Niobium oxalate
# Niobium oxalate

Niobium(V) oxalate is the hydrogen oxalate salt of niobium(V). The neutral salt has not been prepared.

## Complexes

Niobium(V) can form complexes with hydroxy acids, as well as oxalic acid. The salt formed is more complex than tartaric acid for niobium (as opposed to tantalum). $NH_4[NbO(C_2O_4)_2(H_2O)_2]·3H_2O$ starts to lose water at 125°C, and at 630°C, it fully decomposes, forming a compound known as niobium pentoxide; Heating this complex and sodium citrate at 650°C can form sodium niobate $(NaNbO_3).$

$Rb_3[NbO(C_2O_4)_3]·2H_2O$ is a colourless crystal, which includes the $[NbO(C_2O_4)_3]^{3-}$ anion. $Sr_3[NbO(C_2O_4)_3]_2·8H_2O$ is a compound containing the same anion, forming the anhydrous at 200°C, starting to decompose at 260°C, and at 875°C it decomposes to $SrCO_3$ and $SrNb_2O_6.$

