21427
The use of Ni - and Co - catalyzed protocols allowed efficient Heck coupling of activated and unactivated alkenes with 1 ( o ) , 2 ( o ) and 3 ( o ) alkyl halides .
 Chemical: Ni; Chemical: Co; Chemical: alkenes; Chemical: alkyl halides
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: alkenes; Chemical: alkyl halides