Understanding d-orbital participation in alkaline earth metal complexes

Abstract

Alkaline earth metal (AEM) complexes have recently been shown to possess electronic characteristics similar to those of transition metal complexes, with their d orbitals participating in bonding interactions. While this surprising discovery changes our understanding of AEM properties, the mechanism of d-orbital participation remains unclear. Moreover, AEM complexes are typically unstable. Thus, herein, we propose a mechanism for the participation of d orbitals in AEM complexes, in which crystal field effects induce an electronic transition. We explain how the crystal field and electronic back-donation influence complex stability. Finally, we provide insights on the synthesis of more stable AEM complexes using the theory proposed herein.