2 syllables:
basins, caissons, chasen's, chastens, hastens, jason's, jasons, kastens, leysen's, mason's, masons

3 syllables:
freemasons, unfastens, washbasins

4 syllables:
diapasons

5 syllables:
cytochalasins

2 syllables:
asians, avens, haitians, havens, nation's, nations, nations', stations

3 syllables:
creations, croatians, donations, foundations, frustrations, locations, notations, occasions, plantations, relations, temptations, vacations, vibrations

4 syllables:
accusations, allegations, appalachians, applications, aspirations, booster stations, calculations, celebrations, combinations, complications, concentrations, confrontations, congregations, consultations, conversations, corporations, declarations, decorations, delegations, demonstrations, deportations, destinations, expectations, explanations, fluctuations, generations, implications, indications, innovations, installations, invitations, law of nations, limitations, medications, motivations, nominations, obligations, observations, occupations, operations, populations, preparations, presentations, publications, regulations, relay stations, reparations, reputations, reservations, revelations, sarajevans, situations, vaccinations, variations, violations

5 syllables:
accommodations, administration's, administrations, appropriations, assassinations, association's, associations, civilizations, communications, congratulations, considerations, deliberations, determinations, evacuations, evaluations, examinations, genus impatiens, immunizations, interpretations, investigations, modifications, negotiations, organization's, organizations, public relations, qualifications, ramifications, recommendations, representations, united nations

6 syllables:
base of operations, comity of nations, commonwealth of nations, trading operations

7 syllables:
chemical operations, statute of limitations, telecommunications, treasury obligations

8 syllables:
calculus of variations, riot control operations

9 syllables:
alternation of generations, diplomatic negotiations

18 syllables:
food and agriculture organization of the united nations