T. Jelinek et al., MACROPOLYHEDRAL BORON-CONTAINING CLUSTER CHEMISTRY - THE 19-VERTEX OXABORANE ANION, [OB18H21](-), Journal of the Chemical Society, Chemical Communications, (16), 1995, pp. 1665-1666
The first structurally characterised polyhedral oxaborane species, the
macropolyhedral anion [OB18H21](-), has been isolated (30-35%) from t
he reaction of water with the products of the reaction between anti-B1
8H22 and either Na or Na[BH4] in THF; the structure is based on the an
ti-B18H22 type of macropolyhedral cluster, with an oxygen atom between
the B(8) and B(9) positions.