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In this mini - review , we also attempt to overview the mechanisms that are proposed in the reactions , aiming at providing insight into the nickel and cobalt - catalyzed coupling of alkyl halides with alkenes .
 Chemical: nickel; Chemical: cobalt; Chemical: alkyl halides; Chemical: alkenes
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: nickel; Chemical: cobalt; Chemical: alkyl halides; Chemical: alkenes