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...

A versatile strategy for the formation of hydride-bridged actinide–iridium multimetallics

“…4,5 The combination of their potential for f-orbital participation in bonding, access to unusual coordination environments, and diversity of accessible oxidation states sets the actinides apart from the more comprehensively studied transition metals or the lanthanides, especially when considering multimetallic species with the potential for d-f intermetallic bonding. Incorporation of these elements, which have been demonstrated to facilitate unique activation of strong bonds [6][7][8][9][10][11] and small molecules, [12][13][14][15][16][17][18] in multimetallic systems could unlock modes of cooperative reactivity currently inaccessible to transition metal multimetallic species. Even in light of this potential, as recently as ten years ago, f-element-metal bonding chemistry was still described as "in its infancy."…”

Progress in the chemistry of molecular actinide-nitride compounds

“…79 First, the heteroleptic complex, [Cs { U IV (OSi(O t Bu) 3 ) 2 (N(SiMe 3 ) 2 ) } 2 (μ-N)] ( 23 ), containing a combination of –OSi(O t Bu) and –N(SiMe 3 ) 2 ligands (4 : 2 ratio), was obtained from the reaction of CsN 3 with the in situ generated heteroleptic U( iii ) precursor, “[U III (OSi(O t Bu) 3 ) 2 (N(SiMe 3 ) 2 )]” (Scheme 6). 79 Complex 23 is quite stable at low temperatures in toluene, but slowly decomposes at −40 °C in THF, and undergoes full decomposition at room temperature forming the U( iv )/U( iv ) bridged imido–cyclometallate complex, [Cs((OSi(O t Bu) 3 ) 3 U IV )(μ-NH)(μ-η 2 :C,N–CH 2 SiMe 2 NSiMe 3 )U IV (N(SiMe 3 ) 2 )(OSi(O t Bu) 3 )] ( 23b ), involving a 1,2-addition of a C–H bond of N(SiMe 3 ) 2 across the uranium–nitride bond, similar to what was observed for the U( iii )/U( iv ) nitride complex 20 . From the same study, a second heteroleptic U( iv )/U( iv ) nitride complex, [K(U IV (OSi(O t Bu) 3 )(N(SiMe 3 ) 2 ) 2 ) 2 (μ-N)] ( 24 ), containing a different combination of –OSi(O t Bu) 3 and –N(SiMe 3 ) 2 ligands (2 : 4 ratio), was prepared by the addition of 2.0 equiv.…”

“…However, addition of N 2 to the putative “[K 3 U III NU III ]” complex, 26 , resulted in the analogous reactivity observed for 8-K , 48 in which 26 promotes the 4e − reduction to yield the mixed-ligand U( v )/U( v )–N 2 4− complex, [K 3 (U V (OSi(O t Bu) 3 ) 2 (N(SiMe 3 ) 2 ) 2 (μ-N)(μ-η 2 :η 2 -N 2 )] ( 113 ) (Scheme 23). 79 Converse to the reaction with 8-K , additional N 2 cleavage products were isolated from the reaction mixture, namely, [K 3 (U VI (OSi(O t Bu) 3 ) 2 (N(SiMe 3 ) 2 )(N))(μ-N) 2 (U V (OSi(O t Bu) 3 ) 2 (N(SiMe 3 ) 2 ))] 2 ( 114 ), and [K 4 ((OSi(O t Bu) 3 ) 2 U V )(N))(μ-NH)(μ-κ 2 :C,N–CH 2 SiMe 2 NSiMe 3 )(U V (OSi(O t Bu) 3 ) 2 ][K(N(SiMe 3 ) 2 ] 2 , ( 115 ) (Scheme 23).…”

“…The synthetic strategy used in the preparation of [Cs(U IV (OSi(O t Bu) 3 ) 3 ) 2 (m-N)] (6-Cs) 71 was also successfully applied by Keener, Mazzanti and co-workers for the isolation of other heteroleptic U(IV)/U(IV) bridged nitrides. 79 First, the heteroleptic complex, [Cs{U IV (OSi(O t Bu) 3 ) 2 (N(SiMe 3 ) 2 )} 2 (m-N)] ( 23), containing a combination of -OSi(O t Bu) and -N(SiMe 3 ) 2 ligands (4 : 2 ratio), was obtained from the reaction of CsN 3 with the in situ generated heteroleptic U(III) precursor, "[U III (OSi(O t Bu) 3 ) 2 (N(SiMe 3 ) 2 )]" (Scheme 6). 79 6), and was found to be stable in various solvents.…”

“…79 First, the heteroleptic complex, [Cs{U IV (OSi(O t Bu) 3 ) 2 (N(SiMe 3 ) 2 )} 2 (m-N)] ( 23), containing a combination of -OSi(O t Bu) and -N(SiMe 3 ) 2 ligands (4 : 2 ratio), was obtained from the reaction of CsN 3 with the in situ generated heteroleptic U(III) precursor, "[U III (OSi(O t Bu) 3 ) 2 (N(SiMe 3 ) 2 )]" (Scheme 6). 79 6), and was found to be stable in various solvents. 79 The increased stability of 24 towards C-H bond activation of a N(SiMe 3 ) 2 ligand, in comparison to complex 23, was attributed to the number of -OSi(O t Bu) 3 ligands (two vs. four).…”