In the given sentence, "when he was working in Brussels" is a dependent clause that functions as an adverbial clause. It modifies the verb "met" and provides additional information about the time and circumstance of the event.
The independent clause in the sentence is "He met his wife". This clause contains the main subject "he" and the main verb "met", which is in the past tense. The phrase "his wife" is the direct object of the verb "met", which indicates the person or thing that received the action of the verb.
The dependent clause "when he was working in Brussels" starts with the subordinating conjunction "when", which indicates a time relationship between the dependent clause and the independent clause. The clause provides information about the time and place where the action in the independent clause took place.
Overall, the sentence describes an event in the past - "he met his wife" - and gives additional details about the circumstances of that event - "when he was working in Brussels".