Synthesis of phenols and naphthol with n-morpholinomethyl pendants and their dimethylgallium complexes: Crystal structure of dimethylgallium-[4-nitro-2-(n-morpholinomethyl)-1-phenoxide]

Article abstract of DOI:10.1016/S0022-328X(99)00148-5

The one-pot Mannich reaction was used to synthesize 2-(n-morpholinomethyl)-1-phenol (1a), 4-methyl-2-(n-morpholinomethyl)-1-phenol (1b), 4-chloro-2-(n-morpholinomethyl)-1-phenol (1c), 4-nitro-2-(n-morpholinomethyl)-1-phenol (1d), and 1-(n-morpholinomethyl)-naphthol (1e). The dimethylgallium complexes of these compounds have been prepared, and compound 2d has been determined by X-ray crystallography. The complex 2d crystallized with one unit having two identical molecules which have intermolecular contacts between the two phenyls caused by face to face π-π stacking. The Ga-O bond distances are noticeably shorter than in the other dimethylgallium phenoxides reported.

Full text of DOI:10.1016/S0022-328X(99)00148-5

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 584 (1999) 240–245
Synthesis of phenols and naphthol with n-morpholinomethyl
pendants and their dimethylgallium complexes: crystal structure of
dimethylgallium-[4-nitro-2-(n-morpholinomethyl)-1-phenoxide]
Jing-zhi Tian a, Jin-qi Zhang a,*, Xi Shen a, Hui-xian Zou b
a Department of Chemistry, Nanjing Uni6ersity, Nanjing 210093, PR China
b Department of En6ironmental Science and Engineering, State Key Laboratory of Pollution and Resource Reuse, Nanjing Uni6ersity,
Nanjing 210093, PR China
Received in revised form 10 March 1999
Abstract
The one-pot Mannich reaction was used to synthesize 2-(n-morpholinomethyl)-1-phenol (1a), 4-methyl-2-(n-morpholi-
nomethyl)-1-phenol (1b), 4-chloro-2-(n-morpholinomethyl)-1-phenol (1c), 4-nitro-2-(n-morpholinomethyl)-1-phenol (1d), and 1-(n-
morpholinomethyl)-naphthol (1e). The dimethylgallium complexes of these compounds have been prepared, and compound 2d has
been determined by X-ray crystallography. The complex 2d crystallized with one unit having two identical molecules which have
intermolecular contacts between the two phenyls caused by face to face p–p stacking. The Ga–O bond distances are noticeably
shorter than in the other dimethylgallium phenoxides reported. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: One-pot Mannich reaction; Phenol; Naphthol; Dimethylgallium complexes; Crystal structure
gallium and indium have been drawing increasing inter-
est because of a wide rang of possible uses: Group III/V
semi-conductor materials as precursor compounds for
MOCVD, Group III/VI compounds as precursors for
ceramic materials [6], and gallium compounds have
found utility in the diagnosis of diseases [7]. In view of
their potential applications in the diagnosis of diseases,
we have initiated a study of trimethylgallium complexes
with n-morpholinomethylphenols or n-morpholi-
nomethylnaphthols.
In the synthesis of the ligands, we used the one-pot
Mannich reaction. Ki-Wan Chi and coworkers reported
a one-pot method using Mannich reaction to synthesis
double-armed ionizable crown ethers [8]; we applied it
to morpholine and it has proven to be a convenient and
efficient method, with high yields.
1. Introduction
Aminomethyl phenols or aminomethyl naphthols
have been known for their uses as pigments [1], insecti-
cides [2], and as intermediates in the pharmaceutical
industry [3]. In recent years, great attention has been
paid to aminomethyl phenols owing to their uses as
excellent mimics for the active site of enzymes. For
example,
mononuclear
iron
complexes
with
monoaminomethylated phenols as ligands have proven
to be remarkable mimics for the active site of iron–ty-
rosinate proteins [4]. However, these studies are largely
limited to mononuclear or binuclear transition metal
complexes [5]. Their complexes with trialkyl Group III
metal derivatives have not been reported. It is also
noted that organometallic compounds of aluminum,
Several studies concerning compounds containing
two or more nitrogen atoms [9], nitrogen and oxygen
atoms [10], nitrogen and sulfur atoms [11] have been
reported. In the molecules of n-morpholinomethyl phe-
nols, there are not only two donor atoms—nitrogen
* Corresponding author.
E-mail address: zhangjq@nju.edu.cn (J. Zhang)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00148-5

J. Tian et al. / Journal of Organometallic Chemistry 584 (1999) 240–245
241
Table 1
dimethylgallium-[4-nitro-2-(n-morpholinomethyl)-1-
phenoxide] (2d), has been subjected to single-crystal
X-ray studies. All complexes have been characterized
Crystal data and structure refinement for compound 2d
Empirical formula
Formula weight
Crystal color, habit
Crystal system
C13H19N2O4Ga
337.02
Yellow, prismatic
Monoclinic
1
by H-NMR, MS, IR and elemental analyses.
Lattice parameters
2. Experimental
,
a (A)
8.796(4)
11.045(5)
30.814(7)
90.71(3)
2993.5601
P21/c (no. 14)
8
1.495
1392.00
18.52
Mo–Ka (u=0.71070)
55.1
4448
2731
362
,
b (A)
2.1. General procedures
,
c (A)
i (°)
3
,
V (A )
All manipulations of trimethylgallium were carried
out under a nitrogen atmosphere in a glove box. Sol-
vents were carefully dried by distillation from sodium
and benzophenone under nitrogen prior to use. 1H-
NMR spectra were recorded on a Jeol PMX-60SI
spectrometer in CDCl3 using SiMe4 as an internal
reference. Mass spectra were obtained on a VG ZAB
MS instrument. Microanalyses (C, H, N) were per-
formed on a Perkin–Elmer 240C elemental analyzer.
IR spectra were recorded on a Shimadzu IR 408 in-
strument in KBr pellets. Melting points of dimethyl-
gallium complexes were determined in a glass tube.
Melting points of ligands were determined on a
Yanaco microscopic melting point apparatus and
were uncorrected. Trimethylgallium was provided by
the National 863 Programme Advanced Material MO
Precursors R&D Center of China.
Space group
Z
Dcalc. (g cm−3
F(000)
)
v(Mo–Ka) (cm−1
)
,
Radiation (A)
2qmax (°)
Total reflections measured
Reflections observed [I\3|(I)]
No. of variables
Reflection/parameter ratio
Residuals R, Rw
Goodness-of-fit
Maximum peak in final difference map
Minimum peak in final difference map
7.54
0.069, 0.100
1.25
0.66 e A
−0.64 e A
−3
,
−3
,
and oxygen, but also an ionizable OH functional
group. In fact, when trimethylgallium reacts with n-
morpholinomethyl phenols at a ratio of 1:1 in our
experiment, only the hydroxyl group takes part in the
reaction to give elimination products with a four-co-
ordinate gallium atom. One of these novel complexes,
2.2. Synthesis of ligands
2.2.1. General
To a solution of morpholine (3.5 ml, 40 mmol) and
paraformaldehyde (1.8 g, 60 mmol) in dry benzene
(80 ml) under a N2 atmosphere was added the corre-
sponding substituted phenol or naphthol (40 mmol)
at room temperature (r.t.). The mixture was then
heated and kept at reflux for 6 h. The solvent was
removed in vacuum, and the crude product was re-
crystallized in petroleum ether:ethyl acetate to give aci
form or lamellar crystals.
Table 2
,
Selected bond lengths (A) and bond angles (°) for compound 2d
Ga1–O3
Ga1–C1
Ga2–O7
Ga2–C14
O1–N2
O3–C13
O4–C5
O8–C17
N1–C3
N1–C7
C7–C8
1.903(6)
1.99(1)
1.895(6)
1.96(1)
1.22(1)
1.31(1)
1.43(1)
1.42(1)
1.49(1)
1.49(1)
1.50(1)
1.43(1)
Ga1–N1
Ga1–C2
Ga2–N3
Ga2–C15
O2–N2
O4–C4
O7–C26
O8–C18
N1–C6
2.092(7)
1.95(1)
2.112(7)
1.96(1)
1.25(1)
1.40(1)
1.32(1)
1.43(1)
1.50(1)
1.45(1)
1.37(1)
1.38(1)
2.2.2. 2-(n-Morpholinomethyl)-1-phenol (1a)
Yield: 7.2 g (93%), m.p. (dec.) 82–84°C. MS (%
intensity, m/z): 192.9 (82.10), 161.9 (15.06), 145.9
(29.85), 133.9 (17.12), 106.9 (100.00), 100.00 (7.59),
87.0 (18.79), 85.9 (61.96), 76.9 (30.38), 57.5 (30.69).
N2–C10
C8–C9
C9–C10
C8–C13
O3–Ga1–N1
O3–Ga1–C2
N1–Ga1–C2
O7–Ga2–N3
O7–Ga2–C15
N3–Ga2–C15
Ga1–O3–C13
Ga1–N1–C7
O5–N4–O6
95.6(3)
O3–Ga1–C1
N1–Ga1–C1
C1–Ga1–C2
O7–Ga2–C14
N3–Ga2–C14
C14–Ga2–C15
Ga2–O7–C26
Ga2–N3–C20
O1–N2–O2
111.0(4)
104.9(4)
123.8(6)
110.5(4)
105.3(4)
122.3(6)
126.6(6)
104.2(5)
124.0(9)
118.9(8)
117.9(8)
103.7(4)
114.5(5)
96.1(3)
105.8(4)
113.8(5)
127.5(6)
103.6(5)
123.0(9)
115.0(7)
122.1(8)
2.2.3. 4-Methyl-2-(n-morpholinomethyl)-1-phenol (1b)
Yield: 7.9 g (95%), m.p. (dec.) 48–51°C. MS (%
intensity, m/z): 206.9 (90.85), 159.9 (28.37), 120.9
(73.99), 100.0 (7.31), 91.0 (34.33), 87.0 (30.82), 85.9
(100.00), 57.5 (42.21), 56.6 (31.40).
2.2.4. 4-Chloro-2-(n-morpholinomethyl)-1-phenol (1c)
Yield: 8.5 g (93%), m.p. (dec.) 66–68°C. MS (%
intensity, m/z): 228.8 (32.71), 227.9 (15.16), 226.9
N1–C7–C8
O3–C13–C8
C7–C8–C13
C8–C13–C12

242
J. Tian et al. / Journal of Organometallic Chemistry 584 (1999) 240–245
Fig. 1. Molecular structure of compound 2d showing 30% probability displacement ellipsoids. Hydrogen atoms are omitted for clarity.
(99.75), 179.9 (38.50), 167.9 (23.62), 142.9 (23.45), 140.9
(72.24), 139.9 (20.85), 100.0 (21.78), 87.0 (86.45), 86.0
(100.00), 76.9 (53.92), 57.5 (60.50).
mixture was then heated to reflux for 2 h, the solvent was
removed by vacuum distillation. The pale yellow oil
residue was recrystallized in petroleum ether to give
colorless crystals (0.81 g, 92%), m.p. (dec.) 94–96°C.
Found: C, 53.36; H, 6.85; N, 4.92 (Anal. Calc. for
2.2.5. 4-Nitro-2-(n-morpholinomethyl)-1-phenol (1d)
Yield: 8.4 g (88%), m.p. (dec.) 96–97°C. MS (%
intensity, m/z): 237.9 (84.17), 236.9 (10.34), 191.0
(47.24), 178.9 (14.99), 151.9 (100.00), 106.0 (20.76),
100.0 (17.40), 86.0 (63.64), 77.9 (15.30), 76.9 (10.69),
57.5 (35.32).
1
C13H20GaNO2: C, 53.47; H, 6.91; N, 4.80%). H-NMR
(l): 7.43–7.57 (m, 1H); 6.67–7.27 (m, 3H); 3.67–4.23
(m, 6H); 2.40–3.37 (b, 4H); −0.23 (s, 6H). IR (cm−1):
3050, 1600, 1485, 1460, 1355, 1260, 1200, 1120, 1075,
875, 810, 765, 590, 540. MS (% intensity, m/z): 292.8
(7.44), 290.9 (11.31), 277.9 (66.71), 275.9 (100.00), 219.9
(2.27), 217.9 (3.54), 192.9 (41.57), 190.8 (48.11), 100.9
(29.98), 98.9 (47.90), 91.0 (2.55), 77.0 (9.91).
2.2.6. 1-(n-Morpholinomethyl)-2-naphthol (1e)
Yield: 9.0 g (93%), m.p. (dec.) 109–110°C (Ref. [16].
119–121°C). MS (% intensity, m/z): 242.8 (4.57), 155.9
(59.44), 127.9 (100.00), 126.9 (21.94), 101.9 (14.69), 86.9
(26.44), 85.9 (19.48), 76.9 (10.21), 57.5 (38.58).
2.3.2. Dimethylgallium-[4-methyl-2-(n-morpholino-
methyl)-1-phenoxide] (2b)
Compound 2b was prepared analogously to 2a. After
the solvent was removed in vacuo, a pale yellow oil was
left. The residue was recrystallized in petroleum to give
colorless crystals (0.82 g, 89%), m.p. (dec.) 88–90°C.
Found: C, 55.12; H, 7.48; N, 4.57 (Anal. Calc. for
2.3. Synthesis of dimethylgallium complexes
2.3.1. Dimethylgallium-[2-(n-morpholinomethyl)-1-
phenoxide] (2a)
To a solution of 1a (0.58 g, 3 mmol) in 10 ml benzene,
0.33 ml (3 mmol) GaMe3 was added dropwise at r.t. The
1
C14H22GaNO2: C, 54.94; H, 7.25; N, 4.58%). H-NMR
(l): 7.33–7.40 (m, 1H); 6.73–7.27 (m, 2H); 3.57–4.07

J. Tian et al. / Journal of Organometallic Chemistry 584 (1999) 240–245
243
Fig. 2. The unit cell packing diagram of compound 2d.
(b, 6H); 2.40–3.33 (b, 4H); −0.23 (s, 6H). IR (cm−1):
3020, 1600, 1490, 1445, 1340, 1260, 1110, 1065, 990,
910, 875, 770, 575, 535. MS (% intensity, m/z): 306.8
(11.97), 304.8 (17.19), 291.8 (68.36), 289.8 (100.00),
277.7 (6.50), 275.7 (10.21), 233.9 (2.09), 231.8 (3.26),
100.9 (35.13), 98.9 (53.26), 91.0 (11.18), 77.0 (5.94).
yellow transparent crystals (0.96 g, 95%), m.p. (dec.)
186–188°C. Found: C, 46.32; H, 5.70; N, 8.38 (Anal.
Calc. for C13H19GaN2O4: C, 46.33; H, 5.69; N, 8.31%).
1H-NMR(l): 7.96–8.26 (m, 2H); 6.73–6.86 (m, 1H);
3.63–4.36 (b, 6H); 2.40–3.53 (b, 4H);−0.19 (s, 6H). IR
(cm−1): 3020, 1600, 1570, 1480, 1320, 1250, 1120, 1070,
980, 910, 865, 760, 545, 520. MS (% intensity, m/z):
337.7 (2.26), 335.7 (2.92), 322.7 (69.20), 320.7 (100.00),
264.7 (2.51), 262.7 (3.97), 237.8 (16.58), 235.8 (17.22),
100.9 (33.02), 98.9 (50.43), 91.0 (1.40), 77.0 (3.99).
2.3.3. Dimethylgalium-[4-chloro-2-(n-morpholino-
methyl)-1-phenoxide] (2c)
Compound 2c was prepared analogously to 2a. Re-
moval of the solvent resulted in a white powder which
was recrystallized in benzene:petroleum ether to give
colorless transparent crystals (0.92 g, 94%), m.p. (dec.)
84–86°C. Found: C, 47.92; H, 5.77; N, 4.37 (Anal.
Calc. for C13H19ClGaNO2: C, 47.82; H, 5.87; N,
4.29%). 1H-NMR (l): 6.91–7.15 (m, 2H); 6.65–6.81
(m, 1H); 3.41–3.93 (b, 6H); 2.25–3.25 (b, 4H); −0.25
(s, 6H). IR (cm−1): 3020, 1600, 1480, 1350, 1290, 1105,
1075, 890, 835, 740, 560, 540. MS (% intensity, m/z):
326.9 (12.51), 324.9 (12.18), 311.9 (97.12), 309.9
(100.00), 253.9 (3.57), 251.9 (3.57), 226.9 (36.59), 224.9
(25.02), 100.9 (43.43), 99.0 (67.29), 91.0 (3.53), 77.0
(16.99).
2.3.5. Dimethylgallium-[1-(n-morpholinomethyl)-2-
naphthoxide] (2e)
Compound 2e was also prepared analogously to 2a.
Removal of the solvent resulted in a white powder
which was recrystallized in benzene:petroleum ether to
Table 3
a
,
Distances of C atoms on one phenyl ring to another (A)
C21–Face 1
C23–Face 1
C25–Face 1
C8–Face 2
C10–Face 2
C12–Face 2
3.479
3.551
3.786
3.657
3.392
3.367
C22–Face 1
C24–Face 1
C26–Face 1
C9–Face 2
C11–Face 2
C13–Face 2
3.403
3.724
3.634
3.569
3.273
3.551
2.3.4. Dimethylgallium-[4-nitro-2-(n-morpholino-
methyl)-1-phenoxide] (2d)
Compound 2d was prepared analogously to 2a. The
yellow powder was recrystallized in benzene to give pale
a Face 1: C8C9C10C11C12C13; Face 2: C21C22C23C24C25C26
.

244
J. Tian et al. / Journal of Organometallic Chemistry 584 (1999) 240–245
give colorless transparent crystals (0.96 g, 94%), m.p.
(dec.) 194–196°C. Found: C, 59.64; H, 6.64; N, 4.16
(Anal. Calc. for C17H22GaNO2: C, 59.69; H, 6.49; N,
drawing substitute, the yield is 88%. Reaction of 2-
naphthol with paraformaldehyde and morpholine in
dry benzene only gave a 1-substituted product, this is
due to the relatively high reactivity of the a-H in the
ortho-position of the hydroxyl group.
1
4.09%). H-NMR(l): 7.67–8.03 (m, 3H); 7.13–7.60 (m,
3H); 3.57–4.33 (b, 6H); 2.53–3.50 (b, 4H); −0.23 (s,
6H). IR (cm−1): 3050, 1620, 1590, 1500, 1460, 1370,
1280, 1170, 1100, 1010, 965, 890, 830, 750, 680, 580,
545, 515. MS (% intensity, m/z): 342.9 (20.96), 340.9
(29.82), 327.8 (62.22), 325.8 (90.60), 299.9 (1.95), 297.8
(3.19), 242.9 (29.09), 240.9 (14.84), 179.9 (6.76), 178.00
(10.30), 155.9 (14.60), 153.9 (1.06), 100.9 (64.32), 98.9
(100.00), 77.0 (2.76).
3.1.2. Complexes
Trimethylgallium reacted with ligands 1a–1e in a 1:1
ratio to give only elimination complexes. These com-
plexes are less air-sensitive than free GaMe3. Only after
being reposed in air for several hours do they begin to
decompose slowly. In the mass spectra, these complexes
all show parent molecular ion peak [M]+, indicating
that the molecules are stable. All the complexes have
[M−15]+, [M−17]+, [M−73]+, [M−100]+ and
[100.9]+ fragments, and isotopic peaks indicate that
these fragments all include Ga. This suggests that these
complexes all fragment in the same way.
2.4. X-ray structure determination of dimethylgallium-
[4-nitro-2-(n-morpholi-nomethyl)-1-phenoxide] (2d)
Single crystals of 2d were grown from benzene solu-
tion at r.t. for 12 h. A single crystal suitable for X-ray
determination was mounted in a thin-walled capillary
tube in a glove box, plugged with grease, removed from
the glove box, then flame sealed. Data were collected at
291 K on a Rigaku RAXIS-IV imaging plate area
detector with graphite monochromate Mo–Ka (u=
1
In the H-NMR spectrum, there is a single peak of
six protons in the region of −0.25 to −0.19 ppm,
which is the absorption of the six protons on the two
methyl groups connecting to Ga. Aromatic protons
resonate in the region 6.65–8.25 ppm. Ten protons on
the five methylenes are divided into two groups. One
group of six protons (3.41–4.36 ppm) includes –CH2–
O–CH2– and Ar–CH2–Nꢀ in low field, another
group in high field (2.25–3.53 ppm) belongs to the four
protons of –CH2–CH2–Nꢀ. In compound 2b, the
chemical shift of protons of the methyl linking to AR is
2.30 ppm. All complexes have a moderate absorption
near 530 cm−1 in IR spectra, which is the Ga–N
stretching vibration frequency [12].
,
0.7170 A) radiation to a maximum 2q value of 55.1°.
Readout was performed in the 0.100 mm pixel mode.
The data were corrected for Lorentz and Polarization
effects during data reduction. A correction for sec-
ondary
extinction
was
applied
(coefficient=
1.25940e07). A total of 4448 reflections were collected.
The structure was solved by direct methods and ex-
panded using Fourier techniques. All nonhydrogen
atoms were refined anisotropically. Hydrogen atoms
were included but not refined. The final cycle of full-
matrix least-squares refinement was based on 2731 ob-
served reflections [I\3.00|(I)] and 362 variable
parameters and converged with unweighted and
weighted agreement factor of R=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ=
0.069, Rw={Sw(ꢀFoꢀ−ꢀFcꢀ)2/SwF2o}1/2=0.100. The stan-
dard deviation of an observation of unit weight was
1.25. The maximum and minimum peaks on the final
difference Fourier map corresponded to 0.66 and −
3.2. X-ray crystal structure of dimethylgallium-[4-
nitro-2-(n-morpholinomethyl)-1-phenoxide] (2d)
The structure of compound 2d was determined by
X-ray crystallography. The complex crystallized in the
monoclinic space group P21/c with two chemically
identical, crystallographically independent, and confor-
mationally only slightly different molecules in the asym-
0.64 e A−3, respectively. Crystal data and details on
,
refinement are presented in Table 1. Selected bond
lengths and bond angles without hydrogen atoms are
shown in Table 2. Additional data are available from
the authors.
metric
unit.
The
molecular
structure
and
atom-numbering scheme of the two molecules in one
unit is shown in Fig. 1. The unit cell packing diagram
is shown in Fig. 2. The complex crystallized in such a
way that one unit has two identical molecules. It can be
seen from Fig. 2 that there are some intermolecular
contacts. The two phenyl rings overlap with each other,
with a dihedral angle of 7.71°. The distances between
the two phenyl rings from one end to the other vary
3. Results and discussion
3.1. Synthesis and characterization
,
from 3.273 to 3.786 A. Since there is no H-bonding and
van der Waals interactions between the two molecules,
3.1.1. Ligands
The yields are high in the syntheses of the Mannich
bases (1a–1e). Effects of substitutes on the yields are
small. Even compound 1d, with a strong electron-with-
we conclude that these are p–p stacking interactions
[13], with
a typical phenyl face to face p–p
arrangement.

J. Tian et al. / Journal of Organometallic Chemistry 584 (1999) 240–245
245
Usually, the reaction of alcohols or phenols with
trimethylgallium results in a dimeric product with a
five-coordinate gallium center containing a planar
Ga2O2 ring [14]. In our experiment, we only get
monomers, each with a four-coordinate gallium center.
This is due to the phenyl p–p stacking interactions and
the relatively more bulky ligands than those previously
reported [14].
research project from the State Science and Technology
Commission.
References
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gallium atoms with Ga1 linking to N1, O3, C1, C2 and
Ga2 linking to N3, O7, C14, C15 are nearly tetrahedral.
However, there are some distortions in the bond angles.
The angle of O3–Ga1–N1 reduces to 95.6°, much less
than the ideal value of 109.5°. This is caused by the
strain in the ring Ga1N1C7C8C13O3 (Face 1) (Table 3).
The angle of C1–Ga1–C2 increases to 123.8°, this is
because that methyl group is bigger than the O3 atom.
The situation for Ga2 is the same as that of Ga1.
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seven-numbered ring Ga1N1C7C8C13O3, whereas
Ga1N1C7 have some distortions to make a boat-
configuration. The six-membered ring O4C5C4N1C3C4 is
in a chair-configuration.
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It is interesting to note that the Ga–O bond dis-
,
tances are 1.903 and 1.895 A for Ga1–O3 and Ga2–O7,
respectively. These Ga–O bond distances in the title
compound are much shorter than in other dimethylgal-
lium phenoxides reported. They are similar to the Ga–
O bond distances in the compound CH3Ga(CH3COO)2
[15]. This indicates that there is a strong interaction
between the Ga and O atoms.
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Chem. 15(5) (1999).
,
The Ga–N bond distances are 2.092 and 2.112 A for
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Ga1–N1 and Ga2–N3, respectively, similar to those in
other four-coordinate Ga–N bond distances reported
[14c].
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Acknowledgements
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This work was financially supported by 863 key
.