Keywords: Sandwich complexes / Nickel / Arenes / EHMO calculations / Cyclopentadienyl ligands Synthesis, structure, reactivity, and theoretical studies of a new type of Ni triple-decker complexes are reported. A prominent feature of its molecular structure is the (η 3 :η 3 )-bis-(enyl) coordination of two [(η 5 -Me 4 EtC 5 )Ni] fragments to the central arene ring of the polycondensed π-perimeter decacyclene. The central arene ring of decacyclene displays a distinct chair conformation with significant tilt angles of 25.5 and 26.1°. The three naphthalene units are twisted in a propeller-like fashion with torsion angles of 16°, 16.6°, and 19°, which is twice the twisting observed for the free decacyclene ligand. According to Extended Hückel Molecular Orbital (EHMO) calculations, a qualitative measure for arene lability in the title compound and a number of related arene-bridged metal complexes can be attributed to a subsequent filling of [ ‡] New address: