Nitrogen difluoride

Nitrogen difluoride, also known as difluoroamino, is a reactive radical molecule with formula NF2. This small molecule is in equilibrium with its dimer tetrafluorohydrazine.


 * N2F4 ⇌ 2 NF2

As the temperature increases the proportion of NF2 increases.

The molecule is unusual in that it has an odd number of electrons, yet is stable enough to study experimentally.

Properties
The energy needed to break the N–N bond in N2F4 is 20.8 kcal/mol, with an entropy change of 38.6 eu. For comparison, the dissociation energy of the N–N bond is 14.6 kcal/mol in N2O4, 10.2 kcal/mol in N2O2, and 60 kcal/mol in N2H4. The enthalpy of formation of N2F4 (ΔfH) is 34.421 kJ/mol.

At room temperature N2F4 is mostly associated with only 0.7% in the form of NF2 at 5 mmHg pressure. When the temperature rises to 225 °C, it mostly dissociates with 99% in the form of NF2.

In NF2, the N–F bond length is 1.3494 Å and the angle subtended at F–N–F is 103.33°.

In the infrared spectrum the N–F bond in NF2 has a symmetrical stretching frequency of 1075 cm−1. This compares to 1115 cm−1 in NF, 1021 cm−1 in NF3 and 998 cm−1 in N2F4.

The microwave spectrum shows numerous lines due to spin transitions, with or without nuclear spin transitions. The lines form set of two triplets for antisymmetric singlet, or two triplets of triplets for symmetric triplet. Lines appear around 14–15, 24, 25, 26, 27, 28–29, 33, 60, 61, 62, and 65 GHz. The rotational constants for the NF2 molecule are A = $70,496 MHz$, B = $11,872.2 MHz$, and C = $10,136.5 MHz$. The inertial defect Δ = 0.1204 mu·Å2. The centrifugal distortion constants are τaaaa = −7.75, τbbbb = −0.081, τaabb = 0.30, and τabab = −0.13.

The dipole moment is 0.13 D ($0 C·m$).

The ground electronic state of the molecule is 2B1.

The gas is often contaminated with NO or N2O.

Use
Nitrogen difluoride is formed during the function of a xenon monofluoride excimer laser. Nitrogen trifluoride is the halide carrier gas, which releases fluoride ions when impacted by electrons:


 * NF3 + e− → NF2 + F−

The free fluoride ion goes on to react with xenon cations.

Nitrogen difluoride can be consumed further to yield nitrogen monofluoride.


 * NF2 + e− → NF + F−