# A neutral homoaromatic heavy allene as a platform for selective conversion to a germylene-coordinated digermavinylidene

## TL;DR

Scientists created a new heavy allene compound that can selectively convert into a germylene-coordinated structure without substituent migration.

## Contribution

The first neutral homoaromatic heavy allene is synthesized and shown to selectively convert into a digermavinylidene.

## Key findings

- The compound exhibits homoaromaticity confirmed by X-ray diffraction and DFT calculations.
- Coordination with DMAP leads to a clean transformation into a germylene-coordinated structure.
- LUMO localization at the bridgehead Ge atom explains the selective reactivity.

## Abstract

We report the synthesis of the first neutral homoaromatic heavy allene, stabilized by a methylene-bridged four-membered framework. Single-crystal X-ray diffraction and DFT calculations reveal a cyclic three-center–two-electron (3c–2e) π interaction, a short bridgehead distance, a delocalized HOMO, and a strongly negative NICS(−1) value (−16.9 ppm), collectively establishing pronounced homoaromaticity. Coordination of 4-dimethylaminopyridine (DMAP) induces a clean and selective transformation into a germylene-coordinated digermavinylidene, without substituent migration. This reactivity originates from LUMO localization at the bridgehead Ge atom supported by Wiberg bond indices and NBO analyses. Our findings highlight neutral homoaromaticity as a structural platform for programmable bonding interconversion in heavy main-group π systems.

The first neutral homoaromatic heavy allene enabling selective, migration-free conversion into a germylene-coordinated digermavinylidene.