Akinobu Naka

Silicon-carbon unsaturated compounds LIV: Nickel-catalyzed reactions of 3,4-benzo-1,1,2,2-tetraethyl-1,2-disilacyclobut-3-ene with alkynes

The nickel-catalyzed reactions of 3,4-benzo-1,1,2,2-tetraethyl-1,2-disilacyclobut-3-ene (1) with disubstituted acetylenes have been investigated. Treatment of 1 with 3-hexyne and diphenylacetylene at 150°C gave two types of adducts: 5,6-benzo-1,4-disilacyclohexa-2,5-diene and 5,6-benzo-1,2-disilacyclohexa-3,5-diene, together with a small amount of the other isomer. The reaction of 1 with phenyl(trimethylsilyl)acetylene produced 5,6-benzo-1,1,4,4-tetraethyl-3-phenyl-2-trimethylsilyl-1,4-disilacyclohexa-2,5-diene and 4,5-benzo-1,1,3,3-tetraethyl-2-[phenyl(trimethylsilyl)methylene]-1,3-disilacyclopent-4-ene (10). Similar reaction of 1 with 1-(trimethylsilyl)hexyne also afforded 5,6-benzo-3-butyl-1,1,4,4-tetraethyl-2-trimethylsilyl-1,4-disilacyclohexa-2,5-diene and 4,5-benzo-2-[butyl(trimethylsilyl)methylene]-1,1,3,3-tetraethyl-1,3-disilacyclopent-4-ene (12). A vinylidene carbene-nickel complex is proposed for the formation of 10 and 12, as a key intermediate.

Influence of π-conjugation length on mobilities of charge carriers in conducting polymers

Mobilities of charge carriers in thin films of a series of copolymers with repeat units consisting of oligothiophenes bridged by Si atoms are measured over a range of oxidation stages in order to study the influence of π-conjugation length on the mobility. The number of thiophene units in oligothiophenes ranges from five to nine, the polymers being designated accordingly by PS5T to PS9T. Mobilities of charge carriers in these polymer films, where intrachain hopping transport is restricted within each oligothienylene unit, are constant in the low doping regions below 1%. As the doping level increases, mobilities for polymers with longer π-conjugation lengths start to rise at lower doping levels. The mobility enhancement follows also an increasing order of the π-conjugation length, although the 30 times enhancement of mobility for PS9T is still smaller than the four orders-of-magnitude increase of mobility observed earlier for electrochemically synthesized poly(3-methylthiophene). The results are discussed with electrochemical and spectroelectrochemical measurements from the viewpoint of the involvement of polarons, π-dimers, and bipolarons as possible charge carriers in the conduction mechanisms.

Silicon–carbon unsaturated compounds. 62. Reactions of silenes produced thermally from pivaloyl- and adamantoyltris(trimethylsilyl)silane with mono(silyl)acetylenes

Abstract Thermolysis of pivaloyltris(trimethylsilyl)silane ( 1a ) with tert -butyldimethylsilylacetylene at 120°C gave 2- tert -butyl-3- tert -butyldimethylsilyl-2-trimethylsiloxy-1,1-bis(trimethylsilyl)-1-silacyclobut-3-ene ( 2a ). Similar treatment of adamantoyltris(trimethylsilyl)silane ( 1b ) at 120°C produced 2-adamantyl-3- tert -butyldimethylsilyl-2-trimethylsiloxy-1,1-bis(trimethylsilyl)-1-silacyclobut-3-ene ( 2b ). Thermolysis of 1a with tert -butyldimethylsilylacetylene at 160°C, however, gave 1- tert -butyl-1-( tert -butyldimethylsilyl)-3-[(trimethylsiloxy)bis(trimethylsilyl)silyl]-1,2-propadiene ( 3a ), along with 1:2 adduct ( 4a ). Similar reaction of 1b gave 1-adamantyl-1-( tert -butyldimethylsilyl)-3-[(trimethylsiloxy)bis(trimethylsilyl)silyl]-1,2-propadiene ( 3b ) similar to 3a , together with 1:2 adduct ( 4b ). Thermolysis of 1a and 1b in the presence of dimethylphenylsilylacetylene or triphenylsilylacetylene at 120°C produced [2+2] cycloadducts arising from the reaction of silenes generated thermally from 1a and 1b with mono(silyl)acetylenes analogous 2a and 2b , along with small amounts of 1:2 adducts. At 160°C, the similar treatment of 1a and 1b afforded propadiene derivatives arising from the ring opening reactions of [2+2] cycloadducts, in addition to 1:2 adducts.

Nickel-catalyzed reactions of 3,4-benzo-1,1,2,2-tetraethyl-1,2-disilacyclobutene

The reaction of 3,4-benzo-1,1,2,2-tetraethyl-1,2-disilacyclobutene (1) with benzene in the presence of a catalytic amount of Ni(PEt3)4 affo

Palladium-catalyzed reactions of 1,1,2,2-tetraethyl- and 1,1,2,2-tetra(isopropyl)-3,4-benzo-1,2-disilacyclobut-3-ene with alkynes

Abstract The reactions of 3,4-benzo-1,1,2,2-tetra(isopropyl)-1,2-disilacyclobut-3-ene ( 2 ) with acetylene, phenylacetylene, 1-hexyne, and o -tolylacetylene in the presence of tetrakis(triphenylphosphine)palladium gave the respective 5,6-benzo-1,4-disilacyclohexa-2,5-dienes 3–6 . Similar reactions of 2 with mesitylacetylene, trimethylsilylacetylene, and dimethylphenylsilylacetylene afforded 1-alkynyl(diisopropylsilyl)-2-(diisopropylsilyl)benzenes 7–9 arising from sp-hybridized CH bond activation of acetylenes. The reactions of 3,4-benzo-1,1,2,2-tetraethyl-1,2-disilacyclobut-3-ene with mesitylacetylene, trimethylsilylacetylene, and dimethylphenylsilylacetylene produced 5,6-benzo-1,4-disilacyclohexa-2,5-dienes 10–12 as the sole product. The stoichiometric reaction of 2 with tetrakis(triphenylphosphine)palladium gave a yield of 3,4-benzo-2,2,5,5-tetra(isopropyl)-1-pallada-2,5-disilacyclopent-3-ene ( A ), arising from insertion of a palladium species into a silicon-silicon bond in 2 .

Optical properties of poly(disilanyleneoligothienylene)s and their doping characteristics

Optical absorption spectra, photoluminescence (PL), Stokes shift, and electroluminescence (EL) in poly(disilanyleneoligothienylene)s have been found to be dependent on the length of oligothienylene units. The color of EL changes from green to red with increasing length of oligothienylene from three to seven thiophene rings. Their stability is much higher than polysilanylene and increases with increasing length of oligothienylene and by C60 doping. Photoconductivity is strongly enhanced and PL is remarkably quenched upon C60 doping, which were discussed by the photo-induced electron transfer between aromatic units in these polymers and C60.

Insight into the pore tuning of triazine-based nitrogen-rich organoalkoxysilane membranes for use in water desalination

A promising new triazine-based nitrogen-rich organosilica (TTESPT) membrane has been developed for molecular separation processes in gas (gas separation) and liquid phases (reverse osmosis (RO)). By adjusting the H2O/TTESPT molar ratio, we found a promising technique for tuning the pore network of TTESPT membranes. An increase in the H2O/TTESPT molar ratio from 60 to 240 fully hydrolyzed all the ethoxide groups in the TTESPT membrane, which reduced the size of the pores in the silica pore network. A TTESPT membrane with a high H2O/TTESPT molar ratio exhibited a high degree of selectivity for H2/SF6 (greater than 4000) at a permeation temperature of 200 °C. This membrane also demonstrated high sodium chloride (NaCl) rejection (>98.5%) with water permeability of >1 × 10−12 m3 m−2 s−1 Pa−1 under operating conditions of 1 MPa and 60 °C during a RO experiment. As the operating temperature was increased from 25 to 60 °C, the NaCl rejection was constant without displaying the characteristic flux deterioration. This showed that the membrane retained a stable hybrid network structure.

Platinum-catalyzed reactions of 3,4-benzo-1,1,2,2-tetra(isopropyl)-1,2-disilacyclobut-3-ene with mono- and di-substituted alkynes

Abstract The reactions of 3,4-benzo-1,1,2,2-tetra(isopropyl)-1,2-disilacyclobut-3-ene ( 1 ) with phenylacetylene and 1-hexyne in the presence of a catalytic amount of ( η 2 -ethylene)bis(triphenylphosphine)platinum(0) at 200°C for 24 h gave two types of 1:1 adducts, 2-phenyl- and 2-butyl-substituted 5,6-benzo-1,1,4,4-tetra(isopropyl)-1,4-disilacyclohexa-2,5-diene and 2-benzylidene- and 2-pentylidene-substituted 4,5-benzo-1,1,3,3-tetra(isopropyl)-1,3-disilacyclopent-4-ene, respectively. With mesityl- and dimethylphenylsilylacetylene. 1 afforded 2-(mesityl)methylene- and 2-(dimethylphenylsilyl)methylene-4,5-benzo-1,1,3,3-tetra(isopropyl)-1,3-disilacylclopent-4-ene. A similar reaction of 1 with trimethylsilylacetylene produced an adduct arising from sp-hybridized CH bond activation of the acetylene, together with a benzodisilacyclopentene derivative. The reaction of 1 with diphenylacetylene yielded a 2,3-diphenyl-5,6-benzodisilacyclohexa-2,5-diene derivative, while with methylphenylacetylene and 2-hexyne, 1 gave 2-benzylidene- and 2-butylidene-5,6-benzo-1,4-disilacyclohex-5-ene, along with the benzodisilacyclohexa-2,5-diene derivatives. Similar treatment of 1 with methyl(trimethylsilyl)acetylene produced a 5,6-benzo-2-(trimethylsilyl)methylenedisilacyclohexene derivative.

Optical and electrochemical properties of a series of monosilanylene–oligothienylene copolymers in solution

Chemical and electrochemical oxidation of a series of copolymers consisting of a repeat unit of monosilanylene and oligothienylene (PSnT, n = 5–9, n denotes the ring number of an oligothienylene unit) is studied at room temperature. It is found that the oligothienylene unit of each copolymer is oxidized in the first oxidation step to cation radicals in equilibrium with π-dimers, and in the subsequent step to dications. Energies of all absorption bands for these oxidized species and oxidation peak potentials for PSnT in solution scale linearly with the inverse of the size of the oligothienylene unit. The formation of π-dimers is found to be favored by extension of the oligothienylene unit in PSnT. The equilibrium constant for the formation of π-dimers for PS5T is evaluated as 5 × 104 M−1.

Silicon-Carbon Unsaturated Compounds. 53. Thermal Reactions of Acylpolysilanes

Thermolysis of six acylpolysilanes, acetyl-, isopropionyl-, pivaloyl-, adamantoyl-, benzoyl-, and mesitoyltris (trimethylsilyl)silane (1–6), in the presence or absence of a trapping agent has been examined. Thermolysis of 1 in benzene at 150°C gave 1,1,1,4,4,4-hexamethyl-2-[1-(trimethylsiloxy)ethenyl]-3-[1-(trimethylsiloxy)ethyl]-2,3-bis(trimethylsilyl)tetrasilane (7). Similar treatment of 2 at 140°C produced 1,1,1,3,3,3-hexamethyl-2[1-isopropyl-3-methyl-2-(trimethylsiloxyl)-1-butenyl] -2-(trimethylsiloxy)trisilane (9), along with a dimer (8), analogous to 7. Thermolysis of 3 and 4 under the same conditions afforded no products, but the starting compounds were recovered quantitatively, while 5 and 6 yielded mainly nonvolatile substances. The thermolysis of 1–4 in the presence of 2,3-dimethyl-1,3-butadiene produced both [2+4] cycloadducts and ene adducts arising from the reaction of silenes generated thermally from 1–4 with butadiene, while 5 and 6 gave only [2 + 4] cycloadducts. With α-methylstyrene, 1–6 ...