Heterobimetallic activation of dioxygen: Characterization and reactivity of novel Cu(I)-Ge(II) complexes

Reaction of the known germylene Ge[N(SiMe3)(2)](2) and a new heterocyclic variant Ge[(NMes)(2)(CH)(2)] with [(LCu)-Cu-Me2](2) (L-Me2) the beta-diketiminate derived from 2-( 2,6- dimethylphenyl) amino- 4-( 2,6- dimethylphenyl) imino- 2- pentene) yielded novel Cu( I) - Ge( II) complexes (LCu)-Cu-Me2 - Ge[( NMes)(2)(CH)(2)] ( 1a) and (LCu)-Cu-Me2 - Ge[ N( SiMe3)(2)](2) ( 1b), which were characterized by spectroscopy and X- ray crystallography. The lability of the Cu( I) - Ge( II) bond in 1a and b was probed by studies of their reactivity with benzil, PPh3, and a N- heterocyclic carbene ( NHC). Notably, both complexes are cleaved rapidly by PPh3 and the NHC to yield stable Cu( I) adducts ( characterized by X- ray diffraction) and the free germylene. In addition, the complexes are highly reactive with O-2 and exhibit chemistry which depends on the bound germylene. Thus, oxygenation of 1a results in scission and formation of thermally unstable (LCuO2)-Cu-Me2, which subsequently decays to [( (LCu)-Cu-Me2)(2)(mu-O)(2)], while 1b yields (LCu)-Cu-Me2(mu-O)(2)Ge[N(SiMe3)(2)](2), a novel heterobimetallic intermediate having a [ Cu-III(mu-O)(2)Ge-IV](3+) core. The isolation of the latter species by direct oxygenation of a Cu( I) - Ge( II) precursor represents a new route to heterobimetallic oxidants comprising copper.