The synthesis and structural characterisation of low-valent dinuclear copper(I) and copper(0) complexes supported by organogallium ligands has been accomplished for the first time by the reductive coordination reaction of [GaCp*] (Cp* = pentamethylcyclopentadienyl) and [Ga(ddp)] (ddp = HC(CMeNC6H3-2,6-iPr2:)2 2-diisopropylphenylamino-4-diisopropylphenylimino-2-pentene) with readily available copper(II) and copper(I) precursors. The treatment of CuBr2 and Cu(OTf)2 (OTf=CF3SO3) with [Ga(ddp)] under mild conditions resulted in elimination of [Ga(L)2(ddp)] (L = Br, OTf) and afforded the novel gallium(I)/copper(I) compounds [{(ddp)GaCu(L)} 2] (L = Br (1), OTf (2)). The single-crystal X-ray structure determinations of 1 and 2 reveal that these molecules are composed of {(ddp)GaCu(L)} dimeric units, with planar Cu1-Ga1 four-membered rings and short CuI CuI distances, with 2 exhibiting the shortest CuI CuI contact reported to date of 2277(3) Å. The allgallium coordinated dinuclear [Cu2 (GaCp* )(μ-GaCp* )3Ga(OTf)3] (3) is formed when Cu(OTf)2 is combined with [GaCp*] instead of [Ga(ddp)]. Notably, in the course of this redox reaction Lewis acidic Ga(OTf)3 is formed, which coordinates to one of the electron-rich copper(0) centres. Compound 3 is suggested as the first case of a structurally characterised complex of copper(I). By changing the copper(II) to a copper(I) source, that is, [Cu(cod)2][OTf] (cod=1,5-cyclooctadiene), the salt [Cu 2(GaCp*)3(μGaCp*)2][OTf] 2 (4) is formed, the cationic part of which is related to previously described isoelectronic dinuclear d10 complexes of the type [M 2(GaCp*)5] (M = Pd, Pt). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim.