Group 13 cation formation with a potentially tridentate ligand

Article abstract of DOI:10.1021/om000058m

A potentially tridentate ligand, Phensal(tBu)H₃, was prepared by the condensation of 1 equiv of phenylenediamine with 3,5-di-tert-butylsalicylaldehyde. When 1 equiv of this new ligand is added to AlMe₃, [[Phensal(tBu)HAlMe]]₂ (1) results. In contrast, this reaction with GaMe₃ produces [Phensal(tBu)H₂]GaMe₂ (2). When 1 or 2 equiv of Phensal(tBu)H₃ is combined with Et₂AlCl, the complex [Phensal(tBu)]₂AlCl (3) forms. However the same reaction with Me₂GaCl leads to [Phensal(tBu)H₂]Ga(Me)Cl (4). A cationic complex, {[Phensal(tBu)]₂Al}⁺Cl^- (5), is formed when 3 is dissolved in MeOH. The MeOH apparently mediates the formation of the cation but does not coordinate the cationic metal. When the solvent is removed, 5 reverts back to neutral 3. When 3 is combined with GaCl₃ in toluene, another cationic complex, {[Phensal(tBu)H₂]₂Al}⁺GaCl₄ ^- (6), is formed. In a similar manner, {[Phensal(tBu)H₂]₂Al}⁺Me₂AlC l₂^- (7) is formed by adding Me₂AlCl to 3. The compounds were characterized by mp, elemental analyses, IR, ¹H and ²⁷Al NMR, and in the case of 2, 5, and 6 single-crystal X-ray analysis.

Full text of DOI:10.1021/om000058m

4416
Organometallics 2000, 19, 4416-4421
Gr ou p 13 Ca tion F or m a tion w ith a P oten tia lly
Tr id en ta te Liga n d
Miguel-Angel Mun˜oz-Herna´ndez,† Timothy S. Keizer, Sean Parkin,
Brian Patrick, and David A. Atwood*
Department of Chemistry, The University of Kentucky, Lexington, Kentucky 40506-0055
Received J anuary 24, 2000
A potentially tridentate ligand, Phensal(tBu)H3, was prepared by the condensation of 1
equiv of phenylenediamine with 3,5-di-tert-butylsalicylaldehyde. When 1 equiv of this new
ligand is added to AlMe3, [[Phensal(tBu)HAlMe]]2 (1) results. In contrast, this reaction with
GaMe3 produces [Phensal(tBu)H2]GaMe2 (2). When 1 or 2 equiv of Phensal(tBu)H3 is
combined with Et2AlCl, the complex [Phensal(tBu)]2AlCl (3) forms. However the same
reaction with Me2GaCl leads to [Phensal(tBu)H2]Ga(Me)Cl (4). A cationic complex,
{[Phensal(tBu)]2Al}+Cl- (5), is formed when 3 is dissolved in MeOH. The MeOH apparently
mediates the formation of the cation but does not coordinate the cationic metal. When the
solvent is removed, 5 reverts back to neutral 3. When 3 is combined with GaCl3 in toluene,
another cationic complex, {[Phensal(tBu)H2]2Al}+GaCl4- (6), is formed. In a similar manner,
{[Phensal(tBu)H2]2Al}+Me2AlCl2- (7) is formed by adding Me2AlCl to 3. The compounds were
1
characterized by mp, elemental analyses, IR, H and 27Al NMR, and in the case of 2, 5, and
6 single-crystal X-ray analysis.
In tr od u ction
The Salen1 class of ligands (Figure 1) have utility in
the isolation of higher coordinate monometallic group
13 complexes. Some examples include those incorporat-
ing boron,2 aluminum,3,4 gallium,5 and indium6,7 and
aluminum amides,8 alkoxides,9 siloxides,10 and chelated
higher coordinate cations.11-15 Under appropriate condi-
tions bimetallic compounds can also be formed.16-18
Beyond their fundamental interest the cations have
F igu r e 1. (a) General view of the Salen(tBu)H2 ligands
(R ) N,N′-alkylene or phenylene and (b) the ligand,
Phensal(tBu)H, used in this study.
† Current address: Universidad Autonoma del Estado de Morelos,
Centro de Investigaciones QuIÅmicas, Av. Universidad No. 1001, Col.
Chamilpa, Cuernavaca, Morelos 62210, Mexico.
(1) “Salen” is the name that has historically been used to describe
the entire class of such ligands possessing various diamino backbones.
However, it is also the specific name of the ethyl derivative, SalenH2.
The Salen(tBu)H2 ligands possess tBu groups at the 4- and 6-positions
of the phenol portion of the ligand.
(2) Wei, P.; Keizer, T.; Atwood, D. A. Inorg. Chem. 1999, 38, 3914.
(3) zugan, S. J .; Goedken, V. L. Inorg. Chem. 1986, 25, 2858.
(4) Leung, W.-H.; Chan, E. Y. Y.; Chow, E. K. F.; Williams, I. D.;
Peng, S.-M. J . Chem. Soc., Dalton Trans. 1996, 1229.
(5) Hill, M. S.; Atwood, D. A. Eur. J . Inorg. Chem. 1998, 67.
(6) Atwood, D. A.; J egier, J . A.; Rutherford, D. Bull. Chem. Soc. J pn.
1997, 70, 2093.
(7) Hill, M. S.; Atwood, D. A. Main Group Chem. 1998, 2, 191.
(8) Rutherford, D.; Atwood, D. Organometallics 1996, 15, 4417.
(9) Gurian, P. L.; Cheatham, L. K. Ziller, J . W.; Barron, A. R. J .
Chem. Soc., Dalton Trans. 1991, 1449.
(10) Atwood, D. A.; Hill, M. S.; J egier, J . A.; Rutherford, D.
Organometallics 1997, 16, 2659.
(11) Atwood, D. A.; J egier, J . A.; Rutherford, D. J . Am. Chem. Soc.
1995, 117, 6779.
(12) Atwood, D. A. J egier, J . A.; Rutherford, D. Inorg. Chem. 1996,
35, 63.
(13) Davidson, M. G.; Lambert, C.; Lopez-Solera, I.; Raithby, P. R.;
Snaith, R. Inorg. Chem. 1995, 34, 3765.
(14) J egier, J . A.; Munoz-Hernandez, M.-A.; Atwood, D. A. J . Chem.
Soc., Dalton Trans. 1999, 2583.
potential as initiators in the cationic oligomerization of
propylene oxide.11 More recently it has been found that
lower coordinate group 13 cations are active as olefin
polymerization agents.19 This has focused attention on
the possible utility of anionic single-charged ligands
with two or three coordinating heteroatoms.
Herein is presented work toward examining the
reaction chemistry of three-coordinate ligands in form-
ing cationic aluminum compounds while still taking
advantage of the low cost, variability, and ease of
synthesis inherent to the components that make up the
Salen ligands. This will be attempted using a tridentate
ligand, Phensal(tBu)H3 (where Phensal(tBu)H ) sali-
cylidene(1-iminophenylene-2-amine)), which is similar
to the Salen ligands but contains only one phenol unit
(see Figure 1). Non-tert-butylated versions of the ligands
have been used previously to prepare interesting transi-
tion metal complexes20-23 and a few organoantimony
(15) Munoz-Hernandez, M.-A.; Sannigrahi, B.; Atwood, D. A. J . Am.
Chem. Soc. 1999, 121, 6747.
(16) Chong, K. S.; Rettig, S. J . Storr, A. Trotter, J . Can. J . Chem.
1977, 55, 2540.
(17) Hill, M. S.; Wei, P.; Atwood, D. A. Polyhedron 1998, 17, 811.
(18) Wei, P.; Atwood, D. A. Inorg. Chem. 1997, 36, 4060.
(19) (a) Coles, M. P.; J ordan, R. F. J . Am. Chem. Soc. 1997, 119,
8125. (b) Ihara, E.; Young, V. G.; J ordan, R. F. J . Am. Chem. Soc. 1998,
120, 8277. (c) Bruce, M.; Gibson, V. C.; Redshaw, C.; Solan, G. A.;
White, A. J . P.; Williams, D. J . Chem. Commun. 1998, 2523.
(20) Co(II), Ni(II), and Cu(II): Dash, G. C.; Mohapatra, B. K. Acta
Chim. Hung. 1986, 122, 85.
10.1021/om000058m CCC: $19.00 © 2000 American Chemical Society
Publication on Web 09/21/2000

Group 13 Cation Formation
Organometallics, Vol. 19, No. 21, 2000 4417
Sch em e 1. Gen er a l Syn th eses of Com p ou n d s 1-4
(th e P h en sa l liga n d is gen er a lized for th e
str u ctu r e of 1 a n d sim p ly n a m ed “L” in th e
for m u la s of 2 a n d 3)
F igu r e 2. Molecu la r str u ctu r e of [P h en sa l(tBu )H2]-
Ga Me2 (2).
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [P h en sa l(tBu )H2]Ga Me2 (2)
Ga(1)-O(1)
Ga(1)-C(1)
O(1)-C(3)
1.893(2)
1.947(3)
1.316(3)
Ga(1)-N(1)
Ga(1)-C(2)
N(1)-C(9)
2.028(2)
1.947(4)
1.290(3)
O(1)-Ga(1)-C(1)
C(1)-Ga(1)-C(2)
C(1)-Ga(1)-N(1)
107.2 (1)
127.4 (2)
109.0 (1)
O(1)-Ga(1)-C(2)
O(1)-Ga(1)-N(1)
C(2)-Ga(1)-N(1)
109.6(1)
91.30(8)
106.4 (1)
ppm) and as two peaks (3472 and 3388 cm-1) in the IR.
The crystal structure reveals that the pendant amine
is oriented away from the four-coordinate, distorted
tetrahedral, gallium atom (Figure 2). The Ga-C dis-
tances are equivalent (1.947 Å) and longer than the
Ga-O (1.893(2) Å) and Ga-N (2.028(2) Å) distances
(Table 1). Distortions from an ideal Td geometry are
observed in the O-Ga-N angle, which is more nar-
rowed (91.30(8)°) (a common feature in bidentate ligands
containing N or O), and in the C-Ga-C angle, which
is more obtuse (127.4(2)°).
It is more difficult to remove the second alkyl group
from gallium by comparison with aluminum. This has
been observed in a related compound, [SalenH]GaMe2,
in which the Ga-C bond coexists with a phenol proton.27
This is not a unique occurrence. It has been demon-
strated previously that the [GaMe2]+ fragment can
remain stable in aqueous sulfuric acid.28 Apparently,
increasing the electronegativity of gallium, either by
making the atom cationic or by substituting a Ga-C
bond for a Ga-O bond (as occurs in 2), has the effect of
making the remaining Ga-C bonds less ionic and
thereby less reactive with protic reagents. Gallium is
like boron in this regard.
compounds.24 However, no group 13 complexes have yet
been prepared with these ligands.
Resu lts a n d Discu ssion
When AlMe3 is mixed with Phensal(tBu)H3 (Scheme
1a) 2 mol of methane are eliminated and the red-colored
[[Phensal(tBu)H]AlMe]2 (1) is formed. The 1H NMR
supports this formulation with an integration of 3H for
the Al-Me group (δ -0.91 ppm) and 18H for the tBu
groups of the ligand. The remaining NH is observed in
the NMR (δ 2.85 ppm) and the IR (3332 cm-1). However,
the 27Al NMR peak at 20 ppm is difficult to interpret.
Resonances for six-coordinate aluminum generally ap-
pear at ∼10 ppm, while those for four-coordinate
aluminum appear at ∼150 ppm.25 The more rare five-
coordinate aluminum resonances generally appear at
∼100 ppm.26 Thus, the resonance observed for 1 is best
interpreted as being six-coordinate, although it is hard
to visualize how this occurs since any dimerization
would lead to a maximum of five-coordination.
A different product is observed when the same reac-
tion is conducted with GaMe3 (Scheme 1b). Only 1 mol
of methane is lost and the product [Phensal(tBu)H2]-
GaMe2 (2) results. There is one resonance for the Ga-
Me groups (δ -0.28 ppm) at lower field than was
observed for the Al-Me group in 1. The NH2 protons
are manifested as a broad singlet in the 1H NMR (δ 3.69
Combination of 2 equiv of Phensal(tBu)H with Et2-
AlCl in toluene leads to the formation of 3 in high yield
(Scheme 1c). Interestingly, this is the product, albeit in
lower yield, when the reaction is conducted in a 1:1
stoichiometry. The 27Al NMR data (δ 17 ppm) was
indicative of a six-coordinate geometry around alumi-
num. This would imply the presence of a free amine
(NH2) group. In fact, there are two widely spaced
(21) Ni(II) and Cu(II): Costes, J . P.; Fernandez-Garcia, M. I. Inorg.
Chim. Acta 1995, 237, 57.
(22) Burke, F. J .; McMillin, D. R. J . Chem. Soc., Dalton Trans. 1980,
1794.
(23) Ni(II): Elder, R. C. Aust. J . Chem. 1978, 31, 35.
(24) J ha, N. K.; J oshi, D. M.; Synth. React. Inorg. Met.-Org. Chem.
1986.
(25) For a molecule that contains both four- and six-coordinate
aluminum see: Atwood, D. A.; J egier, J . A.; Liu, S.; Rutherford, D.;
Wei, P.; Tucker, R. C. Organometallics 1999, 18, 976.
(26) Lewinski, J .; Gos, P.; Kopec, T.; Lipkowski, J .; Luboradzki, R.
Inorg. Chem. Comm. 1999, 2, 374.
1
resonances in the H NMR which can be attributed to
these groups (δ ∼3.7 and 8.0 ppm). The more deshielded
resonance is assumed to be the one that is not coordi-
nated. Moreover, the resonance at higher field corre-
sponds closely with what is observed in the free ligand
(27) Hill, M. S.; Wei, P.; Atwood, D. A. Polyhedron 1998, 17, 811.
(28) Beachley, O. T., J r,; Kirss, R. U.; Bianchini, R. J .; Royster, T.
L. Organometallics 1987, 6, 724.

4418 Organometallics, Vol. 19, No. 21, 2000
Mun˜oz-Herna´ndez et al.
Sch em e 2. F or m a tion of th e Ca tion ic P r od u cts
Sta r tin g w ith Com p ou n d 3
(see Experimental Section). Noncoordinated NH2 groups
are a rather rare situation when “half-unit” ligands
derived from salicylaldehyde and diamines are used. For
example, the only crystal structure known so far that
features a free pendant NH2 is the one found in [PPh4]2-
[Mo(CN)3O(Ensal)]‚5.5H2O (where Ensal ) salicylidene-
(1-iminoethylene-2-amine).29 In the other crystal struc-
tures known with similar ligands, the NH2 groups are
coordinating the metal.30-32 Therefore, on the basis of
the spectroscopic evidence and the crystal structures
obtained for the derivatives 5 and 6 (see discussion
below), compound 3 may be the first example of a
complex showing a tridentate and bidentate coordina-
tion with the same kind of ligand. Substituting Me2GaCl
into this reaction, conducted under the same conditions,
leads to the more traditional product, [Phensal(tBu)H2]-
F igu r e 3. Molecular structure of {[Phensal(tBu)-
H2]2Al}+Cl- (5).
1
Ga(Me)Cl (4) (Scheme 1d). The Me resonance in the H
NMR appears as a singlet (δ -0.14 ppm), and there is
no reason to suppose that the molecule is dimeric in
solution.
Dissolution of 3 in MeOH leads to the formation of a
compound having a six-coordinate aluminum and equiva-
lent imine (HCdN) groups (Scheme 2a). Furthermore,
removal of the solvent causes 3 to re-form, as shown by
1
the H NMR. It is likely that the compound in solution
is the cation, [{Phensal(tBu)}2Al]+ Cl- (5). The cation
1
5 in CD3OD does not show NH2 resonances in the H
NMR, which might be a consequence of hydrogen
bonding or due to exchange of the amine protons with
deuterium of the NMR solvent. The 27Al NMR data (δ
20.34 ppm) are consistent with a six-coordinate ar-
rangement about aluminum. It definitely is six-coordi-
nate in the solid (Figure 3).
We have previously demonstrated that group 13
cations can be formed through the base-promoted
displacement of halide.33 This occurred when the base
was H2O, MeOH, and, proving that hydrogen bonding
was not critical, with Ph3P(O).34 In these examples the
added base remained on the group 13 element after
departure of the halide. In 5, however, this is not the
case, and also contrasting with past results, hydrogen
bonding is implicated. The MeOH must facilitate re-
moval of the halide through hydrogen bonding. The
F igu r e 4.
Dimeric structure of {[Phensal(tBu)-
H2]2Al}+Cl- (5) resulting from hydrogen bonding (HN-
H- - -Cl-).
Lewis basicity of the MeOH is not sufficient to allow it
to compete for a coordination site with internal solvation
of an amine. Although there is MeOH in the crystal
lattice, it is not involved in hydrogen bonding with the
resulting cation. Rather, there is hydrogen bonding
between the chlorides and the amine groups. These
organize two cations into a dimeric structure (Figure
4).
The chloride of 3 can be permanently displaced by
the addition of GaCl3 in CH2Cl2 (Scheme 1f). The
-
resulting cationic complex, [Phensal(tBu)}Al]+GaCl4
(6), still features two NH2 resonances, but they are
now more closely spaced (δ ∼4.0 and 4.8 ppm). The
27Al NMR confirms the six-coordinate nature of 6 in
solution (δ 18 ppm). The compound is also cationic
in the solid (Figure 5). The same cation can be pre-
pared by adding Me2AlCl to 3 to form the ion pair
(29) Nowick B.; Samotus, A.; Szklarzewicz, J .; Heinemann, F. W.;
Kisch, H. J . Chem. Soc., Dalton Trans. 1998, 4009.
(30) ardner, A. P.; Gatehouse, B. M.; White, J . C. B. Acta Crystal-
logr., Sect. B 1971, 27, 1505.
(31) Summerton, A. P.; Diamantis, A. A.; Snow, M. R. Inorg. Chim.
Acta 1978, 27, 123.
(32) Root, C. A.; Hoeschele, J . D.; Cornman, C. R.; Kampf, J . W.;
Pecoraro, V. L. Inorg. Chem. 1993, 32, 3855.
(33) J egier, J . A.; Atwood, D. A. Inorg. Chem. 1997, 36, 2034.
(34) Atwood, D. A. Coord. Chem. Rev. 1998, 176, 407.
[Phensal(tBu)}Al]+Me2AlCl2 (7). This serves to dem-
onstrate the general utility of this cation-forming reac-
tion.
-

Group 13 Cation Formation
Organometallics, Vol. 19, No. 21, 2000 4419
is observed in the [SalenAl(base)2]+Cl-. These distances
are similar to what is observed in [{η3-HB(3-Phpz)2(5-
Phpz)}2Al]+[AlCl4]- (where the distances fall in the
range 1.951(9)-2.066(8) Å.35 The oxygen distances are
shorter yet, 1.799(4)-1.816(5) Å. The greater deviations
from an Oh geometry in 5 and 6 are the result of the
rigidity of the ligand imposed by the phenylene ring.
(e.g., compound 6: N(1)-Al(1)-O(1), 168.0(3)°, and
N(3)-Al(1)-O(2), 169.7(3)°). The molecular structures
of cations 5 and 6 are similar to the cationic complexes
[(Ensal)2M]+X-‚nH2O (where M ) Cr, Fe, Co; X ) Cl,
I).14b Coordination of the NH2 groups is also observed
in dimeric [(1,2-Pnsal)VO2]2 (where 1,2-Pnsal ) sali-
cylidene(1-iminopropylene-2-amine).14cAn interesting fea-
ture in both structures is the hydrogen bonding. These
bonds are made with the amine groups and the anions.
In 5, these contacts form a dimer (which contrasts with
6, which remains monomeric).
F igu r e 5. Molecular structure of {[Phensal(tBu)]2Al}+-
-
GaCl4 (6) showing the hydrogen bonding HN-H- - -
-
ClGaCl3
.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 5 a n d 6
Con clu sion s
New tridentate ligand complexes of aluminum were
formed, three of which were cationic. It was demon-
strated that one of the cations was formed through a
new route: hydrogen-bond-mediated halide displace-
ment.
5
6
Al(1)-O(1)
1.799(4)
1.816(5)
2.073(6)
1.961(6)
2.059(7)
1.972(6)
95.6(2)
171.1(2)
88.3(2)
80.7(2)
86.9(3)
94.9(2)
92.3(2)
171.9(3)
91.0(2)
95.2(2)
90.3(2)
170.4(2)
92.9(2)
91.5(2)
1.804(6)
1.799(5)
2.114(8)
1.970(6)
2.061(8)
1.971(6)
97.4(3)
168.0(3)
88.9(3)
79.1(3)
87.1(4)
93.8(3)
93.5(3)
170.9(3)
90.1(3)
95.1(3)
88.3(4)
169.7(3)
96.4(3)
90.5(3)
Al(1)-O(2)
Al(1)-N(1)
Al(1)-N(2)
Al(1)-N(3)
Al(1)-N(4)
Exp er im en ta l Section
O(1)-Al(1)-O(2)
N(1)-Al(1)-O(1)
N(1)-Al(1)-O(2)
N(1)-Al(1)-N(2)
N(1)-Al(1)-N(3)
N(1)-Al(1)-N(4)
N(2)-Al(1)-N(3)
N(2)-Al(1)-N(4)
N(2)-Al(1)-O(1)
N(2)-Al(1)-O(2)
N(3)-Al(1)-O(1)
N(3)-Al(1)-O(2)
N(4)-Al(1)-O(1)
N(4)-Al(1)-O(2)
Gen er a l Con sid er a tion s. All manipulations were con-
ducted using Schlenk techniques in conjunction to an inert
atmosphere glovebox. All solvents were rigorously dried prior
to use. NMR data were obtained on J EOL-GSX-400 and -270
instruments operating at 270.17 and 399.78 MHz and are
reported relative to SiMe4 in ppm. Elemental analyses were
obtained on a Perkin-Elmer 2400 analyzer and were satisfac-
tory for all compounds. Infrared data were recorded as KBr
pellets on a Matheson Instruments 2020 Galaxy Series spec-
trometer and are reported in cm-1. Mass spectral data were
obtained on a Kratos CONCEPT IH instrument at 70 eV. The
reagent 3,5-di-tert-butyl-2-hydroxybenzaldehyde was prepared
according to the literature.36
Adequate crystals of 5 and 6 for X-ray diffraction were
obtained from MeOH and CH2Cl2, respectively. Several
crystals were coated with a dense oil (Paraton-N), and
data for the best looking ones were collected at -100
°C. The final crystal structures show residual disordered
solvent that adversely affects the R values. Additionally,
5 always produced twinned crystals, even under vari-
able crystal growth conditions. However, the connectiv-
ity of compounds 5 and 6 is unambiguous, and no
exceptional claims are being made for the bond dis-
tances or angles within the structures.
Selected bond distances and angles for compounds 5
and 6 are summarized in Table 2, and crystallographic
data are presented in Table 3. Although it was not
possible to obtain ideal data on crystals of these two
compounds, the molecular structures of compounds 5
and 6 (Figures 3 and 4) confirm the six-coordinate
environment of the aluminum atoms. The ligands are
arranged in a meridional configuration about alumi-
num. The overall geometry around the metallic center
can be described as distorted octahedral. The amine
groups of the ligands are coordinated to the metal with
distances in the range of 2.059(7)-2.114(8) Å, which are
longer than the imine nitrogen distances, 1.961(6)-
1.972(6) Å. These latter distances are similar to what
X-ray diffraction data were collected at 173 K on a Nonius
kappa-CCD diffractometer from irregularly shaped crystals.37
The structure(s) was solved by direct methods (SHELXS97)38
and difference Fourier (SHELXL97) techniques. Refinement
was carried out against F2 by weighted full-matrix least-
squares (SHELXL97) methods. Hydrogen atoms were either
found in difference maps or placed at calculated positions, and
refined using a riding model. Non-hydrogen atoms were refined
with anisotropic displacement parameters. Atomic scattering
factors were taken from the International Tables for Crystal-
lography.39 The best data obtained on multiple crystals for
compounds 5 and 6 were poor. Compound 5 crystallizes
twinned from MeOH regardless of crystal growth conditions.
Compound 6 produces weakly diffracting crystals in CH2Cl2.
Attempts to grow X-ray quality crystals from other solvents
was unsuccessful. Consequently, no undo claims are being
(35) Darensbourg, D. J .; Maynard, E. L.; Holtcamp, M. W.; Klaus-
meyer, K. K.; Reibenspies, J . H. Inorg. Chem. 1996, 35, 2682.
(36) Casiraghi, G.; Casnati, G.; Puglia, G.; Sartori, G.; Terenghi, G.
J . Chem. Soc., Perkin Trans. 1980, 1862.
(37) Otwinowski, Z.; Minor, W. Processing of x-ray diffraction data
collected in oscillation mode. Methods in Enzymology, Vol. 276:
Macromolecular Crystallography part A; Carter, C. W., J r., Swet, R.
M., Eds.; Academic Press: New York, 1997; pp 307-326.
(38) Sheldrick, G. M. SHELX97, Programs for Crystal Structure
Solution and Refinement; University of Gottingen: Germany, 1997.
(39) International Tables for Crystallography, Vol. A: Space Group
Symmetry; Hahn, Th., Ed.; Kluwer Academic Publishers: Holland.

4420 Organometallics, Vol. 19, No. 21, 2000
Mun˜oz-Herna´ndez et al.
Ta ble 3. Cr ysta llogr a p h ic Da ta for Str u ctu r a lly Ch a r a cter ized Com p ou n d s 2, 5, a n d 6
2
5
6
formula
fw
C
23H33GaN2O
C47H54AlClN4O7
849.37
C45H59AlCl13GaN4O2
1245.51
423.23
cryst size (mm)
cryst syst
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
0.8 × 0.4 × 0.3
monoclinic
12.540(1)
9.380(1)
20.3240(2)
90.0
99.77(1)
90.0
2356.0(4)
4
0.3 × 0.4 × 0.4
monoclinic
15.065(3)
18.004(4)
17.825(4)
90.0
90.91(3)
90.0
4834.07(2)
4
0.43 × 0.29 × 0.24
triclinic
12.485(1)
14.1770(1)
17.509(1)
85.90(1)
84.88(1)
74.33(1)
2968.4(4)
2
Z
space group
P21/n
1.193
1.181
P21/c
1.167
0.148
P1h
D
calc (g/cm3)
1.394
abs coeff (mm-1
)
1.101
radiation, KR; λ (Å)
temp (K)
Mo; 0.71073
173
Mo; 0.71073
173
Mo; 0.71073
173
2θ range (deg)
reflns collected
ind reflns
4.80-50.0
5.34-41.48
3.70-44.98
8285
8954
13 075
4075
4665
7590
no. of reflns used
no. of params
R
3925 [F > 4.0σ(F)]
4653 [F > 4.0σ(F)]
7578 [F > 4.0σ(F)]
244
545
660
0.0401
0.1219
0.1043
Rw
0.0894
0.2927
0.2524
GOF
1.056
0.310 and -0.224
1.122
0.434 and -0.357
1.091
1.571 and -0.804
electron density (e/Å3)
made for the bond distances and angles within these struc-
tures; they are only presented to verify the molecular con-
nectivity. The data are sufficient for this purpose. Spatial
variation in the R value as a function of position in reciprocal
space was checked by the R-tensor method.40 For 5 the fit is
noticeably anisotropic, which is consistent with twinning. This
analysis indicated that the solution for 6 was correct, but the
quality was reduced by the weakness of the data. Further
details of the structure analyses are given in Table 3.
[P h en sa l(tBu )H2]Ga Me2 (2). A solution of trimethylgal-
lium (1.05 g, 9.2 mmol) in toluene (15 mL) was added slowly
at room temperature to a quickly stirred solution of Phensal-
(tBu)H (3.0 g, 9.2 mmol) in toluene (40 mL). The resulting
orange solution was stirred for 5 h. Removal of the solvent
left an orange solid, which was recrystallized from 30 mL of
hexanes, affording adequate crystals for X-ray analysis.
Yield: 3.2 g (82%). Mp: 118 °C. 1H NMR (CDCl3): δ -0.28 [s,
6H, GaCH3], 1.30 [s, 9H, C(CH3)3], 1.44 [s, 9H, C(CH3)3], 3.69
[s, 2H, PhNH2], 6.79-7.54 [m, 6H, C6H2+C6H4], 8.15 [s, 1H,
CHN]. IR: 3472 (w), 3388 (m), 3004 (s), 2962 (s), 2908 (m),
2867 (m), 1624 (s), 1615 (m), 1600 (s), 1593 (m), 1535 (s), 1499
(m), 1459 (m), 1431 (m), 1386 (m), 1256 (m), 1203 (m), 1189
(m), 1165 (s), 751 (m). MS (EI+): 421.3 (5%) M+ - H, 407.3
(100%) M+ - CH3. Anal. Calcd (Found) for C23H33GaN2O: C,
65.37 (65.21); H, 7.88 (7.92).
P r ep a r a tion of P h en sa l(tBu )H3. To a solution of phe-
nylendiamine (5.12 g, 85.34 mmol) disolved in EtOH (100 mL)
was added 3,5-di-tert-butyl-2-hydroxybenzaldehyde (10 g, 42.7
mmol) in EtOH (150 mL). The reaction mixture was heated
to reflux for 4 h and then concentrated to ∼100 mL by
distillation. Storage at -30 °C deposited yellow crystals of
Phensal(tBu)H3, which were filtered by suction filtration and
washed twice with cold EtOH (10 mL). Yield: 12.1 g, 87%.
Mp: 126-127 °C. 1H NMR (199.97 MHz, CDCl3): δ 1.14 [s,
9H, C(CH3)3], 1.28 [s, 9H, C(CH3)3], 3.81 [s (br), 2H, NH2], 6.61
[m, 2H, C6H4], 6.88 [m, 2H, C6H4], 7.05 [d, 1H, C6H2], 7.25 [d,
1H, C6H2], 8.44 [s, 1H, CHN]. IR (cm-1): 3487 (m), 3290 (m),
2958 (m), 2943 (m), 2909 (w), 2866 (w), 2364 (w), 2333 (w),
1615 (s), 1492 (m), 1461 (m), 1434 (m), 1392 (w), 1353 (m),
1311 (m), 1268 (m), 1245 (m), 1160 (s), 1025 (w), 975 (w), 929
(w), 875 (w), 751 (s), 685 (w), 635 (w), 574 (w). Anal. Calcd
(found) for C21H27N2O: C, 77.96 (77.84); H, 8.36 (8.41).
[[P h en sa l(tBu )H]AlMe]2 (1). A solution of trimethylalu-
minum (1.11 g, 15.4 mmol) in toluene (25 mL) was added
slowly at room temperature to a quickly stirred solution of
Phensal(tBu)H3 (5.0 g, 15.4 mmol) in toluene (150 mL). The
resulting red solution was stirred for 5 h. Removal of the
solvent left a red solid. The solid was washed with 10 mL of
hexanes twice and then dried under vacuum to yield 3.4 g
(78%). Mp: 182 °C (dec). 1H NMR (CDCl3): δ -0.91 [s, 3H,
AlCH3], 0.99 [s, 18H, C(CH3)3], 2.85 [s, 1H, PhNH], 6.41-7.12
[m, 6H, C6H2+C6H4], 7.99 [s, 1H, CHN]. 27Al (CDCl3): 20.14
(w1/2 ) 190.1 Hz). IR: 3332 (w), 3225 (w), 2977 (s), 2900 (m),
2865 (m), 1619 (s), 1614 (m), 1593 (m), 1537 (s), 1489 (m), 1464
(m), 1436 (s), 1412 (w), 1387 (m), 1362 (w), 1328 (w), 1258 (w),
1203 (m), 1169 (m), 751 (m). MS (EI+): 728.7 (8%) M+, 713.7
(32%) M+ - CH3, 671.6 (100%) M+ - tBu. Anal. Calcd (Found)
for C22H29AlN2O: C, 72.50 (71.96); H, 8.02 (7.92).
P r ep a r a tion of [P h en sa l(tBu )H]2AlCl (3). X-ray quality
crystals of 3, in ∼40% yield, were obtained from a reaction
employing a ligand-to-metal ratio of 1:1. A higher yield
preparation requires a 2:1 ligand-to-metal ratio. Accordingly,
a solution of diethylaluminum chloride (2.79 g, 23.11 mmol)
in toluene (25 mL) was added at room temperature to a quickly
stirred solution of Phensal(tBu)H3 (15.0 g, 46.23 mmol) in
toluene (150 mL). The resulting yellow solution was stirred
for 5 h. Removal of the solvent left a yellow-greenish powder
of Phensal(tBu)AlCl, which was washed twice with hexanes
(20 mL) and then dried under vacuum. Yield: 15.6 g (95%).
1
Mp: 291-292 °C. H NMR (CDCl3): δ 0.66 [s, 18H, C(CH3)3],
1.11 [s, 18H, C(CH3)3], 3.68 [d, 2H, PhNH2], 6.99-7.40 [m, 12H,
C6H2+C6H4], 8.03 [d, 2H, PhNH2], 8.65 [s, 2H, CHN]. 27Al-
{1H} NMR (CDCl3): δ 17.13 (w1/ 2 ) 198.5 Hz). The NMR
spectra taken in CD3OH match those for 5. IR (cm-1): 3297
(m), 2945 (s), 2341 (w), 1712 (w), 1621 (s), 1603 (s), 1497 (m),
1461 (s), 1434 (s), 1389 (s), 1358 (m), 1320 (m), 1278 (w), 1258
(s), 1176 (s), 1139 (m), 1097 (w), 1041 (w), 936 (m), 841 (m),
751 (s), 607 (m), 501 (w), 478 (w). MS (EI+): 671.4 (100%) M+
- Cl - 2H. Anal. Calcd (Found) for C42H54AlClN4O2: C, 70.93
(71.23); H, 7.96 (7.92).
[P h en sa l(tBu )H2]Ga MeCl (4). A solution of dimethylgal-
lium chloride (1.24 g, 9.2 mmol) in toluene (15 mL) was added
slowly at room temperature to a quickly stirred solution of
Phensal(tBu)H3 (3.0 g, 9.2 mmol) in toluene (40 mL). The
resulting green solution was stirred for 5 h. Removal of the
solvent left a yellow solid, which was washed several times
(40) Parkin, S. Acta Crystallogr. 2000, A56, 157.

Group 13 Cation Formation
Organometallics, Vol. 19, No. 21, 2000 4421
{[P h en sa l(tBu )]2Al}+Me2AlCl2 (7). A solution of dim-
-
with hexanes and then dried under vacuum to afford 2.8 g
(69%) of 4. Mp: 71 °C. 1H NMR (CDCl3): δ -0.14 [s, 3H,
GaCH3], 1.04 [s, 9H, C(CH3)3], 1.21 [s, 9H, C(CH3)3], 3.79 [s,
2H, PhNH2], 6.57-7.38 [m, 6H, C6H2+C6H4], 8.16 [s, 1H,
CHN]. IR: 3374 (w), 3336 (w), 3299 (w), 2965 (s), 2950 (m),
2936 (m), 2895 (m), 1613 (s), 1588 (s), 1537 (s), 1461 (m), 1426
(m), 1389 (m), 1251 (m), 1173 (m). MS (EI+) 442.3 (10%) M+,
427.2 (85%) M+ - CH3, 406.3 (100%) M+ - HCl, 391.3 (100%)
M+ - HCl - CH3. Anal. Calcd (Found) for C22H30ClGaN2O:
C, 59.71 (59.66); H, 6.84 (6.72).
ethylaluminum chloride (0.29 g, 3.08 mmol) in toluene (10 mL)
was added at room temperature to a quickly stirred solution
of Phensal(tBu)H (1.0 g, 3.08 mmol) in toluene (30 mL). The
resulting yellow solution was stirred for 3 h, and the solvent
was removed in vacuo. The resulting solid was washed twice
with hexanes and dried under vacuum to afford 1.13 g (78%)
of 7. Mp: 176-180 °C (dec). 1H NMR (CDCl3): δ -0.97 [s, 6H,
Al(CH3)2], 0.65 [s, 18H, C(CH3)3], 1.04 [s, 18H, C(CH3)3], 3.83
[d, 2H, PhNH2], 6.10 [d, 2H, PhNH2], 6.97-7.40 [3m, 12H,
C6H2+C6H4], 8.62 [s, 2H, CHN]. 27Al{1H} NMR (CDCl3): δ
16.91 (w1/ 2 ) 708.8 Hz); 101.08 (w1/ 2 ) 104.2 Hz). IR (cm-1):
3289 (w), 3192 (w), 2970 (s), 2908 (m), 2873 (m), 1617 (s), 1603
(m), 1593 (s), 1537 (s), 1494 (m), 1460 (s), 1433 (s), 1361 (m),
1257 (m), 1193 (m), 1174 (s), 754 (s). Anal. Calcd (Found) for
P r ep a r a tion of {[P h en sa l(tBu )H2]2Al}+Cl- (5). A solu-
tion of Phensal(tBu)AlCl (0.5 g) in MeOH (20 mL) was stored
at -30 °C, and after several weeks adequate crystals for X-ray
analysis of {[Phensal(tBu)]2Al}Cl were obtained. When the
crystals are dried in a vacuum, the cation goes back to
[Phensal(tBu)Al]2Cl (3) (as determined by 1H and 27Al NMR
in CDCl3). This occurs partially on exposure to nitrogen within
a drybox. 1H NMR (CD3OD): δ 0.90 [s, 18H, C(CH3)3], 1.25 [s,
18H, C(CH3)3], 7.21-7.93 [m, 12H, C6H2+C6H4], 9.17 [s, 2H,
CHN]. 27Al{1H} NMR (CD3OD): δ 20.34 (w1/ 2 ) 148.9 Hz).
P r ep a r a tion of {[P h en sa l(tBu )]2Al}+Ga Cl4- (6). A solu-
tion of GaCl3 (0.13 g, 0.71 mmol) in CH2Cl2 (10 mL) was added
at room temperature to a quickly stirred solution of Phensal-
(tBu)AlCl (0.5 g, 0.71 mmol) in CH2Cl2 (30 mL). The resulting
orange solution was stirred for 3 h and concentrated in a
vacuum to ∼10 mL. Storage of the solution at -30 °C for
several weeks and separation by cannula filtration afforded
crystlline {[Phensal(tBu)]2Al}GaCl4 adequate for X-ray analy-
C
42H54AlCl4GaN4O2: C, 71.12 (71.35); H, 7.67 (7.48).
Ack n ow led gm en t. This work was supported by the
National Science Foundation NSF-CAREER award
(CHE 9625376) and the donors of the Petroleum Re-
search Fund (Grant 31901-AC3), administered by the
American Chemical Society. NMR instruments used in
this research were obtained with funds from the CRIF
program of the National Science Foundation (CHE
997841) and from the Research Challenge Trust Fund
of the University of Kentucky.
1
sis. Yield: 0.46 g (72%). Mp: 268-271 °C. H NMR (CDCl3):
δ 0.67 [s, 18H, C(CH3)3], 1.03 [s, 18H, C(CH3)3], 4.04 [d, 2H,
PhNH2], 4.78 [d, 2H, PhNH2], 6.89-7.43 [m, 12H, C6H2+C6H4],
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data for compounds 2, 5, and 6, which includes full tables of
bond lengths and angles, full atom-labeled ORTEP views, and
unit cell views. This material is available free of charge via
the Internet at http://pubs.acs.org. Observed and calculated
structure factor tables are available upon request. This data
may also be obtained at the Cambridge Crystallographic
Database (CCDC 139436, 139437, 139438).
8.64 [d, 2H, CHN]. 27Al{1H} NMR (CDCl3): δ 17.63 (w1/ 2
62.52 Hz). IR (cm-1): 3293 (m), 3236 (s), 2963 (s), 2908 (s),
2869 (s), 2723 (w), 2356 (w), 1822 (w), 1605 (s), 1538 (s), 1496
(s), 1462 (s), 1434 (s), 1412 (s), 1388 (s), 1361 (s), 1324 (m),
1276 (m), 1257 (s), 1229 (m), 1174 (s), 1132 (m), 1088 (m), 1027
(w), 979 (w), 927 (w), 886 (w), 847 (m), 824 (m), 787 (m), 755
(s), 726 (m), 695 (w), 620 (m). Anal. Calcd for C42H54AlCl4-
GaN4O2: C, 71.12 (70.98); H, 7.67 (7.72).
)
OM000058M