A comprehensive account of the coordination chemistry of alkylcycloarsoxanes (RAsO) n and alkylcycloarsathianes (RAsS) n is presented. The former ambi- and multidentate ligands are characterised by their unique ability to undergo metal-mediated ring expansion to n=5,6 or 8. Cyclotetramers, -pentamers and hexamers of their sulphur analogues have also been stabilised as intact species in metal coordination spheres. At elevated temperatures As-S bond cleavage and metal-assisted reassembly afford novel linear and macrocyclic As-S ligands. Cyclotetramers (RAsO) 4 can be employed for the self-assembly of copper(I) halide based porous lamellar and framework coordination polymers capable of hosting alkali cations or polar molecules as guests.