Homoatomic clusters E-9(3-) with E = Ge, Sn, and Pb: EPR spectra, magnetism and electrochemistry

The properties of the compounds [K-([2.2.2]-crypt)](3)E-9 (E = Ge (1), Sn ( 2), Pb (3)), which contain isolated E-9 units, have been examined by EPR me asurements at room temperature and at 77 K, magnetic susceptibility measure ments in the range from 2 K to 300 K and cyclovoltammetric experiments. The EPR signals of powder samples and of single crystals are analyzed using th ree g tensor components, indicating low symmetric E-9(3-) clusters. Magneti c susceptibility data of 2 and 3 follow the expression (chi(mol) = C/(T - t heta(p)) + chi(0), with theta(p) approximate to 0 and C corresponding to th e presence of about 50% paramagnetic E-9(3-) species (S = 1/2). In solution , 2 and 3 show irreversible oxidation processes. Current intensities and pe ak forms indicate that adsorption processes play an important role irrespec tive of the material of the working electrode (silver, platinum, glassy car bon).