[susan53]

I'm not exactly sure what you mean here, but I imagine to + infinitive, eg I told you not to do it!.

In this context (ie with tell) it would be much more usual to place the negation before to+ infinitive -I searched for both in a Concordancer and came up with only one example of tell + to + not ...
a memo a few days ago to Republican candidates telling them to not hesitate to run against the
versus the full 40 (the maximum the programme will provide) for tell + to + not

However, in other contexts lots of examples came up, including the first one below which has three examples strung together :
... fun to not make stupid faces into the camera to not move around to not cross our arms and most ...
... she claims to not like the song ...
if a juror wanted to not believe Mr. King,...
You'd have to be cynical to the marrow to not feel it as so much more.

To me, all of these sound awkward - in each case I'd generally move the negation before to - but it is frequently used.

So - there isn't really a rule. With some verbs, like tell there is a definite tendency for one particular order. But in other contexts it's much more arbitrary. The old rule of "never split an infinitive" is prescriptive rather than descriptive - it doesn't describe the way native speakers actually use the language. However, stylistically, the sentence sometimes seems (to me anyway, but this may be personal) to flow better if the rule is followed.

Hope that helps. If you didn't mean to + infinitive but to as a preposition, then give examples of the sentences you were thinking of and we'll deal with those too