Divalent Lanthanide Complexes Supported by the Bridged Bis(amidinates) L [L = Me<sub>3</sub>SiN(Ph)CN(CH<sub>2</sub>)<sub>3</sub>NC(Ph)NSiMe<sub>3</sub>]: Synthesis, Molecular Structures and One-Electron-Transfer Reactions

Metathesis reactions of YbI<sub>2</sub> with Li<sub>2</sub>L (L = Me<sub>3</sub>SiN­(Ph)­CN­(CH<sub>2</sub>)<sub>3</sub>NC­(Ph)­NSiMe<sub>3</sub>) in THF at a molar ratio of 1:1 and 1:2 both afforded the Yb­(II) iodide complex [{YbI­(DME)<sub>2</sub>}<sub>2</sub>(μ<sub>2</sub>-L)] (<b>1</b>), which was structurally characterized to be a dinuclear Yb­(II) complex with a bridged L ligand. Treatment of EuI<sub>2</sub> with Li<sub>2</sub>L did not afford the analogous [{EuI­(DME)<sub>2</sub>}<sub>2</sub>(μ<sub>2</sub>-L)], or another isolable Eu­(II) complex, but the hexanuclear heterobimetallic cluster [{Li­(DME)<sub>3</sub>}<sup>+</sup>]<sub>2</sub>[{(EuI)<sub>2</sub>(μ<sub>2</sub>-I)<sub>2</sub>(μ<sub>3</sub>-L)<sub>2</sub>(Li)<sub>4</sub>}­(μ<sub>6</sub>-O)]<sup>2–</sup> (<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 EuI<sub>2</sub> with Li<sub>2</sub>L and H<sub>2</sub>O in a molar ratio of 1:1.5:0.5. The reduction reaction of LLnCl­(THF)<sub>2</sub> (Ln = Yb and Eu) with Na/K alloy in THF gave the corresponding Ln­(II) complexes [Yb<sub>3</sub>(μ<sub>2</sub>-L)<sub>3</sub>] (<b>3</b>) and [Eu­(μ<sub>2</sub>-L)­(THF)]<sub>2</sub> (<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(μ<sub>2</sub>-L)­(THF)] are connected by two μ<sub>2</sub>-amidinate groups from the two L ligands. Complex <b>3</b> reacted with CyNCNCy and diazabutadienes [2,6-<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>NCRCRNC<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>-2,6] (RH, CH<sub>3</sub>) (DAD) as a one-electron reducing agent to afford the corresponding Yb­(III) derivatives: the complex with an oxalamidinate ligand [LYb­{(NCy)<sub>2</sub>CC­(NCy)<sub>2</sub>}­YbL] (<b>5</b>) and the complexes containing a diazabutadiene radical anion [LYb­(<sup><i>i</i></sup>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>NCRCRNC<sub>6</sub>H<sub>3</sub><sup><i>i</i></sup>Pr<sub>2</sub>)] (R = H (<b>6</b>), R = CH<sub>3</sub> (<b>7</b>)). Complexes <b>5</b>–<b>7</b> were confirmed by an X-ray structure determination.