On the Gallanyls R~(*_3)Ga_2 and R_~(*_4)Ga_3 As Well As Gallanides R~(*_3)Ga_(2~-) and R~(*_4)Ga_(3~-) (R~* = SitBu_3)-Syntheses,Characterization,Structures

摘要

The reduction of black-blue tris(supersilyl)digallanyl [R~(*_2)Ga-GaR~*] (R~*=SitBu_3=supersilyl) in organic solvents with Na,NaC_(10)H_8, or NaR~* leads to deep-red sodium tris(supersilyl)digallanide-THF(1/3) NaGa_2R~(*_3) X3THF = [R~(*_2)Ga-GaR~*Na(THF)_3],which transforms in the presence of 18-crown-6 into deep-bule sodium tetrakis(supersilyl)trigallanide-18-crown-6(1/1)-THF(1/2) [Na(18-C-6)(THF)_2~+[R~(*_2)Ga-GaR~*-GaR~*]~-.The oxidation of the latter anion with R~*Br or TCNE as well as the reaction of the digallanyl R~(*_3)Ga_2 with R~*Br leads to deep-green tetra(supersilyl)cyclotrigallanyl […R~*BrGa-GaR~(*_2)-GaR~*…]. The latter radical thermolizes at 100degC to dark-violet tetrakis(supersilyl)-tetrahedro-tetragallane R~(*_4)Ga_4 besides the digallanyl R~(*_3)Ga_2.This is also prepared from NaR~* and GaCl_3 or R~(*_2)GaCl,as well as by oxidation of R~(*_3)Ga_2~-, and itself thermolizes with formation of the tetrahedrane R~(*_4)Ga_4.According to X-ray structure analyses of the mentioned compounds,the Ga-Ga bond of the digallanide NaGa_2R~(*_3)X3THF (NMR spectroscopically observed) is comparably short (2.380 A),approaching a bond order of 2.In fact,it is distinctly shorter than the Ga-Ga bond (2.420A) in the digallanyl R~(*_3)Ga_2 (EPR) spectroscopically observed).The Ga atoms of the trigallanyl R~(*_4)Ga_3 (EPR spectroscopically observed) are located at the comers of a triangle with two shorter R~(*_2)Ga-GaR~* sides (2.527 A) and a comparably longer R~*Ga-GaR~* basis (2.879 A).The mean value of the two Ga-Ga bonds in the trigalanide R~(*_4)Ga_3~- (NMR spectroscopically observed) is as long (2.53A) as the short Ga-Ga bonds in R~(*_4)Ga_3.The anion shows an intramolecular CH_3…Ga contact (C-Ga 2.10 A) between one peripheral methyl group of the R~(*_2)Ga entity and the anionic Ga atom in [R~(*_2)Ga-GaR~*-GaR~*]~-