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

Reaction of the imidazolium‐substituted iphosphate‐diide, (Ipr)(2)C(2)P(2) (IDP), with GeCl(2) ⋅ dioxane and KBArF(24) [(BarF(24))(−)=tetrakis[(3,5‐trifluoromethyl)phenyl]borate)] afforded the dicationic spherical‐aromatic nido‐cluster [Ge(η(4)‐IDP)](2+) ([1](2+)) (Ipr=1,3‐bis(2,6‐diisopropylphenyl)imidazolium‐2‐ylidene). This complex is a rare heavy analogue of the elusive pyramidane [C(η(4)‐C(4)H(4))]. [1](2+) undergoes two reversible one‐electron reductions, which yield the radical cation [2]⋅( + ) and the neutral Ge(II) species 3. Both [2]⋅( + ) and 3 rearrange in solution forming the 2D aromatic and planar imidazolium‐substituted digermolide [4](2+) and germole‐diide 5, respectively. Both planar species can be oxidized back to [1](2+) using AgSbF(6). 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.