Tobias van Almsick

Review. Solvothermal Synthesis and Structure of Chalcogenidoarsenate Anions

A rich variety of chalcogenidoarsenate anions and ligands have been prepared under mild solvothermal conditions in strongly polarizing solvents such as water, methanol and amines in the temperature range 100 - 200 ◦C. This review covers synthetic and structural aspects of such species ASxEyz− with particular emphasis being placed on the trends and differences observed for E = S, Se, Te and on developments within the past decade. These include the preparation of quaternary Main Group element chalcogenidoarsenates(III) such as Cs3AsGeSe5 and polymeric selenidoarsenates(II, III) such as Cs2As4Se6. A currently expanding area of interest involves the employment of transition metal-polyamine or -polyimine fragments such as {Mn(tren)}2+ or {Mn(terpy)}2+ as structuredirecting agents. The metal atoms of such cations can be connected to the terminal chalcogen atoms of oligomeric or polymeric anions AsxEy z− to prevent their further condensation or can be directly incorporated into anionic or neutral networks when at least two free coordination sites are available in the fragment. This strategy has led to the characterization of novel ligands including cyclo- [As4S8]4−, As2Se62−, As2Se64− and 1∞[As4Se72−]. The syntheses and structures of the new compounds Cs5As5Se9 and Cs[{Mn(trien)}(AsSe4-K2Se)] ・CH3OH are also presented. Whereas the former phase contains infinite selenidoarsenate(II,III) chains 1∞[As5Se95−], the [{Mn(trien)}(AsSe4)]− anion of the latter compound represents the first example of a transition metal-containing ternary selenidoarsenate( V) Graphical Abstract Review. Solvothermal Synthesis and Structure of Chalcogenidoarsenate Anions

Tetra­caesium octa­selenidotetra­arsenate(III)

The title compound, Cs4As4Se8, contains discrete cyclic [As4Se8]4− anions consisting of corner-sharing AsSe3 pyramids. A twist–chair conformation is observed for the eight-membered As4Se4 rings, which exhibit a crystallographic inversion centre. Both of the crystallographically independent Cs+ cations contain eight Se atoms in their coordination spheres.