A Germapyramidane Switches Between 3D Cluster and 2D Cyclic Structures in Single-Electron Steps.

Reaction of the imidazolium-substituted iphosphate-diide, (Ipr) C P (IDP), with GeCl  ⋅ dioxane and KBArF [(BarF ) =tetrakis[(3,5-trifluoromethyl)phenyl]borate)] afforded the dicationic spherical-aromatic nido-cluster [Ge(η -IDP)] ([1] ) (Ipr=1,3-bis(2,6-diisopropylphenyl)imidazolium-2-ylidene). This complex is a rare heavy analogue of the elusive pyramidane [C(η -C H )]. [1] undergoes two reversible one-electron reductions, which yield the radical cation [2]⋅ and the neutral Ge species 3. Both [2]⋅ and 3 rearrange in solution forming the 2D aromatic and planar imidazolium-substituted digermolide [4] and germole-diide 5, respectively. Both planar species can be oxidized back to [1] using AgSbF . These redox-isomerizations correspond to the fundamental transformation of a 3D aromatic cluster into a 2D aromatic ring compound upon reduction and vice versa. The mechanism of these reactions was elucidated using DFT calculations and cyclic voltammetry experiments.