Synthesis of Unsupported Ln–Ga Bonds by Salt Metathesis and Ga–Ga Bond Reduction

Three gallyl lanthanide complexes [{(dipp-Bian)­Ga}<sub>2</sub>Ln­(thf)<sub>4</sub>] (Ln = Sm, Eu, Yb; dipp-Bian = 1,2-bis­[(2,6-diisopropylphenyl)­imino]­acenaphthene), in which the lanthanide atoms are coordinated by only two {(dipp-Bian)­Ga}<sup>−</sup> ligands and THF, are reported. Two unsupported Ln–Ga bonds are found in each compound. The gallyl lanthanide complexes have been obtained by two synthetic pathways: (1) reductive insertion of the lanthanide metals into the Ga–Ga bond of [{(dipp-Bian)­Ga}]<sub>2</sub> and (2) salt metathesis of [(dipp-Bian)­GaK­(thf)<sub>5</sub>] with LnI<sub>2</sub>. Moreover, the samarium compound [{(dipp-Bian)­Ga}<sub>2</sub>Sm­(thf)<sub>4</sub>] was additionally obtained in a reductive pathway from SmI<sub>3</sub> and [(dipp-Bian)­GaK­(thf)<sub>5</sub>]. The length of the Ln–Ga bond strongly depends on packing effects. The reaction of TmI<sub>2</sub>(thf)<sub>5</sub> and [(dipp-Bian)­GaK­(thf)<sub>5</sub>] gave the Tm­(III) complex [{(dipp-Bian)­Ga–Ga­(dipp-Bian)}­(C<sub>4</sub>H<sub>8</sub>O)­TmI­(thf)<sub>5</sub>], in which one THF ring was opened and reduced twice, forming the formal double negative charged anion (O-CH<sub>2</sub>-CH<sub>2</sub>-CH<sub>2</sub>-CH<sub>2</sub>)<sup>2–</sup>. This thulium compound and its dysprosium analogue [{(dipp-Bian)­Ga–Ga­(dipp-Bian)}­(C<sub>4</sub>H<sub>8</sub>O)­DyI­(thf)<sub>5</sub>] were also obtained in an alternative approach by reacting LnI<sub>2</sub>(thf)<sub><i>x</i></sub> (Ln = Tm, Dy) with [(dipp-Bian)­Ga]<sub>2</sub> in THF. All new compounds were structurally characterized by single-crystal X-ray diffraction. The ytterbium complex shows the shortest Yb­(II)–Ga bond distances reported so far.