Different metal phosphinates and phosphonates were obtained containing zinc, calcium and magnesium as cations by means of a salt metathesis reaction with sodium salts of DOPO and DOPO-OH. The synthesized complexes [Zn(DOPO) 2 ] n , [Zn(DOPO-OH) 2 ] n and [Ca(DOPO) 2 (H 2 O)] n are featured a polymeric structure. The open-ring metal phosphinate coordination compound [Zn(DOPO) 2 ] n is able to undergo a non-reversible thermally induced oxidative cyclisation to the corresponding metal phosphonate [Zn(DOPO-OH) 2 ] n. The magnesium and calcium phosphinates cannot be oxidized to their corresponding [a