| 556 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
| * | DD | ORGANIC COMPOUNDS (Class 532, Subclass 1) {3} |
| 1 | DF | .~ HEAVY METAL CONTAINING (e.g., Ga, In or T1, etc.) {19} |
| 51 | DF | .~.~ Titanium, zirconium, or hafnium containing (Ti, Zr, or Hf) {2} |
| 52 | | .~.~.~ Carbon bonded directly to the metal {1} |
| 53 | DF | .~.~.~.~> Plural unsaturated 5-membered carbocyclic rings bonded directly to the metal |