Synthesis and characterization of Group 13 hydrides and metal-metal bonded dimers stabilized by the macrocyclic bis(amidophosphine) ligand [P2N2] ([P2N2]=[PhP(CH2SiMe2NSiMe 2CH2)2PPh])

Article abstract of DOI:10.1016/S0022-328X(99)00548-3

Addition of LiAlH₄ to the monomeric chlorides syn-MCl[P₂N₂] (M=Al (1), Ga (2), In (3)) results in the formation of the aluminum hydride syn-AlH[P₂N₂] (4). The solution ¹H- and ³¹P{¹H}-NMR spectra are consistent with a C_2v symmetric species in solution. The X-ray crystal structure shows the hydride to be monomeric, and free from interaction with either salt (LiCl) or external base (Et₂O). The coordination of both phosphines of the macrocycle to the metal center is found in the solid state. Solution molecular weight measurements are consistent with a monomeric structure. The gallium hydride syn-GaH[P₂N₂] (5) is synthesized by the addition of LiGaH₄ to syn-MCl[P₂N₂] (M=Ga (2), In (3)). This species is unstable and could only be characterized in solution. Reduction of syn-MCl[P₂N₂] (M=Ga (2), In (3)) with KC₈ yields the reduced, dimeric species {syn-M[P₂N₂]}₂ (M=Ga (6), In (7)). The solution ¹H- and ³¹P{¹H}-NMR spectra are consistent with C_2v symmetric species in solution. The X-ray crystal structures of the gallium and indium complexes confirm the presence of unsupported metal-metal bonds in both cases. The features of the solution ¹H- and ³¹P{¹H}-NMR spectra suggest that both dimers are fluxional in solution.

Full text of DOI:10.1016/S0022-328X(99)00548-3

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 591 (1999) 63–70
Synthesis and characterization of Group 13 hydrides and
metalꢀmetal bonded dimers stabilized by the macrocyclic
bis(amidophosphine) ligand [P2N2]
([P2N2]=[PhP(CH2SiMe2NSiMe2CH2)2PPh])
Michael D. Fryzuk a,*, Garth R. Giesbrecht a, Steven J. Rettig a,1, Glenn P.A. Yap b
a Department of Chemistry, Uni6ersity of British Columbia, 2036 Main Mall, Vancou6er, B.C., Canada V6T 1Z1
b Department of Chemistry, Uni6ersity of Ottawa, Ottawa, ON, Canada K1N 6N5
Received 23 June 1999; accepted 17 September 1999
Abstract
Addition of LiAlH4 to the monomeric chlorides syn-MCl[P2N2] (M=Al (1), Ga (2), In (3)) results in the formation of the
1
aluminum hydride syn-AlH[P2N2] (4). The solution H- and 31P{1H}-NMR spectra are consistent with a C26 symmetric species in
solution. The X-ray crystal structure shows the hydride to be monomeric, and free from interaction with either salt (LiCl) or
external base (Et2O). The coordination of both phosphines of the macrocycle to the metal center is found in the solid state.
Solution molecular weight measurements are consistent with a monomeric structure. The gallium hydride syn-GaH[P2N2] (5) is
synthesized by the addition of LiGaH4 to syn-MCl[P2N2] (M=Ga (2), In (3)). This species is unstable and could only be
characterized in solution. Reduction of syn-MCl[P2N2] (M=Ga (2), In (3)) with KC8 yields the reduced, dimeric species
1
{syn-M[P2N2]}2 (M=Ga (6), In (7)). The solution H- and 31P{1H}-NMR spectra are consistent with C26 symmetric species in
solution. The X-ray crystal structures of the gallium and indium complexes confirm the presence of unsupported metalꢀmetal
bonds in both cases. The features of the solution 1H- and 31P{1H}-NMR spectra suggest that both dimers are fluxional in solution.
© 1999 Elsevier Science S.A. All rights reserved.
Keywords: Aluminum; Gallium; Indium; Hydride; Macrocycle; Metalꢀmetal bonds
1. Introduction
groups [6,13], amides [12,15] and carboranes [16] have
also been reported. We recently reported the Group 13
bis(amidophosphine) complexes MCl[P2N2] ([P2N2]=
[PhP(CH2SiMe2NꢀSiMe2CH2)2PPh], M=Al, Ga), in
which the central metal was found to exist in a
monomeric environment [17]. Herein we report our
findings regarding the synthesis of aluminum and gal-
lium hydride species, as well as reduced forms of gal-
lium and indium, stabilized by the macrocyclic ligand
system [P2N2].
The generation of monomeric, salt- and base-free
aluminum, gallium, and indium hydrides has been the
subject of continued research [1–11], as well as being
intimately linked to the study of lower oxidation states
of these elements [1–14] and metalꢀmetal bonded
dimers [5–14]. Recent work has shown that it is possi-
ble to use bulky aryl groups to synthesize unassociated
halide derivatives of aluminum, gallium and indium,
and hydride species of aluminum and gallium [2–4].
Similarly, dimeric species containing bonds between
two reduced Group 13 metal centers often employ
bulky aryl groups [14], although substituted alkyl
2. Results and discussion
2.1. Synthesis of hydride complexes of aluminum and
gallium
* Corresponding author. Fax: +1-604-8222847.
E-mail address: fryzuk@chem.ubc.ca (M.D. Fryzuk)
1 Experimental Officer: UBC Crystallographic Service. Deceased
October 27, 1998.
The reaction of syn-AlCl[P2N2] (1) [17] with LiAlH4
in ether generates syn-AlH[P2N2] (4) in moderate yield
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00548-3

64
M.D. Fryzuk et al. / Journal of Organometallic Chemistry 591 (1999) 63–70
1
(Eq. (1)); the H-NMR spectrum of the product indi-
cates a C26 symmetric complex in solution. Due to the
quadrupolar aluminum center, the hydride resonance in
Prolonged standing of solutions of 5 results in the
formation of syn-H2[P2N2] (detected by H-NMR spec-
1
troscopy) concurrent with the deposition of gallium
metal. The instability of syn-GaH[P2N2] (5) did not
allow for characterization by IR spectroscopy, mass
spectrometry, elemental analysis or X-ray diffraction,
and is reflected in the low yield of 5. The greater
thermal stability of syn-AlH[P2N2] (4) versus syn-
GaH[P2N2] (5) may be due to aluminum’s preference
for higher coordination numbers. For example, pro-
gressively increasing the number of tertiary donors
results in higher thermal stability of alane, whereas
polydentate donors destabilize gallane relative to
monodentate donors [21].
The analogous synthesis of an indium hydride is
more problematic. Although some cationic compounds
containing InꢀH bonds have been structurally charac-
terized [22–26], neutral indium hydrides have only re-
cently been isolated [27–29]. Attempts at in situ
reactions with LiInH4, as well as those with reagents
such as LiH, KH, or KEt3BH either result in no
reaction or decomposition to syn-H2[P2N2], indium
metal, and other unknown products.
the H-NMR spectrum was not observed. The 31P{1H}-
1
NMR spectrum of 4 consists of a singlet at −46.5
ppm; this is in contrast to the broad peak found for
syn-AlCl[P2N2] (1) and that expected for a phosphorus
atom bound to a quadrupolar nucleus [18,19]. Treat-
ment of the gallium (2) and indium (3) analogues with
LiAlH4 also results in syn-AlH[P2N2] (4), although in
lower yields (Eq. (1)). This type of transmetallation has
been seen previously for Group 13 metals complexed by
the [2,6-bis(dimethylaminomethyl)phenyl] ligand system
[2–4] as well as yttrium bis(benzamidinato) complexes
[20].
(1)
2.1.1. Solid-state structure of syn-AlH[P2N2] (4)
The molecular structure and numbering scheme of 4
are illustrated in Fig. 1. Complete details of the struc-
tural analyses of 4, 6 and 7 are compiled in Table 1. As
the hydride ligand was located, but not refined, infor-
mation regarding the aluminum hydride bond length or
angles involving this proton are not available. The
metal center exhibits trigonal bipyramidal geometry,
with the bond angles involving Al, P(1) and P(2) being
nearly identical in hydride 4 and chloride 1 [17].
The aluminumꢀphosphorus bond lengths (2.517(3)
The aluminum hydride complex 4 is isolated as a
colorless, air- and moisture-sensitive solid. Mass spec-
tral and microanalytical data along with solution
molecular-weight studies suggest that 4 is monomeric
and free from interaction with LiCl or external base.
The addition of syn-MCl[P2N2] (M=Ga (2), In (3))
to an ethereal solution of LiGaH4 yields syn-
GaH[P2N2] (5) in low yield (Eq. (2)). The 1H-NMR
spectrum of the product exhibits the same general
features as aluminum hydride 4. The lower quadrupolar
moment of gallium allows for the GaH signal to be
observed (l 5.25), although the peak is still broad
enough to mask any coupling to phosphorus-31. This is
in the region reported for other molecules with a termi-
nal GaH moiety [3,4]. The 31P{1H}-NMR spectrum
of syn-GaH[P2N2] (5) consists of a singlet at −34.7
ppm.
,
and 2.522(3) A) are longer than those in syn-AlCl[P2N2]
(2)
Fig. 1. Molecular structure of syn-AlH[P2N2] (4); 33% probability
thermal ellipsoids are shown. Hydrogen atoms are omitted for clarity.

M.D. Fryzuk et al. / Journal of Organometallic Chemistry 591 (1999) 63–70
65
Table 1
Crystallographic data
Compound
syn-AlH[P2N2] (4)
{syn-Ga[P2N2]}2 (6)
{syn-In[P2N2]}2 (7)
Formula
C24H43AlN2P2Si4
560.88
Colorless plate
0.20×0.10×0.10
Monoclinic
C2/c
37.865(2)
9.1760(4)
22.687(1)
123.954(1)
6538.6(5)
8
C48H84Ga2N4P4Si8
1205.24
Colorless needle
0.50×0.15×0.10
Tetragonal
C48H84In2N4P4Si8
1295.44
Colorless needle
0.35×0.25×0.22
Tetragonal
Formula weight (g mol−1
Color (habit)
Size (mm)
)
Crystal system
Space group
(
(
P421c
P421c
,
a (A)
16.9622(4)
–
17.149(2)
,
b (A)
–
,
c (A)
21.2288(2)
–
6107.9(2)
4
21.649(2)
–
6366.5(13)
4
i (°)
3
,
V (A )
Z
T (°C)
Radiation
25
Mo–Ka
0.71073
3.22
−93
21
Mo–Ka
0.71069
9.93
Mo–Ka
0.71069
11.79
,
u (A)
v (cm−1
)
Transmission factors
R
Rw
–
0.80–1.00
0.97–1.00
0.0815 a
0.052 a
0.038 b
0.1307 a
0.087 a
0.032 b
Rint
2q range
0.0786
2.60–42.00
3452
301
None
0.05408
3.40–60.06
4353
0.10709
3.76–59.98
5247
298
Reflections
Parameters
Absorption correction
Data collection
Diffractometer
298
Semi-empirical
D*TREK
Rigaku ADSC CCD
„ scan
Siemens SMART
Siemens SMART CCD
MSC/AFC Diffractometer Control
Rigaku AFC6S
4 1/2
a R(F)=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ (I]3|(I)), Rw (F2)=(S w(ꢀF2oꢀ−ꢀFc2ꢀ)2/S wꢀFoꢀ )
.
2 1/2
b R(F)=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ, Rw(F)=(S w(ꢀFoꢀ−ꢀFcꢀ)2/S wꢀFoꢀ )
.
most often appear at ꢀ −38 ppm in the 31P{1H}-
NMR spectrum [17].
,
(1) (2.481(1) and 2.465(1) A) [17]. No variation is seen
in the aluminumꢀamide bond lengths of 1.903(5) and
,
1.910(5) A, which are similar to those in the starting
A fluxional process also seems unlikely given the fact
that the macrocycle while flexible always has the donors
poised for coordination. Indeed, cooling a toluene-d8
solution of 4 to −90°C does not result in any apprecia-
ble difference in the 31P{1H}-NMR spectrum. The pos-
sibility that the monomer 4 is in equilibrium with a
dimer via bridging hydrides that somehow weakens the
AlꢀP interaction can be excluded since solution molecu-
lar weight measurements (isopiestic method, Signer ap-
paratus, 520950 g mol−1) indicate a monomeric
solution structure. Compound 4 exhibits a w(AlꢀH)
stretch at 1594 cm−1 in the IR spectrum; this medium
,
aluminum chloride 1 (1.886(3) and 1.903(3) A) [17], as
well as that determined for AlCl2[N(SiMe2CH2PPri2)2]
,
(1.89(1) A) [30]. The hydride complex 4 represents a
structurally characterized aluminum mono-hydride spe-
cies which does not interact with either salt or external
base. A list of selected bond lengths and angles for 4
are presented in Table 2.
2.1.2. Solution structure of syn-AlH[P2N2] (4)
Although the crystal structure of 4 clearly indicates
the presence of two bound phosphine donors, the ob-
servation of a sharp singlet in the 31P{1H}-NMR spec-
trum of 4 is somewhat counterintuitive. As already
mentioned, in the starting chloride syn-AlCl[P2N2] (1),
the 31P{1H}-NMR spectrum consists of a very broad
singlet at −43.6 ppm (s, D1/2=340 Hz) due to cou-
pling of the bound phosphine donors with the quadru-
polar 27Al nucleus. The observation of a sharp singlet
would suggest that the phosphine donors in 4 are
unbound in solution; however, the chemical shift of the
singlet at −46.5 ppm is inconsistent with this since we
have previously shown that phosphines which do not
coordinate to a metal center in the [P2N2] ligand system
Table 2
,
Selected bond lengths (A) and angles (°) for syn-AlH[P2N2] (4)
Bond lengths
N(1)ꢀAl(1)
P(1)ꢀAl(1)
1.903(5)
2.522(3)
N(2)ꢀAl(1)
P(2)ꢀAl(1)
1.910(5)
2.517(3)
Bond angles
N(1)ꢀAl(1)ꢀN(2) 114.9(2)
N(1)ꢀAl(1)ꢀP(1)
N(2)ꢀAl(1)ꢀP(1)
P(1)ꢀAl(1)ꢀP(2)
Al(1)ꢀP(2)ꢀC(12)
89.2(2)
82.6(2)
165.53(11)
131.2(3)
N(1)ꢀAl(1)ꢀP(2)
N(2)ꢀAl(1)ꢀP(2)
83.3(2)
89.3(2)
Al(1)ꢀP(1)ꢀC(6) 130.0(3)

66
M.D. Fryzuk et al. / Journal of Organometallic Chemistry 591 (1999) 63–70
intensity peak shifts to 1129 cm−1 upon deuteration.
This is at the lower end of the determined range for a
terminal aluminum hydride. The low solubility of 4 in
ether or toluene did not allow for a definitive solution
IR peak assignment to be made. In spite of this unusu-
ally low value, we conclude that 4 is monomeric both in
the solid and solution states. We suggest that the sharp
singlet in the 31P{1H}-NMR spectrum of 4 is the result
of hybridization along the axial positions of the trigonal
bipyramid, such that coupling of the 27Al nucleus to 31
P
is significantly reduced as compared to the chloride 1.
2.2. Synthesis of metalꢀmetal bonded dimers of gallium
and indium
The addition of either syn-GaCl[P2N2] (2) or syn-
InCl[P2N2] (3) to a slurry of KC8 (1.1 equivalent) in
diethyl ether is accompanied by the gradual dissipation
of the brown color of the reducing agent to yield a black
slurry of graphite (Eq. (3)). Extraction into toluene
yields a white solid which crystallizes as colorless
Fig. 2. Molecular structure of {syn-Ga[P2N2]}2 (6); 50% probability
thermal ellipsoids are shown. Hydrogen atoms and phenyl rings are
omitted for clarity.
ported metalꢀmetal bond between two Ga(II) centers.
1
needles. The H-NMR spectra of the products indicate
,
The galliumꢀgallium bond length of 2.5206(8) A is
a single symmetric species in solution. The 31P{1H}-
NMR spectra exhibit a single slightly broadened peak
similar to that reported for the tetra(amido) species
(tmp)2GaꢀGa(tmp)2
(tmp=2,2,6,6-tetramethylpipe-
downfield of the starting chloride (l −25.5 ppm, D1/2
=
,
ridino) (GaꢀGa=2.525(1) A) [12]. The metalꢀmetal
bond lengths in gallium(II) dimers fall into two approx-
imate categories: those supported by bulky alkyls such
10 Hz for {syn-Ga[P2N2]}2 (6); l −37.7 ppm, D1/2=24
Hz for {syn-In[P2N2]}2 (7)).
,
as substituted aryls or organosilyls (ꢀ2.5–2.6 A)
,
[6,12–14] and those ligated by halides (ꢀ2.4 A) [10,11],
although some anomalously short contacts are also
known [15,16]. Compound 6 exhibits a slightly stag-
gered geometry; the dihedral angle between the two
GaN2 planes is 27.92°. By comparison, the GaC2
planes in (Trip)2GaꢀGa(Trip)2 (Trip=2,4,6-triiso-
propylphenyl) are skewed by 43.8° [14], and the GaSi2
planes in [(Me3Si)3Si]2GaꢀGa[Si(SiMe3)3]2 by 80° [13].
The galliumꢀnitrogen bond lengths (1.958(3) and
,
1.968(3) A) are slightly longer than in other amidoꢀ
,
gallium systems (ꢀ1.84–1.90 A) [12,15] and may reflect
the steric constraints of the macrocyclic [P2N2] ligand
(3)
system. Compound
6
also contains two short
,
,
(2.6591(11) A) and two long (3.1459(11) A) galliumꢀ
phosphorus bonds. The gallium center is best described
as a distorted tetrahedron, with angles involving the
metal ranging from 126.63(9) to 81.59(9)°. Bond lengths
The gallium(II) and indium(II) species can be pre-
pared in moderate yields; however the attempted reduc-
tion of syn-AlCl[P2N2] (1) with KC8 did not yield a
characterizable product, although metalꢀmetal dimers
of Al(II) have been reported [5,8,31]. The unfavorable
steric interaction of the phenyl rings of two syn-
Al[P2N2] units may prevent the close approach of two
monomers and a metalꢀmetal bond from being formed.
The reduced species {syn-Ga[P2N2]}2 (6) and {syn-
In[P2N2]}2 (7) were studied by X-ray crystallography.
Table 3
,
Selected
bond
lengths
(A)
for
{synꢀGa[P2N2]}2
(6)
and{synꢀIn[P2N2]}2 (7)
{synꢀGa[P2N2]}2 (6)
{synꢀIn[P2N2]}2 (7)
Ga(1)*ꢀGa(1)
P(1)ꢀGa(1)
P(2)ꢀGa(1)
N(1)ꢀGa(1)
N(2)ꢀGa(1)
2.5206(8)
In(1)*ꢀIn(1)
P(1)ꢀIn(1)
P(2)ꢀIn(1)
N(1)ꢀIn(1)
N(2)ꢀIn(1)
2.7618(12)
2.870(4)
2.879(4)
2.170(8)
2.160(8)
3.1459(11)
2.6591(11)
1.958(3)
2.2.1. Structure of {syn-Ga[P2N2]}2 (6) and
{syn-In[P2N2]}2 (7)
Fig. 2 presents the molecular structure and number-
1.968(3)
ing scheme of 6. The compound contains an unsup-

M.D. Fryzuk et al. / Journal of Organometallic Chemistry 591 (1999) 63–70
67
t
Table 4
,
NBu )In}2 (2.768(1) A) [9]. The dihedral angle between
the two InN2 planes in 7 is 24.65°, which is slightly less
than that observed in the gallium analogue 6.
Selected bond angles (°) for {synꢀGa[P2N2]}2 (6) (left)
and{synꢀIn[P2N2]}2 (7) (right)
{synꢀGa[P2N2]}2 (6)
{synꢀIn[P2N2]}2 (7)
P(1)ꢀIn(1)ꢀP(2)
2.2.2. Solution structure of {syn-Ga[P2N2]}2 (6) and
{syn-In[P2N2]}2 (7)
P(1)ꢀGa(1)ꢀP(2)
N(1)ꢀGa(1)ꢀN(2)
Ga(1)*ꢀGa(1)ꢀP(1)
Ga(1)*ꢀGa(1)ꢀP(2) 109.75(3)
Ga(1)*ꢀGa(1)ꢀN(1) 125.47(9)
Ga(1)*ꢀGa(1)ꢀN(2) 126.63(9)
155.22(3)
149.87(10)
107.32(9)
105.46(12) N(1)ꢀIn(1)ꢀN(2)
1
The observation of H- and 31P{1H}-NMR spectra
95.00(3)
In(1)*ꢀIn(1)ꢀP(1) 102.79(10)
In(1)*ꢀIn(1)ꢀP(2) 125.6(2)
In(1)*ꢀIn(1)ꢀN(1) 131.1(2)
In(1)*ꢀIn(1)ꢀN(2) 103.3(3)
for 6 and 7 indicate that these monomers couple via
metalꢀmetal bonds and are dimeric in solution. Differ-
ent phosphorus environments were not observed in the
31P{1H}-NMR spectrum of 6; cooling to −90°C re-
sulted in no evidence for decoalescence and some flux-
ional process. We conclude that the solid-state structure
for the gallium dimer is different than that observed in
solution, and that in solution, both 6 and 7 exhibit
structures similar to that observed in the solid state for
the indium dimer 7; in other words, the unsymmetrical
GaꢀP bond lengths are only found in the solid state.
Ga(1)ꢀP(1)ꢀC(13)
Ga(1)ꢀP(2)ꢀC(19)
156.51(13) In(1)ꢀP(1)ꢀC(13) 143.9(5)
144.86(13) In(1)ꢀP(2)ꢀC(19) 142.8(4)
and angles for 6 and 7 are presented in Tables 3 and 4,
respectively.
The molecular structure and numbering scheme of 7
are illustrated in Fig. 3. As for 6, {syn-In[P2N2]}2 (7) is
dimeric with a metalꢀmetal bond between two In(II)
nuclei. The indium centers in 7 exhibit distorted trigo-
nal bipyramidal geometries (Table 4). The
P(1)ꢀIn(1)ꢀP(2) and N(1)ꢀIn(1)ꢀN(2) bond angles
(149.87(10) and 103.3(3)° respectively) are smaller than
expected (180 and 120°) and indicate larger deviations
from ideal than in syn-AlCl[P2N2] (1) or syn-
GaCl[P2N2] (2) [17]. The indium centers are each
equally coordinated by two phosphine donors (2.870(4)
3. Experimental
3.1. General methods
Unless otherwise stated, all manipulations were per-
formed under an atmosphere of dry, oxygen-free dini-
trogen or argon by means of standard Schlenk or
glovebox techniques. The glovebox used was a Vacuum
Atmospheres HE-553-2 model equipped with a MO-40-
,
and 2.879(4) A) in contrast to the situation found for
the gallium analogue. A limited number of indium(II)
dimers have been structurally characterized; among
these are those supported by bulky alkyl [7] or aryl
groups [32], cyclic bis(amides) [9] or halogens [33]. The
1
2H purification system and a −40°C freezer. H- and
31P{1H}-NMR spectroscopy were performed on an
AMX 500 instrument operating at 500.1 and 121.4
1
MHz, respectively. H-NMR spectra were referenced to
,
metalꢀmetal bond in 7 (2.7618(12) A) is similar to that
in the cyclic bis(amido) species {(ButNMe2SiSiMe2-
internal C6D5H (7.15 ppm) or C6D5CD2H (2.09 ppm).
31P{1H}-NMR spectra were referenced to external
P(OMe)3 (141.0 ppm with respect to 85% H3PO4 at 0.0
ppm). Mass spectral studies were carried out on a
Kratos MS 50 using an EI source. Infrared spec-
troscopy was performed on a BOMEM MB-100 spec-
trometer. Microanalyses (C, H, N) were performed by
Mr P. Borda of this department.
syn-Li2(dioxane)[P2N2] [34], syn-AlCl[P2N2] [17], and
syn-GaCl[P2N2] [17] were prepared by published proce-
dures. InCl3 was purchased from Alfa Chemicals and
sublimed prior to use. LiAlH4 was purchased from
Aldrich and used as received. LiGaH4 was prepared by
a literature method [35]. KC8 was prepared by the
addition of potassium metal to solid graphite at 160°C
under a purge of argon.
Toluene was refluxed over CaH2 prior to a final
distillation from sodium benzophenone ketyl under an
argon atmosphere. Diethyl ether was refluxed over
sodium benzophenone ketyl under an argon atmo-
sphere. Deuterated solvents were dried by distillation
from sodium benzophenone ketyl; oxygen was removed
by three freeze–pump–thaw cycles.
Fig. 3. Molecular structure of {syn-In[P2N2]}2 (7); 33% probability
thermal ellipsoids are shown. Hydrogen atoms and phenyl rings are
omitted for clarity.

68
M.D. Fryzuk et al. / Journal of Organometallic Chemistry 591 (1999) 63–70
3.2. Synthesis of syn-InCl[P2N2] (3)
1129sh (AlꢀD). m/z 559 [M+ꢀH]. Mol. wt. (Signer,
isopiestic method, toluene) 520950; calc. 560.88.
To a slurry of InCl3 (180 mg; 0.79 mmol) in toluene
(10 ml) was added a toluene solution (10 ml) of syn-
Li2(dioxane)[P2N2], (500 mg; 0.79 mmol). The reaction
mixture was stirred for 12 h. The reaction mixture was
then passed through a frit lined with Celite to remove
LiCl. The solvent was removed in vacuo to yield 3
(430 mg; 80% yield) as a waxy white solid. Anal. Calc.
for C24H42InClN2P2Si4: C, 42.19; H, 6.20; N, 4.10.
3.4. Synthesis of syn-GaH[P2N2] (5)
Method 1: To a freshly prepared solution of
LiGaH4 maintained at −78°C (21 mg; 0.25 mmol) in
ether (10 ml) was added an ethereal solution (10 ml)
of syn-GaCl[P2N2] (2) (150 mg; 0.24 mmol). The reac-
tion mixture was left to warm with stirring, during
which time some metal deposition was evident. The
reaction mixture was then passed through a frit lined
with Celite to remove LiCl and Ga(0). The solvent
was removed in vacuo and the residue extracted into
toluene. Evaporation of the solvent afforded a white
powder (34 mg; 24% yield).
1
Found: C, 42.55; H, 6.20; N, 3.99. H-NMR (C6D6): l
7.95 (t, 4H, o-Ph, 3JHꢀH=8.5 Hz, 3JHꢀP=8.5 Hz),
7.07 (m, 6H, m, p-Ph), 0.90 (ABX m, 8H, ring CH2,
2JHꢀH=15.5 Hz, 2JHꢀP=14.0 Hz), 0.28 and 0.20 (s,
12H, SiMe2). 31P{1H}-NMR (C6D6): l −40.5 (s, 400
Hz peak width at half height). m/z 684 [M+].
Method 2: To a freshly prepared solution of
LiGaH4 maintained at −78°C (21 mg; 0.26 mmol) in
ether (10 ml) was added an ethereal solution (10 ml)
of syn-InCl[P2N2] (3) (160 mg; 0.23 mmol). Upon
warming, the mixture became black and deposited gal-
lium and indium metal. The reaction mixture was then
passed through a frit lined with Celite to remove LiCl,
Ga(0) and In(0). The solvent was removed in vacuo
and the residue extracted into toluene. Evaporation of
the solvent gave a white powder (15 mg; 11% yield).
The unstable nature of 5 did not allow for a suitable
IR, elemental analysis or mass spectrum to be ob-
tained. Prolonged standing (ꢀdays) of solutions of 5
resulted in the slow decomposition to syn-H2[P2N2]
and gallium metal. 1H-NMR (C6D6): l 7.47 (t, 4H,
o-Ph, 3JHꢀH=6.6 Hz, 3JHꢀP=6.6 Hz), 7.11 (m, 6H,
m, p-Ph), 5.25 (br s, 1H, GaH), 1.75 and 0.93 (ABX
m, 8H, ring CH2, 2JHꢀH=13.2 Hz, 2JHꢀP=7.6 Hz),
0.48 and 0.25 (s, 12H, SiMe2). 31P{1H}-NMR (C6D6):
l −34.7 (s).
3.3. Synthesis of syn-AlH[P2N2] (4)
Method 1: To a −78°C solution of LiAlH4 (12 mg;
0.32 mmol) in ether (10 ml) was added an ethereal
solution (10 ml) of syn-AlCl[P2N2] (1) (160 mg; 0.26
mmol). The reaction vessel was left to warm with
stirring. The reaction mixture was then passed through
a frit lined with Celite to remove LiCl. The solvent
was removed in vacuo and the residue extracted into a
minimum amount of toluene (approximately 3 ml).
Slow evaporation of the solvent gave large colorless
plates of 4 (54 mg; 37% yield).
Method 2: To a −78°C solution of LiAlH4 (12 mg;
0.32 mmol) in ether (10 ml) was added an ethereal
solution (10 ml) of syn-GaCl[P2N2] (2) (170 mg; 0.27
mmol). The reaction mixture was left to warm with
stirring. The reaction mixture was then passed through
a frit lined with Celite to remove LiCl. The solvent
was removed in vacuo and the residue extracted into
toluene. Evaporation of the solvent afforded 4 as a
white powder (45 mg; 30% yield).
Method 3: To
a
−78°C solution of LiAlH4
3.5. Synthesis of {syn-Ga[P2N2]}2 (6)
(12 mg; 0.32 mmol) in ether (10 ml) was added an
ethereal solution (10 ml) of syn-InCl[P2N2] (3) (200
mg; 0.30 mmol). Upon warming, the mixture became
black and deposited indium metal. The reaction mix-
ture was then passed through a frit lined with Celite to
remove LiCl and In(0). The solvent was removed
in vacuo and the residue extracted into toluene. Evap-
oration of the solvent yielded 4 (26 mg; 16% yield)
as a white powder. Anal. Calc. for C24H43AlN2P2Si4:
C, 51.39; H, 7.65; N, 4.86. Found: C, 51.26; H, 7.65;
N, 4.86. 1H-NMR (C6D6): l 7.77 (t, 4H, o-Ph,
3JHꢀH=6.9 Hz, 3JHꢀP=6.9 Hz), 7.08 (m, 6H, m, p-
Ph), 1.01 (ABX m, 8H, ring CH2, 2JHꢀH=13.8 Hz,
2JHꢀP=6.9 Hz), 0.34 and 0.21 (s, 12H, SiMe2).
31P{1H}-NMR (C6D6): l −46.5 (s, 340 Hz peak
width at half height). IR (KBr, cm−1): 1594m (AlꢀH),
To a slurry of KC8 (25 mg; 0.19 mmol) in ether (10
ml) was added an ethereal solution (10 ml) of syn-
GaCl[P2N2] (2) (100 mg; 0.17 mmol). The reaction
mixture was stirred for 24 h. The reaction mixture was
then passed through a frit lined with Celite to remove
KCl and C(gr). The solvent was removed in vacuo to
yield a white solid. The residue was taken up in a
minimum amount of toluene (approximately 2 ml).
Slow evaporation of the solvent afforded 6 (33 mg; 33%
yield) as small colorless needles. Anal. Calc. for
C48H84Ga2N4P4Si8: C, 47.84; H, 7.02; N, 4.65. Found:
1
C, 47.54; H, 6.94; N, 4.49. H-NMR (C6D6): l 7.48 (br
t, 4H, o-Ph), 7.20 and 7.08 (m, 6H, m, p-Ph), 0.93
2
2
(ABX m, 8H, ring CH2, JHꢀH=12.9 Hz, JHꢀP=5.9
Hz), 0.52 and 0.33 (s, 12H, SiMe2). 31P{1H}-NMR

M.D. Fryzuk et al. / Journal of Organometallic Chemistry 591 (1999) 63–70
69
(C6D6): l −25.5 (10 Hz peak width at half height). m/z
4. Supplementary material
603 [M+(monomer)].
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC, no. 128893 for compound 4, no.
129641 for compound 6 and no. 129642 for compound
7. Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ [fax: +44-1223-336033 or e-
mail: deposit@ccdc.cam.ac.uk or http://www.ccdc.
cam.ac.uk].
3.6. Synthesis of {syn-In[P2N2]}2 (7)
To a slurry of KC8 (22 mg; 0.16 mmol) in ether (10
ml) was added an ethereal solution (10 ml) of syn-
InCl[P2N2] (3) (98 mg; 0.14 mmol). The reaction mix-
ture was stirred for 24 h. The reaction mixture was then
passed through a frit lined with Celite to remove KCl
and C(gr). The solvent was removed in vacuo to yield a
white solid. The residue was taken up in a minimum
amount of toluene (approximately 2 ml). Slow evapora-
tion of the solvent afforded large colorless needles of 7
(54 mg; 58% yield). Anal. Calc. for C48H84In2N4P4Si8 C,
44.50; H, 6.54; N, 4.32. Found: C, 44.14; H, 6.23; N,
Acknowledgements
Financial support was generously provided by the
NSERC of Canada in the form of grants to M.D.
1
4.19. H-NMR (C6D6): l 7.48 (br t, 4H, o-Ph), 7.02 (br
Fryzuk and
Giesbrecht.
a postgraduate scholarship to G.R.
m, 6H, m, p-Ph), 1.13 (br ABX m, 8H, ring CH2), 0.42
and 0.39 (s, 12H, SiMe2). 31P{1H}-NMR (C6D6): l
−37.4 (24 Hz peak width at half height). m/z 647 [M+
(monomer)].
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