Synthesis and characterisation of selected group 14 derivatives of the 2,5-(CF3)2C6H3 (Ar) ligand

Article abstract of DOI:10.1039/c2dt12369j

Selected group 14 tetrahalides EX₄ (E = Si, Ge or Sn; X = Cl or Br) have been reacted in various molar ratios with ArLi, where Ar = 2,5-(CF ₃)₂C₆H₃. The compounds Ar ₂SiCl₂1, Ar<

Full text of DOI:10.1039/c2dt12369j

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PAPER
Synthesis and characterisation of selected group 14 derivatives of the
2,5-(CF3)2C6H3 (Ar) ligand†
Philippa K. Coffer (née Monks), Keith B. Dillon,* Judith A. K. Howard, Dmitry S. Yufit and
Natalia V. Zorina
Received 7th December 2011, Accepted 13th January 2012
DOI: 10.1039/c2dt12369j
Selected group 14 tetrahalides EX4 (E = Si, Ge or Sn; X = Cl or Br) have been reacted in various molar
ratios with ArLi, where Ar = 2,5-(CF3)2C6H3. The compounds Ar2SiCl2 1, Ar3SiF 3, Ar2Si(OH)2 4,
Ar2GeCl2 7, Ar2Ge(Br)Ge(Br)Ar2 8, Ar3SnCl 10, Ar4Sn 11 and Ar3SnBr 12 have been isolated, and
characterised by single-crystal X-ray diffraction, elemental analysis and 19F solution-state NMR
spectroscopy.
Introduction
Results and discussion
Many studies have taken place in recent years using the bulky
electron-withdrawing ligand 2,4,6-(CF3)3C6H2 (fluoromes) to
stabilise both main group and transition metal species, including
group 14 derivatives, some of which have been structurally
characterised.1–19 Fewer reactions have been attempted with the
2,6-(CF3)2C6H3 (fluoroxyl) substituent, since lithiation of 1,3-
(CF3)2C6H4 occurs in two positions, either ortho to both CF3
groups to give the desired 2,6-(CF3)2C6H3 derivatives, or ortho
to one CF3 and meta to the second, leading to the isomeric 2,4-
(CF3)2 species. Consequently mixtures of products are often
obtained, which are sometimes difficult to separate.1 In a recent
paper, we described the synthesis, characterisation and com-
plexation behaviour towards Pt(II) of some phosphorus deriva-
tives of the 2,5-(CF3)2C6H3 (Ar) substituent, formed by
lithiation of 1,4-(CF3)2C6H4 (ArH) and subsequent reaction with
a phosphorus(III) halide.20 The hydrocarbon starting material has
the advantage that all four potential lithiation sites are equival-
ent, so only one set of derivatives was produced from each reac-
tion, with the CF3 groups always in the 2- and 5-positions. With
only one bulky ortho-CF3 group this ligand does not confer the
same kinetic stability as fluoromes or fluoroxyl groups, but it
should have similar electron-withdrawing properties. We have
now extended the previous work20 to the synthesis and character-
isation of group 14 compounds with two or more Ar substituents
attached to the central element Si, Ge or Sn. There have been no
previous reports of structurally characterised group 14 deriva-
tives of the Ar ligand.
(a) Synthesis
The group 14 tetrahalides EX4 (E = Si, Ge or Sn; X = Cl or Br)
were reacted initially in a 1 : 2 molar ratio with ArLi, formed by
lithiation of ArH with n-BuLi (Experimental section). Usually
the ArLi solution in Et2O was added slowly to a solution of EX4
in hexane at 195 K, with stirring. In each case, crystalline pro-
ducts were isolated suitable for X-ray diffraction.
(i) Reactions with SiX4. The main product from the SiCl4
reaction in a 1 : 2 molar ratio with ArLi was the dichloride
Ar2SiCl2 1 (Scheme 1). This compound was isolated in crystal-
line form (Fig. 1), although structure determination by single-
crystal X-ray diffraction was not straightforward (section (b)).
Small quantities of Ar3SiCl 2 and Ar3SiF 3 were also present in
the reaction mixture, Ar3SiF clearly identified by 19F NMR sol-
ution-state spectroscopy (Table 1), where the Si–F signal was
split into a decet and the o-CF3 resonance into a doublet, JFF
11.2 Hz. The hydrolysis product Ar2Si(OH)2 4 was also isolated
in crystalline form (Fig. 2) from a sample of Ar2SiCl2 left in an
NMR tube.
Reaction with SiBr4 led to formation of Ar2SiBr2 5; crystals
of this compound were obtained which appeared to be isostruc-
tural with 1, but X-ray data recorded at temperatures down to
100 K were not of high enough resolution to produce a satisfac-
tory refinement. Nonetheless the molecular structure and connec-
tivities were clearly established, and there was no doubt about its
identification as Ar2SiBr2. Small amounts of Ar3SiBr 6 and
Ar3SiF 3 were also present in the solution; Ar3SiF 3 was isolated
from one of these reactions, and characterised by single-crystal
X-ray diffraction (Fig. 3) and elemental analysis, as well as by
19F NMR spectroscopy.
5
=
Chemistry Department, Durham University, South Road, Durham, DH1
3LE, UK. E-mail: k.b.dillon@durham.ac.uk; Fax: +44 (0)191 384
4737; Tel: +44 (0)191 334 2092
†CCDC reference numbers 857420–857427. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/c2dt12369j
The present results for SiX4 indicate that Ar2SiX2 is the predo-
minant initial product (Scheme 1), with some Ar3SiX also
formed which then exchanges rapidly to yield Ar3SiF 3. The
isolation of a fluoride rather than a chloride from reaction of
4460 | Dalton Trans., 2012, 41, 4460–4468
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Scheme 1 Reaction of ArLi with SiX4 (where X = Cl or Br).
Table 1 19F NMR data for Ar derivatives
19F (ppm)
δ
5JFF
Compound
o- CF3
p- CF3 X–F
(Hz)
ArH
ArLi
−64.6
−62.6
−58.2
−59.3
−63.4
−64.2
−64.6
—
—
—
—
—
—
Ar2SiCl2 1
Ar3SiCl 2
Ar3SiF 3
Ar2Si(OH)2 4
Ar2SiBr2 5
Ar3SiBr 6
Ar2GeCl2 7
Ar2Ge(Br)Ge(Br)Ar2 8 −58.4
Ar2SnCl2 9
Ar3SnCl 10
Ar4Sn 11
−59.6 (d) −64.2
−157.4 (decet) 11.2
—
−59.1
−57.5
−58.5
−59.1
−63.7
−63.8
−64.2
−64.2
−63.7
−64.1
−64.7
−63.9
−64.0
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
−61.6
−60.8
−61.3
−59.8
Ar3SnBr 12
Fig. 1 Molecular structure of 1.
SiCl4 with 2,4,6-(CF3)3C6H2Li (fluoromesLi) has been well-
documented in the literature,1,3 and a possible exchange
mechanism proposed,1 although in that system the product was
(fluoromes)2SiF2, perhaps because of greater steric hindrance
around the Si atom. With fluoroxyl ligands, the presence of [2,6-
(CF3)2C6H3]2SiCl2, [2,6-(CF3)2C6H3]2SiF2, [2,4-(CF3)2C6H3]2-
SiCl2 and [2,4-(CF3)2C6H3]2SiF2 was established in solution,
showing rather slower exchange than with fluoromes; the crystal
and molecular structures of both [2,6-(CF3)2C6H3]2SiF2 and
[2,4-(CF3)2C6H3]2SiCl2 were determined.1 Again substitution
into SiX4 apparently ceased with two fluoroaromatic groups on
Si under the given experimental conditions. The present behav-
iour is thus similar in some respects to that of the fluoroxyl
systems, except that X–F exchange seems to be slower for
Ar2SiX2. The main difference is that further substitution to
Ar3SiX occurs, followed by rapid halogen exchange to yield
Fig. 2 Molecular structure of 4.
Dalton Trans., 2012, 41, 4460–4468 | 4461
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Fig. 4 Molecular structure of 7.
Fig. 3 Molecular structure of 3.
Scheme 2 Reaction of ArLi with GeCl4 and GeBr4.
Ar3SiF. This result and those for tin(IV) discussed below suggest
that reaction is more facile with ArLi, particularly where the
E–X bond is weaker, leading to more Ar groups on E. In the
reactions of ArLi with phosphorus(III) halides, even 1 : 1 molar
ratios of reactants yielded more Ar2PX than ArPX2, suggesting
that the latter may react more readily than PX3 with ArLi,20 and
this may well be true for ArSiX3 relative to SiX4. No evidence
for 1 : 1 products was found here. The 19F NMR solution data
for all new compounds are presented in Table 1.
Fig. 5 Molecular structure of 8.
(iii) Reactions with SnX4. Reaction with tin(IV) halides in a
2 : 1 molar ratio led to extensive substitution (Scheme 3), with
both Ar3SnCl 10 (Fig. 6) and Ar4Sn 11 (Fig. 7) being isolated
from SnCl4, and Ar3SnBr 12 (Fig. 8) from SnBr4 (Table 1). The
ArLi–SnCl4 reaction was repeated in a 4 : 1 molar ratio, to try to
obtain Ar4Sn in larger quantities. The 19F solution-state NMR
spectra showed three species present, assigned as Ar2SnCl2 9,
Ar3SnCl 10 and Ar4Sn 11 (Table 1), and clearly confirmed that
no Cl–F exchange was occurring. The SnBr4 reaction was also
repeated in a 1 : 1 molar ratio, but this, too, yielded Ar3SnBr 12
as the isolated product, thus supporting the contention that
further substitution may be facile when the E–X bonds are com-
paratively weak.
(ii) Reactions with GeX4. Reactions of ArLi with GeCl4 and
GeBr4 in a 2 : 1 molar ratio both stopped at the stage with two
Ar groups attached to Ge, but the products were different
(Scheme 2). The monomeric species Ar2GeCl2 7 was formed
from GeCl4 (Fig. 4), while the dinuclear compound Ar2Ge(Br)
Ge(Br)Ar2 8, with a germanium-germanium bond, resulted from
the GeBr4 reaction (Fig. 5). The dimeric nature was shown by
single-crystal X-ray diffraction (section b) and elemental analy-
sis; this structure could not have been deduced from the 19F
NMR spectra alone (Table 1). There was no evidence of X–F
exchange in either the Ge or Sn systems discussed below, again
similar to fluoromes and fluoroxyl derivatives.1
(b) Crystal and molecular structures
The crystal and molecular structures of 3, 4, 7, 8, 10, 11 and 12
were determined at 120 K; crystallographic details are provided
4462 | Dalton Trans., 2012, 41, 4460–4468
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Scheme 3 Reaction of ArLi with SnX4 (where X = Cl or Br).
Fig. 6 Molecular structure of 10.
in the experimental section, while selected geometrical par-
ameters are given in Tables 2–4. In all structures, except dinuc-
lear 8, some CF3 groups are rotationally disordered, as is
frequently found in this type of compound.1,3–19 Good quality
crystals of Ar2SiCl2 1 were obtained, but these proved to be
incommensurate down to 90 K. The structure was determined
successfully at 40 K (Fig. 1), and contains four crystallographi-
cally independent almost identical molecules (Fig. 9), which
differ in the orientation of their CF3 groups. Each of these mol-
ecules exhibits slightly distorted tetrahedral geometry, with the
C–Si–C angle as the largest and the Cl–Si–Cl angle as the smal-
lest (Table 2). The bromo-analogue 5 appeared to be isostructural
with 1, but good X-ray data could not be obtained at 120 K.
There was no doubt, however, about the connectivities and
overall geometry of the compound, enabling it to be clearly
identified. The molecular structure of 4 is shown in Fig. 2. The
arrangement around Si is approximately tetrahedral, with bond
angles between 106.07(9) and 113.93(9)°. In the crystal, mol-
ecules of 4 are linked together by O–H⋯O hydrogen bonds in
double stranded chains (Fig. 10), formed by alternating OH
groups.21 Such “step-ladder” structures22 are typical for organic
dialcohols.23 In 3 (Fig. 3), the geometry around Si is again
Fig. 7 Molecular structure of 11.
approximately tetrahedral, with bond angles ranging from
102.27(11) to 116.84(12)° (Table 2).
The compound Ar2GeCl2 7 (Fig. 4) has two independent
molecules in the asymmetric unit. There is distorted tetrahedral
geometry about each Ge atom, with the C–Ge–C angle larger
(123.94(19)° for Ge(1), 124.65(19)° for Ge(2)) than the others.
This parallels the structures found for [2,4,6-(CF3)3C6H2]2GeCl2
and [2,4-(CF3)2C6H3]2GeCl2, where the C–Ge–C angles were
120.07(12) and 119.95(10)° respectively.1 The dinuclear struc-
ture 8 (Fig. 5) also has approximately tetrahedral geometry about
each germanium atom, though the largest angle is now C(1)Ge
(1)Ge(1)#1 at 118.40(6)°. While Ge–Ge bonds are quite
common in the literature, with over 350 examples in the Cam-
bridge Structural Database,24 only seven such structures are
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Table 3 Selected bond distances (Å) and angles (°) for 7 and 8
Ar2GeCl2 7
(X = Cl)
Ar2Ge(Br)Ge(Br)Ar2
8 (X = Br)
Compound
Ge(1)-X
Ge(2)-X
Ge(1)-C
Ge(2)-C
2.1420(13)
2.1472(13)
2.1411(12)
2.1491(13)
1.954(4)
1.958(5)
1.954(4)
1.960(5)
—
104.35(5)
104.18(5)
105.16(14)
106.55(14)
107.25(14)
108.02(14)
105.62(14)
106.15(14)
106.81(14)
107.72(14)
123.94(19)
124.65(19)
—
2.3209(3)
—
—
—
1.970(2)
1.972(2)
—
—
Ge-Ge
2.4511(4)
—
—
105.96(6)
107.46(7)
—
—
—
—
—
—
114.71(9)
—
110.27(7)
118.40(6)
97.993(10)
X-Ge(1)-X
X-Ge(2)-X
X-Ge(1)-C
X-Ge(2)-C
C-Ge(1)-C
C-Ge(2)-C
C-Ge(1)-Ge(1)#1
Fig. 8 Molecular structure of 12.
—
—
Br-Ge(1)-Ge(1)#1
Table 2 Selected bond distances (Å) and angles (°) for 1, 3 and 4
Ar2SiCl2 1
(X = Cl)
Ar3SiF 3
(X = F)
Ar2Si(OH)2 4
(X = O)
Table 4 Selected bond distances (Å) and angles (°) for 10, 11 and 12
Compound
Si-X
Compound Ar3SnCl 10 (X = Cl) Ar4Sn 11
Ar3SnBr 12 (X = Br)
2.0384(10)
2.0493(9)
1.886(3)
1.5934(17)
—
1.881(3)
1.883(3)
1.890(3)
1.6284(15)
1.6407(15)
1.878(2)
Sn-X
Sn-C
2.3323(8)
2.140(3)
2.149(3)
2.144(3)
—
—
2.4924(5)
2.155(4)
2.161(4)
2.162(4)
—
Si-C
2.154(3)
2.155(3)
2.167(3)
2.168(3)
1.890(3)
1.892(2)
X-Si-X
X-Si-C
104.52(4)
107.30(9)
107.56(9)
109.29(9)
109.78(9)
117.57(12)
—
106.08(8)
106.07(9)
107.56(8)
108.83(9)
113.77(9)
113.93(9)
—
102.27(11)
107.38(11)
108.35(11)
—
109.67(12)
111.61(12)
116.84(12)
X-Sn-C
C-Sn-C
101.25(8)
107.20(8)
108.70(8)
105.69(12)
110.98(11)
122.11(11)
—
—
—
—
102.30(10)
107.00(10)
109.46(10)
107.87(13) 108.13(14)
108.14(12) 111.35(14)
109.47(12) 117.77(13)
109.92(12)
110.70(12)
110.71(13)
C-Si-C
—
—
—
—
—
—
known with a bromine attached to one or both germanium
atoms.25–29 In these, the Ge–Ge distances range from 2.4191
(9)28 to 2.623(1)27 Å for single bonds, while the Ge–Br bond
lengths vary between 2.337(1)26 and 2.4253(10)28 Å (Table 3).
The Ge–Ge distance in 8 lies towards the shorter end of this
range, while the Ge–Br distance of 2.3209(3) Å is the shortest
yet reported for this type of compound.
The structure of Ar4Sn 11 (Fig. 7), as expected, is very close
to tetrahedral, with C–Sn–C bond angles between 107.87(13)
and 110.71(13)°. The compounds Ar3SnCl, 10 (Fig. 6) and
Ar3SnBr, 12 (Fig. 8), have rather more distorted structures
(Table 4), the largest angle being C(5)–Sn(1)–C(9) at 122.11
(11)° and 117.77(13)° for 10 and 12 respectively. The smallest
angle is C(9)–Sn(1)–Cl(1) and C(9)–Sn(1)–Br(1), at 101.25(8)°
and 102.30(10)° respectively (Table 4).
In all of the new compounds there are comparatively short
contacts between fluorine atoms of ortho-CF3 groups and the
central element E, Table 5, with one such interaction per group.
Fig. 9 Overlay diagram of the four crystallographically independent
molecules in 1 which differ in the orientation of their CF3 groups.
4464 | Dalton Trans., 2012, 41, 4460–4468
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monomer Ar2GeCl2, whereas GeBr4 produces the binuclear
compound Ar2Ge(Br)Ge(Br)Ar2, with a Ge–Ge bond. Reactions
of SiX4 (X = Cl or Br) with ArLi in a 1 : 2 molar ratio led
initially to Ar2SiX2, but a small quantity of Ar3SiX was also
identified by 19F solution-state NMR spectroscopy; this appeared
to exchange readily with F to form Ar3SiF, which has been iso-
lated and fully characterised. X–F exchange has been observed
previously in other organosilicon(IV) halides with CF3-substi-
tuted aromatic groups present.1,3 No such exchange was detected
in the Ge or Sn systems. The hydrolysis product Ar2Si(OH)2
was also characterised by single-crystal X-ray diffraction. With
SnX4, further substitution takes place, and the isolated products
were Ar3SnCl and Ar4Sn for X = Cl, and Ar3SnBr for X = Br. A
1 : 1 reaction between ArLi and SnBr4 yielded the identical
product. All of the new compounds demonstrate short F⋯E con-
tacts from the o-CF3 groups.
Experimental
All manipulations, including NMR sample preparation, were
carried out either under an inert atmosphere of dry nitrogen or
in vacuo, using standard Schlenk line or glovebox techniques.
Chemicals of the best available commercial grade were used, in
general without further purification. The 19F NMR spectrum of
ArH was recorded, to verify that no major impurities were
present. 19F NMR spectra were recorded on a Varian Mercury
300 or Varian VXR 400 Fourier-transform spectrometer at 282.2
and 376.4 MHz, respectively. Chemical shifts were measured
relative to external CFCl3 (19F), with the higher frequency direc-
tion taken as positive. Microanalyses were performed by the
microanalytical services of the Department of Chemistry,
Durham University. Mass measurements were performed in a
Xevo QToF mass spectrometer (Waters Ltd, UK) equipped with
Atmospheric Solids Analysis Probe (ASAP) or a Trace GCMS
(Thermo-Finnigan Corporation) instrument equipped with Elec-
tron Impact (EI) ionization.
Fig. 10 Double chain of hydrogen bonded molecules in structure 4
(CF3-groups and aryl hydrogen atoms are omitted for clarity).
Table 5 Short E⋯F contacts Å in 1, 3, 4, 7, 8, 11 and 12
Compound
E
E⋯F (Å)
Ar2SiCl2 1
Si(1)
Si(2)
Si(3)
Si(4)
Si
2.908, 2.963
2.870, 3.015
2.831, 2.843
2.869, 2.947
Ar3SiF 3
Ar2Si(OH)2 4
Ar2GeCl2 7
2.819, 2.907, 2.932a
2.812, 3.029
Si
Ge(1)
Ge(2)
Ge
Sn
Sn
2.800, 2.815
2.817, 2.823
2.854, 2.924
2.916, 2.962, 2.976
2.883a, 2.884, 2.888, 2.889a
2.788, 2.965, 2.967
Ar2Ge(Br)Ge(Br)Ar2 8
Ar3SnCl 10
Ar4Sn 11
Ar3SnBr 12
Sn
a Average over two disordered positions.
Synthesis
ArLi
(For compounds with disorder in o-CF3 groups, the shortest
F⋯E distances for both of the disordered positions have been
averaged.) These distances are appreciably shorter than the sum
of the van der Waals radii,30 and are comparable with those
reported previously for group 14 derivatives of the 2,4,6-
(CF3)3C6H2, 2,6-(CF3)2C6H3 or 2,4-(CF3)2C6H3 ligands.1,3–19,31
Such interactions have generally been considered to enhance the
stability of the compound concerned, including the dimer of
2,4,6-tris(trifluoromethyl)phenyl lithium diethyletherate.32
WARNING: It is important to keep a slight excess of the hydro-
carbon (ArH) to n-butyllithium at all times, to avoid any attack
on a CF3 group and the possible explosive formation of LiF.
BuLi (18.4 ml, 2.5 M in hexanes; 46 mmol) was added to a
stirred solution of ArH (8 ml; 52 mmol) in diethyl ether (50 ml)
at −78 °C. The resulting dark brown solution was allowed to
warm to room temperature and stirred for four hours. 19F NMR
(376.3 MHz, CD6D6): δ −62.6 ppm (s, ortho F), δ −63.4 ppm
(s, para F).
Conclusions
Ar2SiCl2 1
We have shown that the 2,5-(CF3)2C6H3 (Ar) ligand can be sub-
stituted into group 14 tetrahalides EX4 (E = Si, Ge or Sn; X = Cl
or Br) to form crystalline products, though the extent of substi-
tution varies with E when reactions are carried out in a
1 : 2 molar ratio. For E = Ge, 1 : 2 compounds are obtained,
though their structures differ considerably. GeCl4 forms the
ArLi solution (∼55 ml; 19 mmol) was added dropwise to a sol-
ution of SiCl4 (1.63g; 1 ml; 9.6 mmol) in hexane at −78 °C. The
solution was allowed to warm to room temperature and stirred
for 3 hours. The precipitated LiCl was filtered off, and the sol-
vents and excess SiCl4 were removed in vacuo. Found: C
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 4460–4468 | 4465

Table 6 Crystal data and structure refinement for 1, 3, 4, 7, 8, 10, 11, 12
Compound
Ar2SiCl2 1
16H6Cl2F12Si
525.20
Monoclinic
Cc
Ar2Si(OH)2 4
Ar3SiF 3
Ar2GeCl2 7
Ar2Ge(Br)Ge(Br)Ar2 8
Ar3SnCl 10
Ar4Sn 11
Ar3SnBr 12
Empirical formula
Formula weight
Crystal system
Space group
C
C16H8F12O2Si
488.31
C24H9F19Si
686.40
Monoclinic
P21/n
C16H6Cl2F12Ge
569.70
C32H12Br2F24Ge2
1157.42
Orthorhombic
Pbcn
C24H9ClF18Sn
793.45
C32H12F24Sn
971.11
Monoclinic
Cc
C24H9BrF18Sn
837.91
Triclinic
Triclinic
Triclinic
Triclinic
ˉ
ˉ
ˉ
ˉ
P1
P1
P1
P1
a (Å)
b (Å)
c (Å)
A (°)
19.4317(8)
17.0627(7)
22.8784(9)
90
120.013(1)
90
7419.4(5)
16
1.881
5.2873(2)
11.8255(4)
14.6695(6)
101.73(1)
94.08(1)
97.17(1)
886.62(6)
2
9.6178(4)
9.6651(4)
26.763(1)
90
92.44(1)
90
2485.6(2)
4
1.834
9.7607(3)
12.0194(4)
16.2537(5)
76.83(1)
89.82(2)
86.76(1)
1853.6(1)
4
20.5512(3)
8.80090(10)
20.5700(3)
90
90
90
3720.48(9)
4
2.066
9.9088(7)
11.4937(8)
13.2397(9)
102.992(10)
96.288(10)
109.995(10)
1351.78(16)
2
13.8685(3)
13.7610(3)
17.4025(4)
90
102.68(1)
90
3240.2(1)
4
1.991
9.4168(5)
9.7943(5)
16.2617(8)
102.743(2)
94.800(2)
112.731(2)
1325.3(1)
2
β (°)
γ (°)
Volume,/Å3
Z
ρcalc/mg mm−3
μ mm−1
1.829
0.267
2.041
2.059
1.949
1.183
2.100
2.614
0.533
0.253
3.910
0.953
F(000)
4128
55903
20056/0.0423
1.043
0.0427
0.1019
484
10701
4469/0.0248
1.025
0.0502
1352
21583
5690/0.0709
0.951
0.0525
0.1451
1104
23901
9356/0.0830
0.981
0.0527
2216
30686
5183/0.0390
1.027
0.0291
764
22531
7175/0.0306
1.095
0.0424
1880
19385
8986/0.0152
1.007
0.0359
0.0987
800
13418
5477/0.0283
1.017
0.0391
Reflections collected
Independent/Rint reflections/R(int)
Goodness-of-fit on F2
Final R1 indices[I > 2 σ (I)]
Final wR2 indices [all data]
0.1436
0.1191
0.0774
0.1197
0.1099

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Ar2Ge(Br)Ge(Br)Ar2 8
37.12% H 1.38% N 0.00% (C16H6Cl2F12Si requires C 36.59%
1.15%
0.00%. 19F NMR (282.2 MHz, CDCl3):
H
N
ArLi solution (∼34 ml; 16 mmol) was added dropwise to a sol-
ution of GeBr4 (3.13g; 8.0 mmol) in hexane at −78 °C. The sol-
ution was allowed to warm to room temperature and stirred for
4 hours. The precipitated LiBr was filtered off, and the solvents
and excess GeBr4 were removed in vacuo. Crystals of Ar2Ge(Br)
Ge(Br)Ar2 were isolated. (Found: C 31.42% H 1.06% N 0.00%
(C32H12F24Br2Ge2 requires C 33.21% H 1.05% N 0.00%). 19F
NMR (282.2 MHz, CDCl3): δ −58.4 ppm (s, ortho F), δ
−63.7 ppm (s, para F).
δ −59.1 ppm (s, ortho F), δ −63.7 ppm (s, para F). m/z (EI)
524 ([35Cl,35Cl]M+, 4%), 313 (ArSi37,35Cl2, 86%), 311
(ArSi35,35Cl2, 100%); 1 was also obtained when addition of the
reagents was carried out in reverse order as follows: a solution of
SiCl4 (1.32 ml; 11.5 mmol) in hexane was added dropwise to a
solution of ArLi (∼38 ml; 23 mmol) at −78 °C. The solution
was allowed to warm to room temperature and stirred overnight.
The precipitated LiCl was filtered off, and the solvents and
excess SiCl4 were removed in vacuo.
Ar2SnCl2 9
Ar3SiF 3
This was not an isolated product but was observed by 19F NMR
and GC–MS as part of the reaction mixture. 19F NMR
(282.2 MHz, CDCl3): δ −61.6 (s, ortho F), δ −64.1 ppm
(s, para F). m/z (EI) 585 (Ar2122Sn37Cl+, 16%), 583
(Ar2120,122Sn37,35Cl+, 28%), 581 (Ar2118,120Sn37,35Cl+, 42%),
579 (Ar2118Sn35Cl+, 28%), 369 (Ar119,121Sn37,35Cl+, 96%).
ArLi solution (∼32 ml; 14.9 mmol) was added dropwise to a sol-
ution of SiBr4 (2.79g; 7.45 mmol) at −78 °C. The solution was
allowed to warm to room temperature and stirred for 4 hours.
The precipitated LiBr was filtered off, and the solvents and
excess SiBr4 were removed in vacuo. After 2 days crystals had
formed. These were isolated, washed with hexane and then
recrystallized from diethyl ether. (Found: C 37.68% H 1.46% N
0.00% F 50.19% (C24H9F19Si requires C 42.06% H 1.32%
N 0.00% F 52.59%). 19F NMR (282.2 MHz, CDCl3): δ
−59.2 ppm (d, ortho F), δ −64.1 ppm (s, para F), δ −157.4 ppm
(decet, Si-F), 5JFF 11.2 Hz.
Ar3SnCl 10
A solution of ArLi (∼38 ml; 23 mmol) was added dropwise to a
solution of SnCl4 (1.35 ml; 11.5 mmol) in hexane at −78 °C.
The solution was allowed to warm to room temperature and
stirred overnight. The precipitated LiCl was filtered off, and the
solvents and excess SnCl4 were removed in vacuo. (Found: C
36.11% H 2.53% N 0.00% (C32H12F24Sn requires C 36.33%
H 1.14% N 0.00%). 19F NMR (376.3 MHz, CD6D6): δ
−60.8 ppm (s, ortho F), δ −64.7 ppm (s, para F). m/z (ASAP+)
759 (Ar3120Sn+, 64%), 585 (Ar2122Sn37Cl+, 17%), 583
(Ar2120,122Sn37,35Cl+, 47%) 581 (Ar2118,120Sn37,35Cl, 100%),
579 (Ar2118Sn35Cl, 49%); 10 was also obtained when addition
of the reagents was carried out in reverse order as follows: a sol-
ution of SnCl4 (1.35 ml; 11.5 mmol) in hexane was added drop-
wise to a solution of ArLi (∼38 ml; 23 mmol) at −78 °C. The
solution was allowed to warm to room temperature and stirred
overnight. The precipitated LiCl was filtered off, and the solvents
and excess SnCl4 were removed in vacuo.
Ar2Si(OH)2 4
Crystals of Ar2Si(OH)2 were isolated from an NMR tube con-
taining a sample of Ar2SiCl2 which had been left standing
for several weeks. Found: C 39.83% H 1.82% N 0.00%
(C16H8F12O2Si requires C 39.36% H 1.65% N 0.00%. 19F NMR
(282.2 MHz, CDCl3): δ −59.1 ppm (s, ortho F), δ −63.7 ppm
(s, para F).
Ar2SiBr2 5
ArLi solution (∼55 ml; 23 mmol) was added dropwise to a sol-
ution of SiBr4 (1.42ml, 11.5 mmol) in hexane at −78 °C. The
solution was allowed to warm to room temperature and stirred
for 3 hours. The precipitated LiBr was filtered off, and the sol-
vents and excess SiBr4 were removed in vacuo. Found: C
32.19% H 1.17% N 0.00% (C16H6Br2F12Si requires C 31.29%
H 0.98% N 0.00%. 19F NMR (282.2 MHz, CDCl3): δ
−57.5 ppm (s, ortho F), δ −63.8 ppm (s, para F). m/z (ASAP+)
535 (Ar2Si81Br+, 80%), 533 (Ar2Si79Br+, 80%).
Ar4Sn 11
ArLi solution (∼40 ml; 23 mmol) was added dropwise to a sol-
ution of SnCl4 (3 g; 1.35 ml; 11.5 mmol) in hexane at −78 °C.
The solution was allowed to warm to room temperature and
stirred for 5 hours. The precipitated LiCl was filtered off, and the
solvents and excess SnCl4 were removed in vacuo. Crystals
of Ar4Sn were isolated. 19F NMR (282.2 MHz, CDCl3): δ
−60.2 ppm (s, ortho F), δ −64.0 ppm (s, para F).
Ar2GeCl2 7
ArLi solution (∼36 ml; 18 mmol) was added dropwise to a sol-
ution of GeCl4 (1.94g; 1.05 ml; 9.1 mmol) in hexane at −78 °C.
The solution was allowed to warm to room temperature and
stirred for 4 hours. The precipitated LiCl was filtered off, and the
solvents and excess GeCl4 were removed in vacuo. Crystals of
Ar2GeCl2 were isolated. (Found: C 33.73% H 1.36% N 0.00%
(C16H6F12Cl2Ge requires C 33.73% H 1.06% N 0.00%). 19F
NMR (282.2 MHz, CDCl3): δ −59.1 ppm (s, ortho F), δ
−64.2 ppm (s, para F).
Ar3SnBr 12
ArLi solution (∼30 ml; 13 mmol) was added dropwise to a sol-
ution of SnBr4 (2.82g; 6.5 mmol) in hexane at −78 °C. The sol-
ution was allowed to warm to room temperature and stirred for
5 hours. The precipitated LiBr was filtered off, and the solvents
and excess SnBr4 were removed in vacuo to afford a dark yellow
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 4460–4468 | 4467

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7 H. Grűtzmacher and H. Pritzkow, Angew. Chem., Int. Ed. Engl., 1991, 30,
1017.
8 H. Grűtzmacher, S. Freitag, R. Herbst-Irmer and G. S. Sheldrick, Angew.
Chem., Int. Ed. Engl., 1992, 31, 437.
9 V. Lay, H. Pritzkow and H. Grűtzmacher, J. Chem. Soc., Chem.
Commun., 1992, 260.
10 H. Grűtzmacher and H. Pritzkow, Chem. Ber., 1993, 126, 2409.
11 H. Grűtzmacher, W. Deek, H. Pritzkow and M. Sander, Angew. Chem.,
Int. Ed. Engl., 1994, 33, 456.
solution. Crystals of Ar3SnBr were isolated. (Found: C 34.25%
H 1.81% N 0.00% (C24H9F18BrSn requires C 34.40% H 1.08%
N 0.00%). 19F NMR (282.2 MHz, CDCl3): δ −59.8 ppm
(s, ortho F), δ −64.0 ppm (s, para F).
Crystals of Ar3SnBr 12 were also isolated from a 1 : 1 reaction
of ArLi (∼30 ml; 8.5 mmol) with SnBr4 (3.7 g; 8.5 mmol).
12 S. Brooker, F. T. Edelmann and D. Stalke, Acta Cryst. C, 1991, 47, 2527.
13 J. F. Van der Maelen Uria, M. Belay, F. T. Edelmann and G.
M. Sheldrick, Acta Cryst. C, 1994, 50, 403.
14 S. Freitag, R. Herbst-Irmer, J. T. Ahlemann and H. W. Roesky, Acta
Cryst. C, 1995, 51, 631.
15 J. E. Bender IV, M. M. Banaszak Holl and J. W. Kampf, Organometal-
lics, 1997, 16, 2743.
16 J. E. Bender IV, A. J. Shusterman, M. M. Banaszak Holl and J.
W. Kampf, Organometallics, 1999, 18, 1547.
X-ray crystallography
Single crystal data were collected at 120 K (40 K for 1) using
graphite monochromated Mo Kα radiation (λ = 0.71073 Å)
on Bruker SMART CCD 6000 (compounds 4, 7, 8, 10, 11),
Bruker APEX Proteum M (3) or Bruker SMART CCD
1K (1,12) diffractometers equipped with open flow N2 Cryo-
stream and open flow He Helix (Oxford Cryosystems) cooling
devices.33 The structures were solved using direct methods
and refined by full-matrix least-squares on F2 using SHELXTL34
and Olex 235 software. All non-disordered non-hydrogen atoms
were refined anisotropically, while all disordered atoms were
refined isotropically with s.o.f. = 0.5. Crystal data are given in
Table 6.
17 K. W. Klinkhammer, T. F. Fassler and H. Grűtzmacher, Angew. Chem.,
Int. Ed. Engl., 1998, 37, 124.
18 S. Brooker, J.-K. Buijink and F. T. Edelmann, Organometallics, 1991, 10,
25.
19 H. Voelker, D. Labahn, F. M. Bohnen, R. Herbst-Irmer, H. W. Roesky,
D. Stalke and F. T. Edelmann, New J. Chem., 1999, 23, 905.
20 V. L. Capel, K. B. Dillon, A. E. Goeta, J. A. K. Howard, P. K. Monks,
M. R. Probert, H. J. Shepherd and N. V. Zorina, Dalton Trans., 2011, 40,
1808.
21 M. C. Etter, J. C. MacDonald and J. Bernstein, Acta Cryst. B, 1990, 46,
256.
Acknowledgements
22 V. T. Nguyen, P. D. Ahn, R. Bishop, M. L. Scudder and D. C. Craig,
Eur. J. Org. Chem., 2001, 4489.
23 R. Taylor and C. F. Macrae, Acta Cryst. B, 2001, 57, 815.
24 F. H. Allen, Acta Cryst. A, 1998, 54, 758; CCDC, November 2009
release.
25 M. Weidenbruch, F.-T. Grimm, S. Pohl and W. Saak, Angew. Chem., Int.
Ed. Engl., 1989, 28, 198.
We thank the Maria da Graça Memorial Fund/Chemistry Depart-
ment, University of Durham for financial support (to PKC),
and Dr. J. D. Sellars for his invaluable assistance with mass
spectrometry.
26 M. Veith and E. Werle, Z. Anorg. Allg. Chem., 1992, 609, 20.
27 M. Weidenbruch, A. Hagedorn, K. Peters and H. G. von Schnering,
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28 A. Sekiguchi, Y. Ishida, N. Fukaya, M. Ichinohe, N. Takagi and
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29 C. Schenk and A. Schnepf, Dalton Trans., 2007, 5400.
30 S. S. Batsanov, Experimental Foundations of Structural Chemistry,
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4468 | Dalton Trans., 2012, 41, 4460–4468
This journal is © The Royal Society of Chemistry 2012