aromatic ring and on the applied tempera-
ture. Whereas solution NMR spectroscopy confirmed the
results of X-ray structure analyses, deoximation products
C
2,6H), 8.24 (s, 1 H, CHN) ppm. 13C NMR (250 MHz, CDCl3): δ
= 26.1 [CH(CH3)2], 77.2 (CHMe2), 127.1 (C2,6), 128.8 (C3,5), 129.8
(C4), 132.0 (C1), 141.4 (C=N) ppm.
[Ti(OiPr)2{benzaldehyde-(E)-oximate}2]2 (2): To a solution of benz-
aldehyde-(E)-oxime (870 mg, 7.18 mmol) in CH2Cl2 (1.10 mL) at
room temperature was dropwise added Ti(OiPr)4 (1.02 g
3.58 mmol). The reaction mixture was stirred for 1 min. Colorless
were also observed when the sparingly soluble Ti(p-anis- crystals of 2 (1.39 g, 95%) were obtained from the yellow solution
after 1 d. They were washed with several portions of n-pentane at
–20 °C and dried in vacuo. H NMR (250 MHz, CDCl3): δ = 1.14
aldoximate)4 was heated in [D6]DMSO.
1
[m, 6 H, CH(CH3)2], 3.97/4.49 [m, 1 H, CH(CH3)2], 7.26 (m, 3 H,
C
3–5H), 7.53/7.69 (d, J = 6.7 Hz, 2 H, C2,6H), 8.21 (s, 1 H, CHN)
Experimental Section
ppm. 13C NMR (250 MHz, CDCl3): δ = 25.8 [CH(CH3)2], 77.2
(CHMe2), 127.1 (C2,6), 128.8 (C3,5), 129.8 (C4), 132.0 (C1), 141.4
(C=N) ppm.
General Procedures: All operations were carried out under a moist-
ure- and oxygen-free argon atmosphere by using Schlenk and glove
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[Ti(OiPr)2(m-anisaldoximate)2]2 (3): To solution of m-anisaldoxime
(664 mg, 4.39 mmol) in CH2Cl2 (0.70 mL) at room temperature was
dropwise added Ti(OiPr)4 (624 mg, 2.19 mmol). The reaction mix-
ture was stirred for 1 min. Colorless crystals of 3 (866 mg, 83%)
were obtained from the yellow solution after 3 d. They were washed
with several portions of n-pentane at –20 °C and dried in vacuo. 1H
precipitate were obtained. NMR spectra of the solution were re-
corded (ox, ald, and nitr refer to anisaldoxime, anisaldehyde, and
4-methoxybenzonitrile, respectively). 1H NMR (250 MHz, [D]6-
DMSO): δ = 11.37 (s, 2 H, NOH), 11.08 (s, 1 H, CHO), 10.95 (s,
2 H, CHN), 7.87 (d, J = 8.9 Hz, 2 H, Cald2,6H), 7.77 (d, J = 8.7 Hz,
2 H, Cnitr2,6H), 7.52 (d, J = 8.7 Hz, 4 H, Cox2,6H), 7.12 (d, J =
NMR (250 MHz, CDCl3): δ = 1.18 [d, J = 5.8 Hz, 6 H, CH(CH3)2], 8.9 Hz, 2 H, Cald2,6H), 7.10 (d, J = 8.9 Hz, 2 H, Cnitr3,5H), 6.96 (d,
3.74 (s, 3 H, OCH3), 3.71/4.49 [m, 1 H, CH(CH3)2], 6.82 (d, J =
J = 8.7 Hz, 4 H, Cox3,5H), 3.86 (s, 3 H, CaldH3), 3.84 (s, 3 H,
nitrH3), 3.77 (s, 6 H, CoxH3) ppm. 13C NMR (75.40 MHz, [D]6-
DMSO): δ = 191.1 (Cald=O), 164.5 (Cald4), 164.5 (Cnitr4), 160.4
8.0 Hz, 1 H, C4H), 7.07 (t, J = 7.9 Hz, 1 H, C2H), 7.19 (m, 2 H,
C
C
5,6H), 8.19 (s, 1 H, CHN) ppm. 13C NMR (250 MHz, CDCl3): δ
= 26.0 [CH(CH3)2], 55.3 (OCH3), 77.2 (CHMe2), 111.0 (C2), 116.5 (Cox4), 147.9 (Cox=N), 134.6 (Cnitr2,6), 132.2 (Cald2,6), 129.8 (Cnitr1),
(C4), 120.1 (C6), 129.7 (C5), 133.4 (C1), 141.5 (C=N), 159.9 (C3) 128.3 (Cox2,6), 125.8 (Cox1), 124.6 (Cald1), 115.3 (Cald3,5), 115.2
ppm.
(Cnitr3,5), 114.3 (Cox3,5), 102.7 (CnitrϵN), 56.1 (OCaldH3), 56.1 (OC-
nitrH3), 55.6 (OCoxH3) ppm.
Ti2(OiPr)3(o-anisaldoximate)5 (4): To solution of o-anisaldehyde
oxime (736 mg, 4.87 mmol) in 1,2-dichloroethane (4.0 mL) at room
temperature was dropwise added Ti(OiPr)4 (0.691 g, 2.43 mmol).
The reaction mixture was heated at reflux for 5 min and then re-
duced to half of its volume in vacuo. Colorless crystals of 4 (1.25 g,
64%) were obtained from the yellow solution after 1 d at 30 °C.
They were washed with several portions of n-pentane at –20 °C and
dried in vacuo. 1H NMR (250 MHz, CDCl3): δ = 1.14 [d, J =
6.2 Hz, 18 H, CH(CH3)2], 3.79 (s, 15 H, OCH3), 3.66/3.96 [m, 3 H,
CH(CH3)2], 6.88 (q, J = 7.7 Hz, 5 H, C5H), 7.27 (d, J = 8.2 Hz, 5
H, C3H), 7.51 (m, 5 H, C4H), 7.64 (d, J = 7.6 Hz, 5 H, C6H), 8.43/
8.63 (s, 5 H, CHN) ppm. 13C NMR (250 MHz, CDCl3): δ = 25.3
[CH(CH3)2], 55.5 (OCH3), 77.2 (CHMe2), 111.1 (C3), 120.6 (C1),
120.8 (C5), 126.8 (C6), 131.2 (C4), 146.7 (C=N), 159.9 (C2) ppm.
[Ti(OiPr)2(perillaldoximate)2]2 (7): To a solution of perillaldehyde
oxime (429 mg, 2.60 mmol) in dichloromethane (0.42 mL) at room
temperature was dropwise added titanium isopropoxide (365 mg,
1.28 mmol). The dark yellow reaction mixture was stirred for
5 min. Colorless crystals of 7 (178 mg, 30%) were obtained from
the yellow solution after 10 d. The crystals were washed with sev-
1
eral portions of n-pentane at –20 °C and dried in vacuo. H NMR
(250 MHz, CDCl3): δ = 7.84 (s, 1 H, CHN), 6.02 (s, 1 H, C2H),
4.68 (s, 2 H, CMeCH2), 4.49 (m, 1 H, CHMe2), 2.63–2.09 (m, 5 H,
C
3,5,6H), 1.82 (d, J = 6.0 Hz, 1 H, C4H), 1.68 [s, 1 H, C(CH3)CH2],
1.42 (m, 1 H, C5H), 1.18 [d, J = 5.4 Hz, 6 H, CH(CH3)2] ppm. 13
C
NMR (13C CP/MAS, 75.40 MHz): δ = 149.0 (C=N), 143.8 (C6),
134.8 (CMeCH2), 133.0 (C1), 109.1 (CMeCH2), 77.2 (CHMe2),
40.8 (C4), 31.4 (C5), 26.9 (C3), 26.8 [CH(CH3)2], 23.9 (C2), 20.7
[C(CH3)CH2] ppm.
Ti(o-anisaldoximate)4 (5)
Method A: To solution of o-anisaldehyde oxime (748 mg,
4.95 mmol) in CH2Cl2 (2.0 mL) at room temperature was dropwise
added Ti(OiPr)4 (701 mg, 2.47 mmol). A whitish solid precipitated
from the yellow solution after 1 min of stirring at room tempera-
ture. Recrystallization from hot CH2Cl2 gave colorless crystals of 5
(482 mg, 30%) after 1 d. They were washed with several portions
of n-pentane at –20 °C and dried in vacuo.
[Ti(OiPr)2(trans-cinnamaldoximate)2]2 (8): To a mixture of cinnam-
aldehyde oxime (231 mg, 1.57 mmol) in toluene (20 mL) at room
temperature was dropwise added Ti(OiPr)4 (221 mg, 777 μmol), re-
sulting in complete dissolution of the oxime and yellow discolor-
ation. The reaction mixture was stirred for 5 min. The yellow solid
foam obtained after removal of the solvent was recrystallized from
CH2Cl2. Colorless crystals of 8 (122 mg, 34%) were obtained from
the yellow solution after 12 d. The crystals were washed with sev-
Method B: To solution of o-anisaldehyde oxime (1.65 g, 10.9 mmol)
in 1,2-dichloroethane (9.0 mL) at room temperature was dropwise
added Ti(OiPr)4 (1.54 g 5.40 mmol). The reaction mixture was
heated at reflux for 5 min. Colorless crystals of 5 (1.21 g, 35%)
were obtained from the yellow solution upon slow cooling to room
temperature after 5 h. They were washed with several portions of
n-pentane at –20 °C and dried in vacuo. C32H32N4O8Ti (648.52):
1
eral portions of n-pentane at –20 °C and dried in vacuo. H NMR
(250 MHz, CDCl3): δ = 7.95 (s, 1 H, CHN), 7.31–7.54 (m, 5 H,
C
2–6H), 7.26 (s, 1 H, CH–CH–CH=N), 6.86 (s, 1 H, CH–CH–
CH=N), 4.49/3.96 [q, J = 5.4 Hz, 1 H, CH(CH3)2], 1.14 [m, 6 H,
CH(CH3)2] ppm. 13C NMR (13C CP/MAS, 75.40 MHz): δ = 150.8
(CH–CH-CH=N), 142.9 (C=N), 132.0 (C1), 130.9 (CH-CH=N),
128.9 (C3,5), 128.8 (C4), 128.7 (C2,6), 77.2 [CH(CH3)2], 25.4
[CH(CH3)2] ppm.
1
calcd. C 59.27, H 4.97, N 8.64; found C 57.70, H 4.90, N 8.25. H
NMR (250 MHz, CDCl3): δ = 3.70 (s, 3 H, OCH3), 6.66 (t, J =
7.1 Hz, 1 H, C5H), 6.78 (d, J = 7.6 Hz, 1 H, C3H), 7.18 (m, 1 H,
C4H), 8.09 (d, J = 6.2 Hz, 1 H, C6H), 8.62 (s, 1 H, CHN) ppm.
13C NMR (250 MHz, CDCl3): δ = 55.6 (OCH3), 111.1 (C3), 120.7
(C1), 121.0 (C5), 127.1 (C6), 131.1 (C4), 137.0 (C=N), 157.2 (C2)
ppm.
X-ray Structure Analyses: Single-crystal X-ray diffraction measure-
ments were performed with a Bruker AXS SMART and a Bruker-
AXS KAPPA APEX II diffractometer with CCD area detectors
and a crystal-to-detector distance of 5.5 cm by using graphite-mo-
nochromated Mo-Kα radiation (λ = 71.073 pm; Table 2). The data
collection at 100 K in a stream of cold nitrogen covered at least a
hemisphere of the reciprocal space by recording three or more sets
of exposures, each of them exhibiting a different Φ angle. The times
for each exposure were 5 to 20 s, each of them covering 0.3° in ω.
The data were corrected for polarization and Lorentz effects, and
an empirical absorption correction (SADABS) was applied. The
structures were solved with direct methods (SHELXS97) and re-
Ti(p-anisaldoximate)4 (6): To solution of p-anisaldehyde oxime
(532 mg, 3.52 mmol) in dichloromethane (2.00 mL) at room tem-
perature was dropwise added Ti(OiPr)4 (499 mg 1.76 mmol). The
reaction mixture was stirred for 1 min. Yellow crystals of 6 (34 mg,
5.4%) were obtained from the yellow solution after 1 h. They were
washed with several portions of n-pentane at –20 °C and dried in
vacuo. C32H32N4O8Ti (648.52): calcd. C 59.27, H 4.97, N 8.64;
found C 58.55, H 4.75, N 8.50. 13C NMR (13C CP/MAS,
75.40 MHz): δ = 153.1 (C4), 130.2 (C=N), 116.5 (C1), 109.1 (C2,6), finement to convergence was carried out with the full-matrix least-
102.3 (C3,5), 46.3/47.9 (OCH3) ppm. 15N NMR (15N MAS, squares method based on F2 (SHELXL97) with anisotropic struc-
30.39 MHz): δ = 291.5, 286.9 (C=N) ppm. An amount of 6 (24 mg)
was dissolved in [D]6DMSO (0.60 mL) in a Young tube. The mix-
ture was heated to 100 °C for 3 d. A yellow solution and a whitish
ture parameters for all non-hydrogen atoms. The hydrogen atoms
were placed on calculated positions and refined riding on their par-
ent atoms. In the crystal structure of 1 the whole molecule is disor-
578
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 573–580

Modification of Titanium Isopropoxide with Aromatic Aldoximes
Table 2. Crystallographic and structural parameters of 1–8.
1
2
3
4·2C2H4Cl2
Empirical formula
Formula weight
Crystal system
Space group
a [pm]
b [pm]
c [pm]
C40H52N4O8Ti2
812.66
orthorhombic
Pbca
1062.88(4)
1851.29(7)
2138.50(10)
C40H52N4O8Ti2
812.66
monoclinic
C2/c
2776.3(3)
961.90(11)
2002.1(4)
C44H60N4O12Ti2
932.76
C53H69Cl4N5O13Ti2
1221.73
triclinic
triclinic
¯
¯
P1
P1
999.78(12)
1129.38(14)
1217.86(15)
75.046(2)
68.727(2)
66.048(2)
1161.1(2)
1
1366.5(3)
1409.8(3)
1608.9(3)
78.646(3)
89.398(3)
76.148(3)
2948.3(11)
2
α [°]
β [°]
γ [°]
130.692(1)
Volume [ϫ106 pm3]
Z
4207.9(3)
4
1.283
4054.1(11)
4
1.331
Calcd. density [gcm–3]
1.334
0.408
1.376
0.516
μ [mm–1]
0.433
0.449
Crystal size [mm]
Θ range [°]
0.30ϫ0.30ϫ0.25
2.40–28.29
30122/5219
5219/488
0.990
0.071
0.184
0.57ϫ0.43ϫ0.34
2.33–28.34
25893/5043
5043/248
1.091
0.039
0.108
0.57ϫ0.43ϫ0.34
2.86–24.99
6099/3967
3967/286
1.107
0.040
0.107
0.42ϫ0.32ϫ0.17
2.14–25.00
15875/10296
10296/819
1.104
0.064
0.191
Reflections coll./unique
Data/parameters
GOF on F2
R [IϾ2σ(I)]
wR2
Largest diff. peak/hole [eÅ–3]
0.431/–0.295
0.621/–0.384
0.684/–0.330
1.036/–1.681
5
6
7
8
Empirical formula
Formula weight
Crystal system
Space group
a [pm]
b [pm]
c [pm]
C32H32N4O8Ti
648.52
C32H32N4O8Ti
648.52
monoclinic
C2/c
2162.48(14)
743.30(5)
1950.20(13)
C52H80N4O8Ti2
985.00
C48H60N4O8Ti2
916.80
monoclinic
C2/c
3641.1(3)
1394.49(11)
1903.60(13)
triclinic
triclinic
¯
¯
P1
P1
1500.3(3)
1602.0(3)
1621.7(3)
107.159(3)
102.799(3)
115.148(3)
3088.2(11)
4
1028.2(3)
1049.2(4)
1296.7(4)
85.293(5)
73.388(5)
89.671(5)
1335.7(8)
1
α [°]
β [°]
γ [°]
97.912(1)
99.326(2)
Volume [ϫ106 pm3]
Z
3104.9(4)
4
1.387
9537.7(12)
8
1.277
Calcd. density [gcm–3]
1.395
0.335
1.225
0.352
μ [mm–1]
0.333
0.390
Crystal size [mm]
Θ range [°]
0.25ϫ0.20ϫ0.12
1.59–25.00
31593/10827
10827/819
1.068
0.060
0.171
0.40ϫ0.40ϫ0.20
2.64–28.29
14737/3844
3844/206
1.031
0.033
0.089
0.22ϫ0.20ϫ0.10
2.65–24.49
7233/4281
4281/342
1.065
0.083
0.216
0.56ϫ0.21ϫ0.19
2.17–24.97
18660/6552
6552/567
1.010
0.053
0.120
Reflections coll./unique
Data/parameters
GOF on F2
R [IϾ2σ(I)]
wR2
Largest diff. peak/hole [eÅ–3]
0.823/–0.587
0.446/–0.321
0.893/–0.449
0.632/–0.393
[2]
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Acknowledgments
This work was supported by the Austrian Fonds zur Förderung der
wissenschaftlichen Forschung (FWF) (Project P20750). The au-
thors thank Michael Fugger for supporting experimental work.
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579

S. O. Baumann, M. Bendova, M. Puchberger, U. Schubert
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Published Online: December 12, 2010
580
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 573–580