Nitride protonation and NH₃ binding versus N–H bond cleavage in uranium nitrides

Abstract

The conversion of metal nitrides to NH3 is an essential step in dinitrogen fixation, but there is limited knowledge of the reactivity of nitrides with protons (H+). Herein, we report...

Nitrogen activation and cleavage by a multimetallic uranium complex

“…The K cation binds to the bridging nitride ligand (2.953(3) Å) and to four oxygens of the two OSi(O t Bu) 3 ligands. The U-N-U bond angle (162.5(1) ) and distances (2.071(2), 2.077(2) Å; Table 1) are consistent with those found for the previously reported all-OSi(O t Bu) 3 ([{U IV (OSi(O t Bu) 3 ) 3 } 2 (m-N)][Cs] (A, Scheme 1); (170.2(3) ; 2.058(5) Å), 4c and the all-N(SiMe 3 ) 2 complexes, E (168.97 (14) ; 2.055(3) Å) 9b and G (179.0(1) ; 2.076(5) Å). 9a Next, we investigated the synthesis of a heteroleptic complex with a different combination of OSi(O t Bu) 3 (four) and N(SiMe 3 ) 2 (two) ligands, to probe the effect of ancillary ligands in N 2 binding and activation.…”

“…The terminal nitride (1.847(13)Å) is elongated compared to the terminal K-capped U( vi ) nitride in complex 8 (1.784(4)Å; Table 2 ), and is comparable to that of the previously reported alkali-capped 24 and borane-capped U( v ) nitrides. 26 The bridging U–N–U (U1–N1: 2.323(13), U2–N1: 1.916(13)Å) and U–NH–U (U1–N2: 2.218(14), U2–N2: 2.318(14)Å) 14 bond distances are consistent with the presence of a U–N single and a short U N multiple bond (similar to complex 8), and a bridging imido, respectively. Complexes 8 and 9 provide the first example of N 2 cleavage promoted by a low-valent U( iii ) complex without addition of alkali reducing agents.…”

“…However, we have previously shown that uranium bridging nitride complexes react readily with strong acids to form NH 3 . 14 Therefore, to determine if the NH 4 Cl was derived from the (N 3À ) and (N 2 4À…”

“…HCl in Et 2 O addition to 7-14/15 N led to a comparable spectrum as 7 (Fig. S57b †), making the assignment to 15 NH 4 Cl or 14 NH 4 Cl ambiguous. Broad resonances are not common in NH 4 Cl quantication experiments, and are most likely due to our ligand system.…”

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.…”