Synthesis and structural aspects of gallium compounds containing tridentate pincer type pyrrolyl ligands: Intramolecular hydrogen bonding of gallium aryloxides

Article abstract of DOI:10.1016/j.jorganchem.2013.07.012

A series of gallium derivatives incorporating with pincer type tridentate symmetric and asymmetric pyrrolyl ligands are conveniently synthesized. Compilation of a symmetrical tridentate pyrrole ligand, [C₄H ₂NH-(2,5-CH₂NH^tBu)₂] (1) with one equiv of n-BuLi in heptane generates lithiated 1 that turns to Ga[C ₄H₂N-(2,5-CH₂NH^tBu) ₂]Cl₂ (2) subjecting the addition of GaCl ₃/ether suspension into diethyl ether. Reacting 2 with two equiv of lithium reagents (LiR) in same solvent originates a series of gallium compounds Ga[C₄H₂N-(2,5-CH₂NH^tBu) ₂]R₂ (3, R = Me; 4, R = O-C₆H₄-4-Me; 5, R = O-C₆H₃-2,6-Me₂) in moderate yield through metathesis reactions. Furthermore, the combination of a tridentate asymmetrical pyrrole ligand, [C₄H₂NH(2-CH ₂NH^tBu)(5-CH₂NMe₂)] and n-BuLi initiates the lithiated 6 that undergoes the formation of a penta-coordinated gallium compound GaCl₂[C₄H₂N(2-CH ₂NH^tBu)(5-CH₂NMe₂)] (7) while reacting with GaCl₃. Furthermore, reacting 7 with two equivs of MeLi affords the gallium-alkyl compound, GaMe₂[C₄H ₂N(2-CH₂NH^tBu)(5-CH₂NMe ₂)] (8) in high yield. The Ga-derivatives are characterized by ¹H and ¹³C NMR spectroscopy and the molecular structures of 2, 3, 4, 5 and 7 are determined by single crystal X-ray diffractometry in solid state.

Full text of DOI:10.1016/j.jorganchem.2013.07.012

Journal of Organometallic Chemistry 745-746 (2013) 12e17
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and structural aspects of gallium compounds containing
tridentate pincer type pyrrolyl ligands: Intramolecular hydrogen
bonding of gallium aryloxides
Yu-Tang Wang a, Yi-Chien Lin a, Shu-Ya Hsu a, Ren-Yung Chen a, Pei-Hsin Liu a,
,
Amitabha Datta a, Chia-Her Lin b, Jui-Hsien Huang a
*
a Department of Chemistry, National Changhua University of Education, Changhua 50058, Taiwan
b Department of Chemistry, Chung-Yuan Christian University, Chung-Li 320, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of gallium derivatives incorporating with pincer type tridentate symmetric and asymmetric
pyrrolyl ligands are conveniently synthesized. Compilation of a symmetrical tridentate pyrrole ligand,
[C4H2NH-(2,5-CH2NHtBu)2] (1) with one equiv of n-BuLi in heptane generates lithiated 1 that turns to Ga
[C4H2N-(2,5-CH2NHtBu)2]Cl2 (2) subjecting the addition of GaCl3/ether suspension into diethyl ether.
Reacting 2 with two equiv of lithium reagents (LiR) in same solvent originates a series of gallium
compounds Ga[C4H2N-(2,5-CH2NHtBu)2]R2 (3, R ¼ Me; 4, R ¼ OeC6H4e4-Me; 5, R ¼ OeC6H3e2,6-Me2)
in moderate yield through metathesis reactions. Furthermore, the combination of a tridentate asym-
metrical pyrrole ligand, [C4H2NH(2-CH2NHtBu)(5-CH2NMe2)] and n-BuLi initiates the lithiated 6 that
undergoes the formation of a penta-coordinated gallium compound GaCl2[C4H2N(2-CH2NHtBu)(5-
CH2NMe2)] (7) while reacting with GaCl3. Furthermore, reacting 7 with two equivs of MeLi affords the
gallium-alkyl compound, GaMe2[C4H2N(2-CH2NHtBu)(5-CH2NMe2)] (8) in high yield. The Ga-derivatives
are characterized by 1H and 13C NMR spectroscopy and the molecular structures of 2, 3, 4, 5 and 7 are
determined by single crystal X-ray diffractometry in solid state.
Received 25 April 2013
Received in revised form
3 July 2013
Accepted 4 July 2013
Keywords:
Gallium
Pyrrolyl
Tridentate
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
{2,5-(CH2NMe2)2}] [32,33] as auxiliary ligands with early transition
metals [34e36] or group 13 metals [37,38] to form organometallic
Gallium compounds containing nitrogen-donor tridentate li-
gands were studied and used in various applications in past de-
cades [1e3]. These gallium compounds can be used as catalysts
for ring opening polymerization [4e7] and olefin polymerization
[8e11], metal-based drugs [12e17] and as precursor for chemical
vapor deposition [18e22]. The NNN tridentate ligands, coupled in
gallium entity are shown in Scheme 1 where (a) and (b) act as
neutral ligands and (c)e(g) function as mono anionic ligands [23e
31]. Considering different ligand moieties, pyrrolyl system is well
capable to bring metal atoms into close proximity and furnishes an
intramolecular or intermolecular pathway for bonding interactions.
In whatever manner, relatively few metal-pyrrole compounds
have been found to be synthetically useful with substituted
pyrrole based architecture. In our previous articles, we have
employed bi- or tri-dentate, substituted pyrrolyl ligands [C4H3N
compounds, and we assessed their reactivity toward small organic
molecules.
As an extension of our prolonged interest in the pyrrolyl
mediated precursors, the current contribution focuses the synthe-
sis and characterizations of a series of gallium compounds con-
taining NNN symmetric and asymmetric tridentate ligands
(Schemes 2 and 3).
2. Results and discussion
2.1. Synthesis and characterization
A series of gallium compounds containing tridentate pincer
type symmetric and asymmetric pyrrole ligands, [C4H2NH-(2,5-
CH2NHtBu)2] and [C4H2NH(2-CH2NHtBu)(5-CH2NMe2)], were syn-
thesized and characterized by NMR spectroscopy and single crystal
X-ray diffractometry. Reacting [C4H2NH-(2,5-CH2NHtBu)2] (1) with
one equiv of n-BuLi in heptane generates lithiated 1 that undergoes
* Corresponding author. Tel.: þ886 4 7232105x3512; fax: þ886 4 7211190.
E-mail address: juihuang@cc.ncue.edu.tw (J.-H. Huang).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.07.012

Y.-T. Wang et al. / Journal of Organometallic Chemistry 745-746 (2013) 12e17
13
Scheme 1. NNN tridentate ligands used in gallium compounds.
with GaCl3/ether suspension in diethyl ether to yield Ga[C4H2N-
intra-molecular hydrogen bonding, tBuNH.OeC6H4e4-Me [42].
Nevertheless, the bulky OeC6H3e2,6-Me2 group in 5 prohibits the
hydrogen bonding as tBuNH.OeC6H3e2,6-Me2.
Similarly, when the tridentate asymmetrical pyrrole ligand
[C4H2NH(2-CH2NHtBu)(5-CH2NMe2)] is compiled with n-BuLi
and GaCl3, a five-coordinated gallium compound GaCl2[C4H2N(2-
CH2NHtBu)(5-CH2NMe2)] (7) forms in moderate yield. Further-
more, the condensation between 7 and two equivs of MeLi af-
fords gallium-methyl compound, GaMe2[C4H2N(2-CH2NHtBu)(5-
CH2NMe2)] (8) in high yield. 1H NMR spectrum of 7 in CDCl3
(2,5-CH2NHtBu)2]Cl2 (2) in 75% yield. Compound 2 shows one
distinct doublet at d
3.45 in the 1H NMR spectrum representing the
methylene protons of the CH2NHtBu fragment [39e41]. The doublet
3
is raised by the JHH coupling of corresponding methylene and
amine proton.
Reacting 2 with two equivs of lithium reagents (LiR) in diethyl
ether initiates a series of gallium compounds Ga[C4H2N-(2,5-CH2
NHtBu)2]R2 (3, R ¼ Me; 4, R ¼ OeC6H4e4-Me; 5, R ¼ OeC6H3e2,6-
Me2) in moderate yield through metathesis pathways. The methy-
lene protons of CH2NHtBu fragments of 3e5 show similar 1H NMR
shows one singlet and one doublet at
d 3.63 and 3.90 for corre-
chemical shift in the range of
chemical shift of amino proton of CH2NHtBu fragment in 3e5, they
belong at 2.10, 1.03, and 2.50, respectively. Among these, com-
d
3.67e3.59. It is noticed that the
sponding methylene protons of CH2NMe2 and CH2NHtBu frag-
ments, respectively. The amino proton of NHtBu appears at
d
d 2.32, quite similar with 2, 3, and 5. In compound 8, the
pounds 3 and 5 show quite similarity with 2, however, 4 remains in
more up-field region than previous ones. This phenomenon can be
described as the consequence of less steric congestion in 4, facing an
chemical shift of corresponding methyl fragments of GaMe2
appears at ꢀ0.28 and ꢀ6.6, respectively for its 1H and 13C NMR
resonances.
Scheme 2. Synthesis of compounds 1e5.

14
Y.-T. Wang et al. / Journal of Organometallic Chemistry 745-746 (2013) 12e17
Scheme 3. Synthesis of compounds 7 and 8.
2.2. Molecular geometries of compounds 2, 3, 4, 5, and 7
in d8-toluene. Apparently, the two NHtBu fragments attached to
gallium atom belong to an oneoff manner having faster fluxionality
rate than the NMR time scale [44].
The molecular geometries of 2e5 and 7 are determined by X-ray
single crystal diffractometer and their data collections and selected
bond lengths and angles are summarized in Tables 1 and 2,
respectively. The corresponding ORTEP’s of 2, 3, 4, 5, and 7 are
depicted in Figs.1e5. Red crystals of 2 are obtained from a saturated
diethyl ether solution at ꢀ20 ꢁC. The five-coordinated gallium
center possesses on a distorted trigonal bipyramidal environment
where two nitrogen atoms of corresponding CH2NHtBu fragments
occupy the axial positions with N(2)eGa(1)eN(3) bond angle as
152.54(4)ꢁ. The Npyrrolyl and adjacent two chlorine atoms configures
a trigonal plane where sum of the three bond angles, N(1)eGa(1)e
Cl(3), N(1)eGa(1)eCl(2), and Cl(2)eGa(1)eCl(3), is ca. 360ꢁ. The
NNO donor sites of substituted pyrrole precursor here conforms
a mer-type orientation. The Ga(1)eCl(2) and Ga(1)eCl(3) bond
Both the molecular geometries, 4 and 5 are very similar to that of
2 and 3. The central Ga atom achieves a trigonal bipyramidal ge-
ometry, into which the two NHtBu fragments of tridentate pyrrolyl
ligand occupy the axial positions with bond angles of 153.96(8) and
155.89(4)ꢁ, respectively. The gallium derivatives consisting two
equiv of mono-dentate aryloixde are rare [45,46]. Interestingly,
compounds 4 and 5 belong to this phenomenon. The GaeO and Gae
OeC(phenyl) bond angles are governed by steric hindrance and
electronic effect, raised from substituted phenyl groups and corre-
sponding GaeO binding modes. The GaeO bond lengths of 4 and 5
ꢀ
are extending from 1.816 to 1.819 A, well comparable with previous
literature [47e51]. The GaeOeCPh bond angle belongs at a range of
122.12e134.8ꢁ, depending upon the outer environment of gallium
atom and substituents on phenyl rings [52]. It is observed that the
ꢀ
lengths, 2.1806(4) and 2.1520(5) A, are comparable with earlier
ꢀ
literature [26,30,43]. The related GaeNpyrrole bond length,
GaeNpyrrolyl bond distance in 3 [1.924(3) A] is quite larger than in
ꢀ
ꢀ
1.8636(11) A, is well consistent with previous reports [32,33] where
compounds 2, 4 and 5 [1.8636(11), 1.872(2) and 1.8665(11) A,
N atom coincides from non-porphyrine and non-conjugated pyr-
rolyl system. Red crystals of 3 are obtained applying same condition
like in 2. In 3, the Ga atom adopts a five-coordinated trigonal
bipyramidal geometry with two axial N atoms of NHtBu fragments.
In contrast, the corresponding GaeNNHtBu bond length in 2
respectively], probably due to steric congestion, caused by two
methyl groups that facilitates longer GaeNpyrrolyl bond. The bond
angles of GaeOeCPh are 125.35(15)ꢁ and 132.06(15)ꢁ for 4 and
131.84(9)ꢁ and 134.19(9)ꢁ for 5. It is observed that one GaeOeCPh
angle in 4 is much smaller than others, presumably due to the for-
mation of an intramolecular hydrogen bonding between aryloxide
ꢀ
[(2.295(1) and 2.357(1) A)] may be assumed as symmetrical
t
ꢀ
manner where as in 3, the bond lengths, [(2.354(3) and 2.741(3) A)],
oxygen and BuNH amino hydrogen atoms [47,53,54]. The N(1)e
ꢀ
are considered as unsymmetrical binding mode due to some extent
of deviation. This result differs with the 1H NMR spectrum of 3
where one kind of tBu and GaMe resonance appear even at ꢀ30 ꢁC
O(2) bond length, 2.93 A falls in same range considering intra-
molecular hydrogen bonding [55]. The NeH.O hydrogen bond
ꢀ
distances in 4 [2.478 and 2.793 A] belong in normal range.
Table 1
Crystallographic data for compounds 2, 3, 4, 5 and 7.
2
3
4
5
7
Formula
Fw
C14H26Cl2GaN3
377.00
C16H32GaN3
336.17
C28H40GaN3O2
520.35
C30H44GaN3O2
548.40
C12H22Cl2GaN3
348.95
Crystal system
Space group
Monoclinic
P 21/c
12.7299(18)
12.0361(18)
11.7848(17)
90
101.258(7)
90
1770.9(4)/4
1.414
Triclinic
P ꢀ 1
Monoclinic
P 21/c
9.5010(9)
27.736(3)
10.4766(10)
90
104.053(6)
90
2678.2(4)/4
1.291
Triclinic
P ꢀ 1
Monoclinic
P 21/c
9.223(2)
9.536(3)
18.678(5)
90
97.901(16)
90
1627.1(8)/4
1.424
ꢀ
a [A]
9.1133(14)
9.8728(15)
10.9690(17)
101.515(10)
95.558(10)
101.396(9)
938.4(2)/2
1.190
9.1170(4)
11.7809(6)
13.8447(7)
84.432(3)
80.838(3)
78.538(2)
1435.47(12)/2
1.269
ꢀ
b [A]
ꢀ
c [A]
a
b
g
[ꢁ]
[ꢁ]
[ꢁ]
3
ꢀ
V [A ], Z
Dcalcd. [Mg m3]
Absorption coeff. [mmꢀ1
T [K]
]
1.850
149(2)
1.463
150(2)
1.506
150(2)
0.989
149(2)
2.008
150(2)
F(000)
784
360
1104
584
720
Reflections collected
Independent reflections
31,166
4605 (Rint ¼ 0.0471]
14,262
37,505
22,293
17,500
4817 (Rint ¼ 0.0387)
4817/0/189
1.050
6924 (Rint ¼ 0.0607)
6924/0/315
1.008
10,083 (Rint ¼ 0.0379)
10,083/0/335
1.024
4157 (Rint ¼ 0.1010)
4157/0/168
1.027
Data/restraints/parameters 4605/0/187
Goodness of fit on F2
1.033
Final R indices [I > 2
R indices (all data)
s
(I)] R1 ¼ 0.0227, wR2 ¼ 0.0577 R1 ¼ 0.0582, wR2 ¼ 0.1483 R1 ¼ 0.0445, wR2 ¼ 0.1176 R1 ¼ 0.0389, wR2 ¼ 0.1044 R1 ¼ 0.0396, wR2 ¼ 0.1198
R1 ¼ 0.0281, wR2 ¼ 0.0600 R1 ¼ 0.0817, wR2 ¼ 0.1655 R1 ¼ 0.0629, wR2 ¼ 0.1279 R1 ¼ 0.0507, wR2 ¼ 0.1109 R1 ¼ 0.1243, wR2 ¼ 0.1911
Largest diff.
peak/hole [eA
0.325/ꢀ0.334
1.529/ꢀ1.074
1.199/ꢀ0.623
1.226/ꢀ0.921
0.808/ꢀ0.943
ꢀꢀ3
]

Y.-T. Wang et al. / Journal of Organometallic Chemistry 745-746 (2013) 12e17
15
Table 2
ꢁ
ꢀ
Selected bond angles ( ) and lengths (A) of compounds 2, 3, 4, 5, and 7.
2
Ga(1)eN(1)
Ga(1)eCl(3)
Ga(1)eCl(2)
N(1)eGa(1)eCl(3)
N(1)eGa(1)eCl(2)
Cl(3)eGa(1)eCl(2)
1.8636(11)
2.1520(5)
2.1806(4)
123.98(4)
122.67(4)
113.338(17)
Ga(1)eN(2)
Ga(1)eN(3)
2.295(1)
2.357(1)
N(2)eGa(1)eN(3)
N(1)eGa(1)eN(3)
N(1)eGa(1)eN(2)
152.54(4)
76.55(5)
78.09(5)
3
Ga(1)eN(1)
2.741(3)
1.963(4)
1.953(4)
115.09(16)
117.84(17)
125.0(2)
Ga(1)eN(2)
Ga(1)eN(3)
1.924(3)
2.354(3)
Ga(1)eC(15)
Ga(1)eC(16)
N(2)eGa(1)eC(15)
N(2)eGa(1)eC(16)
C(15)eGa(1)eC(16)
N(2)eGa(1)eN(3)
N(1)eGa(1)eN(3)
N(1)eGa(1)eN(2)
77.08(11)
147.63(9)
70.5(1)
Fig. 2. The molecule structure of compound 3, thermal ellipsoids were drawn at 30%
probability. Hydrogen atoms attached to carbon atoms were omitted for clarity.
4
Ga(1)eN(1)
Ga(1)eN(2)
Ga(1)eO(2)
C(8)eO(2)
N(1)eGa(1)eN(3)
N(2)eGa(1)eO(1)
N(2)eGa(1)eN(3)
Ga(1)eO(1)eC(1)
2.206(2)
1.872(2)
1.8157(16)
1.356(3)
153.95(8)
127.47(8)
73.36(8)
Ga(1)eN(3)
Ga(1)eO(1)
C(1)eO(1)
2.502(3)
1.8194(16)
1.360(3)
small organic molecules using symmetric and asymmetric tri-
dentate precursors. The enhancement of substituted pyrrolyl-
N(2)eGa(1)eO(2)
O(1)eGa(1)eO(2)
N(1)eGa(1)eN(2)
Ga(1)eO(2)eC(8)
117.30(8)
114.65(7)
80.58(8)
linked anionic ligands with Ga-compounds subjecting -capro-
3
lactone and/or ethylene polymerization in the presence of MAO as
co-catalyst is under investigation as well.
125.35(15)
132.06(15)
5
Ga(1)eN(1)
Ga(1)eN(2)
Ga(1)eO(2)
O(2)eC(37)
N(1)eGa(1)eN(3)
N(2)eGa(1)eO(1)
N(2)eGa(1)eN(3)
Ga(1)eO(1)eC(29)
2.3192(12)
1.8665(11)
1.8197(9)
1.3529(16)
155.89(4)
123.58(5)
78.46(5)
Ga(1)eN(3)
Ga(1)eO(1)
O(1)eC(29)
2.2847(12)
1.8189(10)
1.3562(16)
4. Experimental
4.1. General procedures
N(2)eGa(1)eO(2)
O(1)eGa(1)eO(2)
N(1)eGa(1)eN(2)
Ga(1)eO(2)eC(37)
122.99(5)
113.40(5)
77.46(5)
All reactions were performed under a dry nitrogen atmosphere
using standard Schlenk techniques or glove box. Diethyl ether was
dried by refluxing over sodium benzophenone ketyl, distilled and
131.84(9)
134.19(9)
ꢀ
7
stored in solvent reservoir which contained 4A molecular sieves
and was purged with nitrogen. 1H and 13C NMR spectra were
recorded on a Bruker Avance 300 spectrometer. Chemical shifts for
1H and 13C spectra were recorded in ppm relative to the residual
Ga(1)eN(1)
1.849(4)
2.1698(14)
2.1630(12)
129.03(12)
117.57(12)
113.37(7)
Ga(1)eN(2)
Ga(1)eN(3)
2.254(4)
2.402(3)
Ga(1)eCl(1)
Ga(1)eCl(2)
N(1)eGa(1)eCl(1)
N(1)eGa(1)eCl(2)
Cl(1)eGa(1)eCl(2)
N(2)eGa(1)eN(3)
N(1)eGa(1)eN(3)
N(1)eGa(1)eN(2)
152.02(13)
75.71(15)
79.06(15)
protons and 13C of CDCl3 (7.24, 77.0) and C6D6
(d 7.15, 128.0).
Elemental analyses were performed on a Heraeus CHN-OS Rapid
Elemental Analyzer at the Instrument Center, NCHU. Due to high
moisture sensitivity and rapid decomposition, the elemental ana-
lyses of some metal complexes could not be performed. The ligands
[C4H2NH(2,5-CH2NHtBu)2] (1) and [C4H2NH(2-CH2NHtBu)(5-CH2
NMe2)] (6) were prepared according to previous procedure [41].
3. Conclusion
The reactions of GaCl3 and small organic molecules like LiOe
C6H4e4-Me, LiOeC6H3e3,5-Me2 as well as Li-alkyls with tridentate
symmetrical and asymmetrical pincer type pyrrolyl ligands, are
concluded to form several Ga-derivatives. All the compounds are
fully characterized by NMR spectroscopy and single crystal X-ray
diffractometry in solid state. We have highlighted mainly the
structural diversity of different gallium aryloxides by intra-
molecular H-bonding. We will extend our research to synthesize
different metal derivatives compiled with Group IV elements and
Fig. 1. The molecule structure of compound 2, thermal ellipsoids were drawn at 30%
Fig. 3. The molecule structure of compound 4, thermal ellipsoids were drawn at 30%
probability. Hydrogen atoms attached to carbon atoms were omitted for clarity.
probability. Hydrogen atoms attached to carbon atoms were omitted for clarity.

16
Y.-T. Wang et al. / Journal of Organometallic Chemistry 745-746 (2013) 12e17
4.2.2. Synthesis of Ga[C4H2N(2,5-CH2NHtBu)2]Me2 (3)
To a solution of 2 (0.50 g, 1.33 mmol) in 15 mL diethyl ether in a
Schlenk flask was added dropwise a solution of MeLi (2.67 mmol,
1.78 mL, 1.5 M in ethyl ether) at ꢀ78 ꢁC. The mixture was stirred at
room temperature for 5 h and filtered through Celite. The filtrate
was vacuum dried and solid was recrystallized from a saturated
diethyl ether solution at ꢀ20 ꢁC to give 0.25 g of red crystals 3
in 46% yield. 1H NMR (C6D6): 0.05 (s, 6H, Ga-Me), 0.89 (s, 18H,
NHCMe3), 2.1 (t, 1H, NHCMe3), 3.67 (d, JHH ¼ 7.8 Hz, 4H,
CH2NHCMe3), 6.41 (s, 2H, pyrrole CH). 13C NMR (C6D6) : ꢀ3.05
(q, JCH ¼ 121 Hz, GaMe2), 28.3 (q, JCH ¼ 125 Hz, NHCMe3), 41.8
(t, JCH ¼ 134 Hz, CH2NHCMe3), 51.9 (s, NHCMe3), 104.1 (d,
JCH ¼ 163 Hz, pyrrole CH), 132.39 (s, pyrrolyl Cipso). Anal. Calcd. for
C
16H32GaN3: C, 57.17; H, 9.59; N, 12.50. Found: C, 56.38; H, 8.97; N,
12.23.
4.2.3. Synthesis of Ga[C4H2N(2,5-CH2NHtBu)2](OC6H4e4-Me)2 (4)
Similar procedure as shown in 3 was employed. Compound 2
(0.50 g, 1.33 mmol) and LiOeC6H4e4-Me (0.34 g, 2.98 mmol) were
used. Dark red solid was obtained in 85% yield (0.58 g). 1H NMR
(C6D6): 0.97 (s, 9H, NHCMe3), 1.03 (t, 2H, NHCMe3), 2.10 (s, 6H, p-
PhMe), 3.60 (br, 4H, CH2NHCMe3), 6.45 (s, 2H, pyrrole CH), 6.79,
6.93 (m, phenyl CH). 13C NMR (C6D6): 20.6 (q, JCH ¼ 125 Hz, PhMe),
27.7 (q, JCH ¼ 125 Hz, NHCMe3), 41.1 (t, JCH ¼ 139 Hz, CH2NHCMe3),
53.8 (s, NHCMe3), 107.2 (d, JCH ¼ 155 Hz, pyrrolyl CH), 127.3 (s,
pyrrolyl Cipso), 130.0 (d, phenyl CH), 130.5 (d, phenyl CH), 131.6 (s,
phenyl Cipso), 158.7 (s, phenyl Cipso).
Fig. 4. The molecule structure of compound 5, thermal ellipsoids were drawn at 30%
probability. Hydrogen atoms attached to carbon atoms were omitted for clarity.
Lithiated 1 and 6 were obtained by reacting 1 and 6 with equal
molar of n-BuLi in heptane at 0 ꢁC, followed by filtration and dry-
ness to yield the lithium salt of 1 and 6. All the chemicals (Aldrich,
Acros) were used as received.
4.2.4. Synthesis of Ga[C4H2N(2,5-CH2NHtBu)2](OeC6H3e2,6-Me2)2
(5)
4.2. Synthesis of the compounds
Similar procedure as for synthesizing compound 3 was adopted.
Compound 2 (0.50 g, 1.33 mmol) and LiOeC6H3e2,6-Me2 (0.35 g,
2.73 mmol) were used. Dark red solid was obtained (0.60 g, 83%). 1H
NMR (C6D6): 0.85 (s, 18H, NHCMe3), 2.24 (s, 12H,C6H3-Me2), 2.50 (t,
2H, NHCMe3), 3.59 (s, 4H, CH2NHCMe3), 6.31 (s, 2H, pyrrole CH),
6.76, 7.01 (m, phenyl CH). 13C NMR (C6D6): 18.0 (q, JCH ¼ 128 Hz,
C6H3Me2), 27.6 (q, JCH ¼ 126 Hz, NHCMe3), 41.1 (t, JCH ¼ 138 Hz,
CH2NHCMe3), 53.7 (s, NHCMe3), 106.0 (d, JCH ¼ 165 Hz, pyrrolyl CH),
119.2 (d, JCH ¼ 160 Hz, o-Me2C6H3), 125.6 (d, JCH ¼ 160 Hz, pyrrolyl
Cipso), 129.1 (t, JCH ¼ 160 Hz, phenyl CH), 129.3 (s, phenyl Cipso), 158.1
(s, phenyl Cipso).
4.2.1. Synthesis of Ga[C4H2N-(2,5-CH2NHtBu)2]Cl2 (2)
To a 15 mL diethyl ether solution of GaCl3 (3.0 g, 17.04 mmol)
was added dropwise
a
Li[C4H2N-(2,5-CH2NHtBu)2] (4.15 g,
17.04 mmol) diethyl ether solution (15 mL) at ꢀ78 ꢁC. The solution
was stirred at room temperature for 5 h and filtered off through
Celite. The filtrate was dried under vacuum to form red solid. The
solid was recrystallized from a saturated diethyl ether solution at
ꢀ20 ꢁC to generate red crystals of 2 in 85 yield. 1H NMR (C6D6): 1.06
(s, 18H, NHCMe3), 2.14 (t, 2H, NHCMe3), 3.45 (d, JHH ¼ 8.1 Hz, 4H,
CH2NHCMe3), 6.27 (s, 2H, pyrrolyl CH). 13C NMR (C6D6): 28.2 (q,
JCH ¼ 126 Hz, NHCMe3), 41.0 (t, JCH ¼ 138 Hz, CH2NHCMe3), 54.5 (s,
NHCMe3), 105.6 (d, JCH ¼ 166 Hz, pyrrolyl CH), 129.8 (s, pyrrolyl
Cipso). Anal. Calcd. for C14H26Cl2GaN3: C, 44.60; H, 6.95; N, 11.15.
Found: C, 45.19; H, 7.15; N, 11.37.
4.2.5. Synthesis of Ga[C4H2N(2-CH2NHtBu)(5-CH2NMe2)]Cl2 (7)
Similar procedure was applied as in 2. Ligand 6 (5.00 g,
23.89 mmol), n-BuLi (9.55 mL, 23.89 mmol, 2.5 M in hexane) and
GaCl3 (4.21 g, 23.89 mmol) were used and 6.98 g of 7 was obtained
(yield 84%). 1H NMR (CDCl3): 1.38 (s, 9H, NHCMe3), 2.32 (t, br, 1H,
NHCMe3), 2.53 (s, 6H, NMe2), 3.63 (s, 2H, CH2NMe2), 3.90 (d,
JHH ¼ 8.4 Hz, 2H, CH2NHCMe3), 5.97 (d, 2H, pyrrolyl CH). 13C NMR
(CDCl3): 28.4 (q, JCH ¼ 126 Hz, NHCMe3), 40.8 (t, JCH ¼ 137.4 Hz,
CH2NHCMe3), 46.6 (q, JCH ¼ 137 Hz, NMe2), 54.7 (s, NHCMe3), 58.4
(t, JCH ¼ 134 Hz, CH2NMe2), 104.2 (d, JCH ¼ 115 Hz, pyrrolyl CH),
105.7 (d, JCH ¼ 115 Hz, pyrrolyl CH), 127.8 (s, pyrrolyl Cipso), 130.0 (s,
pyrrolyl Cipso). Anal. Calcd. for C12H22Cl2GaN3: C, 41.30; H, 6.36; N,
12.04. Found: C, 41.37; H, 6.77; N, 12.06.
4.2.6. Synthesis of Ga[C4H2N(2-CH2NHtBu)(5-CH2NMe2)]Me2 (8)
Similar procedure was adopted as in 3. Compound 7 (0.50 g,
1.44 mmol) and LiMe (1.92 mL, 2.87 mmol, 1.5 M in ethyl ether)
were used. 1H NMR (CDCl3): ꢀ0.28 (s, 6H, GaMe2), 1.18 (s, 9H,
NHCMe3), 2,32 (s, 6H, NMe2), 3.51 (s, 2H, CH2NMe2), 3.76 (d,
JHH ¼ 8.4 Hz, 2H, CH2NHCMe3), 5.92 (d, JHH ¼ 3.3 Hz, 2H, pyrrolyl
CH). 13C NMR (CDCl3): ꢀ6.6 (q, JCH ¼ 122 Hz, GaMe2), 28.9 (q,
JCH ¼ 126 Hz, NHCMe3), 41.1 (t, JCH ¼ 138 Hz, CH2NHCMe3), 45.9 (q,
JCH ¼ 136 Hz, NMe2), 51.9 (s, NHCMe3), 59.1 (t, JCH ¼ 137 Hz,
Fig. 5. The molecule structure of compound 7, thermal ellipsoids were drawn at 30%
probability. Hydrogen atoms attached to carbon atoms were omitted for clarity.

Y.-T. Wang et al. / Journal of Organometallic Chemistry 745-746 (2013) 12e17
17
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CH2NMe2), 102.9 (d, JCH ¼ 30 Hz, pyrrolyl CH), 103.3 (d, JCH ¼ 31 Hz,
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4.3. X-ray crystallography
Suitable crystals of compounds 2e5, and 7 were attached to a
fine glass fiber with paratone oil and mounted in goniostat for data
collection. Data collections were performed at 150 K under liquid
nitrogen vapor for all compounds. Data were collected on a Bruker
SMART CCD diffractometer with graphite monochromated Mo-Ka
radiation. No significant crystal decay was found. Data were cor-
rected for absorption empirically by means of
j scans. All non-
hydrogen atoms were refined with anisotropic displacement pa-
rameters. For all the structures, the hydrogen atom positions were
calculated and they were constrained to idealized geometries and
treated as riding where the H atom displacement parameter was
calculated from the equivalent isotropic displacement parameter of
the bound atom. An absorption correction was performed with the
program SADABS [56] and the structures of all compounds were
determined by direct methods procedures in SHELXS [57] and
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[58]. All the relevant crystallographic data and structure refinement
parameters are summarized in Table 1.
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Acknowledgments
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Organometallics 20 (2001) 5788e5791.
The authors gratefully acknowledge the National Science
Council of Taiwan for financial assistance. We would also like to
thank the National Changhua University of Education for providing
the X-ray diffractometer and NMR spectrometer.
[37] J.-H. Huang, H.-J. Chen, J.-C. Chang, C.-C. Zhou, G.-H. Lee, S.-M. Peng, Organ-
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Appendix A. Supplementary material
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CCDC 932458e932462 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Center via www.
ccdc.cam.ac.uk/data_request/cif.
Appendix B. Supplementary data
Supplementary material associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/j.jorgan
chem.2013.07.012.
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