Gallium-gallium bonds bridged by functionalized carboxylato ligands

Article abstract of DOI:10.1002/zaac.200900579

Treatment of the tetraalkyldigallium compound R₂Ga-GaR ₂ [R = CH(SiMe₃)₂] (1) with a large number of different functionalized carboxylic acids afforded dicarboxylatodigallium compounds R₂Ga₂(μ- O₂C-R)₂, in which two carboxylato ligands bridge the Ga-Ga bonds. The chelating ligands have additional nitrogen, oxygen or phosphorus donor atoms and may be suitable to act as Lewis-bases to yield supramolecular aggregates in future investigations. Four compounds havebeen characterized by crystal structure determinations. One gave unprecedented dimeric formula units in the solid state by Ga-N interactions. The similar reaction with isonicotinic acid resulted in the cleavage of the Ga-Ga bond. A tetragallium compound was formed in which four isolated metal atoms were bridged by four organic ligands to give a square molecular core.

Full text of DOI:10.1002/zaac.200900579

ARTICLE
DOI: 10.1002/zaac.200900579
Gallium–Gallium Bonds Bridged by Functionalized Carboxylato Ligands
Werner Uhl,*[a] Henrik R. Bock,[a] Jutta Kösters,[a] and Matthias Voß[a]
Dedicated to Professor Bernd Harbrecht on the Occasion of His 60th Birthday
Keywords: Gallium; Carboxylato ligands; Subvalent compounds; Gallium–gallium bonds; π Stacking
Abstract. Treatment of the tetraalkyldigallium compound R2Ga–GaR2 been characterized by crystal structure determinations. One gave un-
[R = CH(SiMe3)2] (1) with a large number of different functionalized precedented dimeric formula units in the solid state by Ga–N interac-
carboxylic acids afforded dicarboxylatodigallium compounds R2Ga2(μ- tions. The similar reaction with isonicotinic acid resulted in the cleav-
O2C–R)2, in which two carboxylato ligands bridge the Ga–Ga bonds. age of the Ga–Ga bond. A tetragallium compound was formed in
The chelating ligands have additional nitrogen, oxygen or phosphorus which four isolated metal atoms were bridged by four organic ligands
donor atoms and may be suitable to act as Lewis-bases to yield supra- to give a square molecular core.
molecular aggregates in future investigations. Four compounds have
very selective reactions, which, depending on the rigidity of
the backbone of the bridging ligands, had two or four Ga–Ga
Introduction
The facile synthesis of the first organoelement compounds
with Al–Al, Ga–Ga or In–In single bonds, R2E–ER2, was a
mile-stone in Group 13 chemistry [1–3]. These compounds
were stabilized by four bulky bis(trimethylsilyl)methyl groups
and initiated broad research activities in that field [4]. They
showed a singular chemical reactivity and many unprecedented
secondary products have been isolated. Insertion reactions suc-
ceeded with atoms and molecules, deprotonation of the C–H
acidic bis(trimethylsilyl)methyl groups gave a heterocyclic
compound, electron transfer yielded radical anions containing
1e-E–E π-bonds, a metathesis reaction afforded a monomeric
gallium telluride, and adducts were formed with suitable neu-
tral or anionic donor ligands [5]. Substituent exchange reac-
tions by retention of the E–E bonds are particularly interesting.
However, the treatment of the dialuminum and diindium com-
pounds with protic reagents gave exclusively cleavage of the
E–E bonds [6], and only the reaction of the digallium com-
pound R2Ga–GaR2 [R = CH(SiMe3)2] (1) with carboxylic ac-
ids, acetylacetone derivatives, or diphenyltriazene resulted in
the replacement of two alkyl groups [5, 7]. The dicarboxylato-
digallium compounds (2, Scheme 1) exhibit a unique molecu-
lar structure, in which the Ga–Ga bonds were bridged by two
chelating groups in a perpendicular arrangement. With this par-
ticular structural motif these compounds are ideally preorgan-
ized to form large macrocycles by the reaction with dicarbox-
ylic acids. Indeed, heterocyclic compounds were formed in
bonds in single molecules (3, Scheme 1) [8]. These com-
pounds may be described as soluble, molecular analogues of
metalorganic frame-work materials, which have been gener-
ated by the application of the same kind of ligands [9]. Surpris-
ingly, also reactions in the presence of an excess of water did
not result in the cleavage of the Ga–Ga bonds, instead molecu-
lar boxes with bridging hydroxo and carboxylato groups (4,
Scheme 1) [10] or a novel subhydroxide of gallium [11] have
been isolated.
We report herein on our first experiments to synthesize func-
tionalized dicarboxylatodigallium compounds, which are po-
tentially suitable to coordinate metal atoms or to form adducts
by hydrogen bonding and may open the access to interesting
supramolecular aggregates.
Results and Discussion
Reactions of the Digallium Compound 1 with Carboxylic
Acids by Retention of the Ga–Ga Bonds
The tetraalkyldigallium compound 1 was treated with 14 dif-
ferent functionalized carboxylic acids having additional nitro-
gen, phosphorus, or oxygen donor atoms [Equation (1),
Scheme 2]. The synthetic procedure followed the standard
method already published in the literature [8]. THF was ap-
plied as a solvent because due to our experience it is the most
effective solvent for these proton transfer reactions. The digal-
lium compound 1 was dissolved in THF and added to a solu-
tion of the acid in the same solvent or treated with the solid
acids at room temperature. The yellow color of 1 disappeared,
and NMR spectroscopy revealed that the starting compounds
were consumed completely after stirring of the mixtures for 12
* Prof. Dr. W. Uhl
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, H. R. Bock, J. Kösters, M. Voß
ARTICLE
Scheme 2. Substituents R of the carboxylic acids applied in Equation (1).
Scheme 1.
to 48 hours. Many of these carboxylic acids are only sparingly
soluble in THF. Suspensions resulted, and the completion of
the reactions was indicated by the formation of clear solutions.
Usually, these solutions were concentrated and cooled to get
colorless solids of the products. In some cases relatively pure
compounds were directly obtained by complete removal of all
volatiles and washing of the remaining raw products with n-
pentane. Only compound 8 was obtained as a highly viscous
liquid, which could not be isolated in a solid form and could
not be purified by recrystallization. However, its purity was
high enough to allow its characterization and unambiguous
identification by spectroscopic methods.
1
The H NMR spectra of all products (5 to 18) exhibit the
expected integration ratios with one bis(trimethylsilyl)methyl
group per one carboxylato ligand in all cases. The resonances
Despite intensive efforts only few compounds (9, 10, 15, and
of the methine protons (GaCHSi2) appear at about δ = –0.1 16) could be obtained as single crystals suitable for crystal
to –0.5. They are considerably shifted to a higher field com- structure determinations. Three of these (9, 15 and 16; Fig-
pared to the corresponding value of the starting compound 1 ure 1, Figure 2, and Figure 3) have the expected molecular
(δ = 1.11) [2], which is essentially caused by the enhancement structures, which have the intact Ga–Ga bonds symmetrically
of the coordination number of the gallium atoms from three to bridged by two chelating carboxylato ligands. The Ga–Ga
four and has been observed several times before for mononu- bond lengths [237.49(4), 237.11(5), 237.48(av) pm] are in a
clear or dinuclear bis(trimethylsilyl)methylgallium compounds very narrow range and correspond to standard values of those
[12]. A similar alteration resulted for the chemical shifts of the digallium dicarboxylates [7, 8, 10]. They are considerably
carbon atoms attached to gallium (δ = 25.9 for 1 compared to shorter than the Ga–Ga distance in the tetraalkyldigallium
about δ = 5 for the digalliumdicarboxylates 5 to 18).
starting compound 1 (254.1 pm), which is caused by the bridg-
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Z. Anorg. Allg. Chem. 2010, 1851–1859

Gallium–Gallium Bonds Bridged by Carboxylato Ligands
tion by π stacking [14]. One-dimensional coordination poly-
mers result, which, caused by the perpendicular arrangement
of the carboxylato ligands at the Ga–Ga bonds, form zigzag
chains of the monomeric formula units. These secondary inter-
actions influence considerably the solubility of 15. Once crys-
tallized it becomes insoluble in organic solvents such as n-
pentane, toluene, 1,2-difluorobenzene, or even THF.
Figure 1. Molecular structure and numbering scheme of 9; the thermal
ellipsoids are drawn at the 40 % probability level; methyl groups and
hydrogen atoms are omitted. Selected bond lengths /pm and angles /°:
Ga1–Ga1' 237.49(4), Ga1–C1 195.7(2), Ga1–O1 202.2(1), Ga1–O2'
201.7(1), Ga1'–Ga1–C1 153.40(5), O1–Ga1–O2' 97.04(5), Ga1'–Ga1–
O1 89.15(4), Ga1'–Ga1–O2' 87.12(4); Ga1' and O2' generated by –x,
y, 0.5–z.
Figure 2. Molecular structure and numbering scheme of 15; the ther-
mal ellipsoids are drawn at the 40 % probability level; methyl groups
and hydrogen atoms are omitted. Selected bond lengths /pm and an-
gles /°: Ga1–Ga1' 237.11(5), Ga1–C1 195.1(2), Ga1–O11 202.6(1),
Ga1–O12' 201.2(2), Ga1'–Ga1–C1 154.25(7), O11–Ga1–O12'
93.86(6), Ga1'–Ga1–O11 86.93(4), Ga1'–Ga1–O12' 89.65(4); Ga1' and
O12' generated by –x, y, 0.5–z.
ing ligands and by the coordination of the gallium atoms to
In contrast, compound 10 shows a completely different and
electronegative oxygen atoms. Also, the Ga–O [200.1(3) to unprecedented structural motif (Figure 5; schematic drawing
202.6(1) pm] and C–O distances of the carboxylato groups in Scheme 3). It forms dimeric formula units, which possess
[126.5(2) to 128.3(4) pm] are in the expected ranges. The car- two Ga–Ga bonds. Each Ga2 couple is bridged by only one
boxylato groups adopt an almost ideal perpendicular arrange- chelating carboxylato group with Ga–O (205.4 pm on average)
ment with angles O–Ga–O between 93.9 and 97.0°. The largest and C–O bond lengths (125.2 pm) in narrow ranges as de-
angle belongs to the sterically most encumbered diphenylphos- scribed before. The Ga–Ga bonds [239.44(8) pm] are only
phanyl derivative 9. The angles C–Ga–Ga including the central slightly lengthened compared to the twofold bridged species
carbon atoms to the terminal alkyl groups approach linearity discussed above. The second type of carboxylato ligands coor-
(153.4 to 159.0°). This particular situation at the Ga–Ga bonds dinates only to a single gallium atom via one of the oxygen
of these molecules has been interpreted in terms of sp-hybrid- atoms. Expectedly the respective Ga–O distances [Ga1–O21
ized gallium atoms [13]. The sp-orbitals are involved in the 192.0(2) pm] are considerably shorter than those including the
formation of the Ga–Ga bonds and the terminal Ga–C bonds, bridging carboxylato groups. Two different C–O distances re-
whereas the Ga–O interactions are essentially mediated by the sult [127.5(4) and 120.6(5) pm] which indicate a more local-
remaining p orbitals. The diphenylisonicotinic carboxylato ized bonding situation including a terminal C=O double bond.
compound 15 shows an interesting arrangement of the molecu- The second gallium atom (Ga2) completes its coordination
les with strong intermolecular interactions in the solid state. sphere by an interaction to a nitrogen atom of a pyrazolyl
The phenyl rings and the central pyridinyl group of one ligand group [Ga2–N14' 219.2(3) pm] of a neighboring molecule.
are almost ideally in a plane with a maximum deviation of an The Ga–N bond length is in the upper range characteristic of
atom from the mean plane of only 9 pm. The pyridyl and one dative Ga–N interactions [15]. Two of these interactions give
phenyl ring of each ligand have close contacts to the pyridyl the dimeric formula unit of 10 in the solid state. The pyrazolyl
ring and a phenyl group of a neighboring molecule, as shown groups involved in this adduct formation are part of those car-
with three formula units of 15 in Figure 4. The average dis- boxylato groups which bridge the Ga–Ga bonds. The determi-
tance between the rings is about 350 pm indicating an interac- nation of the molar mass of 10 in benzene by cryoscopy clearly
Z. Anorg. Allg. Chem. 2010, 1851–1859
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W. Uhl, H. R. Bock, J. Kösters, M. Voß
ARTICLE
Figure 3. Molecular structure and numbering scheme of 16; the ther-
mal ellipsoids are drawn at the 40 % probability level; hydrogen atoms
and methyl groups are omitted. Selected bond lengths /pm and angles /°
(values of the second molecule in square brackets): Ga1–Ga2
237.68(6) [237.27(6)], Ga1–C1 195.9(4) [195.2(4)], Ga2–C2 195.3(4)
[195.8(4)], Ga1–O11 200.9(3) [201.7(3)], Ga1–O21 202.3(2)
[200.1(3)], Ga2–O12 202.4(2) [200.3(3)], Ga2–O22 200.5(3)
[201.9(2)], Ga1–Ga2–C2 155.0(1) [155.1(1)], Ga2–Ga1–C1 159.0(1)
[157.5(1)], O11–Ga1–O21 95.9(1) [96.3(1)], O12–Ga2–O22 95.0(1)
[94.7(1)], Ga1–Ga2–O12 88.83(7) [88.84(8)], Ga1–Ga2–O22 88.82(8)
[88.46(8)], Ga2–Ga1–O11 87.62(8) [87.77(7)], Ga2–Ga1–O21
87.76(8) [88.28(8)].
indicated the complete dissociation of the dimers to yield the
monomeric molecular fragments. In accordance with results of
mass spectrometric investigations also compound 11 seems to
adopt a dimeric or oligomeric structure in the solid state.
Figure 4. Part of the polymeric chain of 15; bis(trimethylsilyl)methyl
groups and hydrogen atoms are omitted.
Cleavage of the Ga–Ga Bonds
The reactions described so far proceeds selectively by the
replacement of alkyl groups and retainment of the Ga–Ga
bonds. Digallium compounds possessing functionalized car-
boxylato ligands became accessible on facile routes which are
important starting materials for the generation of secondary
products by, for instance, adduct formation. With the particular
perpendicular arrangement of the carboxylato ligands they may
open the access to the formation of macrocyclic or cage-like
compounds and to supramolecular chemistry. However, these
substituent exchange reactions are by no means trivial, and the
additional donor atoms prevented the desired reaction courses
in several cases. We observed cleavage of the Ga–Ga bonds
by hydrogen release and oxidation of the gallium atoms when
we treated the digallium compound 1 with particular function-
alized carboxylic acids such as 3-aminopyrazine-2-carboxylic
acid, 2,2-dithiosalicylic acid, dl-methionine, 1H-imidazole-4-
monomeric mononuclear compounds were formed in which a
GaR2 fragment is coordinated by a chelating carboxylato li-
gand. We do not want to go into detail here. However, in one
case a relatively interesting molecular structure resulted which
is worth mentioning. When we treated compound 1 with iso-
nicotinic acid we isolated colorless crystals of compound 19
in a moderate yield of 30 % [Equation (2)]. The 1H NMR spec-
trum showed the resonances of the bis(trimethylsilyl)methyl
groups and the carboxylato ligands in a molar ratio of 2:1,
which is in accordance with the cleavage of the Ga–Ga bond.
Chemical shifts are similar to those of the digallium species.
The resonance of the methine protons close to gallium (δ =
–0.28) may indicate a coordination number of four at the gal-
carboxylic acid, or 1,2,4-triazole-3-carboxylic acid. Generally, lium atoms in solution.
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Gallium–Gallium Bonds Bridged by Carboxylato Ligands
Crystal structure determination of 19 revealed an interesting
tetrameric compound in the solid state (Figure 6). It possesses
a square molecular core in which four isolated gallium atoms
(GaR2 groups) are bridged by four isonicotinic carboxylato li-
gands. With this particular structural motif it resembles numer-
ous tetrameric transition metal compounds reported in recent
literature [16]. Each gallium atom is coordinated by two termi-
nal alkyl groups, by a nitrogen atom of a pyridyl ring and an
oxygen atom of a carboxylato group. The second oxygen atom
is not involved in the coordination of the metal atom. The Ga–
O (192.3 pm on average) and Ga–N distances (209.3 pm) are
Figure 5. Molecular structure and numbering scheme of (10)2; the
thermal ellipsoids are drawn at the 40 % probability level; methyl
groups and hydrogen atoms are omitted. Selected bond lengths /pm
and angles /°: Ga1–Ga2 239.44(8), Ga1–C1 196.0(3), Ga2–C2
196.4(3), Ga1–O11 206.5(2), Ga1–O21 192.0(2), Ga2–O12 204.2(2),
Ga2–N14' 219.2(3), Ga2–Ga1–C1 140.96(9), Ga1–Ga2–C2 148.23(9),
O11–Ga1–O21 91.0(1), O12–Ga2–N14' 83.52(9), Ga2–Ga1–O11
85.41(6), Ga2–Ga1–O21 110.20(7), Ga1–Ga2–O12 90.13(6), Ga1–
Ga2–N14' 99.72(7); N14' generated by –x+2, –y+1, –z+1.
Figure 6. Molecular structure and numbering scheme of 19; the ther-
mal ellipsoids are drawn at the 40 % probability level; trimethylsilyl
groups and hydrogen atoms are omitted. Selected bond lengths /pm
and angles /°: Ga1–C1 198.0(4), Ga1–C2 198.2(4), Ga2–C3 198.0(4),
Ga2–C4 198.3(4), Ga1–O11 192.2(6), Ga1–N21 208.5(7), Ga2–O21
Scheme 3. Schematic drawing of the molecular structure of 10 [R = 192.4(5), Ga2–N11' 210.1(8), O11–Ga1–N21 89.3(2), O21–Ga2–N11'
CH(SiMe3)2].
88.7(2); Ga1', Ga2' and N11' generated by –x+1, –y+2, –z.
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W. Uhl, H. R. Bock, J. Kösters, M. Voß
ARTICLE
1246 m δCH3; 1151 m, 1124 w νCC, νCN; 1018 w δCH; 966 w, 937
w, 916 vw, 872 m, 845 s, 781 m, 758 m ρCH3(Si); 721 s (paraffin);
669 w νasSiC; 642 w, 624 w νsSiC; 548 w, 513 w, 463 w νGaC, νGaO
cm–1. MS (EI, 20 eV, 410 K): m/z (%) 756 (0.7), 758 (1), 760 (0.5)
(M+), 597 (30), 599 (46), 601 (19) [M+ – CH(SiMe3)2], 378 (58), 380
(45) (1/2 M+).
similar to or slightly shorter than those of the digallium com-
pound 10 described above. The C–O bond lengths (129.3 and
121.3 pm) show the differences expected for a localized bond-
ing situation in the CO2 group. Owing to the molecular sym-
metry of 19 in the solid state the four gallium atoms are exactly
in a plane. They form an ideal square with Ga–Ga separations
along the edges of 892 pm and angles of 90°. The overall di-
ameter of these molecules is at about 2.1 nm.
Reaction with 4-Methylamino-benzoic Acid; Characterization of
7: Yield: 36 %. M.p. (argon, sealed capillary): 134 °C (dec). 1H NMR
(400 MHz, C6D6): δ = 8.28 (d, 4 H, 3JH,H = 8.4 Hz, ortho-H of phenyl),
3
3
6.08 (d, 4 H, JH,H = 8.4 Hz, meta-H of phenyl), 2.93 (q, 2 H, JH,H
=
3
4.8 Hz, NH), 2.05 (d, 6 H, JH,H = 4.8 Hz, N–CH3), 0.48 (s, 36 H,
SiMe3), –0.10 (s, 2 H, Ga–CH). 13C NMR (100 MHz, C6D6): δ =
177.8 (CO2), 153.8 (C–N), 133.1 (ortho-C of phenyl), 119.6 (ipso-C
of phenyl), 111.3 (meta-C of phenyl), 29.5 (N–CH3), 4.3 (Ga–C), 3.7
Experimental Section
All procedures were carried out under purified argon in dried solvents
(n-pentane with LiAlH4; toluene and THF over Na/benzophenone).
The tetraalkyldigallium compound 1 was obtained according to a liter-
ature procedure [2]. Most acids are commercially available; they were
dried in vacuo prior to use. Bis(pyrazol-1-yl)acetic acid was synthe-
sized according to a procedure reported by Burzlaff [17]. Only the
most intensive masses of a particular molecular fragment are given in
the description of the mass spectra; the isotopic patterns are in agree-
ment with the calculated ones.
(SiMe3). 29Si NMR (79.5 MHz, C D ): δ = 0.4. IR (CsI, paraffin): ν =
˜
6
6
3424 m νNH; 2949 vs, 2914 vs, 2847 vs. (paraffin); 1607 s, 1524 m
νCO2, phenyl; 1462 vs, 1377 vs. (paraffin); 1339 m, 1279 w, 1246 m
δCH3; 1180 s, 1157 w, 1105 w, 1063 w νCN, νCC; 964 w, 868 m, 841
vs, 781 m, 760 w ρCH3(Si); 721 m (paraffin); 704 w, 677 w νasSiC;
644 w, 629 w νsSiC; 505 w, 436 w νGaC, νGaO cm–1. MS (EI, 20 eV,
300 K): m/z (%) 757 (8), 759 (13), 760 (6), 761 (6) (M+ + H), 378
(16), 380 (12) (1/2 M+).
Reaction with 4-Diphenylphosphino-benzoic Acid; Characteriza-
tion of 8: A highly viscous liquid remained after removal of all volatile
components. It could not be obtained as a solid. The raw product con-
tained less than 5 % impurities which allowed an unequivocal spectro-
scopic characterization. 1H NMR (400 MHz, C6D6): δ = 8.18 (d, 4 H,
Syntheses of Compounds 5 to 10; General Procedure
A solution of the digallium compound 1 (0.2 to 0.7 mmol) in THF
(20 mL) was added to a solution of two equivalents of the respective
carboxylic acid in THF (10 mL) at room temperature. The mixture
was stirred at room temperature for 12 h. The solvent was removed in
vacuo. The residue was washed with n-pentane (5 to 7; 10) or recrys-
tallized from THF (9) to yield the colorless digalliumdicarboxylates in
high purity. Compound 8 was soluble in n-pentane, but could not be
crystallized.
3
3JH,H = 8.0 Hz, ortho-H of phenyl-CO2), 7.29 (d, 4 H, JH,H = 8.0 Hz,
meta-H of phenyl-CO2), 7.29 (m, 8 H, ortho-H of PPh2), 7.05 (m, 4
H, para-H of PPh2), 7.04 (m, 8 H, meta-H of PPh2), 0.37 (s, 36 H,
SiMe3), –0.17 (s, 2 H, Ga–CH). 13C NMR (100 MHz, C6D6): δ =
1
174.4 (s, CO2), 145.7 (d, JC,P = 16.0 Hz, para-C of phenyl–CO2, C–
1
2
P), 136.9 (d, JC,P = 11.8 Hz, ipso-C of PPh2), 134.3 (d, JC,P
=
2
Reaction with 4-Aminobenzoic Acid; Characterization of 5: Yield
49 %. M.p. (argon, sealed capillary): 145 °C (dec.). 1H NMR
(400 MHz, C63D6): δ = 8.18 (d, 4 H, 3JH,H = 8.1 Hz, ortho-H of phenyl),
6.04 (d, 4 H, JH,H = 8.1 Hz, meta-H of phenyl), 2.85 (s, 4 H, NH2),
0.44 (s, 36 H, SiMe3), –0.12 (s, 2 H, Ga–CH). 13C NMR (100 MHz,
C6D6): δ = 177.6 (CO2), 151.8 (C–N), 133.1 (ortho-C of phenyl), 120.7
(ipso-C of phenyl), 113.7 (meta-C of phenyl), 4.3 (Ga–C), 3.6 (SiMe3).
20.3 Hz, ortho-C of PPh2), 133.6 (d, JC,P = 20.3 Hz, meta-C of phe-
nyl–CO2), 131.3 (s, C–CO2 of phenyl), 130.7 (d, 3JC,P = 6.4 Hz, ortho-
C of phenyl–CO2), 129.3 (s, para-C of PPh2), 129.0 (d, 3JC,P = 7.4 Hz,
meta-C of PPh2), 5.0 (s, Ga–C), 3.7 (s, SiMe3). 29Si NMR (79.5 MHz,
C6D6): δ = 0.2. 31P NMR (162 MHz, C6D6): δ = –4.6.
Reaction with 2-Diphenylphosphino-benzoic Acid; Characteriza-
tion of 9: Yield 21 %. M.p. (argon, sealed capillary): 172 °C (dec.).
1H NMR (400 MHz, C6D6): δ = 8.11 (m, 2 H, 6-H of phenyl-CO2),
29Si NMR (79.5 MHz, C D ): δ = 0.3. IR (CsI, paraffin): ν = 3483 w,
˜
6
6
3362 w, 3200 w νNH2; 2957 vs, 2851 vs. (paraffin); 1919 vw, 1651
w, 1643 w, 1601 w, 1557 vw, 1514 vw δNH2, νCO2, phenyl; 1460 vs,
1375 vs. (paraffin); 1298 w, 1244 w δCH3; 1205 w, 1171 m, 1152 w,
1051 vw νCC, νCN; 1011 w δCH; 964 w, 874 w, 843 m, 781 w
ρCH3(Si); 721 s (paraffin); 675 vw νasSiC; 633 w νsSiC; 546 vw, 501
vw, 461 vw νGaC, νGaO cm–1. MS (EI, 20 eV, 470 K): m/z ( %) 728
(1), 730 (3), 732 (5) (M+), 364 (10), 366 (7) (1/2 M+).
3
7.42 (2 H, pseudo-t, JH,H = 7.4 Hz, 5-H of phenyl-CO2), 7.37 (2 H,
3
pseudo-t, JH,H = 7.2 Hz, 4-H of phenyl–CO2), 7.26 (m, 12 H, meta-
H and para-H of PPh2), 7.18 (m, 8 H, ortho-H of PPh2), 6.88 (m, 2
H, 3-H of phenyl–CO2), 0.10 (s, 36 H, SiMe3), –0.47 (s, 2 H, Ga–
CH). 13C NMR (100 MHz, C6D6): δ = 178.4 (s, CO2), 141.7 (d, 1JC,P
=
1
29.2 Hz, 2-C of phenyl–CO2), 139.9 (d, JC,P = 13.3 Hz, ipso-C of
2
PPh2), 136.8 (d, JC,P = 20.3 Hz, 1-C of phenyl–CO2), 135.2 (s, 3-C
Reaction with 4-Amino-3-methylbenzoic Acid; Characterization of of phenyl–CO2), 134.7 (d, 2JC,P = 20.8 Hz, ortho-C of PPh2), 133.2 (s,
6: Yield 34 %. M.p. (argon, sealed capillary): 116 °C (dec). 1H NMR 4-C of phenyl–CO2), 132.7 (s, br., 6-C of phenyl–CO2), 129.3 (d,
(400 MHz, C6D6): δ = 8.15 (d, 2 H, 3JH,H = 8.1 Hz, ortho-H of phenyl), 3JC,P = 7.0 Hz, meta-C of PPh2), 129.3 (s, para-C of PPh2), 129.0 (s,
3
8.07 (s, 2 H, ortho-H of phenyl, CH–C–CH3), 6.11 (d, 2 H, JH,H
=
5-C of phenyl–CO2), 4.5 (s, Ga–C), 3.4 (s, SiMe3). 29Si NMR
8.1 Hz, meta-H of phenyl), 2.96 (s, 4 H, NH2), 1.63 (s, 6 H, CH3 of (79.5 MHz, C6D6): δ = –0.4. 31P NMR (162 MHz, C6D6): δ = –3.9.
phenyl), 0.46 (s, 36 H, SiMe3), –0.07 (s, 2 H, Ga–CH). 13C NMR IR (CsI, paraffin): ν = 1973 vw, 1956 w, 1888 w, 1803 vw, 1590 w,
˜
(100 MHz, C6D6): δ = 177.8 (CO2), 150.0 (C–N), 3.6 (SiMe3), 134.0 1568 m, 1533 m phenyl, νCO2; 1462 vs. (paraffin); 1447 s P-phenyl;
(ortho-C of phenyl, CH–C–CH3), 130.1 (ortho-CH of phenyl, CH– 1377 vs. (paraffin); 1306 w, 1281 w, 1258 m, 1246 s δCH3; 1180 w,
CH), 120.9 (ipso-C of phenyl), 120.7 (meta-C–CH3 of phenyl), 113.7 1153 m, 1117 vw, 1092 m, 1061 w νCC; 1016 s δCH; 999 m, 949 s,
(meta-CH of phenyl), 16.9 (CH3 of phenyl), 4.3 (Ga–C). 29Si NMR 912 vw, 841 vs, 775 vw, 756 m, 746 m ρCH3(Si); 719 s (paraffin);
(79.5 MHz, C D ): δ = 0.2. IR (CsI, paraffin): ν = 3487 w, 3395 m, 694 s νasSiC; 654 s, 627 w, 610 w νsSiC, νPC; 523 m, 509 s, 476 s
˜
6
6
3213 vw νNH2; 2924 vs, 2853 vs. (paraffin); 1684 w, 1653 w, br., νGaC, νGaO cm–1. MS (EI, 20 eV, 430 K): m/z (%) 1066 (0.7), 1068
1558 w, 1521 w νCO2, phenyl; 1458 vs, 1375 vs. (paraffin); 1304 m, (1), 1069 (0.5), 1070 (0.5) (M+), 1051 (0.7), 1053 (1), 1054 (0.5),
1856
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© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2010, 1851–1859

Gallium–Gallium Bonds Bridged by Carboxylato Ligands
1055 (0.5) (M+ – CH3), 907 (55), 909 (85), 910 (48), 911 (45) [M+ – 1915 w, 1689 w, 1603 vs, 1564 m, 1541 vw, 1520 w, 1497 m δNH2,
CH(SiMe3)2], 533 (57), 535 (45) (1/2 M+).
νCO2, phenyl; 1462 vs, 1377 vs. (paraffin); 1350 vs, 1302 w, 1246 vs.
δCH3; 1179 vs, 1136 sh, 1103 m, 1057 w νCC, νCN; 1015 vs. δCH;
947 vs, 843 vs, 783 s, 756 m ρCH3(Si); 727 m (paraffin); 705 vw, 671
m νasSiC; 646 m, 625 m νsSiC; 586 vw, 552 vw, 513 m, 498 m, 465
vw, 432 m νGaC, νGaO cm–1. MS (EI, 70 eV, 473 K): m/z (%) 758
Reaction with Bis(pyrazol-1-yl)acetic Acid; Characterization of 10:
Yield 88 %. M.p. (argon, sealed capillary): 123 °C (dec.). 1H NMR
(400 MHz, C6D6): δ = 7.55 (d, 4 H, 3JH,H = 1.6 Hz, 3-H of pyrazolyl),
7.44 (d, 4 H, 3JH,H = 2.4 Hz, 5-H of pyrazolyl), 7.15 (s, 2 H, CHCO2),
(0.7), 760 (1), 762 (0.5) (M+), 743 (0.7), 745 (1), 747 (0.5) (M+
–
3
CH3), 599 (29), 601 (40), 603 (17) [M+ – CH(SiMe3)2], 379 (93), 381
(70) (1/2 M+).
5.98 (4 H, pseudo-t, JH,H = 2.2 Hz, 4-H of pyrazolyl), 0.13 (s, 36 H,
SiMe3), –0.47 (s, 2 H, Ga–CH). 13C NMR (100 MHz, C6D6): δ =
177.1 (CO2), 141.0 (3-C of pyrazolyl), 130.4 (5-C of pyrazolyl), 107.1
(4-C of pyrazolyl), 76.2 (CCO2), 5.1 (Ga–C), 3.3 (SiMe3). 29Si NMR
Reaction with 3,4-Diaminobenzoic Acid; Characterization of 13:
Yield 65 %. M.p. (argon, sealed capillary): 155 °C (dec.). 1H NMR
(400 MHz, [D8]THF): δ = 7.40 [2 H, dd, 3JH,H = 8.5 and 1.6 Hz, ortho-
(79.5 MHz, C D ): δ = 0.0. IR (CsI, paraffin): ν = 1701 m, 1603 s,
˜
6
6
1516 w νCO2, pyrazolyl; 1456 vs. (paraffin); 1410 w δCH3; 1377 s
(paraffin); 1366 m, 1310 w, 1300 w, 1279 w, 1248 s δCH3; 1190 w,
1175 vw, 1088 m, 1047 m νCC, νCN; 1011 w δCH; 961 w, 951 w,
917 w, 843 vs, 752 s ρCH3(Si); 727 w (paraffin); 673 m νasSiC; 631
w, 609 vw νsSiC; 587 vw, 503 w, 438 vw νGaC, νGaO cm–1. MS (EI,
20 eV, 400 K): m/z (%) 838 (1.5), 840 (2.5), 841 (1.6), 842 (1.5) (M+),
823 (2), 825 (3), 826 (1.5), 827 (1.5) (M+ – CH3), 679 (6), 681 (9),
682 (4), 683 (4) [M+ – CH(SiMe3)2], 419 (100), 421 (77) (1/2 M+).
3
C(H)–C–H], 7.33 [2 H, s, JH,H = 1.6 Hz, ortho-C(H)–C–NH2], 6.49
3
(d, 2 H, JH,H = 8.5 Hz, meta-C–H), 3.94 and 4.68 (each 4 H, s, br.,
NH2), 0.19 (s, 36 H, SiMe3), –0.36 (s, 2 H, Ga–CH). 13C NMR
(100 MHz, [D8]THF): δ = 178.4 (CO2), 142.9 (para-C), 134.5 (meta-
C–NH2), 124.1 (ortho-C), 120.8 (ipso-C), 118.5 (ortho-C), 113.9
(meta-C–H), 4.2 (Ga–C), 3.7 (SiMe3). 29Si NMR (79.5 MHz,
[D ]THF): δ = 0.1. IR (CsI, paraffin): ν = 3437 m, 3375 m, 3197 w
˜
8
νNH; 2924 vs, 2853 vs. (paraffin); 1927 w, 1871 w, 1771 w, 1626 m,
br. δN–H, νCO2, phenyl; 1462 vs, 1375 vs. (paraffin); 1302 w, 1244
m δCH3; 1152 m, 1070 m, 1051 m νCC, νCN; 1015 m δCH; 966 w,
841 s, br., 773 m ρCH3(Si); 723 m (paraffin); 673 vw νasSiC; 648 vw,
613 vw νsSiC; 556 vw, 513 w, 449 m νGaC, νGaO cm–1.
Syntheses of Compounds 11 to 16; General Procedure
A solution of the digallium compound 1 (0.3 to 0.6 mmol) in THF
[50 mL (20 mL in the case of 15 and 16)] was treated with two equiva-
lents of the solid carboxylic acids in small portions at room tempera-
ture. The suspensions were stirred at room temperature for 12 to 48 h
until clear solutions resulted. The solutions were concentrated and
cooled to +4 °C (11, 12, and 16) or –30 °C (15) to obtain colorless
solids of the respective carboxylates. In the cases of the compounds
13 and 14, all volatiles of the reaction mixtures were completely re-
moved in vacuo, and the residues were washed with n-pentane to get
colorless amorphous solids.
Reaction with 3,5-Diaminobenzoic Acid; Characterization of 14:
Yield 79 %. M.p. (argon, sealed capillary): 181 °C (dec.). 1H NMR
(400 MHz, [D8]THF): δ = 6.66 (s, 4 H, ortho-C-H), 6.04 (s, 2 H, para-
C–H), 4.28 (s, 8 H, NH2), 0.19 (s, 36 H, SiMe3), –0.32 (s, 2 H, Ga–
CH). 13C NMR (100 MHz, [D8]THF): δ = 179.0 (CO2), 149.9 (meta-
C), 133.3 (ipso-C), 106.9 (ortho-C), 105.8 (para-C), 4.6 (Ga–C), 3.6
(SiMe3). 29Si NMR (79.5 MHz, [D8]THF): δ = 0.1. IR (CsI, paraffin):
ν = 3445 m, 3360 m, 3210 w νN–H; 2951 vs, 2851 vs. (paraffin); 1927
˜
vw, 1856 vw, 1630 vs, br., 1533 m νCO2, δNH2, phenyl; 1456 vs, 1375
vs. (paraffin); 1341 sh, 1306 s, 1244 s δCH3; 1188 m, 1090 w, 1049
m νCC, νCN; 1015 s δCH; 955 m, 869 s, 844 s, 770 m, 754 m
ρCH3(Si); 723 s (paraffin); 669 m νasSiC; 623 w, 613 w νsSiC; 565 w,
515 m, 465 m νGaC, νGaO cm–1. MS (EI, 70 eV, 300 K): m/z (%)
379 (93), 381 (42) (1/2 M+).
Reaction with 2-Aminonicotinic Acid; Characterization of 11:
Yield 75 %. M.p. (argon, sealed capillary): 253 °C (dec.). 1H NMR
3
(400 MHz, [D8]THF): δ = 8.19 (d, 2 H, JH,H = 7.7 Hz, ortho-C–H),
8.13 (d, 2 H, 3JH,H = 4.6 Hz, para-C–H), 6.92 (s, 4 H, NH2), 6.53 (dd,
2 H, 3JH,H = 7.7 and 4.6 Hz, meta-C–H), 0.21 (s, 36 H, SiMe3), –0.20
(s, 2 H, Ga–CH). 13C NMR (100 MHz, [D8]THF): δ = 178.5 (CO2),
161.2 (ortho-C–NH2), 155.5 (para-C), 142.2 (ortho-C–H), 112.9
(meta-C), 107.3 (ipso-C), 5.0 (Ga–C), 3.6 (SiMe3). 29Si NMR
Reaction with 2,6-Diphenylisonicotinic Acid; Characterization of
15: Yield 64 %. M.p. (argon, sealed capillary): 195 °C (dec.). 1H
NMR (400 MHz, [D8]THF): δ = 8.40 (s, 4 H, ortho-H of pyridyl),
8.21 (m, 8 H, ortho-H of phenyl), 7.49 (m, 8 H, meta-H of phenyl),
7.42 (m, 4 H, para-H of phenyl), 0.33 (s, 36 H, SiMe3), –0.09 (s, 2
H, Ga–CH). 13C NMR (100 MHz, [D8]THF): δ = 177.0 (CO2), 158.7
(meta-C of pyridyl), 141.5 (ipso-C of pyridyl), 139.6 (ipso-C of phe-
nyl), 130.3 (para-C of phenyl), 129.5 (meta-C of phenyl), 127.7 (or-
tho-C of phenyl), 118.8 (ortho-C of pyridyl), 5.7 (Ga–C), 3.7 (SiMe3).
(79.5 MHz, [D ]THF): δ = 0.0. IR (CsI, paraffin): ν = 3630 w, 3499
˜
8
w, 3422 m, 3366 m, 3277 w νN–H; 2924 vs, 2853 vs. (paraffin); 1674
s, 1618 s, 1595 s, 1578 s, 1558 s νCO2, δNH2; 1460 vs, 1375 vs.
(paraffin); 1248 s δCH3;1202 w; 1148 m, 1086 w νCC, νCN; 1015 m
δCH; 970 w, 914 vw, 897 vw, 843 vs, 777 m ρCH3(Si); 723 w (paraf-
fin); 679 s νasSiC; 633 vw, 615 vw νsSiC; 583 w, 536 w, 515 w, 469
w νGaC, νGaO cm–1. MS (EI, 70 eV, 400 K): m/z (%) 1458 (0.06),
1460 (0.12), 1462 (0.05), 1464 (0.02) (2M+ – 4 H), 1298 (0.35), 1300
(0.43), 1302 (0.43), 1304 (0.16) [2M+ – 4H – CH(SiMe3)2], 728 (2),
730 (3), 732 (2) (M+ – 2 H), 569 (7), 571 (11), 365 (13), 367 (9) (1/2
M+).
29Si NMR (79.5 MHz, [D ]THF): δ = 0.6. IR (CsI, paraffin): ν = 1653
˜
8
w, 1599 w, 1580 w, 1535 s, 1512 sh νCO2, pyridyl; 1462 vs. (paraffin);
1418 m δCH3; 1377 s (paraffin); 1317 m, 1244 m δCH3; 1182 w, 1153
vw, 1117 vw, 1072 w, 1055 w νCC; 1016 s δCH; 932 m, 896 w, 845
s, 827 s, 764 s, 750 m ρCH3(Si); 723 m (paraffin); 687 m, 673 w
νasSiC; 652 w, 627 w, 613 w νsSiC; 536 w, 517 w, 503 m, 462 w
νGaC, νGaO cm–1. MS (EI, 20 eV, 490 K): m/z (%) 1005 (8), 1007
(13), 1008 (8), 1009 (8) (M+ + H), 845 (30), 847 (48), 848 (25), 849
(25) [M+ – CH(SiMe3)2], 502 (83), 504 (64) (1/2 M+).
Reaction with 4-Hydrazinobenzoic Acid; Characterization of 12:
Yield 82 %. M.p. (argon, sealed capillary): 170 °C (dec). 1H NMR
3
(400 MHz, [D8]THF): δ = 7.89 (d, 4 H, JH,H = 8.9 Hz, ortho-C-H),
6.86 (s, 2 H, NH–NH2), 6.72 (d, 4 H, 3JH,H = 8.9 Hz, meta-C–H), 3.90
(s, 4 H, br., NH2), 0.20 (s, 36 H, SiMe3), –0.37 (s, 2 H, Ga–CH). 13C
NMR (100 MHz, [D8]THF): δ = 177.9 (CO2), 157.6 (para-C), 133.2 Reaction with 2-Furoic Acid (furan-2-carboxylic acid); Characteri-
(ortho-C), 119.5 (ipso-C), 110.5 (meta-C), 4.3 (Ga–C), 3.6 (SiMe3). zation of 16: Yield 80 %. M.p. (argon, sealed capillary): 121 °C
1
29Si NMR (79.5 MHz, [D ]THF): δ = 0.2. IR (CsI, paraffin): ν = 3318 (dec.). H NMR (400 MHz, [D8]THF): δ = 7.74 (s, 2 H, OCH), 7.25
˜
8
3
s, 3289 s, 3252 s, 3205 m, 3125 w νNH; 2927 vs, 2866 vs. (paraffin); (d, 2 H, JH,H = 3.5 Hz, OCHCHCH), 6.55 (m, 2 H, OCHCH), 0.19
Z. Anorg. Allg. Chem. 2010, 1851–1859
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1857

W. Uhl, H. R. Bock, J. Kösters, M. Voß
ARTICLE
(s, 36 H, SiMe3), –0.29 (s, 2 H, Ga–CH). 13C NMR (100 MHz, H, SiMe3), –0.46 (s, 2 H, Ga–CH). 13C NMR (100 MHz, [D8]THF):
[D8]THF): δ = 169.4 (CO2), 148.6 (OCH), 120.5 (OCHCHCH), 112.9 δ = 187.5 (CO2), 156.5 (para-C of phenyl), 140.6 (ipso-C of phenyl),
(OCHCH), 5.0 (Ga–C), 3.4 (SiMe3). 29Si NMR (79.5 MHz, [D8]THF): 128.9 (ortho-C of phenyl), 115.4 (meta-C of phenyl), 45.2 (H3C–C–
δ = 0.3. IR (CsI, paraffin): ν = 1925 w, 1871 w, 1856 w, 1798 w, 1778 CH2–CH2), 38.4 (H3C–C–CH2–CH2), 33.4 (H3C–C–CH2–CH2), 28.2
˜
w, 1740 w, 1701 vw, 1659 w, 1584 vs, 1535 m νCO2, νCC, νCO; 1464 (H3C–C–CH2–CH2), 4.5 (Ga–C), 3.5 (SiMe3). 29Si NMR (79.5 MHz,
vs, 1375 s (paraffin); 1296 w, 1244 vs, 1231 sh δCH3; 1200 s, 1139 s, [D ]THF): δ = 0.1. IR (CsI, paraffin): ν = 3406 w, br., 3175 w, br.
˜
8
1078 m νCC; 1015 vs. δCH; 934 s, 883 m, 866 m, 845 vs, 758 m νOH; 2947 vs, 2843 vs. (paraffin); 1703 w, 1645 m, 1611 m, 1591 m,
ρCH3(Si); 723 m (paraffin); 673 s νasSiC; 613 s νsSiC; 594 m, 573 vw, 1557 m, 1502 sh νCO2, phenyl; 1463 vs, 1377 vs. (paraffin); 1304 m,
515 vs. νGaC, νGaO cm–1. MS (EI, 20 eV, 360 K): m/z (%) 678 (1), 1266 w, 1248 m δCH3; 1169 s, 1155 m, 1082 w, 1049 w νCC, νCO;
680 (2), 682 (1) (M+), 519 (33), 521 (49), 523 (19) [M+ – CH(SiMe3)2], 1013 m δCH; 972 m, 918 w, 889 m, 866 m, 845 s, 762 s ρCH3(Si);
339 (100), 341 (75) (1/2 M+).
723 m (paraffin); 679 w νasSiC; 635 vw νsSiC; 579 m, 559 m, 513 w,
485 w νGaC, νGaO cm–1.
Reaction with Coumalic Acid (2-oxo-2H-pyran-5-carboxylic acid);
Characterization of 18: Yield 79 %. M.p. (argon, sealed capillary):
132 °C (dec.). 1H NMR (400 MHz, [D8]THF): δ = 8.39 (s, 2 H, OCH),
Syntheses of Compounds 17 and 18; General Procedure
The digallium compound 1 (0.3 mmol) and two equivalents of the
carboxylic acids were suspended in THF (20 mL) at room temperature.
The suspensions were stirred at room temperature for 16 h until clear
solutions resulted. All volatiles were completely removed in vacuo,
and the residues were washed with n-pentane to get colorless amor-
phous solids.
3
3
7.71 (d, 2 H, JH,H = 9.8 Hz, CH=CH–C=O), 6.29 (d, 2 H, JH,H
=
9.8 Hz, CH=CH–C=O), 0.18 (s, 36 H, SiMe3), –0.28 (s, 2 H, Ga–CH).
13C NMR (100 MHz, [D8]THF): δ = 175.3 (CO2), 161.4 (H–C–O),
159.3 (C=C–C=O), 141.9 (C=C–C=O), 115.5 (C=C–C=O), 113.3 (C–
CO2), 5.3 (Ga–C), 3.5 (SiMe3). 29Si NMR (79.5 MHz, [D8]THF): δ =
0.3. IR (CsI, paraffin): ν = 1755 vs. νC=O; 1713 s, 1639 s, 1564 m,
˜
Reaction with 4,4-Bis(4-hydroxyphenyl)valeric Acid; Characteri- 1533 m νCO2, νC=C; 1462 vs, 1377 vs. (paraffin); 1306 m, 1246 s
zation of 17: Yield 66 %. M.p. (argon, sealed capillary): 181 °C δCH3; 1155 m, 1125 m, 1090 s, 1040 m νCC, νCO; 1015 s δCH; 943
(dec.). 1H NMR (400 MHz, [D8]THF): δ = 7.94 (s, 4 H, OH), 6.95 s, 841 vs, 758 m ρCH3(Si); 721 s (paraffin); 675 m νasSiC; 648 m, 620
3
3
(d, 8 H, JH,H = 8.5 Hz, ortho-H of phenyl), 6.59 (d, 8 H, JH,H
=
w νsSiC; 557 w, 519 w, 484 m, 438 w νGaC, νGaO cm–1. MS (EI,
8.5 Hz, meta-H of phenyl), 2.37 (m, 4 H, H3C–C–CH2–CH2), 2.12 (m, 20 eV, 390 K): m/z (%) 734 (4), 736 (7), 738 (3) (M+), 575 (59), 577
4 H, H3C–C–CH2–CH2), 1.47 (s, 6 H, H3C–C–CH2–CH2), 0.12 (s, 36 (85), 579 (37) [M+ – CH(SiMe3)2], 367 (100), 369 (77) (1/2 M+).
Table 1. Crystal data and structure refinement for compounds 9, 10, 15, 16, and 19.
9
10
15
16
19
Formula
C60H82Ga2O6P2Si4
C74H120Ga4N16O8Si8
triclinic
C50H62Ga2N2O4Si4
monoclinic
C2/c; No. 15
4
C24H44Ga2O6Si4
triclinic
C112H232Ga4N4O16Si16
triclinic
Crystal system monoclinic
¯
¯
¯
Space group [18] C2/c; No. 15
P1; No. 1
P1; No. 2
P1; No. 2
Z
T /K
4
1
4
1
153(2)
153(2)
1.284
153(2)
153(2)
1.315
153(2)
1.161
Density (calc) / 1.297
1.313
g·cm–3
a /pm
b /pm
c /pm
α /°
3442.4(2)
1228.0(3)
1437.8(4)
1609.6(5)
67.326(5)
67.681(5)
86.671(5)
2.4128(12)
1.259
2659.1(2)
855.48(5)
2551.2(2)
90
980.1(1)
1468.30(8)
1662.35(9)
1798.7(1)
64.336(1)
77.526(1)
71.940(1)
3.7452(4)
0.892
870.80(6)
2657.3(3)
90
1223.4(2)
2992.2(4)
93.172(2)
99.343(2)
102.783(2)
3.467(8)
β /°
128.752(1)
90
120.022(2)
90
γ /°
V /nm3
6.2121(9)
1.043
5.0928(5)
1.196
μ /mm–1
1.739
0.12 × 0.08 × 0.02
Crystal size /mm 0.17 × 0.13 × 0.05
Radiation
0.12 × 0.05 × 0.04
0.09 × 0.06 × 0.04
0.16 × 0.13 × 0.08
Mo-Kα, graphite-monochromator
Θ range for data 1.52 ≤ θ ≤ 27.92
collection /°
1.49 ≤ θ ≤ 30.04
1.75 ≤ θ ≤ 27.51
1.39 ≤ θ ≤ 31.59
1.26 ≤ θ ≤ 27.54
Index ranges
–45 ≤ h ≤ 45, –11 ≤ k –17 ≤ h ≤ 17, –20 ≤ k –34 ≤ h ≤ 34, –11 ≤ k –13 ≤ h ≤ 14, –17 ≤ k –19 ≤ h ≤ 19, –21 ≤ k
≤11, –34 ≤ l ≤ 34
≤ 20, –22 ≤ l ≤ 22
13877 (Rint = 0.0317) 5842 (Rint = 0.0454)
≤ 11, –33 ≤ l ≤ 33
≤ 17, –43 ≤ l ≤ 44
21140 (Rint = 0.0515) 17170 (Rint = 0.0379)
≤ 21, –23 ≤ l ≤ 23
Independent re- 7425 (Rint = 0.0331)
flections
Reflections I > 6096
2σ(I)
10156
4260
11731
11911
Parameters
340
0.0316
0.0818
469
286
673
772
R [I > 2σ(I)]
wR2 (all data)
0.0590
0.0345
0.0853
+572/–256
0.0612
0.0652
0.1662
0.1537
0.2137
Max./min. resid- +597/–462
ual electron den-
+1855a)/–2649
+1354a)/–1246
+1327b)/–1026
sity /1030·em–3
R1 = Σ||Fo| – |Fc||/Σ|Fo|, wR2 = {Σw(Fo – Fc ) /Σw(Fo ) }1/2
2
2 2
2 2
a) Close to gallium. b) Close to THF.
1858
www.zaac.wiley-vch.de
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2010, 1851–1859

Gallium–Gallium Bonds Bridged by Carboxylato Ligands
Reaction with Isonicotinic Acid; Synthesis of 19: A solution of the
tetraalkyldigallium compound 1 (0.395 g, 0.51 mmol) in THF (50 mL)
was treated with solid isonicotinic acid (0.125 g, 1.02 mmol) in small
portions at room temperature. The suspension was stirred overnight. A
clear, yellow solution resulted, which was concentrated and cooled to
+4 °C to yield colorless crystals of the cleavage product 19. Yield
0.157 g (30 %); M.p. (argon, sealed capillary): 153 °C (dec.). 1H
NMR (400 MHz, C6D6): δ = 8.50 (dd, 2 H, 3JH,H = 4.3, 4JH,H = 1.6 Hz,
References
[1] W. Uhl, Z. Naturforsch. 1988, 43b, 1113.
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3
4
meta-C–H), 7.61 (dd, 2 H, JH,H = 4.3, JH,H = 1.6 Hz, ortho-C–H),
0.23 (s, 36 H, SiMe3), –0.28 (s, 2 H, Ga–CH). 13C NMR (100 MHz,
C6D6): δ = 180.1 (CO2), 151.4 (meta-C), 136.3 (ipso-C), 123.0 (ortho-
C), 11.0 (Ga–C), 3.6 (SiMe3). 29Si NMR (79.5 MHz, [D8]THF): δ =
–0.5. IR (CsI, paraffin): ν = 1921 w, 1865 w, 1663 vs, 1620 m, 1562
˜
s, 1564 s, 1502 m νCO2, pyridyl; 1464 vs, 1377 vs. (paraffin); 1242
vs. δCH3; 1213 m, 1144 s, 1061 m, 1030 s νCC; 1015 vs. δCH; 968
vs, 843 vs, 773 m, 756 m ρCH3(Si); 725 m (paraffin); 704 w, 667 m
νasSiC; 627 m, 610 w νsSiC; 573 m, 498 s, 471 w, 446 m νGaC, νGaO
cm–1. MS (EI, 20 eV, 390 K): m/z (%) 494 (63), 496 (53) (M+ of
the monomer – CH3), 350 (100), 352 (76) [M+ of the monomer –
CH(SiMe3)2].
Crystal Structure Determinations
Single crystals were obtained directly from the reaction mixtures (9,
15, 16, and 19) or by recrystallization from toluene (10). The crystallo-
graphic data were collected with a Bruker APEX diffractometer with
graphite-monochromated Mo-Kα radiation. The crystals were coated
with a perfluoropolyether, picked up with a glass fiber and immediately
mounted in the cooled nitrogen stream of the diffractometer. The crys-
tallographic data and details of the final R values are provided in Ta-
ble 1. The structures were solved by direct methods and refined with
the program system SHELXL-97 [19] with full-matrix and all inde-
pendent structure factors (F2). All non-hydrogen atoms were refined
with anisotropic displacement parameters; hydrogen atoms were calcu-
lated on ideal positions and allowed to ride on the bonded atom with
U = 1.2Ueq(C). The molecules of 9 and 15 reside on twofold rotational
axes. Compound 9 crystallizes with two molecules of THF per formula
unit. They are located close to the diphenylphosphino ligands and are
parallel to a phenyl group. The dimeric molecules of 10 are located
on crystallographic centers of symmetry. Two toluene molecules are
enclosed which are disordered with two different positions for the
methyl groups. Compound 16 crystallizes with two independent mole-
cules in the asymmetric unit. Compound 19 is tetrameric in the solid
state. The molecules reside on crystallographic centers of symmetry.
The bridging ligands are disordered over two positions. Their atoms
were refined on split positions (0.76:0.24). The unit cell contains eight
molecules of THF, which were refined with isotropic displacement
parameters.
The crystallographic data were deposited as supplementary publication
no. CCDC-752592 (9), -752589 (10), -752590 (15), -752591 (16),
and -752592 (19). These data can be obtained free of charge from
the Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, Great Britain (Fax: +44-1223-336-033; E-Mail:
deposit@ccdc.cam.ac.uk).
[19] SHELXTL-Plus, REL. 4.1; Siemens Analytical X-RAY Instru-
ments Inc.: Madison,WI, 1990; G. M. Sheldrick, SHELXL-97,
Program for the Refinement of Structures; Universität Göttingen,
Germany, 1997.
Acknowledgement
We are grateful to the Deutsche Forschungsgemeinschaft (IRTG-1444)
for generous financial support.
Received: December 21, 2009
Published Online: March 5, 2010
Z. Anorg. Allg. Chem. 2010, 1851–1859
© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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