No hay ningún cambio en el infinitivo en voz pasiva si el infinitivo con to es el sujeto de la frase.

Ejemplos     He was supposed to be at home but I found him in the pub.   A new power plant was planned to be built.   She is known to be a real beauty.

El infinitivo con to en frases en voz pasiva puede utilizarse   1) Con verbos que describen sensaciones sensuales (incluso en el caso de que en una frase activa se añadiera el infinitivo sin to, vea Infinitivo )   2) después de verbos como decir y pensar (wie to think, to believe, to suppose, to consider, to know, to say)   3) con los verbos to ask, to advise, to allow, to compel, to encourage, to forbid, to force, to help, to instruct to invite, to permit, to request (vea también 26.4.9)

Ejemplo     She was seen to kiss another man.   They were believed to have a lot of money.   We were asked to bring some blankets to the park.