The properties of the aromatic compounds, polyhedral compounds, and radical cations whose skeletons are made of germanium atoms are investigated by means of ab initio molecular orbital calculations. Investigated are (1) the electronic and structural aspects of hexagermabenzene and its fused benzenoid systems, (2) the strain energies of the germanium-based polyhedra such as tetrahedrane, prismane, cubane, and dodecahedrane, and (3) the interesting structures of polycyclic radical cations such as cyclotrigermane, bicyclo[1.1.0]tetragermane, pentagerma[1.1.1]propellane, and their derivatives. In an attempt to characterize systematically germanium skeletons, the corresponding carbon, silicon, tin, and lead compounds and radical cations are also investigated and compared at the same level of calculations. Several interesting properties and new types of compounds are predicted which are helpful for the future experiment.

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The structure of germacyclohexane was estimated by means of molecular mechanics calculations (MM2) which indicate that: (i) the ring is flat around germanium (i. e., ω_{1, 2} is smaller than that of cyclohexane)while the ring is an enhanced chair at C4 ( i. e., ω_{3, 4}i s larger than that of cyclohexane). The other characteristic point is narrower C-Ge-C bond angle (θ₁). These features are experimentally confirmed by electron diffraction study of germacyclohexane and 1, 1dimethylgermacyclohexane. An X-ray analysis of a solid derivative of germacyclohexane also gave the similar structure features.
An interesting consequence of these structural features is a reduced conformational energies of methyl, tbutyl and phenyl groups on germanium. The conformational energies of methyl and phenyl groups on germanium as determined by MM2 and MNDO calculations are nearly zero, and that of tbutyl group barely exceeds 1.3 kcal/mol. These values are again in a good agreement with the results obtained by NMR chemical shifts.
₇₃Ge Chemical shifts for many germacyclohexanes are also reported.

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The authors established the rapid and convenient determination method for trace amounts of vanadium, nickel, zinc, germanium, arsenic and molybdenum in biological reference materials by inductively coupled plasma mass spectrometry.
For the dissolution o f these reference materials, two decomposition methods were examined: the one was the method that the sample was decomposed with nitric acid-hydrogen peroxide-hydrofluoric acid mixture in an open system; the other was the method using the teflon double-vessel digestion bomb. The latter decomposition method has the advantage that the risk of contamination and sample leakage can be greatly reduced for especially germanium determination. About 250 mg of these samples were weighed in a Teflon Tuf-Tainer screw-cap vial (7 cm³) and 3 cm³ of ultra-high purity nitric acid was added. The vial was put into a Teflon vessel (24 cm³) and then the vessel was placed into a stainless-steel jacket. The bomb was heated in an air-oven at 90°C for 2 h and then 130°C for 4 h. After cooling, the digest in the Tuf-Tainer vial was gently warmed on a hot plate to release nitrogen dioxde. Except for pepperbush, all samples examined (chlorella, human hair, mussel, tea leaves, sargasso of NIES reference materials and bovine liver of NBS reference material) cleanly dissolved. For pepperbush, 1 cm3hydrofluoric acid (1: 2.33) was added to dissolve siliceous material. In this case, heating of the sample caused the loss of germanium. In the present work, following analytical results were obtained in, ug/g: germanium in chlorella, mussel and sargasso were (0.76 ± 0.20), (23.5 ± 0.4) and (1.23 ± 0.21), respectively; vanadium in human hair and tea leaves were (0.64 ± 0.10) and (0.17 ± 0.05), respectively; nickel in sargasso was (1.75 ± 0.86); arsenic in human hair was (0.056 ± 0.022); molybdenum in pepperbush, chlorella, h uman h air, m ussel, t ea l eaves a nd s argasso w ere (0.57 ± 0.04), (1.10 ± 0.24), (0.074± 0.001), (1.11 ± 0.1, 1 )(0.18 ± 0.10) and (0.36 ± 0.02), respectively.

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A new modification of the title compound was obtained by the recrystallization from benzene solution. Th M e crystal structure has been determined by X-Ray diffraction: Crystal data; Ge₆ (C₆H₅)₁₂⋅ 5 (C₆H₆), Mw=1741.39 PI, a. =15.438(3) Å, c=19.111(2) Å, a74.90(1)°, β=70.29(2)°, γ =71.37(1)°, Z=2, R =0.054, Rw =0.046 for 9592 observed (_??_Fo_??_ ≥ 3σ (_??_Fo_??_) ) reflections.
There are two Ge₆Ph₁₂ molecules, both having a center of symmetry. The cyclohexagermane rings adopt chair conformations. As for the molecular packing, the dihedral angle between the 6-membered G e ring and that of the nearest neighbor is 58°. The packing is different from that of the Ge₆Ph₁₂ ⋅ 7benzene and the Ge₆Ph₁₂⋅ 2toluene.

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It was examined whether the thermodynamic pKa calculation method, which has been established by Breslow et al. for carbon-centered compounds, is applicable to organogermanium compounds. The coincidence of the calculated pKa value with that obtained by the extrapolation of the experimental data indicated the applicability.

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The selective adsorption resins for Ge (IV) with the 1, 2-diol type ligands were prepared by the amination of a chloromethylated styrene-divinylbenzene beads with 3-dimethylamino-1, 2-propanediol (3DMA-PD), 3-diethylamino-1, 2-propanediol (3DEA-PD) and 3-amino-1, 2-propanedio l (3A-PD). Ge (IV) was adsorbed on these resins from the neutral or alkaline solutions. The 3DMA-PD and 3DEA-PD resins exhibited the adsorption capacities for Ge(IV) at 1.14 and 0.98 mmolg^-1, resp ectively, whereas the 3A-PD resin showed the lower capacity at 0.65 mmol g^-1. The breakthrough capacities of the columns packed with 2 cm³ of these resins were evaluated by loading the various buffered solutions of Ge (1V). The Ge (IV) adsorbed in the column was eluted completely with dilute hydrochloric acid.

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A series of chalcogen cage compounds are derived from removal of chalcogen of adamantane (II a)and double-decker(IIb) sesquichalcogenide. These chalcogenide are termed nor-adamantane (VIIIa), bisnor-adamantane (VIIb), nor-doubledecker (VIIIb)a nd bisnor-doubledecker (IXb ), respectively. After trichloromonogermane ([1a] and [1b]), trichloromonosilane ([8a] and [8b]), trichloromonostannane ([10a]and[10b]) were subjected to sulfation reaction using H₂S/pyridine, Li₂S, Na₂S, (NH₄)₂S₅, and (Me₃Si)₂S, only trichloromonogermane ([la] and [1b]) produced tetrakis(t-butylgermane)pentasulfide as minor products, which has Ge-Ge bonds. As major products, adamantane sesquisulfides ([9a], [9b], [lla], and [11b]) were formed from trichloromonosilane, trichloromonostannan e as well as trichloromonogermane. On the contrary, the sulfation and selenation of tetrachlorodisilane [12] and tetrachlorodigermane [15] disclosed with efficient formation of tetrakis[t-butylsilane (germane) ]pentasulfide and pentaselenide ([13a], [13b], and [5a]). The X-ray analysis of [13a], and [13b] established nor-adamantane structures, which are formed from Si-Si bonds cleavage. Interestingly, tetrachlorodigermane also produced tetrakis(t-butylgermane)tetrasulfide (DC), which is derived without Ge-Ge bond cleavage. X-ray analysis confirmed bisnor-adamantane structure for [16].

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Recent work on polygermanes containing germanium catenates as main chain are summarized and reviewed.
High molecular weight polygermanes were prepared by Wurtz coupling reactions of dichlorogermanes with sodium metal, and by a novel method using diiodogermylene and Grignard reagents (or organolithiums). In solution, the polygermanes showed characteristic electronic absorption bands and thermochromism for alkyl-substituted derivatives. Photolysis of the polygermanes proceeded by both the contraction of the chain with loss of diorganogermylenes and the homolytic scission of germaniumgermanium bond.
Charge-tran sfer interaction between polygermanes with electron acceptors and catalytic reactions of transition-metal complexes in polygermanes are also notable.

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Anomalous intense ultraviolet emission bands in the region 320-370 nm with a maximum at 340 nm were observed in radio frequency (rf) glow discharges of CF₄-H₂m ixtures containing 0.3-1 % of GeH4. The corresponding emission system was not observed in the discharge spectra of GeH₄-CH₄-H₂ and SiH₄-CF₄-H₂ mxtures.
Intense ultra violet emission bands around 340 nm were also measured in microwave and rf glow discharges of GeF₄. From the vibrational analysis of the bands, it was found that these 340 nm emission bands completely agree with weak emission system of GeF2, which has been tentatively assigned, in earlier work, as the ³B₁-¹A₁ta rnsition. It confirmed that the emissive carrier is GeF₂ and a rearrangement reaction occurs in the plasma of GeH₄-CF₄-H₂ mxtures.

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Novel diaryl-substituted germylenes Tb (Ar)Ge: [Ar =mesityl (Mes) or 2, 4, 6-triisopropylphenyl (Tip)] stable in solution were synthesized by taking advantage of a new steric protection group, 2, 4, 6tris[bis (trimethylsilyl) methyl]phenyl (denoted as Tb in this article). While Tb (Mes) Ge: survived only at low temperature, the more crowded germylene Tb (Tip) Ge: (λ_max in hexane at room temperature = 580 nm) was stable in hexane even at 60°C to give the corresponding insertion and cycloaddition products in the reactions with methyl iodide, 2, 3-dimethyl-1, 3-butadiene, and benzil.

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Phenylated cyclotetragemane, [ ^t Bu( Ph)Ge]₄( 3 ), was prepared and converted to 1, 2, 3, 4-tetra-tbuty11, 2, 3, 4-tetrachlorocyclotetragerm(a4n)e b y treatment with hydrogenc hloridei n the presenceo f A1C13 in benzene. Among the four possible stereoisomers, only one isomer with the configuration of trans-trans-trans, determined by X-ray diffraction method, was produced. The functionalized cy clotetragermane (4) was reacted with sodium in refluxing THF to give 4, 8-dichloroocta-t-butyltetracyclo [3.3.0.0^{2, 7}.0^{3, 6}]o ctagermane (6) and 3, 4, 7, 8-tetrachlorpocata-t-butyltricyclo [4.2.0.0^{2, 5}] octagermane (7). The molecular structure of the anti-ladder polygermane (7) was unequivocally established by X-ray diffraction method.

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Recent investigations on photochemistry of peralkylpolygermanes have disclosed that they show two photochemical degradation patterns, namely, one is a successive loss of dialkylgermylene, and the other is the formation of polygermyl radicals generated from homolytic fission of a Ge-Ge bond. In this paper in order to clarify photochemical properties of simple Ge-Ge and Ge-C bonds, the solution phase farUV photolysis of more fundamental oligogermanes has been investigated.
On far-UV irradiation a tetraalkylgermane undergoes homolyt ic fission of a Ge-C bond to give the corresponding germyl radical which yields a trialkylgermane by abstraction of hydrogen and a digermane by coupling reaction, respectively. On far-UV photolysis digermane and trigermane show photochemical behavior formally similar to that of their higher homologues, namely the germylene and germyl radical are generated competitively. As the number of germanium atoms in the chain increases, the former process becomes more preferential. Photolysis in the presence of duterated alcohol implies that the germyl radical intervened undergoes disproportionation to give the corresponding hydrogermane and germene.

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New optically active benzylmethylphenylgermylacetic acid (1) and benzylmethylphenylgermanecarboxylic acid (2) were obtained successfully by a fractional crystallization method using a-methylbenzylamine (MBA) as a resolving agent. The optical purities of both 1 and 2 were determined by NMR to be 94%. The relative configurations of 1 and 2 were also discussed.

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Single crystals of a new ternary intermetallic compound Nb₅ (Ge_xSn_1-x)₂Ge have been synthesized by a self flux method using molten tin as a solvent. Solid solution range of the compound is from x=0.25 to x= 0.40. The crystal structure shows a tetragonal symmetry, space group D¹⁸_4h-I4/mcm, W₅Si₃-typ e structure. Lattice constants are a = 10.450 (1), c= 5.1932 (7) Å for x= 0.25 and a= 10.439 (2), c=5.1933 (9) Å for x=0.40. Crystal habit is columnar, (100) and (110) facets are well developed and crystals are elongated along the c-axis. However these crystals do not show superconductivity down to 1.4 K.

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The mechanism and intermediates of photoinduced electron-transfer reaction from hexamethyldigermane to 2, 5-dichloro-1, 4-benzoquinone were studied at room temperature by means of a CIDNP technique. After irradiation, only trimethylgermyl chloride was confirmed by GC, GC-MS, ¹H-NMR spectra. However, the absorptive CIDNP signals for ring and hydroxyl-H of 4- (trimethylgermyloxy) phenol were observed during irradiation. The observed CIDNP phase indicates that the reaction intermediate is hexamethyldigermane cation radical rather than trimethylgermyl radical. These results suggest the instability of the cation radical.

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Irradiation (λ>390 nm) of peralkyltrisilagermacyclobutanes in a mixed solvent (MeCN-CH₂Cl₂CCl₄), with a catalytic amount of 9, 10-dicyanoanthracene (DCA) as a photosensitizer gave the corresponding 1, 4-dichloro-1, 2, 3-trisila-4-germabutanes derived from the scission of Si-Ge bonds.

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Reactions of chlorotrimethylgermane with the lithium salts of acetonitrile, acetic esters, and acetamides were investigated. The germyl groups were introduced in stepwise on the α-carbanions to give finally tris (trimethylgermyl) methyl compounds. Peterson olefination reaction of (trimethylgermyl)acetic esters with aldehydes gave selectively (E)-α, β- Bunsaturated esters.

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Novel copolymerizations for the synthesis of germanium-containing polymers using a divalent germanium species, germylene, have been developed. The copolymerization involves a redox process between a germylene (Mred) and an oxidant monomer (Mox). Oxidant monomers employed are p-benzoquinones, N-phenyl-p-benzoquinone monoimines, cyclic α, β-unsaturated ketones, cyclic sulfides, and substituted acetylenes. During the copolymerization, the germylene is oxidized and an oxidant monomer is reduced (“oxidation-reduction copolymerization”). A new germanium-containing polymer having a dithiol unit in the main chain has been synthesized by the oxidative addition of poly (dithioalkylene)toward the germylene.
The reaction m echanism for the copolymerization between germylenes and p-benzoquinone derivatives has been definitely established as a biradical polymerization system involving a germyl radical and a semiquinone radical. This providesthe first clear-cut evidence for a biradical mechanism in the polymerization chemistry.
In addition, a ligand exchange polymerization has been found as a new concept in polymerization chemistry, which affords a polygermane of higher molecular weight.

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There has been considerable interest in recent years in the synthesis of bioactive organogermanium compounds. Previously, we observed that poly[3, 3'-(1, 3-dioxo-1, 3-digermoxanediy1) bispropanoic acid] (Ge-132) has a unique chemical structure and shows various physiological activities. Therefore, we synthesized the number of Ge-132 relates compounds (poly (1, 3-dioxodigermoxanes) and bis (1, 3dithioxodigermathianes), germatranes and thiagermatranes, 4, 5-dihydro-5-germafuran-2 (3H)-ones and 4, 5-dihydro-5-germathiophen-2 (3H) -ones, and 3- (trialkylgermyl)propanoic acids). We also clarified and the chemical proparties of these compounds which were found to exhibit more or less active than Ge-132.
Ge-132 and related compounds showed the following pharmacological activities.
1) Antitumor activities against certain tumor being animals.
2) Antiviral activities in virus-infected animals.
These two activities were considered to be based on BRM activities such as activation of macrophase increase of NK activity and increase of humoral immunity. These BRM activities are considered to be based by interferon-γ (IFN) induction, because the formation of IFN γ m-RNA by Ge-132 and related compounds in confirmed by means of PCR method.
3) Regulation of Ca²⁺ metabolism.
4) Alleviation of concerous pain and osteocope.
5) A protective effect against free radicals.
6) Inhibitory activity of the formation of advanced glycation end products (AGE) in tissue, which is accelerated in diabetes mellitus.
Although more soph isticated molecular biological studies remain to be conducted, we believe that a new type of therapeutic agents may be derived from these oraganogermanium derivatives.

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The Friedel-Crafts type reaction of (substituted allyl) triethylgermanes (1) with anisole was studied. When allylgermanes (1) were treated with two equimolar amounts of copper (II) chloride in an isole at room temperature, the allylated products (2) were obtained in good yields.
The regioselectivity of the reaction is largely affected by substituents on allylgermanes (1); a methoxyphenyl group is selectively introduced to the less substituted side of an allylic system. In the case of the reactions of regioisomeric (1, 3disubstituted allyl) germanes (1c and d), the allylated compounds (2)with almost the same product distribution were obtained regardless of the original location of triethylgermyl group. These results suggest that the present reaction proceeds via the allylic carbocation intermediate (4).
It was found that the Friedel-Crafts type reaction of 1 was effected also with tin (IV) chloride, and the allylated products (2) were obtained with the similar regioselectivity observed in the copper (II) chloridepromoted reactions. On the basis of the fact that allyltriphenylstannane (6) was formed by the successive treatments of allyltriethylgermane with tin (IV) chloride and phenylmagnesium bromide, it is assumed that the tin (IV) chloride promoted reaction may proceed through the allyltrichlorostannane intermediate (5).

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Organic germanium compounds [bis (2-carboxyethylgermanium) trioxide: Ge-132, bis (2-amino-2carboxy-1-phenylethylgermanium) triwdde: Ge-373, bis (2-amino-2-carboxyethylgermanium) trioxide: Ge-385] were found effective in suppressing the formation of Advanced Glycation Endproducts (AGE)from serum proteins, collagen and lens crystallin. We examined the Maillard reaction between amino acids and ribose, and the effects of organic Ge-compounds on the reaction. Ge-compounds did not prevent the formation of Amadori-rearranged substances (ARS), but inhibited further progress toward AGE formation. Specifically, Ge-385 caused the decrease in AGE after incubating the mixtures for longer than 10 days. The mode of action of Ge-compounds in the Maillard reaction was investigated by a NMR to clarify the interaction between glucose and organic Ge-compounds. These compounds could conjugate glucose directly through hydroxyl residues of glucose at the sites 1 and 2. The glucose Gecompound complexes might result in the disconnection of amino-carbonyl products to glucosone and amino residues. Organic germanium compound, specifically Ge-385, which has two amino residues in its one molecule, appears to be much more effective than Ge-132 in the prevention of AGE formation by making carbonyl-NH₂- (Ge-385) conjugates as the substitute of reactive amino residues on functional polypeptides. The effects of organic Ge-compounds were examined in DM-rats induced by streptozotocin (STZ). Both drugs, Ge-132 and 385, were respectively administered to STZ-DM-rats via peroral rout, and clinico-pathological examinations revealed that the formation of glycated serum albumin, serum fructosamine, and cataract (turbidity of lens) were remarkably improved. Ge-compounds are the first candidates that prevent and reversibly solubilize the Maillard products which induce severe clinical complications in patients with diabetes mellitus.

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