Synthesis of Heterobimetallic Group 13 Compounds via Oxidative Addition Reaction of Gallanediyl LGa and InEt3

Article abstract of DOI:10.1021/acs.organomet.5b00302

Equimolar amounts of LGa (L = [(2,6-i-Pr₂-C₆H₃)NC(Me)]₂CH) and InEt₃ were found to react with insertion into the In-carbon bond and formation of LGa(Et)InEt₂ (1), while in the presence of the N-heterocyclic carbene It-Bu [C(Nt-Bu₂CH)₂], the base-stabilized compound LGa(Et)Et₂In←It-Bu (2) was formed, which shows an abnormal binding mode of the NHC group. In addition, the reaction of InEt₃ with two equivalents of LGa occurred with double insertion and formation of [LGa(Et)]₂InEt (3). 1-3 were characterized by heteronuclear NMR (¹H, ¹³C) and IR spectroscopy, their solid-state structures were determined by single-crystal X-ray analyses, and their thermal stability was investigated by in situ NMR spectroscopy. (Chemical Equation Presented).

Full text of DOI:10.1021/acs.organomet.5b00302

Article
pubs.acs.org/Organometallics
Synthesis of Heterobimetallic Group 13 Compounds via Oxidative
Addition Reaction of Gallanediyl LGa and InEt3
Chelladurai Ganesamoorthy, Dieter Blaser, Christoph Wolper, and Stephan Schulz*
̈
̈
Institute of Inorganic Chemistry, University of Duisburg−Essen, 45117 Essen, Germany
S
* Supporting Information
ABSTRACT: Equimolar amounts of LGa (L = [(2,6-i-Pr2-
C6H3)NC(Me)]2CH) and InEt3 were found to react with
insertion into the In−carbon bond and formation of
LGa(Et)InEt2 (1), while in the presence of the N-heterocyclic
carbene It-Bu [C(Nt-Bu2CH)2], the base-stabilized compound
LGa(Et)Et2In←It-Bu (2) was formed, which shows an
abnormal binding mode of the NHC group. In addition, the
reaction of InEt3 with two equivalents of LGa occurred with
double insertion and formation of [LGa(Et)]2InEt (3). 1−3 were characterized by heteronuclear NMR (1H, 13C) and IR
spectroscopy, their solid-state structures were determined by single-crystal X-ray analyses, and their thermal stability was
investigated by in situ NMR spectroscopy.
reactions of LGa with Bi(OR)3,9 whereas reactions of LGa with
INTRODUCTION
■
GaX3 (X = Me, Cl) occurred with insertion into the Ga−X
Monovalent group 13 diyls of the type RM [M = Al, Ga, In; R
bond and subsequent formation of the digallane LGa(X)GaX2
= Cp*, diketiminates, ...] have emerged from laboratory
and trigallane [LGa(X)]2GaX, respectively.10 Analogous
curiosities to versatile compounds in inorganic and organic
insertion reactions were reported for reactions with Me2SnCl2,
syntheses1 since the discovery of the first compound of this
SiCl4, and as t-BuCl.10
type, [Cp*Al]4, more than 20 years ago.2 Among many
Despite these significant findings, there still remains interest
compounds that have been synthesized and structurally
in understanding the bonding situation in such intermetallic
characterized since then, the gallanediyl LGa (L = [(2,6-i-Pr2-
compounds and how the reactions occur in order to predict
C6H3)NC(Me)]2CH), containing the sterically crowded β-
diketiminate ligand, has been intensely studied in chemical
what kind of complexes are accessible. Due to our general
interest in the synthesis, bonding situation, and chemical
reactivity of low-valent organometallics of group 12,11 13,12
reactions. LGa is monomeric in the solid state and in solution,
14,13 and 15 elements,14 we recently became interested in
and the gallium valence shell contains two-bond electron pairs,
one electron lone pair, and an empty p-orbital.3 As a
consequence of this specific electronic situation, LGa can
insertion reactions of the gallandiyl LGa into metal−carbon as
well as metal−metal bonds and reported on reactions with
group 15 metalorganics such as Et3Bi15 and Et4E2 (E = Sb,
react as both an electrophilic and nucleophilic reagent. LGa is a
Bi),16 which proceeded with insertion into the Bi−C and E−E
good σ-donor but a poor π-acceptor according to computa-
tional calculations as a result of the high s-character of the
bond and subsequent formation of LM(Et)BiEt2 and LM-
HOMO and the large energy difference (95.3−110 kcal/mol)
between the donor orbital (HOMO) and the diffuse acceptor
4p-orbital (LUMO+1).4 The σ-donor capacity of LGa was
shown with the synthesis of the Lewis acid−base adduct LGa→
(EEt2)2, respectively. In addition, reactions of LGa with
diisopropyltellane (i-Pr2Te) and diphenylditellane (Ph2Te2)
were found to occur with insertion into the Te−C and Te−Te
bond.17 We herein report on the reactions of LGa with InEt3,
yielding heterobimetallic group 13 element complexes contain-
ing direct In−Ga covalent bonds.
5
B(C6F5)3 and other p- or d-block metal complexes as well as
with the synthesis of a large variety of late transition metal
complexes,6 which are promising candidates for small-molecule
activation and cluster formation reactions.7 In addition to their
general reactivity to act as σ-donor reagents, β-diketiminate
gallynes LGa also show powerful reducing activity, as was
demonstrated in reduction reactions of main group metal
compounds such as SnCl2. These reactions proceeded with
oxidation of LGa and subsequent metal−metal bond formation,
resulting in the formation of unprecedented gallyl-supported tin
clusters [Sn7{Ga(Cl)(L)}2] and [Sn17{Ga(Cl)(L)}4].8 In
addition, the galla-dibismuthenes [LGa(OR)Bi]2 (R = C6F5,
SO2CF3) containing BiBi double bonds were obtained from
RESULTS AND DISCUSSION
■
The reaction of equimolar amounts of LGa and InEt3 in
toluene at 0 °C occurred with insertion of the gallane diyl into
the In−C bond and formation of the heterobimetallic complex
LGa(Et)InEt2 (1) (Scheme 1). Solutions of 1 in benzene and
toluene tend to decompose slowly at ambient temperature, and
Received: April 10, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.5b00302
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1H NMR spectrum of 1 in C6D6 exhibits single resonances for
the γ-CH and two methyl groups of the C3N2Ga ring at 4.83
and 1.48 ppm, while the magnetically inequivalent methyl and
methine protons of the isopropyl substituents exhibit four
doublets (1.39, 1.15, 1.12, 1.08 ppm) and two septets (3.56,
3.01 ppm), respectively. Proton resonances of the Ga−Et group
are shifted to higher field (0.85, 0.37 ppm), whereas those of
the InEt groups appear as a triplet and a multiplet at lower field
(1.82, 1.11 ppm). The 13C{1H} NMR spectrum of 1 shows 18
signals including the characteristic resonances due to the γ-CH
(96.32 ppm), the remaining two C3N2Ga ring carbons (167.98
ppm), the methine (29.23, 28.99 ppm), and the methyl carbon
atoms of isopropyl groups (25.42, 25.07, 24.28, 23.36 ppm) as
well as the methyl (13.52, 11.21 ppm) and methylene carbon
atoms (7.23 ppm) of the ethyl groups.
Scheme 1. Synthesis and Thermal Stability of 1−3
The 1H and 13C NMR spectra of 2 show additional
resonances due to the carbene It-Bu. No significant chemical
shifts were observed in the NMR spectra of 2 for the L and Et
groups in comparison with 1, which indicates that It-Bu binds
1
only weakly in solution to the InEt2 moiety. The H NMR
spectrum of 3 in toluene-d8 exhibits very broad signals for the i-
Pr groups of the β-diketiminate ligands [3.90−2.80 ppm,
−CH(CH3)2; 1.33−1.07 ppm, −CH(CH3)2] and the GaEt
groups (0.77 to −0.4 ppm). The γ-CH and two methyl groups
of the C3N2Ga ring show singlets at 4.70 and 1.47 ppm,
respectively, while the InEt group appears as a triplet and a
quartet at 1.97 and 1.00 ppm, respectively. At −40 °C (Figure
S8), two separate singlets were observed for the γ-CH (4.71,
4.65 ppm) and the ring NCCH3 (1.46, 1.45 ppm).
Furthermore, the methine protons of the isopropyl substituents
exhibit three multiplets (3.75, 3.48, 3.04 ppm) in 2:1:1 molar
ratio. Due to the asymmetric nature of 3, the region between
2.3 and −0.5 ppm shows several overlapping multiplets, which
prohibits their assignment to appropriate groups. It should be
noted that the signals do not correspond to those of a mixture
of 1 and LGa at very low temperatures.
3 gradually decomposes at 80 °C in C6D6, yielding LGa and
LGaEt2 in a 1:3 molar ratio after 24 h (Figure S16). The
decomposition products confirm the activation of all In−Et
groups. There are two possible pathways: (i) One of the
[LGa(Et)] in 3 abstracts the remaining ethyl group from the
indium center and leaves LGaEt2 and an intermediate species
[LGa(Et)In], which then disproportionate into indium metal,
1/2 LGaEt2, and 1/2 LGa. (ii) Alternatively, 3 dissociates at
high temperature into LGa and 1, which then decomposes as
observed previously with isolated 1. In order to understand the
reaction pathway, 3 was gradually heated in C6D6 and the
reaction progress was monitored periodically by 1H NMR
spectroscopy. Compound 3 is thermally stable up to 50 °C and
starts to dissociate at 70 °C with subsequent formation of LGa
and 1 (Figure S17), as was observed for [LGa(Me)]2GaMe.10
Gradually formed (thermolabile) 1 decomposes under these
conditions with formation of indium metal and LGaEt2.
However, it should be noted that two new additional γ-CH
peaks (5.05, 4.80 ppm) appear at 80 °C after 3 h, which could
not be assigned to any known species yet (Figure S18).
However, prolonged heating of 3 afforded only LGa, LGaEt2,
and In metal. Again, the formation of deeply colored solutions
was not observed.
15
the formation of LGaEt2 and InEt3, which were clearly
1
identified by their H NMR spectra, and In metal has been
1
observed within a day. The H NMR spectrum of the reaction
mixture (Figure S15) shows the formation of LGaEt2 and InEt3
in 3:1 molar ratio, while the corresponding two equivalents of
In metal were isolated in an independent large-scale reaction
and characterized by energy-dispersive X-ray diffraction (EDX,
Figure S20). The observation of 3:1:2 stoichiometry of LGaEt2,
InEt3, and indium metal from 1 evidences the in situ formation
of monovalent [InEt]x, which further disproportionates into
two equivalents of indium metal and one equivalent of InEt3 as
was observed. It should further be mentioned that the
formation of deeply colored solutions, which may indicate
the presence of larger cluster-type complexes as was observed
in reaction with SnCl2,8 was not observed. In order to confirm
the possible formation of In(I) in the reaction mixture, LGa
was reacted with Cp*InEt2. The reaction leads to the formation
of LGaEt2 and Cp*In. However, we were able to isolate only
21% of the Cp*In, which might result from the simultaneous
insertion of LGa into the In−C bond of both the In−Cp* and
In−Et moieties as well as due to a gradual decomposition of as-
formed Cp*In in solution.18
Compound 1 is quite stable below −30 °C both in its
isolated pure form and in solution, while noticeable
decomposition was observed at higher temperatures. Further-
more, 1 can be stabilized upon reaction with the strong σ-donor
It-Bu [C(Nt-Bu2CH)2], resulting in a quantitative formation of
the respective NHC-stabilized compound LGa(Et)Et2In←It-Bu
(2) (Scheme 1). It should be noted that the reaction of 1 with
one additional equivalent of LGa, which can also serve as a σ-
donor, leads to 2-fold insertion and subsequent formation of
[LGa(Et)]2InEt (3) in good yield, while the reaction of 1 with
two additional equivalents of LGa failed to give the 3-fold
insertion product [LGa(Et)]3In. 2 and 3 are thermally more
stable in solution than 1 and can be stored for several days at
ambient temperature in solution and in their isolated forms
under an argon atmosphere. 1−3 are moisture sensitive, yellow
to orange crystalline solids but moderately stable toward air.
They dissolve well in benzene, toluene, and n-hexane.
Single crystals of 1−3 suitable for X-ray diffraction analysis
were grown from saturated n-hexane (1, 3) and toluene (2)
solutions at −30 °C. 1 and 3 crystallize in the monoclinic space
groups C2/c (1) and P21/c (3), whereas 2 crystallizes in
1H and 13C NMR spectra of freshly prepared 1 show
characteristic resonances of the organic substituents; that is, the
B
DOI: 10.1021/acs.organomet.5b00302
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
triclinic space group P1, respectively. Figures 1−3 show the
̅
solid-state structures of 1−3. Selected bond lengths and bond
angles are given in the footnote of the figures, and
crystallographic details are summarized in Table S1.
Figure 2. Molecular structure of LGa(Et)Et2In←It-Bu, 2. H atoms and
lattice solvent have been omitted for clarity, and displacement
ellipsoids are drawn at the 30% probability level. Selected bond
lengths (Å) and angles (deg): Ga(1)−N(1) 2.0278(12), Ga(1)−N(2)
2.0350(12), In(1)−Ga(1) 2.62080(19), Ga(1)−C(41) 2.0235(14),
In(1)−C(43) 2.2209(15), In(1)−C(45) 2.2247(15), In(1)−C(30)
2.3148(15), N(1)−C(1) 1.3289(18), N(2)−C(3) 1.3263(18), C(1)−
C(2) 1.402(2), C(2)−C(3) 1.401(2); N(2)−Ga(1)−N(1) 91.63(5),
C(41)−Ga(1)−In(1) 115.85(4), C(43)−In(1)−Ga(1) 128.93(4),
C(45)−In(1)−Ga(1) 113.87(4), C(30)−In(1)−Ga(1) 104.16(4),
C(43)−In(1)−C(45) 103.51(6), C(43)−In(1)−C(30) 93.90(6),
C(45)−In(1)−C(30) 109.81(5), C(41)−Ga(1)−N(1) 104.12(5),
C(41)−Ga(1)−N(2) 103.24(5), N(1)−Ga(1)−In(1) 120.24(3),
N(2)−Ga(1)−In(1) 117.99(3).
Figure 1. Molecular structure of LGa(Et)InEt2, 1. H atoms and
disordered Et group have been omitted for clarity, and displacement
ellipsoids are drawn at the 30% probability level. Selected bond lengths
(Å) and angles (deg): Ga(1)−N(1) 2.0022(18), Ga(1)−N(2)
1.9953(17), In(1)−Ga(1) 2.6268(3), Ga(1)−C(30) 1.987(2),
In(1)−C(32) 2.187(3), In(1)−C(34) 2.189(11), N(1)−C(1)
1.317(3), N(2)−C(3) 1.328(3), C(1)−C(2) 1.408(3), C(2)−C(3)
1.397(3); N(2)−Ga(1)−N(1) 92.50(7), C(30)−Ga(1)−In(1)
118.45(7), C(34)−In(1)−Ga(1) 126.7(3), C(32)−In(1)−Ga(1)
124.44(7), C(32)−In(1)−C(34) 108.8(3), C(30)−Ga(1)−N(1)
111.98(8), C(30)−Ga(1)−N(2) 110.04(9), N(1)−Ga(1)−In(1)
111.24(5), N(2)−Ga(1)−In(1) 109.56(5).
less stable than the corresponding n-NHCs since the carbene-C
atom is stabilized by only one N atom21 and the proton at C2
in imidazolium salts is much more acidic than the C4/5 proton;
hence the conversion of an a-NHC into an n-NHC is
thermodynamically favored.19 However, the formation of 2
most likely results from the high σ-donor capacity of a-NHCs,
which is even substantially enhanced compared to classical
imidazol-2-ylidenes (n-NHC), which are already considered as
very strong σ-donor ligands.22a Moreover, repulsive sterical
interactions between the bulky t-Bu groups of the NHC base
and the Et and L substituents bound to In and Ga further favor
the formation of the a-NHC.23
As expected, the Ga−C distances [1.987(2) Å (1);
2.0235(14) Å (2); 2.014(3), 1.986(4) Å (3)] are shorter
than the In−C bonds [2.187(3), 2.189(11) Å (1); 2.2209(15),
2.2247(15) Å (2); 2.223(4) Å (3)], while the In−C distance to
the coordinated a-NHC (2.3148(15) Å) is even longer, as was
expected due to the dative bonding character. It-Bu binds
almost perpendicular to the Ga−In bond, showing a C30−
In1−Ga1 bond angle of 104.16(4)°. The bite angle of the
chelating ligand L 92.50(7)° (1), 91.63(5)° (2), and
92.64(12)−90.97(13)° (3) is comparable to those previously
observed in these types of complexes. The Ga−In−Ga bond
angle of 3 [127.123(16)°] is smaller than the same observed in
[LGa(Me)]2GaMe (138.37°).
The molecular structure of 1 is similar to those of recently
reported group 13−bismuth compounds LM(Et)BiEt2 (M = Al,
Ga, In),15 and LGa(Me)GaMe2 and 3 is similar to [LGa-
(Me)]2GaMe.10 Each Ga atom in 1 to 3 adopts a distorted
tetrahedral coordination geometry, and the Ga atom is slightly
out of the C3N2 plane (deviation from the best plane of the
ligand backbone 0.616(3) Å (1), 0.7040(17) Å (2), 0.651(4)
and 0.748(4) Å (3)). In 1 and 3, the indium atoms adopt
trigonal-planar coordination geometries and the sum of the
bond angles is close to 360°. Bonding of It-Bu to the InEt2
moiety converts the planar geometry of indium (1) to a
distorted tetrahedral geometry (2). The Ga−N distances in 1−
3 are virtually the same [1.9953(17), 2.0022(18) Å (1); 2.0278
(12), 2.0350(12) Å (2); 2.020(3), 2.042(3), 2.016(3), 2.018(3)
Å (3)], and the almost identical Ga−In bond distances of 1 and
2 [2.6268(3) Å (1), 2.62080(19) Å (2)] are slightly shorter
than those found in 3 [2.6910(5), 2.6902(5) Å (3)]. In
addition, they are comparable to the sum of covalent radii (Ga
= 1.24 Å; In = 1.42 Å),19 indicating the formation of Ga−In σ-
bonds.
CONCLUSION
■
The molecular structure of 2 shows the presence of an
abnormally bonded NHC (a-NHCs), or so-called mesionic
carbene. A similar bonding mode was observed in the Lewis
acid−base reaction of AlMe3 with It-Bu.20 a-NHCs are typically
We showed that the redox transmetalation reaction of Et3In to
indium metal using the gallanediyl LGa initially starts with the
insertion of one or two LGa moieties into one or two In−C
bonds of InEt3, resulting in the formation of the insertion
C
DOI: 10.1021/acs.organomet.5b00302
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
referenced to internal C6D5H (1H: δ = 7.154; 13C: δ = 128.39) and
C6D5CHD2 (1H: δ = 2.09; 13C: δ = 20.40). Microanalyses were
performed at the elemental analysis laboratory of the University of
Duisburg−Essen. IR spectra were measured in an ALPHA-T FT-IR
spectrometer equipped with a single-reflection ATR sampling module.
LGa,3 InEt3,25 and It-Bu26 were prepared according to literature
methods. While purifying 1 and 2, traces of gray precipitates was
observed, which were filtered using an oven-dried Teflon cannula (3.5
mm D) in which one end of the tip was wrapped with Whatman glass
microfiber filters (cat. no. 1823-025) using Teflon tape.
Synthesis of 1. A mixture of InEt3 (0.0252 g, 20 μL, 0.125 mmol)
and LGa (0.0608 g, 0.125 mmol) in 2 mL of toluene was stirred at 0
°C for 30 min. The solvents were removed under reduced pressure,
and the residue was dissolved in 0.6 mL of n-hexane. Storage of the
solution at −30 °C for 3 days afforded an analytically pure form of 1 as
yellow-orange crystals. Yield: 89% (0.077 g). Anal. Calcd for
C35H56GaInN2: C, 60.98; H, 8.19; N, 4.06. Found: C, 60.67; H,
1
8.07; N, 4.01. H NMR (C6D6, 300 MHz): δ 7.13−6.92 (m, 6H,
3
C6H3(i-Pr)2), 4.83 (s, 1H, γ-CH), 3.56 (sept, JHH = 7.0 Hz, 2H,
3
CH(CH3)2), 3.01 (sept, JHH = 7.0 Hz, 2H, CH(CH3)2), 1.82 (t, 3JHH
3
= 7.0 Hz, 6H, InCH2CH3), 1.48 (s, 6H, ArNCCH3), 1.39 (d, JHH
=
Figure 3. Molecular structure of [LGa(Et)]2InEt, 3. H atoms have
been omitted for clarity, and displacement ellipsoids are drawn at the
30% probability level. Selected bond lengths (Å) and angles (deg):
Ga(1)−N(1) 2.020(3), Ga(1)−N(2) 2.042(3), Ga(2)−N(3)
2.018(3), Ga(2)−N(4) 2.016(3), Ga(1)−C(30) 2.014(3), Ga(2)−
C(32) 1.986(4), Ga(1)−In(1) 2.6910(5), Ga(2)−In(1) 2.6902(5),
In(1)−C(34) 2.223(4), N(1)−C(1) 1.333(5), N(2)−C(3) 1.323(4),
N(3)−C(41) 1.322(5), N(4)−C(43) 1.330(5); N(1)−Ga(1)−N(2)
92.64(12), N(4)−Ga(2)−N(3) 90.97(13), Ga(2)−In(1)−Ga(1)
127.123(16), C(34)−In(1)−Ga(1) 122.02(11), C(34)−In(1)−
Ga(2) 110.86(11), C(30)−Ga(1)−In(1) 113.84(11), C(32)−
Ga(2)−In(1) 120.61(13), C(30)−Ga(1)−N(1) 106.86(13), C(30)−
Ga(1)−N(2) 102.33(14), C(32)−Ga(2)−N(3) 109.61(16), C(32)−
Ga(2)−N(4) 109.40(16), N(1)−Ga(1)−In(1) 119.05(9), N(2)−
Ga(1)−In(1) 119.08(8), N(3)−Ga(2)−In(1) 111.20(9), N(4)−
Ga(2)−In(1) 111.07(9).
7.0 Hz, 6H, CH(CH3)2), 1.16−1.06 (m, 22H, CH(CH3)2,
3
3
InCH2CH3), 0.85 (t, JHH = 7.0 Hz, 3H, GaCH2CH3), 0.37 (q, JHH
= 7.0 Hz, 2H, GaCH2CH3). 13C NMR (C6D6, 75.5 MHz): δ 168.0
(ArNCCH3), 144.0 (C6H3), 143.9 (C6H3), 142.3 (C6H3), 127.0
(C6H3), 124.7 (C6H3), 124.6 (C6H3), 96.3 (γ-CH), 29.2 (CH(CH3)2),
29.0 (CH(CH3)2), 25.4 (CH(CH3)2), 25.1 (CH(CH3)2), 24.3
(CH(CH3)2), 23.4 (CH(CH3)2), 20.5 (ArNCCH3), 13.5
(InCH2CH3), 11.2 (GaCH2CH3), 7.2 (GaCH2CH3). IR (neat): ν
3063, 2959, 2923, 2856, 1562, 1519, 1440, 1385, 1312, 1263, 1178,
1106, 1020, 936, 856, 796, 759, 637, 522, 443 cm−1.
Decomposition of 1. A solution of 1 (0.215 g, 0.312 mmol) in 3
mL of toluene was stirred at ambient temperature for 24 h. The
reaction mixture was filtered, and the gray precipitate was washed with
10 mL of n-hexane. The combined filtrates were concentrated under
reduced pressure and stored at −30 °C. Colorless crystals of LGaEt2,
which was identified by NMR spectroscopy,15 were formed within 2
days. Yield: 94% (0.1603 g, LGaEt2); 96% (0.0230 g, In metal).
Reaction of LGa with Cp*InEt2. A solution of Cp*InEt2 (0.1168 g,
0.379 mmol) in 3 mL of toluene was added to a solution of LGa
(0.185 g, 0.379 mmol) in 5 mL of toluene at ambient temperature, and
the reaction mixture was stirred for 24 h. The solvents were removed
under reduced pressure, and the residue was sublimed at 55 °C (10−3
mbar). Yield of isolated Cp*In: 21% (20 mg).
complexes LGa(Et)InEt2 (1) and [LGa(Et)]2InEt (3),
respectively. 1 is thermolabile in solution, but can be stabilized
by coordination of It-Bu, yielding LGa(Et)Et2In←It-Bu (2)
with an abnormal binding mode. A solution of 1 decomposes at
ambient temperature in a controlled manner with quantitative
formation of indium metal, LGaEt2, and InEt3, whereas thermal
treatment of a solution of 3 at moderate temperatures (80 °C)
yielded indium metal as well as LGa and LGaEt2. The
decomposition of 1 probably proceeds through formation of a
monovalent In(I) species, [EtIn]x. This proposed reaction
mechanism is supported by the analogous reaction of
Cp*InEt2, which proceeded with formation of Cp*In. The
described reaction pathway therefore may offer a general
synthetic pathway to (metalloid) low-valent main group
element cluster compounds in the near future. It should be
noted that Aldridge et al. recently reported on the formation of
the large metalloid In cluster In19{B(NDippCH)2}6, which was
obtained from the thermal decomposition of {(MeCCH2)2}-
[In{B(NDippCH)2}2]2 in hexane at ambient temperature.24
Synthesis of 2. A mixture of InEt3 (0.0882 g, 70 μL, 0.437 mmol)
and It-Bu (0.0787 g, 0.437 mmol) in 5 mL of toluene was stirred at
ambient temperature for 1 h. LGa (0.213 g, 0.437 mmol) dissolved in
5 mL of toluene was added, and the reaction mixture was stirred for an
additional 4 h. The golden yellow solution was concentrated to 5 mL
and stored at −30 °C for 24 h to afford a pure form of 2 as yellow
crystals. Yield: 73% (0.277 g). Anal. Calcd for C46H76N41GaIn: C,
63.53; H, 8.81; N, 6.44. Found: C, 63.19; H, 8.69; N, 6.31. H NMR
(C6D6, 300 MHz): δ 7.11−6.92 (m, 6H, C6H3(i-Pr)2), 6.79 (s, 2H, It-
3
Bu, NCH), 4.83 (s, 1H, γ-CH), 3.55 (sept, JHH = 7.0 Hz, 2H,
3
CH(CH3)2), 3.01 (sept, JHH = 7.0 Hz, 2H, CH(CH3)2), 1.82 (t, 3JHH
= 7.0 Hz, 6H, InCH2CH3), 1.52 (s, 18H, It-Bu, C(CH3)3), 1.49 (s, 6H,
3
ArNCCH3), 1.39 (d, JHH = 7.0 Hz, 6H, CH(CH3)2), 1.16−1.07 (m,
3
22H, CH(CH3)2, InCH2CH3), 0.84 (t, JHH = 7.0 Hz, 3H,
3
GaCH2CH3), 0.37 (q, JHH = 7.0 Hz, 2H, GaCH2CH3). 13C NMR
(C6D6, 75.5 MHz): δ 213.3 (It-Bu, NCN), 168.0 (ArNCCH3), 144.0
(C6H3), 144.0 (C6H3), 142.3 (C6H3), 127.0 (C6H3), 124.7 (C6H3),
124.6 (C6H3), 115.4 (It-Bu, NCCN), 96.3 (γ-CH), 56.2 (It-Bu,
C(CH3)3), 31.8 (It-Bu, C(CH3)3), 29.2 (CH(CH3)2), 29.0 (CH-
(CH3)2), 25.4 (CH(CH3)2), 25.1 (CH(CH3)2), 24.3 (CH(CH3)2),
23.4 (CH(CH3)2), 20.5 (ArNCCH3), 13.5 (InCH2CH3), 11.2
(GaCH2CH3), 7.3 (GaCH2CH3). IR (neat): ν 2920, 2843, 1556,
1531, 1403, 1312, 1239, 1185, 1118, 984, 936, 850, 795, 747, 649, 619,
546, 437 cm−1.
EXPERIMENTAL SECTION
■
General Procedures. All manipulations were performed in an
atmosphere of purified argon using standard Schlenk and glovebox
techniques. Toluene and hexane were dried using an mBraun solvent
purification system. Deuterated solvents were dried over activated
molecular sieves (4 Å) and degassed prior to use. The anhydrous
1
nature of the solvents was verified by Karl Fischer titration. The H
(300 MHz) and 13C{1H} NMR (75.5 MHz) spectra (δ in ppm) were
Synthesis of 3. A solution of InEt3 (0.0378 g, 30 μL, 0.187 mmol)
recorded using a Bruker Avance DPX-300 spectrometer and were
in 3 mL of toluene was added dropwise to a toluene solution (10 mL)
D
DOI: 10.1021/acs.organomet.5b00302
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
of LGa (0.182 g, 0.374 mmol). After stirring for 24 h, the solution was
concentrated to 2 mL and stored at 0 °C to give red crystals of 3.
Yield: 73% (0.160 g). Anal. Calcd for C64H97N4Ga2In: C, 65.32; H,
8.31; N, 4.76. Found: C, 65.03; H, 8.22; N, 4.57. 1H NMR (300 MHz,
toluene-d8): δ 7.14−7.04 (m, 6H, C6H3(i-Pr)2), 4.70 (s, 1H, γ-CH),
3.52 (br m, 4H, CH(CH3)2), 1.97 (t, 3JHH = 7.0 Hz, 3H, InCH2CH3),
1.47 (s, 6H, ArNCCH3), 1.15 (br, 6H, GaCH2CH3), 1.13 (2 d, 24H,
(3) Hardman, N. J.; Eichler, B. E.; Power, P. P. Chem. Commun.
2000, 1991−1992.
(4) (a) Hardman, N. J.; Power, P. P. ACS Symp. Ser. 2002, 822, 2.
(b) Chen, C.-H.; Tsai, M.-L.; Su, M.-D. Organometallics 2006, 25,
2766−2773. (c) Hill, M. S.; Hitchcock, P. B.; Pontavornpinyo, R.
Dalton Trans. 2005, 273−277.
(5) Hardman, N. J.; Power, P. P.; Gorden, J. D.; Macdonald, C. L. B.;
Cowley, A. H. Chem. Commun. 2001, 1866−1867.
3
CH(CH3)2), 0.97 (q, JHH = 7.0 Hz, 2H, InCH2CH3), 0.60 (br, 4H,
GaCH2CH3). IR (neat): ν 3057, 2959, 2923, 2862, 1556, 1519, 1446,
1391, 1319, 1263, 1172, 1106, 1020, 936, 856, 796, 753, 643, 607, 522,
443 cm−1.
(6) (a) Gemel, C.; Steinke, T.; Cokoja, M.; Kempter, A.; Fischer, R.
A. Eur. J. Inorg. Chem. 2004, 4161−4176. (b) Baker, R. J.; Jones, C.
Coord. Chem. Rev. 2005, 249, 1857−1869. (c) Whitmire, K. H.
Comprehensive Organometallic Chemistry, Vol. 3; Housecraft, C. E., Ed.;
Elsevier, 2007; pp 343−407. (d) Schulz, S. Top. Organomet. Chem.
2013, 41, 59−90.
Single-Crystal X-ray Diffraction. Crystallographic data of 1−3,
which were collected on a Bruker D8 Kappa APEX2 diffractometer
(Mo Kα radiation, λ = 0.710 73 Å) at 100(1) K, are summarized in
Table S1. The solid-state structures of 1−3 are shown in Figures 1−3.
The structures were solved by direct methods (SHELXS-97)27 and
refined anisotropically by full-matrix least-squares on F2 (SHELXL-
2014)28,29 Absorption corrections were performed semiempirically
from equivalent reflections on the basis of multiscans (Bruker AXS
APEX2). Hydrogen atoms were refined using a riding model or rigid
methyl groups.
The crystallographic data of 1 to 3 (excluding structure factors)
have been deposited with the Cambridge Crystallographic Data Centre
as supplementary publication nos. CCDC-1048240 (1), CCDC-
1048239 (2), and CCDC-1048238 (3). Copies of the data can be
obtained free of charge on application to CCDC, 12 Union Road,
Cambridge, CB21EZ (fax: (+44) 1223/336033; e-mail: deposit@ccdc.
cam-ak.uk).
(7) Kempter, A.; Gemel, C.; Cadenbach, T.; Fischer, R. A.
Organometallics 2007, 26, 4257−4264. (b) Kempter, A.; Gemel, C.;
Fischer, R. A. Chem.−Eur. J. 2007, 13, 2990−3000.
(8) Prabusankar, G.; Kempter, A.; Gemel, C.; Schroter, M.-K.;
̈
Fischer, R. A. Angew. Chem. 2008, 120, 7344−7347; Angew. Chem., Int.
Ed. 2008, 47, 7234−7237.
(9) Prabusankar, G.; Gemel, C.; Parameswaran, P.; Flener, C.;
Frenking, G.; Fischer, R. A. Angew. Chem. 2009, 121, 5634−5637;
Angew. Chem., Int. Ed. 2009, 48, 5526−5529.
(10) Kempter, A.; Gemel, C.; Fischer, R. A. Inorg. Chem. 2008, 47,
7279−7285.
(11) (a) Gondzik, S.; Schulz, S.; Blaser, D.; Wolper, C. Chem.
̈
̈
Commun. 2014, 1189−1191. (b) Gondzik, S.; Schulz, S.; Blaser, D.;
̈
Wolper, C.; Haack, R.; Jansen, G. Chem. Commun. 2014, 927−929.
(c) Nayek, H. P.; Luhl, A.; Schulz, S.; Koppe, R.; Roesky, P. W.
Chem.−Eur. J. 2011, 17, 1773−1777. (d) Gondzik, S.; Blaser, D.;
Wolper, C.; Schulz, S. Chem.−Eur. J. 2010, 16, 13599−13602.
̈
̈
̈
ASSOCIATED CONTENT
* Supporting Information
̈
■
S
̈
(e) Schulz, S.; Gondzik, S.; Schuchmann, D.; Westphal, U.;
Dobrzycki, L.; Boese, R.; Harder, S. Chem. Commun. 2010, 46,
7757−7759. (f) Schulz, S.; Schuchmann, D.; Westphal, U.; Bolte, M.
Organometallics 2009, 28, 1590−1592. (g) Schulz, S.; Schuchmann, D.;
Cif files of 1, 2, and 3. In addition, NMR and IR spectra of 1−3,
Et3In−It-Bu, Et3In, LGaEt2, and Cp*InEt2 and 1H NMR
spectra of thermal treatment of 1 and 2 as well as
crystallographic details are given in the SI. The Supporting
Information is available free of charge on the ACS Publications
website at DOI: 10.1021/acs.organomet.5b00302.
Krossing, I.; Himmel, D.; Blaser, D.; Boese, R. Angew. Chem. 2009,
̈
121, 5859−5862; Angew. Chem., Int. Ed. 2009, 48, 5748−5751.
(h) Schuchmann, D.; Westphal, U.; Schulz, S.; Florke, U.; Blaser, D.;
̈
̈
Boese, R. Angew. Chem. 2009, 121, 821−824; Angew. Chem., Int. Ed.
AUTHOR INFORMATION
Corresponding Author
*Phone: +49 0201-1834635. Fax: + 49 0201-1833830. E-mail:
stephan.schulz@uni-due.de.
2009, 48, 807−810.
■
(12) (a) Schulz, S.; Kuczkowski, A.; Schuchmann, D.; Florke, U.;
̈
Nieger, M. Organometallics 2006, 25, 5487−5491. (b) Schulz, S.;
Schoop, T.; Roesky, H. W.; Haming, L.; Steiner, A.; Herbst-Irmer, R.
Angew. Chem. 1995, 107, 1015−1016; Angew. Chem., Int. Ed. Engl.
1995, 34, 919−920. (c) Schulz, S.; Haming, L.; Herbst-Irmer, R.;
̈
Author Contributions
̈
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
Roesky, H. W.; Sheldrick, G. M. Angew. Chem. 1994, 106, 1052−1054;
Angew. Chem., Int. Ed. Engl. 1994, 33, 969−971. (d) Schulz, S.; Roesky,
H. W.; Koch, H.-J.; Sheldrick, G. M.; Stalke, D.; Kuhn, A. Angew.
Chem. 1993, 105, 1828−1830; Angew. Chem., Int. Ed. Engl. 1993, 32,
1729−1731.
Notes
The authors declare no competing financial interest.
(13) (a) Steiniger, P.; Bendt, G.; Blaser, D.; Wolper, C.; Schulz, S.
̈
̈
Chem. Commun. 2014, 50, 15461−15463. (b) Bendt, G.; Lapsien, S.;
ACKNOWLEDGMENTS
S.S. thanks the University of Duisburg−Essen for financial
support.
■
Steiniger, P.; Blaser, D.; Wolper, C.; Schulz, S. Z. Anorg. Allg. Chem.
̈
̈
2015, 641, 797−602.
(14) (a) Heimann, S.; Blaser, D.; Wolper, C.; Schulz, S.
̈
̈
Organometallics 2014, 33, 2295−2300. (b) Schulz, S.; Heimann, S.;
REFERENCES
Kuczkowski, A.; Blaser, D.; Wolper, C. Organometallics 2013, 32,
̈
̈
■
3391−3394. (c) Heimann, S.; Schulz, S.; Blaser, D.; Wolper, C. Eur. J.
̈
̈
(1) (a) Dohmeier, C.; Loos, D.; Schnockel, H. Angew. Chem. 1996,
̈
Inorg. Chem. 2013, 4909−4915. (d) Kuczkowski, A.; Heimann, S.;
Weber, A.; Schulz, S.; Blaser, D.; Wolper, C. Organometallics 2011, 30,
108, 141−161; Angew. Chem., Int. Ed. Engl. 1996, 35, 129−149.
(b) Rao, M. N. S.; Roesky, H. W.; Anantharaman, G. J. Organomet.
Chem. 2002, 646, 4−14. (c) Roesky, H. W.; Kumar, S. S. Chem.
Commun. 2005, 4027−4038. (d) Roesky, P. W. Dalton Trans. 2009,
1887−1893. (e) Asay, M.; Jones, C.; Driess, M. Chem. Rev. 2011, 111,
354−396. (f) Tsai, Y.-C. Coord. Chem. Rev. 2012, 256, 722−758.
̈
̈
4730−4735. (e) Kuczkowski, A.; Schulz, S.; Nieger, M. Angew. Chem.
2001, 113, 4351−4353; Angew. Chem., Int. Ed. 2001, 40, 4222−4224.
(15) Ganesamoorthy, C.; Blaser, D.; Wolper, C.; Schulz, S. Chem.
̈
̈
Commun. 2014, 50, 12382−12384.
(16) Ganesamoorthy, C.; Blaser, D.; Wolper, C.; Schulz, S. Angew.
(2) (a) Dohmeier, C.; Robl, C.; Tacke, M.; Schnockel, H. Angew.
̈
̈
̈
Chem. 2014, 126, 11771−11775; Angew. Chem., Int. Ed. 2014, 53,
Chem. 1991, 103, 594−595; Angew. Chem., Int. Ed. Engl. 1991, 30,
564−565. (b) Schulz, S.; Roesky, H. W.; Koch, H. J.; Sheldrick, G. M.;
Stalke, D.; Kuhn, A. Angew. Chem. 1993, 105, 1828−1830; Angew.
Chem., Int. Ed. Engl. 1993, 32, 1729−1731.
11587−11591.
(17) Ganesamoorthy, C.; Bendt, G.; Blaser, D.; Wolper, C.; Schulz, S.
̈
̈
Dalton Trans. 2015, 44, 5153−5159.
E
DOI: 10.1021/acs.organomet.5b00302
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(18) Beachley, O. T., Jr.; Blom, R.; Churchill, M. R.; Faegri, K., Jr.;
Fettinger, J. C.; Pazik, J. C.; Victoriano, L. Organometallics 1989, 8,
346−356.
(19) Pyykko, P.; Atsumi, M. Chem.−Eur. J. 2009, 15, 186−197.
̈
(20) Schmitt, A.-L.; Schnee, G.; Welter, R.; Dagorne, S. Chem.
Commun. 2010, 46, 2480−2482.
(21) (a) Arnold, P. L.; Pearson, S. Coord. Chem. Rev. 2007, 251, 596−
609. (b) Albrecht, M. Chem. Commun. 2008, 3601−3610. (c) Schuster,
O.; Yang, L.; Raubenheimer, H. G.; Albrecht, M. Chem. Rev. 2009, 109,
3445−3478. (d) Poulain, A.; Iglesias, M.; Albrecht, M. Curr. Org.
Chem. 2011, 15, 3325−3336. (e) Crabtree, R. H. Coord. Chem. Rev.
2013, 257, 755−766.
(22) (a) Tonner, R.; Heydenrych, G.; Frenking, G. Chem.Asian J.
2007, 2, 1555−1567. (b) Magill, A. M.; Yates, B. F. Aust. J. Chem.
2004, 57, 1205−1210. (c) Magill, A. M.; Kavell, K. J.; Yates, B. F. J.
Am. Chem. Soc. 2004, 126, 8717−8724. (d) Sini, G.; Eisenstein, O.;
Crabtree, R. H. Inorg. Chem. 2002, 41, 602−604.
(23) (a) Day, B. M.; Pugh, T.; Hendriks, D.; Guerra, C. F.; Evans, D.
J.; Bickelhaupt, F. M.; Layfield, R. A. J. Am. Chem. Soc. 2013, 135,
́
13338−13341. (b) Eguillor, B.; Esteruelas, M. A.; Olivan, M.; Puerta,
M. Organometallics 2008, 27, 445−448. (c) Saha, S.; Ghatak, T.; Saha,
B.; Doucet, H.; Bera, J. K. Organometallics 2012, 31, 5500−5505.
(d) Tan, K. V.; Dutton, J. L.; Skelton, B. W.; Wilson, D. J. D.; Barnard,
P. J. Organometallics 2013, 32, 1913−1923. (e) Segarra, C.; Mas-
Marza,
́
E.; Mata, J. A.; Peris, E. Organometallics 2012, 31, 5169−5176.
(f) Kruger, A.; Kluser, E.; Muller-Bunz, H.; Neels, A.; Albrecht, M. Eur.
̈
̈
J. Inorg. Chem. 2012, 1394−1402. (g) Chen, S.-J.; Lin, Y.-D.; Chiang,
Y.-H.; Lee, H. M. Eur. J. Inorg. Chem. 2014, 1492−1501. (h) Guo, T.;
Dechert, S.; Meyer, F. Organometallics 2014, 33, 5145−5155.
(24) Protchenko, A. V.; Dange, D.; Blake, M. P.; Schwarz, A. D.;
Jones, C.; Mountford, P.; Aldridge, S. J. Am. Chem. Soc. 2014, 136,
10902−10905.
(25) Todt, V. E.; Dotzer, R. Z. Anorg. Allg. Chem. 1963, 321, 120−
̈
123.
(26) Scott, N. M.; Dorta, R.; Stevens, E. D.; Correa, A.; Cavallo, L.;
Nolan, S. P. J. Am. Chem. Soc. 2005, 127, 3516−3526.
(27) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467−473.
(28) Sheldrick, G. M. SHELXL-2014, Program for the Refinement of
Crystal Structures; University of Gottingen: Gottingen, Germany),
̈
̈
2014. See also: Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112−122.
(29) shelXle, A Qt GUI for SHELXL: Hubschle, C. B.; Sheldrick, G.
̈
M.; Dittrich, B. J. Appl. Crystallogr. 2011, 44, 1281−1284.
F
DOI: 10.1021/acs.organomet.5b00302
Organometallics XXXX, XXX, XXX−XXX