Uranium−Nitrogen Multiple Bonding: Isostructural Anionic, Neutral, and Cationic Uranium Nitride Complexes Featuring a Linear U═N═U Core

Abstract

Reaction of the uranium(III) tris(anilide) complex (THF)U(N[t-Bu]Ar)(3) (1, THF = tetrahydrofuran; Ar = 3,5-Me(2)C(6)H(3)) with MN(3) (M = Na, [N(n-Bu)(4)]) results in the formation of the bimetallic diuranium(IV/IV) complexes M[(mu-N)(U(N[t-Bu]Ar)(3))(2)] (M[3]), which feature a single nitride ligand engaged as a linear, symmetric bridge between two uranium centers. The stability of the U=N=U core across multiple charge states is illustrated by stepwise chemical oxidation of Na[3] to the diuranium(IV/V) complex (mu-N)(U(N[t-Bu]Ar)(3))(2) (3) and the diuranium(V/V) complex [(mu-N)(U(N[t-Bu]Ar)(3))(2)][B(Ar(F))(4)] {[3][B(Ar(F))(4)]; Ar(F) = 3,5-(CF(3))(2)C(6)H(3)}. M[3], 3, and [3][B(Ar(F))(4)] were characterized by NMR spectroscopy, single-crystal X-ray diffraction, and elemental analysis. The cyclic voltammogram of 3 reveals two clean, reversible one-electron electrochemical events at E(1/2) = -1.69 and -0.67 V, assigned to the [3](-)/3 and 3/[3](+) redox couples, respectively. The X-ray crystal structures of [N(n-Bu)(4)][3], 3, and [3][B(Ar(F))(4)] reveal a linear U=N=U core that contracts by only approximately 0.03 A across the [3](n) (n = -1, 0, +1) series, an effect that is rationalized as being primarily electrostatic in origin. [3][B(Ar(F))(4)] reacts with NaCN, eliminating Na[B(Ar(F))(4)] and forming the known diuranium(IV/IV) cyanoimide complex (mu-NCN)(U(N[t-Bu]Ar)(3))(2), suggesting that the U=N=U core has metallonitrene-like character.

Cation‐Mediated Conversion of the State of Charge in Uranium Arene Inverted‐Sandwich Complexes

“…. A few mixed-valent diuranium complexes have been structurally characterized [56][57][58][59][60][61] with only one example of mixed valent inverted-sandwich complex. [23] Such species are attractive for the study of the possible presence of valence delocalization in uranium systems.…”

Molecular and electronic structure of terminal and alkali metal-capped uranium(V) nitride complexes

“…The few methods of preparing isolable uranium nitrides303132333435363738394041 contrast to the plethora of methods in the transition metal series4647, and for uranium most involve redox activity of azide. In this work, we have found new and reliable methods to a wide family of terminal uranium nitrides based on the U(Tren TIPS ) framework (Supplementary Note 2), and it is our hope that this could be applicable to other ligand systems.…”

“…Complex 4Na could also be oxidized to [U VI (Tren TIPS )(N)] ( 6 )21. Terminal uranium nitrides were without precedent outside of matrix isolation experiments22242526272829; molecular species always exhibited bridging nitrides303132333435363738394041 or decomposed via C–H activation to give amides2142. These difficulties stand in contrast to the common terminal uranium oxides914434445 and transition metal nitrides4647.…”

The shortest Th–Th distance from a new type of quadruple bond

“…15,16,17,18,19,20 Nevertheless, computational quantum chemistry has been extensively employed to study An-An bonded systems. In addition to the seminal investigation of U 2 in 2005, 5 molecules reported include An 2 (An = Ac, Th, Pa and U), 21 H 2 UUH 2 (diuranium hydrides), 4 HThThH, 22 PhUUPh, 23 U 2…”