Ketiminate-supported LiCl cages and group 13 complexes

Article abstract of DOI:10.1002/ejic.201000123

The coordination preferences of the ketiminato ligands L¹H, [[RN(H)(C(Me))₂C(Me)=O], R = 2,6-diisopropylphenyl (Dipp) or 2,6-dimethylphenyl (Dmp)} and L²H ([RN(H)C(Me)CHC(Me)=O], R = C ₂H₄NEt₂) with group 13 elements were investigated. The expected N,O-chelated products [DmPL¹BF ₂] (1), [L²Al(Me)Cl] (2A and 2B), and [L ²InMe₂] (6), were obtained from reactions with BF ₃·OEt₂, AlMe₂Cl and InMe₃ respectively, but the reaction of DippL¹ with. GaCl₃ afforded a metal-halide, neutral ligand adduct, [GaCl₃· DippL¹H] (3). More interestingly the reactions of DippL¹ with InMe₃, formed in situ from InCl₃ and MeLi, led to the isolation of two ketiminate-supported LiCl cages [InMe₂Li ₇Cl₅(DippL^1-)₂(DippL ¹(THF)₃] (4) and [Li₅(Cl)-(DippL ¹)₄]·2PhMe (5). The lithium cage 4 features reaction of InMe₃ with one backbone methyl group from each of two DippL₁ ligands, to afford a tetraalkylindate moiety in the framework of two doubly deprotonated ligands (L^-).

Full text of DOI:10.1002/ejic.201000123

FULL PAPER
DOI: 10.1002/ejic.201000123
Ketiminate-Supported LiCl Cages and Group 13 Complexes
Audra F. Lugo (née Gushwa)[a] and Anne F. Richards*[b]
Keywords: Lithium / Gallium / Chelates / N,O ligands / Cage compounds
The coordination preferences of the ketiminato ligands L1H,
{[RN(H)(C(Me))2C(Me)=O], R = 2,6-diisopropylphenyl (Dipp)
or 2,6-dimethylphenyl (Dmp)} and L2H {[RN(H)C(Me)-
CHC(Me)=O], R = C2H4NEt2} with group 13 elements were
investigated. The expected N,O-chelated products
[DmpL1BF2] (1), [L2Al(Me)Cl] (2A and 2B), and [L2InMe2] (6),
were obtained from reactions with BF3·OEt2, AlMe2Cl and
InMe3 respectively, but the reaction of DippL1 with GaCl3
[GaCl3·DippL1H] (3). More interestingly the reactions of
DippL1 with InMe3, formed in situ from InCl3 and MeLi, led
to the isolation of two ketiminate-supported LiCl cages
[InMe2Li7Cl5(DippL1–)2(DippL1)(THF)3] (4) and [Li5(Cl)-
(DippL1)4]·2PhMe (5). The lithium cage 4 features reaction of
InMe3 with one backbone methyl group from each of two
DippL1 ligands, to afford a tetraalkylindate moiety in the
framework of two doubly deprotonated ligands (L–).
afforded
a
metal-halide,
neutral
ligand
adduct,
properties, their use as laser dyes and molecular probes.[4]
Aluminum complexes continue to be an important presence
in the field of catalysis[5–7] due to their strong Lewis acidity
and low cost.[6] Of particular interest has been the partial
hydrolysis reactions of aryl- and alkylaluminum com-
pounds,[8–12] with the goal of mimicking methylalumoxane
(MAO). MAO is an extremely potent cocatalyst in polyme-
rization processes,[10] but at present lacks structural charac-
terization.[11] Roesky and co-workers have used β-diketimin-
ate ligands to fine-tune the steric and electronic properties
of the partial hydrolysis products by inhibiting unpredict-
able aggregation and providing electronic relief to the
Lewis-acidic Al center by chelation.[9,13] Analogous work
with ketiminate ligands has not been reported. Further-
more, gallium- and indium-containing complexes with a
variety of ligands have been resourceful precursors to in-
dustrially significant thin films such as Ga2O3 and
In2O3.[14,15] Herein we report the coordination preferences
and reactivity of the ketiminato ligands, L1 and L2 with
selective group 13 halides and alkyl compounds.
Introduction
β-Diketiminate ligands (Figure 1, A) constitute one of
the most important and investigated class of ligands in re-
cent years and have been employed in the formation of
complexes from all parts of the periodic table.[1] Relative
to their β-diketiminato counterparts, the related ketiminato
ligands (B and C, Figure 1) have seen less attention, a sur-
prising fact in light of the many attractive features shared
by the two related ligand classes.[2] We were interested in
exploring the general coordination chemistry of the more
bulky, bidentate ArL1 (B) (Ar = Dipp = 2,6-diisoprop-
ylphenyl or Dmp = 2,6-dimethylphenyl) and the more flex-
ible, tridentate L2 (C) (Figure 1), with group 13 elements.
Results and Discussion
Discussion of [DmpL1BF2] (1)
Treatment of DmpL1Li with a threefold excess of boron
Figure 1. Structures of β-diketiminato and ketiminato ligands ArL1 trifluoride–diethyl ether in dichloromethane at room tem-
and L2.
perature yields air-stable, colorless crystalline needles of
[DmpL1BF2] (1) in moderate (51%) yield (Scheme 1). The
Group 13 elements have proven useful in a wide array of
applications.[3] For example, BF2-chelate products of or-
ganic ligands have been exploited for their photoelectric
[a] Department of Chemistry, Texas Christian University,
Fort Worth, Texas 76129, U.S.A.
[b] Department of Chemistry, La Trobe Institute for Molecular
Science, La Trobe University,
3086 Bundoora, Australia
Scheme 1. Synthesis of [DmpL1BF2] (1).
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A. F. Lugo née Gushwa, A. F. Richards
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1:1 and 1:2 reactions were also performed and the reaction
monitored by 11B NMR spectroscopy. Both of these reac-
tions result in the formation of 1, but from these reactions
a crystalline product could not be obtained. Therefore, a
threefold excess of boron trifluoride–diethyl ether was
found to optimize the isolation of 1.
BF2-chelate products are typically prepared by reaction
of BF3 with the neutral ligand in the presence of a base.[16]
The HF elimination method was recently employed by Gar-
dinier et al.,[17] in their extensive survey of β-diketonate, β-
ketoiminato and β-diiminate BF2 complexes. This study
found that the electronic properties of boron difluoride
complexes were greatly influenced by the nitrogen and car-
bon substituents of the chelate ring. Incidentally, 1 can also
be prepared by salt metathesis as has been documented for
the synthesis of β-diketiminato boron dihalides.[18]
Figure 3. Resonance structures A and B of 1.
Discussion of [L2Al(Me)Cl] (2A and 2B)
In view of the successful formation of aluminum hydroxo
and oxo aluminum products with β-diketiminates[13,21] and
with our continued interest in aluminum oxide and hydrox-
ide complexes, we wished to use DippL1H and L2H to ex-
amine the effect of partial hydrolysis on the reaction prod-
ucts of AlMe2Cl (Scheme 2). Thus, AlMe2Cl was treated
with neutral L2H at ambient temperature. With the intent
of introducing trace moisture into the reaction mixture to
obtain a partial hydrolysis product, the reaction was per-
formed under N2 but not under strictly anhydrous condi-
tions. Therefore, the Schlenk flask was not flame-dried
prior to the reaction and the reaction was carried out in
un-dried hexane. The addition of AlMe2Cl to L2 resulted
in the immediate formation of a bright yellow precipitate.
Following workup in toluene (directly from the bottle) large
colorless crystals of 2A were obtained.
Figure 2 displays the X-ray structure of one of two crys-
tallographically independent molecules of 1. Due to the
similarity in metrical parameters of the two molecules, only
the molecule shown in Figure 2 will be discussed. Complex
1 exhibits tetrahedral geometry around the boron center,
with angles between 108.87(16)–110.47(16)°. The B–N dis-
tance of 1.563(2) Å is slightly longer than a normal B–N
single bond (ca. 1.52 Å), and the B–O distance of
1.445(3) Å is slightly shorter than a normal B–O single
bond (B–O ≈ 1.48 Å).[19] Although the intermediate bond
lengths of the ligand backbone indicate π-delocalization,
they are consistent with the prominence of resonance form
B, which contains a B–N dative bond (Figure 3), which is
in agreement to previously reported related examples.[17]
The B–N and B–O bond lengths of 1 show good agreement
with those of other conjugated, six-membered ring (NC3O)-
BF2 chelate complexes [B–N: 1.543(6)–1.560(8) Å; B–O:
1.446(5)–1.459(3) Å].[17,20] As was observed in the β-ketoim-
inato BF2 complexes reported by Gardinier, the 11B and 19
F
NMR resonances are indicative of a symmetric tetrahedral
coordinated boron center supported by a planar chelate
ring.[17]
Scheme 2. Synthesis of complex [L2Al(Me)Cl] (2).
Examination of the crystals by single-crystal X-ray dif-
fraction revealed that no deliberate introduction of oxygen
into the final product had occurred. Instead, the CH4-elimi-
nation product 2A, [L2Al(Me)Cl], was formed in low yield
(Figure 4). The Al-methyl carbon exists at mixed occupancy
with a chlorine atom (C: ca. 70%, Cl: ca. 30%). This disor-
der is possibly due to the fact that that (Me2AlCl)2 can
disproportionate to form AlMe3 and MeAlCl2 in the pres-
ence of a base,[22] but could also be due to the reaction
conditions. The carbon and chlorine atoms sharing this po-
sition have bond lengths of Al(1)–C(6) 2.023(6) Å and
Al(1)–Cl(1) 2.079(4) Å. The latter is significantly shorter
than the other Al(1)–Cl(2) bond length of 2.1964(8) Å in
2A, but this difference is attributable to the disorder at that
position. To ascertain whether the mixed occupancy in 2A
was due to the reaction conditions employed, the reaction
was repeated under strictly anhydrous conditions
(Scheme 2, procedure ii)). The toluene solution was concen-
trated, filtered, and stored at room temperature to again
afford large colorless crystalline blocks. Solid state analysis
revealed that the product was identical to 2A, but with the
Figure 2. Molecular structure of 1. Thermal ellipsoids drawn at
30% probability. Hydrogen atoms omitted for clarity. Select bond
lengths [Å] and angles [°]: B(1)–F(1) 1.374(3), B(1)–F(2) 1.392(3),
B(1)–O(1) 1.445(3), C(1)–O(1) 1.328(2), N(1)–C(3) 1.318(2), C(1)–
C(2) 1.358(3), C(2)–C(3) 1.424(3), C(3)–N(1)–B(1) 121.81(15),
F(1)–B(1)–F(2) 109.30(17).
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Ketiminate-Supported LiCl Cages and Group 13 Complexes
Figure 4. Molecular structures of 2A (left) and 2B (right). Thermal ellipsoids drawn at 30% probability. Hydrogen atoms omitted for
clarity. Selected bond lengths [Å] and angles [°]: 2A: Al(1)–O(1) 1.8560(15), Al(1)–N(1) 1.9498(17), Al(1)–N(2) 2.2374(17), Al(1)–C(6)
2.023(6), Al(1)–Cl(1) 2.079(4), Al(1)–Cl(2) 2.1964(8), O(1)–Al(1)–N(1) 89.92(7), O(1)–Al(1)–C(6) 91.63(18), O(1)–Al(1)–N(2) 168.63(7),
N(1)–Al(1)–N(2) 79.15(7), N(1)–Al(1)–C(6) 125.60(16), N(1)–Al(1)–Cl(2) 14.61(6), C(6)–Al(1)–Cl(2) 112.66(15); 2B: Al(1)–O(1) 1.859(2),
Al(1)–N(1) 1.950(2), Al(1)–N(2) 2.252(2), Al(1)–C(6) 2.020(2), Al(1)–Cl(1) 2.190(11), O(1)–Al(1)–N(1) 89.59(9), O(1)–Al(1)–C(6)
94.90(10), O(1)–Al(1)–N(2) 168.07(10), N(1)–Al(1)–N(2) 79.03(9), N(1)–Al(1)–C(6) 124.48(11), N(1)–Al(1)–Cl(1) 120.64(9), C(6)–Al(1)–
Cl(1) 114.44(8).
methyl carbon at full occupancy, 2B (Figure 4). It is note- Therefore, the isolation of 2 suggests the superior ability of
worthy to mention that our attempts to partially hydrolyze tridentate L2 to protect the metal center from further ligand
complex 2 through addition of one equivalent of water to attack, thus forming the mono-ligated products. Although
the reaction mixture using procedure (ii), Scheme 2, re- it might appear intuitive that any tridentate ligand would
sulted in the formation of a mixture of products that were be more likely to form mono-ligated products over a similar
not crystalline. Further attempts at the deliberate hydrolysis bidentate ligand, the formation of mono-ketiminate Al
of ketiminate-Al complexes were not pursued.
complexes does not necessarily extend to other tridentate
In both 2A and 2B, the pentacoordinate aluminum cen- ketiminate ligands. For example, the tridentate ketimine li-
ter exists in a trigonal bipyramidal environment.[23] The gand SC6H4N=C(Me)CH2C(O)Me acts only as a bidentate
N(1)–Al(1) bond lengths in both complexes [2A: 1.9498(17), chelating agent upon reaction with Al(OiPr)3, forming
2B: 1.950(2) Å] are expectedly shorter than the N(2)–Al(1) tris{SC6H4N=C(Me)CH2C(O)Me}Al which features only
dative bonds [2A: 2.2374(17), 2B: 2.252(2) Å]. The Al(1)– N,S contacts with the Al center and no Al–O interac-
C(6) bond lengths of 2A [2.023(6) Å] and 2B [2.020(2) Å] tions.[27]
are almost identical and are somewhat longer than other
N,O-chelated Al–C(methyl) bond lengths [1.932(7)–
1.9857(11) Å].[23] 1H NMR confirmed the assignment of a Synthesis and Discussion of [GaCl3·DippL1H] (3)
methyl carbon in the solid-state structures, with peaks cor-
A stoichiometric quantity of nBuLi was added to
responding to the Al–methyl at –0.68 ppm in each spec-
DippL1H in THF at –78 °C and, after allowing the reaction
trum, which is in the normal range for N,O-chelated Al–
mixture to warm to room temperature, the lithiation reac-
CH3 protons (–0.7 to –1.11 ppm).[24,25]
tion was stirred overnight (Scheme 3). At this time, the
Aluminum complexes of aryl-substituted ketiminate li-
solution of DippL1Li was added to a THF solution of
gands have been reported,[6,7,25,26] so synthesis of a novel
GaCl3 at –78 °C. Instead of loss of LiCl, and formation of
aluminum-ArL1 complex was not pursued. However, the
[DippL1GaCl2], [DippL1H-GaCl3] (3), a ligand–metal ha-
structure of 2 can be compared to previously reported
lide adduct was isolated as colorless crystals (Figure 5).
Dipp-substituted ketiminate aluminum complexes. For ex-
Preferential formation of the neutral-ligand adduct of
ample, Huang and co-workers have synthesized several
bis(ketiminate)AlX complexes [ketiminate
main-group halides over salt metathesis with L1 has been
= MeC(O)-
previously observed by us in the isolation of
CHC(Me)NHAr, Ar = Dipp; X = H, OCOH, SCHS, OCH
= NPh].[6] The authors were unable to isolate any mono-
ketiminate products, even with an excess of the aluminum
precursor.[6] Similar inability to isolate the mono-ketiminate
product was observed in the synthesis of bis-
(ketiminate)AlCl [ketiminate = MeC(O)CHC(Me)NHAr,
Ar = p-C6H4F].[7] The isolation of bis products in the pre-
viously reported cases highlights the inability of aryl-substi-
tuted bidentate ketiminate ligands to stabilize the metal cen-
[SbCl3·DippL1H] and [SnCl2·DippL1H] adducts,[28] and
ter from further ligand attack, despite their steric bulk. Scheme 3. Synthesis of [GaCl3·DippL1H] (3).
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A. F. Lugo née Gushwa, A. F. Richards
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Lappert and co-workers in the isolation of a related com- resulted in loss of LiCl to form L2GaCl2. These findings
plex, β-dialdiminium pentachlorotellurate–diethyl ether.[29] are likely due to the increased stabilization of the metal cen-
In the former cases (Sb, Sn) the lithiations were not per- ter by the pendant arm nitrogen of tridentate L2. The π-
formed in situ, as the lithiation leading to 3 had been, elimi- bonding tendencies of aryl-substituted ketiminato ligands is
nating this as the cause for lack of salt displacement. In reportedly lower than that of diaryl-substituted β-diketimi-
the case of Sb, the analogous reaction of L2Li with SbCl3 nates;[30] therefore, the electron-donor ability of bidentate
successfully displaced LiCl, and [L2SbCl2] prevailed.[28a] Al- ArL1H, is presumably insufficient to form the stable chela-
though the inclusion of moisture into the reaction cannot tion products with these particular metals, instead favoring
be eliminated, given the repeated isolation of 3 and other adducts.
neutral ligand adducts, coupled with the observation that
One of the two crystallographically independent mole-
an acidic gas is evolved on addition of solvent to GaCl3, it cules of [GaCl3·DippL1H] is shown in Figure 5. Despite all
is more likely that HCl is the source of protonation. of the angles in the unit cell being equal to 90.00°, the data
Furthermore, given the fairly low yield (20%) of crystalline could not be solved and refined in an orthorhombic crystal
material that was isolated, we believe 3 to be the minor system, instead, converging in the monoclinic space group
product of the reaction, with the major product, L1GaCl2, P21/c. The hydrogen atom on the nitrogen atom [N(2)], of
formed from LiCl displacement. 1H NMR spectroscopic one DippL1H molecule in the asymmetric unit was located
data on the crude reaction product reveals a mixture of using the electron-density difference map and freely refined,
products, therefore it is possible that both products form but could not be located on the nitrogen atom [N(1)] in the
but 3 is isolated because it preferentially crystallizes. The remaining molecule. Nevertheless, the existence of the NH
comparison reaction of DippL1H with GaCl3 was per- hydrogen is detectable in the proton NMR spectrum at δ =
formed, but surprisingly 3 could not be isolated, instead an 13.01 ppm and as an N–H stretch at 3285 cm–1 in the infra-
oily product was obtained. Pertinent to the formation of 3 red spectrum. The bond lengths and angles of 3 are unex-
is the equivalent reaction of L2Li with GaCl3,[28b] which ceptional.
Discussion of [InMe2Li7Cl5(DippL1–)2(DippL1)(THF)3] (4)
There has been recent interest in generating lithium chlo-
ride cages as they sometimes bear close resemblance to the
structure of the parent ionic lattice of LiCl.[31] These cages
or clusters often exhibit properties different from the parent
ionic compound such as lower melting points and solubility
in organic solvents.[31] Previously reported reactions involv-
ing InMe3 (freshly prepared from InCl3 and MeLi) and a
lithiated ligand have been utilized as a synthetic pathway to
heterobimetallic InCH3-containing LiCl cages or clus-
ters.[32]
The reaction of in situ generated DippL1Li and InMe3,
the latter freshly prepared from InCl3 and 3 equiv. of MeLi
afforded extremely air-sensitive, large colorless crystals of 4
in 25% yield (Scheme 4).
X-ray structural analysis reveals that complex 4 is a
highly unusual heterobimetallic LiCl cage supported by
Figure 5. Molecular structure of 3. Thermal ellipsoids drawn at
30% probability. Hydrogen atoms omitted for clarity. Selected
bond lengths [Å] and angles [°]: Ga(1)–O(1) 1.864(5), O(1)–C(1)
1.308(8), C(1)–C(2) 1.386(10), C(2)–C(3) 1.424(9), N(1)–C(3)
1.333(9),
O(1)–Ga(1)–Cl(1)
113.13(18),
O(1)–Ga(1)–Cl(2)
107.38(1), O(1)–Ga(1)–Cl(3) 98.05(16).
Scheme 4. Synthesis of complex 4.
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Ketiminate-Supported LiCl Cages and Group 13 Complexes
Figure 6. Molecular structure of 4, on the left is the full molecule, on the right hand side the Dipp groups and carbon atoms from the
backbone have been omitted for clarity. Thermal ellipsoids drawn at 30% probability. Hydrogen atoms omitted for clarity.
three deprotonated ketiminate ligands, three THF mole- cally as occupying the apex of a square pyramid. The Li–
cules, and most intriguingly, an In(CH3)2(CH2)2 moiety Cl–Licis angles around these chlorides in 4 are [°] Cl(1):
(Figure 6). Key bond lengths and angles are recorded in Li(1)–Cl(1)–Li(4) 68.0(2), Li(1)–Cl(1)–Li(6) 81.5(3), Li(3)–
Table 1. The [Li7O3Cl3] core is comprised of seven tetrahe- Cl(1)–Li(4) 69.1(2), Li(3)–Cl(1)–Li(6) 76.6(3); Cl(2): Li(1)–
drally-bonded lithium cations, three tetrahedrally-bonded Cl(2)–Li(6) 82.5(3), Li(1)–Cl(2)–Li(7) 69.5(3), Li(2)–Cl(2)–
ketiminate oxygen atoms bonded to three lithiums each, Li(6) 77.6(3), Li(2)–Cl(2)–Li(7) 67.0(3); Cl(3): Li(2)–Cl(3)–
and 3 interstitial, µ4-Cl atoms. These core atoms make up Li(5) 70.8(3), Li(2)–Cl(3)–Li(6) 77.5(3), Li(3)–Cl(3)–Li(5)
nine fused four-membered rings of two different composi- 71.1(3), Li(3)–Cl(3)–Li(6) 76.5(3).
tions, capped with one six-membered ring. All nine four-
The most unusual feature of 4 is the additional cage sup-
membered rings have two lithium cations occupying oppo- port provided by the tetraalkylindate moiety. From our pre-
site corners, with the other two corners being occupied by vious work on selenium and tellurium halides with β-diket-
2 chlorine atoms in three of the rings, and an oxygen atom iminate ligands,[28c,28d] it was observed that reaction with a
and a chlorine atom in six of the rings. The six-membered backbone methyl group occurred, leading to the formation
Li–O heterocycle capping the core of the cage consists of of a ligand–CH2–M (M = Se, Te) fragment. Similarly, com-
alternating lithium and oxygen atoms.
plex 4 contains a ligand–InCH2 moiety but also includes an
additional ligand–CH2–(In) fragment from a second mole-
cule of L1. Although the complicated structure implies a
less straightforward mechanism than the imine–enamine
tautomerization observed with β-diketiminate Se and Te
complexes,[28c,28d] this portion of the complex was osten-
sibly formed by the consecutive reactions of InMe3 with the
enamine form of two ketiminate ligands with the loss of
1 equiv. of CH4. The indium atom retains two of the methyl
groups, one of which is terminal [C(55)] and the other
bridging [C(56)], the latter occupying the fourth coordina-
tion site of a core lithium atom [Li(7)–C(56) distance:
2.40(1) Å]. Bridging methyl groups are well known[34] and
have been observed in indium compounds[35] as well as in
Li–CH3(bridging) interactions.[36] The bridging methyl car-
bon atom distance of 2.207(6) Å to the indium center is
expectedly longer than that of the terminal methyl carbon
of 4 [2.172(6) Å] and of other InCH3 compounds [2.139(5)–
2.211(5) Å].[37] The In–CH2 distances in 4 [2.287(5),
2.294(5) Å] are longer than those of other In–CH2
[2.130(3)–2.193(2) Å] compounds due to the greater steric
demands of DippL1.[38] Both the In–CH2 and In–CH3
groups are detectable in the NMR spectra (1H NMR: CH3
Table 1. Selected bond lengths [Å] and angles [°] of [InMe2Li7Cl5-
(DippL1–)2(DippL1)(THF)3] (4).
In(1)–C(4)
In(1)–C(55)
In(1)–C(56)
Li(1)–O(1)
Li(2)–O(2)
Li(3)–O(3)
Li(4)–O(4)
Li(1)–N(1)
Li(2)–N(2)
Li(3)–N(3)
Li(4)–O(4)
Li(5)–O(5)
2.294(5)
2.172(6)
2.207(6)
1.869(8)
1.849(8)
1.875(8)
1.901(9)
1.933(8)
1.920(9)
1.921(8)
1.901(9)
1.917(9)
Li(6)–O(6)
Li(7)–O(2)
Li(7)–C(1)
Li(7)–Cl(2)
Cl(1)–Li(1)
Cl(1)–Li(3)
Cl(1)–Li(4)
Cl(1)–Li(6)
Cl(2)–Li(1)
Cl(2)–Li(2)
Cl(2)–Li(6)
1.862(9)
1.937(8)
2.792(9)
2.387(8)
2.447(8)
2.381(8)
2.492(8)
2.343(9)
2.446(8)
2.449(8)
2.295(9)
C(22)–In(1)–C(5)
C(4)–In(1)–C(55)
C(4)–In(1)–C(56)
C(22)–In(1)–C(55) 117.8(2)
C(22)–In(1)–C(56) 105.83(19)
C(55)–In(1)–C(56) 116.0(3)
O(1)–Li(7)–O(2)
O(1)–Li(4)–O(3)
Li(4)–O(3)–Li(5)
99.48(18)
109.5(2)
106.5(2)
O(2)–Li(5)–O(3)
Li(5)–O(2)–Li(7)
Li(1)–Cl(2)–Li(6)
Li(1)–Cl(2)–Li(7)
Li(2)–Cl(2)–Li(6)
Li(2)–Cl(2)–Li(7)
Li(1)–Cl(1)–Li(6)
Li(2)–Cl(3)–Li(6)
128.4(4)
111.3(4)
82.5(3)
69.5(3)
77.6(3)
67.0(3)
81.5(3)
77.5(3)
126.1(5)
126.7(4)
109.8(3)
Four-coordinate chloride anions surrounded by four lith- 0.30 ppm, CH2 0.37 ppm. 13C NMR: CH3 –8.4 ppm, CH2
ium atoms are common[33] and the geometry around Cl– –3.1 ppm).
varies significantly, ranging from tetrahedral[33a–33d] to see-
Each of the two indium-bound ligands is also N,O-che-
saw[33e–33j] arrangements, depending on cluster size and li- lated with a lithium cation, making each ligand formally
gand sterics. In several cases,[33k–33l] including the three Cl– dianionic (DippL1–). Dianionic ketiminate and β-diketimin-
anions in 4, each chloride anion is best described geometri- ate ligands are far less common but have been documen-
Eur. J. Inorg. Chem. 2010, 2025–2035
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2029

A. F. Lugo née Gushwa, A. F. Richards
FULL PAPER
ted.[39] The third ketiminate ligand at the base of the com- coordination environment, with the fifth, Li(5), featuring
plex makes no indium contacts and is monoanionic, exhib- square pyramidal geometry.
iting only the typical N,O-chelation to a lithium cation. For
charge balance the +10 cationic charge from the seven Li+
cations and one In3+ atom balance the ten negative charges
from the three chlorides, one monoanionic ketiminate li-
gands, two dianionic ketiminate ligands, and two CH3
groups on the indium center.
Discussion of [Li5(Cl)(DippL1)4]·2PhMe (5)
To investigate whether another cage with increased in-
dium content could be synthesized, the same reaction in
THF was performed using two equivalents of in situ-gener-
ated InMe3 [Scheme 5, procedure (i)]. Upon workup of the
THF reaction mixture in toluene and storage at –30 °C,
large colorless crystals of a second ketiminate-supported
LiCl cage 5 were formed in 79% yield (Figure 7). Complex
5 was reproducibly obtained when the 1:1 reaction was re-
peated, but in diethyl ether rather than THF [Scheme 5,
procedure (ii)]. Attempts were made at generating analo-
gous cages using GaMe3 under the same conditions, but no
crystalline material could be isolated from these reactions.
X-ray structural determination shows that 5 exhibits sev-
eral distinctions from 4. No indium is contained in the final
Figure 7. X-ray structure of 5 (full structure, left; cone-shaped core,
product, and the [Li5O4Cl] core is supported by four ketim-
right). Ketiminate ligands shown with wire frames in full structure,
and core shown with ellipsoids drawn at 30% probability. Hydro-
inate ligands and no THF molecules. Four of the five lith-
ium cations in the core of this cage are in a tetrahedral gen atoms omitted for clarity.
Scheme 5. Synthesis of complex 5.
Figure 8. Representative “rectangle” (left) and kite (right) making up the core of 5 (bond lengths given in Å, angles in °).
2030
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Eur. J. Inorg. Chem. 2010, 2025–2035

Ketiminate-Supported LiCl Cages and Group 13 Complexes
This geometry is less common for lithium atoms,[40] but
The elimination of methane for the formation of 6 is in
examples include lithium bis(methoxycarbony1)phosphan- contrast to that observed in the reaction with DippL1H un-
ide-1,2-dimethoxyethane,[40a] bis(l,2-dimethoxyethan-O,OЈ)- der the same conditions, which resulted in the cage complex
bis(THF-O){µ-1,2,4-triphospholo[1,2-a]-1,2,4-triphosphol- 4, rather than [DippL1InMe2] (the analogous complex to
1,3,5,7-tetraonato(2–)-O1,O7:O3,O5} dilithium,[40b] Li2- 6). This occurrence is consistent with our comparison of
V6O13,[40c] and Li[B(C2O4)2].[40d] Like 4, the listed examples ArL1 and L2 with aluminum, specifically the exploitation
have oxygen atoms occupying the basal positions of the of the tridentate functionality of L2 to form three contacts
square pyramid at average distances to the lithium atom with the metal. Again we observe the formation of a mono-
(ca. 2.039–2.294 Å) similar to that of 5 (ca. 2.072 Å). The ketiminate product 6 when employing tridentate L2 and the
core can be described as roughly cone-shaped (Figure 7), inability of bidentate ArL1 to stabilize such a mono-ligated
with the square pyramidal Li+ occupying the center of the product. Thus, in the case of 6, the availability of the neu-
base and a µ5-Cl capping the cone. The lithium–oxygen– tral ligand in solution to react with InMe3 and eliminate
chloride core is comprised of eight fused four-membered methane, forming three ligand contacts with the indium
rings of two types. The first type are Li–O–Li–O rectangles, center, is the primary driving force. The deliberate synthesis
the second, Li–O–Li–Cl kites (Figure 8). Select bond of 6 by reaction of L2H and InMe3 was performed and
lengths and angles are listed in Table 2.
afforded 6 in higher yield.
Although complex 6 (Figure 9) was not the targeted L2-
supported LiCl cage, it is desirable in its own right due to
its structural similarity to the previously reported complex
Table 2. Selected bond lengths [Å] and angles [°] of [Li5(Cl)-
(DippL1)4]·2PhMe (5).
Li(1)–O(1)
Li(1)–O(2)
Li(2)–O(2)
Li(2)–O(3)
Li(3)–O(3)
Li(3)–O(4)
Li(4)–O(4)
Li(4)–O(1)
Li(1)–N(1)
Li(2)–N(2)
Li(3)–N(3)
1.881(5)
1.923(5)
1.868(5)
1.922(5)
1.874(5)
1.919(5)
1.877(5)
1.926(5)
1.967(5)
1.985(6)
1.968(5)
Li(4)–N(4)
Li(1)–Cl(1)
Li(2)–Cl(1)
Li(3)–Cl(1)
Li(4)–Cl(1)
Li(5)–O(1)
Li(5)–O(2)
Li(5)–O(3)
Li(5)–O(4)
Li(5)–Cl(1)
1.984(5)
2.421(5)
2.524(5)
2.463(5)
2.519(5)
2.059(5)
2.081(5)
2.077(5)
2.069(5)
2.742(4)
[InMe2(ketiminate)] {ketiminate
=
O=C(CF3)CH2C-
(CF3)=NCH2CH2NMe2} with CF3 substituents in place of
the backbone methyls[41] which was shown to be a useful
precursor in the chemical vapor deposition of indium oxide
thin films. In spite of the extreme air and moisture sensitiv-
ity of InMe3, [L2InMe2] is relatively stable upon exposure
to ambient air, as determined by a unit cell check of the
crystals after exposure to air for 1 h. Complex 6 has fairly
low thermal stability melting cleanly between 88–91 °C, but
attempts at sublimation were unsuccessful. The bond
lengths and angles of 6 compare well with that of the CF3-
substituted complex, [InMe2(ketiminate)] {ketiminate =
O=C(CF3)CH2C(CF3)=NCH2CH2NMe2}, with expected
variations around the indium center attributed to the elec-
tron-withdrawing CF3 groups.[41] Namely, the In–N
[2.321(2) Å] and In–O [2.251(3) Å] distances are slightly
O(1)–Li(1)–N(1) 92.8(2)
O(2)–Li(2)–N(2) 92.9(2)
O(3)–Li(3)–N(3) 93.8(2)
O(4)–Li(4)–N(4) 93.5(2)
O(1)–Li(5)–O(2) 88.2(2)
O(2)–Li(5)–O(3) 88.5(2)
O(3)–Li(5)–O(4) 88.1(2)
O(4)–Li(5)–O(1) 87.6(2)
O(1)–Li(5)–Cl(1) 79.95(15)
O(2)–Li(5)–Cl(1) 79.66(15)
O(3)–Li(5)–Cl(1) 78.62(15)
O(4)–Li(5)–Cl(1) 79.99(16)
Li(1)–Cl(1)–Li(2) 73.23(17)
Li(2)–Cl(1)–Li(3) 74.50(16)
Li(3)–Cl(1)–Li(4) 72.97(16)
Li(4)–Cl(1)–Li(1) 73.40(17)
greater than those of
6 [In–N: 2.242(2) Å, In–O:
Discussion of [L2InMe2] (6)
Having identified a synthetic route to LiCl cages, we per-
formed the analogous reaction as that employed for the for-
mation of 4 to determine whether L2 would support similar
cages. Thus, in situ-generated L2Li was treated with InMe3
in THF. Following reaction work-up, colorless crystals of
[L2InMe2] (6) the CH4 elimination product were isolated
(Scheme 6).
Figure 9. Molecular structure of 6. Thermal ellipsoids drawn at
30% probability. Hydrogen atoms omitted for clarity. Selected
bond lengths [Å] and angles [°]: In(1)–C(12) 2.153(3), In(1)–C(13)
2.156(3), In(1)–O(1) 2.238(2), In(1)–N(1) 2.242(2), In(1)–N(2)
2.538(2),
C(12)–In(1)–C(13)
131.76(14),
C(12)–In(1)–O(1)
95.38(11), C(13)–In(1)–O(1) 93.65(11), O(1)–In(1)–N(1) 82.61(8),
N(1)–In(1)–N(2) 74.10(9), O(1)–In(1)–N(2) 156.47(8).
Scheme 6. Synthesis of 6.
Eur. J. Inorg. Chem. 2010, 2025–2035
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2031

A. F. Lugo née Gushwa, A. F. Richards
FULL PAPER
using paratone oil. The data were corrected for absorption. Struc-
tures were solved by direct methods[43] and refined[43] via full-ma-
trix least-squares. Crystal data for 1–6 can be found in Table 3.
Hydrogen atoms were placed in idealized positions except certain
M-CH3 groups and NH groups that were localized from the elec-
tron-density map and refined with distant restraints. The 1H and
13C NMR spectra were recorded at 300.05 and 75.45 MHz, respec-
tively, on a Varian XL-300, IR analysis was conducted as Nujol
mulls with NaCl plates on a MIDAC M4000 Fourier transform
infrared (FT IR) spectrometer, and mass spectrometry analysis was
carried out using a Bruker Esquire 6000 Mass Spectrometer and
North Carolina, Mass Spectrometry Facility. Melting or decomp.
points were determined in capillaries under a nitrogen atmosphere.
2.238(2) Å], making the In–C bonds slightly stronger and
shorter in the CF3 complex [2.141(2), 2.142(2) Å] than in 6
[2.153(3), 2.156(3) Å].
Conclusions
The coordination preferences of bidentate ArL1 and tri-
dentate L2 were investigated with several group 13 precur-
sors, affording a range of products. Aside from the expected
N,O-chelation, a monomeric adduct (in the case of gallium)
and two novel LiCl cages were synthesized, one of which
featured an InMe2 moiety bridging two ketiminate ligands.
Despite some variability in the favorability of deproton-
ation in both ArL1 and L2, the commonality among these
complexes is the ability of L2 to better stabilize metal cen-
Synthesis of [DmpL1BF2] (1): To a stirring CH2Cl2 solution of
DmpL1Li (0.35 g, 1.57 mmol) was slowly added via syringe a three-
fold excess of BF3·Et2O (0.59 mL, 4.7 mmol) at room temperature.
Within minutes, the initially pale yellow reaction mixture became
ters with its 3 ligand contacts, relative to ArL1, with 2 li- darker yellow. After stirring overnight, the reaction mixture became
cloudy and straw colored. Following removal of the volatiles in
vacuo and extraction into a hexane/diethyl ether mix, colorless
needles of 1 were obtained; yield 51%; m.p. 102–106 °C. H NMR
gand contacts. In addition, the isolation of bimetallic cage
4 shows the versatility of ketiminato ligands and highlights
their diverse coordination modes.
1
(CDCl3, 25 °C): δ = 1.80 (s, 3 H, backbone γ CMe), 1.88 (s, 3 H,
NCMe), 2.09 (s, 6 H, ArMe), 2.1 (s, 3 H, OCMe), 7.02–7.10 (m, 3
H, ArH) ppm. 13C NMR (CDCl3, 25 °C): δ = 13.7 (backbone Me),
18.27 (backbone Me), 18.30 (ArMe), 4.7 (ArMe), 103.0 (γ back-
bone C), 128.0 (para ArC), 128.9 (meta ArC), 134.4 (ortho ArC),
138.8 (ArC-N), 172.9 (backbone CN), 173.2 (backbone CO) ppm.
11B NMR (28.88 MHz, CDCl3, 25 °C): δ (ppm) 0.91 (t, J =
14.1 Hz) ppm. 19F NMR (CDCl3, 25 °C): δ = –139.5 ppm. IR (Nu-
Experimental Section
General: All manipulations were performed under anaerobic condi-
tions using standard Schlenk techniques. Hexane and toluene were
dried using an MBraun-SPS solvent purification system. The li-
gands, L1H and L2H were prepared according to published pro-
cedures.[6a,42] All other reagents were purchased from Aldrich and
used as received. Crystal data were collected with a Bruker
jol mull): ν = 772 (w), 892 (w), 1078 (m), 1162 (m), 167 (m), 1309
˜
(s), 1613 (m) cm–1.
SMART 1000 diffractometer, molybdenum radiation (λ
0.7107 Å) at –50 or –60 °C. Crystals were mounted on glass fibers
=
Synthesis of [L2Al(Me)Cl] (2A and 2B): To a Schlenk flask that had
not been flame dried was added L2H (0.29 g, 1.5 mmol) under a
Table 3. Crystal data for compounds 1–6.
1
2B (2A)
3
4
5
6
Chemical formula
C14H18BF2NO
C12H24AlClN2O
(C11.70H23.11AlCl1.29N2O)
274.76 (280.78)
monoclinic
C36H53Cl6Ga2N2O2 C68H106Cl3InLi7N3O6 C86H121ClLi5N4O4 C13H27InN2O
Formula weight
Crystal system
Space group
265.10
orthorhombic
Pna21
897.94
monoclinic
P21/c
1331.31
triclinic
P1
1344.01
monoclinic
P21/c
342.19
monoclinic
P21/c
¯
P21/c
T /K
a /Å
b /Å
c /Å
α /°
β /°
γ /°
V /Å3
213(2)
213(2)
213(2)
27.085(11)
9.660(4)
16.725(7)
90
90
90
4376(3)
4
223(2)
223(2)
213(2)
24.2280(18)
14.2005(10)
8.1794(6)
90
90
90
11.6821(13), [11.6627(13)]
11.1958(19), [11.1893(12)]
14.456(2)/[14.4605(12)]
90
128.223(6)/[128.209(6)]
90
15.1948(10)
15.6781(10)
17.3832(11)
95.8990(10)
103.5820(10)
107.6320(10)
3768.0(4)
2
18.257(2)
26.669(3)
17.976(2)
90
107.875(2)
90
8.8945(19)
13.435(3)
27.261(6)
90
91.387(4)
90
2814.1(4)
8
1485.4(4)/[1482.8(3)]
4
8329.9(16)
4
3256.7(12)
8
Z
Reflections collected
Independent reflections
Data/restraints/
parameter ratio
Rint
13671
4781
4781/1/353
4995/(7655)
2363/(2668)
2363/0/159/ (2668/0/158)
18102
6678
6678/0/448
32460
13551
13551/7/814
65797
15051
15051/0/931
27186
5902
5902/0/319
0.0235
1.251
0.0361/(0.0220)
1.229/(1.258)
0.305/(0.358)
0.0979
1.363
1.629
0.0502
1.173
0.466
0.0468
1.072
0.094
0.0290
1.396
1.441
Dcalc /Mgm–3
Absorption coefficient /mm–1 0.095
F(000)
1120
592/(601)
1852
1408
2912
1408
R indices (all data)
R1 = 0.0417
wR2 = 0.0908
R1 = 0.0315
wR2 = 0.0809
R1 = 0.0709, wR2 = 0.1450/
R1 = 0.1554,
R1 = 0.1052,
wR2 = 0.1676
R1 = 0.0580,
wR2 = 0.1339
R1 = 0.1089,
wR2 = 0.1840
R1 = 0.0646,
wR2 = 0.1573
R1 = 0.0320,
wR2 = 0.0647
R1 = 0.0237,
wR2 = 0.0571
(R1 = 0.0469, wR2 = 0.1024) wR2 = 0.1915
R1 = 0.0505, wR2 = 0.1348/ R1 = 0.0649,
(R1 = 0.0356, wR2 = 0.0917) wR2 = 0.1464
Final R indices [IϾ2σ(I)]
Largest difference in peak
and hole /eÅ–3
0.194 and –0.134 0.458 and –0.224/
(0.372 and –0.315)
0.462 and –0.829 2.348 and –0.572
0.466 and –0.289 0.536 and –0.358
2032
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 2025–2035

Ketiminate-Supported LiCl Cages and Group 13 Complexes
nitrogen atmosphere. Approximately 10 mL of undried hexane
(from the reagent bottle) was poured in and the stirring solution
cooled to –78 °C. AlMe2Cl (1.0  in hexanes, 1.5 mL, 1.5 mmol)
was syringed in dropwise, immediately resulting in a bright yellow
solution and precipitate. The cooling bath was removed after
10 min, and stirring was maintained at room temp. overnight. Ex-
traction into toluene, concentration, and storage overnight at room
temp. yielded large colorless rectangular crystalline blocks of 2A;
yield 0.11 g, 28%. 2B was prepared in same manner, using strictly
anaerobic conditions and toluene as the solvent; yield 0.16 g, 39%;
3.9 (sept, 1JH,H = 6.7 Hz, 4 H, iPr CHMe2), 4.05 (m, THF OCH2),
1
1
7.46 (d, JH,H = 7.6 Hz, 8 H, meta ArH), 7.57 (t, JH,H = 7.7 Hz,
4 H, para ArH) ppm. 13C NMR (CDCl3, 25 °C): δ (ppm) = –8.4
[In(CH3)2]; –3.1 [In(CH2)2]; 15.0, 17.4, 1.9, 20.9, 4.6, 4.7 (iPr Me),
6.0, 6.1, 7.4, 8.6, 8.8 (backbone Me), 7.4, 7.6, 9.8,28.0 (iPr CH),
8.8 (THF OCCH2), 68.2 (THF OCH2), 90.6, 96.2 (backbone γ
CMe), 16.7, 17.1, 18.5, 1.0, 128.5, 129.3, 132.5, 138.1, 138.9, 141.5,
142.8, 146.3 (ArC), 166.5, 169.7 (CN), 171.0, 174.4 (CO) ppm. IR
(Nujol mull): ν = 770 (s), 891 (m), 971 (s), 1159 (m), 1561 (s), 1606
˜
(s) cm–1. MS m/z; found (calcd.): 1130 (1130.6) M – 4Li – In(CH3)2-
1
m.p. 111–113 °C. H NMR (CDCl3, 25 °C): δ = –0.68 (s, 3 H, Al-
(CH2)2; 274 (274.4) DippL1H.
CH3), 1.08 (t, 1JH,H = 7.0 Hz, 6 H, CH2Me), 1.98 (s, 3 H, backbone
NCMe), 2.02 (s, 3 H, OCMe), 2.69, 2.90 (overlapping multiplets,
Synthesis of [Li5(Cl)(DippL1)4]·2PhMe (5): Compound 5 was syn-
thesized and worked up analogously to 4 but carried out in diethyl
ether rather than THF. Alternatively, 5 was prepared in THF as
described in the synthesis of 6 but by using 2 equiv. of InMe3
(rather than 1), prepared from InCl3 (0.57 g, 2.6 mmol) and MeLi
(1.6  in diethyl ether, 4.8 mL, 7.8 mmol), yield 0.33 g, 79%; de-
comp. point 93–95 °C (turns yellow), 129–133 °C (turns orange),
142–145 °C (turns maroon), 188–191 °C (turns black). 1H NMR
(CDCl3, 25 °C): δ = 0.39, 0.61, 1.01, 1.07 (doublets, 1JH,H = 6.7 Hz,
12 H each, iPr CMe2), 1.57 (s, 12 H, γ backbone Me), 1.84 (s, 12
H, backbone NCMe), 1.89 (s, 12 H, backbone OCMe), 2.33, 2.72
1
6 H, NCH2CH3 and NCH2CH2N), 3.30 (t, JH,H = 5.9 Hz, 2 H,
NCH2CH2N), 5.16 (s, 1 H, backbone γ CH) ppm. 13C NMR
(CDCl3, 25 °C): δ = 8.4 (CH2Me), 6.0 (NCMe), 9.0 (OCMe), 43.9,
44.3, 48.5 (NCH2), 99.9 (backbone γ CH), 176.5 (CN), 183.5 (CO)
ppm, Al-CH3 not observed. IR (Nujol mull): ν = 1347 (w), 1532
˜
(w), 1581 (w) cm–1.
Synthesis of [GaCl3·DippL1H] (3): To a stirring THF solution of
DippL1H (0.35 g, 1.3 mmol) at –78 °C was added dropwise nBuLi
(2.5  in hexanes, 0.51 mL, 1.3 mmol). The cooling bath was imme-
diately removed and the lithiation reaction was stirred overnight at
room temperature. The ligand solution was then added to a stirring
THF suspension of GaCl3 at –78 °C, resulting in the evolution of
colorless gas and the formation of a yellow solution. Stirring was
maintained at low temperature for 10 min, at which time the THF
was removed and the white solid extracted into toluene. Crystals
of 3 were obtained at room temperature from a toluene/hexane
1
(2 sept, JH,H = 6.5 Hz, 4 H each, iPr CHMe2), 2.38 (s, PhMe),
6.91–7.04 (m, 12 H, ArH), 7.1 (m, toluene ArH), 7.9 (m, toluene
ArH) ppm. 13C NMR (CDCl3, 25 °C): δ (ppm) 17.4, 20.9, 6.1, 7.1
(iPr Me), 7.5, 8.3, 27.5 (backbone Me), 28.2, 28.7 (iPr CH), 101.6
(backbone γ CMe), 15.9, 16.3, 16.5, 16.6, 16.7, 18.5, 128.5 129.3,
138.9, 139.4, 146.1, 146.5 (ArC), 168.7(CN), 171.0 (CO) ppm. IR
(Nujol mull): ν = 880 (w), 1534 (m), 1598 (m) cm–1. MS m/z; found
˜
(calcd.): 827 (827.2) 3DippL1H + Li; 553 (553.8) 2DippL1H + Li;
1
mix; yield 0.12 g, 20%; m.p. 92–95 °C. H NMR (CDCl3, 25 °C):
274 (274.4) DippL1H.
1
δ = 1.16, 1.20 (overlapping doublets, JH,H = 7.0 Hz, 12 H, iPr
Synthesis of [L2InMe2] (6): To a stirring THF solution of L2H
(0.25 g, 1.3 mmol) at –78 °C was added dropwise nBuLi (2.5  in
hexanes, 0.51 mL, 1.3 mmol). The reaction warmed to room temp.
slowly and stirring was continued an additional 2 h. In a separate
Schlenk flask, a cloudy, colorless THF suspension of InCl3 (0.28 g,
1.3 mmol) was cooled to –78 °C and MeLi (1.6  in diethyl ether,
2.4 mL, 3.9 mmol) added dropwise. Stirring at –78 °C of the InMe3
was maintained for 30 min, after which time the L2Li was added
rapidly via cannula. After 10 min, the cooling bath was removed
and the reaction mixture became clear yellow with a small amount
of yellow solid. After stirring overnight at room temp., the volatiles
were removed in vacuo and the yellow oily residue extracted into
toluene. Colorless crystals of 6 suitable for X-ray diffraction were
grown from hexane at –10 °C; yield 0.11 g, 25%. Complex 6 can
also be prepared deliberately with analogous conditions, using
L2H, rather than L2Li; yield 0.33 g, 75% and spectroscopic data
CMe2), 1.80 (s, 3 H, γ backbone Me), 1.95 (s, 3 H, backbone
NCMe), 2.35 (s, 3 H, backbone OCMe), 2.92 (sept, 1JH,H = 6.7 Hz,
1
2 H, iPr CHMe2), 7.20 (d, JH,H = 7.6 Hz, 2 H, meta ArH), 7.32
(t, 1JH,H = 7.6 Hz, 1 H, para ArH), 13.01 (broad s, 1 H, NH) ppm.
13C NMR (CDCl3, 25 °C): δ = 15.0, 17.6 (iPr Me), 5.9, 7.7, 27.6
(backbone Me), 28.8 (iPr CH), 100.4 (backbone γ CMe), 17.0 (para
ArC), 128.8 (meta ArC), 133.6 (ortho ArC), 145.9 (N-ArC), 166.8
(CN), 12.7 (CO) ppm. IR (Nujol mull): ν = 773 (w), 974 (m), 1136
˜
(m), 1151 (m), 1170 (m), 1592 (w), 3285 (w, br) cm–1. MS m/z;
found (calcd.) 273.3 (273.4) LH.
Synthesis of [InMe2Li7Cl5(DippL1–)2(DippL1)(THF)3] (4): A THF
solution of DippL1H (0.35 g, 1.3 mmol) was cooled to –78 °C and
nBuLi (2.5  in hexanes, 0.51 mL, 1.3 mmol) added dropwise, and
was then allowed to stir for 1 h at low temperature. In a separate
Schlenk flask, 3 equiv. of MeLi (1.6  in diethyl ether, 2.4 mL,
3.9 mmol) were added dropwise to a stirring suspension of InCl3 at
–78 °C, and stirring was maintained at this temperature for 30 min.
Following that, the cold solution of DippL1Li was added rapidly
by cannula to the stirring InMe3 solution at –78 °C. After 15 min,
the cooling bath was removed, and the resultant clear bright yellow
solution was allowed to stir overnight at ambient temperature. A
clear amber solution was observed, from which the volatiles were
removed in vacuo. After extraction of the foamy yellow solid into
PhMe, filtration, and storage at –30 °C, large colorless crystalline
chunks of 4 were afforded; yield 0.43 g, 25%; decomp. point 92–
94 °C (turns orange), 122–126 °C (turns red), 135–139 °C (turns
matched that of the originally obtained crystals; m.p. 88–91 °C. 1H
1
NMR (CDCl3, 25 °C): δ = –0.32 (s, 6 H, InMe2), 0.97 (t, JH,H
=
7.0 Hz, 6 H, CH2CH3), 1.88 (s, 3 H, NCMe), 1.93 (s, 3 H, OCMe),
1
1
2.61 (quart, JH,H = 7.9 Hz, 4 H, NCH2CH3), 2.71 (t, JH,H
=
H,
1
5.9 Hz,
2
H, NCH2CH2N), 3.32 (t, JH,H = 5.9 Hz,
2
NCH2CH2N), 4.79 (s, 1 H, backbone γ CH) ppm. 13C NMR
(CDCl3, 25 °C): δ = –8.1 (InMe2), 8.2 (CH2Me), 6.5 (NCMe), 28.0
(OCMe), 42.2, 45.9, 51.2 (NCH2), 97.0 (backbone γ CH), 173.9
(CN), 184.4 (CO) ppm. IR (Nujol mull): ν = 939 (w), 1346 (m),
˜
1407 (m), 151 (s), 1575 (s) cm–1. MS m/z; found (calcd.) 341.1
(342.2) M+, 199.2 (198.2) Et2NCH2CH2N(H)C(Me)CHC(Me)O.
1
maroon), 191–194 °C (turns black). H NMR (CDCl3, 25 °C): δ =
0.30 (s, 6 H, InMe2), 0.37 [s, 4 H, In(CH2)2]; 1.30, 1.37, 1.41, 1.43,
1.45, 1.48 (overlapping doublets, JH,H = 6.7 Hz, 36 H, iPr CMe2),
CCDC-755673 (for 1), -755674 (for 2A), -755675 (for 2B), -755676
(for 3), -755677 (for 4), -755678 (for 5), and -755679 (for 6) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
1
1.87 (s, 3 H, backbone Me), 2.02 (m, THF OCCH2), 2.07 (s, 3 H,
backbone Me), 2.14, 2.20 (s, 6 H each, backbone Me), 2.42 (s, 3
1
H, backbone Me), 3.02 (sept, JH,H = 6.7 Hz, 2 H, iPr CHMe2),
Eur. J. Inorg. Chem. 2010, 2025–2035
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2033

A. F. Lugo née Gushwa, A. F. Richards
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Published Online: March 23, 2010
Eur. J. Inorg. Chem. 2010, 2025–2035
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2035