Complexes of cyclopropane-1,1-dicarboxylic acid with cobalt, nickel and copper have been prepared in aqueous solution from cobalt carbonate and the hydroxides of copper and nickel. Only the copper compound is not hydrated. The complexes show the loss of water (except for copper) which is followed by the decomposition of the cyclopropane-1,1-dicarboxylate to give the metal oxides. The Co2+ and the Ni2+ ions are expected to have octahedral environment and the Cu2+ ion to have a square planar environment, which corresponds to the data obtained by single crystal X-ray investigations of copper cyclopropane-1,1-dicarboxylate.