Metalcarbonyl analogues of annelated cyclooctatetraene and cyclodecapentaene derivatives with a planar core cycle: a quantum chemical study

Abstract

With the help of DFT calculations the possibility of stabilizing non-standard flat conformations of cyclooctatetraene and cyclodecapentaene by equatorially located metalcarbonyl substituents has been predicted. Structures and stabilities of a new family of metalcarbonyl Cr(CO)₅, Fe(CO)₄, Ni(CO)₃, Ti(CO)₄, and Ni(CO)₂ cyclooctatetraene and cyclodecapentaene derivatives have been studied. All cyclooctatetraene derivatives, except the Ti(CO)₄ derivative, have planar structures and are characterized by the pronounced anti-aromaticity of the core cycle. In the case of cyclodecapentaene complexes, the planar structures are formed by only Fe(CO)₄ and Ni(CO)₃ derivatives. Stabilization of non-standard planar forms is caused by both sterically enforced flattening of the core cycles and their π-interactions with metalcarbonyl moieties.