Synthesis, Structure, and Reactivity of Lanthanide Complexes Incorporating Indolyl Ligands in Novel Hapticities

The chemistry of interactions of 2-(2,6-diisopropylphenylaminomethylene)­indole ligand (1) with europium and ytterbium amides is described. Reaction of 2-(2,6-diisopropylphenylaminomethylene)­indole 2-(2,6-i-Pr2C6H3NHCH2)­C8H5NH (1) with europium amide [(Me3Si)2N]3EuIII(μ-Cl)­Li­(THF)3 afforded a novel europium­(II) complex formulated as {[μ-η6:η1:η1-2-(2,6-i-Pr2C6H3NCH)­C8H5N]­Eu­[2-(2,6-i-Pr2C6H3NCH)­C8H5N]}2 (2), having a bridged indolyl ligand in the novel μ-η6:η1:η1 hapticities with the reduction of europium­(III) to europium­(II) and the oxidation of amino to imino group. Reaction of 2-(2,6-diisopropylphenylaminomethylene)­indole 2-(2,6-i-Pr2C6H3NHCH2)­C8H5NH (1) with ytterbium­(III) amide [(Me3Si)2N]3YbIII(μ-Cl)­Li­(THF)3 produced the only deprotonated ytterbium­(III) complex formulated as [2-(2,6-i-Pr2C6H3NCH2)­C8H5N]­Yb­[N­(SiMe3)2]­(THF)2 (3), having an η1 hapticity indolyl ligand. Reaction of 2 with formamidine [(2,6-Me2C6H3)­NCHNH­(C6H3Me2-2,6)] produced {[μ-η3:η1:η1-2-(2,6-i-Pr2C6H3NCH)­C8H5N]­Eu­[(2,6-Me2C6H3)­NCHN­(C6H3Me2-2,6)]­(THF)}2 (4), which has a bridged indolyl ligand in the novel μ-η3:η1:η1 hapticities, whereas the reaction of 2 with the more sterically bulky formamidine [(2,6-i-Pr2C6H3)­NCHNH­(C6H3i-Pr2-2,6)] afforded complex {[μ-η2:η1:η1-2-(2,6-i-Pr2C6H3NCH)­C8H5N]­Eu­[(2,6-i-Pr2C6H3)­NCHN­(C6H3i-Pr2-2,6)]­(THF)}2 (5), having the indolyl ligand in the novel μ-η2:η1:η1 hapticities. The results represent the first example of organometallic complexes having indolyl ligands in the novel μ-η6:η1:η1, μ-η3:η1:η1, and μ-η2:η1:η1 bonding modes with metal.