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

摘要

Reaction of the imidazolium-substituted iphos-phate-diide, (Ipr)2C2P2 (1DP), with GeCl2;; dioxane and KBArF_(24) [(BarF_(24))~- = tetrakis[(3,5-trifluorometh- yl)phenyl]borate)] afforded the dicationic spherical-aromatic nido-cluster [Ge(η4-1DP)]~(2+) ([1]~(2+)) (Ipr = l,3-bis(2,6-diisopropylphenyl)imidazolium-2-ylidene). This complex is a rare heavy analogue of the elusive pyramidane [C(η~4-C4H4)]. [1]~(2+) undergoes two reversible one-electron reductions, which yield the radical cation [2]~(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 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.