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Tripodal ligands are tri- and tetradentate ligands with C3 symmetry. They are popular in research in the areas of coordination chemistry and homogeneous catalysis. Because the ligands are polydentate, they do not readily dissociate from the metal centre. ==Coordination chemistry== When used in coordination complexes with an octahedral molecular geometry the tridentate tripod ligands occupy one face, leading to a fixed facial (or ''fac'') geometry. The tetradentate tripodal ligands occupy four contiguous sites, leaving two ''cis'' positions available on the octahedral metal center. When bound to four- and five-coordinate metal centres, these ligands impose C3 symmetry, which can lead to uncommon ligand field splitting patterns. Tripodal ligands are often able to coordinately saturate metal ions with lower coordination numbers. One tripodal ligand of commercial significance is nitrilotriacetate, N(CH2CO2−)3 because it is cheaply produced and has a high affinity for divalent metal ions. Other tripodal ligands include tren (N(CH2CH2NH2)3) and certain triphosphines such as RC(CH2PPh2)3. Many kinds of donor groups have been incorporated into the arms of these ligands, including amido ,〔Verkade, J. G., "Atranes: new examples with unexpected properties", Acc. Chem. Res. 1993, volume 26, 483.〕 and N-heterocyclic carbenes. File:TripodalPhosphine.png|A tripodal triphosphine, X can be CR, SiR, Si−, BR−, B, N, P etc.〔Saouma, C. T., Peters, J. C., "M-E and M=E complexes of iron and cobalt that emphasize three-fold symmetry (E = O, N, NR)", Coord. Chem. Rev. 2011, 255, 920. 〕 File:Tris(pyridylmethyl)amine (structural diagram).png|Tris(2-pyridylmethyl)amine, a tetradentate tripodal ligand popular in bioinorganic chemistry.〔Blackman, A. G., "Tripodal tetraamine ligands containing three pyridine units: the other polypyridyl ligands", Eur. J. Inorg. Chem. 2008, p 2633. 〕 File:LnMTp.png|Structure of a metal complex of trispyrazolylborate, an anionic tridentate tripod ligand because it simulates three imidazole ligands.〔Parkin, G. "The bioinorganic chemistry of zinc: synthetic analogues of zinc enzymes that feature tripodal ligands" Chemical Communications 2000, 1971-1985. 〕 File:Nitrilotriacetic-acid-2D-skeletal.png|NTA is a commercially important tripodal ligand. Its three carboxylic acid groups undergo deprotonation upon complexation. File:KlauiCmpx.png|The Kläui ligand, a dianionic organometallic ligand. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Tripodal ligand」の詳細全文を読む スポンサード リンク
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