21430
The recent development of Ni - and Co - catalyzed addition of alkyl halides to alkenes displays much improved reactivity and functional group tolerance .
 Chemical: Ni; Chemical: Co; 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: Ni; Chemical: Co; Chemical: alkyl halides; Chemical: alkenes