# Reactivity of Nickel Complexes Bearing P(C=X)P Ligands (X = O, N) Toward Diazoalkanes: Evidence for Phosphorus Ylide Intermediates

## TL;DR

This paper explores how nickel complexes with specific ligands react with diazoalkanes, revealing phosphorus ylide intermediates in the process.

## Contribution

The study provides evidence for phosphorus ylide intermediates formed during nickel carbene reactions with P(C=X)P ligands.

## Key findings

- Nickel pincer complexes with P(C=O)P or P(C=N)P ligands react with diazoalkanes to form phosphorus ylides.
- DFT calculations clarify the reaction mechanisms involving nickel carbene intermediates.
- The phosphorus ylide intermediates react further with the unsaturated backbone of the complex.

## Abstract

Nickel carbenes are attracting attention for the development
of
more sustainable catalysts, among others, for cyclopropanation. Intramolecular
trapping of a nickel carbene intermediate with an olefin incorporated
in a P(C=C)P Ni pincer complex
had previously allowed the isolation of a nickelacyclobutane intermediate and a detailed characterization of its reactivity.
Herein, we report the reactivity of related nickel pincer complexes
bearing a ketone P(C=O)P or
an imine P(C=N)P with diazoalkanes as the carbene precursor.
The observed reactivity suggests, in both cases, the reaction of the
transient nickel carbene with one of the phosphine arms to form phosphorus
ylides that subsequently react with the unsaturated backbone. Density
functional theory (DFT) calculations are used to shed light on the
mechanisms of these reactions.