Aluminum chain in LiAlH 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 LiAlH 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 LiAlH 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 CsH[GaH] compound featuring the propane-like [GaH] 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 LiAlH cluster has revealed two classical Al-Al σ bonds constituting the propane-like kernel.