Mono- and di-anionic coordination modes of arylazosalicylates in their bis(η5-cyclopentadienyl)titanium(IV) complexes: Syntheses and crystal structures

Article abstract of DOI:10.1016/j.ica.2018.09.076

The bis(η⁵-cyclopentadienyl)titanium(IV) complexes of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids (H₂L^XASA) where the aryl group is an X-substituted phenyl ring such that X = CH, COEt, CMe, CF, CCl, CBr and N have been synthesised. Two types of titanium(IV) compounds viz. (i) [Ti(η⁵-C₅H₅)₂(O₂CC₆H₃(OH-2)(N[dbnd]NC₆H₄(H-4)-5))₂] (3) and [Ti(η⁵-C₅H₅)₂(O₂CC₆H₃(OH-2)(N[dbnd]NC₆H₄(OC₂H₅-4)-5))₂] (4), and (ii) [Ti(η⁵-C₅H₅)₂(O₂CC₆H₃(O-2)(N[dbnd]NC₆H₄(CH₃-4)-5))] (5), [Ti(η⁵-C₅H₅)₂(O₂CC₆H₃(O-2)(N[dbnd]NC₆H₄(F-4)-5))] (6), [Ti(η⁵-C₅H₅)₂(O₂CC₆H₃(O-2)(N[dbnd]NC₆H₄(Cl-4)-5))] (7), [Ti(η⁵-C₅H₅)₂(O₂CC₆H₃(O-2)(N[dbnd]NC₆H₄(Br-4)-5))] (8) and [Ti(η⁵-C₅H₅)₂(O₂CC₆H₃(O-2)(N[dbnd]NC₅H₄(N-4)-5))] (9) were isolated and characterised by IR, ¹H and ¹³C NMR spectroscopic techniques. The crystal and molecular structures of 3–9 have been determined by single crystal X-ray crystallography. Compounds 3 and 4 conform to the formula Cp₂Ti(HL^XASA-κO)₂ with a monodentate carboxylate ligand while those of 5–9 conform to Cp₂Ti(L^XASA-κ²O¹,O²) with the dianions chelating the titanium atoms via carboxylate-O and hydroxy-O atoms. The common feature of the molecular structures is the adoption of distorted tetrahedral geometries based (Cp)₂O₂ donor sets. Hydroxyl–O–H^…O(carbonyl) bonding leads to supramolecular chains in the crystal of 4 but, these are absent in 3. Persistent Cp–C–H^…O(carbonyl) interactions, with the carbonyl atoms accepting two or three such interactions, lead to supramolecular chains with helical (5, 7 and 8) or linear (6 and 9) topologies; C–X^…π interactions also play an important role in the packing of 6–8.

Full text of DOI:10.1016/j.ica.2018.09.076

Accepted Manuscript
Research paper
5
Mono- and di-anionic coordination modes of arylazosalicylates in their bis(ƞ -
cyclopentadienyl)titanium(IV) complexes: Syntheses and crystal structures
Tushar S. Basu Baul, Rajesh Manne, Edward R.T. Tiekink
PII:
S0020-1693(18)31370-7
https://doi.org/10.1016/j.ica.2018.09.076
ICA 18534
DOI:
Reference:
To appear in:
Inorganica Chimica Acta
Received Date:
Revised Date:
Accepted Date:
31 August 2018
26 September 2018
26 September 2018
Please cite this article as: T.S. Basu Baul, R. Manne, E.R.T. Tiekink, Mono- and di-anionic coordination modes of
5
arylazosalicylates in their bis(ƞ -cyclopentadienyl)titanium(IV) complexes: Syntheses and crystal structures,
Inorganica Chimica Acta (2018), doi: https://doi.org/10.1016/j.ica.2018.09.076
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Mono- and di-anionic coordination modes of arylazosalicylates in their
5
bis(ƞ -cyclopentadienyl)titanium(IV) complexes: Syntheses and crystal
structures
,
a
a
**,b
Tushar S. Basu Baul,* Rajesh Manne, Edward R. T. Tiekink,
aCentre for Advanced Studies in Chemistry, North-Eastern Hill University, NEHU Permanent
Campus, Umshing, Shillong 793 022, India
bResearch Centre for Crystalline Materials, School of Science and Technology, Sunway
University, 47500 Bandar Sunway, Selangor Darul Ehsan, Malaysia
Abstract
5
The bis(η -cyclopentadienyl)titanium(IV) complexes of 5-[(E)-2-(aryl)-1-diazenyl]-2-
hydroxybenzoic acids (H2LXASA) where the aryl group is an X-substituted phenyl ring such
that X = CH, COEt, CMe, CF, CCl, CBr and N have been synthesised. Two types of
5
titanium(IV) compounds viz. (i) [Ti(η -C H ) (O CC H (OH-2)(N=NC H (H-4)-5)) ] (3) and
5
5 2
2
6
4
6
4
2
5
[Ti(η5-
[
Ti(η -C H ) (O CC H (OH-2)(N=NC H (OC H -4)-5)) ]
(4),
and
(ii)
5
5 2
2
6
4
6
4
2
5
2
5
C H ) (O CC H (O-2)(N=NC H (CH -4)-5))]
(5),
[Ti(η -C H ) (O CC H (O-
5
5 2
2
6
4
6
4
3
5
5 2
2
6
4
5
5
2
)(N=NC H (F-4)-5))] (6), [Ti(η -C H ) (O CC H (O-2)(N=NC H (Cl-4)-5))] (7), [Ti(η -
6 4 5 5 2 2 6 4 6 4
5
C H ) (O CC H (O-2)(N=NC H (Br-4)-5))]
(8)
and
[Ti(η -C H ) (O CC H (O-
5 5 2 2 6 4
5
5 2
2
6
4
6
4
)(N=NC H (N-4)-5))] (9) were isolated and characterised by IR, H and 13C NMR
1
2
6
4
spectroscopic techniques. The crystal and molecular structures of 3-9 have been determined
by single crystal X-ray crystallography. Compounds 3 and 4 conform to the formula
XASA
Cp Ti(HL
-κO) with a monodentate carboxylate ligand while those of 5-9 conform to
2
2
XASA
2
1
2
Cp Ti(L
-κ O ,O ) with the dianions chelating the titanium atoms via carboxylate-O and
2

hydroxy-O atoms. The common feature of the molecular structures is the adoption of
…
distorted tetrahedral geometries based (Cp) O donor sets. Hydroxyl-O‒H O(carbonyl)
2
2
bonding leads to supramolecular chains in the crystal of 4 but, these are absent in 3.
…
Persistent Cp-C–H O(carbonyl) interactions, with the carbonyl atoms accepting two or three
such interactions, lead to supramolecular chains with helical (5, 7 and 8) or linear (6 and 9)
…
topologies; C‒X  interactions also play an important role in the packing of 6-8.
Keywords: Titanocene complexes, Arylazosalicylates, NMR spectroscopy, Crystal structure
_
_________________________
*
Corresponding author. E-mail address: basubaul@nehu.ac.in, basubaulchem@gmail.com (T. S.
Basu Baul)
*
* Additional corresponding author. E-mail: edwardt@sunway.edu.my (E.R.T. Tiekink)
1
. Introduction
Organometallic and coordination titanium(IV) compounds are of interest due to their
reactivity and uses including as reagents for catalytic enantioselective processes [1], organic
transformations [2], as initiators for polymerization reactions [3], polymerisation catalysts [4-
1
0] to metal organic frameworks [11-13] and metallo-supramolecular chemistry [14-19].
Other applications include the use of alkoxides or aryloxides precursors for the generation of
titanium-based materials [20-26] and their uses as photo-sensitisers and photo-catalysts
[27,28], titanium-based drugs [29-39] and cell imaging [40-41]. In recent years, substituted
titanium-oxo-clusters, such as those substituted by acetylacetonate, carboxylates and
catecholate derivatives, have attracted a great deal of attention, owing to their hydrolytic
stability and versatile coordination modes [42-46].
On the other hand, salicylic acid, an ancient anti-inflammatory drug having cancer-
fighting properties, has attracted attention for biological applications and shows a great

affinity for titanium(IV) ions [47,48]. In spite of the rich chemistry and diverse biological
applications of titanocene and titanium(IV) based compounds, the synthetic methodologies
are not well established (vide infra) and the number of isolated and structurally characterised
titanocene salicylates is scarce. As anticipated, both unsubstituted derivatives, bis(η5-
cyclopentadienyl)titanium(IV) salicylates e.g. [Ti(η -C H ) (O CC H OH) ] (bis(η5-
5
5
5 2
2
6
4
2
cyclopentadienyl)bis(salicylato-κO)titanium(IV)) (1) [49], with a monodentate carboxylate
5
5
ligand,
and
[Ti(η -C H ) (O CC H O)]
(bis(η -cyclopentadienyl)(salicylato-
5
5 2
2
6
4
2
1
2
κ O ,O )titanium(IV)) (2) [50], with a chelating dianion, have been described. Compound 1
has been synthesised by treating Cp TiCl with sodium salicylate (1:2 molar ratio) in water
2
2
containing acetylacetone wherein the role of the latter reagent is not known [49]. In an
another endeavour, compound 2 was prepared from aqueous solutions of Cp TiCl , salicylic
2
2
acid and sodium carbonate (1:1.1 molar ratio), the isolation of pure product required
meticulous control of the experimental conditions as to minimise hydrolytic side reactions.
Additionally, shorter or prolonged reaction times led to the isolation of either unreacted
starting materials or oxotitanium(IV) impurities, respectively. In view of the reactions’
complexities, both 1 and 2 were reinvestigated [51]. Compound 2 was isolated in high yield
(
86%) from a reaction containing equivalent amounts of Cp TiCl , triethylamine and sodium
2 2
salicylate (generated from NaOH and salicylic acid) in degassed water under stirring
conditions for 10 min. The structure of 2 was determined from the results of single crystal X-
ray crystallography that confirms the bidentate chelating nature of the doubly deprotonated
salicylate ligand [51]. On the other hand, attempted preparations of pure 1 by reacting (i)
sodium salicylate and Cp TiCl in two different solvents e.g. toluene and water, (ii) salicylic
2
2
acid and Cp TiMe in toluene and (iii) sodium salicylate and acetylacetone treated Cp TiCl
2
2
2
2
in water [49] provided either a mixture of 1 and 2 or products could not be separated [51],
underscoring the synthetic difficulties in this field.

In spite of such complications, reports on the synthesis of bis(η5-
cyclopentadienyl)titanium(IV) substituted salicylates are available [51,52] but, none of these
were characterised crystallographically. In an attempt to design molecules that offer the
potential of hydrogen bonding in their supramolecular structures, i.e. ligands such as 2-
mercapto-, 3,5-dichloro-2-hydroxy- and 3,5-dinitro-2-hydroxybenzoic acids, these were
reacted with Cp TiCl in the presence of aquatic β-cyclodextrin polymer in chloroform,
2
2
5
[Ti(η5-
which
provided
high
yield
of
[Ti(η -C H ) (O CC H S)·0.5C H ],
5
5 2
2
6
4
6
6
5
C H ) (O CC H (3,5-Cl )O)] and [Ti(η -C H ) (O CC H (3,5-(NO ) )O)]; the role of β-
5
5 2
2
6
2
2
5
5 2
2
6
2
2 2
cyclodextrin was not fully understood [53]. As a consequence of bidentate chelating nature of
salicylates in these compounds, a pseudo-tetrahedral geometry around titanium(IV) was
proposed on the basis of diffraction results. Reports on the synthesis of [Ti(η5-
5
(
CH )C H ) (O CC H O)] [54], [Ti(η -(CH )C H ) {(O CC H -p-O)(NN(C H -4-Br))}]
3
5
4 2
2
6
4
3
5
4 2
2
6
3
6
4
5
5
[
55], [Ti(η -(CH )C H ) (O CC H (3,5-(NO ) )O)] [56] and [Ti(η -(CH )C H ) (O CC H (5-
3
5
4 2
2
6
2
2 2
3
5
4 2
2
6
2
NO ) )O)] [57] are also available which were synthesised by reacting MeCp TiCl , aqueous
2
2
2
2
acetylacetone and substituted salicylic acid in chloroform/diethylether mixture but their
yields and NMR data are missing. Diffraction data on the isolated crystals conform to a
distorted tetrahedral/pseudo-tetrahedral geometry around titanium(IV), as observed
5
previously. The rarity of bis(η -cyclopentadienyl)titanium(IV) salicylates can be attributed to
the high oxophilic character of titanium cations preventing their crystallisation under ambient
conditions and/or in the presence of any oxygenated source (water or adventitious moisture).
Moreover, monitoring the kinetics of crystallisation also remains one of the most obvious
strategies allowing crystalline materials to be obtained. Recently, the monodentate mode of
salicylates in 1 [49] was confirmed from crystallographic data [58]; however, the product was

obtained from the reactions of Cp TiCl , 5-sulfosalicylic acid and salicylic acid in
2
2
aqueous/chloroform medium wherein the role of 5-sulfosalicylic acid was not explained.
In view of the above technical difficulties and on the basis of previous success with
the synthesis and structure determination of titanocene carboxylates of the type
Cp Ti(O CR) [59], the present work aimed to synthesise a series of bis(η5-
2
2
2
cyclopentadienyl)titanium(IV) substituted salicylates using a straightforward and
reproducible synthetic methodology. For this purpose, 5-[(E)-2-(aryl)-1-diazenyl]-2-
hydroxybenzoic acids (H2LXASA, Scheme 1) was used where the aryl group is an X-
substituted phenyl ring. The pro-ligand H2LXASA possesses several interesting features: (i) a
flexible carboxylate and phenol groups to endow it with strong coordination affinity toward
titanium ions; (ii) the presence of hydrogen bond donors such as the hydroxyl oxygen and the
carboxylate oxygen atoms (and acceptors such as the pyridyl nitrogen) can collaborate in
self-assemblies, (iii) the diazenyl group linking a bio-compatible salicylate moiety and the
aryl ring can provide additional flexibility to the ligand molecule and (iv) a pyridine ring
which provides not only a N-donor atom but also offers rigidity to promote the formation of
crystalline products. The pro-ligand H2LXASA is a salicylic acid derivative functionalised with
a aryldiazenyl group and the molecule can function as a mono- (HLXASA)– or dianionic
XASA 2–
(L
)
ligands. In the present contribution, the coordination chemistry of pro-ligand
H2LXASA was explored systematically towards Cp TiCl which provided two types of
2
2
titanium(IV) compounds viz. (a) bis(η -cyclopentadienyl)bis(HLXASA-κO)titanium(IV) e.g.
5
5
5
[
Ti(η -C H ) (O CC H (OH-2)(N=NC H (H-4)-5)) ] (3) and [Ti(η -C H ) (O CC H (OH-
5 5 2 2 6 4 6 4 2 5 5 2 2 6 4
bis(η -cyclopentadienyl)(LXASA-
5
2
)(N=NC H (OC H -4)-5)) ]
(4),
and
(b)
6
4
2
5
2
2
1
2
5
5
κ O ,O )titanium(IV) e.g. [Ti(η -C H ) (O CC H (O-2)(N=NC H (CH -4)-5))] (5), [Ti(η -
5
5 2
2
6
4
6
4
3
5
C H ) (O CC H (O-2)(N=NC H (F-4)-5))] (6), [Ti(η -C H ) (O CC H (O-2)(N=NC H (Cl-
5
5 2
2
6
4
6
4
5
5 2
2
6
4
6
4

5
[Ti(η5-
4
)-5))]
(7),
[Ti(η -C H ) (O CC H (O-2)(N=NC H (Br-4)-5))]
(8)
and
5
5 2
2
6
4
6
4
C H ) (O CC H (O-2)(N=NC H (N-4)-5))] (9). Compounds 3-9 were characterised by IR,
5
5 2
2
6
4
6
4
1
13
H and C NMR spectroscopic techniques. Further, the crystal and molecular structures of
each of the compounds has been determined by single crystal X-ray crystallography.
Scheme 1. Synthesis of pro-ligand H2LXASA and chemical structures of the Ti(IV) compounds
3
-9 along with the atom-numbering protocol.
2
. Experimental
2
.1. Materials and measurements
Aniline (Sd Fine) and p-phenetidine (Spectrochem) were freshly distilled and p-
toludine (Merck) was treated with water/ activated charcoal and recrystallised prior to use,
while all other chemicals were used as purchased without purification: bis(η5-
cyclopentadienyl)titanium(IV) dichloride, salicylic acid (Merck), p-fluoroaniline, 4-

aminopyridine (Spectrochem), p-chloroaniline and p-bromoaniline (SRL). The solvents used
in the reactions were of AR grade and were dried using standard procedures. Benzene,
toluene, hexane and THF were distilled from benzophenone/sodium while methanol was
distilled over activated magnesium. Triethylamine was dried over calcium hydride and
distilled. All manipulations were performed using standard Schlenk anaerobic lines in an
atmosphere of dry dinitrogen or argon, unless otherwise stated. Melting points were
measured using a Büchi M-560 melting point apparatus and are uncorrected. IR spectra in the
range 4000-400 cm–1 were obtained on a Perkin Elmer Spectrum BX series FT-IR
1
13
spectrophotometer with samples investigated as KBr discs. H and C NMR spectra were
1
recorded on a Bruker AMX 400 spectrometer at 400.13 and 100.62 MHz, respectively. H
1
3
and C chemical shifts were referenced to Me Si and CDCl set at 0.00 and 77.0 ppm,
4
3
respectively. Note: Reactions can be conducted in toluene, however, synthetic conveniences,
particularly the higher boiling point of toluene, led to the choice of benzene. Care in
handling benzene should be exercised.
2
.2. Synthesis of pro-ligands and sodium salts
Pro-ligands H2LXASA viz. 5-[(E)-2-phenyl-1-diazenyl]-2-hydroxybenzoic acid
(
H2LASA), 5-[(E)-2-(4-methylphenyl)-1-diazenyl]-2-hydroxybenzoic acid (H2LMASA), 5-[(E)-
-(4-bromophenyl)-1-diazenyl]-2-hydroxybenzoic acid (H2LBASA) [60], 5-[(E)-2-(4-
2
chlorophenyl)-1-diazenyl]-2-hydroxybenzoic acid (H2LCASA) [61], 5-[(E)-2-(4-pyridyl)-1-
diazenyl]-2-hydroxybenzoic acid (H2LPASA) [62] were prepared starting from salicylic acid
and the corresponding aniline using conventional diazonium salt chemistry, in accordance
with literature procedures. Synthetic and spectral details for the pro-ligands 5-[(E)-2-(4-
ethoxyphenyl)-1-diazenyl]-2-hydroxybenzoic acid (H2LOEASA) and 5-[(E)-2-(4-fluorophenyl)-
1
-diazenyl]-2-hydroxybenzoic acid (H2LFASA) are described below.

2
.2.1. Synthesis of 5-[(E)-2-(4-ethoxyphenyl)-1-diazenyl]-2-hydroxybenzoic acid (H2LOEASA)
An analogous method to that used for the preparation of H2LASA [60] was followed
using p-phenetidine (5.00 g, 36.44 mmol) and salicylic acid (5.02 g, 35.85 mmol). The
yellow reaction mixture was acidified with dilute acetic acid and the obtained precipitate was
washed with water and dried. The crude product was washed with hexane to remove any
tarry materials and recrystallised from methanol to yield orange crystalline material of
H2LOEASA. Yield: 6.72 g (64%). M. p.: 190-192 ˚C. Anal. found: C, 62.80; H, 4.80; N, 10.03.
-1
Calcd for C H N O : C, 62.93; H, 4.93; N, 9.79%. IR absorptions (cm ): 1656 ν(OCO)asym,
1
5
14
2
4
1
1
600, 1581, 1478, 1460, 1250, 1221, 1140, 840, 767, 520, 468. H NMR (DMSO-d /CDCl )
6 3
H: 8.34 [d, 2.1 Hz, 1H, H-6], 7.95 [dd, 9.0 & 2.1 Hz, 1H, H-4], 7.78 [XX' portion of
AA'XX', 2H, H-3' & H-5'], 6.97 [d, 9.0 Hz, 1H, H-3], 6.91 [AA' portion of AA'XX', 2H, H-2'
&
H-6'], 4.62 [brs, 1H, OH], 4.04 [q, 2H, CH ], 1.37 [t, 3H, CH ]. Signal for the carboxylic
2 3
acid were exchanged due to presence of water in the solvent. 13C{ H} NMR (DMSO-
1
d /CDCl )  : 172.54 [COO], 163.72 [C-2], 161.02 [C-1'], 146.54 [C-5], 145.20 [C-4'],
6
3
C
1
28.16 [C-4], 126.78 [C-6], 124.35 [C-3' & C-5'], 117.94 [C-3], 114.54 [C-2' & C-6'], 112.82
[
C-1], 63.67 [CH ], 14.64 [CH ].
2
3
2
.2.2. Synthesis of 5-[(E)-2-(4-fluorophenyl)-1-diazenyl]-2-hydroxybenzoic acid (H2LFASA)
An analogous method to that used for the preparation of H2LCASA [61] was followed
using p-fluroaniline (5.0 g, 45.02 mmol) and salicylic acid (6.21 g, 45.02 mmol). The yellow
reaction mixture was acidified with dilute acetic acid and the obtained precipitate was washed
with water and dried. The crude product was washed with hexane to remove any tarry
materials and recrystallised from methanol to yield yellow microcrystalline product of
H2LCASA. Yield: 6.72 g (57%). M. p.: 235-236 ˚C. Anal. found: C, 59.80; H, 4.10; N, 10.93.
-1
Calcd for C H FN O : C, 60.00; H, 3.49; N, 10.77%. IR absorptions (cm ): 1665
1
3
9
2
3
ν(OCO)asym,1616, 1575, 1477, 1455, 1395, 1379, 1311, 1217, 1201, 1178, 1078, 1065, 1009,

1
8
8
97, 840, 829, 708, 663, 567, 469. H NMR (DMSO-d /CDCl )  ; 11.65 [brs, 1H, COOH],
6 3 H
.39 [d, 1H, H-6], 7.97 [dd, 1H, H-4], 7.81 [XX' portion of AA'XX', 2H, H-3' & H-5'], 7.11
[AA' portion of AA'XX', 2H, H-2' & H-6'], 7.00 [d, 9.0 Hz, 1H, H-3], 6.14 [brs,1H, OH].
1
3
1
13
19
C{ H} (DMSO-d /CDCl )  : 172.11 [COO], 165.17 and 162.67 [C-4', ( C- F = 251 Hz)],
6
3
H
1
3
64.29 [C-2], 148.86 [C-1'], 144.87 [C-5], 128.20 [C-4], 127.33 [C-6], 124.52 and 124.44 [C-
1
3
19
13
19
' & C-5', ( C- F = 8.0 Hz)], 118.05 [C-3], 115.99 and 115.76 [C-2' & C-6', ( C- F = 23
Hz)], 113.02 [C-1].
Sodium salts viz. sodium 5-[(E)-2-(phenyl)-1-diazenyl]-2-hydroxybenzoate
NaHLASA
NaHLPASA) [62] were prepared by the method described earlier. An analogous method to
(
(
)
[60]
and
sodium
5-[(E)-2-(4-pyridyl)-1-diazenyl]-2-hydroxybenzoate
that used for the preparation of NaHLASA [60] was followed for the preparation of sodium 5-
(E)-2-(4-ethoxyphenyl))-1-diazenyl]-2-hydroxybenzoate (NaHLOEASA). Dark-red powder;
[
-1
M. p.: > 350 ˚C. IR absorptions (cm ): 1600 ν(OCO)asym, 1585, 1493, 1484, 1464, 1441,
1
367, 1317, 1292, 1257, 1176, 1141, 1026, 834, 767, 691, 575.
2
.3. Synthesis of titanocene compounds 3-9
5
2
.3.1. Synthesis of [Ti(η -C H ) (O CC H (OH-2)(N=NC H (H-4)-5)) ] (3)
5
5 2
2
6
4
6
4
2
A freshly prepared solution of titanocene dichloride (0.100 g, 0.401 mmol) in
anhydrous benzene (15 ml) was added to a stirred suspension of NaHLASA (0.230 g, 0.883
mmol) in anhydrous benzene (15 ml) and the stirring was continued at 40 ˚C for 4 h. The
dark-red reaction mixture was evaporated to dryness, washed with hot hexane and dried in
vacuo. The residue was extracted into hot anhydrous chloroform (20 ml) and filtered through
a frit covered with pre-dried neutral silica (3 cm layer, mesh size 100-200) and eluted further
with anhydrous chloroform (3 x 1 ml). The clear red filtrate was concentrated using a rotary
evaporator to around 3 ml, which upon standing overnight afforded orange crystals of 3 at

ambient temperature. Crystals were washed with a small amount of benzene and dried in
vacuo. Yield: 0.15 g, 56 %. M. p.: 180-183 ˚C. Anal. found: C, 65.20; H, 4.12; N, 9.03. Calcd
-1
for C H N O Ti: C, 65.46; H, 4.27; N, 8.48%. IR absorptions (cm ): 1633 ν(OCO)asym,
3
6
28
4
6
1
1
593, 1570, 1484, 1417, 1384, 1356, 1295, 1251, 1174, 824, 802, 766, 684, 462. H NMR
(
CDCl )  : 12.32 [s, 2H, OH], 8.37 [d, 2H, H-6], 7.82 [m, 4H, H-2' & H-6'], 7.35-7.43 [m,
3
H
4
H, H-4 & H-4'], 7.22 [m, 4H, H-3' & H-5'], 6.98-7.03 [m, 2H, H-3], 6.70 [s, 10H, C H ].
5 5
1
3
1
C{ H} NMR (CDCl )  : 175.52 [COO], 163.82 [C-2], 151.84 [C-1'], 145.04 [C-5], 130.18
3
C
[
C-4'], 129.02 [C-4], 128.47 [C-3' & C-5'], 127.38 [C-6], 122.59 [C-2' & C-6'], 119.41
C H ], 117.87 [C-3], 115.52 [C-1].
[
5
5
5
2
.3.2. Synthesis of [Ti(η -C H ) (O CC H (OH-2)(N=NC H (OC H -4)-5)) ] (4)
5 5 2 2 6 4 6 4 2 5 2
Two synthetic procedures are described below.
Method 1: An analogous method to that used for the preparation of 3 was followed using
titanocene dichloride (0.100 g, 0.401 mmol) and NaHLOEASA (0.256 g, 0.832 mmol) except
that the reaction mixture was directly filtered and washed with benzene. Red-orange crystals
were washed with small amount of hexane and dried in vacuo. Yield: 0.19 g, 64 %. M. p.:
1
4
1
2
71-173 ˚C. Anal. found: C, 64.50; H, 4.18; N, 7.40. Calcd for C H N O Ti: C, 64.18; H,
40 36 4 8
-1
.85; N, 7.48%. IR absorptions (cm ): 1631 ν(OCO)asym, 1604, 1582, 1499, 1477, 1392,
1
335, 1247, 1216, 923, 825, 774, 462, 517. H NMR (CDCl )  : 12.25 [s, 2H, OH], 8.32 [d,
3
H
H, H-6], 7.80 [XX' portion of AA'XX', 4H, H-3' & H-5'], 7.35 [AA' portion of AA'XX', 4H,
H-2' & H-6'], 6.90-7.02 [m, 4H, H-3 & H-4], 6.69 [s, 10H, C H ], 4.01 [q, 4H, CH ], 1.37 [t,
5
5
2
1
3
1
6
5
H, CH ]. C{ H} NMR (CDCl )  : 175.64 [COO], 163.31 [C-2], 160.78 [C-1'], 146.23 [C-
3 3 C
], 145.19 [C-4'], 128.04 [C-4], 127.15 [C-6], 124.43 [C-3' & C-5'], 119.41 [C H ], 119.27
5
5
[
C-2' & C-6'], 114.65 [C-3], 114.10 [C-1], 63.67 [CH ], 14.78 [CH ].
2 3

Method 2: A freshly prepared solution of titanocene dichloride (0.10 g, 0.40 mmol) in
anhydrous benzene (15 ml) was added to a stirred solution of H2LOEASA (0.23 g, 0.80 mmol)
in anhydrous benzene (15 ml). Subsequently to the clear reaction mixture, a benzene solution
(
10 ml) of NEt (0.080 g, 0.79 mmol) was added drop-wise where upon the wine-red solution
3
turns dark-red along with precipitation of Et N∙HCl. The reaction mixture was slowly heated
3
to 40 ˚C and stirring was continued for an additional 4 h. The dark-red solution was filtered
through a frit covered with pre-dried neutral silica (3 cm layer, mesh size 100-200) and eluted
with anhydrous benzene (3 x 1 ml). The clear filtrate was concentrated using a rotary
evaporator to around 3 ml, which upon standing overnight afforded red-orange crystals of 4
at ambient temperature. Crystals were washed with small amount of anhydrous hexane and
dried in vacuo. Yield: 0.17 g, 53%. M. p.: 171-173 ˚C. Spectroscopic data of the compound
closely match with that reported for 4 synthesised by method 1.
5
2
.3.3. Synthesis of [Ti(η -C H ) (O CC H (O-2)(N=NC H (CH -4)-5))] (5)
5
5 2
2
6
4
6
4
3
A freshly prepared solution of titanocene dichloride (0.100 g, 0.401 mmol) in
anhydrous benzene (20 ml) was added to a clear stirred solution of H2LMASA (0.102 g, 0.401
mmol) in anhydrous benzene (50 ml). Subsequently, to a clear reaction mixture, a benzene
solution (10 ml) of NEt (0.080 g, 0.790 mmol) was added drop-wise where upon the wine-
3
red solution turned dark-red along with precipitation of Et N∙HCl. The reaction mixture was
3
slowly heated to 40 ˚C and stirring was continued for additional 4 h. The dark-red solution
was filtered through a frit covered with pre-dried neutral silica (3 cm layer, mesh size 100-
2
00) and eluted with anhydrous benzene (3 x 1 ml). The clear filtrate was concentrated using
a rotary evaporator to around 15 ml, which upon standing for a week afforded dark-red
crystals of 5 at ambient temperature. Crystals were washed with small amount of anhydrous
benzene and dried in vacuo. Yield: 0.13 g, 74 %. M. p.: 150-152 ˚C. Anal. found: C, 67.10;
-
H, 4.19; N, 7.80. Calcd for C H N O Ti: C, 66.68; H, 4.66; N, 6.48%. IR absorptions (cm
2
4
20
2
3

1)
: 1614 ν(OCO)asym, 1598, 1472, 1414, 1310, 1248, 1175, 1128, 1128, 822, 644, 501. H
1
NMR (CDCl )  : 8.45 [d, 1H, H-6], 8.06 [dd, 1H, H-4], 7.74 [XX' portion of AA'XX', 2H,
3
H
H-3' & H-5'], 7.25 [AA' portion of AA'XX', 2H, H-2' & H-6'], 7.05 [d, 1H, H-3], 6.60 [s,
1
3
1
1
1
1
0H, C H ], 2.37 [t, 3H, CH ]. C{ H} NMR (CDCl )  : 173.89 [COO], 165.49 [C-2],
5 5 3 3 C
51.84 [C-1'], 146.51 [C-5], 142.56 [C-4'], 131.12 [C-3' & C-5'], 129.65 [C-4], 128.49 [C-6],
23.95 [C-2' & C-6'], 121.69 [C H ], 119.44 [C-3], 114.45 [C-1], 22.84 [CH ].
5
5
3
5
2
.3.4. Synthesis of [Ti(η -C H ) (O CC H (O-2)(N=NC H (F-4)-5))] (6)
5 5 2 2 6 4 6 4
An analogous method to that used for the preparation of 5 was followed using
titanocene dichloride (0.100 g, 0.401 mmol), H2LFASA (0.113g, 0.401 mmol) and Et N (0.080
3
g, 0.790 mmol). The clear filtrate was concentrated using a rotary evaporator to around 15
ml, which upon standing overnight afforded dark-red crystals of 6 at ambient temperature.
Crystals were washed with small amount of anhydrous benzene and dried in vacuo. Yield:
0
.12 g, 68 %. M. p.: 187-189 ˚C. Anal. found: C, 63.40; H, 3.59; N, 6.10. Calcd for
-1
C H FN O Ti: C, 63.32; H, 3.93; N, 6.42%. IR absorptions (cm ): 1622 ν(OCO)asym, 1597,
2
3
17
2
3
1
1
497, 1471, 1450, 1417, 1308, 1247, 1225, 1166, 1129, 1019, 837, 823, 497. H NMR
(
CDCl )  : 8.40 [d, 1H, H-6], 7.98 [dd, 1H, H-4], 7.82 [XX' portion of AA'XX', 2H, H-3' &
3
H
H-5'], 7.11 [AA' portion of AA'XX', 2H, H-2' & H-6'], 6.99 [d, 1H, H-3], 6.53 [s, 10H, C H ].
5
5
1
3
1
13
19
C{ H} NMR (CDCl )  : 175.18 [COO], 167.96 and 165.42 [C-4', ( C- F = 255 Hz)],
3
C
1
3
1
67.04 [C-2], 151.63 [C-1'], 147.61 [C-5], 130.95 [C-4], 130.10 [C-6], 127.28 and 127.20 [C-
1
3
19
' & C-5', ( C- F = 8.0 Hz)], 122.94 [C H ], 120.81[C-3], 118.76 and 118.53 [C-2' & C-6'],
5
5
15.75 [C-1].
.3.5. Synthesis of [Ti(η -C H ) (O CC H (O-2)(N=NC H (Cl-4)-5))] (7)
5
2
5
5 2
2
6
4
6
4
An analogous method to that used for the preparation of 5 was followed using
titanocene dichloride (0.100 g, 0.401 mmol), H2LCASA (0.117 g, 0.401 mmol) and Et N (0.080
3

g, 0.790 mmol)). The turbid reaction mixture was filtered; filtrate was concentrated to
dryness using a rotary evaporator. The brick-red residue was washed with anhydrous hexane
and dried in vacuo. The solid material was dissolved in anhydrous chloroform (15 ml),
filtered through a frit which upon standing overnight afforded dark-red crystals of 7 at
ambient temperature. Crystals were washed with small amount of anhydrous benzene and
dried in vacuo. Yield: 0.13 g, 71 %. M. p.: 148-150 ˚C. Anal. found: C, 60.68; H, 3.70; N,
-1
6
.30. Calcd for C H ClN O Ti: C, 61.02; H, 3.78; N, 6.19%. IR absorptions (cm ): 1629
23 17 2 3
1
ν(OCO)asym,1598, 1499, 1467, 1499, 1412, 1311, 1248, 1175, 1125, 1043, 821, 658, 466. H
NMR (CDCl )  : 8.42 [d, 1H, H-6], 8.00 [dd, 1H, H-4], 7.77 [XX' portion of AA'XX', 2H,
3
H
H-3' & H-5'], 7.38 [AA' portion of AA'XX', 2H, H-2' & H-6'], 7.00 [d, 1H, H-3], 6.54 [s,
1
3
1
1
0H, C H ]. C{ H} NMR (CDCl )  : 175.05 [COO], 167.17 [C-2], 153.39 [C-1'], 147.55
5 5 3 C
[C-5], 138.90 [C-4'], 131.88 [C-3' & C-5'], 130.94 [C-4], 130.26 [C-6], 126.50 [C-2' & C-6'],
1
22.89 [C H ], 120.80 [C-3], 115.75 [C-1].
5 5
5
2
.3.6. Synthesis of [Ti(η -C H ) (O CC H (O-2)(N=NC H (Br-4)-5))] (8)
5 5 2 2 6 4 6 4
An analogous method to that used for the preparation of 5 was followed using
titanocene dichloride (0.100 g, 0.401 mmol), H2LBASA (0.117 g, 0.401 mmol) and Et N (0.080
3
g, 0.790 mmol)). The turbid reaction mixture was filtered; filtrate was concentrated to
dryness using a rotary evaporator. The brick-red residue was washed with anhydrous hexane
and dried in vacuo. The solid material was dissolved in anhydrous chloroform (30 ml),
filtered through a frit, which upon standing for three days afforded dark-red crystals of 8 at
ambient temperature. Crystals were washed with small amount of anhydrous benzene and
dried in vacuo. Yield: 0.11 g, 55 %. M. p.: 150-152 ˚C. Anal. found: C, 56.10; H, 3.40; N,
-1
5
.30. Calcd for C H BrN O Ti: C, 55.56; H, 3.45; N, 5.63%. IR absorptions (cm ): 1629
23 17 2 3
ν(OCO)asym, 1618, 1599, 1449, 1472, 1413, 1393, 1309, 1261, 1248, 1171, 1127, 1065, 1024,
1
8
18, 707, 567, 472. H NMR (CDCl )  : 8.42 [d, 1H, H-6], 7.99 [dd, 1H, H-4], 7.69 [XX'
3
H

portion of AA'XX', 2H, H-3' & H-5'], 7.56 [AA' portion of AA'XX', 2H, H-2' & H-6'], 7.00
1
3
1
[
d, 1H, H-3], 6.53 [s, 10H, C H ]. C{ H} NMR (CDCl )  : 175.36 [COO], 167.53 [C-2],
5 5 3 C
1
1
54.07 [C-1'], 147.88 [C-5], 135.16 [C-3' & C-5'], 131.26 [C-4'], 130.64 [C-4], 127.70 [C-6],
27.07 [C-2' & C-6'], 123.21 [C H ], 121.14 [C-3], 116.07 [C-1].
5
5
5
2
.3.7. Synthesis of [Ti(η -C H ) (O CC H (O-2)(N=NC H (N-4)-5))] (9)
5 5 2 2 6 4 6 4
An analogous method to that used for the preparation of 3 was followed using
titanocene dichloride (0.100 g, 0.401 mmol) and excess NaHLPASA (0.230 g, 0.883 mmol). The
resulting dark-red suspension was evaporated to dryness, washed with hot hexane and dried in
vacuo. The residue was extracted into hot anhydrous dichloromethane (30 ml) and filtered
through a frit covered with pre-dried neutral silica (3 cm layer, mesh size 100-200) and eluted
further with anhydrous dichloromethane (3 x 1 ml). The clear red filtrate was concentrated
using a rotary evaporator to around 20 ml, which upon standing overnight afforded fine dark-
red crystals of 9 at ambient temperature. Crystals were dissolved by boiling in
dichloromethane/DMF (20 ml/1ml, v/v) and the clear solution was concentrated to 10 ml,
which upon standing at ambient temperature for about an hour afforded X-ray quality crystals.
Crystals were washed with small amount of benzene and dried in vacuo. Yield: 0.13 g, 77 %.
M. p.: 328-330 ˚C. Anal. found: C, 63.50; H, 4.50; N, 10.26. Calcd for C H N O Ti: C,
2
2
17
3
3
-
1
6
1
3.02; H, 4.09; N, 10.02%. IR absorptions (cm ): 1617 ν(OCO)asym, 1590, 1465, 1419, 1309,
1
253, 1174, 1122, 825, 790, 603. H NMR (CDCl /DMSO-d )  : 8.76 [d, 1H, H-6], 8.70 [XX'
3
6
H
portion of AA'XX', 2H, H-3' & H-5'], 7.97 [dd, 1H, H-4], 7.63 [AA' portion of AA'XX', 2H,
1
3
1
H-2' & H-6'], 6.74 [d, 1H, H-3], 6.45 [s, 10H, C H ]. C{ H} NMR (CDCl /DMSO-d )  :
5
5
3
6
C
1
1
70.57 [COO], 168.98 [C-2], 156.96 [C-1'], 150.60 [C-3' & C-5'], 144.63 [C-5], 130.50 [C-4],
26.03 [C-6], 120.25 [C-3], 120.01 [C-1], 119.18 [C H ], 115.77 [C-2' & C-6'].
5
5
2
.4. Single crystal X-ray structure determinations of 3-9

Crystals of compounds 3, 7, 8 (chloroform), 4 and 6 (benzene), 5 (benzene/THF; 2/1
v/v) and 9 (dichloromethane/DMF; 20/1 v/v) suitable for single-crystal X-ray diffraction
analysis were grown from the respective solutions by slow solvent evaporation at room
temperature. Intensity data for compounds 3-9 were measured at room temperature on an
Agilent Xcalibur Eos Gemini diffractometer equipped with a CCD area detector and graphite-
monochromated Mo Kα radiation (λ = 0.71073 Å); Cu Kα radiation (λ = 1.54184 Å) was
employed for 5. Data reduction and empirical absorption corrections, based on a multi-scan
technique, were applied [63]. Each structure was solved by direct methods [64] and refined on
F2 with anisotropic displacement parameters and C-bound H atoms in the riding model
approximation [65]. For 3 and 4, the hydroxyl-O‒H atoms were located from difference maps
but, were refined with the distance restraint O‒H = 0.82±0.01 Å. A weighting scheme of the
2
2
2
2
2
form w = 1/[ (F ) + aP + bP] where P = (F + 2F )/3) was introduced for each refinement.
o
o
c
The structures were determined at room temperature and uniformly featured high displacement
parameters, in particular for the cyclopentadienyl (Cp) groups. However, the structures were
determined unambiguously and are entirely consistent with the spectroscopic data. In the
refinement of 3, the (-1 0 4), (-1 0 3), (4 1 3) and (0 2 6) reflections were omitted from the final
cycles of refinement owing to poor agreement. In 6, the C17 atom was restrained to be nearly
isotropic. The (2 0 4) reflection was omitted from the refinement of 7. In 7, the maximum and
-3
minimum residual electron density peaks of 1.17 and 0.45 eÅ were located 1.45 and 0.72 Å
from the C5 and Cl1 atoms, respectively. The crystal of 8 was a two-component twin [twin
law: 1 0 0.382 0 -1 0 0 0 -1] with the minor component comprising 0.343(5) of the sample.
Crystal data and refinement details are collected in Table 1. The molecular structure diagrams
were generated by ORTEP for Windows [66] at the 25% probability level and the packing
diagrams with DIAMOND [67]. Additional data analysis was made with PLATON [68].
3
. Results and discussion

3
.1. Synthesis and spectroscopic characterisation of compounds 3-9
5
The paucity of bis(η -cyclopentadienyl)titanium(IV) salicylates is mainly due to the
high oxophilic character of Ti-cations, preventing them to crystallise under ambient conditions
and/or in the presence of any oxygenated source. In view of this, the primary objective herein
was set to standardise the synthetic procedure and secondly to crystallise the powder/
microcrystalline materials to obtain X-ray quality single crystals to enable the determination of
their hitherto unknown molecular structures. In the current investigation, titanocene
arylazosalicylates 3 and 4 were synthesised by the reactions of titanocene dichloride with two
molar equivalents of the freshly prepared corresponding sodium salts of the respective pro-
ligands in benzene at 40 ˚C under stirring. As a representative case, attempted reaction of
titanocene dichloride, H2LOEASA and NEt using 1:2:2 molar ratio in benzene also afforded
3
compound 4. However, the cumbersome workup procedure was detrimental to the overall yield
and thus synthetic success led to the choice of sodium salt method. On the other hand, 5-8
were prepared by the reactions of titanocene dichloride with the respective pro-ligands in
benzene in the presence of triethylamine in 1:1:2 molar proportions (Scheme 1). As an
exception, by adopting the analogous methodology, compound 9 could not be isolated owing
to the insolubility of H2LPASA, nevertheless the reaction of titanocene dichloride with excess
NaHLPASA (1:2 molar proportions) proceeded smoothly in benzene (refer to the Experimental
section for details). The final yields of the products were >50% which were dependent on the
workup conditions applied for the purification and recovery of the crystals. Crystalline samples
of the compounds 3-9 can be stored for several months in an inert environment; of these
compounds 3-5 and 9 retain their colour, lustre and melting points. However, compounds 4-6
turns into powder with time but retain their original melting points. The compounds were
characterised by NMR, IR spectroscopy and by single-crystal X-ray crystallography.
The IR spectra of 3-9 show two intense bands in the regions between 1633-1617 and

-1
1
417-1384 cm corresponding to ν(OCO)
and ν(OCO)sym vibrations, respectively. The
asym
-1
observed differences between the asymmetric and symmetric vibrations are >200 cm ;
suggesting a monodentate coordination of the carboxylate ligand [69]; this assumption was
subsequently confirmed from the results of single crystal X-ray diffraction studies (see section
3
.2). Since the titanocene arylazosalicylates in the present investigation were generated from
solution methods, it was therefore necessary to confirm the purity of the bulk material and also
1
13
1
to comprehend the solution behaviour of 3-9. For this purpose, solution-state H and C{ H}
NMR studies were undertaken using vacuum dried crystalline samples of 3-9 that were
dissolved in CDCl . All the samples confirm the purity and displayed the expected signals due
3
to the carboxylate and Cp ligands, and the integration values in the spectra are in agreement
XASA
-κO) (3 and 4) and Cp Ti(LXASA-
2 2
with those expected for the structure types Cp Ti(HL
2
2
1
2
1
13
1
κ O ,O ) (5-9) as shown in Scheme 1 (refer to Figs S1-S14 for H and C{ H} NMR spectra).
NMR solutions of the compounds prepared under dinitrogen/ argon were found to be stable for
at least two hours but, tended to decompose slowly. Compounds 3 and 4 displayed a singlet at
around 12.3 ppm due to phenolic OH which is absent in rest of the compounds, corroborating
that the ligand bonds to titanium(IV) via carboxylate oxygen atom while in 5-9 the di-anionic
ligand chelate the titanium atom via carboxylate-O and hydroxy-O atoms. Two chemically
1
equivalent Cp rings were detected as sharp singlet in the range 6.53-6.70 ppm in the H NMR
1
3
spectra while a single signal was observed between 119.2 and 123.2 ppm in the C NMR
spectra. The carboxylate carbonyl-carbon resonances for the compounds 3-8 were observed at
δ 175 ppm and for compound 9 at 170.6 ppm. As such, no sign of decomposition was noticed
in NMR spectra after dissolution of the crystalline samples, confirming that the solid-state
structures were retained in solution at least for two hours. The subtle changes in the ligand
substitution did not affect the general pattern of the NMR spectra and the observed signals
were generally broad and unresolved which prevented the measurement of coupling constants.

3
.2. Description of the crystal and molecular structures of 3-9
The molecular structures of 3-9 are illustrated in Fig. 1 and selected geometric
parameters for the seven structures are collated in Table 2. Each crystal is solvent-free and
comprises a single molecule in the asymmetric unit. The structures fall into two classes, with 3
XASA
and 4 having the general formula Cp Ti(HL
-κO) , and those of 5-9 conforming to
2
2
XASA
2
1
2
Cp Ti(L
-κ O ,O ). The difference arises as in the latter series, the hydroxyl group of the
2
carboxylate ligand is also deprotonated leading to a dianion so that each complex features a
titanium(IV) centre.
In 3, the titanium atom is coordinated by two oxygen atoms derived from two
monodentate hydroxylbenzoate ligands. This is confirmed by the observation that the C‒O1,
O3 bond lengths are 0.03-0.04 Å longer than the C=O2, O4 bond lengths and that the
carbonyl-O2 and O4 atoms are approximately 3.5 Å distant from the titanium centre.
…
Intramolecular hydroxyl-O‒H O(carbonyl) hydrogen bonds close S(6) loops, Table 3, and
confer co-planarity to the carboxyl and attached phenyl rings, with the CO /C dihedral angles
2
6
being 5.1(8) and 3.9(8)° for the O1- and O4- carboxylate ligands, respectively. The dihedral
angle between the CO /CO planes is 23.4(8)°, indicating a non-planar relationship. The
2
2
5
coordination geometry is best described as pseudo-tetrahedral the two η -cyclopentadienyl
Cp) anions assumed to occupy a single position each. The Ti‒O1, O4 bond lengths are
(
experimentally equivalent. While the Ti–C(Cp) bond lengths span an experimentally distinct
…
range of 2.332(5) to 2.397(5) Å, no pattern to the variations are apparent. Indeed, the Ti Cg
ring centroid distances of 2.049(3) and 2.058(3) Å suggest any differences are not chemically
significant. The tetrahedral angles range from a narrow 90.24(12)°, for O1–Ti–O4, to a broad
1
31.69(12)°, subtended by the more bulky Cp rings. The O1-carboxylate ligand is close to co-
planar with the dihedral angle between the aromatic residues being 2.5(3)° but, the O4-
carboxylate ligand is twisted with the equivalent angle being 15.6(2)°. The molecular structure

of 4 presents very similar features as for 3. The carboxylate residues tend to be more co-planar
with the CO /CO dihedral angle being 13.2(3)° but, greater twists are noted between the
2
2
CO /C planes, i.e. 6.1(4) and 11.85(14)° for the O1- and O4-carboxylate ligands, respectively,
2
6
…
even though the intramolecular hydroxyl-O‒H O(carbonyl) hydrogen bonds persist, Table 3.
The dihedral angle between the aromatic residues in each ligand is similar, i.e. 10.60(10) and
7
.23(7)°.
Fig. 1. Molecular structures of 3-9, showing atom labelling schemes and displacement
ellipsoids at the 25% probability level.

The molecular structures of 5-9 are very similar to each other. In 5, the titanium atom
is chelated by the carboxylate-O1 and hydroxyl-O3 atoms with the former bond being about
0
.05 Å longer, an observation correlated with the influence of the proximate electronegative
carbonyl-O2 atom; the C1‒O1, O2 distances of 1.295(3) and 1.221(3) Å are significantly
different in accord with expectation. The six-membered chelate ring is not planar and is best
described as being based on a half-chair with the titanium atom lying 0.592(2) Å above the
least-squares plane through the O1,O3,C1-C3 atoms [r.m.s. deviation = 0.054 Å]. The
coordination geometry is distorted tetrahedral within a C O donor set as described above. The
2
2
O1–Ti–O3 chelate angle is a little more acute than the O1–Ti–O4 angles in 3 and 4, and the
average Ti–C(Cp) bond lengths tend to be a little longer, Table 2. The angle between the
carboxylate and phenyl rings is 8.1(3)°, and the angle between aromatic residues 15.83(12)°.
Essentially the same molecular structures are noted for 6-9. The structures of 6 and 7 exhibit
the maximum [0.699(2) Å] and minimum [0.567(6) Å] deviations of the titanium atom from
the chelate ring. The dihedral angle between the CO /C planes is minimum in 6, i.e. 1.9(4)°,
2
6
and the maximum twist in the carboxylate ligands is seen in 9, i.e. 18.01(14)°.
As discussed in a recent contribution [59], the structural motif observed for 3 and 4
conforms with expectation for the approximately 25 compounds of the general formula
Cp Ti(O CR) . By contrast, an evaluation of the crystallographic literature [70] shows there
2
2
2
are only five precedents for Cp Ti(salicylate derivatives), which exhibit very similar structural
2
features with one notable exception. In the structure of the parent compound, Cp Ti(salicylate)
2
[51], the chelate ring is somewhat more planar than reported for other derivatives and for the
structures described herein. Thus, the titanium atom lies 0.4180(11) above the remaining five
atoms of the chelate ring with the maximum deviation from the plane being 0.019(6) Å for the
C1 atom.

…
In the crystal of 3,   stacking interactions predominate, Table 3. Thus, connections
between Cp and hydroxylbenzoate rings, and between hydroxylbenzoate and phenyl rings of
like molecules connect molecules into a supramolecular layer parallel to (0 1 1), Fig. 2a.
Layers stack without directional interactions between them as shown in the diagram of the unit
cell contents in Fig. S15. Quite distinct supramolecular association is evident in the crystal of 6
with hydrogen bonding interactions formed between the hydroxyl-O‒H atoms and the
carbonyl-O atoms of symmetry-related molecules indicating the hydroxyl-O‒H hydrogen
atoms are bifurcated owing to their participation in intramolecular hydroxyl-
O‒H…O(carbonyl) hydrogen bonds. This is consistent with the relatively weak nature of the
intermolecular hydrogen bonding. As shown in Fig. 2b, these interactions lead to a
…
…
supramolecular chain and four-membered { HO } synthons. Being propagated by 2 -screw
2
1
symmetry along the b-axis direction, the chain has a helical topology. The chains are sustained
…
into a three-dimensional architecture by a variety of C‒H  interactions with methylene-,
methyl- and Cp-H being donors and hydroxylbenzoate and Cp rings being acceptors, Table 3.
A view of the unit cell contents is shown in Fig. S16.

Fig. 2. Supramolecular association in the crystals of 3 and 4: (a) 3, a view of the
…
supramolecular layer parallel to (0 1 1) sustained by   interactions (shown as purple dashed
lines) and (b) 4, a view of the supramolecular chain sustained by hydroxyl-O‒H…O(carbonyl)
hydrogen bonds (shown as orange dashed lines); non-participating hydrogen atoms are omitted
for reasons of clarity.

The geometric parameters characterizing the supramolecular association operating in
the crystals of 5-9 are summarised in Table 4. In the molecular packing of 5,
…
C‒H O(carbonyl) interactions feature prominently with the carbonyl-O2 atom accepting
three such interactions from two Cp rings to generate a supramolecular chain along the b-
axis, Fig. 3a. In essence, two Cp rings of one molecule of 5 connect to a carbonyl-O2 of a
symmetry-related molecule and a second Cp-H atom of the original molecules connects to a
second symmetry-related molecule to form a chain with a helical topology (2 screw
1
…
symmetry). The main connections between chains are   stacking between
hydroxybenzoate and Cp rings to form supramolecular layers that stack along the a-axis
without directional interactions between them, at least based on the distance criteria assumed
in PLATON [68]; a view of the unit cell contents is shown in Fig. S17. In 6, a linear
supramolecular chain along the b-axis is again formed through the agency of Cp-
…
C‒H O(carbonyl) interactions, again with the carbonyl-O2 atom accepting three contacts,
…
Fig. 3b. While the pattern of Cp-C‒H O(carbonyl) interactions in 6 matches that described
for 5, the difference is that in 6, the chain is propagated by translational symmetry. As
highlighted in Fig. S18, the chains are consolidated into the three-dimensional arrangement
…
by   interactions between centrosymmetrically-related Cp rings and side-to-side
…
C‒F (hydroxybenzoate) interactions. Despite having a chlorophenyl group, the crystal of 7
is isostructural with 5 rather than with 6. Thus, a helical supramolecular chain is formed
along the b-axis, Fig. S19a, and supramolecular layers are formed in the bc-plane by …
stacking interactions between hydroxybenzoate and Cp rings. The difference between 5 and 7
…
arises as directional interactions, i.e. of the type parallel C‒Cl (hydroxybenzoate), occur
between layers to establish the three-dimensional molecular packing, Fig. S19b. Distinctive
packing patterns are found in the crystals of 8 and 9.

…
Fig. 3. Views of the supramolecular association sustained Cp-C‒H O(carbonyl) interactions
in the crystals of 5, 6, 8 and 9: (a) 5, helical chain, (b) 4, linear chain, (c) 8, layer parallel to (0
…
1
1) and (d) 9, linear chain. The Cp-C‒H O(carbonyl) interactions are shown as orange
dashed lines and non-participating hydrogen atoms are omitted for reasons of clarity.
…
In the molecular packing of 8, the carbonyl-O2 atom accepts two C‒H O(carbonyl)
interactions with the donors derived from two symmetry-related molecules. As these
interactions extend laterally, a supramolecular layer ensures, Fig. 3c. These stack along the c-
…
axis being connected by hydroxybenzoate-C‒H (bromophenyl) and side-on
…
C‒Br hydroxybenzoate) interactions, Table 4 and Fig. S20. The only identifiable
…
intermolecular interactions in the crystal of 9 are C‒H O(carbonyl) interactions whereby the

carbonyl-O2 atom accepts two contacts derived from two symmetry-related molecules to
sustain a linear supramolecular chain, Fig. 3d. A view of the unit cell contents is shown in Fig.
S21. While no formal role for the pyridyl-nitrogen atom is noted, it is proximate to a
symmetry-related Cp-H atom, being separated by 2.67 Å.
…
In summary, the crucial role of C‒H O(carbonyl) interactions in stabilising
supramolecular chains in the crystals of 5-9 is established. The topology of the chain, helical
(5, 7 and 8) or linear (6 and 9) is dependent on the space group symmetry, Table 1. The
presence of halide substituents in 6-8 ensures higher dimensionality of the supramolecular
…
architectures through their participation in C‒X  interactions.
4
. Conclusions
5
Several new members of bis(η -cyclopentadienyl)titanium(IV) arylazosalicylates were
synthesised by conventional synthetic routes in anaerobic conditions in benzene. The
1
13
compounds were characterised by IR and H and C NMR spectroscopic methods. The bulk
samples of 3-9 were found to be consistent with their solid-state structures as revealed from
NMR spectroscopy. The general solid-state constructs of 3-9 appear to be maintained in CDCl3
solutions at least for couple of hours. X-ray crystallography established the stoichiometry of 3
XASA
XASA
2
1
2
and 4 as Cp Ti(HL
-κO) and those of 5-9 as Cp Ti(L
-κ O ,O ) with the molecular
2
2
2
structures being based on distorted tetrahedral geometries based (Cp) O donor sets and to be
2
2
largely independent of the nature of the substituents in the terminal phenyl rings. The
…
…
molecular packing in 3 is based on   interactions but hydroxyl-O‒H O(carbonyl) bonding
…
leads to supramolecular chains in 4. In 5-9, Cp-C–H O(carbonyl) interactions persist and lead
to supramolecular chains with helical (5, 7 and 8) or linear (6 and 9) topologies; C‒X…
interactions play an important role in the packing of 6-8.
Conflict of interest

The authors declare that they have no conflicts of interest with the contents of this
article.
Supplementary materials
Crystallographic data for compounds 3-9 reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre (CCDC) as supplementary publication nos.
CCDC-1850180-CCDC-1850186. These data can be obtained free of charge via
1
13
www.ccdc.cam.ac.uk/getstructures. ESI file contains the (a) Figs. S1-S14. H NMR and C
NMR spectra of compounds 3-9, respectively. (b) (i) Fig. S15. A view of the unit cell contents
of 3 in projection down the a-axis highlighting the stacking of supramolecular layers. The …
interactions are shown as purple dashed lines. (ii) Fig. S16. A view of the unit cell contents of
…
…
4
in projection down the b-axis. The O‒H O hydrogen bonding and C‒H  interactions are
shown as orange and purple dashed lines, respectively. (iii) Fig. S17. A view of the unit cell
…
…
contents of 5 in projection down the b-axis. The C‒H O and   interactions are shown as
orange and purple dashed lines, respectively. (iv) Fig. S18. A view of the unit cell contents of
…
…
…
6
in projection down the b-axis. The C‒H O,   and C‒H F interactions are shown as
orange, purple and blue dashed lines, respectively. (v) Fig. S19. (a) a view of the
supramolecular chain in 7 sustained by C‒H…O(carbonyl) interactions; non-participating
hydrogen atoms are omitted for reasons of clarity, and (b) a view of the unit cell contents of 7
…
…
…
in projection down the b-axis. The C‒H O,   and C‒H Cl interactions are shown as
orange, purple and blue dashed lines, respectively. (vi) Fig. S20. A view of the unit cell
…
…
…
contents of 8 in projection down the c-axis. The C‒H O,   and C‒H Br interactions are
shown as orange, purple and blue dashed lines, respectively. (vii) Fig. S21. A view of the unit
…
cell contents of 9 in projection down the b-axis. The C‒H O interactions are shown as orange
dashed lines.

Acknowledgements
Financial support from the University Grants Commission, New Delhi (Grant No.
th
Sanction No. 42-396/2013 (SR) Dated 25 March, 2013, TSBB) and the University Grants
Commission, New Delhi, India through SAP-CAS, Phase-I (Grant No. F 540/21/CAS/2013
(SAP-I) are gratefully acknowledged. TSBB and RM acknowledge DST-PURSE for the
diffractometer facility.
Table 1
Crystal data and refinement details for compounds 3-9.
Compound 3 4 5 6 7
Formula C H N O Ti C H N O Ti C H N O Ti C H FN O Ti C H ClN O Ti
3
6
28
4
6
40 36
4
8
24 20
2
3
23 17
2
3
23 17
2
3
Formula weight 660.52 748.63 432.32 436.28 452.73
Crystal colour Orange Orange Dark-orange Dark-red Dark-red
3
Crystal size/mm 0.21 x 0.21 x 0.25 0.22 x 0.26 x 0.28 0.08x 0.09 x 0.15 0.09 x 0.09 x 0.25
0
.21 x 0.25 x 0.26
Crystal system Triclinic Monoclinic Monoclinic Triclinic Monoclinic
Space group P ¯1 P2 /c P2 /c P ¯1 P2 /c
1
1
1
a/Å 7.5735(6) 15.3444(6) 7.9077(2) 7.9774(4) 7.8967(7)
b/Å 14.0769(12) 17.0218(6) 8.8807(2) 8.8773(4) 8.8897(9)
c/Å 15.0774(13) 14.0822(8) 28.7042(6) 13.7253(7) 28.644(2)
/° 76.855(7) 90 90 85.038(4) 90

/° 85.748(7) 98.493(5) 91.637(2) 81.644(4) 91.894(7)


/° 78.948(7) 90 90 87.753(4) 90
3
V/Å 1535.5(2) 3637.8(3) 2014.96(8) 957.72(8) 2009.7(3)
Z 2 4 4 2 4
-3
D /g cm 1.429 1.367 1.425 1.513 1.496
c
F(000) 684 1560 896 448 928
-1

(MoK)/mm 0.334 0.295 3.837 0.485 0.587
Measured data 12263 18513 7278 7227 8875
range/° 3.0 – 28.8 2.9 – 28.8 3.1 – 71.3 3.2 – 28.8 3.1 – 28.8

Unique data 6978 8273 3843 4282 4550
Observed data (I ≥ 2.0(I)) 4098 5455 3255 3537 2316
No. parameters 430 486 272 271 271
R, obs. data; all data 0.076; 0.136 0.055; 0.095 0.042; 0.052 0.047; 0.060 0.081; 0.164
a; b in weighting scheme 0.066; 1.344 0.058; 0.633 0.050; 0.193 0.055; 0.523 0.090; 0.511
Rw, obs. data; all data 0.171; 0.202 0.119; 0.138 0.096; 0.101 0.112; 0.120 0.180; 0.226
GoF 1.05 1.03 1.05 1.03 1.00
Range of residual electron
-3
density peaks/eÅ -0.24 – 0.47 -0.27 – 0.23 -0.24 – 0.31 -0.28 – 0.52 -0.45 – 1.17
Table 1 cont.
Compound 8 9
Formula C H BrN O Ti C H N O Ti
2
3
17
2
3
22 17
3
3

Formula weight 497.19 419.28
Crystal colour Dark-orange Maroon
3
Crystal size/mm 0.25 x 0.26 x 0.29 0.19 x 0.19 x 0.21
Crystal system Monoclinic Triclinic
Space group P2 /c P¯1
1
a/Å 11.464(3) 7.9997(4)
b/Å 15.566(3) 8.9354(4)
c/Å 11.788(3) 13.3310(8)
/° 90 85.090(4)

/° 101.32(2) 78.659(5)

/° 90 82.736(4)
3
V/Å 2062.6(8) 924.99(9)
Z 4 2
-3
D /g cm 1.601 1.505
c
F(000) 1000 432
-1

(MoK)/mm 2.380 0.493
Measured data 4668 7018
range/° 3.1 – 28.7 3.1 – 28.7

Unique data 4668 4152
Observed data (I ≥ 2.0(I)) 1935 3513