Heteronuclear Polycationic Clusters from Group 15 and 16 Elements Synthesized in Chlorido Gallate Melts

Abstract

Polycationic clusters are positively charged molecules made of main group elements. They are specially found in the groups 15 and 16 of the periodic table. The chemistry of these clusters began in 1798 when chalcogen elements dissolved in concentrated sulfuric acid led to coloured solutions. It took 170 years until the first structural characterization of a homonuclear cluster, namely Se₄²⁺. With the upcoming availability of single crystal structure determinations the number of publications on both homonuclear and heteronuclear pentele and chalcogen clusters arised. It was no longer necessary to rely on spectroscopy or conductivity measurements only. <br /> The following PhD thesis demonstrates the latest results of the search for heteronuclear polycationic clusters of group 15 and 16 elements. <br /> Reactions of the pentele elements arsenic, antimony and bismuth with the chalcogen elements selenium and tellurium in chlorido gallate melts in the presence of the oxidants arsenic trichloride, antimony trichloride and bismuth trichloride yielded various new polycationic clusters. Experiments were carried out in moisture free and sealed vacuum glass ampoules. The preparative work was performed in an argon filled glove box, exclusively. All investigated compounds are highly moisture sensitive. Certain added salt-like compounds have a huge influence on the reactions. Several mono-charged cations like Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, NH₄⁺, In⁺, Tl⁺, Cu⁺, Ag⁺, Au⁺, Hg₂²⁺, PPh₄⁺, used as the respective chlorides and the pentele oxides, were added as the reaction triggering adjuvants. Depending on the compositions of these melts, monomeric clusters as well as cationic and neutral bridged chains could be obtained. The monomeric clusters form polyhedra like prisms, cubes and double cubes. The polymeric chains show motifs of helices, ladders and connected rings. The new compounds mainly made of main group elements are characterized by their crystal structures, by chemical analyses via energy dispersive electron-beam X-ray fluorescence, Raman spectroscopy, solid-state NMR, mass spectrometry, electron paramagnetic resonance, differential scanning calorimetry and powder diffraction. Additional supporting density functional calculations were carried out for various purposes. Some of the new compounds show crystallographic phenomena like phase transitions and systematic crystal twinning, which are demonstrated and discussed.