TACN ligand

For nearly two decades TACN-type ligands are of continuing interest for oxidation chemistry. A more recent example is described by ShuFpin and cow-orkers, who prepared novel di- and tetranuclear complexes with TACN ligands 25 bearing pendant acetato arms bridging the iron(lll) centers (Scheme 18) [111]. The... 

The sandwich complex [Ni(tacn)2]2+ (555) is known as a kinetically inert, thermodynamically stable system. Functionalized tacn ligands with innocent alkyl substituents like, for... 

A number of bis(tacn) ligands, composed of pairs of covalently linked tacn macrocycles, can form similar structures, provided the linker group between the sandwiching macrocycles is sufficiently flexible (e.g., (556)).1411-1413 In particular, several Ni11 complexes of poly(tacn) derivatives with a central benzene have been studied, where the Ni is sandwiched between pairs of tacn macrocycles when these are attached to the ortho positions of the aromatic spacer group (e.g., (557)).1412,1413... 

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-... 

Table 6 Electronic spectral data for selected Ni11 complexes of donor-substituted tacn ligands.

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... 

Nickel(II) complexes of various heteroanalogues of the tridentate tacn ligand ([9]aneN3) have been reported, where one, two, or all three N-donor atoms of the macrocycle are replaced by S, O, or combinations thereof. Such moieties have also been incorporated in bicyclic ligand systems that form complexes with Ni11.1440... 

Pyrazolato-bridged bis(tacn) ligands and their dinickel complexes are mentioned in Sections 6.3.4.12.6 and 6.3.4.12.7. 

From this perspective they reported the structure (complex (791) Cu-Cu 10.061 A) of a m-xylyl-based TACN ligand.583 Structures of four mononuclear copper(I) complexes ((792)-(795)), supported by tridentate macrocycle, were also reported by this group. They investigated their oxygenation behavior and in each case clean formation of side-on peroxo-dicopper(II) species was demonstrated.416... 

Figure 6.12. Fluourinated TACN ligand used in epoxidation reactions.[48]...

Figure 4. The structure of [Mn O (TACN) j] only the nitrogen atoms of the TACN ligands are shown. (Reproduced with permission from ret 20. Copyright 1983 VCH VerlagsgesellschafL)...

The azamacrocycle 1,4,7-triazacyclononane (tacn) and its tris(A -methyl) analog (Me3tacn) are popular ligands in macrocyclic chemistry. Complexes of both and M (M = Ru, Os) containing the tacn ligand are dealt with together in this section along with several dinuclear, M—M bonded species. 

Figure 5.39. Molecular structures of other molecular magnetic materials. Illustrated are (a) tris(oxalato) metalates [M M (ox)3], where M I=Mn, Fe, Ni, Co, Cu, Zn M =Cr, Fe, Ru, and (b) the simplified crystal structure of Prussian Blue, with an example of the analogue structure [(tacn)8Co8(CN)i2], where the tacn ligand is 1,4,7-triazacyclononane. Reproduced with permission from (a) Min, K. S. Rhine-gold, A. L. Miller, J. S. Inorg. Chem., 2005, 44, 8433, and (b) Belttan, L. M. C. Long, J. R. Acc. Chem. Res., 2005, 38, 325. Copyright 2005 American Chemical Society.

Fish reported that a Zn(ll)-imprinted resin, containing a sandwich arrangement of the well known 1,4,7-triazacyclononane (TACN) ligand, was found to be highly selective toward reintroduced Cu(II) in the presence of Fe(lll), Co(II), Ni(II), Zn(II) and Mn(II), after the removal of the Zn(II) template with 6 N HCl [36]. The following parameters were addressed structures of the monomers of the A-(4-vinyl-benzyl)TACN-Zn(II) complexes, polymerisation parameters, structure of the polymer TACN-template metal ion complex and selectivity to reintroduced metal... 

Figure 4. Covalent attachment of tacn ligands to silica.

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