Reactivity of cis-bis(acetylacetonato)dichlorotitanium(IV) towards hydroxy-containing ligands: Isolation and characterisation of products

Article abstract of DOI:10.1039/a906985b

The reactivity of cis-[Ti(acac)₂Cl₂] with a number of OH containing ligands has been explored. Corresponding products have been synthesized, isolated and characterised. Three dimensional structures of some of the products were established by single crystal X-ray diffraction. The reactivity of these ligands towards non-oxo titanium centres has been found to be different from that of oxometal centres of V^V, Mo^VI and U^VI. All the products of Ti^IV isolated were mononuclear complexes possessing one or two ligands. Both the molecular and crystal structures of the titanium products are found to be different from those of the oxometal ones. The Royal Society of Chemistry 1999.

Full text of DOI:10.1039/a906985b

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Reactivity of cis-bis(acetylacetonato)dichlorotitanium(IV) towards
hydroxy-containing ligands: isolation and characterisation of
products†
a
a
b
b
P. Venkateshwara Rao, Chebrolu Pulla Rao,* Elina K. Wegelius, Erkki Kolehmainen and
Kari Rissanen
b
a
Bioinorganic laboratory, Department of Chemistry, Indian Institute of Technology Bombay,
Powai, Mumbai - 400 076, India. E-mail: cprao@ether.chem.iitb.ernet.in
Department of Chemistry, University of Jyvaskyla, Jyvaskyla, Fin 40351, Finland
b
Received 31st August 1999, Accepted 25th October 1999
The reactivity of cis-[Ti(acac) Cl ] with a number of OH containing ligands has been explored. Corresponding
2
2
products have been synthesized, isolated and characterised. Three dimensional structures of some of the products
were established by single crystal X-ray diffraction. The reactivity of these ligands towards non-oxo titanium centres
V
VI
VI
IV
has been found to be different from that of oxometal centres of V , Mo and U . All the products of Ti isolated
were mononuclear complexes possessing one or two ligands. Both the molecular and crystal structures of the
titanium products are found to be different from those of the oxometal ones.
Introduction
The chemistry of hydroxy (OH) rich ligands with oxometal
2
ϩ
3ϩ
ϩ
2
2ϩ
centres, such as VO , VO , cis-VO , cis-MoO and trans-
2
2ϩ
1–5
UO2 , is well understood.
However their co-ordination
behaviour towards non-oxo metal species has not received
much attention in spite of some interesting aspects of the com-
plexation chemistry of these ligands particularly in differentiat-
ing cis from trans dioxometal centres. It is rather interesting to
understand the co-ordination role of hydroxy rich ligands with
non-oxo metal centres possessing oxophilicity. The synthesis,
configuration and reactivity aspects of some titanium()
6
7
bis(acetylacetonate) and bis(β-diketonate) complexes have
8
been reported. Some phenoxo-bound Schiff base complexes
have been used in synthesis as precursors or as catalysts. In all
these reactions the nuclearity of titanium is preserved in its
products. However, when reactions were carried out using TiCl4
the nuclearity of the products was found to be increased by
9
bridging the titanium centres through an oxo group. Therefore,
we have chosen cis-bis(acetylacetonato)dichlorotitanium(),
cis-[Ti(acac) Cl ], as a non-oxo metal precursor possessing
2
2
oxophilic character for studying its reactivity towards ligands
1
5
containing varying numbers of OH groups H L –H L . The
2
2
corresponding products were isolated and characterised
primarily by NMR studies and in a few cases also by single
crystal X-ray diffraction methods.
1
4
ately before use. The ligands, H
confirmed as reported by us earlier. The complex cis-
Ti(acac) Cl ] 1 was prepared by treating TiCl with two
L to H L were prepared and
4
10
2
[
2
2
4
Experimental
equivalents of acetylacetone and isolated and purified by
recrystallisation before use. Synthetic details of H L and also
of the products obtained (2a, 2b, 3a, 3b, 3c and 4a) from the
reactions of 1 with different ligands are given in this paper.
11
5
All operations were carried out under a nitrogen/argon atmos-
phere using standard Schlenk apparatus unless otherwise men-
tioned. All the solvents were dried and distilled under nitrogen
from either sodium diphenylketyl or calcium hydride immedi-
2
Preparations
5
†
Supplementary data available: rotatable 3-D crystal structure diagram
1,1Ј-Methylenebis(2-naphthol) (MBN), H
2
L . To a solution of
in CHIME format. See http://www.rsc.org/suppdata/dt/1999/4469/
Also available: stereoviews. For direct electronic access see http://
www.rsc.org/suppdata/dt/1999/4469/, otherwise available from BLDSC
3.44 g (20 mmol) 2-hydroxy-1-naphthaldehyde in 25 ml MeOH
was added 2-amino-2-methylpropan-1-ol (1.9 ml, 20 mmol) and
the reaction mixture stirred under reflux for 3 h. It was then
cooled to room temperature and subsequently to 0 ЊC and
(
No. SUP 57674, 2 pp.) or the RSC library. See Instructions for
Authors, 1999, Issue 1 (http://www.rsc.org/dalton).
This paper is dedicated to Professor Stephen J. Lippard on his 60th
birthday.
equilibrated. At 0 ЊC, solid NaBH (0.760 g, 20 mmol) was
4
added pinch by pinch over a period of about 0.5 h. After
J. Chem. Soc., Dalton Trans., 1999, 4469–4474
This journal is © The Royal Society of Chemistry 1999
4469

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completing the addition, the temperature was slowly raised to
ambient and stirring continued for 3 h. Solvent was evapor-
ated to dryness in order to obtain an off-white residue. To this a
solution of sodium acetate (4.00 g) in 30 ml of water was added
and the product extracted into dichloromethane. The dichloro-
ml CH CN. The resulting orange suspension was refluxed for
4 h then cooled to room temperature and filtered through
Celite. The filtrate was evaporated to dryness and the residue
3
recrystallised from CH CN by adding hexane. Yellow single
3
crystals were obtained, washed with hexane and dried under
vacuum. Yield 66%. Calc. (%) C, 67.93; H, 5.70; N, 5.28.
methane fraction was dried over anhydrous MgSO , filtered and
4
5
Ϫ1
concentrated to give a white fluffy product, H L , in 70% yield.
Obs. (%) C, 67.61; H, 5.74; N, 5.48. FTIR (KBr, cm ) 1611
2
1
1
NMR (CDCl ): H, δ 4.82 (s, 2 H, CH ); 7.05, 7.66, 8.21 (d, 2 H
(νC᎐N). H NMR (CDCl ): δ 9.49 (s, 2 H, HC᎐N); 8.20 (d,
3
2
᎐
3
13
each, aromatic); 7.33, 7.45 (t, 2 H, aromatic); C, δ 21.8 (CH ),
2 H), 7.81 (d, 2 H), 7.74 (d, 2 H), 7.56 (dt, 2 H), 7.34 (dt, 2 H)
and 6.94 (d, 2 H, naphthalene H); 4.45, 4.15 (d, 2 H each,
2
1
1
17.1, 118.1, 119.6, 123.1, 123.3, 126.9, 128.9, 129.8, 133.5 and
51.6 (aromatic).
13
bound CH O); 1.67, 1.57 (s, 6 H each, CH ). C NMR
2
3
(
CDCl ): δ 24.14, 27.68 (CH ); 72.60 (tert-carbon); 82.25
3 3
Ϫ
1
1
[
Ti(L )(acac)Cl] 2a. To 15 ml of CH CN, H L (0.215 g, 1
(CH O ); 112.16, 119.4, 121.3, 123.1, 127.7, 127.9, 129.2, 133.9,
3
2
2
mmol) and sodium acetate (0.082 g, 1 mmol) were added and the
mixture was stirred at room temperature. A solution of com-
plex 1 (0.316 g, 1 mmol) dissolved in 15 ml of CH CN was added
135.9, 165.1 (aromatic); 155.6 (CH᎐N).
᎐
1
2
1
[Ti(L )(L )] 3d. A mixture of H L (0.054 g, 0.25 mmol) and
3
2
dropwise. The initial yellow solution turned into a reddish sus-
pension, and was stirred at room temperature for 6 h. The solu-
tion was then filtered and the filtrate concentrated. Hexane
was added upon which small red crystals of the product were
formed. The product was separated through filtration, washed
with hexane and dried under vacuum. Yield 55%. Calc. (%) C,
sodium acetate (0.021 g, 0.25 mmol) was added to 20 ml of
CH CN and stirred at room temperature. Complex 2b (0.106 g,
3
0.25 mmol) in 15 ml of CH CN was added dropwise. The initial
3
yellow suspension turned orange-yellow and was refluxed for
4.5 h, then cooled to room temperature and filtered through
Celite. The filtrate was concentrated to give a yellow, micro-
crystalline solid. Yield 49%. Calc. (%) C, 66.94; H, 5.22; N, 5.57.
5
4.64; H, 4.59; N, 3.54. Obs. (%) C, 54.98; H, 4.27; N, 3.77.
Ϫ1 1
Ϫ1
FTIR (KBr, cm ) 1608 (νC᎐N). H NMR (CDCl ): δ 9.42 (s,
Obs. (%) C, 66.50; H, 5.00; N, 5.26. FTIR (KBr, cm ) 1612
3
1
1
1
H, CH᎐N); 8.16 (d, 1 H), 7.86 (d, 1 H), 7.74 (d, 1 H), 7.56
(νC᎐N). H NMR (CDCl ): δ 9.55 (s, 1 H, HC᎐N of L ); 9.47 (s,
᎐
3
2
᎐
(
t, 1 H), 7.37 (t, 1 H) and 6.91 (d, 1 H, naphthalene H); 4.94 (m,
H, CH CH O); 4.62 (m, 3 H, CH CH O); 2.04 (s, 6 H, 2CH ).
1 H, HC᎐N of L ); 8.19 (t, 2 H), 7.80 (d, 2 H), 7.73 (d, 2 H),
1
7.56 (m, 2 H), 7.34 (t, 2 H) and 6.91 (dd, 2 H, naphthalene H);
2
2
2
2
3
13
Ϫ
1
C NMR (CDCl ): δ 67.6, 74.2, 105.3, 112.9, 119.7, 124.0,
4.60, (m, 1 H), 4.48 (m, 3 H, CH CH O , L ); 4.46, 4.21 (d, 1 H
2 2
Ϫ
3
1
28.2, 128.6, 129.1, 133.1, 136.6, 165.39, 191.3, 157.9 (C᎐NH).
each, bound CH O , J = 9.27 Hz); 1.67, 1.57 (2s, 3 H each, CH ,
2 3
2 13 2
᎐
L ). C NMR (CDCl ): δ 27.5, 24.5 (CH , L ); 72.7 (tert-
3
3
2
2
2
1
Ϫ
1
Ϫ
[
Ti(L )(acac)Cl] 2b. A mixture of H L (0.121 g, 0.5 mmol)
carbon, L ); 67.5 (CH , L ); 70.9 (CH O , L ); 82.5 (CH O ,
2 2 2
2
2
and sodium acetate (0.041 g, 0.5 mmol) in 15 ml of acetonitrile
was stirred at room temperature. Complex 1 (0.158 g, 0.5 mmol)
in 15 ml of acetonitrile was added dropwise, the initial yellow
suspension turning to reddish orange, which was then refluxed
for 3 h. The reaction mixture was cooled to room temperature
and filtered through Celite. The filtrate was evaporated to dry-
L ); 111.8, 112.0, 119.4, 119.4, 121.3, 121.5, 123.1, 123.1, 127.8,
127.7, 127.9, 129.1, 129.2, 133.5, 133.9, 135.9, 136.0, 165.1,
2
1
166.0 (aromatic); 155.6 (CH᎐N, L ); 159.0 (CH᎐N, L ).
5
5
[Ti(L )(acac) ] 4a. To 15 ml of CH CN, H L (0.30 g,
2
3
2
1 mmol) was added and stirred at room temperature. Complex 1
ness and recrystallised from CH CN by adding hexane. Red
(0.316 g, 1 mmol) in 15 ml of CH CN was added dropwise to
3
3
single crystals were obtained in 75% yield. Calc. (%) C, 59.69;
H, 5.23; N, 3.30. Obs. (%) C, 59.48; H, 5.44; N, 3.24. FTIR
give a deep red solution which was refluxed for 6 h. The reaction
mixture was then cooled to room temperature and the solvent
evaporated to dryness to remove volatile products. The residue
Ϫ1
1
(
KBr, cm ) 1608 (νC᎐N). H NMR (CDCl ): δ 9.41 (s, 1 H,
3
HC᎐N); 8.20 (d, 1 H), 7.88 (d, 1 H), 7.78 (dd, 1 H), 7.60 (dt,
was redissolved in CH CN. Small, red single crystals were
᎐
3
1
1
2
H), 7.39 (dt, 1 H) and 6.93 (d, 1 H, napthalene H); 5.97 (s,
obtained. Yield 62%. Calc. (%) C, 68.39; H, 5.18. Obs. (%) C,
1
H, CH, acac); 4.89, 4.32 (d, 1 H each, bound CH O); 2.28,
67.93; H, 5.64. H NMR (CDCl ): δ 8.36 (br, 2 H), 7.72 (d, 3 H),
2
3
13
.00 (s, 3 H each, CH ); 1.71, 1.60 (s, 3 H each, CH ). C NMR
7.53 (d, 2 H), 7.38 (br, 2 H) and 6.94 (br, 3 H, naphthalene H);
3
3
2
(
CDCl ): δ 25.0, 28.5 (CH , L ); 25.6, 26.4 (CH , acac); 74.4
5.97 (s, 2 H, acac H); 5.15, 4.74 (br, 1 H each, CH ); 2.06 (m, 6 H,
3
3
Ϫ
3
2
2
(
tert-carbon); 85.8 (CH O , L ); 105.3 (CH᎐, acac); 113.2,
2CH ).
2
3
1
19.4, 119.6, 123.9, 128.2, 128.7, 129.3, 133.4, 136.6, 164.4
2
(
aromatic); 155.2 (CH᎐N, L ); 189.8, 192.2 (CO, acac).
Spectral studies
᎐
Fourier transform infrared spectra were recorded on an Impact
1
1
[
Ti(L ) ] 3a. To 15 ml of CH CN, H L (0.215 g, 1 mmol) and
2 3 2
1
13
4
00 Nicolet FTIR machine in KBr matrix, H and C NMR
sodium acetate (0.082, 1 mmol) were added and the mixture
was stirred at room temperature. Complex 1 (0.158 g, 0.5 mmol)
in 15 ml of CH CN was added dropwise. The initial yellow
solution turned to a yellow suspension and was stirred for 6 h
spectra using a JEOL JNM GSX-270 FT or Varian XL-300
spectrometer in CDCl or (CD ) SO (complexes) or CDCl
3
3
3
2
3
10
(
ligands).
at room temperature. It was then filtered and the yellow solid
X-Ray crystallography
obtained extracted into CHCl , filtered and concentrated to
3
dryness under vacuum. The product was washed with hexane
and dried under vacuum. Yield 58%. Calc. (%) C, 65.83; H, 4.67;
Standard procedures were used for mounting the crystals. The
diffraction data were collected on an Enraf Nonius CAD-4 dif-
fractometer in the ω–2θ scan mode using Mo-Kα radiation
Ϫ1
N, 5.90. Obs. (%) C, 65.74; H, 4.54; N, 5.30. FTIR (KBr, cm )
1
12
(
νC᎐N). H NMR (CDCl ): δ 9.55 (s, 2 H, HC᎐N); 8.18 (d,
(0.71073 Å). The structures were solved using SHELXS 86
᎐
3
13
2
6
H), 7.79 (d, 2 H), 7.72 (d, 2 H), 7.56 (d, 2 H), 7.34 (t, 2 H) and
and refined using SHELXL 93 program packages. The
Ϫ
.88 (d, 2 H, napthalene H); 4.63, 4.49 (m, 4 H, CH CH O ).
diagrams were generated using ORTEP III and PLUTON 98
2
2
1
3
Ϫ
Ϫ
14
C NMR (CDCl ): δ 67.5 (CH CH O ); 71.0 (CH O ); 111.7,
programs. The hydrogen atoms were fixed through the
3
2
2
2
1
1
19.4, 121.5, 123.2, 127.8, 129.1, 133.5, 136.1, 166.0 (aromatic);
SHELXL program. Empirical absorption corrections were car-
ried out for all the data. Full matrix least-squares refinement
with anisotropic thermal parameters for all non-hydrogen
atoms was used. The hydrogen atoms were treated as riding
atoms with fixed thermal parameters. Other details of data
collection and structure refinement are provided in Table 1.
59.1 (CH᎐N).
᎐
2
[
Ti(L ) ] 3b. A solution of complex 1 (0.158 g, 0.5 mmol) in
2
2
1
5 ml of CH CN was added dropwise to a solution of H L
3
2
(
0.243 g, 1 mmol) and sodium acetate (0.082 g, 1 mmol) in 15
470 J. Chem. Soc., Dalton Trans., 1999, 4469–4474
4

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CCDC reference number 186/1706.
See http://www.rsc.org/suppdata/dt/1999/4469/ for crystallo-
graphic files in .cif format.
Results and discussion
Reactivity
Scheme 1 represents the reaction scheme. When cis-[TiCl2-
Fig. 1 Molecular structure of complex 2b showing 50% probability
level thermal ellipsoids and using ORTEP for all non-hydrogen atoms
as in all structures).
(
3
reaction with one equivalent of H L with a view to obtaining a
3
mixed ligand complex of titanium led to a mixture of non-
characterisable products. In contrast, the reaction of 2b with
4
H L led to homoleptic complex 3c.
4
5
Reaction of complex 1 with H L ligand in 1:1 ratio yielded
a mixed ligand complex 4a. Even the reactions of 1 with H L
2
5
2
ligand in 1:2 or 1:3 ratio yielded 4a rather than the expected
5
products possessing more than one L in the co-ordination
5
sphere of Ti. Reactions of 2b carried out with H L both in the
2
absence and in the presence of bases, such as sodium acetate or
2
aniline, yielded only complex 4a by replacing L and chloro-
5
groups, but not the expected mixed ligand complex, [Ti(L )-
2
(
L )(solvent)]. Thus 2b has shown good reactivity towards dif-
ferent ligands containing OH groups of alkoxo and phenoxo
types.
2
Reaction of complex 4a with one equivalent of H L did
not yield the expected product, [Ti(L )(L )(solvent)], instead
2
5
2
uninterpretable NMR spectra indicating the presence of a mix-
5
1
ture of products. Similarly one or two equivalents of H
L both
2
Scheme 1 Reaction scheme: (i) for 2a H L , NaO CMe, CH CN, rt,
2
2
3
2
1
in the absence and in the presence of base did not give the
expected products.
6
2
h; for 2b H L , NaO CMe, CH CN, reflux, 3 h; (ii) for 3a 2H L ,
2 2 3 2
2
NaO CMe, CH CN, rt, 6 h; for 3b 2H L , 2NaO CMe, CH CN,
2
3
2
2
3
1
2
reflux, 4 h; (iii) for 3a H L , NaO CMe, CH CN, rt, 6 h; for 3b H L ,
2
2
3
2
4
NaO CMe, CH CN, reflux, 4 h; for 3c H L , NaO CMe, CH CN, rt,
Structures of compounds 2b, 3b and 4a
2
3
4
2
3
5
5
6
h; (iv) for 4a H L , NaO CMe, CH CN, reflux, 6 h; (v) H L ,
2
2
3
2
Though all the three compounds crystallised in centro-
symmetric space groups (Table 1), there exists no centre of
symmetry in any of the molecules. The six bond lengths and the
fifteen bond angles covering the primary co-ordination sphere
are given in Table 2.
NaO CMe, CH CN, reflux, 4 h; ‘*’ indicates single crystal structure
2
3
determination.
2
(
acac) ], 1 was treated with H L in 1:1 mol ratio in CH CN the
2 2 3
reaction yielded a heteroleptic complex 2b. However, when the
same reaction was carried out in 1:2 mol ratio it resulted in the
The molecular structure of complex 2b is shown in Fig. 1
formation of a homoleptic complex, 3b. Similar reactions of 1
using ORTEP. The titanium() centre is octahedral possessing
1
2
with H L yielded corresponding complexes, 2a and 3a respec-
L , a bidentate acac group and a chloro-group. The tridentate
2
2
tively. Further, the conversion of 2a into 3a and 2b into 3b may
ligand, L occupies the equatorial positions by co-ordinating
1
be achieved by treating 2a and 3a with one equivalent of H L
through its alkoxo and phenoxo oxygens and an imine nitrogen.
The metric parameters around the metal centre (Table 2) are
clearly indicative of the distortion in the octahedral geometry
around titanium. The trans angles range from 157.8 to 170.9Њ
indicating a large distortion in the primary co-ordination
sphere. Five-membered chelate bite angles in 2b range from 77.1
to 82.5Њ.
2
2
3
and H L respectively. However, reactions of 1 with H L or
H L in both 1:1 and 1:2 ratios yielded products that are
2
3
4
4
generally insoluble in common organic solvents. Such a differ-
3
4
1
ence in the reactivity of H L and H L over that of H L and
3
4
2
2
H L with 1 is interpretable based on the presence of additional
CH OH groups in H L and H L (one in the case of H L and
2
3
4
3
2
3
4
3
4
two in the case of H L ).
The structure of complex 3b possesses two tridentate lig-
4
1
2
Reaction of complex 2b with one equivalent of H L in
ands L as shown in Fig. 2. Each ligand is bound through
2
acetonitrile yielded 3d as shown in Scheme 2. However, the
oxygen atoms of alkoxo and phenoxo groups and also
through an imine nitrogen. The ligands are bound in a
meridional fashion as seen from the stereoview of 3b. The
metric parameters around the titanium centre are clearly
indicative of the distortion in the octahedral geometry. The
trans angles range from 156.7 to 174.3Њ exhibiting a large
deviation of ≈23Њ. The 5-membered chelate bite angles range
from 77.3 to 80.2Њ.
The molecular structure of complex 4a possesses one
5
ligand L and two acac groups as shown in Fig. 3. The stereo-
5
view demonstrates that L adopts a partially open book type
structure. All the three ligands act as bidentate. Based on the
metric parameters around the titanium centre, the complex is
1
Scheme 2 The conversion of complex 2b into 3d: (i) H L , NaO CMe,
2
2
CH CN, rt, 6 h.
3
J. Chem. Soc., Dalton Trans., 1999, 4469–4474
4471

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Table 1 Summary of crystallographic data for complexes 2b, 3b and
4
a
2
b
3b
4a
Molecular formula C H ClNO Ti
C H N O Ti
530.46
293(2)
C H O Ti
544.43
293(2)
2
0
22
4
30 30
2
4
31 28
6
M
423.74
293(2)
T/K
Crystal System
Space group
Orthorhombic
Pbca
Monoclinic
Monoclinic
P2 /n
P2 /n
1
1
Cell constants
a/Å
b/Å
c/Å
8.757(1)
16.150(8)
27.766(3)
—
3927(2)
4
13.769(2)
10.985(2)
17.055(2)
102.38(1)
2519.8(6)
2
8.254(1)
22.121(4)
14.582(2)
102.34(1)
2601.1(7)
2
β/Њ
V/Å
3
Z
Ϫ3
D /g cm
1.433
1.398
1.390
c
Total reflections
Unique reflections 3455
3607
4613
4419
4896
4562
Parameters
Final R
RЈ
244
0.0394
0.1043
344
0.0370
0.0848
353
0.0376
0.0876
Fig. 4 Lattice structure of complex 2b showing intermolecular hydro-
gen bond interaction (---). Filled circles refer to oxygen, hatched
circles to the metal.
C ؒ ؒ ؒ O and C–H ؒ ؒ ؒ O): 2.566, 3.477 Å, 158.7Њ, 2.570, 3.301 Å,
1
33.1Њ. However, no such interactions are observed in the
crystal lattice of 3b or 4a.
Spectral studies
Proton NMR spectra of complexes 2a, 2b, 3a, 3b and 3d
showed disappearance of the phenolic proton and one of the
alkoxo-OH protons. The spectra also exhibited a downfield
shift of the imine proton by 0.79, 0.48, 0.92, and 0.56 ppm upon
co-ordination in 2a, 2b, 3a, and 3b respectively when compared
with the corresponding unbound ligands. In case of 3d two
Fig. 2 Molecular structure of complex 3b.
1
2
singlet peaks were observed for the imine protons of L and L
at δ 9.55 and 9.47 respectively and were shifted downfield by
.92 and 0.54 ppm.
For complex 2a the bound CH CH O appeared as multi-
0
Ϫ
2
2
plets centred at δ 4.94 (1 H) and 4.62 (3 H). Similarly, in the case
of 3a, these were observed at δ 4.63 (1 H) and 4.49 (3 H). For 2b
Ϫ
the protons of the bound CH O group appeared as an ‘AB’
2
quartet, where the doublets are centred around δ 4.32 and
4
.89, exhibiting a downfield shift of 0.89 and 1.42 ppm respec-
tively in comparison with those for the corresponding “free”
ligand. Similarly, in the case of 3b, the doublets are centred
around δ 4.45 and 4.15 indicating downfield shifts of 0.98
Ϫ
1
and 0.68 ppm respectively. For 3d the CH O protons of L
2
appeared as two sets of multiplets centred around δ 4.60 and
Ϫ
2
4
.49 respectively. The protons of the bound CH O group of L
2
Fig. 3 Molecular structure of complex 4a.
in 3d appear as an ‘AB’ type quartet, where the individual
doublets are centred around δ 4.46 and 4.21.
2
identified as distorted octahedral. The trans angles are in the
range 166.8–175.7Њ. The bite angle of L is about 10Њ wider
owing to its chelate ring size when compared to the other
The methyl protons of L appeared as two singlets for com-
5
plex 2b, and these are shifted downfield by 0.17 and 0.33 ppm
with respect to those of free L . Similarly the methyl protons
2
complexes. The structure of 4a has close resemblance to that
from the acac group also appeared as two singlets. For 3b the
methyl protons of L appeared as two singlets shifted downfield
i
15
2
of [Ti(acac) (OC H Pr -2,6) ] where the phenoxo-ligands are
2
6
3
2
2
5
monodentate, while 4a has bidentate ligand L .
by 0.28 and 0.18 ppm respectively. For 3d the methyl protons of
2
Comparison of metric parameters around the metal centre
reveals a trend in the distortion of octahedral geometry,
L appeared at δ 1.67 and 1.57.
The proton NMR spectrum of complex 4a showed methyl
protons of acac as a singlet at δ 2.06 and the methine proton of
acac also as a singlet at δ 5.79. The protons of the methylene
2
b > 3b > 4a. The Ti–O bond lengths are in the order, Ti–
Oalk < Ti–Ophe < Ti–Oacac in all the complexes reported in this
8
5
paper and further are in agreement with those in the literature.
group that bridges the two naphthyl rings of L appeared as two
Weak intermolecular hydrogen bond interactions occur
between C3–H3 and O3 and C8–H8 and O4 in the lattice of 2b.
The lattice structure indicating these bonds in 2b is shown in
Fig. 4. The hydrogen bond parameters are as follows (H ؒ ؒ ؒ O,
broad peaks centred at δ 5.15 and 4.74.
FTIR spectra of all the products 2a, 2b, 3a, 3b, 3c, 3d, and 4a
were compared with the spectra of the corresponding ligands
and precursors. Products 2a, 2b, 3a, 3b and 4a did not exhibit
4
472
J. Chem. Soc., Dalton Trans., 1999, 4469–4474

View Article Online
Table 2 Selected bond lengths (Å) and angles (Њ) in complexes 2b, 3b and 4a
2
b
3b
4a
Ti(1)–O(1)
Ti(1)–O(2)
Ti(1)–O(3)
Ti(1)–O(4)
Ti(1)–N(1)
Ti(1)–Cl(1)
1.892(2)
1.803(2)
2.028(2)
1.968(2)
2.167(2)
2.347(1)
Ti(1)–O(1)
Ti(1)–O(2)
Ti(1)–O(3)
Ti(1)–O(4)
Ti(1)–N(1)
Ti(1)–N(1)
1.918(2)
1.857(2)
1.936(2)
1.856(2)
2.158(2)
2.178(2)
Ti(1)–O(1)
Ti(1)–O(2)
Ti(1)–O(3)
Ti(1)–O(4)
Ti(1)–O(5)
Ti(1)–O(6)
1.861(2)
1.806(2)
2.009(2)
2.034(2)
1.988(2)
2.045(2)
O(1)–Ti(1)–O(2)
O(1)–Ti(1)–O(3)
O(1)–Ti(1)–O(4)
O(1)–Ti(1)–N(1)
O(1)–Ti(1)–Cl(1)
O(2)–Ti(1)–O(3)
O(2)–Ti(1)–O(4)
O(2)–Ti(1)–N(1)
O(2)–Ti(1)–Cl(1)
O(3)–Ti(1)–O(4)
O(3)–Ti(1)–N(1)
O(3)–Ti(1)–Cl(1)
O(4)–Ti(1)–N(1)
O(4)–Ti(1)–Cl(1)
N(1)–Ti(1)–Cl(1)
157.79(9)
88.08(9)
103.19(8)
80.73(8)
87.98(7)
93.40(9)
98.98(9)
77.13(8)
93.76(7)
82.48(8)
89.45(8)
169.91(7)
170.86(8)
89.38(7)
99.07(7)
O(1)–Ti(1)–O(2)
O(1)–Ti(1)–O(3)
O(1)–Ti(1)–O(4)
O(1)–Ti(1)–N(1)
O(1)–Ti(1)–N(2)
O(2)–Ti(1)–O(3)
O(2)–Ti(1)–O(4)
O(2)–Ti(1)–N(1)
O(2)–Ti(1)–N(2)
O(3)–Ti(1)–O(4)
O(3)–Ti(1)–N(1)
O(3)–Ti(1)–N(2)
O(4)–Ti(1)–N(1)
O(4)–Ti(1)–N(2)
N(1)–Ti(1)–N(2)
157.42(7)
90.64(7)
90.06(7)
80.20(6)
104.80(7)
93.47(7)
94.77(8)
77.26(7)
97.78(7)
156.68(7)
97.39(7)
79.89(7)
105.69(7)
77.41(7)
174.25(7)
O(1)–Ti(1)–O(2)
O(1)–Ti(1)–O(3)
O(1)–Ti(1)–O(4)
O(1)–Ti(1)–O(5)
O(1)–Ti(1)–O(6)
O(2)–Ti(1)–O(3)
O(2)–Ti(1)–O(4)
O(2)–Ti(1)–O(5)
O(2)–Ti(1)–O(6)
O(3)–Ti(1)–O(4)
O(3)–Ti(1)–O(5)
O(3)–Ti(1)–O(6)
O(4)–Ti(1)–O(5)
O(4)–Ti(1)–O(6)
O(5)–Ti(1)–O(6)
93.99(7)
96.39(7)
90.55(7)
92.33(7)
175.66(7)
93.10(7)
174.55(7)
96.18(7)
88.50(7)
83.38(7)
166.79(7)
87.01(7)
86.64(7)
87.16(7)
83.01(7)
5,10
any peaks in the νOH region. The binding of the imine function
resulted in the formation of corresponding complexes
where
through nitrogen has been revealed by the low frequency shift
the metal to ligand ratio is 1:1. However, the reactions of these
ligands with non-oxo Ti resulted not only in 1:1 but also 1:2
Ϫ1
IV
of 15 to 18 cm observed with the νCN peaks.
13
In C NMR spectra the imine carbon in complexes 2a, 2b, 3b
complexes (3a, 3b, 3c and 3d) due to the absence of any Ti᎐O
᎐
2
IV
and 3d(L ) showed downfield shifts of 1.5, 0.9, 1.24 and 1.33
moiety. All the complexes of Ti reported in this paper are
1
ppm respectively. However, 3a and 3d(L ) showed marginal
mononuclear, in spite of the fact that in some cases there exists
upfield shifts for the imine carbon by 0.37 and 0.44 ppm
respectively.
additional unbound CH OH groups. Thus this property of
2
titanium complexes is in agreement with that observed in the
case of oxometal complexes using the same ligands. The co-
Considerable downfield shifts were also observed with the
Ϫ
1
V
VI
VI
bound CH O carbon in complexes 2a, 2b, 3a and 3d(L ) by
ordination numbers exhibited in V O, Mo O, U O and non-
oxo titanium() complexes are 5, 6, 7 and 6 respectively. Only
the lattice structure of 2b has shown some weak intermolecular
interactions. In this context the nature of the titanium complex
2
1
2.5, 27.3, 9.2 and 9.1 ppm respectively. The bound methylene
2
carbon of L shifted downfield by 23.7 ppm for 3b and 24.0
ppm for 3d. In effect, the downfield shift observed in the carbon
Ϫ
VI
chemical shift of the bound CH O in the 1:1 complex is
is somewhat intermediate to that observed between Mo O and
2
VI
higher than that in the 1:2 complex due to a decrease in the
effective positive charge of the metal centre per ligand in the 1:2
case. Thus the downfield shifts observed for 2a and 2b are
higher than those for 3a and 3b respectively. Such shifts
observed in mixed ligand complexes parallel the behaviour of
the 1:2 cases as expected.
The methine carbon of the acac group was shifted upfield by
about 3.5 ppm for both complexes 2a and 2b. The carbonyl
carbon of the acac group appeared as two peaks each for 2a
and 2b. For 2a the carbonyl carbons were shifted downfield by
U O lattice structures. In effect, the reactivity of these OH
containing ligands has been found to be somewhat different in
the case of the non-oxo titanium when compared to that of the
V
VI
VI
oxometal centres of V , Mo and U .
Acknowledgements
C. P. R. acknowledges financial support from Department of
Science and Technology, New Delhi, Department of Atomic
Energy, Mumbai and Council for Scientific and Industrial
Research (CSIR), New Delhi. P. V. R. gratefully acknowledges a
SRF fellowship from CSIR. We thank Mr Kuppinen for some
experimental help.
0
.44 and 1.66 ppm. In the case of 2b one peak was shifted
upfield by 1.84 and the other downfield by 0.57 ppm when
compared with those of 1.
Conclusions
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4
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