It was thought that …

Clause objects: Nobody thought that she was a spy.

Some sentences have clauses as their objects. These cannot normally become the subjects of passive sentences.

• Nobody thought that she was a spy. (but not That she was a spy was thought by nobody.)
• We felt that he was the right man for the job. (but not That he was … was felt.)
• The newspapers say that his company is in trouble. (but not That his company is in trouble is said …)

However, passive structures are often possible with preparatory it (see here).

• It was thought that she was a spy.
• It was felt that he was the right man for the job.
• It is said that his company is in trouble.

Infinitive objects: They decided to …

A few verbs that are followed by infinitives (for example decide, agree) can also be used in passive structures beginning with it.

• They decided to meet at twelve. → It was decided to meet at twelve.
• We agreed to open a new branch. → It was agreed to open a new branch.

However, most verbs cannot be used in this way.

• not It is started to make a profit. or It is not expected to rain today.