Li 2 [SeC 2 Se]·2NH 3 : A Crystalline Ammoniate with a - Se-C≡C-Se - Dianion.

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 high-resolution synchrotron powder diffraction data ( P 2 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 electronic-structure 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 ( N egative I on P hoto e lectron) and VMI ( V elocity- M ap I maging) 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.