# Synthesis of Chromium(IV) Nitrides Through High-Spin Tetrahedral Chromium(I) Intermediates

## TL;DR

Scientists synthesized chromium(IV) nitrides using high-spin tetrahedral chromium(I) intermediates, revealing unique chemical properties and synthesis challenges.

## Contribution

The paper reports the first synthesis of chromium(IV) nitrides via high-spin tetrahedral chromium(I) intermediates.

## Key findings

- Chromium(I) dinitrogen complexes were formed under nitrogen gas.
- Chromium(IV) nitrides were confirmed using spectroscopy and X-ray crystallography.
- The nitrides showed limited reactivity toward H2 and diphenylsilane.

## Abstract

Reduction of (depe)2CrCl2 (depe
= 1,2-bis­(diethylphosphino)­ethane)
and (dep-benz)2CrCl2 (dep-benz = 1,2-bis­(diethylphosphino)­benzene)
under 1 atm of N2 furnished the dinitrogen complexes (depe)2Cr­(N2)2 and (dep-benz)2Cr­(N2)2, respectively. One-electron oxidation of these
products with FcBArF
4 (Fc = ferrocenium, BArF
4 = B­(3,5-(CF3)2C6H3)4) yielded the unusual, high-spin tetrahedral
complexes [(depe)2Cr]­[BArF
4] and
[(dep-benz)2Cr]­[BArF
4] with concomitant
loss of dinitrogen. Reaction of the chromium­(I) derivatives with Ph3CN3 furnished rare examples of chromium­(IV) nitrides
as confirmed spectroscopically and by X-ray crystallography. While [(depe)2Cr(N)][BArF
4] underwent association of isocyanides accompanied by partial ligand
dissociation, neither chromium nitride was reactive toward H2 or diphenylsilane under thermal or photochemical conditions. These
results distinguish the unique properties of the chromium­(IV) nitrides
as compared to heavier group 6 congeners and demonstrate both the
feasibility of nitride synthesis and the limitations of dinitrogen
cleavage and subsequent N–H bond formation.