Does one owe expiation for telling someone: "I swear by Allah that you take such and such a thing," when one did not swear, and the person did not take the thing?

Intention is the basis of people's deeds and words, for the Prophet, peace and blessings be upon him, said: "Indeed, actions are by intentions." So, your statement "I swore by Allah that you would take such and such a thing" – if you intended it as the creation of an oath, then it is an oath, and expiation is binding upon you if your companion does not take that thing. However, if you intended it as informing that you had sworn falsely in the past, then it is not an oath, and no expiation is binding upon you, but you must repent from lying.