Organogermanium compounds are organometallic compounds containing carbon-germanium chemical bonds. Germanium shares the group 14 with silicon, tin and lead in the periodic table. One reason for the limited synthetic value of organic synthetic germanium compounds is the cost of germanium compounds. However, germanium is considered as a non-toxic alternative of many toxic organotin reagents. Compounds such as tetramethylgermanium and tetraethylgermanium are used as precursors for germanium dioxide
chemical vapor deposition in the microelectronics industry.
Organic chemistry: The insertion reaction of silicon-transition metal bonds usually results in a first germanium with a germanium-transition metal bond by an elimination process. These new bivalent germanium species give rise to specific germane reactions. The cycloaddition with 2,3-dimethylbutadiene produces germacyclopentene and shows unusual thermal reversibility. Inserting these new methylene olefins into the transition metal-transition metal bonds yields a polymetallated compound. The reaction with small organic or organometallic heterocycles such as ethylene oxide, thiophene, oxazolidine and 1,3-cycloaddition with nitrones results in unstable quaternary germanium heterocycles giving the germanium double bond in the middle body. The reaction of germanium with diazonium derivatives and organic azides is a new and interesting approach that can be used for synthesizing germane and germa-imines, which are the compounds with germanium doubly bonded to carbon and nitrogen. Digermenes can be generated by the photolysis of polygermylmercury compounds or cyclopolygermanes, which have been characterized by several trapping reactions with dimethyl disulfide, biacetyl and 2,3-dimethylbutadiene.
Immunological use: The earlier work involving carboxyethyl germanium sesquioxide indicates that this compound can be used as an immune adjuvant. Carboxyethyl germanium sesquioxide normalizes the immune response when administered to immunocompromised aged mice. The same compound reverses the suppression of interferon in thermally injured mice. The dose of 300 mg/kg enhances natural killer cell activity and interferon levels in mice. Carboxyethyl germanium sesquioxide shows an immune adjuvant effect in mice that had been innoculated with L-1210 tumor cells when combined with mitomycin C. Oral administration of carboxyethyl germium sesquioxide activates peripheral macrophages of mice; it significantly suppressed the latter's growth when cultivated with leukemia or Ehrlichi carcinoma cells, indicating that that the antitumor activity of carboxyethyl germanium sesquioxide might result from activation of macrophage. And the combination of carboxyethyl germanium sesquioxide and indomethacin enhances the latter.
Bacteriostatic use: It is known that certain organogermanium compounds show bactericidal or bacteriostatic activity. Compounds such as [RNHCOCH2CH(C6H5)Ge]2O3 (where R is a β-lactam) inhibit the growth of Staphylococcus aureus, Staphylococcus epidermidis and related species.
Fig.1. Staphylococcus aureus SEM.