Does divorce occur by saying "for divorce to occur" without intention, and is expiation obligatory after five years if the wife leaves whenever she wishes?

As long as you did not intend to bring about divorce, then no divorce results from this wording, nor are you required to offer expiation for your wife leaving whenever she pleases. This is because the mentioned wording is not an explicit declaration of divorce; rather, it is a promise of it, and divorce does not occur merely by promising it.