Reactivity of digermylenes toward potassium graphite: Synthesis and characterization of germylidenide anions

The synthesis and characterization of the digermylenes [LGe-GeL] [L = L ¹ (3A), L ² (3B)] supported by the 2,6-diiminophenyl (L ¹) and 2-imino-5,6-methylenedioxylphenyl (L ²) ligands are described. Their reactivities toward potassium graphite are also reported. The reaction of [LGeCl] [L = L ¹ (2A), L ² (2B)] with KC ₈ in tetrahydrofuran (THF) at room temperature afforded the digermylenes [LGe-GeL] [L = L ¹ (3A), L ² (3B)], which are the first examples of diaryldigermylenes stabilized by o-imino donor(s). The treatment of 3A with 2 equiv of KC ₈ in Et ₂O, followed by the addition of excess tetramethylethylenediamine (TMEDA), results in cleavage of the Ge ^I-Ge ^I bond to afford the germylidenide anion [L ¹GeK·TMEDA] (4A). Similarly, the reaction of 3B with excess KC ₈ in THF afforded the germylidenide anion [L ²GeK] (4B). The molecular structures of compounds 4A and 4B as determined by single-crystal X-ray diffraction analysis show that the K atoms are ¹-coordinated with the low-valent Ge atoms. Moreover, the negative charges at the Ge atoms in compounds 4A and 4B are stabilized by electron delocalization in the germanium heterocycles.