Thorium-nitrogen multiple bonds provide evidence for pushing-from-below for early actinides

Abstract

Although the chemistry of uranium-ligand multiple bonding is burgeoning, analogous complexes involving other actinides such as thorium remain rare and there are not yet any terminal thorium nitrides outside of cryogenic matrix isolation conditions. Here, we report evidence that reduction of a thorium-azide produces a transient Th≡N triple bond, but this activates C-H bonds to produce isolable parent imido derivatives or it can be trapped in an N-heterocycle amine. Computational studies on these thorium-nitrogen multiple bonds consistently evidences a σ > π energy ordering. This suggests pushing-from-below for thorium, where 6p-orbitals principally interact with filled f-orbitals raising the σ-bond energy. Previously this was dismissed for thorium, being the preserve of uranium-nitrides or the uranyl dication. Recognising that pushing-from-below perhaps occurs with thorium as well as uranium, and with imido ligands as well as nitrides, suggests this phenomenon may be more widespread than previously thought.

The “Hidden” Reductive [2+2+1]‐Cycloaddition Chemistry of 2‐Phosphaethynolate Revealed by Reduction of a Th‐OCP Linkage

“…Complexes 6 and 7 are isostructural to one another, and their molecular structures are similar to our reported diactinide parent imido complexes [{An(Tren TIPS )-(m-NHM)} 2 ] (An = Th, U; M = Li, Na, K, Rb, Cs) [10,18] and diuranium nitrides [{U(Tren TIPS )(m-NM)} 2 ]. [19] The ThÀO bond distances in 6 (2.026( 9) ) and 7 (2.016 (12) ) are comparable to those for a few reported thorium oxo compounds, for example Th À O distances of 1.929(4) and 1.983 (7) , were reported for [Th(O)(h 5 -1,2,4-(Me 3 C) 3 -C 5 H 2 ) 2 (DMAP)] (DMAP = 4-dimethylaminopyridine) [20] and [K(18-crown-6)][Th(O){N(SiMe 3 ) 2 } 3 ], [21] respectively.…”

“…Forschungsartikel thorium and oxygen (2.38 ), [9] suggesting the O[C 2 P 3 ] ligand is a strong donor, but they compare well with the Th À OMe bond length (2.1563 ) for a related [Th(Tren TIPS )(OMe)] complex, [10] as well as those for the reported Th-OAr complexes. [17] The coordination of Th1 to one of the [C 2 P 3 ] rings is unique with a long Th1ÀC34 bond distance (2.579( 18) ), which compares well with ThÀC single bonds for 4 (2.590 (8) ) and the benzyl compound [Th(Tren TIPS )-(CH 2 Ph)] (2.563( 4) ) supported by the same Tren TIPS ligand.…”

“…[9] The 1 H NMR spectrum of 2 exhibits three resonances spanning the range from 1.0 to 4.0 ppm, with the protons of the isopropyl groups being overlapped, which was previously observed in the closely related compound [Th(Tren TIPS )(N 3 )]. [10] The 13 C-{ 1 H} NMR spectrum of 2 shows five resonances within the range 10.0 to 160.0 ppm, with the (OCP) À carbon resonance identified at 157.6 ppm. Single resonances at 3.4 and À339.9 ppm in the 29 Si{ 1 H} and 31 P{ 1 H} NMR spectra of 2, respectively, support the C 3v symmetric formulation (Supporting Information, Figures S7-S10).…”

Indentation-strain stiffening in tungsten nitrides: Mechanisms and implications

“…By contrast, the calculated results show that hP6-WN 2 is in a semiconducting state at equilibrium but is driven into metallic states by the Vickers indentation loadings near the peak stress. The electronic densities of states of the six tungsten nitrides at equilibrium and under Vickers indentation shear loadings at the indicated strains near the peak stress values along (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)[001] and (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)[110] shear directions corresponding to the stress-strain relations discussed above are shown in Figs. S2-S7 [39].…”

“…Transition-metal nitrides have attracted much attention in recent years due to their rich characteristics as hightemperature ceramics, superconductors, magnets, and catalysts, etc. [1][2][3][4][5][6][7][8][9]. Among these materials, tungsten nitrides represent a distinct family of compounds that exhibit high melting temperatures and desirable mechanical properties [10][11][12].…”