Complex chemistry with complex compounds

Abstract

Abstract. In recent years gas-phase chemical studies assisted by physical pre-separation allowed for the investigation of fragile single molecular species by gas-phase chromatography. The latest success with the heaviest group 6 transactinide seaborgium is highlighted. The formation of a very volatile hexacarbonyl compound Sg(CO) 6 was observed similarly to its lighter homologues molybdenum and tungsten. The interactions of these gaseous carbonyl complex compounds with quartz surfaces were investigated by thermochromatography. Second-generation experiments are under way to investigate the intramolecular bond between the central metal atom of the complexes and the ligands addressing the influence of relativistic effects in the heaviest compounds. Our contribution comprises some aspects of the ongoing challenging experiments as well as an outlook towards other interesting compounds related to volatile complex compounds in the gas phase.

The influence of chemical parameters on the in-situ metal carbonyl complex formation studied with the fast on-line reaction apparatus (FORA)

“…significant effect was only visible at O 2 concentrations as high as 1 vol-%. During previous, accelerator-based studies, the yield for the formation of Mo(CO) 6 was determined to be only about 40% [26]. It was assumed, that this might be caused by O 2 -impurities being present in the process gas during those experiments.…”

“…However, since the experiments using FORA were performed using single-atom chemistry conditions, the dilution of atoms is too high to allow for the formation of such polynuclear complexes. It is therefore not clear yet, what carbonyl-species are exactly formed for Tc and Rh [10,11,26,27]. For group 7 elements, the formation of hydrides (e.g.…”

“…Experiments targeted at investigating and comparing the chemistry of group 6 MCCs were suffering so far from low chemical and transport yields, ranging from about 40% for Mo(CO) 6 to 10-20% for W(CO) 6 and 5% for Sg(CO) 6 [26]. This caused serious doubts about investigating heavier TAs in form of MCCs in general.…”

The influence of physical parameters on the in-situ metal carbonyl complex formation studied with the Fast On-line Reaction Apparatus (FORA)

“…For example, Mo(CO) 6 could only be produced with a yield of about 40%. For W(CO) 6 and Sg(CO) 6 , the overall yields were at maximum about 20 and 5%, respectively [27]. These low yields represent a critical problem for the application of MCCs in transactinide research.…”

“…It is expected that Sg, Bh, Hs and Mt form volatile MCCs, based on the behavior or their lighter homologous in the corresponding groups of the periodic table. Mt was not chemically investigated in the past at all [14,27]. The synthesis of a volatile MCC from Sg, Sg(CO) 6 was recently accomplished by an international research group [28].…”