6D5X:
reference: Sacrificial Cobalt-Carbon Bond Homolysis in Coenzyme B12 as a Cofactor Conservation Strategy., Campanello GC, Ruetz M, Dodge GJ, Gouda H, Gupta A, Twahir UT, Killian MM, Watkins D, Rosenblatt DS, Brunold TC, Warncke K, Smith JL, Banerjee R, J Am Chem Soc. 2018 Oct 8. doi: 10.1021/jacs.8b08659. PMID: 30282455

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).