Tohoku University · Materials Science
Professor Shintaro Ishida's research lab specializes in the synthesis, characterization, and reactivity of low-valent main-group element compounds, particularly those featuring silicon, phosphorus, antimony, and bismuth in unusual oxidation states. The lab focuses on generating and stabilizing highly reactive intermediates such as silylenes, phosphinyl, stibinyl, and bismuthinyl radicals using steric protection and electronic stabilization. Their work explores novel bonding motifs, including silicon-silicon π single bonds and unique metal-ligand interactions with disilenes and silylenes, often combining experimental techniques with DFT calculations to elucidate electronic structures and reaction mechanisms.
Figures are computed from collected data and may differ slightly.
Dialkylphosphinyl radical 1 was synthesized as thermally stable yellow crystals and found to be monomeric both in solution and in the solid state. EPR spectrum showed that the spin density of 1 is mainly localized on the 3p orbital of the dicoordinated phosphorus atom. A distinct absorption band due to the electronic transition from nonbonding electron pair orbital to singly occupied 3p orbital on the phosphorus atom of 1 was observed at 445 nm in solution. Phosphinyl radical 1 underwent facile
Stibinyl and bismuthinyl radicals are recognized as representative intermediates of antimony and bismuth compounds, but still elusive in the condensed phase. We successfully synthesized persistent stibinyl and bismuthinyl radicals in solution by facile dissociation of the corresponding dimers with bulky substituents. We characterized the radicals by NMR and UV/Vis spectroscopy and estimated the thermodynamic parameters for the dissociation equilibria. The radicals show n→p (HOMO→SOMO) transition
Not so alkyne like: A dialkyldisilyne (left, green) that can be isolated is synthesized and fully characterized. It coordinates to palladium and platinum in a η(2) -fashion giving complexes (red) with a trans-bent geometry, in contrast to η(2) -alkyne complexes. The complexes showed significant metallacycle character.
Abstract The reactions of an isolable dialkylsilylene, 2,2,5,5‐tetrakis(trimethylsilyl)silacyclopentan‐1,1‐diyl ( 1 ) with ethylene, (Z)‐2‐butene, acetylene, bis(trimethylsilyl)acetylene, and 2,3‐dimethylbutadiene at room temperature gave the corresponding silacycles as isolable compounds. Because of the large steric hindrance, the reaction of 1 with (E)‐2‐butene gave a complex mixture, indicating no formation of the corresponding silirane. The reaction of 1 with 2,3‐dimethylbutadiene afforded t
A carbon-carbon double bond consists of a σ bond and a π bond. Recently, the concept of a π single bond, where a π bond is not accompanied by a σ bond, has been proposed in diradicals containing carbon and heteroatom radical centers. Here we report a closed-shell compound having a silicon-silicon π single bond. 1,2,2,3,4,4-Hexa-tert-butylbicyclo[1.1.0]tetrasilane has a silicon-silicon π single bond between the bridgehead silicon atoms. The X-ray crystallographic analysis shows that the silicon-s
The reactions of isolable dialkylsilylene 2,2,5,5-tetrakis(trimethylsilyl)-1-silacyclopentane-1,1-diyl with different types of ketones such as adamantanone, acetone, benzophenone, and cyclopropenones proceed smoothly at room temperature to afford the corresponding siloxirane, silyl enol ether, 2-oxa-silacyclopentene, and unusual cyclopropenylsilanes, respectively, without formation of any secondary or side-reaction products. The electronic structure of various types of model carbonyl silaylides
By the reduction of an isolable dialkylsilylene, 2,2,5,5-[tetrakis(trimethylsilyl)]-1-silacyclopentane-1,1-diyl (1), with cesium, rubidium, potassium, sodium, and lithium 4,4'-di(tert-butyl)biphenylide in DME at low temperatures, the corresponding silylene radical anion 2 was generated as the first persistent silylene radical anion in solution and characterized by ESR spectroscopy. Radical anion 2 is rather stable at -70 degrees C in DME but decomposes rapidly at room temperature with a half-lif
Cagey silicon: A silicon cluster, consisting of sixteen silicon atoms and composed of an octasilacuneane core (red, see picture) fused with cyclotetrasilanes (orange), was synthesized by reductive tetramerization of tetrachlorocyclotetrasilane. Analytical and theoretical studies reveal the unique structural and electronic features of this organosilicon cluster.
Abstract Stibinyl and bismuthinyl radicals are recognized as representative intermediates of antimony and bismuth compounds, but still elusive in the condensed phase. We successfully synthesized persistent stibinyl and bismuthinyl radicals in solution by facile dissociation of the corresponding dimers with bulky substituents. We characterized the radicals by NMR and UV/Vis spectroscopy and estimated the thermodynamic parameters for the dissociation equilibria. The radicals show n→p (HOMO→SOMO) t
Abstract Reactions of an isolable dialkylsilylene with dichloromethane and (chloromethyl)cyclopropane occur in solution to afford the double silylene insertion product and an unusual 5-silaspiro[4.4]nonane derivative, respectively. The activation of the carbon–chlorine bonds due to the complexation of haloalkanes with the silylene may facilitate the nucleophilic attack of another silylene under the present reaction conditions.
A persistent dialkylsilanone was synthesized by the dehydrobromination of a dialkylbromosilanol with tris(trimethylsilyl)silyl potassium in solution at -80 °C: It was characterized by NMR and IR spectroscopy, and was tested in several reactions. In (29) Si NMR spectrum in [D8 ]toluene, the signal due to the unsaturated silicon nuclei was observed at 128.7 ppm. Reactions of the dialkylsilanone with water and mesitonitrile oxide gave a silanediol and a [2+3] cycloadduct, respectively. The silanone
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