Exercise 8.5 One possible reason why there are no ECM adjectives in English is that adjectives do not license case. If ECM is an extension of the accusative case licensing property of transitive verbs, then ECM adjectives would not be expected. It would still be a puzzle, however, why the case marker of cannot appear in an ECM context. Perhaps this is because of is a form of genitive case and the genitive is for some reason incompatible with ECM. Note that adjectives can take for-to infinitive complements in which the for licenses case in the expected way:
Mary is eager for us to arrive on time.