Those containing polydentate ligands are called chelates and examples include vitamin B12, chlorophyll, and hemoglobin.  
The number for these compounds was proposed by Alfred Werner, with the value of 6 corresponding to an octahedral structure.  Those containing polydentate ligands are called chelates and examples include vitamin B12, chlorophyll, and hemoglobin.  For ten points, a central metal atom is surrounded by non-metal groups in what class of compounds?
The number for these compounds was proposed by Alfred Werner, with the value of 6 corresponding to an octahedral structure.  
coordination compounds or complexes