Formation of 1:1 complexes of ferrocene-containing salen ligands with Mg, Ti and Zr

Article abstract of DOI:10.1039/b107066p

Condensation of 1,1′-diaminoferrocene with a range of salicylaldehydes resulted in the formation of the corresponding salen-type ligands in high yields. The ability of these compounds to serve as ligands was demonstrated by the formation of several 1:1 Zr

Full text of DOI:10.1039/b107066p

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Formation of 1 : 1 complexes of ferrocene-containing salen ligands
with Mg, Ti and Zr
Alexandr Shafir,a,b Dorothea Fiedlera,b and John Arnold*a,b
a Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA
b Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley,
CA 94720-1460, USA
Received 3rd August 2001, Accepted 12th November 2001
First published as an Advance Article on the web 28th January 2002
Condensation of 1,1Ј-diaminoferrocene with a range of salicylaldehydes resulted in the formation of the
corresponding salen-type ligands in high yields. The ability of these compounds to serve as ligands was demonstrated
by the formation of several 1 : 1 Zr and Ti complexes, one of which was structurally characterized and was found
to feature a t-BuSalfen2Ϫ ligand in a square-planar conformation. In addition, a related Schiff-base ligand was
synthesized by condensing diaminoferrocene with 2,4-petanedione and a Zr complex of this ligand was isolated.
Introduction
Ferrocene-containing ligands are of widespread interest in
coordination chemistry, where they are used in such diverse
applications as catalysis,1 molecular recognition and sensing.2–5
In most of these applications, polydentate ligands are most
useful due to the range of structural and electronic properties
they engender on the resulting metal complexes. For example,
due to the ease of acylation of ferrocene, Schiff-base ligands
derived from various acyl ferrocenes provide a useful class of
widely used polydentate ligands.6–8
(1)
We envisaged a related class of ligands with the imine
nitrogen atoms attached directly to ferrocene, which we felt
would lead to more electron-rich complexes that might display
interesting structures and reactivity. Our recent improvement of
the synthesis of 1,1Ј-diaminoferrocene,9 which allows it to be
prepared on useful scales in good yields, provides an excellent
precursor to such ligands. Here we report the synthesis of a
series of salen-like ligands incorporating a ferrocene group
in the backbone. The ability of these ligands to form metal
complexes was demonstrated by the synthesis and structural
characterization of Group IV metal complexes.
bis-t-BuSalfen-H2 ligands. As part of our work on ferrocene-
containing Group IV metal complexes,11,12 2 was reacted with
Zr(CH2Ph)4 in toluene. This reaction proceeded cleanly and
afforded the desired (t-BuSalfen)Zr(CH2Ph)2 (4) in 48% yield
(eqn. (2)). The 1H and 13C NMR spectra of this complex
indicate a C2v symmetric structure in solution. The ferrocene
resonances appear as two pseudo-triplets at 4.28 and 3.93 ppm,
and the benzyl CH2 resonance appears as a singlet at 2.52 ppm.
The compound was isolated as a red crystalline solid from
pentane/toluene as a solvate with one equivalent of toluene.
The analogous (bis-t-BuSalfen)Zr(CH2Ph)2 (5) was prepared in a
Results and discussion
Addition of salicylaldehyde to a solution of diaminoferrocene
in EtOH resulted in the immediate darkening of the reaction
mixture and, after five minutes, the appearance of a burgundy-
1
colored precipitate. The H NMR spectrum of the compound
(Salfen-H2, 1) is consistent with a time-averaged C2v symmetry
in solution, including two pseudo-triplets at 4.19 and 3.90 ppm
assigned to the ferrocenyl resonances.10 The low solubility of
this compound prompted us to prepare the more soluble deriv-
atives using 3-tert-butylsalicylaldehyde and 3,5-bis-tert-butyl-
salicylaldehyde (eqn. (1)).
1
similar fashion from bis-t-BuSalfen-H2. Its H NMR spectrum is
very similar to that of 4 and features two ferrocene pseudo-
triplets at 4.33 and 3.96 ppm and a benzyl CH2 resonance at
2.55 ppm. Attempts to reproduce these results with Ti(CH2Ph)4
led to compounds whose 1H NMR spectra show a high degree
of fluxionality and whose identities remain unknown.
As expected, these products (t-BuSalfen-H2, 2 and bis-t-BuSalfen-
H2, 3) were found to be soluble in low polarity solvents (Et2O
and pentane). The NMR spectra of these compounds are
analogous to that of the unsubstituted 1. All three compounds
undergo reversible oxidation in THF at ϩ10, Ϫ44 and Ϫ88 mV
vs. Fc/Fcϩ for 1, 2 and 3 respectively as gauged by cyclic
voltammetry.
Single crystals of (t-BuSalfen)Zr(CH2Ph)2 were grown from
C6D6 and the structure of the compound, determined by X-ray
crystallography, confirmed the C2v symmetry in the solid state
(Fig. 1 and Table 1). The crystals incorporate 1.5 equivalents of
C6D6 per molecule of the complex. Zirconium resides in an
approximate octahedral environment comprised of a square-
Due to the low solubility of the unsubstituted Salfen-H2 we
limited our further studies to the more soluble t-BuSalfen-H2 and
DOI: 10.1039/b107066p
J. Chem. Soc., Dalton Trans., 2002, 555–560
This journal is © The Royal Society of Chemistry 2002
555

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synclinal conformation of 1,1Ј-diaminoferrocene.9 The nitrogen
atoms adopt a trigonal planar geometry with an average N–Zr
distance of 2.36 Å and an N1–Zr–N2 bite angle of 103.3Њ.
Salt metathesis with metal chlorides provided an alternate
route to Group IV metal complexes. To form the necessary
reagents, the ligands were deprotonated by Bu2Mg in THF
affording orange solids formulated as (t-BuSalfen)Mg(THF)2.5
1
(6) and (bis-t-BuSalfen)Mg(THF)3 (7) (eqn. (3)). The H NMR
(2)
(3)
planar t-BuSalfen2Ϫ ligand and two benzyl groups located in the
axial positions. The benzylic carbons are directed away from the
bulky t-Bu groups and towards ferrocene, with the C33–Zr–C40
angle of 142.8Њ. The phenyl groups, on the other hand, are
pointed away from ferrocene. Ferrocene adopts an almost
perfectly eclipsed conformation allowing for the two ligand
arms to be in the same plane. The molecule, however, is some-
what strained as conveyed by the 3.90Њ tilt of the Cp rings. This
tilt, coupled with the slight bending of the nitrogen atoms out-
wards from the plane of the Cp rings, allows for the N1 ؒ ؒ ؒ N2
distance of 3.70 Å which is 0.35 Å longer than in the eclipsed
spectra of these salts are consistent with a C2v symmetric struc-
ture in solution. In both cases the two ferrocene resonances are
almost coincidental and appear as one singlet in a spectrum
recorded on a 300 MHz spectrometer. Using a higher field
instrument (500 MHz) the two signals are resolved into two
pseudo-triplets separated by 0.01 ppm.
The solid-state structure of 7 was determined by X-ray
crystallography (Fig. 2 and Table 2). The Mg ion resides
Fig. 1 An ORTEP plot of (t-Bu-Salfen)Zr(CH2Ph)2 drawn with 50%
probability ellipsoids. All hydrogen atoms and the co-crystallized
molecules of benzene are omitted for clarity.
Table 1 Selected bond lengths (Å) and angles (Њ) for 4
Zr1–O1
Zr1–O2
Zr1–N1
Zr1–N2
2.013(3)
2.013(3)
2.356(4)
2.361(4)
Zr1–C33
Zr1–C40
N1–C1
2.312(5)
2.319(4)
1.440(5)
1.453(5)
Fig. 2 An ORTEP plot of (bis-t-BuSalfen)Mg(THF)2 molecule drawn
with 50% probability ellipsoids. t-Bu groups and
a THF of
N2–C6
crystallization are omitted. All hydrogen atoms are also omitted for the
sake of clarity.
O1–Zr1–O2
O1–Zr1–N1
O1–Zr1–N2
N1–Zr1–N2
100.5(1)
78.1(1)
177.6(1)
103.3(1)
N1–Zr1–O2
176.5(1)
142.8(2)
105.6(3)
107.4(3)
C33–Zr1–C40
Zr1–C33–C34
Zr1–C40–C41
in an approximate octahedral environment composed of
the bis-t-BuSalfen2Ϫ ligand and two THF molecules. Despite the
fact that the overall geometry in 7 is reminiscent of that for 4,
556
J. Chem. Soc., Dalton Trans., 2002, 555–560

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Table 2 Selected bond lengths (Å) and angles (Њ) for 7
Mg1–O1
Mg1–O2
Mg1–N1
Mg1–N2
1.974(5)
1.984(5)
2.238(6)
2.236(7)
Mg1–O3
Mg1–O4
N1–C1
2.161(5)
2.141(4)
1.433(9)
1.442(9)
N2–C6
O1–Mg1–O2
O1–Mg1–N1
O1–Mg1–N2
93.0(2)
83.8(2)
169.1(2)
N1–Mg1–O2
O3–Mg1–O4
N1–Mg1–N2
170.9(2)
169.3(2)
101.3
significant differences exist. Whereas in 4 the two ligand arms
form a nearly perfect plane containing the Zr atom, in 7 the two
ligand planes are at a 17Њ angle to each other. In addition, the
Cp rings of the ferrocene group are in a staggered gauche con-
formation, i.e. rotated by approximately 36Њ from the fully
eclipsed conformation. In addition to two coordinated THF
molecules, the unit cell contains one THF of crystallization.
The ability of these magnesium complexes to undergo salt
metathesis was assessed by combining 7 with TiCl4(THF)2
and ZrCl4. In both cases the desired LMCl2 (M
=
Ti, 8; M = Zr, 9) were obtained in high yields (eqn. (4)) and,
Scheme 1
that, unlike the intensely colored Salfen ligands, 10 is light-
yellow. We attribute this difference in part to the presence in
Acfen-H2 of methyl groups attached to the imine carbon atoms.
The steric bulk of these groups prevents the ligand arms
from being coplanar with the Cp rings thus disrupting the
π-conjugation. The geometry of Acfen-H2 was determined in
the solid state by X-ray crystallography (Fig. 3), and the ligand
(4)
Fig. 3 An ORTEP plot of Acfen-H2 drawn with 50% probability
ellipsoids. All hydrogen atoms, except NH, are omitted for clarity.
arms were in fact found to be almost orthogonal to the plane of
the Cp rings. The molecule adapts a staggered (antiperiplanar)
conformation with the imine substituent in a trans orientation.
Each ligand arm is held in a cisoid orientation through an
intramolecular N–H ؒ ؒ ؒ O hydrogen bond. We expected 10 to
bind metals in a manner similar to the Salfen ligands. Indeed,
reaction of Acfen-H2 with Zr(CH2Ph)4 resulted in the form-
ation of (Acfen)Zr(CH2Ph)2 (11) whose 1H NMR spectrum
includes two ferrocene pseudo-triplets (4.00 and 3.70 ppm),
a benzylic CH2 singlet (2.27 ppm) and a vinylic singlet (5.23
according to their NMR spectra, have structures similar to
(
t-BuSalfen)Zr(CH2Ph)2. The compounds are sparingly soluble
in non-polar solvents and are quite soluble in chlorinated
solvents.
In all cases, the dark-burgundy color of the Schiff-base
ligands changed to yellow or red upon coordination to a metal
center. We attribute these changes to the relative orientation of
ppm) attributed to the N᎐C–CH᎐C proton. The compound was
᎐
᎐
the N᎐C–Ph group with respect to the Cp π-system. In the free
᎐
isolated from toluene as a yellow crystalline solid incorporating
1 equivalent of toluene.
Work in progress is aimed at uncovering the reactivity of
these molecules. Details will be the focus of a separate
publication.
ligands these groups are most likely coplanar which results
in an extended delocalized π-system. Complexation to a metal
leads to the rotation of the N᎐C–Ph bond and to the disruption
᎐
the π-conjugation.
Encouraged by the ease of Schiff-base condensations with
diaminoferrocene, we attempted to extend this chemistry to the
generation of macrocyclic compounds. ortho-Phenylenediamine
is known to undergo a condensation with 2,4-pentanedione
(“acac”) in the presence of a Ni template to generate the
Goedken tetrazaannulene macrocycle, which has found wide-
spread use in transition metal chemistry.13 However, reaction of
diaminoferrocene with 2,4-pentanedione under analogous
conditions resulted in the formation of another salen-like
ligand Acfen-H2 (10) (Scheme 1), and the same product is
obtained without the use of the Ni template. It is noteworthy
Experimental
General considerations
Standard Schlenk-line and glove box techniques were used
unless otherwise indicated. EtOH was deoxygenated by purging
with N2 gas. THF was passed through a column of activated 4Å
molecular sieves and degassed with argon prior to use. All other
solvents used in the preparation of metal complexes were
purified by passage through a column of activated alumina and
J. Chem. Soc., Dalton Trans., 2002, 555–560
557

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degassed with argon prior to use. Fc(NH2)2,9 Zr(CH2Ph)4 14 and
TiCl4(THF)2 were prepared according to the literature
procedures. Salicylaldehyde, 3-tert-butylsalicylaldehyde, 3,5-
bis-tert-butylsalicylaldehyde, 2,4-pentanedione and Bu2Mg
were purchased from Aldrich and used as received. TiCl4 and
ZrCl4 were purchased from Strem Chemicals. C6D6 was vacuum
transferred from sodium/benzophenone and CDCl3 was
vacuum transferred from CaH2. 1H and 13C{1H} NMR spectra
were recorded at room temperature on a Bruker AM-300 or
DRX-500 spectrometer. 1H NMR chemical shifts are given
relative to C6D5H (7.16 ppm) and CHCl3 (7.26 ppm). 13C{1H}
NMR spectra are relative to C6D6 (128.0 ppm) and CDCl3 (77.2
ppm). Electrochemical measurements were performed using
a BAS-100b electrochemical analyzer with a BAS C3 cell stand
mounted inside an inert atmosphere glove box. The solutions
studied were prepared in THF, contained 0.1 mol LϪ1
[Bu4N][PF6] and were approximately 1 mM in analyte. Elem-
ental analyses were determined at the Microanalytical Labor-
atory of the College of Chemistry, University of California,
Berkeley. Single crystal X-ray structure determinations were
performed at CHEXRAY, University of California, Berkeley.
(
t-BuSalfen)Zr(CH2Ph)2 (4). To a cooled solution (Ϫ60 ЊC)
of t-BuSalfen-H2 (0.600 g, 1.11 mmol) in 80 mL of toluene
was added a solution of Zr(CH2Ph)4 in 80 mL of toluene. The
resulting dark-red solution was allowed to warm to room tem-
perature and stirred for 12 h. The volume of the mixture was
reduced to 20 mL and 10 mL of pentane was added. The
mixture was cooled to Ϫ40 ЊC resulting in the formation of
a red crystalline solid found to incorporate 1 equivalent of
1
toluene Yield: 480 mg, 48%. H NMR (C6D6), δ 8.03 (s, 2H,
N᎐CH), 7.40 (dd, 2H, Ar), 7.13 (m, 2H, Ar), 7.06–7.00 (m, 3H,
᎐
Ar), 6.87 (dd, 2H, Ar), 6.82 (m, 4H, Ar), 6.75–6.72 (m, 6H, Ar),
6.53 (m, 2H, Ar), 4.28 (t, 4H, CpH), 3.93 (t, 4H, CpH), 2.52 (s,
4H, benzylic CH2), 2.11 (s, 3H, toluene CH3), 1.54 (s, 18H, t-Bu
CH3) ppm. 13C NMR (C6D6), δ 174.0, 161.9, 174.5, 139.8,
134.0, 132.7, 130.1, 126.3, 125.7, 125.3, 122.1, 119.1 (all aromat-
ics and N᎐CH), 109.7 (Cp C–N), 67.6 (Cp), 67.2 (Cp), 61.2
᎐
(CH2Ph), 35.70 (C(CH3)3), 30.87 (C(CH3)3), 21.4 (toluene).
Anal. Calcd. for C46H48N2O2FeZrؒC7H8: C, 70.72; H, 6.27; N,
3.11. Found: C, 70.40; H, 6.59; N, 3.37%.
(
bis-t-BuSalfen)Zr(CH2Ph)2 (5). To a cooled solution (Ϫ60 ЊC)
of bis-t-BuSalfen-H2 (1.28 g, 1.97 mmol) in 50 mL of toluene was
added a solution of Zr(CH2Ph)4 (898 mg, 1.97 mmol) in 50 mL
of toluene. The dark-red reaction mixture was allowed to warm
to room temperature and stirred for 12 h. The volume was
reduced and the solution was cooled to Ϫ40 ЊC overnight. A
red, microcrystalline solid precipitate was isolated by filtration
and was found to incorporate 1 equivalent of toluene. The solid
was dried in vacuo affording 1.12 g of product (56%). 1H NMR
Syntheses
Salfen-H2 (1).10 A solution of Fc(NH2)2 (1.0 g, 4.6 mmol) in
60 mL of deoxygenated absolute EtOH was treated with salicyl-
aldehyde (0.98 mL, 9.2 mmol). The solution turned dark-red
immediately and after five min a dark-burgundy precipitate
formed. After 30 min of stirring the volatile fraction was
removed under reduced pressure and the solid was recrystal-
lized from a CH2Cl2–Et2O mixture at Ϫ30 ЊC. Dark-red crystals
(C D ), δ 8.10 (s, 2H, N᎐CH), 7.65 (d, 2H, ArH), 6.97 (d, 2H,
᎐
6
6
ArH), 6.79–6.76 (m, 8H, ArH), 6.48–6.43 (m, 2H, ArH), 4.33 (t,
4H, CpH), 3.96 (t, 4H, CpH), 2.55 (s, 4H, CH2Ph), 2.11 (s, 3H,
toluene CH3), 1.62 (s, 18H, t-Bu CH3), 1.31 (s, 18H, t-Bu CH3)
ppm. 13C NMR (C6D6), δ 174.2, 160.0, 147.6, 141.0, 139.0,
130.1, 129.9, 129.3, 128.3, 126.3, 125.6, 124.8 (all aromatics
1
were isolated by filtration (1.8 g, 93% yield). H NMR (C6D6),
δ 13.32 (s, 2H, OH), 8.10 (s, 2H, N᎐CH), 7.04–6.93 (m, 4H,
᎐
ArH), 6.83 (dd, 2H, ArH), 6.59 (td, 2H, ArH), 4.19 (t, 4H,
CpH), 3.90 (t, 4H, CpH) ppm. 13C NMR (C6D6), δ 161.0
(COH), 160.5 (N᎐CH), 131.8 (Ar), 131.1 (Ar), 119.6 (Ar), 118.5
᎐
and N᎐CH), 109.7 (Cp C–N), 67.1 (Cp), 66.8 (Cp), 60.7
᎐
(Ar), 117.0 (Ar), 102.56 (Cp C–N), 68.7 (Cp), 64.0 (Cp) ppm.
Mp: 197–199 ЊC. Anal. Calcd. for C24H20N2O2Fe: C, 67.94; H,
4.75; N, 6.60. Found: C, 68.09; H, 4.91; N, 6.83%.
(CH2Ph), 35.9 (C(CH3)3), 34.2 (C(CH3)3), 31.6 (C(CH3)3), 30.9
(C(CH3)3), 21.4 (toluene). Anal. Calcd. for C54H64FeN2O2Zrؒ
C7H8: C, 72.37; H, 7.17; N, 2.77. Found: C, 72.61; H, 7.48; N,
2.88%.
t-BuSalfen-H2 (2). A solution of Fc(NH2)2 (1.60 g, 7.40 mmol)
in 40 mL of deoxygenated EtOH was treated with 3-tert-
butylsalicylaldehyde (2.53 mL, 14.81 mmol). The dark-red
reaction mixture was allowed to stir for 14 h resulting in the
formation of a red-burgundy precipitate. The precipitate was
collected on a fritted glass filter, washed with 2 × 5 mL of cold
EtOH and dried under reduced pressure. Yield: 3.69 g, 92%. 1H
(
t-BuSalfen)Mg(THF)2.5 (6). To a cooled solution (Ϫ60 ЊC) of
t-BuSalfen-H2 (2.50 g, 4.65 mmol) in 40 mL of THF was
added a heptane solution of Bu2Mg (1.00 M, 4.8 mL, 4.8
mmol). The reaction mixture was allowed to warm to room
temperature and stirred for 12 h. The volume of the solution
was reduced to 15 mL and 50 mL of pentane was added causing
an orange solid to precipitate. The flask was cooled overnight
to Ϫ40 ЊC resulting in the formation of an orange crystalline
NMR (C D ), δ 14.23 (s, 2H, OH), 8.19 (s, 2H, N᎐CH), 7.31 (d,
᎐
6
6
2H, ArH), 6.81 (d, 2H, ArH), 6.68 (t, 2H, ArH), 4.17 (t, 4H,
CpH), 3.90 (t, 4H, CpH), 1.63 (s, 18H, CH3) ppm. 13C NMR
solid which was collected and dried in vacuo. Yield: 2.294 g,
66%. H NMR (C D ), δ 8.24 (s, 2H, N᎐CH), 7.54 (dd, 2H,
1
(C D ), δ 162.3 (COH), 161.0 (N᎐CH), 137.9 (Ar), 130.5 (Ar),
᎐
6
6
᎐
6
6
130.2 (Ar), 120.3 (Ar), 119.0 (Ar), 103.4 (Cp C–N), 69.6 (Cp),
65.0 (Cp), 35.5 (C(CH3)3), 30.1 (C(CH3)3) ppm. Anal. Calcd.
for C32H36N2O2Fe: C, 71.64; H, 6.76; N, 5.22. Found: C, 71.66;
H, 6.70; N, 5.22%.
ArH), 7.04 (dd, 2H, ArH), 6.65 (t, 4H, ArH), 3.98 (m, 4H,
CpH), 3.97 (m, 4H, CpH), 3.52 (m, 10H, THF), 1.84 (s, 18H,
CH3), 1.28 (m, 10H, THF). 13C NMR (C6D6), δ 171.9, 170.2,
142.1, 134.3, 131.7, 121.4, 112.9 (all aromatics and imine
N᎐CH), 110.1 (Cp C–N), 69.0 (CpH), 68.2 (CpH), 64.8 (THF),
᎐
bis-t-BuSalfen-H2 (3). Fc(NH2)2 (1.38 g, 6.40 mmol) and 3,5-bis-
tert-butylsalicylaldehyde (3.00 g, 12.8 mmol) were combined in
a flask and dissolved in 80 mL of deoxygenated EtOH. The
burgundy-red reaction mixture was allowed to stir for 14 h. The
resulting microcrystalline solid (3.71 g, 89% yield) was isolated
by filtration and washed with 2 × 20 mL of cold Et2O. 1H NMR
35.9 (C(CH3)3), 30.2 (C(CH3)3), 25.4 (THF) ppm. Anal. Calcd.
for C32H34FeMgN2O2ؒ2.5(C4H8O): C, 68.24; H, 7.36; N, 3.79.
Found: C, 68.22; H, 7.40; N, 3.94%.
(
bis-t-BuSalfen)Mg(THF)3 (7). To a cooled solution (Ϫ60 ЊC) of
bis-t-BuSalfen-H2 (4.35 g, 6.71 mmol) in 100 mL of THF was
added a heptane solution of Bu2Mg (1.00 M, 7.38 mL, 7.38
mmol). The reaction mixture was allowed to warm to room
temperature and stirred for 12 h. The volume of the solution
was reduced to 30 mL and pentane was added causing an
orange solid to precipitate. The flask was cooled overnight to
Ϫ40 ЊC. The precipitate was isolated as an orange microcrystal-
line solid (4.58 g, 77% yield) and dried in vacuo. The product
was found to incorporate 3 equivalents of THF. 1H NMR
(C D ), δ 14.17 (s, 2H, OH), 8.36 (s, 2H, N᎐CH), 7.61 (d, 2H,
᎐
6
6
ArH), 7.07 (d, 2H, ArH), 4.24 (t, 4H, CpH), 3.94 (t, 4H, CpH),
1.68 (s, 18H, CH3), 1.34 (s, 18H, CH3) ppm. 13C NMR (C6D6),
δ 161.9, 158.4, 140.2 (Ar), 137.0 (Ar), 127.0 (Ar), 126.0 (Ar),
119.0 (Ar), 103.4 (Cp C–N), 69.2 (Cp), 63.9 (Cp), 35.0
(C(CH3)3), 33.9 (C(CH3)3), 31.4 (C(CH3)3), 29.4 (C(CH3)3)
ppm. Anal. Calcd. for C40H53N2O2Fe: C, 74.06; H, 8.08; N,
4.32. Found: C, 74.02; H, 8.44; N, 4.17%.
558
J. Chem. Soc., Dalton Trans., 2002, 555–560

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Table 3 Crystallographic data and refinement details for 4, 7 and 10
Compound
4ؒ1.5(C6H6)
7
10
Empirical formula
Mw
C55H57N2FeO2Zr
935.13
C52H74N2O5FeMg
887.32
C20H24N2FeO2
380.27
Crystal system
Space group
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
a/Å
b/Å
c/Å
α/Њ
14.2776(1)
18.4431(3)
17.6247(3)
90
10.2080(5)
24.114(1)
20.3211(9)
90
9.5758(6)
22.837(1)
9.6336(6)
90
β/Њ
95.439(1)
90
4620.1(1)
4
104.503(1)
90
4842.8(3)
4
119.290(1)
90
1837.4(2)
4
γ/Њ
V/Å3
Z
T /K
152.2
0.582
137.1
0.371
162.3
0.835
µ/mmϪ1
Refl. total
Refl. independent
Rint
Residuals: R; Rw; Rall
GOF
20932
8080
0.025
0.038; 0.050; 0.057
2.10
18965
7088
0.106
0.042; 0.043; 0.108
0.98
8945
3378
0.054
0.032, 0.034, 0.085
0.99
(C D ), δ 8.31 (s, 2H, N᎐CH), 7.78 (d, 2H, ArH), 7.12 (d, 2H,
for 18 h. The volatile fraction was removed under reduced
pressure and the resulting yellow oil was recrystallized from
Et2O at Ϫ30 ЊC affording a yellow crystalline product (1.65 g,
᎐
6
6
ArH), 4.02 (m, 4H, CpH), 4.01 (m, 4H, CpH), 3.54 (m, 12H,
THF), 1.91 (s, 18H, CH3), 1.42 (s, 18H, CH3), 1.28 (m, 12H,
THF) ppm. 13C NMR (C6D6), δ 170.6, 170.3, 141.5, 134.0,
1
63% yield). H NMR (C6D6), δ 12.54 (s, br, 2H, OH), 4.94 (s,
129.7, 129.5, 120.0 (all aromatics and imine N᎐CH), 110.4 (Cp
2H, C᎐CH), 4.02 (t, 4H, CpH), 3.84 (t, 4H, CpH), 2.02 (s, 6H,
᎐
᎐
C–N), 68.9 (Cp), 68.1 (Cp), 64.8 (THF), 36.2 (C(CH3)3), 34.0
(C(CH3)3), 31.8 (C(CH3)3), 30.3 (t-Bu C(CH3)3), 25.5 (THF)
ppm. Anal. Calcd. for C40H50FeMgN2O2ؒ3(C4H8O) : C, 70.39;
H, 8.41; N, 3.16. Found: C, 70.11; H, 8.61; N, 3.24%.
CH3), 1.59 (s, 6H, CH3) ppm. 13C NMR (C6D6), δ 195.0, 160.5,
97.1, 95.7, 67.4 (Cp), 66.2 (Cp), 28.7 (CH3), 18.8 (CH3) ppm.
Anal. Calcd. for C20H24N2O2Fe: C, 63.17; H, 6.36; N, 7.37.
Found: C, 63.50; H, 6.37; N, 7.47%.
(
bis-t-BuSalfen)TiCl2 (8). To a cooled solution (Ϫ60 ЊC) of
(Acfen)Zr(CH2Ph)2 (11). To a cooled solution (Ϫ60 ЊC) of
Acfen-H2 (0.500 mg, 1.32 mmol) in 40 mL of toluene was added
a solution of Zr(CH2Ph)4 in 40 mL of toluene. The yellow
mixture was allowed to stir for 12 h, then the solution was
filtered, concentrated to 20 mL and cooled to Ϫ40 ЊC overnight
affording 505 mg of a yellow crystalline material which was
found by NMR to contain 1 equivalent of toluene. Yield: 51%.
1H NMR (C6D6), δ 7.22–7.11 (m, 6H, Ar), 7.07–7.00 (m, 3H,
TiCl4(THF)2 (164 mg, 0.470 mmol) in 25 mL of THF was
added a solution of (bis-t-BuSalfen)Mg(THF)3 (417 mg, 0.470
mmol) in 25 ml of THF. The red solution was stirred for 2 h at
Ϫ60 ЊC, then at room temperature for 1 h. All volatile materials
were removed under reduced pressure and the resulting dark
red solid was extracted with toluene and filtered. Toluene was
removed in vacuo and the residue was washed with 10 mL of
Et2O. The product was isolated as a dark red solid (299 mg,
83%). H NMR (C D ), δ 8.46 (s, 2H, N᎐CH), 7.65 (d, 2H,
ArH), 7.33 (d, 2H, ArH), 4.94 (t, 4H, CpH), 4.26 (t, 4H, CpH),
1.61 (s, 18H, CH3), 1.33 (s, 18H, CH3). 13C NMR (C6D6),
δ 169.4, 161.7, 145.3, 136.8, 130.8, 129.9, 127.1 (all aromatics
Ar), 6.90–6.79 (m, 6H, Ar), 5.23 (s, 2H, C᎐CH), 4.00 (t, 4H,
᎐
1
᎐
6
6
Cp), 3.70 (t, 4H, Cp), 2.27 (s, 4H, CH2Ph), 2.11 (s, 3H, toluene
CH3), 1.73 (s, 6H, CH3), 1.58 (s, 6H, CH3). Anal. Calcd. for
C34H36FeZrN2O2ؒC7H8: C, 66.20; H, 5.96; N, 3.77. Found: C,
66.42; H, 6.28; N, 3.84%.
and imine N᎐CH), 110.8 (Cp C–N), 69.3 (Cp), 66.7 (Cp), 35.8
᎐
(C(CH3)3), 34.5 (C(CH3)3), 31.3 (C(CH3)3), 30.6 (C(CH3)3).
Anal. Calcd. for C40H50ClFeN2O2Ti: C, 62.76; H, 6.58; N, 3.66.
Found: C, 62.60; H, 6.80; N, 3.55%.
X-Ray crystallography
Crystals of 4 suitable for X-ray diffraction were grown from
C6D6 at room temperature. Crystals of 7 were grown by a slow
diffusion of pentane into a solution of 7 in THF. Crystals of 10
were grown from Et2O at Ϫ30 ЊC. A crystal of appropriate size
was mounted on a glass capillary using Paratone-N hydro-
carbon oil. The crystal was transferred to a Siemens SMART
diffractometer/CCD area detector,15 centered in the beam, and
cooled by a nitrogen flow low-temperature apparatus that had
been previously calibrated by a thermocouple placed at the
same position as the crystal. Preliminary orientation matrices
and cell constants were determined by collection of 60 10-s
frames, followed by spot integration and least-squares refine-
ment. An arbitrary hemisphere of data was collected, and the
raw data were integrated using SAINT.16 Cell dimensions
reported were calculated from all reflections with I > 10σ. Data
analysis and absorption corrections were performed using
Siemens XPREP17 and SADABS,18 respectively. The data
were corrected for Lorentz and polarization effects, but no
correction for crystal decay was applied. The structures were
solved and refined with the teXsan software package,19 and
the experimental details are given in Table 3. A unit cell of
(
bis-t-BuSalfen)ZrCl2 (9). To a cooled solution (Ϫ60 ЊC) of
ZrCl4 (194 mg, 0.833 mmol) in 30 mL of THF was added a
solution of (bis-t-BuSalfen)Mg(THF)3 (739 mg, 0.833 mmol) in 40
mL of THF. The red solution was allowed to warm to room
temperature and was stirred for 12 h. All volatile materials were
removed under reduced pressure; the red residue was extracted
with toluene and filtered. Toluene was evaporated in vacuo and
the crude product was washed with 5 mL of Et2O. The product
was isolated as a light-red microcrystalline solid (499 mg, 74%).
1H NMR (C D ), δ 8.24 (s, 2H, N᎐CH), 7.63 (d, 2H, ArH), 7.22
᎐
6
6
(d, 2H, ArH), 4.74 (t, 4H, CpH), 4.32 (t, 4H, CpH), 1.58 (s,
18H, CH3), 1.30 (s, 18H, CH3). 13C NMR (C6D6), δ 173.9,
169.1, 159.0, 142.9, 138.5, 131.8, 130.3, 124.7 (Ar, N᎐CH),
᎐
107.3 (Cp C–N), 68.4 (Cp), 66.1 (Cp), 35.7 (C(CH3)3), 34.3
(C(CH3)3), 31.3 (C(CH3)3), 30.1 (C(CH3)3). Anal. Calcd. for
C40H50ClFeN2O2Zr: C, 59.40; H, 6.23; N, 3.46. Found: C, 59.21;
H, 6.19; N, 3.28%.
Acfen-H2 (10). A solution of Fc(NH2)2 (1.50 g, 6.94 mmol)
in 60 mL of deoxygenated EtOH was treated with 2,4-pentane-
dione (1.5 mL, 14.6 mmol). The solution was brought to reflux
(
t-BuSalfen)Zr(CH2Ph)2 contains one molecule of C6D6 residing
on a general position and one residing on a crystallographic
J. Chem. Soc., Dalton Trans., 2002, 555–560
559

View Article Online
7 M. Ertas, V. Ahsen, A. Gurek and O. Bekaroglu, J. Organomet.
Chem., 1987, 336, 183.
8 Z. Hong-Yun, C. Dong-Li, C. Pei-Kun, C. De-Ji, C. Guang-Xia and
Z. Hong-Quan, Polyhedron, 1992, 11, 2313.
9 A. Shafir, M. P. Power, G. D. Whitener and J. Arnold, Organo-
metallics, 2000, 19, 3978.
10 During the preparation of our manuscript, a brief note reporting
the synthesis of Salfen-H2 appeared: V. C. Gibson, N. J. Long,
E. L. Marshall, P. J. Oxford, A. J. P. White and D. J. Williams,
J. Chem. Soc., Dalton Trans., 2001, 1162.
11 A. Shafir, M. P. Power, G. D. Whitener and J. Arnold,
Organometallics, 2001, 20, 1365.
12 A. Shafir and J. Arnold, J. Am. Chem. Soc., 2001, 123, 9212–9213.
13 M. C. Weiss, G. Gordon and V. L. Goedken, Inorg. Chem., 1977, 16,
305.
inversion center leading to the formulation of the compound as
4ؒ1.5(C6H6). A unit cell of 7 contains a cocrystallized molecule
of THF in addition to the two coordinated THF molecules. In
4 and 10 all non-hydrogen atoms were refined anisotropically,
however in 7 the ferrocene and phenyl carbons were refined
isotropically in order to maintain a high enough data/
parameter ratio. In 10 the positions of hydrogen atoms H1 and
H2 (the amine nitrogens) were refined, all other hydrogens were
included as fixed contributions. ORTEP diagrams were created
using the ORTEP-3 software package.20
CCDC reference numbers 168571–168573.
See http://www.rsc.org/suppdata/dt/b1/b107066p/ for crystal-
lographic data in CIF or other electronic format.
14 J. J. Felten and W. P. Anderson, J. Organomet. Chem., 1972, 36,
87.
15 SMART Area-Detector Software package, Siemens Analytical
Instrumentation, Inc., Madison, WI, 1995.
16 SAINT: SAX Area Detector Integration Program, Siemens
Analytical Instrumentation, Inc., Madison, WI, 1995.
17 XPREP: Part of SHELXTL Crystal Structure Determination
Package, Siemens Analytical Instrumentation, Inc., Madison, WI,
1995.
18 SADABS: Siemens Area Detector ABSorption correction program,
G. Sheldrick, 1996, Advance copy, private communication.
19 TeXsan: Crystal Structure Analysis Software Package, Molecular
Structure Corporation, The Woodlands, TX, 1992.
20 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565.
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J. Chem. Soc., Dalton Trans., 2002, 555–560