Fe in bacteria light-harvesting system Reaction Center
After reading the comments in the first answer, I believe OP's question is this:


  What kind of bond occurs in the Fe of the reaction center of bacteria light-harvesting system?


Before continuing, it's worth mentioning that an ionic bond is a kind of bond, and that atom would not be considered free (whatever that means) even if its bonds were only ionic ones.

However, to make things here even more unequivocal, the bonds of that Fe are covalent bonds (thus, that atom is not free under any definition...).

According to the Protein Data Bank in Europe, this is the x-ray high resolution structure of the photosynthetic reaction center from Rhodobacter sphaeroides at pH 10, zoomed at the portion that contains the Fe (link here):



You can see that the Fe has 5 bonds, thus summarised:


  [SQUARE_PYRAMIDAL] - HIS 190L - HIS 219M - HIS 230L - GLU 234M - HIS 266M


And what kind of bond are those? 

According to the same PDBE entry, they are covalent. Have a look at the color code in this page: http://www.ebi.ac.uk/pdbe-site/pdbemotif/?tab=boundmolecule&amp;pdb=2uxj&amp;ligandCode3letter=FE

Here is a screenshot, in case the link above doesn't work. Have a look at the 5 red bonds (red represents covalent... not very legible, I know):



Source: Protein Data Bank in Europe