Ben Macarz
CHM 331S – Inorganic Chemistry
April 12, 2000
Library Research Assignment
The Major Advances in Germanium Chemistry: 1990-2000
In spite of the wide array of technical applications that germanium complexes are
speculated and have been recently observed to exhibit, the field of germanium chemistry has
remained largely dormant until the past decade. Particularly during the last five years, there has
been an upsurge of research into a multitude of synthetic and technological applications of
germanium complexes. Specifically germanium complexes can be utilized as fundamental
organometallic and astrophysical building blocks. Germanium complexes can also be used in
order to improve existing experimental protocols and well-known synthetic reactions such as the
Reformatsky reaction. Through the study of many germanium compounds, specific mechanistic
pathways that involve many other vital elements can be elucidated such as the process of free
radical homolytic substitution and the varying reductive capabilities of elemental/metal hydrides.
A brief glimpse at the recent germanium-based research/literature suggests that the role of
germanium in organometallic and organic chemistry has been underestimated and understudied
during the past two centuries. It appears as though chemists are no longer intimidated by the
inherent risks that accompany the study of the highly unstable germanium complexes.
(Note: Many of the complexes discussed herein cannot be purchased directly, but can be
synthesized via the reaction pathways indicated in the literature and herein that utilize materials
that can be readily purchased.)
Germanium Methylidyne: A Fundamental Organometallic Building Block.
Recent research into transition metal methylidynes of the formula M
CH have
consisted of a substantially large amount of experimentation into the structure and synthesis of
GeCH (and SiCH) compounds due their likely role as intermediated in the synthesis of
amorphous Ge (and Si) semiconductor films and carbides. It had been postulated that
germylidene (H2CGe) is the most abundant source of germanium methylidyne radicals. The
GeCH radical had been previously undetected, however UV spectroscopy analysis of Ge(CH3)4
had led to the detection of a weak series of bands between 550 nm and the IR region, an
experimental find that had been theorized to reflect the presence of the GeCH radical. It has since
been elucidated through deuterium substitution that the observed results must have originated
from a single atom germanium isotope.
In order to fully understand the results observed for the GeCH compounds, all of the
obtained data had been compared to previously obtained data for the analogous silicon
methylidyne complexes. It should be noted herein that the two sets of bands had been easily
distinguished by the fact that the SiCH absorbs light in the 605-855 nm region. As of 1999, it had
been reported that the sub-bands of GeCH had been observed to be too complicated to
thoroughly analyze via specific techniques, such as rotational analysis. This area of research is
expected to flourish within the next few years.
Activated Germanium and a Diastereoselective Reformatsky Reaction.
The Reformatsky Reaction, a well-known name reaction in organic chemistry involves the
formation of a -hydroxy carboxylic ester from an -bromo ester, a carbonyl compound and zinc
metal compound. Thus, the Reformatsky Reaction, alongside the aldol reaction, constitutes a vital
means by which carbon-carbon bonds can be generated. Unfortunately, while the Reformatsky
Reaction can be carried out under relatively neutral conditions, it provides poor stereoselectivity.
However, recent studies have demonstrated the reductive effects of low-valent germanium
complexes, specifically activated germanium metal complexes, that can in turn be utilized in the
formation of carbon-carbon bonds.
Initial studies had first tested the application of germanium diiodide in the Reformatsky
Reaction, leaving all other reactants the same as those employed using zinc complexes.
O
OH
Ph
O
GeI2
PhCHO +
THF
Ph
Ph
Br
+
O
Ph
It had been observed that the reaction yield had been an only minimally improved 38%, a fact
that can be best attributed to the fact that GeI2 is a poor nucleophile (with regards to its ability to
attack the aldehyde unit) even though it exhibits a high reducing capacity. These results had
subsequently led to the necessity to study germanium (IV) reaction intermediates, which are
known to exhibit a high reactivity to aldehydes. Finally, researchers set out to study the reduction
of C-H bonds using germanium metal. Once all of the various valence number germanium
complexes had been analyzed, the following reaction pathway had been proposed as the most
plausible.
Reducing agent
(1)
GeX4
(or GeX2)
Ge
THF
OH
O
O
O
Ge
(2)
PhCHO +
+
Ph
Br
THF
Ph
Ph
Ph
The conclusions that had been subsequently drawn had emphasized the fact that activated
germanium metal complexes do increase both the stereoselectivity and the yield of the products
generated via the Reformatsky Reaction. The results of this experimentation can be further
applied to asymmetric Reformatsky Reaction of enantiomerically pure oxazolidinone derivatives
with various aldehydes.
Thermal Decomposition of Platinum(IV)-Germanium Complexes.
Using a technique known as thermogravimetric analysis (TGA), the thermal decomposition
of a series of complexes of the chemical formula [PtMe2(Me3Ge)X(diimine)] where X = Cl, Br, I.
In order to study the structural aspects of the resultant decomposition products, 1H NMR had
been utilized. It had been determined that decomposition could proceed by either of three distinct
pathways; -elimination of Me2E, reductive elimination of Me3EX, and reductive elimination of
Me4E. The pathway that occurs depends on the nature of the halide X, as well as on the nature of
the metal element E. It would be logical to theorize that it is the increasing halide size which
corresponds with the increase in elimination activity. In addition to the above, it should be noted
that the calculated methyl-germanium bond energies for the Me4E complexes had been 265
kJ/mol.
Table 1. Decomposition Data Obtained Experimentally via Thermogravimetric Analysis.
Me3EX
Me3GeCL
Me3GeBr
Me3GeI
Diimine
Ligand
bpy-tbu2
bpy-tbu2
bpy-tbu2
Onset
Temp. (C)
131
140
140
Final
Temp. (C)
165
176
226
1ST Mass
Loss (%)
21.6
28.5
28.9
Theor . (%)
Me3EX
23.7
28.6
33.1
Theor. (%)
Me4E
20.5
19.2
18.0
Theor. (%)
Me2E
15.9
14.9
13.9
It had been concluded that the thermal stability of these platinum germanium complexes increases
when X = Cl  Br  I, as well as with respect to the diimine ligand that has been selected. In
addition, further experimentation has indicated that stability also increases depending on which
group 14 metal atom is selected; ie. Sn  Ge  Si. It had been hypothesized that it is the
increasing methyl-group 14 metal bond dissociation energies that had made the transfer of a
methyl group from germanium to platinum incrementally difficult.
Formation of Microporous Germanate 4-Connected Nets from GeO2.
The areas of improved catalytic and separation technology is currently being advanced via
research into the synthesis of new zeolites and/or their analogous microporous crystalline
materials. Prior to 1998, silicon zeolitic networks had predominated previous research
endeavours, whereas the germanium analogues had been largely overlooked. In the winter of
1998, Hailian Li and O. M. Yaghi at the Arizona State University performed a series of
experimental steps in order to synthesize germanate 4-connected nets starting with GeO2. The
experimental procedure that had been employed had been as outlined below.
(1) 150 mg (1.434 mmol) GeO2 dissolved in 1.26 mL (10.04mmol) DMA, 3.20 mL
(39.78 mmol) pyridine and 0.02 mL (0.572 mmol) HF.
(2) Solution had been heated in a Teflon-lined vessel for 4 days @ 165C.
(3) Solution had been cooled to room temperature and 90 mg of crystals had been
collected.
Two types of building block arrangements had been observed; one tetrahedral in geometric
structure, one octahedral in geometric structure. It should be noted that both of these structures
had been determined via X-ray crystallographic studies.
O
Ge
where
O
= oxygen
O
O
GeO4
[tetrahedral geometry]
Ge8O12
[octahedral geometry]
Li and Yaghi had concluded that the typical Ge-O-Ge bond angle had been 130, a value that had
been 16 less than the 146 bond angle that had been previously recorded for a typical Si-O-Si
bond. This evidence points toward the possibility that the microporous germanate nets that had
been synthesized had an inherent stability that has been thus far largely unobserved for zeolitic
networks. It appears that further research will be published within the next few years, expanding
the current results into more pratical applications.
Pentacoordinate Germanium Atoms.
The chemistry of pentacoordinate silicon has been well-documented and investigated,
whereas the chemistry of pentacoordinate germanium has remained for the most part unexplored.
One specific pentacoordinate germanium complex that had been successfully synthesized had been
meso-[1,3-Piperaziniumdiylbis(methylene)]bisl{bis-[2-methyllactato(2-)-O1,O2]gemanate}
Octahydrate. For simplicity this complex will be referred to as GeComp8H2O. The
synthesis of GeComp8H2O had been performed in accordance with the reaction pathway
illustrated below. The synthesis of the first reaction compound had been performed in
accordance with the published results contained in the 1994 article published in Chem.
Ber. by R. Tacke et al.
OMe
piperazine
2 Net3
OMe
2 MeO – Ge – CH2Cl
OMe
MeO – Ge – CH2 – N
N – CH2 – Ge – OMe
- 2 [HNEt3]Cl
OMe
OMe
OMe
+ 4
O
HO
OH
O
O
O
O
O
Ge – CH2 – N H
O
O
O
H N – CH2 – Ge
O
O
O
O
The synthesized pentacoordinate germanium compound depicted above had been analyzed
via standard crystallographic procedures, and all of the obtained data had been subsequently
compared to the similar parameters that had been measured for the analogous silicon complex. It
had been noted that the germanium-carbon bonds had been observed to have been distorted
trigonal bipyramidal. (Note: All of the experimentally determined parameters observed had been
tabulated in the table bellow.)
Table 2. Physical Properties and Parameters Observed for GeComp8H2O.
Empirical Formula
C22H54Ge2N2O20
Molecular Weight (g/mol)
811.85
-100
Collection Temp. (C)
Crystal System
monoclinic
m.p.
215-220C
1H NMR spec.
300.1 MHz
1H NMR spec.
75.5 MHz
The synthesis, and subsequent analysis, of pentacoordinate germanium complexes has been made
possible largely due to the relatively large amount of analogous pentacoordinate silicate
complexes. At this point in time, such research is largely academic and the precise future
applications remain inconclusive. However, such experimental manipulations can be utilized in
order to gain further insight into the nature of germanium-carbon interactions and may be
subsequently applied to the study of germanium clusters and networks.
Germanium Free Radical Chemistry.
The vital field of free radical chemistry typically involves chemical strategies that utilize the
hydrides of group 14 elements, especially under reduction conditions, most prominently tin
(Bu3SnH) and silicon [(TMS)3SiH]. Prior to January 1999, only the rate constants of a series of
C-centred radicals of tributylgermanium hydride had been reported with respect to the
germanium hydride series. A recently published paper by Jean Escudie and Isabelle Paiihous,
two chemists working out of Paul Sabatier University in France, had reported the successful
application of one carbon ring expansion of cylcopentanones in order to quantitatively time the
rate constants for the reaction of a series of germanium hydrides with primary alkyl radicals.
The two reaction pathways that had been monitored are illustrated below.


(1)
kc
O
O

(2)
CO2Me

CO2Me
Chryssostomos Chatgilialoglu and Marco Ballestri had observed that the rate constants
had increased alongside the order Bu3GeH  Ph3GeH  (Me3Si)3GeH. The researchers had
attempted to explain the basis for these experimental results based upon thermodynamic trends
across the series. Specifically, the Ge-H bond dissociation energy for Ph3GeH is 2.5 kcal/mol
less than that for Bu3GeH. The researchers had also noted that the polarized transition states
formed could have also contributed to the observed results. Specifically, it had been observed
that by replacing an alkyl group with a phenyl group had resulted in the rate constant having
increased by a factor of ten and that the replacement of an alkyl group by a trimethylsilyl group
had resulted in a 400-fold increase in the rate constant. All of the experimental values have been
tabulated below.
Table 3. Table of Rate Constant Parameters Obtained for the Various Germanium Hydrides.
XH
Radical Clock
kH/kre (M-1)
kH (M-1/s-1)
Temp. (C)
Bu3GeH
80
0.91 + 0.22
3.8 x 105
12
ArGeH3
80
6.7 + 2.0
2.8 x 106
34
Ar2GeH2
80
5.1 + 2.3
2.1 x 106
34
Ph3GeH
80
9.1 + 2.8
3.8 x 106
34
PhCH2(Et)GeH2 3  4
80
3.2 + 0.5
1.3 x 106
(PhCH2)3GeH
80
7.1 + 1.4
3.0 x 106
34
Ph4Ge2H4
80
44.8 + 4.9
1.9 x 106
34
(Me3Si)3GeH
80
18.3 + 3.2
1.5 x 107
12
The above experimentation can be subsequently applied in order to develop and select for more
effective reducing agents.
Germanium-Substituted Enol Ethers as Formed from Fischer Carbene Complexes and
Vinylgermanes.
The range of applications in organic synthesis reactions for Fischer carbene complexes
cannot be underestimated. Of the most prominent, Fischer carbene complexes can be employed in
order to successfully perform cyclopropanation transformation reactions of both electron-rich and
electron-poor alkene species. It had been recently elucidated that by reacting Fischer carbene
complexes with vinylgermanes that a stable trialkylgermanium-substituted enol ether can be
isolated. The experimentation that had given rise to the aforementioned reaction pathway had
been published by Jose Barluenga et al. in May 1997 in Organometallics. In order to successfully
monitor the reaction mechanism, the Fischer carbene complex had been reacted with 2,2dideuteriated vinylgermanium derivative.
ie.
Ome
D
PhCH3
MeO
D
(CO)5Cr
+
GeBuEt2
D
D
80C
Ph
GeBuEt2
Ph
Low-Coordinate, Unhindered Germanium Compounds.
It had been formerly believed that low-coordinate germanium compounds were too
reactive to isolate for structural observation. It has since been observed through the extensive
experimentation of group 14 compounds (Si, Ge, Sn) that in spite of the high reactivity that these
compounds may exhibit, they do contain an intrinsic thermodynamic stability. More recent
studies, initiated during the early to mid 1980’s, led to the subsequent realization that these species
could be stabilized kinetically upon the addition of selective bulky groups. As a result, the
structures of these low-coordinate element compounds were readily rendered stable enough to
study via the various methods of structural detection; including matrix isolation, IR/UV
spectroscopy, flash vacuum thermolysis (FVT), vacuum gas-solid reactions (VGSR) coupled with
mass spectrometry or UV-photoelectron spectroscopy (UV-PES).
Recently, Severine Foucat et al had utilized photoelectron spectroscopy, coupled with flash
vacuum thermolysis, as a means to observe the structural characteristics of three low-coordinate
germanium compounds, in particular germaimines (Ge=N-), germaisonitriles (:Ge
N-), and
gemylenes (Ge: ). Specific complexes studied for each of the aforementioned germanium
complexes can be presented best by the following.
SiH3
Cl
Ge = N
:Ge
N(SiHMe2)2
(1) Germaimine
:Ge
(2) Germylene
N – SiHMe2
(3) Germaisonitrile
Thermolytic spectra had been prepared for each of the three classes of low-coordinate
germanium complexes described above and a subsequent analysis of the data had been performed.
First of all it had been observed that the bond lengths of the Ge=N bond had been measured as
1.683 A, a value that had been noted to correspond to the published values for the analogous Si=N
compounds. However, the Ge=N had been noted to be quite larger than the N-C bonds observed.
Furthermore, analysis of the electronic structure of HGeN had illustrated the presence of a triple
bond. The results obtained from the study of these germanium complexes had demonstrated the
application of photoelectron spectroscopy in the identification of the three classifications of lowcoordinate germanium complexes, a series of compounds that can be easily characterized.
Germanium Linking Strategies Utilized for Traceless Solid-Phase Synthesis.
Germanium, like silicon, can be applied in the solid-phase synthesis of aromatic
compounds. Numerous organic compounds can be synthesized via either solid-support synthesis
or solution-phase synthesis. However, solid-phase synthesis allows for a more efficient and less
intense purification procedure as the undesired material may be rinsed away while the desired
synthesized compound remains bound. The most integral component of solid-support synthesis is
the linking element which must be easily linked to the desired compound and then easily cleaved
following a successful synthesis. The effects of silicon linking strategies had been extensively
researched and it has become a recently theorized that other group 14 metals might be capable of
exhibiting similar characteristics. Specifically, experimental focus has shifted to encompass the
study of germanium complexes.
As has been noted previously herein, organogermanium chemistry had remained dormant
for the most part until recently. Of note, the research of Matthew Plunkett and Jonathan Ellman,
both chemists at the University of California, had focused on the successful solid-support synthesis
of the aromatic compound 1,4-benzodiazepine on a germanium-linked resin. The synthesis had
been initiated using 4-bromoaniline as the starting material. The 4-bromoaniline had been
protected using the Mpc protecting group. Next, a deprotonation step had been performed and
the compound had been coupled to a a germanium solid-support resin. Subsequent reaction
pathways had consisted of a Grignard reaction, followed by an elimination reaction. Once the
desired 1,4-benzodiazepine compound had been synthesized, the metal-aryl bond that had been
linking the product to the germanium resin had been cleaved easily using either protons or
bromine. This process had also been applied in order to synthesize a series of other compounds
through eight or nine steps. This research is vital as it illustrates the applications of germanium
(and other metal elements) in the preparation of organic compounds through solid-phase synthesis
mechanisms.
Synthesis of Germanium Nanocrystals in Solution.
It has been elucidated through extensive silicon semiconductor nanocrystal analysis that
the resulting luminescence that is observed results from quantum confinement. Due to the fact
that germanium exhibits comparable semiconducting characteristics as silicon, it has been
anticipated that germanium nanocrystals also display quantum confinement. Unfortunately,
there are very few successful solution synthesis reactions that allow for the production of Ge (or
Si) nanocrystals. In addition, until very recently the very limited series of reactions were both
time consuming and had required substantially high temperature and pressure conditions, while
at the same time having failed to allow for control over particle size.
Recent research by B.R. Taylor and S.M. Kauzlarich has allowed for the control over the
germanium nanocrystal particle size, evidence in support quantum confinement, as well as having
provided a means by which the nanocrystal surfaces can be terminated chemically via the
application of either lithium alkyls or Grignard reagents. Taylor and Kauzlarich noted that all
their experimentation had been performed under dry N2/Ar gas, under the security provided by
either a glovebox or a Schlenk line. In addition, all of the appropriated solvents utilized had been
dried prior to their application over Na-K alloy. The synthesis sequence reported by the authors
has been simplified below.
(1)
NaGe
Purified NaGe
(2)
NaGe Powder
NaGe Powder
 soak in 5% SiCl3(CH3)
and toluene
 rinse with toluene and
methanol
 Dry in 110C oven
 Add 100 mL
distilled and degassed
diglyme (or glyme)
Purification via
Vacuum sublimation
@ 300C for 4 h
Ge Nanocrystals
GeCl4 in excess
And reflux for 8 – 120 hr.
It has been hypothesized that the germanium atoms on the surface of the obtained Ge
nanocrystals had been terminated by the formation of germanium-chlorine bonds, a theory
that has been confirmed due to the fact that further reaction with CH3Li and or CH3MgBr
results in methyl terminated nanaclocrystals. Therefore, the preparation of germanium
nanocrystals has become possible via the synthetic pathway outlined above. In addition, the
size of the crystals can be determined, giving rise to a variety of sizes. It should be noted
herein that the researchers involved had utilized high-resolution transmission electron
microscopy, photoluminescence and UV/vis absorption spectra, as well as FTIR
spectroscopy, in order to classify the germanium nanocrystal complexes that had been
obtained. All results had been compared to the published values for the analogous silicon
nanocrystals.
Germanium Containing Zeolites.
The application of aluminosilicate zeolites as catalysts in industry have elevated this
class of compounds to be considered as one of the most vital families of inorganic compounds
due to their selectivity and activity. Recently, experimentation has been performed into the
substitution of gallium and germanium in place of the silicon atom. Gallium substituted
zeolites have been successfully obtained, whereas the germanium substituted analogues have
presented a great deal of additional difficulty. Recent research, published late last year,
demonstrated a newly elucidated synthetic approach by which germanium containing
zeolites could be produced within Teflon/polymethylpentene vessels in order to avoid Si
contamination. The synthesis appears to operate optimally using an alkali-metal
In light of the above information, it has been concluded that Ge zeolites can indeed be
generated via considerably mild reaction conditions. In addition to the above, all of the
physical characteristics that had been obtained had been compared to those measured for the
analogous silicon complexes, and it had been observed that these values had been strikingly
similar. There is a future requirement for more structural investigation in order to
completely elucidate the structural functional relationship of these compounds in order for
these compounds to gain importance in industrial applications.
References:
The information contained within the resources compiled in the Erindale College library
had been more than sufficient with regards to organization of the research document contained
herein. In the reference section, there had been an ample supply of books that had been useful
in determining the number of known germanium compounds, synthesis reactions, and technical
applications of the elucidated complexes. Any subsequent research that had to be performed
thereafter within the bound journals at the Erindale College library also proved to have been
quite successful. The possibility always exists for there to have been a larger pool of available
data at the University of Toronto’s other libraries. While the Internet is not a suitable source
for reliable research information, with regards to random web pages, there are a few universityoperated sites that consist of useful Safety Data Sheets as well as extensive collections of
electronic journals. With the required software (Citrix), it is possible for one to access an
electronic version of the Chemical Abstracts on-line through the University of Toronto’s
‘Libraries’ web page. In addition, there are approximately eight thousand journals available
over the net that can be searched and cross-referenced through the on-line Chemical Abstracts
search option. Specific searches can also be performed through ‘Pub Med’, ‘ACS’, ‘Web of
Science’, and ‘Ideal’, a few prominent research sites that offer access to an array of prominent
journals. As a result, the Internet had only been utilized for limited areas of research and all of
the necessary information had been gathered from the various University of Toronto libraries.
I.
Books and Catalogues.
1. Aldrich Catalogue Handbook of Fine Chemicals, 1998-1999, Sigma-Aldrich
Chemical Co., Inc., United States of America, 1998.
2. CRC Handbook of Chemistry and Physics, David R. Lide, Ph.D, editor-in-chief,
CRC Press, Inc., United States of America, 1997.
3. Comprehensive Organic Functional Group Transformations – Volume 5,
Christopher J. Moody, volume editor, Cambridge University Press, Great Britain,
1995.
4. Comprehensive Organic Functional Group Transformations – Volume 6, Thomas
L. Gilchrist, volume editor, Cambridge University Press, Great Britain, 1995.
5. Dictionary of Inorganic Compounds – Volume 3 (C46 – Zr), Chapman and Hall,
Cambridge University Press, Great Britain, 1992.
[ISBN 0 412 30120 2 (5 Volume Set)]
6. Greenwood, N. N. and A. Earnshaw, Chemistry of the Elements – 2ND Edition,
Butterworth-Heinemann, Great Britain, 1997.
[ISBN 07506 3365 4]
7. Merck Index, Merck Co., Inc., United States of America, 1983,
[ISBN 911910 27 1]
II.
Journal Entries.
1. Barluenga, Jose, et al. ‘Tin- and Germanium- Substituted Enol Ethers from
Fischer Carbene Complexes and Group 14 Vinyl Derivatives’. Organometallics, 16
(May 1997), 4525-4526.
2.
Chan, Vee Yee, et al. ‘Ground-State Stereoelectronic Effects Involving Si and Ge:
A Comparison of the Effects of Ge and Si Substituents on C-O Bond Lengths at the
-Position’. J. Org. Chem., 61 (Feb. 1996), 5227-5233.
3. Chen, Tuqiang, et al. ‘Synthesis of Cage Compounds Containing Boron,
Germanium, and Phosphorous Atoms’. Inorg. Chem., 36 (Jan. 1997), 802-808.
4. Chatgilialoglu, Chryssostomos, et al. ‘Hydrogen Donor Abilities of Germanium
Hydrides’. Organometallics, 18 (Jan. 1999), 2395-2397.
5. Foucat, Severine, et al. ‘Gas-Phase Characterization by Photelectron Spectroscopy
of Unhindered, Low-Coordinate Ge Compounds: Germaimines, Germylenes, and
Germaisonitriles’. Organometallics, 18 (April 1999), 5322-5329.
6. Guo, Li, et al. ‘Cobalt Complexes of Silicon and Germanium Heterocyclotriynes
with One or Two Cyclyne Rings’. Organometallics, 18 (March 1999), 1767-1773.
7. Herberich, Gerhard E., et al. ‘Borabenzene Derivatives. Bis(1methylboratabenzene) Compounds of Ge, Sn, and Pb’. Organometallics, 18 (July
1999), 4747-4752.
8. Horvat, Sonia M., et al. ‘Free Radical Homolytic Substitution by the Frontside
Mechanism: Ab Initio Study of Homolytic Substitution Reactions at Si, Ge, and Sn’.
Organometallics, 19 (Feb. 2000), 1239-1246.
9. Ishii, Kazuyuki, et al. ‘Time-Resolved Electron Spin Resonance of Gallium and
Germanium Porphyrins, in the Excited Triplet State’. Inorg. Chem., 39 (Feb. 2000),
468-472.
10. Johnson, Geoffrey M., et al. ‘Novel Routes for the Preparation of a Range of
Germanium Containing Zeolites’. Chemical Materials, 11 (Jan. 2000), 10-12.
11. Kagoshima, Hirotaka, et al. ‘An Activated Germanium Metal-Promoted, Highly
Diastereoselective Reformatsky Reaction’. J. Org. Chem., 63 (March 1998), 691697.
12. Rangan, K. Kasthuri, et al. ‘Aqueous Mediated Synthesis of Mesostructured
Manganese Germanium Sulfide with Hexagonal Order’. Chem. Mater., 11 (July
1999), 2629-2632.
13. Levy, Christopher J., et al. ‘Thermal Decomposition of Pt(IV)-Si, -Ge, and –Sn
Complexes’. Organometallics, 16 (March 1997), 4115-4120.
14. Li, Hailian and O. M. Yaghi. ‘Transformation of Germanium Dioxide to
Microporous Germanate 4-Connected Nets’. J. Am. Chem. Soc., 120 (July 1998),
10569-10570.
15. MacLachlan, Mark J., et al. ‘Mesostructured Metal Germanium Sulfides’. J. Am.
Chem. Soc., 121 (July 1999), 12005-12017.
16. Maroun, F., F. Ozanam, and J.-N. Chazalviel. ‘In-Situ Infrared Monitoring of
Surface Chemistry and Free-Carrier Concentration Correlated with Voltammetry:
Germanium, a Model Electrode’. J. Phys. Chem., 103 (April 1999), 5280-5288.
17. Ossig, Gunter, et al. ‘Bis[(2-pyridyl)bis(trimethylsilyl)methyl-C,N]germanium(II):
A Base-Stabilized Germylene and the Corresponding Germanethione,
Germaneselenone andGermanetellurone’. Organometallics, 16, (Jan. 1997), 21162120.
18. Pastor, Stephen D., et al. ‘A Neutral Spirocyclic Hexacoordinated Germanium(IV)
Complex: Hypervalent Germanium Compounds with Sulfur-Containing EightMembered Rings’. Inorg. Chem., 36(25) (August 1997), 5966-5968.
19. Plunkett, Matthew J. and Jonathan A. Ellman. ‘Germanium and Silicon Linking
Strategies for Traceless Solid-Phase Synthesis’. J. Org. Chem., 62 (Jan. 1997),
2885-2893.
20. Pu, Lihung, et al. ‘Triple Bonding to Germanium’. J. Am. Chem. Soc., 122 (Feb.
2000), 650-656.
21. Scholeller, Wolgang W., et al. ‘Bonding Properties of Amidinate Complexes of the
Group 14 Elements Si, Ge, Sn and Pb in Their Divalent and Tetravalent Oxidation
States’. Inorg. Chem., 38 (Jan. 1999), 29-37.
22. Smith, Tony C., et al. ‘Spectroscopic Characterization of Silicon and Germanium
Methylidyne’. J. Am. Chem. Soc., 121 (March 1999), 6068-6069.
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III. Internet Web Pages (Limited exclusively for the collection of toxicity information and MSDS
sheets.).
1. http://msds.pdc.cornell.edu
2. http://physchem.ox.ac.uk
3. www.utoronto.ca/safety