text: Examples of these species with C2 symmetry can increase enantioselectivity, as in their Josiphos variety.
full_question: Examples of these species with C2 symmetry can increase enantioselectivity, as in their Josiphos variety. Two of these species combine in migratory insertion, an important step in carbonylation reactions. These species are classified as either L, X, or Z based on how many electrons they donate. Carbon monoxide functions as this type of group in a metal carbonyl. "Agents" that can cure heavy metal poisoning in chelation therapy are polydentate examples of these species, such as EDTA. For 10 points, name these species that bind to a central metal atom in coordination complexes.
first_sentence: Examples of these species with C2 symmetry can increase enantioselectivity, as in their Josiphos variety.