Kunio Mochida

Synthesis, absorption characteristics and some reactions of polygermanes

Abstract A number of high molecular weight polygermanes were prepared by an improvement on Wurtz coupling reactions of dichlorogermanes and sodium metal, and by a method using diiodogermylene and Grignard reagents (or organolithiums). Most of the polygermanes thus prepared showed a narrow molecular distribution containing molecular weights 10 3 –10 4 . In solution, the polygermanes showed characteristic electronic absorption bands at 300–350 nm and were strongly thermochromic for alkyl-substituted derivatives. Photolysis of the polygermanes proceeded by both contraction of the chain with loss of diorganogermylenes and homolytic scission of the germanium—germanium σ bond.

CIDEP study of the formation of a cyclohexadienyl-type radical in the hydrogen abstraction reactions of triplet xanthone

Abstract From CIDEP measurements a new reaction of triplet xanthone, hydrogen abstraction by a benzene ring, was found to occur in the reactions with triethylgermane and sodium borohydride. An anomalous E/A phase pattern within each hyperfine line was also observed for the generated cyclohexadienyl-type radical in a micelle.

Preparation and reactions of solvent-free arylcalcium halides ArCaX (X = F, Cl, Br)

Abstract Reactions of aryl halide vapor and calcium metal vapor were found to give the corresponding arylcalcium halides, ArCaX (X = F, Cl, and Br). Phenylcalcium halides, PhCaX (X = F and Cl), reacted with trimethylchlorosilane to give phenyltrimethylsilane. The reactions of phenylcalcium halides with acetone and benzaldehyde readily gave good yields of 1-methyl-1-phenylethanol and diphenylmethanol, respectively. Phenylcalcium halides reacted slowly with acetonitrile to afford acetophenone in poor yields. With ethyl acetate, phenylcalcium halides gave a mixture of 1,1-di-phenylethanol and acetophenone.

A new method for preparation of organocalcium halides by cocondensation of calcium vapor with solvents

Abstract Calcium vapor (atom) when cocondensed with various solvents at 77 K was found to be very reactive toward alkyl and aryl halides. A series of organocalcium halides was prepared in good yields by addition of alkyl or aryl halides to the resultant calcium atom-solvent slurries at ambient temperatures.

Photochemistry of aryl-substituted trigermanes. Generation and mechanism of formation of germylenes

Photochemical reactions of aryl-substituted trigermanes have studied by trapping experiments, matrix isolation, and laser flash-photolysis techniques. Photolysis of the phenylated trigermanes involved both the simple extrusion of germylenes and the formation of germyl radicals and digermyl radicals. The photochemically generated germylenes react with 2,3-dimethylbutadiene or CCl4 to give germacyclopentenes or trichloromethylchlorogermanes, respectively. The germyl radicals and digermyl radicals abstract chlorine atoms from CCl4 to produce chlorogermanes and chlorodigermanes. Two well-separated transient absorption bands (320–330 and 420–450 nm) obtained by laser flash-photolysis of the trigermans in cyclohexane at 293 K were found to be due to phenylated digermyl radicals and germylenes, respectively. The rates of the reactions of phenylated digermyl radicals and germylenes with some substrates have been examined. In 3-methylpentane, glass germylenes show an absorption band at 420–462 nm. The mechanism is discussed.

Photodegradation of thin films of polygermanes

Abstract Upon ultraviolet irradiation of thin films of linear polygermanes in air, the germanium-germanium bond in thin films of polygermanes changed into digermoxane chains. The laser flash photolysis of the linear polygermane films showed the formation of polygermyl radicals generated by germanium-germanium bond homolysis as reactiev intermediated during photodegradation.

Reactivity, absorption and emission of dimethylgermylene photo-generated from dodecamethylcyclohexagermane

Abstract The UV photolysis of dodecamethylcyclohexagermane ( 1 ) in cyclohexane at room temperature proceeds readily with loss of dimethylgermylene species to give two of the lower homologs, decamethylcyclopentagermane ( 3 ). The photochemically generated dimethylgermylene species reacts with 2,3-dimethylbuta-1,3-diene or CCl 4 to give 1,1,3,4-tetramethyl-1-germacyclopent-3-ene or trichloromethyldimethylchlorogermane, respectively. The transient absorption of 1 in cyclohexane at 450 nm obtained by laser flash-photolysis is due to dimethylgermylene. The reaction rates of dimethylgermylene with some substances are examined. In 3-methylpentane glass dimethylgermylene shows an absorption band at 430 nm and a fluorescence peak at 650 nm. The photo-generated germylene appears to be the singlet ground state.

Preparation and structural characterization of trimethylsilyl-substituted germylzinc halides, (Me3Si)3GeZnX (X=Cl, Br, and I) and silylzinc chloride, R(Me3Si)2SiZnCl (R=SiMe3 and Ph)

Abstract The trimethylsilyl-substituted germylzinc halides, (Me3Si)3GeZnX (X=Cl, Br, and I), and silylzinc chlorides, R(Me3Si)2SiZnCl (R=SiMe3, Ph), have been prepared and their molecular structures have been full determined by spectroscopic and single-crystal X-ray diffraction methods. The germylzinc halides and silylzinc chlorides have dimeric structures consisting of two μ-halogen atoms. The reactivity of germylzinc chloride with substrates is also examined.

Laser-photolysis study of the photochemical primary processes of hydrogermanes in solution

Abstract The mechanisms of the photochemical reactions of triphenylgermane and 1-naphthylpitenylmethylgermane in solution were studied, by measurement of the transient absorption spectra of their triplet states and germyl radicals. The rate constant for the chlorine abstraction reaction by each radical with CCl 4 was determined to be (6.6 ± 1.0) × 10 8 s −1 mol −1 dm 3 at 28.5°C.

Organogermanium compounds : III. Reduction of substituted benzyl chlorides with triethylgermane

Abstract The reactivities of seven nuclear-substituted benzyl chlorides relative to that of unsubstituted benzyl chloride in reaction with triethylgermane containing dibenzoyl peroxide in benzene at 80.0° have been investigated. Electron-withdrawing substituents increase the reactivity, and the rates can be correlated by the Hammett equation with a ϱ value of 0.312. It is concluded that the resonance effect ois not important in the transition state, and that the relative rates are governed mainly by polar effects, with the germyl radical behaving as a nucleophile.