Compounds of silicon and homologues, 145. - Supersilyl Compounds of boron and homologues, 14. On the gallanyls R*3Ga2.bul. and R*4Ga3.bul. as well as gallanides R*3Ga2- and R*4Ga3- (R* = SitBu3) - syntheses, characterization, structures
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European Journal of Inorganic Chemistry (2001)

The redn. of black-blue tris(supersilyl)digallanyl R*2Ga-GaR*.bul. (R* = SitBu3 = supersilyl) in org. solvents with Na, NaC10H8, or NaR* leads to deep-red Na tris(supersilyl)digallanide-THF (1/3) NaGa2R*3$\times$3THF = R*2Ga-GaR*Na(THF)3, which transforms in the presence of 18-crown-6 into deep-blue Na tetrakis(supersilyl)trigallanide-18-crown-6 (1/1)-THF (1/2) Na(18-C-6)(THF)2+R*2Ga-GaR*-GaR*-. The oxidn. of the latter anion with R*Br or TCNE as well as the reaction of the digallanyl R*3Ga2.bul. with R*Br leads to deep-green tetra(supersilyl)cyclotrigallanyl cyclo-R*Ga-GaR*2-GaR*.bul.. The latter radical thermolyzes at 100° to dark-violet tetrakis(supersilyl)-tetrahedro-tetragallane R*4Ga4 besides the digallanyl R*3Ga2.bul.. This is also prepd. from NaR* and GaCl3 or R*2GaCl, as well as by oxidn. of R*3Ga2-, and itself thermolyzes with formation of the tetrahedrane R*4Ga4. According to x-ray structure analyses of the mentioned compds., the Ga-Ga bond of the digallanide NaGa2R*3$\times$3THF (NMR spectroscopically obsd.) is comparably short (2.380 \AA), approaching a bond order of 2. In fact, it is distinctly shorter than the Ga-Ga bond (2.420 \AA) in the digallanyl R*3Ga2.bul. (EPR spectroscopically obsd.). The Ga atoms of the trigallanyl R*4Ga3.bul. (EPR spectroscopically obsd.) are located at the corners of a triangle with two shorter R*2Ga-GaR* sides (2.527 \AA) and a comparably longer R*Ga-GaR* basis (2.879 \AA). The mean value of the two Ga-Ga bonds in the trigallanide R*4Ga3- (NMR spectroscopically obsd.) is as long (2.53 \AA) as the short Ga-Ga bonds in R*4Ga3.bul.. The anion shows an intramol. CH3···Ga contact (C-Ga 2.10 \AA) between one peripheral Me group of the R*2Ga entity and the anionic Ga atom in R*2Ga-GaR*-GaR*-. on SciFinder(R)
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