What is the ruling of Islamic law regarding an oath of divorce taken to not accept a specific job, then being compelled to accept it, and is expiation possible for this oath?

The authoritative view we hold is that swearing an oath by divorce triggers a divorce upon breaking the oath, regardless of whether divorce was intended or merely a threat. Accordingly, if you swore an oath by divorce and then broke it by accepting the job, your wife is divorced with one pronouncement. If this is the first or second pronouncement, you may take her back before her waiting period (iddah) expires. However, if it is the third pronouncement, she becomes irrevocably divorced (baynunah kubra).

As for the view of Sheikh al-Islam Ibn Taymiyyah, swearing an oath by divorce that is not intended to effect a divorce, but rather meant as a threat or an emphasis, falls under the ruling of an oath by Allah. Thus, if you break it, you are obligated to perform an expiation for an oath (feeding ten poor people, or clothing them, or fasting three days if you cannot find that), and no divorce occurs.

It must be known that the permissible oath is by Allah Almighty, whereas swearing by divorce is among the oaths of the dissolute.