Kunio Mochida

Polystyrene-supported hydrogermanes (1-4) were prepared by functionalization of polystyrenes or functionalization of a styrene followed by polymerization. The hydrogermanes, 1-4, reduced organic halides with or without a catalyst to give alkanes under mild conditions in the order: C-I>C-Br>C-Cl. The hydrogermanes, 1-4, were easily separated after use by filtering and could be regenerated with lithium aluminum hydride after their reactions with organic halides. (C) 2003 Elsevier Ltd. All rights reserved.

Thermal reactions of 1,2-dimetallacyclohexa-3,5-dienes (1-3) with tetracyanoethylene (TCNE) were investigated. The reaction of 1,2-disilacyclohexa-3,5-diene (1) with TCNE mainly gave 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10-tetraphenyl-3-aza-2, 11-disilatricyclo[6.2.1.03,7]undeca-4,6,9-triene through a charge-transfer complex. The reaction of 1,2-digermacyclohexa-3,5-diene (2) with TCNE afforded 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9, 10-tetraphenyl-3-aza-2,11-digermatricyclo[6.2.1.03,7] undeca-4,6,9-triene. 2,2,3,3-Tetracyano-7,7-dimethyl-1,4,5,6- tetraphenyl-7-germabicyclo[2.2.1]hept-5-ene was also detected. On the other hand, 1-germa-2-silacyclohexa-3,5-diene (3) reacted with TCNE to give 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10- tetraphenyl-3- aza-11-germa-2-silatricyclo[6.2.1.03,7] undeca-4,6,9-triene, 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10- tetraphenyl-3-aza-11- germa-2-silatricyclo[6.3.01,8 .03,7]undeca-4,6,9- triene, and 2,2,3,3-tetracyano-7,7-dimethyl-1,4,5, 6-tetraphenyl-7- germabicyclo[2.2.1]hept-5-ene as main products. The mechanism of the formation of new heterocyclic compounds through electron-transfer reactions of 1,2-dimetallacyclohexa-3,5-dienes with TCNE is discussed. © 2003 Elsevier Science B.V. All rights reserved.

Thermal reactions of 1,2-dimetallacyclohexa-3,5-dienes (1-3) with tetracyanoethylene (TCNE) were investigated. The reaction of 1,2-disilacyclohexa-3,5-diene (1) with TCNE mainly gave 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10-tetraphenyl-3-aza2,11-disilatricyclo[6.2. 1.0(3,7)]undeca-4,6,9-triene through a charge-transfer complex. The reaction of 1,2-digermacyclohexa-3,5-diene (2) with TCNE afforded 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10-tetraphenyl-3-aza-2,11-digermatricyclo[6.2. 1.0(3,7)]undeca-4,6,9-triene. 2,2,3,3-Tetracyano-7,7-dimethyl-1,4,5,6-tetraphenyl-7-germabicyclo[2.2.1]hept-5-ene was also detected. On the other hand, 1-germa-2-silacyclohexa-3,5-diene (3) reacted with TCNE to give 4-amino-5,6-dicyano-2,2,1 1,11-tetramethyl-1,8,9,10-tetraphenyl-3-aza-11-germa-2-silatricyclo[6.2. 1.0(3,7)]undeca-4,6,9-triene, 4-amino-5,6-dicyano-2,2,1 1,11-tetramethyl-1,8,9,10-tetraphenyl-3-aza-11-germa-2-silatricyclo[6.3.0(1,8).0(3,7)]undeca-4,6,9-triene, and 2,2,3,3-tetracyano-7,7-dimethyl-1,4,5,6-tetraphenyl-7-germabicyclo[2.2.1]hept-5-ene as main products. The mechanism of the formation of new heterocyclic compounds through electron-transfer reactions of 1,2-dimetallacyclohexa-3,5-dienes with TCNE is discussed. (C) 2003 Elsevier Science B.V. All rights reserved.

The trimethylsilyl-substituted germylzine halides, (Me3Si)(3)GeZnX (X = Cl, Br, and 1), and silylzinc chlorides, R(Me3Si)(2)SiZnCl (R = SiMe3, Ph), have been prepared and their molecular structures have been full determined by spectroscopic and single-crystal Xray diffraction methods. The germylzinc halides and silylzinc chlorides have dimeric structures consisting of two mu-halogen atoms. The reactivity of germylzinc chloride with substrates is also examined. (C) 2003 Elsevier Science B.V. All rights reserved.

Preparation and structural characterization of trimethylsilyl-substituted germylzinc halides, (Me<sub>3</sub>S<sub>i</sub>)<sub>3</sub>GeZ<sub>n</sub>X(X=Cl, Br, and I)and silylzinc chlorides, R(Me<sub>3</sub>S<sub>i</sub>)<sub>2</sub>SiZnCl(R=S<sub>i</sub>Me<sub>3</sub>andPh)

Alkyl(chloro)ethoxygermanes were hydrolyzed with water to give 1,3,5-trialkyl-1,3,5-trichlorocyclotrigermoxanes. Hydrolysis of 1,3,5-trichlorocyclotrigermoxanes gave 5,7-dichloro-1,3,5,7,9,11-hexaalkyltricyclo[7.3.1.13,7 ]-hexagermoxanes. The tricylic anti-form ladder hexagermoxanes reacted with water to afford hexakis(alkylgermasesquioxane)s. These cage and ladder germoxanes were identified by spectrospcopic and X-ray diffraction methods.

Alkyl(chloro)ethoxygermanes were hydrolyzed with water to give 1,3,5-trialkyl-1,3,5-trichlorocyclotrigermoxanes. Hydrolysis of 1,3,5-trichlorocyclotrigermoxanes gave 5,7-dichloro-1,3,5,7,9,11-hexaalkyltricyclo[7.3.1.13,7 ]-hexagermoxanes. The tricylic anti-form ladder hexagermoxanes reacted with water to afford hexakis(alkylgermasesquioxane)s. These cage and ladder germoxanes were identified by spectrospcopic and X-ray diffraction methods.

The molecular structure of (Me3Si)3GeZnCl (1) has been determined by single-crystal X-ray diffraction. The germylzinc chloride 1 has a dimeric structure consisting of two μ-Cl atoms. The compound 1 reacted with (Me3Si)3GeLi in diethyl ether to give [(Me3Si)3Ge]2Zn (2), quantitatively. The structure of bis(germyl)zinc 2 has been also elucidated by X-ray diffraction.

Sublevel properties of the lowest excited triplet (T1) nπ* states of α-silyl and α-germyl ketones were examined by means of ODMR, time-resolved EPR and optical spectroscopy. The EPR parameters, D, E and g, population ratios, and triplet lifetimes were obtained. The D value and the triplet lifetime varied among the molecules. In contrast the E value and population ratio remains nearly the same. These properties together with their solvent dependence and emission properties are interpreted in terms of spin-orbit couplings between T1 (nπ*) and higher S1 (nπ*), T2 (ππ*) and S2 (ππ*) states. An origin of the remarkable red-shifts of 1,3(nπ*) are discussed based on a model of delocalized n, π and π* electrons over the Si and Ge atoms. This model is also consistent with all the triplet properties obtained.

The reactivity of lithium (triethylgermyl)triphenylborate, prepared from unsolvated triethylgermyllithium and triphenylborane, with organic substrates in methanol was investigated. The germylborates reacted with organic halides and acyl halides to give the corresponding germyl-substituted compounds. From the reaction with carbonyl compounds, esters, carboxylic acid, alkenes, and alkynes, germylborates were completely recovered.

EPR signals of the triphenylsilyl and triphenylgermyl radicals were observed for the first time in fluid solution by direct photolysis of hexaphenyldisilane and hexaphenyldigermane. Observed electron spin polarization was interpreted in terms of a triplet mechanism (TM). Along with the main signal, the Si-29 isotope signal was also observed and the polarization was tentatively explained by combination of a TM and a radical pair mechanism. An electron density on the silicon atom of the silyl radical was determined as 0.52 from the isotropic hyperfine coupling constant of Si-29. The triphenylstannyl radical was not observed with the time resolution (ca. 80 ns) of our system.

The reactivity of lithium (triethylgermyl)triphenylborate, prepared from unsolvated triethylgermyllithium and triphenylborane, with organic substrates in methanol was investigated. The germylborates reacted with organic halides and acyl halides to give the corresponding germyl-substituted compounds. From the reaction with carbonyl compounds, esters, carboxylic acid, alkenes, and alkynes, germylborates were completely recovered.

The photochemistry of 1,4-diphenyl-2,3-benzo-7,7,8,8-tetraalkyl-7,8-digermabicyclo[2.2.2]octadienes in solution has been studied in detail by steady-state, nanosecond laser flash photolysis, and matrix isolation techniques. Photolysis of 7,8-digermabicyclo[2.2.2]octadienes in solution resulted mainly in the formation of tetraalkyldigermenes and 1,4-diphenylnaphthalene in the triplet excited state. The 7,8-digermabicyclo[2.2.2]octadiene also photochemically isomerized to 1,4-diphenyl-2,3-benzo-6,6,7,7-tetraalky-6,7-digermatricyclo[3.3.0.0]octane as minor product. The reactions of tetraalkyldigermenes with butadienes (2,3-dimethylbuta-1,3-diene and 2-methylbuta-1,3-diene), carbon tetrachloride, and methanol gave the corresponding digermene trapped products: 1,2-digennacyclohex-4-enes, 1,2-dichlorodigermanes together with hexachloroethane, and methoxydigermanes, respectively, in good yields. The transient bands of tetraalkyldigermenes using nanosecond laser flash photolysis appeared at ca. 380 nm. The rate constants for the quenching reactions of the digermene with oxygen, polyhalomethanes, alcohols, 2,3-dimethylbuta-1,3-diene, 1-hexyne, and triethylsilane were also measured under various conditions. The quenching reactions of digermenes with carbon tetrachloride and ethanol (k = similar to 10(7) M-1 s(-1)) are 100 times faster than that with 1,3-butadiene (h = similar to 10(5): M-1 s(-1)). The digermenes were very rapidly quenched with oxygen (h = similar to 10(8) M-1 s(-1)), but very slowly with 1-hexyne and triethylsilane (k < 10(4) M-1 s(-1)) under reaction conditions. The UV absorption bands of tetraalkyldigermenes generated from 7,8-digermabicyclo[2.2.2]octadienes in matrix at 77 K were also observed at 370-380 nm. The mechanism of digermene formation was also discussed.

Calcium vapor (atom) when co-condensed with THF reacts very smoothly with alpha -bromo- and alpha -chloroesters at -20 similar to -50 degreesC to afford enolates, which react with aldehydes to give good yields of beta -hydroxyesters in high stereoselectivity after hydrolysis.

Various cyanofluoromethylated amides, thioamides, and phosphorus compounds were synthesized from the corresponding chlorides using a 2-fluoro-2-phenylthio-2-phenylacetonitrile/ Et3GeNa combination. These preparative reactions proceeded smoothly under mild reaction conditions to give the desired compounds in good yields.

The radical cation of dodecamethylcyclohexagermane, (Me2Ge)6, generated by pulse radiolysis technique showed two transient absorption bands at 310 and 410 nm. These transient peaks were quenched with triphenylamine as a radical cation scavenger.

Some new germanium analogues of 1,3-cyclohexadiene,3,4,5,6-tetraphenyl-, 3,6-diphenyl-, and 3,4,5,6-tetramethyl-1,2-digermacyclohexa-3,5-diene and 3,4,5,6-tetraphenyl-1-germa-2-silacyclohexa-3,5-diene, were prepared and fully characterized by spectroscopic methods. On photolysis, the 1,2-digermacyclohexa-3,5-diene underwent extrusion of dialkylgermylene (R2Ge:) to give the corresponding germacyclopentadiene. On irradiation the 1-germa-2-silacyclohexa-3,5-diene yielded preferentially the silacyclopentadiene via extrusion of R2Ge:. The mechanism of these photolyses is discussed.

Photochemical reactions of digermanyl-substituted naphthalenes have been investigated by chemical studies using trapping agents, laser flash photolysis, and ab initio MO calculations. Irradiation of 1-(pentamethyldigermanyl)naphthalene (1) afforded mainly an isomer, 1-(dimethylgermyl)-8-(trimethylgermyl)naphthalene (4), via photochemical formation of a pair of trimethylgermyl radical and 1-naphthyldimethylgermyl radical, and then recombination at the 8-position of the latter followed by an intramolecular 1,4-hydrogen shift. At the same time a small amount of 1-(trimethylgermyl)naphthalene (5) was formed through the dimethylgermylene extrusion from 1. From photolysis of 2-(pentamethyldigermany)naphthalene a high molecular weight polymer was obtained. The excited states of digermanyl-substituted naphthalenes responsible for the photodecomposition are also discussed. (C) 1998 Elsevier Science S.A.

Oligo(digermanylene-phenylene)s and related oligomers were prepared by treatment of di-Grignard reagents of the corresponding aryl dibromides with 1,2-dichlorotetramethyldigermane. Upon ultraviolet irradiation of films of oligo(digermanylene-phenylene) and related oligomer in air, the germanium-germanium bond in the oligomer films changed into a digermoxane chain probed by XPS. The laser flash photolysis of the oligo(digermanylene-phenylene) film showed the formation of an oligogermyl radical as a reactive intermediate during photodegradation. Iodine doping of the oligomers showed the conductivities of the order of 10(-4) S cm(-1) (C) 1998 Elsevier Science Ltd. All rights reserved.