A topological study of bonding in the Al2H2 and Al2H4 hydrides

Abstract A topological analysis of the hydrogen-bridged and non-bridged Al 2 H 2 and Al 2 H 4 hydrides has been carried out using energies and geometries found at the CCSD(T)/cc-pvtz level and B3LYP/cc-pvtz Kohn–Sham wavefunctions at the optimized geometries for ELF and AIM analyses. Our topological analysis confirms earlier bonding pictures and leads to a better understanding of these unusual systems. Virtually all cases involving bridged species can be pictured in terms of donor–acceptor interactions involving hydrogen and lone pairs. Two cases of relatively weak bent Al–Al bonds are found and the unusual trans -bent HAlAlH molecule is seen to have a bond order just somewhat larger than unity.