First Dinuclear Copper/Gallium Complexes: Supporting Cu-0 and Cu-I Centres by Low-Valent Organogallium Ligands

The synthesis and structural characterisation of low-valent di nuclear 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*=pentamethyl-cyclopentadienyl) and [Ga(ddp)] (ddp=HC(CMeNC6H3-2,6-iPr(2))(2) 2-di-isopropylphenylamino-4-diisopropyl- phenylimino-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 Cu-I-Ga-I four-membered rings and short Cu-I center dot center dot center dot Cu-I distances, with 2 exhibiting the shortest Cu-I center dot center dot center dot Cu-I contact reported to date of 2.277(3) angstrom. The allgallium coordinated dinuclear [Cu-2-(GaCp*)(mu-GaCp*)(3)Ga(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(0). 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)(mu-GaCp*)(2)][OTf](2) (4) is formed, the cationic part of which is related to previously described isoelectronic dinuclear dw complexes of the type [M-2-(GaCp*)(5)) (M=Pd, Pt).