The structures of dimethylzinc adducts with the macrocyclic amines 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, 1, and 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane, 2, have been determined by X-ray diffraction analysis. The adducts each contain two dimethylzinc moieties. In 1 the dimethylzinc moiety forms a six-membered chelate ring with adjacent nitrogen atoms, in preference to the more sterically strained 5-membered ring. In 2 dimethylzinc exists in a 5-membered chelate ring configuration. Compounds 1 and 2 can be used as intermediate adducts in the adduct purification of dimethylzinc for use in the MOCVD of II-VI and III-V materials.The structures of dimethylzinc adducts with the macrocyclic amines 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, 1, and 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane, 2, have been determined by X-ray diffraction analysis. The adducts each contain two dimethylzinc moieties. In 1 the dimethylzinc moiety forms a six-membered chelate ring with adjacent nitrogen atoms, in preference to the more sterically strained 5-membered ring. In 2 dimethylzinc exists in a 5-membered chelate ring configuration. Compounds 1 and 2 can be used as intermediate adducts in the adduct purification of dimethylzinc for use in the MOCVD of II-VI and III-V materials.