Are they asking you to sign a release or any other document as you depart? If so, you could insist on a non-disparagement clause. If they want to wait until a

Are they asking you to sign a release or any other document as you depart? If so, you could insist on a non-disparagement clause. If they want to wait until after you leave to tell everyone, that's their business, but if they mislead people as to the circumstances of your departure, that potentially injures you.