Redox-Active Ligand-Assisted Two-Electron Oxidative Addition to Gallium(II)

Article abstract of DOI:10.1002/chem.201704128

The reaction of digallane (dpp-bian)Ga?Ga(dpp-bian) (2) (dpp-bian=1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with allyl chloride (AllCl) proceeded by a two-electron oxidative addition to afford paramagnetic complexes (dpp-bian)Ga(η¹-All)Cl (3) and (dpp-bian)(Cl)Ga?Ga(Cl)(dpp-bian) (4). Treatment of complex 4 with pyridine induced an intramolecular redox process, which resulted in the diamagnetic complex (dpp-bian)Ga(Py)Cl (5). In reaction with allyl bromide, complex 2 gave metal- and ligand-centered addition products (dpp-bian)Ga(η¹-All)Br (6) and (dpp-bian-All)(Br)Ga?Ga(Br)(dpp-bian-All) (7). The reaction of digallane 2 with Ph₃SnNCO afforded (dpp-bian)Ga(SnPh₃)₂ (8) and (dpp-bian)(NCO)Ga?Ga(NCO)(dpp-bian) (9). Treatment of GaCl₃ with (dpp-bian)Na in diethyl ether resulted in the formation of (dpp-bian)GaCl₂ (10). Diorganylgallium derivatives (dpp-bian)GaR₂ (R=Ph, 11; tBu, 14; Me, 15; Bn, 16) and (dpp-bian)Ga(η¹-All)R (R=nBu, 12; Cp, 13) were synthesized from complexes 3, 10, Bn₂GaCl, or tBu₂GaCl by salt metathesis. The salt elimination reaction between (dpp-bian)GaI₂ (17) and tBuLi was accompanied by reduction of both the metal and the dpp-bian ligand, which resulted in digallane 2 as the final product. Similarly, the reaction of complex 10 with MentMgCl (Ment=menthyl) proceeded with reduction of the dpp-bian ligand to give the diamagnetic complex [(dpp-bian)GaCl₂][Mg₂Cl₃(THF)₆] (18). Compounds 11, 12, 13, 15, and 16 were thermally robust, whereas compound 14 decomposed when heated at reflux in toluene to give complex (dpp-bian-tBu)GatBu₂ (19). Both complexes 7 and 19 contain R-substituted dpp-bian ligand: in the former compound the allyl group was attached to the imino-carbon atom, whereas in complex 19, the tBu group was situated on the naphthalene ring. Crystal structures of complexes 3, 8, 9, 10, 13, 14, 18, and 19 were determined by single-crystal X-ray analysis. The presence of dpp-bian radical anions in 3, 6, 8, and 10–16 was determined by ESR spectroscopy.

Full text of DOI:10.1002/chem.201704128

A Journal of
Accepted Article
Title: Redox-Active Ligand Assisted Two-Electron Oxidative Addition to
Gallium(II)
Authors: Igor L. Fedushkin, Vladimir Dodonov, Alexandra Skatova,
Vladimir Sokolov, Alexander Piskunov, and Georgii Fukin
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.201704128
Link to VoR: http://dx.doi.org/10.1002/chem.201704128
Supported by

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
Redox-Active Ligand Assisted Two-Electron Oxidative Addition to
Gallium(II)
Igor L. Fedushkin,*[a] Vladimir A. Dodonov,[a] Alexandra A. Skatova,[a] Vladimir G. Sokolov,[a] Alexander
V. Piskunov,[a] and Georgii K. Fukin[a]
Abstract: The reaction of digallane (dpp-bian)Ga–Ga(dpp-bian) (2)
(dpp-bian 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with
review article dealing with this subject, namely with aluminium
complexes of non-innocent ligands, has been published in
2015.[2] It is worth noting that some low-valent as well as metal-
metal bonded species of the p elements supported by sterically
encumbered ligands also reveal a reactivity that corresponds to
that of d metal complexes. Thus, Ga(I) and Al(I) ketiminates
[{HC(MeCNAr)2}M:] (Ar = 2,6-iPr2C6H3, M = Al, Ga) react with a
bulky organic azide resulting Ga(III) and Al(III) azides.[3] Similar
product has been obtained from the reaction of azide with
monovalent arylgallium [Ar'Ga:] (Ar' = 2,6-(2,6-iPr2C6H3)2C6H3).[4]
The latter compound reacts also in oxidative addition manner
with H2 or NH3 to afford gallium(III) species [Ar'Ga(µ-H)H]2 and
[Ar'Ga(µ-NH2)H]2 correspondingly.[5] With simple alkenes, e.g.
ethylene, propene, 1-hexene and styrene compound [Ar'Ga:] (Ar'
= 2,6-(2,6-iPr2C6H3)2C6H3) behaves as heavy group 13 carbene
analogue to afford the products of addition of two olefins per
Ar’GaGaAr’.[6] Further, the ketiminate [{HC(MeCNAr)2}Ga:]
smoothly reacts with triphenyltin hydride, ethanol, diethylamine,
and diphenylphosphine yielding the products of oxidative
addition.[7] But, the reductive elimination of a neutral organic
molecule or radical from the main group metal complex,
accompanied with the reduction of the metal to a lower oxidation
state, has not yet been observed. The only examples here are
decomposition of some organometallic compounds, e.g. R2Hg.
The latter thermally decomposes to give hydrocarbon radicals
and the products of their transformation besides the mercury
metal.
=
allylchloride (AllCl) proceeds as the two-electron oxidative addition
and affords paramagnetic complexes (dpp-bian)Ga(η1-All)Cl (3) and
(dpp-bian)(Cl)Ga–Ga(Cl)(dpp-bian) (4). Treatment of complex 4 with
pyridine induces intramolecular redox-process resulting diamagnetic
(dpp-bian)Ga(Py)Cl (5). With allylbromide complex 2 gives metal-
and ligand-centered addition products, (dpp-bian)Ga(η1-All)Br (6)
and (dpp-bian-All)(Br)Ga–Ga(Br)(dpp-bian-All) (7). The reaction of
digallane 2 with Ph3SnNCO affords (dpp-bian)Ga(SnPh3)2 (8) and
(dpp-bian)(NCO)Ga–Ga(NCO)(dpp-bian) (9). Treatment of GaCl3
with (dpp-bian)Na (in situ from Na and dpp-bian) in diethyl ether
results in the formation of (dpp-bian)GaCl2 (10). Diorganylgallium
derivatives (dpp-bian)GaR2 (R = Ph, 11; tBu, 14; Me, 15; Bn, 16) and
(dpp-bian)Ga(η1-All)R (R = nBu, 12; Cp, 13) were synthesized
starting from 3, 10, Bn2GaCl and tBu2GaCl by the salt metathesis.
The salt elimination reaction between (dpp-bian)GaI2 (17) and tBuLi
is accompanied with the reduction of the metal and of the dpp-bian
ligand resulting in digallane 2 as the final product. Similarly, the
reaction of 10 with MentMgCl (Ment = menthyl) proceeds with
reduction of dpp-bian ligand and results in diamagnetic complex
[(dpp-bian)GaCl2][Mg2Cl3(thf)6] (18). Compounds 11, 12, 13, 15 and
16 are rather thermally robust, while compound 14 decomposes in
toluene at reflux to complex (dpp-bian-tBu)GatBu2 (19). Both 7 and
19 contain R-substituted dpp-bian ligand: in the former compound
the allyl group is attached to imino-carbon atom, while in complex 19
the tBu group is situated in the naphthalene ring. Crystal structures
of 3, 8, 9, 10, 13, 14, 18 and 19 have been determined by single
crystal X-ray analysis. The presence of dpp-bian radical-anions in 3,
6, 8, 10-16 have been documented by the ESR spectroscopy.
1,2-Bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian)
is redox-active ligand system, which combines a high electron
affinity (four anionic states: 1–, 2–, 3– and 4–),[8] a steric
hindrance and a conformational rigidity. Since 2003 we reported
over 100 examples of dpp-bian complexes of s-, p-, d- and f-
elements. Most of them consist of mono- or dianionic dpp-bian
[9]
Introduction
ligand. A reactivity of two representatives, (dpp-bian)Mg(thf)3
(1) and (dpp-bian)Ga–Ga(dpp-bian)[10] (2) has been studied
utmost. Typical for compound 1 are: (i) addition of substrates in
the course of one-electron oxidation of the ligand resulting
magnesium–substrate bond;[9b, 9c] (ii) addition of organic halides
R–X to the both, ligand and metal, to afford L–R and M–X
bonds;[9d, 9e] (iii) addition of terminal alkynes, nitriles and enols
via protonation of dianionic dpp-bian ligand resulting magnesium
acetylenides, keteniminates and enolates.[9f-i] In contrast,
Redox-active ligands can substantially expand reactivity of metal
complexes, thus providing for an entry to catalysis. However, up
to now redox-active ligands are designated to construct mainly
complexes of transition metals.[1] Among them are accessible Ni,
Co and Fe, whose complexes with redox-active ligands may be
alternatives for classical Pd, Pt, Rh and Ru spectator ligand-
based catalysts. Main group metal complexes of redox-active
ligands also reveal specific reactivity, but they have not yet been
recognized as promising catalysts for organic synthesis. A sole
compound 2 reacts with different alkynes to form cycloadducts
10c]
that liberate “coordinated” alkyne at heating.[10b,
Towards
oxidizing reagents compound 2 reveals an electron transfer
dualism: depending on the substrate oxidation may occur first on
the ligands[10d, 10e] or involve the metal–metal bond[10f, 10g]. The
substrates used before in oxidative addition reactions to
complex 2 are limited to iodine and disulfides. Here we report on
(i) reactivity of digallane 2 towards AllX (X = Cl, Br) and
Ph3SnNCO; and (ii) syntheses and characterization of
diorganylgallium species supported by radical-anion of dpp-bian.
[a]
Prof. Dr. Igor L. Fedushkin, Mr. Vladimir A. Dodonov, Prof. Dr.
Alexandra A. Skatova, Dr. Vladimir G. Sokolov, Prof. Dr. Alexander
V. Piskunov, Prof. Dr. Georgii K. Fukin
G.A. Razuvaev Institute of Organometallic Chemistry of Russian
Academy of Sciences
Tropinina 49, 603137 Nizhny Novgorod, Russian Federation
E-mail: igorfed@iomc.ras.ru
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
Results and Discussion
solvent-induced intramolecular electron transfer when dissolved
in pyridine.[10d] Similarly, treatment of the brown solid obtained in
the reaction of 2 with allylchloride resulted in blue solution, from
which complex (dpp-bian)Ga(Py)Cl (5) was isolated as blue
crystals (Scheme 2).
Addition of two molar equivalents of allylchloride to a solution of
digallane 2 in thf at –50 °С caused a change of color of a
mixture within 1 h from deep-blue to red-brown. This color
change is indicative for oxidation of dpp-bian dianion to radical-
anion. Addition of hexane to the residue left after evaporation of
thf gave a brown powder and a clear red-brown hexane solution.
Crystallization from hexane afforded (dpp-bian)Ga(η1-All)Cl (3)
in 31 % yield in a form of brown crystals (Scheme 1).
Ar
N
Cl
120 °C
ampule
pyridine,
5
Ga
4
sealed
Py
N
Ar
Ar
N
Ar
N
Scheme 2. Synthesis of compound 5.
Ga Ga
=
Ar
iPr
H3
2C6
2,6-
N
N
The 1H NMR spectrum of compound 5 is rather simple. It
consists of four doublets and two septets of iso-propyl groups;
naphthalene protons appear as triplet and two doublets in
aromatic region. Thus, the brown powder formed in the reaction
of digallane 2 with allylchloride, probably, consists of compound
(dpp-bian)(Cl)Ga–Ga(Cl)(dpp-bian) (4). Notable, the reactions of
digallane with allylchloride in the molar ratio of 1:2.5, 1:5, 1:25
led to the same products in analogous yields. The reactivity of
digallane 2 towards allylchloride can be compared with that of
gallium complexes of redox-active o-iminobenzoquinone. Thus,
the reactions of [(AP)2Ga]Na(thf)2 [AP = 4,6-di-tert-butyl-N-(2,6-
di-iso-propylphenyl)-o-amidophenolate] with allylhalides proceed
with transfer of the allyl radical to the redox-active ligand and
afford five-coordinate species (All-AP)2GaX (X = Cl, Br, I).[11] Tin
and indium amidophenolates react with alkyl- and allylhalides in
the same manner: a ligand-centered oxidative addition along
with a C–C bond formation.[12] Reactivity of magnesium complex
(dpp-bian)Mg(thf)3 towards RX is similar.[9d, 9e]
Ar
Ar
2
-50 °C
+ Cl
thf,
Ar
N
Ar
N
Cl
Ar
N
Ga
+
Ga
N
Ga
N
Cl
Ar
N
Ar
Cl
Ar
3
4
Scheme 1. The reaction of digallane 2 with allylchloride.
In the course of the reaction, each half of the dimeric molecule
2 undergoes two-electron oxidation: gallium atoms change their
oxidation state from +2 to +3 and dpp-bian ligands change their
reduction state from –2 to –1. Due to the presence of dpp-bian
radical-anion compound 3 reveals the ESR signal (Figure 1),
whose hyper-fine structure is caused by the interaction of the
unpaired electron with two equivalent 14N nuclei, four equivalent
protons, magnetic isotopes of gallium 69Ga and 71Ga as well as
chlorine isotopes 35Cl and 37Cl.
Addition of four molar equivalents of allylbromide to a solution
of digallane 2 in toluene (–50 °С) caused a change of a color of
the mixture from deep-blue to brown. A study of the reaction
mixture by ESR spectroscopy (Figure 2) indicates the presence
of complex (dpp-bian)Ga(η1-All)Br (6).
Figure 1. ESR spectra of complex 3: (red) experimental (thf, 295 K); (blue)
simulated (gi = 2.0021; hfs constants: ai(2×14N) = 0.52, ai(69Ga) = 1.02,
ai(71Ga) = 1.30, ai(35Cl) = 0.22, ai(37Cl) = 0.18, ai(4×1H) = 0.10 mT).
Figure 2. ESR spectra of complex 6: (red) experimental (Et2O, 295 K); (blue)
simulated (gi = 2.0014; hfs constants: ai(2×14N) = 0.48, ai(69Ga) = 1.06,
ai(71Ga) = 1.35, ai(79Br) = 1.07, ai(81Br) = 1.15, mT, ai(4×1H) = 0.10 mT).
The brown powder left after the isolation of compound 3 is
poorly soluble in hexane, toluene and thf. At 293 K it does not
reveal any ESR signal neither in solution, nor in the solid state,
although it’s IR spectrum is identical to recently reported iodine
derivative (dpp-bian)(I)Ga–Ga(I)(dpp-bian), which undergoes
However, the work up of the reaction mixture afforded in 66 %
yield diamagnetic complex (dpp-bian-All)(Br)Ga–Ga(Br)(dpp-
bian-All) (7) (Scheme 3). Calculating on gallium moiety, the
complexes 6 and 7 have the same chemical composition. Both 6
and 7 are formed in the course of a formal two-electron oxidative
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
addition of allylbromide to digallane 2. Compound 6 is a metal-
NCO bond under electron transfer from digallane 2. In turn it
centered addition product.
should result in isocyanate anions and stannyl radicals.
2
2
toluene,
Et
70 °C
2O,
+ Br
Ph3SnNCO
+
-50 °C
Ar
Ar
Ar
Ar
N
NCO
Br
N
Ar
N
Ar
N
N
N
SnPh3
Ga
Ga
Br
Ga
+
+
Ga
N
Ga
N
Ar
Ga
N
SnPh3
N
Br
Ar
N
N
Ar
OCN
Ar
Ar
Ar
6
7
9
8
Scheme 3. The reaction of digallane 2 with allylbromide.
Scheme 4. The reaction of digallane 2 with Ph3SnNCO.
Then, anions might coordinate to gallium centers in [2]2+
resulting product 9, while the radicals might recombine to give
Ph3SnSnPh3. Later on, the subsequent oxidative addition of
Ph3SnSnPh3 to digallane 2 would give compound 8. However,
the test reaction shows that it is not the case: compound 2 and
Ph3SnSnPh3 do not interact even at reflux in toluene. Moreover,
Ph3SnSnPh3 was not detected in the mixture. Therefore, one
can suggest that Ga–Sn bonded species (including product 8)
were formed at the stage of electron transfer from compound 2
to Ph3SnNCO. On the other hand, generation of gallene species
[(dpp-bian)Ga:] (similar to ketiminate[13] and amidinate[14] gallium
Complex 7 is a result of a ligand-metal cooperative behavior: the
N,N-ligand is participating directly in bond-breaking/making
steps within the reaction. Since X-ray quality crystals of complex
7 could not be isolated we have used different NMR experiments
(see Supporting Information) to determine the atom connectivity
in 7. Addition of the allyl group to one of imino carbon atoms
makes this atom chiral. The 13C NMR spectrum of complex 7
reveals 39 signals. It means that carbon atoms in each
metallofragment in 7 are not equal. Also, all the protons of each
half of dimeric molecule, except protons in the CH3 groups, are
magnetically nonequivalent: the 1H NMR spectrum consists of
eight doublets and of four septets of the iso-propyl groups;
naphthalene protons appear as one pseudo triplet and one
doublet of doublets + three doublets in aromatic region; allyl
protons give rise to five distinct signals at 4.62, 4.57, 4.20, 4.17
and 3.44 ppm. The signals at 195 and 80 ppm in the 13C NMR
spectrum correspond to two carbon atoms in the metallacycle:
the low-field signal arises from imino-group (>C=N(Ar)→Ga),
while the amido-group (>C(All)–N–Ga) results in the signal at 80
ppm. Accordingly, the long-range 1H-13C correlation displays
coupling of the imino-group carbon (195 ppm) to α-methylene
protons of the allyl substituents as well as to two naphthalene
protons; the amido-group carbon (80 ppm) is coupled to α-
methylene and methine protons of the allyl substituent as well as
to two other protons of the naphthalene moiety.
Heating of digallane 2 with two molar equivalents of
Ph3SnNCO in diethyl ether at 70 °С (sealed under vacuum glass
ampoule) within 7 days resulted in a gradual color change of the
reaction mixture from deep-blue to red-brown. Concentration of
the reaction solution gave a mixture of crystals – pink needles
and brown prisms. The X-ray single crystal analysis has shown
that the needles consist of complex (dpp-bian)Ga(SnPh3)2 (8),
while the prismatic crystals are assembled from compound
(dpp-bian)(NCO)Ga–Ga(NCO)(dpp-bian) (9) (Scheme 4). An
estimation of the ratio of compounds 8 and 9 in the mixture of
the crystals obtained is difficult: the NMR spectroscopy cannot
be applied for identification of 8 and 9 due to the presence of the
dpp-bian radicals. The ESR spectroscopy is not useful as well
because only mononuclear compound 8 can be detected.
Considering the amount of dpp-bian used for the preparation of
starting digallane 2 (0.5 g) a yield of the mixture 8 and 9 (0.4 g)
seems to be moderately good. The presence of complex 9
among the products allows suggesting a cleavage of the Sn–
carbene analogues) from digallane
2 under attack from
Ph3SnNCO cannot be excluded. Recently, [(dpp-bian)Ga:] has
been generated from digallane 2 and stabilized by coordination
to transition metals.[15] An oxidative addition of Ph3SnNCO to
[(dpp-bian)Ga:] would afford [(dpp-bian)Ga(NCO)SnPh3], which
in its turn might react with 2 resulting products 8 and 9. It is
worth noting, that oxidative addition of triphenyltinhydride to
ketiminate-based gallium carbenioide [LGa:] (L = HC(MeCNAr)2)
has been reported.[7] The latter also reacts with SnCl2 to afford
compound featuring Ga–Sn bond, [(LGaCl)2Sn7].[16]
Complexes 8 and 9 are paramagnetic due to the presence of
dpp-bian radical-anions. For the ESR experiments the crystals of
8 were separated manually from those of compound 9. The ESR
signal of complex 8 (Figure 3) reveals a hyper-fine structure due
to the coupling of the unpaired electron to the hydrogen,
nitrogen, gallium and tin nuclei. Twenty-one narrow lines in the
central part of the spectrum depicted in Figure 3 correspond to
the molecules that contain magnetic as well as nonmagnetic tin
isotopes. The molecules of 8 that contain either 117Sn or 119Sn
magnetic isotopes are responsible for the low intensity satellites
located left and right from the central part. The signals marked
with asterisks are satellites of satellites. These components
belong to the complex molecules containing simultaneously
117Sn and 119Sn isotopes. Earlier, this spectroscopic pattern was
reported for tin derivatives of o-semiquinonate radical ligand.[17]
Due to the biradical character compound 9 does not reveal a
well resolved ESR signal. In the solid state and in solution
(toluene) compound 9 exhibits only broad signal. In the IR
spectrum of manually separated crystals of complex 9 the
intense absorption at 2220 cm–1 correspond to N=C=O
stretching vibrations.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
Before examining transmetalation reactions with compound
(dpp-bian)Ga(η1-All)Cl (3) we decided to develop synthetic
procedure that would allow isolation of 3 in a better yield. A first
step might be a complex (dpp-bian)GaCl2 (10). This compound
was prepared earlier by treatment (dpp-bian)CoCl2 with gallium
metal.[18] We have found that a salt metathesis reaction between
GaCl3 and (dpp-bian)Na in diethyl ether results in the complex
10 as brown crystals in 89 % yield (Scheme 5).
unstable complex (dpp-bian)GatBu2 (14), which undergoes
reductive elimination of tetramethylbutane to result digallane 2.
Since we failed to detect complex (dpp-bian)GatBu2 (14) among
the products of the reaction between 10 and tBuMgCl we
attempted preparation of complex 14 starting from tBu2GaCl,
which is stable both in the solid state and in solution. Notably,
treatment of tBu2GaCl with (dpp-bian)Na is not accompanied
with a change of color of the reaction mixture from red-brown to
blue. Crystallization from diethyl ether gave brown crystal of
compound 14 (47 %), which is stable in the solid state as well as
in solution at ambient temperature. Although complex 14 indeed
decomposes in toluene at high temperature, digallane 2 was not
detected among the decomposition products (vide infra).
Dimethyl- and dibenzylgallium derivatives supported by dpp-bian
radical-anion, (dpp-bian)GaMe2 (15) and (dpp-bian)GaBn2 (16),
were prepared similarly using Me2GaCl and Bn2GaCl as starting
materials correspondingly. Complexes 11-16 demonstrate well-
resolved isotropic ESR signals (Table 1, Figure 4).
Table 1. The parameters of the ESR signals of complexes 11-16.
Ar
N
Ar
N
R
R
All
Ga
Ga
N
N
R
Ar
Ar
= n
R
=
12
;
Cp,
13
11
;
14
15
;
Bn,
16
R
t
;
Bu,
Ph,
Bu,
Me,
Figure 3. ESR spectra of compound 8: (red) experimental (toluene, 295 K);
(blue) simulated (gi = 2.0025; hfs constants: ai(2×14N) = 0.53, ai(4×1H) = 0.11,
ai(69Ga) = 2.05, ai(71Ga) = 2.60, ai(2×117Sn) = 11.3, ai(2×119Sn) = 11.8 mT). The
spectral components arisen from the molecules containing simultaneously
117Sn and 119Sn isotopes are marked by asterisks.
ai(69Ga)
ai(71Ga)
1.70
2.16
1.78
2.26
1.50
1.91
1.57
2.00
1.73
2.20
1.73
Complex
gi
ai(2×14N)
ai(4×1H)
11a
12b
13b
14c
15c
16c
2.0025
2.0027
2.0025
2.0028
2.0026
2.0025
0.55
0.54
0.52
0.50
0.54
0.54
0.10
0.10
0.10
0.10
0.10
0.10
Ar
(dpp-bian)Na
+
Cl
Cl
N
Et
RT
2O,
10
Ga
-
NaCl
N
GaCl3
Ar
Scheme 5. Preparation of complex 10.
2.19
a in thf; b in toluene; c in Et2O
Treatment of complex 10 with one equivalent of AllMgCl in
diethyl ether resulted in a slight color change from brown to red-
brown. Crystallization from hexane gave compound 3 in 92 %
yield. The identity of compound 3 prepared by the salt
metathesis reaction has been confirmed by ESR and IR
spectroscopy as well as by the single crystal X-ray analysis.
As intended, the formation of diorganylgallium species
supported by dpp-bian ligand was achieved by the reactions of
complexes 3 and 10 with organolithium or -sodium reagents.
Thus, the reaction of complex 10 with PhLi produces compound
(dpp-bian)GaPh2 (11), while the reactions of complex 3 with
nBuLi and CpNa afford compounds (dpp-bian)Ga(η1-All)nBu (12)
and (dpp-bian)Ga(η1-All)Cp (13) correspondingly. Since the
reduction state of the dpp-bian ligands was not changed on
going from compounds 3 and 10 to the products 11, 12 and 13
no significant color alteration was observed in these reactions.
In contrast, treatment of complex 10 with two equivalents of
tBuMgCl in diethyl ether resulted in instant color change from
Figure 4. ESR spectra of compound 16: (red) experimental (Et2O, 295 K);
(blue) simulated (for parameters used in simulation see Table 1).
1
red-brown to deep-blue. The H NMR spectrum of the reaction
The formation of digallane 2 in the reaction of compound 10 with
tBuMgCl may happen if the latter is strong enough to reduce
mixture indicates the formation of digallane 2. Based on this fact
we have suggested that the reaction of 10 with tBuMgCl gives
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
radical-anion of dpp-bian to dianion. In order to prove the redox
process we decided to try tBuLi as reducing agent towards
complex (dpp-bian)GaI2 (17).[19] These reagents are easily
available. For instance, compound 17 can be obtained
quantitatively reacting digallane 2 with iodine. The former, in its
turn, can be prepared directly from gallium metal and dpp-bian in
quantitative yield. Addition of one molar equivalent of tBuLi to
red-brown solution of complex 17 in hexane at 20 °C resulted
instantly in brown solid, which was identified by IR spectroscopy
as complex (dpp-bian)(I)Ga–Ga(I)(dpp-bian).[10d] Upon addition
of a second equivalent of tBuLi the brown solid dissolved
completely to give deep blue solution. Examination of this
solution by the 1H NMR spectroscopy revealed formation of
digallane 2. This result was supported by NMR scale reaction of
crystalline (dpp-bian)(I)Ga–Ga(I)(dpp-bian) with two equivalents
of tBuLi in C6D6 resulting in the formation of digallane 2 as well
as isobutane and isobutene as main products. The formation of
C4H10 and C4H8 is indicative for a radical mechanism. Two
reaction routes to tert-butyl radicals in this system are possible.
The first one – intermolecular electron transfer from tBuLi to 17
resulting [(dpp-bian)GaI2]–Li+ and tBu radicals. The latter
undergo the known evolution to isobutane and isobutene, while
the former eliminates lithium iodide resulting in the known
compound (dpp-bian)(I)Ga–Ga(I)(dpp-bian). The second route
includes the formation of (dpp-bian)Ga(tBu)I, which undergoes
one-electron reductive elimination of tBu radical. At present we
are not able to make a preference for one of the mechanisms
considered. But, it is worth noting that stable in hexane solution
magnesium complex (dpp-bian)Mg(iPr)(Et2O) being dissolved at
room temperature in Et2O rapidly eliminates iPr radical.[20]
Another example of the reduction of dpp-bian radical-anion with
organometallic reagent is the reaction of compound 10 with
bulky Gringard reagent MentMgCl (Ment = menthyl) (Scheme 6).
The product [(dpp-bian)GaCl2][Mg2Cl3(thf)6] (18) was isolated in
a form of green diamagnetic crystals in 42 % yield.
tBu2GaCl. An extremely high solubility of complex 19 allows its
isolation only in a low yield (14 %).
Ar
N
Ar
N
tBu
tBu
tBu
tBu
90
3h
toluene,
sealed
°C,
tBu
Ga
Ga
ampule
N
N
H
Ar
Ar
14
19
Scheme 7. Thermally induced transformation of complex 14 to compound 19.
To determine an atom-connectivity in compound 19 numerous
NMR experiments were undertaken. Finally, it has been found
that complex 19 resulted from recombination of tBu radical with
dpp-bian radical-anion. Addition of tert-butyl radical to compound
14 made the molecule of the product 19 to chiral. An asymmetry
of the molecule causes non-equivalence of all the carbon atoms
as well as of all the protons except of those in the CH3 groups.
Methyl hydrogens of isopropyl groups appear as six doublets
(3H each) and one pseudotriplet (6H). Methine protons give rise
to 4 septets (1H each), while tBu substituents produce three
singlets at 1.45, 1.20, 0.72 ppm (9H each). A proton attached to
the sp3 carbon gives rise to a doublet at 2.9 ppm, while the
hydrogens of non-aromatic double C–C bond give rise to two
1
signals (1H each) at 5.22 and 5.32 ppm. According to the H-1H
NOESY experiment the protons of the tBu groups at gallium
interacts with methine protons of iso-propyl groups. The protons
of the tBu group in the six-membered cycle give rise to NOE
signals with one aromatic and two olefinic protons (see
Supporting Information). The molecular structure of complex 19
has been further confirmed by the single crystal X-ray analysis.
Compounds 7 and 19 represent the metal complexes with
substituted dpp-bian ligand. Earlier we have shown that the
reactions of the dpp-bian with Grignard reagents,[9e] nBuLi[22] and
group 13 organometallics proceed with alkylation of the dpp-bian
at one of the imino carbon atoms.[23] Related metal complexes
with substituted bian ligands were obtained by Dagorne and co-
workers reacting bians with Zn-organometallics.[24] These zinc
derivatives were found to be highly active catalysts in the ROP
of ε-caprolactone.[24] A different type of addition to dpp-bian was
reported by Hill and co-workers in 2011. Thus, the reactions of
bulky organometallics, e.g. K[CH(SiMe3)2] and M[CH(SiMe3)2]2
(M = Mg, Ca, Sr) with dpp-bian led to dearomatisation of one of
the six-membered rings via an addition of the nucleophile to
naphthalene ring.[25] These processes have been studied in
details by Cowley and co-workers in 2013.[26] They concluded
that functionalization of bians by organometallic species is
sterically directed. Apparently, the formation of the complexes 7
and 19 are also sterically controlled processes.
The charge states of the dpp-bian ligands in the compounds
reported here were further confirmed by spectroscopic methods.
According to the UV/VIS/NIR spectroscopy (see Supporting
Information, Figs. 20-24) all compounds reveal strong absorption
in the ultra-violet region (< 350 nm). This absorption can be
found in the absorption spectrum of free dpp-bian[27] and can be
assigned to intra-ligand transitions in the aromatic fragments.
The spectra of compounds 3, 8, 9, 11, 13, 15 and 16 in a visible
region are similar and indicate the presence of radical-anion of
dpp-bian. To compare, complexes (dpp-bian)Li[28] and [(dpp-
bian)CrCl(thf)]2[29] exhibit the absorption in the range 420-550 nm.
M
g2
l
THF
r
C 3
(
)
6
+
r
M l
C
g
A
N
A
l
C
l
C
N
a
G
a
G
N
N
l
C
l
C
-
50 °
Et2
O
,
C
r
r
A
A
18
10
Scheme 6. Reaction of complex 10 with menthylmagnesiumchloride.
Seeking for a reductive elimination in the dpp-bian gallium
derivatives we have studied solution behavior of compounds 11-
[21]
16 as well as of complex (dpp-bian)Ga(C≡CPh)2
at high
temperature. Except of complex 14 all the compounds are stable
in solution under heating up to 130 °С and UV irradiation. In
contrast, in toluene at 90 °С within 3 h compound 14 undergoes
complete decomposition, which is accompanied with a color
changed from brown to green. Decomposition products are
extremely soluble in hexane. One of the products - (dpp-bian-
tBu)GatBu2 (19) (Scheme 7) was isolated from a highly
concentrated hexane solution (< 1 mL) in a form of green
crystals. Alternatively compound 19 can be obtained reacting
(dpp-bian-tBu)Li (in situ from dpp-bian and tBuLi in hexane) with
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
The spectra of complexes 5 and 18 consist of absorptions with
maxima at 528 and 704 nm that correspond to dianionic dpp-
bian ligand.[10b, 28]
The Ga–Sn bonds (2.6464(8) and 2.6406(9) Å) in complex 8
(Figure 6) are practically equal to the sum of the covalent radii
for two elements (2.65 Å).[31] These values are somewhat longer
than the Ga–Sn bond lengths in the gallium β-diketoiminates
[(ddp)Ga(Ph3Sn)(H)] (2.6020(5) Å)[7] and [Sn7(Ga(ddp)Cl)2]
(2.598(3) and 2.580(4) Å)[16] (ddp = HC(MeCNAr)2). On the other
hand, the Ga–Sn bonds in 8 are shorter compare to coordinative
Ga–Sn bonds in [K(tmeda)][R2SnGa{[N(Ar)C(H)]2}] (2.7186(6) Å),
Molecular structures of compounds 3, 8, 9, 10, 13, 14, 18
and 19. Molecular structures were determined by the single
crystal X-ray analysis. Crystal data and structure refinement
details are collected in Supporting Information. Compounds 3, 8,
9, 10, 13 and 14 represent the four-coordinate monomeric
gallium complex of dpp-bian radical-anion. For instance, the
C(1)–N(1) (1.344(5) Å) and C(2)–N(2) (1.330(5) Å) bonds in
compound 3 (Figure 5) are ca. 0.05 Å longer compared to free
dpp-bian.[30] On the other hand these bonds are ca. 0.05 Å
shorter than those bonds in the dpp-bian dianion in the metal
complexes, for instance, in digallane 2 (1.393(3) and 1.389(3)
[K(tmeda)][Ar''2SnGa{[N(Ar)C(H)]2}] (2.6660(18) Å) (R
=
CH(SiMe3)2, Ar = dpp, Ar'' = C6H2iPr3-2,4,6)[32] and in complex
[{Li(thf)Sn(2-pyR)3}GaEt3] (2.7196(11) Å) (pyR = C5H3N-5-Me).[33]
The molecule of compound 9 (Figure 7) is situated on the
crystallographic inversion center, which is located at the middle
of the gallium–gallium bond. Coordination tetrahedrons of the
Å).[10a] As expected, the Ga–N distances in complexes 3, 8, 9, 10, both metal atoms are slightly distorted. The acenaphthene-1,2-
13 and 14 are longer than in compound 2 (average 1.860 Å). In
complex 3 the allyl group binds to Ga in η1-fashion.
diimine planes are parallel to each other with gallium atoms lying
almost perfectly within the planes estimated with atoms N(1)–
C(1)–C(2)–N(2) and their symmetry equivalent counterparts.
The Ga–Ga distance in compound 9 (2.4605(7) Å) corresponds
to covalent bond. This distance is remarkably longer than that in
starting digallane (dpp-bian)Ga–Ga(dpp-bian) (2.3598(3) Å)[10a]
,
but is virtually the same with the metal–metal bond length in
(dpp-bian)Ga(I)–Ga(I)(dpp-bian) (2.4655(5) Å)[10d]. Equality of
the Ga–N(1) and Ga–N(2) bonds in 9 (1.990(3) and 1.992(3) Å)
indicates an effective delocalization of the electron density within
the diimine fragment. In the isocyanate ligands distances N(3)–
C(37) (1.125(6) Å) and C(37)–O(1) (1.183(6) Å) correspond to
the double bonds and are close to those in Ge(tmtaa)(NCO)2
(tmtaa
=
tetramethyldibenzotetraazacyclotetradecine; N=C,
1.163 Å; C=O, 1.188 Å).[34]
Figure 5. Molecular structure of 3. Thermal ellipsoids are 50 % probability.
Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (°): Ga–
N(1) 1.956(3), Ga–N(2) 1.961(4), Ga–C(37) 1.981(4), Ga–Cl(1) 2.1920(12),
N(1)–C(1) 1.344(5), N(2)–C(2) 1.330(5), C(1)–C(2) 1.428(5), C(37)–C(38)
1.484(6), C(38)–C(39) 1.303(8), N(2)–Ga–C(37) 118.43(15), N(1)–Ga–Cl(1)
108.93(10), N(1)–Ga–N(2) 86.19(14), N(1)–Ga–C(37) 116.81(15).
Figure 7. Molecular structure of 9. Thermal ellipsoids are 20 % probability.
Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (°): Ga–
N(3) 1.893(3), Ga–N(1) 1.990(3), Ga–N(2) 1.992(3), Ga–Ga' 2.4605(7), O(1)–
C(37) 1.183(6), N(1)–C(1) 1.342(4), N(2)–C(2) 1.336(4), N(3)–C(37) 1.125(6),
C(1)–C(2) 1.427(5), N(1)–Ga–N(2) 84.92(11), C(37)–N(3)–Ga 149.2(4), N(3)–
Ga–N(1) 107.02(13).
Unlike the literature data,[18] compound 10 (Figure 8)
crystallized in the monoclinic space group P21/c with two
molecules in the unit cell. In contrast to the reported structure
compound 10 does not contain the lattice Et2O molecules. On
the other hand the key bond lengths in the metallofragment are
almost identical to that published[18] and thus confirm radical-
anionic state of the dpp-bian ligand.
Figure 6. Molecular structure of 8. Thermal ellipsoids are 70 % probability.
Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (°): C(1)–
N(1) 1.343(8), C(2)–N(2) 1.346(8), C(1)–C(2) 1.435(9), Ga–Sn(1) 2.6464(8),
Ga–Sn(2) 2.6406(9), Ga–N(1) 1.988(5), Ga–N(2) 2.019(6), N(1)–Ga–N(2)
86.1(2), N(1)–Ga–Sn(2) 118.69(16), Sn(1)–Ga–Sn(2) 110.97(3).
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
In complex 13 (Figure 9) the allyl and Cp groups are η1-bound
to Ga atom. The Ga–C(Cp) distance (2.0421(18) Å) is slightly
longer than that in (dpp-dad)GaCp* (1.973(4) Å).[35] The
alternation of C–C distances within the Cp ring is typical for a σ-
bonding. The bond lengths in allyl fragment (C(37)–C(38)
1.492(4) and C(38)–C(39) 1.309(3) Å) are very close to those in
complex 3 (C(37)–C(38) 1.484(6) and C(38)–C(39) 1.303(8) Å).
gallium atom. All these features of the structure of complex 14
may determine its thermal lability.
In the crystal of complex 18 the anions [(dpp-bian)GaCl2] and
cations [Mg2Cl3(thf)6] are isolated from each other (Figure 11).
The same structure was found in [(dpp-bian)AlCl2][Mg2Cl3(thf)6],
which was isolated from the reaction of (dpp-bian)Mg(thf)3 with
AlCl3.[37] The alteration of bond lengths in gallium metallacycles
on moving from the neutral complex (dpp-bian)GaCl2 (10) to
anion [(dpp-bian)GaCl2] in 18 (Figures 8 and 11 respectively)
reflects the geometrical differences between the radical-anion
and the dianion of dpp-bian.
Figure 8. Molecular structure of 10. Thermal ellipsoids are 50 % probability.
Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (°): Ga–
N(1) 1.9412(17), Ga–N(2) 1.9410(16), Ga–Cl(1) 2.1592(6), Ga–Cl(2)
2.1584(6), N(1)–C(1) 1.341(2), N(2)–C(2) 1.336(3), C(1)–C(2) 1.435(3), N(1)–
Ga–N(2) 88.02(7), Cl(1)–Ga–Cl(2) 109.02(2), N(1)–Ga–Cl(2) 115.64(6), N(2)–
Ga–Cl(2) 115.30(6).
Figure 10. Molecular structure of 14. Thermal ellipsoids are 50 % probability.
Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (°): Ga–
N(1) 2.0729(10), Ga–N(2) 2.0496(10), Ga–C(37) 2.0275(12), Ga–C(41)
2.0162(12), N(1)–C(1) 1.3404(14), N(2)–C(2) 1.3354(15), C(1)–C(2)
1.4285(16), N(1)–Ga–N(2) 83.19(4), C(37)–Ga–Cl(41) 116.64(5), N(1)–Ga–
C(37) 110.15(5), N(2)–Ga–C(37) 111.18(5).
Figure 9. Molecular structure of 13. Thermal ellipsoids are 30 % probability.
Hydrogen atoms are omitted. Selected bond lengths (Å) and angles (°): Ga–
N(1) 2.0044(14), Ga–N(2) 1.9982(14), Ga–C(37) 1.9855(19), Ga–C(40)
2.0421(18), N(1)–C(1) 1.331(2), N(2)–C(2) 1.334(2), C(1)–C(2) 1.431(2),
C(37)–C(38) 1.492(4), C(38)–C(39) 1.309(3), C(41)–C(42) 1.355(3), C(42)–
C(43) 1.414(4), C(43)–C(44) 1.358(4), N(1)–Ga–C(37) 111.23(10), N(2)–Ga–
C(37) 119.40(15), N(1)–Ga–C(40) 111.12(7), N(1)–Ga–N(2) 84.28(6), Ga–
C(40)–C(41) 99.50(13), Ga–C(40)–C(44) 99.16(13).
Figure 11. Molecular structure of anion [(dpp-bian)GaCl2] in complex 18.
Thermal ellipsoids are 20 % probability. Hydrogen atoms are omitted. Selected
bond lengths (Å) and angles (°): Ga–N(1) 1.890(4), Ga–N(2) 1.877(4), Ga–
Cl(1) 2.1880(15), Ga–Cl(2) 2.254(3), N(1)–C(1) 1.378(7), N(2)–C(2) 1.394(6),
C(1)–C(2) 1.370(7), N(1)–Ga–N(2) 90.83(18), Cl(1)–Ga–Cl(2) 104.28(8),
N(1)–Ga–Cl(2) 115.97(14), N(2)–Ga–Cl(2) 116.15(12).
In contrast to 3, 8-10 and 13, the gallium atom in complex 14
is positioned out of dpp-bian plane (the torsion angle C(1)–C(2)–
N(2)–Ga is 10.9°). For comparison, the respective torsion angles
in compounds 3 and 10 are 0.2 and 2.1° correspondingly.
Further the Ga–N(1) and Ga–N(2) distances (2.0729(10) and
2.0496(10) Å correspondingly) in complex 14 are the longest
among the compounds 3, 8-10 and 13. In compound 14 the
bonds Ga–C(37) and Ga–C(41) (2.0275(12) and 2.0162(12) Å
correspondingly) are elongated in comparison to Ga–C(tBu)
bonds in trimeric (tBu2GaCl)3 (1.981 Å).[36] It could be attributed
to sterical hindrance caused by interaction of di-iso-propylphenyl
substituents in the bian ligand and the bulky tBu groups at the
The bond distances within metallacycle in anion [(dpp-
bian)GaCl2] (Ga–N(1) 1.890(4), Ga–N(2) 1.877(4), N(1)–C(1)
1.378(7), N(2)–C(2) 1.394(6), C(1)–C(2) 1.370(7) Å) are well
compared with those in digallane 2 (Ga–N(1) 1.8624(18), Ga–
N(2) 1.8583(18), N(1)–C(1) 1.393(3), N(2)–C(2) 1.389(3), C(1)–
C(2) 1.375(3) Å)[10a] and in dithiocarbamate derivative (dpp-
bian)Ga[SC(S)NMe2] (Ga–N(2) 1.8718(18), Ga–N(2) 1.8826(17),
N(1)–C(1) 1.385(3), N(2)–C(2) 1.397(3), C(1)–C(2) 1.373(3)
Å).[10f]
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
Compound 19 represents a four-coordinate gallium complex.
But, in contrast to all the structures discussed above chelation of
the gallium atom in complex 19 is not symmetrical. Thus, the
Ga–N bond distances in compound 19 differ significantly
(1.9664(13) and 2.1921(13) Å) due to the differences in the type
of bonding between nitrogen atoms and gallium center. Addition
of the tBu group to one of the six-membered ring caused its
dearomatization and resulted via recombination of two radicals
(dpp-bian and tBu) in a closed-shell amido-imino ligand system.
The longer Ga–N(2) bond (2.1921(13) Å) reflects donation of the
imino-nitrogen lone pair to gallium, while the shortened Ga–N(1)
bond (1.9664(13) Å) corresponds to the amido bonding type.
However, due to a low reactivity of the newly formed C–C bond
the potential of such species as catalytic intermediates in
organic cross-coupling reactions is probably not so high. The
reaction of digallane 2 with Ph3SnNCO besides the expected
product (dpp-bian)(NCO)Ga–Ga(NCO)(dpp-bian) (9) resulted in
mononuclear distannyl complex (dpp-bian)Ga(SnPh3)2 (8). We
suggest that the reaction of Ph3SnNCO with digallane affords
initially [(dpp-bian)Ga(NCO)SnPh3], which then reacts with
starting 2 resulting in the compounds 8 and 9. A series of
galliumdiorganyls, compounds 11-16, have been prepared by
the salt metathesis reaction using 3, 10, Bn2GaCl and tBu2GaCl
as gallium precursors. Unfortunately, complexes (dpp-
bian)Ga(R’)R (11-16) (R and R’ = hydrocarbyl radical) are
unable to undergo two-electron elimination reactions to result
digallane 2 and homo- or hetero-coupling products R’–R. One
can expect that a delicate tuning of a steric bulk and of redox
potential of the redox-active ligand could make the genuine two
electron reductive elimination process on main group metal
complex possible.
Experimental Section
All manipulations were carried out under vacuum using glass ampoules.
Toluene, diethyl ether, thf, dimethoxyethane, benzene, benzene-d6,
Et2O-d10 and thf-d8 were dried over sodiumbenzophenone, hexane and
pyridine – over sodium. The IR spectra were recorded on a FSM-1201
Figure 12. Molecular structure of complex (dpp-bian-tBu)GatBu2 (19). Thermal
ellipsoids are 50 % probability. Hydrogen atoms are omitted. Selected bond
lengths (Å) and angles (°): Ga–N(1) 1.9664(13), Ga–N(2) 2.1921(13), Ga–
C(41) 2.0125(16), Ga–C(45) 2.0219(18), N(1)–C(1) 1.3576(19), N(2)–C(2)
1.2922(19), C(1)–C(2) 1.486(2), C(8)–C(13) 1.571(2), N(1)–Ga–C(41)
110.47(6), N(1)–Ga–C(45) 120.66(8), N(1)–Ga–N(2) 81.71(5).
1
spectrometer in a Nujol, the H NMR spectra – on Bruker DPX-200 (200
MHz) and Bruker Advance III 400 (400 MHz) spectrometers. Chemical
shifts are reported in ppm and referenced to the residual 1H and 13C
resonances of the deuterated solvents. The UV/VIS/NIR spectra were
recorded with Perkin-Elmer Lambda 25 spectrometer at 20 °C in a 10
mm quarz cell. The ESR spectra were obtained using a Bruker EMX
spectrometer (9.75 GHz), the signals were referred to the signal of
diphenylpicrylhydrazyl (g = 2.0037). HFC constants were obtained by
simulation with the WinEPR SimFonia Software (Bruker). Melting points
were measured in sealed capillaries. The yields of the products were
calculated on dpp-bian used in the syntheses. Compounds dpp-bian,[30]
(dpp-bian)Ga−Ga(dpp-bian),[10h] (dpp-bian)IGa−GaI(dpp-bian),[10d] (dpp-
We believe that complex 7, whose crystal structure could not
been determined, consists of the related amido-imino ligand.
The chelating ligands in compound 7 and 18 differ only in the
position of the hydrocarbyl group (allyl and tBu correspondingly).
Initially, the tBu radical may attack one of the carbon atoms in
metallcycles in compound 14 due to the delocalization of the
unpaired electron mainly over this fragment. But, a crowding that
is caused by the iPr groups favors the 1,5-shift of the bulky tBu
group to the six-membered ring to result complex 19.
[21]
[19]
bian)Ga(C≡CPh)2
and (dpp-bian)Gal2
were obtained according to
published procedures. Solution of [(dpp-bian)Na] in Et2O was prepared,
unless otherwise stated, by vigorous stirring of a mixture of dpp-bian (0.5
g, 1 mmol) and sodium (0.024 g, 1.05 mmol) in diethyl ether (10 ml) at
ambient temperature within few hours.[8] Allylchloride (99 %), nBuLi
(23.38 wt % in hexane), tBuLi (17.7 wt % in pentane), GaCl3 (granules,
99.999 %), GaMe3 (99.9 %) were purchased from Dalchem Ltd. AgNCO
was purchased from Aldrich. Allylbromide was distilled and stored under
Cu-wire. CpNa was obtained reacting cyclopentadiene and sodium in thf
and was isolated by evaporation of the solvent in vacuum. Diethyl ether
solutions of AllMgCl and BnMgCl were prepared reacting allylchloride
and benzylchloride with magnesium in diethyl ether. Solution
concentrations were estimated by titration. Solution of MentMgCl in thf
was prepared as reported.[38] Benzene solution of PhLi was prepared by
the reaction of lithium metal and bromobenzene in diethyl ether. After
filtration, the solvent was evaporated in vacuum and benzene was added.
Solution concentration was estimated by titration. Instead of two-step
synthesis[39] compound Bn2GaCl was prepared as following. To a solution
of 880 mg (5 mmol) of GaCl3 in diethyl ether (10 ml) 5.6 ml of 1.8 M
solution (10 mmol) of BnMgCl in diethyl ether were added. A colorless
precipitate formed immediately. The mixture was stirred for 24 h at
ambient temperature. Solvent was evaporated in vacuum. Residue was
distilled at 190 °С/0.01 mm Hg to give 824 mg (57 %) of Bn2GaCl.
Compound tBu2GaCl was prepared using modified literature
procedure.[40] To a suspension of GaCl3 (1.76 g, 10 mmol) in hexane two
equivalents of tBuLi (7.23 g of 17.7 wt % solution in pentane, 20 mmol)
were added at –78 °C. Mixture was stirred for 24 h at ambient
Conclusions
In conclusion, we have demonstrated for the first time a
ligand-assisted two-electron oxidative addition of an organic
halide to a single main group metal center. Thus, the reaction of
diamagnetic digallane (dpp-bian)Ga–Ga(dpp-bian) (2) results in
the mononuclear paramagnetic (dpp-bian)Ga(η1-All)Cl (3). But,
formation of complex (dpp-bian)(Cl)Ga–Ga(Cl)(dpp-bian) (4)
besides complex 3 indicates the existence of at least two parallel
processes. We believe that the formation of complex 4 from
compound 3 is implausible. Compound 4 might result from
recombination of Cl– with [(dpp-bian)Ga–Ga(dpp-bian)]2+, which,
in its turn, can be produced in the course of the electron transfer
from digallane 2 to AllCl. Notably, the reaction of digallane 2 with
allylbromide proceeds different of the reaction with allylchloride.
The major product here is diamagnetic digallane 7. Within the
reaction not only metal but also the ligand participates in the
direct bonding with the substrate via the C–C bond formation.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
temperature. Solvent was removed in vacuum. Residue was distilled at
130 °С/0.01 mm Hg to give 1.5 g (68 %) of tBu2GaCl.
140.9, 140.2, 139.1, 137.2, 133.4, 131.6, 130.6, 129.0, 128.7, 127.3,
127.2,126.3, 125.8, 125.7, 125.3, 124.4, 123.9, 123.6, 123.5, 118.4, 79.8,
50.5, 29.7, 29.0, 28.5, 28.3, 27.3, 27.2, 25.5, 25.1, 25.0, 24.8, 23.4, 21.0.
(dpp-bian)Ga(η1-All)Cl (3), (dpp-bian)(Cl)Ga–Ga(Cl)(dpp-bian) (4) and
(dpp-bian)Ga(Py)Cl (5). To a deep-blue solution of compound 2 (0.5
mmol) in thf (30 mL) a solution of allylchloride (0.077 g, 1.0 mmol) in thf
(5 mL) was added by syringe at –50 °С at stirring within 10 min. After that
a cooling bath was removed and the mixture was left stirring at ambient
temperature. Within 1 h the mixture turned red-brown. All volatiles were
removed in vacuum. The residue was extracted with hexane (40 mL)
three times. The brown powder left after extraction is insoluble in toluene,
thf and hexane. The hexane solution obtained was concentrated (15 mL).
Storage at 10 °С for 24 h caused formation of brown crystals of
compound 3. Yield 0.1 g (31 %). Mp. = 208-210 °С (dec.). Anal. calcd. for
C39H45ClGaN2 (646.96): C, 72.40; H, 7.01. Found: C, 71.94; H, 7.31. IR
(Nujol): 1736 w, 1627 w, 1593 w, 1539 vs, 1364 m, 1322 s, 1256 m, 1187
m, 1149 w, 1113 w, 1082 w, 1057 w, 1046 w, 986 w, 936 w, 895 m, 878
w, 823 m, 804 m, 787 w, 765 s, 671 w, 594 w, 548 w, 532 w, 458 m cm–1.
UV/VIS (Et2O): 422, 510, 538 nm. ESR (thf, 295 K): gi = 2.0021, ai(2×14N)
= 0.52, ai(69Ga) = 1.02, ai(71Ga) = 1.30, ai(35Cl) = 0.22, ai(37Cl) = 0.18,
ai(4×1H) = 0.10 mT. According to IR spectroscopic data the brown
powder left after extraction appeared to be compound 4. A biradical
character of 4 prevents its characterization by NMR as well as ESR
spectroscopy. However, the IR spectrum of complex 4 is the same with
that of iodine analog (dpp-bian)(I)Ga–Ga(I)(dpp-bian).[10d] In order to
prepare a solution of compound 4 the residue was transferred in a glass
ampule containing pyridine (15 mL). The ampule was sealed off and was
heated at 120 °С. Within 12 h the solid dissolved completely and resulted
blue solution. Evaporation of the solvent led to blue crystalline compound
5 (0.2 g, 58 %). Anal. calcd. for C41H45N3ClGa (684.99): C, 71.89; H, 6.62.
Found: C, 71.55; H, 6.72. UV/VIS (toluene): 528 nm. 1H NMR (200 MHz,
C6D6): δ 8.57-8.37 (br s, 2 H, Py), 7.27-7.37 (m, 4 H, CH ar.), 7.10 (d, 2 H,
CH ar., J = 8.3 Hz), 6.90 (pst, 2 H, CH ar., J = 7.5 Hz), 6.74-6.58 (br s, 1
H, Py), 6.40 (d, 2 H, CH ar., J = 6.8 Hz), 6.38-6.20 (br s, 2 H, Py), 4.01
(sept, 2 H, CH(CH3)2, J = 6.8 Hz), 3.41 (sept, 2 H, CH(CH3)2, J = 6.8 Hz),
1.60 (d, 6 H, CH(CH3)2, J = 6.8 Hz), 1.16 (d, 6 H, CH(CH3)2, J = 6.8 Hz),
0.86 (d, 6 H, CH(CH3)2, J = 6.8 Hz), 0.29 (d, 6 H, CH(CH3)2, J = 6.8 Hz).
(dpp-bian)Ga(SnPh3)2 (8) and (dpp-bian)Ga(NCO)–Ga(NCO)(dpp-
bian) (9). To a solution of (dpp-bian)Ga–Ga(dpp-bian) in 20 ml of diethyl
ether, prepared in situ in toluene from 1 mmol (0.5 g) dpp-bian, 0.39 g (1
mmol) of Ph3SnNCO was added. Mixture was heated within 7 days at
70 °C. Solution color changed from deep-blue to red-brown.
Concentration of the solution gave a mixture of pink needles of (dpp-
bian)Ga(SnPh3)2 (8) and brown prisms of (dpp-bian)Ga(NCO)–
Ga(NCO)(dpp-bian) (9). Manually separated crystals of 8 and 9 have
been studied by the single crystal X-ray analysis, ESR and IR
spectroscopy. Total yield of 8 and 9 0.4 g. Due to difficulties in separation
of 8 and 9 elemental analyses for 8 and 9 were not carried out.
Compound 8: IR (Nujol): 1576 m, 1519 m, 1307 m, 1254 m, 1183 m,
1148 w, 1109 w, 1070 m, 1043 w, 1019 m, 997 m, 943 w, 820 m, 808 m,
771 m, 765 m, 698 s, 671 w, 619 w, 546 w, 453 m. UV/VIS (Et2O) 418,
511, 540 nm. ESR (toluene, 295 K): gi = 2.0025; ai(2×14N) = 0.53,
ai(69Ga) = 2.05, ai(71Ga) = 2.60, ai(2×117Sn) = 11.3, ai(2×119Sn) = 11.8,
ai(4×1H) = 0.11 mT. Compound 9: IR (Nujol): 2220 vs, 1673 w, 1592 w,
1533 s, 1527 w, 1363 w, 1340 w, 1318 w, 1256 m, 1211 w, 1189 m, 1150
m, 1111 m, 1069 m, 1055 w, 1041 w, 1018 w, 998 m, 940 w, 892 w, 878
w, 819 m, 803 m, 772 m, 761 m, 702 s, 674 w, 626 w, 593 w, 545 w, 455
s. UV/VIS (Et2O): 441, 474, 511 nm.
(dpp-bian)GaCl2 (10). Addition of GaCl3 (0.18 g, 1 mmol) to a solution of
[(dpp-bian)Na] (in situ from 0.5 g, 1 mmol of dpp-bian and 0.023 g of
sodium) in Et2O (30 mL) gave a dark-brown mixture. Colorless precipitate
was filtered off. Concentration of the solution afforded brown crystals of
complex 10 (0.57 g, 89 %). Mp = 247 °С. Anal. calcd. for C36H40Cl2GaN2
(641.32): C, 67.42; H, 6.29. Found: C, 66.87; H, 6.39. UV/VIS (Et2O): 400,
518, 553 nm. IR (Nujol): 1689 w, 1592 m, 1537 s, 1320 m, 1254 m, 1213
w, 1187 w, 1147 w, 1112 w, 1080 w, 1077 w, 1039 w, 976 w, 932 w, 898
m, 880 w, 822 s, 802 s, 785 m, 770 s, 762 s, 672 m, 649 w, 623 w, 591
m, 547 m, 518 w, 495 w, 461 s cm–1. ESR (Et2O, 295 K): gi = 2.0020;
ai(2×14N) = 0.45, ai(69Ga) = 1.60, ai(71Ga) = 2.032, ai(2×35Cl) = 0.13,
ai(2×37Cl) = 0.11, ai(4×1H) = 0.10 mT.
(dpp-bian)Ga(η1-All)Br (6) and (dpp-bian-All)(Br)Ga–Ga(Br)(dpp-
bian-All) (7). To a deep-blue solution of 2 (0.5 mmol) in toluene (30 mL)
a solution of allylbromide (0.24 g, 2.0 mmol) in toluene (5 mL) was added
at –50 °С at stirring within 10 min. Warming up the mixture to ambient
temperature resulted in a change of the solution color to brown.
Evaporation of volatiles in vacuum and addition of hexane (5 mL) led to
precipitation of yellow-green solid. The mixture was filtered off. According
to ESR spectroscopy (see Results and Discussion) the hexane solution
consists of compound 6. Recrystallization of the yellow-green residue
from dme afforded complex 7 as yellow crystalline powder. Yield 0.23 g
(66 %). Mp ≥ 143 °С (dec.). Anal. calcd. for C78H90N4Br2Ga2 (1243.4): C,
67.75; H, 6.56. Found: C, 68.19; H, 6.62. IR (Nujol): 1670 w, 1650 w,
1639 w, 1614 s, 1581 s, 1366 m, 1316 m, 1305 w, 1253 s, 1222 w, 1206
m, 1186 w, 1178 w, 1159 m, 1134 w, 1104 m, 1073 w, 1054 w, 1040 m,
1012 w, 988 m, 971 w, 916 s, 858 m, 828 s, 804 s, 788 m, 779 s, 766 w,
760 w, 749 w, 704 w, 672 w, 655 w, 643 w, 626 w, 617 w, 599 w, 586 w,
575 w, 547 w, 529 w, 515 w, 500 w, 467 w cm–1. 1H NMR (400 MHz,
C6D6): δ 7.32 (dd, 1 H, CH ar., J = 7.8 Hz, J = 1.8 Hz), 7.20-7.28 (m, 4 H,
CH ar.), 7.13 (d, 1 H, CH napht., J = 7.3 Hz), 7.02 (dd, 1 H, CH ar., J =
7.5 Hz, J = 1.5 Hz), 6.88 (dd, 1 H, CH napht., J = 8.3 Hz, J = 7.0 Hz),
6.64 (pst, 1 H, CH napht., J = 7.8 Hz), 6.42 (d, 1 H, CH napht., J = 7.3
Hz), 6.30 (d, 1 H, CH napht., J = 7.0 Hz), 4.77 (sept, 1 H, CH(CH3)2, J =
6.8 Hz), 4.62 (dd, 1 H, -CH2CHCH2, J = 16.9 Hz, J = 2.9 Hz), 4.57 (m, 1
H, -CH2CHCH2), 4.20 (dd, 1 H, -CH2CHCH2, J = 13.0 Hz, J = 2.9 Hz),
4.17 (dd, 1 H, -CH2CHCH2, J = 13.0 Hz, J = 6.8 Hz), 3.79 (sept, 1 H,
CH(CH3)2, J = 6.8 Hz), 3.44 (dd, 1 H, CH2CHCH2, J = 13.0 Hz, J = 6.0
Hz), 3.28 (sept, 1 H, CH(CH3)2, J = 6.8 Hz), 2.78 (sept, 1 H, CH(CH3)2, J
= 6.8 Hz), 1.54 (d, 3 H, CH(CH3)2, J = 6.8 Hz), 1.51 (d, 3 H, CH(CH3)2, J
= 6.8 Hz), 1.45 (d, 3 H, CH(CH3)2, J = 6.8 Hz), 1.32 (d, 3 H, CH(CH3)2, J
= 6.8 Hz), 1.21 (d, 3 H, CH(CH3)2, J = 6.8 Hz), 1.08 (d, 3 H, CH(CH3)2, J
= 6.8 Hz), 0.44 (d, 3 H, CH(CH3)2, J = 6.8 Hz), 0.06 (d, 3 H, CH(CH3)2, J
= 6.8 Hz). 13C NMR (100 MHz, C6D6): δ 195.1, 150.7, 145.0, 142.8, 141.2,
(dpp-bian)Ga(η1-All)Cl (3) from 10 and AllMgCl. To a solution of (dpp-
bian)GaCl2 (in situ as described above from 1 mmol of GaCl3) in diethyl
ether (25 mL) 1.7 ml of diethyl ether solution (0.58 M) of AllMgCl (1
mmol) was added. After 30 min colorless solid was filtered off. Volatiles
were removed in vacuum. Crystallization of the residue from hexane
gave 0.6 g (92 %) of complex 3, whose IR and ESR spectra are identical
with those described above.
(dpp-bian)GaPh2 (11). Compound 10 was prepared from GaCl3 (0.18 g,
1 mmol) and [(dpp-bian)Na] (in situ from 0.5 g of dpp-bian and 0.023 g of
sodium) in diethyl ether (20 mL). After removal of diethyl ether the crude
compound 10 was dissolved in benzene (10 mL). To this solution 5.5 mL
of a benzene solution (0.38 M) of PhLi (2 mmol) was added. The mixture
instantly turned red. Precipitated LiCl was filtered off. Volatiles were
removed and residue was dissolved in diethyl ether. Concentration of the
resulted solution afforded red crystals of (dpp-bian)GaPh2 (11). Anal.
calcd. for C48H50GaN2 (724.65): C, 79.56; H, 6.95. Found: C, 78.99; H,
7.40. UV/VIS (Et2O): 410, 481, 526 nm. ESR (thf, 295 K): gi = 2.0025,
ai(2×14N) = 0.545, ai(69Ga) = 1.701, ai(71Ga) = 2.162, ai(4×1H) = 0.10 mT.
(dpp-bian)Ga(η1-All)nBu (12). To a solution of (dpp-bian)Ga(η1-All)Cl
(0.53 g, 0.82 mmol) in hexane (30 mL) 0.25 g of 23.3 wt % solution of
nBuLi in hexane (0.91 mmol) was added. Ampule was sealed off and
was heated within 15 min. Precipitated solid was filtered off. The volatile
components were removed under vacuum. Crude product 12 was
dissolved in toluene. The resulting solution was studied by the ESR
spectroscopy. ESR (toluene, 295 K): gi = 2.0027, ai(2×14N) = 0.543,
ai(69Ga) = 1.778, ai(71Ga) = 2.260, ai(4×1H) = 0.10 mT.
(dpp-bian)Ga(η1-All)Cp (13). To a solution of (dpp-bian)Ga(η1-All)Cl
(0.48 g, 0.74 mmol) in diethyl ether (20 mL ) 0.07 g (0.82 mmol) of
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
sodium cyclopentadienide was added. Mixture was stirred for 8 h at
ambient temperature. Sodium chloride was separated by filtration.
Concentration of the solution gave brown crystals of (dpp-bian)Ga(η1-
All)Cp (13). Yield 0.32 g (64 %). Anal. calcd for C44H50GaN2 (676.58): C,
78.10; H, 7.45. Found: C, 78.43; H, 7.73. Mp = 120-122 °С (dec.).
UV/VIS (Et2O): 515 nm. IR (Nujol): 1671 w, 1627 m, 1593 w, 1536 w,
1435 w, 1382 m, 1364 w, 1319 w, 1257 m, 1212 w, 1147 w, 1111 m,
1080 w, 1057 w, 1040 w, 973 w, 950 w, 897 w, 886 w, 870 w, 834 m, 815
w, 804 m, 786 w, 769 w, 744 w, 672 w, 641 m, 630 m, 592 w, 548 w, 519
w, 458 m. ESR (toluene, 295 K): gi = 2.0025, ai(2×14N) = 0.516, ai(69Ga)
= 1.501, ai(71Ga) = 1.908, ai(4×1H) = 0.10 mT.
[(dpp-bian)GaCl2][Mg2Cl3(thf)6] (18). 1.15 mL of a thf solution (0.87 M)
of MentMgCl (1 mmol) was added to a solution of compound 10 (in situ
from 1 mmol of GaCl3) in diethyl ether (90 mL) at –50 °С. Ampule was
sealed off and left to warm up slowly. Green crystals of compound 18
precipitated within 24 h. Yield 0.52
g (42 %). Anal. calcd. for
C60H88Cl5GaMg2N2O6 (1228.91): C, 58.64; H, 7.22. Found: C, 59.40; H,
7.00. Mp = 180°С (dec.). UV/VIS (Et2O): 704 nm. IR (Nujol): 1771 w,
1612 w, 1591 w, 1515 s, 1434 m, 1346 s, 1299 w, 1266 w, 1254 w, 1211
w, 1177 m, 1137 w, 1109 w, 1033 s, 957 w, 920 s, 889 s, 810 s, 772 m,
763 m, 680 m, 649 w, 621 w, 594 w, 552 w, 522 w, 500 w. 1H NMR (400
MHz, THF-d8): δ 7.25-7.19 (m, 8 H, ar.), 6.92 (pst, 2 H, ar., J = 7.0 Hz),
6.08 (d, 2 H, ar., J = 7.0 Hz), 3.65 (sept, 4 H, CH(CH3)2, J = 6.8 Hz),
3.60 (s, 10 H,thf), 1.74 (s, 10 H, thf), 1.23 (d, 12 H, CH(CH3)2, J = 6.8 Hz),
1.07 (d, 12 H, CH(CH3)2, J = 6.8 Hz). 13C NMR (100 MHz, THF-d8): δ
145.4, 138.5, 136.2, 126.9, 126.5, 126.0, 125.5, 125.3, 124.0, 123.2,
119.0, 27.9, 23.8, 22.8.
(dpp-bian)GatBu2 (14). To a solution of [(dpp-bian)Na] (in situ from 0.5 g
of dpp-bian and 0.023 g of sodium) in diethyl ether (10 mL) 0.22 g (1
mmol) of tBu2GaCl was added. Precipitated NaCl was filtrated off.
Compound (dpp-bian)GatBu2 (14) was isolated as brown crystals from
concentrated mother liquor. Yield 0.32 g (47 %). Anal. calcd for
C44H58GaN2 (684.64): C, 77.19; H, 8.54. Found: C, 76.60; H, 8.69. IR
(Nujol): 1670 w, 1590 w, 1526 w, 1366 w, 1311 m, 1255 m, 1242 m,
1228 w, 1206 w, 1181 s, 1145 w, 1109 w, 1081 w, 1057 w, 1043 w, 1015
w, 968 w, 935, m, 883 w, 858 m, 819 m, 800 m, 772 m, 761 m, 667 w,
620 w, 590 w, 537 m, 455 m. ESR (toluene, 295 K): gi = 2.0028,
ai(2×14N) = 0.503, ai(69Ga) = 1.573, ai(71Ga) = 2.000, ai(4×1H) = 0.10 mT.
(dpp-bian-tBu)GatBu2 (19) from (dpp-bian)GatBu2 (14). An ampule
was loaded with 0.6 g (0.88 mmol) of crystalline (dpp-bian)GatBu2.
Addition of toluene (15 mL) resulted in red-brown solution. The ampule
was sealed off. Heating at 90 °С within 3 h caused a change the color of
the solution to green. No paramagnetic species were detected in this
solution by ESR spectroscopy. All volatiles were removed in vacuum.
Residue was dissolved in 0.5 ml of hexane. Crystallization at –30 °С
afforded green crystals of compound 19. Yield 0.13 g (19 %). Anal. calcd.
for C48H67GaN2 (741.78): C, 77.72; H, 9.10. Found: C, 77.18; H, 8.98. 1H
UV/VIS (hexane) 574, 762 nm. NMR (400 MHz, C6D6): δ 7.21 (s, 3 H),
6.54 (d, 1 H, CH ar., J = 7.8 Hz), 6.11 (pst, 1 H, CH ar., J = 7.8 Hz), 5.43
(d, 1 H, CH ar., J = 7.0 Hz), 5.32 (d, 1 H, CH olefinic, J = 10.0 Hz), 5.22
(dd, 1 H, CH olefinic, J = 10.0 Hz, J = 5.5 Hz), 3.94 (sept, 1 H, CH(CH3)2,
J = 6.8 Hz), 3.52 (sept, 1 H, CH(CH3)2, J = 6.8 Hz), 3.49 (sept, 1 H,
CH(CH3)2, J = 6.8 Hz), 3.48 (sept, 1 H, CH(CH3)2, J = 6.8 Hz), 2.90 (d, 1
H, CH-tBu, J = 5.5 Hz), 1.46 (d, 3 H, CH(CH3)2, J = 6.8 Hz), 1.45 (s, 9 H,
Ga-tBu), 1.40 (d, 3 H, CH(CH3)2, J = 6.8 Hz), 1.33 (d, 3 H, CH(CH3)2, J =
6.8 Hz), 1.32 (d, 3 H, CH(CH3)2, J = 6.8 Hz), 1.26 (pst, 6 H, CH(CH3)2, J
= 7.0 Hz), 1.20 (s, 9 H, Ga-tBu), 1.07 (d, 3 H, CH(CH3)2, J = 6.8 Hz), 1.05
(d, 3 H, CH(CH3)2, J = 6.8 Hz), 0.72 (s, 9 H, CH-tBu). 13C NMR (100 MHz,
C6D6): δ 180.78 (C-imino-N), 157.2, 150.6, 146.3, 145.5, 145.3, 145.1,
143.5, 141.5, 140.5, 134.4, 127.0, 125.8, 125.5, 125.0, 124.9, 124.7,
123.5, 122.8, 121.9, 113.9, 49.9, 38.3, 31.5, 31.1, 28.8, 28.5, 28.3, 28.0,
27.7, 27.6, 26.7, 26.3, 25.6, 25.6, 25.1, 25.1, 25.1, 23.4, 23.1.
(dpp-bian)GaMe2 (15). Addition of Me2GaCl (in situ from 0.29 g, 1.67
mmol of GaCl3 and 0.38 g, 3.33 mmol of GaMe3 in 5 mL of diethyl ether;
–50 °C to ambient temperature) to a solution of [(dpp-bian)Na] (in situ
from 2.50 g of dpp-bian and 0.12 g, 5.25 mmol of sodium) in diethyl ether
(30 mL) resulted only a slight change of color of the solution. Precipitated
NaCl was separated by centrifugation. Compound (dpp-bian)GaMe2 (15)
was isolated as brown crystals from concentrated reaction solution. Yield
0.24 g (8 %). Anal. calcd. for C38H46GaN2 (600.51): C, 76.00; H, 7.72.
Found: C, 75.48; H, 7.49. UV/VIS (Et2O): 475, 511 nm. IR (Nujol): 1667 w,
1626 w, 1598 w, 1580 w, 1543 s, 1362 w, 1318 m, 1255 m, 1225 w, 1184
m, 1156 w, 1110 w, 1099 w, 1084 w, 1052 w, 1039 w, 1006 w, 971 w,
963 w, 948 w, 934 m, 901 w, 885 w, 867 w, 820 s, 802 m, 784 w, 772 w,
761 m, 745 w, 702 w, 682 w, 670 w, 638 w, 617 w, 592 w, 563 m, 546 w,
529 w, 490 w. ESR (toluene, 295 K): gi = 2.0026, ai(2×14N) = 0.541,
ai(69Ga) = 1.732, ai(71Ga) = 2.201, ai(4×1H) = 0.10 mT.
(dpp-bian)GaBn2 (16). To a solution of [(dpp-bian)Na] (in situ from 0.5 g
of dpp-bian and 0.023 g of sodium) in diethyl ether (10 mL) 0.29 g (1
mmol) of Bn2GaCl was added. Precipitated NaCl was filtered off.
Compound (dpp-bian)GaBn2 (16) was isolated from concentrated mother
liquor in a form of brown crystals. Yield 0.15 g (20 %). Anal. calcd for
C50H54GaN2 (752.70): C, 79.78; H, 7.23. Found: C, 80.19; H, 7.44.
UV/VIS (Et2O): 423, 481, 512 nm. IR (Nujol): 1673 w, 1598 s, 1538 s,
1491 m, 1364 m, 1317 s, 1250 m, 1226 w, 1209 m, 1187 s, 1148 w, 1118
m, 1098 m, 1079 w, 1054 w, 1038 w, 1012 w, 969 w, 949 w, 935 w, 894
w, 866 m, 841 w, 821 s, 802 s, 786 w, 771 m, 764 m, 750 s, 695 s, 670 w,
656 m, 637 w, 623 w, 598 w, 586 w, 547 s, 516 w, 491 w, 460 s. ESR
(toluene, 295 K): gi = 2.0025, ai(2×14N) = 0.535, ai(69Ga) = 1.725, ai(71Ga)
= 2.192, ai(4×1H) = 0.10 mT.
(dpp-bian-tBu)GatBu2 (19) from dpp-bian, tBuLi and tBu2GaCl. An
ampule was loaded with 0.5 g (1 mmol) of dpp-bian, 15 mL of hexane
and 0.36 g of solution (17.7 wt %) of tBuLi (1 mmol) in pentane. Stirring
of the mixture for 30 min at ambient temperature gave a brown-green
solution. After addition of 0.22 g (1 mmol) of tBu2GaCl the mixture was
stirred for 1 h. Solution color has slightly changed to a more deep green.
Precipitated LiCl was filtered off. Solution was concentrated to ca. 10 ml.
Storage of the resulted solution overnight at –30 °C gave 25 mg of light-
blue crystals that were separated from the solution. Solution was further
concentrated to 1 ml. Storage at –30 °C overnight afforded 0.11 g (14 %)
of green crystals of complex 19. Spectral parameters of the crystals
isolated are identical with those obtained in the course of the thermal
decomposition of compound (dpp-bian)GatBu2 (14).
Thermal and UV stability tests of compounds 11-16. In a standard
experiment NMR tube was loaded with ca. 50 mg of crystals of one of the
following compound 11, 13, 14, 15, 16, or (dpp-bian)Ga(C≡CPh)2 and 0.5
ml of C6D6. In the case of complex 12 its hexane solution (1 mL)
prepared as described above was added into NMR tube. Volatiles were
removed in vacuum, the residue was dissolved in C6D6 (0.5 mL). After
sample preparation all the NMR tubes were sealed off. NMR tubes were
heated at 130 °С within 6 h. No changes in the NMR spectra for
compounds 11, 12, 13, 15, 16 and (dpp-bian)Ga(C≡CPh)2 were observed.
From the NMR samples the solutions were transferred into quartz tubes
that were then exposed to UV Hg medium pressure lamp DRT-220
(180 mW/m2) within 4 h. After UV irradiation the NMR spectra were
recorded. Again, no changes in NMR spectra for compounds 11, 12, 13,
15, 16 and (dpp-bian)Ga(C≡CPh)2 could be detected.
Reaction of (dpp-bian)GaCl2 (10) with tBuMgCl. NMR tube was loaded
with 0.39 mL of diethyl ether solution (0.7 M) of tBuMgCl (0.27 mmol).
Volatiles were removed in vacuum. Then 88 mg (0.137 mmol) of
compound 10 and 0.5 ml of Et2O-d10 were added and the tube was
sealed off. Within shaking the sample for 10 min crystals of compound 10
dissolved resulting in the blue solution. The ampule was left for three
days to settle the precipitate. 1H NMR (400 MHz, Et2O-d10): compound 2:
7.35-7.05 (m, 16 H, CH ar.), 6.88 (pst, 4 H,CH ar., J = 7.8 Hz), 5.79 (d, 4
H, CH ar., J = 7.0 Hz), 3.22 (sept, 8 H, CH(CH3)2, J = 7.0 Hz), 0.93 (d, 24
H, CH(CH3)2, J = 6.8 Hz), 0.85 (d, 24 H, CH(CH3)2, J = 6.8 Hz);
isobutane: 1.71 (dectet, 1 H CH(CH3)3, J = 6.5 Hz), 0.90 (d, 9 H CH(CH3)3,
J = 6.5 Hz); isobutylene: 4.63 (s, 2 H CH2C(CH3)2), 1.70 (s, 6 H
CH2C(CH3)2).
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
Reaction of (dpp-bian)IGa−GaI(dpp-bian) with tBuLi. NMR tube was
loaded with 29 mg (0.02 mmol) of (dpp-bian)IGa−GaI(dpp-bian), 2.7 mg
(0.04 mmol) of solid tBuLi, 0.5 ml of C6D6 and then was sealed off. Within
shaking the sample for several minutes brick-red powder of complex
(dpp-bian)IGa−GaI(dpp-bian) dissolved resulting in the blue solution. The
ampule was left for two days to settle the precipitate. 1H NMR (400 MHz,
C6D6): compound 2: 7.53-7.10 (m, 16 H, CH ar.), 6.81 (dd, 4 H, CH ar., J
= 7.0 Hz, J = 8.2 Hz), 6.17 (d, 4 H, CH ar., J = 7.0 Hz), 3.45 (sept, 8 H,
CH(CH3)2, J = 6.8 Hz), 0.99 (d, 24 H, CH(CH3)2, J = 6.8 Hz), 0.95 (d, 24
H, CH(CH3)2, J = 6.8 Hz); isobutane;[41] 1.62 (dectet, 1.8 H, CH(CH3)3, J =
6.5 Hz), 0.85 (d, 16 H, CH(CH3)3, J = 6.5 Hz); isobutylene:[42] 4.74 (q, 0.4
H, CH2C(CH3)2, J = 1.00 Hz), 1.58 (t, 0.6 H, CH2C(CH3)2, J = 1.0 Hz).
Molar ratio of the products: 2 : C4H10 : C4H8 = 1 : 1.8 : 0.2.
[7]
[8]
[9]
A. Seifert, D. Scheid, G. Linti, T. Zessin, Chem. Eur. J. 2009, 15,
12114-12120.
I. L. Fedushkin, A. A. Skatova, V. A. Chudakova, G. K. Fukin, Angew.
Chem. Int. Ed. 2003, 42, 3294-3298.
a) I. L. Fedushkin, A. A. Skatova, V. A. Chudakova, G. K. Fukin, S.
Dechert, H. Schumann, Eur. J. Inorg. Chem. 2003, 3336-3346; b) I. L.
Fedushkin, A. A. Skatova, V. K. Cherkasov, V. A. Chudakova, S.
Dechert, M. Hummert, H. Schumann, Chem. Eur. J. 2003, 9, 5778-
5783; c) I. L. Fedushkin, A. G. Morozov, V. A. Chudakova, G. K. Fukin,
V. K. Cherkasov, Eur. J. Inorg. Chem. 2009, 2009, 4995-5003; d) I. L.
Fedushkin, A. A. Skatova, A. N. Lukoyanov, V. A. Chudakova, S.
Dechert, M. Hummert, H. Schumann, Russ. Chem. Bull. 2004, 53,
2751-2762; e) I. L. Fedushkin, V. M. Makarov, E. C. E. Rosenthal, G. K.
Fukin, Eur. J. Inorg. Chem. 2006, 827-832; f) I. L. Fedushkin, N. M.
Khvoinova, A. A. Skatova, G. K. Fukin, Angew. Chem. 2003, 115, 5381-
5384; g) I. L. Fedushkin, N. M. Khvoinova, A. A. Skatova, G. K. Fukin,
Angew. Chem. Int. Ed. 2003, 42, 5223-5226; h) I. L. Fedushkin, A. G.
Morozov, O. V. Rassadin, G. K. Fukin, Chem. Eur. J. 2005, 11, 5749-
5757; i) I. L. Fedushkin, A. A. Skatova, G. K. Fukin, M. Hummert, H.
Schumann, Eur. J. Inorg. Chem. 2005, 2005, 2332-2338.
X-ray crystallography. The X-ray data for 3, 8, 10, 13, 14, 18 and 19
were collected at 100(2) K, for complex 9 at 298(2) K, on a Bruker AXS
D8 Quest Photon and Oxford Xcalibur Eos (MoKa-radiation, ω-scan
technique, λ = 0.71073 Å). The structures were solved by direct methods
and were refined by full-matrix least squares on F2 using SHELXTL.43 All
hydrogen atoms were placed in calculated positions and were refined in
the riding model. Area-detector scaling and absorption corrections for 3,
9, 13, 14, 18 and 19 were performed using SADABS,44 for 8, 10 using
SCALE3 ABSPACK.45 Crystallographic data and structural refinement
details are given in Supporting Information (Tables 1S and 2S). CCDC-
1430953 (3), 1571387 (8), 1571388 (9), 1430954 (10), 1571389 (13),
1571390 (14), 1571391 (18) and 1584416 (19) contain 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.
[10] a) I. L. Fedushkin, A. N. Lukoyanov, S. Y. Ketkov, M. Hummert, H.
Schumann, Chem. Eur. J. 2007, 13, 7050-7056; b) I. L. Fedushkin, A. S.
Nikipelov, K. A. Lyssenko, J. Am. Chem. Soc. 2010, 132, 7874-7875; c)
I. L. Fedushkin, A. S. Nikipelov, A. G. Morozov, A. A. Skatova, A. V.
Cherkasov, G. A. Abakumov, Chem. Eur. J. 2012, 18, 255-266; d) I. L.
Fedushkin, A. A. Skatova, V. A. Dodonov, V. A. Chudakova, N. L.
Bazyakina, A. V. Piskunov, S. V. Demeshko, G. K. Fukin, Inorg. Chem.
2014, 53, 5159-5170; e) I. L. Fedushkin, A. A. Skatova, V. A. Dodonov,
X.-J. Yang, V. A. Chudakova, A. V. Piskunov, S. Demeshko, E. V.
Baranov, Inorg. Chem. 2016, 55, 9047-9056; f) I. L. Fedushkin, A. S.
Nikipelov, A. A. Skatova, O. V. Maslova, A. N. Lukoyanov, G. K. Fukin,
A. V. Cherkasov, Eur. J. Inorg. Chem. 2009, 3742-3749; g) V. A.
Dodonov, A. A. Skatova, A. V. Cherkasov, I. L. Fedushkin, Russ. Chem.
Bull. 2016, 65, 1171-1177; h) I. L. Fedushkin, A. N. Lukoyanov, A. N.
Tishkina, G. K. Fukin, K. A. Lyssenko, M. Hummert, Chem. Eur. J. 2010,
16, 7563-7571.
Acknowledgements
We thank Russian Science Foundation for financial support
(project No. 14-13-01063).
[11] A. V. Piskunov, I. V. Ershova, G. K. Fukin, A. S. Shavyrin, Inorg. Chem.
Commun. 2013, 38, 127-130.
Keywords: redox-active ligands • gallium • oxidative addition
[12] a) A. V. Piskunov, I. N. Meshcheryakova, G. K. Fukin, A. S. Shavyrin, V.
K. Cherkasov, G. A. Abakumov, Dalton Trans. 2013, 42, 10533-10539;
b) A. V. Piskunov, M. S. Piskunova, M. G. Chegerev, Russ. Chem. Bull.
2014, 63, 912-915.
[1]
a) M. R. Ringenberg, S. L. Kokatam, Z. M. Heiden, T. B. Rauchfuss, J.
Am. Chem. Soc. 2008, 130, 788-789; b) M. R. Ringenberg, T. B.
Rauchfuss, Eur. J. Inorg. Chem. 2012, 2012, 490-495; c) I. M. Lorkovic,
R. R. Duff, M. S. Wrighton, J. Am. Chem. Soc. 1995, 117, 3617-3618;
d) P. J. Chirik, K. Wieghardt, Science 2010, 327, 794-795; e) C. A.
Lippert, K. Riener, J. D. Soper, Eur. J. Inorg. Chem. 2012, 2012, 554-
561; f) A. I. O. Suarez, V. Lyaskovskyy, J. N. H. Reek, J. I. van der
Vlugt, B. de Bruin, Angew. Chem. Int. Ed. 2013, 52, 12510-12529; g) K.
J. Blackmore, N. Lal, J. W. Ziller, A. F. Heyduk, J. Am. Chem. Soc.
2008, 130, 2728-2729; h) A. I. Nguyen, R. A. Zarkesh, D. C. Lacy, M. K.
Thorson, A. F. Heyduk, Chemical Science 2011, 2, 166-169; i) P.
Chaudhuri, M. Hess, U. Flörke, K. Wieghardt, Angew. Chem. Int. Ed.
1998, 37, 2217-2220; j) K. Wang, E. I. Stiefel, Science 2001, 291, 106-
109; k) W. Liu, M. Brookhart, Organometallics 2004, 23, 6099-6107.
L. A. Berben, Chem. Eur. J. 2015, 21, 2734-2742.
[13] N. J. Hardman, B. E. Eichler, P. P. Power, Chem. Commun. 2000,
1991-1992.
[14] C. Jones, P. C. Junk, J. A. Platts, A. Stasch, J. Am. Chem. Soc. 2006,
128, 2206-2207.
[15] a) I. L. Fedushkin, V. G. Sokolov, A. V. Piskunov, V. M. Makarov, E. V.
Baranov, G. A. Abakumov, Chem. Commun. 2014, 50, 10108-10111; b)
I. L. Fedushkin, V. G. Sokolov, V. M. Makarov, A. V. Cherkasov, G. A.
Abakumov, Russ. Chem. Bull. 2016, 65, 1495-1504.
[16] G. Prabusankar, A. Kempter, C. Gemel, M.-K. Schröter, R. A. Fischer,
Angew. Chem. Int. Ed. 2008, 47, 7234-7237.
[17] A. V. Piskunov, A. V. Lado, E. V. Ilyakina, G. K. Fukin, E. V. Baranov, V.
K. Cherkasov, G. A. Abakumov, J. Organomet. Chem. 2008, 693, 128-
134.
[2]
[3]
a) N. J. Hardman, C. Cui, H. W. Roesky, W. H. Fink, P. P. Power,
Angew. Chem. 2001, 113, 2230-2232; b) N. J. Hardman, C. Cui, H. W.
Roesky, W. H. Fink, P. P. Power, Angew. Chem. Int. Ed. 2001, 40,
2172-2174.
[18] P. A. Petrov, S. N. Konchenko, V. A. Nadolinny, Russ. J. Coord. Chem.
2014, 40, 885-890.
[19] R. J. Baker, C. Jones, M. Kloth, D. P. Mills, New J. Chem. 2004, 28,
207.
[4]
[5]
R. J. Wright, M. Brynda, J. C. Fettinger, A. R. Betzer, P. P. Power, J.
Am. Chem. Soc. 2006, 128, 12498-12509.
[20] I. L. Fedushkin, A. A. Skatova, M. Hummert, H. Schumann, Eur. J.
Inorg. Chem. 2005, 2005, 1601-1608.
a) Z. Zhu, X. Wang, Y. Peng, H. Lei, J. C. Fettinger, E. Rivard, P. P.
Power, Angew. Chem. 2009, 121, 2065-2068; b) Z. Zhu, X. Wang, Y.
Peng, H. Lei, J. C. Fettinger, E. Rivard, P. P. Power, Angew. Chem. Int.
Ed. 2009, 48, 2031-2034.
[21] I. L. Fedushkin, O. V. Kazarina, A. N. Lukoyanov, A. A. Skatova, N. L.
Bazyakina, A. V. Cherkasov, E. Palamidis, Organometallics 2015, 34,
1498-1506.
[22] I. L. Fedushkin, M. Hummert, H. Schumann, Eur. J. Inorg. Chem. 2006,
2006, 3266-3273.
[6]
a) C. A. Caputo, Z. Zhu, Z. D. Brown, J. C. Fettinger, P. P. Power,
Chem. Commun. 2011, 47, 7506-7508; b) C. A. Caputo, J. Koivistoinen,
J. Moilanen, J. N. Boynton, H. M. Tuononen, P. P. Power, J. Am. Chem.
Soc. 2013, 135, 1952-1960.
[23] A. N. Tishkina, A. N. Lukoyanov, A. G. Morozov, G. K. Fukin, K. A.
Lyssenko, I. L. Fedushkin, Russ. Chem. Bull. 2009, 58, 2250-2257.
[24] C. Romain, V. Rosa, C. Fliedel, F. Bier, F. Hild, R. Welter, S. Dagorne,
T. Aviles, Dalton Trans. 2012, 41, 3377-3379.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
[25] M. Arrowsmith, M. S. Hill, G. Kociok-Köhn, Organometallics 2014, 33,
206-216.
[26] D. A. Evans, I. Vargas-Baca, A. H. Cowley, J. Am. Chem. Soc. 2013,
135, 13939-13946.
[27] a) V. Rosa, C. I. M. Santos, R. Welter, G. Aullón, C. Lodeiro, T. Avilés,
Inorg. Chem. 2010, 49, 8699-8708; b) D. A. Evans, L. M. Lee, I.
Vargas-Baca, A. H. Cowley, Organometallics 2015, 34, 2422-2428.
[28] I. L. Fedushkin, A. A. Skatova, V. A. Chudakova, V. K. Cherkasov, G. K.
Fukin, M. A. Lopatin, Eur. J. Inorg. Chem. 2004, 2004, 388-393.
[29] I. L. Fedushkin, V. M. Makarov, V. G. Sokolov, G. K. Fukin, Dalton
Trans. 2009, 8047-8053.
[30] a) A. Paulovicova, U. El-Ayaan, K. Shibayama, T. Morita, Y. Fukuda,
Eur. J. Inorg. Chem. 2001, 2641-2646; b) I. L. Fedushkin, V. A.
Chudakova, G. K. Fukin, S. Dechert, M. Hummert, H. Schumann, Russ.
Chem. Bull. Int. Ed. 2004, 53, 2744.
[31] R. Steudel, J. Huheey, E. Keiter, R. Keiter, Anorganische Chemie:
Prinzipien von Struktur und Reaktivität, De Gruyter, Berlin, 2014.
[32] S. P. Green, C. Jones, K.-A. Lippert, D. P. Mills, A. Stasch, Inorg. Chem.
2006, 45, 7242-7251.
[33] K. Zeckert, Dalton Trans. 2012, 41, 14101-14106.
[34] X. Shen, A. Nakashima, K. Sakata, M. Hashimoto, Synth. React. Inorg.
Met.-Org. Chem. 2004, 34, 211-222.
[35] T. Pott, P. Jutzi, B. Neumann, H.-G. Stammler, Organometallics 2001,
20, 1965-1967.
[36] W. Uhl, L. Cuypers, G. Geiseler, K. Harms, W. Massa, Z. Anorg. Allg.
Chem. 2002, 628, 1001-1006.
[37] A. N. Lukoyanov, I. L. Fedushkin, M. Hummert, H. Schumann, Russ.
Chem. Bull. 2006, 55, 422-428.
[38] J. Beckmann, D. Dakternieks, M. Dräger, A. Duthie, Angew. Chem.
2006, 118, 6659-6662.
[39] B. Neumüller, F. Gahlmann, Z. Anorg. Allg. Chem. 1992, 612, 123-129.
[40] a) R. A. Kovar, H. Derr, D. Brandau, J. O. Callaway, Inorg. Chem. 1975,
14, 2809-2814; b) K. T. Higa, C. George, Organometallics 1990, 9, 275-
277; c) H. U. Schwering, E. Jungk, J. Weidlein, J. Organomet. Chem.
1975, 91, C4-C6.
[41] B. Schoofs, J. Schuermans, R. A. Schoonheydt, Microporous
Mesoporous Mater. 2000, 35, 99-111.
[42] S. A. Francis, E. D. Archer, Anal. Chem. 1963, 35, 1363-1368.
[43] Sheldrick G.M. (2003). SHELXTL v. 6.14, Structure Determination
Software Suite, Bruker AXS, Madison, Wisconsin, USA.
[44] Sheldrick G.M. (2012). SADABS v.2012/1, Bruker/Siemens Area
Detector Absorption Correction Program, Bruker AXS, Madison,
Wisconsin, USA.
[45] CrysAlisPro - Software Package, Agilent Technologies (2012): Data
Collection, Reduction and Correction Program,SCALE3 ABSPACK:
Empirical absorption correction.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704128
Chemistry - A European Journal
FULL PAPER
Entry for the Table of Contents
FULL PAPER
Ar
N
Ar
N
Redox-active ligands can substantially
expand reactivity of metal complexes,
thus providing for an entry to catalysis.
However, up to now redox-active
ligands are designated to construct
mainly complexes of transition metals.
The present paper reports on
oxidative addition of a typical organic
substrate, e.g. allylchloride to gallium
complex of redox-active dpp-bian.
Igor L. Fedushkin,* Vladimir A. Dodonov,
Alexandra A. Skatova, Vladimir G.
Sokolov, Alexander V. Piskunov, and
Georgii K. Fukin
Ga Ga
N
N
Ar
Ar
2
+
RT
2
2
Cl
toluene,
Page No. – Page No.
Ar
N
Redox-Active Ligand Assisted Two-
Electron Oxidative Addition to
Gallium(II)
Ga
Cl
3
N
Ar
This article is protected by copyright. All rights reserved.