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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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DOE OSTI2022

Tale of Three Molecular Nitrides: Mononuclear Vanadium (V) and (IV) Nitrides As Well As a Mixed-Valence Trivanadium Nitride Having a V 3 N 4 Double-Diamond Core

Here, transmetallation of [VCl 3 (THF) 3 ] and [TlTp tBu,Me ] afforded [(Tp tBu,Me )VCl 2 ] (1, Tp tBu,Me = hydro-tris(3-tert-butyl-5-methylpyrazol-1-yl)borate), which was reduced with KC 8 to form a $C_{3v}$ symmetric V II complex, [(Tp tBu,Me )VCl] (2). Complex 1 has a high-spin ($\textit{S}$ = 1) ground state and displays rhombic high-frequency and -field electron paramagnetic resonance (HFEPR) spectra, while complex 2 has an $\textit{S}$ = 3/2 4 A 2 ground state observable by conventional EPR spectroscopy. Complex 1 reacts with NaN 3 to form the V V nitride-azide complex [(Tp tBu,Me )V≡N(N 3 )] (3). A likely V III azide intermediate en route to 3, [(Tp tBu,Me )VCl(N 3 )] (4), was isolated by reacting 1 with N 3 SiMe 3 . Complex 4 is thermally stable but reacts with NaN3 to form 3, implying a bis-azide intermediate, [(Tp tBu,Me )V(N 3 ) 2 ] (A), leading to 3. Reduction of 3 with KC 8 furnishes a trinuclear and mixed-valent nitride, [{(Tp tBu,Me )V} 2 ($μ_{4-}$VN 4 )] (5), conforming to a Robin–Day class I description. Complex 5 features a central vanadium ion supported only by bridging nitride ligands. Contrary to 1, complex 2 reacts with NaN 3 to produce an azide-bridged dimer, [{(Tp tBu,Me )V} 2 (1,3-$μ_2$-N 3 ) 2 ] (6), with two antiferromagnetically coupled high-spin V II ions. Complex 5 could be independently produced along with [($κ_2$-Tp tBu,Me ) 2 V] upon photolysis of 6 in arene solvents. The putative {V IV ≡N} intermediate, [(Tp tBu,Me )V≡N] (B), was intercepted by photolyzing 6 in a coordinating solvent, such as tetrahydrofuran (THF), yielding [(Tp tBu,Me )V≡N(THF)] (B-THF). In arene solvents, B-THF expels THF to afford 5 and [($κ_2$-Tp tBu,Me ) 2 V]. A more stable adduct (B-OPPh 3 ) was prepared by reacting B-THF with OPPh 3 . These adducts of B are the first neutral and mononuclear V IV nitride complexes to be isolated.

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DOE OSTI2023

Breaking New Ground: MB ene Route toward Selective Vinyl Double Bond Hydrogenation in Nitroarenes

Doping, or incremental substitution of one element for another, is an effective way to tailor a compound’s structure as well as its physical and chemical properties. Herein, we replaced up to 30% of Ni with Co in members of the family of layered LiNiB compounds, stabilizing the high-temperature polymorph of LiNiB while the room-temperature polymorph does not form. By studying this layered boride with in situ high-temperature powder diffraction, we obtained a distorted variant of LiNi 0.7 Co 0.3 B featuring a perfect interlayer placement of [Ni 0.7 Co 0.3 B] layers on top of each other–a structural motif not seen before in other borides. Because of the Co doping, LiNi 0.7 Co 0.3 B can undergo a nearly complete topochemical Li deintercalation under ambient conditions, resulting in a metastable boride with the formula Li 0.04 Ni 0.7 Co 0.3 B. Heating of Li 0.04 Ni 0.7 Co 0.3 B in anaerobic conditions led to yet another metastable boride, Li 0.01 Ni 0.7 Co 0.3 B, with a CoB-type crystal structure that cannot be obtained by simple annealing of Ni, Co, and B. No significant alterations of magnetic properties were detected upon Co-doping in the temperature-independent paramagnet LiNi 0.7 Co 0.3 B or its Li-deintercalated counterparts. Finally, Li 0.01 Ni 0.7 Co 0.3 B stands out as an exceptional catalyst for the selective hydrogenation of the vinyl C=C bond in 3-nitrostyrene, even in the presence of other competing functional groups. Finally, this research showcases an innovative approach to heterogeneous catalyst design by meticulously synthesizing metastable compounds.

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