Highly Bent 1,3‐Digerma‐2‐silaallene

Abstract

A 1,3-digerma-2-silacyclopenta-1,2-diene, that is, a 1,3-digerma-2-silaallene incorporated into a five-membered ring system, was synthesized and obtained as a stable orange solid. Owing to incorporation into a cyclic framework, the 1,3-digerma-2-silaallene moiety is highly bent, exhibiting a Si character for the central silicon moiety.

Tetrylones: An Intriguing Class of Monoatomic Zero‐valent Group 14 Compounds

“…The subsequent treatment of 19 with four molar equivalents of KC 8 in benzene at ambient temperature afforded orange crystals of 1,3‐digerma‐2‐silaallene 20 in 57 % yield. The 29 Si NMR spectrum of a [D 8 ]THF solution of 20 revealed a signal at δ 29 Si=−16.5 ppm for the central silicon atom, which is strongly upfield shifted compared to that of 1,3‐digermasilaallene 7 (δ 29 Si=236.6 ppm) and that calculated for the less hindered 1,1′,3,3′‐tetramethyl‐digermasilaallene (δ 29 Si=129.4 ppm), which indicates that the Si(0) character should be a consequence of the rigid cyclic structure . The unexpectedly upfield‐shifted 29 Si NMR shift is probably due to the σ‐donating properties of the germylene moieties and the acute Ge‐Si‐Ge angle caused as a result of rigid cyclic skeleton.…”

“…Sasamori and Tokitoh have recently devised a molecular design to reduce the central E=E=E angle in trimetallallenes by incorporating the E=E=E moiety into a rigid five‐membered ring skeleton, which enhances the ylidone E(0) character. Specifically, heating 1,2‐Bbt 2 ‐1,2‐digermacyclobutene 18 in neat SiCl 4 for 12 h to 55 °C resulted in the formation of 1,1,2,5‐tetrachloro‐2,5‐digerma‐1‐sila‐cyclopentane 19 in quantitative yield as colorless crystals (Scheme ).…”

“…The unexpectedly upfield‐shifted 29 Si NMR shift is probably due to the σ‐donating properties of the germylene moieties and the acute Ge‐Si‐Ge angle caused as a result of rigid cyclic skeleton. Therefore, the bonding situation in 20 is probably best described as >Ge:→Si(0)←:Ge< . The UV/Vis spectrum of a hexane solution of 20 showed its longest absorption maximum at λ max =451 nm ( ϵ 7400), which was assigned to the HOMO→LUMO transition …”

Synthesis of a Dichlorodigermasilane: Double Si–Cl Activation by a Ge=Ge Unit

“…In this regard, Si(II) or Ge(II) species should be an important building block for creating such halogenated oligosilanes/germanes because silylenes (divalent Si(II) species) or germylenes (divalent Ge(II) species) have been known to undergo ready Si-Cl insertion reactions, i.e., Si-Cl activation reactions [8][9][10][11]. For example, Iwamoto and Kira reported the facile Si-Cl insertion of the isolable dialkylmetallylenes towards SiCl 4 under mild conditions [10].…”

“…Finally, it was found that the stable 1,2-digermacyclobutadiene 1 (1,2-Tbb 2 -3,4-Ph 2 -digermacyclobutadiene, Tbb = 2,6-[CH(SiMe 3 ) 2 ] 2 -4-t-Bu-C 6 H 2 , Scheme 2) [24] with SiCl 4 afforded the corresponding 1,3-digerma-2-sila-cyclopent-4-ene derivative, the cyclic >Ge(Cl)-SiCl 2 -Ge(Cl)< compound. 1,2-Digermacyclobut-1-ene derivative was reacted with SiCl 4 to give the double-Si-Cl-insertion product, and the following reduction reaction gave the corresponding > Ge = Si = Ge < species [11]. Although 1 could undergo facile double Si-Cl activation toward SiCl 4 , neither double Ge-Cl nor C-Cl activation could occur in the reaction of 1 with GeCl 4 /CCl 4 .…”