Complexes of germanium(iv) fluoride with phosphane ligands: Structural and spectroscopic authentication of germanium(iv) phosphane complexes

Article abstract of DOI:10.1039/b716765b

The first phosphane complexes of germanium(iv) fluoride, trans-[GeF ₄(PR₃)₂] (R = Me or Ph) and cis-[GeF ₄(diphosphane)] (diphosphane = R₂P(CH₂) ₂PR₂, R = Me, Et, Ph or Cy; o-C₆H ₄(PR₂)₂, R = Me or Ph) have been prepared from [GeF₄(MeCN)₂] and the ligands in dry CH₂Cl ₂ and characterised by microanalysis, IR, Raman, ¹H, ¹⁹F{¹H} and ³¹P{¹H} NMR spectroscopy. The crystal structures of [GeF₄(diphosphane)] (diphosphane = Ph₂P(CH₂)₂PPh₂ and o-C₆H₄(PMe₂)₂) have been determined and show the expected cis octahedral geometries. In anhydrous CH ₂Cl₂ solution the complexes are slowly converted into the corresponding phosphane oxide adducts by dry O₂. The apparently contradictory literature on the reaction of GeCl₄ with phosphanes is clarified. The complexes trans-[GeCl₄(AsR₃)₂] (R = Me or Et) are obtained from GeCl₄ and AsR₃ either without solvent or in CH₂Cl₂, and the structures of trans-[GeCl₄(AsEt₃)₂] and Et ₃AsCl₂ determined. Unexpectedly, the complexes of GeF ₄ with arsane ligands are very unstable and have not been isolated in a pure state. The behaviour of the germanium(iv) halides towards phosphane and arsane ligands are compared with the corresponding silicon(iv) and tin(iv) systems. The Royal Society of Chemistry.

Full text of DOI:10.1039/b716765b

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/dalton | Dalton Transactions
Complexes of germanium(IV) fluoride with phosphane ligands: structural and
spectroscopic authentication of germanium(IV) phosphane complexes†
Martin F. Davis, William Levason,* Gillian Reid and Michael Webster
Received 31st October 2007, Accepted 11th February 2008
First published as an Advance Article on the web 19th March 2008
DOI: 10.1039/b716765b
The first phosphane complexes of germanium(IV) fluoride, trans-[GeF4(PR3)2] (R = Me or Ph) and
cis-[GeF4(diphosphane)] (diphosphane = R2P(CH2)2PR2, R = Me, Et, Ph or Cy; o-C6H4(PR2)2, R =
Me or Ph) have been prepared from [GeF4(MeCN)2] and the ligands in dry CH2Cl2 and characterised
1
1
by microanalysis, IR, Raman, 1H, 19F{ H} and 31P{ H} NMR spectroscopy. The crystal structures of
[GeF4(diphosphane)] (diphosphane = Ph2P(CH2)2PPh2 and o-C6H4(PMe2)2) have been determined and
show the expected cis octahedral geometries. In anhydrous CH2Cl2 solution the complexes are slowly
converted into the corresponding phosphane oxide adducts by dry O2. The apparently contradictory
literature on the reaction of GeCl4 with phosphanes is clarified. The complexes trans-[GeCl4(AsR3)2]
(R = Me or Et) are obtained from GeCl4 and AsR3 either without solvent or in CH2Cl2, and the
structures of trans-[GeCl4(AsEt3)2] and Et3AsCl2 determined. Unexpectedly, the complexes of GeF4
with arsane ligands are very unstable and have not been isolated in a pure state. The behaviour of the
germanium(IV) halides towards phosphane and arsane ligands are compared with the corresponding
silicon(IV) and tin(IV) systems.
[PnBu3Cl][GeCl3]. Similar redox reactions occur with primary
Introduction
and secondary phosphanes, although the initial products often
undergo further reaction with elimination of HX to form species
such as R2PGeX3 or RHPGeX3.10 However Godfrey et al.9 were
able to prepare and structurally characterise the first GeIV arsane,
trans-[GeCl4(AsMe3)2]. The redox chemistry in the GeX4–PR3
reactions (at least under some conditions) contrasts with that of
the SnX4 systems where simple adduct formation occurs with the
majority of phosphanes and diphosphanes.4–7 It should be noted
however that PtBu3 and SnX4 produce [PtBu3X][SnX3].8 Here we
report the synthesis, structural and spectroscopic characterisation
of a series of phosphane complexes of GeF4, further studies into
the GeCl4 and GeBr4 reactions, and also studies of complexes of
GeX4 with arsane ligands.
In marked contrast to the very extensive chemistry with d-block
metals, complexes of the p-block metals and metalloids with soft
neutral ligands such as phosphanes or arsanes have been relatively
little investigated. Whilst a variety of phosphane complexes are
known for the heavier halides of GaIII, InIII, BiIII and SnIV, little
is known about other Lewis acids in this block.1–4 Complexes of
the p-block fluorides with phosphanes are extremely rare, and
apart from some very early work on SiF4,1 the only examples
are from our recent study of SnF4 adducts,5 which provided
detailed spectroscopic and structural data on a range of complexes
including [SnF4(diphosphane)] (diphosphane = o-C6H4(PR2)2,
R = Me or Ph; R2P(CH2)2PR2, R = Me, Et, Cy or Ph) and trans-
[SnF4(PR3)2] (R = Me or Cy).5 There are no reports of tertiary
phosphane complexes of GeF4, and with GeCl4 the reports are
few and apparently contradictory. Beattie6 and Ozin7 and their
coworkers reported the formation of trans-[GeCl4(PMe3)2] and
[GeX4(PMe3)] (X = Cl or Br) respectively, by reaction of GeX4
and PMe3 in the absence of a solvent, and used detailed IR and
Raman studies to identify the products. In contrast, the reactions
Results and discussion
Germanium(IV) phosphanes
Our previous studies have shown that towards hard N- or O-
donor ligands GeF4 is a much stronger Lewis acid than GeCl4
or GeBr4.11 The reaction of [GeF4(MeCN)2]11 with two mol.
equivalents of PMe3 in anhydrous CH2Cl2 gave [GeF4(PMe3)2]
(Scheme 1) as a white, moisture sensitive powder, only slightly
soluble in chlorocarbons. The 1H NMR spectrum in CD2Cl2
solution contained a single doublet at d = 1.46 (2JPH = 12 Hz),
t
i
of PR3 (R = Bu or Pr) with GeX4 in benzene gave the redox
products [PR3X][GeIIX3].8 In a recent study by Godfrey et al.,9 the
reaction of GeCl4 with a wide range of tertiary phosphanes (PR3,
R = Me, Et, nPr, nBu, Cy etc.) in diethyl ether solution was found
to give exclusively [PR3Cl][GeIICl3], identified by microanalysis,
the 19F{ H} NMR spectrum is a 1 : 2 : 1 triplet at 295 K, and was
1
1
31P{ H} NMR spectroscopy and by the crystal structure of
unchanged on cooling, showing only the trans isomer was present
1
in detectable amounts. As expected, the 31P{ H} NMR spectrum
School of Chemistry, University of Southampton, Southampton, UK SO17
1BJ. E-mail: wxl@soton.ac.uk
† Electronic supplementary information (ESI) available: Structures
(Fig. S1 and S2), and bond lengths and angles (Table S1 and S2)
of [Me2P(H)(CH2)2P(H)Me2][GeCl3]2 and [Me2P(O)(CH2)2P(O)Me2H]-
[GeCl3]. CCDC reference numbers 665905–665910. For ESI and crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/b716765b
is a quintet at d = −12.4 (2JPF = 196 Hz). The corresponding
reaction using PPh3 gave white trans-[GeF4(PPh3)2] (Table 1) which
was easily soluble in chlorocarbons, but extensively dissociated at
1
1
room temperature in solution. The 19F{ H} and 31P{ H} NMR
data were recorded at 210 K and show the expected multiplets, but
This journal is
The Royal Society of Chemistry 2008
Dalton Trans., 2008, 2261–2269 | 2261
©

View Article Online
Scheme 1
on warming to >240 K the resonances are lost. In view of the easy
chlorination of phosphanes by GeCl4 (vide infra), the reaction
of [GeF4(MeCN)2] with excess molten PPh3 was also carried
out, which constitutes more forcing conditions, but examination
of the products by 31P{ H} and 19F{ H} NMR spectroscopy
revealed only trans-[GeF4(PPh3)2], traces of [GeF4(OPPh3)2]11 and
excess PPh3, and there is no evidence for fluorination of the
ligand (to Ph3PF2). Attempts to isolate trans-[GeF4(PCy3)2] were
unsuccessful, the products obtained were extremely moisture
sensitive and NMR studies suggested a mixture of species was
present.
stretches: 2a1 + b1 + b2) which may be compared with the t1u
mode in [GeF6]2− at 600 cm−1.12 [GeF4{Me2P(CH2)2PMe2}] is
only slightly soluble in CH2Cl2 but the other complexes dissolve
easily in chlorocarbons. The 1H NMR spectra in CD2Cl2 or
CDCl3 solution at 295 K are simple, showing only coordinated
diphosphane ligands present. At ambient temperatures both the
19F{ H} and 31P{ H} NMR spectra are broad lines with ill-defined
or unresolved couplings, indicative of reversible dissociation or
chelate ring-opening on the appropriate NMR time-scales. On
moderate cooling of the solutions (273–243 K depending on the
ligand present), the resonances sharpen and show the coupling
patterns expected for cis-octahedral complexes (Table 1).5 The
1
1
1
1
The reactions of [GeF4(MeCN)2] with the diphosphanes
R2P(CH2)2PR2 (R = Me, Et, Ph or Cy) and o-C6H4(PR2)2
(R = Me or Ph) in anhydrous CH2Cl2 were undertaken with
the aim of obtaining cis isomers and in the expectation that
chelation would produce more stable complexes. These readily
gave cis-[GeF4(diphosphane)] as white powders, which can be
handled briefly in air with no detectable decomposition. Like the
tin analogues, the solids tenaciously retain chlorinated solvents
1
1
31P{ H} spectra are 12 line patterns (d,d,t) and the 19F{ H} spectra
show two resonances; a t,t for the two axial fluorines and a d,d,t for
the fluorines trans to phosphorus. The chemical shifts and coupling
constants are shown in Table 1. Notably the spectra show no other
species present in significant amounts and are unchanged after the
solutions have been allowed to stand for several hours. The 31P{ H}
1
chemical shifts are very similar to those observed in the analogous
[SnF4(diphosphane)] complexes,5 and as in those cases the co-
ordination shifts D (D = dcomplex − dligand) are irregular, although
generally the stronger r-donor ligands produce high frequency
1
(evident in the H NMR spectra). The complexes exhibit several
strong, overlapping m(GeF) vibrations in their IR spectra in the
range 620–560 cm−1 (theory for a cis-MF4P2 is four IR active
Table 1 Selected NMR data for GeF4 complexesa
1
b
1
Compound
d 31P{ H}
Dc
23
d 19F{ H}
2J(31P–19F)/Hz
2J(19F–19F)/Hz
[GeF4{o-C6H4(PMe2)2}]
[GeF4{o-C6H4(PPh2)2}]
[GeF4{Et2P(CH2)2PEt2}]
[GeF4{Me2P(CH2)2PMe2}]
[GeF4{Ph2P(CH2)2PPh2}]
[GeF4{Cy2P(CH2)2PCy2}]
trans-[GeF4(PMe3)2]
−31.8(t, d, d)
−17.1(t, d, d)
−9.2(t, d, d)
−24.6(t, d, d)
−17.1(t, d, d)
−8.7(t, d, d)
−12.4(q)
−97.2(t,t), −126.0(d,d,t)
−81.9(t,t), −121.9(d,d,t)
−91.9(t,t), −113.6(d,d,t)
−96.2(t,t), −121.2(d,d,t)
−73.7(t,t), −110.3(d,d,t)
−81.2(t,t), −103.1(d,d,t)
−96.9(t)
77, 135, 155
64, 110, 129
66, 131, 136
80, 135, 149
64, 119, 151
60, 121, 122
196
54
65
55
55
61
57
−4
9
23
−4
−11
50
trans-[GeF4(PPh3)2]d
2.8(q)
8
−70.6(t)
180
a In CH2Cl2–10% CDCl3. Spectra were typically recorded at 240 K to resolve couplings (see text). b Ligand chemical shifts are: o-C6H4(PMe2)2 −55;
o-C6H4(PPh2)2 −13; Ph2P(CH2)2PPh2 −13; Et2P(CH2)2PEt2 −18; Me2P(CH2)2PMe2 −48; Cy2P(CH2)2PCy2 +2; PMe3 −62; PPh3 −6 ppm. c Coordination
shift (D = dcomplex − dligand). d At 190 K. Resonances disappear >240 K.
2262 | Dalton Trans., 2008, 2261–2269
This journal is
The Royal Society of Chemistry 2008
©

View Article Online
Table 3 Selected bond lengths (A) and angles (◦) for [GeF4-
{Ph2P(CH2)2PPh2}]
˚
coordination shifts and the weaker donor aryl-diphosphanes
low frequency shifts. Only [GeF4{Cy2P(CH2)2PCy2}] does not
conform to this pattern, exhibiting a coordination shift of −11,
despite being a strong r-donor. It is likely that steric factors from
this bulky ligand on the small germanium centre are a major
contributor here. These erratic coordination shifts are seen in phos-
phane complexes of SnIV 4 and GaIII,13 but the cause is presently
Ge1–F1
Ge1–F2
Ge1–P1
1.7987(14)
1.7829(13)
2.4636(7)
Ge1–F3
Ge1–F4
Ge1–P2
1.7731(14)
1.7692(14)
2.4822(7)
F4–Ge1–F3
F3–Ge1–F2
F4–Ge1–F1
F4–Ge1–P2
F2–Ge1–P2
F3–Ge1–P1
93.21(7)
93.44(7)
92.71(7)
90.18(5)
88.08(5)
92.44(5)
F4–Ge1–F2
F3–Ge1–F1
F2–Ge1–P1
F1–Ge1–P1
F1–Ge1–P2
P1–Ge1–P2
93.44(6)
93.02(7)
89.28(4)
83.94(5)
85.08(5)
84.08(2)
1
unclear. The 19F{ H} chemical shifts are higher frequency than
those observed in the [SnF4(diphosphane)] analogues5 and the
2
2JFF and JPF couplings are larger in the germanium systems.
2
Similar JFF values (50–60 Hz) are found in cis-[GeF4(OPR3)2]11
and in [GeF4(L–L)] (L–L = 2,2ꢀ-bipyridyl, 1,10-phenanthroline,
Me2N(CH2)2NMe2),14 although rather larger values (70–80 Hz)
are seen in [GeF4{RS(CH2)2SR}].15
Confirmation of the [GeF4(diphosphane)] constitution was
provided by X-ray crystal structures of two examples, with the
diphosphanes o-C6H4(PMe2)2 and Ph2P(CH2)2PPh2. The structure
of the former is shown in Fig. 1, and Table 2 contains selected
bond lengths and angles. The germanium environment is approx-
imately octahedral with the angles F–Ge–F slightly greater than
90◦, F–Ge–P slightly less than 90◦, and P–Ge–P 85.61(4)◦. As
observed in GeF4 complexes with N- or O-donor ligands,11,14 Ge–
˚
FtransF (1.809(2), 1.815(2) A) are longer than Ge–FtransP (1.765(2),
˚
1.772(2) A). Similar patterns of bond lengths and angles are found
in the structure of [GeF4{Ph2P(CH2)2PPh2}] (Fig. 2, Table 3)
although the Ge–P bonds are slightly longer in the complex of
the aryl-diphosphane, possibly due to its weaker r-donation.
Fig. 2 Structure of [GeF4{Ph2P(CH2)2PPh2}] with the atom numbering
scheme adopted. H atoms are omitted for clarity and displacement
ellipsoids are shown at the 50% probability level. Only the ipso C atom
labels are shown and C atoms are numbered sequentially round the ring
starting at the label shown.
Studies of the SnX4–PR3 systems5 showed that in the pres-
ence of air, the corresponding phosphane oxide complexes,
[SnX4(OPR3)2],16 form, and we have shown17 using 18O2, that the
source of the oxygen is dioxygen rather than water. Using SnI4
the reaction provides a convenient catalytic route to phosphane
oxides.17 A solution of [GeF4(PPh3)2] in CH2Cl2 exposed to dry
air, deposited crystals identified by an X-ray structure to be trans-
[GeF4(OPPh3)2],11 and since PPh3 is air stable in solution, this
demonstrates that the reaction was promoted by the germanium
complex. In view of the generation of [PR3X][GeX3] in the
cases of X = Cl or Br, which could hydrolyse to OPR3, it
was important to establish the source of the oxygen atoms
incorporated. Exposure of a solution of [GeF4{Ph2P(CH2)2PPh2}]
in CH2Cl2 to dry 18O2 resulted in the slow formation of the
Fig. 1 Structure of [GeF4{o-C6H4(PMe2)2}] with the atom numbering
scheme adopted. H atoms are omitted for clarity and displacement
ellipsoids are shown at the 50% probability level.
1
diphosphane dioxide complex (monitored in situ by 31P{ H}
Table 2 Selected bond lengths (A) and angles (◦) for [GeF4{o-
˚
NMR spectroscopy). After the reaction appeared complete the
complex was decomposed by treatment with aqueous NaOH, and
separation of the organic layer, drying and evaporation produced a
white solid. The EI mass spectrum of this solid showed a base peak
at m/z = 433 corresponding to [Ph2P(18O)(CH2)2P(18O)PPh2 −
H]+, and the IR spectrum showed m(PO) at 1153 cm−1. The
Ph2P(16O)(CH2)2P(16O)PPh2 exhibits m(PO) at 1177 cm−1, and
the simple diatomic oscillator model predicts the effect of 18O
substitution will lower this vibration to 1133 cm−1. Coupling
with the m(PC) mode at ∼1120 cm−1 probably causes the higher
frequency observed experimentally.17 Thus, like SnX4,5,17 GeF4
C6H4(PMe2)2}]
Ge1–F1
Ge1–F2
Ge1–P1
1.815(2)
1.765(2)
2.4273(12)
Ge1–F3
Ge1–F4
Ge1–P2
1.772(2)
1.809(2)
2.4273(11)
F2–Ge1–F3
F3–Ge1–F4
F3–Ge1–F1
F4–Ge1–P1
F3–Ge1–P2
F1–Ge1–P2
93.91(10)
93.18(12)
91.56(12)
87.65(9)
90.70(9)
87.59(8)
F2–Ge1–F4
F2–Ge1–F1
F2–Ge1–P1
F1–Ge1–P1
F4–Ge1–P2
P1–Ge1–P2
92.49(12)
92.76(12)
89.80(8)
87.26(8)
86.77(9)
85.61(4)
This journal is
The Royal Society of Chemistry 2008
Dalton Trans., 2008, 2261–2269 | 2263
©

View Article Online
promotes air/dioxygen oxidation of phosphanes, although the
reaction is considerably slower with germanium.
feature, but new medium intensity bands at 314 and 260 cm−1
which correspond to [GeCl3]− ([NBu4][GeCl3] has features at
320, 255 cm−1). The reactions can also be monitored by NMR
spectroscopy. The initial solid, dissolved in CH2Cl2 at 273 K
GeX4–PMe3 (X = Cl or Br) systems
1
and immediately cooled to 200 K, does not show a 31P{ H}
Following the successful characterisation of the phosphane
adducts of GeF4, we re-examined the GeCl4–PMe3 reaction in
an attempt to elucidate the apparently contradictory literature,6–9
and found that the reports from Beattie6 and Godfrey9 and
coworkers are both valid, and that the species formed are extremely
dependent upon the conditions. We distilled GeCl4 onto neat
PMe3 at 77 K and allowed the mixture to thaw slowly. On
melting, a vigorous reaction occurred which was moderated by
judicious cooling, resulting in formation of a white powder.
The Raman spectrum of this product (Fig. 3, top) was in
excellent agreement with that reported by Beattie with a very
strong feature at 267 cm−1 assigned as the a1g vibration of trans-
[GeCl4(PMe3)2] (lit.,6 268 cm−1)—compare also the values of the
corresponding vibration in the crystallographically characterised
trans-[GeCl4(AsR3)2] (vide infra). The sample was then dissolved
in rigorously dried CH2Cl2 and the mixture immediately pumped
to dryness. The Raman spectrum of this sample showed the
features of the initial spectrum and some new bands in the region
>350 cm−1. The sample was redissolved in CH2Cl2, allowed to
stand for 3 h and then taken to dryness. The Raman spectrum
of this sample (Fig. 3, bottom) showed loss of the 267 cm−1
NMR resonance from the initial complex, but on standing a
new feature at d = +92 attributable‡ to [PMe3Cl]+ appeared.
The absence of a phosphorus resonance for the GeIV complex
is consistent with extensive dissociation/fast exchange even at
low temperatures. This explanation is supported by the 1H NMR
spectrum of trans-[GeCl4(PMe3)2] obtained immediately after
dissolution in CDCl3, which shows a doublet at d = 2.75, 2JPH
=
13.5 Hz (assigned to [PMe3Cl]+) and a doublet at d = 1.8, 2JPH
=
13 Hz for the GeIVcomplex. Trace hydrolysis of the solution
also produces [PMe3H][GeCl3], d(31P) = −4.9, and from such a
hydrolysed sample we obtained crystals identified by their unit cell
as [PMe3H][GeCl3].19 Hence, as described by Beattie and Ozin,6
the reaction of GeCl4 with PMe3 in the absence of a solvent
does indeed give trans-[GeCl4(PMe3)2], but this rapidly rearranges
in solution in chlorocarbons or ethers to [PMe3Cl][GeCl3], and
the latter is obtained when the reaction is performed in solution
(Scheme 1).8,9 The recrystallisation of [GeCl4(PMe3)2] from hot
GeCl4 was reported to give [GeCl4(PMe3)], believed to be an
axially-substituted trigonal bipyramid molecule,7 however the re-
ported Raman spectrum is very similar to that of [PMe3Cl][GeCl3]
and we suggest the latter is the correct formulation. We also reacted
GeBr4 and PMe3 in the absence of solvent and obtained a cream
powder with a Raman spectrum identical to that reported7 for
[GeBr4(PMe3)]. In this case also, the strongest features in the low
energy region correspond to [GeBr3]−, and on dissolution in dry
1
CH2Cl2 the 31P{ H} NMR resonance is found at d = +68, probably
corresponding to [PMe3Br]+.
We have not examined other tertiary phosphanes, but is seems
likely that similar reactions would occur with initial formation
of a tetrachlorogermanium(IV) adduct which then (especially in
solution) undergoes a redox reaction to form [PR3Cl][GeCl3]—in
some cases the rearrangement may be so rapid that the Ge(IV)
species is only a transient intermediate. The GeBr4–PMe3 reaction
appears to give [PMe3Br][GeBr3] without any evidence that a
Ge(IV) complex is isolable. In contrast, the silicon(IV) and tin(IV)
complexes are stable (although very moisture sensitive) and trans-
[SiCl4(PMe3)2]20 and several SnX4–phosphane complexes4,5 have
been authenticated by X-ray crystal structures.
In the hope of obtaining more stable Ge(IV) complexes, we
examined the reaction of the bidentate Me2P(CH2)2PMe2 with
GeCl4 under a variety of reaction conditions (mixed in the
absence of solvent, in solution in CH2Cl2 or Et2O, at room or
1
low temperatures) and monitored reactions by in situ 31P{ H}
NMR spectroscopy. The reactions are very sensitive to the
conditions, and resonances due to mono- and di-chlorinated and
-protonated phosphane groups could be identified, the relative
amounts varying with conditions and reaction times, and with
trace hydrolysis in some samples. We were unable to unequivocally
1
identify resonances in the 1H or 31P{ H} NMR spectra due
Fig.
3
Raman spectrum of [GeCl4(PMe3)2] (above) and of
‡ The observed 31P chemical shift of “[PMe3Cl]+” seems to vary with
solvent, concentration and anion, probably due to subtle speciation
involving [PMe3Cl]+, Me3PCl2 and Me3PCl · · · Cl forms (see reference 18
and references therein).
[PMe3Cl][GeCl3] (below). From comparison of the intensities in the ligand
modes (not shown) the features in the upper spectrum are ∼10 times more
intense than those in the lower.
2264 | Dalton Trans., 2008, 2261–2269
This journal is
The Royal Society of Chemistry 2008
©

View Article Online
Table 4 Selected bond lengths (A) and angles (◦) for trans-
˚
to [GeCl4{Me2P(CH2)2PMe2}], although this may be due to
fast dissociative ligand exchange even at low temperature. The
only species identified crystallographically were [GeCl3]− salts
with [Me2PH(CH2)2PHMe2]2+ or [Me2P(O)(CH2)2P(O)Me2H]+
deposited over several days or weeks (see ESI†). We conclude that
the reactions of the diphosphane with GeCl4 are similar to those
with PMe3, with the trichlorogermanate(II) as the final product.
The reason for the easier reduction of GeX4 (X = Cl or Br)
by phosphanes compared with SnX4 or SiX4 (or the relative
instability of the [GeX4(PR3)2]), may be an example in germanium
chemistry of the lower stability of the element of period 4 in the
group oxidation state compared with analogues in periods 3 or
5. This effect is well known for AsV, SeVI and BrVII and is usually
rationalised as the result of increased nuclear charge from the 3d
transition metals not completely balanced by screening from the
3d electrons.21
[GeCl4(AsEt3)2]
Ge1–Cl1
Ge1–As1
2.3296(19)
2.4904(9)
Ge1–Cl2
As1–C
2.3233(19)
1.930(8)–1.944(8)
Cl2–Ge1–Cl1
Cl2–Ge1–As1
Cl1–Ge1–As1
90.67(7)
87.03(5)
88.29(5)
Ge1–As1–C
C–As1–C
110.9(2)–116.0(2)
105.1(4)–106.4(4)
Germanium(IV) arsanes
The reactions of [GeF4(MeCN)2] with o-C6H4(AsMe2)2 or AsMe3
in CH2Cl2 afford unstable, very moisture sensitive white solids,
with IR and Raman spectra which show the presence of the
appropriate ligand and Ge–F bonds and no MeCN. The 1H
NMR spectra in CD2Cl2 show the arsane resonances shifted to
high frequency from those of the “free” ligands. None of the
Fig. 4 Structure of the centrosymmetric trans-[GeCl4(AsEt3)2] with the
atom numbering scheme adopted. H atoms are omitted for clarity and
displacement ellipsoids are shown at the 50% probability level. Symmetry
operation: a = −x, −y, −z.
1
samples showed 19F{ H} NMR resonances at room temperature,
but on cooling to < 220 K two triplets of equal intensity appear
in regions typical of “cis”-GeF4 units. However, microanalytical
data obtained from different samples were always significantly
low in C and H compared with expectation for [GeF4{o-
C6H4(AsMe2)2}], and the microanalytical data on the GeF4–
AsR3 systems reproducibly approximate to 1 : 1 compounds. In
the latter case, the spectroscopic data (see Experimental section)
would be consistent with either a cis disubstituted octahedron
or an equatorially substituted trigonal bipyramid. We have been
unable to obtain crystals of these complexes for X-ray studies
and their precise nature remains unclear. There appeared to
be no complex formation between GeF4 and the weaker r-
donor Ph2As(CH2)2AsPh2. Thus, although GeF4 appears to form
adducts with some arsane ligands, these appear to be extensively
dissociated in solution and far less stable than the phosphane
analogues—a pattern also observed in the SnF4 systems.5 Isolation
of pure complexes in the tin systems is complicated by the “SnF4”
formed on dissociation, precipitating as polymeric [SnF4]n, but in
the germanium systems dissociation simply forms GeF4 monomer,
and the instability is therefore a direct result of the low affinity of
the hard germanium Lewis acid for the soft arsenic centre.
Fig. 5 Structure of Et3AsCl2 with the atom numbering scheme adopted.
H atoms are omitted for clarity and displacement ellipsoids are shown at
the 50% probability level. There are two molecules in the asymmetric unit.
The second has the same symmetry and similar bond lengths and angles
(see Table 5). Symmetry operations: a = 1 − y, x − y, z; b = 1 − x + y,
1 − x, z; c = x, y, −z.
The reaction of GeCl4 with AsMe3 in CH2Cl2 or Et2O at
ambient temperatures, produced colourless crystals of trans-
[GeCl4(AsMe3)2] which were identified by comparison of their unit
cell with the literature data.9 A similar reaction using AsEt3 in
CH2Cl2 followed by rapid isolation of the product gave white
trans-[GeCl4(AsEt3)2] and crystals obtained from CH2Cl2 showed
a similar structure (Fig. 4, Table 4). The centrosymmetric molecule
Table 5) which showed the expected trigonal bipyramid geometry
with similar As–Cl and As–C bond lengths to those in related
compounds such as Me3AsCl2 and Cy3AsCl2.23,24 The trans-
[GeCl4(AsR3)2] were also made by reaction of GeCl4 with the
ligands in the absence of a solvent (cf. the GeCl4–PMe3 reactions
vide supra) and had identical Raman spectra to samples obtained
using CH2Cl2 as solvent.
˚
has Ge–As = 2.490(1) A, slightly longer than that in trans-
˚
[GeCl4(AsMe3)2] (2.472(1) A). If the solution was allowed to stand
for a few days very pale yellow crystals were deposited which
22
were identified by their IR and Raman spectra as Et3AsCl2.
The Raman spectra obtained from solid trans-[GeCl4(AsR3)2]
The identity was confirmed by the crystal structure (Fig. 5,
(R = Me or Et) show very strong bands at 266 cm−1 (Me) or
This journal is
The Royal Society of Chemistry 2008
Dalton Trans., 2008, 2261–2269 | 2265
©

View Article Online
◦
˚
Br or I) all of which form phosphane adducts, although again
the affinity of SnF4 for arsanes is much less than for phosphanes.
The chemistry observed with GeX4 also seems to differ from the
limited data reported for the SiX4 systems, but we reserve detailed
comparisons here until much more complete data are available.
Studies are underway on the silicon tetrahalide complexes.
Table 5 Selected bond lengths (A) and angles ( ) for Et3AsCl2
As1–Cl1
As1–C1
C1–C2
2.382(4)
1.927(6)
1.604(13)
As2–Cl2
As2–C3
C3–C4
2.362(4)
1.918(7)
1.637(12)
C–As1–C
C–As1–Cl
As1–C1–C2
120.0
90.0
105.4(5)
C–As2–C
C–As2–Cl
As2–C3–C4
120.0
90.0
105.9(6)
Experimental
259 cm−1 (Et) which are assigned as the a1g modes, but in Nujol
mulls (the solids dissolve in the Nujol), the strongest band in
each far-IR spectrum is at 456 cm−1 which corresponds to the t2
mode of tetrahedral GeCl4,25 showing that they are substantially
GeF4 was obtained from Aldrich and used as received. GeCl4
(Aldrich) was distilled from a mixture of CaCl2–Na2CO3, which
removes traces of water and HCl. MeCN and CH2Cl2 were
dried by distillation from CaH2, and diethyl ether from sodium
benzophenone ketyl. Ligands were obtained from Aldrich or
Strem: PMe3, PPh3, PCy3, AsMe3, AsEt3, Me2P(CH2)2PMe2,
Et2P(CH2)2PEt2, Cy2P(CH2)2PCy2, or were made by literature
methods: o-C6H4(PPh2)2, Ph2P(CH2)2PPh2, o-C6H4(PMe2)2, o-
C6H4(AsMe2)2.26–29 All reactions were conducted using Schlenk,
vacuum line and glove-box techniques and under a dry dinitrogen
atmosphere. IR spectra were recorded from Nujol mulls on a
Perkin Elmer PE 983G spectrometer, Raman spectra using a
Perkin Elmer FT Raman 2000R with a Nd:YAG laser. 1H NMR
spectra were from CDCl3 or CD2Cl2 solutions on a Bruker AV300,
1
dissociated even in this medium. The H NMR spectra of both
complexes are little different to those of the ligands and do not
change even on cooling to 190 K, again consistent with extensive
dissociation. Upon standing, the solution of trans-[GeCl4(AsEt3)2]
3
in CD2Cl2 develops new features at d = 1.60 (t, JHH = 7.5
Hz) and 3.06 (q), which correspond to Et3AsCl2,22 confirming
the slow decomposition. We confirm the previous report9 that
no reaction occurs between GeCl4 and AsPh3 in either CH2Cl2
or Et2O at ambient temperatures. No reaction occurred with
GeCl4 and the diarsane Ph2As(CH2)2AsPh2, or (very surprisingly)
with o-C6H4(AsMe2)2, which suggests that the stereochemistry at
germanium also plays a role (i.e. cis isomers are even less favoured
than the trans and the normally expected greater stability of chelate
complexes is not found here). The reaction of GeBr4 and AsEt3
in the absence of solvent gave a clear viscous yellow liquid with
strong bands in the Raman spectrum at 311, 267, 240 and 205 cm−1
which do not correspond with tetrahedral GeBr4 (328, 234 cm−1)
19F{ H} and 31P{ H} NMR spectra on a Bruker DPX400 and
referenced to CFCl3 and 85% H3PO4 respectively. Microanalytical
measurements on new complexes were performed by the micro-
analytical service at Strathclyde University. [GeF4(MeCN)2] was
made as described.11
1
1
[GeF4{o-C6H4(PMe2)2}]
1
or to Et3AsBr2,22 and when dissolved in CD2Cl2 the H NMR
[GeF4(MeCN)2] (0.23 g, 1.0 mmol) was dissolved in CH2Cl2
(10 mL) and o-C6H4(PMe2)2 (0.198 g, 1.0 mmol) added dropwise;
the mixture was stirred for 4 h at ambient temperatures. Most of
the solvent was removed in vacuo and the white powder produced
was filtered off and dried in vacuo. Yield 0.32 g, 92%. Required for
C10H16F4GeP2 (346.8): C, 34.6; H, 4.7. Found: C, 34.9; H, 4.9%.
spectrum is little different to that of AsEt3. This suggests that
the oil may be trans-[GeBr4(AsEt3)2], again extensively dissociated
in solution; extrapolation from the chloride suggests the Raman
active a1g Ge–Br vibration will be ∼180 cm−1, below the limit of
the instrument.
These results show that weak adducts form between GeCl4 and
AsR3 (R = alkyl), but these are highly dissociated in solution, and
slowly convert into R3AsCl2. The slower reduction by AsR3 than
by PR3 reflects the relatively weaker reducing power of the arsanes.
2
5
1H NMR (300 MHz, CDCl3, 295 K): d = 1.81 (t, J + JPH
=
4.5 Hz, 12H, Me), 7.73–7.83 (m, 4H, C6H4). IR (Nujol): 607(br),
580(sh), 567(br) m(GeF) cm−1.
[GeF4{Ph2P(CH2)2PPh2}]
Conclusions
[GeF4(MeCN)2] (0.23 g, 1.0 mmol) was dissolved in CH2Cl2
(10 mL), Ph2P(CH2)2PPh2 (0.40 g, 1.0 mmol) in CH2Cl2 (5 mL)
was added and the mixture stirred for 3 h. Most of the solvent
was removed in vacuo and the white precipitate was washed with
hexane (10 mL), filtered off and dried in vacuo. Yield 0.37 g, 68%.
Required for C26H24F4GeP2 (547.0): C, 57.1; H, 4.4. Found: C,
56.2; H, 4.5%. 1H NMR (300 MHz, CDCl3, 298 K): d = 2.71 (s,
br, H, CH2), 7.79–7.38 (m, 5H, Ph). IR (Nujol): 603(s), 586(br)
m(GeF) cm−1.
The work has resulted in characterisation of the first phosphane
adducts of GeF4 and has shown that while GeCl4 forms (unstable)
complexes with some arsanes (but not others), these slowly convert
into R3AsCl2. With phosphanes the reduction to GeII is usually
rapid and [GeCl4(PR3)2] complexes can only be obtained in the
absence of solvents. The stability of Lewis acid–base complexes
depends upon two major factors—the strength of the donor–
acceptor bond and the energy needed to reorganise the tetrahedral
GeX4 unit into the four-coordinate fragment of the octahedron.
The latter is constant for fixed X, and thus the relative affinity
for PR3 vs. AsR3 which is GeF4 > GeCl4 for the phosphanes, but
appears to be reversed for the arsane compounds, must mainly
reflect the difference in orbital energies and donor atom ‘softness’
between P and As. The reduction of GeIV to GeII is not evident
in the fluoride systems, but is favoured for the GeCl4 (and GeBr4)
reactions. This contrasts with the chemistry of SnX4 (X = F, Cl,
[GeF4{o-C6H4(PPh2)2}]
[GeF4(MeCN)2] (0.23 g, 1.0 mmol) and o-C6H4(PPh2)2 (0.45 g,
1.0 mmol) were weighed out and CH2Cl2 (10 mL) added, the
solution was stirred for 4 h, during which the solution began to
turn cloudy and a white precipitate formed. The precipitate was
filtered off and dried in vacuo. Yield 0.25 g, 42%. Required for
2266 | Dalton Trans., 2008, 2261–2269
This journal is
The Royal Society of Chemistry 2008
©

View Article Online
1
3
Reaction of GeF4 with o-C6H4(AsMe2)2
C30H24F4GeP2· CH2Cl2 (623.4): C, 58.5; H, 4.0. Found: C, 58.7;
1
H, 3.8%. H NMR (300 MHz, CDCl3, 298 K): d = 7.2–7.65 (m,
o-C6H4(AsMe2)2 (0.29 g, 1.0 mmol) was added dropwise to a
solution of [GeF4(MeCN)2] (0.23 g, 1.0 mmol) in CH2Cl2 (10 mL).
The mixture was stirred for 2 h. The white precipitate was filtered
off and dried in vacuo. Yield 0.15 g. 1H NMR (300 MHz, CD2Cl2,
Ph). IR (Nujol): 619(s), 607(vs, br) m(GeF) cm−1.
[GeF4{Me2P(CH2)2PMe2}]
295 K): d = 1.45 (s, 12H, Me), 7.43–7.56 (m, 4H, C6H4). 19F{ H}
1
Me2P(CH2)2PMe2 (0.15 g, 1.0 mmol) was added dropwise to a
solution of [GeF4(MeCN)2] (0.23 g, 1.0 mmol) in CH2Cl2 (10 mL);
the mixture was stirred overnight at room temperature. A white
precipitate was filtered off and dried in vacuo. Yield 0.29 g,
NMR (CD2Cl2, 220 K): d = −77.7 (t), −118.1 (t); 2JFF = 66 Hz.
IR (Nujol): 657(s), 629(m), 613(m), 595(m) m(GeF) cm−1. Raman:
664(w), 630(s, br), 602(s, br), m(GeF) cm−1.
1
97%. Required for C6H16F4GeP2· CH2Cl2 (341.2): C, 22.9; H, 5.0.
2
Reaction of GeF4 with AsMe3
1
Found: C, 22.6; H, 5.2%. H NMR (300 MHz, CDCl3, 295 K):
GeF4 was bubbled through a stirred solution of trimethylarsine
(0.30 g, 2.5 mmol) in hexane (10 mL). A white solid precipitated
d = 1.39 (m, 3H, Me), 2.05 (m, 2H, CH2). IR (Nujol): 565(vbr)
m(GeF) cm−1.
1
which was filtered off and dried in vacuo. H NMR (300 MHz,
1
CDCl3, 295 K): d = 1.16 (s, Me). 19F{ H} NMR (CD2Cl2, 220 K):
[GeF4{Et2P(CH2)2PEt2}]
d = −127.3 (t), −149.8 (t); 2JFF = 80 Hz. IR (Nujol): 646(s), 635(s),
600(sh) m(GeF) cm−1. Raman: 642(s), 596(s, br), m(GeF) cm−1.
The same product was isolated from reaction of AsMe3 with
[GeF4(MeCN)2] in CH2Cl2 solution.
Et2P(CH2)2PEt2 (0.206 g, 1.0 mmol) was added dropwise to a
solution of [GeF4(MeCN)2] (0.23 g, 1.0 mmol) in CH2Cl2 (10 mL);
the mixture was stirred for 4 h. Most of the solvent was removed
in vacuo, the solid filtered off and dried in vacuo. Yield 0.29 g,
1
trans-[GeCl4(AsMe3)2]
82%. Required for C10H24F4GeP2· CH2Cl2 (397.3): C, 31.7; H, 6.3.
2
1
Found: C, 31.2; H, 7.0%. H NMR (300 MHz, CDCl3, 295 K):
Trimethylarsine (0.341 mL, 3.19 mmol) was added to a stirred
solution of germanium(IV) chloride (0.343 g, 1.59 mmol) in diethyl
ether (10 mL). This was stirred for 2 d before 5 mL of solvent
was removed in vacuo and a white solid precipitated out. The
solid was filtered off and the filtrate was put in a freezer for 5
d. Colourless crystals formed which were identified by a unit cell
determination as trans-[GeCl4(AsMe3)2].9 The crystals and powder
were the same spectroscopically. IR (Nujol): 456(s) m3(GeCl4) cm−1.
Raman: 266(vs) a1g (GeCl) cm−1.
d = 1.25 (m, 3H, Me), 1.97 (m, 2H, CH2), 2.06 (m, 2H, CH2). IR
(Nujol): 605(sh), 577(vbr), 560(sh) m(GeF) cm−1.
[GeF4{Cy2P(CH2)2PCy2}]
1,2-Bis(dicyclohexylphosphino)ethane (0.47 g, 1.1 mmol) in
CH2Cl2 (5 mL) was added to a stirred solution of [GeF4(MeCN)2]
(0.28 g, 1.2 mmol) in CH2Cl2 (10 mL) and the mixture was stirred
for 2 h. The solvent was removed in vacuo to give a white solid
which was washed with hexane (10 mL), filtered off and dried in
trans-[GeCl4(AsEt3)2]
1
2
vacuo. Yield 0.43 g, 68%. Required for C26H48F4GeP2· CH2Cl2
(613.5): C, 51.8; H, 8.3. Found: C, 52.0; H, 8.5%. 1H NMR
(300 MHz, CDCl3, 295 K): d = 1.28–2.22 (m, CH2). IR (Nujol):
592(s,vbr) m(GeF) cm−1.
Triethylarsine (0.388 mL, 2.76 mmol) was added to a stirred
solution of germanium(IV) chloride (0.296 g, 1.38 mmol) in diethyl
ether (10 mL). This was stirred overnight before 5 mL of solvent
was removed in vacuo and was refrigerated when a white solid
precipitated, which was filtered off and dried in vacuo. Yield 45%.
Required for C12H30As2Cl4Ge (538.6): C, 26.8; H, 5.6. Found: C,
trans-[GeF4(PMe3)2]
1
24.3, H 5.5%. H NMR (300 MHz, CDCl3, 295 K): d 1.15 (t,
Trimethylphosphine (0.152 g, 2.0 mmol) was added dropwise to a
solution of [GeF4(MeCN)2] (0.23 g, 1.0 mmol) in CH2Cl2 (10 mL);
the mixture was stirred for 2 h. Most of the solvent was removed
in vacuo and then filtered to give a white powder which was dried
3H CH3), 1.42 (q, 2H, CH2). IR (Nujol): 456(s) m3(GeCl4) cm−1.
Raman: 259(vs) a1g (GeCl) cm−1.
The filtrate was put in a freezer for 5 days before the solvent
was removed in vacuo which gave pale yellow crystals identified
1
2
in vacuo. Yield 0.15 g, 48%. Required for C6H18F4GeP2· CH2Cl2
1
as Et3AsCl2 from an X-ray structure determination. H NMR
(343.5): C, 22.7; H, 5.5. Found: C, 22.7; H, 5.6%. 1H NMR
(300 MHz, CDCl3, 295 K): d = 1.46 (d); 2JPH = 12 Hz. IR (Nujol):
575(s,vbr). Raman: 508(ms) m(GeF) cm−1.
3
(300 MHz, CDCl3, 295 K): d = 1.60 (t, JHH = 7.5 Hz, 9H,
Me), 3.06 (q, 6H, CH2). Raman: 611(m), 527(vs), 413(m), 338(m),
254(vs) cm−1.
trans-[GeF4(PPh3)2]
Oxidation reactions of germanium coordinated phosphanes
A solution of triphenylphosphine (0.52 g, 2.0 mmol) in CH2Cl2
(5 mL) was added dropwise to a solution of [GeF4(MeCN)2]
(0.23 g, 1.0 mmol) in CH2Cl2 (10 mL); the mixture was stirred
for 3 h. A white precipitate was filtered off and dried in vacuo.
A sample of [GeF4{Ph2P(CH2)2PPh2}] (0.1 g) was dissolved in
degassed anhydrous CH2Cl2 under dinitrogen in a small Schlenk
tube and the solution frozen solid at 77 K. The system was
evacuated and then filled with 18O2 to 1 atm and allowed to
warm to room temperature. After 2 weeks a sample was removed
for 31P NMR study, and the remaining solution shaken up with
1 M aqueous NaOH. The organic layer was separated, dried
1
Yield 0.60 g, 89%. Required for C36H30F4GeP2· CH2Cl2 (694.4): C,
4
62.7; H, 4.4. Found: C, 63.0; H, 4.4%. 1H NMR (300 MHz, CDCl3,
295 K): d = 7.2–7.6 (m). IR (Nujol): 607(s,vbr) m(GeF) cm−1.
This journal is
The Royal Society of Chemistry 2008
Dalton Trans., 2008, 2261–2269 | 2267
©

View Article Online
Table 6 Crystal data and structure refinement detailsa
Compound
[GeF4{o-C6H4(PMe2)2}]
[GeF4{Ph2P(CH2)2PPh2}]
[GeCl4(AsEt3)2]
Et3AsCl2
Formula
M
C10H16F4GeP2
346.76
Orthorhombic
Pna21 (33)
12.307(3)
10.1285(10)
10.749(3)
90
90
90
1339.9(4)
4
2.547
696
8863
2871
0.057
0.742, 1.000
158, 1
1.04
C26H24F4GeP2
546.98
Monoclinic
C12H30As2Cl4Ge
538.59
Monoclinic
P21/n (14)
7.849(2)
13.643(4)
9.537(3)
90
93.721(15)
90
1019.1(5)
2
5.238
536
9942
2340
0.079
0.713, 1.000
91, 0
C6H15AsCl2
233.00
Crystal system
Space group (no.)
Hexagonal
¯
Cc(9)
P6 (174)
˚
a/A
10.6765(12)
16.466(2)
14.2710(16)
90
105.003(8)
90
2423.3(5)
4
1.439
1112
12784
4506
0.024
8.354(2)
8.354(2)
8.629(2)
90
90
120
521.5(2)
2
3.702
236
7342
861
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
U/A
Z
3
˚
l(Mo-Ka)/mm−1
F(000)
Total no. reflections
Unique reflections
Rint
Min., max. transmission
No. of parameters, restraints
Goodness-of-fit on F2
0.050
0.721, 1.000
36, 2
0.886, 1.000
298, 2
1.05
1.21
1.02
−3
˚
Resid. electron density/e A
−0.53 to +0.46
−0.26 to +0.29
−0.81 to +1.00
−0.47 to +0.60
0.034
0.044
0.088
0.093
b
R1 [Io > 2r(Io)]
0.039
0.022
0.067
R1 (all data)
0.051
0.070
0.074
0.023
0.054
0.054
0.114
0.109
0.126
b
wR2 [Io > 2r(Io)]
wR2 (all data)
ꢀ
ꢀ
ꢀ
◦
a
2
Common items: temperature = 120 K; wavelength (Mo-Ka) = 0.71073 A; h(max) = 27.5 . b R1
=
ꢁFo| − |Fcꢁ / |Fo|. wR2 = [ w(Fo
−
˚
ꢀ
Fc2)2/ wFo
] .
4
1/2
with molecular sieve, and then the solution decanted off and
pumped dry. The white solid obtained was used directly for EI
mass spectrometry and IR spectroscopy studies (see Results and
discussion for spectroscopic data).
The data for Et3AsCl2 was collected as a monoclinic C lattice using
the automated software with b close to 90◦, however inspection
of the data with Layer34 gave an orthorhombic system as being
probable. No satisfactory solution emerged in any of the possible
orthorhombic space groups with the initial promising molecules
failing to refine. The strategy of trying to solve the structure in
P1 was explored and the transformation matrix by good fortune
produced a cell that looked remarkably hexagonal. A solution
with Z = 2 in P1 readily followed (R1 = 0.042), but with severe
correlation problems during refinement. The triclinic coordinates
were finally transformed to the correct hexagonal system. The
systematic absences for the transformed data gave 000l = 2n, but
it was likely from the As positions that this was not arising from
relationships between symmetry related molecules, but rather from
the difference in the z coordinates of these two atoms (and the other
atoms). The only hexagonal space group that would accommodate
The GeCl4–PMe3 reaction
In a small Schlenk tube, GeCl4 (∼0.15 g) was distilled in vacuo onto
PMe3 (0.105 g, 1.38 mmol) at 77 K. The mixture was cautiously
allowed to warm and on melting immediately transformed into
a white solid. The Schlenk was briefly evacuated to remove any
excess reagent and then filled with dry dinitrogen; the Raman
spectrum of the solid was recorded without removing it from the
Schlenk. The solid was then dissolved in CH2Cl2 (20 mL) and the
solution allowed to stand for 3 h and then pumped dry. The solid
was identified as [PMe3Cl][GeCl3] (see text for spectroscopic data).
¯
the molecular symmetry found in the triclinic model was P6
(no. 174). This model converged to R1 = 0.034 with 36 refined
parameters compared with 164 parameters in the triclinic model.
Chemically the two models are the same, but in crystallographic
terms the higher symmetry is preferred. Selected bond lengths and
angles are given in Tables 2–5.
CCDC reference numbers 665905–665910.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b716765b
X-Ray crystallography
Details of the crystallographic data collection and refinement pa-
rameters are given in Table 6. Crystals of [GeF4{o-C6H4(PMe2)2}]
were obtained from a solution in CH2Cl2–n-hexane by slow
evaporation; [GeF4{Ph2P(CH2)2PPh2}] from CH2Cl2–n-hexane
cooled in a freezer; and Et3AsCl2 and trans-[GeCl4(AsEt3)2]
from Et2O solution by slow evaporation under dinitrogen. Data
collection used a Nonius Kappa CCD diffractometer using
graphite or confocal mirror monochromated Mo-Ka X-radiation
˚
(k = 0.71073 A). Crystals were held at 120 K in a nitrogen
Acknowledgements
gas stream. Structure solution and refinement were generally
routine,30–33 except as described below with hydrogen atoms on C
introduced in calculated positions using the default C–H distance.
We thank the EPSRC (GR/T09613/01) for support and Dr
F. Cheng for help in running the Raman spectra.
2268 | Dalton Trans., 2008, 2261–2269
This journal is
The Royal Society of Chemistry 2008
©

View Article Online
16 M. F. Davis, W. Levason, G. Reid and M. Webster, Polyhedron, 2006,
References
25, 930–936.
1 W. Levason and C. A. McAuliffe, Coord. Chem. Rev., 1976, 19, 173–185.
2 N. C. Norman and N. L. Pickett, Coord. Chem. Rev., 1995, 145, 27–54.
3 Comprehensive Coordination Chemistry II, ed. J. A. McCleverty and
T. J. Meyer, Elsevier, Oxford, 2004, vol. 3.
17 W. Levason, R. Patel and G. Reid, J. Organomet. Chem., 2003, 688,
280–282.
18 S. M. Godfrey and A. Hinchcliffe, J. Mol. Struct., 2006, 761, 1–5 and
references therein.
4 A. R. J. Genge, W. Levason and G. Reid, Inorg. Chim. Acta, 1999,
288, 142–149; N. Bricklebank, S. M. Godfrey, C. A. McAuliffe and
R. G. Pritchard, J. Chem. Soc., Chem. Commun., 1994, 695–696; D.
Dakternieks, H. Zhu and E. R. T. Tiekink, Main Group Met. Chem.,
1994, 17, 519–535; F. Kunnkel and K. Dehnicke, Z. Naturforsch., B:
Chem. Sci., 1995, 50, 848–850.
¨
19 G. Kociok-Kohn, J. G. Winter and A. C. Filippou, Acta Crystallogr.,
Sect. C, 1999, 55, 351–353.
20 H. E. Blayden and M. Webster, Inorg. Nucl. Chem. Lett., 1970, 6, 703–
705.
21 N. N. Greenwood and A. Earnshaw, Chemistry of the Elements,
Butterworth, Oxford, 2nd edn, 1997; W. E. Dasent, Non-existent
Compounds, Dekker, New York, 1965.
22 L. Verdonck and G. P. Van der Kelen, Spectrochim. Acta, Part A, 1977,
13, 601–606.
23 M. B. Hursthouse and I. A. Steer, J. Organomet. Chem., 1971, 27,
5 M. F. Davis, M. Clarke, W. Levason, G. Reid and M. Webster,
Eur. J. Inorg. Chem., 2006, 2773–2782.
6 I. R. Beattie and G. A. Ozin, J. Chem. Soc. A, 1970, 370–377.
7 D. K. Frieson and G. A. Ozin, Can. J. Chem., 1973, 51, 2685–2696;
D. K. Frieson and G. A. Ozin, Can. J. Chem., 1973, 51, 2697–2709.
8 W.-W. Du Mont, H.-J. Kroth and H. Schumann, Chem. Ber., 1976, 109,
3017–3024; W.-W. Du Mont, Z. Anorg. Allg. Chem., 1979, 458, 85–88;
F. Ruthe, W.-W. Du Mont and P. G. Jones, Chem. Commun., 1997,
1947–1948.
C11–12.
24 S. Pascu, L. Silaghi-Dumitrescu, A. J. Blake, W.-S. Li, I. Haiduc and
D. B. Sowerby, Acta Crystallogr., Sect. C, 1998, 54, 219–221.
25 K. Nakamoto, Infrared Spectra of Inorganic and Coordination Com-
pounds, Wiley, New York, 2nd edn, 1970.
26 R. D. Feltham, R. S. Nyholm and A. Kasenally, J. Organomet. Chem.,
1967, 7, 285–288.
27 H. C. E. McFarlane and W. McFarlane, Polyhedron, 1983, 2, 303–
9 S. M. Godfrey, I. Mushtaq and R. G. Pritchard, J. Chem. Soc., Dalton
Trans., 1999, 1319–1323.
10 L. Apostolico, M. F. Mahon, K. C. Molloy, R. Binions, C. S. Blackman,
C. J. Carmalt and I. P. Parkin, Dalton Trans., 2004, 470–475.
11 F. Cheng, M. F. Davis, A. L. Hector, W. Levason, G. Reid, M. Webster
and W. Zhang, Eur. J. Inorg. Chem., 2007, 2488–2495.
12 K. O. Christe, C. J. Schack and R. D. Wilson, Inorg. Chem., 1976,
15, 1275–1282; J. E. Griffiths and D. E. Irish, Inorg. Chem., 1964, 3,
1134–1137.
304.
28 A. M. Aguiar and J. Beisler, J. Org. Chem., 1964, 29, 1660–1662.
29 E. P. Kyba, S. T. Liu and R. L. Harris, Organometallics,, 1983, 2, 1877–
1879.
30 G. M. Sheldrick, SHELXS-97, Program for solution of crystal struc-
tures, University of Gottingen, Germany, 1997.
¨
13 M. Sigl, A. Schier and H. Schmidbaur, Eur. J. Inorg. Chem., 1998, 203–
210; F. Cheng, A. L. Hector, W. Levason, G. Reid, M. Webster and W.
Zhang, Inorg. Chem., 2007, 46, 7215–7223.
14 F. Cheng, M. F. Davis, A. L. Hector, W. Levason, G. Reid, M. Webster
and W. Zhang, Eur. J. Inorg. Chem., 2007, 4897–4905.
31 G. M. Sheldrick, SHELXL-97, Program for refinement of crystal
structures, University of Go¨ttingen, Germany, 1997.
32 G. M. Sheldrick, SADABS, Bruker-Nonius area detector scaling and
absorption correction (V2.10), University of Gottingen, Germany,
¨
2003.
15 M. F. Davis, W. Levason, G. Reid, M. Webster and W. Zhang, Dalton
Trans., 2008, 533–538.
33 H. D. Flack, Acta Crystallogr., Sect. A, 1983, 39, 876–881.
34 L. J. Barbour, J. Appl. Crystallogr., 1999, 32, 351.
This journal is
The Royal Society of Chemistry 2008
Dalton Trans., 2008, 2261–2269 | 2269
©