Triazacyclononanes metal complexes

Diebold, A., Elbouadili, A., and Hagen, K.S. Crystal structures and solution behaviour of paramagnetic divalent transition metal complexes (Fe, Co) of the sterically encumbered tridentate macrocycles l,4,7-R3-l,4,7-triazacyclononane coordination numbers 5 (R = i-Pr) and 6 (R = /-Bu), Inorg. Chem. 39 (2000), 3915-3923. 

Giesbrecht, G.R., Cui, C.M., Shafir, A. etal. (2002) Divalent lanthanide metal complexes of atriazacyclonoane-functionalized tetramethylcyclopentadienyl ligand X-ray crystal structures of [C5Me4SiMe2( Pr2-tacn)]Lnl (Ln=Sm, Yb tacn=l,4-diisopropyl-l,4,7-triazacyclononane). Organometallics, 21, 3841. 

Immobilization of triazacyclononane-type metal complexes on inorganic supports via covalent linking spectroscopy and catalytic activity in olefin oxidation... 

Fig. 7. Schematic diagram to show the columnar stacking present in mesomorphic metal complexes of tri-suhstituted triazacyclononanes...

Whereas for anion binding, the charge and shape of the macrocycle are of paramount importance the stability and selectivity in metal complexation are governed by several other factors, which have been summarized into the term macrocyclic effect <88Mi 928-01 >. The higher stability of metal complexes with cyclic polyamines compared to that with open-chain polyamines is, however, only found for smaller rings such as 1,4,7-triazacyclononane and 1,4,8,11-tetraazacyclotetradecane, for which a favorable enthalpic contribution to the stability has been observed. 

Rational syntheses of multinuclear high-spin metal complexes with pyridine or 1,4,7-triazacyclononane-derived ligands 07BCJ608. 

An interesting class of capping reagents based on 3d metal complexes of 1,4,7-triazacyclononane has recently been discovered [111-113], It is well known that manganese(III), iron(III) or chromium(III) form octahedral complexes with 1,4,7-triazacyclononane or its derivatives with 1 1 stoichiometry [114]. The macrocyclic amine in these complexes has been shown to be coordinated facially to the central metal ion, the remaining three coordination sites being occupied by monodentate ligands. The latter, in contrast to the tridentate macrocyclic amine, can easily be... 

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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