The coordination chemistry of o,o′-i-Pr2C6H3-bis(imino)acenaphthene to group 13 trihalides

Article abstract of DOI:10.1139/v02-084

The preparation of several complexes of the diimine ligand o,o′-i-Pr₂C₆H₃-bis(imino)acenaphthene (Ar-BIAN) (1)) with group 13 trihalides (EX₃, E = B, Al, Ga: X = Cl, Br) is reported. Four compounds with the general formula [(Ar-BIAN)(EX₂)][EX₄] (2) have been prepared and isolated. Two complexes have been crystallographically character)ized: [(Ar-BIAN)(BCl₂)][BCl₄] (orthorhombic, P2₁2₁2₁, a = 10.408(3) A, b = 14.376(4) A, c = 30.908(8) A, Z = 4) and [(Ar-BIAN)(GaCl₂)][GaCl₄] (monoclinic, P2₁/m, a = 9.0822(7) A, b = 15.390(1) A, c = 15.458(1) A, β = 92.519(2)°, Z = 2). Attempts to prepare diazametaloles via reduction of the [(Ar-BIAN)(EX₂)][EX₄] compounds using sodium or potassium have thus far been unsuccessful.

Full text of DOI:10.1139/v02-084

1398
The coordination chemistry of o,o>-i-Pr2C6H3-
bis(imino)acenaphthene to group 13 trihalides
Hilary A. Jenkins, Carla L. Dumaresque, Dragoslav Vidovic, and
Jason A. C. Clyburne
Abstract: The preparation of several complexes of the diimine ligand o,o>-i-Pr2C6H3-bis(imino)acenaphthene (Ar-BIAN
(1)) with group 13 trihalides (EX3, E = B, Al, Ga; X = Cl, Br) is reported. Four compounds with the general formula
[(Ar-BIAN)(EX2)][EX4] (2) have been prepared and isolated. Two complexes have been crystallographically character-
ized: [(Ar-BIAN)(BCl2)][BCl4] (orthorhombic, P212121, a = 10.408(3) Å, b = 14.376(4) Å, c = 30.908(8) Å, Z = 4)
and [(Ar-BIAN)(GaCl2)][GaCl4] (monoclinic, P21/m, a = 9.0822(7) Å, b = 15.390(1) Å, c = 15.458(1) Å, ꢀ =
92.519(2)°, Z = 2). Attempts to prepare diazametaloles via reduction of the [(Ar-BIAN)(EX2)][EX4] compounds using
sodium or potassium have thus far been unsuccessful.
Key words: boron, aluminium, gallium, complex, crystal structure, heterocycle.
Résumé : On a préparé plusieurs complexes du ligand diimide o,o>-i-Pr2C6H3-bis(imino)acénaphtène (Ar-BIAN (1))
avec des halogénures d’éléments du groupe 13 (EX3, E = B, Al, Ga; X = Cl, Br). On a spécifiquement préparé et isolé
quatre composés de formule générale [(Ar-BIAN)(EX2)][EX4] (2). On a caractérisé deux de ces complexes par diffrac-
tion des rayons X, le [(Ar-BIAN)(BCl2)][BCl4] (orthorhombique, P212121, a = 10,408(3), b = 14,376(4) et c =
30,908(8) Å, Z = 4) et le [(Ar-BIAN)(GaCl2)][GaCl4] (monoclinique, P21/m, a = 9,0822(7), b = 15,390(1) et c =
15,458(1) Å, ꢀ = 92,519(2)°, Z = 4). On n’a pas réussi à préparer des diazamétaloles par le biais d’une réduction des
composés [(Ar-BIAN)(EX2)][EX4] à l’aide du sodium ou du potassium.
Mots clés : bore, aluminium, gallium, complexes, structure cristalline, hétérocycle.
[Traduit par la Rédaction] Jenkins et al. 1403
Introduction
gous to hydroboration and haloboration. The ideal candidates
for such reactions would be heterocyclic compounds, with
donor substituents bound to the group 13 metal site; these
donors would stabilize a tricoordinate metal centre via
delocalization. The presence of a bulky substituent would fa-
cilitate synthesis and enhance the thermal stability of the
complex. Currently there is great interest in unusual main
group element heterocycles, including B (4, 5), Al (6), and
Ga (7, 8) derivatives.
Hydroborations are an important class of reaction in syn-
thetic organic chemistry because the B—H bond readily
adds across a wide variety of unsaturated fragments, includ-
ing C=O and C=N bonds (1). Recently, reactions involving
chloroboration (B-Cl addition) have been identified (2). To
our knowledge, these reactions have not been extended to
heavier group 13 elements, although enhanced reactivity
would be anticipated for Al—Cl and Ga—Cl bonds as com-
pared with the B—Cl bonds.
It became apparent to us that the bulky diimine ligand 1
(9) would be ideal for our studies since it is both a good do-
nor and extremely bulky.
Our interest in group 13 element chemistry (3) led us to
look at the synthesis of suitable heterocyclic systems as pre-
cursors to compounds that may engage in reactions analo-
Received 21 January 2002. Published on the NRC Research
Press Web site at http://canjchem.nrc.ca on 23 September 2002.
This paper is dedicated to Professor Tristram Chivers for his
many contributions to main group chemistry.
H.A. Jenkins.1 Department of Chemistry, Saint Mary’s
University, Halifax, NS B3H 3C3, Canada.
C.L. Dumaresque, D. Vidovic, and J.A.C. Clyburne.2
Department of Chemistry, 8888 University Drive, Simon
Fraser University, Burnaby, BC V5A 1S6, Canada.
1Corresponding author (crystallography) (e-mail:
hilary.jenkins@stmarys.ca).
Diimines are bidentate ligands consisting of two nitrogen
atoms bridged by at least two carbon atoms, and having two
C=N double bonds (10). The bis(arylimino)acenaphthene
2Corresponding author (e-mail: clyburne@sfu.ca).
Can. J. Chem. 80: 1398–1403 (2002)
DOI: 10.1139/V02-084
© 2002 NRC Canada

Jenkins et al.
1399
diimine ligand (1) is different from other diimine ligands as
it has both better ꢁ-donating and ꢂ-accepting properties than
nonrigid diimines (9). Therefore, 1 could serve as an ideal
starting material for the preparation of stable heterocyclic
metal-containing ions (metal = boron, aluminium, and gal-
lium) (2), which would serve as precursors to the requisite
heterocycles (3). The nitrogen atoms are locked into a rigid
s-cis conformation due to the presence of the naphthalene
backbone, thus allowing for better metal coordination.
Brookhart and co-workers (11) have recently reported Ni(II)
and Pd(II) complexes of 1 that catalyze the polymerization
of ethylene. These catalysts have activities similar to those
of the early transition metal catalysts; however, they produce
polymers with different structures and properties. Despite
extensive use in transition metal chemistry ligand design, 1
has not been used in main group chemistry.
Synthesis of [(Ar-BIAN)(BBr2)][BBr4]
Ar-BIAN (1.20 g, 2.5 mmol in 10 mL of CH2Cl2) was
added to a solution of 25 mL of CH2Cl2 and 5 mL
(5.0 mmol) of 1 M BBr3 in CH2Cl2 to produce a dark red so-
lution. The volume of solvent was reduced to ca. 25% of the
original volume, and then the solution was cooled to –30°C.
Solvent was removed under an argon atmosphere and dark
red crystals were isolated in the dry box. Yield: 1.35 g
(1.38 mmol, 55%), decomposition temperature W 185°C. IR
(Nujol mull) (cm–1): 1635, 1597, 1570, 1319, 834, 733, 615,
588, 541. 1H NMR (CD2Cl2, poor solubility) ꢃ (ppm): 1.0 (d,
JHH = 6Hz, 12H), 1.45 (d, JHH = 6 Hz, 12H), 3.3 (broad,
4H), aromatic region broad and not resolved. Anal. calcd.
for C36H40B2Br6N2: C 43.16, H 4.02, N 2.80; found: C 42.80,
H 3.92, N 2.65.
Herein we report our synthetic and structural studies on a
series of bulky diazametalolium (2) complexes. A series of
reactions involving 1 with EX3 (E = B, Al, Ga; X = Cl, Br)
has been examined, and the reaction products have been iso-
lated and characterized. The products have the general for-
mula [(Ar-BIAN)(EX2)][EX4] (3). Attempts to prepare
molecules such as 3 via reduction of 2 have thus far been
unsuccessful.
Synthesis of [(Ar-BIAN)(AlCl2)][AlCl4]
Aluminium trichloride (1.0 g, 7.50 mmol) was added to
an oven-dried Schlenk flask containing 40 mL of CH2Cl2.
Ar-BIAN (1.80 g, 3.75 mmol) in 5 mL of CH2Cl2 was
added, and the solution turned dark red. Half of the solvent
was removed under vacuum, and the reaction was cooled to
–30°C in the freezer. A microcrystalline powder was ob-
tained, and this material was washed with CH2Cl2. Yield:
0.95 g (1.27 mmol, 34%), decomposition temperature W 185°C.
IR (Nujol mull) (cm–1): 1626, 1617, 1569, 1418, 1366, 1318,
1
1221, 854, 835, 802, 774, 490, 460. H NMR (CD2Cl2) ꢃ
Experimental methods
(ppm): 1.14 (d, JHH = 6Hz, 12H), 1.30 (d, JHH = 6 Hz, 12H),
3.0 (m, 4H), 7.2 (d, JHH = 7 Hz, 4H), 7.3–7.8 (6 H aryl),
7.70 (m, 2H), 8.50 (d, JHH = 8 Hz, 2H). Anal. calcd. for
C36H40Al2Cl6N2: C 56.34, H 5.25, N 3.65; found: C 56.20,
H 5.11, N 3.59.
An MBraun UL-99–245 dry box and standard Schlenk
techniques on a double manifold vacuum line were used in
the manipulation of air- and moisture-sensitive compounds.
Anhydrous solvents were used as received from Aldrich
Chemical Company. NMR spectra were recorded on a
Bruker AMX 400 MHz spectrometer in 5-mm quartz tubes.
1H chemical shifts were reported in parts per million (ppm)
downfield from tetramethylsilane (TMS) and were calibrated
to the residual signal of the solvent. Infrared spectra were
obtained using a Bomem MB spectrometer with the % trans-
mittance reported in cm–1. Melting points were measured us-
ing a Mel-Temp apparatus and are uncorrected. Ligand 1
was prepared using the published procedure (9). Note that
13C NMR spectra were not obtained due to decomposition
and low solubility of the ionic compounds.
Synthesis of [(Ar-BIAN)(GaCl2)][GaCl4]
Gallium trichloride (1.00 g, 5.68 mmol) in 15 mL of
CH2Cl2 was added to an oven-dried Schlenk flask. Ar-BIAN
(1.37 g, 2.84 mmol in 5 mL of CH2Cl2) was added to this
colourless solution, which turned dark red. Another 5 mL of
CH2Cl2 was added, and this solution was then cooled to
–30°C. Flat red crystals were obtained and isolated after re-
moval of the supernatant, via cannula, under an atmosphere
of argon. Yield: 1.75 g (2.10 mmol, 74%), decomposition
temperature W 140°C. IR (Nujol mull) (cm–1): 1621, 1596,
1572, 1488, 1420, 1366, 1300, 1270, 1055, 803, 777, 734,
1
584, 545. H NMR (CD2Cl2) ꢃ (ppm): 1.02 (broad, s, 12H),
Synthesis of [(Ar-BIAN)(BCl2)][BCl4]
1.45 (d, JHH = 6 Hz, 12H), 3.1 (m, 4H), 6.90 (d, JHH
7 Hz, 2H), 7.3–7.8 (6 H aryl), 7.64 (m, 2H) 8.42 (d, JHH
8 Hz, 2H). Anal. calcd. for C36H40Ga2Cl6N2: C 50.70,
H 4.73, N 3.28; found C 50.54, H 4.63, N 3.15.
=
=
Ar-BIAN (1.20 g, 2.5 mmol in 10 mL CH2Cl2) was added
to a solution of 25 mL CH2Cl2 and 5 mL (5.0 mmol) of 1 M
BCl3 in hexanes, resulting in the formation of a dark red so-
lution. The volume of solvent was reduced to ca. 25% of the
original volume, and then the solution was cooled to –30°C.
Small red crystals were obtained and the supernatant was re-
moved via cannula under an atmosphere of argon. Yield:
1.05 g (1.47 mmol, 59%), decomposition temperature W
140°C. IR (Nujol mull) (cm–1): 1643, 1600, 1569, 1418,
1366, 1318, 1260, 854, 835, 802, 774, 691, 658, 634, 546.
1H NMR (CD2Cl2) ꢃ (ppm): 1.14 (broad, 12H), 1.42 (d,
JHH = 6 Hz, 12H), 3.01 (m, 4H), 6.9 (d, 7 Hz), 7.6 (m, 2H),
8.28 (d, JHH = 8 Hz, 2H), 7.3–7.8 (6H aryl). Anal. calcd. for
C36H40B2Cl6N2: C 58.82, H 5.48, N 3.81; found: C 59.16,
H 5.60, N 3.64.
Attempts to reduce the compounds above in THF (1 to
2 mmol scale) with sodium or potassium were made, but un-
fortunately in our hands no pure compounds could be iso-
lated from the reaction mixtures. The only compound
identified (by NMR and melting point) was Ar-BIAN. Like-
wise, attempts were made to exchange the [EX4] anions with
the weakly coordinating anion [B(C6F5)4] by treating 3 with
Li[B(C6F5)4] in CH2Cl2 solution. In general, these attempts
were unsuccessful, resulting in the formation of dark col-
oured solutions, from which the only pure compound iso-
lated was Ar-BIAN.
© 2002 NRC Canada

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Can. J. Chem. Vol. 80, 2002
Table 1. Crystal data and structure refinement for [(Ar-BIAN)BCl2][BCl4]·1.25 CH2Cl2 and [(Ar-BIAN)GaCl2][GaCl4].
Compound
[(Ar-BIAN)BCl2][BCl4]·1.25 CH2Cl2
[(Ar-BIAN)GaCl2][GaCl4]
Empirical formula
Formula weight (g ml–1)
C37.26H42.50B2Cl8.5N2
841.18
C37H40Cl8Ga2N2
935.75
Temperature (K)
223(2)
223(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
ꢄ (°)
Orthorhombic
P212121
10.408(3)
14.376(4)
30.908(8)
90
Monoclinic
P21/m
9.0822(7)
15.390(1)
15.458(1)
90
ꢀ (°)
ꢆ (°)
Volume (Å3)
90
90
4625(2)
4
1.239
0.572
1780
0.20 × 0.20 × 0.20
1.32–25.00
9 ? h ? 12
92.519(2)
90
2158.5(3)(2)
2
1.440
1.771
Z
Density (calculated) mg m–3
Absorption coefficient ( ) (mm–1)
F(000)
948
Crystal size (mm3)
ꢇ range for data collection (°)
Index ranges
0.20 × 0.20 × 0.30
1.87–25.00
–10 ? h ? 8
–16 ? k ? 17
–18 ? k ? 18
–29 ? l ? 36
–17 ? l ? 18
Reflections collected
Independent reflections
Absorption correction
Max and min transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F 2
Final R indices [I > 2ꢁ(I)]
R indices (all data)
24 923
8146
none
10 799
3907 (Rint = 0.0608)
none
0.447 and ꢈ0.597
Full-matrix least-squares on F 2
3907/0/251
0.745 and ꢈ0.392
Full-matrix least-squares on F 2
8137/3/516
1.162
1.018
R1 = 0.1152, wR2 = 0.2798
R1 = 0.2117, wR2 = 0.3222
0.018(4)
R1 = 0.0534, wR2 = 0.1094
R1 = 0.1092, wR2 = 0.1290
0.0014(5)
Extinction coefficient
Crystallographic studies
Results and discussion
The Ar-BIAN ligand 1 was treated with a variety of group
13 compounds to prepare Lewis base coordination com-
plexes. Lewis acids studied included BCl3, BBr3, AlCl3, and
GaCl3. Of these reactions, solid materials were successfully
isolated from BCl3, BBr3, AlCl3, and GaCl3. In general,
treatment of 1 with 2 equiv of EX3 in CH2Cl2 solution, fol-
lowed by reduction of the solvent volume, resulted in the
formation of a solid, bright red material. These compounds
A single crystal of either [(Ar-BIAN)BCl2][BCl4]·1.25[CH2Cl2]
or [(Ar-BIAN)GaCl2][GaCl4] was mounted on a glass fibre
and centred on a Seimens 1K SMART/CCD diffractometer.
Data were collected at –50°C using Mo (Kꢄ) radiation. Lo-
rentz and polarization corrections were applied, and data
were also corrected for absorption using redundant data and
the SADABS program. Direct methods and Fourier tech-
niques were used to solve the crystal structures. Refinement
was conducted using full-matrix least-squares calculations
and SHELX-TL PC V 5.03. All non-hydrogen atoms were
refined with anisotropic displacement parameters. The hy-
drogen atoms were included in calculated positions and were
refined using a riding model. In the final stages of the refine-
ment of [(Ar-BIAN)BCl2][BCl4]·1.25[CH2Cl2], R1 = 0.1152,
wR2 = 0.2798, and the largest peak was 0.745 e Å–3 and was
associated with one of the methylene chloride solvent mole-
cules. In the final stages of refinement of [(Ar-
BIAN)GaCl2][GaCl4]· [CH2Cl2], R1 = 0.0534, wR2 = 0.1094,
and the largest residual peak was 0.447 e Å–3 and was asso-
ciated with the residual methylene chloride solvent. Full
crystallographic details can be found in Table 1.
1
were characterized by H NMR and IR spectroscopy. Poor
solubility of these ionic compounds made NMR studies dif-
ficult, and it was discovered that the compounds decompose
in CD2Cl2 solution (12). Fortunately, X-ray-quality crystals
were obtained from the mother liquors of [(Ar-
BIAN)BCl2][BCl4] and [(Ar-BIAN)GaCl2][GaCl4].
IR spectroscopic studies were performed on the [(Ar-
BIAN)(EX2)][EX4] series of compounds. The stretching fre-
quencies observed between 1660 and 1610 cm–1 have been
tentatively assigned to the ꢅ(C=N) stretches. The assign-
ments for the [(Ar-BIAN)(EX2)][EX4] complexes are as fol-
lows (cm–1): free ligand (1660 or 1640); E = B, X = Cl
(1646); E = B, X = Br (1636); E = Al, X = Cl (1627);
© 2002 NRC Canada

Jenkins et al.
1401
Fig. 1. ORTEP view of cation [(Ar-BIAN)BCl2]+ showing the labelling scheme. Thermal ellipsoids are shown at 50% probability level;
hydrogen atoms have been removed for clarity.
E = Ga, X = Cl (1621). The C=N stretching frequency in the
free ligand cannot be assigned unambiguously because of
the presence of C—C stretching frequencies from the naph-
thalene backbone in this region (9). The absorptions for the
C=N stretches in the complexes have been assigned because
of the fact that these peaks were discernible as being quite
strong and broad, consistent with a C=N stretch. More im-
portantly, the position of this absorption shifts upon complex
formation, and is dependent on the Lewis acid used in the
complexation reaction.
The absorptions for the E—X bonds are also informative.
The IR spectrum for [(Ar-BIAN)EX2][EX4] reveals two dif-
ferent E—X stretches from the two types of E—X bonds
present (i.e., one from the cation and one from the anion).
These two stretching bands are present at 691(s-br) and
658(s-br) cm–1 (E = B, X = Cl), 588(s) and 541(s) cm–1 (E =
B, X = Br), and 490(s) and 460(m) cm–1 (E = Al, X = Cl).
The stretching bands have been assigned based on known
E—X stretching regions and intensities (13). The stretches
for Ga—Cl bonds were not observed in the IR spectrum of
the [(Ar-BIAN)GaCl2][GaCl4] complex, as Ga—Cl bonds
absorb below 450 cm–1.
that [(Ar-BIAN)BCl2][BCl4] exists in the solid state as
discrete anions and cations, with no unusual interactions be-
tween the ions or the solvent.
The anion ([BCl4]–) is a distorted tetrahedron, with bond
angles between 100(1)° and 118(1)°, and B—Cl bond
lengths ranging from 1.74(3) to 1.95(3) Å. There are no un-
usual structural features associated with this anion. The closest
interactions between ions are between Cl4 and C21 (3.77 Å),
and B2 and the centre of the ring formed by C2ꢈC9 (4.25 Å).
The primary coordination sphere of the boron centre in the
[(Ar-BIAN)BCl2]+ cation features two NJB dative bonds
from the Ar-BIAN ligand (1.57(2) and 1.54(2) Å). Two
B—Cl bonds complete the [(Ar-BIAN)BCl2]+ coordination
sphere. The B—Cl bond lengths in the cationic fragment,
1.78(2) and 1.89(1) Å, are about the same as those of the an-
ionic fragment. For comparison, the B—Cl bond length in
BCl3 is 1.74 Å.3 An ORTEP view of the cation [(Ar-
BIAN)BCl2]+ is shown in Fig. 1, and important bond lengths
and angles are presented in Table 2.
[(Ar-BIAN)GaCl2][GaCl4] crystallizes in the monoclinic
space group P21/m, with two molecules in the unit cell. The
X-ray analysis of this complex also revealed that it exists in
the solid state as discrete anions and cations. The [GaCl4]–
anion is tetrahedral, with Ga—Cl bond angles between
106.54(9)° and 111.26(6)°, and bond lengths between
2.159(2) and 2.175(1) Å. There are no unusual structural
features associated with this anion.
Crystallographic studies on [(Ar-BAIN)BCl2][BCl4] and
[(Ar-BAIN)GaCl2][GaCl4]
[(Ar-BIAN)BCl2][BCl4]·1.25[CH2Cl2] crystallizes in the
uniquely determined orthorhombic space group P212121,
with four molecules in the unit cell. Crystals of this com-
pound were not well-formed, and resulted in overall R val-
ues that are somewhat high. The X-ray analysis does show
The primary coordination sphere of the cationic [(Ar-
BIAN)GaCl2]+ fragment features two NJGa dative bonds
from the Ar-BIAN ligand (1.985(3) Å). This Ga—N bond
3 Recently the reaction of a bulky 1,4-diazabutadiene with BCl3 was reported, and the isolated compound was characterised as a 2,4,5-
trichloro-1,3,2-diazaborolidine, which is a covalent alternative to the ionic diazaborolium salt. See reference 12. It is possible that a similar
rearrangement occurs in the [(Ar-BIAN)(EX2)][EX4] compounds reported here.
© 2002 NRC Canada

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Can. J. Chem. Vol. 80, 2002
Table 2. Comparison of [(Ar-BIAN)GaCl2][GaCl4], [(Ar-BIAN)BCl2][BCl4], and [(DAB)GaCl2][GaCl4].
General structure for comparison of bond lengths and angles in Ar-BIAN and DAB complexes
Parameter
[(Ar-BIAN)BCl2]+
[(Ar-BIAN)GaCl2]+
[(DAB)GaCl2]+
N—E
1.57(2), 1.54(2)
1.78(2), 1.89(1)
99.6(9)
115(1), 115(1), 108(1), 110.7(9)
108.5(7)
1.985(3)
2.106(2), 2.124(3)
85.1(2)
114.1(1), 111.9(1)
115.9(1)
1.979(5), 1.982(6)
2.105(2), 2.104(2)
84.4(2)
Not reported
118.2(1)
E—Cl
N-E-N
N-E-Cl
Cl-E-Cl
view of [(Ar-BIAN)GaCl2]+ is presented in Fig. 2. As shown
in Table 2, the metrical parameters observed for [(Ar-
BIAN)GaCl2][GaCl4] are similar to those reported for
[DABGaCl2][GaCl4] (DAB = t-BuN=C(H)-C(H) = NtBu)
(14).
Fig. 2. ORTEP view of cation [(Ar-BIAN)GaCl2]+ showing the
labelling scheme. Thermal ellipsoids are shown at 50% probabil-
ity level; hydrogen atoms have been removed for clarity.
There are no unusual long-range interactions between
ions, and the closest interactions are the Cl5—C18 distance
at 3.582 Å, and the Cl4 — centre of C13-C13A distance of
3.528 Å, and Ga2—C19 at 4.808 Å.
Attempts to prepare [(Ar-BIAN)ECl2][B(C6F6)4] via ion-
exchange reactions were unsuccessful. It was hoped that the
strong electron donating ability of 1 would facilitate forma-
tion of [(Ar-BIAN)ECl]++, via ion-exchange and halide ab-
straction from [(Ar-BIAN)ECl2]+, but this was not realised.
We are currently working on the preparation of amido-
substituted derivatives to facilitate the formation of [(Ar-
BIAN)ENR2]++, recognising the isoelectronic relationship
with, for example, the carbocation [CR3]+. Finally, attempts
to reduce [(Ar-BIAN)(EX2)][EX4] using Na or K to generate
compounds such as 3 have thus far been unsuccessful.
Conclusions
Several new main group complexes were prepared based
upon the o,o>-i-Pr2C6H3-bis(imino)acenaphthene ligand. The
Ar-BIAN ligand is easily prepared and is a robust ligand for
supporting highly Lewis acidic main group element sites.
Unfortunately, attempted reduction of [(Ar-BIAN)(EX2)][EX4]
to produce heterocycles such as 3 were unsuccessful.
distance is somewhat unusual because in most acyclic
trialkylamine adducts, the Ga—N bond distances are much
longer, being somewhere between 2.1 and 2.2 Å (14). This
is, however, not so surprising because N is sp2 hybridized
and therefore has a shorter covalent radius than an sp3 hy-
bridized nitrogen centre. The coordination sphere around the
cationic gallium centre in [(Ar-BIAN)GaCl2]+ is completed
by two Ga—Cl bonds of 2.106(2) and 2.124(3) Å. Important
bond lengths and angles are reported in Table 2. An ORTEP
Acknowledgements
The authors would like to thank the Natural Sciences and
Engineering Research Council of Canada (NSERC) and Si-
mon Fraser University for financial support.
© 2002 NRC Canada

Jenkins et al.
1403
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