title: Potassium [1-(tert-but-oxy-carbon-yl)-1H-indol-3-yl]trifluoro-borate hemihydrate.
abstract: 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 mol-ecule. Within the indolyltrifluoro-borate 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 inter-action (K⋯centroid = 3.722 Å). The packing is stabilized by sequential O-H⋯O hydrogen bonds along [100] between water mol-ecules and also by O-H⋯F hydrogen bonds.
authors.affiliation: Ludwig-Maximilians-Universität, Department of Chemistry, Butenandtstrasse 5-13, 81377 München,  Germany.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Berionni
authors.forename: Peter
authors.initials: P
authors.lastname: Mayer
authors.forename: Herbert
authors.initials: H
authors.lastname: Mayr