1) Chelating agent 2) Rough 
A ligand that has two 'teeth' or atoms that coordinate directly to the central atom in a complex. For example, 1,10-phenanthroline is a bidentate ligand of iron. 
Having two teeth
• (a.) Having two teeth or two toothlike processes; two-toothed.
Having two anchorage points
With two teeth.
Bi·den'tate adjective (Bot. & Zoology) Having two teeth or two toothlike processes; two- toothed. 
Having two teeth
[adj] - having toothlike projections that are themselves toothed
adjective having toothlike projections that are themselves toothed
having two teeth or toothlike parts or processes.