I have not taken an oath to divorce my wife if she does a particular thing, but when my mother complained to me about something that my wife had done, I told her that she would never do it again. When she asked me about the guarantee I said to her, "I have taken an oath to divorce her if she does that again." But I did not say so to my wife. I said it to my mother just to pacify her anger.

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

What you did is just a lie, as you said, which is ineffective in the marital bond because it is a statement rather than will.  Unless the statement is meant to express will, it does not introduce a new ruling.

Based on this, as long as you have not suspended the divorce of your wife by any conditional phrase, but you have just intended to please your mother with something which has not taken place, then, what you have done is not a suspended divorce  under Sharee‘ah (Islamic law); rather, it is a lie. Therefore, you should not do such a thing again or think that it is alright to do this,  so long as there is another way to deal with the matter. Certainly, to please your mother and solve the problems with no need to tell a lie is preferable. Telling a lie should be the last resort in such situations.

Allaah Knows best.