Moving a constituent to the beginning of the sentence to give it prominence is called fronting (or preposing). Fronting is one aspect of information structure (or information packaging).
The Oxford Dictionary of English Grammar (p166) has the following explanation of fronting:
The placing of a constituent at the beginning of a sentence, clause,
etc., often to achieve a certain effect.
English sentences typically begin with a subject, but other functional
elements—object, predicative complement, adverbial, and even part of
the predicate—can be placed at the beginning, typically for
information structuring reasons, for instance in order to mark the
The specific construction you are asking about:
Those who stole money from the company — we will fire them
as opposed to:
Those who stole money from the company we will fire.
includes them as a kind of resumptive pronoun.
There may be a specific term of which I am unaware for this kind of fronting/information structure.