Tridentate ligand

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The iminodiacetic anion is a tridentate ligand forming a complex with a metal labelled "M" Mida.svg
The iminodiacetic anion is a tridentate ligand forming a complex with a metal labelled "M"

A tridentate ligand (or terdentate ligand) is a ligand that has three atoms that can function as donor atoms in a coordination complex. [1]

Contents

Well-known tridentate ligands include diethylenetriamine with three nitrogen donor atoms, and the iminodiacetate anion which consists of one deprotonated amine nitrogen and a pair of carboxylate groups. [1]

An octahedrally coordinated atom has six positions around it. Two tridentate ligands may form a complex with such an atom. There are two possible arrangements for such a complex: fac where the coordination is in a triangle on one face of the octahedron, and mer where the coordinating atoms are in an arc around the central atom, with two atoms of the ligand opposite each other. Fac tridentate ligands are termed scorpionate ligands, especially in reference to polypyrazolylborates. [2]

If the tridentate ligand is not symmetrical, then in the fac complexes in octahedral coordination there are three possible isomers. In the mer complexes there are two enantiomers, mirror images of each other.

List

NameAbbreviationChemical FormulaCAS NumberShapeTypeFormal ChargeCentral atomsStructure
1,4,7-trioxonane 9-Crown-3 (C2H4O)327725-91-3ringOOO0Li 9-Crown-3.svg
methyl Tm ligand TmMetripodS31−Li Na K
Trispyrazolylborate TptripodN31−K Ru U Tris(pyrazol)borat.svg
Tris(4,4-dimethyl-2-oxazolinyl)phenyl borateToMtripodN31− ToM ligand.jpg
Tris(4S-isopropyl-2-oxazolinyl)phenylborateToPtripodN31− ToP ligand.jpg
N,N,N′,N′′,N′′-pentamethyldiethylenetriamine PMDTA [(CH3)2NCH2CH2]2NCH33030-47-5linearNNN0 or +1Li AlH2 PMDTA.png
Bis(diphenylphosphinoethyl)phenylphosphine Triphos23582-02-7linearPPP0transition metals LinearTriphos.png
1,4,7-Trithiacyclononane 9-ane-S3(CH2CH2S)36573-11-1ringSSS0Fe Cu 1,4,7-Trithiacyclononane.svg
1,4,7-Trimethyl-1,4,7-triazacyclononane Me3TACN(CH2CH2N(CH3))396556-05-7RingNNN0Re Mn Ru Cu Fe Me3TACN.png
1,4,7-Triazacyclononane TACN(CH2CH2NH)34730-54-5RingNNN0Mo 1,4,7-triazacyclononane.svg
cis,cis-1,3,5-Triaminocyclohexane tach(CH2CHNH2)326150-46-9tripodN30Ni Mn Cis,cis-1,3,5-triaminocyclohexane.png

See also

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References

  1. 1 2 Cotton, F. Albert; Wilkinson, Geoffrey (1966). Advanced Inorganic Chemistry. John Wiley. pp. 140–141.
  2. Trofimenko, Swiatoslaw (1999). Scorpionates: the coordination chemistry of polypyrazolborate ligands (Reprinted. ed.). River Edge, NJ: Imperial College Press. pp. 3–5. ISBN   1860941729.