While methylsodium forms tetramers like methyllithium, methylpotassium is more ionic and has the nickel arsenide structure with discrete methyl anions and potassium cations.
wˌaɪl mˌɛθəlsˈoʊdiəm fˈɔːɹmz tˈɛtɹeɪmɚz lˈaɪk mˌɛθəlˈɪθiəm, mˌɛθəlpətˈæsiəm ɪz mˈoːɹ aɪˈɑːnɪk ænd hɐz ðə nˈɪkəl ˈɑːɹsənˌaɪd stɹˈʌktʃɚ wɪð dɪskɹˈiːt mˈɛθəl ˈænaɪənz ænd pətˈæsiəm kˈæɾaɪənz.