Self-defeating-in-context sentences are not usually called fallacies, but they do have a name, contextually determined contradictions, or Moor sentences. They are closely related to the knowability paradox anticipated by Church, see Is it provable that epistemically possible (possible for all I know) does not imply possible?. A Moorean sentence if true renders any assertion of it false. Some examples are "I am not here now", "I am asleep" (disregarding talking sleepwalkers), "I am dead" (disregarding talking ghosts, vampires, zombies, and other such beings). The radical skeptical claim "nothing is true" is often interpreted as self-refuting, although what actual skeptics assert is more like a counterfactual "if there was such a thing as truth nothing would be true". Here is a more complicated example that plays a role in disputes between realists and anti-realists: "P is provable but hasn't been proved". To know that P is provable one needs a proof, but any proof of provability of P is convertible into a proof of P, so P has been proved.
Negations of Moorean sentences, contextually determined tautologies, are interesting beasts in their own right. Albeit controversially, they are examples of contingent tautologies, logically true but not necessary. "I am here now" is a tautology, but it could be otherwise, I could be surfing in Hawaii instead. "I am awake", "I am alive" display the same thing. Classically, logical tautologies were considered necessary, but some recent logicians admit contingent ones, see How can a tautology not be necessarily true?