Convenient Access to Gallium(I) Cations through Hydrogen Elimination from Cationic Gallium(III) Hydrides.

Although gallium hydrides XnGaH3-n (X = monoanionic substituent) are usually stable compounds, cationic arene-solvated species [H2Ga(arene)2]+ spontaneously eliminate dihydrogen at room temperature to afford the arene-solvated gallium(I) compounds [Ga(PhF)2][CHB11Cl11] (1) and [Ga(Ph3CH)][B(C6F5)4] (3). A key requirement appears to be the presence of a weakly coordinating anion. Use of the more basic triflimide anion, [NTf2]-, reverses the stability, i.e., the gallium(III) hydride H2GaNTf2 (4) is more stable than the gallium(I) compound GaNTf2 (5). The experimental results are supported by DFT calculations. Compounds 1 and 3 can be used as catalysts for the oligomerization of 2,4,4-trimethyl-1-pentene and the hydrosilylation of benzophenone and 1-hexene.