Cyclic triborate ($[{\mathrm{B}}_3{\mathrm{O}}_6{]}^{3-}$)

The anion $[{\mathrm{B}}_3{\mathrm{O}}_6{]}^{3-}$ formed from three trigonal $\mathrm{B}{\mathrm{O}}_3$ units sharing corners in an alternating six-membered B–O ring. Each boron also has one terminal oxygen.