# Boradigermaallyl: inhibition of CH bond activation by borane CO adduct formation followed by CO insertion

## TL;DR

This paper explores how a borane compound called boradigermaallyl reacts with various organic molecules, and how CO gas prevents certain reactions while enabling new ones.

## Contribution

The study reveals a novel mechanism where CO adduct formation inhibits CH bond activation and enables CO insertion into B–C bonds.

## Key findings

- CO adduct formation prevents CH activation in reactions with phenylacetylene and anthracene.
- CO insertion into the B–C bond produces an α,β-unsaturated acylboron compound.
- Biphenylene reacts with boradigermaallyl at room temperature by inserting boron into a phenyl group.

## Abstract

Boradigermaallyl, valence-isoelectronic to an allyl cation, stabilized by Ge-bound C6H3-2,6-(Trip)2 (Trip = 2,4,6-C6H2iPr3) groups shows triple insertion of ethylene into the Ge–B bonds (2) or an addition of styrene at the Ge atoms (3) followed by CH addition of a Trip methyl group at a GeB unit. Phenylacetylene forms two addition products (4, 5) with the GeB unit or both Ge atoms, which are also followed by a CH insertion of a methyl group. Under CO atmosphere the CH addition was prevented in the case of the phenylacetylene addition, and a CO adduct of this cycloaddition product (6) was characterized. Subsequently this CO adduct exhibits a CO insertion into the B–C bond and an α,β-unsaturated acylboron compound (7) was characterized. In the case of the anthracene addition to boradigermaallyl the observed CH addition was also suppressed by CO adduct formation (8). Biphenylene reacts with boradigermaallyl at room temperature under insertion of a boron atom into a phenyl moiety (9).

Multifaceted reactions of boradigermaallyl with unsaturated organic molecules are presented. CH activation is suppressed by CO borane adduct formation and subsequent CO insertion results in an α,β-unsaturated acylboron compound.