Decomposition of monochlorogallane, [H2GaCl]n, and adducts with amine and phosphine bases: Formation of cationic gallane derivatives

Article abstract of DOI:10.1021/ic050986j

Thermal decomposition of monochlorogallane, [H₂GaCl] _n, at ambient temperatures results in the formation of subvalent gallium species. To Ga[HGaCl₃], previously reported, has now been added a second mixed-valence solid, Ga₄-[HGaCl₃] ₂[Ga₂Cl₆] (1), the crystal structure of which at 150 K shows a number of unusual features. Adducts of monochlorogallane, most readily prepared from the hydrochloride of the base and LiGaH₄ in appropriate proportions, include not only the 1:1 molecular complex Me ₃P·GaH₂Cl (2), but also 2:1 amine complexes which prove to be cationic gallane derivatives, [H₂Ga(NH₂R) ₂]⁺Cl^-, where R = ^tBu (3a) or ^sBu (3b). All three of these complexes have been characterized crystallographically at 150 K.

Full text of DOI:10.1021/ic050986j

Inorg. Chem. 2005, 44, 7143−7150
Decomposition of Monochlorogallane, [H2GaCl]n, and Adducts with
Amine and Phosphine Bases: Formation of Cationic Gallane Derivatives
Christina Y. Tang,† Anthony J. Downs,*,† Tim M. Greene,‡ Sarah Marchant,† and Simon Parsons*,§
Inorganic Chemistry Laboratory, UniVersity of Oxford, South Parks Road, Oxford OX1 3QR, U.K.,
Department of Chemistry, UniVersity of Exeter, Stocker Road, Exeter EX4 4QR, U.K., and School
of Chemistry, UniVersity of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K.
Received June 16, 2005
Thermal decomposition of monochlorogallane, [H2GaCl]n, at ambient temperatures results in the formation of subvalent
gallium species. To Ga[HGaCl3], previously reported, has now been added a second mixed-valence solid, Ga4-
[HGaCl3]2[Ga2Cl6] (1), the crystal structure of which at 150 K shows a number of unusual features. Adducts of
monochlorogallane, most readily prepared from the hydrochloride of the base and LiGaH4 in appropriate proportions,
include not only the 1:1 molecular complex Me3P‚GaH2Cl (2), but also 2:1 amine complexes which prove to be
cationic gallane derivatives, [H2Ga(NH2R)2]+Cl-, where R
have been characterized crystallographically at 150 K.
)
tBu (3a) or sBu (3b). All three of these complexes
1. Introduction
The partially chlorinated derivatives of gallane [HnGaCl3-n m
mediator, like tributyltin hydride,7 or to bring about hydro-
gallation,8 (ii) to form complexes with a variety of donors,
e.g. quinuclidine,9 substituted pyridines,10 and PCy3,11 (iii)
to act via metathesis as a source of other monohydrogallanes,
e.g. [{tBuN2(CH)2}GaH]2,12 and (iv) to function via thermal
decomposition as a precursor to subvalent gallium com-
pounds, e.g. Ga[GaCl4] and [GaCl2(PEt3)]2.13 Monochloro-
gallane is somewhat less robust and more difficult to handle,
but since first reported in 1988,14 it too has found applica-
tions, primarily through metathesis as a source of not only
gallane itself1 but also other monosubstituted derivatives of
gallane, e.g. H2GaBH4,15 H2GaB3H8,16 and H2GaN3.17 Mo-
]
(n ) 1 or 2) are distinctly more robust than the parent
compound.1-4 Nevertheless, the weakness and lability of the
Ga-H bond causes them to share with gallane itself both
reducing properties and the ability to enter into hydrogallation
reactions. Not only does the chlorine act as a ligand to
produce Lewis acids stronger than GaH3 but, by its ability
also to support GaI and Ga-Ga bonded species, it makes
the chlorogallanes potentially useful as sources of subvalent
gallium compounds. In this last respect, there is an obvious
parallel with halogenated derivatives of indium(III) hydride,
which have been shown to act as an entry point to subvalent
indium chemistry, as exemplified by the formation of
[In5Br8(quin)4]- (quin ) quinuclidine).5 From the first report
in 1965,6 for example, dichlorogallane has been shown (i)
to react with various organic substrates as either a radical
(7) Mikami, S.; Fujita, K.; Nakamura, T.; Yorimitsu, H.; Shinokubo, H.;
Matsubara, S.; Oshima, K. Org. Lett. 2001, 3, 1853.
(8) Ohshita, J.; Schmidbaur, H. J. Organomet. Chem. 1993, 453, 7.
(9) Luo, B.; Young, V. G., Jr.; Gladfelter, W. L. Chem. Commun. 1999,
123.
(10) Nogai, S.; Schriewer, A.; Schmidbaur, H. Dalton Trans. 2003, 3165.
(11) Elms, F. M.; Koutsantonis, G. A.; Raston, C. L. Chem. Commun. 1995,
1669.
(12) Schmidt, E. S.; Jockisch, A.; Schmidbaur, H. J. Chem. Soc., Dalton
Trans. 2000, 1039.
(13) Nogai, S.; Schmidbaur, H. Inorg. Chem. 2002, 41, 4770. Schmidbaur,
H.; Nogai, S. D. Z. Anorg. Allg. Chem. 2004, 630, 2218.
(14) Goode, M. J.; Downs, A. J.; Pulham, C. R.; Rankin, D. W. H.;
Robertson, H. E. J. Chem. Soc., Chem. Commun. 1988, 768.
(15) Downs, A. J.; Greene, T. M.; Johnsen, E.; Brain, P. T.; Morrison, C.
A.; Parsons, S.; Pulham, C. R.; Rankin, D. W. H.; Aarset, K.; Mills,
I. M.; Page, E. M.; Rice, D. A. Inorg. Chem. 2001, 40, 3484.
(16) Pulham, C. R.; Downs, A. J.; Rankin, D. W. H.; Robertson, H. E. J.
Chem. Soc., Dalton Trans. 1992, 1509. Morrison, C. A.; Smart, B.
A.; Brain, P. T.; Pulham, C. R.; Rankin, D. W. H.; Downs, A. J. J.
Chem. Soc., Dalton Trans. 1998, 2147.
* To whom correspondence should be addressed. E-mail: tony.downs@
chem.ox.ac.uk (A.J.D.); s.parsons@ed.ac.uk (S.P.).
† University of Oxford.
‡ University of Exeter.
§ University of Edinburgh.
(1) Pulham, C. R.; Downs, A. J.; Goode, M. J.; Rankin, D. W. H.;
Robertson, H. E. J. Am. Chem. Soc. 1991, 113, 5149.
(2) Downs, A. J.; Pulham, C. R. AdV. Inorg. Chem. 1994, 41, 171.
(3) Downs, A. J.; Pulham, C. R. Chem. Soc. ReV. 1994, 23, 175.
(4) Aldridge, S.; Downs, A. J. Chem. ReV. 2001, 101, 3305.
(5) Jones, C. Chem. Commun. 2001, 2293. Cole, M. L.; Jones, C.; Kloth,
M. Inorg. Chem. 2005, 44, 4909.
(6) Schmidbaur, H.; Findeiss, W.; Gast, E. Angew. Chem., Int. Ed. Engl.
1965, 4, 152.
10.1021/ic050986j CCC: $30.25
Published on Web 09/08/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 20, 2005 7143

Tang et al.
lecular complexes with bases such as NMe3,18 quinuclidine,9
and PCy3 have been described, although the 1:2 complex
a period of 3 months while checking the progress of any
change by reference to the Raman spectrum of the original
liquid21 and of any solid subsequently formed. After 4 weeks,
colorless crystalline plates were observed to have formed
on the walls of the vessel; these could be identified as Ga-
[HGaCl3] on the basis of their Raman spectrum.18 After 8
weeks, the crystalline plates had disappeared, giving place
to a white crystalline solid 1 and a white powder. The white
powder was shown by its Raman spectrum22 to be the well-
known compound Ga[GaCl4]. The Raman spectrum of the
crystalline solid 1 resembled quite closely that of Ga-
[HGaCl3]18 with prominent scattering at 1978 and 336 cm-1
suggestive of ν(Ga-H) and ν(Ga-Cl) vibrations, respec-
tively. However, additional scattering at 377 and, more
conspicuously, at 234 cm-1 gave the first hint23 that the
[HGaCl3]- anion was accompanied by the gallium-gallium-
bonded dianion [Ga2Cl6]2-. No further change in the contents
of the ampule occurred after an additional 4 weeks at 0 °C,
at least to judge by the Raman spectra of the solids.
Hence the product 1 was found to be long-lived at 0 °C.
It decomposed slowly at room temperature with the evolution
of dihydrogen gas and formation of gallium metal and a
white solid appearing to be Ga[GaCl4]. A single crystal at
150 K was shown by X-ray diffraction to be the new mixed-
valence compound Ga4[HGaCl3]2[Ga2Cl6]. The structure is
notable for including no less than five distinct gallium
centers: (i) two different four-coordinated Ga centers in the
[HGaCl3]- and [Ga2Cl6]2- units; (ii) an eight-coordinated GaI
cation; (iii) a six-coordinated GaI cation; (iv) a four-
coordinated GaI cation. Figure 1a-c shows the essential
features of these three environments, while Figure 2 is a
packing diagram. Crystallographic details are given in Table
1, and selected bond lengths and interbond angles of the
[HGaCl3]- and [Ga2Cl6]2- units in Table 2.
11
with NH3 is believed on the evidence of its IR spectrum to
be more aptly formulated as [H2Ga(NH3)2]+Cl-.18 That
monochlorogallane also provides a route into subvalent
gallium chemistry is demonstrated by the finding18 that
thermal decomposition at ambient temperatures releases H2
and gives rise to a mixture of products that includes the
mixed valence compound Ga[HGaCl3].
Here we report the isolation of a second solid decomposi-
tion product of monochlorogallane, formed presumably from
Ga[HGaCl3]. This has been shown by X-ray analysis of a
single crystal at 150 K to be the mixed-valence compound
Ga4[HGaCl3]2[Ga2Cl6] (1) featuring three distinct GaI centers
with different coordination environments (including, unusu-
ally, a near-square planar arrangement). Complexes of
monochlorogallane are more easily prepared not from the
isolated compound but by the reaction of the hydrochloride
of the base (or the base + HCl) with LiGaH4 in appropriate
proportions. Crystallographic characterization at 150 K shows
that the 1:1 complex of H2GaCl with Me3P is made up of
neutral Me3P‚GaH2Cl molecules (2), whereas the corre-
sponding 1:2 complexes with primary amines provide the
first authenticated examples of cationic gallium hydrides in
t
s
[H2Ga(NH2R)2]+Cl- [R ) Bu (3a) or Bu (3b)].
2. Results and Discussion
2.1. Decomposition of Monochlorogallane: Character-
ization of Ga4[HGaCl3]2[Ga2Cl6], 1. As reported previ-
ously,14,18,19 monochlorogallane was prepared by the reaction
of gallium(III) chloride with an excess of trimethylsilane (eq
1). It is a relatively viscous liquid which decomposes slowly
at ambient temperatures and more rapidly at temperatures
above 353 K, ultimately with the formation of Ga[GaCl4],
gallium metal, and dihydrogen.18 The vapor is composed of
dimeric H2Ga(µ-Cl)2GaH2 molecules, with the properties of
the liquid and the solid implying a higher degree of
aggregation in the condensed phases, although the solid has
so far eluded attempts at crystallographic characterization.19,20
The [HGaCl3]- anions approximate quite closely to C3V
symmetry with a mean Ga-Cl bond length of 2.219 Å and
Cl-Ga-Cl angle of 103.9°, values not significantly different
from those reported previously (2.210 Å and 104.0°) for the
same anion in Ga[HGaCl3] at 100 K.18 For comparison, the
mean Ga-Cl bond length in [GaCl4]- in Ga[GaCl4] is 2.180-
(2) Å.24 The Cl atoms of the [HGaCl3]- anion each form
either a single or a double bridge with one of the nearest
GaI centers (GaI‚‚‚Cl ) 3.02-3.49 Å). Hence, the anions
fulfill a multifunctional bridging role for the surrounding GaI
cations analogous to that of the same anions and [GaCl4]-
in the compounds Ga[HGaCl3]18 and Ga[GaCl4],24 respec-
tively.
1
2
1
n
[GaCl3]2 + 2Me3SiH f [H2GaCl]n + 2Me3SiCl (1)
Earlier studies of the decomposition of monochlorogallane
in vacuo at room temperature succeeded in isolating crystals
of the mixed-valence intermediate Ga[HGaCl3], an optimum
yield of which was realized in about 14 days.18 We have
enlarged upon these studies by leaving a sample of the
compound at 0 °C in an evacuated Pyrex glass ampule for
The [Ga2Cl6]2- ion contains a Ga-Ga bond measuring
2.4070(9) Å with roughly tetrahedral coordination of each
of the Ga atoms. The pyramidal GaCl3 units are characterized
by Ga-Cl distances and Cl-Ga-Cl angles averaging to
(17) McMurran, J.; Kouvetakis, J.; Nesting, D. C.; Smith, D. J.; Hubbard,
J. L. J. Am. Chem. Soc. 1998, 120, 5233. McMurran, J.; Dai, D.;
Balasubramanian, K.; Steffek, C.; Kouvetakis, J. Inorg. Chem. 1998,
37, 6638.
(18) Johnsen, E.; Downs, A. J.; Goode, M. J.; Greene, T. M.; Himmel,
H.-J.; Mu¨ller, M.; Parsons, S.; Pulham, C. R. Inorg. Chem. 2001, 40,
4755.
(19) Johnsen, E.; Downs, A. J.; Greene, T. M.; Souter, P. F.; Aarset, K.;
Page, E. M.; Rice, D. A.; Richardson, A. N.; Brain, P. T.; Rankin, D.
W. H.; Pulham, C. R. Inorg. Chem. 2000, 39, 719.
(20) Tang, C. Y.; Marchant, S.; Downs, A. J.; Greene, T. M.; Parsons, S.
Unpublished results.
(21) Pulham, C. R.; Downs, A. J.; Goode, M. J.; Greene, T. M.; Mills, I.
M. Spectrochim. Acta, Part A 1995, 51, 769.
(22) Chemouni, E. J. Inorg. Nucl. Chem. 1971, 33, 2325.
(23) Evans, C. A.; Tan, K. H.; Tapper, S. P.; Taylor, M. J. J. Chem. Soc.,
Dalton Trans. 1973, 988.
(24) Schmidbaur, H.; Nowak, R.; Bublak, W.; Burkert, P.; Huber, B.;
Mu¨ller, G. Z. Naturforsch., B: Chem. Sci. 1987, 42, 553. Wilkinson,
A. P.; Cheetham, A. K.; Cox, D. E. Acta Crystallogr. 1991, B47, 155.
7144 Inorganic Chemistry, Vol. 44, No. 20, 2005

Decomposition of Monochlorogallane
Figure 1. (a) Coordination about the Ga1 site Ga4 which resides on a site with m symmetry. Bonds to Cl2 and Cl5 are shorter [Ga4‚‚‚Cl2 3.0270(12) and
Ga4‚‚‚Cl5 3.1101(13) Å] than to Cl1 and Cl7 [Ga4‚‚‚Cl1 3.4879(14) and Ga4‚‚‚Cl7 3.4727(14) Å]. (b) Coordination about the Ga1 site Ga5. The six contacts
to H and Cl form a distorted trigonal prism with Ga5‚‚‚H1 2.41 Å and Ga‚‚‚Cl in the range 3.07-3.30 Å. The three “capping” contacts span 3.26-3.47 Å,
the longest being shown as a broken line. Distances (Å): Ga5‚‚‚Cl1, 3.0715(11); Ga5‚‚‚Cl5 3.1519(12); Ga5‚‚‚Cl5, 3.1567(12); Ga5‚‚‚Cl6, 3.1935(9); Ga5‚
‚‚Cl3, 3.3028(12); Ga5‚‚‚Cl7, 3.2591(12); Ga5‚‚‚Cl7, 3.3801(13); Ga5‚‚‚Cl2, 3.4660(12). (c) Coordination about the Ga1 site Ga6. Ga6, Cl4, and Cl6 all
occupy sites with m symmetry. The six shortest contacts form a trigonal prism with Ga‚‚‚Cl distances spanning 3.04-3.13 Å; two longer contacts (3.25 Å)
then occur to capping Cl3 atoms. Distances (Å): Ga6‚‚‚Cl6, 3.0462(14); Ga6‚‚‚Cl1, 3.0668(11); Ga6‚‚‚Cl2, 3.0970(12); Ga6‚‚‚Cl4, 3.1319(15); Ga6‚‚‚Cl3,
3.2504(11) Å.
Figure 2. Packing in 1 as viewed along the c-axis. GaI (Ga4-Ga6) and GaII and GaIII (Ga1-Ga3) sites are shown in turquoise and magenta, respectively.
2.231 Å and 102°, respectively. Hence the Ga-Cl bonds
are bent away from the Ga-Ga bond (Ga-Ga-Clav ) 116°),
in keeping with the expectations of VSEPR theory.25 The
dimensions are consistent with those reported in earlier
crystallographic studies of compounds containing the
[Ga2Cl6]2- ion (average distances in Å, angles in deg): Li2-
Ga2Cl6, Ga-Ga 2.391, Ga-Cl 2.238, Ga-Ga-Cl 113.7;26
(25) See for example: Gillespie, R. J.; Hargittai, I. The VSEPR Model of
Molecular Geometry; Allyn and Bacon: Boston, MA, 1991.
(26) Ho¨nle, W.; Miller, G.; Simon, A. J. Solid State Chem. 1988, 75, 147.
Inorganic Chemistry, Vol. 44, No. 20, 2005 7145

Tang et al.
Table 1. Crystallographic Data for Compounds 1, 2, and 3a,b
param
empirical formula
1
2
3a
3b
H2Cl12Ga8
985.18
C3H11ClGaP
183.26
C8H24ClGaN2
253.46
C8H24ClGaN2
fw
253.46
cryst dimens (mm)
cryst system
space group
unit cell dimens
a (Å)
0.47 × 0.39 × 0.39
orthorhombic
Pmn21
0.04 × 0.12 × 0.09
monoclinic
P21/m
0.50 × 0.19 × 0.18
monoclinic
P21/c
0.82 × 0.48 × 0.20
monoclinic
P21/n
14.193(3)
9.2745(19)
8.0839(16)
6.215(3)
9.704(3)
7.286(3)
115.153(6)
397.7(3)
2
1.530
3.887
28.27
2507
8.3160(8)
10.7950(11)
15.2538(16)
96.351(2)
1360.9(2)
4
1.237
2.182
26.39
7818
5.6404(2)
11.4417(4)
21.3438(9)
96.744(2)
1367.91(9)
4
1.231
2.171
25.00
12 018
b (Å)
c (Å)
â (deg)
V (Å3)
1064.1(4)
2
3.075
11.454
29.22
13 881
2795 (0.0321)
101
Z
d(calcd) (Mg m-3
)
abs coeff (mm-1
max (deg)
reflcns measd
)
θ
unique reflcns (Rint
no. of params
)
1012 (0.0208)
46
2786 (0.022)
133
2408 (0.0427)
105
conventional R [F > 4σ(F)]
weighted R (F2 and all data)
goodness-of-fit on F2 (S)
0.0218
0.0448
1.004
0.0464
0.1023
1.178
0.0260
0.0637
0.9661
+0.62/-0.27
0.0660
0.1815
1.131
+1.221/-0.914
largest difference peak/hole (e Å-3
)
+0.925/-0.511
+0.95/-0.56
Table 2. Selected Distances (Å) and Interbond Angles (deg) for the
Anions in Ga4[HGaCl3]2[Ga2Cl6], 1, at 150 Ka
Å (as against 3.55 Å for the sum of the relevant van der
Waals radii29). We consider each of the three centers in turn.
[HGaCl3]-
[Ga2Cl6]2-
Ga(2)-Ga(3)
Ga(2)-Cl(4)
(i) Most unusual is the four-coordinated GaI center which
adopts a nearly square-planar geometry with relatively short
Ga‚‚‚Cl contacts of 3.027 (×2) and 3.110 (×2) Å and a trans
Cl-Ga-Cl angle of 176.3°. This is the first example of a
Ga+ ion to be found in such an environment, as compared
with the more commonly observed eight-coordinated one.18,24
Closer inspection reveals that it also possesses four other
significantly longer Ga‚‚‚Cl contacts of 3.473 (×2) and 3.488
(×2) Å, respectively (see Figure 1a). Accordingly, the center
may be viewed as being coordinated by eight chlorines
situated at the corners of a distorted square-based prism and
thus revealing the kind of unsymmetrical hemidirected
environment often favored by metal ions formally possessing
an ns2 valence shell.30,31
Ga(1)-Cl(1)
Ga(1)-Cl(2)
Ga(1)-Cl(3)
2.2254(9)
2.2269(9)
2.2052(10) Ga(2)-Cl(5)
2.4070(9)
2.1902(13)
2.2549(9)
2.2549(9)
2.2278(13)
2.2282(10)
2.2282(10)
Ga(2)-Cl(5)#1
Ga(3)-Cl(6)
Ga(3)-Cl(7)
Ga(3)-Cl(7)#1
Cl(1)-Ga(1)-Cl(3) 105.69(4)
Cl(2)-Ga(1)-Cl(3) 104.22(4)
Cl(1)-Ga(1)-Cl(2) 101.87(3)
Cl(4)-Ga(2)-Cl(5)
103.11(4)
Cl(4)-Ga(2)-Cl(5)#1 103.11(4)
Cl(5)-Ga(2)-Cl(5)#1 100.42(5)
Cl(4)-Ga(2)-Ga(3)
Cl(5)-Ga(2)-Ga(3)
124.00(4)
111.67(3)
Cl(5)#-Ga(2)-Ga(3) 111.67(3)
Cl(6)-Ga(3)-Cl(7)#1 99.89(4)
Cl(6)-Ga(3)-Cl(7)
99.89(4)
Cl(7)-Ga(3)-Cl(7)#1 103.46(6)
Cl(6)-Ga(3)-Ga(2) 121.47(4)
Cl(7)#1-Ga(3)-Ga(2) 114.70(3)
Cl(7)-Ga(3)-Ga(2) 114.70(3)
(ii) As indicated in Figure 1b, the atoms of the six-
coordinated shell of the second GaI center make up a very
distorted trigonal prism with five Ga‚‚‚Cl contacts ranging
from 3.072 to 3.303 Å and one Ga‚‚‚H contact of 2.41 Å.
With respect to the [HGaCl3]- ions, the Ga+ ion establishes
a Ga‚‚‚H distance much shorter (by 0.36 Å) than that found
in Ga[HGaCl3];18 the Ga‚‚‚Cl distance (3.072 Å) is also at
the short end of the range (3.069-3.552 Å) displayed by
Ga[HGaCl3]. In addition, however, there are three other Ga‚
‚‚Cl contacts in excess of 3.2 Å (3.259, 3.380, and 3.466 Å)
that go to complete an irregular tricapped trigonal prism.
With the inclusion of these longer interactions, the coordina-
tion shell of the Ga+ ion can be seen to resemble that in
Ga[HGaCl3].18 In both cases, the barytes structure Ba-
[SO4]18,32,33 provides a point of reference. The eight shortest
a See Figure 1 for atom labeling. Symmetry transformation used to
generate equivalent atoms: (#1) -x + y, y, z.
[Ph3PH]2[Ga2Cl6], Ga-Ga 2.407, Ga-Cl 2.209, Ga-Ga-
Cl 116.7;27 [Me4N]2[Ga2Cl6], Ga-Ga 2.390, Ga-Cl 2.196,
Ga-Ga-Cl 113.9.28 In 1, as in Li2Ga2Cl6,26 the ion adopts
an eclipsed conformation approximating to D3h symmetry
that contrasts with the staggered ethane-like conformation
found in [Ph3PH]2[Ga2Cl6]27 and [Me4N]2[Ga2Cl6].28 While
being less favorable for the isolated ion, the eclipsed
geometry probably reflects the influence of secondary
interactions, for example by maximizing the number of
Ga-Cl‚‚‚MI contacts the [Ga2Cl6]2- ions establish with
neighboring MI cations (M ) Ga or Li).
In comparison with the GaIII centers, all three different
GaI centers feature environments that are more diffuse and
involve coordination numbers that may be judged to range
from 4 to 8 for GaI‚‚‚Cl contacts between 3.027 and 3.303
(29) Bondi, A. J. Phys. Chem. 1964, 68, 441.
(30) Downs, A. J., Ed. Chemistry of Aluminium, Gallium, Indium and
Thallium; Blackie: Glasgow, U.K., 1993.
(31) Shimoni-Livny, L.; Glusker, J. P.; Bock, C. W. Inorg. Chem. 1998,
37, 1853.
(27) Khan, M. A.; Tuck, D. G. J. Crystallogr. Spectrosc. Res. 1986, 16,
895.
(28) Brown, K. L.; Hall, D. J. Chem. Soc., Dalton Trans. 1973, 1843.
(32) Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Clarendon
Press: Oxford, U.K., 1984.
(33) Staffel, T.; Meyer, G. Z. Anorg. Allg. Chem. 1987, 552, 108.
7146 Inorganic Chemistry, Vol. 44, No. 20, 2005

Decomposition of Monochlorogallane
Ba‚‚‚O contacts in that structure are replaced by seven
shortest Ga‚‚‚Cl contacts and one Ga‚‚‚H contact. A ninth
(longest) contact is then formed through what would be a
rectangular face of the trigonal prism.
in [H2Ga(NH3)2]+Cl- or a neutral molecule in Me3N‚GaH2-
Cl. However, the comparative difficulty of preparing, purify-
ing, and manipulating monochlorogallane18,19 has led to the
devising of an alternative route to such complexes. For
example, the groups of Gladfelter9 and Raston11 have
prepared molecular complexes of the type base‚GaH2Cl by
hydride/chloride redistribution between species such as base‚
GaHCl2 and base‚GaH3 (base ) quinuclidine or PCy3). We
have also used hydride/chloride exchange reactions to prepare
a 1:1 complex of GaH2Cl with Me3P (2) and 1:2 complexes
with tBuNH2 (3a) and sBuNH2 (3b). The method, involving
in effect the reaction of the base hydrochloride with LiGaH4
in ether solution, is essentially analogous to that normally
favored to access the corresponding GaH3 complexes36,37 but
with appropriate changes in the relative proportions of
gallium and chloride, as in eq 2 for example.
(iii) The eight-coordinated Ga+ ion in 1 has eight Ga‚‚‚Cl
contacts at distances ranging from 3.046 to 3.250 Å, which
can be separated into two sets of Ga‚‚‚Cl interactions with
average distances of 3.075 Å (×5) and 3.211 Å (×3). The
six shortest contacts form what again approximates to a
trigonal prism with Ga‚‚‚Cl distances spanning 3.05-3.13
Å; the two longer contacts (3.25 Å) then complete a bicapped
trigonal prism (see Figure 1c). The resulting polyhedron can
also be regarded as approximating a bisdisphenoid such as
that defining the coordination shell of Ca in scheelite, Ca-
[WO4].32 Significantly, too, it prefigures the eight-coordinated
environment of GaI in Ga[GaCl4],24 i.e., one of the ultimate
solid products of thermal decomposition of monochlorogal-
lane.
2[baseH]+Cl- + LiGaH4
98
[(base)2GaH2]+Cl- + 2H2 + LiCl (2)
Earlier studies18 have indicated that ligand scrambling
precedes the elimination of H2 in the decomposition of liquid
monochlorogallane. One such product, H(Cl)Ga(µ-Cl)2GaH2,
is then thought to lose H2 with the formation of Ga[HGaCl3],
while a second, H2Ga(µ-Cl)(µ-H)GaH2, decomposes to H2,
Ga metal, and Ga[GaCl4]. On the evidence of the present
studies, solid Ga[HGaCl3] decomposes slowly at 0 °C to 1
without any change in the proportions Ga:Cl ) 2:3. Half of
the [HGaCl3]- ions eliminate H2, presumably by pairwise
interaction of adjacent ions and so give rise in 1 to the
[Ga2Cl6]2- anion. 1 could thus be regarded as a double salt
composed of 2 mol of Ga[HGaCl3] and 1 mol of Ga2[Ga2-
Cl6]; unsurprisingly, therefore, it retains some of the structural
features of Ga[HGaCl3].18 Ga2[Ga2Cl6] would correspond to
a binary gallium chloride with the composition Ga2Cl3. No
such compound has been described, the solid with this
composition being apparently unstable at normal tempera-
tures to disproportionation into Ga metal and Ga[GaCl4].30
By contrast, Ga2Br3 is known, being stable at temperatures
up to 154 °C. Its crystal structure34 confirms that it is indeed
to be formulated as Ga2[Ga2Br6] with eclipsed Ga2Br6 units.
There are two different environments for the GaI centers,
one eight-coordinated, roughly cubic, and the other nine-
coordinated, roughly tricapped trigonal prismatic (cf. 1). The
structure of the bromide is also noteworthy for some
relatively close GaI‚‚‚GaI contacts and for the vacancy it
leaves in the GaI partial structure, implying the formulation
Ga40[Ga4Br12] and leading to significant Ga+ ion conductiv-
ity. Both these features may have a bearing on the instability
of the corresponding chloride, Ga2[Ga2Cl6], but it is evident
that this is effectively a key intermediate in the decomposi-
tion of Ga[HGaCl3], ultimately to H2, Ga, and Ga[GaCl4].
(a) Trimethylphosphine-Monochlorogallane, Me3P‚
GaH2Cl, 2. This was synthesized, like Me3P‚GaH3,37 from
freshly prepared LiGaH4 and 1 mol equiv of Me3P but with
an excess of HCl, in dry Et2O solution at room temperature.
It was isolated as a white solid at room temperature, purified
by sublimation in vacuo at 50 °C, and characterized by its
1
IR and Raman spectra and by the H NMR spectrum of a
toluene-d8 solution. The Raman spectrum of the solid
included, in addition to the features characteristic of internal
vibrations of the Me3P unit,38 scattering at 1889.5, 759/724,
538, and 349 cm-1. Most prominent of these is the band at
1889.5 cm-1 clearly identifiable with the ν(Ga-H) modes
of a GaH2 unit, occurring at higher wavenumber than the
corresponding modes of Me3P‚GaH3 (average 1816 cm-1 38
)
but at lower wavenumber than those of matrix-isolated H2-
GaCl (average 1962 cm-1 39). The other extra bands can be
attributed to δ(GaH2), F(GaH2), ν(Ga-P), and ν(Ga-Cl)
motions, although coupling of some of these motions is
likely, as in Me3P‚GaH3,38 to preclude simple descriptions
of the vibrations at wavenumbers <700 cm-1. The spectro-
scopic properties are thus consistent with the formulation of
2 as a simple molecular complex, Me3P‚GaH2Cl.
Such a structure has been confirmed by X-ray analysis of
a single crystal at 150 K. Crystallographic details are given
in Table 1, and selected molecular dimensions in the legend
to Figure 3. The compound resembles closely the gallane
40
complex Me3P‚GaH3 featuring monomeric Me3P‚GaH2Cl
molecules with a distorted tetrahedral geometry about the
metal center and no hint of significant intermolecular
(35) Greenwood, N. N. In New Pathways in Inorganic Chemistry; Ebsworth,
E. A. V., Maddock, A. G., Sharpe, A. G., Eds.; Cambridge University
Press: Cambridge, U.K., 1968; p 37.
(36) Shriver, D. F.; Shirk, A. E. Inorg. Synth. 1977, 17, 45.
(37) Greenwood, N. N.; Ross, E. J. F.; Storr, A. J. Chem. Soc. 1965, 1400.
(38) Odom, J. D.; Chatterjee, K. K.; Durig, J. R. J. Phys. Chem. 1980, 84,
1843.
(39) Ko¨ppe, R.; Schno¨ckel, H. J. Chem. Soc., Dalton Trans. 1992, 3393.
(40) Tang, C. Y.; Coxall, R. A.; Downs, A. J.; Greene, T. M.; Kettle, L.;
Parsons, S.; Rankin, D. W. H.; Robertson, H. E.; Turner, A. R. Dalton
Trans. 2003, 3526.
2.2. Complexes of Monochlorogallane with Nitrogen
and Phosphorus Bases. Earlier experiments have estab-
lished18 that monochlorogallane adds NH3 or NMe3 to form
a 1:2 or 1:1 adduct presumed on the evidence of its
vibrational spectrum to feature either a cationic gallane unit
(34) Ho¨nle, W.; Gerlach, G.; Weppner, W.; Simon, A. J. Solid State Chem.
1986, 61, 171.
Inorganic Chemistry, Vol. 44, No. 20, 2005 7147

Tang et al.
Figure 3. Structure of crystalline Me3P‚GaH2Cl, 2. Atoms C1, P1, Ga1,
and Cl1 lie on a crystallographic mirror plane. Bond distances (Å): Ga1-
Cl1, 2.237(2); Ga1-P1, 2.3797(18); P1-C2, 1.791(6); P1-C1, 1.795(4).
Angles (deg): Cl1-Ga1-P1, 100.48(6); C2-P1-C1, 106.3(2); C1A-P1-
C1, 105.2(3); C2-P1-Ga1, 112.2(2); C1-P1-Ga1, 113.17(15). “A” refers
to the symmetry operator (x, -y + 3/2, z).
interactions. At 2.3797(18) Å, the Ga-P distance is not
significantly different from that in either Me3P‚GaH3 [2.3857-
(6) Å]40 or Cy3P‚GaH2Cl [2.403(4) Å]11 but longer than that
in Me3P‚GaCl3 [2.352(2) Å].41 The Ga-Cl distance [2.237-
(2) Å] is somewhat longer than those found or predicted in
t
Figure 4. Structure of crystalline [H2Ga(NH2 Bu)2]Cl, 3a, showing the
cation and a packing plot that highlights the NH‚‚‚Cl hydrogen bonds with
H‚‚‚Cl ) 2.5 Å.
39
Me3P‚GaCl3,41 Cy3P‚GaH2Cl,11 and free H2GaCl [2.171-
(2), 2.107(8), and 2.169 Å, respectively]. There is no clear
pattern to the Ga-P and Ga-Cl bond lengths, and it is likely
that, with bonds as polar as these, the general influence of
the permittivity of the crystal environment as a whole or the
particular influence of specific intermolecular interactions
is at least as important as that of the acid strength of the
GaHnCl3-n unit (expected to follow the order GaH3 < GaH2-
Cl < GaCl3). Another noteworthy feature of crystalline 2 is
the eclipsed conformation adopted by the Me3P‚GaH2Cl
Such compounds are of interest as potential sources of cyclic
amido- or cagelike imidogallanes.4,30,45 Prepared in ac-
cordance with eq 2, both are white, sublimable solids (cf. 2)
lastingly stable in vacuo at room temperature. Unlike 2, they
do not dissolve readily in organic solvents with which they
do not react. The Raman spectra of the solids show numerous
features attributable to internal vibrations of the coordinated
amine molecule but, in addition, significant scattering at
1927/1910 and 762/733 cm-1 (3a) and 1923 and 740 cm-1
(3b). The intense bands at 1920-1930 cm-1 patently
correspond to ν(Ga-H) vibrations, the high wavenumber
contrasting with those of the corresponding vibrations of
Me3P‚GaH2Cl (1889.5 cm-1), quin‚GaH2Cl (1892 cm-1 9),
and MeH2N‚GaH3 (1815 cm-1 44). Indeed, the wavenumber
is comparable with that found for the ν(Ga-H) modes (1915
cm-1) in the 1:2 complex of monochlorogallane with NH3
believed to contain cationic [H2Ga(NH3)2]+ units.18
40
molecules. In this respect, it resembles Me3P‚GaH3 and
Me3P‚GaCl341 but differs from Cy3P‚GaH2Cl,11 Cy3P‚GaH3,43
and quin‚GaHCl2,9 the molecules of which have a staggered
conformation. That the eclipsed structure should be favored
by any of these compounds points to crystal packing or
intermolecular forces as a factor that may or may not
overcome the natural preference of the free molecule for a
staggered conformation, depending on the bulk of the
substituents at the donor atom.
The first definitive structural evidence of a base-supported
+
(b) 2:1 tert-Butylamine and sec-Butylamine Complexes
GaH2 cation has now been provided by X-ray analysis of
of Monochlorogallane, [H2Ga(NH2R)2]+Cl-, R ) tBu (3a)
a single crystal of 3a at 150 K. This confirms the spectro-
s
and Bu (3b). Our recent studies of the adducts formed by
scopic evidence that the solid comprises an array of [H2Ga-
t
t
(NH2 Bu)2]+ cations (Figure 4) and Cl- anions. Selected
gallane with the primary amines MeNH2, BuNH2, and
44
sBuNH2 have led to the preparation and isolation of the
dimensions of the cation are given in Table 3. The shortest
interionic contacts are those between Cl- and the N-H
protons (ranging from 2.365 to 2.461 Å as against 2.95 Å
for the sum of the relevant van der Waals radii29); the shortest
Ga‚‚‚Cl distance is >4 Å, well in excess of the normal range
for covalent GaIII‚‚‚Cl interactions (cf. 2). The cation is
characterized by Ga-H and Ga-N distances averaging
1:2 adducts of GaH2Cl with tBuNH2 (3a) and sBuNH2 (3b).
(41) Carter, J. C.; Jugie, G.; Enjalbert, R.; Galy, J. Inorg. Chem. 1978, 17,
1248.
(42) Tang, C. Y.; Downs, A. J.; Greene, T. M.; Parsons, S. Dalton Trans.
2003, 540.
(43) Atwood, J. L.; Elms, F. M.; Gardiner, M. G.; Koutsantonis, G. A.;
Raston, C. L.; Robinson, K. D. J. Organomet. Chem. 1993, 449, 45.
(44) Marchant, S.; Tang, C. Y.; Downs, A. J.; Greene, T. M.; Himmel,
H.-J.; Parsons, S. Dalton Trans., in press.
(45) Carmalt, C. J. Coord. Chem. ReV. 2001, 223, 217.
7148 Inorganic Chemistry, Vol. 44, No. 20, 2005

Decomposition of Monochlorogallane
Table 3. Selected Distances (Å) and Interbond Angles (deg) in the
t
[H2Ga(NH2 Bu)2]+ Cation of 3a
Distancesa
Ga(1)-N(1)
Ga(1)-N(2)
Ga(1)-H(1)
Ga(1)-H(2)
N(1)-C(11)
N(1)-H(11)
N(1)-H(21)
C(11)-C(21)
2.0163(15)
2.0180(15)
1.575(9)
1.583(9)
1.508(2)
0.899(9)
0.894(9)
1.522(3)
C(11)-C(31)
C(11)-C(41)
N(2)-C(12)
N(2)-H(12)
N(2)-H(22)
C(12)-C(22)
C(12)-C(32)
C(12)-C(42)
1.520(3)
1.521(3)
1.511(2)
0.897(9)
0.896(9)
1.522(3)
1.526(3)
1.523(3)
s
Figure 5. Structure of the framework of the cation in [H2Ga(NH2 Bu)2]-
Cl, 3b.
Anglesa
N(1)-Ga(1)-N(2)
N(1)-Ga(1)-H(1)
N(2)-Ga(1)-H(1)
N(1)-Ga(1)-H(2)
N(2)-Ga(1)-H(2)
H(1)-Ga(1)-H(2)
97.55(6)
106.3(8)
111.4(8)
107.7(8)
106.1(8)
124.5(12)
Ga(1)-N(2)-C(12)
Ga(1)-N(2)-H(12)
Ga(1)-N(2)-H(22)
C(12)-N(2)-H(12)
C(12)-N(2)-H(22)
122.20(12)
103.7(13)
105.8(14)
108.2(13)
108.1(14)
t
Ga center of [H2Ga(NH2 Bu)2]+, illustrating yet again the
way in which aluminum significantly more than gallium
favors coordination numbers greater than 4.30
C(21)-C(11)-C(31) 111.07(16)
Ga(1)-N(1)-C(11) 120.08(11) C(21)-C(11)-C(41) 110.34(16)
Ga(1)-N(1)-H(11) 104.8(14)
C(11)-N(1)-H(11) 108.9(15)
Ga(1)-N(1)-H(21) 105.4(14)
C(11)-N(1)-H(21) 110.3(14)
H(11)-N(1)-H(21) 106.5(18)
C(31)-C(11)-C(41) 110.96(16)
H(12)-N(2)-H(22)
N(2)-C(12)-C(22)
N(2)-C(12)-C(32)
N(2)-C(12)-C(42)
108.1(20)
108.03(15)
108.04(16)
107.73(16)
N(1)-C(11)-C(21) 107.64(15) C(22)-C(12)-C(32) 110.36(17)
N(1)-C(11)-C(31) 107.94(15) C(22)-C(12)-C(42) 111.74(17)
N(1)-C(11)-C(41) 108.78(14) C(32)-C(12)-C(42) 110.80(17)
a See Figure 4 for atom labeling.
1.579(9) and 2.017(2) Å and by H-Ga-H and N-Ga-N
angles of 124.5(12) and 97.55(6)°, respectively. The Ga-N
bonds are thus at the short end of the range found for
coordinate links involving a tetracoordinated gallium hydride
acceptor and a nitrogen donor (1.988-2.134 Å 4,44). The two
tert-butyl groups are bent away from the metal, giving Ga-
N-C angles of 120.1(1) and 122.2(1)°, and are arranged
mutually trans to each other. Despite the reduction in steric
repulsion thus achieved and unremarkable internal dimen-
sions for the coordinated tBuNH2 molecules, relatively close
Ga‚‚‚H contacts of 2.83 and 2.89 Å are established between
the metal and a hydrogen of one of the CH3 groups carried
by each amine (cf. 3.22 Å for the sum of the relevant van
der Waals radii29). As shown in Figure 4, a network of
hydrogen bonding engages the Cl- anions with the NH2
groups of the coordinated amine molecules.
X-ray analysis of a single crystal of the sec-butylamine
derivative 3b at 150 K was frustrated by complete disordering
of the amine fragments, making it impossible to establish
more than a rudimentary structure. Nevertheless, the results
s
are in keeping with the formulation [H2Ga(NH2 Bu)2]+Cl-.
The cation appears to have a skeletal geometry similar to
that of the cation in 3a (see Figure 5), with Ga-N distances
of 1.998(5) and 2.027(5) Å and an N-Ga-N angle of 99.5-
(2)°. Unsurprisingly in the circumstances, none of the
hydrogen atoms could be located.
3. Experimental Section
3.1. General Methods. The vacuum-line methods used for the
preparation, purification, and manipulation of monochlorogallane
have been described previously.1-3,19 Elemental analyses were
mostly ruled out by problems of scale and/or reactivity but were
performed, where possible, by the analytical service of the Inorganic
Chemistry Laboratory at Oxford. IR spectra were recorded in the
range 4000-400 cm-1 with a Nicolet Magna 560 FTIR spectrom-
eter, typically at a resolution of 1 cm-1. Raman spectra were excited
at λ ) 632.8 nm with a He-Ne laser and recorded with a Dilor
“Labram” 14/23IM instrument, typically for 10 accumulations each
Perhaps the closest analogy is provided by the cation
t
[Me2Ga(NH2 Bu)2]+ isolated as the bromide following the
reaction of Me2GaBr with tBuNH2.46 Although this features
a slightly longer average Ga-N distance of 2.040(7) Å, the
t
geometry is generally much like that of [H2Ga(NH2 Bu)2]+,
with a wide C-Ga-C angle [121.5(5)°] and a narrow
N-Ga-N one [95.6(3)°]. Cationic alane derivatives of the
type [H2AlL]+[AlH4]- have been prepared by treatment of
Me3N‚AlH3 with a tridentate or macrocyclic tetradentate
nitrogen base L.47 The crystal structures determined for the
compounds with L ) (Me2NC2H4)2NMe and Me4Cyclam
reveal cations with the structures I and II displaying Al-H
distances and H-Al-H angles of 1.62/1.82 Å and 132° (I)
and 1.60/1.64 Å and 171° (II), respectively. The penta- and
hexacoordinated Al centers contrast with the tetracoordinated
1
with a duration of 10 s; the resolution was normally 2 cm-1. H
NMR measurements were made at 500 MHz using a Varian
UNITY-plus spectrometer, and mass spectra (of 3a) were recorded
with a Micromass GCTof instrument with field ionization, using a
temperature-programmed solid probe inlet.
All the source materials (LiH, GaCl3, Me3SiCl, LiAlH4, Me3P,
tBuNH2, and sBuNH2) and toluene-d8 were from Aldrich. LiH and
GaCl3 were used without purification, Me3SiCl and Me3P were
purified before use by fractionation in vacuo, and LiAlH4 was
purified before use (to prepare Me3SiH) by recrystallization from
Et2O. Toluene-d8 was purified after drying over sodium by
(46) Atwood, D. A.; Jones, R. A.; Cowley, A. H.; Bott, S. G.; Atwood, J.
L. J. Organomet. Chem. 1992, 425, C1.
(47) Atwood, J. L.; Robinson, K. D.; Jones, C.; Raston, C. L. Chem.
Commun. 1991, 1697.
t
s
fractionation in vacuo. BuNH2 and BuNH2 were each converted
Inorganic Chemistry, Vol. 44, No. 20, 2005 7149

Tang et al.
to the corresponding hydrochloride which was recrystallized from
dry EtOH/Et2O.
X-ray diffraction data [λ(Mo KR) ) 0.710 73 Å] were collected
on a Bruker Smart Apex diffractometer, the temperature of the
crystal being controlled at 150 K by an Oxford Cryosystems
CRYOSTREAM device.48 Absorption corrections were performed
using the program SADABS.49 The structures of 1 and 3a,b were
solved by Patterson methods (DIRDIF50), and that of 2 was solved
by direct methods (SHELXS);51 full-matrix least-squares refinement
(against F2) was accomplished with the programs SHELXL52 for
1, 2, and 3b or CRYSTALS53 for 3a. The H atom attached to Ga
in 1 was modeled with the Ga-H distance fixed at 1.6 Å, being
placed in a calculated position and allowed to ride on its parent
atom. H atoms attached to Ga in 2 and to Ga and N in 3a were
located in difference maps and refined freely; those remaining were
placed in calculated positions. Non-hydrogen atoms were assigned
anisotropic displacement parameters.
3.2. Decomposition of Monochlorogallane: Characterization
of Ga4[HGaCl3]2[Ga2Cl6], 1. To study the thermal decomposition,
a small sample of monochlorogallane (ca. 100 mg) was isolated in
a sealed, preconditioned all-glass ampule equipped with a break-
seal. The progress of the change at 0 °C was monitored by periodic
reference to the Raman spectrum of the liquid and/or solid contents
of the ampule. Crystals of 1 formed after 8 weeks were selected
and transferred under dry nitrogen to a Schlenk tube for storage
and transport prior to X-ray analysis of an individual crystal. The
scale was insufficient to permit elemental analysis of 1, and NMR
measurements could not be made since the crystals were not
appreciably soluble in any organic solvent with which they did not
react. Raman spectrum (wavenumbers in cm-1): 1978 s ([HGaCl3]-),
607 w ([HGaCl3]-), 589 w ([HGaCl3]-), 377 w ([Ga2Cl6]2-), 336
m ([HGaCl3]-), ca. 315 sh ([Ga2Cl6]2-), 234 s ([Ga2Cl6]2-).18,23
3.3. Me3P‚GaH2Cl, 2. This was prepared on the millimole scale
in yields of ca. 60% by a method similar to that used for the
synthesis of Me3P‚GaH337 but with an excess of HCl. After filtering
of the reaction mixture, the Et2O solvent was evaporated from the
solution under vacuum. Heating the white solid residue, also under
vacuum, to 50 °C resulted in sublimation of white crystals of 2.
Raman spectrum (wavenumbers in cm-1): 2985 s, 2915 vs, 1889.5
s [ν(Ga-H)], 1424 w, 1121 w, 966 w, 759 m/724 w [δ(GaH2)],
672 m, 642 mw, 538 mw, 349 w. 1H NMR (C6D5CD3): δ 5.54 (s
2, GaH2), 0.81 (d 9, CH3).
s
The structure of 3b is extensively disordered. Both Bu ligands
are disordered over two orientations (60:40 for ligand 1 and 50:50
for ligand 2, where ligands 1 and 2 are based on N11 and N12,
respectively). In the major fraction of ligand 1 the terminal C atom
of the ethyl moiety is further disordered over three positions. In
one fraction of ligand 2 the ethyl group is distributed over two
sites. It is likely that disorder is, in reality, more extensive than
described here, as some displacement parameters of the disordered
methyl groups adopted very high values and a single overall Uiso
had to be adopted for these groups. All chemically equivalent bond
distances and angles were restrained to be similar. Only full-weight
atoms were refined with anisotropic displacement parameters. The
identity of the chloride anion was inferred from H-bonding to the
NH groups. N‚‚‚Cl interactions imply that the N is doubly
protonated. At ca. 100°, the N-Ga-N angle implies that the Ga,
too, is attached to two H atoms; these were placed in symmetrical
positions assuming r(Ga-H) ) 1.6 Å.
t
3.4. [H2Ga(NH2 Bu)2]Cl, 3a. This was prepared on the millimole
scale in yields of ca. 20% by the reaction of LiGaH4 with [tBuNH3]-
Cl in Et2O solution at room temperature following a procedure
analogous to that described previously for the synthesis of Me3N‚
36
GaH3 but adding the LiGaH4 to the [tBuNH3]Cl which was
therefore in excess. The product was purified by fractional
condensation at pressures <10-4 Torr. A sample of 3a was stored
at 273 K for 3 weeks whereupon small colorless crystals formed
on the walls of the vessel. Anal. Found: Cl, 13.7; Ga, 27.6%. Calcd
for C8H24ClGaN2: Cl, 14.0; Ga, 27.5%. Raman spectrum (wave-
numbers in cm-1): 3214 w, 3142 w, 2982 s, 2916 s, 2873 mw,
2796 w, 2734 w, 1927 vs/1910 m [ν(Ga-H)], 1479/1460 w, 1323/
1310 w, 1220 w, 1164 w, 1032 w, 937 w, 912 mw, 762/733 m
[δ(GaH2)], 686 w, 608 mw, 546 m, 504 mw, 431 w, 391 vw, 367
Acknowledgment. The Engineering and Physical Sci-
ences Research Council is thanked for financial support of
the Oxford and Edinburgh research groups and for funding
an Advanced Research Fellowship (T.M.G.) and research
studentships (C.Y.T. and S.M.).
Supporting Information Available: ORTEP plots and crystal-
lographic data in CIF format for all the compounds 1, 2, and 3a,b.
This material is available free of charge via the Internet at
http://pubs.acs.org.
t
vw, 270 mw. Field ionization MS (m/e): [M]+ 253/255, [M - -
BuNH2]+ 180/182, [tBuNH2]+ 73.
s
3.5. [H2Ga(NH2 Bu)2]Cl, 3b. Prepared from LiGaH4 and [s-
IC050986J
BuNH3]Cl in yields of less than 5% by a method similar to that
used for 3a, the product was purified by fractional condensation.
When a sample of 3b was stored at 273 K for 6 months, small
platelike crystals formed on the walls of the vessel. Raman spectrum
(wavenumbers in cm-1): 3077 mw, 2980 ms, 2930 s, 2913 ms,
2881 m, 1923 s [ν(Ga-H)], 1466 mw, 1126 w, 1044 w, 1005 w,
921 w, 835 mw, 740 m, 605 w, 485 m, br.
3.6. X-ray Crystallography. Table 1 gives crystal data and other
information on the structure determination and refinement for single
crystals of 1, 2, and 3a,b. Each set of measurements was made on
a crystal mounted under perfluoropolyether oil on a glass fiber.
(48) Cosier, J.; Glazer, A. M. J. Appl. Crystallogr. 1986, 19, 105.
(49) Sheldrick, G. M. SADABS, version 2.05; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 2001.
(50) Beurskens, P. T.; Beurskens, G.; Bosman, W. P.; de Gelder, R.; Garc´ıa-
Granda, S.; Gould, R. O.; Israe¨l, R.; Smits, J. M. M. DIRDIF-96;
Crystallography Laboratory, University of Nijmegen: Nijmegen, The
Netherlands, 1996.
(51) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A. J. Appl.
Crystallogr. 1993, 26, 343.
(52) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
(53) Betteridge, P. W.; Carruthers, J. R.; Cooper, R. I.; Prout, K.; Watkin,
D. J. J. Appl. Crystallogr. 2003, 36, 1487.
7150 Inorganic Chemistry, Vol. 44, No. 20, 2005