Reagents leading to difluoramino (NF2) products

Crystal Structures of α- and β-Nitrogen Trifluoride

The crystal structures of α-NF₃ and β-NF₃ are reported for the first time. As shown by powder neutron diffraction, the low-temperature α-NF₃ crystallizes in the orthorhombic space group Pnma ( oP16) with lattice parameters a = 6.71457(13) Å, b = 7.30913(14) Å, c = 4.55189(8) Å, V = 223.396(7) ų, and Z = 4 at T = 6 K. The intramolecular atom distances in α-NF₃ are 1.3639(16) and 1.3677(11) Å for N-F, and 2.1216(16) and 2.120(2) Å for F···F. The F-N-F bond angles are 101.92(7)° and 101.63(10)°. All data are in excellent agreement with quantum-chemical predictions and previously reported experimentally obtained gas-phase data. The high-temperature β-NF₃ is a plastic crystal, space group P4₂/ mnm ( tP120), with the lattice parameters a = 15.334(6) Å, c = 7.820(3) Å, V = 1838.6(12) ų, and Z = 30 at T = 60 K. Its crystal structure is closely related to that of the Frank-Kasper sigma phase.

Energetic materials with fluorinated four-membered heterocyclic ring: 3,3′-difluoroazetidine (DFAZ) salts

Fluorine atoms and four-membered rings form 3,3′-difluoroazetidinium (DFAZ) salts, which have a better detonation property than ammonium dinitramide (ADN).

From strong to weak NF bonds: on the design of a new class of fluorinating agents

A set of 50 molecules with NF bonds was investigated to determine the factors that influence the strength of a NF bond, with the aim of designing a new class of fluorinating agents. The intrinsic bond strength of the NF bonds was used as bond strength measure, derived from local stretching NF force constants obtained at the CCSD(T)/aug-cc-pVTZ and ωB97XD/aug-cc-pVTZ levels of theory. The investigation showed that the NF bond is a tunable covalent bond, with bond strength orders ranging from 2.5 (very strong) to 0.1 (very weak). NF bond strengthening is caused by a combination of different factors and can be achieved by e.g. ionization. Whereas, the NF bond weakening can be achieved by hypervalency on the N atom, using a N→Ch (Ch: O, S, Se) donor-acceptor type bond with different electron-withdrawing groups. These new insights into the nature of the NF bond were used to propose and design a new class of fluorinating agents. Hypervalent amine-chalcogenides turned out as most promising candidates for efficient electrophilic fluorinating agents.