Divalent Lanthanide Complexes Supported by the Bridged Bis(amidinates) L [L = Me₃SiN(Ph)CN(CH₂)₃NC(Ph)NSiMe₃]: Synthesis, Molecular Structures and One-Electron-Transfer Reactions

Metathesis reactions of YbI₂ with Li₂L (L = Me₃SiN­(Ph)­CN­(CH₂)₃NC­(Ph)­NSiMe₃) in THF at a molar ratio of 1:1 and 1:2 both afforded the Yb­(II) iodide complex [{YbI­(DME)₂}₂(μ₂-L)] (<b>1</b>), which was structurally characterized to be a dinuclear Yb­(II) complex with a bridged L ligand. Treatment of EuI₂ with Li₂L did not afford the analogous [{EuI­(DME)₂}₂(μ₂-L)], or another isolable Eu­(II) complex, but the hexanuclear heterobimetallic cluster [{Li­(DME)₃}⁺]₂[{(EuI)₂(μ₂-I)₂(μ₃-L)₂(Li)₄}­(μ₆-O)]^2– (<b>2</b>) was isolated as a byproduct in a trace yield. The rational synthesis of cluster <b>2</b> could be realized by the reaction of EuI₂ with Li₂L and H₂O in a molar ratio of 1:1.5:0.5. The reduction reaction of LLnCl­(THF)₂ (Ln = Yb and Eu) with Na/K alloy in THF gave the corresponding Ln­(II) complexes [Yb₃(μ₂-L)₃] (<b>3</b>) and [Eu­(μ₂-L)­(THF)]₂ (<b>4</b>) in good yields. An X-ray crystal structure analysis revealed that each L in complex <b>3</b> might adopt a chelating ligand bonding to one Yb atom and each Yb atom coordinates to an additional amidinate group of the other L and acts as a bridging link to assemble a macrocyclic structure. Complex <b>4</b> is a dimer in which the two monomers [Eu­(μ₂-L)­(THF)] are connected by two μ₂-amidinate groups from the two L ligands. Complex <b>3</b> reacted with CyNCNCy and diazabutadienes [2,6-^<i>i</i>Pr₂C₆H₃NCRCRNC₆H₃^<i>i</i>Pr₂-2,6] (RH, CH₃) (DAD) as a one-electron reducing agent to afford the corresponding Yb­(III) derivatives: the complex with an oxalamidinate ligand [LYb­{(NCy)₂CC­(NCy)₂}­YbL] (<b>5</b>) and the complexes containing a diazabutadiene radical anion [LYb­(^<i>i</i>Pr₂C₆H₃NCRCRNC₆H₃^<i>i</i>Pr₂)] (R = H (<b>6</b>), R = CH₃ (<b>7</b>)). Complexes <b>5</b>–<b>7</b> were confirmed by an X-ray structure determination