Li₂[SeC₂Se]·2NH₃: A Crystalline Ammoniate with a ^–Se–C≡C–Se^– Dianion

Abstract

Reaction of Li 2 C 2 with elemental selenium in a molar ratio of 1:2 in liquid ammonia led to the formation of the ammoniate Li 2 [SeC 2 Se]•2NH 3 . Its crystal structure was solved and refined from highresolution synchrotron powder diffraction data (P2 1 /c, Z = 4). It contains the − Se−C�C−Se − anion, unprecedented in a crystalline material, whose existence was corroborated by IR/Raman spectra and electronicstructure theory, showing an almost perfect agreement with calculated spectra. Elaborated magnetic-bottle and velocity-map imaging photoelectron spectroscopic investigations show that the − Se−C�C−Se • radical anion can be transferred to the gas phase, where it was analyzed by NIPE (Negative Ion Photoelectron) and VMI (Velocity-Map Imaging) spectra, which correlate nicely with simulated spectra based on 2 Π u → 3 Σ g − and 2 Π u → 1 Σ g + transitions including spin−orbit couplings.