Arylaminopyridinato complexes of zirconium

Article abstract of DOI:10.1039/b407008a

A range of 2-arylaminopyridines (HL) are synthesised readily from bromopyridines and amines using palladium-catalysed animation. Protonolysis reactions of these proligands with ZrX₄ (X = NMe₂, CH ₂Ph, CH₂Bu^t) yield zirconium complexes of the type [ML_nX_4-n], several of which have been characterised by X-ray crystallography. Control of metal/ligand stoichiometry and structure is pursued by investigation of the effects on substitution patterns of the pyridine and aryl rings. Some distinct patterns emerged; (i) the 6-methyl position on the pyridine appears to be particularly important with regards to control of stoichiometry, although there are co-ligand effects; (ii) structures of the metal alkyl derivatives [ZrL_n(CH₂R)_4-n] are dominated by aromatic π-π stacking, even when bulky arene substituents are employed at L. This leads to the complexes adopting a C_2v- symmetric core; (iii) the amides [ZrL₂(NMe₂)₂] have structures for which aromatic π-π stacking is unfeasible, and correspondingly C₂-symmetric or similar structures are adopted. All the structural data presented is consistent with a trans influence order at zirconium Me₂N > RCH₂ > py.

Full text of DOI:10.1039/b407008a

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F U L L P A P E R
Arylaminopyridinato complexes of zirconium†
Edward J. Crust, Ian J. Munslow, Colin Morton and Peter Scott*
Department of Chemistry, University of Warwick, Coventry, UK CV4 7AL.
E-mail: peter.scott@warwick.ac.uk; Fax: +024 7652 2710; Tel: +024 7652 3238
Received 10th May 2004, Accepted 10th June 2004
First published as an Advance Article on the web 29th June 2004
A range of 2-arylaminopyridines (HL) are synthesised readily from bromopyridines and amines using palladium-catalysed
amination. Protonolysis reactions of these proligands with ZrX4 (X = NMe2, CH2Ph, CH2But) yield zirconium complexes
of the type [MLnX4−n], several of which have been characterised by X-ray crystallography. Control of metal/ligand
stoichiometry and structure is pursued by investigation of the effects on substitution patterns of the pyridine and aryl
rings. Some distinct patterns emerged; (i) the 6-methyl position on the pyridine appears to be particularly important with
regards to control of stoichiometry, although there are co-ligand effects; (ii) structures of the metal alkyl derivatives
[ZrLn(CH2R)4−n] are dominated by aromatic – stacking, even when bulky arene substituents are employed at L. This
leads to the complexes adopting a C2v-symmetric core; (iii) the amides [ZrL2(NMe2)2] have structures for which aromatic
– stacking is unfeasible, and correspondingly C2-symmetric or similar structures are adopted. All the structural data
presented is consistent with a trans influence order at zirconium Me2N > RCH2 > py.
Introduction
Complexes of the amidinate ligand I have an extensive chemis-
try.1–3 In particular, Sita has developed a class of cyclopentadienyl/
amidinate complexes II that support catalysis of the polymerisa-
tion of vinylcyclohexane4 and 1-hexene,5,6 and have potential for
the development of reagents for asymmetric hydrozirconation.7 In
comparison to these amidinates, the related aminopyridinates III
are much less well developed in their catalytic8 and stoichiometric
chemistry.9 Aminopyridinato (APy) complexes of the later transition
metals where the substituent R is relatively small show a tendency
to form bi-10 or polynuclear11,12 complexes. For the early transition
metals, bimetallic structures have also been identified.9a,13 Kempe et
al. have employed aminopyridines such as IV incorporating bulkier
(trimethylsilyl) substituents at the amido N and has synthesised
many complexes including the group 4 systems [M(APy)nX4−n
]
(X = e.g. halide, alkyl, amide).14 Of this type of complex the
[M(APy)2X2] class15,16,20 is arguably the most important because of
its structural similarity to the metallocenes Cp2MX2. Unfortunately,
these compounds are relatively difficult to synthesise without resort-
ing to the use of bis(aminopyridine) proligands.17–19 For example,
treatment of [Zr(NEt2)2Cl2] with aminopyridine IV gave complexes
with one or three (but not two) aminopyridinato ligands, depend-
ing on the substitution of the pyridine. We have previously shown
that despite its similar steric demand to Kempe’s trimethylsilylated
aminopyridinates, III (R = adamantyl, R′ = H) readily formed com-
plexes of the type [M(APy)2X2] (X = Cl, NMe2, CH2Ph, CH2But).20
This suggests that the proton acidity of the parent aminopyridine is
an important factor in determining metal–ligand stoichiometry.
These latter complexes provide a moderately active alkene poly-
merisation system. Also we were surprised to find that the barrier
to inversion of chirality-at-metal in the C2-symmetric complexes
[Zr(APy)2(CH2R)2]20 is as high as ca. 60 kJ mol−1. Hence we were
interested to develop further proligands III (R = alkyl, aryl) for
potential applications in polymer and stereoselective synthesis. In
this paper we describe the synthesis and structural characterisation
of a number of aminopyridines III (R = aryl) and their zirconium
complexes.
plexes of the type [M(APy)2X2]n. The advent of Pd catalysed aryla-
tion of amines22 opens the way for the synthesis of a much wider
range of sterically-demanding aminopyridines than have hitherto
been available from commercial sources.Arange of aminopyridines
(HL1–HL6) was thereby synthesised (Scheme 1).
Scheme 1 Synthesis of N-aryl aminopyridines (conditions; ArNH2, cat.
dppp/[Pd2(dba)3], toluene, 90 °C, 24 h, 60–80%).
Complexes of L1 and L2
Results and discussion
Kempe and Arndt,15 and Polamo and Leskelä9a,21 have used the
t
Treatment of [Zr(NMe2)4], [Zr(CH2Ph)4] and [Zr(CH2 Bu)4] with
two equivalents of HL1 in pentane gave, according to NMR spectra
a mixture of compounds with varying metal to ligand ratios. The use
of three equivalents gave a similar mixture, while four equivalents
of HL1 gave the clean formation of [ZrL14]. Polamo21 reported a haf-
nium complex using the unsubstituted aminopyridine III (R′ = H,
R = Ph) with stoichiometry [M(APy)4]. The 1H NMR spectrum of
aminopyridine III (R′ = H, R = Ph) to synthesise group 4 com-
† Electronic supplementary information (ESI) available: Rotatable 3-D
crystal structure diagrams and NMR spectra. See http://www.rsc.org/
suppdata/dt/b4/b407008a/
T h i s j o u r n a l i s
©
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
D a l t o n T r a n s . , 2 0 0 4 , 2 2 5 7 – 2 2 6 6
2 2 5 7

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Table 1 Experimental data for the X-ray diffraction studies
[ZrL2 ]
[ZrL3 (NMe2)2]
[ZrL4 (NMe2)2]
[ZrL5 (CH2Ph)]
[ZrL6 (NMe2)2]
[ZrL62(CH2Ph)2]
4
2
2
3
2
Molecular formula
Formula weight
C152H200N16Zr2·C5H12
2505.87
C32H42N6Zr
601.94
C34H46N6Zr
629.99
C49H52N6Zr·C5H12
888.33
C34H46N6Zr
629.99
C44H48N4Zr
724.08
Crystal system
Space group
a/Å
b/Å
Orthorhombic
Pna2(1)
42.2168(13)
21.6512(7)
16.5244(5)
90
Monoclinic
P2(1)/n
18.233(5)
9.202(3)
19.792(6)
90
111.862(5)
90
3082.0(15)
4
Monoclinic
P2(1)/c
20.017(3)
11.6567(19)
14.995(2)
90
111.197(4)
90
3262.0(9)
4
Triclinic
P1
Triclinic
P1
Orthorhombic
Pbca
12.1162(15)
17.401(2)
35.707(5)
90
11.43920(10)
13.9372(3)
14.9971(3)
85.4960(10)
89.2130(10)
88.76
2382.88(7)
2
0.273
9.5430(18)
9.681(4)
18.882(4)
98.120(15)
100.776(16)
98.72(3)
1667.8(8)
2
c/Å
/°
/°
/°
90
90
90
90
Cell volume/Å3
Z
15104.0(8)
4
0.190
7528.4(17)
8
0.328
/mm−1
0.387
0.369
0.361
Total reflections
59679
23222
20984
15699
12703
47058
Independent reflections
18707
7661
7912
11236
7899
9457
(Rint = 0.1511)
0.0730, 0.1316
(Rint = 0.1260)
0.0695, 0.1135
(Rint = 0.1393)
0.0632, 0.0905
(Rint = 0.0414)
0.0526, 0.1067
(Rint = 0.0182)
0.0307, 0.0763
(Rint = 0.0343)
0.0371, 0.0817
R1a, wR2b [I > 2(I)]
2
2
a Conventional R = ∑||Fo| − |Fc||/∑|Fo| for observed reflections having Fo2 > 2(Fo ). b wR2 = [∑w(Fo2 − Fc2)2/∑w(Fo )2]1/2 for all data. c GoF = [∑w(Fo2 − Fc2)2/
(no. unique reflns − no. of params)]1/2
Table 2 Selected bond lengths [Å] and angles [°] for [ZrL2 ]
.
4
Zr(1)–N(1)
Zr(1)–N(2)
Zr(1)–N(3)
Zr(1)–N(4)
2.218(6)
2.341(7)
2.228(6)
2.349(7)
Zr(1)–N(5)
Zr(1)–N(6)
Zr(1)–N(7)
Zr(1)–N(8)
2.213(6)
2.372(7)
2.210(7)
2.365(8)
N(1)–Zr(1)–N(2)
N(1)–Zr(1)–N(3)
N(1)–Zr(1)–N(4)
N(1)–Zr(1)–N(6)
N(1)–Zr(1)–N(8)
N(2)–Zr(1)–N(4)
N(2)–Zr(1)–N(6)
N(2)–Zr(1)–N(8)
N(3)–Zr(1)–N(2)
N(3)–Zr(1)–N(4)
N(3)–Zr(1)–N(6)
N(3)–Zr(1)–N(8)
N(4)–Zr(1)–N(6)
N(4)–Zr(1)–N(8)
58.5(3)
86.1(2)
80.5(3)
155.9(3)
76.7(3)
124.5(2)
133.7(2)
75.2(2)
80.9(3)
58.8(3)
77.3(2)
155.5(3)
76.0(2)
133.0(3)
N(5)–Zr(1)–N(1)
N(5)–Zr(1)–N(2)
N(5)–Zr(1)–N(3)
N(5)–Zr(1)–N(4)
N(5)–Zr(1)–N(6)
N(5)–Zr(1)–N(8)
N(7)–Zr(1)–N(1)
N(7)–Zr(1)–N(2)
N(7)–Zr(1)–N(3)
N(7)–Zr(1)–N(4)
N(7)–Zr(1)–N(5)
N(7)–Zr(1)–N(6)
N(7)–Zr(1)–N(8)
N(8)–Zr(1)–N(6)
143.0(3)
85.2(2)
95.5(3)
131.3(3)
57.3(3)
88.1(3)
96.6(3)
132.0(3)
142.4(3)
84.5(3)
103.9(3)
86.4(3)
58.4(3)
123.9(2)
Fig. 1 Thermal ellipsoid plot of the molecular structure of [ZrL2 ] (H
atoms omitted).
4
[ZrL1 ] at 293 K showed one set of aminopyridinato resonances
[ZrL3 (NMe2)2] has adopted an orientation with cis pyridine units
4
2
only, indicating high symmetry or a system in rapid flux on this
at the “back” of the complex and trans to the dimethylamido
co-ligands [N(1)–Zr(1)–N(5) = 150.58(16)° and N(3)–Zr(1)–
N(6) = 152.14(15)°]. Other parameters are comparable with litera-
timescale. The ligand L2 gave a similar complex [ZrL2 ] despite the
4
increased steric bulk. The 1H NMR spectrum of this compound at
t
ture values23 and [ZrL2 ].
293 K showed eight equivalent Bu groups at 1.32 ppm. Some of
4
The reaction of HL3 with [Zr(CH2Ph)4] followed by crystal-
the aryl CH resonances were broadened, probably due to hindered
rotation about the N–Caryl bond since on raising the temperature to
343 K the spectrum sharpened to give the expected four pyridine
and two aryl peaks between 5.95 and 7.29 ppm.
lisation from pentane gave yellow [ZrL3 (CH2Ph)2] in 71% yield.
2
1
The H NMR spectrum at 293 K showed slight broadening of
peaks, particularly the Zr–CH2 resonance at 2.50 ppm. At 333 K
The molecular structure of eight-coordinate [ZrL2 ] was deter-
all the resonances sharpen giving a singlet for the benzyl CH2 at
4
t
2.53 ppm. The neopentyl complex [ZrL3 (CH2 Bu)2] was formed
mined by X-ray crystallography and is shown in Fig. 1, with experi-
mental details and selected bond lengths and angles in Tables 1 and
2. The aminopyridinato ligands in approximately trans positions to
one another are oriented ‘head to tail’ such as to avoid collision of
the bulky arene units. The bond lengths for the Zr–Namide [2.213(6)–
2.228(6) Å] and Zr–Npyridine [2.341(7)–2.372(7) Å] are comparable
to those found by Kempe et al.23 and ourselves,20 despite the high
coordination number.
2
similarly, and in 64% yield. Variable temperature 1H studies showed
similar results to that of the benzyl complex. Single crystals of
t
[ZrL3 (CH2 Bu)2] were analysed by X-ray crystallography, but the
2
relatively poor quality data allowed only partial refinement. The
t
structure elucidated for [ZrL3 (CH2 Bu)2] is depicted in Scheme 2
2
(related molecules are described later in more detail). The unex-
pected presence of an approximate mirror plane containing the two
pyridine rings, and an accompanying arene – interaction motif
explains the symmetry indicated by the NMR spectra. Polamo and
Leskelä have reported a dimeric zirconium dichloride complex that
we have found to exhibit similar – stacking.9a
Complexes of L3
HL3, which contains a 2-methyl substituent at the aryl group, was
treated with [Zr(NMe2)4] to give the yellow complex [ZrL32(NMe2)2]
in 56% yield. Evidently, increasing the steric bulk in the arylamido
ortho position has facilitated some control over metal/ligand stoi-
chiometry. The molecular structure determined by X-ray structure
crystallography (Fig. 2) showed a C2-symmetric complex with
mutually cis amides [N(6)–Zr(1)–N(5) = 100.47°(16)]. In contrast
to the structure of a related dialkyl complex [Zr(APy)2(CH2Ph)2]
for which trans orientation of the pyridine units was observed,
Complexes of L4
The proligand HL4 was synthesised to explore the effect increasing
the size of the single ortho substituent present in HL3. The 1H NMR
spectrum of the subsequent amide complex [ZrL4 (NMe2)2] is con-
2
sistent with the presence of two independent ligands L4 in that two
i
sets of arene and methyl resonances are observed. The Pr methyl
2 2 5 8
D a l t o n T r a n s . , 2 0 0 4 , 2 2 5 7 – 2 2 6 6

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Table 3 Selected bond lengths [Å] and angles [°] for [ZrL3 (NMe2)2]
Table 4 Selected bond lengths [Å] and angles [°] for [ZrL4 (NMe2)2]
2
2
Zr(1)–N(1)
Zr(1)–N(2)
Zr(1)–N(3)
2.398(4)
2.238(4)
2.385(4)
Zr(1)–N(4)
Zr(1)–N(5)
Zr(1)–N(6)
2.262(4)
2.038(4)
2.034(4)
Zr(1)–N(1)
Zr(1)–N(2)
Zr(1)–N(3)
2.369(3)
2.249(3)
2.390(3)
Zr(1)–N(4)
Zr(1)–N(5)
Zr(1)–N(6)
2.258(3)
2.023(4)
2.035(4)
N(2)–Zr(1)–N(1)
N(2)–Zr(1)–N(3)
N(2)–Zr(1)–N(4)
N(3)–Zr(1)–N(1)
N(4)–Zr(1)–N(1)
N(4)–Zr(1)–N(3)
N(5)–Zr(1)–N(1)
N(5)–Zr(1)–N(2)
57.60(14)
98.74(14)
148.19(14)
85.00(13)
96.35(14)
57.76(13)
150.58(16)
93.84(16)
N(5)–Zr(1)–N(3)
N(5)–Zr(1)–N(4)
N(6)–Zr(1)–N(1)
N(6)–Zr(1)–N(2)
N(6)–Zr(1)–N(3)
N(6)–Zr(1)–N(4)
N(6)–Zr(1)–N(5)
93.45(14)
107.64(15)
94.05(15)
104.21(15)
152.14(15)
94.84(15)
100.47(16)
N(1)–Zr(1)–N(3)
N(2)–Zr(1)–N(1)
N(2)–Zr(1)–N(3)
N(2)–Zr(1)–N(4)
N(4)–Zr(1)–N(1)
N(4)–Zr(1)–N(3)
N(5)–Zr(1)–N(1)
N(5)–Zr(1)–N(2)
79.09(10)
57.99(12)
100.28(12)
153.85(12)
101.12(11)
57.42(12)
144.97(14)
90.48(13)
N(5)–Zr(1)–N(3)
N(5)–Zr(1)–N(4)
N(5)–Zr(1)–N(6)
N(6)–Zr(1)–N(1)
N(6)–Zr(1)–N(2)
N(6)–Zr(1)–N(3)
N(6)–Zr(1)–N(4)
93.57(13)
103.45(13)
104.11(15)
98.72(13)
104.24(13)
149.42(14)
93.82(14)
one amide group only suffering from restricted rotation. We postu-
late that the structure in solution is similar to that of [ZrL6 (NMe2)2]
2
(vide infra). Variable temperature NMR studies on this system gave
very complicated spectra and we are only able to conclude that the
complex was undergoing a number of exchange processes between
different diastereomers.
The molecular structure of this complex [ZrL4 (NMe2)2] (Fig. 3)
2
sheds no light on this isomer problem given that it is approximately
C2-symmetric in the solid state. The structure is very similar
to that of [ZrL3 (NMe2)2] (Fig. 2) with cisoid dimethylamides
2
[N(5)–Zr(1)–N(6) = 104.11(15)°]. The pyridine moieties are ap-
proximately trans to the above amides, leaving the unsymmetri-
cally-substituted 2-isopropylphenyl groups projecting to the ‘front’
of the molecule alongside the dimethylamido co-ligands.
Fig. 3 Thermal ellipsoid plot of the molecular structure of [ZrL42(NMe2)2]
(H atoms omitted).
The reaction of HL4 with [Zr(CH2Ph)4] followed by crystallisa-
tion from pentane gave yellow [ZrL4 (CH2Ph)2] in 61% yield. The
2
1H NMR spectrum at 293 K was rather broad, and this situation
was not alleviated at higher temperatures. Treatment of HL4 with
Fig. 2 Molecular structure of [ZrL3 (NMe2)2] (H atoms omitted)
(a) thermal ellipsoid plot and (b) Chem3D representation, viewed along the
approximate C2 axis.
2
t
[Zr(CH2 Bu)4] followed by crystallisation from pentane gave yel-
t
low [ZrL4 (CH2 Bu)2] (49%) which had similar NMR properties to
2
the benzyl complex. On the basis of the results presented later we
propose that these complexes have the -stacked structure such as
t
that shown for [ZrL3 (CH2 Bu)2] in Scheme 2.
2
Zirconium complexes of L5
Treatment of [Zr(NMe2)4] and [Zr(CH2Ph)4] with two equivalents
of HL5 yielded mixtures of complexes, but in this case analysis of
NMR spectra indicated that [ZrL5 X] was the predominant stoichi-
3
ometry. The two complexes (X = NMe2, CH2Ph) were synthesised
Scheme 2 Synthesis of [ZrL3 (CH2But)2] showing the structure with
coplanar pyridine units and -stacked arene groups.
using 3 equivalents of HL5.
2
1H NMR spectra of the benzyl complex [ZrL5 (CH2Ph)] in d2-
3
dichloromethane gave integral ratios showing only one benzyl CH2
singlet, and interestingly two types of aminopyridinato ligand in
the ratio 2:1.
The molecular structure determined by X-ray crystallography
(Fig. 4) is very unusual; for two of the aminopyridinato units, the
bulky mesityl groups are face-to-face parallel and the pyridine rings
region is unusual in that one apparent doublet and one apparent
triplet is observed, however these are interpreted as arising from a
completely overlapping and partially overlapping pair of doublets
respectively. In support of this, each composite resonance correlates
with two 13C resonances in the HMQC spectrum. The iso-propyl
CH groups overlap to give a complex grouping at ca. 3.4 ppm. The
amide NMe2 resonances most surprisingly appear as 3 singlets in
the ratio 3:6:3 at ca. 2.6–3.0 ppm. These spectra are consistent with
are mutually coplanar [Fig. 4(b)]. The presence of this – interac-
t
tion, also proposed for the alkyls [ZrL3 (CH2 Bu)2] (Scheme 2) and
2
[ZrL4 (CH2R)2] (R = tBu, Ph), is rather surprising given the rather
2
D a l t o n T r a n s . , 2 0 0 4 , 2 2 5 7 – 2 2 6 6
2 2 5 9

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Table 5 Selected bond lengths [Å] and angles [°] for [ZrL5 (CH2Ph)]
Table 6 Selected bond lengths [Å] and angles [°] for [ZrL6 (NMe2)2]
2
3
Zr(1)–N(1)
Zr(1)–N(2)
Zr(1)–N(3)
Zr(1)–N(4)
2.209(2)
2.371(2)
2.217(2)
2.314(2)
Zr(1)–N(5)
Zr(1)–N(6)
Zr(1)–C(43)
2.208(2)
2.312(3)
2.297(3)
Zr(1)–N(1)
Zr(1)–N(2)
Zr(1)–N(3)
2.3776(15)
2.1980(16)
2.3254(16)
Zr(1)–N(4)
Zr(1)–N(5)
Zr(1)–N(6)
2.3031(15)
2.0729(16)
2.0230(16)
N(2)–Zr(1)–N(1)
N(2)–Zr(1)–N(3)
N(2)–Zr(1)–N(4)
N(3)–Zr(1)–N(1)
N(4)–Zr(1)–N(1)
N(4)–Zr(1)–N(3)
N(5)–Zr(1)–N(1)
N(5)–Zr(1)–N(2)
58.37(5)
142.45(5)
97.22(5)
88.44(5)
82.25(5)
58.10(5)
89.42(6)
100.64(6)
N(5)–Zr(1)–N(3)
N(5)–Zr(1)–N(4)
N(6)–Zr(1)–N(1)
N(6)–Zr(1)–N(2)
N(6)–Zr(1)–N(3)
N(6)–Zr(1)–N(4)
N(6)–Zr(1)–N(5)
95.63(6)
152.44(6)
152.60(6)
94.26(6)
116.88(6)
101.71(6)
97.73(7)
N(1)–Zr(1)–N(2)
N(1)–Zr(1)–N(3)
N(1)–Zr(1)–N(4)
N(1)–Zr(1)–N(6)
N(3)–Zr(1)–N(2)
N(3)–Zr(1)–N(4)
N(3)–Zr(1)–N(6)
N(4)–Zr(1)–N(2)
58.19(8)
101.50(8)
87.54(8)
88.00(9)
134.92(8)
59.12(8)
146.05(9)
78.86(8)
N(5)–Zr(1)–N(1)
N(5)–Zr(1)–N(2)
N(5)–Zr(1)–N(3)
N(5)–Zr(1)–N(4)
N(5)–Zr(1)–N(6)
N(6)–Zr(1)–N(2)
N(6)–Zr(1)–N(4)
106.74(9)
135.13(9)
87.30(9)
145.83(9)
58.80(9)
77.63(9)
154.69(9)
Zirconium complexes of L6
heavily substituted aryl rings. The rings are aligned almost face-
to-face rather than the frequently observed offset structure (vide
infra).24 The distance between mesityl ring centroids is ca. 3.69 Å,
perhaps at the upper end of the expected range, but the shortest
inter-ligand distance [C(20)–C(34)] is ca. 3.43 Å. The third ami-
nopyridinato unit and the benzyl ligand occupy the remaining
coplanar coordination sites in the open face of the complex thereby
generated.
The molecular structure of [ZrL5 (CH2Ph)] above indicated that a
3
6-methyl group on the pyridine ring would point into the area oc-
cupied by the third ligand in that complex and therefore possibly
promote the formation of [M(APy)2X2] compounds.
The reaction of HL6 with [Zr(NMe2)4] followed by crystallisation
from toluene gave yellow [ZrL6 (NMe2)2] in 74% yield. H NMR
1
2
spectra of this complex indicated that the two aminopyridinato li-
gands are spectroscopically equivalent in the range 193–298 K. An
X-ray crystallographic study however indicated a rather unusual
structure (Fig. 5); the aminopyridinato ligands are “head to tail”,
i.e. one ligand presents its amido N atom and one its pyridine ring
toward the “front” of the complex. Hence one dimethylamido unit is
trans to a pyridine [N(6)–Zr(1)–N(1) = 152.60(6)°] and the other is
trans to arylamido [N(5)–Zr(1)–N(4) = 152.44(6)°]. The dimethyl-
amido units are mutually cis [N(6)–Zr(1)–N(5) = 97.73(7)°].
Interestingly, steric compression between C(33) and the mesityl
ring C(7)–C(14) appears to have led to an unusually large angle
Zr(1)–N(6)–C(33) [143.09(14)°]. Angle Zr(1)–N(6)–C(34) is cor-
respondingly small at [105.35(13)°]. A similar phenomenon has
been reported by Kempe et al.23
Fig. 5 Thermal ellipsoid plot of the molecular structure of [ZrL62(NMe2)2]
(H atoms omitted).
The adoption of this rather sterically compressed structure is
surprising given the C2-symmetric structure of [ZrL3 (NMe2)2]
2
(Fig. 2); evidently the situation is rather finely balanced. For the
overall structure of [ZrL6 (NMe2)2] we propose that the apparent
Fig. 4 Molecular structure of [ZrL5 (CH2Ph)] (H atoms omitted);
2
3
symmetry indicated by the NMR spectra results from the complex
being in rapid flux on the 1H NMR chemical shift timescale between
structures such as that in Fig. 5 rather than there being a more sym-
metrical structure (i.e. C2-symmetry) adopted in solution.
(a) thermal ellipsoid plot and (b) Chem3D projection showing the parallel
pyridine units and arene -stacking motif.
t
In contrast to the above, reaction of [Zr(CH2 Bu)4] with two
equivalents of HL5 yielded the desired [ZrL5 (CH2 Bu)2] in 69%
Reaction of HL6 with [Zr(CH2Ph)4] gave the yellow, heat and
t
2
yield. In the 1H NMR spectrum, the presence of a singlet for the neo-
pentyl CH2 group at 1.88 is consistent with the presence of a mirror
plane (a structure similar to those in Scheme 2 and Fig. 4) or with a
C2-symmetric compound in rapid exchange between other structural
isomers on the 1H-NMR chemical shift timescale.
light sensitive product [ZrL6 (CH2Ph)2] in 65% yield. The 1H
2
NMR spectrum, which indicated the presence of two equivalent
aminopyridinato ligands, contains rather broad peaks including a
singlet CH2 peak at 2.95 ppm for two benzyl ligands. The spectra
showed little change except further broadening of all peaks down to
2 2 6 0
D a l t o n T r a n s . , 2 0 0 4 , 2 2 5 7 – 2 2 6 6

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Table 7 Selected bond lengths [Å] and angles [°] for [ZrL6 (CH2Ph)2]
2
Zr(1)–N(1)
Zr(1)–N(2)
Zr(1)–N(3)
2.3747(16)
2.1667(16)
2.3258(16)
Zr(1)–N(4)
Zr(1)–C(31)
Zr(1)–C(38)
2.1665(15)
2.289(2)
2.285(2)
N(2)–Zr(1)–N(1)
N(2)–Zr(1)–N(3)
N(3)–Zr(1)–N(1)
N(4)–Zr(1)–N(1)
58.81(6)
150.01(6)
151.15(6)
148.98(6)
N(4)–Zr(1)–N(2)
N(4)–Zr(1)–N(3)
C(38)–Zr(1)–C(31)
90.19(6)
59.83(6)
121.75(8)
193 K. Fig. 6 and Fig. 7 show the X-ray crystallographic structure
of [ZrL6 (CH2Ph)2], with coplanar pyridines and parallel mesityl
2
groups as for [ZrL5 (CH2Ph)] (Fig. 4). The distance between cen-
3
troids of the mesityl rings is ca. 3.65 Å with the shortest [C(7)–
C(22)] contact of ca. 3.44 Å. It is also apparent from Fig. 7 that as
a result of this interaction the two aminopyridinato units are pulled
together toward one side of the Zr(N–C–N)2 coordination plane; the
inter-ligand distance between pyridine methyl group H atoms is >
4 Å, indicating that steric compression at this side of the coordina-
tion plane is not responsible for the distortion. The benzyl ligand
CH2 carbon atoms are distorted from a mutually trans arrangement
[C(38)–Zr(1)–C(31) = 121.75°(8)] at least partially as a result of
the above distortion, and also as a result of the steric demand of the
mesityl 2,6-substituents. The benzyl phenyl groups are rotated back
toward the mesityl substituents in order to avoid the pyridine meth-
yls. Overall, given the strong possibility that the above structural
features will lead to restricted rotation of e.g. the benzyl groups it
Fig. 7 Chem3D representations of [ZrL6 (CH2Ph)2] (a) showing the co-
planarity of pyridine units and (b) parallel orientation of mesityl groups;
benzyl ligands in the latter removed for clarity.
2
1
is not surprising that the H NMR spectrum contains rather broad
peaks. This also goes some way to explaining the similar NMR
spectra for [ZrL5 (CH2But)2] above.
2
There seems to be a pattern emerging (i) that alkyls20 adopt struc-
ture similar to V (which in the case R′ = aryl allows formation of
the arene – interaction) and (ii) that the amides adopt a structure
similar to VI (which in the case R′ = aryl does not lead to a –
interaction simply because the arene units are not appropriately
oriented). This structural pattern leads us to the conclusion that the
trans influence at zirconium for the ligands used here is in the order
Me2N >Ar(Py)N > PhCH2 > py; the strongest trans influence ligand
is to be found opposite py. In particular for the series of compounds
described here, dialkylamido avoids being trans to dialkylamido.‡
While the ordering of aminopyridinate amido unit [Ar(Py)N] lower
than dialkyl amido is not surprising, given that in the former the
negative charge is substantially delocalised, the ordering of alkyl
lower than both amido units is perhaps unexpected. We will address
this issue in future studies.
Fig. 6 Thermalellipsoidplotofthemolecularstructureof[ZrL62(CH2Ph)2]
(H atoms omitted).
In contrast to the above reaction of HL6 with [Zr(CH2Ph)4], the
reaction with [Zr(CH2But)4] gave only [ZrL6(CH2But)3]. Presum-
ably, this complex is too sterically crowded to react with a second
aminopyridine to give the desired [M(APy)2X2].
Conclusions
Experimental details
General comments
While we have previously shown that certain alkylaminopyridine
proligands readily form complexes [Zr(APy)2X2] with well-defined
C2-symmetric structures,20 the arylaminopyridines described here
present considerable structural diversity. Firstly, significant steric
bulk in the aryl substituent, and more importantly a 6-methyl substi-
tution at the pyridine, is required to furnish control of metal/ligand
stoichiometry. Secondly, the structures are highly dependent on the
identity of the co-ligands X; the amido compounds (X = NMe2)
give cis-C2-symmetric or similar complexes while the alkyls
(X = CH2Ph, CH2But) adopt the unexpected -stacked C2v struc-
tures with an almost trans arrangement of X. Thirdly, there are a
number of discrepancies between the structures adopted in the solid
state and those in solution, especially for the amido compounds.
Evidently the factors that control structure in these compounds
are rather finely balanced, and apart from the formation of the -
stacked motif in the alkyls, are rather difficult to predict.
Where necessary, procedures were carried out under an inert atmo-
sphere of argon by using a dual manifold vacuum/argon line and
standard Schlenk techniques, or in an MBraun dry box. Solvents
were dried by refluxing for three days under dinitrogen over the ap-
propriate drying agents (sodium for toluene; potassium for THF and
benzene; sodium–potassium alloy for diethyl ether, petroleum ether,
and pentane; calcium hydride for dichloromethane) and degassed
before use. Solvents were stored in glass ampoules under argon. All
glassware and cannulae were stored in an oven (>373 K) and flame
dried immediately prior to use. Most chemicals and reagents were
purchased from eitherAldrich Chemical Company,Acros Chemical
‡ The structure of [ZrL6 (NMe2)2] is a minor exception in that it suggests
Me2N ~ Ar(Py)N [one py (the weakest trans ligand) is trans to dimethyl-
amido and the other is trans to arylamido].
2
D a l t o n T r a n s . , 2 0 0 4 , 2 2 5 7 – 2 2 6 6
2 2 6 1

View Article Online
Company, Lancaster or Strem and used without further purifica-
tion. Deuterated solvents were freeze–thaw degassed and dried by
heating to their normal boiling points over potassium (or calcium
hydride for d2-dichloromethane) in vacuo for three days before
vacuum distilling (trap-to-trap) to a clean, dry Young’s tap ampoule
and being stored in the dry box. Deuterated chloroform was dried in
the bottle over molecular sieves (4 Å).
NMR spectra were recorded on Bruker ACF-250, DPX-300,
DPX-400, AV-400 and DRX-500 spectrometers and the spectra
were referenced internally using residual protio solvent resonances
relative to tetramethylsilane ( = 0 ppm). EI/CI mass spectra were
obtained on a VG Autospec mass spectrometer. Infrared spectra
were obtained either as Nujol mulls using a Perkin-Elmer Paragon
1000 FTIR spectrometer, or directly using an Avatar 320 FTIR
instrument. Elemental analyses were performed by Warwick
Analytical Services. Carbon analysis for these compounds were
consistently low by ca. 1%, despite the use of high combustion
temperatures and combustion aids. This can be ascribed to carbide
formation.25 NMR spectra are deposited as ESI† as evidence of
purity. Flash chromatography was performed with a FlashMaster
Personal chromatography system and a selection of pre-packed dis-
posable columns. Thin-layer chromatography was performed using
Merck 0.25 mm silica layer foil-backed plates.
Anal. Calcd. for C19H26N2: C, 80.80; H, 9.28; N, 9.92. Found: C,
80.93; H, 9.25; N, 9.89.
MS (EI) m/z 282 (M+)
(2,4-Dimethylphenyl)(6-methylpyridin-2-yl)amine HL3. Tol-
uene (50 mL) was added to a Schlenk vessel charged with 2,4-di-
methylaniline (2.0 g, 17 mmol), 2-bromo-6-methylpyridine (3.0 g,
17.4 mmol), [Pd2(dba)3] (200 mg, 0.22 mmol), dppp (200 mg,
0.48 mmol) and NaOBut (2.2 g, 22.9 mmol). The resulting deep
red/brown mixture was heated overnight at 90 °C with stirring.
After cooling to ambient temperature the solution was passed
though silica and the silica was washed with diethyl ether (75 mL).
The resultant red mixture was treated with activated charcoal and
passed through MgSO4. The pale yellow solution was then concen-
trated in vacuo. The resulting white crystalline product was isolated
by filtration, washed with cold pentane and dried in vacuo. (yield
2.15 g, 61%).
1H NMR (293 K, d6-benzene):  2.02 (s, 3H, Ar–CH3), 2.16
(s, 3H, Ar–CH3), 2.39 (s, 3H, Py–CH3), 6.32 (d, 1H, Py–CH,
3JHH = 8 Hz), 6.36 (d, 1H, Py–CH, 3JHH = 7 Hz), 6.74 (s, 1H, NH),
6.88 (d + s, 2H, Ar–CH), 7.04 (t, 1H, Py–CH, 3JHH = 8 Hz), 7.28 (d,
1H, Ar–CH, 3JHH = 8 Hz).
13C{1H} NMR (293 K d6-benzene):  18.2 (Ar–CH3), 21.3
(Ar–CH3), 24.8 (Py–CH3), 104.2 (Py–CH), 113.8 (Py–CH), 125.2
(Ar–CH), 128.0 (Ar–CH), 132.3 (Ar–CH), 133.1 (Ar–Cq), 134.5
(Ar–Cq), 137.1 (Ar–Cq), 138.3 (Py–CH), 158.1 (Py–Cq).
IR (nujol, cm−1): 3172 (NH), 2728, 1595, 1583, 1519, 1333,
1265, 1238, 1224, 1156, 1123, 1092, 1030, 992, 880, 802, 787,
723, 616.
(3,5-Dimethylphenyl)pyridin-2-ylamine HL1. Toluene (30 mL)
was added to a Schlenk vessel charged with 3,5-dimethylaniline
(2.02 g, 16.67 mmol), 2-bromopyridine (2.08 g, 13.16 mmol),
[Pd2(dba)3] (204 mg, 0.22 mmol), dppp (204 mg, 0.49 mmol)
and NaOBut (1.73 g, 18.00 mmol). The resulting deep red/brown
mixture was heated overnight at 90 °C with stirring. After cooling
to ambient temperature the solution was passed though silica and
the silica was washed with diethyl ether (75 mL). The resultant red
mixture was treated with activated charcoal overnight and passed
through MgSO4. The pale yellow solution was then concentrated
in vacuo. The resulting white product was isolated by filtration and
washed with cold pentane (yield 2.57 g, 78%).
Anal. Calcd. for C14H16N2: C, 79.21; H, 7.60; N, 13.20. Found: C,
79.28, H, 7.57, N, 12.81.
MS (EI) m/z 212 (100%, M+), 197 (M+ − CH3).
(2-Isopropylphenyl)(6-methylpyridin-2-yl)amine HL4. Tolu-
ene (30 mL) was added to a Schlenk vessel charged with 2-isopro-
pylaniline (2.25 g, 16.7 mmol), 2-bromo-6-methylpyridine (3.0 g,
17.4 mmol), [Pd2(dba)3] (200 mg, 0.22 mmol), dppp (200 mg,
0.49 mmol) and NaOBut (2.25 g, 23.4 mmol). The resulting deep
red/brown mixture was heated overnight at 90 °C with stirring.
After cooling to ambient temperature the solution was passed
though silica and the silica was washed with diethyl ether (75 mL).
The resultant red mixture was treated with activated charcoal and
passed through MgSO4. The pale yellow solution was then concen-
trated in vacuo. The resulting white crystalline product was isolated
by filtration and washed with cold pentane (yield 2.18 g, 58%).
1H NMR (293 K, d6-benzene)  1.04 (s, 3H, iPr–CH3), 1.06 (s, 3H,
1H NMR (293 K, d6-benzene)  2.17 (s, 6H, CH3), 6.41 (t, 1H,
3
Py–CH, JHH = 8 Hz), 6.61 (s, 1H, Ar–CH), 6.64 (d, 1H, Py–CH,
3JHH = 8 Hz), 6.67 (br s, 1H, NH), 6.92 (s, 2H, Ar–CH), 7.06 (t, 1H,
Py–CH, 3JHH = 8 Hz), 8.31 (d, 1H Py–CH, 3JHH = 8 Hz).
13C{1H} NMR (293 K d6-benzene)  21.8 (Ar–CH3), 108.8
(Py–CH), 115.0 (Py–CH), 118.9 (Ar–CH), 125.0 (Ar–CH), 137.7
(Py–CH), 139.1 (Ar–CCH3), 149.2 (Py–CH), 151.5 (Ar–CN), 157.4
(Py–NCN).
IR (thin film, cm−1) 3228, 3012, 2914, 1579, 1530, 1468, 1439,
1334, 1150, 989, 833, 767.
Anal. Calcd. for C13H14N2: C, 78.75; H, 7.12; N, 14.13. Found: C,
78.78; H, 7.12; N, 14.25.
MS (EI) m/z 197 (M+)
i
3
iPr–CH3), 2.40 (s, 3H, Py–CH3), 3.08 (heptet, 1H, Pr–CH, JHH
=
7 Hz), 7.02 (t, 1H, Py–H, 3JHH = 8 Hz), 7.05–7.35 (m, 4H, Ar–CH),
7.15 (s, 1H, NH).
13C{1H} NMR (293 K d6-benzene)  23.6 (iPr–CH3), 24.7
(Py–CH3), 28.5 (iPr–CH), 104.0 (Py–CH), 113.8 (Py–CH), 126.3
(Ar–CH), 126.7(Ar–CH), 126.9 (Ar–CH), 127.2 (Ar–CH), 138.4
(Py–CH), 144.5 (Ar–CqN), 158.0 (Py–CqN), 158.8 (Py–NCqN).
IR (nujol, cm−1): 3188, 1591, 1520, 1487, 1338, 1280, 1262,
1235, 1158, 1087, 1033, 990, 780, 759, 723, 638.
Anal. Calcd. for C15H18N2: C, 79.61; H, 8.02; N, 12.38. Found: C,
79.47; H, 7.98; N, 12.22.
(3,5-Di-tert-butylphenyl)pyridin-2-ylamine HL2. Toluene
(30 mL) was added to a Schlenk vessel charged with 3,5-di-
tert-butylaniline (2.0 g, 9.74 mmol), 2-bromopyridine (1.6 g,
10.13 mmol), [Pd2(dba)3] (200 mg, 0.22 mmol), dppp (200 mg,
0.49 mmol) and NaOBut (1.3 g, 13.53 mmol). The resulting deep
red/brown mixture was heated overnight at 90 °C with stirring.
After cooling to ambient temperature the solution was passed
though silica and the silica was washed with diethyl ether (75 mL).
The resultant red mixture was stirred with activated charcoal over-
night and passed through MgSO4. The pale yellow solution was then
concentrated in vacuo. The resulting yellow product was isolated by
filtration and washed with cold pentane (yield 2.04 g, 74%).
1H NMR (293 K, d6-benzene)  1.34 (s, 18H, tBu), 6.42 (m, 1H,
Py–CH), 6.79 (d, 1H, Py–CH, 3JHH = 8 Hz), 7.09 (m, 1H, Py–CH),
7.30 (m, 3H, Ar–CH), 7.47 (br s, 1H, NH), 8.34 (m, 1H, Py–CH).
13C{1H} NMR (293 K d6-benzene)  31.6 (tBu–CH3), 35.0
(tBu–Cq), 107.8 (Py–CH), 114.5 (Py–CH), 116.0 (Ar–CH), 117.1
(Ar–CH), 137.4 (Py–CH), 140.8 (tBu Ar–Cq), 149.0 (Py–CH),
152.0 (Ar–CqN), 157.5 (NCqN).
MS (EI) m/z 226 (90%, M+).
Pyridin-2-yl(2,4,6-trimethylphenyl)amine HL5. Toluene
(30 mL) was added to a Schlenk vessel charged with 2,4,6-trimethyl-
aniline (2.6 g, 19.0 mmol), 2-bromopyridine (3.0 g, 19.0 mmol),
[Pd2(dba)3] (200 mg, 0.11 mmol), dppp (200 mg, 0.25 mmol) and
NaOBut (2.6 g, 26.5 mmol). The resulting deep red/brown mixture
was heated overnight at 90 °C with stirring.After cooling to ambient
temperature the solution was passed though silica and the silica was
washed with diethyl ether (75 mL). The resultant red mixture was
treated with activated charcoal and passed through MgSO4. The pale
yellow solution was then concentrated in vacuo. The resulting white
crystalline product was isolated by filtration and washed with cold
pentane (yield 2.00 g, 51%).
IR (DCM layer, cm−1) 2961 (NH), 1582, 1537, 1468, 1431, 1333,
1247, 1153, 995, 768, 712.
2 2 6 2
D a l t o n T r a n s . , 2 0 0 4 , 2 2 5 7 – 2 2 6 6

View Article Online
1H NMR (293 K, d6-benzene)  2.17 (s, 6H,Ar–CH3), 2.20 (s, 3H,
Ar–CH3), 5.96 (d, 1H, Py–CH, JHH = 8 Hz), 6.32 (t, 1H, Py–CH,
13C{1H} NMR (293 K d6-benzene)  31.9 (tBu–CH3), 35.0
(tBu–Cq), 105.7 (Py–CH), 115.7 (Ar–CH), 117.4 (Ar–CH), 119.9
(Py–CH), 139.1 (Py–CH), 143.5 (Py–CH), 148.6 (Ar–CqN), 151.6
(NCqN).
1H NMR (343 K, d6-benzene)  1.32 (s, 72H, tBu–CH3), 5.95 (br
t, 4H, Py–CH, 3JHH = 6 Hz), 6.28 (d, 4H, Py–CH, 3JHH = 8 Hz), 6.73
(s, 8H, Ar–CH), 6.94 (br t, 4H, Py–CH, 3JHH = 7 Hz), 7.14 (br d, 4H,
Py–CH, 3JHH = 4 Hz), 7.29 (s, 4H, Ar–CH).
3
3JHH = 8 Hz), 6.84 (s, 2H, Ar–H), 6.99 (t, 1H, Py–CH, 3JHH = 8 Hz),
7.48 (s, 1H, NH), 8.15 (d, 1H, Py–CH, 3JHH = 8 Hz).
13C{1H} NMR (293 K d6-benzene)  18.7 (Ar–CH3), 21.4
(Ar–CH3), 105.8 (Py–CH), 113.7 (Py–CH), 129.9 (Ar–CH), 135.3
(Ar–Cq), 136.5 (Ar–CN), 137.3 (Ar–Cq), 138.1 (Py–CH), 149.2
(Py–CH) 159.6 (Py–NCN).
IR (nujol, cm−1): 3154, 3088, 1594, 1575, 1518, 1325, 1292,
1252, 1241, 1227, 1152, 1100, 1034, 1011, 993, 852, 819,
697, 614.
Anal. Calcd. for C76H100N8Zr: C, 75.01; H, 8.28; N, 9.21. Found:
C, 74.06; H, 8.30; N, 8.81.
MS (EI) m/z 1215 (M+)
Anal. Calcd. for C14H16N2: C, 79.21; H, 7.60; N, 13.20. Found: C,
79.24; H, 7.58; N, 13.08.
[ZrL32(NMe2)2]. Toluene (20 mL) was added to a Schlenk vessel
charged with HL3 (250 mg, 1.2 mmol) and [Zr(NMe2)4] (158 mg,
0.6 mmol). The reaction mixture was stirred for 1 h at ambient tem-
perature under argon. The solvent was removed in vacuo to give a
yellow solid. The solid was then dissolved in pentane (10 mL) and
the solution was filtered.After cooling to −30 °C overnight a yellow
crystalline product was isolated by filtration (yield 168 mg, 56%).
1H NMR (293 K, d6-benzene)  2.32 (s, 6H, Py–CH3), 2.39 (s,
6H, Ar–CH3), 2.45 (s, 6H, Ar–CH3), 3.15 (s, 12H, NMe), 5.96 (m
(d + d), 4H, Py–CH), 6.94 (t, 2H, Py–CH, 3JHH = 7 Hz), 7.12–7.30
(m, 6H, Ar–CH).
13C{1H} NMR (293 K d6-benzene)  17.1 (Py–CH3), 19.6
(Ar–CH3), 21.2 (Ar–CH3), 41.3 (NMe), 101.7 (Py–CH), 107.4
(Py–CH), 124.5 (Ar–CH), 126.2 (Ar–CH), 130.7 (Ar–CH), 131.5
(Ar–C), 131.9 (Ar–C). 138.7 (Py–CH), 143.3 (Ar–Cq–N), 152.8
(Py–NCqN), 166.9 (pyridine-Cq–CH3).
MS (EI) m/z 600 (100%, M+), 556 (M+ − NMe2), 512
(M+ − 2NMe2), 301 (ZrL3).
MS (EI) m/z 212 (M+), 197 (M+ − CH3).
(6-Methylpyridin-2-yl)(2,4,6-trimethylphenyl)amine HL6.
Toluene (30 mL) was added to a Schlenk vessel charged with 2,4,6-
trimethylaniline (1.0 g, 7.5 mmol), 2-bromo-6-methylpyridine
(1.0 g, 5.9 mmol), [Pd2(dba)3] (101 mg, 0.11 mmol), dppp (102 mg,
0.25 mmol) and NaOBut (0.85 g, 8.9 mmol). The resulting deep red/
brown mixture was heated overnight at 100 °C with stirring. After
cooling to ambient temperature diethyl ether (50 mL) was added.
The resultant dark red mixture was washed with brine (2 × 30 ml),
dried over MgSO4 and concentrated in vacuo. The resulting white
product was precipitated by trituration with n-hexane from the ini-
tial yellow oil (yield 0.78 g, 59%).
1H NMR (293 K, d6-benzene)  2.18 (s, 6H,Ar–CH3), 2.30 (s, 3H,
Ar–CH3), 2.40 (s, 3H, Py–CH3), 5.75 (d, 1H, Py–CH, 3JHH = 7 Hz),
3
6.05 (s, 1H, NH), 6.47 (d, 1H, Py–CH, JHH = 7 Hz), 6.94 (s, 2H,
Ar–CH), 7.23 (t, 1H, Py–CH, 3JHH = 8 Hz).
13C{1H} NMR (293 K d6-benzene)  18.7 (Ar–CH3), 21.3
(Ar–CH3), 24.7 (Ar–CH3), 102.6 (Py–CH), 113.3 (Py–CH), 129.6
(Ar–CH), 134.3 (Ar–Cq), 136.7 (Ar–CqN), 137.1 (Ar–Cq), 138.5
(Py–CH), 157.6 (Py–Cq), 158.0 (Py–NCqN).
Anal. Calcd. for C32H42N6Zr: C, 63.85; H, 7.03; N, 13.96. Found:
C, 62.93; H, 6.91; N, 13.72.
[ZrL3 (CH2Ph)2]. Toluene (20 mL) was added to a Schlenk
2
vessel charged with HL3 (300 mg, 1.4 mmol) and [Zr(CH2Ph)4]
(322 mg, 0.86 mmol). The reaction mixture was stirred overnight at
ambient temperature, under argon and in the absence of light. The
solvent was removed under reduced pressure. The resulting yellow
solid was redissolved in pentane and the solution filtered and con-
centrated under reduced pressure. Upon cooling to −4 °C a yellow
crystalline product was obtained (yield 379 mg, 71%).
IR (nujol, cm−1): 3189, 2728, 1594, 1582, 1515, 1456, 1377,
1335, 1261, 1234, 1154, 1092, 1033, 990, 860, 820, 788, 722, 621.
Anal. Calcd. for C15H18N2: C, 79.61; H, 8.02; N, 12.38. Found: C,
79.55; H, 8.01; N, 12.40.
MS (EI) m/z 226 (100%, M+), 211 (M+ − CH3).
[ZrL14]. Pentane (20 mL) was added to a Schlenk vessel charged
t
with HL1 (250 mg, 1.27 mmol) and [Zr(CH2 Bu)4] (120 mg,
1H NMR (293 K, d6-benzene)  1.85 (s, 6H, Ar–CH3), 2.08 (s, 6H,
Py–CH3), 2.19 (s, 6H, Ar–CH3), 2.50 (br s, 4H, Bn–CH2), 5.52 (d,
2H, Py–CH, 3JHH = 7 Hz), 5.96 (d, 2H, Py–CH, 3JHH = 7 Hz), 6.31 (d,
2H,Ar–CH, 3JHH = 8 Hz), 6.87–6.82 (m, 8H,Ar–CH + Py–CH), 7.05
(d, 4H, Bn–CH, 3JHH = 7 Hz), 7.16 (t, 4H, Bn–CH, 3JHH = 7 Hz).
13C{1H} NMR (293 K d6-benzene)  18.0 (Ar–CH3), 21.1
(Ar–CH3), 24.6 (Py–CH3), 104.0 (Py–CH), 113.7 (Py–CH), 124.9
(Ar–CH), 127.8 (Ar–CH), 132.1 (Ar–CH), 132.8 (Ar–Cq), 134.3
(Ar–Cq), 137.0 (Ar–CqN), 138.1 (Py–CH), 157.9 (Py–CqN).
1H NMR (333 K, d6-benzene)  1.86 (s, 6H, Ar–CH3), 2.13 (s,
6H, Py–CH3), 2.19 (s, 6H, Ar–CH3), 2.53 (s, 4H, Bn–CH2), 5.51 (d,
2H, Py–CH, 3JHH = 7 Hz), 5.99 (d, 2H, Py–CH, 3JHH = 7 Hz), 6.33
0.32 mmol). The reaction mixture was stirred overnight at ambient
temperature, under argon and in the absence of light. The solu-
tion was then filtered and concentrated under reduced pressure.
Upon cooling to −4 °C a yellow precipitate was obtained (yield
608 mg, 56%).
1H NMR (293 K, d6-benzene)  2.24 (s, 24H, Ar–CH3), 5.93 (t,
4H, Py–CH, 3JHH = 8 Hz), 6.38 (d, 4H, Py–CH, 3JHH = 8 Hz), 6.51
3
(s, 8H, Ar–CH), 6.72 (s, 4H, Ar–CH), 6.83 (t, 4H, Py–CH, JHH
=
8 Hz), 7.08 (d, 4H, Py–CH, 3JHH = 8 Hz).
13C{1H} NMR (293 K d6-benzene)  21.8 (Ar–CH3), 106.5
(Py–CH), 109.0 (Py–CH), 123.2 (Ar–CH), 125.2 (Ar–CH), 138.7
(Ar–CCH3), 139.4 (Py–CH), 143.5 (Py–CH), 149.2 (Ar–CN), 171.1
(Py–NCN).
3
(d, 2H, Ar–CH, JHH = 6 Hz), (m (s + d + t), 6H, Ar–CH (s + d),
Bn–CH (t)), 6.86 (t, 2H, Py–CH, 3JHH = 7 Hz), 7.01 (d, 4H, Bn–CH,
3JHH = 6 Hz), 7.12 (t, 4H, Bn–CH, 3JHH = 6 Hz).
13C{1H} NMR (333 K d6-benzene)  18.6 (Ar–CH3), 21.5
(Ar–CH3), 23.1 (Py–CH3), 75.9 (Bn–CH2), 103.8 (Py–CH), 111.7
(Py–CH), 122.7 (Bn–CH), 127.0 (Ar–CH), 128.3 (Bn–CH), 130.0
(Bn–CH), 132.2 (Ar–CH), 134.0 (Ar–Cq), 134.5 (Ar–Cq), 141.2
(Bn–Cq), 142.0 (Py–CH), 144.6 (Ar–CqN), 154.9 (Py–CqN), 170.0
(Py–NCqN).
Anal. Calcd. for C52H52N8Zr: C, 70.95; H, 5.95; N, 12.73. Found:
C, 69.87; H, 5.90; N, 12.19.
MS (EI) m/z 878 (M+)
[ZrL24]. Toluene (20 mL) was added to a Schlenk vessel charged
t
with HL2 (500 mg, 1.77 mmol) and [Zr(CH2 Bu)4] (170 mg,
0.45 mmol). The reaction mixture was stirred overnight at ambient
temperature, under argon and in the absence of light. The solution
was then filtered and the solvent removed under reduced pressure.
The resulting yellow solid was then redissolved in a minimum of
diethyl ether. Upon cooling to −4 °C a yellow crystalline product
was obtained (yield 1.13 g, 52%).
1H NMR (293 K, d6-benzene)  1.32 (s, 72H, tBu–CH3), 5.97 (br
s, 4H, Py–CH), 6.35 (d, 4H, Py–CH, 3JHH = 9 Hz), 6.70 (br m, 8H,
Ar–CH), 6.91 (br m, 4H, Py–CH), 7.09 (br m, 4H, Py–CH), 7.33
(s, 4H, Ar–CH).
Anal. Calcd. for C42H44N4Zr: C, 72.47; H, 6.37; N, 8.05. Found:
C, 71.55, H, 6.46, N, 7.87.
MS (EI) m/z 605 (M+ − CH2Ph), 514 (M+ − 2 × CH2Ph), 303
(ZrL3).
t
[ZrL3 (CH2 Bu)2]. Pentane (20 mL) was added to a Schlenk
2
vessel charged with HL3 (300 mg, 1.4 mmol) and [Zr(CH2 Bu)4]
t
(266 mg, 0.7 mmol). The reaction mixture was stirred overnight at
ambient temperature, under argon and in the absence of light. The
D a l t o n T r a n s . , 2 0 0 4 , 2 2 5 7 – 2 2 6 6
2 2 6 3

View Article Online
t
yellow solution was filtered and concentrated under reduced pres-
sure to 15 mL. Upon cooling to −4 °C a yellow crystalline product
was obtained (yield 298 mg, 64%).
[ZrL4 (CH2 Bu)2]. Toluene (20 mL) was added to a Schlenk
2
vessel charged with HL4 (200 mg, 0.88 mmol) and [Zr(CH2 Bu)4]
t
(166 mg, 0.44 mmol). The reaction mixture was stirred overnight at
ambient temperature under argon. The solvent was removed under
reduced pressure to give a yellow solid. The solid was then dis-
solved in pentane (10 mL) and the solution filtered. The solvent was
then removed under reduced pressure to give a yellow solid (yield
295 mg, 49%).
1H NMR (343 K, d6-benzene)  1.08 (s, 18H, Np–tBu), 1.29 (br
s, 6H, Pr–CH3), 1.78 (s, 4H, Np–CH2), 2.27 (br s, 6H, Py–CH3),
3.77 (br sept, 2H, iPr–CH), 5.74 (d, 2H, Py–CH, 3JHH = 7 Hz), 5.93
(d, 2H, Py–CH, JHH = 7 Hz), 6.85 (t, 2H, Py–CH, JHH = 7 Hz),
7.13–7.17 (m, 6H, Ar–CH), 7.36–7.38 (m, 2H, Ar–CH).
13C{1H} NMR (343 K d6-benzene)  22.6 (Py–CH3), 27.9
(iPr–CH3), 35.0 (Np–tBu), 103.8 (Py–CH), 110.8 (Py–CH), 125.7
(Ar–CH), 127.0 (Ar–CH), 127.2 (Ar–CH), 141.5 (Py–CH), 145.0
(Ar–CqN), 153.9 (Py–Cq), 170.6 (Py–NCqN).
Anal. Calcd. for C40H56N4Zr: C, 70.23; H, 8.25; N, 8.19. Found:
C, 69.85; H, 8.05; N, 7.61.
MS (EI) m/z 613 (M+ − CH2 Bu), 542 (M+ − 2 × CH2 Bu), 317
1H NMR (293 K, d6-benzene)  1.20 (s, 18H, Np–tBu), 1.75 (br s,
4H, Np–CH2), 2.21 (s, 6H, Ar–CH3), 2.27 (br s, Ar–CH3), 2.43 (br
s, 6H, Py–CH3), 5.62 (d, Py–CH, 3JHH = 4 Hz), 5.95 (d, 2H, Py–CH,
3JHH = 4 Hz), 6.80 (t + br m, 6H, Py–CH + Ar–CH), 7.05 (br m, 2H,
Ar–CH).
13C{1H} NMR (293 K d6-benzene)  19.3 (Ar–CH3), 21.4
(Ar–CH3), 23.2 (Py–CH3), 35.3 (Np–tBu), 82.0 (Np–CH2), 103.2
(Py–CH), 111.6 (Py–CH), 142.1 (Py–CH).
i
3
3
1H NMR (343 K, d6-benzene)  1.15 (s, 18H, Np–tBu), 1.73 (s,
4H, Np–CH2), 2.22 (s, 6H, Ar–CH3), 2.26 (s, 6H, Ar–CH3), 2.43
3
(br s, 6H, Py–CH3), 5.61 (d, 2H, Py–CH, JHH = 7 Hz), 5.99 (d,
2H, Py–CH, 3JHH = 7 Hz), 6.79 (br d + s, 4H, Ar–CH), 6.85 (t, 2H,
Py–CH, 3JHH = 7 Hz), 7.06 (br d, 2H, Ar–CH, 3JHH = 6 Hz).
13C{1H} NMR (343 K d6-benzene)  18.9 (Ar–CH3), 20.9
(Ar–CH3), 22.8 (Py–CH3), 35.0 (Np–tBu), 103.1 (Py–CH), 111.2
(Py–CH), 127.0 (Ar–CH), 127.7 (Ar–CH), 131.7 (Ar–CH), 133.3
(Ar–Cq), 133.9 (Ar–Cq), 141.5 (Py–CH), 143.9 (Ar–CqN), 153.8
(Py–CqN), 169.2 (Py–NCqN).
t
t
(ZrL4).
Anal. Calcd. for C38H52N4Zr: C, 69.57; H, 7.99; N, 8.54. Found:
C, 68.71; H, 7.75; N, 8.64.
[ZrL5 (NMe2)]. Diethyl ether (30 mL) was added to a Schlenk
3
vessel charged with HL5 (250 mg, 1.16 mmol) and [Zr(NMe2)4]
(155 mg, 0.58 mmol). The reaction mixture was stirred overnight at
ambient temperature under argon. The solvent was removed under
reduced pressure to give a yellow solid. The yellow solid was then
redissolved in a minimum of diethyl ether and cooled to give a white
crystalline product, which was isolated by filtration and identified
by 1H NMR to be unreacted proligand. The remaining yellow solu-
tion was then concentrated to precipitate a yellow crystalline prod-
uct (yield 106 mg, 35%).
t
t
MS (EI) m/z 583 (M+ − CH2 Bu), 512 (M+ − 2 × CH2 Bu), 301
(ZrL3).
[ZrL42(NMe)2]. Toluene (50 mL) was added to a Schlenk vessel
charged with HL4 (250 mg, 1.1 mmol) and [Zr(NMe2)4] (148 mg,
0.55 mmol). The reaction mixture was stirred for 2 d at ambient
temperature under argon. The solvent was removed under reduced
pressure to give a yellow solid. The solid was then dissolved in
pentane (10 mL) and then filtered. Upon cooling to −4 °C a yellow
crystalline product was obtained (yield 236 mg, 68%).
1H NMR (293 K, d6-benzene)  1.80 (s, 6H,Ar–CH3), 1.89 (s, 6H,
Ar–CH3), 2.23 (s, 6H, Ar–CH3), 2.25 (s, 3H, Ar–CH3), 2.27 (s, 6H,
i
1H NMR (293 K, d6-benzene)  0.99–1.02 (m (d + d), 6H, Pr–
i
3
CH3), 1.10–1.12 (m (d + d), 6H, Pr–CH3), 1.94 (s, 3H, Py–CH3),
Ar–CH3), 3.26 (s, 6H, NMe2), 5.64 (d, 2H, Py–CH, JHH = 8 Hz),
1.98 (s, 3H, Py–CH3), 2.68 (s, 3H, NMe), 2.82 (s, 6H, NMe), 2.94
(s, 3H, NMe), 3.40 (m, 2H, iPr–CH), 5.64 (m (d + d), 4H, Py–CH),
6.49–7.22 (m, 8H, Ar–CH), 6.61 (t, 2H, Py–CH, 3JHH = 7 Hz).
13C{1H} NMR (293 K d6-benzene)  20.8 (Py–CH3), 21.2 (Py–
CH3), 21.8 (iPr–CH3), 22.6 (iPr–CH3), 23.4 (iPr–CH3), 23.8 (iPr–
CH3), 26.3 (iPr–CH), 39.5 (NMe), 41.2 (NMe), 42.7 (NMe), 101.5
(Py–CH), 102.1 (Py–CH), 107.0 (Py–CH), 107.4 (Py–CH), 123.4
(Ar–CH), 124.6 (Ar–CH), 124.8 (Ar–CH), 125.1 (Ar–CH), 125.3
(Ar–CH), 138.9 (Py–CH), 143.5 (Ar–Cq–iPr), 144.7 (Ar–CqN),
152.7 (Py–Cq–CH3), 167.9 (Py–NCqN).
5.82 (d, 1H, Py–CH, 3JHH = 8 Hz), 5.84 (t, 2H, Py–CH, 3JHH = 8 Hz),
6.15 (t, 1H, Py–CH, 3JHH = 7 Hz), 6.57 (s, 2H, Ar–CH), 6.47 (s, 2H,
3
Ar–CH), 6.76 (t, 2H, Py–CH, JHH = 7 Hz), 6.89 (s, 2H, Ar–CH),
6.93 (t, 1H, Py–CH, 3JHH = 7 Hz), 7.25 (d, 2H, Py–CH, 3JHH = 7 Hz),
7.90 (d, 1H, Py–CH, 3JHH = 7 Hz).
13C{1H} NMR (293 K d6-benzene)  15.0 (Ar–CH3), 18.3
(Ar–CH3), 19.3 (Ar–CH3), 19.4 (Ar–CH3), 21.4 (Ar–CH3), 25.4
(Ar–CH3), 46.1 (NMe2), 90.4 (Ar–CH), 106.6 (Py–CH), 106.9
(Py–CH), 107.7 (Py–CH), 108.0 (Py–CH), 108.7 (Py–CH), 129.0
(Ar–CH), 129.8 (Ar–CH), 139.9 (Py–CH), 141.0 (Py–CH), 142.8
(Py–CH), 143.3 (Py–CH), 164.6 (Py–NCN).
Anal. Calcd. for C34H46N6: C, 64.82; H, 7.36; N, 13.34. Found: C,
63.11; H, 7.15; N, 13.38.
MS (EI) m/z 628 (M+), 584 (M+ − NMe2), 540 (M+ − 2 NMe2).
Anal. Calcd. for C44H51N7Zr: C, 68.71; H, 6.68; N, 12.75. Found:
C, 66.37; H, 7.06; N, 12.47.
MS (EI) m/z 767 (M+), 723 (M+ − NMe2), 512 (ZrL2 ), 301
2
[ZrL4 (CH2Ph)2]. Toluene (20 mL) was added to a Schlenk
(ZrL5).
2
vessel charged with HL4 (200 mg, 0.88 mmol) and [Zr(CH2Ph)4]
(205 mg, 0.45 mmol). The reaction mixture was stirred overnight at
ambient temperature, under argon and in the absence of light. The
solvent was removed under reduced pressure to give a yellow solid.
The solid was then dissolved in pentane (10 mL) and the solution
filtered. The solvent was then removed under reduced pressure
(yield 392 mg, 61%).
[ZrL53(CH2Ph)]. Toluene (20 mL) was added to a Schlenk vessel
charged with HL5 (250 mg, 1.16 mmol) and [Zr(CH2Ph)4] (267 mg,
0.98 mmol). The reaction mixture was stirred overnight at ambient
temperature, under argon and in the absence of light. The solvent
was removed under reduced pressure to give a yellow solid. The
yellow solid was then redissolved in pentane (20 mL), filtered and
cooled to −4 °C. The yellow crystalline product obtained was then
isolated by filtration (yield 118 mg, 36%).
i
1H NMR (343 K, d6-benzene)  0.99 (s, 6H, Pr–CH3), 1.00 (s,
6H, iPr–CH3), 2.04 (s, 6H, Py–CH3), 2.34 (br s, 4H, Bn–CH2), 3.04
(sept, 2H, iPr–CH), 5.55 (d, 2H, Py–CH, 3JHH = 7 Hz), 5.99 (d, 2H,
1H NMR (293 K, d2-dichloromethane)  1.41 (s, 6H, Ar–CH3),
1.52 (s, 6H, Ar–CH3), 2.16 (s, 12H, Ar–CH3), 2.22 (s, 3H, Ar–CH3),
2.83 (s, 2H, Bn–CH2), 5.60 (d, 1H, Py–CH, 3JHH = 7 Hz), 5.69 (d,
2H, Py–CH, 3JHH = 7 Hz), 6.27–6.30 (m, 3H, Py–CH), 6.32 (s, 2H,
Ar–CH), 6.48 (s, 2H, Ar–CH), 6.53 (br d, 1H, Py–CH), 6.68 (d, 2H,
3
3
Py–CH, JHH = 7 Hz), 6.31 (d, 2H, Ar–CH, JHH = 6 Hz), 6.85 (t,
2H, Py–CH, 3JHH = 7 Hz), 6.86 (br s, 2H, Bn–CH), 7.04 (br s, 4H,
Bn–CH), 7.07 (m, 4H, Ar–CH), 7.04–7.10 (br t, 4H, Bn–CH), 7.27
(d, 2H, Ar–CH, 3JHH = 6 Hz).
13C{1H} NMR (343 K d6-benzene)  22.5 (Py–CH3), 27.8
(iPr–CH), 103.8 (Py–CH), 111.4 (Py–CH), 125.6 (Ar–CH), 126.4
(Ar–CH), 126.6 (Bn–CH), 127.1 (Bn–CH), 129.7 (Bn–CH), 141.2
(Py–CH), 145.0 (Ar–Cq), 146.1 (Ar–NCq), 154.8 (Py–C).
Anal. Calcd. for C44H48N4Zr: C, 72.98; H, 6.68; N, 7.74. Found:
C, 71.84; H, 6.52; N, 7.76.
3
Bn–CH, JHH = 7 Hz), 6.71 (s, 2H, Ar–CH), 6.78 (t, 1H, Bn–CH,
3JHH = 7 Hz), 7.09 (t, 2H, Bn–CH, 3JHH = 7 Hz), 7.28–7.33 (m, 5H,
Ar–CH).
13C{1H} NMR (293 K d2-dichloromethane)  16.2 (Ar–CH3), 17.7
(Ar–CH3), 18.6 (Ar–CH3), 19.7 (Ar–CH3), 64.4 (Bn–CH2), 104.7
(Py–CH), 105.0 (Py–CH), 108.5 (Bn–CH), 108.7 (Bn–CH), 118.3
(Bn–CH), 124.7 (Bn–CH), 126.9 (Ar–CH), 127.2 (Ar–CH), 127.9
MS (EI) m/z 647 (M+ − Ph).
2 2 6 4
D a l t o n T r a n s . , 2 0 0 4 , 2 2 5 7 – 2 2 6 6

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(Ar–CH), 139.2 (Py–CH), 140.1 (Py–CH), 141.9 (Py–CH), 142.9
(Py–CH), 151.3 (Ar–CqN), 167.5 (Py–NCqN), 171.0 (Py–NCqN).
Anal. Calcd. for (C49H52N6Zr): C, 72.11; H, 6.42; N, 10.30.
Found: C, 71.47; H, 6.38; 10.14.
(208 mg, 0.54 mmol). The reaction mixture was stirred overnight at
ambient temperature, under argon and in the absence of light. The
solvent was removed under reduced pressure to give a yellow solid.
The solid was dissolved in a minimum of pentane and cooled over-
night. The resulting white solid was isolated by filtration and was
found to be unreacted proligand. The yellow pentane solution was
reduced to dryness under reduced pressure to give a thick yellow oil
MS (EI) m/z 422 (M+ − L5 ), 331 (ZrL5).
2
t
[ZrL5 (CH2 Bu)2]. Toluene (30 mL) was added to a Schlenk
2
vessel charged with HL5 (250 mg, 1.16 mmol) and [Zr(CH2 Bu)4]
t
t
and determined to be [ZrL1(CH2 Bu)3] via 1H NMR.
1H NMR (293 K, d6-benzene)  1.22 (s, 27H, Np–tBu), 1.63 (s,
(222 mg, 0.98 mmol). The reaction mixture was stirred overnight at
ambient temperature, under argon and in the absence of light. The
solvent was removed under reduced pressure to give a yellow solid.
The yellow solid was then redissolved in a minimum of pentane and
cooled to give a yellow precipitate which was isolated by filtration
(yield 230 mg, 69%).
6H, Np–CH2), 2.23 (s, 3H, Py–CH3), 2.24 (s, 3H, Ar–CH3), 2.42
3
(s, 6H, Ar–CH3), 5.45 (d, 1H, Py–CH, JHH = 7 Hz), 5.86 (d, 1H,
3
3
Py–CH, JHH = 7 Hz), 6.76 (t, 1H, Py–CH, JHH = 7 Hz), 6.94 (s,
2H, Ar–CH).
13C{1H} NMR (293 K d6-benzene)  19.8 (Ar–CH3), 21.3
(Py–CH3), 23.4 (Ar–CH3), 35.2 (Np–tBu), 36.6 (Np–Cq), 83.7
(Np–CH2), 102.5 (Py–CH), 111.1 (Py–CH), 130.1 (Ar–CH), 133.9
(Ar–Cq), 134.7 (Ar–Cq), 142.9 (Py–CH), 144.0 (Ar–CqN), 154.5
(Py–Cq), 169.2 (Py–NCqN).
1H NMR (293 K, d6-benzene)  1.25 (s, 18H, Np–tBu), 1.88 (s,
4H, Np–CH2), 2.22 (s, 6H, Ar–CH3), 2.24 (s, 12H, Ar–CH3), 5.54
3
3
(d, 2H, Py–CH, JHH = 6 Hz), 6.01 (t, 2H, Py–CH, JHH = 6 Hz),
6.62 (s, 4H, Ar–CH), 6.76 (t, 2H, Py–CH, 3JHH = 6 Hz), 7.96 (d, 2H,
Py–CH, 3JHH = 6 Hz).
13C{1H} NMR (293 K d6-benzene)  20.1 (Ar–CH3), 21.4
(Ar–CH3), 35.3 (Np–tBu), 94.0 (Np–CH2), 106.0 (Py–CH), 110.2
(Py–CH), 129.5 (Ar–CH), 142.0 (Py–CH), 144.9 (Py–CH), 169.5
(Py–NCqN).
Anal. Calcd. for (ZrC38H52N4): C, 69.57; H, 7.99; N, 8.54. Found:
C, 68.73; H, 7.83; N, 8.42.
MS (EI) m/z 583 (M+ − CH2tBu).
Crystallography
Crystals were coated in an inert oil prior to transfer to a cold nitro-
gen gas stream on a Bruker-AXS SMART three circle CCD area
detector diffractometer system equipped with Mo K radiation
( = 0.71073 Å). Data were collected using narrow (0.3° in )
frame exposures. Intensities were corrected semiempirically for
absorption, based on symmetry-equivalent and repeated reflections
(SADABS). Structures were solved by direct methods (SHELXS)
or by the location of heavy atom sites by Patterson interpretation of
F-data with additional light atoms found by Fourier methods. All
non-hydrogen atoms were refined anisotropically.All H atoms were
constrained with a riding model; U(H) was set at 1.2 (1.5 for methyl
groups) times Ueq for the parent atom. Programs used were Bruker
AXS SMART (control), SAINT (integration), and SHELXTL for
structure solution, refinement, and molecular graphics.
[ZrL62(NMe2)2]. Toluene (50 mL) was added to a Schlenk vessel
charged with HL6 (200 mg, 0.89 mmol) and [Zr(NMe2)4] (119 mg,
0.44 mmol). The reaction mixture was stirred for 30 min at ambi-
ent temperature under argon. The solution was concentrated under
reduced pressure to give a yellow crystalline solid isolated by filtra-
tion (yield 413 mg, 74%).
1H NMR (293 K, d6-benzene)  2.07 (s, 12H, Ar–CH3), 2.18 (s,
6H, Py–CH3), 2.26 (s, 6H, Ar–CH3), 2.92 (s, 12H, NMe2), 5.59 (d,
2H, Py–CH, 3JHH = 7 Hz), 5.86 (d, 2H, Py–CH, 3JHH = 8 Hz), 6.79
(t, 2H, Py–CH, 3JHH = 7 Hz), 6.93 (s, 4H, Ar–CH).
13C{1H} NMR (293 K d6-benzene)  18.4 (Ar–CH3), 21.4
(Ar–CH3), 22.5 (Py–CH3), 42.4 (4C, NMe2), 103.6 (Py–CH), 108.2
(Py–CH), 133.3 (Ar–CH), 134.6 (Ar–CH), 141.0 (Py–CH), 154.3
(Py–CqCH3), 168.8 (Py–CqN).
CCDC reference numbers 238254–238259.
See http://www.rsc.org/suppdata/dt/b4/b407008a/ for crystallo-
graphic data in CIF or other electronic format.
Acknowledgements
PS thanks the University of Warwick for a studentship (to EJC) and
EPSRC for support.
Anal. Calcd. for C34H46N6Zr: C, 64.82; H, 7.36; N, 13.34. Found:
C, 63.50; H, 7.19; N, 13.17.
MS (CI) m/z 630 (100%, M+), 585 (M − NMe2).
References
[ZrL6 (CH2Ph)2]. Toluene (20 mL) was added to a Schlenk
1 F. T. Edelmann, Coord. Chem. Rev., 1994, 137, 403.
2 E. A. C. Brussee, A. Meetsma, B. Hessen and J. H. Teuben, Chem.
Commum., 2000, 497.
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2
vessel charged with HL6 (250 mg, 1.1 mmol) and [Zr(CH2Ph)4]
(251 mg, 0.55 mmol). The reaction mixture was stirred for 1 h at
ambient temperature, under argon and in the absence of light. The
solvent was removed under reduced pressure to give a yellow solid.
The solid was then washed in pentane (10 mL) and recrystallised
from diethyl ether (yield 227 mg, 65%).
1H NMR (293 K, d6-benzene)  1.85 (s, 12H, Ar–CH3), 2.18 (s,
6H, Ar–CH3), 2.35 (s, 6H, Py–CH3), 2.89 (s, 4H, Bn–CH2), 5.40 (d,
2H, Py–CH, 3JHH = 8 Hz), 6.01 (d, 2H, Py–CH, 3JHH = 8 Hz), 6.46
3
(s, 4H, Ar–CH), 6.80 (t, 2H, Py–CH, JHH = 8 Hz), 6.85 (m, 2H,
3
Bn–CH), 6.88 (d, 4H, Bn–CH, JHH = 7 Hz), 7.10 (t, 4H, Bn–CH,
3JHH = 7 Hz).
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Commum., 1997, 18, 635.
13C{1H} NMR (293 K d6-benzene)  19.4 (Ar–CH3), 21.4
(Ar–CH3), 23.1 (Py–CH3), 72.1 (Bn–CH2), 102.8 (Py–CH), 111.9
(Py–CH), 121.9 (Bn–CH), 122.0 (Bn–Cq), 127.2 (Ar–Cq), 128.1
(Bn–CH), 128.8 (Ar–CH), 128.8 (Bn–CH), 129.7, (Ar–CqN), 133.6
(Ar–Cq), 142.4 (Py–CH), 148.7 (Py–Cq–CH3), 161.2 (Py–NCqN).
Anal. Calcd. for C44H48N4Zr: C, 72.98; H, 6.68; N, 7.74. Found:
C, 71.91; H, 6.60; N, 7.63.
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MS (EI) m/z 633 (50%, M+ − CH2Ph), 542 (100%,
M+ − 2 × CH2Ph).
t
[ZrL6(CH2 Bu)3]. Toluene (20 mL) was added to a Schlenk
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t
vessel charged with HL6 (250 mg, 1.1 mmol) and [Zr(CH2 Bu)4]
D a l t o n T r a n s . , 2 0 0 4 , 2 2 5 7 – 2 2 6 6
2 2 6 5

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2 2 6 6
D a l t o n T r a n s . , 2 0 0 4 , 2 2 5 7 – 2 2 6 6