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(2)O, followed by the addition of excess tetramethylethylenediamine (TMEDA), results in cleavage of the Ge(I)-Ge(I) bond to afford the germylidenide anion L(1)GeK·TMEDA] (4A). Similarly, the reaction of 3B with excess KC(8) in THF afforded the germylidenide anion L(2)GeK] (4B). The molecular structures of compounds 4A and 4B as determined by single-crystal X-ray diffraction analysis show that the K atoms are η(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.