What is "orthonitrate"

n. (context inorganic chemistry English) The anion NO₄^3- or any salt containing this anion

Orthonitrate is a tetrahedral oxoanion of nitrogen with the formula . It was first identified in 1977 and is currently known in only two compounds, sodium orthonitrate (NaNO) and potassium orthonitrate (KNO). These can be prepared by fusion of the nitrate and metal oxide under high temperatures and ideally high pressures (several GPa).

NaNO + NaO → NaNO (300 °C for 3 days)

The resulting orthonitrates are white solids which are extremely moisture and CO sensitive, decomposing within minutes to carbonate and hydroxide upon exposure to air.

NaNO + CO → NaNO + NaCO NaNO + HO → NaNO + 2NaOH

The orthonitrate ion is tetrahedral with N–O bond lengths of 139 pm, which is unexpectedly short, indicating that polar interactions are shortening the bond as dπ orbitals are too high in energy to be involved.