In particular, the quaternary ammonium cations () are very useful since they are permanently charged, and they are often used as an alternative to the expensive Cs+ to stabilise very large and very easily polarisable anions such as .
ɪn pɚtˈɪkjʊlɚ, ðə kwətˈɜːnɚɹi æmˈoʊniəm kˈæɾaɪənz ɑːɹ vˈɛɹi jˈuːsfəl sˈɪns ðeɪ ɑːɹ pˈɜːmənəntli tʃˈɑːɹdʒd, ænd ðeɪ ɑːɹ ˈɔfən jˈuːzd æz ɐn ɔːltˈɜːnətˌɪv tə ðɪ ɛkspˈɛnsɪv sˌiːˈɛs plˈʌs tə stˈeɪbəlˌaɪz vˈɛɹi lˈɑːɹdʒ ænd vˈɛɹi ˈiːzili pˈoʊlɚɹˌaɪzəbəl ˈænaɪənz sˈʌtʃ ɐz .