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

Abstract

Reaction of the imidazolium-substituted iphosphate-diide, (Ipr)2C2P2 (IDP), with GeCl2 ⋅ dioxane and KBArF24 [(BarF24)−=tetrakis[(3,5-trifluoromethyl)phenyl]borate)] afforded the dicationic spherical-aromatic nido-cluster [Ge(η4-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(η4-C4H4)]. [1]2+ undergoes two reversible one-electron reductions, which yield the radical cation [2]⋅+ and the neutral GeII 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 AgSbF6. 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.