Aluminum chain in Li2Al3H8(-) as suggested by photoelectron spectroscopy and ab initio calculations.

Group 13 elements are very rarely observed to catenate into linear chains and experimental observation of such species is challenging. Herein we report unique results obtained via combined photoelectron spectroscopy and ab initio studies of the Li2Al3H8(-) cluster that confirm the formation of an Al chain surrounded by hydrogen atoms in a very particular manner. Comprehensive searches for the most stable structure of the Li2Al3H8(-) cluster have shown that the global minimum isomer I possesses a geometric structure, which resembles the structure of propane, similar to the experimentally known Zintl-phase Cs10H[Ga3H8]3 compound featuring the propane-like [Ga3H8](3-) polyanions. Theoretical simulations of the photoelectron spectrum have demonstrated the presence of only one isomer (isomer I) in the molecular beam. Chemical bonding analysis of the Li2Al3H8(-) cluster has revealed two classical Al-Al σ bonds constituting the propane-like kernel.