The Role of Sequestering Agents in the Formation and Structure of Germanium Anion Cluster Polymers

Large blue-green, transparent crystalline needles of [K-(2,2)diaza-[18]-crown-6]KGe9·3en are prepared, in high
yield, from the reaction of (2,2)diaza[18]-crown-6 in toluene with a solution of “KGe4” in ethylenediamine (en). The
compound crystallizes in the orthorhombic space group Pnma (a = 10.9763(12) Å, b = 27.265(3) Å, c = 13.880(1) Å; Z = 4). The crystal structure of [K-(2,2)diaza-[18]-crown-6]KGe9·2en features one-dimensional [KGe9]- bare
intermetallic chains formed from the linking, via exo-bonds, of nido-Ge92- clusters. Uncomplexed K atoms effectively
cap the square bases of the monocapped square antiprismatic [Ge9]2- clusters. The optical band gap of the title
compound is 1.25 eV. The use of weaker sequestering agents in the isolation of Ge cluster anions from en solutions
provides an additional handle in a controlled molecular route to preparing new low-dimensional Zintl phases.