Synthesis, structure, and properties of the hexagermane Pri 3Ge(GePh2)4GePri3

Article abstract of DOI:10.1139/cjc-2013-0485

The synthesis of the hexagermane Prⁱ₃Ge(GePh ₂)₄GePrⁱ₃ was achieved starting from the cyclotetragermane (Ph₂Ge)₄.Ring-opening of (Ph ₂Ge)₄ with B

Full text of DOI:10.1139/cjc-2013-0485

533
ARTICLE
Synthesis, structure, and properties of the hexagermane
Pri3Ge(GePh2)4GePri3
Kimberly D. Roewe, James A. Golen, Arnold L. Rheingold, and Charles S. Weinert
Abstract: The synthesis of the hexagermane Pri3Ge(GePh2)4GePri3 was achieved starting from the cyclotetragermane (Ph2Ge)4.
Ring-opening of (Ph2Ge)4 with Br2 yielded Br(GePh2)4Br that was converted to H(GePh2)4H, and this material was treated with two
equiv. of Pri3GeNMe2 to furnish Pri3Ge(GePh2)4GePri3 via the hydrogermolysis reaction. The X-ray crystal structures of (Ph2Ge)4,
Br(GePh2)4Br and Pri3Ge(GePh2)4GePri3 were determined. The hexagermane Pri3Ge(GePh2)4GePri3 represents the longest struc-
turally characterized linear oligogermane reported to date and exhibits physical properties that resemble those of the larger
polygermane systems. The hexagermane is luminescent and interacts with polarized light, appearing pale yellow under one
orientation of polarized light and deep blue under the opposite orientation. The electrochemistry of Pri3Ge(GePh2)4GePri3 was
also explored, and this species exhibits the expected five irreversible oxidation waves.
Key words: germanium, main group chemistry, luminescence, X-ray crystal structure, electrochemistry.
Résumé : La synthèse de l’hexagermane Pri3Ge(GePh2)4GePri3 a été réalisée a` partir d’un cyclotetragermane (Ph2Ge)4. L’ouverture
du cycle de (Ph2Ge)4 en présence de Br2 a donné la molécule Br(GePh2)4Br, qui a été convertie en H(GePh2)4H. Celle-ci est mise en
présence de deux espèces de formule Pri3GeNMe2 de façon a` produire le composé Pri3Ge(GePh2)4GePri3 par hydrogermolyse. On
a ensuite déterminé les structures cristallines de (Ph2Ge)4, Br(GePh2)4Br et de Pri3Ge(GePh2)4GePri3, obtenues par cristallographie
aux rayons X. L’hexagermane de formule Pri3Ge(GePh2)4GePri3 constitue l’oligogermane possédant la plus longue structure
linéaire caractérisée a` ce jour et présente des propriétés physiques ressemblant a` celles des polygermanes de plus grande taille.
L’hexagermane est luminescent et interagit avec la lumière polarisée, apparaissant en jaune pâle sous une lumière polarisée
dans une certaine direction et en bleu foncé sous une lumière polarisée dans la direction opposée. L’analyse électrochimique du
composé Pri3Ge(GePh2)4GePri3 permet de confirmer que ce dernier présente les cinq vagues d’oxydation auxquelles on
s’attendait. [Traduit par la Rédaction]
Mots-clés : germanium, chimie des groupes principaux, luminescence, cristallographie cristallographie aux rayons X, électrochimie.
H(GeMeAr)nMe (Ar = Ph, p-Tol, p-FC6H4, p-F3CC6H4, m-Me2C6H3,
p-(H3CO)C6H4),23 (R2Ge)n, (R = Me. Bun, or Ph),27 and m-(S)-2-methyl-
butylphenyldimethylpolygermane,29 have a number of interesting
and potentially useful properties, including fluorescence and con-
ductivity. These properties might result in germanium-based poly-
mers being used as new materials, especially as the limitations of
silicon-based materials begin to be realized.
Oligogermanes, which are discrete compounds that have defined
compositions and structures, can function as small-molecule models
for the larger polygermane systems.30–34 In addition, these mole-
cules are expected to exhibit physical properties similar to those
of the polygermanes, provided a sufficient number of catenated
germanium atoms can be obtained. We have postulated for some
time that long-chain oligogermanes would behave in this fashion,
since the polygermanes can be regarded as having several arrays
of trans-coplanar germanium atoms. A few of these types of com-
pounds are known, including the long-chain methyl substituted
Introduction
Catenated compounds of the Group 14 elements are of signifi-
cant interest due to their inherent ␴-delocalization, which occurs
though the overlap of the sp3 orbitals on each individual atom
when these atoms are disposed in a trans-coplanar configura-
tion.1,2 A number of polymeric Group 14 catenates have been pre-
pared and characterized, but the exact composition of these species
are unknown. However, it has been postulated that multiple re-
gions of trans-coplanar atoms are present in these molecules that
are terminated by a strong out-of-plane twist. Thus, these mole-
cules can be described as having regions of order that are inter-
rupted by regions of disorder. Of these systems, those containing
silicon2–12 or tin13–21 have been the most extensively studied, but
only a few reports of germanium-containing polymers22–29 have
appeared.
An effective method for the preparation of polygermanes in-
volves the demethanative coupling of germanes, having the gen-
eral formula RR’GeMeH, using a ruthenium-based catalyst,22–25,29
and other preparative routes including the electropolymerization
of germanium halides26,28 have also been described. Polygermanes,
examples of which are [(p-(MeO)3SiC6H4)MeGe]n,22 H(GeMe2)nMe,25
oligogermanes Ge6Me1435 and Ge10Me22 36 However, these two oli-
.
gogermanes have not been fully characterized, and the pentager-
mane Ge5Ph12 represents the longest structurally characterized
oligogermane that has been reported to date.37,38 We have re-
Received 24 October 2013. Accepted 20 January 2014.
K.D. Roewe and C.S. Weinert. Department of Chemistry, Oklahoma State University, Stillwater, OK 74078, USA.
J.A. Golen. Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, USA; Department of
Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093-0358, USA.
A.L. Rheingold. Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093-0358, USA.
Corresponding author: Charles S. Weinert (e-mail: weinert@chem.okstate.edu).
This article is part of a Special Issue commemorating the 14th International Conference on the Coordination and Organometallic Chemistry of Germanium, Tin, and Lead
(ICCOC-GTL 2013) held in Baddeck, NS, July 2013.
Can. J. Chem. 92: 533–541 (2014) dx.doi.org/10.1139/cjc-2013-0485
Published at www.nrcresearchpress.com/cjc on 3 February 2014.

534
Can. J. Chem. Vol. 92, 2014
Scheme 1.
Fig. 1. ORTEP diagram of ClPh2GeGePh2Cl (4). Thermal ellipsoids
are drawn at 50% probability.
cently prepared Ge5Ph12 via the hydrogermolysis reaction and did
not observe any luminescent behavior or unusual optical proper-
ties for this compound; rather, Ge5Ph12 was a colorless solid with
a UV–vis absorbance maximum at 295 nm.37,38
Over the past several years we have employed the hydrogermolysis
reaction for the formation of single germanium–germanium
bonds.30,32,33,38–49 This method employs a germanium amide
R3GeNMe2 and a germanium hydride R’3GeH as starting materials
and proceeds in acetonitrile solvent. The CH3CN solvent acts not
only as a reaction medium but also as a reagent, as we have shown
that the amide R3GeNMe2 is converted in situ to the ␣-germyl
nitrile R3GeCH2CN, and it is this species that is the active reagent
in the Ge–Ge bond forming process.39,50 Using this methodology,
we have prepared an array of linear and branched oligogermanes
that have been characterized using NMR (1H, 13C, 73Ge43,45,46,51
)
spectroscopy, elemental analysis, and in many cases X-ray crystal-
lography. We have endeavored to prepare linear systems having
more than five catenated germanium atoms, with the expectation
that some of these long-chain systems would have physical prop-
erties that would mirror those of the polymeric systems. We have
recently prepared the hexagermane Pri3Ge(GePh2)4GePri3 (1) in
three steps starting from the cyclotetragermane (GePh2)4 (2),
where the final step involves attachment of two germanium at-
oms to the hydride-terminated tetragermane H(GePh2)4H (3) via
the hydrogermolysis reaction.52,53 The hexagermane 1 has been
shown to be luminsescent in CH2Cl2 solution and also displays
dramatic dichroic behavior when observed under opposite direc-
tions of polarized light. The detailed synthesis of 1, as well as an
investigation of its physical properties, are the foci of this article.
Results and discussion
The synthesis of the cyclotetragermane (GePh2)4 (2) was re-
ported in 1986 and was prepared via treatment of Ph2GeCl2 with
sodium metal in refluxing toluene.54 Although this is a reliable
preparative route for 2, the reported yield was only 33%. We have
recently obtained 2 via a different route that illustrates that the
hydrogermolysis reaction can be used for the preparation of
cyclic oligogermanes in addition to the branched and linear
systems (Scheme 1). The preparation of the 1,2-dichlorodigermane
ClPh2GeGePh2Cl (4) was carried out via the literature proce-
dure,42,55 and we have for the first time obtained the X-ray crystal
structure of this material.
An ORTEP diagram of 4 is shown in Fig. 1 and selected bond
distances and angles are collected in Table 1. Compound 4 crystal-
lizes with two independent molecules in the unit cell, and both of
these lie on a two-fold axis of rotation. Molecule 1 is completely
ordered, while molecule 2 is a composite of two orientations hav-
ing Ge(2) and Cl(2) disordered over two positions with relative
occupancies of 50% in each case. The bond lengths listed in
Table 1 for molecule 2 of 4 are an average of these two orienta-
tions. The average Ge–Ge bond distance in 4 in the two molecules
is 2.394(2) Å, which is shorter than the Ge–Ge bond distance in
Ge2Ph6•C6H6 that measures 2.446(1) Å,56 and this is due to the
Table 1. Selected bond distances (Å) and angles (°) for ClPh2GeGePh2Cl (4).
Molecule 1
Molecule 2
Bond distances (Å)
Ge(1)–Ge(1=)
2.397(1)
2.182(2)
1.931(6)
1.879(7)
Ge(2)–Ge(2=)
Ge(2)–Cl(2)
Ge(2)–C(31)
Ge(2)–C(41)
2.391(2)
2.178(3)
2.000(7)
1.953(8)
Ge(1)–Cl(1)
Ge(1)–C(11)
Ge(1)–C(21)
Bond angles (°)
Cl(1)–Ge(1)–C(11)
Cl(1)–Ge(1)–C(21)
C(11)–Ge(1)–C(21)
Cl(1)–Ge(1)–Ge(1=)
C(11)–Ge(1)–Ge(1=)
C(21)–Ge(1)–Ge(1=)
106.4(2)
107.2(2)
110.7(3)
104.67(5)
110.5(2)
116.7(2)
Cl(2)–Ge(2)–C(31)
Cl(2)–Ge(2)–C(41)
C(31)–Ge(2)–C(41)
Cl(2)–Ge(2)–Ge(2=)
C(31)–Ge(2)–Ge(2=)
C(41)–Ge(2)–Ge(2=)
115.4(4)
115.7(3)
105.9(3)
103.36(9)
106.9(2)
109.1(3)
Published by NRC Research Press

Roewe et al.
535
Fig. 2. ORTEP diagram of (Ph2Ge)4 (2). Thermal ellipsoids are drawn
at 50% probability.
Table 2. Selected bond distances (Å) and angles (°)
for Ge4Ph8 (2).
Bond distances (Å)
Ge(1)–Ge(2)
Ge(1)–Ge(4)
Ge(2)–Ge(3)
Ge(3)–Ge(4)
Ge(1)–C(1)
Ge(1)–C(7)
Ge(2)–C(13)
Ge(2)–C(19)
Ge(3)–C(25)
Ge(3)–C(31)
Ge(4)–C(37)
Ge(4)–C(43)
2.4534(4)
2.4580(4)
2.4730(4)
2.4713(4)
1.950(3)
1.952(3)
1.956(3)
1.958(3)
1.956(3)
1.955(3)
1.952(3)
1.958(3)
Bond angles (°)
Ge(1)–Ge(2)–Ge(3)
Ge(2)–Ge(3)–Ge(4)
Ge(3)–Ge(4)–Ge(1)
Ge(4)–Ge(1)–Ge(2)
C(1)–Ge(1)–C(7)
C(13)–Ge(2)–C(19)
C(25)–Ge(3)–C(31)
C(37)–Ge(4)–C(43)
C(1)–Ge(1)–Ge(2)
C(1)–Ge(1)–Ge(4)
C(7)–Ge(1)–Ge(2)
C(7)–Ge(1)–Ge(4)
C(13)–Ge(2)–Ge(1)
C(13)–Ge(2)–Ge(3)
C(19)–Ge(2)–Ge(1)
C(19)–Ge(2)–Ge(3)
C(25)–Ge(3)–Ge(2)
C(25)–Ge(3)–Ge(4)
C(31)–Ge(3)–Ge(2)
C(31)–Ge(3)–Ge(4)
C(37)–Ge(4)–Ge(1)
C(37)–Ge(4)–Ge(3)
C(43)–Ge(4)–Ge(1)
C(43)–Ge(4)–Ge(3)
90.53(1)
89.03(1)
90.46(1)
89.79(1)
107.6(1)
110.3(1)
106.4(1)
105.4(1)
113.03(8)
116.46(8)
113.42(8)
115.87(8)
114.56(8)
115.85(7)
111.43(8)
112.90(8)
118.70(8)
113.20(8)
114.71(8)
114.48(8)
114.81(7)
115.64(8)
116.78(8)
113.75(8)
replacement of two phenyl substituents with two chlorine
atoms, which are both sterically less encumbering and also more
electron-withdrawing.
Compound 4was converted to both the 1,2-dihydride HPh2GeGePh2H
and the 1,2-bis(dimethylamido) compound (Me2N)Ph2GeGePh2(NMe2)
42
via reaction with LiAlH4 and LiNMe2, respectively. These two
products were then combined in acetonitrile solution in dilute
(0.0005 mol/L) conditions to minimize the formation of linear
polymeric products, and provided (GePh2)4 (2) in 78% yield. The 1H
and 13C NMR spectra of 2 match those described in the litera-
ture.54 We have obtained a low-temperature (150 K) X-ray struc-
ture of 2, and an ORTEP diagram is shown in Fig. 2, while the
metric parameters of 2 are collected in Table 2. The average Ge –
Ge bond length in 2 is 2.464(3) Å and the average Ge-Ge-Ge bond
angle is 89.95(1)°, which is nearly identical to the expected 90°
bond angle, and these parameters are also nearly identical to
those reported for the structure that was determined at 22 °C.54
The related species (GeTol2)4 (Tol = p-CH3C6H4)57 is C2 symmetric
and has an average Ge–Ge bond length and angle of 2.4610(7) Å
and 89.02(1)°, respectively. The Ge–Ge distances in the para-tolyl
substituted species are slightly shorter than those in 2, and this
has been observed in some other para-tolyl substituted oligoger-
manes when compared to their phenyl-substituted analogues.42
The average Ge–Ge bond distances in the cyclotetragermanes
Ge4But4Cl4 and Ge4Pri8 are 2.465(2)58 and 2.4745(9) Å,59 respec-
tively, while the average Ge-Ge-Ge bond angles in these species are
89.09(6) and 89.38(2)°. The Ge4 plane in 2 is puckered by 4.6° and
is slightly more distorted than the structure obtained at room
temperature that had a ring puckering of 3.9°. The ring puckering
in Ge4Tol8 is 21.1°, while the corresponding values in the struc-
tures of Ge4But4Cl4 and Ge4Pri8 are 14.6 and 11.9°, respectively. The
structure of 2 is less distorted than those of the other three cy-
clotetragermanes due to the more efficient packing of the phenyl
substituents in 2. The average Ge–Ge bond distance in 2 and
Ge4But4Cl4 are nearly identical despite the presence of the large
tert-butyl groups in Ge4But4Cl4, but these four substituents are
disposed on opposite sides of the Ge4 plane in an alternating
fashion, which alleviates much of the steric strain.
The ring-opening of 2 with molecular bromine yields the 1,4-
dibromo species Br(GePh2)4Br (5) in 54% yield (Scheme 2), which is
similar to the reported reaction of 2 with I2 that yielded the
1,4-diiodo substituted analogue I(GePh2)4I (6).60 The UV–vis spec-
trum of 5 has an absorbance maximum at 278 nm that is slightly
blue-shifted relative to the reported value for the tetragermane
Ge4Ph10 at 282 nm.61 The difference in the position of ␭
for
max
these two species likely stems from the presence of an additional
phenyl group at each of the terminal germanium atoms in
Ge4Ph12, as it has been shown that the ␲-system of the phenyl
rings can perturb the energies of the frontier orbitals in these
molecules such that the HOMO–LUMO gap in Ge4Ph10 is slightly
diminished versus that in 5.
The X-ray crystal structure of 5 was obtained, and an ORTEP
diagram is shown in Fig. 3, while selected bond distances and
angles are collected in Table 3. The six heavy atoms in 5 are all
disposed in a trans-coplanar arrangement and the average Ge–Ge
bond distance in 5 is 2.4473(7) Å. The two Ge–Br bond distances
average 2.3540(8) Å, and the average Ge-Ge-Ge and Ge-Ge-Br bonds
angles are 113.29(3) and 103.65(3)°, respectively. Each of the ger-
manium atoms in 5 is present in a distorted tetrahedral environ-
ment and the Ge–Cipso are all approximately 1.95 Å. The structure
of 5 can be compared to the related 1,4-dihalo substituted tetrager-
manes I(GePh2)4I (6)60 and Cl(GePh2)4Cl (7),62 both of which have
an inversion center along the central Ge–Ge bond that is absent in
Published by NRC Research Press

536
Can. J. Chem. Vol. 92, 2014
Scheme 2.
Fig. 3. ORTEP diagram of Br(GePh2)4Br (5). Thermal ellipsoids are
Table 3. Selected bond distances (Å) and angles (°)
drawn at 50% probability.
for Br(GePh2)4Br (5).
Bond distances (Å)
Ge(1)–Ge(2)
Ge(2)–Ge(3)
Ge(3)–Ge(4)
Ge(1)–Br(1)
Ge(1)–C(1)
Ge(1)–C(7)
Ge(2)–C(13)
Ge(2)–C(19)
Ge(3)–C(25)
Ge(3)–C(31)
Ge(4)–Br(2)
Ge(4)–C(37)
2.4470(7)
2.4548(6)
2.4401(7)
2.3468(8)
1.952(5)
1.944(5)
1.959(5)
1.957(5)
1.964(5)
1.948(5)
2.3612(8)
1.950(5)
1.952(5)
Ge(4)–C(43)
Bond angles (°)
Ge(1)–Ge(2)–Ge(3)
Ge(2)–Ge(3)–Ge(4)
Br(1)–Ge(1)–Ge(2)
Br(1)–Ge(1)–C(1)
C(1)–Ge(1)–Ge(7)
Br(1)–Ge(1)–C(7)
C(1)–Ge(1)–Ge(2)
C(7)–Ge(1)–Ge(2)
Ge(1)–Ge(2)–C(13)
Ge(1)–Ge(2)–C(19)
C(13)–Ge(2)–C(19)
C(13)–Ge(2)–Ge(3)
C(19)–Ge(2)–Ge(3)
Ge(2)–Ge(3)–C(25)
Ge(2)–Ge(3)–C(31)
C(25)–Ge(3)–C(31)
C(25)–Ge(3)–Ge(4)
C(31)–Ge(3)–Ge(4)
Ge(3)–Ge(4)–C(37)
Ge(3)–Ge(4)–C(43)
Br(2)–Ge(4)–Ge(3)
Br(2)–Ge(4)–C(37)
Br(2)–Ge(4)–C(43)
C(37)–Ge(4)–C(43)
115.33(3)
111.25(3)
103.36(3)
104.7(2)
111.6(2)
106.0(2)
110.6(1)
119.2(2)
100.5(1)
112.9(1)
109.4(2)
110.5(2)
108.0(2)
111.2(2)
111.9(2)
108.3(2)
111.3(1)
102.6(2)
118.4(2)
115.3(1)
103.94(3)
104.8(2)
102.8(2)
109.6(2)
5. The average Ge–Ge bond distances in 6 and 7 are 2.4549(5) and
2.445(3) Å, respectively, and so there is a slight increase in the
average Ge–Ge bond distance as the size of the halogen increases.
The germanium–halogen distances in 6 and 7 are 2.5594(4) and
2.134(7), respectively, and the germanium–halogen distance in
5–7 therefore increases with the covalent radius of the halogen
atom. The unique Ge-Ge-Ge bond angles in 6 and 7 measure
114.2(1) and 116.24(8)°, and the Ge-Ge-X bond angles are 103.4(1) and
100.3(2)°, respectively. The Ge4X2 chains in the heavier analogues
5 and 6 are very similar, and that of the chloride-substituted tet-
ragermane 7 differs from those of 5 and 6.
Compound 5 was converted to the hydrogen-terminated tet-
ragermane H(GePh2)4H (3) by reaction with LiAlH4 (Scheme 2). We
had attempted to convert the iodide-substituted species 6 to 3
under identical conditions but obtained a mixture of 3 combined
with several other intractable products. This is likely due to the
more highly reducing nature of the iodide anion that may react
with the LiAlH4 after the iodine is liberated from the Ge4 chain.
However, 5 could reproducibly be converted to 3 in high yield. The
1H NMR spectrum of 3 contains a singlet at ␦ 5.67 ppm arising
from the two equivalent germanium-bound protons of 3, and the
infrared spectrum of 3 contains a ␯Ge-H stretching band at 2000 cm−1.
These values correspond well with those reported for 3 that was
prepared from Ph2GeH2 and ButLi and was identified as a compo-
nent of a product mixture with H(GePh2)3H and H(GePh2)2H. The
them easier to oxidize and also that the introduction of more
highly electron-donating groups at one germanium atom also fa-
cilitates the oxidation of the oligogermanes.49 In addition, we
have observed that linear oligogermanes having aryl substituents
on at least one germanium atom exhibit n – 1 successive irreversible
oxidation waves, where n is equal to the number of germanium
atoms.38,42,52 However, oligogermanes having halide substituents
have not been characterized using these methods, and to our
knowledge only one example of a hydride-terminated oligoger-
mane has been studied by CV and DPV.38
␭max for 3 in its UV–vis spectrum was observed at 257 nm, and this
is blue shifted compared to the corresponding ␭ values for 5
max
and Ge4Ph10, since the orbitals of the hydrogen atoms in 3 do not
interact with the ␴-system of the Ge4 chain.
A number of oligogermane systems have been characterized
using cyclic voltammetry (CV) and differential pulse voltammetry
(DPV),35,38,40,42,45,46,49,52,63 and it has been established that an in-
crease in the degree of catenation in these compounds renders
The CV and DPV of the tetragermane Br(GePh2)4Br (5) were
obtained, and the DPV plot is shown in Fig. 4. Three successive
oxidation waves at 1664, 1840, and 2062 mV were observed in the
DPV, but these three features were not resolved in the CV of 5,
which is typical for oligogermanes having four our more germa-
nium atoms. A fourth wave was repeatedly observed at ca. 680 mV,
Published by NRC Research Press

Roewe et al.
537
Fig. 4. Differential pulse voltammogram of H(GePh2)4H (3, solid
line) and Br(GePh2)4Br (5, dashed line) in CH2Cl2 solution using
0.1 mol/L [Bun4N][PF6] as the supporting electrolyte. Conditions used:
pulse period = 0.1 s, pulse width = 0.05 s, sample time = 0.02 s.
ing 107.95(6) and 105.92(6)° at Ge(2) and Ge(3), respectively. The
nearly tetrahedral environment at the terminal germanium at-
oms is typical when three relatively large substituents need to be
accommodated at a single germanium atom.
The overall geometry of the Ge6 chain in 1 can be regarded from
two different perspectives (Fig. 6). The Ge6 chain can be consid-
ered as being comprised of two sets of three trans-coplanar ger-
manium atoms (Fig. 6a), or the four central germanium atoms of
1 can be considered to be mutually coplanar and arranged in a
trans-fashion (Fig. 6b), with one terminal germanium atom
canted above the plane and the other below. In either case, the
␴-delocalization present in 1 would carry across all six germanium
atoms. However, the second case having four coplanar germa-
38
nium atoms is similar to the structure of Ge5Ph12 but is ex-
tended by one germanium atom, and it is this geometry that
can be used to explain the unusual optical and spectral attri-
butes of 1.
The absorbance maxima for polygermanes (GeR2)n fall into the
range of approximately 290–340 nm,22–29,64 and luminescence
has been reported for some of these materials as well. The
hexagermane 1 has an absorbance maximum (␭max) at 310 nm in
its UV–vis spectrum that is red-shifted relative to those for all
other reported linear oligogermanes, including Ge5Ph12 and
Ge4Ph10 that have ␭max values of 295 and 282 nm, respectively. The
and we have determined that this is due to a trace amount of Br2
that was present in the sample. However in contrast to all previ-
ous investigations, the tetragermane H(GePh2)4H (3) exhibits four
successive oxidation waves in its DPV at 1421, 1772, 1883, and
2101 mV (Fig. 4). The first oxidation of 3 occurs at a less positive
potential than that of 5, and this is expected since 5 contains two
electronegative bromine substituents at the termini of the Ge4
chain. However, the first oxidation of 5 was observed at the same
potential as for Ge4Ph10, suggesting that the highest occupied
molecular orbitals of these two species are at approximately the
same energy.
␭
max for 1 falls within the range observed for polygermanes and is
similar to the values reported for the alkyl-substituted species
(GeR2)n (R = Et, ␭
= 305 nm; R = Prn, ␭ = 300 nm; R = Bun,
max
max
␭
max = 316 nm).64 Thus, the degree of ␴-delocalization present in 1
is similar to those in the polygermane systems.
The hexagermane 1 is luminescent and exhibits a broad emis-
sion band at 370 nm when excited at 312 nm. An overlaid absor-
bance and emission spectrum of 1 is shown in Fig. 7. Hexagermane
1 is the first discrete oligogermane to exhibit luminescent behav-
ior, and its emission wavelength is nearly identical to that of
the polygermane ((Me3SiOC6H4)MeGe)n that was observed at 369 nm.22
This indicates that oligogermanes might function as useful small-
molecule models for the larger polymeric systems. In addition to
its luminescence, 1 also interacts with polarized light in dramatic
fashion (Fig. 8). When viewed under ambient light, crystals of 1
appear colorless, and when viewed under left-polarized light they
appear pale yellow in color. However, when the direction of po-
larization is reversed, crystals of 1 appear deep blue in color. This
phenomenon is due to the packing of 1 in the crystal (Fig. 8),
where the four trans-coplanar germanium atoms are stacked in
a columnar fashion and the remaining two germanium atoms
that are canted above and below the plane are also disposed in
a column-like fashion. This imparts long-range chirality for 1 in
the solid state, which leads to their observed dichroism.
The DPV of 1 is shown in Fig. 9. The expected pattern of five
irreversible oxidation waves was observed with features at 1100,
1383, 1785, 1942, and 2182 mV. The first oxidation wave for 1 was
observed at a lower potential than other linear oligogermanes
characterized by this method, and this indicates that the
␴-bonding HOMO of 1, which is presumably the source of the first
electron that is removed, is destabilized relative to those in other
oligogermanes having less than six catenated germanium atoms.
We have endeavored to ascertain the reasons that n – 1 oxidation
waves are observed for these systems. By analogy to photolytic
investigations,64 we postulate that three possible decomposition
pathways might be occurring after an oxidation event takes place.
A proposed decomposition pathway for 1 after the first oxidation
event occurs is shown in Scheme 4. The possible decomposition
pathways include germylene extrusion with concomitant chain
contraction by one germanium atom, homolytic cleavage of a
germanium–germanium single bond to generate two germanium-
based radicals, or homolytic Ge–Ge bond cleavage with simulta-
neous germylene extrusion followed be recombination of the two
radical species to generate a new oligogermane. The decomposi-
The tetragermane 3 was converted to the hexagermane
Pri3Ge(GePh2)4GePri3 (1) via the hydrogermolysis reaction using
Pri3GeNMe2 in 76% yield (Scheme 3). This reaction proceeds via
the in situ conversion of Pri3GeNMe2 to the ␣-germyl nitrile
Pri3GeCH2CN by the acetonitrile solvent,39 where Pri3GeCH2CN is
the active species in the germanium–germanium bond forming
1
process. The H NMR spectrum of 1 exhibits a characteristic pat-
tern for the six iso-propyl substituents with a septet at ␦ 1.48 ppm
(J = 7.2 Hz) corresponding to the methine protons and a doublet at
␦ 0.89 ppm (J = 7.2 Hz) for the methyl groups. The 13C NMR spec-
trum of 1 contains two resonances at ␦ 21.2 and 18.2 ppm that are
assigned to the germanium-bound carbon atom and the methyl
carbon atoms, respectively.
The X-ray crystal structure of 1 was determined, and an ORTEP
diagram is shown in Fig. 5, and selected bond distances and angles
are collected in Table 4. Compound 1 crystallizes in the P–1 space
group, and the central Ge–Ge single bond of 1 is located on the
inversion center. The germanium–germanium bond distances av-
erage 2.4710(3) Å, and the longest of the three crystallographically
unique Ge–Ge bond distances is at the central bond. However, the
two terminal Ge–Ge bond distances each measure 2.4670(2) and
are elongated compared to the typical distance of ca. 2.45 Å due to
the presence of three sterically encumbering iso-propyl groups at
each atom. Compound 1 is the longest structurally characterized
oligogermane to be reported to date, and the length across the Ge6
chain in 1 measures 12.3515(3) Å.
Each of the germanium atoms in 1 are present in a distorted
tetrahedral environment. The average of the two unique Ge-Ge-Ge
bond angles is 115.74(1)°, and the more obtuse of the two angles are
located at the ends of the molecule, again due to the steric effects
of the iso-propyl substituents. The average C-Ge-C bond angle at
the terminal germanium atoms is 108.74(7)°, which is close to the
idealized tetrahedral angle of 109.5°, while the C-Ge-C bond angles
at the internal germanium atoms are slightly more acute, measur-
Published by NRC Research Press

538
Can. J. Chem. Vol. 92, 2014
Scheme 3.
Fig. 5. ORTEP diagram of Pri3Ge(GePh2)4GePri3 (1). Thermal
ellipsoids are drawn at 50% probability.
Fig. 6. Structure of the Ge6 skeleton of 1, viewed as two sets of three
coplanar Ge atoms (a) or one array of four coplanar Ge atoms (b).
Fig. 7. Absorbance (solid line) and emission spectra (dashed line) of
1 in CH2Cl2 solution.
Table 4. Selected bond distances (Å) and angles (°)
for Pri3Ge(GePh2)4GePri3 (1).
Bond distances (Å)
Ge(1)–Ge(2)
Ge(2)–Ge(3)
2.4670(2)
2.4715(3)
2.4745(3)
1.995(2)
1.989(2)
1.995(2)
1.970(2)
1.955(2)
1.967(2)
1.968(2)
Ge(3)–Ge(3=)
Ge(1)–C(1)
Ge(1)–C(4)
Ge(1)–C(7)
Ge(2)–C(10)
Ge(2)–C(16)
Ge(3)–C(22)
Ge(3)–C(28)
Bond angles (°)
Ge(1)–Ge(2)–Ge(3)
Ge(2)–Ge(3)–Ge(3=)
C(1)–Ge(1)–C(4)
C(1)–Ge(1)–C(7)
C(4)–Ge(1)–C(7)
C(1)–Ge(1)–Ge(2)
C(4)–Ge(1)–Ge(2)
C(7)–Ge(1)–Ge(2)
C(10)–Ge(2)–C(16)
C(10)–Ge(2)–Ge(1)
C(16)–Ge(2)–Ge(1)
C(10)–Ge(2)–Ge(3)
C(16)–Ge(2)–Ge(3)
C(22)–Ge(3)–C(28)
C(22)–Ge(3)–Ge(2)
C(28)–Ge(3)–Ge(2)
C(22)–Ge(3)–Ge(3=)
C(28)–Ge(3)–Ge(3=)
117.330(8)
114.15(1)
108.74(7)
108.48(7)
108.99(7)
111.91(4)
109.19(5)
109.49(5)
107.95(6)
110.80(4)
107.71(4)
100.93(4)
111.71(4)
105.92(6)
115.68(4)
99.69(4)
108.47(4)
112.43(4)
tion products are then oxidized as the sweep continues, and all
three sets of possible products shown in Scheme 4 would lead to
four additional oxidation events. It is at present unclear which
decomposition pathway is occurring for 1, and we will investigate
this in more detail by conducting bulk electrolysis experiments
on 1 in the presence of the germylene trapping reagents 2,3-
dimethyl-1,3-butadiene (DMB),65 benzil, acetic acid,66 and 1,2-
diphenylacetlyene,67 and also will conduct similar studies using
lower oligogermanes.
Conclusions
The hexagermane 1 has been prepared and characterized and
represents the longest structurally characterized linear oligoger-
Published by NRC Research Press

Roewe et al.
539
Fig. 8. Single crystals of 1 viewed under left-polarized light (a) and right-polarized light (b) and the crystal packing of 1 viewed along the
b-axis (c).
Fig. 9. Differential pulse voltammogram of 1 in CH2Cl2 solution
using 0.1 mol/L [Bun4N][PF6] as the supporting electrolyte. Conditions
used: pulse period = 0.1 s, pulse width = 0.05 s, sample time = 0.02 s.
Synthesis of Me2NPh2GeGePh2NMe2
To a solution of ClPh2GeGePh2Cl (0.546 g, 1.04 mmol) in ben-
zene (20 mL) was added LiNMe2 (0.117 g, 2.29 mmol). The reaction
mixture was stirred for 18 h, filtered through Celite, and the
solvent was removed from the filtrate in vacuo to yield
1
Me2NPh2GeGePh2NMe2 (0.518 g, 92%) as a pale yellow solid. H
NMR (C6D6, 25 °C) ␦ 7.71–7.68 (m, 8H, o-H), 7.21–7.18 (m, 12H, m-H
and p-H), 2.78 (s, 12H, –N(CH3)2) ppm. 13C NMR (C6D6, 25 °C) ␦ 136.3
(ipso-C), 135.5 (o-C), 129.6 (p-C), 128.7 (m-C), 42.0 (–N(CH3)2) ppm.
Anal. calcd. for C28H32Ge2N2: C, 62.05; H, 5.96. Found: C, 61.89; H,
5.88.
Synthesis of (Ph2Ge)4 (2)
To a solution of Me2NPh2GeGePh2NMe2 (0.461 g, 0.851 mmol) in
CH3CN (170 mL) was added a solution of HPh2GeGePh2H (0.388,
0.851 mmol) in CH3CN (170 mL). The reaction mixture was sealed
in a Schlenk tube and was heated at 85 °C for 48 h. The volatiles
were removed in vacuo to yield a white solid that was recrystal-
lized from hot toluene to yield 2 (0.602 g, 78%) as colorless crystals.
1H NMR (C6D6, 25 °C) ␦ 7.56–7.52 (m, 16H, m-H), 7.09–6.98 (m, 24H,
o-H and p-H) ppm. 13C NMR (C6D6, 25 °C) ␦ 139.5 (ipso-C), 136.5 (o-C),
128.5 (m-C), 128.7 (p-C) ppm. Anal. calcd. for C48H40Ge4: C, 63.52; H,
4.45. Found: C, 63.44; H, 4.48.
mane to be reported to date. The synthesis of 1 employs the
cyclotetragermane 2 as the starting material, and it has been dem-
onstrated that 2 can be synthesized using the hydrogermolysis reac-
tion. Compound 1 is a discrete oligogermane that possesses some
of the properties that are known for polygermane systems and is
the first such species to exhibit luminescent behavior. Compound
1 also interacts in with different orientations of polarized light,
appearing pale yellow under one orientation and deep blue under
the other. Thus, 1 serves as a discrete small molecule model for the
larger polygermane systems and likely is the first member of a
series of long-chain oligogermanes that will possess useful optical
and electronic properties.
Synthesis of Br(GePh2)4Br (5)
A suspension of 2 (1.69 g, 1.86 mmol) in benzene (100 mL) was
titrated with a 0.059 mol/L solution of bromine in benzene, until
the solution remained colorless. The volatiles were removed in
vacuo and the resulting solid was washed with Et2O (3 × 5 mL) and
1
dried in vacuo to yield 3 (1.06 g, 54%) as a white solid. H NMR
(C6D6, 25 °C) ␦ 7.60 (d, J = 7.8 Hz, 8 H, o-C6H5), 7.41 (d, J = 7.5 Hz, 8 H,
o-C6H5), 7.06–6.90 (m, 24 H, m-C6H5 and p-C6H5) ppm. 13C NMR
(C6D6, 25 °C) ␦ 136.7 (ipso-C6H5), 134.7 (ipso-C6H5), 130.0 (o-C6H5),
129.4 (o-C6H5), 128.8 (m-C6H5), 128.6 (m-C6H5), 128.1 (p-C6H5), 127.9
(p-C6H5) ppm. Calcd. for C48H40Br2Ge4: C, 54.00; H, 3.78. Found: C,
53.87; H, 3.83.
Experimental section
Synthesis of H(GePh2)4H (3)
All manipulations were carried out under a nitrogen atmo-
sphere using standard Schlenk, syringe, and glovebox techniques.
Solvents were purified using a Glass Contour solvent purification
system. The reagents ClPh2GeGePh2Cl (4),42 HPh2GeGePh2H,42
Pri3GeNMe239 were prepared using literature procedures. The re-
agents Br2 and LiAlH4 were purchased from Sigma-Aldrich and
To a solution of 5 (1.20 g, 1.12 mmol) in Et2O (60 mL) was added
LiAlH4 (0.09 g, 2 mmol) under blowing nitrogen. The reaction
mixture was stirred for 18 h at room temperature and the volatiles
were removed in vacuo. The resulting material was taken up in
benzene and filtered through Celite. The benzene was removed in
vacuo, and the resulting solid was washed with hexane (3 × 5 mL)
and dried in vacuo to yield 3 (1.00 g, 98%) as a white solid. 1H NMR
(C6D6, 25 °C) ␦ 7.50 (d, J = 6.3 Hz, 8 H, o-C6H5), 7.38 (d, J = 6.3 Hz, 8 H,
o-C6H5), 7.04–6.95 (m, 24 H, m-C6H5 and p-C6H5), 5.63 (s, 2H, -Ge-H)
ppm. 13C NMR (C6D6, 25 °C) ␦ 136.5 (ipso-C6H5), 136.0 (ipso-C6H5),
128.9 (o-C6H5), 128.8 (o-C6H5), 128.5 (m-C6H5), 128.3 (m-C6H5), 128.1
(p-C6H5), 127.7 (p-C6H5) ppm. Anal. calcd. for C48H42Ge4: C, 63.37; H,
4.66. Found: C, 63.26; H, 4.59.
1
used without further purification. H and 13C NMR spectra were
recorded at 300 and 75.46 MHz, respectively, using an INOVA
Gemini 2000 spectrometer. IR spectra were obtained using a
PerkinElmer 1720 infrared spectrometer, and UV–vis spectra were
recorded using a Hewlett-Packard 8453 diode array spectrometer.
Electrochemical data (CV, DPV, LSV, BE) data were obtained using
a DigiIvy DY2312 potentiostat using a glassy carbon working elec-
tron, a platinum wire counter electrode, and an Ag/AgCl reference
electrode in CH2Cl2 solution using 0.1 mol/L [Bu4N][PF6] as the
supporting electrolyte. Elemental analyses were conducted by
Galbraith Laboratories.
Synthesis of Pri3Ge(GePh2)4GePri3 (1)
To a solution of Pri3GeNMe2 (0.203 g, 0.824 mmol) in CH3CN
(15 mL) was added a solution of 4 (0.43 g, 0.47 mmol) in CH3CN
Published by NRC Research Press

540
Can. J. Chem. Vol. 92, 2014
Scheme 4.
Table 5. Crystallographic data for 1, 2, 4, and 5.
Compound
4
2
5
1
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
␣ (°)
␤ (°)
C
24H30Cl2Ge2
C48H40Ge4
907.16
150(2)
0.71073
Monoclinic
P21/c
21.0256(7)
10.2387(3)
20.4770(7)
90
115.583(2)
90
3976.0(2)
4, 0
1.515
3.028
C48H40Br2Ge4
1066.98
100(2)
1.54178
Monoclinic
P21
12.8805(2)
11.9670(2)
13.7534(2)
90
92.259(1)
90
2111.04(6)
2, 0
1.679
C66H82Ge6
1310.86
100(2)
0.71073
Triclinic
P-1
11.0685(7)
11.3771(6)
12.7949(8)
97.447(2)
91.495(2)
108.292(2)
1513.1(2)
1, 0
524.48
100(2)
0.71073
Monoclinic
C2
14.947(5)
11.754(4)
13.109(5)
90
108.573(4)
90
2183(1)
4, 2
1.596
3.006
1048
␥ (°)
V (Å3)
Z, Z=
␳ (g·cm−1
)
1.439
2.980
670
0.30 × 0.25 × 0.20
1.91 to 28.36°
Absorption coefficient (mm−1
F(000)
)
5.751
1052
0.27 × 0.24 × 0.22
3.23 to 68.08°
1824
0.20 × 0.10 × 0.10
1.07 to 26.52°
Crystal size (mm3)
␪ range for data collection
Index ranges
0.40 × 0.12 × 0.08
1.64 to 24.83
−17 ≤ h ≤ 17
−13 ≤ k ≤ 13
−15 ≤ l ≤ 15
14 519
3719 (Rint = 0.0906)
␪ = 24.83 (98.7%)
Multi-scan
Full-matrix
least-squares on F2
3719/1/274
−26 ≤ h ≤ 25
−12 ≤ k ≤ 11
−25 ≤ l ≤ 25
−15 ≤ h ≤ 12
−13 ≤ k ≤ 14
−16 ≤ l ≤ 16
13 170
6320 (Rint = 0.0445)
␪ = 66.50 (97.5%)
Multi-scan
Full-matrix
least-squares on F2
6320/1/488
−14 ≤ h ≤ 12
−11 ≤ k ≤ 15
−17 ≤ l ≤ 16
16 375
7179 (Rint = 0.0221)
␪ = 25.00 (97.6%)
Multi-scan
Full-matrix
least-squares on F2
7179/0/325
Reflections collected
Independent reflections
Completeness to ␪
Absorption correction
Refinement method
28 504
8180 (Rint = 0.0352)
␪ = 25.00 (99.7%)
Multi-scan/SADABS
Full-matrix
least-squares on F2
8180/0/469
Data/restraints/parameters
Goodness-of-fit on F2
1.130
1.040
1.019
1.040
Final R indices (I < 2␴(I))
R1
wR2
0.0955
0.2438
0.0327
0.0689
0.0362
0.0890
0.0197
0.0472
Final R indices (all data)
R1
0.1017
0.0500
0.0376
0.0244
wR2
0.2479
0.0741
0.0902
0.0487
Largest diff. peak and
1.870 and −0.948
0.889 and −0.669
0.791 and −0.561
0.397 and −0.366
hole (e Å−3
)
(15 mL). The reaction mixture was sealed in a Schlenk tube and
was stirred in an oil bath at 90 °C for 72 h, after which a white
precipitate was present. The reaction mixture was cooled and the
solid was collected by filtration and washed with hexane (3 × 5 mL)
to yield 1 (0.33 g, 53%) as a white solid. 1H NMR (C6D6, 25 °C) ␦ 7.39
(d, J = 7.5 Hz, 8 H, o-C6H5), 7.34 (d, J = 7.5 Hz, 8 H, o-C6H5), 7.15–6.96
(m, 24 H, m-C6H5 and p-C6H5), 1.48 (sept, J = 7.2 Hz, 6H, –CH(CH3)2),
0.89 (d, J = 7.2 Hz, 18 H, –CH(CH3)2) ppm. 13C NMR (C6D6, 25 °C) ␦
137.3 (ipso-C6H5), 137.0 (ipso-C6H5), 128.3 (o-C6H5), 128.2 (o-C6H5),
128.1 (m-C6H5), 127.9 (m-C6H5), 127.7 (p-C6H5), 127.6 (p-C6H5), 21.2
(–CH(CH3)2), 18.2 (–CH(CH3)2) ppm. Anal. calcd. for C66H82Ge6: C,
60.44; H, 6.31. Found: C, 60.36; H, 6.36.
Published by NRC Research Press

Roewe et al.
541
(27) Kobayashi, S.; Cao, S. Chem. Lett. 1993, 1385.
(28) Okano, M.; Takeda, K.; Toriumi, T.; Hamano, H. Electrochim. Acta 1998, 44,
659. doi:10.1016/S0013-4686(98)00173-X.
(29) Motonaga, M.; Nakashima, H.; Katz, S.; Berry, D. H.; Imase, T.; Kawauchi, S.;
Watanabe, J.; Fujiki, M.; Koe, J. R. J. Organomet. Chem. 2003, 685, 44. doi:10.
1016/S0022-328X(03)00236-5.
(30) Amadoruge, M. L.; Weinert, C. S. Chem. Rev. 2008, 108, 4253. doi:10.1021/
cr800197r.
(31) Weinert, C. S. In Comprehensive Organometallic Chemistry III; Crabtree, R. H.,
Mingos, D. M. P., Eds.; Elsevier: London, 2006; Vol. 3, p. 699.
(32) Weinert, C. S. Dalton Trans. 2009, 1691. doi:10.1039/B816067H.
(33) Weinert, C. S. Comments Inorg. Chem. 2011, 32, 55. doi:10.1080/02603594.2011.
618854.
(34) Dräger, M. Rev. Silicon Germanium Tin Lead Cmpd. 1983, 7, 299.
(35) Okano, M.; Mochida, K. Chem. Lett. 1990, 701. doi:10.1246/cl.1990.701.
(36) Mochida, K.; Hata, R.; Chiba, H.; Seki, S.; Yoshida, Y.; Tagawa, S. Chem. Lett.
1998, 263. doi:10.1246/cl.1998.263.
(37) Roller, S.; Dräger, M. J. Organomet. Chem. 1986, 316, 57. doi:10.1016/0022-
328X(86)82075-7.
(38) Samanamu, C. R.; Amadoruge, M. L.; Schrick, A. C.; Chen, C.; Golen, J. A.;
Rheingold, A. L.; Materer, N. F.; Weinert, C. S. Organometallics 2012, 31, 4374.
doi:10.1021/om300385n.
(39) Amadoruge, M. L.; DiPasquale, A. G.; Rheingold, A. L.; Weinert, C. S.
J. Organomet. Chem. 2008, 693, 1771. doi:10.1016/j.jorganchem.2008.01.045.
(40) Amadoruge, M. L.; Gardinier, J. R.; Weinert, C. S. Organometallics 2008, 27,
3753. doi:10.1021/om800240w.
(41) Amadoruge, M. L.; Golen, J. A.; Rheingold, A. L.; Weinert, C. S. Organometallics
2008, 27, 1979. doi:10.1021/om800040f.
(42) Amadoruge, M. L.; Short, E. K.; Moore, C.; Rheingold, A. L.; Weinert, C. S.
J. Organomet. Chem. 2010, 695, 1813. doi:10.1016/j.jorganchem.2010.04.015.
(43) Amadoruge, M. L.; Yoder, C. H.; Conneywerdy, J. H.; Heroux, K.;
Rheingold, A. L.; Weinert, C. S. Organometallics 2009, 28, 3067. doi:10.1021/
om900035r.
(44) Samanamu, C. R.; Amadoruge, M. L.; Weinert, C. S.; Golen, J. A.;
Rheingold, A. L. Phosphorus Sulfur Silicon Relat. Elem. 2011, 186, 1389. doi:10.
1080/10426507.2010.543114.
(45) Samanamu, C. R.; Amadoruge, M. L.; Yoder, C. H.; Golen, J. A.; Moore, C. E.;
Rheingold, A. L.; Materer, N. F.; Weinert, C. S. Organometallics 2011, 30, 1046.
doi:10.1021/om101091c.
(46) Samanamu, C. R.; Materer, N. F.; Weinert, C. S. J. Organomet. Chem. 2012, 698,
62. doi:10.1016/j.jorganchem.2011.10.026.
(47) Subashi, E.; Rheingold, A. L.; Weinert, C. S. Organometallics 2006, 25, 3211.
doi:10.1021/om060115x.
(48) Schrick, A. C.; Weinert, C. S. Mater. Res. Bull. 2013, 48, 4390. doi:10.1016/j.
materresbull.2013.05.113.
X-ray crystal structure determinations
Diffraction intensity data were collected with a Siemens P4/CCD
diffractometer. Crystallographic data for the X-ray analysis of 1, 2,
4, and 5 are collected in Table 5. The crystal-to-detector distance
was 60 mm, and the exposure time was 20 s per frame using a scan
width of 0.5°. The data were integrated using the Bruker SAINT
software program. Solution by direct methods (SIR-2004) pro-
duced a complete heavy atom phasing model consistent with the
proposed structures. All non-hydrogen atoms were refined aniso-
tropically by full-matrix least-squares (SHELXL-97). All hydrogen
atoms were placed using a riding model. Their positions were
constrained relative to their parent atom using the appropriate
HFIX command in SHELXL-97.
Supplementary data
Supplementary data are available with the article through the
journal Web site at http://nrcresearchpress.com/doi/suppl/10.1139/
cjc-2013-0485.
Acknowledgements
Funding for this work was provided by a CAREER grant from the
National Science Foundation (No. CHE-0844758) and is gratefully
acknowledged.
References
(1) Balaji, V.; Michl, J. Polyhedron 1991, 10, 1265. doi:10.1016/S0277-5387(00)
86103-3.
(2) Miller, R. D.; Michl, J. Chem. Rev. 1989, 89, 1359. doi:10.1021/cr00096a006.
(3) Corey, J. Y. Adv. Organomet. Chem. 2004, 51, 1. doi:10.1016/S0065-3055(03)
51001-2.
(4) Feigl, A.; Bockholt, A.; Weis, J.; Rieger, B. Adv. Polym. Sci. 2010, 235, 1. doi:10.
1007/12_2009_1.
(5) Jones, R. G.; Holder, S. J. Polym. Int. 2006, 55, 711. doi:10.1002/pi.1945.
(6) Lambert, J. B.; Pflug, J. L.; Wu, H.; Liu, X. J. Organomet. Chem. 2003, 685, 113.
doi:10.1016/S0022-328X(03)00640-5.
(7) Lukevics, E.; Pudova, O. Main Group Met. Chem. 1998, 21, 123. doi:10.1515/
MGMC.1998.21.3.123.
(8) Marschner, C.; Baumgartner, J.; Wallner, A. Dalton Trans. 2006, 5667. doi:10.
1039/b613642g.
(9) Nanjo, M.; Sekiguchi, A. Adv. Silicon Sci. 2009, 2, 75. doi:10.1007/978-1-4020-
8174-3_4.
(10) Krempner, C. Polymers 2012, 4, 408. doi:10.3390/polym4010408.
(11) Miller, R. D.; Schellenberg, F. M.; Baumert, J. C.; Looser, H.; Shukla, P.;
Torruellas, W.; Bjorklund, G. C.; Kano, S.; Takahashi, Y. In Materials for
Nonlinear Optics: Chemical Perspectives (ACS Symposium Series No. 455); Marder,
S. R., Sohn, J. E., Stucky, G. D., Eds.; American Chemical Society: Washing-
ton DC, 1991.
(49) Schrick, E. K.; Forget, T. J.; Roewe, K. D.; Schrick, A. C.; Moore, C. E.;
Golen, J. A.; Rheingold, A. L.; Materer, N. F.; Weinert, C. S. Organometallics
2013, 32, 2245. doi:10.1021/om400132z.
(50) Samanamu, C. R.; Rheingold, A. L.; Weinert, C. S. J. Organomet. Chem. 2011,
696, 3721. doi:10.1016/j.jorganchem.2011.08.029.
(51) Weinert, C. S. ISRN Spectrosc. 2012, Article ID 718050. doi:10.5402/2012/
718050.
(52) Roewe, K. D.; Rheingold, A. L.; Weinert, C. S. Chem. Commun. 2013, 49, 8380.
doi:10.1039/c3cc45450a.
(53) Ritter, S. K. Chem. Eng. News 2013, 91, 6.
(12) West, R. J. Organomet. Chem. 1986, 300, 327. doi:10.1016/0022-328X(86)
84068-2.
(13) Khan, A.; Gossage, R. A.; Foucher, D. A. Can. J. Chem. 2010, 88 (10), 1046.
doi:10.1139/V10-130.
(54) Ross, L.; Dräger, M. J. Organomet. Chem. 1980, 199, 195. doi:10.1016/S0022-
328X(00)83852-8.
(55) Simon, D.; Häberle, K.; Dräger, M. J. Organomet. Chem. 1984, 267, 133. doi:10.
1016/0022-328X(84)80168-0.
(14) Sita, L. R. Organometallics 1992, 11, 1442. doi:10.1021/om00040a007.
(15) Sita, L. R. Acc. Chem. Res. 1994, 27, 191. doi:10.1021/ar00043a002.
(16) Sita, L. R. Adv. Organomet. Chem. 1995, 38, 189. doi:10.1016/S0065-3055(08)
60429-3.
(17) Beckmann, J.; Duthie, A.; Grassmann, M.; Semisch, A. Organometallics 2008,
27, 1495. doi:10.1021/om8000026.
(56) Dräger, M.; Ross, L. Z. Anorg. Allg. Chem. 1980, 469, 115. doi:10.1002/zaac.
19804690117.
(57) Rupar, P. A.; Jennings, M. C.; Baines, K. M. Organometallics 2008, 27, 5043.
doi:10.1021/om800368d.
(58) Sekiguchi, A.; Yatabe, T.; Naito, H.; Kabuto, C.; Sakurai, H. Chem. Lett. 1992,
1697. doi:10.1246/cl.1992.1697.
(18) Choffat, F.; Smith, P.; Caseri, W. Adv. Mater. 2008, 20, 2225. doi:10.1002/adma.
200702268.
(19) Trummer, M.; Choffat, F.; Rami, M.; Smith, P.; Caseri, W. Phosphorus Sulfur
Silicon Relat. Elem. 2011, 186, 1330. doi:10.1080/10426507.2010.543100.
(20) Trummer, M.; Choffat, F.; Smith, P.; Caseri, W. Macromol. Rapid Commun.
2012, 33, 448. doi:10.1002/marc.201100794.
(59) Mochida, K.; Kawajiri, Y.; Goto, M. Bull. Chem. Soc. Jpn. 1993, 66, 2773. doi:10.
1246/bcsj.66.2773.
(60) Dräger, M.; Simon, D. Z. Anorg. Allg. Chem. 1981, 472, 120. doi:10.1002/zaac.
19814720114.
(61) Roller, S.; Simon, D.; Dräger, M. J. Organomet. Chem. 1986, 301, 27. doi:10.1016/
0022-328X(86)82053-8.
(21) Trummer, M.; Nauser, T.; Lechner, M.-L.; Uhlig, F.; Caseri, W. Polym. Degrad.
Stab. 2011, 96, 1841. doi:10.1016/j.polymdegradstab.2011.07.012.
(22) Huo, Y.; Berry, D. H. Chem. Mater. 2005, 17, 157. doi:10.1021/cm0490524.
(23) Katz, S. M.; Reichl, J. A.; Berry, D. H. J. Am. Chem. Soc. 1998, 120, 9844.
doi:10.1021/ja981806q.
(24) Reichl, J. A.; Berry, D. H. Adv. Organomet. Chem. 1998, 43, 197. doi:10.1016/
S0065-3055(08)60671-1.
(25) Reichl, J. A.; Popoff, C. M.; Gallagher, L. A.; Remsen, E. E.; Berry, D. H. J. Am.
Chem. Soc. 1996, 118, 9430. doi:10.1021/ja961777o.
(26) Kashimura, S.; Ishifune, M.; Yamashita, N.; Bu, H.-B.; Takebayashi, M.;
Kitajima, S.; Yoshiwara, D.; Kataoka, Y.; Nishida, R.; Kawasaki, S.;
Murase, H.; Shono, T. J. Org. Chem. 1999, 64, 6615. doi:10.1021/jo990180z.
(62) Häberle, K.; Dräger, M. J. Organomet. Chem. 1986, 312, 155. doi:10.1016/0022-
328X(86)80294-7.
(63) Mochida, K.; Hodota, C.; Hata, R.; Fukuzumi, S. Organometallics 1993, 12, 586.
doi:10.1021/om00026a052.
(64) Mochida, K.; Chiba, H. J. Organomet. Chem. 1994, 373, 45. doi:10.1016/0022-
328X(94)80104-5.
(65) Leigh, W. J.; Toltl, N. P.; Apodaca, P.; Castruita, M.;
Pannell, K. H. Organometallics 2000, 19, 3232. doi:10.1021/om000174p.
(66) Huck, L. A.; Leigh, W. J. Organometallics 2007, 26, 1339. doi:10.1021/
om0609362.
(67) Harrington, C. R.; Leigh, W. J.; Chan, B. K.; Gaspar, P. P.; Zhou, D. Can. J. Chem.
2005, 83 (9), 1324. doi:10.1139/v05-148.
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