Gold(I)···Lanthanide(III) Bonds in Discrete Heterobimetallic Compounds: A Combined Computational and Topological Study.

The chemical nature of the ligand-unsupported gold(I)-lanthanide(III) bond in the proposed [Ln III (η 5 -Cp) 2 ][Au I Ph 2 ] ( Ln-Au ; Ln III = La III , Eu III , or Lu III ; Cp = cyclopentadienide; Ph = phenyl) models is examined from a theoretical viewpoint. The covalent bond-like Au-Ln distances (Au-La, 2.95 Å; Au-Eu, 2.85 Å; Au-Lu, 2.78 Å) result from a strong interaction between the oppositely charged fragments (Δ E int MP2 > 600 kJ mol -1 ), including the aforementioned metal-metal bond and additional Ln III -C ipso and C-H···π interactions. The Au-Ln bond has been characterized as a chemical bond rather than a strong metallophilic interaction with the aid of energy decomposition analysis, interaction region indicator, and quantum theory of atoms in molecules topological tools. The chemical nature of the Au-Ln bond cannot be fully ascribed to a covalent or an ionic model; an intermediate situation or a charge shift bond is proposed. The [Au I Ph 2 ] - anion has also been identified as a suitable lanthanide(III) emission sensitizer for La-Au and Lu-Au .