Group 4 metal complexes bearing new tridentate (NNO) ligands: Benzyl migration and formation of unusual C-C coupled products

Article abstract of DOI:10.1016/j.jorganchem.2008.11.064

Group 4 metal complexes bearing new phenoxy(benzimidazolyl)-imine, -amine and -amide ligands have been synthesized. A series of metal chloride derivatives has been prepared via treatment of MCl₄(THF)₂ (M = Ti, Zr, Hf) with the in sit

Full text of DOI:10.1016/j.jorganchem.2008.11.064

Journal of Organometallic Chemistry 694 (2009) 703–716
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Group 4 metal complexes bearing new tridentate (NNO) ligands: Benzyl
migration and formation of unusual C–C coupled products
*
Renan Cariou, Vernon C. Gibson , Atanas K. Tomov, Andrew J.P. White
Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Group 4 metal complexes bearing new phenoxy(benzimidazolyl)-imine, -amine and -amide ligands
have been synthesized. A series of metal chloride derivatives has been prepared via treatment of
MCl4(THF)2 (M = Ti, Zr, Hf) with the in situ generated sodium salt of the (benzimidazolyl)imine phenol
1. Reaction of the pro-ligand 2 with TiCl4(THF)2 afforded the corresponding complex 8 in which the
amine proton remains bound to the nitrogen donor. Benzyl complexes of zirconium and hafnium
were synthesized via treatment of pro-ligands 1 and 2 with M(CH2Ph)4 precursors. The complexes
[NNO]M(CH2Ph)3 (6 M = Zr, 7 M = Hf) were found to undergo benzyl migration from the metal cen-
tre to the imine carbon of the ligand backbone giving complexes 11 and 12; the migration follows
first order kinetics. The reaction of 1 with Ti(NMe2)4 led to the formation of an unusual C–C coupled
product in which a new piperazine ring has formed. Complexes 11 and 12 undergo related transfor-
mations, leading to analogous C–C coupled products which were characterized by X-ray crystallogra-
phy. Deuterium labelling experiments were carried out to determine the mechanistic pathway of the
reactions. Chloride and benzyl complexes 3–12 were screened as pre-catalysts for olefin
polymerization.
Received 24 September 2008
Received in revised form 21 November 2008
Accepted 28 November 2008
Available online 7 December 2008
Keywords:
Group 4 metal complexes
Intramolecular benzyl migration
Carbon–carbon coupling
Ethylene polymerization
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
coupled products, along with their ethylene polymerization
behavior.
Over the past twenty years, academic and industrial research
programmes have successfully targetted new catalysts for con-
trolled olefin polymerization. Numerous highly active single-site
homogeneous catalysts based on metals across the transition ser-
ies have been reported [1,2]. While many different donor groups
have been explored, there are certain types, steric affects aside,
that seem to be specially suited to the stabilization of high activ-
ity catalysts. Among these are imine and phenoxy donors and
especially a combination of these two donors (I, Chart 1) [3–
29]. In recent studies, we have found that benzimidazole donors
can also afford exceptionally active catalysts (II, Chart 1) [30,31].
We were, therefore, attracted by the possibility of combining
phenoxy, imine and benzimidazolyl donors within a single tri-
dentate ligand system with a view to seeing if the beneficial af-
fects of these donors might be retained within an extended
ligand frame. Here, we report, the synthesis and characterization
of a family of Group 4 metal complexes bearing the new phen-
oxy(benzimidazolyl)-imine and phenoxy(benzimidazolyl)amide
ligands, their unusual benzyl migration reactivity to give C–C
2. Results and discussion
2.1. Pro-ligand synthesis
Pro-ligand 1 was synthesized in moderate yield using a modi-
fied literature procedure [34], via condensation of 3,5-di-tert-
butylsalicyladehyde with 2-aminomethyl-1-methylbenzimidazole
dihydrochloride in the presence of K2CO3 (Scheme 1).
The 1H NMR spectrum of 1 shows characteristic signals for the
tBu substituents, at 1.28 and 1.41 ppm, and resonances for the
imine hydrogen and the aromatic protons of the phenol unit at
8.54 and 13.10 ppm, respectively. The methylene bridge resonates
3
as a doublet at 5.09 ppm due to a small JHH coupling of 1.2 Hz to
the amine proton.
Reaction of 1 with 2.0 equivalents of tBuLi, followed by aqueous
work-up, afforded the pro-ligand 2, in which the imine has been
reduced to a secondary amine (Scheme 1). Consistently, the 1H
NMR spectrum of 2 revealed an ABX coupling pattern centered at
3.98 ppm attributable to the presence of diastereotopic methylene
bridge protons. The amine proton was found to resonate at
2.86 ppm as a doublet of doublet resonance again due to coupling
to the two diastereotopic protons of the CH2 group.
* Corresponding author. Tel.: +44 02075945830; fax: +44 02075945810.
E-mail addresses: v.gibson@imperial.ac.uk, v.gibson@ic.ac.uk (V.C. Gibson).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.11.064

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R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
Chart 1. Bis(phenoxyimine) and bis(benzimidazolyl)amine pre-catalysts.
Scheme 1. Synthesis of pro-ligands 1 and 2.
Scheme 2. Synthesis of complexes ((i) NaH in THF, then MCl4(THF)2; (ii) M(CH2Ph)4 in toluene at RT).
2.2. Synthesis and structure of metal chloride derivatives
1 was converted to its sodium salt using NaH and immediately
reacted with MCl4(THF)2 (M = Ti, Zr, Hf) to afford the desired chlo-
ride complexes 3, 4 and 5 (Scheme 2).
1H NMR spectra of these complexes showed a characteristic
peak for the imine proton in the region 8.5–8.7 ppm. Complexes
3 and 5 display singlet resonances at ca. 5.60 ppm assignable to
the equivalent protons of the methylene bridge indicating that
the ligand is coordinated in a meridional fashion. For 4, an addi-
tional small coupling of 1.4 Hz is observed between the methylene
bridge and the imine proton.
Fig. 1. The molecular structure of 3-A, one of the four. crystallographically
independent complexes present in the crystals of 3.
Single crystals of 3 suitable for X-ray analysis were grown from
a saturated acetonitrile solution.
The solid state structure was found to contain four crystallo-
graphically independent complexes, (A–D) with essentially identi-
cal geometries except for the positions of the methyl carbons of the
t-butyl groups; complex 3-A is shown in Fig. 1, complexes 3-B, 3-C
and 3-D are shown in Figs. S2–S8. The geometry at the metal centre
is distorted octahedral with the tridentate ligand coordinated in a
meridional fashion, and with the Ti–Cl bond trans to N(8) notice-
ably shorter than those trans to chlorine (Table 1). The six-mem-
bered N,O and the five-membered O,O0 chelate rings are both flat
and coplanar, a planarity that extends to include the fused ring sys-
tems; with the exception of Cl(1), Cl(2) and the two t-butyl groups,
the whole of the complex is approximately planar with mean devi-
ations of ca. 0.05, 0.06, 0.06 and 0.06 Å for 3-A, 3-B, 3-C and 3-D,
respectively [35].
The reaction of 2 with TiCl4(THF)2 in THF at room temperature
led to the formation of the trichloride complex 8 (Scheme 3). The
ligand appears to be monoanionic and tridentate, in which the
amine proton remains bonded to the central nitrogen donor. This
proton resonates as a broad doublet resonance at 4.90 ppm with
coupling (by COSY NMR) to the diastereotopic methylene protons
as well as with the methine proton on the adjacent carbon atoms.
Slow cooling of a saturated toluene solution led to the formation of
single crystals suitable for X-ray analysis.

R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
705
Table 1
Table 2
Comparative selected bond lengths (Å) and angles (°) for the four crystallographically
independent complexes present in the crystals of 3.
Selected bond lengths (Å) and angles (°) for 8.
Ti–Cl(1)
Ti–Cl(3)
Ti–N(8)
C(7)–N(8)
Cl(1)–Ti–Cl(2)
Cl(1)–Ti–O(1)
Cl(1)–Ti–N(11)
Cl(2)–Ti–O(1)
Cl(2)–Ti–N(11)
Cl(3)–Ti–N(8)
O(1)–Ti–N(8)
N(8)–Ti–N(11)
2.3487(13)
2.3384(13)
2.249(3)
1.513(4)
92.66(5)
94.52(9)
88.68(9)
104.68(9)
97.66(9)
86.47(10)
82.50(12)
75.11(12)
Ti–Cl(2)
Ti–O(1)
Ti–N(11)
N(8)–C(9)
Cl(1)–Ti–Cl(3)
Cl(1)–Ti–N(8)
Cl(2)–Ti–Cl(3)
Cl(2)–Ti–N(8)
Cl(3)–Ti–O(1)
Cl(3)–Ti–N(11)
O(1)–Ti–N(11)
2.2730(11)
1.787(3)
2.139(3)
3-A
3-B
3-C
3-D
Ti(1)–Cl(1)
Ti(1)–Cl(2)
Ti(1)–Cl(3)
Ti(1)–O(1)
Ti(1)–N(8)
Ti(1)–N(11)
C(7)–N(8)
N(8)–C(9)
Cl(1)–Ti(1)–Cl(2)
Cl(1)–Ti(1)–Cl(3)
Cl(1)–Ti(1)–O(1)
Cl(1)–Ti(1)–N(8)
Cl(1)–Ti(1)–N(11)
Cl(2)–Ti(1)–Cl(3)
Cl(2)–Ti(1)–O(1)
Cl(2)–Ti(1)–N(8)
Cl(2)–Ti(1)–N(11)
Cl(3)–Ti(1)–O(1)
Cl(3)–Ti(1)–N(8)
Cl(3)–Ti(1)–N(11)
O(1)–Ti(1)–N(8)
O(1)–Ti(1)–N(11)
N(8)–Ti(1)–N(11)
2.3403(11)
2.2929(11)
2.3450(11)
1.790(2)
2.180(3)
2.145(3)
1.296(4)
1.470(4)
91.46(4)
168.65(4)
94.94(8)
87.91(8)
84.25(8)
92.06(4)
101.05(9)
176.76(9)
102.26(9)
94.97(8)
87.98(8)
84.46(8)
82.18(11)
156.69(12)
74.51(11)
2.3516(11)
2.2973(11)
2.3266(11)
1.797(2)
2.175(3)
2.157(3)
1.282(4)
1.469(4)
91.09(4)
169.70(4)
94.07(8)
88.68(8)
84.44(8)
92.21(4)
101.52(8)
176.45(8)
101.77(8)
94.82(8)
87.43(8)
85.34(8)
82.03(11)
156.69(11)
74.68(11)
2.3357(11)
2.2880(11)
2.3390(11)
1.791(2)
2.169(3)
2.168(3)
1.276(5)
1.479(4)
91.19(4)
168.56(4)
94.76(8)
86.96(8)
84.98(8)
92.76(4)
101.28(8)
176.13(9)
101.80(9)
94.99(8)
88.43(8)
83.70(8)
82.28(11)
156.93(11)
74.66(11)
2.3357(11)
2.2870(11)
2.3331(11)
1.797(2)
2.193(3)
2.144(3)
1.280(4)
1.475(5)
91.52(4)
169.24(4)
94.05(8)
88.52(8)
84.36(8)
91.79(4)
100.53(8)
177.81(9)
103.18(9)
95.40(8)
87.79(8)
84.91(8)
81.65(11)
156.27(11)
74.65(11)
1.478(4)
171.97(5)
87.61(10)
92.54(5)
172.76(10)
90.08(9)
84.55(9)
157.24(11)
0.07 Å] that results in the C(1)/C(6) aromatic C6 ring being inclined
by ca. 42° to the equatorial {Ti,Cl(2),O(1),N(8),N(11)} plane. The
five-membered N,N0 chelate ring is also distorted away from pla-
narity, having an envelope conformation with N(8) lying ca.
0.42 Å out of the {Ti,C(9),C(10),N(11)} plane which is coplanar to
within ca. 0.02 Å. The bonds to the metal atom (Table 2) show
the same pattern as seen in the structure of 3, though here the dif-
ference between the two Ti–N bonds is much clearer as a result in
the change in the hybridisation of N(8).
2.3. Synthesis and structure of metal benzyl derivatives
NMR scale reactions of compounds 1 and 2 with (separately)
Zr(CH2Ph)4 and Hf(CH2Ph)4 proceeded cleanly in C6D6 and indi-
cated quantitative conversion into the corresponding tribenzyl
complexes 6 and 7 (from 1) and the dibenzyl complexes 9 and
10 (from 2) as well as affording toluene as a by-product (Schemes
2 and 3). Reactions on a preparative scale were carried out in tol-
uene at room temperature to afford 6 and 7 as orange, and 9 and
10 as white, microcrystalline powders. The 1H NMR spectrum of
6 revealed a pair of AB doublets centered at 2.77 and 2.94 ppm
integrating for four protons and assigned to diastereotopic benzyl
protons (2JHH = 9.2 Hz). A singlet at 3.25 ppm was assigned to
equivalent protons of a third benzyl group. The aromatic region
of the spectrum revealed signals attributable to the ortho-protons
of the benzyl phenyl unit to relatively high-field (5.90–
Scheme 3. Legend: (i) TiCl4(THF)2 in THF; (ii) M(CH2Ph)4 in toluene at RT.
6.40 ppm), suggesting
g
2-coordination at the metal centre. This
is supported by a relatively low 2JHH value of 9.2 Hz for the diaste-
1
reotopic protons of the CH2Ph groups and a JCH value of 126 Hz.
[36–40] The methylene bridge of the ligand appears as a singlet
at 2.67 ppm indicating that the ligand is coordinated in a meridio-
nal fashion, in accord with the NMR observations of the chloride
complexes. An analogous 1H NMR spectrum was observed for the
corresponding hafnium derivative, 7.
The dibenzyl complexes 9 and 10 have essentially similar 1H
NMR spectra and show no fluxionality at room temperature. In
10, the benzylic protons resonate as two sets of AB doublets cen-
2
tered at 1.55, 2.18 and 2.44, 2.86 ppm (2JHH = 11.1 Hz, JHH
=
11.3 Hz). The corresponding benzyl carbons appear as triplets at
65.7 and 67.3 ppm, in the 1H-coupled 13C NMR spectrum, with
1JCH values of 122 and 127 Hz, respectively, values that suggest that
the benzyl units are bonded in
g
2-fashion.
Fig. 2. The molecular structure of 8.
Single crystals of the hafnium derivative 10 were grown from a
toluene solution at ꢀ20 °C. The solid state structure showed the
presence of two crystallographically independent complexes, (A
and B) with broadly similar geometries (the major exception being
the C(51) phenyl ring); complex 10-A is shown in Fig. 3, complex
10-B in Fig. S13, and an overlay of the two complexes is shown
in Fig. S15. The geometry at the five-coordinate hafnium centre
is intermediate between square-based pyramidal (sbp) and trigo-
The change from an sp2 geometry for the N(8) nitrogen in 3 to
an sp3 geometry for the same nitrogen in 8 leads to a very marked
change in the conformation of the ligand (Fig. 2). Although the li-
gand is coordinated in a meridional fashion to the octahedral metal
centre, the six-membered N,O chelate ring has a distorted folded
conformation [O(1) and C(1) lying ca. 0.77 and 0.48 Å, respectively
out of the {Ti,C(6),C(7),N(8)} plane which is coplanar to within ca.
nal bipyramidal (tbp) as indicated by
s parameter [41] values of

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R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
[1.482(4) Å] for N(1)–C(12) in 10, suggesting a degree of sp2
hybridisation. The most noticeable effect, however, is seen in the
Hf–N bond lengths with that to N(1) ca. 0.25 Å shorter than that
to the sp2 nitrogen N(4), though part of this will be due to a length-
ening of the Hf–N(4) bond caused by N(4) occupying a pseudo-axial
position (if the metal coordination geometry is viewed as tbp, N(4)
and O(18) would be in the axial sites) trans to a phenoxide donor.
This flattening of the geometry at the amino nitrogen results in
an overall flattening of the tridentate ligand cf. the conformation
seen in 8. Here in 10 the C(13)/C(18) aromatic C6 ring is inclined
to the {Hf,N(1),N(4),O(18)} plane by ca. 30° [35°] cf. ca. 42° in 8.
The six-membered N,O chelate ring has a boat conformation with
C(12) and O(18) lying ca. 0.48 [0.44] and 0.28 Å [0.36 Å] out of
the {Hf,N(1),C(13),C(18)} plane which is coplanar to within ca.
0.02 Å [0.03 Å]. The five-membered N,N0 chelate ring has a enve-
lope geometry with the metal lying ca. 0.62 Å [0.48 Å] out of the
{N(1),C(2),C(3),N(4)} plane which is coplanar to better than
0.01 Å [0.01 Å].
Fig. 3. The molecular structure of 10-A, one of the two crystallographically
independent complexes present in the crystals of 10.
2.4. Intramolecular benzyl migration reactions
Table 3
The square-based pyramidal/trigonal bipyramidal parameter
s for the solid state
Zirconium benzyl complexes are known to undergo benzyl
migration processes [43]. Scott and coworkers reported that tita-
nium and zirconium benzyl complexes bearing bridged phenoxyi-
mine ligands can undergo migrations of one of the benzyls to the
imino carbon of the ligand backbone [19,44–46]. Other systems
structures of complexes 10-A, 10-B, 14, 15 and 16.a
A
a
(°)
b (°)
s [s = (b ꢀ a)/60°]
10-A
10-B
14
15
16
C(40)
C(40)
N(31)
C(30)
C(30)
126.76(13)
124.62(12)
129.28(6)
125.92(6)
126.83(7)
158.03(9)
158.48(9)
161.09(8)
157.41(6)
158.55(5)
0.52
0.56
0.53
0.52
0.53
based on pyrrolylimines and a-diimine ligands show similar reac-
tivities [47–50]. We have found that 6 and 7 also undergo benzyl
transfer reactions in solution leading to the corresponding dibenzyl
complexes 11 and 12 (Scheme 4).
a
Donor A defined as being the atom not involved in either of the two largest
Typically, three different benzyl signals are observed in 1H NMR
of complexes 11 and 12: two sets of AB doublets for the benzyl
groups bound the metal centre and an ABC multiplet for the pro-
tons of the benzyl group attached to the ligand backbone. The
methylene bridge protons are diastereotopic and appear as an AB
system. As observed in 9 and 10, the aromatic protons of one of
the benzyl ligands appear upfield (6.10–6.50 ppm) indicative of
angles at the metal centre; angles b and
a are the largest and second largest angles
at the metal centre, respectively.
0.52 and 0.56 for 10-A and 10-B, respectively (Table 3). The two
equatorial Hf–C bond lengths are identical within error (Table 4),
but it is interesting to note that the Hf–C–C(Ph) angle at C(50) in
complex 10-B is ca. 7° smaller than the other three, suggesting a
g
2-coordination. The 1H NMR spectrum of the starting tribenzyl
degree of
g
2-coordination for this benzyl ligand [the Hfꢁ ꢁ ꢁC(51)
complex 6 and the product 11 following benzyl migration are
shown in Fig. 4.
separation is 2.879(3) Å in complex 10-B cf. 2.994(3) Å in 10-A].
It is unclear, however, why this effect should be present in only
one of the two independent complexes as there are no other signif-
icant conformational differences, and the closest intra and
intermolecular approaches to the centroid of the C(51) phenyl ring
are shorter for complex 10-A than for complex 10-B [42].
The transformation of 6 to 11 occurred over several hours and
thus could be conveniently followed by 1H NMR spectroscopy.
The reaction followed first order kinetics with a kobs value of
2.3 ꢂ 10ꢀ4 sꢀ1 at 313 K (t1/2 = 50 min) (Fig. 5). The conversion of 7
into 12 proceeds a little slower, with a kobs value of 4.3 ꢂ 10ꢀ5 sꢀ1
at 313 K (t1/2 = 271 min). Eyring plots revealed negative
DS
# values
The geometry at the amido nitrogen is significantly flattened,
N(1) lying only ca. 0.08 Å [0.11 Å] out of the plane of its substitu-
ents (the value in square parentheses refers to complex 10-B),
compared to ca. 0.36 Å for the equivalent nitrogen [N(8)] in the
structure of 8. Associated with this is a shortening of the N–
C(H)(t-Bu) bond from 1.513(4) Å for C(7)–N(8) in 8, to 1.467(4) Å
(ꢀ79 and ꢀ139 J Kꢀ1 molꢀ1, respectively for the conversion of 6 into
11 and 7 into 12; Fig. 6) indicative of non-dissociative intramolec-
ular processes [46].
The corresponding titanium tribenzyl complex could not be ac-
cessed since the reaction of 1 with Ti(CH2Ph)4 in an NMR scale reac-
Table 4
Comparative selected bond lengths (Å) and angles (°) for the two crystallographically independent complexes present in the crystals of 10.
10-A
10-B
10-A
10-B
Hf–N(1)
Hf–O(18)
Hf–C(50)
2.056(3)
1.952(2)
2.267(3)
2.063(2)
1.950(2)
2.276(3)
Hf–N(4)
Hf–C(40)
N(1)–C(2)
2.319(3)
2.270(3)
1.454(4)
2.301(3)
2.276(3)
1.444(4)
N(1)–C(12)
1.467(4)
1.482(4)
N(1)–Hf–N(4)
N(1)–Hf–C(40)
N(4)–Hf–O(18)
N(4)–Hf–C(50)
O(18)–Hf–C(50)
Hf–C(40)–C(41)
73.75(10)
113.03(12)
158.03(9)
92.30(11)
104.66(12)
105.7(2)
73.68(10)
111.68(11)
158.48(9)
92.82(11)
103.49(11)
104.9(2)
N(1)–Hf–O(18)
N(1)–Hf–C(50)
N(4)–Hf–C(40)
O(18)–Hf–C(40)
C(40)–Hf–C(50)
Hf–C(50)–C(51)
84.84(10)
126.76(13)
84.17(11)
100.18(11)
116.28(14)
104.1(2)
85.43(9)
124.62(12)
83.87(11)
99.53(11)
120.04(13)
97.8(2)

R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
707
Scheme 4.
Fig. 4. 1H NMR (C6D6) spectra of 6 and 11.
Fig. 5. First order plots for the conversion of 6 into 11 at various temperatures.
tion afforded a mixture of unidentified products, while the reaction
2.5. Formation of unusual C–C coupled products
2.5.1. From reaction with Ti(NMe2)4
Compound 1 reacted with Ti(NMe2)4 in a NMR scale reaction (in
C6D6) to liberate free dimethylamine and give a new complex (14;
Scheme 6). The compound has low solubility in C6D6 and precipi-
tated out of the solution after a few hours. Single crystals suitable
of 3 with PhCH2MgCl in THF afforded exclusively the migration
product 13 (Scheme 5). Compound 13 possesses the same NMR fea-
tures as its zirconium and hafnium congeners 11 and 12. A key dif-
ference, however, is that 13 decomposes rapidly in solution at room
temperature to give an unusual C–C coupled product. The nature of
this species will be probed in the following section.

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R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
Fig. 6. Eyring plot of the transformation of 6 into 11.
Scheme 5.
Scheme 6. NMR scale reaction of 1 with Ti(NMe2)4 in C6D6.
only two other examples of such coupling have been reported
[51,52], this being the first example with a Group 4 metal. The
resulting central piperazine C4N2 ring has a chair conformation
with the four carbon atoms perfectly planar (a consequence of
the centre of symmetry at the middle of the ring) and the nitrogens
lying ca. 0.71 Å out of, and on opposite sides of this plane. The
pyramidalisation of the N(8) centre is intermediate between those
seen for the equivalent nitrogens in the structures of 8 and 10, the
nitrogen here in 14 sitting ca. 0.28 Å out of the plane of its substit-
uents, cf. ca. 0.36, 0.08 and 0.11 Å in 8, 10-A and 10-B, respectively.
That this nitrogen has retained significant sp2 character is also
shown by the two N(8)–C bonds being the same (Table 5) and sim-
ilar to those seen in 10.
The
s parameter value of 0.53 shows that the geometry at the
metal centre is intermediate between sbp and tbp (Table 3), with
O(1) and N(11) occupying the pseudo-axial sites. The six-membered
N,O chelate ring has a distorted folded geometry, Ti and N(8) lying
ca. 0.55 and 0.69 Å, respectively out of the {O(1),C(1),C(6),C(7)}
plane which is coplanar to within ca. 0.02 Å. The five-membered
N,N0 chelate ring has an envelope conformation with C(9) lying ca.
0.42 Å out of the {Ti,N(8),C(10),N(11)} plane which is coplanar to
within ca. 0.04 Å. The tridentate ligand has a flatter conformation
here in 14 than seen in either 8 or 10, the C(1)/C(6) aromatic C6 ring
here being inclined by ca. 19° to the {Ti,O(1),N(8),N(11)} plane cf.
ca. 42, 30 and 35° in 8, 10-A and 10-B, respectively.
Fig. 7. The molecular structure of the Ci-symmetric complex 14.
for X-ray analysis could be grown from a CD2Cl2 solution; the
molecular structure is shown in Fig. 7.
The X-ray analysis revealed an unexpected Ci-symmetric dinu-
clear species, formed by the back-to-back cross-coupling of the
imine bonds of two adjacent complexes (Fig. 4). To our knowledge

R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
709
Table 5
B (deprotonation at the methylene bridge), 14d2 will be formed
and the 1H NMR spectrum will then show a singlet resonance inte-
grating for two protons. The 1H NMR spectrum of the product of
the reaction showed one singlet at 4.51 ppm, corresponding to
14d2, thus indicating that the reaction occurs via route B.
Selected bond lengths (Å) and angles (°) for 14.
Ti–Cl
Ti–N(8)
Ti–N(31)
N(8)–C(9)
Cl–Ti–O(1)
Cl–Ti–N(11)
O(1)–Ti–N(8)
O(1)–Ti–N(31)
N(8)–Ti–N(31)
2.3029(8)
1.9909(19)
1.898(2)
1.460(3)
99.06(6)
86.54(5)
86.28(7)
99.11(9)
114.80(8)
Ti–O(1)
Ti–N(11)
C(7)–N(8)
C(7)–C(9A)
Cl–Ti–N(8)
Cl–Ti–N(31)
O(1)–Ti–N(11)
N(8)–Ti–N(11)
N(11)–Ti–N(31)
1.8219(17)
2.179(2)
1.468(3)
1.577(3)
129.28(6)
113.98(7)
161.09(8)
76.35(7)
94.97(9)
2.5.2. From benzyl complexes
Complexes 11 and 12, arising from benzyl migration, appear to
undergo a further transformation in solution over a period of sev-
eral weeks. Indeed, while attempting to grow crystals of 11 and 12
for X-ray analysis, we discovered that the crystals formed were in
fact the new complexes 15 and 16. A single crystal X-ray diffraction
study 15 revealed a structure analogous to that of the titanium
species 14, but with the chloro and dimethylamino ligands in the
latter replaced by a pair of benzyl groups (Fig. 8). The complex is
again centrosymmetric, and the piperazine ring has a chair confor-
mation (the four carbon atoms are perfectly coplanar and the nitro-
gens lie ca. 0.72 Å out of this plane on opposite sides). The N(8)
nitrogen atom is markedly less pyramidalised than seen in 14, here
sitting only ca. 0.16 Å out of the plane of its substituents cf. ca.
0.28 Å in 14.
Plausible mechanistic pathways for the formation of 14 are
shown in Scheme 7. The free dimethylamine formed during the
complexation of 1 could deprotonate the ligand backbone either
at the methylene bridge or at the imine carbon. If deprotonation
occurs at the imine, the imine carbon will be negatively charged
and a 1,3-hydrogen shift of a methylene proton may then occur
(Scheme 7, route A). The alternative pathway proceeds via depro-
tonation of the methylene bridge (Scheme 7 route B).
Deuterium labelling experiments were conducted to identify
the site of deprotonation. Pro-ligand 1d2, in which the methylene
bridge protons are substituted by deuterium atoms, was synthe-
sized and reacted with Ti(NMe2)4 on an NMR scale in C6D6. Two
products can be envisaged from this reaction: 14d4 in which the
ring is entirely deuterated and 14d2 in which the ring is ‘‘half-deu-
terated”, with the protons and deuterons lying opposite to each
other (Scheme 8).
The most interesting aspect of this structure is the difference
between the coordination of the C(30) and C(40) benzyl ligands.
Whilst the C(40) ligand binds in an g1 fashion with a Zr–C(40)–
C(41) angle of 106.71(12)°, the equivalent angle at C(30) is ca.
11° smaller [Zr–C(30)–C(31) 95.76(13)°]. Associated with this is a
ca. 0.2 Å reduction in the Zrꢁ ꢁ ꢁC(31) separation [2.832(2) Å] cf. that
to C(41) [3.0568(19) Å]; the Zr–C(30) and Zr–C(40) bond lengths
are the same (Table 6). This clearly points to a significant
g
2 inter-
If the mechanism occurs via route A (deprotonation at the imine
followed by a 1,3-hydrogen shift), 14d4 will be formed and no sig-
nals attributable to the piperazine ring will be observable in the 1H
NMR spectrum. By contrast, should the reaction proceed via route
action for the C(30) benzyl ligand. Interestingly, the ‘‘inner” face of
the C(41) phenyl ring is involved in a pair of intramolecular C–
Hꢁ ꢁ ꢁ
p contacts, the protons on C(7A) and C(9A) being ca. 2.94
Scheme 7. Plausible mechanism for the formation of 14.

710
R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
Scheme 8. Possible products of the reaction between 1d2 and Ti(NMe2)4.
case for 10-A, 10-B and 14, the geometry at the metal centre here
in 15 is again intermediate between sbp and tbp as shown by a
value of 0.52 (Table 3).
s
The six-membered N,O chelate ring has a boat geometry, O(1)
and C(7) lying ca. 0.21 and 0.32 Å, respectively out of the
{Zr,C(1),C(6),N(8)} plane which is coplanar to within ca. 0.02 Å.
The five-membered N,N0 chelate ring has an envelope conformation
with C(10) lying ca. 0.31 Å out of the {Zr,N(8),C(9),N(11)} plane
which is coplanar to within ca. 0.05 Å. The tridentate ligand has a
flatter conformation than seen in 14, with here the C(1)/C(6) aro-
matic C6 ring here being inclined by ca. 15° to the {Zr,O(1),
N(8),N(11)} plane cf. ca. 19° in 14.
The structure of 16 is isomorphous with that of its Zr analogue
(see Supplementary material). If the complexes 15 and 16 arise
from 11 and 12, two molecules of toluene must be formed during
the process. Therefore, we considered a radical mechanism for the
formation of these C–C coupled products, the initiation step involv-
ing homolytic cleavage of the C–CH2Ph bond, leading to the forma-
tion of a benzyl radical and a radical species A in which the radical
character is retained by the ligand. The benzyl radical can attack
the ligand (at the methylene bridge) on another complex molecule
to form a new radical species B. Coupling of the radical A and B oc-
curs leading to the intermediate C. Further cleavage of the remain-
ing benzyl carbon bond would lead to the second coupling step
(Scheme 9).
Fig. 8. The molecular structure of the Ci-symmetric complex 15.
In order to probe this mechanistic hypothesis, the reaction of
1d2 with Zr(CH2Ph)4was followed. The order of the reaction was
determined to be 3/2, consistent with Rice–Herzfeld radical prop-
agation kinetics [53,54], with rate constants of 2.75 ꢂ 10ꢀ5
molꢀ0.5 L1.5 minꢀ1 and 1.48 ꢂ 10ꢀ5 molꢀ0.5 L1.5 minꢀ1 for 11 and
11d2, respectively. Furthermore, the ratio of the rate constants
kH/kD is 1.8, a value corresponding to a secondary kinetic isotope
effect. This suggests that, if a C–H (C–D) bond is broken during
the reaction, it is not the rate-determining step. Therefore the
homolytic cleavage of the C–CH2Ph bond can be reasonably consid-
ered the rate-determining step. In addition, formation of toluene is
observed during the decomposition of both complexes. According
to the mechanism proposed in Scheme 9, d1-toluene should be
formed during the decomposition of 11d2; a 2H NMR spectrum
confirmed the formation of d1-toluene (see Supplementary mate-
rial). Furthermore, a small quantity of bibenzyl is observed, a con-
sequence of benzyl radical coupling, and consistent with the
proposed radical pathway. An example of the dissociation of a car-
bon-benzyl (C–CH2Ph) bond has been reported for a coenzyme B12
model complex; in this system a benzyl group migrates reversibly
from the cobalt centre to the imine carbon of the ligand. It was
found that the bond dissociation energy of the carbon-benzyl (C–
CH2Ph) bond was about one third lower than that of a normal car-
bon-benzyl bond [55–59].
Table 6
Selected bond lengths (Å) and angles (°) for 15.
Zr–O(1)
Zr–N(11)
Zr–C(40)
N(8)–C(9)
O(1)–Zr–N(8)
O(1)–Zr–C(30)
N(8)–Zr–N(11)
N(8)–Zr–C(40)
N(11)–Zr–C(40)
Zr–C(30)–C(31)
1.9650(13)
2.2952(15)
2.2861(18)
1.469(2)
84.32(5)
99.45(7)
74.25(6)
125.92(6)
89.54(6)
Zr–N(8)
Zr–C(30)
C(7)–N(8)
C(7)–C(9A)
O(1)–Zr–N(11)
O(1)–Zr–C(40)
N(8)–Zr–C(30)
N(11)–Zr–C(30)
C(30)–Zr–C(40)
Zr–C(40)–C(41)
2.1058(15)
2.278(2)
1.469(2)
1.581(2)
157.41(6)
97.51(6)
111.26(7)
94.99(7)
121.48(7)
106.71(12)
95.76(13)
and 3.19 Å from the ring centroid. The closest approach to the
C(31) ring centroid is from a methyl proton on the N(18)–Me group
in an adjacent complex to the ‘‘outer” face of the C(31) phenyl ring
with an Hꢁ ꢁ ꢁ
p separation of ca. 3.22 Å.
Comparing the titanium (14) to the zirconium complex (15), the
bonds between the metal and O(1), N(8) and N(11) are all length-
ened by ca. 0.12 Å in the zirconium derivative, and there is an asso-
ciated ca. 4° contraction of the O(1)–Zr–N(11) angle. As was the

R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
711
Scheme 9. Postulated mechanism for the formation of 15 and 16.
Table 7
Ethylene polymerization results.
Entry
Pre-catalysta
Co-catalyst
T (°C)
Yield (g)
Activityb
Mn (g molꢀ1
c
)
Mw (g molꢀ1
c
)
PDI
1
2
3
4
5
6
7
3
4
5
3
3
8
8
MAO (500 eq)
MAO (500 eq)
MAO (500 eq)
Al(iBu)3/DMAOd
Al(iBu)3/DMAOd
MAO (500 eq)
Al(iBu)3/DMAOd
25
25
25
25
50
25
25
Trace
–
–
–
–
150
133
–
–
–
–
–
–
–
–
–
–
47.9
23.2
–
0.55
0.50
–
10 300
19 400
–
–
493 200
450 200
–
–
Trace
–
–
Conditions: Schlenk, toluene (200 ml); 1.5 bar ethylene; 30 min.
a
Pre-catalyst loading: 5 lmol.
b
c
Activity in g mmolꢀ1 hꢀ1 barꢀ1
Determined by GPC.
.
d
Al(iBu)3/Ti = 100, DMAO/Ti = 200.
2.6. Ethylene polymerization tests
labelling experiments and found to proceeds via a radical pathway
for the benzyl complexes and via deprotonation of the ligand back-
bone by in situ formed free dimethylamine in the case of the ami-
do-titanium system. The reactivity of the ligand backbone may
account for the poor performance of these complexes in ethylene
polymerization.
Complexes 3–12 were investigated as catalyst precursors for
ethylene polymerization. Among the chloride pre-catalysts, 3
showed only trace activity upon activation with MAO. However,
when Al(iBu)3/DMAO (TMA free) was used as cocatalyst, an activity
of 150 g mmolꢀ1 hꢀ1 barꢀ1 was obtained. The resulting polyethyl-
ene has a molecular weight of about Mw of ꢃ500000 g molꢀ1 with
a broad molecular weight distribution (Table 7). In contrast, 4 and
5 were inactive under these conditions. The benzyl complexes of
zirconium and hafnium, 6, and 9–12, were also inactive upon acti-
vation with MAO or Al(iBu)3/[Ph3 C][B(C6F5)4].
4. Experimental
All manipulations of air and moisture sensitive compounds were
carried out under an atmosphere of N2 using standard Schlenk tech-
niques or by using a conventional nitrogen-filled glove box. Diethyl
ether was distilled under nitrogen, over sodium benzophenone ke-
tyl. THF was distilled under nitrogen, over potassium. Dichloro-
methane was dried and distilled over calcium hydride under an
atmosphere of nitrogen. Toluene and pentane, were dried by pass-
ing through a column filled with commercially available Q-5 reac-
tant (Cu(II)O on alumina 13% w/w) and activated alumina (pellets,
3 mm) and stored over a potassium mirror. Glycine-2-d2 ethyl ester
hydrochloride [60], 2-aminomethyl-1-methylbenzimidazole dihy-
drochloride [61], TiCl4(THF)2 [62], ZrCl4(THF)2 [62], HfCl4(THF)2
[62], Zr(CH2Ph)4 [63] and Hf(CH2Ph)4 [63] were prepared according
to published procedures. 3,5-di-tert-Butyl-salicylaldehyde, and
3. Conclusion
In summary, we have synthesized and characterized a series of
new Group 4 metal complexes bearing tridentate (NNO) ligands. It
was found that benzyl derivatives undergo ready migration of a
benzyl ligand from the metal centre to the imine carbon of the li-
gand backbone. Unusual dinuclear C–C coupled complexes were
identified as products of decomposition and an analogous product
was obtained from a titanium-amido precursor. The mechanism of
the coupling processes have been elucidated using deuterium

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R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
Ti(NMe2)4 were purchased from Aldrich and used without further
purification. Ethylene (CP grade) was purified by passing it through
an Oxy-trap and gas drier (Alltech Associates). MAO was purchased
from Chemtura. NMR spectra were recorded on Bruker, DRX-400,
Avance-400, Avance-500 spectrometers. IR spectra were recorded
on a Perkin–Elmer spectrum 1760X FT-IR spectrometer. Elemental
analyses were performed by the microanalytical services at London
Metropolitan University. Mass spectra were recorded on a VG Auto-
spec or a VG Platform II spectrometer.
1287 (w), 1249 (s), 1236 (m), 1203 (m), 1163 (m), 1150 (w),
1130 (w), 1070 (m), 1024 (s), 1009 (w), 996 (m), 921 (w), 888
(w), 866 (w), 824 (m), 767 (w), 740 (s), 727 (w), 696 (m), 650
(w), 575 (w), 507 (w), 436 (w).
4.2. Synthesis of complexes
4.2.1. [NNO]TiCl3 (3)
To a suspension of NaH (0.035 g, 1.48 mmol) in THF (10 mL) at
ꢀ78 °C was added a solution of 1 (0.557 g, 1.48 mmol) in THF
(10 mL). The reaction was allowed to warm up to room tempera-
ture and stirred for 1 h30. The resulting yellow solution was added
slowly onto a solution of TiCl4(THF)2 (0.493 g, 1.48 mmol) in THF
(5 mL) at ꢀ78 °C. The reaction became red and was left 2 h at room
temperature. The solution was filtered, and volatiles were evapo-
rated to afford a red powder. Yield = 0.55 g (70%). Anal. Calc. for
C24H30Cl3N3OTi (530.74): C, 54.30; H, 5.70; N, 7.92. Found: C,
54.19; H, 5.53; N, 7.81%. 1H NMR (500 MHz, THF-d8, 298 K): d
8.63 (dd, 1H, ArH), 8.59 (broad s, 1H, N@CH), 7.70 (d, 1H, ArH),
7.57 (m, 1H, ArH), 7.49 (d, 1H, ArH), 7.42 (m, 2H, ArH benz), 5.53
(s, 2H, N-CH2), 3.89 (s, 3H, N-CH3), 1.59 (s, 9H, C(CH3)3), 1.36 (s,
9H, C(CH3)3). 13C{1H} NMR (126 MHz, THF-d8, 298 K): d 166.7
(N@CH), 159.8 (Cq), 153.7 (Cq), 146.2 (Cq), 138.6 (Cq), 137.0 (Cq),
135.8 (Cq), 131.4 (CH), 129.9 (CH), 127.2 (Cq), 124.9 (CH), 124.7
(CH), 120.5 (CH), 110.6 (CH), 56.5 (N-CH2), 35.9 (C(CH3)3), 35.2
(C(CH3)3), 31.5 (C(CH3)3), 30.9 (N-CH3), 30.2 (C(CH3)3). IR (KBr (s),
cmꢀ1): 2956 (s), 2904 (m), 2864 (m), 2357 (w), 1617 (s), 1566
(m), 1505 (m), 1480 (w), 1457 (s), 1416 (m), 1391 (m), 1362 (m),
1316 (m), 1267 (m), 1247 (s), 1210 (w), 1184 (w), 1060 (m),
1008 (w), 934 (w), 919 (w), 905 (w), 870 (s), 760 (s), 618 (w),
603 (w), 578 (m), 497 (s), 410 (m).
4.1. Synthesis of pro-ligands
4.1.1. NNO (1)
2-aminomethyl-1-methylbenzimidazole
dihydrochloride
(2.00 g, 8.55 mmol) was dissolved in 5 mL of distilled water and
neutralized with potassium carbonate (1.18 g, 8.55 mmol). A stir-
red
solution
of
3,5-di-tert-butyl-salicylaldehyde
(2.00 g,
8.55 mmol) in 15 ml of methanol was added dropwise and the mix-
ture stirred for 12 h at room temperature. A yellow solid precipi-
tated out of the solution. The solid was filtered, dried and
crystallized from hot acetonitrile to afford a yellow crystalline
product. The product was dried at 60 °C under vacuum overnight.
Yield = 2.05 g (64%). Anal. Calc. for C24H31N3O (377.53): C, 76.35;
H, 8.28; N, 11.13. Found: C, 76.51; H, 8.30; N, 10.97%. 1H NMR
(500 MHz, CDCl3, 298 K): d 13.10 (s, 1H, OH), 8.54 (t, 1H, N@CH,
4
3JHH = 1.2 Hz), 7.76 (d, 1H, ArH), 7.39 (d, 1H, ArH, JHH = 2.5 Hz),
7.37 (m, 1H, ArH), 7.31 (dt, 1H, ArH), 7.28 (m, 1H, ArH), 7.09 (d,
4
3
1H, ArH, JHH = 2.5 Hz), 5.09 (s, 2H, CH2, JHH = 1.2 Hz), 3.91 (s, 3H,
N-CH3), 1.41 (s, 9H, C(CH3)3), 1.28 (s, 9H, C(CH3)3). 13C{1H} NMR
(126 MHz, CDCl3, 298 K): d 169.1 (N@CH), 157.7 (Cq), 150.7 (Cq),
142.3 (Cq), 140.5 (Cq), 136.7 (Cq), 136.2 (Cq), 127.7 (ArCH), 126.5
(ArCH), 122.9 (ArCH), 122.3 (ArCH), 119.9 (ArCH), 117.8 (Cq),
109.4 (ArCH), 55.5 (CH2), 35.00 (C(CH3)3), 34.1 (C(CH3)3), 31.4
(C(CH3)), 30.4 (N-CH3), 29.4 (C(CH3)). MS (positive ES; m/z): 378
[MꢀH]+. IR (KBr (s), cmꢀ1): 2995 (w), 2955 (s), 2906 (m), 2866
(m), 1625 (s), 1595 (m), 1507 (w), 1473 (s), 1441 (s), 1405 (m),
1393 (w), 1361 (m), 1323 (m), 1287 (w), 1272 (m), 1252 (s), 1243
(m), 1222 (w), 1206 (w), 1175 (m), 1151 (w), 1132 (w), 1059 (w),
1046 (w), 1006 (w), 944 (w), 881 (w), 860 (w), 828 (m), 805 (w),
768 (w), 756 (w), 739 (s), 646 (w), 414 (w).
4.2.2. [NNO]ZrCl3 (4)
An analogous procedure was employed to that described for 3,
using NaH (0.024 g, 1 mmol),
1 (0.376 g, 1.00 mmol) and
ZrCl4(THF)2 (0.375 g, 1.00 mmol). Yield = 0.42g (73%). Anal. Calc.
for C24H30Cl3N3OZr (574.09): C, 50.21; H, 5.27; N, 7.32. Found: C,
50.08; H, 4.99; N, 7.26%. 1H NMR (400 MHz, THF-d8, 298 K): d
4
8.68 (t, 1H, N@CH, JHH = 1.4 Hz), 8.35 (m, 1H, ArH benz), 7.71 (d,
4
1H, ArH, JHH = 2.5 Hz), 7.64 (m, 1H, ArH benz), 7.46 (m, 2H, ArH
4
benz), 7.42 (d, 1H, ArH, JHH = 2.5 Hz), 5.55 (d, 2H, N-CH2,
4.1.2. tBuNNO (2)
4JHH = 1.4 Hz), 3.94 (s, 3H, N-CH3), 1.55 (s, 9H, C(CH3)3), 1.35 (s,
9H, C(CH3)3). 13C{1H} NMR (101 MHz, THF-d8, 298 K): d 171.4
(N@CH), 157.5 (Cq), 155.2 (Cq), 143.9 (Cq), 138.8 (Cq), 137.9 (Cq),
135.8 (Cq), 132.2 (CH), 130.5 (CH), 125.3 (CH), 125.2 (CH), 124.3
(CH), 119.7 (CH), 111.1 (CH), 55.9 (N-CH2), 35.9 (C(CH3)3), 34.9
(C(CH3)3), 31.5 (C(CH3)3), 30.9 (N-CH3), 30.1 (C(CH3)3). IR (KBr (s),
cmꢀ1): 2958 (s), 2910 (m), 2872 (m), 1611 (s), 1566 (s), 1550 (m),
1506 (s) 1480 (w), 1461 (s), 1416 (s), 1395 (m), 1362 (w), 1321
(w), 1290 (m), 1276 (s), 1252 (s), 1212 (w), 1184 (m), 1136 (w),
1058 (m), 1012 (w), 940 (w), 920 (w), 900 (w), 864 (s), 816 (w),
758 (s), 699 (w), 619 (w), 602 (w), 562 (m), 497 (w), 475 (w), 433
(w), 410 (w).
To a solution of 1 (0.788 g, 2.09 mmol) in Et2O (10 mL) was
added t-butyllithium (2.8 mL, 4.18 mmol) at ꢀ78 °C. The red solu-
tion was allowed to warm up slowly to room temperature and stir-
red for 1 h. The reaction was quenched with a saturated aqueous
NH4Cl solution. The organic phase was separated, washed with
NH4Cl, brine; dried over Na2SO4 and evaporated to dryness. Recrys-
tallisation of the white residue in acetonitrile afforded white nee-
dles. Yield = 0.65 g (72%). Anal. Calc. for C28H41N3O (435.65): C,
77.20; H, 9.49; N, 9.65. Found: C, 77.27; H, 9.41; N, 9.78%. 1H
NMR (500 MHz, CDCl3, 298 K): d 11.61 (s, 1H, OH), 7.76 (m, 1H,
4
ArH), 7.30 (m, 3H, ArH), 7.22 (d, 1H, ArH, JHH = 2.4 Hz), 6.72 (d,
4
2
1H, ArH, JHH = 2.4 Hz), 3.98 (m, 2H, CH2, JHaHb = 14.1 Hz,
3JHaNH = 5.3 Hz, JHbNH = 9.0 Hz), 3.62 (s, 3H, N-CH3), 3.46 (s, 1H,
4.2.3. [NNO]HfCl3 (5)
3
CH-tBu), 2.86 (dd, 1H, NH, JHaNH = 5.3 Hz, JHbNH = 9.0 Hz)), 1.44
(s, 9H, C(CH3)3), 1.29 (s, 9H, C(CH3)3), 0.98 (s, 9H, C(CH3)3).
13C{1H} NMR (126 MHz, CDCl3, 298 K): d 154.3 (Cq), 152.1 (Cq),
142.4 (Cq), 139.1 (Cq), 135.7 (Cq), 135.7 (Cq), 126.7 (ArCH), 122.7
(ArCH), 122.5 (ArCH), 122.2 (ArC), 119.8 (ArC), 119.5 (ArCH),
109.4 (ArCH), 75.0 (CH-tBu), 43.9 (CH2), 36.3 (C(CH3)3), 34.9
(C(CH3)3), 34.0 (C(CH3)3), 31.6 (C(CH3)3), 29.8 (N-CH3), 29.6
(C(CH3)3), 27.3 (C(CH3)3). MS (positive ES; m/z): 436 [MꢀH]+. IR
(KBr (s), cmꢀ1): 3273 (m), 3060 (w), 2954 (s), 2906 (m), 2866
(m), 1964 (w), 1880 (w), 1616 (w), 1602 (w), 1511 (w), 1478 (s),
1439 (w), 1401 (m), 1359 (m), 1336 (w), 1326(w), 1298 (w),
An analogous procedure was employed to that described for 3,
3
3
using NaH (0.013 g, 0.53 mmol),
1 (0.201 g, 0.53 mmol) and
HfCl4(THF)2 (0.247 g, 0.53 mmol). Yield = 0.29g (82%). Anal. Calc.
for C24H30Cl3HfN3O (661.36): C, 43.59; H, 4.57; N, 6.35. Found: C,
43.78; H, 4.60; N, 6.31%. 1H NMR (400 MHz, THF-d8, 298 K): d
8.68 (broad s, 1H, N@CH), 8.37 (m, 1H, ArH), 7.73 (d, 1H, ArH,
4JHH = 2.5 Hz), 7.64 (m, 1H, ArH), 7.46 (m, 2H, ArH benz), 7.41 (d,
4
1H, ArH, JHH = 2.7 Hz), 5.60 (s, 2H, N-CH2), 3.93 (s, 3H, N-CH3),
1.54 (s, 9H, C(CH3)3), 1.34 (s, 9H, C(CH3)3). 13C{1H} NMR
(101 MHz, THF-d8, 298 K): d 172.1 (N@CH), 158.2 (Cq), 156.3
(Cq), 143.4 (Cq), 139.6 (Cq), 138.0 (Cq), 136.0 (Cq), 132.6 (CH),

R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
713
130.5 (CH), 125.5 (CH), 125.3 (CH), 124.5 (Cq), 119.8 (CH), 111.3
(CH), 55.8 (N-CH2), 35.9 (C(CH3)3), 35.0 (C(CH3)3), 31. 7 (C(CH3)3),
31.1 (N-CH3), 30.2 (C(CH3)3). IR (KBr (s), cmꢀ1): 2956 (s), 2909
(m), 2869 (m), 1612 (s), 1565 (s), 1553 (m), 1506 (m), 1482 (w),
1460 (s), 1419 (s), 1395 (m), 1362 (w), 1321 (m), 1292 (m), 1279
(s), 1254 (m), 1209 (w), 1201 (w), 1183 (m), 1136 (w), 1059 (m),
1010 (w), 939 (w), 919 (w), 902 (w), 864 (s), 773 (m), 756 (s),
700 (w), 643 (w), 616 (w), 605 (w), 557 (m), 492 (w), 475 (w),
433 (w), 410 (w).
(s), 883 (w), 861 (m), 798 (w), 744 (s), 698 (s), 681 (m), 601 (w),
568 (w), 542 (w), 518 (w), 466 (w).
4.2.6. tBu[NN(H)O]TiCl3 (8)
To a solution of TiCl4(THF)2 (0,092 g, 0.275 mmol) in THF
(10 ml), was added a solution of 2 (0.120 g, 0.275 mmol) in THF
(10 mL). The resulting red solution was stirred 2 h at room temper-
ature. The volatiles were removed in vacuo to afford a dark red so-
lid. Crystallisation from hot toluene affords dark red crystals.
Yield = 0.12 g (74%). Anal. Calc. for C28H40Cl3N3OTi (588.86): C,
57.11; H, 6.85; N, 7.14. Found: C, 57.18; H, 6.75; N, 7.06%. 1H
4.2.4. [NNO]Zr(CH2Ph)3 (6)
3
In
a
glove box,
a
solution of the pro-ligand
1
(0.200 g,
NMR (500 MHz, CDCl3, 298 K): d 8.60 (d, 1H, JHH = 8.1 Hz, ArH),
0.53 mmol) in toluene (5 mL) was added to
a
solution of
7.49–7.38 (m, 3H ArH), 7.31 (d, 1H, ArH), 6.89 (d, 1H, ArH), 4.92
3
3
Zr(CH2Ph)4 (0.241 g, 0.53 mmol) in toluene (5 ml). The resulting
solution was stirred at RT for 30 min and volatiles were removed
under reduced pressure. The solid residue was washed with cold
pentante to afford 6 as an orange powder. Yield = 0.25 g (65%).
Anal. Calc. for C45H51N3OZr (741.14): C, 72.93; H, 6.94; N, 5.67.
Found: C, 72.87; H, 6.89; N 5.58%. 1H NMR (500 MHz, C6D6,
283 K): d 7.86 (d, 1H, 3JHH = 2.5 Hz, ArH), 7.56 (d, 2H, 3JHH = 7.3 Hz,
ArH), 7.42 (t, 2H, 3JHH = 7.7 Hz, ArH), 7.35 (t, 1H, 3JHH = 8.2 Hz, ArH),
(dd (br), 1H, JHH = 1.4 Hz, JHH = 12.0 Hz, NH), 4.71 (t (br), 1H,
2
2JHH = 12.0 Hz, C(H)H), 4.37 (d (br), 1H, JHH = 12.0 Hz, C(H)H),
3
3.84 (s, 3H, N-CH3), 3.64 (br d, 1H, JHNH = 1.4 Hz, CH-tBu), 1.59
(s, 9H, C(CH3)3), 1.31 (s, 9H, C(CH3)3), 1.07 (s, 9H, C(CH3)3).
13C{1H} NMR (126 MHz, CDCl3, 298 K): d 151.9 (Cq), 144.5 (Cq),
137.9 (Cq), 134.3 (Cq), 133.5 (Cq), 126.6 (Cq), 126.0 (CH), 125.2
(CH), 122.9 (CH), 120.1 (CH), 109.5 (CH), 75.6 (CH-tBu), 52.4
(CH2), 37.7 (C(CH3)3), 35.1 (C(CH3)3), 34.5 (C(CH3)3), 31.4
(C(CH3)3), 31.0 (N-CH3), 30.4 (C(CH3)3), 27.3 (C(CH3)3). IR (KBr (s),
cmꢀ1): 3265 (w), 3233 (w), 2960 (s), 2910 (m), 2871 (m), 1615
(w), 1595 (w), 1502 (s), 1482 (m), 1459 (s), 1439 (w), 1419 (m),
1365 (m), 1327(w), 1294 (w), 1259 (w), 1235 (s), 1204 (w), 1171
(m), 1109 (w), 1053 (w), 1036 (w), 1012 (w), 932 (w), 913 (w),
875 (m), 861 (w), 785 (w), 761 (m), 750 (s), 643 (w), 600 (m),
475(w), 411 (m).
3
7.00–7.20 (m, 5H, 4 ArH + N@CH), 6.83 (d, 1H, JHH = 8.2 Hz, ArH),
6.38 (m, 6H, meta + para-CH2Ph), 5.91 (broad s, 4H, ortho-CH2Ph),
2
3.25 (s, 2H, Zr-CH2Ph), 2.94 (d, 2H, JHH = 9.2 Hz, Zr-CH(H)Ph),
2
2.77 (d, 2H, JHH = 9.2 Hz, Zr-CH(H)Ph), 2.67 (s, 2H, NCH2), 2.51 (s,
3H, NCH3), 1.87 (s, 9H, C(CH3)3), 1.35 (s, 9H, C(CH3)3). 13C{1H}
NMR (126 MHz, C6D6, 283 K): d 168.9 (N@CH), 158.5 (Cq), 152.1
(Cq), 150.4 (Cq), 149.8 (Cq), 141.6 (Cq), 139.5 (Cq), 134.3 (Cq),
131.1 (CH), 128.8 (CH), 128.7 (CH), 127.1 (CH), 127.0 (CH), 125. 8
(CH), 124.4 (CH), 122.6 (Cq), 119.8 (CH), 119.4 (CH), 118.5 (CH),
109.1 (CH), 71.5 (Zr-CH2Ph), 68.0 (Zr-CH2Ph), 54.7 (N-CH2), 35.7
(C(CH3)3), 34.4 (C(CH3)3), 31.6 (C(CH3)3), 29.8 (C(CH3)3), 28.9 (N-
CH3). IR (KBr (s), cmꢀ1): 3061 (m), 3007 (m), 2960 (s), 2908 (m),
2865 (m), 1617 (s), 1588 (s), 1561(m), 1546 (w), 1495 (m), 1478
(s), 1459 (m), 1438 (m), 1422 (m), 1415(m), 1403 (m), 1393 (m),
1362 (w), 1319 (m), 1292 (m), 1277 (m) 1257 (m), 1208 (s),
1177 (m), 1152 (w), 1094 (w), 1055 (w), 1027 (w), 1007 (w), 938
(s), 915 (m), 879 (w), 858 (m), 796 (m), 744 (s), 732 (m), 699 (s),
603 (w), 543 (w), 466 (w).
4.2.7. tBu[NNO]Zr(CH2Ph)2 (9)
Employing an analogous procedure to that described for 6, 2
(0.150 g, 0.34 mmol) was reacted with Zr(CH2Ph)4 (0.156 g,
0.34 mmol) to give 9 as a white powder. Yield = 0.19 g (78%). Anal.
Calc. for C42H53N3OZr (707.13): C, 71.34; H, 7.55; N, 5.94. Found: C,
71.68; H, 7.23; N 5.87%. 1H NMR (500 MHz, C6D6, 298 K): d 7.93 (d,
3
1H, JHH = 8.1 Hz, ArH), 7.53 (m, 3H, ArH), 7.47 (m, 2H, ArH), 7.19
3
(dt, 1H, ArH), 7.09–7.14 (m, 2H, ArH), 6.71 (d, 1H, JHH = 8.0 Hz,
3
ArH), 6.45 (t, 2H, JHH = 7.5 Hz, meta-CH2Ph), 6.36 (t, 1H,
3JHH = 7.2 Hz, para-CH2Ph), 5.74 (d, 2H, 3JHH = 7.2 Hz, ortho-CH2Ph),
2
2
4.09 (d, 1H, JHH = 19.2 Hz, NC(H)H), 3.48 (d, 1H, JHH = 19.2 Hz,
2
4.2.5. [NNO]Hf(CH2Ph)3 (7)
NC(H)H), 3.33 (s, 1H, NCHtBu), 2.95 (d, 1H, JHH = 9.8 Hz, Zr-CH(H)
2
Using an analogous procedure to that described for 6, reaction
of 1 (0.175 g, 0.46 mmol) with Hf(CH2Ph)4 (0.251 g, 0.46 mmol)
afforded 7 as an orange powder. Yield = 0.29 g (76%). Anal. Calc.
for C45H51HfN3O (828.41): C, 65.24; H, 6.21; N, 5.07. Found: C,
65.39; H, 6.14, N 4.97%. 1H NMR (400 MHz, C6D6, 298 K): d 7.90
Ph), 2.61 (d, 1H, JHH = 9.8 Hz, Zr-CH(H)Ph), 2.41 (s, 3H, N-CH3),
2
2.14 (d, 1H, JHH = 10.5 Hz, Zr-CH(H)Ph), 1.67 (s, 9H, C(CH3)3),
2
1.63 (d, 1H, JHH = 10.5 Hz, Zr-CH(H)Ph), 1.48 (s, 9H, C(CH3)3),
1.19 (s, 9H, C(CH3)3). 13C{1H} NMR (126 MHz, C6D6, 298 K): d
160.4 (Cq), 156.1 (Cq), 149.5 (Cq), 141.6 (Cq), 139.7 (Cq), 139.0
(Cq), 135.4 (Cq), 135.2 (Cq), 132.1 (Cq), 131.8 (CH), 128.3 (CH),
127.4 (CH), 126.9 (CH), 126.3 (CH), 124.6 (CH), 123.7 (CH), 123.6
(CH), 123.5 (CH), 121.7 (CH), 119.2 (CH), 118.7 (CH), 109.5 (CH),
80.8 (NCHtBu), 59.4 (Zr-CH2Ph), 58.8 (Zr-CH2Ph), 56.9 (N-CH2),
40.0 (C(CH3)3), 35.3 (C(CH3)3), 34.4 (C(CH3)3), 32.1 (C(CH3)3), 30.6
(C(CH3)3), 28.6 (N-CH3), 28.1 (C(CH3)3). IR (KBr (s), cmꢀ1): 3062
(w), 3048 (w), 3005 (w), 2954 (s), 2904 (m), 2865 (m), 2787 (w),
1619 (w), 1590 (m), 1494 (m), 1481 (s), 1457 (s), 1443 (m), 1418
(w), 1389 (w), 1361 (m), 1314 (m), 1284 (m), 1248 (s), 1239 (m),
1202 (m), 1169 (m), 1133 (w), 1110 (m), 1068 (m), 1020 (w),
914 (w), 868 (w), 848 (m), 790 (w), 740 (s), 697 (m), 655 (w),
580 (w), 566 (w), 536 (w), 426 (w).
3
3
(d, 1H, JHH = 2.8 Hz, ArH), 7.49 (d, 2H, JHH = 7 Hz, ArH), 7.41 (t,
3
3
2H, JHH = 7.7 Hz, ArH), 7.31 (t, 1H, JHH = 7 Hz, ArH), 7.17 (d, 1H,
3JHH = 8 Hz, ArH), 7.07 (m, 2H, ArH and N@CH), 7.03 (d, 1H,
3JHH = 2.4 Hz, ArH), 6.91 (d, 1H, JHH = 8 Hz, ArH), 6.85 (d, 1H,
3
3JHH = 8 Hz, ArH), 6.41 (m, 6H, meta + para-CH2Ph), 5.84 (d, 4H,
3JHH = 6.8 Hz, ortho-CH2Ph), 2.84 (broad s, 2H, Hf-CH2Ph), 2.67 (s,
2
2H, N-CH2), 2.55 (s, 3H, N-CH3), 2.48 (d, 2H, JHH = 9.6 Hz, Hf-
CH(H)Ph), 2.32 (d, 2H, JHH = 9.6 Hz, Hf-CH(H)Ph), 1.86 (s, 9H,
2
C(CH3)3), 1.34 (s, 9H, C(CH3)3). 13C{1H} NMR (101 MHz, C6D6,
298 K): d 169.6 (N@CH), 158.3 (Cq), 152.5 (Cq), 152.1 (Cq), 149.5
(Cq), 142.1 (Cq), 139.9 (Cq), 137.6 (Cq), 134.6 (Cq), 131.4 (CH),
128.8 (CH), 128.6 (CH), 128.5 (Cq), 127.5 (CH), 126.8 (CH), 125.4
(CH), 124.9 (CH), 124.4 (CH), 123.1 (Cq), 120.1 (CH), 119.7 (CH),
118.3 (CH), 109.9 (CH), 77.9 (Hf-CH2Ph), 69.5 (Hf-CH2Ph), 54.0
(N-CH2), 35.7 (C(CH3)3), 34.4 (C(CH3)3), 31.6 (C(CH3)3), 29.8
(C(CH3)3), 28.9 (N-CH3). IR (KBr (s), cmꢀ1): 3063 (m), 3035 (w),
3007 (m), 2954 (s), 2906 (m), 2869 (m), 1617 (s), 1589 (s), 1561
(m), 1506 (m), 1478 (s), 1459 (m), 1441 (m), 1424 (m), 1415 (m),
1403 (m), 1360 (w), 1318 (w), 1289 (m), 1279 (m), 1256 (m),
1241 (w), 1208 (m), 1176 (m), 1057 (w), 1027 (w), 100 (w), 950
4.2.8. tBu[NNO]Hf(CH2Ph)2 (10)
Employing an analogous procedure to that described for 6, 2
(0.154 g, 0.35 mmol) was reacted with Hf(CH2Ph)4 (0.192 g,
0.35 mmol) to afford 10 as a white powder. Yield = 0.22 g (77%).
Anal. Calc. for C42H53HfN3O (794.38): C, 63.50; H, 6.72; N, 5.29.
Found: C, 63.37; H, 6.80; N 5.24%. 1H NMR (400 MHz, C6D6,
3
298 K): d 7.87 (d, 1H, 3JHH = 7.9 Hz, ArH), 7.56 (d, 3H, JHH = 8.3 Hz,

714
R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
ArH), 7.45 (t, 2H, 3JHH = 7.7 Hz, ArH), 7.20 (m, 1H, ArH), 7.13 (m, 3H,
ArH), 7.47 (d, 2H, 3JHH = 7.1 Hz, ArH), 7.40 (t, 2H, 3JHH = 7.7 Hz, ArH),
7.00–7.07 (m, 7H, ArH), 6.89 (d, 1H, 4JHH = 2.2 Hz, ArH), 6.64 (d, 1H,
3
3
ArH), 6.72 (d, 1H, JHH = 7.9 Hz, ArH), 6.48 (t, 2H, JHH = 7.2 Hz,
3
3
meta-CH2Ph), 6.37 (t, 1H, JHH = 7.2 Hz, para-CH2Ph), 5.74 (d, 2H,
3JHH = 8.1 Hz, ArH), 6.55 (t, 2H, JHH = 7.6 Hz, meta-CH2Ph), 6.40 (t,
2
3
3
3JHH = 7.1 Hz, ortho-CH2Ph), 4.25 (d, 1H, JHH = 19 Hz, N-CH(H)),
1H, JHH = 7.2 Hz, para-CH2Ph), 6.18 (d, 2H, JHH = 7.5 Hz, ortho-
2
3
3.50 (d, 1H, JHH = 19 Hz, N-CH(H)), 3.46 (s, 1H, NCHtBu), 2.86 (d,
CH2Ph), 4.02 (t, 1H, JHH = 6.7 Hz, CH-CH2Ph), 3.77 (q, 2H,
2
2
2
3
1H, JHH = 11.3 Hz, Hf-CH(H) Ph), 2.44(d, 1H, JHH = 11.3 Hz, Hf-
2JHH = 18.6 Hz, N-CH2), 3.21 (m, 2H, JHH = 12.7 Hz, JHH = 6.8 Hz,
2
2
CH(H)Ph), 2.41 (s, 3H, N-CH3), 2.18 (d, 1H, JHH = 11.1 Hz,
Hf-CH(H)Ph), 1.72 (s, 9H, C(CH3)3), 1.55 (d, 1H, JHH = 11.1 Hz, Hf-
CH-CH2Ph), 2.62 (d, 1H, JHH = 10.9 Hz, Hf-CH(H)Ph), 2.46 (d, 1H,
2
2JHH = 10.9 Hz, Hf-CH(H)Ph), 2.26 (s, 3H, N-CH3), 2.16 (d, 1H,
2JHH = 11.5 Hz, Hf-CH(H)Ph), 1.83 (s, 9H, C(CH3)3), 1.67 (d, 1H,
2JHH = 11.5 Hz, Hf-CH(H)Ph), 1.38 (s, 9H, C(CH3)3). 13C{1H} NMR
(126 MHz, C6D6, 298 K): d 161.3 (Cq), 155.3 (Cq), 148.3 (Cq),
142.4 (Cq), 141.0 (Cq), 140.7 (Cq), 138.8 (Cq), 136.6 (Cq), 135.1
(Cq), 134.4 (Cq), 130.5 (CH), 129.9 (CH), 128.5 (CH), 127.8 (CH),
127.3 (CH), 125.8 (CH), 124.0 (CH), 123.8 (CH), 123.7 (CH), 123.0
(CH), 122.2 (CH), 120.1 (CH), 119.0 (CH), 109.5 (CH), 73.1 (CH-
CH2Ph), 66.9 (Hf-CH2Ph), 66.2 (Hf-CH2Ph), 54.6 (N-CH2), 48.2
(CH-CH2Ph), 35.6 (C(CH3)3), 34.4 (C(CH3)3), 32.0 (C(CH3)3), 30.8
(C(CH3)3), 28.6 (N-CH3). IR (KBr (s), cmꢀ1): 3054 (w), 3020 (w),
2951 (s), 2899 (m), 2858 (m), 2801 (w), 2772 (w), 1589 (m),
1497 (m), 1477 (s), 1457 (s), 1442 (m), 1414 (w), 1356 (w), 1316
(w), 1284 (m), 1253 (s), 1238 (m), 1201 (m), 1178 (m), 1126 (w),
1118 (w), 1083 (m), 1026 (w), 1006 (w), 971 (w), 931 (w), 873
(w), 850 (m), 805 (w), 787 (w), 773 (w), 741 (s), 695 (m), 606
(w), 566 (w), 529 (w), 431 (w).
CH(H)Ph), 1.49 (s, 9H, C(CH3)3), 1.18 (s, 9H, C(CH3)3)). 13C{1H}
NMR (101 MHz, C6D6, 298 K): d 161.0 (Cq), 156.0 (Cq), 148.6 (Cq),
142.1 (Cq), 139.7 (Cq), 138.9 (Cq), 136.3 (Cq), 135.3 (Cq), 132.4
(Cq), 130.7 (CH), 128.3 (CH), 127.9 (CH), 126.8 (CH), 126.2 (CH),
125.3 (CH), 123.9 (CH), 123.8 (CH), 123.3 (CH), 121.8 (CH), 119.7
(CH), 118.7 (CH), 109.6 (CH), 80.3 (NCH(tBu)), 67.4 (Hf-CH2Ph),
65.8 (Hf-CH2Ph), 56.5 (N-CH2), 40.0 (C(CH3)3), 35.3 (C(CH3)3),
34.3 (C(CH3)3), 32.1 (C(CH3)3), 30.7 (C(CH3)3), 28.5 (N-CH3), 28.1
(C(CH3)3). IR (KBr (s), cmꢀ1): 3063 (w), 3048 (w), 3006 (w), 2952
(w), 2905 (m), 2863 (m), 2786 (w), 1590 (m), 1531 (w), 1494
(m), 1481 (s), 1456 (s), 1442 (m), 1417 (w), 1388 (w), 1360 (m),
1313(w), 1287 (m), 1250 (s), 1240 (m), 1200 (m),1167 (m), 1133
(w), 1115 (m),1073 (m), 1027 (w), 1006 (w), 975 (w), 936 (w),
869 (w), 848 (m), 791 (m), 742 (s), 704 (m), 657 (w), 648 (w),
581 (w), 570 (w), 536 (w), 480 (w), 428 (w).
4.2.9. Bn[NNO]Zr(CH2Ph)2 (11)
In
a
glove box,
a
solution of the pro-ligand
1
(0.169 g,
4.2.11. Bn[NNO]Ti(CH2Ph)2 (13)
0.45 mmol) in toluene (5 mL) was added to
a
solution of
To a solution of 3 (0.21 g, 0.39 mmol) in THF (20 mL) at ꢀ78 °C
was added 0.9 mL (1.18 mmol) of a PhCH2MgCl solution (20 wt%)
in THF. The reaction was stirred for 3 h at ꢀ78 °C, filtered and
the volatiles then evaporated under vacuum keeping the tempera-
ture below 0 °C, to afford a brown-red solid. The solid was washed
with cold pentane, filtered and dried under vacuum. Yield = 0.12g
(44%). Satisfactory elemental analysis could not be obtained due
to the thermal sensitivity of the sample. 1H NMR (400 MHz, C6D6,
Zr(CH2Ph)4 (0.204 g, 0.45 mmol) in toluene (5 ml). The resulting
solution was stirred at 40 °C overnight and volatiles were removed
under reduced pressure. The solid residue was washed with cold
pentane, filtered and dried under vacuum to afford a pale pink so-
lid. Yield = 0.28g (86%). Anal. Calc. for C45H51N3OZr (741.14): C,
72.93; H, 6.94; N, 5.67. Found: C, 72.81; H, 6.81; N 5.48%. 1H
3
NMR (500 MHz, C6D6, 298 K): d 7.89 (d, 1H, JHH = 8.1 Hz, ArH),
4
4
7.54 (d, 1H, JHH = 2.4 Hz, ArH), 7.48 (m, 4H, ArH), 7.19 (dt, 1H,
298 K): d 7.94 (d, 1H, 3JHH = 7.9 Hz, ArH), 7.54 (d, 1H, JHH = 2.4 Hz,
3JHH = 8.1 Hz, ArH), 7.00–7.12 (m, 7H, ArH), 6.94 (d, 1H,
ArH), 7.40 (d, 2H, 3JHH = 7.2 Hz, ArH), 7.22 (t, 2H, 3JHH = 7.5 Hz, ArH),
3
4
4JHH = 2.4 Hz, ArH), 6.64 (d, 1H, JHH = 8.1 Hz, ArH), 6.46 (t, 2H,
7.00 (m, 7H, ArH), 6.81 (d, 1H, JHH = 2.4 Hz, ArH), 6.74 (d, 1H,
3
3
3JHH = 7.6 Hz, meta-CH2Ph), 6.34 (t, 1H, JHH = 7.2 Hz, para-CH2Ph),
3JHH = 7.9 Hz, ArH), 6.50 (t, 2H, JHH = 7.4 Hz, meta-CH2Ph), 6.40 (t,
3
3
3
3
6.09 (d, 2H, JHH = 7.2 Hz, ortho-CH2Ph), 3.89 (t, 1H, JHH = 6.9 Hz,
1H, JHH = 7.2 Hz, para-CH2Ph), 6.01 (d, 2H, JHH = 7.3 Hz, ortho-
2
3
CH-CH2Ph), 3.70 (q, 2H, JHH = 18.8 Hz, N-CH2), 3.30 (m, 2H,
CH2Ph), 3.79 (t, 1H, JHH = 6.9 Hz, CH-CH2Ph), 3.64 (q, 2H,
3
2
2
2JHH = 12.7 Hz, JHH = 6.9 Hz, CH-CH2Ph), 2.79 (d, 1H, JHH = 9.4 Hz,
2JHH = 19.4 Hz, N-CH2), 3.28 (d, 1H, JHH = 9.2 Hz, Ti-CH(H)Ph),
2
2
2
Zr-CH(H)Ph), 2.59 (d, 1H, JHH = 9.4 Hz, Zr-CH(H) Ph), 2.28 (s, 3H,
3.22 (d, 1H, JHH = 9.2 Hz, Ti-CH(H)Ph), 2.97 (m, 2H, JHH = 12.8 Hz,
2
N-CH3), 2.10 (d, 1H, JHH = 10.7 Hz, Zr-CH(H)Ph), 1.79 (s, 9H,
3JHH = 6.9 Hz, CH-CH2Ph), 2.57 (d, 1H, 2JHH = 9 Hz, Ti-CH(H)Ph), 2.39
2
2
C(CH3)3), 1.64 (d, 1H, JHH = 10.7 Hz, Zr-CH(H)Ph), 1.39 (s, 9H,
(d, 1H, JHH = 9 Hz, Ti-CH(H)Ph), 2.38 (s, 3H, N-CH3), 1.91 (s, 9H,
C(CH3)3). 13C{1H} NMR (126 MHz, C6D6, 298 K): d 160.7 (Cq),
155.5 (Cq), 149.2 (Cq), 141.6 (Cq), 141.0 (Cq), 140.7 (Cq), 138.8
(Cq), 135.7 (Cq), 135.0 (Cq), 134.3 (Cq), 131.9 (CH), 130.0 (CH),
128.2 (CH), 127.4 (CH), 127.2 (CH), 125.9 (CH), 125.0 (CH), 123.8
(CH), 123.7 (CH), 123.5 (CH), 123.2 (CH), 122.0 (CH), 119.5 (CH),
119.1 (CH), 109.5 (CH), 73.6 (CH-CH2Ph), 58.9 (Zr-CH2Ph), 57.7
(Zr-CH2Ph), 55.0 (N-CH2), 48.9 (CH-CH2PH), 35.5 (C(CH3)3), 34.4
(C(CH3)3), 32.0 (C(CH3)3), 30.8 (C(CH3)3), 28.6 (N-CH3). IR (KBr (s),
cmꢀ1): 3054 (w), 3020 (w), 2951 (s), 2904 (m), 2858 (m), 1617
(w), 1600 (w), 1589 (w), 1495 (m), 1480 (s), 1457 (s), 1440 (s),
1418 (m), 1390 (w), 1359 (m), 1289 (m), 1260 (m), 1237 (m),
1203 (w), 1176 (w), 1128 (w), 1099 (w), 1078 (m), 1027 (w),
1008 (w), 929 (w), 876 (w), 845 (w), 799 (w), 740 (s), 698 (m),
532 (m), 463 (w), 449 (w).
C(CH3)3), 1.34 (s, 9H, C(CH3)3). 13C{1H} NMR (101 MHz, C6D6,
298 K): d 162.9 (Cq), 157.4 (Cq), 152.6 (Cq), 149.6 (Cq), 141.7
(Cq), 141.1 (Cq), 137.0 (Cq), 136.1 (Cq), 135.0 (Cq), 134.8 (Cq),
129.8 (CH), 129.1 (CH), 128.8 (CH), 126.7 (CH), 126.0 (CH), 125.5
(CH), 125.0 (CH), 123.5 (CH), 123.2 (CH), 123.0 (CH), 122.0 (CH),
121.8 (CH), 120.3 (CH), 119.0 (CH), 109.4 (CH), 75.9 (Ti-CH2Ph),
74.8 (Ti-CH2Ph), 64.8 (CH-CH2Ph), 56.2 (N-CH2), 37.8 (CH-CH2Ph),
35.6 (C(CH3)3), 34.2 (C(CH3)3), 31.7 (C(CH3)3), 31.0 (C(CH3)3), 28.5
(N-CH3).
4.2.12. {[NNO]Ti(NMe2)2}2 (14)
A solution of 1 (0.347 g, 0.92 mmol) in toluene (4 mL) was
added to a solution of Ti(NMe2)4 (0.206 g, 0.92 mmol) in toluene
(2 mL). The resulting dark brown solution was stirred for 30 min
at room temperature and allowed to stand overnight. An orange
crystalline solid precipitated out of the solution and was isolated
by filtration and dried under vacuum. Yield = 0.32 g (68% in respect
to 1). Anal. Calc. for C56H82N10O2Ti2 (1022.56): C, 65.74; H, 8.08; N,
13.69. Found: C, 65.61; H, 7.92; N, 13.58%. 1H NMR (400 MHz, THF-
d8, 298 K): d 7.70 (d, 2H, ArH, 3JHH = 7.5 Hz), 7.23–7.30 (m, 6H, ArH),
7.16 (d, 2H, ArH, 4JHH = 2.4 Hz), 6.18 (d, 2H, ArH, 4JHH = 2.4 Hz), 4.50
4.2.10. Bn[NNO]Hf(CH2Ph)2 (12)
Employing an analogous procedure to that described for 11, 1
(0.168 g, 0.45 mmol) was reacted with Hf(CH2Ph)4 (0.241 g,
0,44 mmol) at 50 °C for 24 h to give a pale pink solid. Yield = 0.33g
(90%). Anal. Calc. for C45H51HfN3O (828.41): C, 65.24; H, 6.21; N,
5.07. Found: C 65.43, H 6.14, N, 5.03%. 1H NMR (500 MHz, C6D6,
3
4
3
3
298 K): d 7.81 (d, 1H, JHH = 8.1 Hz, ArH), 7.56 (d, 1H, JHH = 2.4 Hz,
(d, 2H, CH, JHH = 7.3 Hz), 4.00 (d, 2H, CH, JHH = 7.3 Hz), 3.49 (s,

R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
715
12H, Ti-N(CH3)2), 2.89 (s, 12H, Ti-N(CH3)2), 2.78 (s, 6H, N-CH3), 1.58
(s, 9H, C(CH3)3), 0.84 (s, 18H, C(CH3)3). 13C{1H} NMR (101 MHz,
THF-d8, 298 K): d 160.6 (Cq), 159.5 (Cq), 135.6 (Cq), 135.1 (Cq),
129.65 (Cq), 128.74 (Cq), 123.5 (ArCH), 122.9 (Cq), 122.7 (ArCH),
122.1 (ArCH), 117.9 (ArCH), 110.1 (ArCH), 84.4 (CH), 72.1 (CH),
46.0 (Ti-N(CH3)2), 35.0 (C(CH3)3), 33.5 (C(CH3)3), 31.0 (C(CH3)3),
29.3 (C(CH3)3), 28.8 (N-CH3). IR (KBr (s), cmꢀ1): 2952 (s), 2905
(m), 2860 (m), 2813 (m), 2765 (m), 1617 (w), 1523 (w), 1494
(m), 1475 (s), 1459 (s), 1442 (s), 1416 (m), 1360 (w), 1333 (w),
1271 (s), 1258 (m), 1202 (w), 1171 (w), 1132 (w), 1101 (w),
1062 (w), 1004 (w), 942 (s), 926 (m), 877 (w), 841 (m), 790 (m),
743 (s), 699 (w), 650 (w), 590 (w) 565 (m), 549 (m), 489 (w),
482 (w).
tert-butyl-salicylaldehyde (1.95 g, 8.26 mmol). Yield = 1.8 g (60%),
Anal. Calc. for C24H29D2N3O (379.53): C, 75.95; H, 7.70; N, 11.07.
Found: C, 75.81; H, 7.80; N, 10.97%. 1H NMR (400 MHz, CDCl3,
298 K): d 13.13 (s, 1H, OH), 8.54 (t, 1H, N@CH), 7.76 (d, 1H, ArH),
4
7.39 (d, 1H, Ar-H, JHH = 2.5 Hz), 7.37 (m, 1H, ArH), 7.31 (m, 2H,
4
ArH), 7.08 (d, 1H, Ar-H, JHH = 2.5 Hz), 3.91 (s, 3H, N-CH3), 1.41 (s,
9H, C(CH3)3), 1.28 (s, 9H, C(CH3)3). 13C{1H} NMR (101 MHz, CDCl3,
298 K): d 169.1 (N@CH), 157.7 (Cq), 150.7 (Cq), 142.3 (Cq), 140.5
(Cq), 136.7 (Cq), 136.2 (Cq), 127.7 (ArCH), 126.5 (ArCH), 122.9
(ArCH), 122.3 (ArCH), 119.9 (ArCH), 117.7 (Cq), 109.4 (ArCH), 55.5
(CD2), 35.00 (C(CH3)3), 34.1 (C(CH3)3), 31.4 (C(CH3)), 30.4 (N-CH3),
29.3 (C(CH3)). MS (positive ES; m/z): 380 [MꢀH]+. IR (KBr (s),
cmꢀ1): 2997 (w), 2956 (s), 2911 (m), 2869 (m), 2362 (m), 2342
(m), 1626 (s), 1594 (m), 1504 (w), 1469 (s), 1441 (s), 1395 (m),
1377 (w), 1361 (m), 1329 (m), 1285 (w), 1271 (m), 1251 (s),
1202 (s), 1175 (m), 1151 (w), 1131 (w), 1087 (w), 1066 (w),
1027 (w), 1010 (w), 964 (w), 925 (w), 891 (w), 828 (m), 802 (w),
773 (w), 752 (w), 739 (s), 669 (w), 645 (w), 512 (w).
4.2.13. 2-aminomethyl-1-methylbenzimidazole dihydrochloride-d2
N-Methylphenylenediamine (5 g, 41 mmol) and glycine-2-d2
ethyl ester hydrochloride (5.8 g, 41 mmol) were refluxed in HCl
6 M (100 mL). After cooling, the blue solution was boiled with
charcoal, filtered and volatiles were evaporated to afford dark blue
oil. Trituration in absolute ethanol afforded a blue crystalline prod-
uct. Yield = 4.8 g (50%), Anal. Calc. for C9H9D2N3 ꢁ 2HCl (236.14): C,
45.78; H, 4.70; N, 17.79. Found: C, 45.83; H, 4.79; N, 17.68%. 1H
NMR (400 MHz, D2O, 298 K): d 7.84 (m, 2H, ArH), 7.66 (m, 2H,
ArH), 4.09 (s, 3H, N-CH3). 13C NMR (101 MHz, D2O, 298 K): d
143.5 (Cq), 132.7 (Cq), 130.4 (Cq), 127.5 (CH), 127.1 (CH), 114.6
(CH), 112.8 (CH), 32.5 (CD2), 31.6 (N-CH3). MS (positive ES; m/z):
164 [Mꢀ2HCl]+.
4.2.15. {[d2-NNO]Ti(NMe2)}2 (14d2)
In a glove box, 1d2 (0.020 g, 0.053 mmol) and Ti(NMe2)4
(0.012 g, 0.053 mmol) were mixed in C6D6, the resulting brown
solution was stirred for 30 min and allowed to stand overnight,
the crystalline precipitate was filtered off, dried and dissolved in
THF-d8. 1H NMR (400 MHz, THF-d8, 298 K): d 7.70 (d, 2H, ArH,
3JHH = 7.5 Hz), 7.23–7.30 (m, 6H, ArH), 7.16 (d, 2H, ArH,
4
4JHH = 2.4 Hz), 6.18 (d, 2H, ArH, JHH = 2.4 Hz), 4.00 (s, 2H, CH),
3.49 (s, 12H, Ti-N(CH3)2), 2.89 (s, 12H, Ti-N(CH3)2), 2.78 (s, 6H,
N-CH3), 1.58 (s, 9H, C(CH3)3), 0.84 (s, 18H, C(CH3)3). 13C{1H} NMR
(101 MHz, THF-d8, 298 K): d 160.6 (Cq), 159.5 (Cq), 135.6 (Cq),
135.1 (Cq), 129.65 (Cq), 128.74 (Cq), 123.5 (ArCH), 122.9 (Cq),
122.7 (ArCH), 122.1 (ArCH), 117.9 (ArCH), 110.1 (ArCH), 84.4
4.2.14. d2-NNO (1d2)
Following similar procedure described for 1, using 2-amino-
methyl-1-methylbenzimidazole
dihydrochloride-d2
(1.95 g,
8.26 mmol), potassium carbonate (1.14 g, 8.26 mmol) and 3,5-di-
Table 8
Crystal data, data collection and refinement parameters for compounds 3, 8, 10, 14, 15 and 16.a
Data
3
8
10
14
15
16
Formula
Solvent
C24H30Cl3N3OTi
MeCN
C28H40Cl3N3OTi
C7H8
C42H53HfN3O
–
C52H70Cl2N8O2Ti2
4CH2Cl2
C76H86N6O2Zr2
4C6H6
C76H86Hf2N6O2
4C6H6
Formula weight
Colour, habit
571.81
Red plates
681.01
Orange platy
needles
794.36
Colourless plates
1345.56
Orange/red blocky
needles
1610.38
Colourless
needles
1784.92
Colourless blocks
Crystal size (mm)
0.14 ꢂ 0.09 ꢂ 0.02
0.29 ꢂ 0.13 ꢂ 0.07
Temperature (K)
Crystal system
Space group
a (Å)
0.42 ꢂ 0.24 ꢂ 0.04
0.17 ꢂ 0.09 ꢂ 0.02
0.41 ꢂ 0.18 ꢂ 0.12
0.14 ꢂ 0.06 ꢂ 0.04
173
173
173
173
173
173
Monoclinic
Pn (no. 7)
11.19494(19)
20.2370(3)
25.4362(4)
–
Monoclinic
P21/c (no. 14)
20.4913(5)
10.8508(2)
16.6923(3)
–
103.126(2)
–
3614.51(13)
4
Monoclinic
P21/c (no. 14)
37.4537(4)
11.71132(11)
17.24202(14)
–
Triclinic
Monoclinic
P21/n (no. 14)
11.76130(6)
17.88338(9)
20.29847(10)
–
Monoclinic
P21/n (no. 14)
11.76313(10)
17.86777(14)
20.30114(19)
–
ꢀ
P1 (no. 2)
10.5096(8)
12.1591(17)
13.562(2)
98.227(12)
94.670(9)
104.768(9)
1645.9(4)
1d
b (Å)
c (Å)
a
(°)
b (°)
102.4417(16)
–
91.3951(9)
–
94.1037(4)
–
93.6476(8)
–
c
(°)
V (Å3)
5627.3(2)
7560.64(11)
4258.47(15)
4258.27(12)
Z
8b
8c
2d
2d
Dc (g cmꢀ3
)
1.350
1.251
1.396
1.358
1.256
1.392
Radiation used
Mo K
0.615
56
a
Cu K
4.274
126
a
Cu K
5.358
126
a
Mo K
0.694
64
a
Cu K
2.410
143
a
Mo Ka
2.489
65
l
(mmꢀ1
)
2hmax (°)
No. of unique reflections
19976
5688
11908
10256
8228
14172
measured
Observed, |Fo| > 4
r(|Fo|)
16983
2265
8651
5894
6163
10774
No. of variables
R1, wR2
1298
0.039, 0.091
365
0.045, 0.062
849
0.028, 0.051
439
0.059, 0.141
498
0.026, 0.061
498
0.025, 0.055
e
a
Details in common: graphite monochromated radiation, refinement based on F2.
There are four independent complexes.
There are two independent complexes.
b
c
d
e
The complex has crystallographic Ci symmetry.
P
P
P
P
2
2
1=2
2
R1
¼
jjFoj ꢀ jFcjj= jFoj; wR2
¼
½wðF2o ꢀ F2c Þ ꢄ= ½wðFo2Þ ꢄ ; wꢀ1
¼
r2ðF2oÞ þ ðaPÞ þ bP.

716
R. Cariou et al. / Journal of Organometallic Chemistry 694 (2009) 703–716
[21] K.V. Axenov, M. Klinga, O. Lehtonen, H.T. Koskela, M. Leskelae, T. Repo,
Organometallics 26 (2007) 1444.
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Organomet. Chem. 665 (2003) 135.
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Chem. Commun. (2005) 3150.
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Organometallics 25 (2006) 6019.
[25] M. Sanz, T. Cuenca, M. Galakhov, A. Grassi, R.K.J. Bott, D.L. Hughes, S.J.
Lancaster, M. Bochmann, Organometallics 23 (2004) 5324.
[26] D.C.H. Oakes, B.S. Kimberley, V.C. Gibson, D.J. Jones, A.J.P. White, D.J. Williams,
Chem. Commun. (2004) 2174.
(CH), 72.1 (CD), 46.0 (Ti-N(CH3)2), 35.0 (C(CH3)3), 33.5 (C(CH3)3),
31.0 (C(CH3)3), 29.3 (C(CH3)3), 28.8 (N-CH3). IR (KBr (s), cmꢀ1):
2953 (s), 2904 (m), 2861 (m), 2812 (m), 2766 (m), 1613 (w),
1492 (m), 1477 (s), 1457 (s), 1443 (s), 1414 (m), 1391 (w), 1360
(w), 1328 (w), 1274 (m), 1250 (m), 1205 (w), 1174 (w), 1174
(w), 1133 (w), 1114 (w), 1057 (w), 1007 (w), 943 (s), 880 (w),
842 (m), 785 (m), 747 (s), 650 (w), 565 (m), 551 (m), 494 (w),
474 (w).
4.3. X-ray crystallography
[27] D.C.H. Oakes, V.C. Gibson, A.J.P. White, D.J. Williams, Inorg. Chem. 45 (2006)
3476.
[28] D.J. Jones, V.C. Gibson, S.M. Green, P.J. Maddox, Chem. Commun. (2002) 1038.
[29] D.J. Jones, V.C. Gibson, S.M. Green, P.J. Maddox, A.J.P. White, D.J. Williams, J.
Am. Chem. Soc. 127 (2005) 11037.
[30] A.K. Tomov, V.C. Gibson, D. Zaher, M.R.J. Elsegood, S.H. Dale, Chem. Commun.
(2004) 1956.
Table 8 provides a summary of the crystallographic data for
compounds 3, 8, 10, 14, 15 and 16. Data were collected using Ox-
ford Diffraction PX Ultra (8, 10 and 15) and Xcalibur 3 (3, 14 and
16) diffractometers, and the structures were refined based on F2
using the SHELXTL and SHELX-97 program systems [64].
[31] A.K. Tomov, J.J. Chirinos, R.J. Long, V.C. Gibson, M.R.J. Elsegood, J. Am. Chem.
Soc. 128 (2006) 7704.
[34] M.R. Maurya, A. Kumar, M. Ebel, D. Rehder, Inorg. Chem. 45 (2006) 5924.
[35] The maximum deviations from planarity are ca. 0.11, 0.12, 0.14 and 0.15 Å for
C(16), C(5), C(9) and C(5) in complexes 3-A, 3-B, 3-C and 3-D, respectively.
[36] S.L. Latesky, A.K. McMullen, G.P. Niccolai, I.P. Rothwell, J.C. Huffman,
Organometallics 4 (1985) 902.
[37] R.F. Jordan, R.E. LaPointe, C.S. Bajgur, S.F. Echols, R. Willett, J. Am. Chem. Soc.
109 (1987) 4111.
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1539.
Acknowledgements
We thank Dr. Stefan Spitzmesser for useful discussions. Ineos
Technologies is thanked for financial support and Aurelie Peters
for GPC analyses.
[39] M. Bochmann, S.J. Lancaster, Organometallics 12 (1993) 633–640.
[40] M. Bochmann, S.J. Lancaster, M.B. Hursthouse, K.M.A. Malik, Organometallics
13 (1994) 2235.
Appendix A. Supplementary material
[41] The
s parameter is defined as s = (b ꢀ a)/60°, where b and a are the largest and
CCDC 683004, 683005, 683006, 683007, 683008 and 683009
contain the supplementary crystallographic data for 3, 8, 10, 14,
15 and 16. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.jorganchem.2008.11.064.
second largest angles at the metal centre, respectively (see J. Chem. Soc.,
Dalton Trans, 1984, 1349–1356 (specifically p. 1352)). For a perfect square-
based pyramid,
s = 0 [as a = b = 180°], and for a perfect trigonal bipyramid s = 1
[as a = 120° and b = 180°].
[42] For both complexes 10-A and 10-B the closest intramolecular approach to the
centroid of the C(51) phenyl ring is from a methyl proton on the t-butyl group
ortho to the oxygen on the C(13)/C(18) aromatic C6 ring, though different
methyl groups are involved in each case. For complex 10-A, a proton on C(29)
approaches the centroid with an Hꢁ ꢁ ꢁ
p separation of ca. 3.13 Å, whilst for
complex 10-B
a
proton on C(310) is ca. 3.30 Å distant. The closest
intermolecular approach to the centroid of the C(51) phenyl ring in complex
10-A is from an N(11)–Me proton of a symmetry related counterpart with an
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