Stable transition metal complexes of an all-metal antiaromatic molecule (Al₄Li₄): role of complexations

Abstract

We propose for the first time a few examples of stable transition metal complexes of an all-metal antiaromatic molecule Al₄Li₄. We demonstrate that these all-metal species can be stabilized by complexation with 3d transition metals very similar to their organic counterpart, C₄H₄. Complexation to transition metal ions reduces the frontier orbital energies and introduces aromatic charactersitics. We consider a series of such complexes: [η⁴-(Al₄Li₄)-Fe(CO)₃, η²,σ²-(Al₄Li₄)-Ni, and (Al₄Li₄)₂Ni] and compare and contrast their energetics with their organometallic counterparts. Fragmentation energy, orbital correlation energy analysis, and the nucleus-independent chemical shift (NICS) values support the complexation-induced stabilities in these systems.