Synthesis and Characterization of Nitro‐, Trinitromethyl‐, and Fluorodinitromethyl‐Substituted Triazolyl‐ and Tetrazolyl‐trihydridoborate Anions

Abstract

The problem of preparing energetic, exclusively mono-azolyl substituted hydridoborate anions in high yield and purity from [BH ] and nitroazoles by hydrogen elimination was overcome by reacting the corresponding nitroazolate anions with the BH adducts BH ⋅S(CH ) or BH ⋅THF. The highly-energetic, nitro-, trinitromethyl-, and fluorodinitromethyl- substituted triazolyl- and tetrazolyl-trihydridoborate anions were synthesized in this manner and characterized by vibrational and multinuclear NMR spectroscopy and their crystal structures. The use of excess BH resulted in some cases in the addition of a second BH molecule bound more-weakly to one of the nitrogen atoms of the azole ring. All monoazolyl-trihydridoborates were thermally less stable than the parent azolate anions. A decomposition product of tetraphenylphosphonium (5-(trinitromethyl)-5H-2λ -tetrazol-2-yl)trihydridoborate, the tetraphenyl-phosphonium (dinitro-1H-tetrazol-5-yl)methanide monohydrate, was also structurally characterized, providing some insight into the decomposition pathways of the nitromethyl-substituted azolyltrihydridoborate anions.

Synthesis of Complex Boron–Nitrogen Heterocycles Comprising Borylated Triazenes and Tetrazenes Under Mild Conditions

“…Although a boryl-iminoborane may be invoked in the formation of 2,4,6-trihalo-1,3,5-tris­(dihaloboryl)­borazine, − our transient boryl-iminoboranes display classical iminoborane chemistry beyond trimerization (i.e., dimerization and cycloaddition) in a relatively controllable fashion. Excluding borylated tetrazoles, − species 5 and 6 also belong to a rare group of (di)­borylated tetrazenes, the only examples of which have recently been isolated from the fixation of dinitrogen by low-valent boron compounds…”

1‐(Azidomethyl)‐5H‐Tetrazole: A Powerful New Ligand for Highly Energetic Coordination Compounds

“…Independent from the synthesis, the resulting 1-(azidomethyl)-5H-tetrazol represents the smallest tetrazole with an Nazidoalkyl functionality, having a drastically increased gas-phase enthalpy of formation (5431 kJ kg À 1 ), compared to its three parent compounds (Figure 1), even surpassing 1-AT. Although methylene bridged functional groups on the tetrazole moiety can be found in literature, [24][25][26] especially 5-(azidomethyl)-1Htetrazole, [27] they always show 5-substitution of the tetrazole ring. [28][29] Sadly, all 5-substituted derivatives still exhibit acidic protons, making them unsuitable for use as ligands in energetic coordination compounds.…”

Syntheses and Reactivity of New Zwitterionic Imidazolium Trihydridoborate and Triphenylborate Species

“…The 11 B-NMR spectra showed a quartet at δ −19.38 and −19.21 ppm for Compounds 1 and 2 , respectively, in CDCl 3 solution, indicating a coordination of the imidazole rings at the BH 3 group [ 62 , 90 ]. The single broad 11 B resonances observed at δ −6.52 ppm for Compound 3 and at δ −6.37 ppm for Compound 4 , in (CD 3 ) 2 CO and CDCl 3 solutions, respectively, are indicative of a four-coordinate boron center; they are in the range observed for analogously triphenylborate species [ 91 ], being considerably shifted in comparison with the triphenylborane one, which is observed at δ −60.2 ppm [ 92 ].…”