The germanium(ii) center of dicationic compound 1 donates an electron pair to transition metal Ag(i) and Au(i) cations, leading to complexes 2 and 3 respectively. Complex 3 is stabilized by [Ge:]→Au(i) σ-donation and π-back donation from filled d-orbitals of Au(i) to the two sets of p-orbitals available on Ge(ii) centers.
Bis(chlorogermyliumylidene) 2 has been strategically obtained within redox-active bis(α-iminopyridine). Metal-free reduction of 2 followed by protonation led to elusive 2,3-di(pyridin-2-yl)piperazine with meso-stereoselectivity. Formation of persistent triplet diradicals upon reduction and isolation of piperazine stabilized Ge(ii) dication intermediates provide convincing evidence for the crucial role of [GeCl]+ units in reductive cyclization.
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