Potassium [1-(tert-but­oxy­carbon­yl)-1H-indol-3-yl]trifluoro­borate hemihydrate

The asymmetric unit of the title salt, K(+)·C(13)H(14)BF(3)NO(2)·0.5H(2)O, consists of two derivatized indolyltrifluoridoborate anions, two potassium cations and one water mol­ecule. Within the indolyltrifluoro­borate anions, the least-square planes consisting of the carboxyl group and the adjacent quarternary C atom of the tert-butyl groups deviate significantly from coplanarity with the indolyl planes [20.44 (11) and 21.02 (10)°]. The potassium ions are coordinated by six atoms (one K(+) ion by two O and four F atoms, and the second K(+) ion by one O and five F atoms), however, one of the potassium ions undergoes an additional weak potassium–π inter­action (K⋯centroid = 3.722 Å). The packing is stabilized by sequential O—H⋯O hydrogen bonds along [100] between water mol­ecules and also by O—H⋯F hydrogen bonds.