Trianionic ligand

The only example of a chiral cuboctahedral assembly 5.58 was reported by Kimura et at The cuboctahedron was self-assembled from trimeric Zn(II)-cyclen building blocks and the tridentate ligand trianionic trithiocyanurate TCA (42) in 4 4 ratio during guest encapsulation and was characterized in the solid state and in solution (Figure 5.18). ... 

Oxidaton of heme goes through the biliverdin species. Octaethylbiliverdin can exist in coordinated form as the fully reduced trianion (OEB)3-, as the two-electron-oxidized monoanion (OEBox), or as the one-electron-oxidized radical (OEB-)2-. Nickel forms complexes with all three moieties, [Nin(OEB)]ra with n I 1, 0, and -1 (689).1787 The most highly oxidized species [Ni(OEBox)]I3 could be crystallized. The structure shows a helical coordination of the linear tetrapyrrole ligand around nickel with Ni—N distances of 1.867 A and 1.879 A. 

Scheme 18 Conversion of Me2Si(C5H5)(C2B1oH11) into mono-, di-, and trianionic ligands. Reproduced by permission of the American Chemical Society from Organometallics 1998, 77, 489.

The possibility of generating a 1 1 complex of aluminium by tethering together three aryloxide moieties has been explored. Synthesis [165] of the tripodal, polydentate ligand N[2-[(CH2)2N(H)CH2]-Ar 3 (Ar = 4-chlor-ophenol) allows subsequent treatment with one equivalent of (H20)9 A1(C104)3 in the presence of excess (H20)3 NaOAc to afford a tris(phen-oxide) complex [166]. More recently, the formation of Al-N(H) interactions has been precluded in the tris(2-hydroxybenzoyl)-2-aminoethylamine and tris(2-hydroxy-3-methoxybenzoyl)-2-aminoethylamine trianion complexes... 

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