Macrocyclic complexes mononuclear systems

Attachment of a cyclodextrin unit to an N-CH3 form of the CR macrocycle (Fig. 39) yielded a zinc complex with only modestly improved effectiveness (k2 = 21.7x 10 2M 1s 1) over the mononuclear system (k2 — (3.80 + 0.05) x 10 2M 1s 1) for the hydrolysis of diphenyl 4-nitrophenyl phosphate under identical conditions.109 This enhancement is proposed to be due to binding of 4-nitrophenolate moiety in the cyclodextrin cavity. 

Fryzuk MD, Kozak CM, Bowdridge MR et al (2001) Macrocyclic complexes of niobium(III) synthesis, structure, and magnetic behavior of mononuclear and dinuclear species that incorporate the [P2N2] system. Organometallics 20 3752-3761... 

Linkage isomerizations, osmium, 37 335-339 Linked cubane clusters, Fe—S proteins, biological implications, 38 55-56 Linked macrocyclic ring systems, 45 75 dinuclear systems, 45 89-95 triaza ring systems, 45 76-87 Li—N—Li linkages, 37 100-101 Lipoxygenase, inhibitors, 36 41 Liquid-liquid extraction of metal ions, 9 1-80 with acidic P-based extractants, 9 34-48 with acidic P-based extractants dinuclear, 9 47-48 mononuclear, 9 34-47 with amines and amine oxides, 9 49-56 complexes in, 9 68-71 countercurrent extraction method, 9 15-25... 

The above study has been extended to encompass the synthesis of a new system incorporating differentially substituted macrocyclic subunits (92). Starting from the mononuclear Ni(II) complex of 52 (n = 3) described above, it proved possible to obtain a selective Michael addition reaction between acrylonitrile and the secondary amine groups of the vacant macrocyclic ring. Reaction of the product with Ni(II) yielded the nonsymmetrical complex 53. Based on comparative visible spectral studies, one nickel atom in this complex was assigned a four-coordinate geometry the second appears to be five-coordinate. 

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