Chlorine-free germanium processing

Last updated February 01, 2024

Chlorine-free germanium processing are methods of germanium activation to form useful germanium precursors in a more energy efficient and environmentally friendly way compared to traditional synthetic routes. Germanium tetrachloride is a valuable intermediate for the synthesis of many germanium complexes. Normal synthesis of it involves an energy-intensive dehydration of germanium oxide, ${\ce {GeO2}}$ , with hydrogen chloride, ${\ce {HCl}}$ ^[1] Due to the environmental and safety impact of non-recyclable, high energy reactions with ${\ce {HCl}}$ , an alternative synthesis of a shelf-stable germanium intermediate precursor without chlorine is of interest. In 2017, a synthesis of organogermanes, ${\ce {GeR4}}$ without using chloride species was reported, allowing for a much more environmentally friendly and low energy synthesis using ${\ce {GeO2}}$ , ${\ce {Ge(0)}}$ , and even selectively activating germanium in the presence of zinc oxide ( ${\ce {ZnO}}$ ), resulting in products that are bench stable and solid.^[2]

Synthesis of organogermanes

Oxidation of germanium metal

Glavinović et al. have synthesized organogermanes using ortho-quinone, which is both redox "non-innocent" and acts as a pseudo-halide, resulting in an air and moisture stable beige solid.^[3]^[4] Referring to the scheme below^{[ specify ]}, when ${\ce {Ge(0)}}$ , ortho-quinone, and pyridine (acting as an auxiliary ligand) were milled via liquid assisted grinding in a 1:1 mixture of toluene and water, the resulting organogermane was recrystallized in toluene resulting in 88% yield. In this reaction, the quinone ligands each undergo a two-electron oxidation, resulting in the ${\ce {Ge(0)}}$ oxidized to ${\ce {Ge(IV)}}$ . This reaction was shown to work both at the milligram and the gram scale, proving its efficiency in the bulk scale.^{[ citation needed ]}

Dehydration of GeO₂

Following a nearly identical reaction scheme as the oxidation of germanium metal with ortho-quinone, dehydration of ${\ce {GeO2}}$ with catechol ligands results in the same product as the oxidation product, with similar yield 74% on milligram scale and 84% on the gram scale. This particular scheme is of much note since the sole byproduct of this reaction is water. These reactions could provide an alternative to normal oxide separations for other metals that are energy intensive and otherwise wasteful. ^[5]

Extraction from ZnO

Industrially, germanium can be extracted from ${\ce {ZnO}}$ , contains amounts of ${\ce {GeO2}}$ . Using ${\ce {HCl}}$ , the key product of ${\ce {GeCl4}}$ and ${\ce {ZnCl2}}$ byproduct can be produced. The zinc byproduct can be distilled at high temperatures, leaving only germanium tetrachloride.^[6] A new^{[ when? ]} method of chlorine-free germanium processing has proven effective in extracting germanium from zinc oxide, giving hope to replace the ${\ce {HCl}}$ leaching and distillation process currently employed by industry. In both 1:1 and 1:5 mass ratios of ${\ce {GeO2}}$ and ${\ce {ZnO}}$ , germanium oxide was selectively activated by simple addition of catechol, and letting the reaction proceed under the same conditions as the dehydration reaction. The unreacted zinc oxide can be washed away with dichloromethane and the bis(catecholate) germanium product recrystallized in cyclohexane. Despite zinc oxide being present in the reaction vessel, the intermediate germanium product yields remain high, being 64 and 66%. This method, as well as other halogen-free germanium extraction methods, make the possibility of halogen free germanium processing a future possibility.^[7]

Other auxiliary ligands

The mechanochemical activation of germanium described above can be used with a variety of auxiliary amine-based ligands and not just pyridine as used in the syntheses above. Uni-dentate ligands such as N-methyl imidazole can be used used to create a trans-disposed octahedral germanium product, isostructural to the complexes of both the catechol and ortho-quinone that contain pyridine. However, chelating ligands can be used to form the product with nitrogens cis to each other. For example, in a reaction using tetramethylethylenediamine as a chelating bi-dentate diamine affords the cis- product with catechol ligands at the other octahedral binding sites. More research as additionally been done to show that the nitrogen-containing ligands can be biologically active ones which operate at very low reduction potentials. This makes the germanium complexes with those ligands easily reducible and highly nucleophilic, making substitution and activation even easier.^[8]

Substitution reactions

Substitutions to form tetraorganogermanes

Reagents and products

The intermediates prepared by the above method are able to easily undergo substitution reactions with nucleophiles to form tetraorganogermanes, ${\ce {GeR4}}$ , of which include, ${\ce {GeH4}}$ , Germane. Germane is a key material in optical and electronic device fabrication.^[9] These substitution reactions return the original catechol ligand, making this germanium activation process easily recyclable. A solution of 20 equivalents of an alkyl or aryl Grignard reagent in tetrahydrofuran, combined with bis(catecholate) complex leads to a homogeneous solution of reagents in THF. Refluxing this solution for 24 hours yields the Grignard product organogermane in relatively high yield across multiple reagents. The figure below shows different reagents used by Glavinović et al, showing the efficacy of the substitution reaction.^{[ citation needed ]}

Proposed mechanism

The substitution reaction described above is thought to process via a mechanism in which steric strain of the complex is slowly alleviated over the course of the reaction.^[10] The first Grignard reagent substitutes the most sterically hindered oxygen position, where the t-butyl group of the catechol ligand is alpha to the oxygen. The second Grignard reagent substitutes the now uni-dentate catechol-grignard adduct, removing the ligand and resulting in two complete substitutions. Referring to the scheme below, treating intermediate 2 with an additional equivalent of Grignard reagent yields 3 at a faster rate than the rate to make 2, and treatment of 3 with two equivalents of reagent yields 4 at even more quickly. This is starkly different from the substitution reactions of ${\ce {GeCl4}}$ , in which the germanium center becomes more sterically hindered over the course of the reaction as ligand exchange of the carbons and the chlorides progresses, making the substitution more difficult.^{[ citation needed ]}

Ratio of products lends validity to the proposed mechanism, that substitution occurs at the most substituted oxygen first. WikiFigure7.jpg — Ratio of products lends validity to the proposed mechanism, that substitution occurs at the most substituted oxygen first.

The stereochemical selectivity of the substitution reaction is further enforced by the identity of the auxiliary amine ligand. By using a more sterically encumbered amine ligand such as triethylamine, a 1.67:1 mixture of dibutyl-germane-η²-catecholate and tributylgermyl-η¹-catecholate is produced after substitution with two equivalents of ${\ce {BuMgCl}}$ . This proves the effect of steric encumbrance on the product of the substitution reaction as the resulting tri-substituted product has the least sterically encumbered oxygen remaining bonded to the catecholate. This reaction pathway could allow new synthetic pathways for more stereo complex and functionalized germanium complexes.^{[ citation needed ]}

Substitution to form germane

Despite being highly volatile and toxic, germane, ${\ce {GeH4}}$ , is extremely important in the field of optoelectronics and is a good candidate for vapor deposition to form thin films of germanium.^[9] However, germane must be extremely pure to use in such a way, and much research has gone into developing methodologies to prepare and purify germane.^[11] Using bis(catecholate) germanium and lithium aluminum hydride ( ${\ce {LiAlH4}}$ ) in dibutyl ether with argon as a carrier gas, the substitution reaction yields high purity germane in the Ar carrier gas with no evolution of volitile Ge byproducts. This reaction pathway for production of germane requires no postsynthetic processing or purification, proving this to be more advantageous than current methods.^{[ citation needed ]}

Substitution of bis(catecholate) germanium complex with lithium aluminum hydride to make germane. WikiFigure8.jpg — Substitution of bis(catecholate) germanium complex with lithium aluminum hydride to make germane.

Related Research Articles

<span class="mw-page-title-main">Chemical reaction</span> Process that results in the interconversion of chemical species

A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei, and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur.

<span class="mw-page-title-main">Oxide</span> Chemical compound where oxygen atoms are combined with atoms of other elements

An oxide is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O^2– ion with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al₂O₃ that protects the foil from further oxidation.

In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom to the substrates in synthetic steps, through nucleophilic addition or simple deprotonation. Organolithium reagents are used in industry as an initiator for anionic polymerization, which leads to the production of various elastomers. They have also been applied in asymmetric synthesis in the pharmaceutical industry. Due to the large difference in electronegativity between the carbon atom and the lithium atom, the C−Li bond is highly ionic. Owing to the polar nature of the C−Li bond, organolithium reagents are good nucleophiles and strong bases. For laboratory organic synthesis, many organolithium reagents are commercially available in solution form. These reagents are highly reactive, and are sometimes pyrophoric.

In organic chemistry, an acyl chloride is an organic compound with the functional group −C(=O)Cl. Their formula is usually written R−COCl, where R is a side chain. They are reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride, CH₃COCl. Acyl chlorides are the most important subset of acyl halides.

The Stille reaction is a chemical reaction widely used in organic synthesis. The reaction involves the coupling of two organic groups, one of which is carried as an organotin compound (also known as organostannanes). A variety of organic electrophiles provide the other coupling partner. The Stille reaction is one of many palladium-catalyzed coupling reactions.

A single-displacement reaction, also known as single replacement reaction or exchange reaction, is a chemical reaction in which one element is replaced by another in a compound.

The Corey–House synthesis (also called the Corey–Posner–Whitesides–House reaction and other permutations) is an organic reaction that involves the reaction of a lithium diorganylcuprate ( $) with an organic halide or pseudohalide () to form a new alkane, as well as an ill-defined organocopper species and lithium (pseudo)halide as byproducts.$

The Reformatsky reaction is an organic reaction which condenses aldehydes or ketones with α-halo esters using metallic zinc to form β-hydroxy-esters:

The Bartoli indole synthesis is the chemical reaction of ortho-substituted nitroarenes and nitrosoarenes with vinyl Grignard reagents to form substituted indoles.

<span class="mw-page-title-main">Grignard reagent</span> Organometallic compounds used in organic synthesis

In organic chemistry, a Grignard reagent or Grignard compound is a chemical compound with the general formula R−Mg−X, where X is a halogen and R is an organic group, normally an alkyl or aryl. Two typical examples are methylmagnesium chloride Cl−Mg−CH₃ and phenylmagnesium bromide (C₆H₅)−Mg−Br. They are a subclass of the organomagnesium compounds.

Organogermanium chemistry is the science of chemical species containing one or more C–Ge bonds. Germanium shares group 14 in the periodic table with carbon, silicon, tin and lead. Historically, organogermanes are considered as nucleophiles and the reactivity of them is between that of organosilicon and organotin compounds. Some organogermanes have enhanced reactivity compared with their organosilicon and organoboron analogues in some cross-coupling reactions.

The Negishi coupling is a widely employed transition metal catalyzed cross-coupling reaction. The reaction couples organic halides or triflates with organozinc compounds, forming carbon-carbon bonds (C-C) in the process. A palladium (0) species is generally utilized as the metal catalyst, though nickel is sometimes used. A variety of nickel catalysts in either Ni⁰ or Ni^II oxidation state can be employed in Negishi cross couplings such as Ni(PPh₃)₄, Ni(acac)₂, Ni(COD)₂ etc.

<span class="mw-page-title-main">Organocopper chemistry</span> Compound with carbon to copper bonds

Organocopper chemistry is the study of the physical properties, reactions, and synthesis of organocopper compounds, which are organometallic compounds containing a carbon to copper chemical bond. They are reagents in organic chemistry.

The Fleming–Tamao oxidation, or Tamao–Kumada–Fleming oxidation, converts a carbon–silicon bond to a carbon–oxygen bond with a peroxy acid or hydrogen peroxide. Fleming–Tamao oxidation refers to two slightly different conditions developed concurrently in the early 1980s by the Kohei Tamao and Ian Fleming research groups.

The Pinnick oxidation is an organic reaction by which aldehydes can be oxidized into their corresponding carboxylic acids using sodium chlorite (NaClO₂) under mild acidic conditions. It was originally developed by Lindgren and Nilsson. The typical reaction conditions used today were developed by G. A. Kraus. H.W. Pinnick later demonstrated that these conditions could be applied to oxidize α,β-unsaturated aldehydes. There exist many different reactions to oxidize aldehydes, but only a few are amenable to a broad range of functional groups. The Pinnick oxidation has proven to be both tolerant of sensitive functionalities and capable of reacting with sterically hindered groups. This reaction is especially useful for oxidizing α,β-unsaturated aldehydes, and another one of its advantages is its relatively low cost.

Chloro(pyridine)cobaloxime is a coordination compound containing a Co^III center with octahedral coordination. It has been considered as a model compound of vitamin B₁₂ for studying the properties and mechanism of action of the vitamin. It belongs to a class of bis(dimethylglyoximato)cobalt(III) complexes with different axial ligands, called cobaloximes. Chloro(pyridine)cobaloxime is a yellow-brown powder that is sparingly soluble in most solvents, including water.

<span class="mw-page-title-main">Metal peroxide</span>

Metal peroxides are metal-containing compounds with ionically- or covalently-bonded peroxide (O²⁻
₂) groups. This large family of compounds can be divided into ionic and covalent peroxide. The first class mostly contains the peroxides of the alkali and alkaline earth metals whereas the covalent peroxides are represented by such compounds as hydrogen peroxide and peroxymonosulfuric acid (H₂SO₅). In contrast to the purely ionic character of alkali metal peroxides, peroxides of transition metals have a more covalent character.

A magnesium(I) dimer is a molecular compound containing a magnesium to magnesium bond (Mg-Mg), giving the metal an apparent +1 oxidation state. Alkaline earth metals are commonly found in the +2-oxidation state, such as magnesium. The M²⁺ are considered as redox-inert, meaning that the +2 state is significant. However, recent advancements in main group chemistry have yielded low-valent magnesium (I) dimers, also given as Mg (I), with the first compound being reported in 2007. They can be generally represented as LMg-MgL, with L being a monoanionic ligand. For example, β-diketiminate, commonly referred to as Nacnac, is a useful chelate regarding these complexes. By tuning the ligand, the thermodynamics of the complex change. For instance, the ability to add substituents onto Nacnac can contribute to the steric bulk, which can affect reactivity and stability. As their discovery has grown, so has their usefulness. They are employed in organic and inorganic reduction reactions. It is soluble in a hydrocarbon solvent, like toluene, stoichiometric, selective, and safe.

m-Terphenyls (also known as meta-terphenyls, meta-diphenylbenzenes, or meta-triphenyls) are organic molecules composed of two phenyl groups bonded to a benzene ring in the one and three positions. The simplest formula is C₁₈H₁₄, but many different substituents can be added to create a diverse class of molecules. Due to the extensive pi-conjugated system, the molecule it has a range of optical properties and because of its size, it is used to control the sterics in reactions with metals and main group elements. This is because of the disubstituted phenyl rings, which create a pocket for molecules and elements to bond without being connected to anything else. It is a popular choice in ligand, and the most chosen amongst the terphenyls because of its benefits in regards to sterics. Although many commercial methods exist to create m-terphenyl compounds, they can also be found naturally in plants such as mulberry trees.

Copper-catalyzed allylic substitutions are chemical reactions with unique regioselectivity compared to other transition-metal-catalyzed allylic substitutions such as the Tsuji-Trost reaction. They involve copper catalysts and "hard" carbon nucleophiles. The mechanism of copper-catalyzed allylic substitutions involves the coordination of copper to the olefin, oxidative addition and reductive elimination. Enantioselective versions of these reactions have been used in the synthesis of complex molecules, such as (R)-(-)-sporochnol and (S)-(-)-zearalenone.

References

↑ Moore, J.J. (1990). Chemical Metallurgy (2nd ed.). Butterworth-Heinemann. pp. 243–309. ISBN 9781483102931.
1 2 Glavinović, Martin; Krause, Michael; Yang, Linju; McLeod, John A.; Liu, Lijia; Baines, Kim M.; Friščić, Tomislav; Lumb, Jean-Philip (2017-05-05). "A chlorine-free protocol for processing germanium". Science Advances. 3 (5): e1700149. Bibcode:2017SciA....3E0149G. doi:10.1126/sciadv.1700149. ISSN 2375-2548. PMC 5419701 . PMID 28508082.
↑ Pierpont, Cortlandt G.; Buchanan, Robert M. (1981-08-01). "Transition metal complexes of o-benzoquinone, o-semiquinone, and catecholate ligands". Coordination Chemistry Reviews. 38 (1): 45–87. doi:10.1016/S0010-8545(00)80499-3. ISSN 0010-8545.
↑ Cerveau, G.; Chuit, C.; Corriu, R. J. P.; Reye, C. (1991). "Reactivity of dianionic hexacoordinate germanium complexes toward organometallic reagents. A new route to organogermanes". Organometallics. 10 (5): 1510–1515. doi:10.1021/om00051a049. ISSN 0276-7333.
↑ Qi, Feng; Stein, Robin; Friščić, Tomislav (2014). "Mimicking mineral neogenesis for the clean synthesis of metal–organic materials from mineral feedstocks: coordination polymers, MOFs and metal oxide separation". Green Chemistry. 16 (1): 121–132. doi:10.1039/C3GC41370E.
↑ Licht, Christina; Peiró, Laura Talens; Villalba, Gara (2015). "Global Substance Flow Analysis of Gallium, Germanium, and Indium: Quantification of Extraction, Uses, and Dissipative Losses within their Anthropogenic Cycles: Global SFA of Ga, Ge, and In". Journal of Industrial Ecology. 19 (5): 890–903. doi:10.1111/jiec.12287. S2CID 153489829.
↑ Nikolaevskaya, Elena N.; Saverina, Evgeniya A.; Starikova, Alyona A.; Farhati, Amel; Kiskin, Mikhail A.; Syroeshkin, Mikhail A.; Egorov, Mikhail P.; Jouikov, Viatcheslav V. (2018-12-04). "Halogen-free GeO2 conversion: electrochemical reduction vs. complexation in (DTBC)2Ge[Py(CN)n] (n = 0…2) complexes". Dalton Transactions. 47 (47): 17127–17133. doi:10.1039/C8DT03397H. ISSN 1477-9234. PMID 30467566.
↑ Nikolaevskaya, Elena N.; Shangin, Pavel G.; Starikova, Alyona A.; Jouikov, Viatcheslav V.; Egorov, Mikhail P.; Syroeshkin, Mikhail A. (2019-09-01). "Easily electroreducible halogen-free germanium complexes with biologically active pyridines". Inorganica Chimica Acta. 495: 119007. doi:10.1016/j.ica.2019.119007. ISSN 0020-1693. S2CID 198368041.
1 2 Venkatasubramanian, R.; Pickett, R. T.; Timmons, M. L. (1989-12-01). "Epitaxy of germanium using germane in the presence of tetramethylgermanium". Journal of Applied Physics. 66 (11): 5662–5664. Bibcode:1989JAP....66.5662V. doi:10.1063/1.343633. ISSN 0021-8979.
↑ Chuit, Claude; Corriu, Robert J. P.; Reye, Catherine.; Young, J. Colin. (1993). "Reactivity of penta- and hexacoordinate silicon compounds and their role as reaction intermediates". Chemical Reviews. 93 (4): 1371–1448. doi:10.1021/cr00020a003. ISSN 0009-2665.
↑ US 4668502,Russotti, Robert,"Method of synthesis of gaseous germane",published 1987-05-26, assigned to Voltaix Inc.

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[1] Moore, J.J. (1990). Chemical Metallurgy (2nd ed.). Butterworth-Heinemann. pp. 243–309. ISBN 9781483102931.

[:1-2] 1 2 Glavinović, Martin; Krause, Michael; Yang, Linju; McLeod, John A.; Liu, Lijia; Baines, Kim M.; Friščić, Tomislav; Lumb, Jean-Philip (2017-05-05). "A chlorine-free protocol for processing germanium". Science Advances. 3 (5): e1700149. Bibcode:2017SciA....3E0149G. doi:10.1126/sciadv.1700149. ISSN 2375-2548. PMC 5419701 . PMID 28508082.

[3] Pierpont, Cortlandt G.; Buchanan, Robert M. (1981-08-01). "Transition metal complexes of o-benzoquinone, o-semiquinone, and catecholate ligands". Coordination Chemistry Reviews. 38 (1): 45–87. doi:10.1016/S0010-8545(00)80499-3. ISSN 0010-8545.

[4] Cerveau, G.; Chuit, C.; Corriu, R. J. P.; Reye, C. (1991). "Reactivity of dianionic hexacoordinate germanium complexes toward organometallic reagents. A new route to organogermanes". Organometallics. 10 (5): 1510–1515. doi:10.1021/om00051a049. ISSN 0276-7333.

[5] Qi, Feng; Stein, Robin; Friščić, Tomislav (2014). "Mimicking mineral neogenesis for the clean synthesis of metal–organic materials from mineral feedstocks: coordination polymers, MOFs and metal oxide separation". Green Chemistry. 16 (1): 121–132. doi:10.1039/C3GC41370E.

[6] Licht, Christina; Peiró, Laura Talens; Villalba, Gara (2015). "Global Substance Flow Analysis of Gallium, Germanium, and Indium: Quantification of Extraction, Uses, and Dissipative Losses within their Anthropogenic Cycles: Global SFA of Ga, Ge, and In". Journal of Industrial Ecology. 19 (5): 890–903. doi:10.1111/jiec.12287. S2CID 153489829.

[7] Nikolaevskaya, Elena N.; Saverina, Evgeniya A.; Starikova, Alyona A.; Farhati, Amel; Kiskin, Mikhail A.; Syroeshkin, Mikhail A.; Egorov, Mikhail P.; Jouikov, Viatcheslav V. (2018-12-04). "Halogen-free GeO2 conversion: electrochemical reduction vs. complexation in (DTBC)2Ge[Py(CN)n] (n = 0…2) complexes". Dalton Transactions. 47 (47): 17127–17133. doi:10.1039/C8DT03397H. ISSN 1477-9234. PMID 30467566.

[8] Nikolaevskaya, Elena N.; Shangin, Pavel G.; Starikova, Alyona A.; Jouikov, Viatcheslav V.; Egorov, Mikhail P.; Syroeshkin, Mikhail A. (2019-09-01). "Easily electroreducible halogen-free germanium complexes with biologically active pyridines". Inorganica Chimica Acta. 495: 119007. doi:10.1016/j.ica.2019.119007. ISSN 0020-1693. S2CID 198368041.

[:0-9] 1 2 Venkatasubramanian, R.; Pickett, R. T.; Timmons, M. L. (1989-12-01). "Epitaxy of germanium using germane in the presence of tetramethylgermanium". Journal of Applied Physics. 66 (11): 5662–5664. Bibcode:1989JAP....66.5662V. doi:10.1063/1.343633. ISSN 0021-8979.

[10] Chuit, Claude; Corriu, Robert J. P.; Reye, Catherine.; Young, J. Colin. (1993). "Reactivity of penta- and hexacoordinate silicon compounds and their role as reaction intermediates". Chemical Reviews. 93 (4): 1371–1448. doi:10.1021/cr00020a003. ISSN 0009-2665.

[11] US 4668502,Russotti, Robert,"Method of synthesis of gaseous germane",published 1987-05-26, assigned to Voltaix Inc.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]