Iminohydroxamato early and late transition metal halide complexes - New precatalysts for aluminoxane-cocatalyzed olefin insertion polymerization

Article abstract of DOI:10.1002/ejic.200300405

We report on new families of non-metallocene metal precatalysts for olefin polymerization with titanium, zirconium, vanadium and nickel as the active metal sites. The novel ligand design concept is based on iminohydroxamic acids and their derivatives as the principal chelating units. Various anionic and neutral [N,O] and [N,N] ligand systems are easily accessible by a modular synthetic sequence of imidoyl chlorides with substituted hydroxylamines or hydrazines, respectively. Steric protection of the metal coordination site, a necessary requirement for suppression of chain termination pathways of non-metallocene catalysts, is brought about by bulky aryl substituents on the imino nitrogen atoms. Crystal structures of some of the hydroxamato ligands reveal interesting intermolecular hydrogen-bridged structures, whereas in the solid-state structure of one titanium precatalyst a five-membered chelate was observed, in line with the design principle of these systems. Preliminary ethylene polymerization studies with methylaluminoxane-activated metal complexes (M = Ti, Zr, V, Ni) show that the most active systems are [N,O]NiBr₂ catalysts containing neutral O-alkyl iminohydroxamate ligands. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejic.200300405

FULL PAPER
Iminohydroxamato Early and Late Transition Metal Halide Complexes ؊ New
Precatalysts for Aluminoxane-Cocatalyzed Olefin Insertion Polymerization
Alexander Krajete,[a] Georg Steiner,[a] Holger Kopacka,[a] Karl-Hans Ongania,[b]
Klaus Wurst,[a] Marc O. Kristen,[c] Peter Preishuber-Pflügl,[d] and Benno Bildstein*[a]
Keywords: N,O ligands / N ligands / Chelates / Transition metals / Polymerization
We report on new families of non-metallocene metal precata- tures of some of the hydroxamato ligands reveal interesting
lysts for olefin polymerization with titanium, zirconium, va- intermolecular hydrogen-bridged structures, whereas in the
nadium and nickel as the active metal sites. The novel ligand
design concept is based on iminohydroxamic acids and their
derivatives as the principal chelating units. Various anionic
solid-state structure of one titanium precatalyst a five-mem-
bered chelate was observed, in line with the design principle
of these systems. Preliminary ethylene polymerization stud-
and neutral [N,O] and [N,N] ligand systems are easily ac- ies with methylaluminoxane-activated metal complexes
cessible by a modular synthetic sequence of imidoyl chlor-
ides with substituted hydroxylamines or hydrazines, respect-
ively. Steric protection of the metal coordination site, a neces-
sary requirement for suppression of chain termination path-
ways of non-metallocene catalysts, is brought about by bulky
aryl substituents on the imino nitrogen atoms. Crystal struc-
(M = Ti, Zr, V, Ni) show that the most active systems are
[N,O]NiBr2 catalysts containing neutral O-alkyl imino-
hydroxamate ligands.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2004)
olefins,[8] giving precise control of polymer molecular
weights and giving access to block copolymers and other
new materials. Due to the economic importance of polyolef-
inic materials in general, academic and industrial research
activity in this area is very high and an ever increasing num-
ber of catalyst improvements and developments are being
published and/or patented.[1]
Introduction
Olefin polymerization catalysis based on transition metal
complexes containing non-cyclopentadienyl ligand frame-
works is an extremely active research area[1] since the recent
key discoveries of very active (i) (diimine)nickel[2] catalysts,
(ii) [bis(imino)pyridine]iron[3] catalysts, and (iii) (salicylaldi-
minato)nickel[4] and -titanium[5] catalysts. These new sys-
tems show some significant advantages in comparison with
the more familiar traditional ZieglerϪNatta titanium/zir-
conium or Phillips chromium systems, including (i) simpli-
fied ligand design, (ii) metal centers ranging from early to
late transition metals, (iii) decreased oxophilicity of the late
transition metal complexes, allowing polymerizations and/
or copolymerizations of polar monomers or even polymer-
izations in water,[6] (iv) access to new branched microstruc-
tures of the polymers due to ‘‘chain-walking’’ of the cata-
lytically active species,[7] and (v) living polymerization of
Here we introduce a new family of ligands based on the
iminohydroxamate backbone and we report on their tran-
sition metal halide complexes as new precatalysts for meth-
ylaluminoxane (MAO) activated olefin polymerizations.[9]
Our design principle is based on chelating [N,O] and [N,N]
ligands in accordance with (salicylaldiminato)nickel and -
titanium systems reported by the groups of Grubbs[4] and
Fujita[5] (Scheme 1). Such salicylaldimine ligands form six-
membered metal chelates and for steric protection they usu-
ally contain bulky aromatic imine moieties (in most cases
2,6-diisopropylphenyl) and sterically shielding groups in the
ortho position of the oxygen donor site. In contrast, in our
newly designed iminohydroxamate ligands, the metal che-
late is an energetically favored five-membered ring and
steric protection is provided by bulky arylimino substitu-
ents. This is similar to most non-cyclopentadienyl transition
metal polymerization catalysts.[1] Scheme 1 outlines the
chemical relationships between the parent iminohydroxamic
acids (A), their O-alkyl esters (B), their N-mono- (C) and
N,N-disubstituted amides (D), showing the large structural
[a]
Institute of General, Inorganic and Theoretical Chemistry;
University of Innsbruck,
Innrain 52a, 6020 Innsbruck, Austria
E-mail: benno.bildstein@uibk.ac.at
[b]
Institute of Organic Chemistry, University of Innsbruck,
Innrain 52a, 6020 Innsbruck, Austria
[c]
Basell Polyolefin GmbH,
67056 Ludwigshafen, Germany
[d]
BASF Aktiengesellschaft,
67056 Ludwigshafen, Germany
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DOI: 10.1002/ejic.200300405
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Iminohydroxamato Early and Late Transition Metal Halide Complexes
FULL PAPER
Results and Discussion
Synthesis and Characterization of Ligands
In general, ligand design is an essential part of the search
for new and improved metal catalysts because steric bulk
and stereoelectronic effects of the ligand architecture con-
trol the selectivity and activity of the metal complexes in
their function as catalysts. From a preparative viewpoint
the synthetic route should be straightforward, avoid tedious
workup and separations, and should be of wide scope,
thereby allowing parallel synthetic optimization.
The preparation of our new families of hydroxamate-
based ligands fulfill these requirements (Scheme 2). N-Sub-
stituted benzamides 1aϪ1d containing N-aryl groups with
different substitution pattern are easily available in large
quantities from the corresponding anilines and benzoyl
chloride. Conversion into the corresponding imidoyl chlo-
rides 2aϪ2d can be brought about quantitatively by treat-
ment with an excess of thionyl chloride employing standard
published chemistry.[12] Usually these synthons were pre-
pared in situ only, and used in the following reactions with-
out being isolated. In one case, however, single crystals were
obtained by chance (Table 2).
Scheme 1. Design principle of chelating [N,O] and [N,N] hydrox-
amate ligands
Figure 1 shows the molecular structure of 2a in the solid
varieties possible and indicating the obvious ligand design state, clearly visible is the steric shielding of the imine func-
opportunities in these [N,O] and [N,N] ligand families. tionality by the bulky N-(2,6-diisopropyl) group. As a result
In a historical perspective, in situ generated hydroxamic of the two ortho-alkyl substituents the aryl group is tilted
acids are well known in qualitative organic analysis for their by 80.56(10)° in relation to the imidoyl chloride plane, as
formation of magenta- or burgundy-colored FeIII com- anticipated and in line with our design principle of axial
plexes,[10] a more or less specific color test for carboxylic steric shielding brought about by bulky N-imino substitu-
acid derivatives in the presence of hydroxylamine. Simple ents (vide infra).
(iminohydroxamato)metal complexes have been investigated
Iminohydroxamic acids 3aϪ3f can be quite easily synthe-
for over 100 years,[11] mainly in spectrophotometric and sized by iminoacylation of N-monosubstituted hydroxylam-
pharmaceutical studies. However, no applications as olefin ines. Similar chemistry has been reported earlier in the lit-
polymerization precatalysts have been reported up to now.
erature employing N-phenylhydroxylamine.[11b] As antici-
Scheme 2. Synthesis of iminohydroxamate ligands
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Figure 2. Molecular structure of 3a; except for NϪHϪO hydrogen
bonds, hydrogen atoms are omitted for clarity; selected bond
lengths [pm]: C(1)ϪN(1) 131.2(3), N(1)ϪO(1) 134.5(3), C(1)ϪN(2)
133.8(3), C(21)ϪN(3) 131.1(3), N(3)ϪO(2) 134.6(3), C(21)ϪN(4)
134.4(3), N(2)ϪH(2N) 87(3), N(4)ϪH(4N) 91(3); tilt angles [°]:
plane of phenyl ring of C(1) versus plane N(1)ϪC(1)ϪN(2):
83.48(15); plane of 2,6-diisopropylphenyl ring of N(2) versus plane
N(1)ϪC(1)ϪN(2): 88.55(21); plane of phenyl ring of C(21) versus
plane N(3)ϪC(21)ϪN(4): 75.17(15); plane of 2,6-diisopropylphenyl
ring of N(4) versus plane N(3)ϪC(21)ϪN(4): 85.38(22)
Figure 1. Molecular structure of 2a; hydrogen atoms are omitted
for clarity; selected bond lengths [pm]: Cl(1)ϪC(1) 178.0(2),
C(1)ϪN(1) 124.8(2); tilt angles [°]: plane of phenyl ring versus
plane Cl(1)ϪC(1)ϪN(1): 3.25(24); plane of 2,6-diisopropylphenyl
ring versus Cl(1)ϪC(1)ϪN(1): 80.56(10)
pated, the more nucleophilic nitrogen atom is acylated first
in these ambident substrates affording the desired ligands in
isolated yields of 18Ϫ63%, followed by O-acylation which
always occurs to a certain degree, dependent on the substi-
tution pattern of the building blocks. Due to the much
higher polarity of the mono(iminoacylated) hydroxamic ac-
ids 3aϪ3f in comparison with the undesired N,O-bis(imi-
noacylated) side products, separation and purification of
the hydroxamic acids can be conveniently accomplished by
a simple filtration through a short silica column (see Exp.
Sect.). In two cases, 4a and 4b, the undesired N,O-bis(imi-
noacylated) products were isolated and characterized spec-
troscopically.
In principle any hydroxylamine can be derivatized in this
manner, including the parent unsubstituted hydroxylamine.
However, the starting hydroxylamines containing one N-or-
gano substituent were chosen because the NϪH acidic site
in these iminohydroxamic acids is blocked. This enables ac-
tivation of the corresponding metal complexes with methyl-
Figure 3. Molecular structure of 3b; except for NϪH and OϪH
hydrogen atoms, all other hydrogen atoms are omitted for clarity;
selected bond lengths [pm]: C(1)ϪN(1) 130.6(3), N(1)ϪO(1)
aluminoxane (vide infra) without undesired N-depro- 135.1(2), C(1)ϪN(2) 135.7(3), C(21)ϪN(3) 139.0(3), N(3)ϪO(2)
142.2(2), C(21)ϪN(4) 128.1(3), N(2)ϪH(2N) 94(2), O(2)ϪH(2O)
tonation or N-alumination, respectively.
106(3); tilt angles [°]: plane of phenyl ring of C(1) versus plane
Iminohydroxamic acids 3aϪ3f are stable organic com-
pounds and white to yellow in color. Relevant spectroscopic
properties include characteristic IR stretching vibrations
due to the imino groups (νCϭN ϭ 1598Ϫ1630 cmϪ1), and
diagnostic low-field 13C NMR chemical shifts of the imino
functionalities (δCϭN ϭ 147.7Ϫ150.5 ppm). The νOϪH
bands of the hydroxy groups (3600 to 3100 cmϪ1) are very
N(1)ϪC(1)ϪN(2): 62.26(13); plane of 2,6-dimethylphenyl ring of
N(2) versus plane N(1)ϪC(1)ϪN(2): 70.93(16); plane of phenyl
ring of C(21) versus plane N(3)ϪC(21)ϪN(4): 43.52(10); plane of
2,6-dimethylphenyl ring of N(4) versus plane N(3)ϪC(21)ϪN(4):
76.18(18)
weak and broad in the IR spectra, due to line broadening
A common feature in all three structures is the tilting of
1
and association. Also in the H NMR spectra the signals both aryl rings relative to the plane of the principal Nϭ
of the hydroxy hydrogen atoms are usually not observed, CϪNϪO unit. These tilt angles range from 43.5 to 83.5°
due to exchange and overlapping with other signals (com- for the C-phenyl ring, and from 34.0 to 88.6° for the substi-
pare Exp. Sect.). For three of these iminohydroxamic acids, tuted N-aryl moiety, respectively. Clearly the tilting in both
suitable single crystals for X-ray structural analyses were cases is caused by steric crowding, especially in the latter
obtained (Figures 2Ϫ4).
case, due to the two ortho-alkyl groups on the N-aryl sub-
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Iminohydroxamato Early and Late Transition Metal Halide Complexes
FULL PAPER
field in comparison with those of the N-alkyl substituents
of 3aϪ3f and 5aϪ5d, respectively.
Amino derivatives of iminohydroxamic acids are access-
ible similarly by iminoacylation of hydrazines. In our hands,
however, this chemistry was only possible for alkylated hy-
drazines affording ligands 6a and 6b, but on attempted
mono(iminoacylation) of N,NЈ-diphenylhydrazine only the
bis(derivative) 7 was obtained. This is a rather unfortunate
result because diarylhydrazines can be easily synthesized
from azobenzenes by reduction, and various substituted di-
arylhydrazines would allow a convenient stereoelectronic
fine-tuning on the amino N-donor site of ligands of type 6.
The spectroscopic data of 6a, 6b and 7 are consistent with
their structures with values similar to those of the other
ligand families discussed above. As a minor issue, we note
that the imidoyl hydrazide 6b is the only ligand of all these
compounds with an NϪH substituent on the benzamidine
moiety, in this case no protection of the NϪH acidic moiety
is present (vide infra).
Figure 4. Molecular structure of 3e; except for NϪHϪO hydrogen
bonds, hydrogen atoms are omitted for clarity; selected bond
lengths [pm]: C(1)ϪN(1) 130.5(4), N(1)ϪO(1) 134.0(3), C(1)ϪN(2)
135.9(4), N(2)ϪH(2N) 98(4); tilt angles [°]: plane of phenyl ring of
C(1) versus plane N(1)ϪC(1)ϪN(2): 78.74(15); plane of 2,6-diiso-
propylphenyl ring of N(2) versus plane N(1)ϪC(1)ϪN(2):
34.02(23)
Metal Complexes
[N,O] Iminohydroxamato Complexes
stituent. As anticipated, in all three structures, hydrogen-
bridging plays a decisive role in the solid-state packing of
In principle, with tetravalent early transition metals,
the molecules. In all three structures two molecules are [N,O]MX3 mono- and [N,O]2MX2 bis(complexes) should be
paired by one or two OϪHϪN hydrogen bonds. Interest- accessible. Hence six differently substituted iminohydro-
ingly, both possible tautomers of the iminohydoxamic acid xamic acids (3aϪ3f) and three different metal halides
functionality were observed, depending on the substitution (ZrCl4, TiCl4, VCl4) would afford a series of 36 different
pattern of the principal NϭCϪNϪOH unit. Compounds metal complexes. In this work, however, only selected ex-
3a and 3e exist in the solid state solely in their zwitterionic amples from this rather large number of compounds were
iminium hydroxamate ϩNHϭCϪNϪOϪ forms connected synthesized on a preparative scale (Scheme 3), based on the
by two hydrogen bonds (see Figures 2 and 4), whereas in following criteria and objectives: (i) in order to compare the
the case of compound 3b both tautomers with only one stereoelectronic influence of all six ligands 3aϪ3f, all six
hydrogen bond are present, the expected and ‘‘usual’’ neu- zirconium mono(complexes) [N,O]ZrCl3 8aϪ8f were syn-
tral NϭCϪNϪOH form and the unexpected and ‘‘exotic’’ thesized, (ii) for comparing the difference between mono-
zwitterionic ϩNHϭCϪNϪOϪ form (Figure 3). It is quite and bis(complexes), one [N,O]2ZrCl2 complex (9a) was pre-
clear, however, that this tautomerism is dominated by solid- pared, (iii) to study the effect of different metals, two ad-
state forces and in solution the position of equilibrium will ditional complexes 10b [M ϭ Ti] and 11b [M ϭ V] with
be almost totally on the side of the uncharged normal im- ligand 3b were synthesized, and (iv) to facilitate characteriz-
inohydroxamic acid species.
ation of the complexes by NMR spectroscopy we focused
The synthesis of iminohydoxamic esters 5aϪ5d can be on the diamagnetic Zr and Ti complexes. Furthermore we
very easily accomplished by iminoacylation of N,O-bis(alk- note that [N,O]NiRL complexes (L ϭ phosphane, R ϭ alkyl
ylated) hydroxylamines (Scheme 2). The isolated yields of or aryl) in analogy to Grubbs’ (salicylaldiminato)Ni com-
78Ϫ94% are much higher than those of the iminohydro- plexes[4] are also accessible, but unfortunately such com-
xamic acids discussed above, simply because there is only pounds are very labile and, according to our preliminary
one nucleophilic site in the substrates. Ligands 5aϪ5d are results, decompose very quickly.
stable compounds which are white to yellow in color. Spec-
As anticipated, the synthesis of metal complexes of
troscopically, the imine functionalities may be corroborated [N,O]H ligands 3aϪ3f was rather simple. Deprotonation
by their typical IR absorptions (νCϭN ϭ 1628Ϫ1636 cmϪ1), with n-butyllithium in THF followed by treatment with the
shifted to higher wave numbers compared with the hydro- appropriate transition metal halide afforded complexes
xamic acids 3aϪ3f, and by their 13C NMR chemical shifts 8aϪ11b (Scheme 3) in isolated yields ranging from 64 to
(δ ϭ 160.8Ϫ162.8 ppm) which are also shifted to lower field 95% (see Exp. Sect.). All the compounds are stable under
in comparison with compounds 3aϪ3f. The signals of the dry and inert conditions. On exposure to air, however, they
methyl groups of the ester functionalities were detected at are quickly hydrolyzed as expected. The zirconium and ti-
1
δ ϭ 3.38Ϫ3.54 ppm in the H NMR spectra and at δ ϭ tanium complexes 8aϪ10b are diamagnetic and are yellow
60.2Ϫ60.6 ppm in the 13C NMR spectra; both sets of to orange in color, in contrast to the dark green vanadium
chemical shifts are in accordance with expectations at lower complex 11b which is strongly paramagnetic.
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Scheme 3. Metal complexes of [N,O] and [N,N] iminohydroxamato ligands
The characterization of the diamagnetic compounds re-
lies mainly on NMR spectroscopy. In the 13C NMR spectra
the coordinated imino functionalities (δCϭN
ϭ
159Ϫ162 ppm) are shifted to lower field by approximately
10 ppm compared with the chemical shifts of the imine car-
bon signals of the free ligands (δCϭN ϭ 146Ϫ151 ppm).
Other resonances were shifted as well, but to a much lesser
1
degree. Most significantly, the H and 13C NMR spectra
clearly show that the [N,O]ZrCl3 mono(complexes) 8aϪ8f
exist predominantly as mixtures of isomers containing THF
as an additional neutral ligand in an octahedral coordi-
nation environment. In principle, 4 pairs of chiral dia-
stereoisomers are possible with these heterotopic [N,O] che-
late ligands in combination with three chloride ions and one
THF ligand (Scheme 4). Mono-Zr complexes containing
the N-(2,6-diisopropylphenyl) substituent exist as one iso-
mer (8a, 8e, 8f), whereas those with sterically less de-
manding N-aryl groups give rise to the observation of two
diastereoisomers (8b, 8c, 8d) according to their NMR spec-
tra (compare Exp. Sect.).
In contrast to the [N,O]ZrCl3 complexes 8aϪ8f, no coor-
dinated THF was present in the titanium complex 10b, most
likely due to the smaller size of the lighter transition metal
atom. Also, complex 9a with two chelating [N,O] ligands
had no coordinated THF, but four structural isomers of the
theoretically possible 5 isomers (Scheme 5) were observed
in this heterotopic and non-homoleptic complex.
In most of the zirconium compounds 8aϪ9a (with the
exception of 8a, 8e, 8f) the occurrence of a mixture of iso-
mers was clearly evident from NMR spectroscopy. On the
Scheme 4. Structural isomers of [N,O]ZrCl3(THF) complexes
one hand this is an expected and interesting stereochemical 10b, however, suitable red single crystals grew after one
observation, on the other hand, however, it hampers further year, together with some amorphous colorless material. Fig-
characterization of these complexes by X-ray crystallogra- ure 5 shows the molecular structure of this crystalline mate-
phy. Unfortunately, under no circumstances we were able to rial. Unexpectedly, the structure corresponds to the [N,O]2-
obtain single crystals. In the case of the titanium complex TiCl2 bis complex 12b which must have been formed from
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Iminohydroxamato Early and Late Transition Metal Halide Complexes
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Figure 5. Molecular structure of 12b; hydrogen atoms are omitted
for clarity; selected bond lengths [pm]: Ti(1)ϪCl(1) 231.97(7),
Ti(1)ϪN(1) 210.83(18), Ti(1)ϪO(1) 192.44(17), C(1)ϪN(1)
132.9(3), C(1)ϪN(2) 132.4(3), N(2)ϪO(1) 136.1(3); selected angles
[°]: Cl(1)ϪTi(1)ϪCl(1A) 90.22(4), O(1)ϪTi(1)ϪO(1A) 95.10(12),
N(1)ϪTi(1)ϪO(1)
74.54(7),
N(1)ϪTi(1)ϪCl(1)
105.26(5),
O(1)ϪTi(1)ϪCl(1) 89.74(6), N(1)ϪTi(1)ϪN(1A) 159.57(10),
Ti(1)ϪN(1)ϪC(1) 115.12(15), N(1)ϪC(1)ϪN(2) 114.9(2),
Scheme 5. Structural isomers of [N,O]2ZrCl2 complexes
Ti(1)ϪO(1)ϪN(2) 120.79(13); tilt angle plane of phenyl group of
C(1) versus plane N(1)ϪC(1)ϪN(2): 66.71(26); tilt angle of 2,6-
dimethylphenyl group of N(1) versus plane N(1)ϪC(1)ϪN(2):
82.46(19)
the [N,O]TiCl3 mono(complex) 10b by ligand scrambling.
Despite the obvious serendipity of this result, the molecular
structure clearly demonstrates the chelating nature of the
hydroxamato ligand 3b, indicating that in all other cases
such five-membered metal chelates are also present. Over-
all, the stereochemistry of 12b corresponds to isomer cis-
II of Scheme 5 with cis-oriented chloro ligands and trans-
oriented imino donor sites of the heterotopic iminohydro-
xamato ligands. The coordination geometry at the central
titanium atom is principally octahedral with only minor de-
viations from the ideal 90° (0.3Ϫ15.5°) and 180°
(16.8Ϫ20.4°) angles. The bond lengths of the titanium atom
to the nitrogen, oxygen, and chlorine atoms of the ligands
are given in the caption of Figure 5. They are unexceptional
and in the commonly observed range. In contrast to the
more or less undistorted coordination geometry, the periph-
eral phenyl groups of the iminohydroxamato ligands are
strongly tilted (66.7 and 82.5°) with respect to the hydroxa-
mate plane, showing that steric shielding by the N-arylimino
substituent is effective, in accordance with the general de-
sign principle of these olefin polymerization precatalysts
(vide supra).
The syntheses of the imidoyl hydrazido complexes 13a
and 14a are analogous to the preparation of the imino-
hydroxamato complexes discussed above (Scheme 3). De-
protonation of ligand 6a in THF by n-butyllithium followed
by treatment with ZrCl4 or TiCl4 in a 1:1 stoichiometric
ratio afforded complexes 13a and 14a, respectively. Besides
the additional N-methyl resonances, both compounds show
NMR spectroscopic properties very similar to those of the
iminohydroxamato complexes 8aϪ8f and 10b. Stereochem-
ically, Zr complex 13a exists as a mixture of two octahedral
idoyl hydrazides 6aϪ6b and 7 was very straightforward.
Treatment with NiBr2 in dichloromethane at room tempera-
ture overnight afforded the corresponding [N,O]NiBr2 com-
plexes 15aϪ15d and [N,N]NiBr2 complexes 16a, 16b, 17 in
good yields (Scheme 3).
With the exception of 17, which is a seven-membered che-
late in contrast to all other complexes, all the Ni complexes
are dark green or brown, air-sensitive and paramagnetic,
thereby thwarting their characterization by NMR spec-
troscopy. In general, broad and shifted signals were ob-
1
served in the H NMR spectra and signal intensities in the
13C NMR spectra were very low allowing, only in one case,
the detection of the carbon resonances (see Exp. Sect.). The
paramagnetism of these complexes clearly indicates a non-
quadratic, non-planar coordination geometry and these
compounds exist either as four-coordinate tetrahedrally dis-
torted monomers or as bromo-bridged five-coordinate di-
mers. Clearly, crystal structures would provide the best in-
formation on the structures of these compounds, but de-
spite many attempts with different solvents employing vari-
ous crystallization procedures no suitable crystals could be
obtained. On the other hand, the observed paramagnetism
shows that steric shielding of the ligands is sufficient to dis-
tort the orientation of the bromo ligands from their pre-
ferred square-planar geometry, as in Grubbs’[4] and Brook-
hart’s[2] [N,O]- and [N,N]Ni catalysts.
Polymerization Studies
The main question to be answered by this work is: ‘‘How
isomers containing one additional THF ligand (in analogy active and selective are these newly designed catalyst famil-
to the isomers in Scheme 4), whereas 14a seems to be either ies for the polymerization of olefins?’’ To evaluate the cata-
five-coordinate or more likely a chloro-bridged dimer with lytic performance of complexes 8aϪ17 a standard polymer-
no coordinated THF.
ization procedure was applied. A steel autoclave containing
The synthesis of nickel() complexes starting from the a toluene solution of the precatalyst was activated with an
neutral (non-acidic) iminohydroxamic esters 5aϪ5d, im- excess of methylaluminoxane and at a temperature of 70 °C
Eur. J. Inorg. Chem. 2004, 1740Ϫ1752
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1745

B. Bildstein et al.
FULL PAPER
Table 1. Polymerization of ethylene (MAO as activator, 70 °C, 40 bar)
Complex
(metal)
Amount precatalyst
[mg]
Polymerization time
[min]
Yield polymer
[g]
Viscosity of polymer
[dL/g]
Activity
[g mmolϪ1 hϪ1 barϪ1
]
8a (Zr)
8b (Zr)
8c (Zr)
8d (Zr)
8e (Zr)
8f (Zr)
9a (Zr)
10b (Ti)
11b (V)
13a (Zr)
14a (Ti)
15a (Ni)
16a (Ni)
16b (Ni)
17 (Ni)
4.8
6.0
1.5
0.9
1.2
2.0
4.0
4.0
8.0
1.4
1.7
3.9
2.7
1.4
1.8
30
30
35
60
90
75
90
60
90
45
15
5
9.5
12.0
4.8
6.7
11.9
8.8
9.4
7.4
6.2
6.2
1.0
7.25
1.0
1.3
1.7
9.51
14.01
11.41
24.95
4.43
8.76
41.38
54.33
19.18
15.6
Ϫ
50.2
45.1
68.4
78.7
88.4
51.3
30.6
18.8
5.3
76.8
28.0
302.8
3.3
3.62
2.15
2.57
2.50
90
90
90
8.4
14.6
ethylene was added up to a pressure of 40 bar, the reaction
was allowed to proceed for 5Ϫ90 min while maintaining a
40 bar pressure by adjusting the feed of ethylene (Table 1,
for further details see Exp. Sect.).
Summary and Conclusions
New bidentate chelate ligands based on an iminohydro-
xamate backbone architecture have been developed. These
new ligands contain an imino nitrogen donor site with a
substituted aryl group to effect steric shielding and an
anionic or neutral oxygen or nitrogen donor site, respec-
tively. The free ligands show interesting solid-state struc-
tures in which hydrogen bonding is responsible for unusual
zwitterionic tautomeric structures. New metal complexes of
zirconium, titanium, vanadium, and nickel have been syn-
thesized and evaluated for their performance as olefin poly-
merization catalysts. Structurally, the five-membered metal
chelates exist in most cases as a number of different octa-
hedral stereoisomers in the case of early transition metals,
and as tetragonally distorted paramagnetic four- or five-
coordinated compounds in the case of nickel. Polymerization
studies were performed in homogeneous solution using
methylaluminoxane as the cocatalyst. These showed that
[N,O]NiBr2 complexes containing neutral iminohydroxa-
mate with O-alkyl substituents are the most active systems
of these various catalyst families. Further optimization of
the ligand substitution pattern is expected to improve long
term stability of the catalysts and the catalytic performance
for applications on a technical scale.
In terms of activity, all [N,O]- and [N,N]zirconium com-
plexes showed a moderate activity of 30.6Ϫ88.4 g polyethyl-
ene ϫ mmolϪ1 ϫ catalyst ϫ hϪ1 ϫ barϪ1. The bis(complex)
[N,O]2ZrCl2 (9a) had the lowest activity of all Zr complexes,
clearly indicating that one ligand per metal center
([N,O]ZrCl3) is superior to a 2:1 ratio. Changing the metal
to either titanium or vanadium resulted in a significantly
reduced activity with either the [N,O] or [N,N] ligand archi-
tecture. In the case of the nickel complexes, compound 15a
truly stands out as a precatalyst with a (very) high activity
of 302.8, suggesting that neutral O-alkyl iminohydroxamate
is the best ligand framework developed in this work. How-
ever, the long-term stability of the [N,O]NiBr2 complexes
15aϪ15d in their MAO-activated form has not yet been op-
timized and only with 15a under short polymerization times
was a polymer obtained, indicating fast deactivation path-
ways. Future work towards improvements of these systems
will focus on altering the O-alkyl substituent to create better
shielding of the active metal center and to increase the sta-
bility of the activated complex.
In terms of polymer properties, the polyethylene samples
obtained by the zirconium catalyst family were very high
molecular weight (Mv ϭ 1.5 to 10 ϫ 106 g/mol, derived
from viscosity measurements) polymers with viscosities
ranging from 4.43 to 54.33 dl/g, dependent on the substi-
tution pattern of the ligands. In contrast, PE samples ob-
tained from nickel complexes 15aϪ17 were of the HDPE
type with no detectable branches and molar masses (Mv) of
1.0 to 2.5 ϫ 105 g/mol.
Experimental Section
General: Commercially available starting materials were used as ob-
tained. Solvents were dried, deoxygenated and saturated with argon
according to standard procedures in organometallic chemistry. Re-
actions of air-sensitive materials were performed in Schlenk glass-
ware under argon by techniques common in inorganic/organomet-
allic chemistry. New compounds were characterized by IR, NMR,
MS, etc. using current state-of-the-art procedures, details of instru-
mentation have been published previously.[13]
In addition, polymerization of propylene and copolymer-
ization of ethylene with n-hexene was briefly investigated.
In both cases, only low activities below 150 g polymer ϫ
mmolϪ1 ϫ catalyst ϫ hϪ1 were achieved.
1746
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Iminohydroxamato Early and Late Transition Metal Halide Complexes
FULL PAPER
Synthesis of Ligands
1436 (m), 1407 (w), 1383 (m), 1362 (w), 1328 (m), 1287 (w), 1264
(m), 1233 (m), 1185 (w), 1108 (m), 1063 (s), 1038 (m), 1030 (m),
1013 (s), 922 (w), 803 (m), 766 (s), 726 (m) cmϪ1. MS (FAB): m/
Representative Procedure for Iminohydroxamic Acids 3aϪ3f: A
Schlenk tube was charged with N-(2,6-diisopropylphenyl)benz-
amide (1a, 1.9 g, 6.7 mmol) and an excess of thionyl chloride
(10 mL). The mixture was heated to reflux for 1 h and the excess
thionyl chloride was removed in a vacuum line, yielding a yellow
oil of the corresponding imidoyl chloride 2a. This material was
dissolved in dry dichloromethane (20 mL). A second Schlenk vessel
was charged with N-methylhydroxylamine hydrochloride (0.56 g,
6.7 mmol), dry ethanol (50 mL), and triethylamine (10 mL,
72 mmol). After the stirred mixture was cooled to Ϫ40 °C, a drop-
ping funnel was attached to the Schlenk vessel, and a dichloro-
methane solution of imidoyl chloride 2a (from above) was added
dropwise over a period of 30 min. The mixture was warmed to
room temperature and stirred at ambient temperature for further
60 min, resulting in a yellow suspension. Workup: the reaction mix-
1
z ϭ 574 [M ϩ H]ϩ. H NMR (300 MHz, CDCl3): δ ϭ 1.14Ϫ1.21
[m, 24 H, 4 ϫ CH(CH3)2], 3.10, 3.42 [sept, 4 H, 4 ϫ CH(CH3)2],
3.61 (s, 3 H, NCH3), 6.46 (m, 2 H, C6H5), 6.91Ϫ7.90 (m, 16 H,
C6H5, C6H3) ppm. 13C NMR (75.432 MHz, CDCl3): δ ϭ 22.0,
23.7, 24.0, 28.9 [CH(CH3)2], 39.7 (NCH3), 122.9, 123.7, 127.1,
127.8, 127.9, 128.5, 128.8, 129.0, 129.3, 130.4, 131.8, 133.1, 142.1,
143.5, 146.4 (C6H5, C6H3), 154.5, 160.4 (CϭN) ppm. C39H47N3O
(573.82): calcd. C 81.63, H 8.26, N 7.32; found C 81.55, H 8.30,
N 7.30.
N-(2,6-Dimethylphenyl)-NЈ-hydroxy-NЈ-methylbenzamidine
(3b)
Starting materials: N-(2,6-dimethylphenyl)benzamide (1b, 2.30 g,
10.2 mmol) and N-methylhydroxylamine hydrochloride (1.30 g,
15.6 mmol). Yield: 1.63 g (63%). IR (KBr): ν˜ ϭ 1627 (s), 1590 (m),
ture was hydrolyzed by addition of water (100 mL), the organic 1578 (m), 1505 (m), 1472 (m), 1445 (m), 1426 (m), 1341 (m), 1258
materials were extracted three times with diethyl ether, the com-
bined organic layers were dried with Na2SO4 and the volatile mate-
(m), 1237 (s), 1179 (s), 1158 (m), 1106 (m), 1092 (m), 1079 (w),
1048 (m), 1025 (m), 957 (s), 783 (s), 774 (s), 762 (s), 754 (s), 726
rials were removed in a rotary evaporator yielding a semi-solid (s), 700 (s) cmϪ1. MS (EI, 70 eV): m/z ϭ 254 [M]ϩ. 1H NMR
crude product consisting of N-(2,6-diisopropylphenyl)-NЈ-hydroxy-
NЈ-methylbenzamidine (3a) and the apolar side product N-(2,6-di-
(300 MHz, CDCl3): δ ϭ 2.16 (s, 6 H, 2 ϫ CH3), 3.47 (s, 3 H,
NCH3), 6.82Ϫ6.92 (m, 3 H, C6H3), 7.08Ϫ7.27 (m, 5 H, C6H5), not
isopropylphenyl)-NЈ-{[2,6-diisopropylphenyl)imino]phenylmethoxy}- observed (s, 1 H, NOH) ppm. 13C NMR (75.432 MHz, CDCl3):
NЈ-methylbenzamidine (4a). To separate this mixture, the crude
product mixture was dissolved in a small volume of dichlorometh-
ane and filtered through a short column of silica. In this manner,
apolar 4a (0.76 g, 1.3 mmol, 19.8% yield) could be removed by fil-
tration, whereas the polar product 3a remained immobilized on the
column. Elution with ethanol and subsequent removal of ethanol
in a rotary evaporator afforded 0.83 g of pure 3a as an off-white
solid in 40% yield.
δ ϭ 18.6 (CH3), 43.6 (NCH3), 126.6, 127.7, 128.0, 128.2, 128.5,
130.1, 135.4, 135.5 (C6H5, C6H3), 149.0 (CϭN) ppm. C16H18N2O
(254.33): calcd. C 75.56, H 7.13, N 11.01; found C 75.62, H 7.18,
N 10.93.
N-(2,6-Dimethylphenyl)-NЈ-{[(2,6-dimethylphenyl)imino]-
phenylmethoxy}-NЈ-methylbenzamidine (4b): Starting materials: N-
(2,6-dimethylphenyl)benzamide (1b, 2.30 g, 10.2 mmol) and N-
methylhydroxylamine hydrochloride (1.30 g, 15.6 mmol). Yield:
1.1 g (23%). IR (KBr): ν˜ ϭ 2919 (w), 1688 (s), 1644 (s), 1592 (m),
1580 (w), 1493 (w), 1466 (m), 1447 (m), 1405 (w), 1326 (s), 1293
(w), 1262 (m), 1246 (m), 1229 (m), 1216 (m), 1183 (w), 1104 (w),
1079 (s), 1069 (s), 1027 (m), 1013 (m), 922 (w), 787 (m), 768 (s),
All other iminohydroxamic acids 3 were prepared according to this
procedure except that different benzamides and hydroxylamines
were employed as starting materials. The bis(imino)-substituted hy-
droxylamines 4 (the apolar side product) were usually only sepa-
rated and not isolated. Isolated yields of ligands 3 ranged from 18 756 (m), 741 (m), 697 (s), 675 (m) cmϪ1. MS (EI, 70 eV): m/z ϭ
1
to 63%, depending on the substitution pattern of the building
blocks.
461 [M]ϩ. H NMR (300 MHz, CDCl3): δ ϭ 1.95, 2.20 (2 ϫ s, 12
H, 4 ϫ CH3), 3.61 (s, 3 H, NCH3), 6.25 (m, 2 H, C6H3), 6.67Ϫ6.96
(m, 6 H, C6H5 and C6H3), 7.05Ϫ7.22 (m, 5 H, C6H5) ppm. 13C
NMR (75.432 MHz, CDCl3): δ ϭ 18.5, 18.8 (CH3), 39.4 (NCH3),
122.3, 122.9, 127.0, 127.1, 127.6, 127.8, 127.9, 128.2, 128.7, 129.4,
129.5, 130.0, 130.5, 131.7, 133.6, 135.5, 144.6, 146.1 (C6H5, C6H3),
154.7, 161.5 (CϭN) ppm. C31H31N3O (461.60): calcd. C 80.66, H
6.77, N 9.10; found C 80.71, H 6.80, N 9.08.
N-(2,6-Diisopropylphenyl)-NЈ-hydroxy-NЈ-methylbenzamidine (3a):
Starting materials: N-(2,6-diisopropylphenyl)benzamide (1a, 1.9 g,
6.7 mmol) and N-methylhydroxylamine hydrochloride (0.56 g,
6.7 mmol). Yield: 0.83 g (40%). IR (KBr): ν˜ ϭ 3065 (w), 2962 (m),
2869 (m), 1630 (s), 1586 (m), 1505 (m), 1470 (s), 1445 (m), 1432
(m), 1383 (m), 1324 (m), 1225 (m), 1187 (s), 1162 (m), 1105 (s),
1077 (w), 1044 (m), 971 (m), 917 (w), 807 (s), 780 (s), 758 (s), 700
N-(Biphenyl-2-yl)-NЈ-hydroxy-NЈ-methylbenzamidine (3c): Starting
(s) cmϪ1. MS (FAB): m/z ϭ 311 [M ϩ H]ϩ. MS(EI, 70 eV): m/z ϭ materials: N-(2-biphenyl)benzamide (1c, 2.62 g, 9.59 mmol) and N-
3
310 [M]ϩ. 1H NMR (300 MHz, CDCl3): δ ϭ 0.96 [d, JH,H
ϭ
methylhydroxylamine hydrochloride (1.28 g, 15.3 mmol). Yield:
1.39 g (48%). IR (KBr): ν˜ ϭ 3257 (w), 2946 (w), 1607 (s), 1580 (m),
6.6 Hz, 6 H, CH(CH3)2], 1.09 [d, 3JH,H ϭ 6.2 Hz, 6 H, CH(CH3)2],
3.18 [sept, 2 H, 2 ϫ CH(CH3)2], 3.47 (s, 3 H, NCH3), 6.95 (m, 2 1509 (s), 1488 (s), 1447 (m), 1436 (s), 1422 (s), 1393 (m), 1387 (m),
H, C6H5), 7.01Ϫ7.12 (m, 3 H, C6H5), 7.17Ϫ7.25 (m, 3 H, C6H3), 1243 (s), 1196 (s), 1073 (m), 963 (s), 783 (m), 770 (s), 756 (s), 743
not observed (s, 1 H, NOH) ppm. 13C NMR (75.432 MHz, CDCl3): (s), 698 (s) cmϪ1. MS (EI, 70 eV): m/z ϭ 302 [M]ϩ. 1H NMR
δ ϭ 21.9, 25.4, 28.2 [CH(CH3)2], 43.7 (NCH3), 123.2, 127.3, 127.8, (300 MHz, CDCl3): δ ϭ 3.38 (s, 3 H, NCH3), 6.48Ϫ6.51 (m, 1
128.2, 128.9, 130.1, 131.9, 146.2 (C6H5, C6H3), 149.1 (CϭN) ppm. H, C6H5), 6.89Ϫ7.02 (m, 4 H, C6H5), 7.11Ϫ7.14 (m, 1 H, C6H5),
C20H26N2O (310.44): calcd. C 77.38, H 8.44, N 9.20; found C
77.42, H 8.48, N 9.16.
7.25Ϫ7.42 (m, 8 H, C6H5), not observed (s, 1 H, NOH) ppm. 13C
NMR (75.432 MHz, CDCl3): δ ϭ 43.5 (NCH3), 122.5, 124.0, 127.4,
127.5, 127.9, 128.7, 128.9, 129.0, 130.1, 130.7, 134.7, 135.5, 138.4
(C6H5, C6H4), 146.8 (CϭN) ppm. C20H18N2O (302.38): calcd. C
79.44, H 6.00, N 9.26; found C 79.35, H 6.04, N 9.21.
N-(2,6-Diisopropylphenyl)-NЈ-{[(2,6-diisopropylphenyl)imino]-
phenylmethoxy}-NЈ-methylbenzamidine (4a): Starting materials: N-
(2,6-diisopropylphenyl)benzamide (1a, 1.9 g, 6.7 mmol) and N-
methylhydroxylamine hydrochloride (0.56 g, 6.7 mmol). Yield:
NЈ-Hydroxy-NЈ-methyl-N-phenylbenzamidine (3d): Starting materi-
0.76 g (19.8%). IR (KBr): ν˜ ϭ 2970 (m), 2931 (m), 2869 (m), 1683 als: benzanilide (1d, 2.12 g, 10.8 mmol) and N-methylhydroxylam-
(s), 1630 (s), 1602 (m), 1590 (m), 1578 (m), 1492 (m), 1459 (m), ine hydrochloride (1.28 g, 15.3 mmol). Yield: 1.03 g (42%). IR
Eur. J. Inorg. Chem. 2004, 1740Ϫ1752
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 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1747

B. Bildstein et al.
(KBr): ν˜ ϭ 3049 (w), 2943 (w), 1615 (s), 1603 (s), 1574 (m), 1509 5a in 93% yield as a yellow viscous oil which solidified on drying
FULL PAPER
(s), 1482 (m), 1447 (m), 1428 (m), 1196 (s), 1160 (m), 1071 (w), 971
(s), 758 (s), 726 (s), 697 (s) cmϪ1. MS (EI, 70 eV): m/z ϭ 226 [M]ϩ.
1H NMR (300 MHz, CDCl3): δ ϭ 3.47 (s, 3 H, NCH3), 6.56 (d, 2
H, C6H5), 6.87 (t, 1 H, C6H5), 7.01 (t, 2 H, C6H5), 7.25 (d, 2 H,
C6H5), 7.24Ϫ7.43 (m, 3 H, C6H5), not observed (s, 1 H, NOH)
ppm. 13C NMR (75.432 MHz, CDCl3): δ ϭ 43.4 (NCH3), 121.0,
123.3, 127.8, 128.6, 129.0, 129.1, 130.4, 138.1 (C6H5), 146.7 (Cϭ
N) ppm. C14H14N2O (254.33): calcd. C 74.31, H 6.42, N 12.38;
found C 74.24, H 6.27, N 12.34.
in vacuo.
All other iminohydroxamic esters 5 and amides 6 were prepared
according to this procedure, only different benzamides and hy-
droxylamines or hydrazines were employed as starting materials,
respectively. Isolated yields of ligands 5 and 6 ranged from 78 to
99%, depending on the substitution pattern of the building blocks.
N-(2,6-Diisopropylphenyl)-NЈ-methoxy-NЈ-methylbenzamidine (5a):
Starting materials: N-(2,6-diisopropylphenyl)benzamide (1a, 1.98 g,
7.0 mmol) and N-methyl-O-methylhydroxylamine hydrochloride
(0.53 g, 4.3 mmol). Yield: 2.11 g (93%). IR (KBr): ν˜ ϭ 2962 (m),
2931 (m), 1634 (s), 1602 (m), 1590 (m), 1461 (m), 1436 (m), 1360
(w), 1324 (m), 1256 (w), 1181 (w), 1104 (m), 1057 (w), 1030 (w),
1007 (m), 778 (m), 760 (m), 722 (w), 700 (s) cmϪ1. MS(EI, 70 eV):
m/z ϭ 324 [M]ϩ. 1H NMR (300 MHz, CDCl3): δ ϭ 0.91 [d,
N-(2,6-Diisopropylphenyl)-NЈ-hydroxy-NЈ-isopropylbenzamidine
(3e): Starting materials: N-(2,6-diisopropylphenyl)benzamide (1a,
1.47 g, 6.7 mmol) and N-isopropylhydroxylamine hydrochloride
(0.85 g, 7.6 mmol). Yield: 0.63 g (36%). IR (KBr): ν˜ ϭ 3433 (w),
3064 (w), 3006 (w), 2968 (s), 2948 (m), 2931 (m), 2867 (m), 1683
(w), 1598 (s), 1503 (s), 1461 (s), 1436 (m), 1385 (m), 1378 (m), 1360
(s), 1343 (w), 1335 (w), 1320 (w), 1256 (w), 1173 (s), 1123 (w), 1104
(w), 1067 (s), 1040 (w), 978 (m), 930 (w), 924 (w), 822 (w), 808 (s),
781 (m), 760 (s), 702 (s) cmϪ1. MS(EI, 70 eV): m/z ϭ 338 [M]ϩ.
3JH,H ϭ 7.0 Hz, 6 H, CH(CH3)2], 1.06 [d, JH,H ϭ 7.0 Hz, 6 H,
CH(CH3)2], 2.89 [sept, JH,H ϭ 7.0 Hz, 2 H, 2 ϫ CH(CH3)2], 3.15
3
3
(s, 3 H, NCH3), 3.49 (s, 3 H, OCH3), 6.82Ϫ6.89 (m, 3 H, C6H3),
7.13 (s, 5 H, C6H5) ppm. 13C NMR (75.432 MHz, CDCl3): δ ϭ
21.9, 23.9, 28.0 [2 ϫ CH(CH3)2], 37.0 (NCH3), 60.2 (OCH3), 122.4,
122.5, 127.5, 128.1, 128.8, 137.1, 144.0 (C6H3, C6H5), 160.8 (CϭN)
ppm. C21H28N2O (324.47): calcd. C 77.74, H 8.70, N 8.63; found C
77.69, H 8.72, N 8.60.
3
1H NMR (300 MHz, CDCl3): δ ϭ 0.98 [d, JH,H ϭ 6.2 Hz, 6 H,
3
CH(CH3)2], 1.11 [d, JH,H ϭ 6.2 Hz, 6 H, CH(CH3)2], 1.37 [d,
3JH,H ϭ 6.6 Hz, 6 H, CH(CH3)2], 3.16 [sept, 2 H, 2 ϫ CH(CH3)2],
3
4.03 [sept, JH,H ϭ 6.6 Hz, 1 H, CH(CH3)2], 6.95 (m, 2 H, C6H5),
7.02Ϫ7.12 (m, 3 H, C6H5), 7.20Ϫ7.27 (m, 3 H, C6H3), not observed
(s, 1 H, NOH) ppm. 13C NMR (75.432 MHz, CDCl3): δ ϭ 20.0,
21.9, 25.4, 28.2 [CH(CH3)2], 54.8 [NCH(CH3)2], 123.0, 127.5,
127.7, 128.3, 128.5, 129.9, 132.5, 145.9 (C6H5, C6H3), 148.1 (CϭN)
ppm. C22H30N2O (338.49): calcd. C 78.06, H 8.93, N 8.28; found C
78.00, H 8.95, N 8.24.
NЈ-Methoxy-NЈ-methyl-N-(2,6-methylphenyl)benzamidine
(5b):
Starting materials: N-(2,6-diisopropylphenyl)benzamide (1a, 2.07 g,
9.2 mmol) and N-methyl-O-methylhydroxylamine hydrochloride
(0.90 g, 9.2 mmol). Yield: 2.33 g (94%). IR (KBr): ν˜ ϭ 2973 (m),
2930 (m), 1636 (s), 1591 (m), 1578 (m), 1466 (m), 1447 (m), 1325
(m), 1260 (m), 1101 (m), 1076 (m), 1051 (m), 1028 (m), 1007 (s),
783 (m), 766 (s), 727 (m), 700 (s) cmϪ1. MS(EI, 70 eV): m/z ϭ 268
N-(2,6-Diisopropylphenyl)-NЈ-hydroxy-NЈ-(4-methylphenyl)-
benzamidine (3f): Starting materials: N-(2,6-diisopropylphe-
nyl)benzamide (1a, 1.21 g, 4.3 mmol) and N-(4-methylphenyl)hy-
droxylamine (0.53 g, 4.3 mmol).[14] Yield: 0.30 g (18%). IR (KBr):
ν˜ ϭ 2964 (s), 2927 (m), 2867 (m), 1600 (s), 1571 (s), 1507 (s), 1461
(s), 1322 (m), 1302 (w), 1285 (w), 1260 (m), 1239 (m), 1187 (w),
1106 (m), 1077 (w), 1044 (m), 818 (s), 787 (s), 776 (s), 758 (s), 697
(s) cmϪ1. MS(FAB): m/z ϭ 387 [M ϩ H]ϩ. 1H NMR (300 MHz,
1
[M]ϩ. H NMR (300 MHz, CDCl3): δ ϭ 2.02 (s, 6 Η, CH3), 3.16
(s, 3 H, NCH3), 3.52 (s, 3 H, OCH3), 6.64Ϫ6.79 (m, 3 H, C6H3),
7.16 (s, 5 H, C6H5) ppm. 13C NMR (75.432 MHz, CDCl3): δ ϭ
18.5 (CH3), 37.2 (NCH3), 60.3 (OCH3), 121.9, 127.2, 127.5, 127.55,
127.6, 129.0, 134.0, 146.7 (C6H3, C6H5), 161.7 (CϭN) ppm.
C17H20N2O (268.36): calcd. C 76.09, H 7.51, N 10.44; found C
76.16, H 7.53, N 10.41.
3
CDCl3): δ ϭ 0.90 [d, JH,H ϭ 7.0 Hz, 6 H, CH(CH3)2], 2.19 (s, 3
N-(Biphenyl-2-yl)-NЈ-methoxy-NЈ-methylbenzamidine (5c): Starting
materials: N-(biphenyl-2-yl)benzamide (1c, 2.08 g, 7.6 mmol) and
3
H, NC6H4CH3), 3.17 [sept, JH,H ϭ 7.0 Hz, 2 H, 2 ϫ CH(CH3)2],
6.82Ϫ6.91 (m, 4 H, C6H4, C6H3), 6.96Ϫ7.23 (m, 8 H, C6H4, C6H3),
not observed (s, 1 H, NOH) ppm. 13C NMR (75.432 MHz, CDCl3):
δ ϭ 14.0, 20.6, 22.0, 22.5, 25.2, 29.4, 31.5 [CH3, 2 ϫ CH(CH3)2],
132.1, 137.4, 141.0, 145.4 (C6H3, C6H4), 150.5 (CϭN) ppm.
C26H30N2O (386.54): calcd. C 80.79, H 7.82, N 7.25; found C
80.86, H 7.83, N 7.26.
N-methyl-O-methylhydroxylamine
hydrochloride
(0.74 g,
7.6 mmol). Yield: 2.18 g (91%). IR (KBr): ν˜ ϭ 1628 (m), 1593 (m),
1578 (m), 1493 (m), 1474 (m), 1447 (m), 1431 (m), 1337 (m), 1267
(m), 1103 (m), 1074 (m), 1049 (m), 1030 (m), 1009 (m), 783 (m),
762 (m), 739 (s), 698 (s), 632 (m) cmϪ1. MS (EI, 70 eV): m/z ϭ 316
[M]ϩ. 1H NMR (300 MHz, CDCl3): δ ϭ 3.03 (s, 3 H, NCH3), 3.38
(s, 3 H, OCH3), 6.68Ϫ7.27 (m, 14 H, C6H5, C6H4) ppm. 13C NMR
(75.432 MHz, CDCl3): δ ϭ 37.0 (NCH3), 60.5 (OCH3), 122.6,
122.8, 126.1, 127.3, 127.34, 127.6, 128.2, 128.5, 129.6, 129.9, 132.9,
133.2, 140.3, 147.1 (C6H5, C6H4), 161.9 (CϭN) ppm. C21H20N2O
(316.40): calcd. C 79.72, H 6.37, N 8.85; found C 79.66, H 6.39,
N 8.83.
Representative Procedure for Iminohydroxamic Esters 5aϪ5d and
Iminohydroxamic Amides 6a, 6b: A dichloromethane solution of
imidoyl chloride 2a (c ϭ 0.108 g/ml or 0.36 mmol/ml, respectively)
was prepared as described above. A second Schlenk vessel was
charged with N-methyl-O-methylhydroxylamine hydrochloride
(0.78 g, 8.0 mmol), dry ethanol (50 mL), and triethylamine
(2.2 mL, 16 mmol). After the stirred mixture was cooled to Ϫ40
°C, a dropping funnel was attached to the Schlenk vessel, and a
stoichiometric amount of a dichloromethane solution of imidoyl
chloride 2a was added dropwise over a period of 30 min. The mix-
ture was warmed to room temperature and stirred at ambient tem-
NЈ-Methoxy-NЈ-methyl-N-phenylbenzamidine (5d): Starting materi-
als: benzanilide (1d, 2.13 g, 10.8 mmol) and N-methyl-O-methylhy-
droxylamine hydrochloride (1.06 g, 10.8 mmol). Yield: 2.03 g
(78%). IR (KBr): ν˜ ϭ 2932 (w), 1628 (m), 1591 (m), 1439 (m), 1335
(m), 1256 (m), 1103 (m), 1074 (m), 1028 (m), 1009 (m), 997 (m),
perature for further 60 min, resulting in a yellow suspension. 920 (m), 903 (m), 781 (s), 762 (s), 744 (s), 696 (s) cmϪ1. MS (EI,
Workup: the reaction mixture was hydrolyzed by addition of of
water (100 mL), the organic material was extracted three times with
diethyl ether, the combined organic layers were dried with Na2SO4,
the volatile materials were removed in a rotary evaporator, yielding
70 eV): m/z ϭ 240 [M]ϩ. 1H NMR (300 MHz, CDCl3): δ ϭ 3.16
(s, 3 H, NCH3), 3.54 (s, 3 H, OCH3), 6.60 (d, 2 H, C6H5), 6.79 (t,
1 H, C6H5), 7.03 (t, 2 H, C6H5), 7.20Ϫ7.28 (m, 5 H, C6H5) ppm.
13C NMR (75.432 MHz, CDCl3): δ ϭ 37.0 (NCH3), 60.6 (OCH3),
1748
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 1740Ϫ1752

Iminohydroxamato Early and Late Transition Metal Halide Complexes
121.9, 122.1, 127.7, 128.2, 128.7, 128.8, 133.1, 149.7 (C6H5), 162.8 removed. Stirring was continued overnight, resulting in a brown
FULL PAPER
(CϭN) ppm. C15H16N2O (240.30): calcd. C 74.97, H 6.71, N 11.66;
found C 74.92, H 6.73, N 11.63.
solution. Workup: THF and other volatile materials were removed
in a vacuum line, the brown residue was dissolved in dry, deoxygen-
ated dichloromethane giving a brown solution and a precipitate of
lithium chloride. The inorganic salt was removed by filtration
through a Schlenk frit, the dichloromethane was removed in a vac-
uum line, and the residue was triturated with dry, deoxygenated n-
hexane (10 mL) to remove apolar impurities from the solid product.
The precipitate was allowed to settle, n-hexane was removed by
pipette followed by drying in vacuo, affording the product as an
orange air-sensitive powder in 90% yield.
N-(2,6-Diisopropylphenyl)-NЈ-methyl-NЈ-(methylamino)benzamidine
(6a): Starting materials: N-(2,6-diisopropylphenyl)benzamide (1a,
1.01 g, 3.6 mmol) and N,NЈ-dimethylhydrazine hydrochloride
(0.55 g, 4.1 mmol). Yield: 1.10 g (94%). IR (KBr): ν˜ ϭ 3244 (w),
3062 (w), 3022 (w), 2973 (m), 2960 (m), 1609 (s), 1596 (s), 1586 (s),
1576 (s), 1492 (w), 1439 (m), 1382 (m), 1364 (s), 1329 (m), 1262
(m), 1183 (w), 1111 (m), 1069 (s), 1046 (m), 1025 (s), 924 (m), 845
(s), 824 (m), 808 (w), 799 (m), 772 (s), 760 (s), 714 (s), 700 (s) cmϪ1
MS(EI, 70 eV): m/z ϭ 323 [M]ϩ. 1H NMR (300 MHz, CDCl3): δ ϭ
.
Trichloro[N-(2,6-diisopropylphenyl)-NЈ-methyl-NЈ-oxybenz-
3
3
0.94 [d, JH,H ϭ 7.0 Hz, 6 H, CH(CH3)2], 1.06 [d, JH,H ϭ 6.6 Hz,
6 H, CH(CH3)2], 2.64 (s, 3 H, NCH3), 2.90 (s, 3 H, NCH3), 2.94
[sept, 2 H, 2 ϫ CH(CH3)2], 6.78Ϫ6.86 (m, 3 H, C6H3), 7.01Ϫ7.14
(m, 5 H, C6H5), not observed (s, 1 H, NH) ppm. 13C NMR
(75.432 MHz, CDCl3): δ ϭ 21.8, 24.1, 28.1 [CH(CH3)2], 36.4, 39.2
(NCH3), 122.1, 122.2, 127.8, 128.1, 128.8, 133.1, 138.2, 144.7
(C6H3, C6H5), 157.3 (CϭN) ppm. C21H29N3 (323.48): calcd. C
77.97, H 9.04, N 12.99; found C 78.01, H 9.07, N 13.02.
amidinato]zirconium(IV) (8a): Starting materials: 3a (0.28 g,
0.90 mmol), n-butyllithium (0.90 mmol, 0.21 g), ZrCl4 (0.90 mmol,
1 mol-equiv. in relation to 3a). Yield: 0.41 g (90%) as an orange,
1
air-sensitive powder. H NMR (300 MHz, CD2Cl2): δ ϭ 1.04 [d, 6
H, 2 ϫ CH(CH3)2], 1.81 (br. s, 4 H, CH2 of coordinating THF),
3.33 [m, 5 H, NCH3, 2 ϫ CH(CH3)2], 3.83 (br. s, 4 H, CH2 of
coordinating THF), 6.94Ϫ7.02 (m, 3 H, C6H3), 7.10Ϫ7.35 (m, 5
H, C6H5) ppm. 13C NMR (75.432 MHz, CD2Cl2): δ ϭ 24.2, 25.9,
28.1 [CH(CH3)2], 41.6 (NCH3), 123.6, 124.2, 126.1, 128.5, 128.7,
129.1, 129.3, 129.4, 130.6, 143.9, 144.2 (C6H3, C6H5), 161.7 (Cϭ
N) ppm. C20H25Cl3N2OZr·THF ϭ C24H33Cl3N2O2Zr (579.11):
calcd. C 49.78, H 5.74, N 4.84; found C 49.67, H 5.70, N 4.77.
N-(2,6-Diisopropylphenyl)-NЈ-(dimethylamino)benzamidine
(6b):
Starting materials: N-(2,6-diisopropylphenyl)benzamide (1a, 1.01 g,
3.6 mmol) and N,N-dimethylhydrazine (0.58 mL, 0.46 g, 7.7 mmol,
excess). Yield: 1.15 g (99%), brown viscous oil. MS (EI, 70 eV):
m/z ϭ 323 [M]ϩ. 1H NMR (300 MHz, CDCl3): δ ϭ 0.88 [d,
Trichloro[N-(2,6-dimethylphenyl)-NЈ-methyl-NЈ-oxybenzamidinato]-
zirconium(IV) (8b): Starting materials: 3b (0.54 g, 2.12 mmol), n-
butyllithium (2.4 mmol, 0.56 g), ZrCl4 (2.4 mmol, 1.1 mol-equiv. in
relation to 3b). Yield: 0.82 g (86%) as an orange, air-sensitive pow-
der. 1H NMR (300 MHz, CD2Cl2): δ ϭ 1.91 (br. s, 4 H, CH2 of
coordinating THF), 2.28, 2.31, 2.34, 2.39 (4 ϫ s, 6 H, CH3), 3.27,
3.33 (2 ϫ s, 3 H, NCH3), 3.85, 4.3 (2 ϫ br. s, 4 H, CH2 of coordin-
ating THF), 6.83Ϫ7.37 (m, 8 H, C6H3, C6H5) ppm. 13C NMR
(75.432 MHz, CD2Cl2): δ ϭ 18.7, 19.5, 19.7, 20.7, 20.9 (CH3,
THF), 39.5, 41.3, 41.9, 42.2 (NCH3), 69.3 (THF), 125.5, 126.0,
127.2, 127.9, 128.0, 128.1, 128.4, 128.7, 128.9, 129.2, 130.1, 130.3,
130.4, 130.5, 130.9, 131.4, 133.1, 133.4, 133.8, 134.4, 134.7, 146.3
3
3JH,H ϭ 6.9 Hz, 6 H, CH(CH3)2], 1.10 [d, JH,H ϭ 6.9 Hz, 6 H,
3
CH(CH3)2], 2.57 [s, 6 H, N(CH3)2], 3.13 (sept, JH,H ϭ 6.9 Hz, 2
H, 2 ϫ CH(CH3)2], 6.98Ϫ7.21 (m, 8 H, C6H3, C6H5), 7.95 (s, 1 H,
NH) ppm. 13C NMR (75.432 MHz, CDCl3): δ ϭ 21.9, 24.9, 26.3
[CH(CH3)2], 46.7 [N(CH3)2], 123.3, 126.9, 127.6, 128.5, 129.1,
132.9, 134.3, 145.2 (C6H3, C6H5), 159.7 (CϭN) ppm. C21H29N3
(323.48): calcd. C 77.97, H 9.04, N 12.99; found C 77.92, H 9.07,
N 12.95.
N-(2,6-Diisopropylphenyl)-NЈ-{[(2,6-diisopropylphenyl)iminobenzyl]-
phenylamino}benzamidine (7): Starting materials: N-(2,6-diisopro-
pylphenyl)benzamide (1a, 2.03 g, 7.2 mmol) and N,NЈ-diphenylhy-
drazine (1.40 g, 7.6 mmol). Yield: 0.42 g (16% based on limiting
reagent 1a). IR (KBr): ν˜ ϭ 2964 (m), 2929 (m), 2869 (m), 1627 (s),
1607 (s), 1589 (m), 1574 (s), 1497 (m), 1463 (m), 1443 (w), 1356
(w), 1328 (m), 1104 (w), 1057 (w), 1007 (w), 822 (w), 805 (w), 789
(C6H3, C6H5), 161.3 (CϭN) ppm. C16H17Cl3N2OZr·THF
ϭ
C20H25Cl3N2O2Zr (523.01): calcd. C 45.93, H 4.82, N 5.36; found
C 45.87, H 4.79, N 5.31.
Trichloro[N-(biphenyl-2-yl)-NЈ-methyl-NЈ-oxybenzamidinato]-
zirconium(IV) (8c): Starting materials: 3c (0.49 g, 1.62 mmol), n-bu-
tyllithium (1.7 mmol, 0.46 g), ZrCl4 (2.0 mmol, 1.2 mol-equiv. in
relation to 3c). Yield: 0.71 g (88%) as an orange-brown, air-sensi-
(w), 778 (w), 762 (w), 700 (m) cmϪ1. MS(FAB): m/z ϭ 712 [M ϩ
3
H]ϩ. 1H NMR (300 MHz, CDCl3): δ ϭ 1.00 [d, 12 H, JH,H
ϭ
3
6.6 Hz, 2 ϫ CH(CH3)2], 1.25 [d, JH,H ϭ 6.6 Hz, 12 H, 2 ϫ
CH(CH3)2], 3.13 [sept, 4 H, 4 ϫ CH(CH3)2], 6.92 (d, 4 H, C6H3),
7.04 (m, 8 H, C6H3, C6H5), 7.13Ϫ7.36 (m, 14 H, C6H5) ppm. 13C
NMR (75.432 MHz, CDCl3): δ ϭ 21.7, 25.5, 28.9 [CH(CH3)2],
123.8, 124.5, 124.6, 124.9, 127.5, 128.6, 128.8, 129.1, 129.3, 129.5,
129.7, 132.6, 135.3, 137.9, 145.3 (C6H3, C6H5), 164.9 (CϭN) ppm.
C50H54N4 (711.01): calcd. C 84.46, H 7.66, N 7.88; found C 84.51,
H 7.66, N 7.85.
1
tive powder. H NMR (300 MHz, CD2Cl2): δ ϭ 1.88 (br. s, 4 H,
CH2 of coordinating THF), 2.33, 2.84, 2.97, 3.15 (4 ϫ s, 3 H,
NCH3), 3.82, 4.56 (2 ϫ br. s, 4 H, CH2 of coordinating THF),
6.90Ϫ7.43 (m, 14 H, C6H4, C6H5) ppm. 13C NMR (75.432 MHz,
CD2Cl2): δ ϭ 25.9 (THF), 41.1 (NCH3), 69.2 (THF), 126.3, 127.2,
127.8, 127.9, 128.1, 128.5, 128.6, 128.7, 129.3, 129.4, 129.7, 130.2,
130.2, 131.2, 139.9, 144.5 (C6H4, C6H5), 160.9 (CϭN) ppm.
C20H17Cl3N2OZr·THF ϭ C24H25Cl3N2O2Zr (571.05): calcd. C
50.48, H 4.41, N 4.91; found C 50.40, H 4.38, N 4.86.
Synthesis of Metal Complexes
Representative Procedure for Iminohydroxamato and Imidoyl Hy-
Trichloro[NЈ-methyl-NЈ-oxybenzamidinato-N-phenyl]zirconium(IV
)
drazido Complexes 8aϪ14a: A Schlenk tube was charged with 3a
(8d): Starting materials: 3d (0.34 g, 1.49 mmol), n-butyllithium
(0.28 g, 0.90 mmol) and dry, deoxygenated THF (20 mL). After the (1.5 mmol, 0.41 g), ZrCl4 (1.8 mmol, 1.2 mol-equiv. in relation to
mixture was cooled to Ϫ80 °C, a 2.0  n-pentane solution of n-
3d). Yield: 0.58 g (92%) as a yellow, air-sensitive powder. 1H NMR
butyllithium (0.90 mmol, 0.45 mL) was added through a syringe. (300 MHz, CD2Cl2): δ ϭ 1.86 (br. s, 4 H, CH2 of coordinating
The stirred mixture changed gradually in color from orange to dark
red, indicating deprotonation of 3a. After 1 h of stirring at Ϫ80
°C, ZrCl4 (0.21 g, 0.90 mmol, 1 mol-equiv. in relation to 3a) was
added under protection from air and the external cooling bath was
THF), 2.78, 3.32 (2 ϫ s, 3 H, NCH3), 3.84, 4.54 (2 ϫ br. s, 4 H,
CH2 of coordinating THF), 6.92Ϫ7.35 (m, 10 H, C6H5) ppm. 13C
NMR (75.432 MHz, CD2Cl2): δ ϭ 25.8 (THF), 40.0 (NCH3),
125.2, 126.5, 128.3, 128.4, 128.6, 128.8, 129.0, 129.1, 129.2, 130.8,
Eur. J. Inorg. Chem. 2004, 1740Ϫ1752
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 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1749

B. Bildstein et al.
FULL PAPER
146.3 (C6H5), 159.3 (CϭN) ppm. C14H13Cl3N2OZr·THF
ϭ
tra were obtained. C16H17Cl3N2OV (410.62): calcd. C 46.80, H
C18H21Cl3N2O2Zr (494.96): calcd. C 43.68, H 4.28, N 5.66; found 4.17, N 6.82; found C 45.72, H 4.25, N 6.70.
C 43.57, H 4.24, N 5.61.
Trichloro[N-(2,6-diisopropylphenyl)-NЈ-methylamino-NЈ-methyl-
benzamidinato]zirconium(IV) (13a): Starting materials: 6a (0.52 g,
1.61 mmol), n-butyllithium (1.6 mmol, 0.49 g ), ZrCl4 (2.1 mmol,
1.3 mol-equiv. in relation to 6a). Yield: 0.71 g (85%) as a yellow,
air-sensitive powder. 1H NMR (300 MHz, CD2Cl2): δ ϭ 0.93Ϫ1.24
[4 ϫ d, 12 H, 2 ϫ CH(CH3)2], 1.82 (br. s, 4 H, CH2 of coordinating
THF), 2.94, 3.07, 3.18, 3.29 [4 ϫ s, sept, 5 H, NCH3, 2 ϫ
CH(CH3)2], 3.39, 3.48, 3.57, 3.89 (4 ϫ s, 3 H, NCH3), 3.84, 4.56
(2 ϫ br. s, 4 H, CH2 of coordinating THF), 6.90Ϫ7.60 (m, 8 H,
C6H3, C6H5) ppm. 13C NMR (75.432 MHz, CD2Cl2): δ ϭ 21.8,
22.6, 24.2, 25.3, 25.9, 27.0, 28.2, 29.2 [CH(CH3)2], 34.9, 38.8, 40.4
(NCH3), 123.0, 124.0, 124.3, 128.3, 128.6, 128.9, 129.5, 129.7,
129.8, 133.0, 143.8, 144.0, 146.1 (C6H3, C6H5), not observed: (Cϭ
N) ppm. C21H28Cl3N3Zr·THF ϭ C25H36Cl3N3Zr (576.16): calcd.
C 52.12, H 6.30, N 7.29; found C 52.06, H 6.26, N 7.21.
Trichloro[N-(2,6-diisopropylphenyl)-NЈ-isopropyl-NЈ-oxybenz-
amidinato]zirconium(IV (8e): Starting materials: 3e (0.28 g,
)
0.83 mmol), n-butyllithium (0.82 mmol, 0.22 g), ZrCl4 (0.90 mmol,
1.2 mol-equiv. in relation to 3e). Yield: 0.28 g (64%) as a colorless,
air-sensitive powder. 1H NMR (300 MHz, CD2Cl2): δ ϭ 1.00Ϫ1.45
3
[m, 15 H, 2 ϫ CH(CH3)2, NCH(CH3)2], 1.61 [d, JH,H ϭ 6.6 Hz, 3
H, NCH(CH3)2], 1.83, 2.10 (br. s, 4 H, CH2 of coordinating THF),
3.28Ϫ4.02 [3 overlapping sept, 3 H, NCH(CH3)2], 3.76, 4.70 (br. s,
4 H, CH2 of coordinating THF), 6.92Ϫ7.46 (m, 8 H, C6H3, C6H5)
ppm. 13C NMR (75.432 MHz, CD2Cl2): δ ϭ 20.0, 20.1, 22.0, 23.8,
24.3, 25.9, 26.1, 16.3, 28.2, 29.0, 29.2 [CH(CH3)2], 55.1
[NCH(CH3)2], 123.5, 123.6, 123.8, 124.1, 126.1, 126.3, 127.9, 128.5,
128.6, 128.8, 129.0, 129.2, 129.6, 129.7, 130.5, 131.9, 143.8, 144.5,
146.9, 147.4, 155.0 (C6H3, C6H5), 162.0 (CϭN) ppm.
C22H29Cl3N2OZr·THF ϭ C26H37Cl3N2O2Zr (607.17): calcd. C
51.43, H 6.14, N 4.61; found C 51.38, H 6.10, 4.56.
Trichloro[N-(2,6-diisopropylphenyl)-NЈ-methylamino-NЈ-methyl-
benzamidinato]titanium(IV) (14a): Starting materials: 6a (0.40 g,
1.24 mmol), n-butyllithium (1.24 mmol, 0.49 g), TiCl4 (1.5 mmol,
1.2 mol-equiv. in relation to 6a). Yield: 0.56 g (95%) as a green, air-
sensitive powder. 1H NMR (300 MHz, CD2Cl2): δ ϭ 1.05 [d,
Trichloro[N-(2,6-diisopropylphenyl)-NЈ-4-methylphenyl-NЈ-oxybenz-
amidinato]zirconium(IV
)
(8f): Starting materials: 3f (0.22 g,
0.56 mmol), n-butyllithium (0.60 mmol, 0.13 g), ZrCl4 (0.56 mmol,
1.0 mol-equiv. in relation to 3f). Yield: 0.29 g (90%) as a tan, air-
sensitive powder. 1H NMR (300 MHz, CD2Cl2): δ ϭ 1.05Ϫ1.35 [m,
12 H, 2 ϫ CH(CH3)2], 1.82, 1.97 (br. s, 4 H, CH2 of coordinating
THF), 2.27 (s, 3 H, CH3), 3.20, 3.40 [2 ϫ sept, 2 H, CH(CH3)2],
3.77, 4.48 (br. s, 4 H, CH2 of coordinating THF), 6.77Ϫ7.67 (m,
3
3JH,H ϭ 6.9 Hz, 6 H, CH(CH3)2], 2.93 [sept, JH,H ϭ 6.9 Hz, 2 H,
CH(CH3)2], 3.38 (s, 3 H, NCH3), 4.38 (s, 3 H, NCH3), 6.99Ϫ7.36
(m, 8 H, C6H3, C6H5) ppm. 13C NMR (75.432 MHz, CD2Cl2): δ ϭ
23.9, 25.3, 28.6 [CH(CH3)2], 38.0, 45.2 (NCH3), 123.8, 128.0, 128.7,
128.9, 129.0, 131.4, 141.2, 150.9 (C6H3, C6H5), 160.0 (CϭN) ppm.
C21H28Cl3N3Ti (476.71): calcd. C 52.91, H 5.92, N 8.81; found C
53.03, H 5.88, N 8.75.
12 H, C6H3, C6H4, C6H5) ppm. C26H29Cl3N2OZr·THF
ϭ
C30H37Cl3N2O2Zr (655.21): calcd. C 54.99, H 5.69, N 4.28; found
C 55.06, H 5.73, N 4.25.
Representative Procedure for Iminohydroxylamino and Hydrazido
Complexes 15aϪ17: A Schlenk tube was charged with 5a (0.97 g,
3.0 mmol), dibromo(dimethoxethane)nickel() (1.25 g, 3.1 mmol)
and dry, deoxygenated dichloromethane (20 mL). The mixture was
stirred overnight, resulting in a dark green solution/suspension.
Workup: dry dichloromethane (60 mL) was added, the solution was
filtered through a Schlenk frit, the green solution was concentrated
in a vacuum line, and the residue was dried in vacuo affording a
green air-sensitive powder in 94% yield.
Dichlorobis[N-(2,6-diisopropylphenyl)-NЈ-methyl-NЈ-oxybenz-
amidinato]zirconium(IV) (9a): Starting materials: 3a (0.65 g,
2.08 mmol), n-butyllithium (2.04 mmol, 0.21 g), ZrCl4 (0.90 mmol,
0.5 mol-equiv. in relation to 3a). Yield: 0.54 g (77%) as a tan, air-
sensitive powder. 1H NMR (300 MHz, CD2Cl2): δ ϭ 0.23, 0.34.
0.29. 1.04 [4 ϫ d, 3JH,H ϭ 6.6 Hz, 24 H, 4 ϫ CH(CH3)2], 2.89 [sept,
2 H, 2 ϫ CH(CH3)2], 3.18 [sept, 2 H, 2 ϫ CH(CH3)2], 3.40, 3.54,
3.60, 3.97 (4 ϫ s, 6 H, NCH3), 6.80Ϫ7.29 (m, 16 H, C6H3, C6H5)
ppm. 13C NMR (75.432 MHz, CD2Cl2): δ ϭ 24.5, 25.1, 25.9, 26.2,
27.9, 28.1 [CH(CH3)2], 43.6 (NCH3), 123.5, 124.2, 124.8, 125.8,
127.7, 127.9, 128.3, 128.3, 128.7, 129.0, 129.4, 130.0, 130.3, 143.3,
143.5, 145.5 (C6H3, C6H5), 159.8 (CϭN) ppm. C40H50Cl2N2O2Zr
(752.98): calcd. C 63.81, H 6.69, N 3.72; found C 63.95, H 6.72,
N 3.70.
Dibromo[N-(2,6-diisopropylphenyl)-NЈ-methoxy-NЈ-methylbenz-
amidinato]nickel(II) (15a): Starting materials: 5a (0.97 g, 3.0 mmol),
NiBr2·DME (1.25 g, 3.1 mmol). Yield: 1.53 g (94%) as a green,
1
paramagnetic, air-sensitive powder. H NMR (300 MHz, CD2Cl2):
δ ϭ 1.10Ϫ1.49 [br. m, 12 H, CH(CH3)2], 2.97Ϫ3.56 [br. m, 8 H,
CH(CH3)2, NCH3, OCH3], 6.80Ϫ8.30 (br. m, 8 H, C6H3, C6H5)
ppm. 13C NMR (75.432 MHz, CD2Cl2): due to paramagnetism,
only very weak signals were observed. C21H28Br2N2NiO (542.96):
calcd. C 46.45, H 5.20, N 5.16; found C 46.52, H 5.25, N 5.07.
Trichloro[N-(2,6-dimethylphenyl)-NЈ-methyl-NЈ-oxybenzamidinato]-
titanium(IV) (10b): Starting materials: 3b (0.44 g, 1.73 mmol), n-bu-
tyllithium (1.9 mmol, 0.68 g), TiCl4 (2.0 mmol, 1.2 mol-equiv. in
relation to 3b). Yield: 0.67 g (95%) as an orange, air-sensitive pow-
der. 1H NMR (300 MHz, CD2Cl2): δ ϭ 2.13, 2.34 (2 ϫ s, 6 H,
CH3), 3.40, 3.49, 3.63 (3 ϫ s, 3 H, NCH3), 6.85 (m, 3 H, C6H3),
7.12Ϫ7.41 (m, 5 H, C6H5) ppm. 13C NMR (75.432 MHz, CD2Cl2):
δ ϭ 19.6, 20.4 (CH3), 30.0, 39.2, 41.5 (NCH3), 125.8, 126.0, 128.1,
128.5, 128.7, 129.0, 129.3, 131.0, 131.7, 133.2, 133.5, 145.4, 149.9
(C6H3, C6H5), 160.3 (CϭN) ppm. C16H17Cl3N2OTi (407.56): calcd.
C 47.15, H 4.20, N 6.87; found C 47.07, H 4.16, N 6.82.
Dibromo[N-(2,6-dimethylphenyl)-NЈ-methoxy-NЈ-methylbenz-
amidinato]nickel(II
2.94 mmol), NiBr2·DME (1.17 g, 2.94 mmol). Yield: 1.08 g (66%)
as
green, paramagnetic, air-sensitive powder. 1H NMR
)
(15b): Starting materials: 5b (0.79 g,
a
(300 MHz, CD2Cl2): δ ϭ 2.75 [br. s, 12 H, CH(CH3)2], 3.99 [br. m,
8 H, CH(CH3)2, NCH3, OCH3], 6.80Ϫ7.70 (br. m, 8 H, C6H3,
C6H5) ppm. 13C NMR (75.432 MHz, CD2Cl2): due to paramagnet-
ism, no informative signals were observed. C17H20Br2N2NiO
(486.86): calcd. C 41.94, H 4.14, N 5.75; found C 42.02, H 4.16,
N 5.70.
Trichloro[N-(2,6-dimethylphenyl)-NЈ-methyl-NЈ-oxybenzamidinato]-
vanadium(IV) (11b): Starting materials: 3b (0.40 g, 1.56 mmol), n-
butyllithium (1.7 mmol, 0.2 mL), VCl4 (1.9 mmol, 1.2 mol-equiv. in Dibromo[N-(biphenyl-2-yl)-NЈ-methoxy-NЈ-methylbenzamidinato]-
relation to 3b). Yield: 0.67 g (95%) as a dark green, air-sensitive
nickel(II) (15c): Starting materials: 5c (0.87 g, 2.75 mmol),
powder. Due to strong paramagnetism no informative NMR spec-
NiBr2·DME (1.10 g, 2.75 mmol). Yield: 1.43 g (97%) as a green,
1750
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 1740Ϫ1752

Iminohydroxamato Early and Late Transition Metal Halide Complexes
FULL PAPER
1
paramagnetic, air-sensitive powder. H NMR (300 MHz, CD2Cl2):
Dibromo[N-(2,6-diisopropylphenyl)-NЈ-(dimethylamino)-
only one very broad signal from δ ϭ Ϫ4 to ϩ24 ppm centered at
δ ϭ 12.0 ppm was observed. 13C NMR (75.432 MHz, CD2Cl2): due 1.6 mmol), NiBr2·DME (0.70 g, 1.8 mmol). Yield: 0.66 g (76%) as
to paramagnetism, no informative signals were observed.
a brown, slightly paramagnetic, air-sensitive powder. 1H NMR
C21H20Br2N2NiO (534.90): calcd. C 47.15, H 3.77, N 5.24; found (300 MHz, CD2Cl2): δ ϭ 0.89, 0.95, 1.08, 2.04, 2.40, 3.47, 5.99 [6
benzamidinato]nickel(II) (16b): Starting materials: 6b (0.52 g,
C 47.04, H 3.81, N 5.18.
ϫ br. s, 21 H, CH(CH3)2, NCH3, NH], 7.11, 7.14, 7.39, 7.82, 8.19,
8.48, 8.57, 8.96 (8 ϫ br. s, 8 H, C6H3, C6H5) ppm. 13C NMR
(75.432 MHz, CD2Cl2): δ ϭ 13.1, 21.8, 22.2, 24.7, 29.8, 30.7
[CH(CH3)2], 50.8 (NCH3), 124.0, 126.0, 127.7, 129.7, 131.2, 131.7,
135.5, 140.0, 143.8 (C6H3, C6H5), not observed: (CϭN) ppm.
C21H29Br2N3Ni (541.98): calcd. C 46.54, H 5.39, N 7.75; found C
46.58, H 5.32, N 7.70.
Dibromo[NЈ-methoxy-NЈ-methyl-N-phenylbenzamidinato]nickel(II
)
(15d): Starting materials: 5d (0.62 g, 2.58 mmol), NiBr2·DME (1.03 g,
2.58 mmol). Yield: 0.70 g (59%) as a green, paramagnetic, air-sensi-
tive powder. 1H NMR (300 MHz, CD2Cl2): δ ϭ 0.07, 0.87, 1.27, 4.33
(4 ϫ br. s, 6 H, NCH3, OCH3), 6.84Ϫ9.96 (br. m, 10 H, C6H5) ppm.
13C NMR (75.432 MHz, CD2Cl2): due to paramagnetism, no in-
formative signals were observed. C15H16Br2N2NiO (458.80): calcd. C
39.27, H 3.52, N 6.11; found C 39.19, H 3.56, N 6.06.
Dibromo[N-2,6-diisopropylphenyl-NЈ-({[(2,6-diisopropylphenyl)-
imino]benzyl}phenylamino)benzamidino]nickel(II) (17): Starting ma-
terials: 7 (0.26 g, 0.37 mmol), NiBr2·DME (0.17 g, 0.40 mmol).
Dibromo[N-(2,6-diisopropylphenyl)-NЈ-methylamino-NЈ-methyl-
benzamidinato]nickel(II
)
(16a): Starting materials: 6a (0.44 g,
Yield: 0.30 g (88%) as a pale green, air-stable powder. 1H NMR
3
1.36 mmol), NiBr2·DME (0.56 g, 1.4 mmol). Yield: 0.70 g (95%) as
a brown, paramagnetic, air-sensitive powder. H NMR (300 MHz, CH(CH3)2], 1.31 [d, JH,H ϭ 6.6 Hz, 12 H, CH(CH3)2], 3.14 [sept,
CD2Cl2): δ ϭ Ϫ0.16, 1.76, 5.16, 5.41 [4 ϫ br. s, 20 H, CH(CH3)2, 4 H, CH(CH3)2], 6.97 (d, 4 H, C6H3), 7.09 (d, 8 H, C6H5),
(300 MHz, CD2Cl2):
δ
ϭ
1.07 [d, JH,H
ϭ
6.9 Hz, 12 H,
1
3
NCH3, OCH3], 15.38, 19.63, 22.57 (3 ϫ br. s, 8 H, C6H3,C6H5)
7.18Ϫ7.39 (m, 14 H, C6H3, C6H5) ppm. 13C NMR (75.432 MHz,
ppm. 13C NMR (75.432 MHz, CD2Cl2): due to paramagnetism, no CD2Cl2): δ ϭ 21.8, 26.7, 29.5 [CH(CH3)2], 124.2, 125.1, 125.3,
informative signals were observed. C21H29Br2N3Ni (541.98): calcd.
C 46.54, H 5.39, N 7.75; found C 46.40, H 5.44, N 7.67.
125.4, 127.5, 127.9, 128.1, 129.1, 129.2, 129.7, 129.8, 130.2, 133.1,
135.5, 138.4, 145.9 (C6H3, C6H5), 165.5 (CϭN) ppm.
Table 2. Crystallographic data for 2a, 3a, 3b, 3e, 12b
Compound
2a
3a
3b
3e
12b
Empirical formula
C19H22ClN
C20H26N2O ϫ
0.75H2O ϫ 0.5EtOH
346.97
monoclinic
P21/c (No. 14)
1385.87(5)
1688.70(7)
1813.58(5)
90
C16H18N2O
C22H30N2O ϫ 0.5H2O
C32H34Cl4N4O2Ti ϫ
CH2Cl2
710.36
monoclinic
C2/c (No. 15)
1705.81(4)
1542.57(3)
1580.06(3)
90
Formula mass
Crystal system
Space group
a [pm]
b [pm]
c [pm]
299.83
254.32
347.49
monoclinic
P21/c (No. 14)
849.30(4)
2683.84(9)
807.69(4)
90
triclinic
orthorhombic
Pbcn (No. 60)
1610.5(1)
1661.4(2)
1579.4(1)
90
¯
P1 (No. 2)
999.74(8)
1096.61(8)
1404.0(1)
α [°]
67.673(4)
β [°]
γ [°]
113.381(2)
90
93.683(2)
90
87.115(4)
87.317(4)
90
90
122.569(2)
90
Z
4
8
4
8
4
V [nm3]
1.68986(13)
1.178
233(2)
0.220
640
4.2356(3)
1.088
223(2)
0.070
1.42140(18)
1.188
223(2)
0.075
544
4.2260(6)
1.092
223(2)
0.068
1512
3.50384(13)
1.347
233(2)
0.584
1472
ρcalcd. [Mg·mϪ3
T [K]
µ [mmϪ1
F(000)
]
]
1508
Color, habit
Crystal size [mm]
θ range for data collection [°]
Index ranges
colorless prism
0.4 ϫ 0.35 ϫ 0.3
2.61Ϫ23.50
Ϫ9 Յ h Յ 0
Ϫ29 Յ k Յ 30
Ϫ8 Յ l Յ 9
5162
2316 (Rint ϭ 0.0251)
1970
none
colorless prism
0.4 ϫ 0.3 ϫ 0.2
1.90Ϫ21.00
0 Յ h Յ 13
Ϫ16 Յ k Յ 17
Ϫ18 Յ l Յ 18
17026
4516 (Rint ϭ 0.0434)
3531
none
colorless prism
0.39 ϫ 0.13 ϫ 0.12
2.01Ϫ22.00
0 Յ h Յ 10
Ϫ11 Յ k Յ 11
Ϫ14 Յ l Յ 14
6271
3468 (Rint ϭ 0.0304)
2501
none
colorless prism
0.3 ϫ 0.15 ϫ 0.08
1.76° to 19.94
0 Յ h Յ 15
Ϫ15 Յ k Յ 15
Ϫ15 Յ l Յ 15
12806
1950 (Rint ϭ 0.1025)
1380
none
red prism
0.2 ϫ 0.12 ϫ 0.08
1.94Ϫ24.00
Ϫ13 Յ h Յ 19
Ϫ12 Յ k Յ 15
Ϫ15 Յ l Յ 15
9665
2759 (Rint ϭ 0.0322)
2299
none
Reflections collected
Independent reflections
Reflections with I Ͼ 2σ(I)
Absorption correction
Refinement method
full-matrix least
squares on F2
2316/0/192
1.044
full-matrix least
squares on F2
4516/0/506
1.047
full-matrix least
squares on F2
3468/0/358
1.045
full-matrix least
squares on F2
1950/0/246
1.033
full-matrix least
squares on F2
2759/0/221
1.037
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I Ͼ 2σ(I)]
R1 ϭ 0.0410
wR2 ϭ 0.0995
R1 ϭ 0.0513
wR2 ϭ 0.1050
0.015(3)
R1 ϭ 0.0489
wR2 ϭ 0.1226
R1 ϭ 0.0674
wR2 ϭ 0.1304
0.0074(8)
R1 ϭ 0.0467
wR2 ϭ 0.1211
R1 ϭ 0.0728
wR2 ϭ 0.1323
0.017(3)
R1 ϭ 0.0501
wR2 ϭ 0.1175
R1 ϭ 0.0814
wR2 ϭ 0.1313
0.0060(10)
292/Ϫ132
R1 ϭ 0.0397
wR2 ϭ 0.0990
R1 ϭ 0.0516
wR2 ϭ 0.1050
R indices (all data)
Extinction coefficient
Largest diff. peak/hole [e nmϪ3
]
166/Ϫ261
202/Ϫ144
343/Ϫ160
335/Ϫ335
Eur. J. Inorg. Chem. 2004, 1740Ϫ1752
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1751

B. Bildstein et al.
FULL PAPER
C50H54Br2N4Ni (929.50): calcd. C 64.61, H 5.86, N 6.03; found C
64.72, H 5.90, N 5.98.
[1]
Recent reviews: [1a] V. C. Gibson, S. K. Spitzmesser, Chem. Rev.
[1b]
2003, 103, 283.
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[1d]
Crystallography: Single-crystal X-ray measurements and structure
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˚
with graphite-monochromated Mo-Kα radiation (λ ϭ 0.71073 A)
and a nominal crystal to area detector distance of 36 mm. Intensit-
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PACK.[15] Several scans in ϕ and ω directions were made to in-
crease the number of redundant reflections, which were averaged
in the refinement cycles. This procedure replaces an empirical ab-
sorption correction. The structures were solved with direct methods
(SHELXS 86) and refined against F2 (SHELX 97).[16] Hydrogen
atoms at carbon atoms were added geometrically and refined using
a riding model. Hydrogen atoms at nitrogen and oxygen atoms of
compounds 3a, 3b, 3e were located and refined isotropically. All
non-hydrogen atoms were refined with anisotropic displacement
parameters. CCDC-213598 (for 2a), -213599 (3a), -213600 (3b),
-213601 (3e) and -213602 (2b) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the
Cambridge Crystallographic Data Center, 12 Union Road, Cam-
bridge CB2 1EZ, UK; Fax: (internat.) ϩ 44-1223/336-033; E-mail:
deposit@ccdc.cam.ac.uk].
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B. Bildstein, A. Krajete, M. O. Kristen (BASF AG), DE
[9b]
10206116, 2002.
B. Bildstein, A. Krajete, M. O. Kristen
Polymerizations: All polymerization studies and polymer charac-
terizations were performed at Basell/BASF AG in Ludwigshafen,
Germany. Ethylene polymerization: a dry 1000-mL steel autoclave
was charged under strict exclusion of air with toluene (400 mL)
and a small amount (1Ϫ6 mg, compare Table 1) of precatalyst
8aϪ17. A 30% toluene solution of methylaluminoxane (MAO) was
added (2 mL) and the temperature of the autoclave was kept con-
stant at 70 °C. Ethylene gas was added up to a pressure of 40 bar
and the reaction was allowed to proceed for 5Ϫ75 minutes, de-
pending on the activity of the catalyst. After the polymerization
time given in Table 1, the reaction was terminated by releasing the
pressure in the autoclave. The solid polymer was isolated by fil-
tration, washed with methanol, and dried in vacuo. Propylene poly-
merization: conditions were similar as those in ethylene polymeriz-
ations, but propylene was used as monomer. Ethylene/n-hexene co-
polymerizations: conditions were similar as in ethylene homopoly-
merizations, but in addition to the other reagents n-hexene
(12.5 mL) was employed.
(BASF AG), DE 10206113, 2002.
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A. Vogel, Vogel’s Textbook of Practical Organic Chemistry, In-
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1978, p. 1075.
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Received June 26, 2003
[12]
[13]
[14]
[15]
[16]
Early View Article
Published Online March 9, 2004
1752
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 1740Ϫ1752