Synthesis of polymetallic Group 4 complexes bridged by benzenediolate and triolate ligands. X-ray crystal structure of [{Ti(C5 Me5)Cl2}2{μ-1,4-O(2,3-C6 H2Me2)O-}]

Article abstract of DOI:10.1016/S0022-328X(03)00624-7

This paper reports the synthesis of polymetallic complexes in which two or three Group 4 metals are linked to a benzene core through oxo groups. Four methods have been evaluated for the synthesis of such derivatives: from the appropriated alcohol with (a) methyl complexes via methane elimination, (b) chloride compounds in the presence of a Lewis base, or (c) a zirconium hydride, and (d) from the lithium salt of the alcohol and chloride complexes. Method a has been used for the synthesis of bimetallic and trimetallic (pentamethylcyclopentadienyl)titanium(IV) complexes [{Ti(C₅Me₅)Cl₂}₂ {μ-1,4-O(C₆H₂XY)O-}] (X=Y=H (1); X = H, Y = Me (2); X=Y=Me (3)), [{Ti(C₅Me₅)Me₂} ₂{μ-1,4-O(C₆H₂Me₂)O-}] (4), and [{Ti(C₅Me₅)X₂}₃ (μ₃-1,3,5-C₆H₃O₃-)] (X = Cl (7), Me (8)) from the corresponding hydroquinones 1,4-HO (2,3-C₆H₂XY)OH (X = Y = H, Me; X = H, Y = Me) or 1,3,5-trihydroxibenzene and [Ti(C₅Me₅) Cl₂Me] or [Ti(C₅Me₅)Me₃], respectively. Bis(cyclopentadienyl)titanium bimetallic complex [{Ti(C₅H₅)₂Cl}₂{μ-1,4-O (C₆H₂Me₂)O-}] (5) is better prepared by method d by treatment of the dilithium salt Li₂[1,4-O (2,3-C₆H₂Me₂)O-] with [Ti(C₅ H₅)₂Cl₂] whereas the trimetallic compound [{Ti(C₅H₅)₂Cl}₃ (μ₃-1,3,5-C₆H₃O₃-)] (9) can be prepared directly from 1,3,5-trihidroxybenzene in the presence of NEt₃ (method b). Finally, bis(cyclopentadienyl)zirconium complexes [{Zr(C₅H₅)₂Cl}₂ {μ-1,4-O(C₆H₂Me₂)O-}] (6) and [{Zr(C₅H₅)₂Cl}₃ (μ₃-1,3,5-C₆H₃O₃-)] (10) are obtained from [Zr(C₅H₅)₂ClH] (method c). The structure of complex 3 has been determined by X-ray diffraction methods.

Full text of DOI:10.1016/S0022-328X(03)00624-7

Journal of Organometallic Chemistry 681 (2003) 228Á236
/
www.elsevier.com/locate/jorganchem
Synthesis of polymetallic Group 4 complexes bridged by
benzenediolate and triolate ligands. X-ray crystal structure of
[{Ti(C5Me5)Cl2}2{m-1,4-O(2,3-C6H2Me2)OÃ
/
}]
Silvia Are´valo, M. Rufina Bonillo, Ernesto de Jesu´s, F. Javier de la Mata *,
Juan C. Flores, Rafael Go´mez *, Pilar Go´mez-Sal, Paula Ortega
Departamento de Qu´ımica Inorga´nica, Universidad de Alcala´, Campus Universitario, Edificio de Farmacia, E-28871 Alcala´ de Henares, Spain
Received 14 April 2003; accepted 25 June 2003
Abstract
This paper reports the synthesis of polymetallic complexes in which two or three Group 4 metals are linked to a benzene core
through oxo groups. Four methods have been evaluated for the synthesis of such derivatives: from the appropriated alcohol with (a)
methyl complexes via methane elimination, (b) chloride compounds in the presence of a Lewis base, or (c) a zirconium hydride, and
(d) from the lithium salt of the alcohol and chloride complexes. Method a has been used for the synthesis of bimetallic and
trimetallic (pentamethylcyclopentadienyl)titanium(IV) complexes [{Ti(C5Me5)Cl2}2{m-1,4-O(C6H2XY)OÃ
H, YꢀMe (2); XꢀYꢀMe (3)), [{Ti(C5Me5)Me2}2{m-1,4-O(C6H2Me2)OÃ}] (4), and [{Ti(C5Me5)X2}3(m3-1,3,5-C6H3O3Ã
(7), Me (8)) from the corresponding hydroquinones 1,4-HO(2,3-C6H2XY)OH (XꢀYꢀH, Me; XꢀH, YꢀMe) or 1,3,5-
trihydroxibenzene and [Ti(C5Me5)Cl2Me] or [Ti(C5Me5)Me3], respectively. Bis(cyclopentadienyl)titanium bimetallic complex
[{Ti(C5H5)2Cl}2{m-1,4-O(C6H2Me2)OÃ}] (5) is better prepared by method d by treatment of the dilithium salt Li2[1,4-O(2,3-
C6H2Me2)OÃ] with [Ti(C5H5)2Cl2] whereas the trimetallic compound [{Ti(C5H5)2Cl}3(m3-1,3,5-C6H3O3Ã)] (9) can be prepared
directly from 1,3,5-trihidroxybenzene in the presence of NEt3 (method b). Finally, bis(cyclopentadienyl)zirconium complexes
[{Zr(C5H5)2Cl}2{m-1,4-O(C6H2Me2)OÃ}] (6) and [{Zr(C5H5)2Cl}3(m3-1,3,5-C6H3O3Ã)] (10) are obtained from [Zr(C5H5)2ClH]
/
}] (Xꢀ
/
Yꢀ
/
H (1); Xꢀ
/
/
/
/
/
/
)] (XꢀCl
/
/
/
/
/
/
/
/
/
/
(method c). The structure of complex 3 has been determined by X-ray diffraction methods.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Aryloxide; Titanium; Zirconium; Cyclopentadienyl
1. Introduction
A large number of mononuclear cyclopentadienyl
titanium and zirconium complexes with aryloxy ligands
have been described in the literature [5]. In contrast,
there are very few examples of complexes in which
benzenepolyolates are bridging two or more metal
centres. Roesky et al. have described the first examples
of Group 4 metal bimetallic complexes with quinonide
bridged ligands using different synthetic routes depend-
ing on the metal complex precursor [6]. Lately, we have
published the synthesis of some monocyclopentadienyl
titanium complexes with quinonide bridged ligands
starting from [Ti(C5H5)Cl3] or [Ti(C5Me5)Cl3] and
different hydroquinones [7].
Group 4 metal complexes containing alkoxy or
aryloxy ligands have been a subject of interest in the
last decade. These compounds are interesting for
industrial applications because of the wide use of these
metal centres as catalysts in, for example, polymerisa-
tion [1], alkene epoxidation [2] or hydroformilation [3]
reactions. In the polymerisation field the importance of
cyclopentadienyl based complexes is especially signifi-
cative due to their use in homogeneous catalysis [4].
* Corresponding authors. Tel.: ꢁ
/
34-1-885-4654; fax: ꢁ34-1-885-
/
In this paper, we wish to present an extension of our
previous work, describing new synthetic methodologies
for some quinonide bridged bimetallic titanium com-
4683.
E-mail addresses: javier.delamata@uah.es (F.J. de la Mata),
rafael.gomez@uah.es (R. Go´mez).
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00624-7

S. Are´valo et al. / Journal of Organometallic Chemistry 681 (2003) 228Á
/236
229
plexes and reporting the synthesis and characterisation
of new bimetallic and trimetallic cyclopentadienyl deri-
vatives containing aryloxide bridged ligands. These
compounds could be used as models and starting point
for the study of the synthesis of rigid peripheral metal-
dendrimers based on polyphenol skeleton, which is an
area of interest in our research group.
lating agent reacts first with the aryloxide ligand than
with the chlorine atoms. Nevertheless, methyl derivative
[{Ti(C5Me5)Me2}2{m-1,4-O(C6H2Me2)OÃ/}] (4) can be
prepared by reaction of 1,4-HO(2,3-C6H2Me2)OH with
two equivalents of [Ti(C5Me5)Me3] (see Scheme 1).
Complex 4 is a moisture sensitive yellow microcrystal-
line solid that is soluble in THF, Et2O, or toluene and
scarcely soluble in hexane. This complex is also soluble
in chlorinated solvents although a transformation of 4
into 3 was slowly occurred.
2. Results and discussion
Phenolysis of titaniumÁmethyl bonds can also be used
/
to prepare bimetallic quinonide bridged complexes
containing bis(cyclopentadienyl)titanium units although
the synthetic procedure is less effective. According to
2.1. Synthesis and characterisation of bimetallic
complexes
this,
[{Ti(C5H5)2Cl}2{m-1,4-O(C6H2Me2)OÃ
of the corresponding
we
have
prepared
the
compound
}] (5) by reaction
We have published recently that the reaction of 1,4-
/
HO(2,3-C6H2XY)OH (Xꢀ
with two equivalents of [Ti(C5H5)Cl3] in diethyl ether at
room temperature gives redÁorange microcrystalline
solids of bimetallic complexes [{Ti(C5H5)Cl2}2{m-1,4-
O(C6H2XY)OÃ}] in high yields [7]. However, for the
/
Yꢀ
/
H, Me; Xꢀ
/
H, Yꢀ
/
Me)
hydroquinone
with
[Ti(C5H5)2ClMe] at 70 8C although low yields (37%)
were achieved probably due to thermal decomposition.
At room temperature, no reaction was observed indicat-
/
/
ing a strong TiÃ
/
Me bond. A more convenient method to
compound [Ti(C5Me5)Cl3] no reaction was observed
with hydroquinones in analogous conditions and it was
necessary the employment of the dilithium salts of such
prepare 5 consists in the reaction of two equivalents of
[Ti(C5H5)2Cl2] with the dilithium salt of the dimethylhy-
droquinone. The analogous zirconium complex
hydroquinones Li2[1,4-O(2,3-C6H2XY)OÃ
Me; XꢀH, YꢀMe) to prepare the bimetallic deriva-
tives [{Ti(C5Me5)Cl2}2{m-1,4-O(C6H2XY)OÃ}] (Xꢀ
YꢀH (1); XꢀH, YꢀMe (2); XꢀYꢀMe (3)) [7].
Now we present here an alternative synthetic route for
complexes 1Á3 consisting in the reaction of hydroqui-
/
] (Xꢀ
/
Yꢀ/H,
[{Zr(C5H5)2Cl}2{m-1,4-O(C6H2Me2)OÃ
/}] (6) can be
/
/
prepared by the method described by Roesky for a
related bis(cyclopentadienyl)zirconium derivative [6],
consisting in the reaction between two equivalents of
[Zr(C5H5)2Cl2] and 1,4-HO(2,3-C6H2Me2)OH in the
presence of two equivalents of triethylamine to separate
the HCl formed during the reaction. Alternatively,
treatment of the corresponding hydroquinone with
[Zr(C5H5)2ClH] affords compound 6 (see Scheme 2).
Complexes 5 and 6 are air stable in the solid state but
solutions of these compounds are partially hydrolysed to
the corresponding m-oxo compounds [{M(C5H5)2Cl}2(m-
/
/
/
/
/
/
/
/
nones 1,4-HO(2,3-C6H2XY)OH with two equivalents of
[Ti(C5Me5)Cl2Me]. This synthetic procedure resulted to
be more accurate and convenient than that using
dilithium salts of hydroquinones because the methane
subproduct was easily removed under vacuum condi-
tions (Scheme 1).
We have already published [7] that attempts to
prepare methyl derivatives by reaction of complexes
O)] where Mꢀ/Ti or Zr [8], when they are opened to the
1Á3 with AlMe3 were unsuccessful because the methy-
/
air. Both of them are soluble in THF and chlorinated
Scheme 1.

230
S. Are´valo et al. / Journal of Organometallic Chemistry 681 (2003) 228Á236
/
Scheme 2.
solvents, partially soluble in toluene and completely
insoluble in saturated hydrocarbons.
d 157.0, 164.7 and 157.5 for 4Á6, respectively, which is
/
indicative of the electronic density around the metal
centre. Hence, for complex 4 the signal is shifted to high-
field respecting to 3, as consequence of the electrodonat-
ing properties of the methyl groups instead of the chloro
atoms. Analogously, in complex 5 the resonance appears
at lower field respecting to 6 due to the higher Lewis
acidity of the titanium atom.
Compounds 4Á6 were characterised by elemental
/
1
analysis, H- and 13C-NMR spectroscopy. These data
(see details in Section 4) are consistent with the
proposed formulation for these complexes. Spectro-
scopic data for complexes 1Á
/
3 obtained by phenolysis
of a TiÃMe bond match perfectly with those previously
/
reported by us [7]. X-ray analysis of compound 3 was
carried out in order to provide precise structural details
of this compound.
2.2. Crystal structure of 3
1H-NMR spectra of complexes 4Á
6 show one singlet
/
Single crystals of 3 suitable for X-ray diffraction
toluene
for the hydrogen atoms of the C5Me5 and C5H5 ligands
at d 1.93 (30H), 6.32 (20H) and 6.36 (20H), respectively.
The equivalence of both metal units in these bimetallic
quinonide bridged complexes is also observed in the 1H-
NMR signals of the quinonide group that appears for
studies were obtained from a mixture of Et2OÁ
/
cooled at ꢂ20 8C. An ORTEP draw of the molecular
/
˚
structure is shown in Fig. 1. Selected bond lengths (A)
and angles (8) are listed in Table 1.
In the asymmetric unit of the unit cell a half molecule
exits. The whole molecule consists in a bimetallic
compound with the two half moieties related by a C2
symmetry axis located in the middle of the 1,4-O(2,3-
4Á6 as two different singlets, one corresponding to the
/
methyl substituents at d 2.23, 1.93 and 2.01, respec-
tively, and another one corresponding to the two
equivalents aromatic hydrogens at d 6.56, 6.58 and 6.29.
These resonance patterns are in agreement with the
symmetry of these compounds observed in the X-ray
structure of 3 (see below), comparable to those shown
by the analogous derivatives [{MoTp(NO)X}2{m-1,4-
C6H2Me2)OÃ
/
system, in which the cyclopentadienyl
rings present an anti conformation in the solid state.
The molecular structure shows each titanium atom with
Cl bond
a three-legged piano stool geometry. The TiÃ
/
˚
lengths (mean 2.27 A) are analogous to that of compar-
able compounds such as [{Ti(C5Me5)Cl2}2(m-O)] [12]
and considerably shorter than the distance reported for
bis(cyclopentadienyl) quinonide bridged titanium com-
O(C6H4)OÃ
/
}] [9], [{MoTp(O)Cl}2{m-1,4-N(C6H4)NÃ
/
}]
[10] or [{M(C5H5)2Cl}2{m-1,4-N(C6H4)NÃ
/
}] [11] (Mꢀ
/
Nb, Ta) and is expected for homobimetallic compounds
bonding to the corresponding diphenoxide ligands.
Respecting to their 13C{1H}-NMR spectra, an inter-
esting feature is the chemical shift of the ipso carbons
bonded directly to the oxygen atoms that are recorded at
plexes [6]. The Ti(1)Ã
opener than that observed in [{Ti(C5Me5)2Cl}2(m-1,4-
OC6H4OÃ)] [6] (155.1(2)8) and consequently the Ti(1)Ã
O(1) bond length in 3 (1.784(5) A) is shorter than in such
/
O(1)Ã
/
C(7) angle (165.2(5)8) is
/
/
˚

S. Are´valo et al. / Journal of Organometallic Chemistry 681 (2003) 228Á
/236
231
Fig. 1. ORTEP (50% termal ellipsoids) view of the molecular structure of compound [{Ti(C5Me5)Cl2}2{m-1,4-O(C6H2Me2)OÃ
/
} (3) with atom-
numbering scheme.
Complex 3 is the first dimetallic aryloxo monocyclo-
pentadienyl compound reported so far. For this reason
we are only able to compare their structural parameters
with similar monometallic compounds. In Table 2 we
show some structural parameters of monometallic Cp*
dichloro aryloxo species reported in the literature and
obtained in the Cambridge Structural Database [13].
Table 1
˚
Bond lengths (A) and angles (8) for compound 3
Bond lengths
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
O(1)Ã
C(4)Ã
C(4)Ã
C(4)Ã
C(2)Ã
C(2)Ã
C(2)Ã
C(5)Ã
/
O(1)
Cl(1)
Cl(2)
C(3)
C(4)
C(5)
C(2)
C(1)
1.784(5)
2.266(2)
2.271(2)
2.342(8)
2.346(7)
2.358(8)
2.385(7)
2.397(7)
1.360(8)
1.408(10)
1.419(10)
1.499(10)
1.406(10)
1.421(10)
1.505(9)
1.424(10)
C(5)Ã
C(1)Ã
/
C(15)
C(11)
1.500(9)
1.505(10)
1.504(10)
1.399(9)
1.427(13)
1.489(9)
1.377(9)
1.379(14)
1.32(6)
/
/
/
C(13)ÃC(3)
/
/
C(8)Ã
C(8)Ã
C(8)Ã
C(7)Ã
C(6)Ã
/
C(7)
C(8)#1
C(9)
There, we can see that the TiÃ
/
OÃ
/
C angle has important
/
/
/
/
differences ranging between 157.6 and 179.48 although
/
/
C(6)
this is not reflected in really significant changes in the
˚
O distances that range from 1.772 to 1.817 A. Every
/
/
C(6)#1
TiÃ
/
/
C(7)
C(19)Ã
C(19)Ã
C(19)Ã
C(18)Ã
C(16)Ã
C(16)Ã
C(16)Ã
Ti(1)Ã
/C(23)
single titanium unit in 3 posses the TiÃ
/
O and TiÃ
/
OÃ/C
/
C(5)
C(3)
C(14)
C(3)
C(1)
C(12)
C(1)
/C(18)
1.417(15)
1.417(15)
1.312(15)
1.31(3)
/
/C(18)#2
parameters almost identical to others similar monome-
tallic complexes like [Ti(C5Me5)(O-2,6-Me2C6H3)Cl2]
[14] or [Ti(C5Me5){O-2,6-(OMe)2C6H3}Cl2] [15] or the
analogue containing the unsubstituted cyclopentadienyl
ligand [Ti(C5H5)(O-2,6-iPr2C6H3)Cl2] [5e,5f]. However,
for a complex with bulkier ligands in the metal
surroundings like in [Ti(C5Me5)(O-2,6-iPr2C6H3)Cl2]
/
/C(17)
/
/C(24)
/
/C(17)#2
1.472(16)
1.472(16)
2.036
/
/C(17)
/
/Cp*
Bond angles
O(1)ÃTi(1)Ã
O(1)ÃTi(1)Ã
Cl(1)ÃTi(1)Ã
C(7)ÃO(1)ÃTi(1)
/
/
Cl(1)
102.89(18)
101.66(18)
103.03(10)
165.2(5)
O(1)Ã
Cl(1)Ã
Cl(2)Ã
/
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
/
Cp*
118.7
114.5
113.8
/
/
Cl(2)
/
/Cp*
[5e,5f], the TiÃ
than in 3 without any consequence in the TiÃ
For the case of [Ti(C5Me5)(O-2,6-Ph23,5tBu2C6H)Cl2]
[5a] with a quasi linear system, TiÃOÃC, the distance is
/
OÃ
/
C bond angle is more open (1738)
/
/
Cl(2)
/
/Cp*
/O distance.
/
/
Symmetry transformations used to generate equivalent atoms: #1 ꢂ
xꢁ1/2, ꢂyꢁ1/2, z; #2 ꢂxꢁ1/2, ꢂyꢁ3/2, z. Cp* is the centroid of
C(1), C(2), C(3), C(4), C(5).
/
/
/
/
/
/
/
/
/
/
longer than in 3 but of the same value than that in
[Ti(C5Me5)(O-2,3,5,6-Ph4C6H)Cl2] [5a] which has a very
close angle. These features describe that the change in
bis(pentamethylcyclopentadienyl) derivative (1.865(2)
˚
the TiÃ
/
OÃ/C bond angle and then a variation of the
A), this is usually invoked to be due to the better p
electronic density donation from the oxygen atom to the
titanium centre in 3.
oxygen donation into the titanium atom is a compro-
mise of electronic and steric influence of both cyclo-
pentadienyl and substituted ariloxide ligands.

232
S. Are´valo et al. / Journal of Organometallic Chemistry 681 (2003) 228Á236
/
Table 2
Structural parameters of Cp*TiCl2(OÃ
Ar) a
/
[Compound]ref
TiÃ/O
TiÃ
/
Cp
TiÃ/Cl
OÃ/C
TiÃ
/
OÃ/C
CpÃ
/
TiÃ/O
ClÃ
/
TiÃCl
/
b
[Ti(C5Me5)Cl2(O-2,6-Me2C6H3)]
[Ti(C5Me5)Cl2(O-2,6-i Pr2C6H3)] c
1.785
1.772
1.803
1.817
1.784
2.034
2.035
2.052
2.041
2.036
2.274
2.304
2.258
2.251
2.269
1.366
1.366
1.369
1.362
1.360
162.2
172.9
176.8
157.6
165.2
120.4
120.4
123.1
119.6
118.7
103.3
103.4
100.4
101.4
103.0
[Ti(C5Me5)Cl2(O-2,6-Ph2-3,5t Bu2C6H)] d
[Ti(C5Me5)Cl2(O-2,3,5,6-Ph4C6H)] d
[{Ti(C5Me5)Cl2}2{m-O(2,3-C6H2Me2)OÃ
}] (3) e
/
˚
Distances in (A) and angles in (8).
a
Data obtained from Cambridge Structural Database.
From reference [13].
b
c
From reference [5e].
From reference [5a].
This work.
d
e
2.3. Synthesis and characterisation of trimetallic
complexes
sensitive and decompose in the presence of air to give
different oxo derivatives. In the chloro complexes 7, 9
and 10 the hydrolysis of TiÃ
that of TiÃCl bond producing well known oxo com-
plexes
[{M(C5H5)2Cl}2(m-O)] where Mꢀ
/
OAr bond occurs before
Synthetic methodologies employed in the preparation
of bimetallic quinonide bridged complexes were tested
for the synthesis of trimetallic cyclopentadienyl Group 4
complexes with different results. Reaction of three
equivalents of [Ti(C5H5)Cl3] with one equivalent of
1,3,5-trihydroxybenzene failed to give the expected
trimetallic complex under the experimental conditions
/
[{Ti(C5Me5)Cl2}2(m-O)]
[12]
and
/
Ti or Zr [8].
Structural characterisation of compounds 7Á
/
10 was
1
carried out by elemental analysis, H- and 13C-NMR
1
spectroscopy (see Section 4). H-NMR spectra of these
complexes show equivalence of the three metal frag-
ments and consequently only one singlet is observed for
the protons of the cyclopentadienyl rings at d 2.23 (45H)
for 7, 1.94 (45H) for 8, 6.39 (30H) for 9 and 6.39 (30H)
for 10. According to this, the three aromatic protons of
the trisphenolate ligand are also equivalent and appear
used for complexes 1Á/3. However, phenolysis of a
titaniumÁmethyl bond of [Ti(C5Me5)Cl2Me] or [Ti(C5-
/
Me5)Me3] resulted to be an accurate method for the
synthesis of two new trimetallic mono(pentamethylcy-
clopentadienyl)titanium
derivatives
[{Ti(C5-
as a seinglet at d 6.24, 6.08, 5.44 and 5.44 for 7Á10,
/
Me5)X2}3(m3-1,3,5-C6H3O3Ã
/
)] (XꢀCl (7), Me (8)) (see
/
respectively. Besides these signals, complex 8 shows an
additional singlet at d 0.40 due to the methyl groups
directly bonded to titanium. 13C-NMR signals are in
agreement with the data observed in the 1H-NMR
spectra. The chemical shift of the ipso carbons of the
phenyl ring directly bonded to the oxygen atoms are
Scheme 3).
In contrast, this method is not convenient for
supporting bis(cyclopentadienyl)titanium derivatives
over the previous trisphenolate ligand probably due
again to the strength of the TiÃ
/Me bond. Hence, the
reaction of three equivalents of [Ti(C5H5)2ClMe] with
1,3,5-trihydroxybenzene led to mixtures that we were
not able to characterise. Fortunately, the desired com-
recorded at d 164.7, 165.6, 174.6 and 166.3 for 7Á10,
/
respectively, which resonate at lower field compared
with the analogous quinonide derivatives described
before. This behaviour could be ascribed to the presence
of three organometallic units in meta position instead of
two in para position in the ariloxy fragment, which
organises differently the electrodonating properties of
both types of ligands.
plex [{Ti(C5H5)2Cl}3(m3-1,3,5-C6H3O3Ã
/)] (9) was suc-
cessfully prepared by reaction of [Ti(C5H5)2Cl2] with
1,3,5-trihydroxybenzene in the presence of triethylamine
(see Scheme 3). A similar reaction to the last one but
using [Zr(C5H5)2Cl2] failed to afford the analogous
zirconium derivative of 9. However, the use
[Zr(C5H5)2ClH] afforded [{Zr(C5H5)2Cl}3(m3-1,3,5-
C6H3O3Ã
/
)] (10) as yellow microcrystals in high yield
via dihydrogen evolution.
3. Conclusions
Trimetallic chloro derivatives 7, 9 and 10 are soluble
in THF and chlorinated solvents, partially soluble in
toluene and unsoluble in diethyl ether and hexane,
whereas, compound 8 is soluble in all previous solvents
except in hexane. All of four complexes can be stored
under argon during long time periods but are moisture
Several synthetic methodologieshavebeenemployedto
prepared aryloxide bridged bi- and trimetallic Group 4
derivatives. In the case of monocyclopentadienyl com-
plexes the reaction of [Ti(C5Me5)Cl2Me] or [Ti(C5-
Me5)Me3] with the hydroxy functionalities cleanly

S. Are´valo et al. / Journal of Organometallic Chemistry 681 (2003) 228Á
/236
233
Scheme 3.
introduce the metal fragment via liberation of inert
methane. For bis(cyclopentadienyl) titanium complexes
more standard procedures like the used of lithium salts of
thehydroquinonesortheemploymentofaLewisbasemust
be used. In the case of the zirconium analogues, the use of
[Zr(C5H5)2ClH] allows the synthesis of the corresponding
complexes via dihydrogen formation. All these synthetic
procedures,mainlythosebasedontitanium,couldbeuseful
for the preparation of rigid peripheral metal-dendrimers
based on polyphenol skeleton.
a dry box. Solvents were previously dried and freshly
distilled under Ar as described elsewhere [16]. Unless
otherwise stated, reagents were obtained from commer-
cial sources and used as received. Et3N was dried over
calcium hydride and then distilled under Ar. [Ti(C5-
Me5)Cl3] [17], [Ti(C5Me5)Cl2Me] [18] and [Ti(C5-
Me5)Me3] [19] were prepared according to reported
methods.
1H- and 13C-NMR spectra were recorded on a Varian
Unity 200, Varian Unity VXR-300 or Varian Unity 500
Plus Instruments. Chemical shifts (d ppm) were mea-
sured relative to residual 1H and 13C resonances for
cloroform-d1 and benzene-d6 used as solvent. C, H
4. Experimental
analyses were carried out with a PerkinÁ
microanalyzer.
/Elmer 240 C
All manipulations were performed under an inert
atmosphere of Ar using standard Schlenck techniques or

234
S. Are´valo et al. / Journal of Organometallic Chemistry 681 (2003) 228Á236
/
4.1. [{Ti(C5Me5)Cl2}2{m-1,4-O(C6H4)OÃ
/
}] (1)
4.5. [{Ti(C5H5)2Cl}2{m-1,4-O(C6H2Me2)OÃ
/
}] (5)
A solution of hydroquinone (0.30 g, 2.72 mmol) in
Et2O (20 cm3) was slowly cannulated into a solution of
[Ti(C5Me5)Cl2Me] (1.47 g, 5.45 mmol) in Et2O (10 cm3).
The mixture was stirred overnight at room temperature
(r.t.). Then, the solvent was evaporated under vacuum
A solution of [Ti(C5H5)2Cl2] (1.08 g, 4.34 mmol) in
THF (40 cm3) was cannulated into a Schlenk containing
the dilithium salt of 2,3-dimethyl hydroquinone( 0.32 g,
2.17 mmol). The mixture was stirred overnight at r.t.,
the solvent was removed under reduced pressure and the
and the product was recrystallised in a mixture Et2OÁ
/
residue extracted with toluene (2ꢃ
15 cm3). The filtrates
/
hexane leading to 1 as an orange microcrystalline solid
(yield: 95%). For analytical and spectroscopic data see
reference [7].
were combined and volatiles removed in vacuo. The
remaining solid was washed with hexane affording
compound 5 as a dark brown microcrystalline solid
(yield: 65%). Anal. Calc. for C28H28O2Cl2Ti2: C, 57.92;
H, 5.23. Found: C, 58.38; H, 5.22%. 1H-NMR (CDCl3):
d 6.58 (s, 2H, C6H2Me2), 6.32 (s, 20H, C5H5), 1.93 (s,
6H, C6H2Me2). 13C{1H}-NMR (CDCl3): d 164.7 (Cipso
bonded to oxygen), 122.0 (Cipso bonded to Me), 117.1
(C5H5), 114.4 (C6H2Me2), 13.6 (C6H2Me2).
4.2. [{Ti(C5Me5)Cl2}2{m-1,4-O(C6H3Me)OÃ
/
}] (2)
A solution of methylhydroquinone (0.30 g, 2.42
mmol) in Et2O (20 cm3) was slowly cannulated into a
solution of [Ti(C5Me5)Cl2Me] (1.30 g, 4.83 mmol) in
Et2O (10 cm3). The mixture was stirred overnight at r.t.
Then, the solvent was evaporated under vacuum and the
4.6. [{Zr(C5H5)2Cl}2{m-1,4-O(C6H2Me2)OÃ
/
}] (6)
product was recrystallised in a mixture Et2OÁhexane
/
4.6.1. Method A
leading to 2 as an orange microcrystalline solid (yield:
95%). For analytical and spectroscopic data see refer-
ence [7].
A solution of 2,3-dimethylhydroquinone (0.236 g,
1.71 mmol) in THF (20 cm3) was cannulated into a
solution of [Zr(C5H5)2Cl2] (1.0 g, 3.42 mmol) in THF
(20 cm3) and then Et3N (0.48 cm3, 3.42 mmol) was
added. The mixture was stirred overnight at r.t., the
solvent was removed under reduced pressure and the
4.3. [{Ti(C5Me5)Cl2}2{m-1,4-O(C6H2Me2)OÃ
/
}] (3)
residue extracted with toluene (2ꢃ
15 cm3). The filtrates
/
A solution of 2,3-dimethylhydroquinone (0.30 g, 2.17
mmol) in Et2O (20 cm3) was slowly cannulated into a
solution of [Ti(C5Me5)Cl2Me] (1.17 g, 4.34 mmol) in
Et2O (10 cm3). The mixture was stirred overnight at r.t.
Then, the solvent was evaporated under vacuum and the
were combined and volatiles removed in vacuo. The
remaining solid was washed with hexane affording
compound 6 as a yellow microcrystalline solid (yield:
70%).
product was recrystallised in a mixture Et2OÁ
/
toluene
4.6.2. Method B
leading to 3 as an orange microcrystalline solid (yield:
95%). For analytical and spectroscopic data see refer-
ence [7].
A solution of 2,3-dimethylhydroquinone (0.08 g, 0.58
mmol) in THF (20 cm3) was cannulated into a solution
of [Zr(C5H5)2HCl] (0.3 g, 1.16 mmol) in THF (20 cm3)
and the mixture stirred for 1 h at r.t. Then, the solution
was filtered and the solvent removed under reduced
pressure affording 6 as yellow microcrystals (yield:
43%). Anal. Calc. for C28H28O2Cl2Zr2: C, 51.75; H,
4.4. [{Ti(C5Me5)Me2}2{m-1,4-O(C6H2Me2)OÃ
/
}] (4)
1
A solution of 2,3-dimethylhydroquinone (0.30 g, 2.17
mmol) in Et2O (20 cm3) was slowly cannulated into a
solution of [Ti(C5Me5)Me3] (1.04 g, 4.56 mmol) in Et2O
(10 cm3). The mixture was stirred overnight at r.t., and
4.34. Found: C, 51.52; H, 4.16%. H-NMR (CDCl3): d
6.36 (s, 20H, C5H5), 6.29 (s, 2H, C6H2Me2), 2.01 (s, 6H,
C6H2Me2). 13C{1H}-NMR (CDCl3): d 157.5 (Cipso
bonded to oxygen), 124.8 (Cipso bonded to Me), 114.2
(C5H5), 112.9 (C6H2Me2), 13.4 (C6H2Me2).
then concentrated and cooled at ꢂ20 8C. After 24 h a
/
yellow solid precipitated, which was filtered off and
dried under vacuum affording 4 as a yellow microcrys-
talline solid (yield: 75%). Anal. Calc. for C32H50O2Ti2:
C, 68.33; H, 8.96. Found: C, 68.49; H, 8.93%. 1H-NMR
(CDCl3): d 6.56 (s, 2H, C6H2Me2), 2.23 (s, 6H,
C6H2Me2), 1.93 (s, 30H, C5Me5), 0.37 (s, 12H, CH3).
13C{1H}-NMR (CDCl3): d 157.0 (Cipso bonded to
oxygen), 126.7 (Cipso bonded to Me), 122.0 (C5Me5),
117.6 (C6H2Me2), 52.6 (CH3), 13.4 (C6H2Me2), 11.5
(C5Me5).
4.7. [{Ti(C5Me5)Cl2}3(m3-1,3,5-C6H3O3Ã
/
)] (7)
A solution of 1,3,5-trihydroxybenzene (0.25 g, 1.98
mmol) in Et2O (20 cm3) was slowly cannulated into a
solution of [Ti(C5Me5)Cl2Me] (1.65 g, 6.15 mmol) in
Et2O (10 cm3). The mixture was stirred overnight at
60 8C in an ampoule and after this time an orange solid
precipitated, which was filtered off, washed with Et2O
(3ꢃ
10 cm3) and dried under vacuum to give 7 as an
/

S. Are´valo et al. / Journal of Organometallic Chemistry 681 (2003) 228Á
/236
235
orange microcrystalline solid (yield: 70%). Anal. Calc.
for C36H48Cl6O3Ti3: C, 48.85; H, 5.46. Found: C, 49.28;
H, 5.53%. 1H-NMR (CDCl3): d 6.24 (s, 3H, C6H3), 2.23
(s, 45H, C5Me5). 13C{1H}-NMR (CDCl3): d 164.7 (Cipso
bonded to oxygen), 133.6 (C5Me5), 106.1 (C6H3), 13.3
(C5Me5).
4.11. Crystal structure determinations
Crystals of compound 3 were obtained by crystal-
lisation from Et2OÁtoluene. Suitable sized crystals
sealed under Ar atmosphere in Lindemann tubes were
mounted in an EnrafÁNonius CAD 4 automatic four-
circle diffractometer white graphite monochromated
/
/
˚
MoÁ
/
Ka radiation (lꢀ0.71073 A). Crystallographic
/
4.8. [{Ti(C5Me5)Me2}3(m3-1,3,5-C6H3O3Ã
/
)] (8)
and experimental details of the structure are summarised
in Table 3. Data were collected at r.t. Intensities were
corrected for Lorentz and polarisation effects in the
usual manner. No absorption or extinction correction
were made. The structure was solved using the WINGX
package [20], by direct methods (SHELXS-97) and refined
A solution of 1,3,5-trihydroxybenzene (0.25 g, 1.98
mmol) in Et2O (20 cm3) was slowly cannulated into a
solution of [Ti(C5Me5)Me3] (1.41 g, 6.15 mmol) and
Et2O (10 cm3). The mixture was stirred overnight at r.t.
The solvent was removed under vacuum and the residue
recrystallised in hexane giving 8 as a bright yellow
microcrystalline solid (yield: 80%). Anal. Calc. for
C42H66O3Ti3: C, 66.14; H, 8.72. Found: C, 65.52; H,
8.72%. 1H-NMR (CDCl3): d 6.08 (s, 3H, C6H3), 1.94 (s,
45H, C5Me5), 0.40 (s, 18H, CH3). 13C{1H}-NMR
(C6D6): d 165.6 (Cipso bonded to oxygen), 122.6
(C5Me5), 105.8 (C6H3), 54.6 (CH3), 11.7 (C5Me5).
by least-squares against F2
(SHELXL-97) [21]. When
solved the structure, a disorder molecule of toluene
was found. All non hydrogen atoms were refined
anisotropically except those of the toluene molecule
which were isotropically refined, and the hydrogen
atoms were introduced from geometrical calculations
and refined using a riding model with thermal para-
meters equivalent to those of the carbon atom to which
they are attached, except the hydrogen atoms of the
methyl groups of the disorder toluene molecule.
4.9. [{Ti(C5H5)2Cl}3(m3-1,3,5-C6H3O3Ã
/
)] (9)
The final coordinates the non hydrogen atom with the
equivalent isotropic thermal parameters, Ueq, the co-
A solution of 1,3,5-trihydroxybenzene (0.07 g, 0.55
mmol) in THF (20 cm3) was cannulated into a solution
of [Ti(C5H5)2Cl2] (0.41 g, 1.64 mmol) in THF (20 cm3)
and then Et3N (0.30 cm3, 2.15 mmol) was added. The
mixture was stirred overnight at r.t., the solvent was
removed under reduced pressure and the residue ex-
Table 3
Crystal data and structure refinement for compound 3
Empirical formula
Formula weight
Temperature (K)
C
28H38Cl4O2Ti2×C7H8
/
732.29
293(2)
tracted with toluene (2ꢃ
15 cm3). The filtrates were
/
˚
Wavelength (A)
combined and volatiles removed in vacuum. The re-
maining solid was washed with hexane affording com-
pound 9 as a red microcrystalline solid (yield: 80%).
Anal. Calc. for C36H33O3Cl3Ti3: C, 56.40; H, 4.73.
0.71073
Orthorombic
Pccn
Crystal system
Space group
Unit cell dimensions
˚
a (A)
30.218(1)
7.605(1)
15.906(1)
3655.3(5)
4
1
Found: C, 56.75; H, 4.86%. H-NMR (CDCl3): d 6.39
˚
b (A)
(s, 30H, C5H5), 5.44 (s, 3H, C6H3). 13C{1H}-NMR
(CDCl3): d 171.6 (Cipso bonded to oxygen), 117.5
(C5H5), 97.5 (C6H3).
˚
c (A)
3
˚
V (A )
Z
Dcalc (Mg mꢂ3
)
1.331
0.758
1520
Absorption coefficient (mmꢂ1
F (000)
)
4.10. [{Zr(C5H5)2Cl}3(m3-1,3,5-C6H3O3Ã
/
)] (10)
Crystal size (mm3)
0.34ꢃ
2.56Á24.96
05h 535, 05
18
/0.25ꢃ0.21
/
Theta range for data collection (8)
Index ranges
/
A solution of 1,3,5-trihydroxybenzene (0.07 g, 0.55
mmol) in THF (20 cm3) was cannulated into a solution
of [Zr(C5H5)2HCl] (0.41 g, 1.64 mmol) in THF (20 cm3)
and the mixture stirred during 1 h at r.t. Then, the
solution was filtered and the volatiles removed under
reduced pressure giving a white foam. This foam was
washed with hexane affording compound 10 as a brown
solid (yield: 52%). Anal. Calc. for C36H33O3Cl3Ti3: C,
/
/
/
k 5
/
9, 05
/
l 5
/
Reflections collected
Independent reflections
3198
3198
Completeness to thetaꢀ
Absorption correction
Refinement method
/24.968
99.9%
None
Full-matrix least-squares on
F2
Data/restraints/parameters
Goodness-of-fit on F2
3198/0/179
0.915
1
48.38; H, 3.72. Found: C, 48.22; H, 3.81%. H-NMR
Final R indices [I ꢀ
R indices (all data)
Largest difference peak and hole (e
/
2s(I)]
R1ꢀ
R1ꢀ
0.427 and ꢂ
/
0.0667, wR2ꢀ
0.2222, wR2ꢀ
0.280
/
0.1510
(CDCl3): d 6.39 (s, 30H, C5H5), 5.44 (s, 3H, C6H3).
13C{1H}-NMR (CDCl3): d 166.3 (Cipso bonded to
oxygen), 114.4 (C5H5), 99.6 (C6H3).
/
/0.2021
/
ꢂ3
˚
A
)

236
S. Are´valo et al. / Journal of Organometallic Chemistry 681 (2003) 228Á236
/
(f) K. Nomura, N. Naga, M. Miki, K. Yanagi, A. Imai,
Organometallics 17 (1998) 2152;
ordinates for the hydrogen atoms with the isotropic
thermal parameters, anisotropic thermal parameters for
the non hydrogen atoms, and a complete list of bond
distances, angles and observed and calculated structure
factors have been deposited in the Cambridge Crystal-
lographic Data Center, CCDC No. 203509 for complex
3.
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¨
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