Synthesis, reactivity, and structures of dialuminum complexes containing linked ketiminate ligands

Article abstract of DOI:10.1016/j.ica.2005.07.001

Linked bis(ketimine) (1) can be prepared with the reaction of excess 2,4-pentanedione and 4,4′-methylene-bis(2,6-diisopropylaniline) in methanol in the presence of catalytic amount of formic acid. The dialuminum alkyl complexes containing the linked bis(k

Full text of DOI:10.1016/j.ica.2005.07.001

Inorganica Chimica Acta 358 (2005) 3761–3767
www.elsevier.com/locate/ica
Synthesis, reactivity, and structures of dialuminum
complexes containing linked ketiminate ligands
*
Pei-Chen Kuo, I-Chun Chen, Hon Man Lee, Cheng-Hsiang Hung, Jui-Hsien Huang
Department of Chemistry, National Changhua University of Education, 1 JinDer Rd., Changhua 50058, Taiwan
Received 7 March 2005; received in revised form 28 June 2005; accepted 1 July 2005
Available online 8 August 2005
Abstract
Linked bis(ketimine) (1) can be prepared with the reaction of excess 2,4-pentanedione and 4,40-methylene-bis(2,6-diisopropylan-
iline) in methanol in the presence of catalytic amount of formic acid. The dialuminum alkyl complexes containing the linked bis(keti-
minate) dianionic ligands, [OC(Me)CHC(Me)N(2,6-iPr2C6H2-4)AlR2]2CH2 (2, R = Me; 3, R = Et), were prepared by a reaction of
2 equiv AlR3 with [OC(Me)CHC(Me)NH(2,6-iPr2C6H2-4)]2CH2 in methylene chloride. Reactions of 2 with 2 and 4 equiv of I2 gave
corresponding aluminum iodo complexes 4 and 5, respectively. Treatment of 5 with 2 equiv of AgBF4, however, gave a diboron
complex, [OC(Me)CHC(Me)N(2,6-iPr2C6H2-4)BF2]2CH2 (6), in 18% isolated yield. All new complexes have been characterized
1
by H and 13C NMR spectroscopy and complexes 2, 3, and 6 are also confirmed by X-ray diffraction.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Dialuminum; Linked ketiminate; Diboron; Aluminum iodo
1. Introduction
containing linked bis(ketiminate) ligands and their re-
lated reactions.
Dinuclear transition metal complexes are rather
common and may be useful as catalysts [1–3] or metal-
loenzymes [4–6]. Dinuclear metal complexes with bis-
multidentate ligands containing two anionic ancillary
ligands linked by a bridge have been studied [7–14] be-
cause of their potential usage as two-center Lewis acid
catalysts. Group 13 dimetallic complexes containing
bis-bidentate ligands have also been reported by Atwood
et al. [15,16]. The bis-bidentate ligands used in the dialu-
minum chemistry are mainly of the Salen classes bridged
with backbones such as 1,4-butylene, 1,4-phenylene, 1,2-
cyclohexylene, etc. The studies of the aluminum com-
plexes with mono anionic bidentate ketiminate ligands
have been reported elsewhere [17]. Here, we report the
syntheses and characterization of dialuminum complexes
2. Results and discussion
2.1. Synthesis and characterization
Linked bis(ketimine) (1) ligands can be prepared
easily by modifying the published procedure [18]. The
reaction of excess (>2 equiv) 2,4-pentanedione and
4,40-methylene-bis(2,6-diisopropylaniline) in methanol
in the presence of catalytic amount of formic acid
(Scheme 1), followed by the removal of excess 2,4-pen-
tanedione under vacuum at elevated temperature, affor-
ded pure bis(ketimine) ligand, 1, in high yield. 1H NMR
spectrum of 1 reveals that the methylene protons be-
tween two phenyl rings appear at d 3.97; while the
methine proton of the ketiminate backbone appears at
d 5.18, which serves as an excellent indicator for evalu-
ating the purity of the metal complexes.
*
Corresponding author. Tel.: +886 4 7232105ext3531; fax: +886 4
7211190.
E-mail address: juihuang@cc.ncue.edu.tw (J.-H. Huang).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.07.001

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P.-C. Kuo et al. / Inorganica Chimica Acta 358 (2005) 3761–3767
formic acid
H
+
N
2
N
O
O
O
NH2
H2N
O
H
1
Scheme 1.
Treatment of 1 with 2 equiv of AlMe3 and AlEt3 in a
methylene chloride solution generates the dialuminum
complexes 2 and 3, respectively, in high yield (Scheme 2).
The reactions were proceeding along with the elimination
of 2 equiv of methane or ethane. The complexes have
and X-ray structure determination. The 1H NMR spectra
for both the complexes 2 and 3 exhibit one methine reso-
nance and two methyl resonances for the isopropyl frag-
ments, consistent with fast ring inversion and slow aryl
rotation [17]. Moreover, the H NMR spectra of the
methine protons of the ketiminate backbones of 2 and
1
1
been characterized by H and 13C NMR spectroscopy
I
I
Al
N
N
O
O
Al
I
I
5
4 I2
Me
Al
Me
2 AlMe3
1
N
N
O
O
Al
Me
2
Me
2 AlEt3
2 I2
Et
Al
Me
Et
I
Al
N
N
N
N
O
O
Al
O
O
Al
Et
I
3
Et
Me
4
Scheme 2.
I
I
I
Al
2 AgBF4
Al
N
[BF4]2
N
N
N
Al
O
O
O
O
Al
I
I
I
5
2 AgBF4
F
F
B
N
N
O
O
B
F
6
F
Scheme 3.

P.-C. Kuo et al. / Inorganica Chimica Acta 358 (2005) 3761–3767
3763
Table 1
3 exhibit one singlet at d 5.33 and 5.32, respectively. The
Selected bond distances and angles of complexes 2, 3, and 6
complex 2 displayed a singlet at d ꢀ0.94 for AlMe2 frag-
ments while the AlEt2 of complex 3 exhibited one set trip-
let and multiplet at d ꢀ0.22 and 0.84 for the CH2 and CH3
fragments. These data indicate symmetric structures for
both the complexes 2 and 3.
2
Al(1)–O(1)
Al(1)–C(1)
O(1)–C(4)
C(3)–C(4)
Al(1)–N(1)
Al(1)–C(2)
N(1)–C(6)
C(4)–C(5)
1.784(4)
1.972(6)
1.305(5)
1.511(6)
1.934(4)
1.937(5)
1.334(5)
1.355(6)
Reactions of 2 with 2 and 4 equiv of iodine yielded
the expected aluminum methyl iodo complex 4 and alu-
minum diiodo complex 5, respectively (Scheme 2). Com-
plexes 4 and 5 have been characterized by elemental
analysis and 1H and 13C NMR spectroscopy. The
methine proton resonances of ketiminate backbone for
complexes 4 and 5 were observed as single resonance
at d 4.00 and 4.01, respectively, in the 1H NMR spectra.
Although complex 4 remains a twofold axis of symmetry
passing through the bridged CH2 fragment, the isopro-
pyl groups of the phenyl rings are not symmetric due
to the unsymmetrical coordination geometry at the alu-
minum center. These phenomena could be detected from
the 13C NMR spectra where the resonances for phenyl
and isopropyl carbons appeared in a more complicated
fashion.
Attempts to remove the iodide of complex 5 to yield
cationic aluminum center by adding AgBF4 have re-
sulted in an unexpected di-boron complex 6, with 18%
isolated yield (Scheme 3). 1H and 13C NMR spectra
are consistent with the existence of the linked ketiminate
ligands and 11B NMR spectrum also indicated the pres-
ence of boron in complex 6. The 11B NMR spectrum
exhibits a triplet at d 0.67 relative to the standard of
BF3 Æ OEt2 showing the coupling of JBF = 15.4 Hz.
O(1)–Al(1)–N(1)
N(1)–Al(1)–C(2)
N(1)–Al(1)–C(1)
O(1)–Al(1)–C(2)
O(1)–Al(1)–C(1)
C(2)–Al(1)–C(1)
94.58(17)
111.6(2)
111.3(2)
111.8(2)
107.9(2)
117.3(2)
3
Al(1)–O(1)
Al(1)–C(8)
Al(2)–O(2)
Al(2)–C(40)
N(1)–C(4)
N(2)–C(36)
O(1)–C(2)
C(2)–C(3)
C(37)–C(38)
Al(1)–N(1)
Al(1)–C(6)
Al(2)–N(2)
Al(2)–C(42)
N(1)–C(10)
N(2)–C(26)
O(2)–C(38)
C(3)–C(4)
C(36)–C(37)
1.7990(18)
1.955(3)
1.7957(18)
1.948(3)
1.317(3)
1.316(3)
1.303(3)
1.354(3)
1.361(3)
1.9356(19)
1.962(3)
1.9316(19)
1.964(3)
1.463(3)
1.453(2)
1.303(3)
1.427(3)
1.423(3)
O(1)–Al(1)–N(1)
N(1)–Al(1)–C(8)
N(1)–Al(1)–C(6)
O(2)–Al(2)–N(2)
N(2)–Al(2)–C(40)
N(2)–Al(2)–C(42)
O(1)–Al(1)–C(8)
O(1)–Al(1)–C(6)
C(8)–Al(1)–C(6)
O(2)–Al(2)–C(40)
O(2)–Al(2)–C(42)
C(40)–Al(2)–C(42)
93.26(8)
113.03(11)
112.21(10)
94.26(8)
114.77(11)
108.83(11)
111.53(10)
107.63(11)
116.62(13)
109.20(13)
118.39(15)
118.39(15)
2.2. Molecular structures of complexes 2, 3, and 6
Crystal structure determination of 2 confirms the for-
mation of bimetallic complex. The colorless crystals of 2
were obtained by cooling a saturated diethyl ether solu-
tion at ꢀ20 ꢁC. The molecular structure of 2 and se-
lected bond distances and angles are shown in Fig. 1
and Table 1, respectively. As expected, both the alumi-
6
B–O(1)
B–F(1)
N(1)–C(4)
C(2)–C(3)
B–N(1)
B–F(2)
1.462(5)
1.367(5)
1.313(4)
1.344(6)
1.572(5)
1.365(5)
1.311(5)
1.412(5)
O(1)–C(2)
C(3)–C(4)
O(1)–B–N(1)
F(2)–B–N(1)
F(1)–B–N(1)
F(2)–B–O(1)
F(1)–B–O(1)
F(2)–B–F(1)
109.8(3)
109.6(3)
110.0(3)
110.0(3)
108.6(3)
108.9(3)
Fig. 1. The molecular structure of complex 2. Thermal ellipsoids are
drawn at 30% probability and all hydrogen atoms are omitted for
clarity.

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P.-C. Kuo et al. / Inorganica Chimica Acta 358 (2005) 3761–3767
num atoms in complex 2 are surrounded by two methyl
groups and one bidentate ketiminate ligand in a tetrahe-
dral geometry. The bite angles of ketiminate ligands,
N(1)–Al(1)–O(1) (which is 94.58(17)ꢁ), are smaller than
a regular tetrahedral bond angle of 109.28ꢁ. The back-
bone of ketiminate, O(1)–C(3)–C(4)–C(5)–N(1), forms
a plane and the aluminum atom is deviated from the
angles are listed in Table 1. Complex 6 is consistent with
a C2 symmetry with two boron atoms located on the two
ketiminate fragments. Each boron atom is surrounded by
two fluorine atoms and one ketiminate fragment forming
a tetrahedral geometry. The two B–F bond distances (ca.
˚
1.36 A) are similar to the reported bidentate ligand che-
lated BF2 complexes [19,20]. The ketiminate fragment
chelates to the boron atom with an angle of 109.8(3), sim-
ilar to the bond angles of tetrahedral geometry.
˚
plane by 0.5821 A. A large dihedral angle (98.5ꢁ is ob-
served between the phenyl ring and the ketiminate back-
bone plane, suggesting minimal steric interaction
between the aluminum methyl groups and the phenyl
rings in the solid state. In viewing half part of the molec-
ular structure of 2, it is similar to that of (OCMeCHC-
MeNAr)AlMe2 [17].
3. Conclusions
In conclusion, the synthesis of a linked bis(ketimine)
ligand has been described. Reactions of the bis(keti-
mine) with AlMe3 yield a new type of dialuminum alkyl
complex 2, which can be converted to corresponding
aluminum iodo complexes by adding various amounts
Crystals of 3 were obtained from a concentrated
diethyl ether solution at ꢀ20 ꢁC. The molecular struc-
ture of 3 is shown in Fig. 2 and selected bond distances
and angles are listed in Table 1.
Crystals of 6 suitable for X-ray structure determina-
tion were directly obtained from sublimation of solids.
Due to the small molecular size, some of the high angle
reflection data were omitted. The molecular structure of
6 is shown in Fig. 3 and selected bond distances and
of I2. A diboron compound, [OC(Me)CHC(Me)-
N(2,6-iPr2C6H2-4)BF2]2CH2 (6), can be obtained from
the reaction of 2 with 2 equiv of AgBF4 via metal ex-
change. A further study of aluminum hydride complexes
containing these bis(ketiminate) ligands is currently
undergoing.
4. Experimental
4.1. General procedures
All reactions were performed under a dry nitrogen
atmosphere using standard Schlenk techniques or in a
glove box. Toluene and diethyl ether were dried by
refluxing over sodium benzophenone ketyl. CH2Cl2
was dried over P2O5. All solvents were distilled and
˚
stored in solvent reservoirs, which contained 4 A molec-
Fig. 2. The molecular structure of complex 3. Thermal ellipsoids are
drawn at 30% probability and all hydrogen atoms are omitted for
clarity.
ular sieves and were purged with nitrogen. H and 13C
1
NMR spectra were recorded on a Bruker AC 200 or
Bruker Avance 300 spectrometer. Chemical shifts for
1H and 13C spectra were recorded in ppm relative to
the residual protons and 13C of CDCl3 (d 7.24, 77.0)
and C6D6 (d 7.15, 128.0). 11B NMR spectra were re-
corded on a Bruker Avance 300 MHz spectrometer with
BF3 Æ OEt2 as reference at d 0 ppm. Elemental analyses
were performed on a Heraeus CHN-OS Rapid Elemen-
tal Analyzer at the Instrument Center, NCHU.
4.2. Synthesis of [OC(Me)CHC(Me)
NH(2,6-iPr2C6H2-4)]2 CH2 (1)
Excess 2,4-pentanedione (6.0 g, 60.0 mmol) and 4,40-
methylenebis-(2,6-diisopropylaniline) (10 g, 27.3 mmol)
were placed in a flask and dissolved in 50 mL methanol.
Small amount of formic acid was added as catalyst. The
mixture was stirred at room temperature for 12 h and
volatiles were removed under vacuum to generate
Fig. 3. The molecular structure of complex 6. Thermal ellipsoids are
drawn at 30% probability and all hydrogen atoms are omitted for
clarity.

P.-C. Kuo et al. / Inorganica Chimica Acta 358 (2005) 3761–3767
3765
1
14.4 g of pale yellow solids in 99.4% H yield. H NMR
(CDCl3): d 1.07 (d, 12H, CHMe2), 1.14 (d, 12H,
CHMe2), 1.62 (s, 6H, CMe), 2.09 (s, 6H, CMe), 2.95
(m, 4H, CHMe2), 3.97 (s, 2H, CH2), 5.18 (s, 2H,
CMeCHCMe), 6.93 (s, 4H, Ph), 11.92 (s, br, 2H, NH).
13C NMR (CDCl3): d 19.1 (q, JCH = 128 Hz, CH3),
22.6 (q, JCH = 126 Hz, CH3), 24.4 (q, JCH = 127 Hz,
CH3), 28.3 (d, JCH = 128 Hz, CHMe2), 28.6 (q,
JCH = 126 Hz, CH3), 41.5 (t, JCH = 127 Hz, CH2), 95.6
3.99(s, 2H, CH2), 5.31 (s, 2H, CMeCHCMe), 6.93 (s,
4H, Ph). 13C NMR (CDCl3): d ꢀ1.1 (t, JCH = 111 Hz,
2
AlCH2CH3), 8.9 (qt, JCH = 124 Hz, JCH = 5 Hz,
AlCH2CH3), 23.0 (q, JCH = 129 Hz, CMe), 24.2 (q,
JCH = 126 Hz, CHMe), 24.6 (q, JCH = 126 Hz, CHMe),
25.7 (q, JCH = 128 Hz, CMe), 27.8 (d, JCH = 129 Hz,
CHMe), 41.1 (t, JCH = 127 Hz, CH2), 100.6 (d, JCH
=
162 Hz, CMeCHCMe), 124.9 (d, JCH = 154 Hz, phenyl
CH), 137.1 (s, phenyl Cipso), 139.5 (s, phenyl Cipso),
142.7 (s, phenyl Cipso), 176.4 (s, CN), 181.2 (s, CO).
(d, JCH = 161 Hz, CMeCHCMe), 124.0 (d, JCH
=
155 Hz, phenyl CH), 131.2 (s, phenyl Cipso), 140.5 (s,
phenyl Cipso), 145.9 (s, phenyl Cipso), 164.2 (s, CN),
195.8 (s, CO). Anal. Calc. for C35H50N2O2: C, 79.20;
H, 9.49; N, 5.28. Found: C, 79.07; H, 9.91; N, 5.22%.
4.5. Synthesis of [OC(Me)CHC(Me)N(2,6-iPr2C6H2-
4)AlIMe]2CH2 (4)
To a 50 mL Schlenk flask containing 1 (3.6 g,
5.6 mmol) was added 20 mL toluene and iodine (2.9 g,
11.4 mmol) and heated at 100 ꢁC for 48 h. Volatiles were
removed under vacuum and the resulting yellow-brown
solid was recrystallized from toluene to yield 4.50 g of
4.3. Synthesis of [OC(Me)CHC(Me)N(2,6-iPr2C6H2-
4)AlMe2]2CH2 (2)
A solution of trimethylaluminum (2 M in toluene,
18.87 mL, 37.74 mmol) was added dropwise at 0 ꢁC to
a stirred solution of 1 (10.0 g, 18.87 mmol) in methylene
chloride (70 mL). The resulting solution was stirred at
room temperature for 5 h. Volatiles were removed under
vacuum to generate 12.0 g of yellow solids in 98% yield.
Colorless crystals of 2, which are suitable for X-ray
structure determination, can be obtained from a satu-
1
yellow brown solids (yield 93%). H NMR (CDCl3): d
ꢀ0.55 (s, 6H, AlMe), 0.97 (d, 6H, CHMe2), 1.07–1.17
(m, 18H, CHMe2), 1.84 (s, 6H, CMe), 2.14 (s, 6H,
CMe), 2.66 (m, 2H, CHMe2), 3.25 (m, 2H, CHMe2),
4.00 (s, 2H, CH2), 5.65 (s, 2H, CMeCHCMe), 6.90 (s,
2H, Ph), 6.97 (s, 2H, Ph). 13C NMR (CDCl3): d ꢀ7.5
(q, JCH = 116 Hz, AlMe2), 23.2 (q, JCH = 128 Hz,
CHMe2), 23.4 (q, JCH = 128 Hz, CMe), 24.1 (q,
JCH = 128 Hz, CHMe2), 24.7 (q, JCH = 126 Hz,
CHMe2), 25.7 (q, JCH = 128 Hz, CMe), 26.8 (q,
JCH = 126 Hz, CHMe2), 28.0 (d, JCH = 128 Hz,
CHMe2), 28.4 (d, JCH = 128 Hz, CHMe2), 40.9 (t,
JCH = 127 Hz, CH2), 102.6 (d, JCH = 163 Hz,
CMeCHCMe), 124.9 (d, JCH = 155 Hz, phenyl CH),
125.4 (d, JCH = 155 Hz, phenyl CH), 135.4 (s, phenyl
Cipso), 140.0 (s, phenyl Cipso), 142.5 (s, phenyl Cipso),
143.7 (s, phenyl Cipso), 178.7 (s, CN), 181.7 (s, CO).
Anal. Calc. for C37H54N2O2Al2I2: C, 51.28; H, 6.28;
N, 3.23. Found: C, 49.94; H, 6.12; N, 3.42%.
1
rated diethyl ether solution. H NMR (CDCl3): ꢀ0.94
(s, 12H, AlMe2), 1.03 (d, 12H, CHMe2), 1.12 (d, 12H,
CHMe2), 1.75 (s, 6H, CMe), 2.07 (s, 6H, CMe), 2.87
(m, 4H, CHMe2), 3.99 (s, 2H, CH2), 5.33 (s, 2H,
CMeCHCMe), 6.90 (s, 4H, Ph). 13C NMR (CDCl3):
ꢀ11.1 (q, JCH = 112 Hz, AlMe2), 23.1 (q, JCH = 129 Hz,
CMe), 24.4 (q, JCH = 129 Hz, CHMe), 24.6 (q,
JCH = 129 Hz, CHMe), 25.8 (q, JCH = 128 Hz, CMe),
27.9 (d, JCH = 132 Hz, CHMe2), 41.0 (t, JCH = 130 Hz,
CH2), 100.5 (d, JCH = 162 Hz, CMeCHCMe), 124.9 (d,
JCH = 154 Hz, phenyl CH), 136.9 (s, phenyl Cipso), 139.4
(s, phenyl Cipso), 142.7 (s, phenyl Cipso), 176.3 (s, CN),
180.7 (s, CO). Anal. Calc. for C39H60N2O2Al2: C,
72.86; H, 9.41; N, 4.36. Found: C, 72.19; H, 9.04; N,
4.27%.
4.6. Synthesis of [OC(Me)CHC(Me)N(2,6-iPr2C6H2-
4)AlI2]2CH2 (5)
4.4. Synthesis of [OC(Me)CHC(Me)N(2,6-iPr2C6H2-
4)AlEt2]2CH2 (3)
By a similar procedure, the reaction of 2 (3.6 g,
5.6 mmol) with I2 (5.8 g, 22.8 mmol) in toluene gave
1
brown solids 4 in 98% yield (6.0 g). H NMR (CDCl3):
A solution of triethylaluminum (1.9 M in toluene,
9.93 mL, 18.87 mmol) was added dropwise at 0 ꢁC to a
stirred solution of 1 (5.0 g, 9.43 mmol) in methylene
chloride (50 mL). The resulting solution was stirred at
room temperature for 12 h. Volatiles were removed un-
der vacuum to generate yellow solids; which were recrys-
tallized from a diethyl ether solution to yield 6.45 g of
pale yellow solids in 98% yield. 1H NMR (CDCl3):
ꢀ0.23 (m, 8H, AlCH2CH3), 0.84 (t, 12H, AlCH2CH3),
1.05 (d, 12H, CHMe2), 1.16 (d, 12H, CHMe2), 1.75 (s,
6H, CMe), 2.09 (s, 6H, CMe), 2.89 (m, 4H, CHMe2),
d 1.04 (d, 12H, CHMe2), 1.21 (d, 12H, CHMe2), 1.91
(s, 6H, CMe), 2.20 (s, 6H, CMe), 2.95 (m, 2H, CHMe2),
4.01 (s, 2H, CH2), 5.75 (s, 2H, CMeCHCMe), 6.96 (s,
4H, Ph). 13C NMR (CDCl3): d 24.5 (q, JCH = 126 Hz,
CMe), 24.6 (q, JCH = 126 Hz, CHMe), 25.4 (q,
JCH = 127 Hz, CHMe), 25.8 (q, JCH = 129 Hz, CMe),
28.7 (d, JCH = 128 Hz, CHMe2), 41.1 (t, JCH = 130 Hz,
CH2), 103.3 (d, JCH = 162 Hz, CMeCHCMe), 125.5 (d,
JCH = 154 Hz, phenyl CH), 135.1 (s, phenyl Cipso), 140.6
(s, phenyl Cipso), 143.3 (s, phenyl Cipso), 180.3 (s, CN),
182.5 (s, CO). Anal. Calc. for C35H48N2O2Al2I4: C,

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Table 2
The summary of crystallographic data for complexes 2, 3, and 6 Æ THF
2
3
6 Æ THF
Empirical formula
Formula weight
Crystal system
Space group
C39H60Al2N2O2
642.85
monoclinic
C2/c
C43H68Al2N2O2
698.95
monoclinic
P21/c
C43H64B2F4N2O3
754.58
monoclinic
C2/c
˚
a (A)
26.197(15)
8.897(5)
16.620(9)
97.177(12)
3843(4)
4
1.111
0.109
1400
17.5663(12)
14.5083(10)
17.5663(12)
90.0170(10)
4421.6(5)
4
1.050
0.099
1528
25.446(9)
6.951(2)
25.287(8)
90.931(11)
4472(3)
˚
b (A)
˚
c (A)
b (ꢁ)
Volume (A )
3
˚
Z
4
Density (calc.) (Mg mꢀ3
Absorption coefficient (mmꢀ1
F(000)
)
1.121
0.080
1624
)
Crystal size
h Range for data collection (ꢁ)
Reflections collected
0.33 · 0.29 · 0.26 mm
2.42–27.65
11858
0.65 · 0.53 · 0.45 mm
1.17–27.54
27426
0.31 · 0.77 · 0.26 mm
2.25–24.00
11394
Independent reflections (Rint
)
4398 (0.1669)
0.9486 and 0.5667
4398/01/208
0.675
11095 (0.0673)
3490 (0.0952)
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
10095/01/458
0.729
3490/0/249
1.009
R indices [I > 2r(I)]
R indices (all data)
Largest difference peak and hole (e A
R1 = 0.0725, wR2 = 0.1521
R1 = 0.2637, wR2 = 0.1933
0.473 and ꢀ0.361
R1 = 0.0456, wR2 = 0.1076
R1 = 0.1304, wR2 = 0.1359
0.232 and ꢀ0.184
R1 = 0.0865, wR2 = 0.2397
R1 = 0.1168, wR2 = 0.2626
0.663 and ꢀ0.410
ꢀ3
˚
)
38.56; H, 4.44; N, 2.57. Found: C, 38.10; H, 4.38; N,
2.43%.
of 6 were obtained directly from the sublimation of vis-
cous complex 6 by storing it in glove box. Crystals of 2
and 6 were mounted on a goniostat and data collections
were preceded at 150(2) K and data of crystal of 3 were
collected at 298(2) K. Data were collected on a Bruker
SMART CCD diffractometer with graphite-monochro-
mated Mo Ka radiation. Structure determinations were
made using the SHELXTL package of programs. All refine-
ments were carried out by full-matrix least squares using
anisotropic displacement parameters for all non-hydro-
gen atoms. All the hydrogen atoms are added at calcu-
lated positions. The crystal data are summarized in
Table 2.
4.7. Synthesis of [OC(Me)CHC(Me)N(2,6-iPr2C6H2-
4)BF2]2CH2 (6)
To a 50 mL Schlenk flask containing 4 (0.5 g,
0.46 mmol) and AgBF4 (0.18 g, 0.92 mmol) was added
20 mL toluene and heated at 90 ꢁC for 8 h. The solution
was filtered through Celite and volatiles were removed
under vacuum. The resulting solids were recrystallized
from a toluene solution to generate 0.050 g of yellow sol-
1
ids in 18% yield. H NMR (CDCl3): d 1.07 (d, 12H,
CHMe2), 1.20 (d, 12H, CHMe2), 1.82 (m, THF), 1.88
(s, 6H, CMe), 2.19 (s, 6H, CMe), 2.80 (m, 2H, CHMe2),
3.72 (m, THF), 3.96 (s, 2H, CH2), 5.56 (s, 2H,
CMeCHCMe), 7.02 (s, 4H, Ph). 13C NMR (CDCl3): d
21.2 (q, JCH = 129 Hz, CMe), 22.8 (q, JCH = 130 Hz,
5. Supporting material
Crystallographic data for the structures reported in
this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publica-
tions nos. CCDC – 264287 (2), CCDC – 264286 (3) and
CCDC – 264285 (6). Copies of the data can be obtained
free of charge on application to The Director, CCDC,
12 Union Road, Cambridge CB2 1EZ, UK, fax: +44
1223 336 033, e-mail: deposit@ccdc.cam.ac.uk or on
the web www: http://www.ccdc.cam.ac.uk.
CMe), 24.2 (q, JCH = 132 Hz, CHMe), 24.5 (q, JCH
126 Hz, CHMe), 28.3 (d, JCH = 131 Hz, CHMe2), 41.6
(t, JCH = 132 Hz, CH2), 67.9 (t, THF), 98.7 (d, JCH
=
=
168 Hz, CMeCHCMe), 124.9 (d, JCH = 153 Hz, phenyl
CH), 132.5 (s, phenyl Cipso), 140.8 (s, phenyl Cipso),
144.6 (s, phenyl Cipso), 172.9 (s, CN), 176.8 (s, CO). 11B
NMR (CDCl3): d 0.67 (t, JBF = 15.4 Hz). MS (FAB):
607 (M ꢀ F), 320 (M ꢀ 306).
4.8. X-ray structure determination of complexes 2, 3, and
6
Acknowledgments
Crystals of complex 2 were obtained from a concen-
trated diethyl ether solution of 2 at ꢀ20 ꢁC. Crystals
We thank the National Science Council of Taiwan for
financial support and the National Center for High

P.-C. Kuo et al. / Inorganica Chimica Acta 358 (2005) 3761–3767
3767
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