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 Sb-I compound and from RhCl3, [Rh-I(HMB)(COD)](+) and [Rh-I(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).