Co-reporter: Dr. Shintaro Ishida;Yoshifumi Misawa;Shohei Sugawara; Dr. Takeaki Iwamoto
Angewandte Chemie 2017 Volume 129(Issue 44) pp:14017-14020
Publication Date(Web):2017/10/23
DOI:10.1002/ange.201707553
AbstractBenzodisilacyclobutadienes 2 a–c were isolated as blue to green crystalline solids from the reaction of stable disilyne 1 and 1,2-dibromobenzenes in the presence of potassium graphite. In the solid state, substantial bond alternation was observed within the benzene rings of 2 a–c. In hexane, 2 a–c showed remarkable bathochromic shifts of the ππ* (HOMOLUMO) absorption bands at 625–670 nm. NMR spectra and theoretical calculations indicated that the diamagnetic ring currents of the benzene rings of 2 a–c are considerably reduced by contributions from the antiaromatic 1,2-disilacyclobutadienes. In their entirety, the obtained results indicate that 2 a–c represent 8π-electron systems that contain an antiaromatic 1,2-disilacyclobutadiene.
Co-reporter:Shintaro Ishida, Takeaki Iwamoto
Coordination Chemistry Reviews 2016 Volume 314() pp:34-63
Publication Date(Web):1 May 2016
DOI:10.1016/j.ccr.2015.11.007
•Synthesis and molecular structures of η2-disilene and η2-disilyne mononuclear complexes are discussed.•Structural parameters and 29Si resonances of η2-disilene and η2-disilyne mononuclear complexes are comprehensively tabulated.•Related transition metal complexes with η2-dimetallenes of heavy group-14 elements are briefly summarized.Recent progress of η2-disilene and η2-disilylne mononuclear transition metal complexes and related complexes are summarized. Although examples for disilene-transition metal complexes are still limited for group 4, 6, 8, 10 and 11 metals, η2-disilene transition metals complexes have been synthesized by various synthetic methods and structural characteristics are well discussed by using X-ray diffraction analysis, 29Si NMR resonances and Dewar–Chatt–Duncanson model. Reactions of these complexes have been also investigated. Very recently, η2-disilyne-group 10 metal complexes have been synthesized. In addition, transition metal complexes with doubly-bonded silicon compounds such as silenes (R2SiCR′2), silanimines (R2SiNR′), silanones (R2SiO) and related doubly-bonded germanium and tin compounds as η2-ligands are briefly summarized.
Co-reporter:Tomoyuki Kosai, Shintaro Ishida and Takeaki Iwamoto
Chemical Communications 2015 vol. 51(Issue 53) pp:10707-10709
Publication Date(Web):08 Jun 2015
DOI:10.1039/C5CC03424H
Regioselective cycloaddition of dialkylsilylene upon irradiation at 440 nm converts azulene and guaiazulene to bicyclic [4]dendralene and heptafulvene derivatives, respectively. Significant σ–π interactions in the resulting new silacycles were suggested using UV-vis spectra and theoretical calculations.
Co-reporter:Dr. Shintaro Ishida;Dr. Takashi Abe;Dr. Fumiya Hirakawa;Tomoyuki Kosai;Katsuhiro Sato;Dr. Mitsuo Kira ;Dr. Takeaki Iwamoto
Chemistry - A European Journal 2015 Volume 21( Issue 43) pp:
Publication Date(Web):
DOI:10.1002/chem.201503516
Abstract
Invited for the cover of this issue is the group of Takeaki Iwamoto and Shintaro Ishida at Tohoku University (Japan). The image depicts the molecular structure of R2SiO with its 29Si NMR spectrum in solution. Read the full text of the article at 10.1002/chem.201501478.
Co-reporter:Dr. Shintaro Ishida;Dr. Takashi Abe;Dr. Fumiya Hirakawa;Tomoyuki Kosai;Katsuhiro Sato;Dr. Mitsuo Kira ;Dr. Takeaki Iwamoto
Chemistry - A European Journal 2015 Volume 21( Issue 43) pp:15100-15103
Publication Date(Web):
DOI:10.1002/chem.201501478
Abstract
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 29Si 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 remains intact in [D8]toluene below −80 °C for at least two days, while it undergoes unprecedented isomerization to give a siloxysilene by means of 1,3-silyl migration at higher temperatures.
Co-reporter:Dr. Kyohei Otsuka;Naozumi Matsumoto;Dr. Shintaro Ishida;Dr. Soichiro Kyushin
Angewandte Chemie 2015 Volume 127( Issue 27) pp:7944-7947
Publication Date(Web):
DOI:10.1002/ange.201500523
Abstract
The radical anion of octa-tert-butyloctasilacubane was generated and isolated. The EPR spectrum showed the satellites due to the tertiary 13C nuclei of the eight tert-butyl groups. The X-ray crystallographic analysis showed that the SiSi bonds are shortened and the SiC bonds are elongated compared with those of octa-tert-butyloctasilacubane. These results are well explained by the distribution of an unpaired electron in the singly occupied molecular orbital (SOMO).
Co-reporter:Fumiya Hirakawa, Hitomi Ichikawa, Shintaro Ishida, and Takeaki Iwamoto
Organometallics 2015 Volume 34(Issue 12) pp:2714-2716
Publication Date(Web):May 26, 2015
DOI:10.1021/acs.organomet.5b00323
A stable dialkylphosphinyl radical, 2,2,5,5-tatrakis(trimethylsilyl)-1-phosphacyclopentan-1-yl (RH2P•), showed both irreversible one-electron oxidation and reduction peaks at −0.24 and −2.29 V vs ferrocene/ferrocenium couple. One-electron reduction of RH2P• with KC8 in the presence of 18-crown-6 (18-c-6) or [2.2.2]cryptand (crypt-222) gave the corresponding phosphides [K(18-c-6)]+[RH2P]− and [K(crypt-222)]+[RH2P]−. Whereas [K(18-c-6)]+[RH2P]− exists as a contact ion pair, [K(crypt-222)]+[RH2P]− exists as a solvent-separated ion pair in the solid state. Reaction of RH2P• with AgOTf afforded an unexpected product, a silver(I) phosphaalkene complex.
Co-reporter:Dr. Shintaro Ishida;Dr. Takashi Abe;Dr. Fumiya Hirakawa;Tomoyuki Kosai;Katsuhiro Sato;Dr. Mitsuo Kira ;Dr. Takeaki Iwamoto
Chemistry - A European Journal 2015 Volume 21( Issue 43) pp:
Publication Date(Web):
DOI:10.1002/chem.201584301
Co-reporter:Dr. Kyohei Otsuka;Naozumi Matsumoto;Dr. Shintaro Ishida;Dr. Soichiro Kyushin
Angewandte Chemie International Edition 2015 Volume 54( Issue 27) pp:7833-7836
Publication Date(Web):
DOI:10.1002/anie.201500523
Abstract
The radical anion of octa-tert-butyloctasilacubane was generated and isolated. The EPR spectrum showed the satellites due to the tertiary 13C nuclei of the eight tert-butyl groups. The X-ray crystallographic analysis showed that the SiSi bonds are shortened and the SiC bonds are elongated compared with those of octa-tert-butyloctasilacubane. These results are well explained by the distribution of an unpaired electron in the singly occupied molecular orbital (SOMO).
Co-reporter:Shintaro Ishida;Kenya Uchida ;Takeaki Iwamoto
Heteroatom Chemistry 2014 Volume 25( Issue 5) pp:348-353
Publication Date(Web):
DOI:10.1002/hc.21162
ABSTRACT
The reaction of isolable dialkylsilylene 1 with benzil gave [1+4] cycloadduct 1,3-dioxa-2-sila-cyclopent-4-ene 2 and unexpected 2,5-dioxa-3-silabicyclo[2.1.0]pentane derivative 3. Compound 3 slowly isomerized to 2. The global reaction route mapping method of the model compounds suggests that three reaction paths from an initial silylene–ketone complex (carbonyl silaylide) to 2. A large ring strain energy of model compound for 3 (3′) (218.9 kJ·mol−1) was estimated by density functional theory calculations.
Co-reporter:Dr. Shintaro Ishida;Fumiya Hirakawa;Dr. Ko Furukawa;Dr. Kenji Yoza;Dr. Takeaki Iwamoto
Angewandte Chemie International Edition 2014 Volume 53( Issue 42) pp:11172-11176
Publication Date(Web):
DOI:10.1002/anie.201405509
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 np (HOMOSOMO) transition bands at 497 nm (stibinyl) and 543 nm (bismuthinyl) in 3-methylpentane and react with a stable nitroxyl radical to give the cross-radical coupling products in good yields.
Co-reporter:Dr. Shintaro Ishida;Fumiya Hirakawa;Dr. Ko Furukawa;Dr. Kenji Yoza;Dr. Takeaki Iwamoto
Angewandte Chemie International Edition 2014 Volume 53( Issue 42) pp:
Publication Date(Web):
DOI:10.1002/anie.201484271
Co-reporter:Dr. Shintaro Ishida;Fumiya Hirakawa;Dr. Ko Furukawa;Dr. Kenji Yoza;Dr. Takeaki Iwamoto
Angewandte Chemie 2014 Volume 126( Issue 42) pp:
Publication Date(Web):
DOI:10.1002/ange.201484271
Co-reporter:Dr. Shintaro Ishida;Fumiya Hirakawa;Dr. Ko Furukawa;Dr. Kenji Yoza;Dr. Takeaki Iwamoto
Angewandte Chemie 2014 Volume 126( Issue 42) pp:11354-11358
Publication Date(Web):
DOI:10.1002/ange.201405509
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 np (HOMOSOMO) transition bands at 497 nm (stibinyl) and 543 nm (bismuthinyl) in 3-methylpentane and react with a stable nitroxyl radical to give the cross-radical coupling products in good yields.
Co-reporter:Takayoshi Kuribara, Shintaro Ishida, Takako Kudo, and Soichiro Kyushin
Organometallics 2013 Volume 32(Issue 7) pp:2092-2098
Publication Date(Web):March 21, 2013
DOI:10.1021/om301170r
9-Phenyl-9,10-disilatriptycene (2) was synthesized by the reaction of bis(2-bromophenyl)silane (1) with magnesium in THF. On conventional heating, 2 and cis-9,10-diphenyl-9,10-dihydro-9,10-disilaanthracene (cis-3) were obtained in 31% and 36% yields, respectively. However, the yield of 2 was significantly increased to 71% on microwave irradiation. Theoretical calculations suggest that the intermediary Grignard reagents generated from trans- and cis-9,10-diaryl-9,10-dihydro-9,10-disilaanthracenes have quite different reactivity for construction of the 9,10-disilatriptycene skeleton. The bridgehead Si–H moiety of 2 was readily functionalized to give several 9,10-disilatriptycene derivatives.
Co-reporter:Dr. Shintaro Ishida;Dr. Kyohei Otsuka;Yuki Toma;Dr. Soichiro Kyushin
Angewandte Chemie 2013 Volume 125( Issue 9) pp:2567-2570
Publication Date(Web):
DOI:10.1002/ange.201208506
Co-reporter:Dr. Shintaro Ishida;Ryutaro Sugawara;Yoshifumi Misawa ;Dr. Takeaki Iwamoto
Angewandte Chemie 2013 Volume 125( Issue 49) pp:13107-13111
Publication Date(Web):
DOI:10.1002/ange.201308517
Co-reporter:Dr. Shintaro Ishida;Ryutaro Sugawara;Yoshifumi Misawa ;Dr. Takeaki Iwamoto
Angewandte Chemie International Edition 2013 Volume 52( Issue 49) pp:12869-12873
Publication Date(Web):
DOI:10.1002/anie.201308517
Co-reporter:Dr. Shintaro Ishida;Dr. Kyohei Otsuka;Yuki Toma;Dr. Soichiro Kyushin
Angewandte Chemie International Edition 2013 Volume 52( Issue 9) pp:2507-2510
Publication Date(Web):
DOI:10.1002/anie.201208506
Co-reporter:Shintaro Ishida, Kenya Uchida, Tsunenobu Onodera, Hidetoshi Oikawa, Mitsuo Kira, and Takeaki Iwamoto
Organometallics 2012 Volume 31(Issue 17) pp:5983-5985
Publication Date(Web):August 9, 2012
DOI:10.1021/om3005178
Cycloaddition of an isolable dialkylsilylene converted nonemissive 2,3,4,5-tetraphenylcyclopentadienone to an emissive siloxycyclopentadiene, which shows aggregation-enhanced emission behavior with a light blue fluorescence (λem = 474 nm, ΦF = 0.11) in the solid state rather than in solution.
Co-reporter:Shintaro Ishida, Fumiya Hirakawa, and Takeaki Iwamoto
Journal of the American Chemical Society 2011 Volume 133(Issue 33) pp:12968-12971
Publication Date(Web):July 20, 2011
DOI:10.1021/ja205001m
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 reaction with carbon tetrachloride, hydrogen abstraction, and a unique reaction with a persistent radical, galvinoxyl, giving a cyclic phosphaalkene and a silylether.
Co-reporter:Tomoyuki Kosai, Shintaro Ishida and Takeaki Iwamoto
Chemical Communications 2015 - vol. 51(Issue 53) pp:NaN10709-10709
Publication Date(Web):2015/06/08
DOI:10.1039/C5CC03424H
Regioselective cycloaddition of dialkylsilylene upon irradiation at 440 nm converts azulene and guaiazulene to bicyclic [4]dendralene and heptafulvene derivatives, respectively. Significant σ–π interactions in the resulting new silacycles were suggested using UV-vis spectra and theoretical calculations.