23926
A structurally unique class of hydrocarbon - soluble , ancillary - ligand - free , tetrametallic Co ( I ) and Ni ( I ) clusters is reported .
 hydrocarbon, Co ( I ), Ni ( I )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 hydrocarbon, Co ( I ), Ni ( I )