What is the ruling on a man saying to his wife, "It is haram upon me concerning you that I did not do such-and-such," when he did do it, and does divorce occur thereby? And what is the difference between "upon me be divorce" and "upon me be divorce concerning you"?

Your statement, "Upon me be haram from you that you did not do such-and-such," is like saying, "Upon me be haram," or "You are haram upon me." You are bound by what you intended. If you intended ẓihār, then it is ẓihār. If you intended an oath (yamīn), then it is an oath. And if you intended divorce (ṭalāq), then you are bound by what you intended. The correct view is that in this matter, the intention is what counts. If you intended divorce, then a divorce occurs according to your intention (one, two, or three divorces). If you intended ẓihār, then it is ẓihār. If you did not intend anything, then the most appropriate and preferable course of action is to offer expiation for an oath (kaffārat yamīn). Shaykh al-Islam Ibn Taymiyyah held the view that it is obligatory to combine the expiations for ẓihār and for an oath. As for other explicit divorce pronouncements, such as "Upon me be divorce," divorce occurs by them according to the majority of scholars upon the occurrence of the breach, and no intention is needed.