ET3NH+CO(CO)4- - HYDROGEN-BONDED ADDUCT OR SIMPLE ION-PAIR - SINGLE-CRYSTAL NEUTRON-DIFFRACTION STUDY AT 15-K

Et3NH+Co(CO)4- contains a short N-H...Co contact, which provides the closest approach between the anion and cation. Accurate structural characterization by neutron diffraction at 15 K shows the N-H...Co interaction to be linear with a long N-H bond length and a relatively short Co...H separation (Co...H = 2.613 (2) angstrom, N-H = 1.054 (1) angstrom, N-H...Co = 180.0-degrees). This evidence is consistent with the presence of a three-center-four-electron hydrogen-bond-like N-H...Co interaction, though it does not rule out simple electrostatic attraction as the principal driving force behind association of the Et3NH+ and Co(CO)4- ions.