1.3.9- triazacyclononane

Mononuclear complexes of palladium and platinum in the +3 oxidation state have only recently been unequivocally characterized [157]. The major advance has come in complexes with macrocyclic ligands such as 1,4,7-trithiacyclononane (ttcn) and 1,4,7-triazacyclononane (tacn) (Figure 3.96). 

NiL2]2+-type sandwich complexes of tacn ligands bearing one or three pendent alkyne arms (L = /V,/V, /V"-tris(3-prop-1 -yne)-1,4,7-triazacyclononane or 7V-(4-but-2-yne)-1,4,7-triazacyclo-... 

Upon recrystallization, [Ni(tpzlmtacn)]2+ affords [Ni(L)(MeCN)]2+ (L = l,4-bis(pyrazol-l-ylmethyl)-l,4,7-triazacyclononane) via a N-dealkylation reaction and loss of a pendent arm.1420 More rational routes to Ni complexes of tacn ligands with only one or two pendent arms have been developed.1431,1432 In [Ni(L)(X) ]x (e.g., L= l-(3-aminopropyl)-l,4,7-triazacyclononane (n = 2) or l-(l-methylimidazol-2-ylmethyl)-l,4,7-triazacyclononane (n = 2) or l,4-bis(l-methyl-imidazol-2-ylmethyl)-l,4,7-triazacyclononane (n = 1), the coordination sphere is completed by additional ligands that bind either terminal (X = C1 , H20) or bridge two metal ions (X = N3 , OH, oxalate). The Ni11 complex of l,4-bis(2-pyridylmethyl)-l,4,7-triazacyclononane has been shown to be extremely inert to ligand dissociation in aqueous solution.1433 In (562), the tacn ligand provides a single bidentate arm.1434... 

With a tetramacrocyclic ligand derived from four 1,4,7-triazacyclononane units that are attached to a central benzene ring, each two of the TACN subunits may sandwich one metal ion. Dinuclear, trinuclear, and tetranuclear Ni11 complexes (713)-(715) have been shown to form, depending on the stoichiometry and reaction conditions.1866... 

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