Reactions of trichlorogermane HGeCl3 and dichlorogallane HGaCl2 with pyridine donors

Article abstract of DOI:10.1039/b305792e

The weak base pyridine has been found to deprotonate trichlorogermane HGeCl₃ with quantitative formation of pyridinium trichlorogermanate(II), Py-H⁺GeCl₃^-, the pyramidal structure of the anion resembling that of the isoelectronic AsCl₃ molecule. This course of the reaction supports the assignment of an inverse polarization (-)Ge-H(+) of the bond in HGeCl₃ as compared to the (+)Si-H(-) bond in trichlorosilane HSiCl₃, which is known to form a 1:2 adduct with pyridine instead. Germanium tetrachloride also undergoes simple addition reactions with pyridine leading ultimately e.g. to GeCl₄L₂ with L = 4-ethyl-pyridine. Dichlorogallane gives 1:1 addition compounds (HGaCl₂L) with L = pyridine, 4-dimethylamino-pyridine, 4-cyano-pyridine, and 3,5-dimethyl-pyridine, the molecular structures of which have been determined by single crystal X-ray diffraction. Simple tetrahedral arrays of substituents around the gallium center with only minor distortions, and characteristic Ga-H stretching vibrations in the IR spectra, show that the Ga-H bond is untouched in the addition reactions. The addition of two equivalents of 3,5-dimethyl-pyridine to HGaCl₂ affords the 1:2 complex which was shown to have a trigonal-bipyramidal geometry with the hydride ligand in an equatorial position. In order to provide benchmark data, the 1:1 adducts GaCl₃(L) and GaH₃(L) with L = 3,5-dimethyl-pyridine were also prepared and structurally characterized. Pyridinium tetrachlorogallate(III) takes up pyridine, but the extra ligand is attached to the cation via hydrogen bonding leaving the anion unchanged: [Py-H ... Py]⁺[GaCl₄]^-.

Full text of DOI:10.1039/b305792e

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Reactions of trichlorogermane HGeCl3 and dichlorogallane
HGaCl2 with pyridine donors
Stefan Nogai, Alexander Schriewer and Hubert Schmidbaur
Anorganisch-chemisches Instutut der Technischen Universität München, Lichtenbergstrasse 4,
85747 Garching, Germany. E-mail: H.Schmidbaur@lrz.tum.de
Received 23rd May 2003, Accepted 26th June 2003
First published as an Advance Article on the web 17th July 2003
The weak base pyridine has been found to deprotonate trichlorogermane HGeCl3 with quantitative formation
of pyridinium trichlorogermanate(), Py-HϩGeCl3Ϫ, the pyramidal structure of the anion resembling that of the
isoelectronic AsCl3 molecule. This course of the reaction supports the assignment of an inverse polarization
(Ϫ)Ge–H(ϩ) of the bond in HGeCl3 as compared to the (ϩ)Si–H(Ϫ) bond in trichlorosilane HSiCl3, which is
known to form a 1 : 2 adduct with pyridine instead. Germanium tetrachloride also undergoes simple addition
reactions with pyridine leading ultimately e.g. to GeCl4L2 with L = 4-ethyl-pyridine. Dichlorogallane gives 1 : 1
addition compounds (HGaCl2L) with L = pyridine, 4-dimethylamino-pyridine, 4-cyano-pyridine, and 3,5-dimethyl-
pyridine, the molecular structures of which have been determined by single crystal X-ray diffraction. Simple
tetrahedral arrays of substituents around the gallium center with only minor distortions, and characteristic Ga–H
stretching vibrations in the IR spectra, show that the Ga–H bond is untouched in the addition reactions. The
addition of two equivalents of 3,5-dimethyl-pyridine to HGaCl2 affords the 1 : 2 complex which was shown to have
a trigonal-bipyramidal geometry with the hydride ligand in an equatorial position. In order to provide benchmark
data, the 1 : 1 adducts GaCl3(L) and GaH3(L) with L = 3,5-dimethyl-pyridine were also prepared and structurally
characterized. Pyridinium tetrachlorogallate() takes up pyridine, but the extra ligand is attached to the cation via
hydrogen bonding leaving the anion unchanged: [Py-H ؒ ؒ ؒ Py]ϩ[GaCl4]Ϫ.
Results and discussion
Introduction
Preparative studies
Owing to a discontinuity of many properties of the elements in
Group IV, and of their electronegativity in particular,1 the
hydridic character of germanium hydrides is greatly reduced as
compared to silicon hydrides. Thus germane GeH4 is stable to
water and even to acid, and chlorogermanes HnGeCl4 Ϫ n may
already be described as weak acids. Mechanistically, this acidic
behaviour can be ascribed to the excellent leaving group proper-
ties of the corresponding anions, vic. [GeH3]Ϫ and [GeCl3]Ϫ,
respectively.2 It should be noted that this ionization out of an
inverted polarization [from (ϩ)Ge–H(Ϫ) to (Ϫ)Ge–H(ϩ)] can
be considered a redox reaction in that the germanium atoms
change their formal oxidation state from ϩ4 to ϩ2, the two
anions being hydride or chloride adducts of the germylenes
GeH2 or GeCl2, respectively. While this mode of reaction has
been established with HGeCl3 and strong bases like trimethyl-
amine,3 the course of reactions with weak bases like pyridine
has not yet been followed. By contrast chlorosilanes HnSiCl4 Ϫ n
are known to form 1 : 1 and 1 : 2 adducts with tertiary amines4
and pyridines5 which is fully in agreement with the presence of
(ϩ)Si–H(Ϫ) bonds.
By contrast, such a discontinuity is not very pronounced in
the series of the Group III elements,1 and the hydridic character
typical for aluminium hydrides is largely preserved in the gal-
lium hydrides.6 Gallium hydrides GaHnCl3 Ϫ n and their adducts
GaHnCl3 Ϫ n(L) with donor ligands L show no protic character.
In the present study the different modes of reaction of
trichlorogermane,2 HGeCl3, and dichlorogallane,7 HGaCl2,
with pyridines have been investigated in order to probe the
donor and acceptor properties towards ligands which are weak
Brønsted bases, but strong nucleophiles for main group metals.
Because there is still a paucity of structural data for gallium
hydrides6,8,9 and especially for complexes of dichlorogallane,9
the crystal structures of a series of representative adducts with
gallium in different coordination geometries have been
determined.
Trichlorogermane HGeCl3. Trichlorogermane HGeCl3 is not
a stable compound at room temperature, hydrogen chloride
being slowly evolved with formation of GeCl2 and its oligomers
or adducts.2 The substrate therefore has to be freshly prepared
prior to reactions with donor molecules and preferably handled
at low temperature. It can be dissolved in an excess of dry pyrid-
ine (Py) at Ϫ40 ЊC to give a clear solution. Evaporation of the
solvent in a vacuum leaves a colourless crystalline residue,
which can be crystallized from toluene, mp 114 ЊC, in quanti-
tative yield calculated for a 1 : 1 adduct. This composition was
confirmed by elemental analysis. The product is hygrocopic and
decomposes in air. It can be dissolved in acetonitrile where it
1
shows the H and 13C resonances typical for pyridinium salts.
There is no absorption in the infrared spectrum which could be
assigned to a Ge–H stretching vibration.
This result suggests that even the weak pyridine base depro-
tonates HGeCl3 instead of forming an adduct HGeCl3(Py)n
with the germanium atom featuring a higher coordination
number. The crystal structure analysis (below) gave the final
proof that the reaction afforded pyridinium trichlorger-
manate(), [Py-H]ϩ[GeCl3]Ϫ (eqn. (1)).
HGeCl3 ϩ Py
[Py-H]ϩ[GeCl3]Ϫ
(1)
It should be noted that GeCl4 readily forms a stable 1 : 2
adduct with pyridine, GeCl4(Py)2, which is known to have a
trans structure.10 To show that this is a general reaction, a 1 : 2
adduct of GeCl4 with 4-ethyl-pyridine was successfully pre-
pared in the present study. It is obvious therefore that there is no
steric hindrance or other kinetic effect to be expected for an
addition of pyridine to HGeCl3 to give hypothetical adducts
HGeCl3(L) or even HGeCl3(L)2. Deprotonation and formation
of pyridinium trichlorogermanites() is clearly the thermo-
dynamically controlled process.
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 3 1 6 5 – 3 1 7 1
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Dichlorogallane HGaCl2. Dichlorogallane HGaCl2 forms a
stable 1 : 1 adduct with pyridine, the IR spectrum of which
shows a strong absorption for a Ga–H stretching vibration.
Similar results were observed with 4-dimethylamino- and
4-cyano-pyridine, as well as with 3,5-dimethyl-pyridine. The
results show that changes of the basic/nucleophilic character of
the pyridine induced by different substituents in the para-
position, or a steric effect of meta-substituents, do not alter the
course of the reaction (eqn. (2)).
(HGaCl2)2 ϩ 2 Py
2 HGaCl2(Py)
(2)
Fig. 1 Molecular structure of [Py-H]ϩ[GeCl3]Ϫ showing the pyramidal
geometry of the [GeCl3]Ϫ anion. Selected bond lengths [Å] and angles
[Њ]: Ge(1)–Cl(1) 2.301(1), Ge(1)–Cl(2) 2.322(1), Ge(1)–Cl(3) 2.325(1);
Cl(1)–Ge(1)–Cl(2) 93.72(4), Cl(1)–Ge(1)–Cl(3) 96.00(4), Cl(2)–Ge(1)–
Cl(3) 94.75(4).
The molecular structures of all four complexes have been
determined (below). For comparison of the structural data for
the 3,5-dimethyl-pyridine complex, the corresponding com-
pounds of gallane, H3Ga(3,5-Me2C5H3N), and of gallium tri-
chloride, Cl3Ga(3,5-Me2C5H3N), were also synthesized and
their structures determined. For the preparation of the GaH3-
complex the reagents employed were LiGaH4 and [3,5-Me2-
C5H3NH]Cl, while for the GaCl3-complex a straightforward
addition of the components is most convenient (eqn. (3), (4)).
other trichlorogermanate() salts.3 The pyridinium cation
shows no anomalies. The distances from the N–H group to
neighbouring Cl atoms are large and do not indicate significant
hydrogen bonding.
The crystallographic data for the 1 : 1 adducts of HGaCl2
with Py, 4-Me2N-Py, 4-NC-Py, and 3,5-Me2-Py have been
summarized in Table 1. All of these crystals contain neutral
molecules, the structures of which are shown in Figs. 2–5.
Because of many similarities among the members of this group
of compounds, only the structure of HGaCl2(Py) is discussed
as a reference in more detail.
Li[GaH4] ϩ [3,5-Me2-Py-H]Cl
H3Ga(3,5-Me2-Py) ϩ H2 ϩ LiCl (3)
(GaCl3)2 ϩ 2 (3,5-Me2-Py)
2 Cl3Ga(3,5-Me2-Py) (4)
The 1 : 1-complexes of HGaCl2 and GaCl3 with pyridines are
obtained from the reactions of equimolar quantities of the
components. An excess of pyridines leads to the formation of
1 : 2-complexes as demonstrated for the 3,5-dimethylpyridine
case (eqn. (5)).
The crystals of HGaCl2(Py) are the only phase to contain
two independent molecules in the asymmetric unit, but the two
(HGaCl2)2 ϩ 4 Py
2 HCl2Ga(Py)2
(5)
This 1 : 2 adduct was isolated in pure, crystalline form and its
IR-spectrum was found to exhibit the absorption band for a
Ga–H stretching vibration. Any deprotonation by the second
mole of pyridine base can therefore be excluded. As shown
by an X-ray diffraction study, the compound has a trigonal-
bipyramidal configuration with a pentacoordinate gallium
atom (below). GaCl3 is also known to form a 1 : 2 complex with
pyridines,11 which indicates that both HGaCl2(Py) and
GaCl3(Py) have sufficient acceptor character towards pyridines.
It should be noted, however, that the 1 : 2 complex of net stoi-
chiometry {GaCl3(Py)2} was in fact found to be an ionic com-
pound11 with the ligands redistributed to give [Cl2Ga(Py)4]ϩ-
[GaCl4]Ϫ.
Fig. 2 Molecular structure of HGaCl2(Py). The two independent
molecules in the asymmetric unit are shown. Selected bond lengths [Å]
and angles [Њ]: Ga(1)–Cl(1) 2.1928(6), Ga(1)–Cl(2) 2.1895(6), Ga(1)–
N(11) 2.000(2), Ga(1)–H(1) 1.45(3), Ga(2)–Cl(3) 2.1893(6), Ga(2)–
Cl(4) 2.1847(7), Ga(2)–N(21) 1.998(2), Ga(2)–H(2) 1.47(3); Cl(1)–
Ga(1)–Cl(2) 107.76(3), Cl(1)–Ga(1)–H(1) 115(1), Cl(2)–Ga(1)–H(1)
117(1), N(11)–Ga(1)–Cl(1) 100.85(6), N(11)–Ga(1)–Cl(2) 103.82(6),
N(11)–Ga(1)–H(1) 111(1), Cl(3)–Ga(2)–Cl(4) 107.37(3), Cl(3)–Ga(2)–
H(2) 119.9(9), Cl(4)–Ga(2)–H(2) 112(1), N(21)–Ga(2)–Cl(3) 102.06(6),
N(21)–Ga(2)–Cl(4) 103.08(6), N(21)–Ga(2)–H(2) 111(1).
The tetrachlorogallate anion in salts M[GaCl4] appears to be
devoid of acceptor properties. It has now been observed that
pyridinium tetrachlorogallate [Py-H]ϩ[GaCl4]Ϫ adds a second
equivalent of pyridine, but the additional donor is accepted by
the cation through hydrogen bonding (eqn. (6)).
[Py-H]ϩ[GaCl4]Ϫ ϩ Py
[Py-H ؒ ؒ ؒ Py]ϩ[GaCl4]Ϫ (6)
The structure of [Py-H ؒ ؒ ؒ Py]GaCl4 has been determined
and the anion shown to be an undistorted tetrahedron (below).
Structural studies
Crystals of [Py-H][GeCl3] are monoclinic, space group P21/c,
with Z = 4 formula units in the unit cell. The asymmetric unit
contains one pyridinium cation and one trichlorogermanate()
Ϫ
anion (Fig. 1). The GeCl3 anion has a pyramidal geometry
Fig. 3 Molecular structure of HGaCl2(4-Me2N-Py). Selected bond
lengths [Å] and angles [Њ]: Ga(1)–Cl(1) 2.2021(5), Ga(1)–Cl(2)
2.1937(5), Ga(1)–N(11) 1.971(2), Ga(1)–H(1) 1.46(3); Cl(1)–Ga(1)–
Cl(2) 105.67(2), Cl(1)–Ga(1)–H(1) 115(1), Cl(2)–Ga(1)–H(1) 117.2(9),
N(11)–Ga(1)–Cl(1) 103.34(5), N(11)–Ga(1)–Cl(2) 104.41(5), N(11)–
Ga(1)–H(1) 109.8(9).
reminiscent of the structure of the molecular analogue AsCl3.
The three Ge–Cl distances are in the range 2.301(1)–2.325(1) Å,
the three angles Cl–Ge–Cl in the range 93.72(4)–96.00(4)Њ.
Deviations from idealized C3v symmetry are therefore quite
small. The data also compare well with dimensions found in
D a l t o n T r a n s . , 2 0 0 3 , 3 1 6 5 – 3 1 7 1
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Table 1 Crystal data, data collection, and structure refinement of [Py-H][GeCl3], HGaCl2(Py), HGaCl2(4-Me2N-Py), HGaCl2(4-NC-Py) and
HGaCl2(3,5-Me2-Py)
[Py-H][GeCl3]
HGaCl2(Py)
HGaCl2(4-Me2N-Py)
HGaCl2(4-NC-Py)
HGaCl2(3,5-Me2-Py)
Empirical formula
M
C5H6Cl3GeN
259.05
C5H6Cl2GaN
220.73
C7H11Cl2GaN2
263.80
C6H5Cl2GaN2
245.74
C7H10Cl2GaN
248.78
Crystal system
Space group
Monoclinic
P21/c
Triclinic
P1
Monoclinic
P21/n
Monoclinic
P21/n
Monoclinic
P21/n
¯
a/Å
b/Å
c/Å
α/Њ
8.8187(2)
9.3672(2)
11.3129(2)
90
101.4859(19)
90
915.80(3)
1.879
4
7.9436(2)
8.5157(2)
13.4892(4)
86.5446(11)
74.6191(13)
65.1942(15)
797.27(4)
1.839
7.3133(1)
16.9338(3)
8.5934(2)
90
96.9279(7)
90
1056.45(3)
1.659
4
10.4429(7)
8.3052(3)
11.0553(7)
90
104.466(3)
90
928.43(9)
1.758
4
8.1301(2)
9.1466(2)
13.7748(4)
90
101.9204(12)
90
1002.24(4)
1.649
4
β/Њ
γ/Њ
V/Å3
ρcalc/g cmϪ3
Z
4
F(000)
504
41.47
143
432
40.32
143
528
30.60
143
480
34.76
143
496
32.18
143
µ(Mo-Kα)/cmϪ1
T/K
Refls. measured
Refls. unique
Refined parameters/restraints
R1 [I≥2σ(I )]
wR2a
21681
1614 [Rint = 0.034]
95/0
0.0321
0.0823
a = 0.0198,
b = 3.0188
0.565/Ϫ0.520
20638
2738 [Rint = 0.024]
211/0
0.0232
0.0621
a = 0.0261,
b = 0.5820
0.395/Ϫ0.470
22853
1833 [Rint = 0.024]
153/0
0.0208
0.0587
a = 0.0312,
b = 0.4095
0.396/Ϫ0.231
11088
1624 [Rint = 0.025]
120/0
0.0230
0.0617
a = 0.0271,
b = 0.4392
0.347/Ϫ0.362
28989
1830 [Rint = 0.039]
140/0
0.0242
0.0637
a = 0.0301,
b = 0.5653
0.352/Ϫ0.418
Weighting scheme
σfin(max/min)/e ÅϪ3
a wR2= {Σ[w(Fo2 Ϫ Fc2)2]/Σ[w(Fo )2]}1/2; w = 1/[σ2(Fo ) ϩ (ap)2 ϩ bp]; p = (Fo2 ϩ 2Fc2)/3.
2
2
2.1895(6), Ga2–Cl3 2.1893(6), Ga2–Cl4 2.1847(7) Å; Cl1–Ga1–
Cl2 107.76(3)Њ, Cl3–Ga2–Cl4 107.37(3)Њ.
The Ga–H bond lengths and H–Ga–Cl angles are generally
less accurate and found in the ranges 1.45(3) to 1.53(2) Å and
112(1) and 119.9(9)Њ, respectively, for all four complexes, in
good agreement with a recent summary.12 The gallium atoms
have a distorted tetrahedral environment with no evidence for
significant intermolecular interactions. The closest approach
appears in HGaCl2(Py) for a pair of molecules related by a
center of inversion (with the central atoms Ga1/Ga1Ј), where
the distance Ga1–H1Ј is 3.199 Å and the angle Cl2–Ga1–H1Ј
176.5Њ (Fig. 6). The remainder of the angles, none of which
is near to 90Њ, show very strong deviations from an idealized
trigonal-bipyramidal geometry, and therefore this “pairing”
should not be taken as a dimerization.
Fig. 4 Molecular structure of HGaCl2(4-NC-Py). Selected bond
lengths [Å] and angles [Њ]: Ga(1)–Cl(1) 2.1878(6), Ga(1)–Cl(2)
2.1705(6), Ga(1)–N(1) 2.017(2), Ga(1)–H(1) 1.49(2); Cl(1)–Ga(1)–Cl(2)
107.77(2), Cl(1)–Ga(1)–H(1) 119.0(9), Cl(2)–Ga(1)–H(1) 116.4(9),
N(1)–Ga(1)–Cl(1) 101.18(5), N(1)–Ga(1)–Cl(2) 100.53(5), N(1)–Ga(1)–
H(1) 109.2(9).
Fig. 6 Shortest intermolecular Ga–H distances in the lattice of
HGaCl2(Py) between two molecules related by a center of inversion.
Fig. 5 Molecular structure of HGaCl2(3,5-Me2-Py). Selected bond
lengths [Å] and angles [Њ]: Ga(1)–Cl(1) 2.1803(6), Ga(1)–Cl(2)
2.1846(6), Ga(1)–N(1) 2.006(2), Ga(1)–H(1) 1.53(2); Cl(1)–Ga(1)–Cl(2)
109.28(3), Cl(1)–Ga(1)–H(1) 119.0(9), Cl(2)–Ga(1)–H(1) 113.0(9),
N(1)–Ga(1)–Cl(1) 102.59(5), N(1)–Ga(1)–Cl(2) 102.51(5), N(1)–Ga(1)–
H(1) 108.6(9).
Crystals of H3Ga(3,5-Me2-Py) contain two independent
molecules in the asymmetric unit (Fig. 7). For one of the two
molecules the three Ga-bound hydrogen atoms were located
and refined, while for the other they were restrained to be
equivalent (local C3 symmetry) in order to obtain meaningful
results. The Ga–H bond lengths [in the range 1.49(4)–1.53(6) Å]
are in good agreement with those observed for the HGaCl2
complexes. The Ga–N distances Ga1–N11 2.073(4) and
structures are fully consistent as shown by the following com-
parison of the most accurate distances and angles: Ga1-N11
2.000(2), Ga2-N21 1.998(2), Ga1–Cl1 2.1928(6), Ga1–Cl2
D a l t o n T r a n s . , 2 0 0 3 , 3 1 6 5 – 3 1 7 1
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Fig. 9 Molecular structure of HGaCl2(3,5-Me2-Py)2. The arrange-
ment shows only small deviations from the maximum attainable
symmetry of point group C2v, with the twofold axis running through
the Ga–H bond and the mirror plane passing through N(11), Ga(1),
H(1) and N(21). Selected bond lengths [Å] and angles [Њ]: Ga(1)–Cl(2)
2.2214(7), Ga(1)–Cl(3) 2.2237(8), Ga(1)–N(11) 2.196(2), Ga(1)–N(21)
2.188(2), Ga(1)–H(1) 1.51(3); Cl(2)–Ga(1)–Cl(3) 111.38(4), N(11)–
Ga(1)–N(21) 179.28(7), Cl(2)–Ga(1)–H(1) 125(1), Cl(3)–Ga(1)–H(1)
123(1), N(11)–Ga(1)–Cl(2) 89.55(6), N(11)–Ga(1)–Cl(3) 89.77(6),
N(11)–Ga(1)–H(1) 91(1), N(21)–Ga(1)–Cl(2) 90.85(6), N(21)–Ga(1)–
Cl(3) 89.52(6), N(21)–Ga(1)–H(1) 89(1).
Fig. 7 Molecular structure of H3Ga(3,5-Me2-Py). The two inde-
pendent molecules in the asymmetric unit are shown. Selected bond
lengths [Å] and angles [Њ]: Ga(1)–H(11) 1.51(4), Ga(1)–H(12) 1.50(4),
Ga(1)–H(13) 1.51(4), Ga(1)–N(11) 2.073(4), Ga(2)–H(21) 1.49(6),
Ga(2)–H(22) 1.51(6), Ga(2)–H(23) 1.53(6), Ga(2)–N(21) 2.060(4);
H(11)–Ga(1)–H(12) 117(1), H(11)–Ga(1)–H(13) 117(2), H(12)–Ga(1)–
H(13) 118(1), N(11)–Ga(1)–H(11) 104(3), N(11)–Ga(1)–H(12) 98(2),
N(11)–Ga(1)–H(13) 96(3), H(21)–Ga(2)–H(22) 114(3), H(21)–Ga(2)–
H(23) 114(3), H(22)–Ga(2)–H(23) 115(3), N(21)–Ga(2)–H(21) 106(2),
N(21)–Ga(2)–H(22) 105(2), N(21)–Ga(2)–H(23) 102(2).
111.38(4)Њ, while the two H–Ga–Cl angles are larger than the
trigonal bipyramidal standard (120Њ): 125(1)Њ and 123(1)Њ. The
sum of the equatorial angles is exactly 360Њ. The axial Ga–N
distances of 2.188(2) and 2.196(2) Å in the 1 : 2 complex are
almost 10% larger than the Ga–N distances in all of the 1 : 1
complexes of HGaCl2 (above). If the rule is accepted that
shorter bonds are generally stronger, bonding of the first ligand
L in the 1 : 1 complexes is thus much tighter than any of the two
donor/acceptor bonds in the 1 : 2 complex. The two pyridine
rings are almost coplanar.
Ga2–N21 2.061(4) Å are significantly longer than those in the
HGaCl2 complexes [2.006(2) Å for HGaCl2(3,5-Me2-Py)] indi-
cating the stronger acceptor character of dichlorogallane as
compared to the chlorine-free gallane.
This suggestion is confirmed by the structure of Cl3Ga-
(3,5-Me2-Py), where the Ga–N distance is again shorter at
1.968(1) Å (Fig. 8). Otherwise this reference structure has no
anomalies.
It should be remembered that the 1 : 2 adduct {GaCl3(Py)2}
has the ionic structure9 [Cl2Ga(Py)4][GaCl4]. There is presently
no evidence for a similar ligand redistribution in the complex of
HGaCl2 with 2 equivalents of 3,5-Me2-Py, possibly involving
[H2Ga(Py)4][GaCl4].
Crystals of [Py-H ؒ ؒ ؒ Py]ϩ[GaCl4]Ϫ are orthorhombic, space
group Cmc21, with Z = 4 formula units in the unit cell. The
asymmetric unit contains one half of the anion and one half
of each of the pyridines, the remainder being generated by
symmetry operations. The anion geometry is based on a
slightly distorted tetrahedron, while the pairs of pyridine rings
are almost coplanar and connected via a N–H–N hydrogen
bond: N21–H21A 0.95(8), H21A–N11 1.77(8), N21–N11
2.706(6) Å, N21–H21A–N11 169(6)Њ (Fig. 10). The stacking
of the anions and the columns of cations is illustrated in
Fig. 11.
Conclusions
Fig. 8 Molecular structure of Cl3Ga(3,5-Me2-Py). The conformation
approaches mirror symmetry (point group Cs) with the virtual mirror
plane passing through N(1), Ga(1) and Cl(2). Selected bond lengths [Å]
and angles [Њ]: Ga(1)–Cl(1) 2.1608(5), Ga(1)–Cl(2) 2.1517(5), Ga(1)–
Cl(3) 2.1610(4), Ga(1)–N(1) 1.968(1); Cl(1)–Ga(1)–Cl(2) 112.29(2),
Cl(1)–Ga(1)–Cl(3) 112.19(2), Cl(2)–Ga(1)–Cl(3) 111.38(2), N(1)–
Ga(1)–Cl(1) 106.55(4), N(1)–Ga(1)–Cl(2) 108.17(4), N(1)–Ga(1)–Cl(3)
105.85(4).
Trichlorogermane HGeCl3 and dichlorogallane HGaCl2
(and its adducts) were found to react with pyridines in an
entirely different way. Even the weak base pyridine is able to
deprotonate HGeCl3 to give a pyridinium salt with trigonal-
pyramidal trichlorogermanate() anions containing german-
ium in its oxidation state ϩ. Since pyridine in its action as a
base should not be considered a reducing agent, HGeCl3 must
also be assigned the ϩ oxidation state for its central atom
owing to the unusual polarization (ϩ)H–Ge(Ϫ) of its Ge–H
bond.
By contrast, HGaCl2 forms 1 : 1 or 1 : 2 addition compounds
with pyridines, which have standard pseudo-tetrahedral [HGa-
Cl2(L)] or trigonal-bipyramidal structures [HGaCl2(L)2]. No
deprotonation is observed even with an excess of pyridine base,
and no ligand redistribution to give ionic isomers9 occurs. Thus
while (GaCl3)2 formally reacts more often than not out of an
ionic form [GaCl2]ϩ[GaCl4]Ϫ, there are presently no examples
Crystals of the 1 : 2 complex HGaCl2(3,5-Me2-Py)2 feature
molecules with a trigonal bipyramidal structure in which the
chlorine atoms and the hydrogen atom occupy the equatorial
positions (Fig. 9). The geometry has no crystallographically
imposed symmetry, but the arrangement shows only small devi-
ations from the maximum attainable symmetry of point group
C2v, the twofold axis running through the Ga–H bond [Ga–H
1.51(3) Å]. The Ga–Cl and Ga–N distances are equal within the
limits of standard deviations, and the angle N–Ga–N is close to
linear [179.28(7)Њ]. Surprisingly, the Cl–Ga–Cl angle is only
D a l t o n T r a n s . , 2 0 0 3 , 3 1 6 5 – 3 1 7 1
3168

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The coordination chemistry of HGeCl3,13 and (HGaCl2)2
with tertiary phospines will be the subject of a forthcoming
report.14
Experimental
All experiments were carried out in an atmosphere of dry and
pure nitrogen. Glassware was oven-dried and filled with nitro-
gen, and solvents and the pyridines were dried following estab-
lished procedures and saturated with nitrogen. Conventional
equipment was used throughout. Anhydrous (GaCl3)2 and the
pyridines were commercially available. (HGaCl2)2 was prepared
employing a published method recently improved to make it
more convenient.7d LiGaH4 and HGeCl3 were prepared accord-
ing to literature procedures.15,16
Fig. 10 Molecular structure of [Py-H ؒ ؒ ؒ Py]ϩ[GaCl4]Ϫ. The asym-
metric unit contains one half of the anion and one half of each of the
pyridines, the remainder being generated by symmetry operations. The
two pyridines are related by a strong hydrogen bond. Selected bond
lengths [Å] and angles [Њ]: Ga(1)–Cl(1) 2.173(1), Ga(2)–Cl(2) 2.187(1),
Ga(3)–Cl(3) 2.1774(9), N(21)–H(21A) 0.95(8), H(21A)–N(11) 1.77(8);
Cl(1)–Ga(1)–Cl(2) 108.91(6), Cl(1)–Ga(1)–Cl(3) 109.49(4), Cl(2)–
Ga(1)–Cl(3) 108.79(4), Cl(3)–Ga(1)–Cl(3)Ј111.34(5), N(21)–H(21A)–
N(11) 169(6).
Syntheses
Pyridinium trichlorogermanate(II), [Py-H][GeCl3]. Freshly
prepared HGeCl3 (2.0 g, 11.1 mmol) is cooled to Ϫ40 ЊC and
slowly dissolved in 10 ml of freshly distilled and then precooled
pyridine (9.60 mmol). The reaction mixture is slowly warmed
to room temperature, excess pyridine is removed in a vacuum,
and the colourless, hygroscopic residue is recrystallized from
1
toluene; 2.8 g (97% yield), mp 114 ЊC (decomp.). H-NMR
(CD3CN, 20 ЊC): δ 2.45, br s, 1H, NH; 8.17, dd, J 6.56 and 7.84
Hz, 2H, CH(3/5); 8.71, t, J 7.85 Hz, 1H, CH(4); 8.85, d, J 6.57 Hz,
2H, CH(2/6).
13C{1H}-NMR: δ 129.1, s, 2C, C(3/5); 142.7, s, 1C,
C(4); 148.8, s, 2C, C(2/6). Analysis found C 24.17, H 2.48, N 5.57,
Cl 40.53; C5H6NGeCl3 (259.08) requires C 23.18, H 2.33, N
5.41, Cl 41.05%.
Bis(4-ethyl-pyridine)tetrachlorogermane,
(4-Et-Py)2GeCl4.
GeCl4 (2.0 g, 1.06 ml, 9.33 mmol) is reacted with 4-ethyl-
pyridine (2.0 g, 2.04 ml, 18.7 mmol) in 10 ml of toluene with
stirring at 20 ЊC. All volatiles are removed in a vacuum to leave
1
a colourless solid; 3.97 g (97% yield), mp 118 ЊC. H-NMR
(CDCl3, 20 ЊC): δ 1.32, t, J 7.67 Hz, 3H, Me; 2.86, q, 2H, CH2;
7.61, d, J 6.18 Hz, 2H, CH3/5; 8.63, d, 2H, CH2/6. Analysis found
C 39.52, H 4.48, N 6.57, Cl 33.53; C14H18N2GeCl4 (428.73)
requires C 39.22, H 4.23, N 6.53, Cl 33.08%.
Pyridine-pyridinium tetrachlorogallate(III), [Py-H ؒ ؒ ؒ Py]-
[GaCl4]. GaCl3 is dissolved (2.00 g, 5.68 mmol) in 10 ml of dry
pyridine, and pyridium chloride (1.32 g, 11.42 mmol) is dissol-
ved in 30 ml of the same solvent. From the combined solutions
excess pyridine is removed in a vacuum after 1 h and the residue
is crystallized from toluene; 4.00 g (95% yield), mp 116 ЊC.
1H-NMR (CDCl3): δ 7.78, m, 2H, CH(3/5); 8.28, m, 1H, CH(4);
Fig. 11 The stacking of the anions and the columns of cations in the
lattice of [Py-H ؒ ؒ ؒ Py]ϩ[GaCl4]Ϫ.
where (HGaCl2)2 would appear to function as [GaH2]ϩ[GaCl4]Ϫ
towards donor molecules.
The structures of the 1 : 1 complexes are similar to those of
the corresponding adducts of the types Cl3Ga(L) or H3Ga(L),
for which two prototypes have also been prepared and investi-
gated. However, tetrachlorgallate() anions [GaCl4]Ϫ have no
acceptor character, and with [Py-H]ϩ[GaCl4]Ϫ excess pyridine
becomes attached to the cation via hydrogen bonding: [Py-H ؒ ؒ ؒ
Py]ϩ[GaCl4]Ϫ.
8.71, m, 2H, CH(2/6).
13C{1H}-NMR: δ 125.1, s, 2C, C(3/5); 141.7,
s, 1C, C(4); 145.0, s, 2C, C(2/6). Analysis found C 32.83, H 3.00, N
7.67, Cl 37.34; C10H11N2GaCl4 (370.73) requires C 32.40, H
2.99, N 7.67, Cl 38.25%.
The results have thus shown that conversion of HGeCl3
(with tetracoordinate germanium atoms) into lower-coordinate
Ge() compounds is a facile process, which can be accom-
plished even with a very weak base. By contrast, the analogous
transformation of HGaCl2 into Ga() compounds is not easily
induced. Action of even strong base is not sufficient, probably
because of the inherent polarization (Ϫ)H–Ga(ϩ) which is the
opposite of (ϩ)H–Ge(Ϫ). It should be noted, however, that
neat (HGaCl2)2 is readily thermolized at slightly above room
temperatures to give hydrogen gas7a–e and Ga[GaCl4] contain-
ing one of the two gallium atoms in the ϩ oxidation state.
This process is an example of reductive elimination of
substrate (H2) from the gallium() center in (HGaCl2)2.
Mechanistically, the process may involve elimination of HCl
followed by a reaction with a second H–Ga function to give
molecular hydrogen.
Pyridine-dichlorogallane,
3,5-dimethyl-pyridine-dichloro-
gallane and 4-cyano-pyridine-dichlorogallane, HGaCl2(Py),
HGaCl2(3,5-Me2-Py) and HGaCl2(4-NC-Py). Freshly prepared
(HGaCl2)2 (2.12 g, 7.48 mmol of dimer) is dissolved in 30 ml of
dry diethyl ether at Ϫ78 ЊC. To this solution one equivalent
of the ligand (1.18 g, 14.9 mmol for pyridine, 1.60 g, 14.9 mmol
for 3,5-dimethylpyridine and 1.55 g, 14.9 mmol for 4-cyano-
pyridine) dissolved in 10 ml of dry diethyl ether is added slowly
at this temperature (an excess of ligand should be avoided in
any case in order to prevent the formation of [HGaCl2(L)2]-
type complexes). After the addition is completed, a colourless
precipitate forms, which redissolves upon warming to room
temperature and stirring for 1 h. Storage on dry ice over night
yields the product in the form of colourless crystals. The solu-
tion is filtered off and the remainder of the product obtained by
removing about two thirds of the solvent from the filtrate and
D a l t o n T r a n s . , 2 0 0 3 , 3 1 6 5 – 3 1 7 1
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Table 2 Crystal data, data collection, and structure refinement of H3Ga(3,5-Me2-Py), Cl3Ga(3,5-Me2-Py), HGaCl2(3,5-Me2-Py)2 and [Py-
H ؒ ؒ ؒ Py][GaCl4]
H3Ga(3,5-Me2-Py)
Cl3Ga(3,5-Me2-Py)
HGaCl2(3,5-Me2-Py)2
[Py-H ؒ ؒ ؒ Py][GaCl4]
Empirical formula
M
C5H12GaN
179.90
C7H9Cl3GaN
283.22
C14H19Cl2GaN2
355.84
C10H11Cl4GaN2
370.73
Crystal system
Space group
Monoclinic
P21/n
Triclinic
P1
Monoclinic
P21/c
Orthorhombic
Cmc21
¯
a/Å
b/Å
c/Å
α/Њ
8.9394(3)
13.8205(5)
14.0935(5)
90
95.1123(15)
90
1734.28(11)
1.378
8
7.1968(1)
9.1925(2)
9.4850(2)
87.3256(7)
71.9435(8)
68.3327(12)
552.805(18)
1.702
11.0572(3)
10.2092(3)
14.7805(6)
90
94.1991(11)
90
1664.02(9)
1.421
4
9.0480(4)
12.1395(7)
13.4546(6)
90
90
90
1477.83(13)
1.666
4
β/Њ
γ/Њ
V/Å3
ρcalc/g cmϪ3
Z
2
F(000)
736
30.94
143
280
31.162
143
728
19.63
143
736
25.64
143
µ(Mo-Kα/cmϪ1
T/K
Refls. measured
Refls. unique
Refined parameters/restraints
R1 [I≥2σ(I )]
wR2a
56453
3127 [Rint = 0.048]
191/6
0.0463
0.1258
a = 0.0453, b = 4.1443
0.869/Ϫ0.453
15084
2374 [Rint = 0.029]
145/0
0.0234
0.0642
a = 0.0324, b = 0.2125
0.489/Ϫ0.311
38639
2930 [Rint = 0.036]
248/0
0.0352
0.0931
a = 0.0467, b = 1.5954
0.441/Ϫ0.476
22132
1367 [Rint = 0.070]
110/1
0.0260
0.0560
a = 0.0057, b = 1.5245
0.328/Ϫ0.531
Weighting scheme
σfin(max/min)/e ÅϪ3
a wR2= {Σ[w(Fo2 Ϫ Fc2)2]/Σ[w(Fo )2]}1/2; w = 1/[σ2(Fo ) ϩ (ap)2ϩbp]; p = (Fo2 ϩ 2Fc2)/3.
2
2
storing the residue on dry ice over night (overall yields are 93 to
95%).
HGaCl2(Py). H-NMR (C6D6): δ 6.18, m, AAЈBBЈC, 2H,
4-Dimethylamino-pyridine-dichlorogallane, HGaCl2(4-Me2N-
Py). The compound is prepared following the conventional
route (above). Due to the limited solubility of the product in
diethyl ether, the reaction mixture is filtered immediately after
warming to room temperature and the complex is obtained as a
colourless solid. Higher yields are obtained after storing the
filtrate on dry ice over night (yield 95%); mp 232 ЊC (decomp.).
1H-NMR (C6D6): δ 1.94, s, 6H, Me(N); 5.52, d, J 7.32 Hz, 2H,
CH(3/5); 7.84, d, J 7.32 Hz, 2H, CH(2/6); not detected: GaH.
13C{1H}-NMR: δ 38.3, s, 2C, C(N); 106.8, s, 2C, C(3/5); 145.0, s,
2C, C(2/6); not detected: C(4). Analysis found C 32.52, H 4.33, N
10.76, Cl 26.16; C7H11N2GaCl2 (263.81) requires C 31.87, H
4.20, N 10.62, Cl 26.88%. IR (Nujol mull/cmϪ1): 1979 m
[Ga–H], 1625 s, 1558 s, 1526 w, 1306 w, 1232 s, 1120 w, 1073 s,
1026 s, 946 w, 816 s, 725 w, 616 s, 559 m, 523 m.
1
CH(3/5); 6.57, t, J 7.92 Hz, 1H, CH(4); 7.99, d, J 4.94 Hz, 2H,
CH(2/6); not detected: GaH. 13C{1H}-NMR: δ 125.5, s, 2C, C(3/5)
;
141.0, s, 1C, C(4); 146.3, s, 2C, C(2/6). Analysis found C 26.87, H
2.90, N 6.25, Cl 31.81; C5H6NGaCl2 (220.74) requires C 27.21,
H 2.74, N 6.35, Cl 32.12%. IR (Nujol mull/cmϪ1): 1970 [Ga–H],
1613 s, 1488 m, 1248 w, 1216 m, 1160 m, 1070 s, 1051 s, 1015 s,
883 w, 761 s, 652 s, 605 s, 588 s.
HGaCl2(3,5-Me2-Py). mp 66 ЊC (decomp.); 1H-NMR
(C6D6): δ 1.37, s, 6H, Me(3/5); 6.28, s, 1H, CH(4); 7.97, s, 2H,
CH(2/6); not detected: GaH. 13C{1H}-NMR: δ 17.5, s, 2C,
Me(3/5), 135.6, s, 2C, C(3/5); 142.2, s, 1C, C(4); 144.0, s, 2C, C(2/6)
.
Analysis found C 34.31, H 4.15, N 5.83, Cl 27.50; C7H10-
NGaCl2 (248.79) requires C 33.79, H 4.05, N 5.63, Cl 28.02%.
IR (Nujol mull/cmϪ1): 1978 [Ga–H], 1611 s, 1285 s, 1251 s, 1175
s, 1149 s, 1046 s, 945 m, 867 s, 791 s, 697 m, 621 m, 540 m.
3,5-Dimethyl-pyridine-gallane, H3Ga(3,5-Me2-Py). This
compound was prepared by a variation of literature pro-
cedures.17 To a solution of freshly prepared LiGaH4 (0.89g,
11.0 mmol) in 30 ml of dry diethyl ether kept at Ϫ78 ЊC is added
a substoichiometric amount of 3,5-dimethyl-pyridinium-chlor-
ide (10.4 mmol, 1.49 g) in small portions under nitrogen. The
resulting slurry is allowed to warm to ambient temperature over
a period of 5 h and is stirred for a further 2 h. Upon warming
gas evolution is observed. The suspension is filtered and about
half of the solvent is removed in vacuo. Crystals are obtained by
slow cooling of the remaining solution to Ϫ78 ЊC over night.
The solution is filtered, and the crystals are dried in vacuo.
Higher yields are obtained by removing most of the solvent and
cooling to Ϫ78 ЊC (yield 71%). The product decomposes slowly
at room temperature, but can be stored without decomposition
at Ϫ25 ЊC; mp 67 ЊC (fast decomp.). 1H-NMR (C6D6): δ 1.43, s,
6H, Me(3/5); 5.64, br s, 3H, GaH; 6.34, s, 1H, CH(4); 7.97, s, 2H,
1
HGaCl2(4-NC-Py). mp 51 ЊC (decomp.), H-NMR (C6D6):
δ 5.97, d, J 5.69 Hz, 2H, CH(3/5); 7.82, d, J 5.69 Hz, 2H, CH(2/6)
;
not detected: GaH. 13C{1H}-NMR: δ 127.0, s, 2C, C(3/5); 147.4,
s, 2C, C(2/6); not detected: C(4) and CN(4). Analysis found C
30.26, H 2.14, N 11.67, Cl 27.40; C6H5N2GaCl2 (245.75)
requires C 29.32, H 2.05, N 11.40, Cl 28.85%. IR (Nujol mull/
cmϪ1): 2239 w [C᎐N], 1977 m [Ga–H], 1620 m, 1548 m, 1221 m,
᎐
᎐
1122 w, 1064 m, 1038 m, 970 w, 835 m, 797 w, 777 w, 728 w, 608
m, 557 m.
Bis-(3,5-dimethyl-pyridine)-dichlorogallane,
HGaCl2(3,5-
Me2-Py)2. To a solution of HGaCl2(3,5-Me2C5H3N) (0.36 g,
1.5 mmol) in 25 ml of diethyl ether is added an excess of liquid
3,5-dimethyl-pyridine (0.17 g, 1.6 mmol) at room temperature.
The solution is stirred for 2 h and then cooled to Ϫ78 ЊC over
night. A colourless precipitate is obtained, which is filtered off
and dried in vacuo. Crystals can be obtained from acetonitrile
at Ϫ25 ЊC. 0.46 g (87% yield). 1H-NMR (C6D6): δ 1.60, s, 12H,
Me(3/5); 6.51, s, 2H, CH(4); 8.15, s, 4H, CH(2/6); not detected:
CH(2/6). ;
13C{1H}-NMR: δ 17.4, s, 2C, Me(3/5); 134.7, s, 2C, C(3/5)
140.1, s, 1C, C(4); 146.1, s, 2C, C(2/6). Analysis found C 46.00, H
6.30, N 7.62; C7H12NGa (179.90) requires C 46.73, H 6.72, N
7.79%. IR (Nujol mull/cmϪ1): 1822 s [Ga–H], 1604 m, 1279 w,
1254 w, 1166 m, 1137 w, 1036 w, 867 m, 786 s, 725 s, 700 s,
548 m.
GaH. 13C{1H}-NMR: δ 17.7, s, 4C, Me(3/5), 134.1, s, 4C, C(3/5)
;
139.7, s, 2C, C(4); 145.9, s, 4C, C(2/6). Analysis found C 46.87, H
5.21, N 7.73, Cl 20.26; C14H19N2GaCl2 (355.84) requires C
47.24, H 5.38, N 7.87, Cl 19.92%. IR (Nujol mull/cmϪ1): 1873
[Ga–H], 1601 s, 1277 w, 1254 w, 1177 m, 1148 s, 1046 m, 1034
m, 943 w, 868 s, 822 m, 736 s, 700 s, 551 m.
3,5-Dimethyl-pyridine-gallium-trichloride,
Cl3Ga(3,5-Me2-
Py). (GaCl3)2 (2.71 g, 7.69 mmol of dimer) is dissolved in 20 ml
of cold diethyl ether and neat 3,5-dimethyl-pyridine (1.65 g,
D a l t o n T r a n s . , 2 0 0 3 , 3 1 6 5 – 3 1 7 1
3170

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Tripathi, G. L. Wegner, A. Schier, A. Jockisch and H. Schmidbaur,
15.38 mmol) is added dropwise at Ϫ30 ЊC. The solution is
stirred for 2 h and then, after evaporating about half of the
solvent in a vacuum, cooled to Ϫ78 ЊC over night. Colourless
crystals are obtained, the solution is filtered off and the product
Z. Naturforsch., Teil B, 1998, 53, 939; (e) G. L. Wegner, A. Jockisch
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1
dried in vacuo (yield: 98%); mp 93–96 ЊC. H-NMR (C6D6):
δ 1.33, s, 6H, Me(3/5); 6.24, s, 1H, CH(4); 8.01, s, 2H, CH(2/6)
.
13C{1H}-NMR: δ 17.5, s, 2C, Me(3/5); 136.7, s, 2C, C(3/5); 142.7, s,
1C, C(4); 144.1, s, 2C, C(2/6). Analysis found C 29.04, H 3.37, N
4.77, Cl 36.34; C7H9NGaCl3 (283.23) requires C 29.68, H 3.20,
N 4.95, Cl 37.55%.
Determination of the crystal structures
Specimens of suitable quality and size of [Py-H][GeCl3], HGa-
Cl2(Py), HGaCl2(4-Me2N-Py), HGaCl2(4-NC-Py), HGaCl2-
(3,5-Me2-Py), H3Ga(3,5-Me2-Py), Cl3Ga(3,5-Me2-Py), HGaCl2-
(3,5-Me2-Py)2 and [Py-H ؒ ؒ ؒ Py][GaCl4] were mounted on the
ends of quartz fibers in inert perfluoropolyalkyl ether and used
for intensity data collection on a Nonius DIP2020 diffract-
ometer, employing graphite-monochromated Mo-Kα radiation.
The structures were solved by a combination of direct methods
(SHELXS-97) and difference-Fourier syntheses and refined by
full matrix least-squares calculations on F 2 (SHELXL-97).18
The thermal motion was treated anisotropically for all non–
hydrogen atoms. The C–H hydrogen atoms were calculated in
ideal positions and allowed to ride on their parent atoms with
fixed isotropic contributions in the structures of [Py-H][GeCl3],
H3Ga(3,5-Me2-Py) and for one hydrogen atom in the structure
of [Py-H ؒ ؒ ؒ Py][GaCl4]. In all other structures the C–H
hydrogen atoms were located and refined with isotropic dis-
placement parameters. In H3Ga(3,5-Me2-Py) all three Ga–H
and all three H–H distances were restrained to be equal for one
of the two independent molecules (Ga1), for the other one
(Ga2) no restraints were applied. The Flack parameter for
[Py-H ؒ ؒ ؒ Py][GaCl4] is 0.009(15). Absorption corrections for
all structures except HGaCl2(3,5-Me2-Py) were carried out
using DELABS, as part of the PLATON suite of pro-
grammes.19 Further informations on crystal data, data collec-
tion and structure refinement are summarized in Tables 1 and 2.
CCDC reference numbers 211295–211303.
9 Bing Luo, V. G. Young, Jr. and W. L. Gladfelter, Chem. Commun.,
1999, 123.
10 (a) K. Hensen and W. Scholz, Theor. Chim. Acta, 1968, 12, 206;
(b) M. Bolte, K. Hensen and S. Faber, Acta Crystallogr., Sect. C,
2000, 56, 497.
See http://www.rsc.org/suppdata/dt/b3/b305792e/ for crystal-
lographic data in CIF or other electronic format.
11 (a) R. Restivo and G. J. Palenik, J. Chem. Soc., Dalton Trans., 1972,
341; (b) I. Sinclair, R. W. H. Small and I. J. Worrall,
Acta Crystallogr., Sect. B, 1981, 37, 1290; (c) E. M. Gordon,
A. F. Hepp, S. A. Duraj, T. S. Habash, P. E. Fanwick, J. D. Schupp,
W. E. Eckles and S. Long, Inorg. Chim. Acta, 1997, 257, 247.
12 C. Y. Tang, A. J. Downs, T. M. Greene and S. Parsons,
Dalton Trans., 2003, 540.
13 (a) W.-W. du Mont, B. Neudert and H. Schumann, Angew. Chem.,
1976, 88, 304; (b) W.-W. du Mont, Z. Anorg. Allg. Chem., 1979, 85,
458; (c) M. Karnop, W.-W. du Mont, P. G. Jones and J. Jeske,
Chem. Ber., 1997, 130, 1611; (d ) G. Kociok-Kohn, J. G. Winter and
A. C. Filippou, Acta Crystallogr., Sect. C, 1999, 55, 351.
14 S. Nogai, H. Schmidbaur, in preparation, 2003.
15 A. E. Shirk and D. F. Shriver, Inorg. Synth., 1977, 17, 45.
16 T. K. Gar, E. M. Berliner, A. V. Kisin and V. F. Mirnov, Zh. Obsh.
Khim., 1970, 40, 2601.
17 (a) P. C. Andrews, M. G. Gardiner, C. L. Raston and V.-A. Tolhurst,
Inorg. Chim. Acta, 1997, 259, 249; (b) D. F. Shriver and A. E. Shirk,
Inorg. Synth., 1977, 17, 42.
Acknowledgements
This work was generously supported by Deutsche Forschungs-
gemeinschaft and Fonds der Chemischen Industrie.
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D a l t o n T r a n s . , 2 0 0 3 , 3 1 6 5 – 3 1 7 1
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