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

Abstract

Inspired by the successful oxidative addition of a P–H bond to univalent Ga[Al(OR^F)₄] that gives the unprecedented dicationic gallium hydride complex [H–Ga(PPh₃)₃][Al(OR^F)₄]₂ (OR^F = 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(OR^F)₄]⁻ salts when reacted with Ga⁺. Thus, Ga[Al(OR^F)₄] allows for a one-pot 2e⁻–3X⁻ reduction with the concomitant introduction of a weakly coordinating anion (WCA).