Ditrielanes (R3Si)2E−E(SiR3)2 and Heterocubanes (R3Si)4E4Y4 (R3Si =tBu3Si,tBu2PhSi; E = Al, Ga, In, Tl; Y = O, Se)

Abstract

Ditrielanes R*2E−ER*2 (R* = SitBu3; E = Al, In, Tl), R′2E−ER′2 (R′ = SitBu2Ph; E = In, Tl) and R*2Ga−GaR*(SiMe3) are prepared in alkanes (i) from ECl3 (E = Al, In, Tl) and NaR* via isolable R*2ECl (reaction of GaCl3 and NaR* leads to R*2GaGaR* instead of R*2Ga−GaR*2), (ii) from EBr (E = In, Tl) and NaR* or NaR′ (reaction of AlBr or GaBr and NaR* leads to R*4Al4 or R*8Ga18 and R*8Ga22), (iii) from NaGa2R*3 and Me3SiCl. According to X-ray structure analyses, the ditrielanes contain two planar groups R2EE which are orthogonal to each other (R = R*; angle REER ca. 90°) or nearly orthogonal (R = R′; angle REER ca. 80°). All compounds are deeply colored. The λmax value of the visible absorption shifts with increasing atomic number of E and with the increasing angle between the R2EE planes to longer wavelengths (ruby R*4Al2, deep-violet R*4In2, dark-green R*4Tl2; red-violet R′4In2, dark-blue R′4Tl2). Thermolysis of R*4E2 in alkanes at about 100 °C leads to R*3Al2·/R*4Al3·/R*4Al4, to R*3Ga2·/R*4Ga4, to (R*4In6)/R*8In12 and to Tl, respectively. R′4E2 thermolizes under formation of an In or Tl mirror. The ditrielanes R*4E2 are stable against R*2ECl (reaction of GaCl3 and NaR* leads to R*2GaGaR* and E−E bond cleavage with the formation of R*EBr2 (e.g. R*InBr2) besides R*H and H2. Air transforms the ditrielanes into R*OH or R′OH. On the other hand, halogens oxidize R*4E2 under formation of R*2EHal (e.g. R*2AlI), R*EHal2 (e.g. R*InBr2) or thermolysis products of the dihalides (e.g. R*Br/TlBr). Selenium gives with R*4E2 heterocubanes R*4E4Se4 (E = Al, In, Tl). Analogous heterocubanes R*4E4O4 (E = Al, Ga) are synthesized from tetrahedranes R*4E4 and oxygen. X-ray structure analyses for R*4In4Se4, R*4Al4O4 − besides the mentioned ditrielanes − are presented.