# Three reversibly interconvertible redox states of boradigermaallyl: syntheses of radical allyl anion and allyl dianion

## TL;DR

This paper describes the synthesis and characterization of three redox states of a boradigermaallyl compound, including its radical anion and dianion forms.

## Contribution

The study presents the first reversible two-step reduction of boradigermaallyl to stable radical anions and dianions.

## Key findings

- EPR data confirms the allyl-type delocalization of radicals in the reduced species.
- Cyclic voltammetry shows a reduction potential for the dianionic species beyond −2.2 V.
- Computed spin densities highlight structural similarities to the organic allyl radical.

## Abstract

A methyl derivate of our previously published chloro-boradigermaallyl, which features a borylene unit stabilized by a chelating bis-germylene ligand, is synthesized by addition of MeBBr2 to the bis(germylene) A followed by KC8 reduction. Both derivatives, the BCl (1a) and BMe (1b) boradigermaallyls, feature an allyl-type delocalized Ge–B–Ge 2π-electron system. In this work, the reversible two step reduction of both compounds to the persistent radical anions and dianions is presented. EPR data and particularly hyperfine coupling constants to the 11B and 73Ge nuclei confirm allyl-type delocalization of the radicals. Computed spin densities illustrate the structural analogy to the organic allyl radical. Cyclic voltammetry measurements of the boradigermaallyl compounds exhibit one reduction wave within the accessible electrochemical window indicating a reduction potential of the dianionic species beyond −2.2 V [vs. (Ag/Ag+)].

Radical anion and dianion were characterized as products of a reversible stepwise two-electron reduction of boradigermaallyl.