Synthesis and structure of neutral and cationic gallium complexes incorporating bis(oxazolinato) ligands

Article abstract of DOI:10.1002/ejic.200500478

The bis(oxazolinato)dimethylgallium complexes [(BOX-Me₂) GaMe₂] (2a) and [{BOX-(S)-iPr}GaMe₂] (2b) are easily obtained in nearly quantitative yield by a methane elimination reaction between GaMe₃ and the corresponding bis(oxazoline) ligands {BOX-Me ₂}H (1a) and {BOX-(S)-iPr}H (1b). Compound 2a was also synthesized by a salt metathesis involving the formation of the dichloro complex [(BOX-Me ₂}GaCl₂] by reaction of [{BOX-Me₂)Li] with GaCl₃, followed by its in situ methylation with MeMgBr. The neutral complexes 2a and 2b are rapidly ionized by B(C₆F₅) ₃ to cations 3a⁺ and 3b⁺, respectively, which are either three-coordinate methylgallium cations or four-coordinate Ga solvent adducts, as their MeB(C₆F₅)₃^- salts. These cationic species exhibit a limited stability and decompose in solution within several hours at room temperature. However, stable four-coordinate Ga-NMe₂Ph cations (4a⁺ and 4b⁺) are isolated in good yield when these ionization reactions are performed in the presence of a Lewis base such as NMe₂Ph. Unlike that of B(C₆F ₅)₃, the reaction of [{BOX-Me₂}GaMe ₂] with [Ph₃C][B(C₆F₅)₄] quantitatively affords an unusual bis(imine)-dimethylgallium cation {H ₂C=C(OX-Me₂)₂}GaMe₂⁺ (5a⁺) in a reaction that proceeds via a hydride abstraction occurring at the Me group located at the back of the bis(oxazolinato) ligand chelated to the Ga center in 2a. Overall, the reactivity and structural trends observed for the Ga derivatives are closely related to those of the Al analogs, with the Ga compounds being more stable. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.

Full text of DOI:10.1002/ejic.200500478

FULL PAPER
Synthesis and Structure of Neutral and Cationic Gallium Complexes
Incorporating Bis(oxazolinato) Ligands
Samuel Dagorne,*[a] Stéphane Bellemin-Laponnaz,*[b] Aline Maisse-François,[b]
Marie-Noëlle Rager,[c] Lauriane Jugé,[c] and Richard Welter[d]
Keywords: Cations / Gallium / Lewis acids / N ligands
The bis(oxazolinato)dimethylgallium complexes [{BOX-
Me2}GaMe2] (2a) and [{BOX-(S)-iPr}GaMe2] (2b) are easily
obtained in nearly quantitative yield by a methane elimi-
nation reaction between GaMe3 and the corresponding bis-
(oxazoline) ligands {BOX-Me2}H (1a) and {BOX-(S)-iPr}H
(1b). Compound 2a was also synthesized by a salt metathesis
involving the formation of the dichloro complex [{BOX-
Me2}GaCl2] by reaction of [(BOX-Me2)Li] with GaCl3, fol-
lowed by its in situ methylation with MeMgBr. The neutral
complexes 2a and 2b are rapidly ionized by B(C6F5)3 to cat-
ions 3a+ and 3b+, respectively, which are either three-coordi-
nate methylgallium cations or four-coordinate Ga solvent ad-
ducts, as their MeB(C6F5)3– salts. These cationic species exhi-
bit a limited stability and decompose in solution within se-
veral hours at room temperature. However, stable four-coor-
dinate Ga-NMe2Ph cations (4a+ and 4b+) are isolated in good
yield when these ionization reactions are performed in the
presence of a Lewis base such as NMe2Ph. Unlike that of
B(C6F5)3, the reaction of [{BOX-Me2}GaMe2] with
[Ph3C][B(C6F5)4] quantitatively affords an unusual bis(imine)-
dimethylgallium cation {H2C=C(OX-Me2)2}GaMe2+ (5a+) in a
reaction that proceeds via a hydride abstraction occurring at
the Me group located at the back of the bis(oxazolinato) li-
gand chelated to the Ga center in 2a. Overall, the reactivity
and structural trends observed for the Ga derivatives are
closely related to those of the Al analogs, with the Ga com-
pounds being more stable.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
cordingly, these cations behave like potent Lewis acids.[6,7]
Thus far, most of the investigations in this area have con-
cerned aluminum derivatives, where it has been found that
the structure and the stability of the formed Al cations are
greatly dependent upon the steric properties of the ancillary
LX– bidentate ligand and the nature of the counterion.[7]
More specifically, the presence of an extremely bulky LX–
Introduction
Cationic group 13 complexes have been the subject of
several studies over the past few years since the enhanced
Lewis acidity at the metal center, which is a result of its
cationic charge, renders these species potentially interesting
as Lewis acid catalysts.[1] As such, they have already found
applications in isobutene,[2] ethylene,[3] alkene oxide,[4] and
,-lactide[5] polymerization catalysis. In this regard, three-
and four-coordinate cationic group 13 complexes of the ge-
neral type [(LX)MR]+ and [(LX)M(R)(L)]+ (L labile), read-
ily accessible by reaction of neutral precursors [(LX)MR2]
with strong Lewis acids such as [Ph3C][B(C6F5)4] and
B(C6F5)3, have appeared as appealing targets because they
incorporate a cationic and low-coordinate metal center; ac-
–
ligand and the use of an inert counterion [B(C6F5)4 or
–
MeB(C6F5)3 ] are required to obtain, in some cases, reason-
ably stable Al cations. However, the frequent poor stability
of these highly reactive alkylaluminum species may limit the
scope of their applications in catalysis.
Although much less studied than their Al counterparts,
low-coordinate cationic alkylgallium complexes are ex-
pected to exhibit an increased stability as a result of the less
polar character of the Ga–C vs. Al–C bond,[8] while still
remaining reactive due to the presence of an electron-de-
ficient metal center. Thus, cationic Ga derivatives may well
represent a reasonable balance of reactivity and stability,
which is a required feature for catalysis involving polar sub-
strates and/or media.
We are interested in the design and synthesis of stable
low-coordinate cationic group 13 complexes of the type
[(LX)MR]+ and [(LX)M(R)(L)]+ for applications in cataly-
sis. To this purpose, we have recently focused our attention
toward the synthesis of [(LX)AlR]+ and [(LX)Al(R)(L)]+
[a] Laboratoire de Chimie Organométallique, UMR CNRS 7576,
Ecole Nationale Supérieure de Chimie de Paris,
11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France
Fax: +33-1-43260061
E-mail: samuel-dagorne@enscp.fr
[b] Laboratoire de Chimie Organométallique et de Catalyse, UMR
7513, Institut Le Bel, Université Louis Pasteur,
4 rue Blaise Pascal, 67000 Strasbourg, France
E-mail: bellemin@chimie.u-strasbg.fr
[c] NMR Service, Ecole Nationale Supérieure de Chimie de Paris,
11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France
[d] Laboratoire DECMET, UMR 7513, Institut Le Bel, Université
Louis Pasteur,
4 rue Blaise Pascal, 67000 Strasbourg, France
4206
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200500478
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Neutral and Cationic Gallium Complexes Incorporating Bis(oxazolinato) Ligands
FULL PAPER
cations bearing either an N,O-aminophenolate or an N,N-
bis(oxazolinato) bidentate ligand (A and B, Scheme 1).[9,10]
In particular, the use of a chiral C2-symmetric N,N-bis(ox-
azolinato) ligand has provided access to chiral cationic alk-
ylaluminum complexes, which are of potential interest in
asymmetric catalysis.[10] However, the instability of the Al
cations incorporating B, especially in catalytic conditions,
prompted us toward the synthesis of the Ga analogs, which
are expected to be more stable. Thus, as part of our con-
tinuous studies of cationic and chiral group 13 alkyl com-
plexes, we here report the synthesis and structure of neutral
and cationic bis(oxazolinato)methylgallium complexes.
Scheme 2.
Scheme 1.
Results and Discussion
Bis(oxazolinato)dimethylgallium compounds were syn-
thesized by the classical alkane elimination route involving
a reaction between the appropriate bis(oxazoline) ligand
and GaMe3. This pathway was found to be the most
straightforward and efficient method to access such com-
pounds.
Thus, the reaction of the bis(oxazoline) ligands (BOX-
Figure 1. Molecular structure of complex 2a. The H atoms have
been omitted for clarity.
Me2)H (1a) and {BOX-(S)-iPr}H (1b; Scheme 2) with an
equimolar amount of GaMe3 in pentane at –35 °C yields
the bis(oxazolinato)dimethylgallium compounds [(BOX-
Me2)GaMe2] (2a) and [{BOX-(S)-iPr}GaMe2] (2b;
Scheme 2), respectively, which were isolated in nearly quan-
titative yields (Ͼ95% yield) as air-stable colorless solids. Al-
ternatively, the achiral Ga derivative 2a was also obtained
by a salt metathesis pathway, although this approach was
less efficient. Thus, the reaction of the bis(oxazolinato)lith-
ium salt [(BOX-Me2)Li], generated by deprotonation of bis-
oxazoline 1a with tBuLi at –78 °C, with an equimolar
amount of GaCl3 (18 h, room temp.) yields [(BOX-Me2)-
Figure 2. Molecular structure of chiral complex 2b. The H atoms
have been omitted for clarity. Selected torsion angles [°]: N(1)–
C(8)–C(9)–C(11) = 5.8(15), Ga–N(2)–C(11)–C(10) = 3.2(4), Ga–
N(2)–C(11)–C(9) = 2.5(11).
1
GaCl2], as observed by H NMR spectroscopy. The in situ
methylation of the dichlorogallium derivative with two
equivalents of MeMgBr affords [(BOX-Me2)GaMe2] (2a) in
moderate yield (48%).
The Ga metal center in 2b adopts a slightly distorted
The molecular structures of the Ga complexes 2a and tetrahedral geometry with a chelate bite angle [N(1)–Ga–
2b were determined by X-ray crystallography analysis, thus N(2) = 91.1(2)°] similar to that in the related β-diketimina-
establishing their monomeric nature as well as the effective todimethylgallium complex [HC{C(Me)N(C6H3-2,6-iPr2)}-
chelation of one bis(oxazolinato) ligand (Figures 1 and 2 GaMe2] [93.92(7)°], which also contains a six-membered
and Table 1). As expected, both Ga species exhibit very sim- C3N2Ga metallacycle.[11] The Ga–N and Ga–C bond
ilar structural features in the solid state and these will only lengths in 2b [1.966(9) Å and 1.98(1) Å average, respec-
discussed for the chiral derivative 2b.
tively] are similar to those observed in related {LX}GaMe2
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S. Dagorne, S. Bellemin-Laponnaz et al.
FULL PAPER
Table 1. Selected bond lengths [Å] and angles [°] for 2a and 2b.
temp., 10 min) results in the nearly quantitative formation
of the cations [{BOX-Me2}GaMe]+ (3a+) and [BOX-(S)-
2a
2b
–
iPr}GaMe]+ (3b+), respectively, as their MeB(C6F5)3 salts,
Ga–N
1.9677(17)
1.970(3)
1.970(3)
1.320(3)
1.395(3)
Ga–N(1)
Ga–N(2)
Ga–C(1)
1.967(6)
1.966(6)
1.963(9)
2.004(10)
1.333(8)
1.306(9)
1.384(11)
1.386(10)
as observed by 1H, 13C, and 19F NMR spectroscopy
(Scheme 3). As expected, the Ga cations 3a,b+ are more
stable than their Al counterparts; however, they slowly de-
compose at room temp. in C6D5Br (t1/2 Ϸ 10 h) to yield
unidentified species, which precluded their isolation in a
pure form. Initial attempts (by 1H NMR) to observe cations
3a,b+ by carrying out the reaction on an NMR-tube scale
in CD2Cl2 were unsuccessful, presumably due to fast de-
composition of the desired cations in CD2Cl2.
Ga–C(1)
Ga–C(2)
N–C(7)
C(7)–C(8)
Ga–C(2)
N(1)–C(8)
N(2)–C(11)
C(8)–C(9)
C(9)–C(11)
N–Ga–N
91.33(10)
109.38(8)
111.85(8)
119.47(14)
N(1)–Ga–N(2) 91.1(2)
C(1)–Ga–N(2) 111.8(4)
C(1)–Ga–N(1) 113.5(3)
C(1)–Ga–C(2) 119.9(4)
N–Ga–C(2)
N–Ga–C(1)
C(1)–Ga–C(2)
species such as [HC{C(Me)N(C6H3-2,6-iPr2)}GaMe2],[11]
[{PhC(NPh)2}GaMe2],[12] and [{tBuC(NCy)2}GaMe2].[13]
The six-membered C3N2Ga metallacycle in [{BOX-(S)-
iPr}GaMe2] (2b) is nearly planar (C–C–Ga–N Ͻ 6°) with
the carbon and nitrogen atoms adopting a trigonal-planar
geometry (sum of angles ca. 360°). The planarity of the six-
membered C3N2Ga backbone in 2b contrasts with the fold-
ing of the C3N2Ga ring observed in [HC{C(Me)N(C6H3-
2,6-iPr2)}GaMe2], in which the Ga metal center lies signifi-
cantly out of the C3N2 plane (0.76 Å). This structural dif-
ference presumably results from much weaker steric interac-
tions between the Ga metal center and the chelating ligand
in 2b compared to [HC{C(Me)N(C6H3-2,6-iPr2)}-
GaMe2].[11] The C–C bond lengths within the C3N2 moiety
[1.38(1) Å average] in 2b are close to the C–C bond length
in aromatic systems (1.395 Å), while the C–N bond lengths
[1.32(1) Å average] lie between the C=N double-bond
length in imines (1.28 Å) and the C(sp2)–N single-bond
length (1.47 Å). Altogether, these structural data are consis-
tent with significant π-delocalization of the bis(oxazolinato)
ligand backbone, resulting in a nearly C2 symmetry for 2b
in the solid state. Similar structural features have been ob-
served for the Al analogs.[10]
Scheme 3.
1
The H, 13C and 19F NMR spectroscopic data for the
[3a,b][MeB(C6F5)3] salt species are consistent with weak in-
teractions between the cation and the anion down to –30 °C
in C6D5Br solution. In particular, the MeB(C6F5)3 reso-
nance (δ = 0.97 ppm) in the H NMR spectra of [3a,b]-
[MeB(C6F5)3] is characteristic of a free MeB(C6F5)3 anion
–
1
–
in solution at room temp. (Figure 3).[14] The NMR spectro-
scopic data for the Ga cations 3a+ and 3b+ are essentially
unchanged between –30 °C and room temp. and agree with
effective C2v- and C2-symmetric species for 3a+ and 3b+,
respectively, under these conditions. For instance, as illus-
trated in Figure 3, the 1H NMR spectrum of
[3a][MeB(C6F5)3] only exhibits four resonances for cation
3a+ (GaMe+, CMe2, O-CH2, and CMe), which is in agree-
ment with a C2v-symmetric complex. In addition, the
GaMe+ resonance in 3a+ (δ = 0.40 ppm) is shifted dramati-
cally downfield relative to the GaMe2 resonance of the neu-
tral precursor 2a (δ = –0.17 ppm) as a result of the cationic
charge on Ga. Overall, on the basis of NMR spectroscopic
data, the Ga cations 3a,b+ are most likely either three-coor-
dinate “base-free” cationic species or four-coordinate cat-
ionic Ga solvent adducts (i.e. C6D5Br adducts) with a fast
coordination/decoordination process on the NMR scale
down to –30 °C. The latter proposal is based on the fact
that a solid-state structure of a four-coordinate cationic Ga-
ClPh adduct has been reported recently.[15]
The NMR spectroscopic data for the Ga complexes 2a
and 2b at room temperature are consistent with these spe-
cies adopting overall C2v and C2 symmetry, respectively, in
solution. These NMR spectroscopic data are therefore in
agreement with the solid-state structures of 2a and 2b being
retained in solution under the conditions studied here. For
1
example, the H NMR spectrum of 2b (C6D6, room temp.)
exhibits one GaMe2 resonance, one N-CH resonance and
two Me-iPr resonances, which is in agreement with a C2-
symmetric complex.
Reaction of Bis(oxazolinato)dimethylgallium Complexes 2a
and 2b with B(C6F5)3
The Lewis acidic Ga cation 3a+ reacts rapidly with an
Cationic alkylgallium complexes could be obtained by excess of propylene oxide (PO; 200 equiv., –20 °C, 5 min) to
reaction of the neutral dimethylgallium derivatives with the yield atactic oligomers with a broad polydispersity (40%
strong Lewis acid B(C6F5)3, which is known to readily ab- conversion, Mn = 448, Mw/Mn = 2.38). A longer reaction
stract a methyl anion from the metal center of group 13 time did not yield higher conversion, which strongly sug-
[{LX}MMe2] species. Thus, the reaction of [{BOX}GaMe2] gests a fast decomposition of cation 3a+ (within 5 min at
(2a,b) with one equivalent of B(C6F5)3 (C6D5Br, room –20 °C) to inactive species in the presence of excess PO.
4208
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Neutral and Cationic Gallium Complexes Incorporating Bis(oxazolinato) Ligands
FULL PAPER
NMe2Ph are strongly downfield shifted relative to those in
free NMe2Ph, which is consistent with an effective coordi-
nation of NMe2Ph to the Ga center. Overall, the NMR
spectroscopic data at room temp. agree with effective C2v-
and C2-symmetric solution structures for cations 4a and
4b+, respectively, thereby indicating a fast face-exchange of
NMe2Ph on the NMR timescale. To probe this issue fur-
1
ther, low temperature H and 13C NMR experiments were
carried out to reach a slow NMe2Ph exchange process.
Thus, the NMR spectroscopic data for cations 4a+ and 4b+
recorded at –25 °C and –35 °C in CD2Cl2, respectively, exhi-
bit an overall Cs symmetry for 4a+ and a C1 symmetry for
chiral 4b+. These data are consistent with a slow face-ex-
change of NMe2Ph on the NMR timescale for both cations
(see Exp. Sect.). For comparison, the labile coordination of
NMe2Ph to Ga observed here for 4a,b+ at room tempera-
ture contrasts with the nonlabile coordination of this amine
to Al in the cationic Al analogs under identical conditions,
which may reflect a more Lewis acidic cationic Al vs. Ga
center.[10]
1
Figure 3. H NMR spectrum of [3a][MeB(C6F5)3] (C6D5Br, room
temp.): δ = 0.40 (1, GaMe), 0.97 (2, MeB), 1.05 (3, CMe2), 1.70 (4,
MeCCN), 3.71 (5, OCH2) ppm.
The Lewis acid character of the Ga–NMe2Ph adduct 4a+
was also tested with PO. Like 3a+, cation 4a+ oligomerizes
PO (200 equiv. of PO, room temp., 15 min) to afford low
molecular weight oligomers in high conversion (85% con-
version, Mn = 339, Mw/Mn = 1.25). The oligomerization
process is clearly multimodal, as deducted from size ex-
clusion chromatographic data, thus suggesting the presence
of several active species.
Synthesis and Structure of Four-Coordinate Methylgallium
Cations (4a,b+)
The lack of stability of cations 3a,b+ prompted us to gen-
erate them in the presence of a Lewis base such as NMe2Ph,
which is expected to trap the Ga cations to yield stable four-
coordinate Ga–NMe2Ph cationic adducts. Thus, the reac-
tion of the bis(oxazolinato)dimethylgallium complexes
(2a,b) with one equivalent of B(C6F5)3 in the presence of
one equivalent of NMe2Ph (CH2Cl2, room temp., 10 min)
yields the quantitative formation of the four-coordinate cat-
ions [{BOX-Me2}Ga(Me)(NMe2Ph)]+ (4a+) and [{BOX-
(S)-iPr}Ga(Me)(NMe2Ph)]+ (4b+), respectively, as their
Solid-State Structure of the Cationic Adduct 4a+
While a few examples of X-ray characterized low-coordi-
nate Al cations are known, solid-state structures of Ga ana-
logs are rather scarce,[1,7a,16] and, to date, none of the type
[{LX}Ga(R)(L)]+ have been reported.
–
MeB(C6F5)3 salts (Scheme 4). The salt compounds [4a,b]-
[MeB(C6F5)3] are stable for days at room temperature in
CH2Cl2 and could thus be isolated in a pure form as color-
less solids in good yields. To the best of our knowledge,
cation 4b+ in [4b][MeB(C6F5)3] is the first example of a chi-
ral cationic alkylgallium complex.
The molecular structure of the salt species
[4a][MeB(C6F5)3] was confirmed by X-ray crystallography
analysis (Tables 2 and 3). It crystallizes as discrete 4a+ cat-
–
ions and MeB(C6F5)3 anions, with no cation–anion inter-
action. As shown in Figure 4, cation 4a+ is an NMe2Ph-
stabilized four-coordinate methylgallium cation in which
the Ga center adopts a distorted tetrahedral structure with
a chelate bite angle N(1)–Ga–N(2) [96.98(7)°] similar to
that in the neutral precursor 2a. Unlike the nearly planar
six-membered C3N2Ga metallacycle in complexes 2a,b, that
in 4a+ is significantly distorted from planarity, with the Ga
center being displaced by 0.33(2) Å from the N(2)–C(6)–
N(1)–C(9) average plane toward the coordinated NMe2Ph.
This distortion may well be to minimize steric interactions
Scheme 4.
Compounds [4a,b][MeB(C6F5)3] are dissociated species between the Ga-NMe2Ph moiety and the bis(oxazolinato)
down to –30 °C in CD2Cl2 with weakly interacting 4a,b+ ligand. The Ga–N bond lengths within the chelate-Ga en-
–
cations and MeB(C6F5)3 . The 1H NMR spectra of the cat- tity [1.9018(19) and 1.9100(16) Å] are rather short as com-
ionic NMe2Ph adducts 4a,b+ both contain a GaMe+ reso- pared to those in 2a [1.966(9) Å], due to the stronger ionic
nance that is significantly downfield shifted as compared to character of these bonds in 4a+ vs. 2a, a result of the cat-
the GaMe2 resonances in the neutral precursors 2a,b, which ionic charge, whereas the Ga–Namine bond length [Ga–N(3)
1
is indicative of a cationic Ga center. Likewise, the H and = 2.124(3) Å] is considerably longer and is comparable to
13C NMR resonances of 4a,b+ assigned to the coordinated those observed in neutral bulky gallium amine adducts such
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S. Dagorne, S. Bellemin-Laponnaz et al.
FULL PAPER
as [Me3Ga(tBuNH2)] [2.12(1) Å].[17] Due to the enhanced the Ga center of 2a, Ph3C+ abstracts a hydride from the Me
Lewis acidity of Ga in 4a+ vs. [Me3Ga(tBuNH2)], a shorter group located at the back of the bis(oxazolinato) ligand in
Ga–N(3) bond length in 4a+ vs. Me3Ga(tBuNH2) would be compound 2a to afford cation 5a+. The outcome of this
expected from an electronic point of view; this rather long reaction confirms a reactivity already observed with the Al
Ga–N distance for 4a+ may be to minimize steric interac- analog [{BOX-Me2}AlMe2], which has been found to yield
tions between the aniline and the chelating ligand.
a similar bis-imine cation when treated with [Ph3C][B-
(C6F5)4].[10] Nevertheless, the observed reactivity, i.e. a hy-
dride abstraction at a group rather far away from the metal
center, contrasts with the usual reactivity of Ph3C+ with
alkyl metal complexes. Typically, hydride abstractions by
Ph3C+ at such dialkyl species occur either at the Cα of the
metal-bonded alkyl group or at the Cβ, both of which, in
any case, are in the vicinity of the metal center.[18]
Table 2. Selected bond lengths [Å] and angles [°] for
[4a][MeB(C6F5)3] and [5a][B(C6F5)4].
4a+
5a+
Ga–N(1)
Ga–N(2)
Ga–C(1)
Ga–N(3)
N(1)–C(9)
N(2)–C(6)
C(7)–C(9)
C(7)–C(6)
1.9018(19)
1.9100(16)
1.944(3)
2.124(2)
1.331(2)
1.339(3)
1.395(3)
1.383(3)
Ga–C(2)
Ga–C(1)
Ga–N(1)
Ga–N(2)
N(2)–C(10)
N(1)–C(3)
C(8)–C(9)
1.953(2)
1.956(2)
2.0171(17)
2.0191(17)
1.282(3)
1.285(3)
1.329(3)
1.466(3)
C(8)–C(3)
C(8)–C(10)
C(1)–Ga–C(2)
N(1)–Ga–N(2)
C(1)–Ga–N(1)
C(1)–Ga–N(2)
1.470(3)
122.76(11)
90.18(8)
107.28(10)
110.12(10)
N(1)–Ga–N(2) 96.98(7)
N(1)–Ga–N(3) 103.06(8)
C(1)–Ga–N(3) 108.60(11)
N(2)–Ga–C(1) 123.12(12)
Scheme 5.
The salt compound [5a][B(C6F5)4], which is stable for
days at room temp. in CH2Cl2, was obtained as an analyti-
cally pure colorless solid in good yield (see Exp. Sect.). Its
molecular structure, as determined by X-ray crystallogra-
phy, shows that [5a][B(C6F5)4] crystallizes as 5a+ cations
–
and B(C6F5)4 anions with no cation–anion interaction in
the solid state. The cationic species 5a+can be seen as a
dimethylgallium cation in which the GaMe2+ moiety is che-
lated by the neutral bisoxaline H2C=C(OX-Me2)2 (Fig-
ure 5). Accordingly, the bonding parameters within the
C3N2 ligand backbone in 5a+ are consistent with a π-local-
ized structure: the C(3)–N(1) and C(10)–N(2) bond lengths
[1.285(3) and 1.282(3) Å] compare with the typical value for
C(sp2)=N double bonds (1.30 Å) while the C(8)–C(9) bond
length [1.329(3) Å] is consistent with that of a C=C double
Figure 4. Molecular structure of the Ga cation 4a+. The H atoms
have been omitted for clarity. Selected torsion angles [°]: N(2)–Ga–
N(1)–C(9) = 13.54(14),; N(1)–Ga–N(2)–C(6) = 15.36(15), N(1)–
C(9)–C(7)–C(6) = 13.0(3).
Reaction of [{BOX-Me2}GaMe2] (2a) with [Ph3C][B(C6F5)4]
As stated in the introduction, the trityl salt
[Ph3C][B(C6F5)4] is the other landmark reagent, along with
B(C6F5)3, that is used to generate group-13 alkyl cations of
the type [{LX}MMe]+ from [{LX}MMe2] by a Me– ab-
straction at the metal center. We thus decided to study the
reaction
between
[{BOX-Me2}GaMe2]
(2a)
and
[Ph3C][B(C6F5)4].
The reaction of [{BOX-Me2}GaMe2] (2a) with one
equivalent of [Ph3C][B(C6F5)4] (CH2Cl2, room temp.,
10 min) yields the quantitative formation of the bis(imine)-
dimethylgallium cation [{H2C=C(OX-Me2)2}GaMe2]+
Figure 5. Molecular structure of the Ga cation 5a+. The H atoms
have been omitted for clarity. Selected torsion angles [°]: N(1)–Ga–
N(2)–C(10) = 12.53(19), N(2)–C(10)–C(8)–C(3) = 3.7(3), N(2)–
–
(5a+) as a B(C6F5)4 salt, along with one equivalent of
Ph3CH (Scheme 5). Thus, instead of abstracting a Me– from C(10)–C(8)–C(9) = 3.0(3).
4210
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 4206–4214

Neutral and Cationic Gallium Complexes Incorporating Bis(oxazolinato) Ligands
FULL PAPER
bond (1.337 Å). In addition, the Ga–N bond lengths in 5a+
[2.018(1) Å average] are comparable to those observed in
neutral Ga imine complexes, e.g. in dimethyl-(N-methylsal-
icylaldiminato)gallium, Ga–N = 2.019 Å,[19] as expected for
a bis-imine gallium complex such as 5a+. All other struc-
tural parameters are very similar to those in the neutral
precursor 2a.
glovebox. Toluene, pentane, and THF were distilled from Na/
benzophenone and stored over activated molecular sieves (4 Å) in
a glovebox prior to use. CH2Cl2 and CD2Cl2, were distilled from
CaH2 and stored over activated molecular sieves (4 Å) in a
glovebox prior to use. C6D6 was degassed under an N2 flow and
stored over activated molecular sieves (4 Å) in a glovebox prior to
use. B(C6F5)3 was purchased from Strem Chemicals and was ex-
tracted with dry pentane prior to use. [Ph3C][B(C6F5)4] was pur-
chased from Asahi Glass Europe and used as received. CD2Cl2,
C6D6, and C6D5Br were purchased from Eurisotop. All other
As for the solution structure of 5a+, the NMR spectro-
scopic data agree with the solid-state structure being re-
tained in solution and with no association between 5a+ and chemicals were purchased from Aldrich and were used as received.
The bisoxazoline ligands 1a,b were synthesized according to a lit-
erature procedure.[10] All NMR spectra were recorded at room tem-
perature (unless otherwise indicated) on a Bruker Avance 300 MHz
or 400 MHz spectrometer. 1H and 13C chemical shifts are reported
relative to SiMe4 and were determined by reference to the residual
1H and 13C solvent peaks. 11B and 19F chemical shifts are reported
relative to BF3·Et2O in CD2Cl2 and CFCl3/CDCl3, respectively.
SEC analysis was carried out on a system equipped with 4 PL Gel
columns (250 mm length×7.5 mm inner diameter) in series and
with THF as solvent. A Shimadzu SPD10Avp UV detector coupled
with a Shimadzu RID6A refractometer was employed. The appara-
tus was calibrated using a POE standard from Polymer Laborato-
ries. Elemental analyses for [4a,b][MeB(C6F5)3] and [5a][B(C6F5)4]
were performed by the Mikroanalytisches Labor Pascher, Re-
magen-Bandorf, Germany, while those for compounds 2a,b were
performed by the microanalysis laboratory of the Université Pierre
et Marie Curie, Paris, France.
its counterion in CD2Cl2 solution at room temp. In particu-
1
lar, the H and 13C NMR spectra of 5a+ both contain one
characteristic resonance at δ = 7.30 and 143.7 ppm, respec-
tively, which can be assigned to the H2C=C group of the
chelating bis(oxazoline).
Summary and Conclusions
Bis(oxazolinato)dimethylgallium complexes of the type
[{BOX}GaMe2] (2a,b) can be obtained in high yield by re-
action of GaMe3 with the desired neutral bis(oxazoline) via
methane elimination. These neutral dimethylgallium pre-
cursors react rapidly with B(C6F5)3, via a Me– abstraction,
to yield the Ga cations 3a,b+, which are either three-coordi-
nate methylgallium cations of the type [{BOX}GaMe]+ or
four-coordinate cationic Ga-solvent adducts. Although
more stable than their Al counterparts, cations 3a,b+ de-
compose over the course of several hours to give unidenti-
fied species. The lack of stability of the [{BOX}GaMe]+
methyl cations reported here contrasts with the stability of
the three-coordinate Al cation [HC{C(Me)N(C6H3-2,6-
iPr2)}AlMe]+, which also incorporates a six-membered Al
metallacycle. The greater steric crowding provided at the
metal center by HC{C(Me)N(C6H3-2,6-iPr2)}– vs. {BOX-
Me2}– or {BOX-(S)-iPr}– may be responsible for this differ-
ence of stability.
When the ionization of [{BOX}GaMe2] (2a,b) with
B(C6F5)3 is performed in the presence of an external Lewis
base such as NMe2Ph, the corresponding four-coordinate
cationic Ga adducts [{BOX}Ga(Me)(NMe2Ph)]+ (4a,b+)
are isolated in good yield, the cation 4b+ being of particular
interest as a chiral cationic derivative. Finally, [{BOX-
Me2}GaMe2] (2a) reacts with [Ph3C][B(C6F5)4] to yield an
unusual cationic bis(imino)gallium adduct [{H2C=C(OX-
Me2)2}GaMe2]+ (5a+) via a hydride abstraction at the back
of the bis(oxazolinato) ligand.
For the compounds listed below, the assignment of all 1H and
13C{1H} NMR resonances was possible using DEPT experiments
combined, when necessary, with HMQC experiments.
[{BOX-Me2}GaMe2] (2a) by Methane Elimination: In a glovebox, a
pentane solution (3 mL) of GaMe3 (285 mg, 2.48 mmol), pre-
viously cooled to –35 °C in a freezer, was slowly added with a
Pasteur pipette to a pentane solution (7 mL) of bisoxazoline 1a
(557 mg, 2.48 mmol), also precooled to –35 °C. The resulting color-
less solution was then allowed to warm to room temperature. Upon
warming to room temperature, a slight bubbling was observed, as
expected for methane formation. After stirring the solution for 2 h
at room temperature, it was then evaporated to dryness under vac-
uum to yield pure 2a as a colorless solid in nearly quantitative yield
(785 mg, 98% yield). 1H NMR (400 MHz, C6D6): δ = 0.03 (s, 6 H,
GaMe2), 1.02 (s, 12 H, CMe2), 2.26 (s, 3 H, MeCCN), 3.41 (s, 4
1
H, OCH2) ppm. H NMR (400 MHz, CD2Cl2): δ = –0.38 (s, 6 H,
GaMe2), 1.29 (s, 12 H, CMe2), 1.70 (s, 3 H, MeCCN), 3.95 (s, 4
1
H, OCH2) ppm. H NMR (400 MHz, C6D5Br): δ = –0.17 (s, 6 H,
GaMe2), 1.11 (s, 12 H, CMe2), 1.99 (s, 3 H, MeCCN), 3.64 (s, 4
H, OCH2) ppm. 13C{1H} NMR (100 MHz, C6D6): δ = –2.8
(GaMe2), 10.3 (MeCCN), 27.7 (CMe2), 62.3 (MeCCN), 63.7
(CMe2), 78.7 (OCH2), 170.2 (OCN) ppm. C14H25GaN2O2 (323.08):
calcd. C 52.05, H 7.80; found C 52.14, H 7.72.
Cations 3a+ and 4a+ were found to rapidly olygomerize
PO at low temperature, thereby illustrating the Lewis acid
character of these species. However, the broad polydisper-
sity of the obtained oligomers suggests a poor stability of
these species in catalytic conditions.
Further studies will focus on the synthesis and use of
bulkier and chiral LX– ligands for coordination to group
13 metals.
[{BOX-Me2}GaMe2] (2a) by Salt Metathesis: On a nitrogen-filled
vacuum line, tBuLi (0.550 mL of a 1.7  pentane solution,
0.934 mmol) was added dropwise, from a syringe, to a THF solu-
tion (10 mL) of bisoxazoline 1a (209 mg, 0.934 mmol) that had
been cooled to –78 °C in an acetone/dry ice bath. Upon addition
of tBuLi, the initial colorless solution turned bright yellow. After
the addition, the resulting yellow solution was allowed to warm to
room temperature and was stirred for 3 h. Evaporation of the vola-
tiles under reduced pressure yielded a yellow sticky residue which
was washed twice with cold pentane (2×10 mL cooled to –35 °C)
to afford a colorless solid. In a glovebox, this solid was dissolved
Experimental Section
General Procedures: All experiments were carried out under N2
using standard Schlenk techniques or in an Mbraun Unilab
Eur. J. Inorg. Chem. 2005, 4206–4214
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4211

S. Dagorne, S. Bellemin-Laponnaz et al.
FULL PAPER
in toluene (10 mL) in a small Schlenk flask and cooled to –35 °C
in a freezer for 1 h. After this time, the cold colorless solution was
taken out of the freezer and stirred vigorously. A toluene solution
(5 mL) of GaCl3 (164 mg, 0.934 mmol), also precooled to –35 °C,
was then quickly added to this solution and the resulting mixture
was allowed to warm to room temperature. Upon warming to room
temperature, the initial solution turned into a colorless suspension
(indicating the formation of LiCl), which was left stirring overnight
at room temperature. The reaction mixture was then filtered
through a glass frit and the resulting filtrate evaporated under vac-
uum to yield crude 2a as a sticky colorless solid. Recrystallization
of this crude product from a 1:1 Et2O/pentane solution cooled to
–35 °C afforded pure 2a as colorless crystals (145 mg, 48% yield).
(s, 3 H, MeCCN), 3.77–3.83 (m, 4 H, OCH2), 3.90–3.95 (m, 2 H,
NCH) ppm. 13C{1H} NMR (100 MHz, C6D5Br, 248 K): δ = –4.1
(GaMe), 9.9 (MeCCN), 11.7 (br., MeB), 15.2 (Me-iPr), 18.7 (Me-
iPr), 33.1 (CH-iPr), 65.9 (CHN), 69.7 (CH2O), 71.9 (MeCCN),
2
2
137.2 (dm, JC,F = 256 Hz, o- or m-C6F5), 137.9 (dm, JC,F
243 Hz, p-C6F5), 148.8 (dm, JC,F = 237 Hz, o- or m-C6F5), 172.3
(OCN) ppm.
=
2
[{BOX-Me2}Ga(Me)(NMe2Ph)][MeB(C6F5)3] ([4a][MeB(C6F5)3]):
In
a glovebox, the dimethylgallium derivative 2a (200 mg,
0.619 mmol) was charged in a Schlenk flask and dissolved in
CH2Cl2 (5 mL). NMe2Ph (78.5 µL, 0.620 mmol) was then first
added from a syringe to the colorless solution, followed by the
addition of B(C6F5)3 (317 mg, 0.619 mmol) all at once. The re-
sulting mixture was stirred for 1 h at room temperature and, after
this time, evaporated to dryness under vacuum to yield a colorless
foamy residue. Trituration of this residue with cold pentane (preco-
oled to –35 °C) caused the precipitation of a colorless solid, which,
after passing the solution through a glass frit nd further drying in
vacuo, was found to be the salt species [4a][MeB(C6F5)3] in a pure
[{BOX-(S)-iPr}GaMe2] (2b): The chiral dimethylgallium compound
2b was synthesized by methane elimination using the same pro-
cedure as for 2a, using an equimolar amount of {BOX-(S)-iPr}H
(300 mg, 1.19 mmol) and GaMe3 (136 mg, 1.19 mmol) to afford
1
pure 2b as a colorless solid in high yield (401 mg, 96% yield). H
3
NMR (300 MHz, C6D6): δ = 0.00 (s, 6 H, GaMe2), 0.49 (d, JH,H
1
= 7.0 Hz, 6 H, Me-iPr), 0.74 (d, 3JH,H = 6.8 Hz, 6 H, Me-iPr), 1.91
form (479 mg, 81% yield). H NMR (400 MHz, CD2Cl2): δ = 0.39
3
3
(s, 3 H, GaMe), 0.48 (MeB), 1.13 (br., 12 H, CMe2), 1.73 (s, 3 H,
MeCCN), 2.96 (s, 6 H, NMe2Ph), 4.05 (br., 4 H, OCH2), 7.00–7.41
(d of septet, JH,H doublet = 3.3, JH,H septet = 6.9 Hz, 2 H, CH-iPr),
2.21 (s, 3 H, MeCCN), 3.56–3.66 (m, 4 H, OCH2), 3.68–3.75 (m, 2
1
1
(br., 5 H, NMe2Ph) ppm. H NMR (400 MHz, CD2Cl2, 253 K): δ
H, CHN) ppm. H NMR (300 MHz, CD2Cl2): δ = –0.45 (s, 6 H,
3
3
= 0.36 (s, 3 H, GaMe), 0.42 (MeB), 0.92 (s, 6 H, CMe2), 1.11 (s, 6
H, CMe2), 1.67 (s, 3 H, MeCCN), 2.93 (s, 6 H, NMe2Ph), 3.81 (br.
GaMe2), 0.80 (d, JH,H = 6.8 Hz, 6 H, Me-iPr), 0.89 (d, JH,H
=
7.0 Hz, 6 H, Me-iPr), 1.68 (s, 3 H, MeCCN), 1.96 (d of septet,
2
2
3
3JH,H doublet = 3.4, JH,H septet = 6.9 Hz, 2 H, CH-iPr), 3.96–4.01
d, JH,H = 8.2 Hz, 2 H, OCH2), 4.16 (br. d, JH,H = 8.2 Hz, 2 H,
3
2
3
OCH2), 7.20 (d, JH,H = 7.2 Hz, 2 H, NMe2Ph), 7.33 (br., 1 H,
NMe2Ph), 7.44 (br.,
(m, 2 H, CHN), 4.06–4.11 (dd, JH,H = 8.4, JH,H = 8.4 Hz, 2 H,
2
H, NMe2Ph) ppm. 13C{1H} NMR
2
3
OCH2), 4.17–4.23 (dd, JH,H = 8.4, JH,H = 9.2 Hz, 2 H, OCH2)
ppm. 1H NMR (300 MHz, C6D5Br): δ = –0.19 (s, 6 H, GaMe2),
0.66 (d, 3JH,H = 7.0 Hz, 6 H, Me-iPr), 0.73 (d, 3JH,H = 6.8 Hz, 6 H,
Me-iPr), 1.90 (d of septet, 3JH,H doublet = 3.3, 3JH,H septet = 6.9 Hz, 2
H, CH-iPr), 1.96 (s, 3 H, MeCCN), 3.84–3.92 (m, 6 H, OCH2 and
CHN) ppm. 13C{1H} NMR (100 MHz, C6D6): δ = –6.4 (GaMe2),
10.4 (MeCCN), 14.5 (Me-iPr), 18.9 (Me-iPr), 30.0 (CH-iPr), 61.4
(MeCCN), 66.5 (CHN), 66.9 (OCH2), 171.1 (OCN) ppm.
C16H29GaN2O2 (351.14): calcd. C 54.73, H 8.32; found C 54.42, H
8.17.
(100 MHz, CD2Cl2): δ = –10.2 (GaMe), 8.3 (MeCCN), 9.1 (br.,
MeB), 26.8 (br., CMe2), 45.2 (br., NMe2Ph), 63.6 (CMe2), 67.4
(MeCCN), 78.4 (OCH2), 118.5 (br., NMe2Ph), 129.0 (br.,
1
NMe2Ph), 129.5 (NMe2Ph), 136.7 (d, JC,F = 233 Hz, m-C6F5),
1
1
137.9 (d, JC,F = 238 Hz, p-C6F5), 148.6 (d, JC,F = 233 Hz, o-
C6F5), 171.7 (OCN) ppm. 13C{1H} NMR (100 MHz, CD2Cl2,
263 K): δ = –10.7 (GaMe), 8.1 (MeCCN), 9.4 (br., MeB), 23.8
(CMe2), 27.6 (CMe2), 45.8 (br., NMe2Ph), 63.2 (CMe2), 69.0
(MeCCN), 77.9 (OCH2), 119.6 (o-PhNMe2), 127.2 (p-PhNMe2),
1
129.4 (m-PhNMe2), 136.7 (d, JC,F = 233 Hz, m-C6F5), 137.9 (d,
1
1JC,F = 238 Hz, p-C6F5), 145.1 (Cipso-PhNMe2), 148.6 (d, JC,F
=
[{BOX-Me2}GaMe][MeB(C6F5)3]
([3a][MeB(C6F5)3]):
In
a
glovebox, an equimolar amount of 2a (30.0 mg, 0.093 mmol) and
B(C6F5)3 (47.5 mg, 0.093 mmol) were charged in a J-Young NMR
tube and 0.75 mL of C6D5Br was added. The NMR tube was vigor-
ously shaken to yield a colorless solution and a 1H NMR spectrum
was immediately recorded, showing the nearly quantitative forma-
tion of [3a][MeB(C6F5)3] as a fully dissociated salt species, along
with minor impurities. Due to the relatively poor stability of
[3a][MeB(C6F5)3], the 13C{1H} NMR spectrum was recorded at
–25 °C to ensure good data. 1H NMR (400 MHz, C6D5Br): δ =
0.40 (s,3 H, GaMe), 0.97 (br. s, 3 H, MeB), 1.05 (s, 12 H, CMe2),
1.70 (s, 3 H, MeCCN), 3.71 (s, 4 H, OCH2) ppm. 13C{1H} NMR
(100 MHz, C6D5Br, 248 K): δ = –4.6 (GaMe), 9.3 (MeCCN), 11.7
(br., MeB), 28.2 (CMe2), 64.4 (CMe2), 71.3 (MeCCN), 79.4
(OCH2), 137.2 (dm, 2JC,F = 256 Hz, o- or m-C6F5), 137.9 (dm, 2JC,F
= 243 Hz, p-C6F5), 148.8 (dm, 2JC,F = 237 Hz, o- or m-C6F5), 171.0
(OCN) ppm.
233 Hz, o-C6F5), 171.2 (OCN) ppm. C40H36BF15GaN3O2 (956.24):
calcd. C 50.24, H 3.79; found C 49.91, H 3.47.
[{BOX-(S)-iPr}Ga(Me)(NMe2Ph)][MeB(C6F5)3] ([4b][MeB(C6F5)3]):
The chiral salt species [4b][MeB(C6F5)3] was generated following
the same procedure as that for [4a][MeB(C6F5)3], using equimolar
amounts of compound 2b (72.0 mg, 0.205 mmol), NMe2Ph (26 µL,
0.205 mmol), and B(C6F5)3 (105 mg, 0.205 mmol). It was isolated
as an analytically pure colorless solid in a similar yield (151 mg,
75% yield). 1H NMR (400 MHz, CD2Cl2): δ = 0.37 (s,3 H, GaMe),
0.48 (br. s, 3 H, MeB), 0.60–0.98 (br., 12 H, Me-iPr), 1.65 (br., 2
H), 1.72 (s, 3 H, MeCCN), 1.78 (br., 1 H), 3.00 (s, 3 H, NMe2Ph),
3.80–4.40 (6 H, CH2O and CHN), 7.24 (d, 3JH,H = 7.3 Hz, 2 H, o-
PhNMe2), 7.31 (br., 1 H, p-PhNMe2), 7.51 (t, 3JH,H = 7.8 Hz, 2 H,
1
m-PhNMe2) ppm. H NMR (400 MHz, CD2Cl2, 243 K): δ = 0.33
(s,3 H, GaMe), 0.40 (br. s, 3 H, MeB), 0.44 (br. d, 3 H, Me-iPr),
0.46 (br. d, 3 H, Me-iPr), 0.99 (br. d, 3 H, Me-iPr), 1.02 (br. d, 3
H, Me-iPr), 1.29 (br., 1 H, CH-iPr), 1.65 (s, 3 H, MeCCN), 1.70
(br., 1 H, CH-iPr), 1.81 (br., 1 H, CHN), 2.88 (s, 3 H, NMe2Ph),
3.00 (s, 3 H, NMe2Ph), 3.81 (t, JH,H = 8.7 Hz, 1 H, CH2O), 4.02
(br., 1 H, CHN), 4.12 (t, JH,H = 8.6 Hz, 1 H, CH2O), 4.30 (t, JH,H
[{BOX-(S)-iPr}GaMe][Me(BC6F5)3] ([3b][MeB(C6F5)3]): The chiral
salt compound [3b][MeB(C6F5)3] was generated on an NMR scale
using the same procedure as that for [3a][MeB(C6F5)3], with an
equimolar amount of 2b (15 mg, 0.043 mmol) and B(C6F5)3
1
(21.9 mg, 0.043 mmol). H NMR (400 MHz, C6D5Br, 298 K): δ = = 8.7 Hz, 1 H, CH2O), 4.41 (t, JH,H = 8.6 Hz, 1 H, CH2O), 7.30
0.36 (s,3 H, GaMe), 0.57 (d, 3JH,H = 6.8 Hz, 6 H, Me-iPr), 0.63 (d,
3JH,H = 6.9 Hz, 6 H, Me-iPr), 0.97 (br. s, 3 H, MeB), 1.57 (d of
(br., 2 H, o-PhNMe2), 7.42 (br., 1 H, p-PhNMe2), 7.52 (br., 2 H,
m-PhNMe2) ppm. 13C{1H} NMR (100 MHz, CD2Cl2, 243 K): δ
= –11.3 (GaMe), 8.6 (MeCCN), 9.5 (br., MeB), 12.8 (Me-iPr), 14.5
3
3
septet, JH,H doublet = 3.1, JH,H septet = 6.6 Hz, 2 H, CH-iPr), 1.74
4212
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 4206–4214

Neutral and Cationic Gallium Complexes Incorporating Bis(oxazolinato) Ligands
FULL PAPER
Table 3. Crystal data and refinements details for compounds 2a, 2b, [4a][MeB(C6F5)3], and [5a][B(C6F5)4].
2a
2b
[4a][MeB(C6F5)3]
[5a][B(C6F5)4]
Formula
C14H25GaN2O2
C16H29GaN2O2
C21H33GaN3O2,
C19H3BF15
956.25
C14H24GaN2O2,
C24BF20
1001.12
monoclinic
P21/c
12.843(2)
19.380(3)
15.829(2)
90.00
97.85(5)
90.00
3902.9(10)
4
Formula mass
Crystal system
Space group
a [Å]
b [Å]
c [Å]
323.08
orthorhombic
Pnma
11.7380(10)
11.0420(10)
12.249(2)
90.00
90.00
90.00
1587.6(3)
4
1.352
351.13
monoclinic
P21
9.3270(4)
11.5310(6)
9.5600(7)
90.00
116.8500(19)
90.00
917.33(9)
2
triclinic
¯
P1
10.397(5)
13.441(5)
15.762(5)
73.66(5)
80.66(5)
73.90(5)
2022.3(14)
2
α [°]
β [°]
γ [°]
V [Å3]
Z
Density [gcm–3]
µ (Mo-Kα) [mm–1]
F(000)
1.271
1.506
372
1.570
0.790
968
1.704
0.840
1992
1.734
680
Data collection
Temperature [K]
θ min./max.
Data set [h,k,l]
Total, unique data, R(int)
Observed data
Refinement
173(2)
2.40/30.03
–16/14, –15/14, –16/17
2445, 1898, 0.0615
I Ͼ 2σ(I)
173(2)
2.39/30.00
–13/11, 0/16, 0/13
2780, 1699, 0.0000
I Ͼ 2σ(I)
173(2)
1.35/30.01
–14/14, –17/18, 0/22
11773, 8935, 0.0000
I Ͼ 2σ(I)
173(2)
1.60/30.04
–18/17, 0/27, 0/22
11395, 7624, 0.0000
I Ͼ 2σ(I)
No. of reflections, parameters 2445, 94
2780, 190
11773, 559
11395, 577
R2, R1, wR2, wR1, Goof
0.0715, 0.0456, 0.0856,
0.0800, 1.074
–
0.0961, 0.0457, 0.1525, 0.0617, 0.0417, 0.1184,
0.0728, 0.0404, 0.1188,
0.1000, 0.929
–
0.1026, 0.951
0.04(3)
0.1089, 1.063
–
Flack x
Min., max. residual electron –0.477, 0.378
–0.855, 0.691
–0.607, 0.365
0.002, 0.000
density [eA–3]
(Me-iPr), 17.3 (Me-iPr), 19.7 (Me-iPr), 31.0 (CH-iPr), 31.2 (CH-
X-ray Structure Analysis of Complexes 2a,b, [4a][MeB(C6F5)3] and
iPr), 43.1 (NMe2Ph), 47.0 (NMe2Ph), 64.2 (NCH), 65.2 (NCH), [5a][B(C6F5)4]: Single crystal of 2a, 2b, [4a][MeB(C6F5)3], and
65.9 (MeCCN), 67.0 (CH2O), 67.5 (CH2O), 119.2 (o-PhNMe2), [5a][B(C6F5)4] were mounted on a Nonius Kappa-CCD area detec-
1
127.3 (p-PhNMe2), 129.8 (m-PhNMe2), 136.7 (d, JC,F = 233 Hz, tor diffractometer (Mo-Kα radiation; λ = 0.71073 Å). The complete
1
m-C6F5), 137.9 (d, JC,F = 238 Hz, p-C6F5), 145.3 (Cipso-PhNMe2), conditions of data collection (Denzo software)[20] and structure re-
148.6 (d, 1JC,F = 233 Hz, o-C6F5), 170.9 (OCN), 172.0 (OCN) ppm.
C42H40BF15GaN3O2 (984.29): calcd. C 51.25, H 4.10; found C
51.03, H 3.88.
finements are given in Table 3. The cell parameters were deter-
mined from reflections taken from one set of 10 frames (1.0° steps
in phi angle), each at 20 s exposure. The structures were solved
by direct methods (SHELXS97) and refined against F2 using the
SHELXL97 software.[21] The absorption was not corrected. All
non-hydrogen atoms were refined anisotropically. Hydrogen atoms
were generated according to stereochemistry and refined using a
riding model in SHELXL97.
CCDC-273080 (for 2a), -273081 (for 2b), -273082 (for
[4a][MeB(C6F5)3]), and -273083 (for [5a][MeB(C6F5)3]) contains the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[{H2C=C(OX-Me2)2}GaMe2][B(C6F5)4] ([5a][B(C6F5)4]): In
a
glovebox, stoichiometric amounts of [{BOX-Me2}GaMe2] (50 mg,
0.155 mmol) and [Ph3C][B(C6F5)4] (143 mg, 0.155 mmol) were
charged in a 25-mL round-bottomed flask and dissolved in CH2Cl2
(2 mL). While under vigorous stirring at room temperature, the ini-
tial bright-red solution turned pale yellow within seconds, indicat-
ing the total consumption of the trityl salt. The mixture was stirred
for 1 h at room temperature, after which it was evaporated to dry-
ness under vacuum. Addition of cold pentane (precooled to –35 °C)
provoked the precipitation of a colorless solid. The mixture was
then filtered through a glass frit and the obtained colorless residue
washed three times with cold pentane to remove any remaining
Ph3CH. Further drying of the residue in vacuo afforded the salt
species [5a][B(C6F5)4] as an analytically pure colorless solid
Acknowledgments
1
(136 mg, 88% yield). H NMR (400 MHz, CD2Cl2): δ = –0.01 (s,
We thank the French Ministry of Research for financial support
through an ACI grant (no. JC4045). We also thank Dr. A. De Cian
for the X-ray diffraction studies.
6 H, GaMe2), 1.53 (s, 12 H, CMe2), 4.44 (s, 4 H, OCH2), 7.30 (s,
2 H, CH2=C) ppm. 13C{1H} NMR (100 MHz, CD2Cl2): δ = –4.3
(GaMe2), 26.8 (CMe2), 69.3 (CMe2), 80.6 (OCH2), 118.4 (H2C=C),
1
1
136.7 (dm, JC,F = 243 Hz, C6F5), 138.6 (dm, JC,F = 243 Hz,
1
C6F5), 143.7 (H2C=C), 148.5 (dm, JC,F = 239 Hz, C6F5), 162.6
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2.42; found C 45.95, H 2.37.
Eur. J. Inorg. Chem. 2005, 4206–4214
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4213

S. Dagorne, S. Bellemin-Laponnaz et al.
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Received: May 26, 2005
Published Online: September 8, 2005
4214
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 4206–4214