Synthesis and characterisation of aluminium and magnesium complexes supported by pendant oxalic amidinate ligands

Article abstract of DOI:10.1039/b301744c

Two pendant oxalic amidine compounds [C₆H ₅N=C{NH(CH₂)₂OMe}-C{NH(CH₂) ₂OMe}=NC₆H₅] (1) (oxam(OMe)₂H ₂) and [C₆H₅N=C{NH(CH

Full text of DOI:10.1039/b301744c

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Synthesis and characterisation of aluminium and magnesium
complexes supported by pendant oxalic amidinate ligands
Chi-Tien Chen,* Chi-An Huang, Yi-Ren Tzeng and Bor-Hunn Huang
Department of Chemistry, National Chung-Hsing University, Taichung 402, Taiwan,
Republic of China
Received 13th February 2003, Accepted 13th May 2003
First published as an Advance Article on the web 23rd May 2003
Two pendant oxalic amidine compounds [C H N᎐C{NH(CH ) OMe}–C{NH(CH ) OMe}᎐NC H ] (1)
᎐
᎐
6
5
2
2
2
2
6
5
(oxam(OMe) H ) and [C H N᎐C{NH(CH ) NMe }–C{NH(CH ) NMe }᎐NC H ] (2) (oxam(NMe ) H ) are
᎐
᎐
2
2
6
5
2
2
2
2
2
2
6
5
2
2
2
described. Reactions of 1 or 2 with two molar equivalents of AlMe3 in toluene give the bimetallic complexes
[(Me2)Al(oxam(OMe)2)Al(Me2)] (3) and [(Me2)Al(oxam(NMe2)2)Al(Me2)] (4), respectively. Treatment of 1 or 2
with two molar equivalents of MeMgBr in THF affords the bimetallic complexes [(Br)(THF)Mg(oxam(OMe)2)-
Mg(THF)(Br)] (5) and [(Br)(THF)Mg(oxam(NMe2)2)Mg(THF)(Br)] (6) respectively. The crystal and molecular
structures are reported for compounds 1, 2, 3, 5 and 6.
Introduction
Since the steric protection of the active site and influence over
selectivity can be varied by the substituents on the N atoms, a
number of research groups are investigating various main and
transition metal complexes with bi- and multi-dentate nitrogen-
based ligands in the coordination sphere.1–4 The mono anionic
nitrogen-based ligands, such as diketiminates, aminotropon-
iminates, and amidinates, which normally act as hard, four-
electron-donors, are extensively being used as ancillary ligands
in a large diversity of metal complexes and their structure and
chemistry have been reviewed.5–9 Among these three types of
bidentate ligand, amidinates have been the most widely applied
in coordination chemistry whereas the diketiminates and ami-
notroponiminates have received relatively less attention. Due to
the steric and electronic properties of amidinato ligands they
are easily programmable by variation of the substituents on
either or both the N and C atoms; many amidinates with vari-
ous substituents have been synthesized. Several types of amid-
inato ligands with pendant functionalities were found to act as
three-coordinate, six-electron-donor ligands.10–15 The amidinato
ligands bridged via the C or N atoms of a CNN moiety have
also been reported.16–25 Recently oxalic amidinate complexes
have attracted interest, mainly owing to the discovery of their
application in catalytic reactions and their versatile bonding
modes found in the various metal complexes.34 In a similar fash-
ion to amidine, the properties of these ligands can be pro-
Scheme 1
grammed by the substituents on the nitrogen atoms. Neutral or
anionic oxalic amidines show potential to work as diimine,26–28
diimine-diamide,28–33 or amidinate ligands.34 Once the pendant
functionality has been formed, the oxalic amidines have the
potential to act as ligands that are up to three-coordinate,
six-electron-donor on each side.35–37
In this paper, we report the preparation and structural prop-
erties of pendant oxalic amidines and their aluminium and
magnesium complexes.
Results and discussion
The desired amidines can be prepared by the reactions of
bis(imidoyl)chloride with the relevant amines, as shown in
Scheme 1. Treatment of bis(imidoyl)chloride with 4 molar
equivalents of 2-methoxyethylamine in toluene affords
[C H N᎐C{NH(CH ) OMe}–C{NH(CH ) OMe}᎐NC H ] (1)
᎐
᎐
6
5
2
2
2
2
6
5
(oxam(OMe)2H2) as a white solid. Crystals suitable for X-ray
refinement were grown from toluene/hexane solution. The crys-
tal structure of amidine 1 has been determined and the molecu-
lar structure is shown in Fig. 1. The interatomic distances and
Fig. 1 Molecular structure of [C6H5N᎐C{NH(CH2)2OMe}–C{NH-
᎐
(CH2)2OMe}᎐NC6H5] (1). Hydrogen atoms and toluene molecule
᎐
omitted for clarity.
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 2 5 8 5 – 2 5 9 0
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Table 1 Selected bond lengths (Å) and angles (Њ) for 1
Table 2 Selected bond lengths (Å) and angles (Њ) for 2
N(1)–C(1)
N(2)–C(2)
N(1)–C(3)
N(3)–C(15)
C(1)–C(2)
1.288(3)
1.281(3)
1.418(3)
1.443(4)
1.499(4)
N(3)–C(1)
N(4)–C(2)
N(2)–C(9)
N(4)–C(18)
1.346(3)
1.343(3)
1.409(3)
1.445(4)
N(1)–C(1)
N(4)–C(12)
N(1)–C(2)
N(2)–C(8)
C(1)–C(12)
N(7)–C(31)
N(10)–C(42)
N(7)–C(32)
N(10)–C(43)
1.294(4)
1.283(4)
1.399(4)
1.450(4)
1.509(4)
1.283(4)
1.281(4)
1.415(5)
1.414(4)
N(2)–C(1)
1.352(4)
1.348(4)
1.431(4)
1.461(4)
1.518(4)
1.342(4)
1.349(4)
1.453(5)
1.446(4)
N(5)–C(12)
N(4)–C(13)
N(5)–C(19)
C(31)–C(42)
N(8)–C(31)
N(11)–C(42)
N(8)–C(38)
N(11)–C(49)
C(1)–N(1)–C(3)
N(1)–C(1)–N(3)
C(1)–N(3)–C(15)
N(1)–C(1)–C(2)
C(1)–C(2)–N(2)
122.7(2)
120.2(2)
122.1(2)
127.1(2)
126.9(2)
C(2)–N(2)–C(9)
N(2)–C(2)–N(4)
C(2)–N(4)–C(18)
C(2)–C(1)–N(3)
C(1)–C(2)–N(4)
123.2(2)
120.6(2)
122.8(2)
112.6(2)
112.5(2)
C(1)–N(1)–C(2)
N(1)–C(1)–N(2)
N(2)–C(1)–C(12)
C(12)–N(5)–C(19)
N(4)–C(12)–C(1)
C(31)–N(7)–C(32)
N(7)–C(31)–N(8)
N(8)–C(31)–C(42)
123.6(3)
120.0(3)
113.4(2)
123.2(3)
126.8(3)
122.1(3)
120.5(3)
113.4(3)
C(1)–N(2)–C(8)
N(1)–C(1)–C(12)
120.8(3)
126.5(3)
C(12)–N(4)–C(13)
N(4)–C(12)–N(5)
N(5)–C(12)–C(1)
C(31)–N(8)–C(38)
N(7)–C(31)–C(42)
C(42)–N(10)–C(43)
N(10)–C(42)–N(11)
N(11)–C(42)–C(31)
121.1(3)
119.6(3)
113.5(3)
122.7(3)
126.1(3)
122.5(3)
120.7(3)
113.6(3)
angles are listed in Table 1. The structure displays a trans-
(E-syn/E-syn) configuration.38–39 The two CNN planes (N1–
C1–N3 and N2–C2–N4 planes) intersect with a dihedral angle
of 75.4Њ. No intra- or inter-molecular hydrogen bonds are
found in this structure. However complex and broad signals,
which are normally observed except in compound with intra-
C(42)–N(11)–C(49) 124.3(3)
N(10)–C(42)–C(31) 125.7(3)
molecular hydrogen bonds,35 were found in the H NMR. In
1
order to study the tautomeric rotation of amidine, variable
temperature NMR experiments of an analytically pure sample
of compound 1 in toluene-d8 were investigated.40 Based on the
integral intensity of the resonances from NH, two major species
were found in a ratio of ca. 1.34 : 1 with tiny amounts of other
species at room temperature. When a sample was heated to 363
10 K, only one set of peaks corresponding to the symmetrical
species was observed which, based on the crystallographic data,
we assign as the trans-(E-syn/E-syn) isomer.40 However, it is dif-
ficult to make the assignments upon cooling the sample below
room temperature due to the complicated spectroscopic data
for this oxalic amidine bearing two asymmetrical units in each
side.
Table 3 Selected bond lengths (Å) and angles (Њ) for 3. The A atoms
are generated by an inversion center
Al–N(1)
Al–O
Al–C(6)
N(1)–C(1)
N(1)–C(2)
1.9374(16)
2.2243(17)
1.975(2)
1.323(2)
1.477(2)
Al–N(2A)
Al–C(5)
C(1)–C(1A)
N(2)–C(1)
N(2)–C(7)
2.0054(17)
1.968(2)
1.523(3)
1.317(2)
1.435(2)
N(1)–Al–C(5)
C(5)–Al–C(6)
N(2A)–Al–O
120.35(9)
121.47(11)
157.30(6)
112.5(2)
N(1)–Al–C(6)
116.39(9)
81.09(7)
133.59(17)
113.91(19)
N(1)–Al–N(2A)
N(1)–C(1)–N(2)
N(1)–C(1)–C(1A)
N(2)–C(1)–C(1A)
The possibility that hydrogen bonds between carboxylate-O
and amidine-NH sites can force protonated amidine into an
E/E configuration was explored by the reaction between
amidine and benzoic acid in solution and was confirmed by the
X-ray structure.41–42 Therefore the reaction between 1 and
benzoic acid in the mole ratio of 1 : 2 was investigated. The 1H
NMR spectrum of 1 becomes more simple and clear after the
addition of benzoic acid in CDCl3. No further impurity was
found in the spectrum. The consequence of the carboxylate
ligand forcing the amidine into an (E/E) configuration can
work as a route to examine the purity of the amidine.
Compound 2 (oxam(NMe2)2H2) was synthesized by treat-
ment of bis(imidoyl)chloride with 2 molar equivalents of N,N-
dimethylethyleneamine in toluene, followed by the addition of
25% aqueous ammonia to afford the free amidine 2 as an oily
1
solid. The H NMR spectrum shows more sharp signals than
those observed for compound 1, with a tiny amount of minor
species, in chloroform-d solution. Similar to compound 1, com-
pound 2 also exhibits tautomeric rotation in solution. Peaks
merge into one species upon heating to 323 10 K, indicating a
symmetrical species which, based on the discussion of com-
pound 1, we assign as the trans-(E-syn/E-syn) isomer. Crystals
suitable for X-ray refinement were grown from a saturated hex-
ane solution. The crystal structure of amidine 2 has been
determined and the molecular structure is shown in Fig. 2. The
interatomic distances and angles are listed in Table 2. The
asymmetric unit of 2 contains two independent molecules in
E-syn/E-syn configuration. Each molecule has a different con-
formation, one with the two Ph groups in cis-position and the
other with the two Ph groups trans. The dihedral angles for
each molecule are 57.3Њ (N1–C1–N2 and N4–C12–N5 planes)
and 57.5Њ (N7–C31–N8 and N10–C42–N11 planes) that are
smaller than that in compound 1 with a difference of 18Њ. This
difference might result from the crowded environment caused
by intermolecular H-bonding (2.286Å) between imine-N (N7)
and amine (N2–H2A). The bridged C–C bonds for 1 (1.499(4)
Å) and 2 (1.509(4) Å and 1.518(4) Å) are a bit shorter than that
Fig. 2 Two conformations found in the solid state of 2.
(1.526(4) Å) in [2,4,6-Me –C H N᎐C{NH(CH )py}–] ,35 indi-
᎐
3
6
2
2
2
cating a less bulky environment in 1 and 2. Two significantly
different sets of C–N bonds (1.281(3)–1.294(4) Å and 1.342(4)–
1.352(4) Å) are found in each amidine fragment of both com-
pounds, indicating the localized nature of the imine C᎐N and
᎐
amine C–N bonds.
Both amidine ligands react readily with two molar equiv-
alents of AlMe3 in toluene to afford pure bimetallic complexes
[(Me2)Al(oxam(OMe)2)Al(Me2)] (3) and [(Me2)Al(oxam-
(NMe2)2)Al(Me2)] (4) with the concomitant elimination of
1
methane. The H and 13C{1H} NMR spectra of each com-
pound are indicative of a highly symmetric species in solution.
On the basis of these results, a penta-coordinated aluminium
center was postulated for each of the two species.
Crystals of 3 suitable for X-ray refinement were grown from
dichloromethane/hexane solution. The crystal structure has
been determined and the molecular structure is shown in Fig. 3.
The interatomic distances and angles are listed in Table 3. The
structure confirmed a symmetric penta-coordinated aluminium
D a l t o n T r a n s . , 2 0 0 3 , 2 5 8 5 – 2 5 9 0
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Table 4 Selected bond lengths (Å) and angles (Њ) for 5. The A atoms
are generated by an inversion center
Mg–N(1A)
Mg–O(1)
Mg–Br
N(1)–C(1)
N(1)–C(2)
2.107(2)
2.155(2)
2.4823(9)
1.329(3)
1.419(3)
Mg–N(2)
Mg–O(2)
C(1)–C(1A)
N(2)–C(1)
N(2)–C(8)
2.044(2)
2.051(2)
1.536(4)
1.316(3)
1.463(3)
N(2)–Mg–O(2)
O(2)–Mg–Br
N(1A)–Mg–O(1)
N(2)–C(1)–C(1A)
123.00(9)
103.91(7)
152.07(9)
112.8(2)
N(2)–Mg–Br
131.99(7)
77.74(8)
132.3(2)
114.9(2)
N(1A)–Mg–N(2)
N(1)–C(1)–N(2)
N(1)–C(1)–C(1A)
Table 5 Selected bond lengths (Å) and angles (Њ) for 6. The A atoms
are generated by an inversion center
Mg–N(1A)
Mg–N(3)
Mg–Br
N(1)–C(1)
N(1)–C(2)
2.119(2)
2.282(3)
2.5082(8)
1.330(3)
1.423(3)
Mg–N(2)
Mg–O
C(1)–C(1A)
N(2)–C(1)
N(2)–C(8)
2.057(2)
2.050(2)
1.546(4)
1.313(3)
1.467(3)
N(2)–Mg–O
O–Mg–Br
N(1A)–Mg–N(3)
N(2)–C(1)–C(1A)
123.64(9)
104.78(7)
153.95(9)
113.2(2)
N(2)–Mg–Br
131.26(7)
77.28(8)
132.6(2)
114.2(2)
N(1A)–Mg–N(2)
N(1)–C(1)–N(2)
N(1)–C(1)–C(1A)
Fig. 3 Molecular structure of [(Me2)Al(oxam(OMe)2)Al(Me2)] (3).
Hydrogen atoms on carbon omitted for clarity.
center with a planar amidine moiety. The ligand shows a
trans configuration and prefers to form bis-five-membered
metallacycles rather than bis-four-membered metallacycles
upon coordination to the aluminium center. The two five-
membered planes are co-planar with the two Al atoms and
two amidine moieties. The central Al atoms adopt distorted
trigonal bipyramidal geometry with distorted-axes O–Al–N2A
(157.30(6)Њ). The N1(N1A), C5(C5A), and C6(C6A) atoms
reside equatorially, forming angles subtended by aluminium
of ≈120Њ. The bond lengths C1–N1 (1.323(2) Å) and
C1–N2 (1.317(2) Å) are almost identical, indicating the
delocalization of π-electrons around N1–C1–N2. The
amidinate nitrogen–aluminium bonds (1.9374(16) and
2.0054(17) Å) are longer than that (1.906(3) Å) in
[(Me2)Al(CH3N)C(NCH3)–(CH3N)C(NCH3)Al(Me2)] where-
as the bite angle (N1–Al–N2A = 81.09(7)Њ) is smaller than that
(85.7(1)Њ) in [(Me2)Al(CH3N)C(NCH3)–(CH3N)C(NCH3)Al-
(Me2)],29 due to the steric effect of the substituents on the
nitrogen atoms. The Al–Me bonds (1.968(2) and 1.975(2) Å)
are within the ranges (1.94–2.03 Å) observed for relevant
aluminium amidinate complexes.11,29,40,43–45
Fig.
4
Molecular structure of [(Br)(THF)Mg(oxam(OMe)2)-
Mg(THF)(Br)] (5). Hydrogen atoms on carbon omitted for clarity.
Treatment of 1 or 2 with two molar equivalents of MeMgBr
in THF affords bimetallic complexes [(Br)(THF)Mg(oxam-
(OMe)2)Mg(THF)(Br)] (5) and [(Br)(THF)Mg(oxam(NMe2)2)-
Mg(THF)(Br)] (6) with the concomitant elimination of meth-
ane. NMR spectroscopy indicates both compounds are highly
symmetric species in solution. Likewise most magnesium
amidinate complexes with a less crowded environment around
the metal center display a tendency to coordinate solvents such
as THF or PhCN,46–49 two multiplets (for 5: δ 1.57 and 3.69
ppm; for 6: δ 1.61 and 3.75 ppm) corresponding to the co-
ordinated THF are found in each compound. The elemental
analysis data are also consistent with a complex containing co-
ordinated THF.
Crystals of 5 were grown from THF/hexane solution. The
crystal structure has been determined and the molecular struc-
ture is shown in Fig. 4. The interatomic distances and angles are
listed in Table 4. The structure also confirmed a symmetric
penta-coordinated magnesium center with a planar amidine
moiety. Similar to the relevant aluminium compounds dis-
cussed above, deprotonated 1 is seen to act as a tridentate
ligand on each side, binding to magnesium via two amidinate
nitrogen atoms from different CNN units and one coordinated
oxygen atom. The geometry at magnesium can be described as
distorted trigonal bipyrimidal with O(1) and N(1A) occupying
the axial positions (O(1)–Mg–N(1A) 152.07(9)Њ). The Br(BrA),
O2(O2A) and N2(N2A) atoms reside equatorially, however
with different angles (131.99(7)Њ, 123.00(9)Њ, 103.91(7)Њ) sub-
tended by magnesium. The bond lengths of C1–N1 (1.329(3) Å)
and C1–N2 (1.316(3) Å) are similar, consistent with the delocal-
ization of π-electrons within the amidine moiety. The amidinate
nitrogen–magnesium bonds (2.044(2) and 2.107(2) Å) are
within the Mg–N single bond ranges (2.04–2.17 Å) found in
magnesium amidinate complexes.11,47–51 The coordinated THF
oxygen–magnesium bond (Mg–O2 2.051(2) Å) is shorter than
those (2.08–2.33 Å)47–49 in magnesium amidinate complexes
and the pendant-armed oxygen–magnesium bond (Mg–O1
2.155(2) Å) in the same molecule, but comparable to those Mg–
O (coordinated-THF) bonds (2.042–2.092 Å) in Mg(diiminato)-
(X)(THF) (X = Me, OtBu, NiPr) complexes.52–54
Crystals of 6 were grown from dichloromethane/hexane solu-
tion and the crystal structure has been determined. The molecu-
lar structure is shown in Fig. 5 and the interatomic distances
and angles are listed in Table 5. Basically, compound 6 is quite
similar to compound 5 with different dative NMe2 instead of
OMe for 5. Bond lengths and bond angles are similar to those
discussed above. The pendant-armed nitrogen–magnesium
bond (Mg–N3 2.282(3) Å) is longer than those found for the
D a l t o n T r a n s . , 2 0 0 3 , 2 5 8 5 – 2 5 9 0
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71.3 (s, CH2), 122.2, 122.7, 128.9 (o-, m-, p-C6H5), 129.1,
150.1(Cipso-C6H5 and CNN). Anal. Calc. for C20H26N4O2: C,
67.8; H, 7.4; N, 15.8. Found: C, 67.4; H, 7.3; N, 15.2%.
NMR tube scale reaction of [C H N᎐C{NH(CH ) OMe}–
᎐
6
5
2 2
C{NH(CH ) OMe}᎐NC H ] (1) with benzoic acid. A solution
᎐
2
2
6
5
of 1 (10 mg, 0.028 mmol) in CDCl3 (2 ml) in a 5 mm NMR
1
tube was treated with ca. 2.0 equiv. of benzoic acid. H NMR
(400 MHz): δ 3.36 (s, CH3, 6H), 3.53 (s, CH2–CH2, 8H),
6.60–7.18 (m, C6H5, 10H, amidine), 7.43 (m, C6H5, 4H,
benzoate), 7.54 (m, C6H5, 2H, benzoate), 8.09 (m, C6H5, 4H,
benzoate).
[C H N᎐C{NH(CH ) NMe }–C{NH(CH ) NMe }᎐NC H ]
᎐
᎐
6
5
2
2
2
2
2
2
6
5
(2) (oxam(NMe ) H ). A yellow solution of [C H N᎐C(Cl)–
᎐
2
2
2
6
5
C(Cl)᎐NC H ] (8.3 g, 30 mmol) in toluene (80 ml) was treated
᎐
6
5
with 6.6 ml of N,N-dimethylethyleneamine (5.3 g, 60 mmol) at
0 ЊC in a dropwise manner. The reaction mixture was allowed to
warm to room temperature and react overnight. After 12 h of
stirring, the resulting precipitate was isolated by filtration and
pumped to dryness to give a white solid 2ؒ2HCl. Yield, 10.9 g,
Fig.
5
Molecular structure of [(Br)(THF)Mg(oxam(NMe2)2)-
Mg(THF)(Br)] (6). Hydrogen atoms on carbon omitted for clarity.
1
80%. H NMR (600 MHz): δ 2.86 (s, CH3, 12H), 3.29 (s, CH2,
amidinate nitrogen–magnesium bonds (2.0406–2.168 Å), but
comparable to the pyridine–magnesium bonds (2.260(4) and
2.264(4) Å) found in [2-Py–(CH2)2NC(p-MePh)NPh]2Mg.11
In conclusion, novel oxalic-amidines with pendant function-
alities can be easily accomplished. Similar to most other oxalic
amidinato complexes these ligands prefer to form five-
membered metallacycles upon coordination to aluminium or
magnesium centers.
4H), 3.71 (br, CH2, 4H), 6.38 (d, o-Ph, 4H, J = 4.2 Hz), 6.89 (t,
p-Ph, 2H, J = 7.2 Hz), 7.03 (t, m-Ph, 4H, J = 7.2 Hz).13C{1H}
NMR (150 MHz): δ 35.5, 56.7 (s, (CH2)2–N), 43.9 (s, N–CH3),
121.9, 122.5, 128.1(o-, m-, p-C6H5), 148.4, 150.7 (Cipso-C6H5 and
CNN). The white solid 2ؒ2HCl (2.2 g, 4.8 mmol) was extracted
with CH2Cl2 (50 ml), and then treated with 2 ml of NH4OH(aq)
to afford a yellowish-green solution. The resulting solution was
filtered and the volatiles were removed in vacuo to give com-
pound 2 as an oily solid. Yield, 1.5 g, 81%. The quality is good
enough for further reaction. Single crystals suitable for X-ray
1
Experimental
analysis were grown from hexane at room temperature. H
NMR (600 MHz, 323K): δ 2.10 (s, CH3, 12H), 2.24 (s, CH2,
4H), 3.25 (s, CH2, 4H), 5.13 (br, NH, 2H), 6.75 (br, o-Ph, 4H),
6.95 (m, p-Ph, 2H), 7.17 (br, m-Ph, 4H).13C{1H} NMR (150
MHz, 323 K): δ 38.5 (s, (CH2)2–N), 57.3 (s, (CH2)2–N), 44.9 (s,
N–CH3), 121.7, 122.3, 128.5 (o-, m-, p-C6H5), 149.3, 151.1
(Cipso-C6H5 and CNN). Anal. Calc. for C22H32N6: C, 69.5; H,
8.4; N, 22.1. Found: C, 68.7; H, 8.9; N, 22.3%.
All manipulations were carried out under an atmosphere of
dinitrogen using standard Schlenk-line or drybox techniques.
Solvents were refluxed over the appropriate drying agent and
distilled prior to use. Deuterated solvents were dried over
molecular sieves.
1H and 13C{1H} NMR spectra were recorded on Varian
Gemini-200 (200MHz), Varian VXR-300 (300MHz), Varian
Mercury-400 (400MHz) or Varian Inova-600 (600 MHz)
spectrometers in chloroform-d at ambient temperature unless
stated otherwise and referenced internally to the residual sol-
vent peak and reported as parts per million relative to tetra-
methylsilane. Elemental analyses were performed by a Heraeus
CHN-O-RAPID instrument.
[(Me2)Al(oxam(OMe)2)Al(Me2)] (3). To a solution of 1
(1.79 g, 5 mmol) in 40 ml of toluene, 5.3 ml of AlMe3 (2 M in
toluene, 10.6 mmol) was added dropwise within 5 min at room
temperature. The reaction mixture was then set to reflux. After
6 h of stirring, the volatiles were removed under vacuum, and
the residue was recrystallized from toluene/hexane to afford a
white crystalline solid. Yield, 0.90 g, 37%. 1H NMR (600 MHz):
δ Ϫ1.02 (s, Al–CH3, 12H), 2.89 (t, CH2, 4H, J = 6 Hz), 3.31 (s,
OMe, 6H), 3.35 (t, CH2, 4H, J = 6 Hz), 7.10 (m, Ph, 4H), 7.12
(m, Ph, 2H), 7.26 (m, Ph, 4H).13C{1H} NMR (150 MHz):
δ Ϫ11.0 (s, Al–CH3), 45.7 (s, (CH2)2), 57.9 (s, O–(CH3)), 69.6 (s,
Oxanilide (Acros), PCl5 (RDH or Merck), benzoic acid
(Showa), AlMe3 (2 M in toluene, Acros) and MeMgBr (3 M in
Et2O, Aldrich) were used as supplied. 2-Methoxyethylamine
and N,N-dimethylethylenediamine were dried over CaH2 and
distilled before use. Bis-phenylimidoylchloride was prepared by
the literature method.55
(CH2)2), 124.3, 126.4, 127.8 (o-, m-, p-C6H5), 144.6, 155.4(Cipso
-
C6H5 and CNN). Anal. Calc. for C24H36Al2N4O2: C, 61.8; H,
7.8; N, 12.0. Found: C, 61.6; H, 7.8; N, 11.6%.
Preparations
[C H N᎐C{NH(CH ) OMe}–C{NH(CH ) OMe}᎐NC H ]
᎐
᎐
6
5
2
2
2
2
6
5
(1) (oxam(OMe) H ). A yellow solution of [C H N᎐C(Cl)–
[(Me2)Al(oxam(NMe2)2)Al(Me2)] (4). To a solution of 2
(1.8 g, 4.7 mmol) in 40 ml of toluene, a diluted solution of 5 ml
of AlMe3 (2 M in toluene, 9.5 mmol) in 80 ml of toluene was
added dropwise at 0 ЊC. The reaction mixture was allowed to
warm to room temperature and reacted overnight. After 8 h of
stirring, the resulting white solid was isolated by filtration and
᎐
2
2
6
5
C(Cl)᎐NC H ] (6.9 g, 25 mmol) in toluene (60 ml) was treated
᎐
6
5
with 8.7 ml of 2-methoxyethylamine (7.5 g, 100 mmol) at 0 ЊC
in a dropwise manner. The reaction mixture was stirred in an
ice-bath for 1 h, and then allowed to warm to room temper-
ature and react overnight. After 18 h of stirring, the resulting
mixture was filtered and the filtrate was concentrated to around
one forth volume. The concentrated filtrate was layered with ca.
20 ml hexane and stood at room temperature overnight to
afford a white crystalline solid. Yield, 5.4 g, 60%. 1H NMR (600
MHz, toluene-d8, 363 K): δ 2.97 (s, CH3, 6H), 3.02 (br, (CH2)2,
4H), 3.15 (br, (CH2)2, 4H), 6.84 (t, p-Ph, 2H,J = 7.8 Hz), 6.88
(br, o-Ph, 4H), 7.08 (t, m-Ph, 4H, J = 7.8 Hz). 13C{1H} NMR
(150 MHz, toluene-d8, 363 K): δ 42.6 (s, CH2), 58.3 (s, O–CH3),
1
pumped to dryness. Yield, 1.9 g, 82%. H NMR (600 MHz):
δ Ϫ1.05 (s, Al–CH3, 12H), 2.14 (s, NMe2, 12H), 2.36 (t, CH2,
4H, J = 6 Hz), 2.72 (t, CH2, 4H, J = 6 Hz), 7.10 (m, Ph, 6H),
7.23 (m, Ph, 4H).13C{1H} NMR (150 MHz): δ Ϫ10.0 (s,
Al–CH3), 43.2 (s, (CH2)2–N), 44.5 (s, N–(CH3)2), 56.7 (s,
(CH2)2–N), 123.7, 126.8, 127.4 (o-, m-, p-C6H5), 146.3, 155.9
(Cipso-C6H5 and CNN). Anal. Calc. for C26H42Al2N6: C, 63.4;
H, 8.6; N, 17.1. Found: C, 62.1; H, 8.4; N, 16.5%.
D a l t o n T r a n s . , 2 0 0 3 , 2 5 8 5 – 2 5 9 0
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View Article Online
Table 6 Summary of crystal data for compounds 1, 2, 3, 5 and 6
1
2
3
5
6
Formula
M
T /K
Crystal system
Space group
a/Å
b/Å
c/Å
C23.5H26N4O2
396.48
293(2)
C44H64N12
761.07
293(2)
Orthorhomic
P212121
9.5940(6)
17.2591(11)
27.7148(18)
90
90
90
4589.1(5)
4
1.102
0.068
25891
505
0.0688
0.1885
1.254
C12H18AlN2O
233.26
293(2)
Monoclinic
P21/c
10.3225(10)
9.2411(8)
14.5906(13)
90
108.326(2)
90
1321.2(2)
4
1.173
0.136
7182
C14H20BrMgN2O2
352.54
293(2)
Monoclinic
P21/n
9.7976(8)
11.4638(10)
15.2253(13)
90
104.651(2)
90
1654.5(2)
4
1.415
2.525
9070
C15H23BrMgN3O
365.58
293(2)
Monoclinic
P21/n
10.3022(7)
12.2215(8)
14.8699(9)
90
108.0400(10)
90
1780.2(2)
4
1.364
2.347
9764
Triclinic
¯
P1
9.2839(11)
11.6924(14)
11.9217(13)
92.341(3)
112.099(2)
106.880(2)
1130.8(2)
2
1.164
0.076
6486
265
α/Њ
β/Њ
γ/Њ
V/Å3
Z
ρcalc/Mg mϪ3
µ(Mo-Kα)/mmϪ1
Reflections collected
No. of parameters
R1a
145
181
190
0.0663
0.1748
1.067
0.0437
0.1449
1.113
0.0390
0.1154
0.864
0.0360
0.1066
0.813
wR2a
GoFb
a R1 = [Σ(|Fo| Ϫ |Fc|]/Σ|Fo|]; wR2 = [Σw(Fo2 Ϫ Fc2)2/Σw(Fo )2]1/2, w = 0.10. b GoF = [Σw(Fo2 Ϫ Fc2)2/(Nrflns Ϫ Nparams)]1/2
.
2
[(Br)(THF)Mg(oxam(OMe)2)Mg(THF)(Br)] (5). To a solu-
tion of 1 (0.71 g, 2 mmol) in 40 ml THF, 1.4 ml of MeMgBr
(3 M in Et2O, 4.2 mmol) was added dropwise at 0 ЊC. The clear
yellow solution gradually turns into a pale-yellow suspension.
The reaction mixture was allowed to warm to room temper-
ature and was reacted overnight. After 13 h of stirring, the
resulting white precipitate was isolated by filtration and
package.57 All non-H atoms were located from successive
Fourier maps, and hydrogen atoms were refined using a riding
model. Anisotropic thermal parameters were used for all non-H
atoms, and fixed isotropic parameters were used for H atoms.
Some details of the data collection and refinement are given in
Table 6.
CCDC reference numbers 203776–203780.
See http://www.rsc.org/suppdata/dt/b3/b301744c/ for crystal-
lographic data in CIF or other electronic format.
1
pumped to dryness. Yield, 0.91 g, 65%. H NMR (200 MHz):
δ 1.57 (m, THF, 8H), 2.90 (m, CH2, 4H), 3.44 (m, CH2, 4H),
3.48 (s, O–CH3, 6H), 3.69 (m, THF, 8H), 6.88–7.20 (m, Ph,
10H).13C{1H} NMR (150 MHz): δ 25.0(s, THF ), 46.5 (s,
(CH2)2), 58.9 (s, O–(CH3)), 69.2 (s,THF ), 73.3 (s, (CH2)2),
124.3, 126.4, 127.8 (o-, m-, p-C6H5), 144.6, 155.4 (Cipso-C6H5
and CNN). Anal. Calc. for C28H40Br2Mg2N4O4: C, 47.7; H, 5.7;
N, 8.0. Found: C, 47.4; H, 5.5; N, 8.0%.
Acknowledgements
We would like to thank the National Science Council of the
Republic of China for financial support.
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to warm to room temperature and reacted for 3 h. The resulting
white solid was isolated by filtration and pumped to dryness.
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