# Phosphonium fullerides: isolable zwitterionic adducts of a phosphine with C60

## TL;DR

Scientists created new zwitterionic compounds by combining a phosphine with C60, which can be modified further for potential applications.

## Contribution

The first isolable zwitterionic phosphonium fullerides formed from a phosphine and C60 are reported.

## Key findings

- The reaction of (tmg)3P with C60 forms zwitterionic adducts (tmg)3PC60 and (tmg)3PC60P(tmg)3 in high yield.
- Up to two (tmg)3P molecules can reversibly bind to C60, forming bisphosphine adducts with reduced P–C bond stability.
- Phosphonium fullerides can be functionalized with electrophiles, showing their reactivity and potential for modification.

## Abstract

Although fullerene derivatization has been extensively studied for decades, zwitterionic adducts with neutral Lewis bases are rare, and those with tertiary phosphines remain elusive. This work presents a combined experimental and computational study on the first isolable zwitterionic phosphonium fullerides. The reaction of tris(tetramethylguanidinyl)phosphine ((tmg)3P) with C60 results in the formation of the zwitterionic adducts (tmg)3PC60 and (tmg)3PC60P(tmg)3 in quantitative yield. Stoichiometric studies demonstrate that up to two (tmg)3P molecules can reversibly bind to C60, forming bisphosphine adducts as regioisomeric mixtures with reduced P–C bond stability. Spectroscopic, crystallographic, and computational analyses reveal the presence of σ-type dative P–C bonds and significant charge redistribution within the fullerene cage. Furthermore, functionalizations of the phosphonium fullerides with electrophiles yield ionic derivatives, highlighting their reactivity and potential for further modification.

The reaction of phosphine (tmg)3P with C60 leads to isolable zwitterionic phosphonium fullerides with reversible P–C dative bonds and increased negative charge on the C60 core, enabling further electrophilic functionalization.