The controlled oxidative coupling of Ge-9(4-) zintl anions to a linear trimer [Ge-9 = Ge-9=Ge-9](6-)

The compound [K(18-crown-6)](6)[Ge-9=Ge-9=Ge-9](.)3en(.)tol (1) featuring a [Ge-9=Ge-9=Ge-9](6-) cluster anion was synthesized from K4Ge9. The neighboured nine-atom clusters are connected by two covalent Ge-Ge exo-cluster bonds with the Ge-Ge distances ranging from 2.581 to 2.640 angstrom. The X-ray single crystal structure analysis shows that, in respect to bond connection and packing style, compound 1 is quite different from the previously reported compound [Rb(2.2.2-crypt)](6)[Ge-9=Ge-9=Ge-9](.)3en (2).