Biaryl-bridged Schiff base complexes of zirconium alkyls: Synthesis structure and stability

Article abstract of DOI:10.1016/S0022-328X(03)00455-8

Three substituted salicylaldimine derivatives H₂ L^1-3 of 2,2′-diamino-6,6′-dimethylbiphenyl give, under appropriate conditions, isolable alkyls of zirconium [ZrL^1-3R₂] (R=CH₂Ph, CH₂ Bu^t). Two molecular structures confirm their cis-α geometry (C₂-symmetric with cis alkyl ligands). They decompose via 1,2-migratory insertion of an alkyl group to imine, followed in some instances by a second similar reaction. The dimeric molecular structure of one such doubly-inserted product is presented. The kinetics of decomposition by this process are studied briefly, and it is noted that the rate increases with increased steric demand of the salicylaldimine unit.

Full text of DOI:10.1016/S0022-328X(03)00455-8

Journal of Organometallic Chemistry 683 (2003) 103ꢀ113
/
www.elsevier.com/locate/jorganchem
Biaryl-bridged Schiff base complexes of zirconium alkyls: synthesis
structure and stability
Paul D. Knight a, Paul N. O’Shaughnessy a, Ian J. Munslow a, Brian S. Kimberley b,
Peter Scott a,*
a Department of Chemistry, University of Warwick, Gibbett Hill Rd Chemistry, Coventry CV4 7AL, UK
b Research and Technology Centre, BP Chemicals snc, Boite Postale No. 6, 13117 Lavera, France
Received 27 April 2003; received in revised form 16 May 2003; accepted 16 May 2003
Abstract
Three substituted salicylaldimine derivatives H2L1ꢀ3 of 2,2?-diamino-6,6?-dimethylbiphenyl give, under appropriate conditions,
isolable alkyls of zirconium [ZrL1ꢀ3R2] (RꢁCH2Ph, CH2But). Two molecular structures confirm their cis-a geometry (C2-
/
symmetric with cis alkyl ligands). They decompose via 1,2-migratory insertion of an alkyl group to imine, followed in some
instances by a second similar reaction. The dimeric molecular structure of one such doubly-inserted product is presented. The
kinetics of decomposition by this process are studied briefly, and it is noted that the rate increases with increased steric demand of
the salicylaldimine unit.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Zirconium alkyls; Schiff base complexes; Synthesis
1. Introduction
reduction of a ligand imine group. These reactions
highlight a fundamental issue in the chemistry of Schiff
base complexes; the imine units are electrophilic,
particularly so when coordinated to an early transition
metal [6]. Jordan has explored the chemistry of zirco-
nium complexes bearing acen ligands, and has exploited
the method of introducing Schiff base ligands via
protonolysis with a metal tetraalkyl [7]. This avoids
the problem of using nucleophilic alkylating agents.
We have developed salicylaldimine proligands based
on 2,2?-diamino-6,6?-dimethylbiphenyl (i.e. H2L,
Scheme 1). Our first reports in this area detailed the
chemistry of various halide, amide and alkyl complexes
of the zirconium system [8]. While these represented the
first examples of cis-a N2O2 Schiff base complexes, it
Coates [1] and Fujita [2] have recently developed
salicylaldimine (iminophenolate, IP) complexes of the
Group 4 metals, [M(IP)2Cl2] (Fig. 1), which yield
extremely active catalysts for the polymerisation of
alkenes. It is assumed, quite reasonably, that metal
alkyls are involved in these catalyses [1,2], but to our
knowledge such species, [M(IP)2R2], have never been
characterised. Indeed, Schiff base complexes of early
transition metal alkyls are rather rare.
Floriani showed that alkylation of the Schiff base
complex [Ti(acen)Cl(THF)] may be achieved by reaction
with nucleophilic alkylating agents in THF solution with
the loss of coordinated THF [3]. The alkylation of
[Ti(salen)Cl2] is less straightforward and found to be
dependent on the alkylating agent involved [4,5]. Out-
comes include dialkylation, monoalkylation with reduc-
tion of the titanium centre, and monoalkylation with
was found that the cis-dichloride complex (Rꢁt
Bu)
/
was completely inactive as a catalyst precursor for
alkene polymerisation. In order to understand why
this is the case [9] we required the synthesis of the alkyls
[ZrLR2]. Attempts at the synthesis of alkyl complexes
from the chlorides using conventional alkylating agents
proved unsuccessful (c.f. Floriani) [3]. Reaction of H2L
* Corresponding author. Tel.:
76572710.
E-mail address: peter.scott@warwick.ac.uk (P. Scott).
ꢂ
/
44-24-76523238; fax:
ꢂ/44-24-
(Rꢁt
precipitate, which was found to be an impure sample of
/
Bu) with zirconium tetrabenzyl gave an orange
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00455-8

104
P.D. Knight et al. / Journal of Organometallic Chemistry 683 (2003) 103ꢀ113
/
Fig. 1. Group IV iminophenolate complexes developed by Coates and
Fujita.
Fig. 2. Numbering scheme for proligands.
the desired dibenzyl complex. The complex was found to
type exist [10]. We found that the most efficient by some
margin was that reported by Skattebøl and Hofsløkken
[11].
decompose readily in solution (B
unidentified products [8]. A similar reaction of H2L
(RꢁH) with zirconium tetrabenzyl gave an orange
/
12 h at ꢃ
/
30 8C) to
/
material that was insoluble in all suitable solvents.
Mass spectrometry and CHN analysis gave promising
indications of this being the desired complex,
[ZrL(CH2Ph)2], but it could not be further charac-
terised.
On the basis of these preliminary results we proposed
to tune the ligand alkyl groups (R, Scheme 1), such that
the complexes would be both sufficiently soluble and
stable for analysis. The products of this work are
currently being used in a detailed study of the mechan-
ism of their decomposition, and some preliminary
results have been communicated [9].
2.2. Synthesis and structure of [ZrL1ꢀ3R2]
The reaction of stoichiometric amounts of H2L1 and
[Zr(CH2Ph)4] in dichloromethane at ꢃ78 8C gave,
/
1
according to the H-NMR spectrum the desired dialkyl
complex (vide infra) with impurities (ca. 15%). Purifica-
tion by recrystallisation was attempted using various
solvents and solvent combinations, but this generally
gave poor yields of impure material, which was not
surprising giving the thermally sensitive nature of the
complex in solution. We found that the complex has
very low solubility in acetonitrile, whilst the proligand
and [Zr(CH2Ph)4] are reasonably soluble at reduced
temperatures. Accordingly, the reaction of H2L1 with a
2. Results and discussion
slight excess of [Zr(CH2Ph)4] in acetonitrile at ꢃ50 8C
/
2.1. Synthesis of proligands, H2L1ꢀ3
gave an orange precipitate which was shown to be
[ZrL1(CH2Ph)2] in reasonably high purity. The complex
[ZrL2(CH2Ph)2] was synthesised in a similar manner.
The reaction of H2L3 with [Zr(CH2Ph)4] in acetonitrile
did not however produce the desired result since H2L3 is
rather insoluble in acetonitrile. The reaction of H2L3
The salicylaldehydes required for the synthesis of
proligands H2L1ꢀ3 (Fig. 2) are not commercially avail-
able and were accessed by formylation of the corespond-
ing phenol. Many literature procedures for this reaction
with [Zr(CH2Ph)4] in dichloromethane at ꢃ78 8C
/
yielded an orange solid which was found to be the
desired complex [ZrL3(CH2Ph)2] in reasonable purity.
1
The H-NMR spectrum of [ZrL2(CH2Ph)2], shown in
Fig. 3, contains a single imine peak at d 7.82 ppm. This
and other features of the spectrum indicate that the
complex is C2-symmetric, consistent with the cis-a
topography (vide infra). A pair of AB doublets at ca.
d 1.51 and 1.88 ppm is assigned to the diastereotopic
CH2Ph groups. In addition, the isopropyl methyl groups
on the phenolic ring of the ligand are diastereotopic and
are observed as a pair of doublets at d 1.40 and 1.21
ppm. The above complexes were found to decompose in
solution over a period of several hours.
Treatment of H2L1 with [Zr(CH2CMe3)4] in an NMR
tube indicated clean formation of the desired C2-
symmetric product, [ZrL1(CH2CMe3)2]. This was found
to be thermally unstable in solution, although the
apparent rate of decomposition was considerably re-
duced, occurring over a period of several days compared
to hours for the similar benzyl complexes. The complex,
Scheme 1. Biaryl bridged iminophenolate proligands and correspond-
ing zirconium complexes [8].

P.D. Knight et al. / Journal of Organometallic Chemistry 683 (2003) 103ꢀ
/113
105
Fig. 3. 1H-NMR spectrum of [ZrL2(CH2Ph)2] at 298 K in d2-dichloromethane.
and similar derivatives of L2 and L3 were isolated
successfully. NMR spectra were analogous to those
recorded for the benzyl complexes.
The relative stability of these complexes allowed for
recrystallisation from toluene, yielding samples of
[ZrL1(CH2CMe3)2] and [ZrL2(CH2CMe3)2] suitable for
X-ray crystallographic analysis. The structures obtained
(Figs. 4 and 5) confirmed the cis-a geometry. The
molecules have approximate C2-symmetry as shown in
(CH2CMe3)2] (ca. 1158). Also, the angles between the
planes of OÃ
/
ZrÃ
/
O? and CÃ
/
ZrÃC? are 86.9(14) and
/
78.8(12)8 for complexes [ZrL1(CH2CMe3)2] and
[ZrL2(CH2CMe3)2], respectively. We suggest that these
differences arise from the greater steric compression
between phenolate ortho-alkyl substituents and the
metal-bound alkyl groups for L2 than for L1.
2.3. Products of decomposition of [ZrL1ꢀ3R2]
Fig. 6. The ZrÃ
O(2) and N(1)Ã
/
O and ZrÃ
ZrÃN(2) angles are similar in both
/
N distances and O(1)Ã
/
ZrÃ
/
NMR tubes were charged with solutions of the pure
/
/
zirconium benzyl complexes of L1ꢀ at 298 K and H-
NMR spectra were recorded at intervals. In the case of
[ZrL1(CH2Ph)2], after ca. 3 h the formation of one major
product was noted. The NMR spectrum (Fig. 7)
indicated that a diastereoselective 1,2-migratory inser-
tion of a benzyl group to the ligand was occurring
(Scheme 2). A new peak at d 8.34 ppm corresponds to
the imine hydrogen atom of the new complex (HD*). The
new peaks appearing at d 5.64, 3.46 and 2.90 ppm
(expanded for clarity in Fig. 7) correspond to the
formation of a new stereogenic centre at the former
imine carbon. The doublets of doublets at ca. d 3.46 and
2.90 ppm are assigned to the migrated diastereotopic
CH2Ph group (HA* and HB*, Scheme 2) and the doublet
of doublets at ca. d 5.64 ppm are attributed to the
hydrogen at the new chiral a-amido carbon (HC*). The
product formed from migratory insertion has C1-sym-
metry, and a total of six new methyl resonances are
observed. The remaining zirconium bound benzyl group
is observed as a pair of AB doublets at d 2.47 and 2.21
ppm, assigned with reference to COSY and HMQC
experiments.
3
1
complexes (Table 1). These angles and distances are in
good agreement with the molecular structure of a similar
chloride complex [8]. The ZrÃ/C distances for the metal
bound neopentyl groups are also similar in both
complexes and are comparable with reported zirconium
compounds [12]. The CÃ
/
ZrÃC? angles are significantly
/
different between the two complexes, being more acute
in [ZrL2(CH2CMe3)2] (ca. 1078) than in [ZrL1-
We have described a similar reaction to the above in a
titanium benzyl complex [13], but here the 1,2-migratory
insertion occurred at a similar rate to that of the
complex formation, making analysis of the kinetics
difficult. Also, unlike the titanium complex, the 1,2-
Fig.
4. X-ray
crystallographic
molecular
structure
of
[ZrL1(CH2CMe3)2].

106
P.D. Knight et al. / Journal of Organometallic Chemistry 683 (2003) 103ꢀ113
/
Table 1
Selected bond lengths and angles for molecular structures of
[ZrL1(CH2CMe3)2] and [ZrL2(CH2CMe3)2]
[ZrL1(CH2CMe3)2]
[ZrL2(CH2CMe3)2]
Bond lengths
Zr(1)Ã
Zr(1)Ã
Zr(1)Ã
Zr(1)Ã
Zr(1)Ã
Zr(1)Ã
/
O(2)
O(1)
C(33)
C(38)
N(1)
N(2)
2.023(3)
2.026(3)
2.271(5)
2.287(5)
2.418(4)
2.425(4)
Zr(1)Ã
Zr(1)Ã
Zr(1)Ã
Zr(1)Ã
Zr(1)Ã
Zr(1)Ã
/
O(2)
O(1)
C(35)
C(40)
N(1)
N(2)
2.022(3)
2.030(3)
2.261(6)
2.268(6)
2.412(4)
2.418(4)
/
/
/
/
/
/
/
/
Scheme 2. 1,2-Migratory insertion of a metal bound benzyl group to
an imine carbon.
/
/
Bond angles
O(2)ÃZr(1)Ã
N(1)ÃZr(1)Ã
C(33)ÃZr(1)Ã
/
/
O(1)
N(2)
C(38) 115.53(19) C(35)Ã
175.04(14) O(2)Ã
71.33(12) N(1)Ã
/
Zr(1)Ã
Zr(1)Ã
Zr(1)Ã
/
O(1)
176.04(14)
70.92(12)
C(40) 107.2(2)
tory insertion for both benzyl groups in the same
absolute sense. Thus, [Zr{(S)-L2}(CH2Ph)2] has given
rise to (S,S) stereochemistry for the migrated benzyl
groups on the a-amino carbon atoms and [Zr{(R)-
L2}(CH2Ph)2] has given (R,R) configuration. The dimer
which crystallised is however heterochiral, i.e. composed
of both these enantiomers. Given that this and similar
species have at least eight elements of chirality, the
observation of a mixture of products in solution is not
surprising.
The decomposition of the complex [ZrL3(CH2Ph)2]
was also followed by 1H-NMR spectroscopy. Again the
highly diastereoselective 1,2-migratory insertion of a
benzyl group from metal centre to an imine carbon was
observed, but unlike [ZrL1,2(CH2Ph)2], the product
formed from this decomposition was stable with respect
to the second migratory insertion reaction [13].
/
/
/
/
N(2)
/
/
/
/
migratory insertion product from [ZrL1(CH2Ph)2] un-
dergoes a further decomposition and the 1H-NMR
spectra become very complex. The disappearance of
peaks in the imine region of the 1H-NMR spectrum
indicates that the remaining metal bound benzyl group
undergoes migratory insertion to the second imine unit.
The decomposition of [ZrL2(CH2Ph)2] was also
1
followed by H-NMR spectroscopy. This revealed that
a 1,2-migratory insertion process, similar to that for
[ZrL1(CH2Ph)2], occurs and is followed again by a more
complex 1,2-migratory insertion decomposition (Scheme
3). In this instance we were able to isolate a few crystals
of a product [{ZrL2?}2], which were analysed by X-ray
crystallography (Fig. 8).
2.4. Rates of decomposition for [ZrL1ꢀ3(CH2Ph)2]
The four coordinate species resulting from the second
1,2-migratory insertion (Scheme 3), dimerises through
bridging of one oxygen atom from each ligand to the
two zirconium centres. Within the monomer unit the
atropisomeric biaryl has (at least for the observed
diastereomer) directed the stereochemistry of 1,2-migra-
Since
the
decomposition
of
complexes
24
[ZrL1ꢀ3(CH2Ph)2] occurred over a period of ca. 12ꢀ
/
1
h, H-NMR spectroscopy provided an ideal means for
obtaining kinetic data. The NMR solvent of choice was
Fig. 6. Comparison of [ZrL1(CH2CMe3)2] and [ZrL2(CH2CMe3)2]
highlighting the C2-symmetry and cis-a geometry of the complexes
(tert-butyl groups removed).
Fig.
5. X-ray
crystallographic
molecular
structure
of
[ZrL2(CH2CMe3)2].

P.D. Knight et al. / Journal of Organometallic Chemistry 683 (2003) 103ꢀ
/113
107
Fig. 7. 1H-NMR spectrum of [ZrL1(CH2Ph)2] at 298 K in d2-dichloromethane after 3 h.
d2-dichloromethane, as this was found to have a residual
3. Conclusion
protio solvent resonance completely separated from
peaks associated with all three complexes as well as
their decomposition products. The complexes (ca. 15
mg) were dissolved in d2-dichloromethane and 1H-NMR
spectra recorded at set time intervals over a period of
several hours. The rate of loss of starting material was
measured by comparison of the integral of the imine
peak with the residual protio resonance of the solvent.
The kinetic plots are shown in Fig. 9 and the relative
rates of decomposition shown in Table 2.
These results show that there is very little difference in
the decomposition rate for the initial 1,2-migratory
insertion between H and Me groups at the R1 position.
Upon increasing steric bulk at R1 to an isopropyl group
a significant increase in the rate of decomposition is
observed. It might then be expected that the more
sterically demanding tert-butyl group would show an
even greater increase in rate of decomposition, and
indeed we have noted the rapid decomposition of such a
compound [8].
It has been shown that by careful ligand and solvent
choice it is possible to isolate biaryl-bridged Schiff base
complexes of zirconium alkyls which have a predeter-
mined cis-a geometry. However, the imine units are
subject to a 1,2-migratory insertion of a metal bound
alkyl group from the metal centre. Evidently, steric
effects control these processes; increasing the size of the
alkyl groups at the position ortho to the phenolate
creates compression at the metal centre, which is
alleviated upon migration of a metal-bound alkyl to
the ligand. Given this instability, the lack of alkene
polymerisation activity in the system is not surprising,
although we have recently shown that with suitable
modification a stable polymerisation system can be
accessed [9].
Scheme 3. Secondary 1,2-migratory insertion and subsequent dimer-
isation.
Fig. 8. X-ray crystallographic molecular structure of secondary
decomposition product of [ZrL2(CH2Ph)2]; hydrogen atoms omitted.

108
P.D. Knight et al. / Journal of Organometallic Chemistry 683 (2003) 103ꢀ113
/
Fig. 9. Plot of ln(integral of imine peak) vs. time/s for [ZrL1 ꢀ 3(CH2Ph)2] at 298 K.
4. Experimental
and the spectra referenced internally using residual
protio solvent resonances relative to tetramethylsilane
(dꢁ0.0 ppm). Proton and carbon NMR assignments
were confirmed routinely by 1Hꢀ1H (COSY) or 1Hꢀ13
C
/
4.1. General details
/
/
(HMQC) experiments. NMR kinetic data were obtained
using Bruker AC-400 or DPX-500 spectrometer with
calibrated temperature probes. Infra-red spectra were
carried out on sodium chloride plates in an airtight
holder, and obtained as thin film (dichloromethane as
Unless stated otherwise, organic preparations were
carried out in air. Organometallic manipulations were
performed under an atmosphere of dry argon, using
conventional Schlenk line techniques and an MBraun
glove box (B1 ppm O2/H2O). For organometallic
/
solvent) or nujol mulls on a PerkinꢀElmer FT-IR
/
preparations, hydrocarbon and ether solvents were
pre-dried over sodium wire. These were then dried
under reflux conditions over sodium (for toluene),
spectrometer. EI and CI mass spectra were obtained
on a VG Autospec mass spectrometer. Elemental
analyses were performed by Warwick Analytical Ser-
vices. For many complexes, analyses of % C were found
to be lower than calculated values; this is frequently the
case in such systems [14].
potassium (THF and benzene), sodiumꢀpotassium alloy
/
(diethyl ether, petroleum ether and pentane), then
distilled and degassed before use. Dichloromethane
and acetonitrile were dried under reflux conditions
over calcium hydride then distilled and degassed.
Deuterated solvents were degassed by the freeze-thaw
method and dried over potassium (toluene, benzene and
THF) or calcium hydride (dichloromethane and aceto-
nitrile) before trap-to-trap distillation and storage in the
glove box. NMR samples of air sensitive species were
prepared in the glovebox in tubes sealed with Young’s
concentric stopcocks.
Unless stated otherwise, commercial chemical re-
agents were used as received. Chiral ligands and
complexes were racemic mixtures unless stated other-
wise.
NMR spectra were recorded at ca. 298 K on Bruker
AC-250, DPX-300, DPX-400 or AC-400 spectrometers
4.2. Synthesis of salicylaldehydes [11]
The reaction was performed under argon to prevent
moist air from entering the reaction vessel. Acetonitrile
and triethylamine were dried over CaH2, paraformalde-
hyde dried over P2O5 and anhydrous MgCl2 (98%)
purchased from Aldrich was dried over P2O5 at 120 8C.
A 1 l side arm round bottom flask with stirrer bar was
placed under an argon atmosphere and charged with the
appropriate phenol (100 mmol) and dry acetonitrile (500
ml). To this was added dry triethylamine (52.2 ml, 375
mmol), anhydrous MgCl2 (14.28 g, 150 mmol) and the
solution was stirred for 15 min. Dry paraformaldehyde
(20.25 g, 675 mmol) was added and a wide bore
condenser fitted to the round bottom flask. The solution
was heated at reflux temperature under argon for ca. 2.5
h. The solution was allowed to cool to room tempera-
ture and added to 5% aq. HCl (800 ml) followed by
stirring for 30 min. This was extracted with diethyl ether
Table 2
Rates of decomposition for [ZrL1 ꢀ 3(CH2Ph)2] at 298 K
a
Complex
R1
kobs 10ꢃ5 sꢃ1
krel
[ZrL1(CH2Ph)2]
[ZrL2(CH2Ph)2]
[ZrL3(CH2Ph)2]
Me
Pri
H
5.70 (9
8.33 (9
5.93 (9
/
0.12)
0.12)
0.08)
1
/
1.46
1.04
(7ꢄ
together and washed with saturated NaCl(aq) (3ꢄ
ml portions). The ether layer was dried over anhydrous
/100 ml portions) and the ether fractions collected
/
/
100
a
Relative rate constant, krel, vs. [ZrL1(CH2Ph)2].

P.D. Knight et al. / Journal of Organometallic Chemistry 683 (2003) 103ꢀ
/113
109
MgSO4 followed by filtration. Volatiles were removed
under reduced pressure to yield the corresponding
salicylaldehydes, usually contaminated with the starting
phenol. Purification prior to reaction with the biaryl
diamine (vide infra) was found to be generally unneces-
sary, as the Schiff base product precipitates from the
reaction solution. Samples of the products were never-
theless isolated and fully characterised, as described
below.
13C{1H}-NMR 75 MHz (CDCl3): d ppm 196.7 (HC Ä
O), 159.0, 136.9, 133.4, 131.1, 120.0, 119.4 (Ar), 26.0
(CHMe2), 22.0 (CHMe2).
IR (Thin film): n cmꢃ1 3049 (w, OH), 2964, 2870,
/
2843, 2746, 2361, 2342, 1652 (s, CÄ
/
O), 1616, 1439, 1386,
1363, 1308, 1265 (s, CÃO), 1219, 1175, 1151, 1109, 1100,
/
1050, 1010, 968, 924, 878, 827, 790, 753, 697, 681, 668,
642.
MS (EI) m/z 164 [M]ꢂ, 149 [MꢃCH3]ꢂ.
/
4.2.3. 5-tert-Butyl-2-hydroxybenzaldehyde
4.2.1. 3,5-Dimethyl-2-hydroxybenzaldehyde
Using the general procedure with 4-tert-butylphenol
(15.00 g), the mixture was heated at reflux temperature
for 3 h, during which time the solution turned yellow. A
yellow oil was obtained which 1H-NMR spectra showed
to be 5-tert-butyl-2-hydroxybenzaldehyde (99% purity).
Using the above procedure with 2,4-dimethylphenol
(12.21 g) the reaction mixture was heated at reflux
temperature for 3 h. During this period the solution
turned yellow. A yellow oil was obtained (14.21 g) which
was found to contain 3,5-dimethyl-2-hydroxybenzalde-
Yieldꢁ17.53 g, 98%.
/
1
hyde (94% by H-NMR). A sample of the oil (2.00 g)
Anal. Found (Calc. for C11H14O2): C, 73.38 (74.13);
H, 7.93% (7.92).
1H-NMR 300 MHz (CDCl3): d ppm 10.86 (s, 1H,
was purified by column chromatography (hexaneꢀ
diethyl ether 6:1).
Yieldꢁ1.79 g, 90% (from 2 g of crude product).
/
/
ArOH), 9.87 (s, 1H, HCÄ
/
O), 7.57 (dd, 1H, ArH,
4
3 Hz), 7.50 (d, 1H, ArH, JHH
4
9 Hz, JHH
Anal. Found (Calc. for C9H10O2): C, 71.89 (71.99); H,
6.72% (6.71).
1H-NMR 300 MHz (CDCl3): d ppm 11.07 (s, 1H,
3JHH
3 Hz), 6.92 (d, 1H, ArH, JHH
CMe3).
ꢁ
/
ꢁ
/
ꢁ
/
3
ꢁ9 Hz), 1.31 (s, 9H,
/
ArOH), 9.81 (s, 1H, HCÄ
/
O), 7.20 (s, 1H, ArH), 7.16 (s,
13C{1H}-NMR 75 MHz (CDCl3): d ppm 190.7 (HC Ä
O), 159.3, 142.6, 134.6, 129.6, 119.8, 117.0 (Ar), 33.9
/
1H, ArH), 2.29 (s, 3H, Me), 2.23 (s, 3H, Me).
13C{1H}-NMR 75 MHz (CDCl3): d ppm 196.6 (HC Ä
O), 157.8, 139.0, 130.8, 128.4, 126.4, 119.6 (Ar), 20.1
(Me), 14.8 (Me).
/
(CMe3), 31.1 (CMe3).
IR (Thin film): n cmꢃ1 3197 (b, OH), 3077, 2963,
2909, 2869, 2743, 2396, 2254, 2064, 1917, 1730, 1700,
IR (CH2Cl2 Thin film): n cmꢃ1 3163 (b, OH), 3103,
1657 (s, CÄ
1289, 1265 (s, CÃ
890, 834, 775, 733, 654, 601.
MS (EI) m/z 178 [M]ꢂ, 163 [Mꢃ
OH]ꢂ, 148 [Mꢃ(CH3)2]ꢂ, 133 [Mꢃ(CH3)3]ꢂ.
/
O), 1622, 1592, 1485, 1395, 1376, 1363, 1318,
2923, 2845, 2740, 1652 (s, CÄ
1323, 1263 (s, CÃO), 1214, 1165, 1036, 969, 953, 863,
788, 745, 711.
MS (EI) m/z 150 [M]ꢂ, 149 [Mꢃ
CH3]ꢂ, 121 [MꢃCHO]ꢂ.
/O), 1621, 1470, 1415, 1380,
/O), 1230, 1185, 1136, 1106, 1025, 924,
/
/
CH3]ꢂ, 161 [Mꢃ
/
/
H]ꢂ, 135 [Mꢃ
/
/
/
/
4.3. Synthesis of Schiff base proligands, H2L1ꢀ3
4.2.2. 3-Isopropyl-2-hydroxybenzaldehyde
A 100 ml round bottom flask with stirrer bar was
charged with the appropropiate salicylaldehyde and a
stoichiometric amount of the amine 2,2?-diamino-6,6?-
dimethylbiphenyl. The reactants were dissolved in
Using the general procedure, 2-isopropylphenol
(13.60 g) was used as the reagent and the reaction
mixture heated at reflux temperature for 2.5 h, during
which time the solution turned yellow. A yellow oil was
ethanol or methanol (40ꢀ100 ml), and heated at reflux
/
1
obtained (14.85 g) and analysis by H-NMR spectro-
for ca. 18 h, using a condenser fitted with a drying tube
containing CaCl2. A precipitate generally formed during
the reaction and the solid was isolated by vacuum
filtration and washed with cold ethanol or methanol. All
remaining volatiles were removed in vacuo.
scopy revealed it to contain 3-isopropyl-2-hydroxyben-
zaldehyde (90%). A small sample of the product mixture
(1.00 g) was purified by column chromatography
(hexaneꢀ
/
diethyl ether 4:1). Yieldꢁ0.84 g, 84% (from
/
1 g of crude product).
Anal. Found (Calc. for C10H12O2): C, 72.71 (73.15);
H, 7.44% (7.37).
4.3.1. H2L1
Following the general procedure, 3,5-dimethyl-2-hy-
droxybenzaldehyde (4.31 g, 28.54 mmol), 2,2?-diamino-
6,6?-dimethylbiphenyl (3.05 g, 14.39 mmol) and ethanol
(50 ml) were used. A bright orange solid was obtained.
1H-NMR 300 MHz (CDCl3): d ppm 11.37 (s, 1H,
ArOH), 9.87 (s, 1H, HCÄ
/
O), 7.46 (dd, 1H, ArH,
4
7 Hz, JHH
3JHH
3JHH
ꢁ
/
ꢁ
/
2 Hz), 7.38 (dd, 1H, ArH,
3
2 Hz), 6.97 (t, 1H, ArH, JHH
4
8 Hz, JHH
ꢁ
/
ꢁ
/
ꢁ
/
Yieldꢁ6.45 g, 95%.
/
8 Hz), 3.37 (m, 1H, CHMe2, 3JHH
ꢁ/7 Hz), 1.24 (d, 6H,
Anal. Found (Calc. for C32H32N2O2): C, 80.69
(80.64); H, 6.80 (6.77); N, 6.00% (5.88).
3
CHMe2, JHH
ꢁ7 Hz).
/

110
P.D. Knight et al. / Journal of Organometallic Chemistry 683 (2003) 103ꢀ113
/
1H-NMR 300 MHz (CDCl3): d ppm 12.12 (s, 2H,
(d, 2H, ArH, 3JHH
Hz), 2.07 (s, 6H, Me), 1.27 (s, 18H, CMe3).
13C{1H}-NMR 75 MHz (CDCl3): d ppm 161.4 (NÄ
CH), 158.5, 146.3, 141.2, 137.0, 133.9, 130.0, 130.0,
128.4, 128.3, 118.4, 116.5, 114.8 (Ar), 33.8 (CMe3), 31.2
(CMe3), 19.7 (Me).
IR (CH2Cl2 Thin film): n cmꢃ1 3426 (b, OH), 2962,
ꢁ
/
8 Hz), 6.80 (d, 2H, ArH, 3JHH
ꢁ9
/
ArOH), 8.32 (s, 2H, NÄ
/
CH), 7.32 (t, 2H, ArH, 3JHH
ꢁ
/
3
8 Hz), 7.21 (d, 2H, ArH, JHH
ꢁ
/
7 Hz), 7.01 (d, 2H,
/
3
ArH, JHH
ꢁ
/
7 Hz), 6.94 (s, 2H, ArH), 6.82 (s, 2H,
ArH), 2.21 (s, 6H, Me), 2.12 (s, 6H, Me), 2.04 (s, 6H,
Me).
13C{1H}-NMR 75 MHz (CDCl3): d ppm 162.3 (NÄ
/
CH), 157.0, 147.4, 137.0, 134.8, 133.2, 129.7, 128.4,
128.2, 126.9, 125.7, 118.1, 115.5 (Ar), 20.2 (Me), 19.8
(Me), 15.5 (Me).
2361, 1623 (s, NÄ
1265 (s, CÃO), 1246, 1209, 1184, 1136, 1108, 1019, 978,
938, 886, 826, 809, 792, 750.
MS (EI) m/z 532 [M]ꢂ, 517 [Mꢃ
/C), 1566, 1490, 1461, 1394, 1364, 1289,
/
IR (CH2Cl2 Thin film): n cmꢃ1 2919, 2361, 1622 (s,
/
CH3]ꢂ.
NÄ
/
C), 1598, 1569, 1470, 1435, 1379, 1362, 1324, 1283,
1266 (s, CÃ
/O), 1242, 1220, 1167, 1108, 1049, 1019, 975,
4.4. Synthesis of zirconium benzyl complexes
943, 860, 806, 788, 751, 738, 700.
MS (EI) m/z 476 [M]ꢂ, 461 [Mꢃ
/
CH3]ꢂ.
4.4.1. [ZrL1(CH2Ph)2]
A Schlenk vessel with stirrer bar was charged with
H2L1 (246 mg, 0.52 mmol) and [Zr(CH2Ph)4] (252 mg,
0.55 mmol). The vessel was placed in an acetone/dry ice
4.3.2. H2L2
Following the general procedure, 3-isopropyl-2-hy-
droxybenzaldehyde (4.50 g, 27.27 mmol), 2,2?-diamino-
6,6?-dimethylbiphenyl (2.91 g, 13.73 mmol) and ethanol
(50 ml) were used. A bright yellow solid was obtained.
bath at ꢃ78 8C and acetonitrile (20 ml) added. This was
/
transferred to an ice bath at 0 8C and allowed to stir for
20 min. An orange precipitate formed and was isolated
by filtration at 0 8C, followed by washing with cold
acetonitrile. The orange solid was dried in vacuo.
Yieldꢁ6.42 g, 93%.
/
Anal. Found (Calc. for C34H36N2O2): C, 80.88
(80.92); H, 7.17 (7.19); N, 5.60% (5.55).
1H-NMR 300 MHz (CDCl3): d ppm 12.54 (s, 2H,
Yieldꢁ251 mg, 65%.
/
Anal. Found (Calc. for C46H44N2O2Zr): C, 72.09
(73.86); H, 5.83 (5.93); N, 4.42% (3.74).
ArOH), 8.42 (s, 2H, NÄ
/
CH), 7.33 (t, 2H, ArH, 3JHH
ꢁ
/
1H-NMR 400 MHz (CD2Cl2): d ppm 7.77 (s, 2H, NÄ
/
3
8 Hz), 7.22 (d, 2H, ArH, JHH
ꢁ7 Hz), 7.20 (dd, 2H,
/
CH), 7.20 (s, 2H, ArH), 7.01 (t, 2H, ArH, 3JHH
6.98 (d, 2H, ArH), 6.93 (t, 4H, ArH, 3JHH
8 Hz), 6.78
(t, 2H, ArH), 6.77 (s, 2H, ArH), 6.63 (d, 4H, ArH,
3JHH 7 Hz), 6.34 (dd, 2H, ArH, 3JHH 7 Hz, 4JHH
1 Hz), 2.33 (s, 6H, Me), 2.24 (s, 6H, Me), 2.04 (s, 6H,
ꢁ
/
8 Hz),
4
ArH, JHH
4
ꢁ
/
1 Hz), 7.05 (dd, 2H, ArH, JHH
ꢁ
/
1 Hz),
7 Hz), 6.79 (t, 2H, ArH,
7 Hz), 2.06
7 Hz), 1.15 (d,
ꢁ
/
3
7.03 (d, 2H, ArH, JHH
ꢁ
/
3JHH
ꢁ
/
8 Hz), 3.24 (m, 2H, CHMe2, 3JHH
ꢁ
/
ꢁ
/
ꢁ
/
ꢁ
/
(s, 6H, Mei), 1.16 (d, 6H, CHMe2, 3JHH
ꢁ
/
3
6H, CHMe2, JHH
ꢁ7 Hz).
/
2
Me), 1.87 (d, 2H, CH2Ph, JHH
8 Hz).
ꢁ8 Hz), 1.44 (d, 2H,
/
13C{1H}-NMR 75 MHz (CDCl3): d ppm 162.3 (NÄ
/
2
CH2Ph, JHH
ꢁ
/
CH), 158.5, 147.1, 137.0, 136.2, 133.3, 129.7, 129.2,
128.4, 128.3, 118.5, 118.2, 115.5 (Ar), 26.3 (CHMe2),
22.3 (CHMe2), 22.2 (CHMe2), 19.8 (Me).
IR (CH2Cl2 Thin film): n cmꢃ1 3058 (w, OH), 2961,
2869, 2360, 2341, 1613 (s, NÄ
1306, 1264 (m, CÃO), 1218, 1176, 1151, 1108, 1097,
1051, 982, 944, 881, 826, 797, 771, 750 (s), 700, 668.
MS (EI) m/z 504 [M]ꢂ, 489 [MꢃCH3]ꢂ.
13C{1H}-NMR 75 MHz (CD2Cl2): d ppm 168.8 (NÄ
/
CH), 160.0, 150.0, 144.2, 138.2, 137.0, 132.1, 131.2,
128.7, 128.5, 128.2, 128.1, 127.2, 127.2, 121.2, 121.2,
119.9 (Ar), 60.8 (CH2Ph), 20.4 (Me), 19.9 (Me), 17.2
(Me).
/C), 1569, 1458, 1438, 1382,
/
IR (Nujol): n cmꢃ1 2729, 2360, 1615 (s, NÄ
1557, 1295, 1264 (s, CÃO), 1218, 1173, 1098, 1054, 1028,
973, 965, 942, 899, 848, 825, 802, 759, 749, 737, 698.
MS (EI) m/z 656 [Mꢃ
CH2Ph]ꢂ, 565 [Mꢃ
(CH2Ph)2]ꢂ, 550 [Mꢃ{(CH2Ph)2 and CH3}]ꢂ.
/C), 1591,
/
/
/
/
4.3.3. Synthesis of H2L3
/
Following the general procedure, 5-tert-butyl-2-hy-
droxybenzaldehyde (8.00 g, 44.9 mmol), 2,2?-diamino-
6,6?-dimethylbiphenyl (4.73 g, 22.3 mmol) and ethanol
(100 ml) were used. An orange/yellow solid was
obtained.
4.4.2. [ZrL2(CH2Ph)2]
Using the same procedure as Section 4.4.1, H2L2 (302
mg, 0.60 mmol) and [Zr(CH2Ph)4] (296 mg, 0.65 mmol)
gave an orange/yellow solid.
Yieldꢁ/10.96 g, 92%.
Yieldꢁ358 mg, 77%.
/
Anal. Found (Calc. for C36H40N2O2): C, 80.82
(81.17); H, 7.55 (7.57); N, 5.21% (5.26).
Anal. Found (Calc. for C48H48N2O2Zr): C, 72.40
(74.28); H, 6.09 (6.23); N, 3.14% (3.61).
1H-NMR 300 MHz (CDCl3): d ppm 12.15 (s, 2H,
1H-NMR 400 MHz (CD2Cl2): d ppm 7.82 (s, 2H, NÄ
/
3
CH), 7.42 (dd, 2H, ArH, JHH
7.00 (t, 2H, ArH), 6.99 (dd, 2H, ArH), 6.98 (d, 2H,
4
8 Hz, JHH
ArOH), 8.57 (s, 2H, NÄ
8 Hz), 7.31 (dd, 2H, ArH, JHH
7.28 (d, 2H, ArH), 7.27 (d, 2H, ArH, 4JHH
/
CH), 7.39 (t, 2H, ArH, 3JHH
ꢁ
2 Hz),
2 Hz), 7.16
/
ꢁ
/
ꢁ/2 Hz),
3
4
ꢁ
/
9 Hz, JHH
ꢁ
/
3
ArH), 6.95 (t, 4H, ArH), 6.81 (t, 2H, ArH, JHH
ꢁ
/
ꢁ8
/

P.D. Knight et al. / Journal of Organometallic Chemistry 683 (2003) 103ꢀ
/113
111
Hz), 6.80 (t, 2H, ArH, 3JHH
ꢁ
/
7 Hz), 6.60 (d, 4H, ArH,
mg, 1.09 mmol). This was cooled to ꢃ
/
78 8C and
3JHH 7 Hz), 6.49 (dd, 2H, ArH, 3JHH
2 Hz), 3.66 (m, 2H, CHMe2, JHH
ꢁ
/
ꢁ
/
8 Hz, 4JHH
7 Hz), 2.07 (s, 6H,
ꢁ
/
dichloromethane (30 ml) added, with stirring of the
solution. The solution was allowed to warm to room
temperature and stirring was continued for a further 30
min, during which time the solution turned from yellow
to orange. This was then filtered and the solvent
removed under reduced pressure to yield a yellow/
orange solid which was dried in vacuo. The product
was recrystallised from toluene to yield crystals suitable
for X-ray analysis. The product was also precipitated
3
ꢁ
/
2
Me), 1.88 (d, 2H, CH2Ph, JHH
ꢁ
/
9 Hz), 1.51 (d, 2H,
2
3
CH2Ph, JHH
Hz), 1.21 (d, 6H, CHMe2, JHH
13C{1H}-NMR 75 MHz (CD2Cl2): d ppm 169.0 (NÄ
ꢁ
/
9 Hz), 1.40 (d, 6H, CHMe2, JHH
ꢁ7
/
3
ꢁ7 Hz).
/
/
CH), 160.3, 150.0, 144.0, 138.7, 137.1, 132.5, 132.2,
131.5, 128.6, 128.5, 128.1, 127.9, 122.0, 121.4, 119.9,
118.4 (Ar), 60.7 (CH2Ph), 26.5 (CHMe2), 24.1
(CHMe2), 22.2 (CHMe2), 20.0 (Mei).
from pentane (100 ml) at ꢃ
orange solid.
Yieldꢁ646 mg, 85%.
/
30 8C to yield a yellow/
IR (Nujol): n cmꢃ1 2283, 1604 (s, NÄ
1264 (m, CÃO), 1233, 1215, 1149, 1106, 1050, 1022, 981,
944, 890, 852, 794, 751, 698.
MS (EI) m/z 760 [Mꢃ
Me]ꢂ, 745 [Mꢃ
[Mꢃ
(Pri)2]ꢂ, 684 [Mꢃ(CH2Ph)]ꢂ, 669 [Mꢃ
and Me)]ꢂ, 598 [Mꢃ{CH2Ph and (Pri)2}].
/
C), 1555, 1321,
/
/
Anal. Found (Calc. for C42H52N2O2Zr): C, 68.75
(71.24); H, 6.95 (7.40); N, 3.60% (3.96).
/
/
(Me)2]ꢂ, 689
(CH2Ph
/
/
/
1H-NMR 300 MHz (CD2Cl2): d ppm 7.79 (s, 2H, NÄ
/
/
CH), 7.21 (s, 2H, ArH), 7.09 (t, 2H, ArH, 3JHH
ꢁ8 Hz),
/
3
7.01 (d, 2H, ArH, JHH
ꢁ7 Hz), 6.91 (d, 2H, ArH,
/
4.4.3. [ZrL3(CH2Ph)2]
3JHH
(s, 6H, Me), 2.12 (s, 6H, Me), 1.12 (d, 2H, CH2CMe3,
ꢁ
/
8 Hz), 6.75 (s, 2H, ArH), 2.38 (s, 6H, Me), 2.24
A Schlenk vessel with stirrer bar was charged with
H2L3 (504 mg, 0.94 mmol) and [Zr(CH2Ph)2] (450 mg,
0.99 mmol). The vessel was placed in a dry ice/acetone
2JHH
0.88 (s, 18H, CH2CMe3).
13C{1H}-NMR 75 MHz (CD2Cl2): d ppm 170.3 (NÄ
ꢁ
/
13 Hz), 0.92 (d, 2H, CH2CMe3, JHH
ꢁ13 Hz),
/
2
bath at ꢃ
added. This was stirred for 30 min and then filtered at
78 8C, followed by removal of solvent under reduced
/
78 8C and dichloromethane (30 ml) was
/
CH), 163.9, 150.4, 137.8, 137.2, 131.6, 131.6, 128.4,
127.7, 126.6, 120.9, 119.3 (Ar), 86.2 (CH2CMe3), 35.0
(CH2CMe3), 34.5 (CH2CMe3), 20.2 (Me), 19.9 (Me),
16.9 (Me).
ꢃ
/
pressure. The orange solid obtained was then washed
with acetonitrile, filtered and dried in vacuo.
Yieldꢁ
/
601 mg, 79%.
IR (Nujol): n cmꢃ1 2733, 1732, 1617 (s, NÄ
1557, 1300, 1264 (s, CÃO), 1218, 1171, 1138, 1097, 1058,
1014, 980, 962, 942, 894, 862, 830 (s), 772, 760, 738.
MS (EI) m/z 707 [M]ꢂ, 693 [MꢃCH3]ꢂ, 651 [Mꢃ
(CH2Ä
CMe2)]ꢂ.
/
C), 1597,
Anal. Found (Calc. for C50H52N2O2Zr): C, 72.30
(74.68); H, 6.06 (6.52); N, 3.28% (3.48).
1H-NMR 400 MHz (d6-benzene): d ppm 7.72 (s, 2H,
/
/
/
3
4
NÄ
Hz), 7.21 (t, 4H, ArH, 3JHH
3JHH
7 Hz), 7.01 (t, 2H, ArH, JHH
2H, ArH, JHH
Hz), 6.81 (t, 2H, ArH, 3JHH
3JHH
8 Hz), 6.57 (d, 2H, ArH, JHH
2H, CH2Ph, 2JHH 8 Hz), 1.91 (d, 2H, CH2Ph, 2JHH
8 Hz), 1.82 (s, 6H, Me), 1.16 (s, 18H, CMe3).
13C{1H}-NMR 100 MHz (d6-benzene): d ppm 168.5
(NÄCH), 161.9, 149.8, 144.1, 140.6, 136.2, 134.2, 131.0,
/CH), 7.23 (dd, 2H, ArH, JHH
ꢁ
/
9 Hz, JHH
ꢁ
/
3
/
ꢁ
/
8 Hz), 7.14 (d, 4H, ArH,
3
ꢁ
/
ꢁ7 Hz), 6.94 (d,
/
4
3
ꢁ
/
3 Hz), 6.93 (d, 2H, ArH, JHH
ꢁ
/
9
4.5.2. Synthesis of [ZrL2(CH2CMe3)2]
ꢁ
/
8 Hz), 6.58 (d, 2H, ArH,
This complex was prepared in an analogous proce-
dure to Section 4.5.1 using H2L2 (572 mg, 1.13 mmol)
and [Zr(CH2CMe3)4] (444 mg, 1.18 mmol). Recrystalli-
sation from toluene yielded crystals suitable for X-ray
analysis.
3
ꢁ
/
ꢁ8 Hz), 2.31 (d,
/
ꢁ
/
ꢁ
/
/
Yieldꢁ699 mg, 84%.
/
130.2, 129.6, 128.6, 128.3, 128.1, 121.8, 121.5, 120.5,
119.6 (Ar), 61.1 (CH2Ph), 31.8 (CMe3), 31.3 (CMe3),
19.7 (Me).
Anal. Found (Calc. for C44H56N2O2Zr): C, 68.35
(71.52); H, 7.06 (7.54); N, 4.23% (3.88).
1H-NMR 300 MHz (CD2Cl2): d ppm 7.83 (s, 2H, NÄ
/
IR (Nujol): n cmꢃ1 2726, 1614 (s, NÄ
1363, 1307, 1266 (m, CÃ
1026, 952, 882, 837, 771, 748, 700, 668.
MS (EI) m/z 804 [Mꢂ], 789 [MꢂꢃCH3], 774 [Mꢂꢃ
(CH3)2], 759 [Mꢂꢃ(CH3)3], 747 [MꢂꢃBut], 690
[Mꢂꢃ(But)2].
/
C), 1590, 1541,
ꢁ
/
ꢁ/2 Hz),
3
CH), 7.42 (dd, 2H, ArH, JHH
4
8 Hz, JHH
8 Hz), 6.97 (d, 2H, ArH), 6.95
/
O), 1208, 1180, 1143, 1127,
7.04 (t, 2H, ArH, 3JHH
ꢁ
/
(dd, 2H, ArH, 3JHH
ꢁ
/
8 Hz, 4JHH
ꢁ
/
2 Hz), 6.93 (dd, 2H,
4
ArH, JHH
3
/
/
ꢁ
/
1 Hz), 6.78 (t, 2H, ArH, JHH
ꢁ
/
8 Hz),
7 Hz), 2.12 (s, 6H, Me),
7 Hz), 1.28 (d, 2H,
3
3.82 (m, 2H, CHMe2, JHH
/
/
ꢁ
ꢁ
/
3
1.33 (d, 6H, CHMe2, JHH
/
/
CH2But), 1.24 (d, 6H, CHMe2, JHH
ꢁ7 Hz), 0.93 (d,
/
3
2
4.5. Synthesis of zirconium neopentyl complexes
4.5.1. [ZrL1(CH2CMe3)2]
A Schlenk vessel with stirrer bar was charged with
2H, CH2CMe3, JHH
CH2CMe3).
ꢁ12 Hz), 0.86 (s, 18H,
/
13C{1H}-NMR 75 MHz (CD2Cl2): d ppm 170.6 (NÄ
CH), 160.5, 150.3, 139.2, 137.3, 132.0, 131.9, 131.8,
127.6, 127.5, 121.7, 119.3, 118.0 (Ar), 86.9 (CH2CMe3),
/
H2L1 (511 mg, 1.07 mmol) and [Zr(CH2CMe3)4] (410

112
P.D. Knight et al. / Journal of Organometallic Chemistry 683 (2003) 103ꢀ113
/
35.2 (CH2CMe3), 34.5 (CH2CMe3), 26.6 (CHMe2), 23.6
(CHMe2), 21.9 (CHMe2), 19.9 (Me).
IR (Nujol): n cmꢃ1 1613 (s, NÄ
1307, 1267 (m, CÃO), 1257, 1232, 1208, 1178, 1146,
1100, 1024, 978, 949, 885, 837, 773, 759, 737, 704, 668.
MS (EI) m/z 764 [M]ꢂ, 707 [MꢃCMe3]ꢂ.
/
C), 1591, 1542, 1362,
/
IR (Nujol): n cmꢃ1 2360, 1605 (s, NÄ
/
C), 1555,1321,
O), 1208, 1148, 1109, 1050, 1017, 978, 942,
888, 851, 804, 751, 728, 710, 668, 651.
MS (EI) m/z 737 [M]ꢂ, 679 [Mꢃ
[Mꢃ
CH2CMe3]ꢂ.
/
1283 (m, CÃ
/
/
CHMe3]ꢂ, 666
4.6. Crystallography
/
Crystals were coated with inert oil and transferred to
the cold (180 K) N2 gas stream on the diffractometer
(Bruker-AXS SMART three-circle with CCD area
4.5.3. [ZrL3(CH2CMe3)2]
detector). Graphite monochromated Moꢀ
/
Ka radiation
This complex was prepared in an analogous proce-
dure to Section 4.5.1, using H2L3 (420 mg, 0.79 mmol)
and [Zr(CH2CMe3)4] (308 mg, 0.82 mmol). Removal of
volatiles under reduced pressure yielded an orange/
yellow solid. This was dissolved in pentane and the
˚
0.71073 A was used. Absorption correction was
lꢁ
/
performed by multi-scan (SADAB). The structures were
solved by direct methods using SHELXS [15] with
additional light atoms found by Fourier methods.
Hydrogen atoms were added at calculated positions
and refined using a riding model with freely rotating
methyl groups. Anisotropic displacement parameters
were used for all non-H atoms; H-atoms were given
solution was filtered, concentrated and kept at ꢃ30 8C
/
overnight to yield a yellow precipitate, which was
isolated by filtration and dried in vacuo.
Yieldꢁ325 mg, 54%.
/
isotropic displacement parameters Uiso(H)ꢁ1.2Ueq(C)
/
Anal. Found (Calc. for C46H60N2O2Zr): C, 70.46
(72.05); H, 7.37 (7.79); N, 3.76% (3.73).
1H-NMR 300 MHz (d6-benzene): d ppm 7.78 (s, 2H,
or 1.5Ueq(C) for methyl groups. The structures were
refined using SHELXL-96 [16]. Experimental data is given
in Table 3.
3
4
NÄ
Hz), 7.21 (d, 2H, ArH, 3JHH
3JHH
7 Hz), 6.94 (d, 2H, ArH, JHH
2H, ArH, JHH
Hz), 1.83 (s, 6H, Me), 1.59 (d, 2H, CH2CMe3, JHH
Hz), 1.51 (s, 18H, CH2CMe3), 1.40 (d, 2H, CH2CMe3,
2JHH
13 Hz), 1.14 (s, 18H, CMe3).
13C{1H}-NMR 75 MHz (d6-benzene): d ppm 170.1
(NÄCH), 162.0, 150.3, 140.5, 136.7, 134.5, 131.3, 130.1,
/
CH), 7.28 (dd, 2H, ArH, JHH
ꢁ
/
9 Hz, JHH
ꢁ3
/
ꢁ
/
9 Hz), 7.16 (d, 2H, ArH,
4
ꢁ
/
ꢁ2 Hz), 6.79 (t,
/
3
3
ꢁ
/
8 Hz), 6.59 (d, 2H, ArH, JHH
ꢁ8
/
5. Supplementary material
2
ꢁ13
/
Crystallographic data for the structural analysis has
been deposited with the Cambridge Crystallographic
ꢁ
/
Data Centre, CCDC nos. 208943ꢀ208945 for
/
[ZrL1(CH2CMe3)2], [ZrL2(CH2CMe3)2] and [{ZrL2?}2],
respectively. Copies of this information may be obtained
free of charge from The Director, CCDC, 12 Union
/
128.2, 127.9, 121.3, 120.1, 119.8 (Ar), 87.0 (CH2CMe3),
35.5 (CH2CMe3), 34.9 (CH2CMe3), 33.8 (CMe3), 31.3
(CMe3), 19.8 (Me).
Road, Cambridge CB2 1EZ, UK (Fax: ꢂ44-1223-
/
Table 3
Experimental data for the X-ray diffraction studies
[ZrL1(CH2CMe3)2]
[ZrL2(CH2CMe3)2]
[{ZrL2a}2]
Molecular formula
Crystal system
Space group
Colour
C42H52N2O2Zr
Triclinic
¯
P1
C58H72N2O2Zr
Triclinic
¯
P1
C48H48N2O2Zr
Triclinic
¯
P1
/
/
/
Yellow
Block
Yellow
Block
Yellow
block
Habit
˚
a (A)
˚
11.2609(13)
13.7172(16)
14.3272(17)
92.709(3)
102.194(3)
113.220(3)
1966.8(4)
2
12.047(2)
13.818(3)
17.511(4)
78.04(3)
75.21(3)
71.06(3)
2641.2(9)
2
12.633(3)
12.953(3)
14.956(3)
83.2180(10)
65.6150(10)
62.3870(10)
1967.1(7)
2
b (A)
˚
c (A)
a (8)
b (8)
g (8)
Cell volume (A )
Z
m (mmꢃ1
Total reflections
3
˚
)
0.314
14 884
0.471
19 551
0.321
8214
Independent reflections
9040 (Rint
0.0860, 0.1772
ꢁ
/
0.0520)
12 195 (Rint
0.0842, 0.1631
ꢁ
/
0.0532)
5087 (Rint
0.0701, 0.1330
ꢁ0.0542)
/
R1, wR2 [I ꢀ
/
2s(I)]

P.D. Knight et al. / Journal of Organometallic Chemistry 683 (2003) 103ꢀ
/113
113
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(1996) 2735;
336033; e-mail: deposit@ccdc.cam.ac.uk or www: http://
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Note added in proof
[10] (a) J.C. Duff, J. Am. Chem. Soc. 63 (1941) 547;
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Acknowledgements
PS thanks EPSRC for support (PDK, PNO’S and
IJM) and BP for a CASE award (PDK).
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