Uranium−Nitrogen Multiple Bonding: The Case of a Four-Coordinate Uranium(VI) Nitridoborate Complex

Abstract

Reaction of the azidoborate salt [N(n-Bu)(4)][(C(6)F(5))(3)B(N(3))] ([N(n-Bu)(4)][1]) with the uranium(III) tris(anilide) complex (THF)U(N[t-Bu]Ar)(3) (2; THF = tetrahydrofuran; Ar = 3,5-Me(2)C(6)H(3)) results in formation of the paramagnetic uranium(V) nitridoborate complex [N(n-Bu)(4)][(C(6)F(5))(3)BNU(N[t-Bu]Ar)(3)] ([N(n-Bu)(4)][3]). Chemical oxidation of [N(n-Bu)(4)][3] is facile and provides the diamagnetic uranium(VI) nitridoborate complex (C(6)F(5))(3)BNU(N[t-Bu]Ar)(3) (3). [N(n-Bu)(4)][3] and 3 are the first nitridoborate complexes of uranium and were characterized by multinuclear NMR spectroscopy, single crystal X-ray diffraction methods, and elemental analysis. The X-ray crystal structures of [N(n-Bu)(4)][3] and 3 reveal extremely short UN(nitrido) distances (1.916(4) A and 1.880(4) A, respectively). Density functional theory was used to calculate the optimized structure of the truncated model (C(6)F(5))(3)BNU(N[Me]Ph)(3); the procedure was carried out similarly for several other relevant complexes featuring UN multiple bonds. Bond multiplicities based on Nalewajski-Mrozek valence indices were calculated, the results of which suggest that the UN(nitrido) interaction in 3 is close to a full triple bond.

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.…”

Formation and Reactivity of the Terminal Vanadium Nitride Functionality

“…Recently, the use of a strong Lewis acid such as B(C 6 F 5 ) 3 . [73] Prior to the evolution of dinitrogen, the reaction must proceed through a putative azide complex, [(Ar[tBu]N) 3 U(N 3 -B(C 6 F 5 ) 3 )]. [73] The exact role of the borane with the uranium azide ligand is unclear, since the interaction may occur at the N α or N γ atom of the azide ligand, or via a borotropic shift.…”

“…[73] Prior to the evolution of dinitrogen, the reaction must proceed through a putative azide complex, [(Ar[tBu]N) 3 U(N 3 -B(C 6 F 5 ) 3 )]. [73] The exact role of the borane with the uranium azide ligand is unclear, since the interaction may occur at the N α or N γ atom of the azide ligand, or via a borotropic shift. [77][78][79] and B(C 6 F 5 ) 3 [75] has been reported to activate otherwise stable terminal Mn V and Cr VI nitrides for subsequent group transfer catalysis.…”

Encapsulating Inorganic Acetylene, HBNH, Using Flanking Coordinative Interactions

“…Ar elated process has been observed by Paetzold,[1a] who prepared iminoboranes via alkyl-group migration (R 2 N À B(R')-N!R 2 N-B N À R') involving at ransient boranitrene. [24] Cummins and Foxa lso observed nitrogen extrusion from the azidoborate salt nBu [ 25] To gain insight into the mechanism by which IPr·HB = NH·BAr (3). Notably thermolysis of the deutero analogue 3d did not yield any discernable H/D kinetic isotope effect ( Figure S4), [26] suggesting that N 2 loss and formation of at ransient nitrene is the rate-determining step.…”