In chemistry, it refers to the ligands around a metal ion - strictly it applies to those molecules that provide several ligands (bidentate or tridentate). Like crab claws, such species can 'grasp' the metal, partly surrounding it.

The cannonical example is EDTA which can provide four chelating groups (tetradentate) - although EGTA, it's close relative, has a more flexible linker between the 'claws'.

EDTA : (OOC)(OOC)NCCN(COO)(COO)
EGTA : (OOC)(OOC)NCCOCCOCCN(COO)(COO)

       O   O            O   O
       |   |            |   |
    O--C   C--O      O--C   C--O
        \ /    \   /     \ /
         N      \ /       N
         |       M        |
         C      /  \      C
          \    /    \    /
           C--O      O--C
               \    /
                C--C

Che"late (?), a. Zool.

Same as Cheliferous.

 

© Webster 1913.

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