- Synthesis of germacyclic compounds by cyclization and annulation reactions utilizing in situ generated germyl cations
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Germyl cations are one of the heavier group 14 element analogues of carbocations and have been extensively studied for their structures, spectroscopic features, and reactivities to various molecules. 4,4′-Di-tert-butyl-2-diphenylgermylbiphenyl (1) was reacted with [Ph3C][B(C6F5)4] in the presence of 2,6-lutidine to produce dibenzogermole 2 in good yield via the Friedel?Crafts-type cyclization of a germyl cation generated in situ at the neighboring benzene ring. This germa-Friedel?Crafts reaction was used to synthesize ladder-type germole 4 and trigermasumanene 6. The emission bands of 2 were red-shifted relative to those of fluorene, which for dibenzosilole are associated with orbital interactions between a heavier group 14 element moiety and a π-conjugated framework, such as σ*?π* conjugation. The following reaction was conducted to demonstrate annulation between an in situ generated germyl cation and alkynes. Benzyldiphenylgermane (7) was treated sequentially with [Ph3C][B(C6F5)4], 2,6-di-tert-butyl-4-methylpyridine, and alkynes to produce 1,2-dihydro-2,2-diphenyl-2-germanaphthalene derivatives 8, together with alkynylgermane 9 in some cases. We compare the products obtained in this study with those obtained from reactions involving an in situ generated silyl cation, which we reported previously.
- Arii, Hidekazu,Iwanami, Yaeko,Kawashima, Takayuki,Masuda, Hideki,Matsumoto, Jin,Mochida, Kunio,Nakane, Daisuke,Shiragami, Tsutomu
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- Multiple Si-H bond activations by tBu2PCH 2CH2PtBu2 and tBu 2PCH2PtBu2 Di(phosphine) complexes of rhodium and iridium
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Reactions of the di(tert-butylphosphino)ethane complex (dtbpe)Rh(CH 2Ph) with Ph2SiH2 and Et2SiH 2 resulted in isolation of (dtbpe)Rh(H)2(SiBnPh 2) (1; Bn = CH2Ph) and (dtbpe)Rh(H) 2(SiBnEt2) (2), respectively. Both 1 and 2 feature strong interactions between the rhodium hydride and silyl ligands, as indicated by large 2JSiH values (44.4 and 52.1 Hz). The reaction of (dtbpm)Rh(CH2Ph) (dtbpm = di(tert-butylphosphino)methane) with Mes2SiH2 gave the pseudo-three-coordinate Rh complex (dtbpm)Rh(SiHMes2) (3), which is stabilized in the solid state by agostic interactions between the rhodium center and two C-H bonds of a methyl substituent on the mesityl group. The analogous germanium compound (dtbpm)Rh(GeHMes2) (4) is also accessible. Complex 3 readily undergoes reactions with diphenylacetylene, phenylacetylene, and 2-butyne to give the silaallyl complexes (dtbpm)Rh[Si(CPh=CHPh)Mes2] (5), (dtbpm)Rh[Si(CH=CHPh)Mes2] (7), and (dtbpm)Rh(Si(CMe=CHMe)Mes 2) (8) via net insertions into the Si-H bond. The germaallyl complexes (dtbpm)Rh[Ge(CPh=CHPh)Mes2] (6) and (dtbpm)Rh[Ge(CMe=CHMe) Mes2] (9) were synthesized under identical conditions starting from 4. The reaction of (dtbpm)Rh(CH2Ph) with 1 equiv of TripPhSiH 2 yielded (dtbpm)Rh(H)2[5,7-diisopropyl-3-methyl-1-phenyl- 2,3-dihydro-1H-silaindenyl-κSi] (11), and catalytic investigations indicate that both (dtbpm)Rh(CH2Ph) and 11 are competent catalysts for the conversion of TripPhSiH2 to 5,7-diisopropyl-3-methyl-1- phenyl-2,3-dihydro-1H-silaindole. A dtbpm-supported Ir complex, [(dtbpm)IrCl]2, was used to access the dinuclear bridging silylene complexes [(dtbpm)IrH](μ-SiPh2)(μ-Cl)2[(dtbpm)IrH] (12) and [(dtbpm)IrH](μ-SiMesCl)(μ-Cl)(μ-H)[(dtbpm)IrH] (13). The reaction of [(dtbpm)IrCl]2 with a sterically bulky primary silane, (dmp)SiH3 (dmp = 2,6-dimesitylphenyl), allowed isolation of the mononuclear complex (dtbpm)Ir(H)4(10-chloro-1-mesityl-5,7-dimethyl-9, 10-dihydrosilaphenanthrene-κSi), in which the dmp substituent has undergone C-H activation.
- Fasulo, Meg E.,Calimano, Elisa,Buchanan, J. Matthew,Tilley, T. Don
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p. 1016 - 1028
(2013/04/23)
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- Acceleration of the substitution of silanes with Grignard reagents by using either LiCl or YCl3/MeLi
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Getting up to speed: Both LiCl and the YCl3/MeLi catalyst system have an acceleration effect upon the substitution of silanes using Grignard reagents (see scheme). The method provides access to benzyl-, allyl-, and arylsilanes in good yields from the starting silanes.
- Hirone, Naoki,Sanjiki, Hiroaki,Tanaka, Ryoichi,Hata, Takeshi,Urabe, Hirokazu
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supporting information; experimental part
p. 7762 - 7764
(2010/12/25)
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