Oxidative addition, reduction and reductive coupling: the versatile reactivity of subvalent gallium cations.

Inspired by the successful oxidative addition of a P-H bond to univalent Ga[Al(ORF)4] that gives the unprecedented dicationic gallium hydride complex [H-Ga(PPh3)3][Al(ORF)4]2 (ORF = OC(CF3)3), the oxidative addition of E-Cl containing substrates was investigated. The reductive coupling of three PPh2Cl to the catenated phosphorus cation [P3Ph6]+ hinted towards a formal two-electron-three-halide reduction (2e--3X- reduction). Similarly, from SbCl3, a cationic formal SbI compound and from RhCl3, [RhI(HMB)(COD)]+ and [RhI(COD)2]+ (HMB = C6Me6, COD = 1,5-cyclooctadiene) are formed as [Al(ORF)4]- salts when reacted with Ga+. Thus, Ga[Al(ORF)4] allows for a one-pot 2e--3X- reduction with the concomitant introduction of a weakly coordinating anion (WCA).