Early transition metal derivatives stabilised by the phenylenediamido 1,2-C6H4(NCH2tBu)2 ligand: Synthesis, characterisation and reactivity studies: Crystal structures of [Ta{1,2-C6H4(NCH2tBu)2} 2Cl] and [Zr{(1,2-C6H4(NCH2tBu)

Article abstract of DOI:10.1016/j.poly.2009.05.055

Li₂[1,2-C₆H₄(NCH₂tBu) ₂] reacts with one equiv of [TiCl₄(THF)₂] in refluxing toluene to give the chelate compound [Ti{1,2-C₆H₄(NCH₂tBu)₂} Cl₂(THF)] (1), isolated as a black product, while the reaction of the dilithio diamido salt with one equiv of [ZrCl₄(THF)₂] in refluxing toluene affords the dinuclear zirconium derivative [Zr{1,2-C₆H₄(NCH₂tBu)₂}Cl(TH F)(μ-Cl)]₂ (2), obtained as an orange solid. Treatment of the dilithio diamido salt with TaCl₅ in a 2:1 molar ratio in toluene yields [Ta{1,2-C₆H₄(NCH₂tBu)₂} ₂Cl] (3) as a red product. The reaction of 1,2-C₆H₄(NHCH₂tBu)₂ with [Zr(NMe₂)₄] in toluene at room temperature affords the dinuclear zirconium complex [Zr{1,2-C₆H₄(NCH₂tBu)₂}( NMe₂)(μ-NMe₂)]₂ (4). The dibenzyl derivative [Ti{1,2-C₆H₄(NCH₂tBu)₂}( CH₂Ph)₂] (5) is obtained by the reaction of 1 with 2 equiv of Mg(CH₂Ph)Cl at -78 °C. Compound 1 reacts with the lithium amide reagent LiN(SiMe₃)₂ to afford [Ti{1,2-C₆H₄(NCH₂tBu)₂}Cl{N( SiMe₃)}] (6). The μ-oxo titanium derivative [(Ti{1,2-C₆H₄(NCH₂tBu)₂}{ CH₂Ph})₂(μ-O)] 7 is precipitated when compound 5 is maintained in solution. The tendency of these compounds to coordinate donor ligands and their reactivity with Lewis acid reagents are described. All compounds were analytically and spectroscopically characterised and the molecular structures of the diamine 1,2-C₆H₄(NHCH₂tBu)₂ and the complexes 3 and 4 were established by single-crystal X-ray diffraction studies. The lack of correlation between the degree of metallacycle folding and phenylene ring distortion is observed in the solid state structures. The performance of precursors 1, 3 and 5 were evaluated in ethylene polymerisation upon activation with B(C₆F₅)₃, methylaluminoxane (MAO) and sMAO as cocatalysts, with very modest activities.

Full text of DOI:10.1016/j.poly.2009.05.055

Polyhedron 28 (2009) 2545–2554
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Early transition metal derivatives stabilised by the phenylenediamido
1,2-C6H4(NCH2tBu)2 ligand: Synthesis, characterisation and reactivity
studies: Crystal structures of [Ta{1,2-C6H4(NCH2tBu)2}2Cl]
and [Zr{(1,2-C6H4(NCH2tBu)2}(NMe2)(l-NMe2)]2
Vanessa Tabernero a, Tomás Cuenca a, , Marta E.G. Mosquera a,1, Carmen Ramírez de Arellano b,1
*
a Departamento de Química Inorgánica, Universidad de Alcalá, Campus Universitario, 28871 Alcalá de Henares, Spain
b Departamento de Química Orgánica, Universidad de Valencia, 46100 Valencia, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Li2[1,2-C6H4(NCH2tBu)2] reacts with one equiv of [TiCl4(THF)2] in refluxing toluene to give the chelate
compound [Ti{1,2-C6H4(NCH2tBu)2}Cl2(THF)] (1), isolated as a black product, while the reaction of the
dilithio diamido salt with one equiv of [ZrCl4(THF)2] in refluxing toluene affords the dinuclear zirconium
Received 2 March 2009
Accepted 7 May 2009
Available online 2 June 2009
derivative [Zr{1,2-C6H4(NCH2tBu)2}Cl(THF)(l-Cl)]2 (2), obtained as an orange solid. Treatment of the
dilithio diamido salt with TaCl5 in a 2:1 molar ratio in toluene yields [Ta{1,2-C6H4(NCH2tBu)2}2Cl] (3)
as a red product. The reaction of 1,2-C6H4(NHCH2tBu)2 with [Zr(NMe2)4] in toluene at room temperature
affords the dinuclear zirconium complex [Zr{1,2-C6H4(NCH2tBu)2}(NMe2)(l-NMe2)]2 (4). The dibenzyl
derivative [Ti{1,2-C6H4(NCH2tBu)2}(CH2Ph)2] (5) is obtained by the reaction of 1 with 2 equiv of
Keywords:
Titanium
Zirconium
Tantalum
Diamido
Mg(CH2Ph)Cl at ꢀ78 °C. Compound 1 reacts with the lithium amide reagent LiN(SiMe3)2 to afford
[Ti{1,2-C6H4(NCH2tBu)2}Cl{N(SiMe3)}] (6). The
l-oxo titanium derivative [(Ti{1,2-C6H4(NCH2tBu)2}
{CH2Ph})2(l-O)] 7 is precipitated when compound 5 is maintained in solution. The tendency of these
compounds to coordinate donor ligands and their reactivity with Lewis acid reagents are described. All
compounds were analytically and spectroscopically characterised and the molecular structures of the
diamine 1,2-C6H4(NHCH2tBu)2 and the complexes 3 and 4 were established by single-crystal X-ray
diffraction studies. The lack of correlation between the degree of metallacycle folding and phenylene ring
distortion is observed in the solid state structures. The performance of precursors 1, 3 and 5 were eval-
uated in ethylene polymerisation upon activation with B(C6F5)3, methylaluminoxane (MAO) and sMAO as
cocatalysts, with very modest activities.
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
uents attached to the nitrogen atoms [5]. Corresponding group 5
metal complexes are less active in polymerisation, so they have
In recent years olefin polymerisation investigations have fo-
cused on the development of non-Cp based catalysts giving rise
to previously unknown polymerisation behaviours and new poly-
olefin materials [1].
Bis(phenoxido-imino) group 4 metal complexes and titanium
and zirconium derivatives with chelating diamido ligands [2,3]
are currently receiving considerable attention, largely because of
not been widely studied as potential catalysts for olefin polymeri-
sation, although they are more tolerant of functionalised olefin
monomers [6,7].
We are interested in the synthesis and chemical behaviour
of MCp0(LL)X derivatives (Cp0 = substituted or unsubstituted
g
5-cyclopentadienyl ring; LL = chelating diamido [8–10] and dial-
koxo [11–13] ligands). The synthesis and characterisation of new
0
their potential use as homogeneous catalyst precursors for the
a
-
chloro diamido complexes of titanium and zirconium MCpR
0
olefin polymerisation process [4]. Chelating diamido ligands are
versatile in view of the large number of possible available substit-
[1,2-C6H4(NR)2]Cl [M = Ti, Zr; CpR
=
g
5-C5H5,
g
5-C5(CH3)5, g5
-
C5H4(SiMe3); R = nPr, Np] have been described [8–10]. These
complexes were tested as potential catalysts for ethylene and
styrene polymerisation after activation with MAO. In this context,
we report here a series of dichloro titanium, zirconium and chloro
tantalum complexes bearing the bulky diamido ligand [1,2-C6H4
(NCH2tBu)2]2ꢀ not supported by a cyclopentadienyl ring. The
presence of the ligand [1,2-C6H4(NCH2tBu)2]2ꢀ in the metal
* Corresponding author. Tel.: +34 91 8854655; fax: +34 91 8854683.
E-mail addresses: tomas.cuenca@uah.es (T. Cuenca), martaeg.mosquera@uah.es
(M.E.G. Mosquera), Carmen.Ramirezdearellano@uv.es (C.R. de Arellano).
1
Correspondence concerning the crystallography data should be addressed to
these authors.
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.05.055

2546
V. Tabernero et al. / Polyhedron 28 (2009) 2545–2554
environment not only provides the delicate electronic balance and
electronic relief to the Lewis acidic metal centre on account of its
electron rich nitrogen atoms, but the bulky neopentyl substituents
also render enough steric protection to the electrophilic metal
centre.
(NCH2tBu)2}Cl(THF)(l-Cl)]2 (2), obtained as an orange solid. The
reaction of Li2[1,2-C6H4(NCH2tBu)2] with ZrCl4 or [ZrCl4(THF)2] in
a molar ratio of 2:1 and the ligand redox reactivity of the corre-
sponding coordinated zirconium complexes have been recently de-
scribed [18]. The standard procedure described for group 4 metal
complexes was also used for tantalum. Thus, when the dilithio
diamido salt reacts with TaCl5 in 2:1 molar ratio in toluene, forma-
tion of [Ta{1,2-C6H4(NCH2tBu)2}2Cl] (3) as a red product is ob-
served immediately.
Complexes 1–3 are air and moisture sensitive in solution and in
the solid state, although they can be stored unaltered for weeks un-
der an inert atmosphere. The complexes were characterised by the
usual analytical and spectroscopic methods (NMR spectra for dif-
ferent solvents are given in the Section 5 as consequence for reso-
lution and assignment). The elemental analysis value found for 2
was inaccurate, caused by small amounts of LiCl in the mixture,
which could not be removed. The molecular structure of 3 has been
confirmed by single-crystal X-ray diffraction.
2. Results and discussion
The synthesis of N,N0-alkyl 1,2-phenylenediamines 1,2-
C6H4(NHR)2 [R = CH2CH2CH3 (nPr), CH2tBu (Np)] has been reported
[8] in three steps, lithiation of the corresponding primary 1,2-
phenylenediamine, reaction with the appropriate acyl chloride
and reduction using LiAlH4. However, no crystallographic data
were published. In the course of the present study, the solid state
structure of the compound 1,2-C6H4(NHCH2tBu)2 has been con-
firmed by single-crystal X-ray diffraction (Fig. 1). Crystals suitable
for the X-ray diffraction were obtained from methanol at room
temperature. The angles around the nitrogen atom show the ex-
pected values for a geometry consistent with secondary amine spe-
cies [14].
The addition of LinBu to a stirred suspension of the diamine 1,2-
C6H4(NHCH2tBu)2 in cold hexane resulted in the immediate
deposition of the corresponding lithium salt, which further reacts
in toluene with [MCl4(THF)2] (M = Ti, Zr) or TaCl5. This strategy
allows the preparation of a series of titanium, zirconium and tan-
talum chloro derivatives synthesized by a metathesis reaction
(Scheme 1). Reaction of Li2[1,2-C6H4(NCH2tBu)2] with one equiv
of [TiCl4(THF)2] in refluxing toluene produces the chelate com-
pound [Ti{1,2-C6H4(NCH2tBu)2}Cl2(THF)] (1) isolated as a black
product. According to literature precedents [15–17], the initial for-
mation of a bis-diamido compound [Ti{1,2-C6H4(NCH2tBu)2}2]
could be suggested, which quickly should undergo an exchange
reaction with the remaining [TiCl4(THF)2] to give complex 1. The
THF coordination seems to be the driving force for this process
since it avoids the possibility of metal reduction that sometimes
occurs during conventional TiCl4 metathesis reactions. Treatment
of the dilithio diamido salt with [ZrCl4(THF)2] in refluxing toluene
affords the dinuclear zirconium derivative [Zr{1,2-C6H4
The formulation of 1 was based on NMR and analytical data in
accordance with analogous complexes [19]. We suggest a five coor-
dinate titanium centre in which the metal atom is surrounded by
two chlorine atoms, the diamido chelating ligand and a molecule
of coordinated THF to stabilise the final product. The 1H NMR spec-
tra (C6D6 or CDCl3, 25 °C) are indicative of a C2 symmetry and
m
exhibits the expected signals assigned to the resonances arising
for the phenylenediamido ligand, two signals for the phenyl ring,
one signal for the methylenic and one singlet for the tert-butyl pro-
tons. The 1H NMR spectra also indicate one coordinated THF mol-
ecule (d 4.01 and 1.93 versus d 3.76 and 1.85 for the free THF
molecule in CDCl3). Similar results were also observed in the 13C
NMR spectra under the same conditions. However, attempts to
grow crystals of this product were unsuccessful.
The resonances observed in the NMR spectra at room tempera-
ture for the zirconium complex 2 in C6D6 or CDCl3 broaden to a
greater degree than those observed for the titanium species 1. On
the basis of the structural properties for the titanium compound
1 and the comparable amido compound 4, we propose for 2 a dinu-
clear structure connected by two chlorine atoms comparable to
that found in similar diamido complexes [20–24]. As in analogous
compounds, in this structural disposition each zirconium centre
must adopt an octahedral coordination surrounded by terminal
diamido, one chloro and one THF ligand, with two chlorine atoms
located in bridge positions. Variable temperature 1H NMR studies
were investigated for this compound. Resonances for the THF li-
gand are observed in the spectra at 40 °C. Upon cooling the sample
to ꢀ70 °C all proton resonances sharpened and the data are consis-
tent with the presence of two products (see Section 5). These spec-
troscopic observations suggest that at room temperature two
rapidly interconverting forms are present in solution. These two
forms are separated (with a 1:1 integrating ratio) at low tempera-
ture and would have the two diamido ligands and the two bridging
chlorine atoms in the equatorial plane and the terminal THF and
the chloro substituents in the cis or trans axial positions, respec-
tively (Scheme 1).
We thought that problems for the spectroscopic characterisa-
tion of 2 might be eliminated by using an alternative synthetic
route through amine elimination. The reaction of 1,2-C6H4
(NHCH2tBu)2 with [Zr(NMe2)4] in toluene at room temperature
affords the dinuclear zirconium complex [Zr{1,2-C6H4
(NCH2tBu)2}(NMe2)(l-NMe2)]2 (4) as a yellow solid in high yield
(Scheme 1). The 1H NMR spectra (C6D6 or CDCl3, 25 °C) of 4 display
three resonances for the NMe2 fragments coordinated to the zirco-
nium centre: one signal at d 2.93 for six protons and two singlets at
d 2.85 and 1.55 (C6D6) integrating for three protons each one. The
CH2 attached to nitrogen atoms appears diastereotopic as doublets
of an AB spin system. This spectroscopic pattern can be explained
Fig. 1. ORTEP view of 1,2-C6H4(NHCH2tBu)2 with 30% probability ellipsoids,
hydrogen atoms have been omitted for clarity. Selected interatomic distances (Å)
and angles (°): C(8)–N(2) = 1.457(2), C(2)–N(2) = 1.418(2), C(1)–C(2) = 1.418(2),
C(2)–C(3) = 1.391(2), C(3)–C(4) = 1.400(2), C(4)–C(5) = 1.378(3), C(5)–C(6) =
1.400(3), C(1)–C(6) = 1.396(2), N(1)–C(7) = 1.454(2), N(1)–C(1) = 1.409(2), C(8)–
N(2)–C(2) = 119.53(14), C(7)–N(1)–C(1) = 121.06(15).

V. Tabernero et al. / Polyhedron 28 (2009) 2545–2554
2547
Scheme 1. Synthesis of titanium, zirconium and tantalum phenylenediamido complexes.
by considering the complex as a dinuclear species connected
through two NMe2 units. The geometry at the zirconium atoms
should be described as a distorted square pyramid with the
NMe2 fragment occupying axial positions and two NMe2 units
bridging the two metal centres. An indication of this conformation
is provided by the proton resonance of the methyl groups posi-
tioned on the bridging amido ligand: two of which appear at d
2.85, with the others at d 1.55. Such a highfield shift would be ex-
pected if these methyl groups were positioned towards the pheny-
lene ring and experience the influence of its magnetic anisotropy.
On heating the sample, coalescence of the methyl signals of the
NMe2 is observed at 70 °C, indicating rapid positional equilibration
of the NMe2 moieties on the NMR timescale. For this process
correlations could not be established and a clear resolution of the
signals was not observed.
The coordinated THF molecule in 1 is labile and tends to
dissociate from the titanium centre in the presence of a donor
ligand. Conversion of 1 to [Ti{1,2-C6H4(NCH2tBu)2}Cl2(py)2] was
studied by NMR spectroscopy and occurs immediately at room
temperature after adding free pyridine to a solution of 1 in CDCl3
(Scheme 2). The NMR data show pyridine coordination [25] of
two molecules with three broadened peaks at d 9.62, 8.00 and
7.62 assigned to the coordinated pyridine and two multiplets at d
3.76 and 1.85 due to free liberated THF, suggesting a six coordi-
nated geometry around the titanium atom. The spectroscopic sig-
nals are broadened and the methylene resonances are not
observed in the spectra, which indicate a coordination environ-
ment that is fluxional on the NMR timescale. Reactions of 1 with
Lewis acids such as E(C6F5)3 (E = B, Al) in CDCl3 were monitored
by NMR spectroscopy and show the abstraction of the coordinated
THF to form [Ti{1,2-C6H4(NCH2tBu)2}Cl2], concomitant with the
formation of the adduct E(C6F5)3ꢁTHF (Scheme 2). In a similar
way, treatment of 2 with B(C6F5)3 gives a CD2Cl2 solution in which
we have obtained Gibbs activation energy values
(D
G#) of
65 0.8 kJ/mol at 343 K. Similar results were also observed in the
13C NMR spectra under the same conditions. The unequivocal
arrangement of metal atoms in this complex has been established
by X-ray diffraction studies (see infra). Addition of THF to C6D6
solutions of 4 did not reveal any tendency of THF coordination
even upon heating the sample to 100 °C (in a Young’s Teflon valve
NMR tube). The lack of coordination could be ascribed to the
crowded environment around zirconium which decreases the Le-
wis acidity at the metal and hinders THF approaching. The conver-
sion of the amido compound 4 to the chloro derivative 2 was tried
by using SiMe3Cl as a chloro transfer reagent, but a mixture of
unidentified products was obtained.
the presence of
a
mixture of the species ‘‘Zr[1,2-C6H4
(NCH2tBu)2]Cl2” and B(C6F5)3ꢁTHF is spectroscopically detected.
We can conclude that the tendency of the titanium compound 1
and the zirconium complex 2 to coordinate donor ligands such as
pyridine or THF reflects their acidic nature and the accessibility
of the metal centre, and prompted us to investigate the polymeri-
sation behaviour of this compound along with the reaction of the
alkyl derivatives with different cocatalysts.
Methylation of 1 with MgMeCl in ether at ꢀ78 °C gave an unsta-
ble, intractable and unresolved mixture of products with a regret-
tably uninformative 1H NMR spectrum. Due to the unexpected
poor behaviour of the methyl ligand to create a stable coordination
environment at the titanium centre, the use of voluminous ligands
was explored to stabilise the alkyl compounds. The dibenzyl
The 1H NMR spectra (C6D6 or CD2Cl2, 25 °C) of complex 3 show
one signal for the CH2 protons attached to the nitrogen atoms and
two multiplets for the aromatic protons, indicating the presence of
a molecule in solution that exhibits equivalent phenylenediamido
fragment ligands in contrast to the molecular disposition observed
in the solid state by X-ray diffraction studies (see infra). This fact
prompted us to carry out structural investigations in solution.
However, on cooling the sample to ꢀ70 °C unambiguous

2548
V. Tabernero et al. / Polyhedron 28 (2009) 2545–2554
Scheme 2. Reactions of the titanium phenylenediamido compound 1.
derivative [Ti{1,2-C6H4(NCH2tBu)2}Bz2] (5) (Bz = CH2Ph) was ob-
tained by the reaction in toluene of 1 with 2 equiv of MgBzCl in
THF solution at ꢀ78 °C (Scheme 2). Recrystallisation from hexane
at ꢀ30 °C affords, after filtration, higher purity material as a red
oil. The 1H NMR spectrum of 5 indicates that THF dissociation
has occurred. The data are consistent with a compound with a de-
gree of high symmetry. The four equivalent methylene protons in
the ‘‘CH2N” linkage appear as a singlet. The two equivalent benzyl
ligands exhibit a singlet resonance integrating for four protons for
the methylenic protons and three sets of o-, m-, and p-phenyl
resonances. The expected signals for the phenylenediamido ligand
are also observed. Complex 1 reacted readily with the lithium
amide reagent LiN(SiMe3)2 to afford [Ti{1,2-C6H4(NCH2tBu)2}
Cl{N(SiMe3)}] (6) (Scheme 2). Thermolysis of 6 was carried out in
the attempt to eliminate SiMe3Cl and to generate an imido [25]
derivative, but after heating an NMR sample at 80 °C for 12 h only
a mixture of unidentified products was observed.
When compound 5 is maintained in solution (toluene or hex-
ane), the oxo derivative [(Ti{1,2-C6H4(NCH2tBu)2}{CH2Ph})2(l-O)]
7 (Scheme 2) precipitates as red crystals, indicating the extreme
sensitivity of 5 to moisture and confirming the formation of a ben-
zyl derivative in the alkylating reaction of 1. All attempts to obtain
this product as a single and pure substance by controlled hydroly-
sis of 5 were unsuccessful with only a mixture of free amine and
unidentified products being obtained. The molecular structure of
7 has been determined by X-ray diffraction methods although
the crystals studied gave X-ray diffraction data of poor quality
(Fig. 2).2
Compound 2 was treated with various alkylating reagents un-
der different reaction conditions. However, all the attempts proved
unfruitful and uninformative broad signals were observed in the
corresponding NMR spectra.
Addition of B(C6F5)3 to a solution of 5 in C6D6 at room temper-
ature affords a cationic species, which was characterised by 1H, 13
C
and 19F NMR spectroscopy. The NMR spectra featured downfield
benzyl resonances assigned to a cationic-electron deficient benzyl
titanium derivative. From these spectroscopic data, we propose the
formation of the ionic [Ti{1,2-C6H4(NCH2tBu)2}Bz][BzB(C6F5)3]
species (Scheme 2). The large difference (4.5 ppm) between p-F
and m-F chemical shifts of the [BzB(C6F5)3]ꢀ anion suggests a
strong interaction between the anion and the titanium centre, as
observed for related cationic species [26–28]. The relative solubil-
ity of this complex in benzene is also consistent with its zwitter-
ionic character. The same electrophilic reaction was tested and
observed in CD2Cl2 at low temperature (ꢀ70 °C) and the spectro-
scopic study reveals that the abstraction reaction was facile even
at this temperature. No reaction was observed when the tantalum
complex 3 was reacted with LiB(C6F5)4 in an attempt to form a cat-
ionic species from which activation of tBu groups attached to nitro-
gen atoms due to the electronic deficiency could be enforced.
Given our interest in the polymerisation chemistry of diamido
[9] or dialkoxo [11,12] early metal complexes, we undertook preli-
minary studies on a-olefin polymerisation and the complexes 1, 3
and 5 were tested as catalysts for ethylene polymerisation in the
presence of B(C6F5)3, methylaluminoxane (MAO) and sMAO
(MAO used as an AlMe3-free solid) [29] as cocatalysts. The dichloro
complex 1 and the dibenzyl compound 5 showed very low activity
(ꢂ10 Kg PE/molcat atm h). These activities are much lower than
those of the best know non-cyclopentadienyl group 4 metal com-
2
Crystal data for 7: C46H66N4OTi2, Mr = 786.83, crystal size 0.39 ꢃ 0.34 ꢃ
3
ꢀ
0.22 mm , Triclinic, space group P1, a = 9.915(5) Å, b = 11.342(6) Å, c = 11.626(11) Å,
a
q
= 70.75(4)°, b = 86.79(6)°, 1,
c
= 65.67(4)°, V = 1119.9(13) Å3
,
Z
=
calcd = 1.167 Mg mꢀ3 = 0.393 mmꢀ1, Mo K
,
l
a radiation (k = 0.71073 Å). Data collec-
tion was performed at 200(2) K on a Nonius KappaCCD single crystal diffractometer.
Reflections collected/unique 13251/3902 [Rint = 0.8802]. The final cycle of full matrix
least-squares refinement based on 3902 reflections and 242 parameters converged to
Fig. 2. X-ray thermal ellipsoid plot of
labelling scheme (hydrogen atoms have been omitted for clarity).
7
(30% probability level) showing the
final values of R1(F2 > 2 (F2)) = 0.1853, wR2(F2 > 2 (F2)) = 0.4554, R1(F2) = 0.2648,
r r
wR2(F2) = 0.5446). Largest diff. peak/hole 0.879/ꢀ1.484 eÅꢀ3
.

V. Tabernero et al. / Polyhedron 28 (2009) 2545–2554
2549
plexes such as McConville’s titanium compounds [30], but are sim-
ilar to other related complexes [31,32]. GPC results are indicative
of polyethylenes that have very broad polydispersities (Mw/Mn
values of 4–6) [9,31]. DSC measurements of the polymers show
melting temperatures (Tm) for the polymers produced that are typ-
ical of high density polyethylene. These results may be a conse-
quence of the gradual generation of low active Ti active species
upon losing the diamido ligand from these diamido titanium pre-
cursors. It is a general observation that the complexes containing
the nPr amido ligand show higher polymerisation activities com-
pared with the Np derivatives [8], suggesting that the activity is
highly influenced by the steric effect [33] at the titanium centre
caused by the n-propyl or neopentyl substituents at the nitrogen
atom of the diamido ligand. Similar cases of strongly bulky substit-
uents influencing catalytic polymerisation activity have been
observed for related amidinate complexes [34,35]. The non-metal-
locene tantalum diamido complex 3 has no site for two alkyls, one
of which is required for the propagation and the other of which is
the source of cationic formation, and it was inactive in ethylene
polymerisation.
Fig. 3. X-ray thermal ellipsoid plot of
3
(50% probability level) showing the
labelling scheme (i: ꢀx + 1, y, ꢀz + 3/2, hydrogen atoms have been omitted for
clarity).
3. Crystal structures of [Ta{1,2-C6H4(NCH2tBu)2}2Cl] (3) and
[Zr{(1,2-C6H4(NCH2tBu)2}(NMe2)(l-NMe2)]2 (4)
angles for the structure are listed in Table 1. The molecular struc-
ture shows the tantalum atom bonded to a chlorine atom and two
chelating phenylenediamido ligands (Fig. 3). In the crystal, the
compound presents a twofold axis along the Ta–Cl bond. The coor-
dination geometry of the Ta(V) centre can be described as a dis-
torted trigonal bipyramid [36]. The Ta, Cl, N(2) and N(2)i (i:
ꢀx + 1, y, ꢀz + 3/2) atoms are in exactly the same plane, defining
the trigonal bipyramidal equatorial plane. The N(1) and the N(1)i
atoms occupy the trigonal bipyramidal axial positions with a
N(1)–Ta–N(1)i angle of 167.37(10)°. Both N(1) and N(2) coordi-
nated nitrogen atoms are essentially planar with a sum of angles
of 359.5° and 354.7°, respectively. Ta–Cl [2.4123(8) Å] bond
lengths compare well with related Ta(V) complexes [10]. Com-
pound 3 is almost isostructural to the previously reported bisphen-
ylenediamido Nb(V) complex [Nb{4,5-Me2-1,2-C6H2(NSiMe3)2}2Cl]
[37].
Red single crystals of 3ꢁC6D6 were grown in a saturated C6D6
solution at room temperature and the molecular structure estab-
lished by X-ray diffraction studies. Selected bond lengths and
Table 1
Selected bond distances (Å) and angles (°) for complexes 3ꢁC6D6 and 4.a
Compound 3ꢁC6D6
Ta–N(1)
Ta–N(2)
Ta–Cl
2.0108(18)
1.9733(17)
2.4123(8)
2.588(2)
2.559(2)
1.412(3)
1.417(3)
1.411(3)
1.424(3)
1.408(3)
1.383(3)
1.397(3)
1.377(3)
N(2)–Ta–N(2)b
N(2)–Ta–N(1)b
N(2)–Ta–N(1)
N(1)b–Ta–N(1)
N(2)–Ta–Cl
108.11(10)
103.44(7)
84.07(7)
167.37(10)
125.95(5)
83.69(5)
119.70(17)
96.67(12)
143.17(14)
121.18(17)
96.63(13)
136.93(14)
Ta–C(1)
Ta–C(2)
N(1)–C(1)
N(2)–C(2)
C(1)–C(6)
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
N(1)–Ta–Cl
C(1)–N(1)–C(11)
C(1)–N(1)–Ta
C(11)–N(1)–Ta
C(2)–N(2)–C(21)
C(2)–N(2)–Ta
C(21)–N(2)–Ta
The related chelating diamido ligands and the Ta atom form a
‘‘TaN2C2” metallacycle that is bent through the NꢁꢁꢁN axis (N(1)–
Ta–N(2) and N(1)–C(1)–C(2)–N(2) planes dihedral angle of
52.05(9)°). The ‘‘TaN2C2” metallacycle structural parameters indi-
cate that the phenylenediamido ligand is bonded to the metal in
a
g4 fashion showing r2
,p
-enediamido behaviour [38]. This type
Compound 4
N(7)–Zr(1)
N(1)–Zr(1)
N(2)–Zr(1)
N(5)–Zr(1)
N(6)–Zr(1)
N(8)–Zr(2)
N(3)–Zr(2)
N(4)–Zr(2)
N(5)–Zr(2)
N(6)–Zr(2)
C(1)–Zr(1)
C(2)–Zr(2)
C(7)–Zr(1)
C(8)–Zr(1)
N(1)–C(1)
N(2)–C(2)
N(3)–C(8)
N(4)–C(7)
2.024(5)
2.085(5)
2.120(5)
2.274(5)
2.349(5)
2.037(5)
2.087(5)
2.118(5)
2.366(5)
2.283(5)
2.761(7)
2.808(6)
2.742(6)
2.795(5)
1.410(10)
1.400(9)
1.423(8)
1.414(8)
C(1)–N(1)–C(17)
C(1)–N(1)–Zr(1)
C(17)–N(1)–Zr(1)
C(2)–N(2)–C(13)
C(2)–N(2)–Zr(1)
C(13)–N(2)–Zr(1)
C(8)–N(3)–C(18)
C(8)–N(3)–Zr(2)
C(18)–N(3)–Zr(2)
C(7)–N(4)–C(23)
C(7)–N(4)–Zr(2)
C(23)–N(4)–Zr(2)
C(38)–N(5)–C(37)
C(38)–N(5)–Zr(1)
C(37)–N(5)–Zr(1)
C(38)–N(5)–Zr(2)
C(37)–N(5)–Zr(2)
Zr(2)–N(5)–Zr(1)
C(40)–N(6)–C(39)
C(40)–N(6)–Zr(2)
C(39)–N(6)–Zr(2)
C(40)–N(6)–Zr(1)
C(39)–N(6)–Zr(1)
Zr(1)–N(6)–Zr(2)
119.6(5)
102.7(4)
136.4(5)
120.1(5)
103.9(4)
135.2(4)
118.7(5)
101.0(3)
138.5(4)
123.0(5)
102.8(3)
133.0(4)
107.9(5)
114.7(4)
108.9(4)
111.6(4)
114.1(4)
99.69(17)
107.3(6)
112.7(4)
108.8(4)
114.1(5)
113.8(4)
99.94(18)
of r2-N,N0-
p
-phenylenediamido coordination allows the donation
of electron density from the phenylene ring to the metal and
should quench the electrophilicity of Ta(V). Similar structural fea-
tures have been reported for analogous X-ray structures of chelat-
ing phenylenediamido group 5 metal complexes found in the CSD
[39]. Thus, the Ta(V) complexes [Ta(
g
5-C5Me5){1,2-C6H4(NSi-
Pri3)2}Cl2], [Ta{ 5-1,3-C5H3(SiMe3)2}{1,2-C6H4(NSiMe3)2}Cl2], and
g
the Nb(V) derivative [Nb{4,5-Me2-1,2-C6H2(NSiMe3)2}2Cl] present
sp2 planar coordinated N atoms and are bent through the NꢁꢁꢁN axis
‘‘MN2C2” (M = metal) metallacycles (dihedral angle range 53.8–
58.7°) [40,41]. The Ta–C(1) and Ta–C(2) bond lengths [2.588(2)
and 2.559(2) Å, respectively] for compound 3 are in good agreement
with
p-bonding involving the Cipso atoms at the phenylene ring.
Slightly shorter Ta–C bond lengths (range 2.40–2.54 Å) are present
in the previously described phenylenediamido Ta(V) complexes with
a
r2
,
p
-enediamido type of coordination [40,41]. Rather short Ta–N
bond lengths [1.9733(17) and 2.0108(18) Å] are observed in the
molecular structure of 3, consistent with a significant p –d contri-
p
p
bution, similar to that found for other amido groups bound to tanta-
lum [40–43]. The 1,2-C6H4(NCH2tBu)2 phenylenediamido ring is
distorted with the carbon–carbon bond distances ranging from the
longest bond for C(1)–C(2) (1.424(3) Å) to both C(3)–C(4) and
a
E.s.d’s are given in parentheses.
Symmetry transformation used to generate equivalent atoms ꢀx + 1, y, ꢀz + 3/2.
b

2550
V. Tabernero et al. / Polyhedron 28 (2009) 2545–2554
C(5)–C(6) as the shortest bonds (1.383(3), 1.377(3) Å), while the N–
Cipso distances (1.412(3) and 1.417(3) Å) are consistent with single
bond formulation.
Analysis of the g2-N,N0-phenylenediamido ligand’s geometrical
parameters reported in the CSD for group 4 and 5 metal complexes
has been performed [8,10,37,40,41,47–50]. Bent and planar
‘‘MN2C2” metallacycles with wide folding through the NꢁꢁꢁN axis
Yellow single crystals of 4 suitable for X-ray diffraction studies,
grown in a saturated hexane solution at ꢀ40 °C, were used to
unequivocally establish the molecular structure of this complex,
shown in Fig. 4. Selected bond distances and angles for the struc-
ture are listed in Table 1. This compound crystallised as an enantio-
meric pure isomer due to conformation chirality arising from the
relative disposition of the phenylene rings in the solid state. By
contrast, C2-symmetry is inferred for 4 in solution as deduced from
the NMR spectroscopic data.
The environment around each Zr atom is approximately square
pyramidal with one of the NMe2 ligands in the axial position. The
zirconium atoms are not located in the planar base of the square
pyramid, as distances of 0.728 Å from the Zr(2) to the
N(4)N(3)N(6)N(5) plane and 0.726 Å from Zr(1) to the
degree range have been reported (0–58° N-metal-N/N–Cipso–Cipso
–
N dihedral angle range) [51]. As should be expected, short M–Cipso
distances correspond to highly bent metallacycles and long M–Cipso
distances are found for planar or slightly bent metallacycles, with
very few exceptions. The N–Cipso bond lengths are in the 1.33–
1.46 Å range for both group 4 and 5
g
2-phenylenediamido metal
complexes. Furthermore, in the analysed complexes the phenylene
ring is distorted, showing a long Cipso–Cipso bond length (range
1.41–1.47 Å) and two short ring bond lengths, generally corre-
sponding to C(3)–C(4) and C(5)–C(6) (a range of 1.35–1.39 Å is ob-
served in compound 3, although in compound 4 the shortest bond
length corresponds to C(4)–C(5) with values of 1.372(17) Å in one
ring and 1.345(13) Å in the other one). Surprisingly, we have found
that a distortion of the phenylene ring is present for both bent and
planar ‘‘MN2C2” metallacycles and it seems not to depend on the
degree of metallacycle folding. The absence of a direct correlation
for the degree of metallacycle folding and phenylene ring distor-
tion could imply that the phenylenediamido ligand ring distortion
N(5)N(6)N(1)N(2) plane were measured. There is
a central
Zr(1)N(5)N(6)Zr(2) core that appears puckered (Zr(2)N(6)Zr(1)
99.94(18)°, Zr(2)N(5)Zr(1) 99.69(17)°). In this central unit, the
Zr–N bond lengths range from 2.274(5) to 2.366(5) Å and the endo-
cyclic angles at N(5) or N(6) are wider than those at Zr(1) or Zr(2).
Within the molecule, the Zr–N bond lengths vary significantly,
ranging from 2.024(5) to 2.366(5) Å, with the longest length corre-
sponding to the bridging ligands (N(5) and N(6)) and the shortest
to the distances between the metal and the terminal NMe2 groups.
This feature can be related to the degree of donation from the
is not related to the p-coordination of the ligand.
4. Conclusions
In summary, we report the synthesis of early metal complexes
stabilised by coordination of the [1,2-C6H4(NCH2tBu)2]2ꢀ ligand
that are fully characterised by various methods. Direct reaction
of Li[1,2-C6H4(NCH2tBu)2] with [TiCl4(THF)2] or TaCl5 in toluene
gives the monomeric derivatives in reasonable yield, while dimeric
complexes were obtained for zirconium. The results indicate that
monomeric titanium and tantalum complexes require the presence
of additional Lewis base molecules to stabilise the final product.
Reactions of the titanium compounds with Lewis acids show the
abstraction of the coordinated Lewis base. Voluminous alkyl li-
gands are required to stabilise the alkyl compounds and the diben-
zyl derivative [Ti{1,2-C6H4(NCH2tBu)2}Bz2] can be obtained.
respective amido ligand to the metal centre, indicating a p –d
p
p
bonding contribution for the amido moieties closer to it
[18,30,44]. In addition, the sum of the angles around the nitrogen
atoms in those groups (N(1), N(2), N(3) and N(4)) are essentially
planar, with a tetrahedral disposition for the bridging N(5) and
N(6) atoms.
As observed in 3, and in similar structures reported for group 4
eneamido complexes [45,46], the ‘‘Zr[C6H4(NCH2tBu)]” metallacy-
cle is folded along the NꢁꢁꢁN axis (41.88° and 43.83° dihedral angles
between the NZrN and NCCN planes). The ‘‘ZrN2C2” metallacycle’s
structural parameters indicate that the phenylenediamido ligands
are bonded to the metal in a g4 fashion showing a r2
,p
-enediam-
g
2-Phenylenediamido group 4 and 5 metal complexes show
ido manner [38]; the Zr–Cipso bond distances [2.742(6)–2.808(6) Å
distorted phenylene rings with the Cipso–Cipso bond length as the
longest length and generally the two conjugated C–C bonds as
range] are also in good agreement with
atoms at the phenylene ring.
p-bonding involving Cipso
Fig. 4. X-ray thermal ellipsoid plot of 4 (30% probability level) showing the labelling scheme (hydrogen atoms have been omitted for clarity).

V. Tabernero et al. / Polyhedron 28 (2009) 2545–2554
2551
the shortest lengths. However, the direct correlation for the degree
5.3. Synthesis of [Zr{1,2-C6H4(NCH2tBu)2}Cl(THF)(l-Cl)]2 (2)
of metallacycle folding and phenylene ring distortion could imply
that the phenylenediamido ligand ring distortion is not related to
the p-coordination of the ligand.
The same procedure described for 1 using 0.300 g (1.15 mmol)
of Li[1,2-C6H4(NCH2tBu)2] and 0.435 g of [ZrCl4(THF)2] (1.15 mmol)
gives [Zr{1,2-C6H4(NCH2tBu)2}Cl(THF)(l-Cl)]2 2, obtained as an or-
ange product which was washed with hexane (0.673 g,
0.700 mmol, 61% yield). The elemental analysis value found for 2
was inaccurate, caused by small amounts of LiCl in the mixture,
which could not be removed. 1H NMR (400 MHz, C6D6, 25 °C): d
6.94 (br, 2H, Ph), 6.68 (br, 2H, Ph), 3.87 (br, 4H, CH2), 1.08 (s,
18H, tBu). 1H NMR (400 MHz, CDCl3, 25 °C): d 6.98 (br, 4H, Ph),
3.94 (br, 4H, CH2), 0.89 (s, 18H, tBu), THF resonances not observed.
1H NMR (400 MHz, CDCl3, 40 °C): d 6.92 (br, 2H, Ph), 6.75 (br, 2H,
Ph), 3.87 (br, 4H, CH2), 3.89 (br, 2H, THF), 1.15 (m, 2H, THF), 1.07
(s, 18H, tBu). 13C{1H} NMR (100.60 MHz, CDCl3, 25 °C): d 128.3,
114.7 (Ph), 74.0 (THF), 60.7 (CH2N), 36.6 (ipso-tBu), 25.5 (THF),
28.1 (tBu), ipso-Ph not observed. 1H NMR (400 MHz, CD2Cl2,
ꢀ70 °C): isomer A: d 6.98 (m, 2H, Ph), 6.86 (m, 2H, Ph), 4.00 (d,
J = 14.4 Hz, 2H, AB spin system, CH2), 3.34 (d, J = 14.4 Hz, 2H, AB
spin system, CH2), 4.31 (br, 2H, THF), 2.02 (m, 2H, THF), 0.92 (s,
18H, tBu); isomer B: d 6.37 (m, 2H, Ph), 6.30 (m, 2H, Ph), 4.30
(br, 2H, CH2), 3.70 (br, 2H, CH2), 4.40 (br, 2H, THF), 2.02 (m, 2H,
THF), 0.92 (s, 18H, tBu). 13C{1H} NMR (100.60 MHz, CD2Cl2,
ꢀ70 °C): isomer A: d 125, 116 (Ph), 75.0 (THF), 60 (CH2N), 27
(THF), 28 (tBu), ipso of Ph and ipso of tBu not observed; isomer
B: d 119, 112 (Ph), 75.0 (THF), 58 (CH2N), 27(THF), 30 (tBu), ipso
of Ph and ipso of tBu not observed.
5. Experimental
5.1. General considerations
All manipulations were performed with rigorous exclusion of
oxygen and moisture under argon using Schlenk and high-vacuum
line techniques or in a glove box model MO40-2. Solvents were
predried by standing over activated 4 Å molecular sieves and then
purified by distillation under argon before use by employing the
appropriate drying/deoxygenated agent. Deuterated solvents were
degassed by several freeze–thaw cycles and stored in ampoules
equipped with Young’s Teflon valves over activated 4 Å molecular
sieves. C, H and N microanalyses were performed on a Perkin–El-
mer 2400 microanalyzer. NMR spectra were recorded on a Bruker
AV400 (1H NMR at 400.13 MHz, 13C NMR at 100.60 MHz and 19F
NMR at 376.40 MHz) spectrometer and chemical shifts were refer-
enced to SiMe4 via the 13C resonances and the residual protons (1H)
of the deuterated solvent, while 19F resonance were measured rel-
ative to external CFCl3. Spectra were recorded at 25 °C unless
otherwise stated. LinBu (1.6 M in hexane solution), MgMeCl (3 M
in THF), MgBzCl (2 M in THF), pyridine, LiN(SiMe3)2 and TaCl5 were
purchased from Aldrich. Br(C6F5) was purchased from ABCR. MAO,
30 wt% solution in toluene was received from Crompton GmbH.
Compounds [TiCl4(THF)2] [52], [ZrCl4(THF)2] [52], B(C6F5)3 [53–
56], Al(C6F5)3ꢁ0.5C7H8 [7] and [Zr(NMe2)4] [57], were synthesized
following established procedures.
5.4. Synthesis of [Ta{1,2-C6H4(NCH2tBu)2}2Cl] (3)
The same procedure described for 1 using 0.207 g (0.79 mmol)
of Li[1,2-C6H4(NCH2tBu)2] and 0.14 g of TaCl5 (0.40 mmol) gives
[Ta{1,2-C6H4(NCH2tBu)2}2Cl] 3 as a red solid (0.130 g, 0.183 mmol,
46% yield). Anal. Calc. for C32H52N4ClTa (709.18 g/mol): C, 54.19; H,
7.33; N, 7.89. Found: C, 54.32; H, 7.09; N, 7.73%. 1H NMR (400 MHz,
C6D6, 25 °C): d 7.01 (m, 4H, Ph), 6.79 (m, 4H, Ph), 4.68 (s, 8H, CH2),
0.71 (s, 36H, tBu). 1H NMR (400 MHz, CD2Cl2, 25 °C): d 7.08 (m, 4H,
Ph), 6.97 (m, 4H, Ph), 4.03 (s, 8H, CH2), 0.75 (s, 36H, tBu). 13C{1H}
NMR (100.60 MHz, C6D6, 25 °C): d 137.8 (ipso-Ph), 129.3, 119.2
(Ph), 66.9 (CH2N), 30.1 (ipso-tBu), 28.4 (tBu).
Polymerisation grade ethylene was used as received. Ethylene
polymerisation was carried out in a glass reactor with magnetic
stirring. The polymerisation solvent (toluene) was dried by reflux-
ing over sodium-benzophenone and distilled before use in an inert
atmosphere. MAO (Witco 10%) was used as a solution in toluene.
Melting temperatures of the polymers were measured by differen-
tial scanning calorimetry (DSC) on
instrument.
a Perkin Elmer DSC6
5.2. Synthesis of [Ti{1,2-C6H4(NCH2tBu)2}Cl2(THF)] (1)
5.5. Synthesis of [Zr{1,2-C6H4(NCH2tBu)2}(NMe2)(l-NMe2)]2 (4)
LinBu (1.6 M in hexane, 4.02 mmol, 2.5 mL) was slowly added to
a suspension of 0.500 g (2.01 mmol) of 1,2-C6H4(NHCH2tBu)2 in
hexane (50 mL) at ꢀ78 °C. The reaction mixture was warmed to
room temperature over 4 h and a white precipitate of Li2[1,2-
C6H4(NCH2tBu)2] was formed with evolution of butane. The desired
amount of the lithium salt (0.296 g, 1.14 mmol) and 0.380 g of
[TiCl4(THF)2] (1.14 mmol) were introduced in a Young’s ampoule
and toluene (50 mL) was charged at ꢀ78 °C. A red–brown suspen-
sion was immediately obtained. After 2 h, the reaction mixture was
heated at reflux for 12 h. After cooling, all volatiles of the dark solu-
tion were removed under vacuum and the black product was ex-
tracted into hexane. Recrystallisation with cold hexane afforded
the product identified as [Ti{1,2-C6H4(NCH2tBu)2}Cl2(THF)] 1, as a
black solid (0.268 g, 0.613 mmol, 54% yield). Anal. Calc. for
C20H34N2Cl2OTi (436.98 g/mol): C, 54.92; H, 7.77; N, 6.40. Found:
C, 54.56; H, 8.59; N, 6.73%. 1H NMR (400 MHz, C6D6, 25 °C): d
7.36 (m, 2H, Ph), 7.07 (m, 2H, Ph), 4.25 (s, 4H, CH2), 3.74 (m, 2H,
THF), 1.26 (m, 2H, THF), 0.85 (s, 18H, tBu). 1H NMR (400 MHz,
CDCl3, 25 °C): d 7.54 (m, 2H, Ph), 7.24 (m, 2H, Ph), 4.31 (s, 4H,
CH2), 4.01 (m, 2H, THF), 1.93 (m, 2H, THF), 0.82 (s, 18H, tBu).
13C{1H} NMR (100.60 MHz, C6D6, 25 °C): d 126.0, 115.7 (Ph),
123.9 (ipso-Ph), 71.0 (CH2), 66.9 (THF), 36.0 (ipso-tBu), 28.9 (tBu),
25.4 (THF).
A solution of 0.185 g (0.75 mmol) of 1,2-C6H4(NHCH2tBu)2 was
added to 0.20 g of Zr(NMe2)4 (0.74 mmol) in toluene (50 mL). The
solution was maintained at room temperature for 16 h and gradu-
ally became golden yellow. The volatiles were evaporated and hex-
ane was added. The solution was set at ꢀ30 °C for 12 h and a
microcrystalline yellow powder precipitated. The solid was iso-
lated by filtration and dried in vacuum. Recrystallisation with cold
hexane led to the product identified as [Zr{1,2-C6H4(NCH2tBu)2}(N-
Me2)(l-NMe2)]2 4 (0.495 g, 0.581 mmol, 78% yield). Anal. Calc. for
C40H76N8Zr2 (850.84 g/mol): C, 56.46; H, 8.93; N, 13.16. Found: C,
56.10; H, 9.01; N, 13.20%. 1H NMR (400 MHz, C6D6, 25 °C): d 6.99
(m, 2H, Ph), 6.90 (m, 2H, Ph), 3.88 (d, 2H, J = 13.2 Hz, AB spin sys-
tem, CH2), 3.65 (d, 2H, J = 13.2 Hz, AB spin system, CH2), 2.93 (s, 6H,
NMe2), 2.85 (s, 3H, NMe2), 1.55 (s, 3H, NMe2), 0.87 (s, 18H, tBu). 1H
NMR (400 MHz, CDCl3, 25 °C): d 6.85 (m, 2H, Ph), 6.67 (m, 2H, Ph),
3.82 (d, 2H, J = 13.4 Hz, AB spin system, CH2), 3.60 (d, 2H,
J = 13.4 Hz, AB spin system, CH2), 3.09 (s, 6H, NMe2), 3.03 (s, 3H,
NMe2), 1.45 (s, 3H, NMe2), 0.71 (s, 18H, tBu). 13C{1H} NMR
(100.60 MHz, C6D6, 25 °C): d 135.1 (ipso-Ph), 120.1, 115.8 (Ph),
60.6 (CH2N), 44.4, 43.2, 42.05 (NMe2), 35.2 (ipso-tBu), 28.8 (tBu).
13C{1H} NMR (100.60 MHz, CDCl3, 25 °C): d 136.1 (ipso-Ph) 118.9,
115.2 (Ph), 60.4 (CH2N), 44.1, 43.3, 42.3 (NMe2), 35.3 (ipso-tBu),
28.8 (tBu).

2552
V. Tabernero et al. / Polyhedron 28 (2009) 2545–2554
5.6. [Ti{1,2-C6H4(NCH2tBu)2}Cl2(py)2]
CH2Ph), 6.86 (d, J = 7.2 Hz, CH2Ph), 3.79 (s, 4H, CH2), 2.40 (s, 4H,
CH2Ph), 0.71 (s, 18H, tBu). 1H NMR (400 MHz, CD2Cl2, 25 °C): d
7.21 (m, 2H, Ph), 7.10 (m, 2H, Ph), 7.19 (t, J = 7.6 Hz, CH2Ph), 6.94
(t, J = 7.6 Hz, CH2Ph), 6.73 (d, J = 7.6 Hz, CH2Ph), 3.84 (s, 4H, CH2),
2.18 (s, 4H, CH2Ph), 0.75 (s, 18H, tBu). 13C{1H} NMR (100.60 MHz,
C6D6, 25 °C): d 128.7 (ipso-Bz), 129.3, 127.2, 125.3 (Bz), 126.7,
115.5 (Ph), 123.1 (ipso-Ph), 81.02 (CH2Ph), 64.6 (CH2N), 34.6
(ipso-tBu), 28.6 (tBu). 13C{1H} NMR (100.60 MHz, CD2Cl2, 25 °C): d
144.4 (ipso-Bz), 129.1, 126.8, 124.9 (Bz), 122.8, 115.3 (Ph), 80.4
(CH2Ph), 64.7 (CH2N), 34.8 (ipso-tBu), 28.5 (tBu), ipso-Ph not
observed.
Pyridine was added at room temperature into a Teflon-valved
NMR tube containing a chloroform-d (0.5 mL) solution of [Ti{1,2-
C6H4(NCH2tBu)2}Cl2(THF)]. The reaction mixture turned brown
and the 1H and 13C NMR spectra were obtained, showing the for-
mation of [Ti{1,2-C6H4(NCH2tBu)2}Cl2(py)2]. 1H NMR (400 MHz,
CDCl3, 25 °C): d 9.62 (br, 4H, py), 8.00 (br, 2H, py), 7.62 (br, 4H,
py), 6.36 (m, 2H, Ph), 5.88 (m, 2H, Ph), 0.75 (s, 18H, tBu), CH2 pro-
tons not observed.
5.7. Reaction of [Ti{1,2-C6H4(NCH2tBu)2}Cl2(THF)] with B(C6F5)3 or
Al(C6F5)3
5.10. Synthesis of [Ti{1,2-C6H4(NCH2tBu)2}Cl{N(SiMe3)}] (6)
In a glovebox, chloroform-d or benzene-d6 (0.5 mL) was added
at room temperature to a Teflon-valved NMR tube containing the
solid mixture of [Ti{1,2-C6H4(NCH2tBu)2}Cl2(THF)] and B(C6F5)3.
The 1H and 13C NMR spectra obtained showed the formation of
[Ti{1,2-C6H4(NCH2tBu)2}Cl2] with B(C6F5)3ꢁ(THF) also present.
[Ti{1,2-C6H4(NCH2tBu)2}Cl2]: 1H NMR (400 MHz, C6D6, 25 °C): d
7.34 (m, 2H, Ph), 7.00 (m, 2H, Ph), 4.16 (s, 4H, CH2), 0.75 (s, 18H,
tBu). 1H NMR (400 MHz, CDCl3, 25 °C): d 7.64 (m, 2H, Ph), 7.31
(m, 2H, Ph), 4.29 (s, 4H, CH2), 0.86 (s, 18H, tBu). 13C{1H} NMR
(100.60 MHz, C6D6, 25 °C): d 129.0, 116.0 (Ph), 67.8 (CH2), 35.8
(ipso-tBu), 28.6 (tBu), ipso-Ph not observed. B(C6F5)3ꢁ(THF): 1H
NMR (400 MHz, C6D6, 25 °C): d 3.23 (m, 2H, OCH2), 0.85 (m, 2H,
CH2). 1H NMR (400 MHz, CDCl3, 25 °C): d 4.25 (m, 2H, OCH2),
2.13 (m, 2H, CH2). 13C{1H} NMR (100.60 MHz, C6D6, 25 °C): d 75.7
(THF), 25.4 (THF). 19F NMR (376.40 MHz, CDCl3, 25 °C): d ꢀ128.7
(broad, o-C6F5), ꢀ143.7 (broad, p-C6F5), ꢀ160.7 (broad, m-C6F5).
19F NMR (376.40 MHz, C6D6, 25 °C): d ꢀ131.6 (broad, o-C6F5),
ꢀ152.6 (broad, p-C6F5), ꢀ161.8 (broad, m-C6F5).
Toluene (50 mL) was added to a mixture of 1 (0.200 g,
0.46 mmol) and Li[N(SiMe3)]2 (0.076 g, 0.46 mmol), at room tem-
perature. The reaction immediately turned black. The mixture
was stirred for 5 h. The solvent was pumped off and subsequent
extraction into hexane afforded a black oil, which was recrystal-
lised from cold hexane giving the product identified as [Ti{1,2-
C6H4(NCH2tBu)2}Cl{N(SiMe3)}] 6 (0.159 g, 0.325 mmol, 70% yield).
Anal. Calc. for C22H44N3Si2ClTi (489.5 g/mol): C, 53.95; H, 8.98; N,
8.57. Found: C, 53.98; H, 8.72; N, 8.36%. 1H NMR (400 MHz, C6D6,
25 °C): d 7.26 (m, 2H, Ph), 7.15 (m, 2H, Ph), 4.45 (d, J = 13.5 Hz,
2H, CH2), 3.78 (d, J = 13.5 Hz, 2H, CH2), 0.83 (s, 18H, tBu), 0.15 (s,
18H, SiMe3). 13C{1H} NMR (100.60 MHz, C6D6, 25 °C): d 126.7,
115.5 (Ph), 123.1 (ipso-Ph), 67.7 (CH2), 35.9 (ipso-tBu), 28.6 (tBu),
4.6 (SiMe3).
5.11. Reaction of [Ti{1,2-C6H4(NCH2tBu)2}Bz2] with B(C6F5)3
About 0.010 g (21.0 mmol) of [Ti{1,2-C6H4(NCH2tBu)2}Bz2] and
0.011 g (21.0 mmol) of B(C6F5)3 were placed in a Teflon-valved
NMR tube and C6D6 was added at room temperature (when the
reaction was cooled to ꢀ78 °C in CD2Cl2, the solvent was vacuum
transferred into the NMR tube that had previously been placed in
a thermostat-controlled bath). The NMR spectrum was obtained
immediately at the desired temperature. 1H NMR (400 MHz,
C6D6, 25 °C): d 7.50 (m, 2H, Ph), 7.20–6.99 (m, 12H, Ph), 5.89 (t,
J = 7.2 Hz, CH2Ph), 5.77 (t, J = 7.2 Hz, CH2Ph), 5.26 (d, J = 7.2 Hz,
CH2Ph), 4.15 (d, J = 12.8 Hz, 4H, CH2), 3.64 (d, J = 13.2 Hz, 4H,
CH2), 3.89 (br, 4H, CH2Ph), 2.70 (br, 4H, CH2Ph), 0.56 (s, 18H,
tBu). 19F NMR (376.40 MHz, C6D6, 25 °C): d ꢀ130.4 (s broad, o-
C6F5), ꢀ160.5 (s broad, p-C6F5), ꢀ165.0 (s broad, m-C6F5). 1H
NMR (400 MHz, CD2Cl2, ꢀ70 °C): d 8.10 (m, 2H, Ph), 7.65 (m, 2H,
Ph), 7.30 (t, J = 7.6 Hz, CH2Ph), 7.19 (t, J = 7.2 Hz, CH2Ph), 7.00–
6.73 (Ph), 5.91 (d, J = 6.8 Hz, CH2Ph), 4.60 (d, J = 13.2 Hz, 2H, CH2),
4.16 (d, J = 13.2 Hz, 2H, CH2), 2.81 (br, 4H, CH2Ph), 2.72 (br, 4H,
CH2Ph), 0.77 (s, 18H, tBu). 19F NMR (376.40 MHz, CD2Cl2, 25 °C):
d ꢀ131.3 (s broad, o-C6F5), ꢀ165.0 (s broad, p-C6F5), ꢀ167.7 (s
broad, m-C6F5).
A similar procedure using [Ti{1,2-C6H4(NCH2tBu)2}Cl2(THF)]
and Al(C6F5)3 gives a mixture of the same compound [Ti{1,2-
C6H4(NCH2tBu)2}Cl2] and Al(C6F5)3.(THF). Al(C6F5)3ꢁ(THF): 19F
NMR (376.40 MHz, CDCl3, 25 °C): d ꢀ123.2 (s broad, o-C6F5),
ꢀ151.7 (s broad, p-C6F5), ꢀ161.0 (s broad, m-C6F5).
5.8. Reaction of [Zr{1,2-C6H4(NCH2tBu)2}Cl(THF)(l-Cl)]2 (2) with
B(C6F5)3
In a glovebox, dichloromethane-d2 (0.5 mL) was added via a
syringe at room temperature to a Teflon-valved NMR tube contain-
ing the solid [Zr{1,2-C6H4(NCH2tBu)2}Cl(THF)(l-Cl)]2 and B(C6F5)3.
The 1H and 13C NMR spectra were obtained showing formation of
‘‘Zr[1,2-C6H4(NCH2tBu)2]Cl2” with B(C6F5)3ꢁ(THF) also present.
Zr[1,2-C6H4(NCH2tBu)2]Cl2: 1H NMR (400 MHz, CD2Cl2, 25 °C): d
7.21 (m, 2H, Ph), 7.17 (m, 2H, Ph), 4.05 (s, 4H, CH2), 0.88 (s, 18H,
tBu). B(C6F5)3ꢁ(THF): 1H NMR (400 MHz, CD2Cl2, 25 °C): d 4.28
(m, 2H, OCH2), 2.12 (m, 2H, CH2). 19F NMR (376.40 MHz, CD2Cl2,
25 °C): d ꢀ132.1 (broad, o-C6F5), ꢀ154.6 (broad, p-C6F5), ꢀ162.9
(broad, m-C6F5).
5.12. Single-crystal X-ray structure determination of compounds 1,2-
5.9. Synthesis of [Ti{1,2-C6H4(NCH2tBu)2}Bz2] (5)
C6H4(NHCH2tBu)2, 3ꢁC6D6, and 4
A solution of 1 (0.250 g, 0.57 mmol) in toluene (50 mL) was
cooled to ꢀ78 °C and a solution of Mg(CH2Ph)Cl in THF (2 M,
1.14 mmol, 0.57 mL) was added. The reaction immediately turned
red. The mixture was warmed to room temperature and stirred for
5 h. The solvent was pumped off and subsequent extraction into
hexane afforded a red oil, which was recrystallised from cold hex-
ane giving the product identified as [Ti{1,2-C6H4(NCH2tBu)2}Bz2] 5
(0.198 g, 0.416 mmol, 73% yield). Anal. Calc. for C30H40N2Ti
(476.17 g/mol): C, 70.66; H, 8.40; N, 5.88. Found: C, 70.45; H,
8.51; N, 5.88%. 1H NMR (400 MHz, C6D6, 25 °C): d 7.26 (m, 2H,
Ph), 7.15 (m, 2H, Ph), 6.99 (t, J = 7.2 Hz, CH2Ph), 6.94 (t, J = 7.2 Hz,
Relevant crystallographic data and details of the refinements for
the structures are given in Table 2. Crystals of 3ꢁC6D6 were grown
by slow evaporation of a C6D6 solution. Crystals suitable for X-ray
diffraction were measured at 100(2) K on a Bruker SMART APEX
diffractometer using graphite-monochromated Mo K
a radiation
(k = 0.71073 Å) and / and scan modes. Crystal structures were
x
solved by direct methods and all non-hydrogen atoms refined
anisotropically on F2 (program SHELXL-97) [58]. The deuterium
atoms were located in a difference Fourier synthesis and refined
with restrained C–D bond lengths. The methyl group hydrogen
atoms were refined as rigid. Other hydrogen atoms were included

V. Tabernero et al. / Polyhedron 28 (2009) 2545–2554
2553
Table 2
Crystal data and structure refinement details for 1,2-C6H4(NHCH2tBu)2, 3ꢁC6D6, and 4.
1,2-C6H4(NHCH2tBu)2
3ꢁC6D6
4
Formula
FW
C16H28N2
248.40
C38H52ClD6N4Ta
793.32
C40H38N4Zr
425.76
Color habit
red prism
2.9 ꢃ 2.5 ꢃ 1.8
monoclinic
P21/c
11.3619(11)
11.462(2)
12.748(2)
97.557(15)
1645.8(4)
4
orange prism
0.09 ꢃ 0.07 ꢃ 0.06
monoclinic
C2/c
13.6723(5)
15.6431(6)
18.5698(7)
110.2660(10)
3725.8(2)
yellow stick
0.44 ꢃ 0.38 ꢃ 0.36
orthorhombic
P212121
13.438(5)
16.869(8)
20.570(2)
90
Crystal dimensions (mm3)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
b (°)
V (Å3)
Z
4663(3)
4
4
T (K)
200(2)
1.003
0.058
552
3.55–27.50
36 908
3772 [Rint = 0.078]
3772/0/172
R1 = 0.0561, wR2 = 0.1327
R1 = 0.1206, wR2 = 0.1559
0.016(3)
1.023
0.262 and ꢀ0.154
100(2)
1.414
3.052
1616
2.05–27.88
25 468
4316 [Rint = 0.0346]
4316/426/252
R1 = 0.0221, wR2 = 0.0494
R1 = 0.0251, wR2 = 0.0507
200(2)
1.213
0.481
1808
3.55–27.50
82 570
10 663 [Rint = 0.0796]
10 663/279/485
R1 = 0.0604, wR2 = 0.1342
R1 = 0.0786, wR2 = 0.1424
0.0456(14)
1.256
0.766 and ꢀ0.773
Dcalcd (g cmꢀ3
)
l
(mmꢀ1
F(0 0 0)
h Range (°)
)
Number of reflections collected
Number of independent reflections/Rint
Data/restraints/parameters
R1/wR2 (I > 2r(I))
R1/wR2 (all data)
Extinction coefficient
Goodness-of-fit (GOF) (on F2)
Difference in peak/hole (e Åꢀ3
1.057
1.026 and ꢀ0.530
)
using a riding model. The deuterated benzene molecule is disor-
dered over two sites. The programs use neutral atom scattering
factors,
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