Monomeric group 13 metal(I) amides: Enforcing one-coordination through extreme ligand steric bulk

Article abstract of DOI:10.1021/ic3022613

Reactions of the extremely bulky amido alkali metal complexes, [KL′( η⁶-toluene)], or in situ generated [LiL′] or [LiL″] {L′/ L″ = N(Ar*)(SiR₃), where Ar* = C ₆H₂{C(H)Ph₂}₂Me-2,6,4 and R = Me (L′) or Ph (L″)} with group 13 metal(I) halides have yielded a series of monomeric metal(I) amide complexes, [ML′] (M = Ga, In, or Tl) and [ML″] (M = Ga or Tl), all but one of which have been crystallographically characterized. The results of the crystallographic studies, in combination with computational analyses, reveal that the metal centers in these compounds are one coordinate and do not exhibit any significant intra- or intermolecular interactions, other than their N-M linkages. One of the complexes, [InL′], represents the first example of a one-coordinate indium(I) amide. Attempts to extend this study to the preparation of the analogous aluminum(I) amide, [AlL′], were not successful. Despite this, a range of novel and potentially synthetically useful aluminum(III) halide and hydride complexes were prepared en route to [AlL′], the majority of which were crystallographically characterized. These include the alkali metal aluminate complexes, [L′AlH₂(μ-H)Li(OEt₂) ₂(THF)] and [{L′Al(μ-H)₃K}₂], the neutral amido-aluminum hydride complex, [{L′AlH(μ-H)}₂], and the aluminum halide complexes, [L′AlBr₂(THF)] and [L′AlI₂]. Reaction of the latter two systems with a variety of reducing agents led only to intractable product mixtures.

Full text of DOI:10.1021/ic3022613

Article
pubs.acs.org/IC
Monomeric Group 13 Metal(I) Amides: Enforcing One-Coordination
Through Extreme Ligand Steric Bulk
Deepak Dange,† Jiaye Li,† Christian Schenk,†,‡ Hansgeorg Schnockel,§ and Cameron Jones*,†
̈
†School of Chemistry, Monash University, P.O. Box 23, Melbourne, Victoria 3800, Australia
‡Im Neuenheimerfeld 270, Anorganische Chemie, Universitat Heidelberg 69120, Germany
̈
§Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, Engesserstrasse 15, Bldg. 30.45, 76128, Germany
S
* Supporting Information
ABSTRACT: Reactions of the extremely bulky amido alkali
metal complexes, [KL′(η6-toluene)], or in situ generated
[LiL′] or [LiL″] {L′/ L″ = N(Ar*)(SiR3), where Ar* =
C6H2{C(H)Ph2}2Me-2,6,4 and R = Me (L′) or Ph (L″)} with
group 13 metal(I) halides have yielded a series of monomeric
metal(I) amide complexes, [ML′] (M = Ga, In, or Tl) and
[ML″] (M = Ga or Tl), all but one of which have been
crystallographically characterized. The results of the crystallo-
graphic studies, in combination with computational analyses, reveal that the metal centers in these compounds are one
coordinate and do not exhibit any significant intra- or intermolecular interactions, other than their N-M linkages. One of the
complexes, [InL′], represents the first example of a one-coordinate indium(I) amide. Attempts to extend this study to the
preparation of the analogous aluminum(I) amide, [AlL′], were not successful. Despite this, a range of novel and potentially
synthetically useful aluminum(III) halide and hydride complexes were prepared en route to [AlL′], the majority of which were
crystallographically characterized. These include the alkali metal aluminate complexes, [L′AlH2(μ-H)Li(OEt2)2(THF)] and
[{L′Al(μ-H)3K}2], the neutral amido-aluminum hydride complex, [{L′AlH(μ-H)}2], and the aluminum halide complexes,
[L′AlBr2(THF)] and [L′AlI2]. Reaction of the latter two systems with a variety of reducing agents led only to intractable product
mixtures.
Carb = bulky carbazolyl15). Monomeric examples of GaI and
INTRODUCTION
■
TlI amides and imino-amides (116,17 and 2,18 Figure 1) have
Considerable progress has been made in the field of molecular
group 13 metal(I) complex chemistry over the past decade.1
been reported, and these can be considered as having quasi
one-coordinate metal centers, that also exhibit weak intra-
molecular arene interactions in the solid state. Related to these
compounds are monomeric amidinato, guanidinato and
phosphaguanidinato InI and TlI complexes (e.g., 3,8,19) that
These systems are often very reactive and have found a variety
of applications in areas which include coordination chemistry
(use as metal-donor Lewis bases),2 organic synthesis,3 materials
chemistry,4 and the activation of small molecules,5 etc.
Generally, sterically bulky ligands are required to kinetically
stabilize group 13 metal(I) complexes from participating in the
disproportionation processes and/or other decomposition
pathways. While most work in this area has involved the use
of bulky aryl, alkyl, or silyl ligands, anionic N-donor ligands
have also played a significant role.1 Of the latter, bi- and
tridentate ligand systems (e.g., β-diketiminates,6 doubly
reduced 1,4-diazabutadienes,7 guanidinates,8 tris(pyrazolyl)-
borates,9 etc.) are especially important due to the extra
stabilization they offer metal(I) centers through “the chelate
effect”. With that said, a handful of bulky monodentate amides
have been successfully utilized in the preparation of examples of
complexes of all the group 13 metals in the +1 oxidation state.
These typically aggregate into oligomers through M−M
bonding (e.g., as in tetrahedral [{ML}4], where M = Al10 or
Ga11 and L = −N(SiMe3)(Dip); Dip = C6H3Pri2-2,6 or
2,2′,6,6′-tetramethylpiperidino),12 weak M···M interactions
(e.g., as in [{TlN(SiMe3)(Dip)}4]13), or bridging ligands
(e.g., as in [{Tl[μ-N(SiMe3)2]}2]14 and [{In(μ-Carb)}∞],
Figure 1. Previously reported examples of structurally characterized,
monomeric group 13 metal(I) amides (PrF = C3F7, Dip = C6H3Pri2-
2,6). The shortest M···Cipso interaction is defined with a dotted line
(distances given in parentheses).
Received: October 16, 2012
Published: November 16, 2012
© 2012 American Chemical Society
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display apparently slightly stronger M···arene interactions in the
solid state.
the complexes. Similarly, the indium(I) amide, 6, could not be
prepared in either toluene or THF using poorly soluble InBr as
the indium source. Instead, a metastable solution of [InBr-
(tmeda)n] was generated by dissolving InBr in a 10% v/v
tmeda/toluene mixture at −30 °C.25 This was then reacted
with [KL′(η6-toluene)] to give 6 in a good isolated yield.
Compounds 4−8 are all colorless to pale yellow crystalline
solids which are extremely air and moisture sensitive, though
If truly one-coordinate group 13 metal(I) amides were
accessible, they could display interesting ambiphilic behavior in
their further reactivity (cf. the known chemistry of metal diyls,
:MR, where M = group 13 metal and R = alkyl, aryl, etc.1). This
would result from them possessing only four valence electrons
at their metal centers (making them potentially electrophilic),
including a metal-based lone pair of electrons (making them
potentially nucleophilic). We have recently developed an
extremely bulky class of amido ligands [e.g., −N(Ar*)(SiR3),
where Ar* = C6H2{C(H)Ph2}2Me-2,6,4 and R = Me (L′) or Ph
(L″)20] which we have shown to have similar stabilizing
properties to the very bulky terphenyl ligand class developed by
the group of Power.3c These ligands have allowed us access to a
range of unprecedented low-coordinate group 14 metal amide
complexes (e.g., monomeric [L′ECl] (E = Ge or Sn),20 a singly
bonded amido-digermyne [L′Ge-GeL′],21 the weak intra-
molecularly arene-stabilized cations [L′E:]+ (E = Ge or Sn),22
and the acyclic boryl-germylene [L′Ge{B(DAB)}] (DAB =
{DipNCH}2).23 It seemed reasonable that these bulky amides
could also prove useful for the stabilization of low-coordinate/
low-oxidation state group 13 metal complexes. Here, we show
that this is the case and report the preparation and
characterization of a series of monomeric, essentially one-
coordinate amido GaI, InI, or TlI complexes. In addition, we
detail our unsuccessful attempts to access the corresponding
monomeric AlI amides.
1
thermally stable at room temperature. Their H and 13C NMR
spectra are consistent with the molecules possessing Cs
symmetry in solution, while the EI mass spectrum of each
compound exhibits a molecular ion peak of moderate intensity.
The 71Ga and 115In NMR spectra were acquired for
concentrated solutions of the gallium and indium amides,
though no signals were observed in each case. This is
presumably due to the quadrupolar nature of these nuclei
(71Ga: I = 3/2, natural abundance = 39.6%; 115In: I = 9/2,
natural abundance = 95.7%) and their unsymmetrical
coordination environments, giving rise to significant line
broadening. In contrast, the 205Tl NMR spectra (205Tl: I = 1/
2, natural abundance = 70.5%) of 7 and 8 displayed resonances
at δ = 3325 ppm (peak width at half height = 760 Hz) and δ =
3029 ppm (peak width at half height = 820 Hz), respectively.
No 29Si satellites were observed about the resonance of either
compound. While 205Tl NMR spectroscopic data for TlI amides
are sparse, these values are comparable to the chemical shift of
δ = 3229 ppm reported for the monomeric, three-coordinate
complex, [TlN{C6H3(PMe2)Me-2,4}2].26
The crystallographic characterization of 4, 6, and 7 revealed
the compounds to be isostructural. As a result, only the
molecular structure of 4 is depicted in Figure 2 (see Supporting
Information for the molecular structures of 6 and 7), while the
structure of the more hindered compound, 5, is also shown in
Figure 2 (see Table 1 for selected metrical parameters of 4−7).
All the compounds are monomeric and exhibit no M···M
separations closer than 5.4 Å. Their N-centers have trigonal
planar geometries, which in the cases of 4, 5, and 7 include M−
N distances close to those reported for related complexes [e.g.,
1a: Ga−N 1.980(2) Å and 1b: Tl−N 2.348(3) Å].17 There are
no examples of one-coordinate InI amides to compare to 6, but
it is of note that its In−N distance is only marginally shorter
than that in 3a, viz. 2.283(2) Å.8a It is apparent that the metal
centers in 4−7 are all essentially one-coordinate. The closest
metal−arene interactions involving the flanking C(H)Ph2
groups are to the ipso-carbon centers, C(15) and C(28),
while the interactions with the o-, m-, and p-carbons of those
phenyl groups are substantially longer. It is of note that in the
more bulky gallium amide, 5, the shortest Ga-arene contact
involving the SiPh3 group is also very long, at 3.194(4) Å. The
lengths of these contacts in the GaI and TlI amides can be put
into context when they are compared with the substantially
shorter M···Cipso distances in the quasi-one-coordinate systems,
1 and 2,16,17 depicted in Figure 1. Similarly, the contacts in the
InI amide, 6, are markedly shorter than those in 3a.8 While it is
likely that there is some interaction between the metal centers
of 4−7 and their flanking phenyl groups, this must be
considered as very weak in each case.
RESULTS AND DISCUSSION
■
(i). Monomeric Gallium(I), Indium(I), and Thallium(I)
Amides. Lithium or potassium complexes of the bulky amide
ligands, L′ and L″, were reacted with group 13 metal(I) halides
affording the metal(I) amide complexes, 4−8, in moderate to
good yields (Scheme 1). It is of note that in these reactions,
Scheme 1. Preparation of Compounds 4−8 (L′ =
N(Ar*)(SiMe3) and L″ = N(Ar*)(SiPh3); Ar* =
C6H2{C(H)Ph2}2Me-2,6,4)
[LiL′] and [LiL″] were generated in situ prior to use, whereas
[KL′] was prepared via the reaction of L′H with [KN(SiMe3)2]
in toluene and purified as the toluene complex [KL′(η6-
toluene)] prior to use. The spectroscopic and crystallographic
characterization of this compound {and the related compound
[KL′(OEt2)]} can be found in the Supporting Information. It is
also noteworthy that the gallium(I) amides, 4 and 5, could only
be prepared in reasonable yields using [{GaICl(THF)}n] as the
gallium source. This metastable complex was synthesized using
a specialized reactor for the co-condensation of GaCl and THF
in a toluene matrix,4a as detailed in the Supporting Information.
Attempts to prepare 4 and 5 using the more accessible and
thermally stable reagent, “GaI”,24 gave only very low yields of
Quantum-chemical calculations (BP86/RI-DFT/def2-
TZVPP/def2-SVP) were carried out on 4, 6, and 7 in the gas
phase. In all cases, their geometries optimized to be very close
to those in the experimental solid state structures, including
similar arrangements of the phenyl groups about the metal
centers (see Table 1 for selected metrical parameters). Analyses
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Figure 2. Thermal ellipsoid plot (25% probability surface) of the molecular structures of (a) 4 and (b) 5. Hydrogen atoms of both structures are
omitted. Selected metrical parameters for these compounds and for 6 and 7 are given in Table 1.
Table 1. Selected Interatomic Distances (Å) and Angles
a
(deg) for 4−7.
b
4
5
6
7
M(1)-N(1)
1.954(2)
(1.988)
1.985(4)
2.188(2)
(2.232)
2.356(13)
(2.348)
C(1)−N(1)
N(1)−Si(1)
M(1)-C(15)
1.425(3)
1.729(2)
3.245(2)
(3.245)
1.435(5)
1.726(4)
3.302(4)
1.413(3)
1.713(2)
3.287(3)
(3.322)
1.414(19)
1.690(14)
3.233(12)
(3.334)
M(1)-C(28)
3.120(2)
(3.225)
3.122(4)
3.201(3)
(3.310)
3.226(15)
(3.321)
M(1)-N(1)−
121.77(11)
120.7(2)
121.65(12)
118.7(7)
Si(1)
M(1)-N(1)−
116.60(15)
118.7(3)
120.5(3)
116.15(16)
122.16(18)
119.0(10)
122.3(11)
C(1)
C(1)−N(1)− 121.55(15)
Si(1)
a
Selected metrical parameters for the calculated (BP86/RI-DFT/def2-
Figure 3. (a) LUMO + 9, (b) LUMO, and (c) HOMO − 4 of 4.
TZVPP/def2-SVP) gas phase structures of 4, 6, and 7 are given in
parentheses. The asymmetric unit of the crystal structure of 7
b
unsymmetrical and one phenyl substituent of the ligand
displays a weak η2-arene interaction with the germanium center
(Ge···Cipso: 2.642(2) Å; Ge···Cortho: 2.661(2) Å). This difference
likely arises from the higher electrophilicity of the cationic
germanium center, relative to the gallium center in neutral 4.
An NBO charge analysis of 4 revealed that the Ga−N bond is
heavily polarized (Ga: +0.88, N: −1.37), as might be expected
given the relative electronegativities of the two elements.
Consistent with this polarization is the low calculated Wiberg
Bond Index (WBI) for the interaction (0.352) and the fact that
the lone pair at Ga is almost exclusively of s-character (99.9%).
As an indication of the weakness of the Ga−arene interactions
in 4, the calculated WBIs for the two closest Ga···Cipso
interactions involving the flanking phenyl groups are both
negligible at 0.016.
(ii). Attempted Preparations of Monomeric
Aluminum(I) Amides. Although a handful of oligomeric
amido aluminum(I) species are known (vide supra), there are
no examples of monomeric, one-coordinate systems that have
been reported in the literature. Indeed, to the best of our
knowledge, there are no reports of any structurally
authenticated one-coordinate aluminum(I) complexes.27 Ac-
cordingly, given our success with the preparation of the heavier
group 13 amides, 4−8, we investigated the preparation of the
analogous aluminum(I) complex, [AlL′].
contains two crystallographically independent molecules. Metrical
parameters for only one are given.
of the frontier orbitals of the calculated molecules revealed
similar electronic structures. Accordingly, only that for the
gallium amide, 4, will be presented here. The LUMO of the
compound essentially comprises an empty Ga-based p-orbital
coplanar with the CNSiGa fragment, while the empty p-orbital
orthogonal to that fragment is associated with LUMO + 9
(Figure 3). This is directed toward a phenyl ring on each side of
the gallium center. However, there does not appear to be any
significant Ga-arene bonding interaction taking place in that
orbital, or any of the filled MOs near the frontier. The HOMO
has character consistent with the N−Ga σ-bond, while the
HOMO-4 largely comprises the Ga lone pair, which appears to
possess a high s-orbital component. Moreover, there appears to
be negligible overlap between the N p-orbital of 4 (HOMO-1)
and either empty p-orbital at Ga. Therefore, it seems likely that
the degree of N−Ga π-bonding in the compound is not
substantial. This picture of the electronic structure of 4 is
similar to that arising from computational studies we recently
reported for the isoelectronic germanium(II) monocation,
[L′Ge:]+.22 Interestingly, the experimentally determined
structure for the cation differs from that of 4, in that it is
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Our initial strategy was to react either [LiL′] or [KL′(η6-
toluene)] with a toluene/THF solution of the metastable
aluminum(I) species, [{AlICl(THF)}n].4a Surprisingly, in both
cases, no salt elimination reaction was observed, and the alkali
metal amide was recovered from the reaction mixture. This
contrasts with the successful preparation of the gallium(I)
amide, 4, and reactions of less bulky amide complexes (e.g.,
[LiN(Dip)(SiMe3)]) with aluminum(I) chloride solutions. The
latter are known to give large mixed valence, metalloid cluster
compounds (e.g., [Si@Al56{N(SiMe3)(Dip)}12]).28 We cannot
be certain why no reactions were observed in this study, but the
considerable steric bulk of the amide ligand, L′, and the
presumably stronger metal−metal bonds in [{AlICl(THF)}n]
relative to those in [{GaICl(THF)}n] are most likely
contributing factors.
Scheme 2. Syntheses of Compounds 9−12
We turned our attention then to the preparation of
aluminum(III) halide precursors, [L′AlX2] (X = Br or I), the
reduction of which could potentially yield the target complex,
[AlL′] (cf. the preparation of [{Al[N(SiMe3)(Dip)]}4] via the
reduction of [AlI2{N(SiMe3)(Dip)}]10). To this end, the 1:1
reaction of [KL′(η6-toluene)] with AlBr3 in THF was carried
out, and this afforded a good yield of the crystalline compound,
[L′AlBr2(THF)]. This complex was spectroscopically charac-
terized and shown by an X-ray crystallographic study (see
Supporting Information) to be monomeric with a distorted
tetrahedral aluminum center. Attempts were made to reduce
the compound using a number of reagents, viz. KC8,
[Na(naphthalide)], or [{MgI(MesNacnac)}2] (MesNacnac =
[(MesNCMe)2CH]−, where Mes = mesityl29), though in all
cases intractable mixtures of products were obtained, the NMR
spectroscopic analyses of which revealed L′H as a significant
component.
It is well-known that p-block metal iodide complexes are
typically more easily reduced than their bromide counterparts.
As a result, the preparation of [L′AlI2] was attempted via the
reaction of [KL′(η6-toluene)] with AlI3. Again, this led to an
intractable mixture of products and was not pursued further. To
overcome this problem, it seemed reasonable, based on the
results of previous studies of Roesky10 and Cui,30 that either
[L′AlMe2] or [L′AlH2] could be iodinated to give [L′AlI2].
However, attempts to prepare those complexes by treatment of
L′H with either AlMe3 or [AlH3(NMe3)] led to no reaction,
even at elevated temperatures (ca. 70 °C). In light of this, the
synthesis of [L′AlH2] was explored using a less direct route. To
this end, the reactions of [LiL′] and [KL′(η6-toluene)] with
[AlH3(NMe3)] were carried out, and these gave moderate and
high yields, respectively, of the alkali metal amido−aluminate
complexes, 9 and 10 (Scheme 2). Subsequent treatment of
either of these with one equivalent of MeI afforded high yields
of the neutral amido−aluminum hydride, 11, the reaction of
which with SiMe3I gave the target aluminum iodide complex,
12, in excellent yield. Unfortunately, all efforts to reduce 12 to
the aluminum(I) amide, [AlL′], by its reaction with KC8,
[Na(naphthalide)], or [{MgI(MesNacnac)}2] proved fruitless
and instead led to unidentifiable product mixtures. That said,
12 and [L′AlBr2(THF)] hold considerable potential for use by
synthetic inorganic chemists as precursors for other low
oxidation state and/or low coordination number aluminum
complexes.
molecular structures of the compounds are depicted in Figure
4. In all compounds, the hydride ligands were located from
difference maps and their positional parameters freely refined.
Compounds 9 and 10 represent rare examples of alkali metal
amido−hydrido−aluminate complexes, while to the best of our
knowledge, compound 10 is the first structurally characterized
potassium salt of such an aluminate. The lithium aluminate, 9,
is a monomeric contact ion pair which exhibits a single hydride
bridge between the Al and Li centers of the salt. This contrasts
to analogous systems incorporating less bulky amide ligands,
which typically form cyclic dimeric structures (e.g., [{(SiMe3)2-
NAlH(μ-H)2Li(OEt2)2}2]31 and [{(Dip)[(Me3Si)2HC]NAlH-
(μ-H)2Li(THF)2}2]),30 through two bridging hydrides per Al
center. The reluctance of 9 to form a similar dimeric structure is
most likely a result of the imposing sterics of its amide ligand. It
is noteworthy that the Li center of 9 is coordinated by both
THF and diethyl ether molecules because both these solvents
were used in the synthesis of the compound. In contrast, no
coordinating solvents were utilized in the preparation of 10,
and as a result, this complex crystallizes as an unusual and
congested dimer in which each potassium center is connected
to both Al centers through three hydride bridges. Furthermore,
both potassium centers enhance their electronic satisfaction
through η6- and η2-interactions with a phenyl group from each
amide ligand.
The steric bulk of the amide ligand can also be used to
account for the nature of the structure of 11. That is, although
unsolvated monodentate amido−aluminum dihydride com-
plexes have been previously described, they typically form
dimeric or higher nuclearity systems with terminal hydride and
bridging amide ligands (e.g., [{H2Al(μ-NMeEt)}2]32 and
[{H2Al(μ-NMe2)}3].33 Such an amide bridging motif is
disfavored for 11, and hence, it dimerizes through unsym-
metrical hydride bridges. While hydride-bridged structures are
unknown for four-coordinate, monodentate amido-aluminum
dihydride complexes, they have been reported for five-
coordinate systems which incorporate bulky, bidentate anionic
N-donor ligands (e.g., as in [{(Piso)AlH(μ-H)}2] (Piso =
[(DipN)2CBut]−).34 Although the crystal structure of the
iodide analogue of 11 (viz. 12) could not be obtained, it seems
likely that it has a similar structure to the aluminum hydride
complex in the solid state.
Despite the lack of success in obtaining an aluminum(I)
amide complex, the aluminum hydride precursor complexes,
9−11, are of significant novelty in their own right, and as such,
a brief discussion of their structural features is worthwhile. The
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Figure 4. Thermal ellipsoid plot (25% probability surface) of the molecular structures of (a) 9, (b) 10, and (c) 11. Selected bond lengths (Å) and
angles (°) for 9: Al(1)−N(1) 1.8767(18), Al(1)−H(1) 1.48(3), Al(1)−H(2) 1.59(3), Al(1)−H(3) 1.56(3), Li(1)−H(3) 1.88(3), N(1)−Al(1)−
H(1) 109.0(11), N(1)−Al(1)−H(2) 112.5(11), N(1)−Al(1)−H(3) 112.9(10). 10: Al(1)−N(1) 1.8531(17), Al(1)−H(1) 1.53(2), Al(1)−H(2)
1.55(2), Al(1)−H(3) 1.56(2), K(1)−H(2) 2.67(2), K(1)′-H(1) 2.73(2), K(1)′-H(3) 2.74(2), K(1)-Ct(1) 2.950(1), K(1)′-C(17) 3.198(3), K(1)′-
C(18), 3.254(3), N(1)−Al(1)−H(1) 111.3(9), N(1)−Al(1)−H(2) 112.0(8), N(1)−Al(1)−H(3) 112.2(9); symmetry operation (′) = −x + 1, −y +
2, −z + 1. 11: Al(1)−N(1) 1.8050(18), Al(1)−H(1) 1.66(2), Al(1)−H(2) 1.48(2), Al(1)′-H(1) 1.79(2), N(1)−Al(1)−H(2) 123.4(8), H(1)−
Al(1)−H(1)′ 81(1); symmetry operation (′) = 1/2 − x, 3/2 − y, 1 − z.
here, including their use as soluble sources of the monovalent
metals in metathesis reactions. Our efforts in this direction will
be reported in due course.
CONCLUSIONS
■
In summary, reactions of alkali metal complexes of extremely
bulky amide ligands with heavier group 13 metal(I) halide salts
or complexes have afforded a series of monomeric, one-
coordinate group 13 metal(I) amides. These include a one-
coordinate indium(I) amide, which has no precedent in the
literature. The results of computational studies on one of the
prepared gallium(I) amides imply that there are negligible
interactions between the phenyl groups of the amide ligand and
the gallium center, which was also shown to possess a lone pair
of essentially s-character. Although attempts to prepare
aluminum(I) amides were not successful, several novel bulky
amido−aluminum(III) hydride complexes were synthesized
and crystallographically characterized en route to the low
oxidation state target complex. We are currently further
examining the chemistry of the metal(I) amides reported
EXPERIMENTAL SECTION
■
General Methods. All manipulations were carried out using
standard Schlenk and glovebox techniques under an atmosphere of
high purity dinitrogen. THF, hexane, and toluene were distilled over
potassium; diethyl ether was distilled over Na/K alloy, while tmeda
was distilled over sodium. 1H and 13C{1H} NMR spectra were
recorded on a Bruker AvanceIII 400 spectrometer and were referenced
to the resonances of the solvent used. Li, 27Al, 29Si{1H}, and 205Tl
7
NMR spectra were recorded on a Bruker AvanceIII 400 spectrometer
and were referenced to external 9.7 M aqueous LiCl, 1 M aqueous
[Al(OH2)6]3+, SiMe4, and 0.1 M aqueous Tl(NO3), respectively. Mass
spectra were obtained from the EPSRC National Mass Spectrometric
Service at Swansea University. IR spectra were recorded using a
Perkin-Elmer RX1 FT-IR spectrometer as Nujol mulls between NaCl
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plates. Microanalyses were carried out by the Science Centre, London
Metropolitan University. Melting points were determined in sealed
glass capillaries under dinitrogen and are uncorrected. The compounds
L′H,20 L″H20, and [AlH3(NMe3)]35 were prepared by literature
procedures, while a 3:1 toluene/THF solution of [{GaICl(THF)}n]
(0.34 M) was prepared by a variation of the co-condensation
CHPh2), 6.49−7.70 (m, 37H, Ar-H). 13C{1H} NMR (C6D6, 100 MHz,
296 K) δ = 21.2 (Ar-CH3), 52.7 (CHPh2), 126.1, 127.5, 128.4, 129.6,
129.8, 129.9, 130.1, 130.2, 130.3, 136.3, 137.0, 137.8, 141.6, 144.0,
144.9, 148.3 (Ar-C). 29Si{1H}NMR (C6D6, 80 MHz, 296 K): δ =
−23.5 (br s). IR (Nujol) ν/cm−1 1596 (m), 1493 (m), 1454 (m), 1375
(m), 1252 (w), 1029 (s), 895 (m), 695 (s). MS (EI 70 eV) m/z (%)
technique developed by Schnockel4a (see Supporting Information for
+
765.2 (M+, 8), 698.3 [(SiPh3)Ar*NH2 , 45]. Anal. Calc. for
̈
further details). All other reagents were used as received.
C51H42GaNSi: 79.89% C, 5.52% H, 1.83% N. Found: 80.06% C,
5.50% H, 1.83% N.
Preparation of [KL′(η6-toluene)]. To a stirred solution of L′H (1.50
g, 2.93 mmol) in THF (30 mL) at −78 °C was added a solution of
[KN(SiMe3)2] (0.61 g, 3.08 mmol) in THF (10 mL). The reaction
mixture was warmed to room temperature and was stirred for 3 h,
whereupon volatiles were removed in vacuo, the resulting solid
extracted with toluene (40 mL) and the extract filtered. The filtrate
was concentrated to ca. 20 mL and stored at −30 °C overnight to give
colorless crystals of the title compound (1.32 g, 71%.). M.p.: 214−216
°C (dec). 1H NMR (C6D6, 400 MHz, 296 K) δ = 0.42 (s, 9H, SiMe3),
2.10 (br s, 6H, overlapping, Ar−CH3/toluene-CH3), 6.55 (s, 2H,
CHPh2), 6.65−7.33 (m, 27H, Ar-H). 13C{1H} NMR (C6D6, 100 MHz,
296 K) δ = 5.4 (SiMe3), 21.4 (br, overlapping Ar-CH3/toluene-CH3),
53.3 (CHPh2), 125.6, 130.0, 129.2, 137.8, 124.5, 125.7, 127.3, 127.7,
128.5, 128.6, 130.2, 130.6, 139.4, 141.9, 146.5, 151.0 (toluene-C and
Ar-C). 29Si{1H}NMR (C6D6, 80 MHz, 296 K): No signal observed,
even for a concentrated sample and long acquisition time. IR (Nujol)
ν/cm−1 1596 (m), 1484 (m), 1456 (m), 1373 (m), 1246 (w), 1029
Preparation of [InL′] (6). A solution of [KL′(η6-toluene)] (0.50 g,
0.78 mmol) in toluene (40 mL) was added to a solution of InBr (0.154
g, 0.79 mmol) in a 10% tmeda/toluene mixture at −30 °C. The
resultant solution was warmed to 0 °C over a period of 5 h. Volatiles
were then removed in vacuo and the residue extracted with diethyl
ether. The extract was filtered, and the filtrate concentrated to ca. 10
mL, then stored at −30 °C overnight to give colorless crystals of 6
(0.27 g, 56%). M.p.: 210−218 °C (decomp to a black solid). 1H NMR
(C6D6, 400 MHz, 296 K) δ = 0.44 (s, 9H, SiMe3), 1.98 (s, 3H, Ar−
CH3), 6.29 (s, 2H, CHPh2), 6.85−7.26 (m, 22H, ArH); 13C{1H}
NMR (C6D6, 100 MHz, 296 K) δ = 4.7 (SiMe3), 21.2 (Ar-CH3), 53.2
(CHPh2), 126.4, 126.6, 128.6, 128.7, 129.5, 130.0, 130.1, 130.4, 130.6,
141.9, 145.5, 148.4 (Ar-C). 29Si{1H}NMR (C6D6, 80 MHz, 296 K) δ =
−9.2 (s). IR (Nujol) ν/cm−1 1597 (m), 1462 (s), 1455 (m), 1377 (s),
1260 (m), 1031 (w), 919 (m), 697 (m). MS (EI 70 eV) m/z (%)
+
+
625.2 (M+, 20), 512.3 [(SiMe3)Ar*NH2 , 100], 167.0 (CHPh2 , 20);
Anal. Calc. for C36H36InNSi: 69.12% C, 5.80% H, 2.24% N. Found:
69.21% C, 5.74% H, 2.30% N.
+
(s), 921 (m), 695 (s). MS (EI 70 eV) m/z (%): 549.2 (M-C7H8 , 42),
+
+
+
512.3 [(SiMe3)Ar*NH2 , 100], 439.2 (Ar*NH2 , 50), 167.0 (CHPh2 ,
21). Anal. Calc. for C43H44KNSi: 80.45% C, 6.91% H, 2.18% N.
Found: 80.37% C, 6.85% H, 2.26% N.
Preparation of [TlL′] (7). LiBun (0.64 mL of a 1.6 M solution in
hexane) was added to a solution of L′H (0.50 g, 0.97 mmol) in THF
(30 mL) at −78 °C over a period of 2 min. The reaction mixture was
warmed to room temperature and stirred for 2 h. The resultant
solution was then added to a suspension of TlBr (0.28 g, 0.99 mmol)
in THF (10 mL) at −78 °C, and the mixture was warmed to room
temperature over a period of 12 h. Volatiles were then removed in
vacuo and the residue extracted with diethyl ether. The extract was
filtered and the filtrate concentrated to ca. 10 mL and stored at −30
°C overnight to give pale yellow crystals of 7 (0.42 g, 60%). M.p.:
Preparation of [GaL′] (4). LiBun (1.8 mL of a 1.6 M solution in
hexane) was added to a solution of L′H (1.40 g, 2.73 mmol) in THF
(40 mL) at −78 °C over a period of 2 min. The reaction mixture was
warmed to room temperature and stirred for 2 h, whereupon it was
concentrated to ca. 10 mL. Toluene (40 mL) was then added to the
solution and the mixture cooled to −78 °C. [{GaICl(THF)}n] (10.1
mL of a 0.34 M solution in 3:1 toluene/THF) at −80 °C was added to
this solution, and the mixture was warmed to room temperature over a
period of 12 h, whereupon volatiles were removed in vacuo. The
resultant solid was extracted with toluene (40 mL) and filtered. The
filtrate was concentrated to ca. 20 mL and stored at −30 °C overnight,
yielding a colorless precipitate. This was recrystallized from a
minimum volume of diethyl ether to give colorless crystals of 4
(0.98 g, 62%). M.p.: 230−240 °C (decomp to a black solid). 1H NMR
(C6D6, 400 MHz, 296 K) δ = 0.42 (s, 9H, SiMe3), 1.92 (s, 3H, Ar−
CH3), 6.13 (s, 2H, CHPh2), 6.85 (s, 2H, m-Ar-H), 7.02−7.26 (m,
20H, Ar-H). 13C{1H} NMR (C6D6, 100 MHz, 296 K) δ = 3.9 (SiMe3),
21.2 (Ar-CH3), 53.3 (CHPh2), 126.4, 126.5, 128.6, 129.7, 129.9, 130.0,
130.3, 130.4, 142.4, 144.8, 145.0, 147.6 (Ar-C). 29Si{1H} NMR (C6D6,
80 MHz, 296 K) δ = 0.1 (br s). IR (Nujol) ν/cm−1: 1597 (s), 1454
(s), 1378 (s), 1240 (s), 1030 (m), 903 (w). MS (EI 70 eV) m/z (%)
1
163−168 °C (decomp to a black solid). H NMR (C6D6, 400 MHz,
296 K) δ = 0.46 (s, 9H, SiMe3), 2.16 (s, 3H, Ar−CH3), 6.59 (s, 2H,
CHPh2), 6.77 (m, 2H m-Ar-H), 6.86−7.27 (m, 20H, Ar-H). 13C{1H}
NMR (C6D6, 100 MHz, 296 K) δ = 4.6 (SiMe3), 21.1 (Ar-CH3), 52.8
(CHPh2), 126.1, 126.4, 128.4, 128.5, 128.6, 129.9, 130.2, 141.7, 141.8,
144.2, 145.7, 150.0 (Ar-C). 29Si{1H} NMR (C6D6, 80 MHz, 296 K): δ
= −12.4 (s); 205Tl NMR (C6D6, 230.8 MHz, 296 K) δ = 3325 (peak
width at half height = 760 Hz). IR (Nujol) ν/cm−1 1597 (m), 1492
(m), 1455 (m), 1377 (s), 1262 (s), 1074 (w), 1028 (w), 937 (m), 697
+
(s). MS (EI 70 eV) m/z (%) 715.2 (M+, 5), 512.3 [(SiMe3)Ar*NH2 ,
+
+
100], 439.2 (Ar*NH2 , 25), 167.0 (CHPh2 , 22). Anal. Calc. for
C36H36NSiTl: 60.46% C, 5.07% H, 1.96% N. Found: 60.37% C, 4.94%
H, 1.87% N.
+
+
579.2 (M+, 55), 512.3 [(SiMe3)Ar*NH2 , 100], 167.0 (CHPh2 , 26).
Anal. Calc. for C36H36GaNSi: 74.49% C, 6.25% H, 2.41% N. Found:
74.38% C, 6.20% H, 2.38% N.
Preparation of [TlL″] (8). LiBun (0.56 mL of a 1.6 M solution in
hexane) was added to a solution of L″H (0.60 g, 0.85 mmol) in THF
(30 mL) at −78 °C over a period of 2 min. The reaction mixture was
warmed to room temperature and stirred for 2 h. The resultant
solution was then added to a suspension of TlBr (0.25 g, 0.87 mmol)
in THF (10 mL) at −78 °C, whereupon it was warmed to room
temperature over a period of 12 h. Volatiles were then removed in
vacuo and the residue extracted with toluene (20 mL). The extract was
filtered and the filtrate concentrated to ca. 10 mL and placed at −30
°C overnight to give 8 as a yellow crystalline solid (0.56 g, 73%). M.p.:
N.B.: Compound 4 was alternatively prepared by the 1:1 reaction of
[LiL′] and “GaI” (prepared by sonication of a solution of I2 over a
large excess of Ga metal). However, this led only to a low yield (7%)
of the compound.
Preparation of [GaL″] (5). LiBun (2.16 mL of a 1.6 M solution in
hexane) was added to a solution of L″H (2.30 g, 3.29 mmol) in
toluene (40 mL) at −78 °C over 2 min. The reaction mixture was
warmed to room temperature and stirred for 2 h, before being cooled
back to −78 °C. [{GaICl(THF)}n] (12.1 mL of a 0.34 M solution in
3:1 toluene/THF) was added to this solution, and the mixture was
warmed to room temperature over a period of 12 h, whereupon
volatiles were removed in vacuo. The resultant solid was extracted with
toluene (40 mL) and filtered. The solution was concentrated to ca. 20
mL and stored at −30 °C overnight, yielding an off-white precipitate.
This was recrystallized from a minimum volume of hexane to give 5 as
1
235−242 °C (decomp to a black solid). H NMR (C6D6, 400 MHz,
296 K) δ = 2.16 (s, 3H, Ar−CH3), 6.49 (s, 2H, CHPh2), 6.66−7.73
(m, 37H, Ar-H). 13C{1H} NMR (C6D6, 100 MHz, 296 K) δ = 20.9
(Ar-CH3), 52.1 (CHPh2), 125.9, 126.3, 128.1, 128.2, 128.8, 129.3,
130.1, 130.5, 135.2, 136.3, 136.8, 140.1, 141.0, 144.6, 145.6, 150.7 (Ar-
C). 29Si{1H}NMR (C6D6, 80 MHz, 296 K) δ = −27.4 (s); 205Tl NMR
(C6D6, 230.8 MHz, 296 K) δ= 3029 (peak width at half height = 820
Hz). IR (Nujol) ν/cm−1 1596 (m), 1493 (m), 1376 (s), 1260 (s),
1104 (s), 1028 (w), 936 (m), 699 (s). MS (EI 70 eV) m/z (%) 901.3
1
colorless crystals (0.86 g, 34%). M.p.: 278−283 °C (dec). H NMR
(C6D6, 400 MHz, 296 K) δ = 1.92 (br s, 3H, Ar−CH3), 6.15 (br s, 2H,
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+
(M+, 25), 698.3 [(SiPh3)Ar*NH2 , 47]. A reproducible microanalysis
mmol). The resultant solution was warmed to room temperature over
12 h, whereupon volatiles were removed in vacuo to give an off-white
solid. This residue was dissolved in toluene and layered with hexane to
for this compound could not be obtained.
Preparation of [L′AlBr2(THF)]. To a solution of AlBr3 (0.20 g, 0.78
mmol) in toluene (10 mL) at −78 °C was added a solution of
[KL′(η6-toluene)] (0.50 g, 0.78 mmol) in toluene (30 mL) over 5
min. The resultant solution was warmed to room temperature over 12
h, whereupon volatiles were removed in vacuo to give an off-white
solid. This residue was dissolved in toluene and layered with hexane to
give colorless crystals of the title compound (0.473 g, 79%.). M.p.:
1
give colorless crystals of 11 (0.40 g, 86%). M.p.: 264−268 °C. H
NMR (C6D6, 400 MHz, 296 K) δ = 0.21 (s, 18H, SiMe3), 1.91 (s, 6H,
Ar−CH3), 3.15 (br s, 4H, AlH), 6.14 (s, 4H, CHPh2), 6.96 (m, 4H m-
Ar-H), 7.00−7.29 (m, 40H, Ar-H). 13C{1H} NMR (C6D6, 100 MHz,
296 K) δ = 3.1 (SiMe3), 21.3 (Ar-CH3), 52.7 (CHPh2), 125.6, 126.5,
128.5, 128.57, 129.1, 129.2, 130.1, 130.4, 130.8, 142.5, 142.6, 145.5
(Ar-C). 29Si{1H} NMR (C6D6, 80 MHz, 296 K) δ = 5.0 (s). IR
(Nujol) ν/cm−1 1890 (Al−H, br s), 1493 (s), 1376 (s), 1250 (s), 1076
(m), 1031 (w), 909 (m), 728 (m), 698 (s). MS (EI 70 eV) m/z (%):
1
119−121 °C. H NMR (C6D6, 400 MHz, 296 K) δ = 0.24 (s, 9H,
SiMe3), 0.74 (m, 4H, THF-CH2), 1.95 (s, 3H, Ar−CH3), 3.36 (m, 4H,
THF-OCH2), 6.82 (s, 2H, CHPh2), 6.94−7.60 (m, 22H, Ar-H).
13C{1H} NMR (C6D6, 100 MHz, 296 K) δ = 4.0 (SiMe3), 21.3 (Ar-
CH3), 24.3 (THF-CH2), 51.4 (CHPh2), 75.0 (THF-OCH2), 126.2,
126.4, 128.3, 128.5, 129.2, 129.9, 130.4, 130.9, 133.7, 141.6, 145.1,
145.6 (Ar-C). 29Si{1H} NMR (C6D6, 80 MHz, 296 K) δ = 4.1 (s). 27Al
NMR (C6D6, 104.2 MHz, 296K) δ = 97.4 (br s). IR (Nujol) ν/cm−1
1598 (s), 1377 (s), 1247 (s), 1123 (m), 1078 (m), 1032 (w), 899 (s),
704 (s), 605 (m). MS (EI 70 eV) m/z (%) 697.1 (M+-THF, 7), 512.3
+
+
+
512.3 [(SiMe3)Ar*NH2 , 100], 439.3 (Ar*NH2 , 25), 167.0 (CHPh2 ,
24). Anal. Calc. for C72H76Al2N2Si2: 80.11% C, 7.10% H, 2.59% N.
Found: 79.99% C, 7.17% H, 2.61% N.
N.B. Compound 11 can be similarly prepared in high yield via the
reaction of 9 with CH3I.
Preparation of [L′AlI2] (12). To a solution of 11 (0.30 g, 0.55
mmol) in toluene (20 mL) at −78 °C was added Me3SiI (0.22 g, 1.11
mmol). The resultant solution was warmed to room temperature over
12 h, whereupon volatiles were removed in vacuo to give an off-white
solid. This residue was dissolved in toluene and layered with hexane to
give colorless crystals of 12 (0.37 g, 84%). Mp: 180−186 °C
(decomp). 1H NMR (C6D6, 400 MHz, 296 K) δ = 0.42 (s, 9H, SiMe3),
1.88 (s, 3H, Ar−CH3), 6.19 (s, 2H, CHPh2), 6.95−7.51 (m, 22H, Ar-
H). 13C{1H} NMR (C6D6, 100 MHz, 296 K) δ = 4.8 (SiMe3), 21.1
(Ar-CH3), 52.5 (CHPh2), 126.7, 128.6, 128.7, 129.2, 129.8, 130.1,
130.3, 132.8, 133.2, 141.3, 143.4, 146.4 (Ar-C). 29Si{1H} NMR (C6D6,
80 MHz, 296 K) δ = 7.1 (s). IR (Nujol) ν/cm−1 1598 (w), 1493 (m),
1250 (m), 1077 (m), 1031 (w), 903 (m), 699 (s). MS (EI 70 eV) m/z
(%) 790.9 (M+, 12), 679.1 (M+−I, 100). Anal. Calc. for
C36H32AlI2NSi: 54.62% C, 4.58% H, 1.77% N. Found: 54.52% C,
4.69% H, 1.80% N.
X-ray Crystallography. Crystals of 4−7, 9−11, [L′AlBr2(THF)],
[KL′(η6-toluene)] and [KL′(OEt2)] suitable for X-ray structural
determination were mounted in silicone oil. Crystallographic measure-
ments were carried out at 123 K with an Oxford Gemini Ultra
diffractometer using a graphite monochromator with Mo Kα radiation
(λ = 0.71073 Å). The structures were solved by direct methods and
refined on F2 by full matrix least-squares (SHELX97),36 using all
unique data. All non-hydrogen atoms are anisotropic with non-hydride
hydrogen atoms included in calculated positions (riding model). The
positional parameters of the hydride ligands of 9−11 were freely
refined. The high r-factors for the crystal structures of 5 and 7 are due
to the samples used in the diffraction experiments being non-
merohedral twins. In both cases, the diffraction pattern arising from
the minor twin component could not be deconvoluted from the
diffraction pattern of the major component. Despite this, the molecular
connectivity of the structures are unambiguous, and their metrical
parameters should be considered as reliable, within the estimated
standard deviations (ESDs) of the parameters. In addition, there are
two crystallographically independent molecules of 7 in the asymmetric
unit of its crystal structure. There are no significant geometric
differences between them. Crystal data, details of data collections, and
refinement are given in Table 2.
+
+
+
[(SiMe3)Ar*NH2 , 30], 439.3 (Ar*NH2 , 100), 167.0 (CHPh2 , 35).
Anal. Calc. for C40H44AlBr2NOSi: 62.42% C, 5.76% H, 1.82% N.
Found: 62.27% C, 5.88% H, 1.93% N.
Preparation of [L′AlH2(μ-H)Li(OEt2)2(THF)] (9). LiBun (0.65 mL of
a 1.6 M solution in hexane) was added to a solution of L′H (0.50 g,
0.97 mmol) in THF (30 mL) at −78 °C over 2 min. The reaction
mixture was warmed to room temperature and stirred for 2 h,
whereupon volatiles were removed in vacuo. The residue was dissolved
in diethyl ether and cooled to −78 °C, after which [AlH3(NMe3)]
(1.53 mL of a 0.67 M solution in toluene) was added, and the mixture
was warmed to room temperature over 12 h. The reaction solution was
then filtered and the filtrate concentrated to ca. 10 mL and stored at
−30 °C overnight to give colorless crystals of 9 (0.37 g, 49%). M.p.:
1
192 °C (dec). H NMR (C6D6, 400 MHz, 296 K) δ = 0.12 (s, 9H,
SiMe3), 1.04 (t, 12H, OCH2CH3), 1.23 (m, 4H, THF-CH2), 2.00 (s,
3H, Ar−CH3), 3.21 (q, 8H, OCH2CH3), 3.42 (m, 4H, THF-OCH2),
6.82 (s, 2H, CHPh2), 7.06−7.59 (m, 22H, Ar-H), AlH resonance not
observed. 13C{1H} NMR (C6D6, 100 MHz, 296 K) δ = 3.0 (SiMe3),
15.2 (OCH2CH3), 21.1 (Ar-CH3), 25.2 (THF-CH2), 51.7 (CHPh2),
65.8 (OCH2CH3), 68.7 (THF-OCH2), 125.7, 126.2, 128.1, 128.2,
129.3, 130.8, 130.9, 131.0, 141.5, 144.9, 148.4, 150.0 (Ar-C). 7Li NMR
(C6D6, 155 MHz, 296K) δ = −0.45 (s). 27Al NMR (C6D6, 104.2 MHz,
296K) δ = 115.0 (br s). IR (Nujol) ν/cm−1 1645 (Al−H, br s), 1595
(m), 1493 (m), 1247 (s), 1257 (s), 1131 (m), 1076 (m), 930 (s), 786
+
(s). MS (EI 70 eV) m/z (%): 512.3 [(SiMe3)Ar*NH2 , 100], 439.2
+
+
(Ar*NH2
, 22), 167.0 (CHPh2 , 20). Anal. Calc. for
C48H67AlLiNO3Si: 75.06% C, 8.79% H, 1.82% N. Found: 74.95% C,
8.81% H, 1.85% N.
Preparation of [{L′Al(μ-H)3K}2] (10). To a solution of [KL′(η6-
toluene)] (0.85 g, 1.32 mmol) in toluene (30 mL) at −78 °C was
added [AlH3(NMe3)] (1.33 mL of a 1.04 M solution in toluene) over
2 min. The resultant solution was warmed to room temperature over
12 h, whereupon volatiles were removed in vacuo to give an off-white
solid. This residue was dissolved in toluene and layered with hexane to
give colorless crystals of 10 (0.69 g, 91%). Mp: 115−118 °C
1
(decomp). H NMR (C6D6, 400 MHz, 296 K) δ = 0.37 (s, 18H,
SiMe3), 1.99 (s, 6H, Ar−CH3), 6.82 (s, 4H, CHPh2), 6.85 (m, 4H m-
Ar-H), 6.97−7.42 (m, 40H, Ar-H), no AlH resonance observed.
13C{1H} NMR (C6D6, 100 MHz, 296 K) δ = 3.0 (SiMe3), 21.3 (Ar-
CH3), 51.3 (CHPh2), 125.7, 126.4, 128.4, 128.4, 129.0, 129.2, 130.3,
130.4, 130.7, 141.6, 145.4, 148.1 (Ar-C). 29Si{1H} NMR (C6D6, 80
MHz, 296 K): No signal observed, even for a concentrated sample and
long acquisition time. 27Al NMR (C6D6, 104.2 MHz, 296K) δ = 117.9
(br s). IR (Nujol) ν/cm−1 1640 (Al−H, br s), 1493 (m), 1377 (s),
1261 (s), 1098 (s), 1029 (w), 922 (m), 795 (s), 761 (s), 722 (s). MS
Computational Studies. For quantum-chemical calculations,
Turbomole37 (version 5.9) was used, employing the Becke−Perdew
86-functional38 at RI-DFT39 level with the def2-SVP basis set40 for Si,
N, C, and H atoms and the def2-TZVPP basis set for Ga, In, and Tl
atoms.41 The molecular orbitals of the global minimum energy
structure of each compound (showing zero imaginary frequencies)
were visualized with the aid of molden.42 NBO orbital and Wiberg
Bond Index analyses were performed for [GaL′] using Gaussian0943
and NBO 3.044 at the very same combination of functional and basis
sets as above.
(EI 70 eV) m/z (%) 1119.4 (M+−K, 15), 540.2 [(SiMe3)Ar*NAlH3 ,
72], 512.2 [(SiMe3)Ar*NH2 , 100], 167.0 (CHPh2 , 8). Anal. Calc. for
C72H78Al2K2N2Si2: 74.57% C, 6.78% H, 2.42% N. Found: 74.62% C,
6.74% H, 2.49% N.
+
+
+
Preparation of [{L′AlH(μ-H)}2] (11). To a solution 10 (0.50 g, 0.86
mmol) in toluene (30 mL) at −78 °C was added CH3I (0.147 g, 1.03
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(b) Schmidt, E. S.; Jockisch, A.; Schmidbaur, H. J. Am. Chem. Soc.
1999, 121, 9758.
ASSOCIATED CONTENT
* Supporting Information
■
S
(8) GaI and InI systems: (a) Jones, C.; Junk, P. C.; Stasch, A.;
Woodul, W. D. New J. Chem. 2008, 32, 835. (b) Jones, C.; Junk, P. C.;
Platts, J. A.; Stasch, A. J. Am. Chem. Soc. 2006, 128, 2206.
(9) See for example: (a) Kuchta, M. C.; Bonanno, J. B.; Parkin, G. J.
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Crystallographic data as CIF files for all crystal structures;
ORTEP diagrams for 6, 7, [L′AlBr2(THF)], [KL′(η6-toluene)],
and [KL′(OEt2)]; selected metrical parameters for [L′AlBr2-
(THF)], [KL′(η6-toluene)], and [KL′(OEt2)], and further
details of the synthetic and computational studies. This material
is available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: cameron.jones@monash.edu.
Notes
■
(11) Siefert, A.; Linti, G. Eur. J. Inorg. Chem. 2007, 5080.
(12) N.B. A variety of related mixed valence amido metalloid clusters,
[Mm(NR2)n]x−, m > n, x = 0, 1, 2 etc., have been reported. See ref 4a.
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The authors declare no competing financial interest.
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3368.
ACKNOWLEDGMENTS
■
This research was supported by the Australian Research
Council (grant to C.J.) and the U.S. Air Force Asian Office
of Aerospace Research and Development (Grant FA2386-11-1-
4110 to C.J.). The EPSRC is also thanked for access to the U.K.
National Mass Spectrometry Facility.
(18) Dias, H. V. R.; Singh, S.; Cundari, T. R. Angew. Chem., Int. Ed.
2005, 44, 4907.
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