Oxotitanium(IV) and dichlorotitanium(IV) complexes with tetradentate Schiff bases

Article abstract of DOI:10.1016/S0020-1693(00)00142-0

Attempts to prepare [TiO(salen)] (H₂salen = 1,2-HOC₆H₄CH=NCH₂CH₂N=CHC₆H₄OH-1,2) and its homologues, analogues of the well known complexes related to [VO(salen)] were only partially successful, in that all the products appear to be polymeric rather than mononuclear, and no crystalline materials were obtained. Homologues of [TiCl₂(salen)] were similarly difficult to obtain pure, though we determined a crystal structure for [TiCl₂(1,2-OC₆H₄CMe=NCH₂CH₂N=CMeC₆H₄O-1,2)]. This has the expected octahedral coordination, though in common with many such materials, there are molecules of solvent, thf and toluene, within the crystal. This complicates characterisation on the basis of microanalysis. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(00)00142-0

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Inorganica Chimica Acta 306 (2000) 24–29
Oxotitanium(IV) and dichlorotitanium(IV) complexes with
tetradentate Schiff bases
Nosheen F. Choudhary, Peter B. Hitchcock, G. Jeffery Leigh *
School of Chemistry, Physics and En6ironmental Science, Uni6ersity of Sussex, Brighton, BN1 9QJ, UK
Received 24 January 2000; accepted 10 March 2000
Abstract
Attempts to prepare [TiO(salen)] (H2salen=1,2-HOC6H4CHꢀNCH2CH2NꢀCHC6H4OH-1,2) and its homologues, analogues of
the well known complexes related to [VO(salen)] were only partially successful, in that all the products appear to be polymeric
rather than mononuclear, and no crystalline materials were obtained. Homologues of [TiCl2(salen)] were similarly difficult to
obtain pure, though we determined a crystal structure for [TiCl2(1,2-OC6H4CMeꢀNCH2CH2NꢀCMeC6H4O-1,2)]. This has the
expected octahedral coordination, though in common with many such materials, there are molecules of solvent, thf and toluene,
within the crystal. This complicates characterisation on the basis of microanalysis. © 2000 Elsevier Science S.A. All rights
reserved.
Keywords: Crystal structures; Titanium complexes; Oxo complexes; Schiff base complexes
1. Introduction
H2{salphen(3-OMe)2} in methanol. The authors mis-
takenly assigned w(TiꢀO) to broad absorptions at 1090
cm−1 but these probably arise from perchlorate
stretches. These complexes actually contain an addi-
tional equivalent of acid per mole of complex, e.g.
[TiO(salen)]·HClO4 [7] and two interconvertible forms
were isolated. They seem not to be five-coordinate
complexes akin to [VO(salen)].
A further series of oxotitanium(IV) tetradentate
Schiff base complexes was obtained [7] by reaction of
[{TiO(acac)2}2] with the Schiff bases in methanol. These
showed no band assignable to w(TiꢀO) in the region
1100–900 cm−1 and are yellow, insoluble solids, proba-
bly polymeric. Typical complexes, such as [TiO(sa-
lophen)]·MeOH and [TiO(salen)]·1/2MeOH, are easily
converted into the former compounds by treatment
with an aqueous solution of the appropriate acid,
though the converse transformation was not possible.
Recently Floriani and co-workers isolated the first
example of a linear polytitanoxane [8], prepared from
[TiCl(salen)(thf)]. The crystal contains linear tetranu-
clear cations [{Ti(salen)}4(m-O)3]2+, linked in an infinite
chain via a titaniumꢁoxygen (phenolate) bonds to
neighbouring cation as in [{V(salen)}4(m-O)3][BPh4]2,
isolated by Leigh and co-workers [9].
Oxovanadium(IV) compounds have been extensively
investigated and the chemistry of vanadium in oxida-
tion states IV and V is really dominated by such species
[1], whereas oxotitanium(IV) analogues are much less
well defined [2]. The titanyl(IV) group is very labile and
readily opens to form polymeric materials, based upon
···TiꢁOꢁTiꢁO··· chains. Some examples of stable TiꢀO
bonds are known, such as in [TiOCl2(NMe3)2] and
[TiOCl4]2−, but these are exceptional [3,4]. Further-
more, [VO(acac)2] is highly soluble in most common
organic solvents, but [{TiO(acac)2}2] is an insoluble
orange powder. We have reported at some length [5] on
vanadyl complexes containing the dianions derived
from potentially tetradentate proligands based upon a
selection of diamines, and here we describe some pre-
liminary experiments on the formally analogous deriva-
tives of titanium(IV).
The first examples [6] of oxotitanium(IV) tetradentate
Schiff base complexes were prepared as dark microcrys-
talline solids, soluble in dmf and dmso, from the reac-
tion of titanyl perchlorate with either H2(salphen) or
* Corresponding author.
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(00)00142-0

N.F. Choudhary et al. / Inorganica Chimica Acta 306 (2000) 24–29
25
niumꢁoxygen stretch is assigned to a broad absorption
in the 800–910 cm−1 region, though the yellow com-
plex formed from H2(hap-1,2-pn) and di(isopropoxo)-
bis(pentane-2,4-dionato)titanium showed no obvious
band assignable to w(TiꢀO).
Oxotitanium(IV) Schiff base complexes differ from
the oxovanadium(IV) Schiff base complexes described
earlier in having a d0 configuration, and are therefore
diamagnetic. They should be amenable to NMR stud-
ies, but their poor solubilities makes this difficult to
realise. Furthermore, neither H2(hapen) nor H2(hap-
1,3-pn) appeared to react despite heating the reaction
mixtures under reflux for long periods. In contrast, the
analogous vanadium complexes, [VO(hapen)] and
[VO(hap-1,3-pn)] were readily synthesised [14], al-
though we were unable to prepare [VO(hap-1,3-pn)] in
a pure form.
Formation of the oxotitanium(IV) tetradentate Schiff
base complexes was confirmed by their mass spectra.
The poor solubilities of these complexes suggests that
they are polymeric, and it is evident that Ti(IV) Schiff
base complexes prefer to be six coordinate, rather than
five coordinate. The microanalyses of all complexes
prepared are also in poor agreement with the required
values, with the exception of [TiO(sal-1,3-pn)] and
[TiO(sal-1,2-pn)], which were isolated with solvent of
crystallisation. It is not clear in general what the impu-
rities might be.
The titanium compound trans-[TiCl2(salen)] is not
clearly defined though the vanadium analogues trans-
[VX2(salen)] (X=Cl, Br, or I) [10] are well known. The
red complex cis-[TiCl2(salen)] was first prepared by
reaction of H2(salen) with titanium tetrachloride in
ethanol [11]. The salophen derivative was also de-
scribed. Ghose and Lasisi then extended this work to a
wider range of tetradentate Schiff bases [12]. However,
the [TiCl2(salen)] reported in their work is pale yellow
rather than the red we found, though the microanalyses
were consistent with this formulation. [TiCl2(salen)] was
later isolated by Gilli and Cruickshank from the reac-
tion of [TiCl3(thf)3] with H2(salen) in tetrahydrofuran
[13]. They were attempting to isolate the TiIII complex
[Ti(salen)Cl], but the green solid isolated changed to
red after 12 h. This red material, recrystallised from
tetrahydrofuran and characterised by X-ray diffraction
studies, was shown to be trans-[TiCl2(salen)]·thf. The
analogous TiIV complex from H2(salphen) is a brown
solid.
In this paper we also present some new data on
complexes [TiCl2(L)] (L=tetradentate Schiff base
dianion).
2. Results and discussion
Following the method of Biradar et al. [5,11], we
formed oxotitanium(IV) tetradentate Schiff base com-
plexes by heating equimolar amounts of the soluble
di(isopropoxo)bis(pentane-2,4-dionato)titanium and the
Schiff base in methanol, acetonitrile, or dichloro-
methane under reflux, from 4 h to 3.5 days. The
products were then isolated by concentrating the or-
ange solutions and precipitating them as yellow pow-
ders by addition of diethyl ether.
A series of additional formally titanyl(IV) complexes
was prepared. Their poor solubilities in organic solvents
has meant that we were unable to isolate crystals
suitable for X-ray diffraction studies, nor, indeed, for
NMR studies. To date there is no example of a crystal-
lographically characterised mononuclear or polynuclear
oxotitanium(IV) tetradentate Schiff base complex of the
type [TiO(L)].
These Schiff bases dianions coordinate in the equato-
rial via both phenolate oxygen and imine nitrogen
groups and remain quasi-planar. The coordination via
imine nitrogen in the present compounds is inferred by
comparison of the IR spectra with those of the proli-
gands. All except one show a reduction in w(CꢀN). The
exception to this is the compound formed from
H2{salen(3-OMe)2} and di(isopropoxo)bis(pentane-2,4-
dionato) titanium, which shows w(CꢀN) 6 cm−1 higher
than w(CꢀN) in the proligand, implying that nitrogen is
not coordinated in this compound. The tita-
In addition to the materials firmly identified (see
Section 4), reactions were also carried out between
di(isopropoxo)bis(pentane-2,4-dionato)titanium
and
H2{salen(3,5-Cl2)2} and H2{salen(5-Br)2}. The reactions
in methanol at reflux give highly insoluble mustard
powders with a strong absorption band at 869 cm−1 in
the first case and at 824 cm−1 in the second. These
were assigned to w(TiꢀO). The FAB mass spectra of the
products were uninformative, due to the poor solubility
in the 3-nitrobenzyl alcohol matrix. The EI mass spec-
tra show ions at m/z=463 and 483 both five mass units
less than those of the expected parent ions. We are
unable to explain this. However the isotopic distribu-
tion suggested that the ion at 463 from [TiO{salen(3,5-
Cl2)2] contains four chlorine atoms, as expected. The
microanalyses were in poor agreement with the required
values. The IR spectrum of the second product shows
w(CꢀN) is at 1640 cm−1, unchanged from the value in
the proligand, and implying that coordination to tita-
nium may not be via the imine nitrogen atoms.
A
similar reaction between di(isopropoxo)bis-
(pentane-2,4-dionato)titanium and H2{salen(5-Br)2}but
in acetonitrile gave a brick red solid in 66% yield. The
EI mass spectrum of this product shows an ion at
m/z=488, relative intensity 63%, consistent with
[TiO{salen(5-Br)2}]+. There are also ions at m/z=486,

26
N.F. Choudhary et al. / Inorganica Chimica Acta 306 (2000) 24–29
sion was heated under reflux, reduced to dryness and
the crude product washed with a 1:1 mixture of acetone
and water and rapidly filtered in air to remove any
residual traces of hydrochloric acid. Whilst this method
worked well for both [TiCl2(salen)] and [TiCl2{salen(3-
OMe)2}], washing the crude red products containing
[TiCl2(hapen)] and [TiCl2(hapnptn)] with an acetone–
water mixture led to decomposition.
All four complexes prepared were isolated as brick
red powders in high yield. The IR spectra showed a
reduction in w(CꢀN) compared to w(CꢀN) in the proli-
gand, consistent with co ordination to titanium via
imine nitrogen. The three complexes [TiCl2{salen-
(3-OMe)2}], [TiCl2(hapen)] and [TiCl2(hapnptn)] are
new. It is noteworthy that although we were unable to
prepare [VO(hapnptn)] we have been able to coordinate
(hapnptn)2− to Ti(IV) to yield [TiCl2(hapnptn)]. How-
ever only microanalyses for [TiCl2{salen(3-OMe)2}]
were in good agreement with the required values, and
for both [TiCl2(hapen)] and [TiCl2(hapnptn)] the C and
N contents are consistently low, perhaps due to traces
of hydrochloric acid in the final product. The product
[TiCl2(hapen)]·thf·0.5toluene was crystallographically
characterised, though surprisingly, the microanalysis of
the red crystals from the same crop that was used for
X-ray studies was also poor.
Deep red needles of [TiCl2(hapen)]·thf·0.5toluene
suitable for X-ray structure analysis were isolated from
the filtrate of the preparative reaction mixture. In con-
trast to [TiCl2(salen)], which is moisture-sensitive, these
are stable in air for a short period. The structure shows
six-coordinate titanium in a distorted octahedral envi-
ronment, with the Schiff base in the equatorial plane
and the two chlorides mutually trans in axial sites (Fig.
1 and Table 1).
Fig. 1. The molecular structure of [TiCl2(hapen)] in the crystal of
[TiCl2(hapen)·thf·0.5toluene.
Table 1
,
Selected
bond
lengths
(A)
and
angles
(°)
in
[TiCl2(hapen)]·thf·0.5toluene a
Ti(1)ꢁO(1)
Ti(1)ꢁO(2)
Ti(1)ꢁN(1)
Ti(1)ꢁN(2)
Ti(1)ꢁCl(1)
Ti(1)ꢁCl(2)
1.827(2)
1.823(2)
2.172(2)
2.151(2)
2.360(1)
2.355(1)
Cl(1)ꢁTi(1)ꢁCl(2)
Cl(1)ꢁTi(1)ꢁO(1)
Cl(1)ꢁTi(1)ꢁO(2)
Cl(1)ꢁTi(1)ꢁN(1)
Cl(1)ꢁTi(1)ꢁN(2)
Cl(2)ꢁTi(1)ꢁO(1)
Cl(2)ꢁTi(1)ꢁO(2)
Cl(2)ꢁTi(1)ꢁN(1)
Cl(2)ꢁTi(1)ꢁN(2)
168.59(4)
90.26(8)
91.49(7)
85.10(7)
84.94(7)
95.21(8)
96.03(7)
85.37(7)
87.10(7)
a Ti removed from mean plane of coordinating N2O2 atoms by 0.01
A.
˚
488, and 490 with the expected isotopic distribution for
two bromine atoms. The microanalyses are reasonably
consistent with this formulation. The IR spectrum
shows the strongest band in the 800–1000 cm −1 region
at 809 cm −1, which we assign to w(TiꢀO), and w(CꢀN)
is at 1632 cm−1 compared to 1638 cm−1 in the proli-
gand. If the band at 809 cm−1 is due to w(TiꢀO) this is
ca. 100 cm−1 lower than expected.
Dichlorotitanium Schiff base complexes were pre-
pared by the method of Floriani and co-workers [8], the
reaction of the Schiff base in tetrahydrofuran with
titanium tetrachloride in toluene [15]. The red suspen-
Two dichlorotitanium tetradentate Schiff base com-
plexes have been previously characterised crystallogra-
phy, [TiCl2(salen)] [13] and [TiCl2{salen(3-But-5-Me)2}]
[16] and Table 2 compares selected bond lengths and
angles of the three complexes [TiCl2(L)].The
TiꢁO(phenolate) and TiꢁN bond distance in all three
complexes are similar, the latter being the shorter. The
dimensions do not vary much and are essentially as
expected.
Table 2
A comparison of selected bond lengths and angles in [TiCl2(salen)], [TiCl2(hapen)] and [TiCl2{salen(3-But-5-Me)2}]
[TiCl2(salen)]14
[TiCl2(hapen)]
[TiCl2{salen(3-tBu,5-Me)2}]17
,
Selected bond lengths (A) and angles (°)
Ti(IV) removed from the mean plane of N2O2 by
ClꢁTiꢁCl
TiꢁCl(1), TiꢁCl(2)
TiꢁO(phenolate)
TiꢁN
not reported
168.7(1)
2.346(2)
1.835(5)
2.141(5)
0.011(1)
168.59(4)
2.355(1), 2.360(1)
1.823(2), 1.827(2)
2.151(2), 2.172(2)
0.003(2)
169.18(10)
2.345(3), 2.353(3)
1.816(4), 1.820(5)
2.110(6), 2.136(5)

N.F. Choudhary et al. / Inorganica Chimica Acta 306 (2000) 24–29
27
Table 3
CE 440 Elemental Analyser. Mass spectra were
recorded by Dr Ali Abdul Sada on a VG Autospec
spectrometer for Electron Impact spectra (EI source at
70 eV) and on a Kratos MS80RF for fast atom bom-
bardment spectra (FAB source at 80 kV, with xenon
gas and a FAB matrix of 3-nitrobenzyl alcohol).
Details of the X-ray structure analysis are given in
Table 3. There is a molecule of thf solvate; and also a
molecule of toluene solvate lying across an inversion
centre for which the methyl group could not be located
and is presumably disordered equally over the three
possible sites. All non-H atoms were anisotropic. H
atoms were included in riding mode with Uiso(H) equal
to 1.2Ueq(C) or 1.5Ueq(C) for methyl groups. The pro-
grams used for data collection and structure analysis
are given in Refs. [17–19].
Crystal data and structure refinement [TiCl2(hapen)]·thf·0.5toluene
Empirical formula
Formula weight
Crystal system
Space group
Unit cell dimensions
C18H18Cl2N2O2Ti·(C4H8O)·0.5(C7H8)
531.3
monoclinic
P21/c (no.14)
,
a (A)
13.426(4)
13.880(2)
14.250(2)
108.58(2)
2517.1(9)
4
0.58
4613
4423 [Rint=0.019]
3485
0.047, 0.117
0.064, 0.130
,
b (A)
,
c (A)
i (°)
3
,
V (A )
Z
v (mm−1
)
Reflections collected
Independent reflections
Reflections with I\2|I
Final R1, wR2 [I\2|I]
All data
4.1. Preparation of [TiO(salen)]
H2(salen) (3.90 g, 14.5 mmol) was dissolved in ace-
tonitrile (100 cm3) and di(isopropoxo)bis(pentane-2,4-
dionato)titanium (5.30 cm3, 14.5 mmol) was added. The
solution was heated under reflux for 13 h, to give an
orange powder, which was filtered off and washed with
diethyl ether (30 cm3). Yield: 2.20 g, 46%. IR (KBr disc,
cm−1): 1631 w(CꢀN), 911 w(TiꢀO) (s).
3. Conclusions
The colour, mass spectra data and IR data of the
yellow solids TiO(L) imply that they are all basically of
the same form, though presumably polynuclear.
Mononuclear titanyl(IV) complexes show w(TiꢀO) in
the region 1050–950 cm−1, whereas our complexes
show w(TiꢀO) at much lower values, 910–865 cm−1
.
4.2. Preparation of [Ti(O(sal-1,3-pn)] · 1.5MeOH
Probably the structures contain ꢁOꢁTiꢁOꢁTiꢁOꢁ poly-
mers. The three novel dichlorotitanium(IV) complexes
proved more tractable and at least one structure was
unequivocally determined.
H2(sal-1,3-pn) (2.50 g, 8.85 mmol) was dissolved in
methanol (50 cm3) to afford a yellow solution. Di(iso-
propoxo)bis(pentane-2,4-dionato)titanium (3.2 cm3,
8.74 mmol) was then added via syringe and the solution
heated under reflux for 6 h. A change to red occurred,
and a yellow–brown precipitate formed. This was
filtered off and washed with diethyl ether (40 cm3).
Additional product was isolated after reducing the
filtrate to approximately 15 cm3 and adding diethyl
ether (100 cm3). [SL1]Yield: 1.22 g, 40%. IR (KBr disc,
cm−1): 1629 w(CꢀN)(s), 905 (m) w(TiꢀO). Found: C,
56.4; H, 4.7; N 7.6. C17H16N2O3Ti·1.5MeOH requires:
C, 56.6; H, 5.6; N, 7.1%. MS (FAB): m/z=345, [MH]+,
(56%), based on m/z=136, 100%.
The propensity for the formation of MꢀO appears to
increase across the first row of d-block metals, perhaps
due to the increase in ionisation potentials. Although
TiIV is the most stable state for titanium under normal
ambient conditions, the double bond structure is con-
siderably stabler for vanadium(IV) and for vanadi-
um(V). Subsequent elements form stable MꢀO species
only in higher oxidation states. The stability of such
bonds in ‘normal’ oxidation states of the metals seems
to be maximal in the middle of the row, with chromium
and manganese.
The product [Ti(O(sal-1,3-pn)] MeCN can be pre-
pared similarly using acetonitrile as solvent.
4. Experimental
4.3. Preparation of [TiO{salnptn(3-OMe)2}]
All reactions were all carried out under dinitrogen,
using standard Schlenk techniques unless otherwise
stated. Solvents used were dried as follows and distilled
under dinitrogen by conventional methods. All reagents
received from commercial suppliers were used as sup-
plied. IR spectra were obtained as dispersions in potas-
sium bromide, or as Nujol mulls using a Perkin–Elmer
model 1710 FT IR spectrophotometer. Carbon, nitro-
gen and hydrogen analyses were carried out by Ms.
Nicola Walker at the University of Surrey on a Leeman
H2{salnptn(3-OMe)2} (3.33 g, 9.0 mmol) was par-
tially dissolved in methanol (75 cm3) to afford a yellow
suspension. Di(isopropoxo)bis(pentane-2,4-dionato)ti-
tanium (3.39 cm3, 9.0 mmol) was added and the suspen-
sion heated under reflux for 6 h. A yellow precipitate
was formed, which was then filtered off and washed
with diethyl ether (40 cm3). Yield: 0.71 g, 18%. IR (KBr
disc, cm−1): 1615 w(CꢀN)(s), 865 w(TiꢀO)(s). MS (EI):
m/z=432, [M]+, (100%), m/z=864, [M2]+, (35%).

28
N.F. Choudhary et al. / Inorganica Chimica Acta 306 (2000) 24–29
cooling to room temperature, diethyl ether (100 cm3)
was added to precipitate the yellow Schiff base com-
plex. This was then filtered off and washed with diethyl
ether (50 cm3) Yield: 2.35 g, 79%. IR (KBr disc, cm−1):
1639 w(CꢀN)(s), 866 w(TiꢀO)(s). MS (EI): m/z=390,
[M]+, (100%).
4.4. Preparation of [TiO(hap-1,2-pn)]
H2(hap-1,2-pn) (2.40 g, 7.78 mmol) was added to
di(isopropoxo)bis(pentane-2,4-dionato) titanium (2.83
cm3, 7.73 mmol) in methanol (75 cm3). The suspension
was heated under reflux for 3.5 days during which time
the solution turned orange. After cooling the solution
to room temperature, diethyl ether (150 cm3) was added
and a yellow clay-like substance was isolated. The
suspension was stirred for 1 h, before the solid was
filtered off and washed with diethyl ether (40 cm3).
Yield: 1.00 g, 35%. IR (KBr disc, cm−1): 1595
w(CꢀN)(s). MS (EI): m/z=372, [M]+ (100%).
4.8. Reaction of di(isopropoxo)bis(pentane-2,4-
dionato)titanium with H2{salen(3,5-Cl)2}
H2{salen(3,5-Cl)2} (4.20 g, 11.3 mmol) was sus-
pended in methanol (75 cm3) and di(isopropoxo)-
bis(pentane-2,4-dionato)titanium (3.79 cm3, 10.4 mmol)
was added. The yellow suspension was heated under
reflux for 4 h to give a mustard powder which was then
filtered off and washed with copious amounts of diethyl
ether until the washings were colourless. Yield: 3.48 g,
72%. IR (KBr disc, cm−1): 1639 w(CꢀN)(s), 869
4.5. Preparation of [TiO(salnptn)]
H2(salnptn) (6.0g, 19 mmol) was suspended in
methanol (50 cm3) and di(isopropoxo)bis(pentane-2,4-
dionato)titanium (7.2 cm3, 20 mmol) was added. The
suspension was heated under reflux for 16 h to give a
red oil. The volume of the solution was reduced to 10
cm3, and petroleum ether (60–80°C, 30 cm3) was
added. This gave a mixture of a lemon powder with a
brown impurity, which was subsequently washed out
using cold methanol (30 cm3) to give the lemon powder.
Yield: 4.17 g, 58%. IR (KBr disc, cm−1): 1618
w(CꢀN)(s), 901 w(TiꢀO)(s). MS (EI): m/z=372, [M]+
(90%), based on m/z=45 (100%).
w(TiꢀO)(s). Found: C, 44.1; H, 2.4;
N
6.3.
C16H10Cl4N2O3Ti (corresponding to[TiO{salen(3,5-
Cl)2}]) requires: C, 41.0; H, 2.1; N, 6.0%. MS (EI):
m/z=463 [M−5]+ (100%).
4.9. Reaction of di(isopropoxo)bis(pentane-2,4-
dionato)titanium with H2{salen(5-Br)2
(a) H2{salen(5-Br)2} (5.0 g, 11.7 mmol) was partially
dissolved in methanol (75 cm3) to afford a yellow
suspension. Di(isopropoxo)bis(pentane-2,4-dionato)ti-
tanium (4.2 cm3, 11.5 mmol) was added and the suspen-
sion heated under reflux for 5 h to give a mustard solid.
This was filtered off and washed with diethyl ether (50
cm3) and dried. Yield: 3.60 g, 63%. IR (KBr disc,
cm−1): 1640 w(CꢀN)(s), 824 w(TiꢀO)(m). Found: C,
40.6; H, 2.5; N, 5.8. C16H12Br2N2O3Ti requires: C, 39.3;
H, 2.5; N. 5.7%. MS (EI): m/z=483 [M−5]+ (27%),
based on m/z=227 (100%).
4.6. Preparation of [TiO(sal-1,2-pn)]·MeOH
H2(sal-1,2-pn) (10.0 g, 35 mmol) was dissolved in
methanol (280 cm3) to afford a yellow solution and
di(isopropoxo)-bis(pentane-2,4-dionato) titanium (13.0
cm3, 35 mmol) was added. The solution was then
heated under reflux overnight to give a red solution,
which was then reduced in volume to 20 cm3 and
diethyl ether (150 cm3) was added to precipitate the
complex as an orange powder. This was filtered off and
washed with diethyl ether (40 cm3). Yield: 8.40 g, 69%.
IR (KBr disc, cm−1): 1631 w(CꢀN)(s), 904 w(TiꢀO)(m).
Found: C, 58.0; H, 4.9; N, 7.3. C17H16N2O3Ti·MeOH
requires: C, 57.4; H, 5.4; N, 7.4% C17H16N2O3-
Ti·0.5MeOH requires: C, 58.3; H, 5.0; N, 7.8%. MS
(EI): m/z=344, [M]+ (100%).
4.10. Reaction of di(isopropoxo)bis(pentane-2,4-
dionato)titanium with H2{salen(5-Br)2} (b)
H2{salen(5-Br)2} (2.97 g, 7.0 mmol) was partially
dissolved in acetonitrile (100 cm3) to afford a yellow
suspension. Di(isopropoxo)bis(pentane-2,4-dionato)ti-
tanium (3.0 cm3, 8.5 mmol) was added and the suspen-
sion heated under reflux for 4 h to give a brick red
solid. This was then filtered off and washed with diethyl
ether (30 cm3). Yield: 2.24 g, 66%. IR (KBr disc,
cm−1): 1632 w(CꢀN)(s). Found: C, 42.2; H, 2.7; N, 5.8.
C16H12Br2N2O3Ti (corresponding to [TiO{salen(5-
Br)2}]) requires: C, 39.4; H, 2.5; N, 5.7%.
C16H12Br2N2O3Ti·MeCN requires: C, 40.8; H, 2.8; N,
5.3%. MS (EI): m/z=488, [M]+, (61%), based on
m/z=80 (100%).
4.7. Reaction between di(isopropoxo)bis(pentane-
2,4-dionato)titanium and H2{salen(3-OMe)2}
H2{salen(3-OMe)2} (2.50 g, 7.6 mmol) was dissolved
in methanol (70 cm3) to afford a yellow solution.
Di(isopropoxo)bis(pentane-2,4-dionato)titanium (2.50
cm3, 6.8 mmol) was added, and the solution was heated
under reflux for 13 h during which time the colour of
the solution changed from yellow to orange to red. On

N.F. Choudhary et al. / Inorganica Chimica Acta 306 (2000) 24–29
29
4.11. Preparation of [TiCl2(salen)]
toluene (40 cm3) was then added to give to brick red
suspension. This red suspension was then heated under
reflux for 40 min, and then stirred at room temperature
for 3 d. The red solid was then filtered off and washed
with tetrahydrofuran and diethyl ether (60 cm3). Yield:
4.39 g, 96%. IR (KBr disc, cm−1): 1609 w(CꢀN)(s).
Found: C, 47.2; H, 5.2; N, 5.2. C21H24Cl2N2O2Ti·2HCl
requires: C, 47.8; H, 5.0; N, 5.3%.
H2(salen) (16.6 g, 60 mmol) was dissolved in thf (250
cm3) to afford a yellow solution which was cooled to
−30°C using an acetone–liquid nitrogen bath. An
orange solution of titanium tetrachloride (6.5 cm3, 60
mmol) in toluene (40 cm3) was added with an immedi-
ate change to dark red. This red suspension was heated
under reflux for 3 h, and the solid was then filtered off,
washed with diethyl ether (50 cm3), and then with a 1:1
mixture of acetone–water and filtered rapidly in air.
Yield: 17.40 g, 73%. IR (KBr disc, cm−1): 1613
w(CꢀN)(s).
References
[1] S. Fairhurst, D.L. Hughes, U. Kleinkes, G.J. Leigh, J.R.
Sanders, J. Weisner, J. Chem. Soc., Dalton Trans. (1995) 321
and references therein.
[2] J.E. Drake, J. Vekris, J.S. Wood, J. Chem. Soc. A (1968) 1000.
[3] R. Guilard, C. Lecomte, Coord. Chem. Rev. 65 (1985) 87.
[4] G.D. Smith, C.N. Caughlan, J.A. Campbell, Inorg. Chem. 11
(1972) 2989.
[5] N. Choudhary, D.L. Hughes, U. Kleinkes, L.F. Larkworthy,
G.J. Leigh, M. Maiwald, C.J. Marmion, J.R. Sanders, G.W.
Smith, C. Sudbrake, Polyhedron 16 (1997) 1517.
[6] N.S. Biradar, V. Biradar, V.H. Kulkarni, Inorg. Nucl. Chem.
Lett. 8 (1972) 997.
[7] M. Gullotti, A. Pasini, Inorg. Chim. Acta 15 (1975) 129 and
references therein.
[8] E. Gallo, E. Solari, F. Franceschi, C. Floriani, A. Chiesi-Villa,
C. Rizzoli, Inorg. Chem. 34 (1995) 2495.
[9] D.L. Hughes, U. Kleinkes, G.J. Leigh, M. Maiwald, J.R.
Sanders, C. Sudbrake, J. Chem. Soc., Dalton Trans. (1994) 2457.
[10] D.L. Hughes, U. Kleinkes, G.J. Leigh, M. Maiwald, J.R.
Sanders, C. Sudbrake, J. Weisner, J. Chem. Soc., Dalton Trans.
(1993) 3093.
4.12. Preparation of [TiCl2{salen(3-OMe)2}]
H2{salen(3-OMe)2} (6.0 g, 20 mmol) was dissolved in
thf (100 cm3) to afford a yellow solution. An orange
solution of titanium tetrachloride (1.60 cm3, 20 mmol)
in toluene (20 cm3) was then added to give a magenta
coloured suspension. This suspension was then heated
under reflux for 2.5 h, filtered and the precipitate
washed with tetrahydrofuran (20 cm3) and diethyl ether
(30 cm3). Yield: 7.73 g, 95%. IR (KBr disc, cm−1): 1625
w(CꢀN)(s). Found: C, 48.6; H, 4.1; N, 6.2.
C18H18Cl2N2O4Ti requires: C, 48.6; H, 4.1; N, 6.3%.
4.13. Preparation of [TiCl2(hapen)] 2HCl
H2(hapen) (5.0 g, 17 mmol) was partially dissolved in
thf (200 cm3) to afford a yellow suspension. An orange
solution of titanium tetrachloride (1.8 cm3, 16 mmol) in
toluene (40 cm3) was added to give a brick red suspen-
sion. This suspension was then heated under reflux for
3.5 h, and stirred at room temperature for 3 days. The
brick red solid was filtered off, and washed with diethyl
ether (50 cm3). Yield: 6.00 g, 86%. IR (KBr disc,
cm−1): 1607 w(CꢀN)(s). Found: C, 42.4; H, 4.5; N, 5.3.
C18H18Cl2N2O2Ti·2HCl requires: C, 44.4; H, 4.1; N,
5.8%.
[11] N.S. Biradar, V.H. Kulkarni, J. Inorg. Nucl. Chem. 33 (1971)
3847.
[12] B.N. Ghose, K.M. Lasisi, Synth. React. Inorg. Met.-Org. Chem.
16 (1986) 1121.
[13] G. Gilli, D.W. Cruickshank, R.L. Beddoes, O.S. Mills, Acta
Crystallogr., Sect. B 28 (1972) 1889.
[14] N.F. Choudhary, N.G. Connelly, P.B. Hitchcock, G.J. Leigh, J.
Chem. Soc., Dalton Trans. (1999) 4437.
[15] M. Mazzanti, J. Rosset, C. Floriani, A. Chiesi-Villa, C. Guastini,
J. Chem. Soc., Dalton Trans. (1989) 953.
[16] T. Repo, M. Klinga, M. Leslela¨, P. Pietika¨inen, G. Brunow,
Acta Crystallogr., Sect. C 52 (1996) 2742.
[17] Data collection: Enraf–Nonius, CAD4 Software, Version 5.0,
Enraf–Nonius, The Netherlands, 1989.
[18] Structure solution: G.M. Sheldrick, SHELXS-86, Program for the
Solution of Crystal Structures, University of Go¨ttingen, Ger-
many, 1985.
[19] Structure refinement: G.M. Sheldrick, SHELXL-93, Program for
Crystal Structure Refinement, University of Go¨ttingen, Ger-
many, 1993.
4.14. Preparation of [TiCl2(hapnptn)]·2HCl
H2(hapnptn) (3.4 g, 10 mmol) was dissolved in thf
(120 cm3) to afford a yellow solution. An orange solu-
tion of titanium tetrachloride (1.0 cm3, 9 mmol) in
.
.