Studies on the active species in olefin polymerisation generated from phenoxo-amido titanium "chiral-at-metal" compounds

Article abstract of DOI:10.1016/j.jorganchem.2011.02.011

Treatment of RHN-CH₂-(3,5-tBu₂C₆H ₂-2-OH) (R = C₆H₅ 1a, p-MeC₆H ₄ 1b, Cy 1c; Cy = cyclohexyl) with 1 equiv of TiCpCl₃ (Cp = η⁵-C₅Me₅) in the presence of 2.5 equiv of NEt₃ in pentane or hexane at room temperature gives the monocyclopentadienyl phenoxo-amido monochloro complexes [TiCp{RN-CH ₂-(3,5-tBu₂C₆H₂-2-O)}Cl] (R = C ₆H₅ 2, p-MeC₆H₄ 4, Cy 5). In a more polar solvent the phenoxo-amino complex [TiCp{(C₆H ₅)(H)N-CH₂-(3,5-tBu₂C₆H ₂-2-O)}Cl₂] (3) is obtained from the reaction with 1a. The reaction of TiCpCl₃ with tBu(H)N-CH₂-(3,5-tBu ₂C₆H₂-2-OH) (1d) affords the complex [TiCp{tBu(H)N-CH₂-(3,5-tBu₂C₆H ₂-2-O)}Cl₂] (6) in which no coordination of the amino group to the metal centre is observed as a consequence of the high steric requirements of the amino substituent in the phenol-amine. All the reported compounds were characterised by the usual analytical and spectroscopic methods and the molecular structures of 2 and 5 were determined by X-ray diffraction analysis from suitable single crystals. Studies of catalytic activity for ethylene or propylene polymerisation using boron or aluminium reagents as cocatalysts were performed under different conditions. In general the trends observed for the phenoxo-amido precatalysts with the aluminium reagent as cocatalyst in the α-olefin polymerisation reactions might suggest a catalyst decomposition process through ligand abstraction by sMAO. The activity found for ethylene or propylene polymerisation when B(C₆F ₅)₃ or [CPh₃][B(C₆F ₅)₄] are used as cocatalysts is related to the strength of the cation-anion interactions.

Full text of DOI:10.1016/j.jorganchem.2011.02.011

Journal of Organometallic Chemistry 696 (2011) 2330e2337
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Studies on the active species in olefin polymerisation generated from
phenoxo-amido titanium “chiral-at-metal” compounds
,
,
Giuseppe Alesso b, Vanessa Tabernero a, Marta E.G. Mosquera a 1, Tomás Cuenca a
*
a Departamento de Química Inorgánica, Universidad de Alcalá, Edificio de Farmacia, Campus Universitario, 28871 Alcalá de Henares, Spain
b Dipartimento di Chimica, Via Vienna 2, 07100 Sassari, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Treatment of RHN-CH2-(3,5-tBu2C6H2-2-OH) (R ¼ C6H5 1a, p-MeC6H4 1b, Cy 1c; Cy ¼ cyclohexyl) with
1 equiv of TiCp*Cl3 (Cp* ¼
h
5-C5Me5) in the presence of 2.5 equiv of NEt3 in pentane or hexane at room
Received 3 December 2010
Received in revised form
17 January 2011
temperature gives the monocyclopentadienyl phenoxo-amido monochloro complexes [TiCp*{RN-CH2-
(3,5-tBu2C6H2-2-O)}Cl] (R ¼ C6H5 2, p-MeC6H4 4, Cy 5). In a more polar solvent the phenoxo-amino
complex [TiCp*{(C6H5)(H)NeCH2-(3,5-tBu2C6H2-2-O)}Cl2] (3) is obtained from the reaction with 1a.
The reaction of TiCp*Cl3 with tBu(H)NeCH2-(3,5-tBu2C6H2-2-OH) (1d) affords the complex [TiCp*{tBu
(H)NeCH2-(3,5-tBu2C6H2-2-O)}Cl2] (6) in which no coordination of the amino group to the metal
centre is observed as a consequence of the high steric requirements of the amino substituent in the
phenol-amine. All the reported compounds were characterised by the usual analytical and spectro-
scopic methods and the molecular structures of 2 and 5 were determined by X-ray diffraction analysis
from suitable single crystals.
Accepted 9 February 2011
Keywords:
Titanium
Phenoxo-amido
Phenoxo-amino
Asymmetric metal centre
Studies of catalytic activity for ethylene or propylene polymerisation using boron or aluminium
reagents as cocatalysts were performed under different conditions. In general the trends observed for the
phenoxo-amido precatalysts with the aluminium reagent as cocatalyst in the a-olefin polymerisation
reactions might suggest a catalyst decomposition process through ligand abstraction by sMAO. The
activity found for ethylene or propylene polymerisation when B(C6F5)3 or [CPh3][B(C6F5)4] are used as
cocatalysts is related to the strength of the cation-anion interactions.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
with these requirements have been extensive [4,14e19] but
examples of precatalysts containing only one group that can be
Since the discovery of ZieglereNatta catalysis, considerable
effort has been devoted to catalyst modification in order to improve
the olefin polymerisation process and to know more about its
mechanistic aspects [1e11]. The more accepted mechanism was
developed by CosseeeArlman [12,13]. In accordance with this
proposal, the minimum requirement for a catalyst precursor has
been established as a transition metal complex containing an
unreactive ancillary ligand system (generally a cyclopentadienyl
type ligand) and at least two coordination sites which can be
activated to provide a metal alkyl bond cis to a vacant coordination
site for monomer binding. Descriptions of group 4 metal complexes
active for olefin polymerisation are scarce [20e22].
Ligands with nitrogen and oxygen as donor atoms are particu-
larly interesting, due to their mode of complexation to an acidic
metal centre [23e25]. Previously, we have reported the synthesis of
a
series of cyclopentadienyl titanium complexes containing
chelating dialkoxo [26e28] and diamido [29,30] ligands and
studied the nature of the catalytic species in the -olefin poly-
a
merisation processes generated by the reaction of these complexes
with aluminium and boron reagents as cocatalyst [31]. As a part of
a broad research programme aimed at investigating the catalytic
performance of compounds with these characteristics, combining
a cyclopentadienyl group and a chelating ligand, we have also
recently reported the synthesis and polymerisation studies of
various phenoxo-amido group 4 metal complexes stabilised by an
unsubstituted cyclopentadienyl ligand (h
5-C5H5) [32].
In this paper we describe the synthesis and characterisation of
a family of this type of compounds containing the permethylated
cyclopentadienyl ring [TiCp*{R0NeCH2-(3,5-tBu2C6H2-2-O)}Cl]
* Corresponding author. Tel.: þ34 918854655; fax: þ34 918854683.
E-mail addresses: martaeg.mosquera@uah.es (M.E.G. Mosquera), tomas.cuenca@
uah.es (T. Cuenca).
1
Correspondence concerning the crystallography data should be addressed to
this author.
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.02.011

G. Alesso et al. / Journal of Organometallic Chemistry 696 (2011) 2330e2337
2331
Scheme 3. Synthesis of the phenoxo-amino compound 6.
Scheme 1. Synthesis of the phenoxo-amido compounds.
Cl2] (6) (Scheme 3). The formation of these compounds can be
interpreted as a result of TieCl bond aminolysis and alcoholysis
reactions. Thetwoprocesses arenot simultaneous and, dependingon
the reaction conditions, the alcoholysis reaction is favoured over the
aminolysis process with the NeH phenol-amine group remaining
unreacted to yield the phenoxo-amino derivatives. Formation of
mononuclear phenoxo-amido derivatives, rather than alternative
dinuclear complexes containing a bridging ligand, is favoured in
these reactions due to the thermodynamic stability imposed by the
six-membered ring exhibited by these species and the inherent
favourable entropy.
(Cp* ¼
h
5-C5Me5) and a concise study of the active species gener-
ated when the precatalysts are treated with different boron or
aluminium reagents as cocatalyst. The variety of synthesised
ligands allows us to modify the electronic properties at the metal
centre as well as the geometry of the complex. An analysis of these
differences helps to elucidate the correlation between the proper-
ties of the metal and catalytic behaviour.
Compounds 2e6 are air-sensitive but thermally stable in solu-
tion and in the solid state and can be stored unaltered for weeks if
strictly inert atmospheric conditions are maintained. They are
soluble in aromatic and chlorinated solvents but poorly soluble in
aliphatic hydrocarbons. All of these compounds were fully char-
acterised by NMR spectroscopy and elemental analysis. The
analytical composition fits well with the proposed formulations. In
addition, the X-ray molecular structures of 2 and 5 are reported.
For compounds 2, 4 and 5 spectroscopic data are consistent with
“chiral-at-metal” coordination geometry in solution. The 1H NMR
spectra (CDCl3 or C6D6 at room temperature) show the expected
singlet assignedtothe Cp* ring protons, two signals for the tert-butyl
groups, two doublets (4J z 2.5 Hz) for the two protons of the phe-
nylene ring, and the expected resonances for the NeR substituent
protons. The methylene protons show the expected diastereotopic
character (2J z 15e16 Hz in C6D6) corresponding to asymmetric
metal centre derivatives. The NMR spectroscopic data (C6D6 at room
temperature) for 6 are in agreement with a Cs-symmetry. A broad
signal for the NH proton, and the expected resonances for the
cyclopentadienyl, tert-butyl and phenyl protons are observed in the
1H NMR spectrum (see Experimental Section).
2. Results and discussion
2.1. Synthesis and characterisation of phenoxo-amido and
phenoxo-amino compounds
We have previously provided a contribution to the synthesis and
characterisation of new and somewhat unusual phenoxo-amido
and phenoxo-amino titanium complexes stabilised by the presence
of the unsubstituted cyclopentadienyl ligand (h
5-C5H5) and con-
taining asymmetric metal centres. These complexes are interesting
from basic coordination chemistry perspectives because only a few
derivatives of this type are known. Initial studies of their ethylene
polymerisation performance under MAO-activation conditions
have also been reported [32]. It is interesting to analyse how the
greater bulkiness and electron donor capacity of the permethylated
cyclopentadienyl ring causes lower acidity at the titanium centre
and consequently influences the behaviour of the analogous
derivatives.
As observed in the reactions with TiCpCl3 [32], treatment of
the phenol-amine compounds RHNeCH2-(3,5-tBu2C6H2-2-OH)
(R ¼C6H51a, 4-MeC6H41b, Cy 1c, tBu 1d, Cy ¼ cyclohexyl) [32e34]in
pentane orhexane with TiCp*Cl3 (Cp* ¼
h
5-C5Me5) in the presence of
The NMR spectroscopic analysis (C6D6 at room temperature)
reveals that 3 is a mixture of two stereoisomers (3a and 3b,
Scheme 2) due to axial or equatorial coordination of the amine
nitrogen atom in a trigonal bipyramidal geometry around the
titanium centre with C1- and Cs-symmetry for 3a and 3b, respec-
tively, and the nitrogen atom is coordinated to the metal centre
[32]. The NH resonances for both isomers appear considerably
NEt3, under different reaction conditions, gives the corresponding
monocyclopentadienyl phenoxo-amido monochloro complexes
[TiCp*{RNeCH2-(3,5-tBu2C6H2-2-O)}Cl] (R ¼ C6H5 (2), 4-MeC6H4 (4),
Cy (5)) (Scheme 1) or the monocyclopentadienyl phenoxo-amino
dichloro derivatives [TiCp*{(C6H5)(H)NeCH2-(3,5-tBu2C6H2-2-O)}
Cl2] (3) (Scheme 2) and [TiCp*{tBu(H)NeCH2-(3,5-tBu2C6H2-2-O)}
Scheme 2. Synthesis of the phenoxo-amino compound 3. Fluxional behaviour in solution.

2332
G. Alesso et al. / Journal of Organometallic Chemistry 696 (2011) 2330e2337
shifted downfield (
d
3.08 for 3a and
d
3.66 for 3b) with respect to
that found for the free amine 1a (
ABX spin system (resolves in an AB system) for the CH2NH frag-
ment with a broad signal for the NH proton at 3.08 and doublets
of doublets for the methylene protons at 4.16 and 4.44, with
d 2.82). The isomer 3a shows an
d
d
a coupling constant value of JAB ¼ 16.8 Hz. The isomer 3b, with the
amino group in the axial position, shows an A2X spin system for
the CH2NH fragment with a triplet for the NH proton at
d 3.66 and
a doublet for the methylene protons at 4.52 (JAx of 6.0 Hz). Similar
d
behaviour has been observed for analogous cyclopentadienyl
titanium derivatives [35e37]. It is interesting to note how the
more electron donating capacity of the Cp* ring causes a high-field
shift for the NH proton and less acidity at the titanium centre
compared with a similar derivative containing the unsubstituted
cyclopentadienyl ring [32], and consequently how it influences the
strength of the amino group coordination.
Fig. 1. Molecular structures of 2 (a) and 5 (b), (30% probability) showing the labelling
scheme (hydrogen atoms have been omitted for clarity).
Attempts to synthesise alkyl complexes from the analogous
chloro derivatives containing the unsubstituted cyclopentadienyl
ring were always unsuccessful and repeated efforts to obtain the
alkyl compounds as pure samples on a preparative scale remain
unfruitful [32]. By contrast, reaction of the chloro compound [TiCp*
{(C6H5)NeCH2-(3,5-tBu2C6H2-2-O)}Cl] (2) or [TiCp*{(p-MeC6H4)
NeCH2-(3,5-tBu2C6H2-2-O)}Cl] (4) with LiMe or MgClMe at low
temperature in ether or hexane affords the methyl derivatives
[TiCp*{(C6H5)NeCH2-(3,5-tBu2C6H2-2-O)}Me] (7) or [TiCp*{(p-
MeC6H4)NeCH2-(3,5-tBu2C6H2-2-O)}Me] (8) (Scheme 4). Reactions
to obtain similar benzyl derivatives using MgClBz as alkylating
reagent or alternatively the synthesis of the alkyl derivatives by
treatment of TiCp*R3 (R ¼ Me, CH2Ph) with phenol-amines were
unsuccessful. This behaviour is indicative of the crucial role played
by the Cp* ligand, where its bulkiness and higher electron donor
ability has a decisive affect in these reactions. The 1H and 13C{1H}
NMR spectra (C6D6, room temperature) for the methyl compounds
7 and 8 show patterns for the proton and carbon resonances similar
to those described for the starting chloro compounds. Furthermore,
the spectra show the expected signals assigned to the methyl ligand
attached to titanium.
ppedp interactions [39e44]. The TieO bonds (1.843(2) Å (2) and
1.866(2) Å (5)) are longer that similar distances (1.801 Å average)
found for diphenoxo complexes with or without a cyclopentadienyl
ligand [26,27]. The “TieOeCPheCPheCmethyleneeN” appears as a six-
membered ring with a boat conformation, where the sp3 methy-
lene carbon and the oxygen atom are located out of the plane
defined by the rest of the atoms. The CeC distances within the
cyclopentadienyl ring, TieCg(centroid) distance and TieCl bond
length are within the range for monocyclopentadienyl and dicy-
clopentadienyl titanium complexes [40,42]. It is interesting to
highlight how the substituent attached to the nitrogen atom (Ph for
compound 2 and Cy for compound 5) influences its donor capacity.
Thus, in 5 the nitrogen bears an alkyl substituent, which is more
electron donating and consequently TieN distances are shorter and
the angles around the nitrogen atoms are closer to ideal sp2
hybridisation than in 2.
2.2. Olefin polymerisation studies
We are interested in the polymerisation behaviour of group 4
monocyclopentadienyl diamido [31] or dialkoxo [26,27] metal
complexes. Using sMAO (solid methylalumoxane) and B(C6F5)3 or
[CPh3][B(C6F5)4] as cocatalysts, the chloro compound [TiCp*{(C6H5)
NeCH2-(3,5-tBu2C6H2-2-O)}Cl] (2) and the methyl derivative
[TiCp*{(C6H5)NeCH2-(3,5-tBu2C6H2-2-O)}Me] (7) were studied as
ethylene and propylene polymerisation precatalyst systems under
various conditions. The observed results show averages of two or, in
some cases, more polymerisation runs, which showed good
reproducibility.
For the chloro complex 2 the results are summarized in Table 2
for ethylene polymerisation and in Table 3 for propylene poly-
merisation. When activated with sMAO, the chloro compound 2
shows moderate activities for ethylene polymerisation (Table 2)
and poor activity for propylene polymerisation (Table 3). The
increase in activity with increasing Al supports the suggestion that
Suitable crystals for X-ray diffraction of compounds 2 and 5
were obtained by cooling a hexane solution to ꢀ10 ꢁC. The
molecular structures of [TiCp*{C6H5NeCH2-(3,5-tBu2C6H2-2-O)}Cl]
(2) (Fig.1(a)) and [TiCp*{CyNeCH2-(3,5-tBu2C6H2-2-O}Cl] (5) (Fig.1
(b)), show mononuclear dispositions with the titanium atom in
a tetrahedral environment, similar to that found for analogous
TiCpL3 compounds [38]. In both complexes, the metal is an asym-
metric centre and the racemic mixture of the two possible enan-
tiomers appears in the unit cell. Compound 5 crystallized with one
molecule of hexane for two titanium molecules. Table 1 summa-
rizes selected bond distances and angles.
The angles around the nitrogen atom (ca. 360ꢁ) are consistent
with sp2 hybridisation (355.97ꢁ for 2 and 359.4 for 5). The TieN
bonds of 1.929(3) Å in 2 and 1.877(3) Å in 5 are consistent with an
appreciable multiple bond character and suggest the presence of
Scheme 4. Synthesis of the methyl derivatives and the corresponding cationic species.

G. Alesso et al. / Journal of Organometallic Chemistry 696 (2011) 2330e2337
2333
Table 1
Selected bond lengths (Å) and angles (ꢁ) for compounds 2 and 5$0.5C6H14
Table 3
.
Polymerisation of propylene with compound
cocatalyst.
2
as precatalyst and sMAO as
Bond
TieO 1.843(2)
TieCl 2.3024(10) 2.2911(12) C(31)eN(1)eTi(1) 124.1(2)
TieN 1.929(3) 1.877(3)
TieCg 2.0491(18) 2.0637
2
5$0.5C6H14 Angle
2
5$0.5C6H14
Run
Time (min)
T (ꢁC)
Activitya
1.866(2) C(31)eN(1)eC(20) 116.3(3)
116.1(3)
127.3(2)
1
2
3
4
15
60
60
60
50
50
20
8
2
8
C(20)eN(1)eTi(1) 115.57(19) 116.0(2)
ꢀ10
10
Reaction conditions: 10ꢀ4 mol Ti, Ti/Al ¼ 1/100, P ¼ 5atm except for run 4: 3.5 atm,
volume 50 mL.
the active species is formed after ligand abstraction. No ethylene
polymerisation was found when the reaction was carried out at
50 ꢁC with 5 atm of monomer and a Ti/Al molar ratio of 1/10.
Ethylene polymerisation activities increase slightly when the Al/Ti
ratio increases (Table 2; entries 1e3) and consequently the Ti/Al
molar ratio 1/100 was chosen as “standard” conditions. Similar
activities were observed at 20 ꢁC and 50 ꢁC, although the activity
decreases with time more markedly at 20 ꢁC. This feature has been
explained as a consequence of monomer diffusion problems [45].
The methyl compound 7, activated with boron reagents and
without the presence of aluminium compounds as scavengers,
remained inactive for ethylene and propylene polymerisations. The
observed activity is high at 25 ꢁC when TIBA is used as a scavenger
(Table 4). The methyl complex 7 activated with [CPh3][B(C6F5)4]
shows higher ethylene and propylene polymerisation activities
than those observed following activation with B(C6F5)3 (Table 4).
The PE polymer samples obtained show melting point values close
to 130 ꢁC, characteristic of high density polyethylene, and
a
Activity ¼ KgPE/mol Ti.h.atm.
tube inside the glovebox, the samples were quickly introduced into
the NMR equipment and the spectra recorded at 25 ꢁC over a period
of time. After 1 h at room temperature, the formation of the ionic
titanium species [TiCp*{(C6H5)NeCH2-(3,5-tBu2C6H2-2-O)}][MeB
(C6F5)3] (9) and [TiCp*{(p-MeC6H4)NeCH2-(3,5-tBu2C6H2-2-O)}]
[MeB(C6F5)3] (10) (Scheme 4) were detected. Complexes 9 and 10
can be isolated as analytically pure samples when the reactions are
carried out in toluene on a preparative scale. They are partially
soluble in C6D6 and stable in solution at room temperature over
long periods of time (days). NMR spectroscopic studies demon-
strate the expected abstraction of the methyl group by the Lewis
acid boron reagents. 1H and 13C{1H} NMR spectra show downfield
shifted resonances, compared with the neutral compounds, as
a consequence of the high Lewis acidity of titanium metal after
formation of the cation (see Experimental Section). Interaction of
the methylborate anion with the cationic metal centre can be
remarkable differences in the
DH enthalpy values and the degree of
crystallinity (
a
). The 1H NMR analysis of the polypropylene showed
deduced from the downfield shift of the methyl group (
1.12 for compounds 9 and 10 respectively) in the 1H NMR spectrum,
compared to that observed in the neutral titanium precursor ( 0.96
d 1.13 and
an atactic stereochemistry.
d
and 0.95 for compounds 7 and 8 respectively) and the Dd(m, p-F)
value of w4.7 ppm deduced from the 19F NMR spectrum. The
partial solubility of these compounds in benzene is also consistent
with anionic coordination to the titanium cationic centre.
2.3. Reaction with Lewis acids
In order to get a better knowledge of the nature of the active
species and the chemical behaviour of these precatalyst systems in
In order to avoid a strong cationeanion interaction a non-
coordinating trytil borate reagent, in place of B(C6F5)3, was
employed. The reaction of 7 or 8 with [CPh3][B(C6F5)4] in C6D6 at
25 ꢁC was spectroscopically studied by NMR. The formation of
Ph3CMe as a by-product of the reaction [46] was immediately
detected, allowing us to deduce that abstraction of the methyl
group initially attached to titanium occurred. The 19F NMR spec-
trum exhibits undisturbed [B(C6F5)4]ꢀ anion resonances. However,
a complicated set of resonances in the 1H NMR spectra of the cation
fragment precludes signal assignment and substance identification.
Therefore, we suggest that initially separated ions were formed, but
because there is no stabilization conferred by anion coordination,
a further decomposition process is induced.
the a-olefin polymerisation processes, the reactions of the methyl
complexes 7 and 8 with Lewis acids B(C6F5)3 and [CPh3][B(C6F5)4]
were monitored by 1H NMR spectroscopy using a stoichiometric
1:1 Ti/B ratio. Likewise, the reactions of the methyl complex 7 and
the chloro derivative 2 with trimethylalumium (TMA) and sMAO
were examined. All the procedures were carried out in NMR tubes,
fitted with Teflon valves to prevent water and oxygen ingress, using
deuterated benzene (C6D6) as the reaction solvent at room
temperature, and when possible analytically pure samples were
isolated on a preparative scale.
Addition of C6D6 to an equimolecular amount of B(C6F5)3 and the
chloro derivative 2 affords the unaltered starting compounds,
suggesting that in these systems the TieN and TieO bonds remain
unreacted upon treatment with boron reagents. After addition of
C6D6 to a mixture of B(C6F5)3 and the corresponding neutral methyl
derivatives 7 or 8 in 1:1 M ratio at room temperature in an NMR
These results permit us to conclude that the Lewis acid B(C6F5)3
reacts with the neutral complexes through the abstraction of the
alkyl group, to give highly stable cationic species, retaining
unreacted TieO and TieN bonds with the bidentate phenoxo-amido
Table 2
Polymerisation of ethylene with compound 2 as precatalyst and sMAO as cocatalyst.
Table 4
Run
Time (min)
T (ꢁC)
Ti/Al
Activitya
Olefin polymerisation with compound 7 as precatalyst and different boron reagents
1
2
3
4
5
6
7
8
15
15
15
30
60
15
30
60
50
50
50
50
50
20
20
20
1/100
1/300
1/500
1/100
1/100
1/100
1/100
1/100
12
19
36
16
9
11
7
4
as cocatalyst in the presence of TIBA as scavenger.
Run
Monomer (atm)
cocat.
T (ꢁC)
Time (min)
Activitya
1
2
3
4
Ethylene (2)
Ethylene (2)
Propylene (5)
Propylene (5)
B(C6F5)3
[CPh3][B(C6F5)4]
B(C6F5)3
25
25
25
25
10
5
40
40
292
775
2
[CPh3][B(C6F5)4]
116
Reaction conditions: 2.10ꢀ5 mol of Ti, 2.10ꢀ5 mol of Cocatalyst, volume 100 mL,
Reaction conditions: 10ꢀ4 mol Ti, P ¼ 5 atm, volume 50 mL.
TIBA/Ti ¼ 50/1.
a
a
Activity ¼ KgPE/mol Ti.h.atm.
Activity ¼ KgPol/mol Ti.h.atm.

2334
G. Alesso et al. / Journal of Organometallic Chemistry 696 (2011) 2330e2337
ligand bonded to the titanium centre. Formation of such a stable
species exhibiting strong interactions with the anionic unit prevents
coordination of the olefin and consequently these systems showlow
activity in ethylene and propylene polymerisation. With the [CPh3]
[B(C6F5)4] reagent, we initially assumed similar reactivity. However,
the anionic unit [B(C6F5)4]ꢀ is a less coordinated anion than [MeB
(C6F5)3]ꢀ and in the absence of an olefin, these [B(C6F5)4]ꢀ anionic
systems show a lack of stability with fast and immediate decom-
position in solution, although in the presence of an olefin a clear
polymerisation reaction is observed.
3. Concluding remarks
Here we report the synthesis and characterisation of new and
unusual phenoxo-amido and phenoxo-amino titanium complexes
stabilised by the permethylated cyclopentadienyl ligand and con-
taining asymmetric metal centres. The results of the studies on
ethylene and propylene polymerisation by using these precatalyst
systems in the presence of different cocatalysts suggest the
formation of catalytic species with variable natures.
During the olefin polymerisation process, aluminium
compounds are normally used as cocatalysts (MAO) to generate the
active species or as scavenger reagents (TIBA). MAO initially
produces alkylation of the halo groups in the precursor and
subsequently the abstraction of one of the alkyl groups generated
to give cationic alkyl species, which are considered as the active
species in the polymerisation reaction. Considering that polymer-
isation studies were made with MAO and given our interest in the
identification of the nature of the active species in olefin poly-
merisation, we studied the reactions of compounds 2 and 7 with
TMA or sMAO.
A solution of the monochloro compound 2 was treated with
sMAO in a 1:20 M ratio in toluene at ꢀ78 ꢁC. Spectroscopic
analysis by 1H NMR revealed the presence of the methyl complex
2, indicating the alkylation of the TieCl bond and the selective
formation of the methyl derivative 7 (Scheme 5). The NMR spectra
also showed the presence of signals assignable to secondary
unidentified products. Similarly, treatment of a solution of the
monochloro compound 2 in hexane with one equiv of TMA
at ꢀ78 ꢁC afforded the same mixture of the methyl compound 7
and the analogous NMR spectroscopic pattern corresponding to
the unidentified species. The intensity of the signals assignable to
the secondary unidentified products increases when an excess of
TMA is used as reagent, along with the disappearance of the
signals assignable to compound 7. The methyl derivative 7 reacts
directly with sMAO in 1:20 M ratio, at room temperature in C6D6
and alternatively with TMA to give this same mixture of secondary
unidentified species. These observations accord with the alkylat-
ing capacity of the sMAO or the TMA to give the methyl derivative.
Transmetallation reactions of the phenoxo-amido ligand from
titanium to aluminium should explain the formation of these
secondary products [47,48]. Consequently, the ligand transfer
processes in the reaction with aluminium reagents are associated
with the activity of the chloro complex 2 for ethylene and
propylene polymerisations.
4. Experimental section
4.1. General considerations
All manipulations and reactions of air- and/or moisture sensitive
compounds were carried out under argon (Air Liquid N45, O2:
1 ppm; H2O: 3 ppm) using Schlenk and high-vacuum line tech-
niques or in a dry argon atmosphere MBraun glovebox model
MB150B-G. Deuterated solvents were firstly degassed by several
freezeethaw cycles, held at room temperature over fresh activated
4 Å molecular sieves and then stored at room temperature over
freshly activated 4 Å molecular sieves. Compounds TiCp*Cl3,
TiCp*Me3 and TiCp*Bz3 were prepared by a known procedure [49].
All reactants for the preparation of the phenoxo-amine derivatives
were purchased and used as received from Aldrich, except tert-
butylamine and N-tert-butyl-methylamine (Aldrich) which were
purified under argon according to literature procedures [50].
MgClMe was used as 3 M solution in THF and MgClBz as 2 M
solution in THF (Aldrich). Solid AlMe3-free methylalumoxane
(sMAO) was obtained from commercial methylalumoxane (MAO)
(CROMPTON, 10 wt. % solution in toluene) by drying under reduced
pressure at 50 ꢁC to remove the uncoordinated AlMe3 and used
after washing with n-hexane and complete drying. The white solid
obtained was stored in dry box before use to prepare the samples.
Calculated quantities of the desired compound and solid MAO were
taken, in the dry box, to provide the samples with the desired Ti/Al
ratio. The NMR samples of air- and/or moisture sensitive
compounds were prepared under argon at room temperature in
5 mm Wilmad 507-PP tubes fitted with J. Young Teflon valves. NMR
spectra were recorded at 400.13 (1H), 376.00 (19F) and 100.60 (13C)
MHz on a Bruker AV400. Chemical shifts (d) are given in ppm using
CDCl3 or C6D6 as solvent. 1H and 13C resonances were measured
relative to solvent peaks considering TMS
d
¼ 0 ppm, while 19F was
measured relative to external CFCl3. Elemental analyses were
obtained on a PerkineElmer Series II 2400 CHNS/O analyser. The
thermal properties of the samples were studied, after recrystalli-
zation, in a Perkin Elmer DSC 6 instrument calibrated by measuring
the melting point of indium. From the second heating curve was
In general, the different results in polymerisation activity
depending on the nature of the cocatalyst can be attributed to the
ability of aluminium derivatives to abstract the chelate ligand and
consequently affect the TieN or TieO bonds providing the alkyl
group necessary to achieve polymerisation in a ZieglereNatta
manner. This possibility is unavailable when the perfluoroborane
compound is used. The activity shown by methyl complex 7 when
aluminium and boron compounds are simultaneously in the reac-
tion medium (Table 4) confirms this suggestion.
obtained the melting point (Tm) and the DHm.
4.2. Polymerisation procedure
For ethylene or propylene polymerisation the typical procedure
was as follows. The desired amount of the selected precatalyst was
weighted in the dry-box and in a sealed glass vial put into a high
pressure glass reaction vessel (Büchi). Then a solution of toluene
(50 mL) containing sMAO (in the desired Al:Ti ratio) was injected
via cannula and the mixture stirred for 15 m. Subsequently, the
polymerisation temperature was adjusted and the argon was
replaced by the monomer by degassing the solution under vacuum
and refilling with the olefin. This procedure was repeated and the
solution was finally saturated with the olefin over 15 m and pres-
surized at 2 or 5 atm for 1 h before cracking the vial. After the
polymerisation time was reached, the monomer gas was vented
and the reaction was quenched with 10 mL of a 5% solution of HCl/
Scheme 5. Methylation reactions of 2 with sMAO or AlMe3.

G. Alesso et al. / Journal of Organometallic Chemistry 696 (2011) 2330e2337
2335
CH3OH. The resultant suspension was then poured in a large excess
of this solvent mixture and the resultant polyethylene was sepa-
rated by filtration, washed several times (HCl/CH3OH) and dried
under vacuum overnight to constant weight.
of TiCp*Cl3 (289.5 mg). After 12 h the solution appeared red and with
[NHEt3]Cl as a white precipitate. The solution was filtered off and
evaporated. Yield 89% (473.2 mg, 0.89 mmol). 1H NMR (C6D6):
d
0.73e1.62 (m,10H, cyclohexyl),1.33 (s, 9H, tBu),1.52 (s, 9H, tBu), 2.04
(s, 15H, C5Me5), 3.58 and 4.84 (AB system, JHꢀH ¼ 16.2 Hz, 2H, CH2),
3.67 (pt, 1H, cyclohexyl), 7.09 (d, JHeH ¼ 2.4 Hz, 1H, PhO), 7.38 (d,
JHeH ¼ 2.4 Hz, 1H, PhO). Anal. Calcd. for C31H48ClNOTi (5343.63 g/
mol): C 69.72; H 9.00; N 2.62. Found: C 68.82; H 8.54; N 2.81.
4.3. [TiCp*{(C6H5)NeCH2-(3,5-tBu2C6H2-2-O)}Cl] (2)
A solution of 1 mmol of 1a (311.5 mg) and 2.5 mmol (0.35 mL) of
NEt3 in 50 mL of pentane was added under vigorous stirring to
1 mmol of TiCp*Cl3 (289.5 mg). After 12 h the solution turned
brown with abundant [NHEt3]Cl as a white precipitate. The solution
was filtered off and concentrated until a brown precipitate started
to appear. The suspension was maintained at ꢀ40 ꢁC for 12 h, when
the liquid phase was filtered off and the solid dried under vacuum.
Yield 72% (384.2 mg, 0.72 mmol).
4.7. [TiCp*{tBu(H)NeCH2-(3,5-tBu2C6H2-2-O)}Cl2] (6)
The procedure is similar to that described for 2. A solution of
1 mmol of 1d (291.5 mg) and 2.5 mmol (0.35 mL) of NEt3 in 50 mL of
pentane was added under vigorous stirring to 1 mmol of TiCp*Cl3
1H NMR (CDCl3):
C5Me5), 4.04 and 5.18 (AB system, JHeH ¼ 14.7 Hz, 2H, CH2),
6.90e7.25 (m, 7H, PhN and PhO). 1H NMR (C6D6):
1.26 (s, 9H, tBu),
d
1.16 (s, 9H, tBu), 1.27 (s, 9H, tBu), 1.90 (s, 15H,
(289.5 mg). Yield 62% (339.6 mg, 0.62 mmol). 1H NMR (C6D6):
d 1.19
(s broad, 9H, tBu), 1.38 (s broad, 9H, tBu), 1.56 (s broad, 9H, tBu), 1.91
(s, 15H, C5Me5), 3.96 (br, 2H, CH2), 7.42 (d, JHeH ¼ 2.2 Hz, 1H, PhO),
7.88 (br, 1H, NH), the Ph signals appear overlapped with the solvent
resonances and are not observed. Anal. Calcd. C29H47Cl2NOTi
(544.5 g/mol): C 63.97; H 8.63; N 2.57. Found: C 63.15; H 9.17; N 3.18.
d
1.57 (s, 9H, tBu), 1.85 (s, 15H, C5Me5), 4.01 and 5.10 (AB system,
JHeH ¼ 16.8 Hz, 2H, CH2), 6.80e6.90 and 7.05e7.10 (m, 5H, PhN),
7.02 (d, JHeH ¼ 2.4 Hz, 1H, o-H, PhO), 7.47 (d, JHeH ¼ 2.4 Hz, 1H, m-H,
PhO). Anal. Calcd. for C31H42ClNOTi (527.60 g/mol): C 70.52; H 8.02;
N 2.65. Found: C 70.65; H 8.16; N 2.34.
4.8. [TiCp*{(C6H5)NeCH2-(3,5-tBu2C6H2-2-O)}Me] (7)
4.4. [TiCp*{(C6H5)(H)NeCH2-(3,5-tBu2C6H2-2-O)}Cl2] (3)
1.2 mmol of MgClMe (3-M solution in THF) was added under
vigorous stirring to a suspension of 1 mmol of 2 (528.0 mg) cooled
at ꢀ78 ꢁC in 50 hexane. After 12 h the solution appeared orange
brown with abundant MgCl2 as a white precipitate. The solution
was filtered off and concentrated until a light brown precipitate
started to appear. The suspension was maintained at ꢀ40 ꢁC for
12 h, when the liquid phase was filtered off and the solid dried
under vacuum. Yield 72% (364.5 mg, 0.72 mmol). 1H NMR (CDCl3):
A solution of 1a (311.5 mg, 1 mmol) and NEt3 (0.35 mL,
2.5 mmol) in toluene (50 mL) was added under vigorous stirring to
TiCp*Cl3 (289.5 mg, 1 mmol). After 12 h the solution appeared red
with the formation of [NHEt3]Cl as a white precipitate. The solution
was filtered off and concentrated to a volume of 10 mL and main-
tained at ꢀ40 ꢁC for 12 h to give a solid, which was recrystallised
from toluene at ꢀ30 ꢁC and characterised as a mixture of 3a:3b
(336.1 mg, 0.59 mmol, 59% yield).
d
0.73 (s, 3H, MeeTi), 1.27 (s, 9H, tBu), 1.32 (s, 9H, tBu), 1.90 (s, 15H,
1H NMR (300 MHz, C6D6) of stereoisomer 3a:
d
1.22 (s, 9 H, tBu),
C5Me5), 4.19 and 5.07 (AB system, JHeH ¼ 15.0 Hz, 2H, CH2), 6.67 (d,
1.42 (s, 9 H, tBu), 1.96 (s, 15H, C5Me5), 3.08 (s broad, 1H, NH), 4.16
and 4.44 (dd, JAB ¼ 16.8 Hz, AB of an ABX spin system, 2H, CH2),
6.40e7.20 (m, 7H, arom.). 1H NMR (300 MHz, C6D6) of stereoisomer
JHeH ¼ 7.4 Hz, 2H, m-H PhN), 6.87 (t, JHeH ¼ 7.4 Hz, 1H, p-H PhN),
7.10e7.23 (m, 4H, arom.). 1H NMR (C6D6):
d 0.96 (s, 3H, MeeTi), 1.32
(s, 9H, tBu), 1.54 (s, 9H, tBu), 1.77 (s, 15H, C5Me5), 4.18 and 5.04 (AB
system, JHeH ¼ 15.0 Hz, 2H, CH2), 6.70 (d, JHeH ¼ 7.5 Hz, 2H, m-H
PhN), 6.85 (t, JHeH ¼ 7.4 Hz, 1H, p-H PhN), 7.09 (d, JHeH ¼ 8.4 Hz, 2H,
o-H PhN), 7.20 (d, JHeH ¼ 2.4 Hz, 1H, m-H, PhO), 7.50 (d,
3b:
d
1.24 (s, 9H, tBu),1.56 (s, 9 H, tBu), 3.66 (pt, JAꢀx ¼ 6.0 Hz, X of an
A2X spin system, 1H, NH), 4.52 (pd, JAꢀx ¼ 6.7 Hz, A of an A2X spin
system, 2H, CH2), 6.62 (d, JHꢀH ¼ 7.8 Hz, 2H, o-H, PhO), 6.74 (d,
JHꢀH ¼ 7.2 Hz, 2H, o-H, PhO), 6.85e7.53 (m, 4H, Ph), 7.46 (1 H, d,
JHeH ¼ 2.4 Hz, PhO). Anal. Calcd. for C31H43Cl2NOTi (564.08 g/mol):
C 66.00; H 7.62; N 2.48. Found: C 65.98; H 7.53; N 2.44.
JHeH ¼ 2.4 Hz, 1H, m-H, PhO). 13C NMR (C6D6):
d 11.8 (C5Me5), 30.6
(tBu), 32.3 (tBu), 35.8 (Cipso, tBu), 38.8 (Cipso, tBu), 51.9 (MeeTi), 58.6
(CH2), 119.6 (Cipso, C5Me5), 122.1e141.9 (arom.), 152.8 (Cipso, PhO),
161.1 (Cipso, PhN). Anal. Calcd. for C32H45NOTi (507.20 g/mol): C
75.72; H 8.87; N 2.76. Found: C 75.75; H 8.81; N 3.00.
4.5. [TiCp*{(4-MeC6H4)NeCH2-(3,5-tBu2C6H2-2-O)}Cl] (4)
A solution of 1 mmol of 1b (325.5 mg) and 2.5 mmol (0.35 mL) of
NEt3 in50mLofpentanewasaddedundervigorousstirringto1mmol
of TiCp*Cl3 (289.5 mg). After 12 h, the solution appeared brown with
abundant [NHEt3]Cl as a white precipitate. The solution was filtered
off and concentrated to give a brown solid. The suspension was
maintained at ꢀ40 ꢁC for 12 h, when the liquid phase was filtered off
and the solid dried under vacuum. Yield 67% (364.1 mg, 0.67 mmol).
4.9. [TiCp*{(4-MeC6H4)NeCH2-(3,5-tBu2C6H2-2-O)}Me] (8)
1.2 mmol of MgClMe (3-M solution in THF) was added under
vigorous stirring to a suspension of 1 mmol of 4 (542.0 mg) cooled
at ꢀ78 ꢁC in 50 mL of hexane. After 12 h the solution appeared
orange-brown with abundant MgCl2 as a white precipitate. The
solution was filtered off and concentrated until a light brown
precipitate started to appear. The suspension was maintained
at ꢀ40 ꢁC for 12 h and then the liquid phase was filtered off and the
solid dried under vacuum. Yield 69% (357.9 mg, 0.69 mmol). 1H NMR
1H NMR (C6D6):
d 1.24 (s, 9H, tBu),1.52 (s, 9H, tBu),1.86 (s,15H, C5Me5),
2.12 (s, 3H, Me), 3.99 and 5.13 (AB system, JHeH ¼ 15.0 Hz, 2H, CH2),
6.89e6.96 (AB system, JHꢀH ¼ 15.0 Hz, 4H, PhN), 7.03 (d, 1H,
JHeH ¼ 2.4 Hz, PhO), 7.47(d,1H, JHeH ¼ 2.4Hz,1H, PhO). Anal. Calcd. for
C32H44ClNOTi (542.0 g/mol): C 70.91; H 8.18; N 2.58; Experimental: C
70.85; H 8.36; N 2.46.
(C6D6):
d 0.95 (s, 3H, MeeTi), 1.31 (s, 9H, tBu), 1.55 (s, 9H, tBu), 1.80
(15H, s; C5Me5), 2.16 (s, 3H, MeePh), 4.20 and 5.10 (AB system,
JHeH ¼ 15.0 Hz, 2H, CH2), 6.67 (d, JHeH ¼ 7.4 Hz, 2H, m-H PhN), 6.93 (t,
JHeH ¼ 7.5 Hz, 2H, o-H PhN), 7.19 (d, JHeH ¼ 2.4 Hz, 1H, m-H, PhO),
7.50 (d, JHeH ¼ 2.4 Hz, 1H, m-H, PhO). Anal. Calcd. for C33H47NOTi
(521.6 g/mol): C 76.04; H 9.09; N 2.70. Found: C 76.30; H 8.93; N
2.67.
4.6. [TiCp*{CyNeCH2-(3,5-tBu2C6H2-2-O)}Cl] (5)
A solution of 1 mmol of 1c (317.3 mg) and 2.5 mmol (0.35 mL) of
NEt3 in50mLofpentanewasaddedundervigorousstirringto1mmol

2336
G. Alesso et al. / Journal of Organometallic Chemistry 696 (2011) 2330e2337
4.10. [TiCp*{(C6H5)NeCH2-(3,5-tBu2C6H2-2-O)}][MeB(C6F5)3] (9)
at ꢀ78 ꢁC in 50 mL of hexane. After 8 h when the reaction mixture
had reached the room temperature, the solution was dried under
vacuum. In the solid obtained, a mixture of the methyl compound 7
and unidentified species was spectroscopically observed.
30 mL of toluene was added to a solid mixture of B(C6F5)3
(1 mmol, 512.0 mg) and of 7 (1 mmol, 507.3 mg) at ꢀ78 ꢁC. The
reaction evolved over 12 h. The solution turned brown and a dark
oil precipitated. The liquid phase was removed by filtration and the
oil dried under vacuum to produce a dark solid. Yield 83% (846.3 mg
4.13. Reaction between [TiCp*{(C6H5)NeCH2-(3,5-tBu2C6H2-2-O)}
Me] (7) and AlMe3
0.83 mmol). 1H NMR (C6D6):
d 1.13 (br, 3H, BeMeeTi), 1.28 (s, 9H,
tBu), 1.30 (s, 9H, tBu), 1.57 (s, 15H, C5Me5), 3.80 and 4.81 (AB system,
JHeH ¼ 16.2 Hz, 2H, CH2), 6.40 (d, JHeH ¼ 7.8 Hz, 2H, m-H PhN), 6.85
(t, JHeH ¼ 7.8 Hz, 1H, p-H PhN), 6.96 and 7.40 (d, JHeH ¼ 2.4 Hz, 2H,
m-H, PhO), 7.09 (t, JHeH ¼ 8.1 Hz, 2H, o-H PhN). 19F NMR (C6D6):
1 mmol of AlMe3 (0.5 mL of 2 M hexane solution) was added
under vigorous stirring to a solution of 1 mmol of 7 (507.4 mg)
at ꢀ78 ꢁC in 50 mL of hexane. After 8 h the reaction mixture had
reached the room temperature, the solution was dried under
vacuum. In the obtained solid a mixture of unidentified species was
spectroscopically observed.
d
ꢀ132.67 (s, o-F C6F5), ꢀ160.35 (s, p-F C6F5), ꢀ165.03 (s, m-F C6F5).
Anal. Calcd. for C50H45BF15NOTi (1019.6 g/mol): C 58.90; H 4.45; N
1.37. Found: C 57.94; H 5.16; N 1.46.
4.14. X-ray crystal structure determinations of compounds 2 and
5$0.5C6H14
4.11. [TiCp*{(4-MeC6H4)NeCH2-(3,5-tBu2C6H2-2-O)}]
[MeB(C6F5)3] (10)
Details of the X-ray experiment, data reduction, and final
structure refinement calculations are summarized in Table 5.
The procedure is similar to that described for 9 using 1 mmol
(512.0 mg) of B(C6F5)3 and 1 mmol (521.6 mg) of 8. Yield 75%
Suitable single crystals of
2 and 5$0.5C6H14 for the X-ray
(775.0 mg 0.75 mmol). 1H NMR (C6D6):
d 1.12 (br, 3H, BeMeeTi),
diffraction study were selected. Data collection was performed at
150(2) K, with the crystals covered with perfluorinated ether oil.
The crystals were mounted on a Bruker-Nonius Kappa CCD single
crystal diffractometer equipped with graphite-monochromated
1.28 (s, 9H, tBu), 1.30 (s, 9H, tBu), 1.59 (s, 15H, C5Me5), 2.07 (s, 3H,
MeePh), 3.83 and 4.83 (AB system, JHeH ¼ 16.2 Hz, 2H, CH2), 6.38 (d,
JHeH ¼ 8.4 Hz, 2H, m-H PhN), 6.96 (t, JHeH ¼ 8.4 Hz, 2H, o-H PhN),
6.98 and 7.42 (d, JHeH ¼ 2.4 Hz, 2H, m-H, PhO). 19F NMR (C6D6):
Mo-K
a
radiation (
l
¼ 0.71073 Å). Multiscan [51] absorption
correction procedures were applied to the data. The structures
were solved, using the WINGX package [52], by direct methods
(SHELXS-97) and refined using full-matrix least-squares against
F2 (SHELXL-97) [53,54]. For compound 2, all non-hydrogen atoms
were anisotropically refined and the hydrogen atoms were
geometrically placed and left riding on their parent atoms. In 5
the carbon atoms C38, C39 and C40 from a tBu group were
disordered in two positions, the disorder was treated and the
atoms left isotropic. The remaining non-hydrogen atoms were
anisotropically refined including the disordered molecule of
hexane that crystallized with every two molecules of 5. The
hydrogen atoms were geometrically placed and left riding on
their parent atoms except for the hydrogen on C31 that was
found on the Fourier map and refined.
d
ꢀ132.60 (s, o-F C6F5), ꢀ160.42 (s, p-F C6F5), ꢀ165.07 (s, m-F C6F5).
Anal. Calcd. for C51H47BF15NOTi (1033.3 g/mol): C 59.26; H 4.58; N
1.36. Found: C 58.61; H 3.76; N 1.33.
4.12. Reaction between [TiCp*{(C6H5)NeCH2-(3,5-tBu2C6H2-2-O)}
Cl] (2) and AlMe3
1 mmol of AlMe3 (0.5 mL of 2 M hexane solution) was added
under vigorous stirring to a solution of 1 mmol of 2 (528.2 mg)
Table 5
Crystal Data and Structure Refinement Details for 5$0.5C6H14 and 2.
2
5$0.5C6H14
Formula
FW
C31H42ClNOTi
528.01
C34H55ClNOTi
577.14
Acknowledgement
Color/habit
Dark red/prism
0.31 ꢂ 0.23 ꢂ 0.20
Monoclinic
P21/c
13.6121(14)
9.4673(6)
22.931(2)
90
102.422(10)
90
2885.9(4)
4
Dark red/prism
0.50 ꢂ 0.31 ꢂ 0.28
Triclinic
P-1
8.691(5)
13.078(5)
15.321(5)
87.510(5)
76.474(5)
78.855(5)
1661.2(13)
2
Cryst dimensions (mm3)
Cryst syst
Space group
a, Å
b, Å
c, Å
Financial support for this research by Dirección General de
Investigación Científica
y Técnica (Project MAT2010-14965),
Comunidad Autónoma de Madrid: (Project S-0505-PPQ/0328-02)
and by European Commission (Contract Nr. HPRN-CT2000-00004)
is gratefully acknowledged.
a
, (deg)
, (deg)
b
g
, (deg)
Appendix A. Supplementary material
V, Å3
Z
CCDC 802062 and 802063 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
T, K
150
1.215
0.412
1128
3.01e27.50
20,800
6615/0.2029
4089
150
1.154
0.363
626
3.07e25.00
11,244
5832/0.0519
4243
rcalcd, g cmꢀ3
m
, mmꢀ1
F(000)
q
range, deg
No. of rflns collected
No. of indep rflns/Rint
No. of obsd rflns (I > 2
References
s
(I))
No. of data/restraints/params
6615/0/317
0.0703/0.1529
0.1216/0.1794
0.0028(9)
1.025
5832/0/346
0.0614/0.1562
0.0913/0.1678
0.005(2)
1.057
þ0.993/ꢀ0.532
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