Digallane reactions

If only two equivalents of lithium tris(trimethylsilyl) silanide-3THF are combined with Ga2Cl4 2dioxane (Eq. 2) colorless crystals of the dimeric bis(hypersilyl)dichloro digallane 2 are isolated. The latter 2 is also formed - in a non uniform reaction - if GaGaCU is used instead of applying a 1 1 molar ratio. 

Digallane, Ga2H5, is prepared by reaction 12.13 the product condenses at low temperature as a white solid (mp 223 K) but decomposes above 253 K. 

In the method of Wiberg and Johannsen, 235.1 mg. of tetra-methyldigallane and 157.5 mg. of trlethylamine, which has been completely dried over pieces of Na and then fractionated, are condensed (3 4 mole ratio) in a cold trap. The trap is sealed and the contents are allowed to thaw. Gentle heating results in conversion to a trlmethylgallium-triethylamine adduct and digallane. The reaction products are separated by fractionation at room temperature, in which Ga(CH3)3 N(C 311 3 (vapor pressure 0.04 mm. at 0°C, m.p. 96°C, b.p. 167°C) is condensed at —10°C and Gas He at -196°C. 

Studies of how the intensities of bands vary as a function of concentration or pressure have been important in determining the identities of reaction products (e.g. Xc2 from XeF" and elemental xenon (Section 12.2.2)). Variations as a function of temperature have been used to estimate the enthalpy changes of various reactions, such as the dissociation of digallane (Ga2Hs) into two monogaUane molecules (GaHa) [17]. An alternative approach has been to trap vapors of equilibrium mixtures of molecules with different conformations or different structures held at different temperatures in cold matrices (Section 2.8.1). Data from IR spectra have then been used to determine equilibrium constants and associated thermodynamic properties for systems such as ds-FC(0)0F trani-FC(0)OF [18]. 

Analogous to Robinson s NHG-supported Ga" digallane complex 106, the NHG-supported E" complexes 109 (E = Al, Ga, In) were also reported by Jones and Gole (Scheme 5.20). The Ga and In complexes are prepared by disproportionation of Ga or In halides in the presence of the NHG ligand or by direct coordination of the carbene to Ga" or In". In contrast, dialane complex 110 was prepared via a hydrogen atom transfer reaction using a procedure developed by Jones and Stasch et al. ... 

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