Triazolide Complexes of Sodium and Potassium in the Gas Phase

Aromatic organometallic complexes, such as ferrocene and the "inverse sandwich complex" [Na₂Cp]⁺, are stabilized via charge-transfer (C-T) interactions and cation-π interactions (i.e., charge-induced dipole and charge-quadrupole interactions). Much effort has gone into investigating systems that contain organic moieties, such as benzene or cyclopentadienyl ligands, but less attention has been paid to aromatic systems that contain heteroatoms (e.g., N), possibly owing to the complexity arising from a lowering of symmetry and the introduction of electron lone pair density and dipole moments. Here we investigate sodiated and potassiated clusters of 1,2,3-triazolide, [M (123T)]⁺ (x = 3, 4; M = Na, K), and 1,2,4-triazolide, [M (124T)]⁺ (x = 3, 4; M = Na, K), using a combination of infrared ion spectroscopy (IRIS) and DFT calculations. Cluster structures are strongly influenced by charge-dipole interactions and C-T interactions from N lone pairs to the metal cations. IRIS spectra indicated that the geometries of the triazolide moieties are essentially unperturbed by the interaction with the metal ions. Additional spectral features, not predicted by DFT calculations, that are observed in the 1500-1800 cm^-1 region seem to be associated with combination bands involving C-H wagging and ring torsion motions.