Exceptional uranium(VI)-nitride triple bond covalency from 15N nuclear magnetic resonance spectroscopy and quantum chemical analysis

Abstract

Determining the nature and extent of covalency of early actinide chemical bonding is a fundamentally important challenge. Recently, X-ray absorption, electron paramagnetic, and nuclear magnetic resonance spectroscopic studies have probed actinide-ligand covalency, largely confirming the paradigm of early actinide bonding varying from ionic to polarised-covalent, with this range sitting on the continuum between ionic lanthanide and more covalent d transition metal analogues. Here, we report measurement of the covalency of a terminal uranium(VI)-nitride by 15N nuclear magnetic resonance spectroscopy, and find an exceptional nitride chemical shift and chemical shift anisotropy. This redefines the 15N nuclear magnetic resonance spectroscopy parameter space, and experimentally confirms a prior computational prediction that the uranium(VI)-nitride triple bond is not only highly covalent, but, more so than d transition metal analogues. These results enable construction of general, predictive metal-ligand 15N chemical shift-bond order correlations, and reframe our understanding of actinide chemical bonding to guide future studies.

Cation assisted binding and cleavage of dinitrogen by uranium complexes

“…The few multimetallic uranium–alkali ion systems reported so far that effect the four-electron reduction of N 2 , 1 j , m ,3 h or even its complete cleavage to nitride, 4 all contain the potassium cation. It should be noted that although the number of reported uranium nitride complexes is rapidly increasing 12,13 only three examples of uranium nitrides have been obtained from N 2 reduction (Chart 1).…”

Uranium–nitride chemistry: uranium–uranium electronic communication mediated by nitride bridges

“…In recent times there has been increasing interest in molecular early actinide nitride complexes 1 due to fundamental questions about their bonding, 2 reactivity, 3 magnetism, 2 a,c ,3 f,i , j and potential relevance to materials science. 4 The quest for isolable, molecular terminal uranium–nitrides was accomplished in 2012 with the synthesis of [U V (N)(Tren TIPS )][Na(12C4) 2 ] (Tren TIPS = {N(CH 2 CH 2 NSiPr i 3 ) 3 } 3− ; 12C4 = 12-crown-4 ether) and then [U VI (N)(Tren TIPS )] in 2013, 5 and since then relatively few uranium( v ) and ( vi ) terminal nitrides have been isolated.…”

Identification of the U(v) complex (C5Me5)2UVI(NSiMe3) in the reaction of (C5Me5)2UIIII(THF) with N3SiMe3

“…Reactions of uranium complexes with azides and oxygen-transfer reagents have been heavily studied due to interest in actinide-ligand multiple bonding. [1][2][3][4][5][6] Additionally, uranium oxo and imido species are of interest for theoretical and reactivity studies. [7][8][9][10][11][12][13] To generate uranium-nitrogen multiple bonds, often a uranium complex is reacted with an organic azide reagent, RN 3 , or azobenzene, PhNvNPh, to oxidize the metal center and install an NR imido ligand or NPh.…”