Salophan complexes of group IV metals

Article abstract of DOI:10.1002/ejic.200500243

The coordination chemistry of tetradentate Salophan ligands with titanium and zirconium alkoxides is described for the first time. Three new Salophan ligand precursors featuring different phenolate substituents (ortho-Me, ortho,para-di-Cl, ortho,para-di-t

Full text of DOI:10.1002/ejic.200500243

FULL PAPER
Salophan Complexes of Group IV Metals
Stanislav Groysman,[a] Ekaterina Sergeeva,[a] Israel Goldberg,[a] and Moshe Kol*[a]
Keywords: Salophan / Tetradentate ligands / N,O ligands / Coordination modes / Octahedral complexes / Titanium /
Zirconium
The coordination chemistry of tetradentate Salophan ligands
with titanium and zirconium alkoxides is described for the
first time. Three new Salophan ligand precursors featuring
different phenolate substituents (ortho-Me, ortho,para-di-Cl,
ortho,para-di-tBu) were synthesized in addition to the known
NMR analysis indicated that these Salophans acted as dian-
ionic ligands, giving rise to hexa-coordinate complexes of C2-
symmetry. X-ray analysis of three complexes supported this
view, and revealed that the ligands wrapping mode was fac-
fac and that the orientation of the labile groups was cis. A
prototypical Salophan precursor, by a sequence of condensa- partial hydrolysis of one of the titanium complexes led to a
tion and reduction. All ligand precursors were reacted with
the metal alkoxides Ti(OiPr)4 and Zr(OtBu)4. The unsubsti-
tuted Salophan led to a complex product mixture for both
titanium and zirconium. The methyl-substituted ligand led to
a clean complex only with zirconium, and the other ligands
gave well-defined coordination chemistry with both metals.
dinuclear bridging oxo complex in which the ligand wrap-
ping mode had changed to fac-mer, as revealed from its crys-
tal structure.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
Zn, this ligand acted as a dianionic ligand, forming a di-
meric pentacoordinate complex.[8d] For MoVI, Lig1H2 may
bind as a tetradentate dianionic ligand, wrapping around
the metal in a fac-fac fashion forming octahedral complex,
or as a tridentate tri-anionic ligand (one of the phenolates
unbound and protonated), forming a mer-bis(homoleptic)
complex.[9] As part of our continuing interest in various
[ONNO]-type ligands, we report herein on the preparation
of new Salophan-type ligands, and describe our initial re-
sults concerning their chemistry with Group IV metals.
Introduction
Tetradentate diamino-diphenolate [ONNO]-type ligands
exhibit a versatile chemistry with many transition and
main-group elements.[1–4] Salan-type ligands bind to early
transition metals almost exclusively in a fac-fac geometry,
forming octahedral C2-symmetrical complexes with the two
labile groups in a cis geometry. This disposition is suitable
for olefin polymerization catalysis.[2,5] In contrast, Salen-
type ligands exhibit mostly a mer-mer geometrical prefer-
ence, leading to trans disposition of the labile groups.[6] It
would thus seem that the hybridization at the nitrogen
atom, i.e. sp2 or sp3, plays a major role on the [ONNO]
ligand wrapping mode.[7] In this regard, the coordination
mode of Salan-type ligands, featuring an aromatic spacer
between the two nitrogen donors (also known as Salophan
ligands), is intriguing when compared with the common Sa-
lan ligands possessing an aliphatic spacer.
Results and Discussion
Two readily available complexes, Ti(OiPr)4 and Zr(OtBu)4,
were used as metal precursors for alcoholysis reactions with
the ligand precursors. All reactions were performed by add-
ing an ethereal solution of the corresponding ligand to a
stirred solution of the metal precursor at –30 °C, followed
by warming to room temp. and stirring for an additional
hour. At first, we explored the reactivity of the prototypical
ligand, Lig1H2. The reaction between Lig1H2 and Ti(OiPr)4
led to the formation of a red material whose NMR spectra
indicated a complex mixture featuring at least six different
methyl groups. Under the same conditions, the reaction of
Lig1H2 and Zr(OtBu)4 also led to a complex mixture. We
therefore turned to substituted ligands.
Lig1H2, the prototypical Salophan ligand that features
no substituents on the phenolate rings, was studied by se-
veral research groups,[8,9] and its coordination behavior was
reported to be versatile. Atwood and co-workers have
shown that, upon binding to group III alkyls (Al, Ga), this
ligand normally acts as a tetra-anionic ligand, forming
complexes of varying nuclearity.[8a–8c] In most cases, the li-
gand was found to bind to the “central” Al in a “flat” fash-
ion, forming the basis of a square-pyramidal complex. For
For this purpose, we prepared three additional Salophan-
type ligands, having varying steric and electronic influence.
In comparison to Lig1H2, Lig2H2 features electron-donat-
ing methyl groups at the ortho positions of the phenolate
[a] School of Chemistry, Raymond and Beverly Sackler Faculty of
Exact Sciences, Tel Aviv University,
Tel Aviv 69978, Israel
E-mail: moshekol@post.tau.ac.il
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200500243
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Salophan Complexes of Group IV Metals
FULL PAPER
rings, Lig3H2 features electron-withdrawing chloro groups Thus, relative to Lig2H2, both the electron withdrawing li-
at the ortho, para positions, and Lig4H2 bears bulky elec- gand Lig3H2 and the bulky ligand Lig4H2 lead to well de-
tron-donating tBu groups at the ortho, para positions. The fined products. The stable Salophan complexes obtained in
ligands were prepared by a two-step route involving con- this work are outlined in Figure 1.
1
densation between the corresponding 2-hydroxybenzalde-
The H and 13C NMR spectra support a C2-symmetry
hyde and 1,2-phenylenediamine, followed by reduction with of all these complexes as judged by the presence of two
sodium borohydride (Scheme 1). For Lig1H2 – Lig3H2, this distinct aromatic doublets for the phenolate hydrogens, an
route is practical, and leads to the desired ligand precursors AB system for the ligand methylene protons, and a single
smoothly in high yields. For Lig4H2, this route is not very type of labile groups. The diastereotopic methyl groups of
1
effective, as the reduction of the Schiff-base intermediate is the isopropoxide ligands give rise to two peaks in both H
very slow, and leads to additional products. Fortunately, the and 13C NMR spectra of the titanium complexes. Accord-
1
solubility of Lig4H2 in methanol is low, so it may be puri- ing to the presence of NH signals in the H NMR spectra
fied by methanol washings of the crude product, or by col- and the number of labile groups, these ligands bind to the
umn chromatography.
metal centers in a dianionic fashion. Interestingly, the li-
gand methylene protons present an additional splitting,
seemingly from the NH proton, and this splitting is dif-
ferent for the diastereotopic CH2 protons. In the sterically
congested 4-Ti complex, two types of splitting are clearly
observed (1.2 Hz, 2.7 Hz), while in the more open 3-Ti com-
plex, only one type of splitting (2.1 Hz) could be observed.
For the zirconium species, only one of the AB signals exhib-
its this additional splitting, and it is consistent throughout
the series (3.0–4.0 Hz).
X-ray quality crystals of the complexes 3-Zr, and 4-Ti,
were obtained upon recrystallization from pentane, and
their crystal structures were solved, in addition to the struc-
ture of 2-Ti, obtained upon recrystallization from ether (for
the crystal structures see Figure 2, Figure 3 and Figure 4).
In agreement with the NMR spectroscopic data, the Salo-
phan ligands wrap around the Group IV metals in a fac-fac
mode to afford non-crystallographic C2-symmetrical com-
plexes. As previously observed for the complexes of the Sa-
lan series, the phenolate oxygen atoms are located mutually
trans (160° for 2-Ti, 156° for 3-Zr, 160° for 4-Ti), and the
monodentate ligands are mutually cis (106° in 2-Ti, 108° in
3-Zr, 105° in 4-Ti), and trans to the amine donors (159–
166°). Thus, the exchange of the aliphatic spacer between
Scheme 1. Synthesis of Salophan ligands Lig1H2 – Lig4H2.
The reaction between Lig2H2 bearing methyl substituents
and Ti(OiPr)4 led to an initial off-white solid whose color
1
changed within a few minutes to deep-red. The H NMR
spectrum of this product exhibited broad signals that may
indicate some equilibrating species. Recrystallization of this
product from cold ether yielded bright-yellow crystals (2-
Ti), whose solid-state structure was consistent with all sub-
sequent structures (vide supra). However, dissolving these
bright-yellow crystals in deuteriobenzene led to a deep red
color in seconds, and the spectrum was consistent with the
spectrum of the crude product, containing only broad ab-
sorptions. In contrast, the initially-formed Zr complex of
this ligand, 2-Zr, did not change color either in the solid
phase or in solution for prolonged periods of time, and its
1H NMR spectrum featured sharp absorptions. Interest-
ingly, Lig3H2 that carries chloro groups, reacted cleanly
with both titanium and zirconium to giving the well-defined
3-Ti and 3-Zr, respectively, albeit the smaller size of the Cl
groups. The bulky Lig4H2, carrying tBu groups near the
metal center, also presented a well-behaved reactivity with
both metals, yielding the species 4-Ti and 4-Zr cleanly.
Figure 1. The C2-symmetrical structure of Salophan-Group IV me-
tal complexes.
Figure 2. ORTEP representation (50% probability ellipsoids) of 2-
Ti; hydrogen atoms are omitted for clarity.
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S. Groysman, E. Sergeeva, I. Goldberg, M. Kol
FULL PAPER
two amine donors by an aromatic one preserves the overall difference for Zr {2.05 Å for 3-Zr vs. 2.01 Å for [Salan]-
binding mode in this ligand family. Moreover, the N–M Zr(CH2Ph)2}[2a] probably resulting from the bulkier mono-
dative bonds for the potentially poorer σ-donor (aniline) dentate ligands. Most notably, the metal is coplanar with
are very close to the N–M dative bonds in the complexes the phenylene diamine unit for the sterically open 2-Ti and
featuring ethylene diamine backbone (2.31 Å for 4-Ti vs. 3-Zr, while for the sterically congested 4-Ti, the metal lies
2.29 Å for the analogous complex with the ethylene diamine slightly outside the phenyl plane (see Figure 5).
backbone).[2b] The M–OPh bond lengths are also compar-
We found that the titanium complexes are relatively un-
able to those reported for Salan complexes, with a slight stable to hydrolysis. For example, the sterically congested
complex 4-Ti undergoes a slow decomposition when stored
in a paraffin-sealed NMR tube outside the glovebox. The
resulting main product, 4-Ti-a, which is only slightly solu-
ble in benzene, crystallizes out to give yellow crystals. The
NMR spectrum of this compound is complicated, and
shows a low symmetry of the ligand backbone, being com-
posed of four tBu peaks, two N–H signals, and four dif-
ferent methylene signals (coupled to two carbon atoms). In
addition, the spectrum contains a single isopropoxide
group. The X-ray structure determination disclosed a dinu-
clear structure with a [Ti2O] μ-oxo core (see Figure 6). Each
Ti center is of nearly octahedral geometry, being sur-
rounded by a bridging oxo ligand (Ti1–O 1.848 Å, Ti2–O
1.834 Å), and the isopropoxo ligand, in addition to the
[ONNO] donor set of the Salophan ligand. The Ti–OPh
distances differ significantly, with the Ti–OPh bond length
trans to the oxo ligand being longer (1.928 Å vs. 1.847 Å).
Figure 3. ORTEP representation (30% probability ellipsoids) of 3-
Zr. A second, chemically identicalmolecule, that is present in the
asymmetric unit, crystallization solvent and the hydrogen atoms
are omitted for clarity.
Figure 6. ORTEP representation of 4-Ti-a, 50% probability; hydro-
Figure 4. ORTEP representation (50% probability ellipsoids) of 4-
Ti; hydrogen atoms were omitted for clarity.
gen atoms, and the crystallization solvent are omitted for clarity.
One of the tBu groups is disordered.
Figure 5. ORTEP representations of the cores of 2-Ti, 3-Zr, 4-Ti, 4-Ti-a (from left to right, respectively) along the plane of the phenylene
ring, demonstrating the relative conformations of the phenylene diamine unit and the metal.
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Salophan Complexes of Group IV Metals
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Na/benzophenone. Pentane was washed with HNO3/H2SO4 prior
to distillation from Na/benzophenone/tetraglyme. Ti(OiPr)4 and
Zr(OtBu)4 were purchased from Aldrich Inc and used without puri-
fication. NMR spectroscopic data for the ligand precursors were
recorded with a Bruker AC-200 spectrometer in CDCl3 and refer-
enced to TMS (δ = 0.00) in proton spectra, or to the chemical shift
of CDCl3 in carbon NMR spectroscopy. NMR spectroscopic data
for the metal complexes were recorded with a Bruker AC-200 or
Bruker Avance 400 spectrometers and referenced to protio impuri-
ties in [D6]benzene (δ, 7.15), and to 13C chemical shift of benzene
(δ, 128.70). Elemental analyses were performed by the microanalyt-
ical laboratory of the Hebrew University of Jerusalem. The metal
complexes were analyzed within a few hours of being taken out of
the freezer of the glovebox. The X-ray diffraction measurements
were performed on a Nonius Kappa CCD diffractometer system,
using Mo-Kα (λ = 0.7107 Å radiation). The analyzed crystals were
embedded within a drop of viscous oil and freeze-cooled to ca.
110 K. The structures were solved by a combination of direct meth-
ods and Fourier techniques using the SIR-92 software,[10] and were
refined by full-matrix least-squares with SHELXL-97.[11] The crys-
tal data are summarized in Table 1. The crystals of 3-Zr and 4-
Most significantly, the ligand binds to the metal in a fac-
mer mode for the first time. The Ti–N bond lengths are
relatively different in this disposition: the Ti–N bond in the
mer fragment is longer than in the fac fragment (2.275 and
2.278 Å for the former, and 2.211 and 2.222 Å for the lat-
ter), possibly indicating a stronger binding in the fac dispo-
sition. Finally, the metal is coplanar with the phenylene di-
amine unit in both parts of the molecule (Figure 5), as pre-
viously encountered in 2-Ti and 3-Zr complexes, and in
contrast to its sterically congested precursor, 4-Ti.
In conclusion, we have prepared a variety of new Salo-
phan-type ligands, and their titanium and zirconium com-
plexes. The coordination chemistry of these ligands with
Group IV metals was found to depend on the phenolate
substituents: The substituents-free Lig1 led to complex mix-
tures, while the 2,4-dichloro- or di-tBu-substituted ligands
Lig3 or Lig4 led to a clean chemistry for both metals. The
ligand bearing ortho-methyl groups Lig2 formed a stable zir-
conium complex, and an unstable titanium complex. In all
cases in which stable complexes were formed, they pos- Ti-a contain partly disordered tBu groups, and partly disordered
solvent, thus affecting to some extent the precision of the structure
determination.
sessed C2-symmetry on the NMR timescale, and their wrap-
ping mode, being supported by X-ray structures, was found
to be fac-fac, as previously found in Salan-Group IV com-
plexes. The sterically congested di(isopropoxo) titanium
complex 4-Ti was found to undergo a facile (partial) hydrol-
ysis, forming a μ-oxo product, in which the Salophan ligand
coordinates to the metal in a fac-mer fashion. We are cur-
rently investigating the reactivity of these species, and ex-
ploring the chemistry of the newly prepared Salophan li-
gands with other early transition metals.
Lig1H2: A solution of salicylaldehyde (4.60 g, 38 mmol) and 1,2-
phenylenediamine (2.05 g, 19 mmol) in 60 mL of methanol was
placed in a 100 mL round-bottomed flask equipped with a mag-
netic stir-bar and a reflux condenser. After several minutes, a yel-
low solution had formed, followed by formation of an orange pre-
cipitate (Salophen intermediate). The reaction mixture was allowed
to stand for 30 min at room temp. and sodium borohydride (2.86 g,
5 equiv.) was added in small portions to the stirred heterogeneous
mixture. The orange precipitate gradually disappeared, and a bright
yellow transparent solution formed. The reaction mixture was
poured into 100 mL of water, and allowed to stand for several
hours. The resulting white solid was isolated by vacuum filtration,
washed several times with water, and dried under vacuum at 50 °C
Experimental Section
1
Materials and Instrumentation: All syntheses of metal complexes
were performed under dry nitrogen in a nitrogen-filled glovebox.
Ether was purified by reflux and distillation under dry argon from
for 2 h, yielding 4.99 g of Lig1H2 (82% yield). The H/13C NMR
spectra indicated its sufficient purity, being consistent with those
previously described.[8]
Table 1. Crystallographic experimental details.
2-Ti
3-Zr
4-Ti
4-Ti-a
Empirical formula
Formula mass
a [Å]
b [Å]
c [Å]
α (°)
β (°)
γ (°)
C28H36N2O4Ti
512.49
10.1360(2)
18.9990(5)
14.4670(3)
90.00
108.9220(15)
90.00
monoclinic
P21/n
C30.5H38Cl4N2O4Zr
729.65
C42H64N2O4Ti
708.85
9.8910(2)
15.8450(3)
26.8520(6)
90.00
97.691(1)
90.00
monoclinic
P21/n
C45H63N2O3.50Ti
735.87
14.2740(8)
16.8810(8)
19.2770(10)
89.727(3)
12.093(1)
17.124(1)
19.413(1)
99.682(5)
93.196(4)
103.812(3)
triclinic
102.663(3)
109.904(3)
triclinic
Crystal system
Space group
V [Å3]
¯
¯
P1
P1
2635.41(10)
1.292
0.360
3828.8(4)
1.266
0.598
4
4170.5 (2)
1.464
0.245
4248.9(4)
1.150
0.242
2
Dcalcd. [g cm–1]
μ [cm–1]
Z
4
4
No. of measd. reflns.
No. of reflns. [I Ͼ 2σ(I)]
R1 [I Ͼ 2σ(I)]
wR2 [I Ͼ 2σ(I)]
GOF
6263
4717
0.0473
0.1257
13401
7095
0.0906
0.2425
1.005
9865
5384
0.0737
0.1549
18165
6917
0.0770
0.1551
0.935
1.033
0.992
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S. Groysman, E. Sergeeva, I. Goldberg, M. Kol
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Lig2H2: A solution of 2-methylsalicylaldehyde (0.95 g, 7.1 mmol)
and 1,2 phenylenediamine (0.38 g, 3.5 mmol) in 30 mL of methanol
was placed in a 100 mL round-bottomed flask equipped with a
magnetic stir-bar and a reflux condenser. The resulting bright yel-
low solution was heated to reflux for 2 h. Upon cooling to room
temp. an orange crystalline solid had formed. The solid was col-
lected by vacuum filtration, and identified by 1H NMR as a Sal-
ophen intermediate. The orange intermediate product was sus-
pended in 60 mL of methanol, and ca. 5 equiv. of sodium borohyd-
ride were added. The reaction mixture became entirely homogen-
eous and colorless. The solution was poured into 100 mL of water,
and the resulting white solid was isolated by vacuum filtration, and
dried under vacuum. The yield of Lig2H2 was 0.49 g (40%).
C22H24N2O2 (348.44): calcd. C 75.83, H 6.94, N 8.04; found C
18 H) ppm. 13C NMR (50.29 MHz, CDCl3): δ = 153.3 (C), 142.0
(C), 136.9 (C), 136.4 (C), 124.2 (CH), 124.0 (CH), 122.3 (C), 121.9
(CH), 114.6 (CH), 49.0 (CH2), 35.1 (C), 34.4 (C), 31.8 (CH3), 29.9
(CH3) ppm.
2-Zr: 80 mg (0.17 mmol) of Lig2H2 was treated with 67 mg
(0.17 mmol) of Zr(OtBu)4. The resulting white solid was washed
with a small volume of pentane. The yield was 105 mg (0.15 mmol,
89%). C30H40N2O4Zr (583.87): calcd. C 61.71, H 6.91, N 4.80;
found C 61.72, H 6.85, N 4.85. 1H NMR (200 MHz, C6D6): δ =
7.00 (t, 3JH,H = 4.6 Hz, 2 H), 6.54 (m, 2 H), 6.44 (d, 3JH,H = 4.7 Hz,
2
2 H), 6.30 (m, 2 H), 4.69 (d, JH,H = 11.9 Hz, 2 H), 3.58 (br. s, 2
2
3
H), 3.46 (dd, J1,H–H = 12.2, J2,H–H = 4.0 Hz, 2 H), 2.33 (s, 6 H),
1.51 (s, 18 H) ppm. 13C NMR (50.29 MHz, C6D6): δ = 161.3 (C),
141.3 (C), 131.3 (CH), 128.4 (CH), 127.3 (CH), 126.6 (C), 125.7
1
75.81, H 6.92, N 8.18. H NMR (200 MHz, CDCl3): δ = 8.21 (s, 2
3
3
(CH), 122.1 (C)116.8 (CH), 75.5 (C), 53.5 (CH2), 33.3 (CH3), 16.9
H, O–H), 7.09 (d, JH,H = 7.6 Hz, 2 H), 7.04 (d, JH,H = 7.6 Hz, 2
¸
3
3
(CH3) ppm.
H), 6.94 (s, 4 H), 6.79 (t, JH,H = 7.5 Hz, 2 H), 4.38 (d, JH,H
=
5.4 Hz, 4 H), 3.66 (t, JH,H = 5.2 Hz, 2 H), 2.21 (s, 6 H) ppm. 13C
NMR (50.29 MHz, CDCl3): δ = 154.8 (C), 136.8 (C), 130.8 (CH),
126.9 (CH), 125.4 (C), 122.1 (C), 121.8 (CH), 119.9 (CH), 114.4
(CH), 48.2 (CH2), 15.8 (CH3) ppm.
3
3-Zr: 69 mg (0.15 mmol) of Lig3H2 was treated with 58 mg
(0.15 mmol) of Zr(OtBu)4. The yield was 105 mg (0.15 mmol,
100%). X-ray quality crystals were obtained upon recrystallization
from a minimal volume of pentane at –30 °C. C28H32N2O4Cl4Zr
(693.60): calcd. C 48.49, H 4.65, N 4.04; found C 48.61, H 4.79, N
Lig3H2: 2,4-Dichlorosalicylaldehyde (4.92 g, 26 mmol) was dis-
solved in ca. 30 mL of methanol and added dropwise to a stirred
suspension of 1,2-phenylenediamine (1.41 g, 13 mmol) in 20 mL of
methanol. The reaction color changed immediately, and the deep-
orange Salophen intermediate crystallized out. The reaction mix-
ture was allowed to stand for 20 min. Sodium borohydride (3
equiv., 2.78 g) was added in small portions to the vigorously stirred
heterogeneous mixture. The resulting homogeneous bright yellow
solution was poured into 100 mL of water, and extracted with two
50 mL portions of dichloromethane. The combined (yellow) or-
ganic phase was dried with anhydrous magnesium sulfate, filtered,
and the solvent was removed. The resulting yellow solid was dried
under vacuum at 50 °C for 2 h, yielding 3.22 g of pure Lig3H2 (54%
yield). C20H16Cl4N2O2·H2O (476.18): calcd. C 50.45, H 3.81, N
5.88; found C 50.74, H 3.55, N 5.95. 1H NMR (200 MHz, CDCl3):
4
3.97. 1H NMR (200 MHz, C6D6): δ = 7.07 (d, JH,H = 2.6 Hz, 2
4
H), 6.36 (m, 2 H), 6.29 (d, JH,H = 2.6 Hz, 2 H), 6.02 (m, 2 H),
2
2
4.65 (d, JH,H = 12.8 Hz, 2 H), 3.58 (br. s, 2 H), 3.10 (dd, JH,H
=
12.9, JH,H = 3.5 Hz, 2 H), 1.57 (s, 18 H) ppm. 13C NMR
(50.29 MHz, CDCl3): δ = 156.9 (C), 139.8 (C), 129.7 (CH), 128.9
(CH), 128.2 (CH), 126.2 (CH), 124.9 (C), 123.7 (C), 120.9 (C), 76.8
(C), 52.9 (CH2), 33.0 (CH3) ppm.
3
4-Zr: Lig4H2 (63 mg, 0.12 mmol) was treated with Zr(OtBu)4
(53 mg, 0.13 mmol). The yield was 83 mg (0.11 mmol, 89%).
C44H68N2O4Zr (780.25): calcd. C 67.73, H 8.78, N 3.59; found C
67.67, H 8.91, N 3.71. 1H NMR (200 MHz, C6D6): δ = 7.30 (d,
2
4JH,H = 2.5 Hz, 2 H), 6.46 (m, 4 H), 6.36 (m, 2 H), 4.94 (d, JH,H
2
= 12.3 Hz, 2 H), 3.73 (br. s, 2 H, N–H), 3.46 (dd, JH,H = 12.3,
4
4
δ = 7.28 (d, JH,H = 2.5 Hz, 2 H), 7.14 (d, JH,H = 2.4 Hz, 2 H),
6.90 (m, 2 H), 6.79 (m, 2 H), 4.37 (s, 4 H) ppm. 13C NMR
(50.29 MHz, CDCl3): δ = 150.0 (C), 136.5 (C), 128.4 (CH), 127.7
(CH), 126.6 (C), 125.2 (C), 121.6 (CH), 121.4 (C), 114.4 (CH), 46.4
(CH2) ppm.
4JH,H = 3.2 Hz, 2 H), 1.72 (s, 18 H), 1.55 (s, 18 H), 1.17 (s, 18 H)
ppm. 13C NMR (50.29 MHz, C6D6): δ = 159.0 (C), 141.2 (C), 138.3
(C), 136.3 (C), 127.1 (CH), 126.4 (CH), 126.1 (CH), 123.4 (CH),
122.7 (C), 75.7 (C), 54.3 (CH2), 35.5 (C), 34.1 (C), 33.5 (CH3), 31.9
(CH3), 30.1 (CH3) ppm.
Lig4H2: A homogeneous bright yellow solution of 3.98 g (17 mmol)
of 2,4-di-tert-butylsalicylaldehyde and 0.89 g (8.5 mmol) of 1,2
phenylenediamine in 50 mL of methanol was heated to reflux in a
100 mL round-bottomed flask equipped with a magnetic stir-bar
and a reflux condenser for 2 h, and then left at room temp. over-
night. The orange solid that had formed was collected by vacuum
3-Ti: Lig3H2 (45 mg, 0.10 mmol) was treated with Ti(OiPr)4
(28 mg, 0.10 mmol). The yield was 60 mg (0.10 mmol, 100%).
C26H28N2O4Cl4Ti (622.19): calcd. C 50.19, H 4.54, N 4.50; found
1
C 50.59, H 4.61, N 4.51. H NMR (200 MHz, C6D6): δ = 7.10 (d,
4
4JH,H = 2.6 Hz, 2 H), 6.39 (m, 2 H), 6.34 (d, JH,H = 2.6 Hz, 2 H),
1
3
2
filtration, and identified by H NMR as a Salophen intermediate.
6.13 (m, 2 H), 5.29 (s, JH,H = 6.1 Hz, 2 H), 4.66 (br. d, JH,H
=
2
3
The yield was 1.54 g (33%). The orange intermediate product was
suspended in 60 mL of methanol, and ca. 10 equiv. of sodium
borohydride were added, and the reaction mixture was stirred over-
night. After hydrolysis, the bright-yellow solid was isolated by vac-
uum filtration. According to 1H NMR, the solid contained at least
two different products. The solid was washed several times with
methanol, yielding the insoluble Lig4H2. Alternatively, Lig4H2
could be isolated by flash chromatography, using chloroform as an
eluent; however, in this case the yield was lower. Drying under vac-
uum for 2 h at 100 °C, yielded 0.5 g of Lig4H2 (34% relative to the
corresponding Salophen). C36H52N2O2·0.5H2O (553.82): calcd. C
12.9 Hz, 2 H), 3.78 (br. s, 2 H), 3.13 (dd, J1, H–H = 13.2, J2, H–H
= 1.9 Hz, 2 H), 1.51 (d, JH,H = 6.2 Hz, 6 H), 1.43 (d, JH,H
3
3
=
6.2 Hz, 6 H) ppm. 13C NMR (50.29 MHz, C6D6): δ = 158.4 (C),
141.0 (C), 130.1 (CH), 129.1 (CH), 129.0 (CH), 128.8 (C), 126.2
(CH), 125.9 (C), 123.5 (C), 122.0 (C), 79.9 (CH), 53.7 (CH2), 26.9
(CH3), 26.8 (CH3) ppm.
4-Ti: Lig4H2 (47 mg, 0.09 mmol) was treated with Ti(OiPr)4
(24 mg, 0.09 mmol). The yield was 63 mg (0.09 mmol, 100%).
Recrystallization from pentane (ca. 1 mL) afforded yellow-orange
crystals of X-ray quality. C44H68N2O4Ti (708.84): calcd. C 71.17,
78.07, H 9.65, N 5.06; found C 78.43, H 9.67, N 5.12. 1H NMR H 9.10, N 3.95; found C 71.42, H 9.14, N 3.96. (400 MHz, C6D6):
4
4
4
(200 MHz, CDCl3): δ = 7.98 (s, 2 H), 7.26 (d, JH,H = 2.2 Hz, 2 δ = 7.31 (d, JH,H = 2.5 Hz, 2 H), 6.55 (d, JH,H = 2.4 Hz, 2 H),
4
3
3
2
H), 7.04 (d, JH,H = 2.2 Hz, 2 H), 6.97 (s, 4 H), 4.35 (d, JH,H
=
6.48 (s, 4 H), 5.03 (s, JH,H = 6.1 Hz, 2 H) 4.79 (dd, JH,H = 12.5,
3
5.9 Hz, 4 H), 3.57 (t, JH,H = 5.9 Hz, 2 H), 1.37 (s, 18 H), 1.28 (s,
3JH,H = 1.2 Hz, 2 H), 4.00 (br. s, 2 H), 3.51 (dd, 2JH,H = 12.6, 3JH,H
2484
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2480–2485

Salophan Complexes of Group IV Metals
FULL PAPER
3
= 2.8 Hz, 2 H), 1.74 (s, 18 H), 1.49 (d, JH,H = 6.0 Hz, 6 H), 1.39
Acknowledgments
3
(d, J = 6.1 Hz, 6 H), 1.17 (s, 18 H) ppm. 13C NMR (50.29 MHz,
C6D6): δ = 160.1 (C), 142.1 (C), 138.9 (C), 135.9 (C), 127.1 (CH),
125.6 (CH), 125.4 (CH), 123.1 (CH), 123.1 (C), 77.4 (CH(CH3)2),
54.3 (CH2), 35.4 (C), 34.1 (C), 31.9 (CH(CH3)3), 30.2 (CH(CH3)3),
26.9 (CH(CH3)2), 26.5 (CH(CH3)2) ppm.
4-Ti-a: Lig4H2 (84 mg, 0.15 mmol) was treated with Ti(OiPr)4
(43 mg, 0.15 mmol) . The solvent was removed, and the crude pro-
duct was re-dissolved in deuteriobenzene and kept outside the
glovebox in a paraffin-sealed capped vial. After two days, bright-
yellow crystals had formed. The crystals were separated from the
solution, washed with cold ether and dried in vacuo to give 23 mg
of 4Ti-a (23% yield). 1H NMR (400 MHz, C6D6): δ = 9.66 (s, 1 H,
We thank the Israel Science Foundation for financial support.
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4
3
N–H), 7.37 (d, JH,H = 2.4 Hz, 1 H), 7.34 (d, JH,H = 7.84 Hz, 1
4
3
H), 7.21 (d, JH,H = 2.4 Hz, 1 H), 6.96 (t, JH,H = 7.8 Hz, 1 H),
6.77 (d, JH,H = 2.4 Hz, 2 H), 6.60 (t, JH,H = 7.8 Hz, 1 H), 6.34
(d, JH,H = 7.8 Hz, 1 H), 5.30 (s, JH,H = 5.9 Hz, 1 H, (CH3)2CH),
4.90 (d, JH,H = 12.5 Hz, 1 H), 4.60 (t, JH,H = 13.0 Hz, 1 H), 4.20
4
3
3
3
2
2
3
3
(dd, JH,H = 12.7, JH,H = 2.2 Hz, 1 H), 3.58 (d, JH,H = 13.2 Hz,
1 H, N–H), 3.54 (d, 2JH,H = 13.4 Hz, 1 H), 1.87 (d, 3JH,H = 6.0 Hz,
3 H, (CH3)2CH), 1.42 (m, 12 H), 1.38 (s, 9 H), 1.34 (s, 9 H), 1.20
(s, 9 H) ppm. 13C NMR (100.58 MHz, C6D6): δ = 160.2, 159.6,
144.4, 142.8, 139.98, 138.7, 135.8, 135.5, 128.2, 128.0, 126.6, 125.9,
125.4, 124.8, 124.4, 123.9, 123.3, 123.3, 74.9, 55.9, 55.1, 35.4, 35.3,
34.4, 34.2, 32.1, 31.9, 30.2, 29.9, 27.8, 27.7 ppm.
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CCDC-266239 to -266242 (for complexes 3-Zr, 4-Ti, 4-Ti-a, and
2-Ti, respectively) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
[11] G. M. Sheldrick, SHELXL-97 Program, University of
Göttingen, Germany, 1996.
Received: March 20, 2005
Eur. J. Inorg. Chem. 2005, 2480–2485
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2485