Nitrene

In chemistry, a nitrene (R–N:) is the nitrogen analogue of a carbene. The nitrogen atom has only 5 valence electrons and is therefore considered an electrophile. A nitrene is a reactive intermediate and is involved in many chemical reactions.

In the most simple nitrene, the linear imidogen (:N–H), two of the 6 available electrons form a covalent bond with hydrogen, two other create a free electron pair and the two remaining electrons occupy two degenerate p orbitals. Consistent with Hund's rule the low energy form of imidogen is a triplet with one electron in each of the p orbitals and the high energy form is the singlet state with an electron pair filling one p orbital and the other one vacant.

As with carbenes, a strong correlation exists between the spin density on the nitrogen atom which can be calculated in silico and the zero-field splitting parameter D which can be derived experimentally from electron spin resonance. Small nitrenes such as NH or CF₃N have D values around 1.8 cm⁻¹ with spin densities close to a maximum value of 2. At the lower end of the scale are molecules with low D (< 0.4) values and spin density of 1.2 to 1.4 such as 9-anthrylnitrene and 9-phenanthrylnitrene.

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