Nitrogen activation and cleavage by a multimetallic uranium complex

Abstract

Multimetallic-multielectron cooperativity plays a key role in the metal-mediated cleavage of N2 to nitrides (N3-). In particular, low-valent uranium complexes coupled with strong alkali metal reducing agents can lead to N2 cleavage, but often, it is ambiguous how many electrons are transferred from the uranium centres to cleave N2. Herein, we designed new dinuclear uranium nitride complexes presenting a combination of electronically diverse ancillary ligands to promote the multielectron transformation of N2. Two heteroleptic diuranium nitride complexes, [K{UIV(OSi(OtBu)3)(N(SiMe3)2)2}2(µ-N)] (1) and [Cs{UIV(OSi(OtBu)3)2(N(SiMe3)2)}2(µ-N)] (3-Cs), containing different combinations of OSi(OtBu)3 and N(SiMe3)2 ancillary ligands, were synthesized. We found that both complexes could be reduced to their U(III)/U(IV) analogues, and the complex, [K2{UIV/III(OSi(OtBu)3)2(N(SiMe3)2)}2(µ-N)] (6-K), could be further reduced to a putative U(III)/U(III) species that is capable of promoting the 4e- reduction of N2, yielding the N24-complex [K3{UV(OSi(OtBu)3)2(N(SiMe3)2)}2(µ-N)(µ-η22-N2)], 7. Parallel N2 reduction pathways were also identified, leading to the isolation of N2 cleavage products, [K3{UVI(OSi(OtBu)3)2(N(SiMe3)2)(≡N)}(µ-N)2{UV(OSi(OtBu)3)2(N(SiMe3)2)}]2, 8, and [K4{(OSi(OtBu)3)2UV)(≡N)}(μ-NH)(μ-κ2:C,N−CH2SiMe2NSiMe3)-{UV(OSi(OtBu)3)2][K(N(SiMe3)2]2, 9. These complexes provide the first example of N2 cleavage to nitride by a uranium complex in the absence of reducing alkali metals.

Article information

Article type
Edge Article
Submitted
27 May 2022
Accepted
21 Jun 2022
First published
22 Jun 2022
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2022, Accepted Manuscript

Nitrogen activation and cleavage by a multimetallic uranium complex

M. Keener, F. Fadaei Tirani, R. Scopelliti, I. Zivkovic and M. Mazzanti, Chem. Sci., 2022, Accepted Manuscript , DOI: 10.1039/D2SC02997A

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