Dinitrogen cleavage by a dinuclear uranium(iii) complex

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Materials Science

Background:

• Designing complexes for dinitrogen (N2) cleavage and functionalization requires understanding multimetallic cooperativity and alkali ion-binding effects.
• Previous work established a K2-bound dinuclear uranium(III) complex for N2 reduction.

Purpose of the Study:

• To investigate the impact of removing alkali metal ions from the second coordination sphere on the reactivity of dinuclear uranium(III) complexes towards N2.
• To elucidate the reaction products and mechanism of N2 reduction in the absence of coordinated K+ ions.

Main Methods:

• Synthesis and characterization of dinuclear uranium(III) complexes with varying K+ ion coordination.
• Electrochemical studies (cyclic voltammetry) to assess reducing ability.
• Reaction product analysis upon N2 addition.

Main Results:

• Complete removal of K+ ions from the coordination sphere enhances the reducing ability of the uranium complex.
• N2 addition to the K+-free complex yields a U(III)/U(IV) complex and a bis-nitride, terminal-oxo complex.
• Evidence for a tetranuclear uranium-N2 intermediate, facilitating six-electron transfer and N2 cleavage.

Conclusions:

• The absence of coordinated alkali ions is crucial for forming a tetranuclear intermediate and achieving N2 cleavage.
• Demonstrates the possibility of a three-electron transfer from U(III) to N2.
• Highlights the tunability of alkali ion binding and multimetallic cooperativity for N2 functionalization.