9069
The Fe - O ( 2 ) pfp site is experimentally determined to have both significant sigma - donation and a strong pi - interaction of the O ( 2 ) with the iron , with the latter having implications with respect to the spin polarization of the ground state .
 Chemical: Fe; Chemical: O ( 2 ); Chemical: pfp; Chemical: O ( 2 ); Chemical: iron
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: Fe; Chemical: O ( 2 ); Chemical: pfp; Chemical: O ( 2 ); Chemical: iron