Phospholyl and Arsolyl Triple-Decker Sandwich Complexes of Europium(II) and Strontium(II)

To study the influence of heteroatoms on the photophysical properties of divalent Eu and Sr complexes, the synthesis of the phospholyl and arsolyl compounds [{(Dtp)(thf)M}₂{μ-η⁸:η⁸-C₈H₈}] (M = Eu^II and Sr^II; Dtp = 3,4-dimethyl-2,5-bis(tert-butyl)phospholyl) and [{(Dtas)(thf)M}₂{μ-η⁸:η⁸-C₈H₈}] (M = Eu^II and Sr^II; Dtas = 3,4-dimethyl-2,5-bis(tert-butyl)arsolyl) is reported. Organometallic compounds of divalent europium with P and As heterocyclic ligands have not been described previously. They were prepared by salt elimination reactions from potassium phospholyl or arsolyl, K₂C₈H₈, and EuI₂(thf)₂ or SrI₂. Photophysical properties were investigated alongside a reference cyclopentadienyl complex with a comparable structure. Critically, the influence of the heteroatom on the photoluminescence emission and excitation and quantum yields of the complexes is significant. Density functional theory calculations were performed to rationalize the ligand influences.