Reactions of the tetraalkyldigallium compound R2Ga-GaR 2 [R = CH(SiMe3)2] with acidic reagents, retention vs. cleavage of the Ga-Ga bond and formation of supramolecular aggregates via hydrogen bonding

Article abstract of DOI:10.1002/zaac.201100252

Treatment of the tetraalkyldigallium compound R₂Ga-GaR ₂ [1, R = CH(SiMe₃)₂] with two equivalents of carboxylic acid hydrazides (4-trifluormethylbenzhydrazide, 2-fuoric acid hydrazide and 2-chlor-6-hydrazineisonicotinic acid hydrazide) afforded new digallium species by the release of CH₂(SiMe₃) ₂. The intact Ga-Ga bonds of the products (2 to 4) are terminally coordinated by two chelating hydrazide ligands via NH₂ groups and the carbonyl oxygen atoms. Interesting supramolecular aggregates are formed in the solid state, which contain dimeric formula units of the digallium species connected via a complex system of hydrogen bonds. Two ether molecules are additionally coordinated to terminal N-H functions. Phenylphosphinic acid and 1 gave the analogous substituent replacement reaction with the formation of a dimeric tetragallium compound (5). Its two Ga-Ga bonds are in a perpendicular arrangement with four phosphinate ligands in the bridging positions. Oxidation of the gallium atoms and insertion of an N=N double bond into the Ga-Ga bond was observed upon treatment of 1 with azodicarbonamide. Copyright

Full text of DOI:10.1002/zaac.201100252

ARTICLE
DOI: 10.1002/zaac.201100252
Reactions of the Tetraalkyldigallium Compound R2Ga–GaR2 [R =
CH(SiMe3)2] with Acidic Reagents, Retention vs. Cleavage of the Ga–Ga
Bond and Formation of Supramolecular Aggregates via Hydrogen Bonding
Werner Uhl,*[a] Matthias Voß,[a] and Alexander Hepp[a]
In Memory of Professor Kurt Dehnicke
Keywords: Gallium; Hydrazides; Phosphinic acid; Subvalent compounds; Hydrogen bonding
Abstract. Treatment of the tetraalkyldigallium compound R2Ga–GaR2
[1, R = CH(SiMe3)2] with two equivalents of carboxylic acid hydra-
system of hydrogen bonds. Two ether molecules are additionally coor-
dinated to terminal N–H functions. Phenylphosphinic acid and 1 gave
zides (4-trifluormethylbenzhydrazide, 2-fuoric acid hydrazide and 2- the analogous substituent replacement reaction with the formation of
chlor-6-hydrazineisonicotinic acid hydrazide) afforded new digallium
species by the release of CH2(SiMe3)2. The intact Ga–Ga bonds of the
products (2 to 4) are terminally coordinated by two chelating hydrazide
ligands via NH2 groups and the carbonyl oxygen atoms. Interesting
a dimeric tetragallium compound (5). Its two Ga–Ga bonds are in a
perpendicular arrangement with four phosphinate ligands in the bridg-
ing positions. Oxidation of the gallium atoms and insertion of an N=N
double bond into the Ga–Ga bond was observed upon treatment of 1
supramolecular aggregates are formed in the solid state, which contain with azodicarbonamide.
dimeric formula units of the digallium species connected via a complex
with an inner diameter of up to 1.9 nm in which four Ga–
Introduction
Ga bonds are bridged by four spacer ligands.[9] However, the
distortion of the angles at the gallium atoms (O–Ga–O ≈ 90°,
C–Ga–Ga ≈ 155°) and relatively short Ga–Ga distances verify
a considerable strain in the resulting molecules. Donor func-
tionalized acids gave large cages with up to six Ga–Ga bonds,
which encapsulated solvent molecules very effectively[10] or
formed supramolecular aggregates by hydrogen bonding.[11]
Further acidic components may be suitable to replace alkyl
groups of 1 and may help to increase the variability of access-
ible structural motifs and functionalities of the digallium com-
pounds. Reactions with acid hydrazides, phenylphosphinic
acid and a diaza compound are reported here.
The tetraalkyldigallium compound R2Ga–GaR2 [1, R =
CH(SiMe3)2] is accessible on a facile route by the treatment
of the digallium subhalide Ga2Br4·2dioxane with four equiva-
lents of bis(trimethylsilyl)methyllithium.[1] It shows a fascinat-
ing and unique chemical reactivity which afforded a broad
variety of different secondary products by electron transfer,
insertion, adduct formation, deprotonation or metathesis.[2]
One of the most exciting secondary reactions comprises the
treatment of 1 with carboxylic acids[3–5] or other acidic sub-
strates[6] having chelating residues. Unexpectedly the Ga–Ga
bonds are retained in most cases, and two alkyl groups of 1
are replaced by two chelating ligands in very selective trans-
formations. Different reaction courses were observed for the
corresponding dialuminium or diindium derivatives,[7] which
gave oxidation of the metal atoms and the quantitative cleav-
age of the metal–metal bonds under similar conditions.[8] The
dicarboxylatedigallium compounds have the chelating ligands
in bridging positions across the Ga–Ga bonds and in an almost
ideal perpendicular arrangement. With this unusual configura-
Results and Discussion
Reactions of the Digallium Compound 1 with
Carboxyhydrazides
Following a standard procedure the digallium compound 1
tion these compounds are perfectly preorganized to form and two equivalents of acid hydrazides (4-trifluormethylbenz-
macrocycles or cages upon treatment of 1 with bifunctional hydrazide, 2-fuoric acid hydrazide and 2-chlor-6-hydrazineiso-
dicarboxylic acids. Indeed we isolated large squaric molecules nicotinic acid hydrazide) were dissolved in THF and stirred
for different reaction times between 12 h and 3 d at room
* Prof. Dr. W. Uhl
temperature [Equation (1)]. H2C(SiMe3)2 was identified as a
Fax: +49-251-8336660
1
by-product by its characteristic singlet signals in the H NMR
spectra. The reaction mixtures were concentrated and cooled
to yield the colorless, solid products in yields of 62 (2), 83 (3)
and 65% (4). Single crystals were obtained from diethyl ether
E-Mail: uhlw@uni-muenster.de
[a] Institut für Anorganische und Analytische Chemie
Universität Münster
Corrensstraße 30
48149 Münster, Germany
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W. Uhl, M. Voß, A. Hepp
ARTICLE
(2) and THF (3); compound 4 was isolated only as an amorph-
ous powder. Crystal structure determinations revealed the ex-
pected molecular structures (Figure 1 and Figure 2). Two alkyl
groups of 1 were replaced by two hydrazide ligands which
adopt terminal positions at the Ga–Ga bonds in the solid state
and are bonded to the gallium atoms via their carboxyl oxygen
atoms and an NH2 group. Five-membered GaCN2O heterocy-
cles including only one metal atom resulted by this particular
coordination mode. This is in remarkable contrast to the di-
carboxylate species which have the chelating ligands in a
bridging position across the metal–metal bond. Quantum-
chemical calculations[5] showed that in these cases this struc-
tural motif is strongly favored over the terminal arrangement
by essentially two reasons: (i) The O–C–O angle is relatively
inflexible. The terminal coordination of a carboxylato group
requires a considerable deformation with a high energetic bar-
rier. (ii) The hypothetical four-membered GaCO2 heterocycle
resulting from the terminal arrangement has a relatively short
transannular distance between the positively charged gallium
and carbon atoms which results in electrostatic repulsion. The
bridging coordination of the Ga2 moieties is limited to carb-
oxylates, but leads to some strain in the molecules as discussed
above (see Introduction). In other cases with the formation of
larger heterocycles the terminal arrangement of the chelating
ligands is preferred as in 2 and 3.[6] The more relaxed bonding
situation results in relatively long Ga–Ga distances (245.5 pm
on average for 2 and 3) compared to the carboxylate bridged
molecules (238 pm) and a closer approach of the angles at the
metal atoms to the ideal value of a tetrahedral coordination.
Figure 1. Molecular structure and numbering scheme of 2; the thermal
ellipsoids are drawn at the 40% probability level; trimethylsilyl groups
and hydrogen atoms with the exception of N–H are omitted, atoms of
the ether molecule with artificial radii. Selected bond lengths /pm and
angles /° (data of the second molecule in square brackets): Ga1–Ga2
245.82(6) [245.57(6)], Ga1–O1 195.6(3) [196.2(3)], Ga1–N11
210.3(3) [209.8(3)], Ga2–O2 193.2(3) [193.7(3)], Ga2–N21 206.9(3)
[206.4(3)], O1–C100 129.0(4) [129.4(4)], C100–N12 129.9(5)
[130.0(5)], N11–N12 147.9(4) [146.0(4)], O2–C200 130.2(4)
[129.7(4)], C200–N22 130.4(5) [130.6(5)], N21–N22 147.3(4)
[146.5(4)], O1–Ga1–N11 79.4(1) [79.5(1)], Ga2–Ga1–O1 105.89(8)
[103.79(8)], N12–C100–O1 125.9(3) [125.3(3)], O2–Ga2–N21 80.7(1)
[79.5(1)], Ga1–Ga2–O2 100.92(9) [101.18(8)], N22–C200–O2
125.9(3) [125.9(3)].
C=N group.[13] The Ga–N distances are long (207.9 pm) indi-
cating a donor interaction of a neutral nitrogen atom with the
Lewis-acidic metal atom,[14] whereas the Ga–O distances
(194.7 pm) are in the upper range of values observed for exam-
ple in alcoholates with negatively charged oxygen atoms.[15]
Both compounds 2 and 3 are dimeric in the solid state via a
complex, but almost identical pattern of hydrogen bonds,
which is described here with the atomic numbering scheme of
2 (Figure 3). There are two different kinds of NH2 groups. Two
NH2 groups of each dimeric formula unit (N11 and N31) point
towards the center of the resulting cage. One hydrogen atom
of each group has a close contact to the nitrogen atom of a
C=N double bond (H11J···N32: 215 pm, H31K···N12: 211 pm;
for a discussion of N–H···N bonding see[16]), whereas two
A schematic drawing of the molecular structures of the mo- longer distances were detected for the remaining two hydrogen
nomeric formula units of 2 and 3 is given in Equation (1). The atoms (H11K···N22: 255 pm, H11K···N42: 261 pm). Also one
NH2 groups adopt cis-positions and are on the same side of half of the hydrogen atoms of the other type of NH2 groups
the molecules. The N–N distances (146.7 pm on average) (N21 and N41) has short distances to nitrogen atoms of C=N
correspond to standard values of N–N single bonds in acid double bonds (N12···H41J: 220 pm, N32···H21K: 208 pm),
hydrazides.[12] C=N (130.1 pm) and C–O bond lengths while the others interact with the oxygen atoms of the ether
(129.6 pm) are in accordance with π-delocalization in the O– molecules (H21J···OE21: 209 pm; H41K···OE11: 205 pm[16]).
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Reactions of R2Ga–GaR2 [R = CH(SiMe3)2] with Acidic Reagents
Figure 2. Molecular structure and numbering scheme of 3; the thermal
ellipsoids are drawn at the 40% probability level; trimethylsilyl groups
and hydrogen atoms with the exception of NH are omitted; atoms of
the THF molecules with artificial radii. Selected bond lengths /pm and
angles /° (data of the second molecule in square brackets): Ga1–Ga2
245.19(4) [245.61(5)], Ga1–O11 195.4(2) [195.2(2)], Ga1–N12
208.6(2) [209.7(2)], Ga2–O21 194.4(2) [193.5(2)], Ga2–N22 205.6(2)
[205.8(3)], O11–C11 128.8(3) [129.0(4)], C11–N11 130.4(3)
[130.0(4)], N11–N12 146.0(3) [146.9(3)], O21–C21 129.7(3)
[130.9(4)], C21–N21 129.6(4) [129.5(5)], N21–N22 147.1(3)
[145.6(4)], O11–Ga1–N12 80.68(8) [80.39(9)], Ga2–Ga1–O11
102.49(6) [102.54(7)], N11–C11–O11 127.3(2) [126.8(3)], O21–Ga2–
N22 81.03(9) [80.7(1)], Ga1–Ga2–O21 104.35(7) [103.33(8)], N21–
C21–O21 127.6(3) [127.3(3)].
Figure 3. Hydrogen bonding in the dimeric formula unit of 2;
CH(SiMe3)2 and C6H4(CF3) groups are omitted; hydrogen atoms and
the atoms of the ether molecules are drawn with artificial radii.
for compounds 2–4 as schematically shown in Scheme 1. The
formation of cis/trans isomers having a different orientation
of the amino groups (Scheme 1) is an alternative explanation.
Cooling had a considerable influence on the ratio between both
isomeric forms. For 2 it changed from 1:0.4 at room tempera-
ture to 1:5 at –63 °C. The products of these reactions contain
sometimes an impurity in a concentration of about 5%, which
could be removed by treatment with n-pentane. It could not be
identified because we were not able to determine a complete
set of resonances in the NMR spectra. We suppose that cleav-
age of the Ga–Ga bond occurs in a minor side reaction to give
mononuclear dialkylgallium compounds similar to previous
observations.[3] Few transition metal complexes of such acid
hydrazides were reported in the literature.[18] However, we
could not find any structural information.
Polymerization of the molecules by hydrogen bonds to give
one-dimensional coordination polymers is probably prevented
by these interactions.
The NMR spectra of 2–4 are complicated and give evidence
for at least two species in solution. Two sets of resonances
were detected with the expected number of resonances and
intensity ratios. Caused by the chiral coordination sphere of
the gallium atoms the trimethylsilyl groups of each species
1
give two resonances in the H, 13C and 29Si NMR spectra. A
singlet resulted for the GaCHSi2 protons at a relatively high
field (δ = –0.46 to –0.54) in accordance with coordination
number four at the metal atoms.[6,9,17] The NH2 hydrogen
atoms of the hydrazide ligands are diastereotopic and give two
doublets in the 1H NMR spectra. For 2 an AB type of splitting
for one species could only be resolved upon cooling of a sam-
ple to –43 °C. The N–H resonances were completely assigned
based on 15N–1H correlated NMR spectroscopic data. A sim-
Reaction of 1 with Phenylphosphinic Acid
The digallium compound 1 and two equivalents of phenyl-
ilar equilibrium between two isomers has previously been ob- phosphinic acid were dissolved in THF. After 12 h at room
served for solutions of dimeric carboxylato-hydroxo digallium temperature the starting compounds were completely con-
compounds.[4] It was explained by a different coordination sumed [Equation (2)]. Concentration and cooling of the reac-
mode of the carboxylate groups which bridge the gallium tion mixture to 4 °C yielded colorless crystals of product 5 in
atoms of a single Ga–Ga bond or are bonded to two gallium 67% yield. 5 slowly decomposed in solution at room tempera-
atoms of different Ga2 pairs. In one case disorder in the solid ture to afford a mixture of unknown components. Therefore,
state resulted in superposition of both forms which gives very the complete NMR spectroscopic characterization proved to
nice evidence for this description. A similar situation may hold be difficult. Two resonances were observed for trimethylsilyl
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W. Uhl, M. Voß, A. Hepp
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remaining four edges are bridged by the chelating ligands. A
tetracyclic compound is formed which possesses four nine-
membered Ga3O4P2 heterocycles. Ga–O (193.3(2) and
196.1(2) pm)[15] and P–O distances (151.1(2) and 151.9(2) pm)
[19]
are in the expected ranges. Some complexes of phenyl-
phosphinate with transition metal atoms are reported in the
literature.[19] They show terminal and bridging coordination
modes of the phosphinate groups. Bond lengths and angles are
similar to those of 5.
Scheme 1. Possible configurations of compounds 2–4 in solution.
1
groups in the H and 29Si NMR spectra which may indicate a
chiral environment of the gallium atoms. The singlet of the
1
inner GaCHSi2 proton occurred at δ = –0.82 in the H NMR
spectrum which is in the characteristic range of four-coordinate
gallium atoms.[6,9,17] Elemental analysis verified the consti-
tution of 5 by an excellent agreement of experimental and cal-
culated data. The mass spectrum showed the molar mass of the
dimeric formula unit minus a bis(trimethylsilyl)methyl group.
Figure 4. Molecular structure and numbering scheme of 5; the thermal
ellipsoids are drawn at the 40% probability level; bis(trimethylsilyl)
methyl groups attached to gallium and hydrogen atoms with the excep-
tion of P–H are omitted. Selected bond lengths /pm and angles /°:
Ga1–Ga1Ј 244.11(6), Ga1–O1 193.3(2), Ga1–O2ЈЈ 196.1(2), P–O1
151.9(2), P–O2 151.1(2), O1–P–O2 114.0(1), Ga1Ј–Ga1–O1
109.97(7), Ga1Ј–Ga1–O2ЈЈ 114.12(7); Ga1Ј generated by –x, –y,
z; O2ЈЈ by –y, x, –z.
Azodicarbonamide and 1 – Cleavage of the Ga–Ga Bond
Treatment of the digallium compound 1 with equimolar
quantities of azodicarbonamide in THF at room temperature
gave cleavage of the Ga–Ga bond [Equation (3)]. CH2(SiMe3)2
as the expected product of substituent exchange reactions
could not be detected by NMR spectroscopy. The colorless
product 6 precipitated from the concentrated reaction mixture
in 70% yield. A singlet of the GaCHSi2 hydrogen atoms at a
relatively high field (δ = –0.58) indicates a coordination
Crystal structure determination (Figure 4) revealed an un- number of four at the gallium atoms.[6,9,17] Two resonances
1
precedented dimeric molecular structure with a perpendicular were observed for the trimethylsilyl groups in the H, 13C and
arrangement of two Ga–Ga bonds which are bridged by four 29Si NMR spectra of 6. They verify a molecular symmetry
chelating phosphinate ligands. The metal–metal distance of with a missing mirror plane bisecting the CSi2 angle. Intact
244.11(6) pm is in accordance with an unsupported Ga–Ga NH2 groups give a broad singlet at δ = 5.29. Hence, a proton
bond coordinated by electronegative substituents. The phenyl- transfer did not occur. Instead, the gallium atoms were oxid-
phosphinate ligands occupy bridging positions and connect ized to GaIII by insertion of the diazene unit of the starting aza
two gallium atoms of different Ga–Ga bonds. The molecular compound into the Ga–Ga bond, and the N=N double bond
structure may be derived from a distorted tetrahedron of gal- was reduced to give a hydrazine moiety with two adjacent car-
lium atoms. Two opposite edges are metal–metal bonds, the bonyl functions.
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Reactions of R2Ga–GaR2 [R = CH(SiMe3)2] with Acidic Reagents
ing the carboxyl carbon atoms (129.3 and 132.9 pm on
average) reflect a delocalized π-bonding in this part of the mo-
lecule (see above) which may influence the relatively short N–
N bond lengths by reduction of electron density at the nitrogen
atoms. The nitrogen atoms of the hydrazide group and the
amido groups as well as the carbon atoms of the carbonyl
groups have ideal planar coordination spheres with sums of
the angles of 360°. Each NH2 group is coordinated to a DME
molecule via hydrogen bonding. The DME molecules are not
in plane with the nitrogen and hydrogen atoms, but are bonded
in an unsymmetric manner. A short H···O distance results per
amido group (H011···O35: 211 pm; H022···O42: 209 pm)
which indicates a relatively strong hydrogen bond[16] and rep-
resents the main contact between both molecules. The second
oxygen atoms of the DME molecules have considerably longer
distances to both hydrogen atoms of the amido groups
(O32···H 278 and 292 pm, O45···H 276 and 295 pm) indicating
a negligible bonding interaction.
Crystal structure determination (Figure 5) verified the mo-
lecular constitution. The gallium atoms have coordination
numbers of four and are bonded to two bis(trimethylsilyl)-
methyl groups, a nitrogen atom of the hydrazine group and
the oxygen atom of the carbonyl group. Two five-membered
GaCN2O heterocycles result which are annulated via the cen-
tral N–N bond. The N–N bond lengths (143.1 pm on average)
are in the lower range of N–N bonds in hydrazine deriva-
tives,[12] but correspond well to values of dicarbonyl hydra-
zides.[20] Ga–O (194.6 pm) and Ga–N distances (201.6 pm on
average) are in normal ranges. C–O and C–N distances includ-
Experimental Section
General: All procedures were carried out under an atmosphere of puri-
fied argon in dried solvents (THF and dimethoxyethane (DME) over
Na/benzophenone). The tetraalkyldigallium compound 1 and 2,6-
dichloroisonicotinic acid were obtained according to literature pro-
cedures.[1,21] 2-Chlor-6-hydrazineisonicotinic acid hydrazide was ob-
tained according to a modified literature procedure[22] by the treatment
of 2,6-dichlorisonicotinic acid with an excess of hydrazine hydrate in
ethanol under reflux conditions. It precipitated directly from the reac-
tion mixture in high purity. The starting compounds 4-trifluormethyl-
benzhydrazide, 2-fuoric acid hydrazide (furan-2-carboxylic acid hydra-
zide) and 2-chlor-6-hydrazineisonicotinic acid hydrazide and azadicar-
bonamide (azodicarboxylic acid diamide) were applied as purchased.
The assignment of the NMR spectra is based on HSQC, HMBC, H/
Si-HMBC, ROESY and DEPT135 data. Only the most intensive
masses of a particular molecular fragment are given in the description
of the mass spectra; the isotopic patterns were in agreement with the
calculated ones.
Synthesis
Compound 2: The solid digallium compound 1 (0.242 g, 0.312 mmol)
and 4-trifluormethylbenzhydrazide (0.128 g, 0.627 mmol) were dis-
solved in THF (20 mL) at room temperature. The mixture was stirred
for 3 d. Concentration of the solution and cooling to +4 °C afforded
colorless crystals of 2. Two isomers were detected in solution by NMR
spectroscopy with an intensity ratio of 1 to 0.4 at room temperature
and 1 to 5 at –63 °C (see Results and Discussion). Yield: 0.180 g
1
(62%; 2·THF). M.p. (argon, sealed capillary): 183 °C (dec). H NMR
(400 MHz, [D8]THF, 298 K): Major component: δ = 8.18 (d , 4 H,
3
3J(H,H) = 8.2 Hz, ortho-H of phenyl), 7.64 (d , 4 H, JH,H = 8.2 Hz,
2
Figure 5. Molecular structure and numbering scheme of 6; the thermal
ellipsoids are drawn at the 40% probability level; trimethylsilyl groups
and hydrogen atoms with the exception of NH2 are omitted; atoms of
the DME molecules with artificial radii. Selected bond lengths /pm
and angles /° (data of the second molecule in square brackets): Ga1–
O1 194.5(1) [194.8(1), Ga1–N11Ј 201.7(1) [201.5(1)], N11–N11Ј
143.0(2) [143.1(2)], C1–N11 132.1(2) [131.9(2)], C1–N12 133.7(2)
[134.0(2)], C1–O1 129.2(2) [129.3(2)], N11Ј–Ga1–O1 80.39(4)
[80.44(4)], C1–N11–Ga1Ј 136.8(1) [136.8(1)]; Ga1Ј and N11Ј gener-
ated by –x + 1, –y, –z.
meta-H of phenyl), 6.29 and 6.18 (each 2 H, d, JH,H = 12.8 Hz,
GaNH2), 0.12 and 0.03 (each 18 H, s, SiMe3), –0.50 (s , 2 H,
GaCHSi2); minor component: δ = 8.14 (d , 4 H, 3JH,H = 8.2 Hz, ortho-
H of phenyl), 7.61 (d , 4 H, JH,H = 8.2 Hz, meta-H of phenyl), 6.20
(4 H, br., s, NH2), 0.06 and 0.03 (each 18 H, s, SiMe3), –0.49 (s , 2
H, GaCHSi2); the resonance of the NH2 protons gave a typical AB
pattern upon cooling to –43 °C: δ = 6.55 and 6.52;[23] intensity ratio
f1,f4 to f2,f3 1:7.3; JH,H = 13.0 Hz. 13C NMR (100 MHz, [D8]THF,
3
2
298 K): Major component: δ = 169.8 (CO), 138.7 (ipso-C of phenyl),
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W. Uhl, M. Voß, A. Hepp
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132.3 (q, JCF = 32.0 Hz, para-C of phenyl), 129.4 (ortho-C of
2
mixture was stirred for 12 h. Concentration of the solution and cooling
to –30 °C afforded colorless crystals of 4, which were treated with n-
1
phenyl), 125.4 (meta-C of phenyl), 125.0 (q, JCF = 271.4 Hz, CF3),
10.0 (GaCSi2), 4.0 and 3.4 (SiMe3); minor component: δ = 169.8 (CO), pentane (10 mL) to remove an unknown impurity. Two isomers were
2
138.8 (ipso-C of phenyl), 132.2 (para-C of phenyl, JCF = 32.2 Hz), detected in solution by NMR spectroscopy with an intensity ratio of 1
1
129.2 (ortho-C of phenyl), 125.4 (meta-C of phenyl), 125.0 (q, JCF
=
to 0.5 at room temperature (see Results and Discussion). Yield: 0.250 g
(65%, 4·THF). M.p. (argon, sealed capillary): 198 °C (dec). H NMR
271.4 Hz, CF3), 10.0 (GaCSi2), 3.8 and 3.5 (SiMe3). 29Si NMR
1
(79.5 MHz, [D8]THF, 298 K): Major component: δ = –1.30 and –1.35; (400 MHz, [D8]THF): Major component: δ = 7.28 (s , 2 H, NH2NH
minor component: δ = –1.35 and –1.41. 19F NMR ([D8]THF,
376.5 MHz, 298 K): Major component: δ = –63.5; minor component:
of hydrazinyl), 7.17 (s , 2 H, ortho-H of pyridyl, NHCCH), 7.04 (s ,
2
2 H, ortho-H of pyridyl, ClCCH), 6.25 and 6.15 (each 2 H, d, JH,H
=
δ = –63.5. IR (CsI, paraffin): ν(bar) = 3319 vw, 3279 w, 3183 w νNH; 13.0 Hz, GaNH2), 3.97 (s , 4 H, NH2 of hydrazinyl), 0.10 und 0.03
2951 vs, 2924 vs, 2853 vs. (paraffin); 1931 m, 1856 vw, 1809 w, 1692
w, 1609 s, 1582 m, 1541 s, 1514 m δNH, νC=N, νC=O, aromatic ring;
(each 18 H, s, SiMe3), –0.53 (s , 2 H, GaCHSi2); minor component: δ
= 7.23 (s , 2 H, NH2NH of hydrazinyl), 7.14 (s , 2 H, ortho-H of
1460 vs, 1375 vs. (paraffin); 1323 s, 1248 s δCH3; 1169 s, 1134 s, pyridyl, NHCCH), 7.04 (s , 2 H, ortho-H of pyridyl, ClCCH), 6.19
1105 m, 1067 s, 1045 w νCC, νCN, νCF, νNN; 1016 s δCHSi2; 955
m, 895 w, 843 vs, 762 m ρCH3(Si); 723 m (paraffin); 671 m νSiC;
588 s, 503 s, 451 s, 401 sh, 388 m, 341 m νGaC, νGaO, νGaN cm–1.
MS (EI, 20 eV, 250 °C): m/z (%) 860 (4), 862 (6), 863 (3), 864 (3)
and 6.16 (each 2 H, m, covered, GaNH2), 3.97 (s , 4 H, NH2 of hy-
drazinyl), 0.06 und 0.03 (each 18 H, s, SiMe3), –0.52 (s , 2 H,
GaCHSi2). 13C NMR (100 MHz, [D8]THF): Major component: δ =
169.4 (CO), 163.3 (meta-C of pyridyl, NH2NHC), 149.9 (meta-C of
(M+ of the monomeric formula unit – 2 H); 431 (100), 433 (75) (½M+). pyridyl, ClC), 145.9 (ipso-C of pyridyl), 110.8 (ortho-C of pyridyl,
CHN (C30H50F6Ga2N4O2Si4+OC4H8) (936.6): calcd. C 43.6, H 6.2, N
6.0; found C 43.6, H 6.1, N 6.3%.
ClCCH), 104.7 (ortho-C of pyridyl, NHCCH), 10.0 (GaCSi2), 4.1 and
3.4 (SiMe3); minor component: δ = 169.4 (CO), 163.3 (meta-C of
pyridyl, NH2NHC), 149.9 (meta-C of pyridyl, ClC), 146.0 (ipso-C of
Compound 3: The solid digallium compound 1 (0.303 g, 0.391 mmol) pyridyl), 110.9 (ortho-C of pyridyl, ClCCH), 104.6 (ortho-C of pyr-
idyl, NHCCH), 10.0 (GaCSi2), 3.8 and 3.5 (SiMe3). 29Si NMR
and 2-fuoric acid hydrazide (0.099 g, 0.786 mmol) were dissolved in
THF (20 mL) at room temperature. The mixture was stirred for 12 h.
Concentration of the solution and cooling to +4 °C afforded colorless
crystals of 3, which were washed with of n-pentane (10 mL) to remove
an unknown impurity. Two isomers were detected in solution by NMR
spectroscopy with an intensity ratio of 1 to 0.5 (see Results and Dis-
cussion). Yield: 0.230 g (83%). M.p. (argon, sealed capillary): 198 °C
(79.5 MHz, [D8]THF): Major component: δ = –1.29 and –1.39; minor
component: δ = –1.39 and –1.43. IR (CsI, paraffin): ν(bar) = 3356 w,
3265 s,br. νNH; 2949 vs, 2922 vs, 2853 vs. (paraffin); 1921 w, 1852
vw, 1688 w, 1653 w, 1605 vs, 1574 m, 1545 s δNH, νC=N, νC=O,
aromatic ring; 1462 vs. (paraffin); 1420 s δCH3; 1377 vs. (paraffin);
1358 vs, 1294 w, 1248 vs. δCH3; 1200 s, 1150 s, 1092 m νCC, νCN,
νNN; 1018 s δCHSi2; 970 w, 937 s, 864 vs, 843 vs, 772 s, 752 s
ρCH3(Si); 725 s (paraffin); 673 s νasSiC; 613 m νsSiC; 571 m, 540 m,
494 s, 465 w, 430 w, 382 w, 341 w νGaC, νGaO, νGaN cm–1. CHN
(C26H52Cl2Ga2N10O2Si4·OC4H8) (931.5): calcd. C 38.7, H 6.5, N 15.0;
found C 39.9, H 6.2, N 15.3%.
1
(dec). H NMR (400 MHz, [D8]THF): Major component: δ = 7.46 (m
, 2 H, OCH), 6.85 (m , 2 H, OCHCHCH), 6.41 (m , 2 H, OCHCH),
2
6.57 and 6.01 (each 2 H, d, JH,H = 12.6 Hz, GaNH2), 0.11 and 0.03
(each 18 H, s, SiMe3), –0.54 (s , 2 H, GaCHSi2); minor component: δ
= 7.30 (m , 2 H, OCH), 6.70 (m , 2 H, OCHCHCH), 6.27 (m , 2 H,
2
OCHCH), 6.94 and 6.00 (each 2 H, d, JH,H = 12.6 Hz, GaNH2), 0.10
and 0.09 (each 18 H, s, SiMe3), –0.46 (s , 2 H, GaCHSi2). 13C NMR
(100 MHz, [D8]THF): Major component: δ = 164.9 (C=N), 149.8
(ipso-C of furyl), 144.8 ((OCHCHCH), 113.6 (OCHCHCH), 111.5
(OCHCHCH), 9.9 (GaCSi2), 4.0 and 3.4 (SiMe3); minor component:
δ = 165.2 (C=N), 149.3 (ipso-C of furyl), 144.8 ((OCHCHCH), 113.6
(OCHCHCH), 111.4 (OCHCHCH), 9.4 (GaCSi2), 3.9 and 3.7 (SiMe3).
29Si NMR (79.5 MHz, [D8]THF): Major component: δ = –1.28 and
–1.33; minor component: δ = –1.06 and –1.24. 15N NMR ([D8]THF,
40.5 MHz): Major component: δ = 220 (C=N), 74.5 (NH2); minor
component: δ = C=N not detected, 75.0 (NH2). IR (CsI, paraffin):
ν(bar) = 3316 vw, 3275 m, 3244 m, 3113 w νNH; 2951 vs, 2920 vs,
2853 vs. (paraffin); 1921 w, 1856 vw, 1748 w, 1738 w, 1676 w, 1616
s, 1587 m, 1543 m, 1522 m, 1487 s δNH, νC=N, νC=O, furyl ring;
1464 vs. (paraffin); 1400 s δCH3; 1377 vs. (paraffin); 1362 vs, 1246
vs. δCH3; 1223 vs, 1204 vs, 1175 s, 1128 m, 1074 m, 1053 s νCC,
νCN, νNN; 1011 vs. δCHSi2; 952 s, 930 sh, 862 vs, 843 vs, 745 m
ρCH3(Si); 727 s (paraffin); 669 s νasSiC; 640 vw, 619 s νsSiC; 592 s,
577 s, 507 s, 494 s, 426 s νGaC, νGaO, νGaN cm–1. MS (EI, 20 eV,
160 °C): m/z (%) 704 (57), 706 (91), 707 (39), 708 (44) (M+ of the
monomeric formula unit – 2 H); 579 (37), 581 (60), 582 (23), 583 (30)
(M+ – H2N-NC(O)-C4H3O (chelating ligand) – 2 H); 547 (22), 549
Compound 5: The solid digallium compound 1 (0.260 g, 0.335 mmol)
and phenylphosphonic acid (0.096 g, 0.676 mmol) were dissolved in
THF (20 mL) at room temperature. The mixture was stirred for 12 h.
Concentration of the solution and cooling to +4 °C afforded colorless
crystals of 5. Compound 5 decomposes slowly in solution (see Results
and Discussion). Yield: 0.165 g (67%). M.p. (argon, sealed capillary):
1
215 °C. 1H NMR (400 MHz, [D8]THF): δ = 8.06 (d , 4 H, JHP
=
562.5 Hz, PH), 7.82 (m , 8 H, ortho-H of phenyl), 7.60 (m , 4 H, para-
H of phenyl), 7.53 (m , 8 H, meta-H of phenyl), –0.07 and –0.11 (s ,
72 H, SiMe3), –0.82 (s , 4 H, GaCHSi2). 13C NMR (100 MHz,
1
[D8]THF): δ = 134.0 (d, JC,P = 145.7 Hz, ipso-C of phenyl), 133.3
2
(para-C of phenyl), 130.3 (d, JC,P = 14.1 Hz, ortho-C of phenyl),
3
129.4 (d, JCP = 14.6 Hz meta-C of phenyl), 10.3 (GaCSi2), 3.8
(SiMe3, both resonances coincide). 29Si NMR (79.5 MHz, [D8]THF):
δ = –0.9 and –1.0. IR (CsI, paraffin): ν(bar) = 2382 vs. νPH; 1977 w,
1956 w, 1910 w, 1883 w, 1850 w, 1809 w, 1759 vw, 1663 w, 1593 m
phenyl; 1464 vs, 1377 vs. (paraffin); 1329 w, 1304 m, 1292 m, 1240
s δCH3; 1179 s, 1132 s, 1055 s νCC; 1020 s δCHSi2; 974 s, 943 vs,
920 vw, 864 s, 847 s, 791 vw, 773 m, 745 s ρCH3(Si); 711 m (paraffin);
689 s, 667 s νasSiC; 619 m νsSiC; 552 vs, 500 s, 464 vs, 409 m, 351
s νGaC, νGaO, νPO cm–1. MS (EI, 20 eV, 160 °C): m/z (%) 1318 (0.2),
1320 (0.3), 1321 (0.2), 1322 (0.2) (M+ – CH2(SiMe3)2); 1109 (0.4),
1110 (0.3), 1111 (0.4), 1112 (0.3) (M+ – GaCH(SiMe3)2PHO2Ph); 738
(0.6), 740 (1.4), 741 (1.7), 742 (1.1) (½ M+); 369 (100), 370 (22),
371 (75), 372 (17) ([GaCH(SiMe3)2PHO2Ph]+). CHN (solvent free)
(29), 551 (13) (M+
– CH2(SiMe3)2). CHN (solvent free)
(C24H48Ga2N4O4Si4) (708.4): calcd. C 40.7, H 6.8, N 7.9; found C
41.2, H 6.9, N 8.2%.
Compound 4: The solid digallium compound 1 (0.321 g, 0.414 mmol)
and 2-chloro-6-hydrazinylisonicotinic acid hydrazide (0.167 g, (C52H100Ga4O8P4Si8) (1480.8): calcd. C 42.2, H 6.8; found C 41.9, H
0.829 mmol) were dissolved in THF (20 mL) at room temperature. The 6.8%.
1850
www.zaac.wiley-vch.de
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 1845–1852

Reactions of R2Ga–GaR2 [R = CH(SiMe3)2] with Acidic Reagents
Compound 6: The solid digallium compound 1 (0.311 g, 0.401 mmol) atoms were calculated on ideal positions and allowed to ride on the
bonded atom with U = 1.2Ueq(C). N–H hydrogen atoms were in all
cases found in the Fourier maps after refinement of all heavier atoms
and the other hydrogen atoms. But they were refined on ideal positions
by using the corresponding HFIX instruction for compounds 2 and 3;
only for 6 they were refined without restrictions. Compound 2 crys-
tallizes with two independent formula units in the asymmetric unit
which are connected by hydrogen bonds. Two trifluormethyl groups
are disordered (C107 and C307). Their fluorine atoms were refined on
split positions (0.59:0.41 and 0.83:0.17, respectively). Two diethyl
ether molecules are connected to the dimeric molecules via hydrogen
bonds. Compound 3 crystallizes with two independent formula units
in the asymmetric unit. In contrast to compound 2 their counterparts
connected by hydrogen bonds are generated by the crystallographic
center of symmetry. A complete furyl group was disordered (C42). Its
atoms were refined on split positions with site occupancy factors of
0.55:0.45. Two THF molecules are coordinated to each dimeric for-
mula unit by hydrogen bonds. Due to the relatively large U values of
their atoms they were refined with isotropic displacement factors. The
crystals of compound 5 enclose two THF molecules per formula unit.
and azodicarbonamide (0.047 g, 0.405 mmol) were dissolved in THF
(20 mL) at room temperature. The mixture was stirred for 12 h. The
solution was concentrated and cooled to 4 °C to yield colorless crystals
of 6. Alternatively all volatiles were removed in vacuo. The remaining
solid was dissolved in DME in an ultrasound bath. Storing of the solu-
tion at room temperature gave crystals of 6. Yield: 0.300 g (70% of
6·2DME). M.p. (argon, sealed capillary): 142 °C (dec). 1H NMR
(400 MHz, [D8]THF): δ = 5.29 (s , 4 H, NH2), 0.10 and 0.18 (each 36
H, s, SiMe3), –0.58 (s , 2 H, GaCHSi2). 13C NMR (100 MHz,
[D8]THF): δ = 160.9 (C=O), 6.9 (GaCSi2), 4.5 and 4.4 (SiMe3). 29Si
NMR (79.5 MHz, [D8]THF): δ = 0.1 and –0.3. IR (CsI, paraffin):
ν(bar) = 3526 s, 3422 s νNH; 2949 vs, 2922 vs, 2853 vs. (paraffin);
1607 s, 1537 s νC=O, δNH; 1464 vs, 1377 vs. (paraffin); 1364 m,
1294 w, 1242 vs. δCH3; 1090 m, 1047 w νNN, νCN; 1018 vs. δCHSi2;
966 s, 956 s, 844 vs, 779 m, 756 m ρCH3(Si); 727 m (paraffin); 671
s νasSiC; 623 m νsSiC; 514 s, 484 s, 347 m νGaC, νGaN cm–1. MS
(EI, 20 eV, 100 °C): m/z (%): 875 (1.6), 877 (3.2), 878 (1.8), 879 (1.9)
(M+ – CH3); 731 (58), 733 (100), 734 (52), 735 (53) (M+ – CH(SiMe3)
2); 387 (43), 388 (15), 389 (37) (Ga[CH(SiMe3)2]2+). CHN (solvent They do not show any close contact to the digallium molecules. Their
atoms were refined with isotropic U values. The molecules of com-
pound 6 are located on crystallographic centers of symmetry with two
independent molecular halves in the asymmetric unit. Two DME mole-
cules are bonded to each dimer via a hydrogen bridge to one oxygen
atom.
free after evacuation) (C30H80Ga2N4O2Si8) (893.1): calcd. C 40.3, H
9.0, N 6.3; found C 40.1, H 8.9, N 6.1%.
Crystal Structure Determinations
Single crystals were obtained directly from the reaction mixtures (3,
5) or by recrystallization from diethyl ether (2) or DME (6). Intensity
data were collected on a Bruker APEX II diffractometer with mono-
chromated Mo-Kα (3, 5, 6) or Cu-Kα (2) radiation. The crystals were
coated with a perfluoropolyether, picked up with a glass fiber and
immediately mounted in the cooled nitrogen stream of the dif-
fractometer. The crystallographic data and details of the final R values
are provided in Table 1. The structures were solved by direct methods
and refined with the program system SHELXL-97[25] with full-matrix
and all independent structure factors (F2). All non-hydrogen atoms
were refined with anisotropic displacement parameters; hydrogen
The crystallographic data were deposited as supplementary publication
no. CCDC-828709 (for 2·OEt2), -828707 (for 3·THF), -828708 (for
5·4THF) and -828710 (for 6·2DME). These data can be obtained free
of charge from the Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, Great Britain (Fax: +44-1223-336-033;
E-mail: deposit@cccd.cam.ac.uk).
Acknowledgement
We are grateful to the Deutsche Forschungsgemeinschaft (IRTG-1444)
for generous financial support.
Table 1. Crystal data and structure refinement for compounds 2, 3, 5, and 6.
2·OEt2
3·THF
5·4THF
6·2DME
Formula
C34H60F6Ga2N4O3Si4 C28H56Ga2N4O5Si4
C68H132Ga4O12P4Si8 C38H100Ga2N4O6Si8
Crystal system
triclinic
P1; No. 2
triclinic
P1; No. 2
tetragonal
I4; No. 82
triclinic
P1; No. 2
Space group[24]
¯
¯
¯
¯
Z
4
4
2
2
T /K
153(2)
1.317
153(2)
1.262
153(2)
1.177
153(2)
1.157
Density (calc) /g·cm–3
a /pm
b /pm
c /pm
α /°
1465.42(9)
1532.8(1)
2364.7(2)
91.959(2)
105.001(1)
111.198(1)
4.7351(5)
2.868
1251.18(8)
1396.45(9)
2574.1(2)
86.707(1)
89.162(1)
66.185(1)
4.1075(5)
1.464
1874.60(6)
1874.60(6)
1420.58(9)
90
90
90
1240.23(5)
1257.10(5)
2074.97(8)
88.496(1)
87.391(1)
72.469(1)
3.0814(2)
1.068
β /°
γ /°
V /nm3
4.9921(4)
1.177
μ /mm–1
Crystal size /mm
Radiation
0.24ϫ 0.20ϫ 0.02
Cu-Kα
0.29ϫ 0.27ϫ 0.16
Mo-Kα
0.43ϫ 0.20ϫ 0.15
Mo-Kα
0.23ϫ 0.11ϫ 0.08
Mo-Kα
Θrange for data collection /°
Independent reflections
Parameters
1.95 Յ 72.63
1.58 Յ 31.86
1.54 Յ 31.68
1.70 Յ 28.04
16155 (Rint = 0.0483) 25635 (Rint = 0.0274) 7900 (Rint = 0.0237) 14883 (Rint = 0.0201)
1026
786
202
563
R1 [I Ͼ 2σ(I)]
0.0539 (12421)
0.1558
+1324/–564
0.0517 (16814)
0.1501
+1850/–969
0.0410 (6934)
0.1304
+1119/–445
0.0285 (12461)
0.0737
+383/–242
wR2 (all data)
Max./ min. residual electron density /1030
e·m–3
R1 = Σ||Fo|–|Fc||/Σ|Fo|, wR2 = {Σ [w(Fo –Fc ) ]/Σ [w(Fo ) ]}1/2
2
2 2
2 2
Z. Anorg. Allg. Chem. 2011, 1845–1852
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1851

W. Uhl, M. Voß, A. Hepp
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Received: June 8, 2011
Published Online: August 31, 2011
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Z. Anorg. Allg. Chem. 2011, 1845–1852