Nitrosyl ligand

Coordinated NO is non-innocent. Conventional neutral counting assigns three electrons to a terminal linear NO, one to a terminal bent NO, and three in total to a simple doubly bridging NO.

A bent M–N–O mode conventionally represented as $\mathrm{N}{\mathrm{O}}^{-}$, a two-electron ionic donor and a one-electron neutral donor. These are formal bookkeeping limits rather than measured atomic charges.

A near-linear M–N–O coordination mode conventionally represented as $\mathrm{N}{\mathrm{O}}^{+}$, a two-electron donor in ionic counting and a three-electron donor in neutral counting.

A nitrosyl shared between metal centres. In the simple mu2 counting model it contributes three electrons overall in the neutral method, or can be represented as an $\mathrm{N}{\mathrm{O}}^{-}$ donor of four electrons overall in ionic counting.