Anticipatory It

 It seemed that she would keep his word

In this clause, the subject is called extraposed subject. It = "dummy subject" or "formal subject". It occupies the place typically occupied by a grammatical subject but that-clause contains the content of the subject.

It is obvious she is right                      is indeed a transformation of

That she is right is obvious (rarely used)

In pattern with introductory it, there is always a finite or non-finite clause occurring at the end of the pattern.

Non-finite pattern (ing and to-inf)

Subject (It) + Verb + Complement (Noun Group) + -ing clause

It is no fun doing things alone

It is no use complaining

Subject (It) + Verb + Object (NG) + Object (NG)  + to infinitive clause

It cost me a fortune to rebuild the house

It will do me good to have a rest

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Anticipatory It + Verb Phrase

(usually passive)-that clause

It can be seen.....

It has been shown ....

It should be noted......

Anticipatory It + Adjective Phrase (followed by -that clause/to inf clause)

It is possible to .....

It is possible that ....

It is likely that .....

It is important to ......

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The impersonal "It" has three uses :

1. Introductory "It"

2. Emphatic "It"

3. Anticipatory "It"

Introductory "It" --> we speak about day, date, time, weather, distance, place or situation

It + Verb (be) + Subject Complement (Noun/Noun Phrase/Adjective)

It is Monday.

It is cold here.

It is five miles from here to the mosque.

Emphatic "It" --> to emphasize a particular piece of information

He graduated in 2023. --- It was in 2023 that he graduated   (Cleft sentence)

Anticipatory "It"

It fills the subject position but it is only the notional subject of the sentence anticipating the real subject.

It + Verb (be) + Adjective Complement+ ( for + N/Pronoun) + infinitive phrase

It is difficult for most people to own up their mistakes --- For most people to own up their mistakes is difficult

It seems best to inform the police ---To inform the police seems best

The anticipatory "It" may take a gerund or gerundial phrase instead of an infinitive phrase

It was well worth taking up the contract

It was fun working in a garage during summer holidays

Reference :

Hunston, S., Francis, G., 2000, Pattern Grammar : A Corpus-driven Approach to the Lexical Grammar of English, John Benjamins Publishing Company

Biber, D., Johansson, S., Leech, G.,N., Conrad, S., Finegan, E., 2021, Grammar of Spoken and Written English, John Benjamins Publishing Company

Narayanaswamy, K.R., 2004, A Teacher's Grammar of English, Orient Longman