NX3 compounds

The nitrogen halides have the general formula NX3, but not NX5 as in the case of phosphorus. However, some mixed halides such as NF2C1 are known. Fluorine also forms N2F4 and N2F2 (these compounds will be discussed later) that are analogous to hydrazine and diimine, respectively. Except for NF3 (b.p. -129 °C), the compounds are explosive. Because of this behavior, most of what is presented here will deal with the fluorine compounds. 

For NF3, AHfc = -109 kJ mol-1. The compound does not hydrolyze in water as do most other nonmetal halides, including NC13  

The electrolysis of NH4F HF, which can also be described as NH4+HF2, yields NF3. Also, the reaction of NH3 and F2 produces NF3, N2F4, N2F2, NHF2, and so on, with the actual distribution of products depending on the reaction conditions. 

The dipole moment of NF3 is only 0.24 D, whereas that of NH3 is 1.47 D. The reason for this large difference is that the bond dipoles are in opposite directions in the two molecules  

the effect of the unshared pair reinforces the bond moments in NH3, but partially cancels them in NF3. As a result of these differences, NF3 does not act as an electron pair donor. 

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All 12 compounds are well known and are available commercially their physical properties are summarized in Table 13.6 Comparisons with the corresponding data for NX3 (p. 438) and PX3 (p. 496) are also instructive. Trends in mp, bp and density are far from regular and reflect the differing structures and bond types. 

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