Complex sentence: One can isolate diazonium compounds as the tetrafluoroborate salt, which is stable at room temperature, but typically diazonium compounds are not isolated and once prepared, used immediately in further reactions.
Split into simpler sentences: One can isolate diazonium compounds as tetrafluoroborate salts, which are stable at room temperature. Typically diazonium compounds are not isolated and once prepared, used immediately in further reactions.