Synthesis and Characterization of New Polyaza Macrocyclic Nickel(Ⅱ) and Copper(Ⅱ) Complexes Two Nitrile or Imidate Ester Pendant Arms: Metal-Mediated Hydrolysis and Alcoholysis of the Nitrile Groups

Abstract

New di-N-cyanomethylated tetraaza macrocycle 2.13-bis(cyanomethyl)-5.16-dimethyl-2,6,13,17-tetraazatricyclo[<TEX>$16.4.0.0^7.12$<TEX>]docosane <TEX>$(L^2)$</TEX> has been prepared by the reaction of 3, 14-dimethyl-2,6,13,17-tetraazatricyclo <TEX>$(L^1)$</TEX> with bromoacetonitrile. The square-planar complexes <TEX>$[ML^2](ClO_4)_2(M=Ni(II)$</TEX> or Cu(II) can be prepared by the reaction of <TEX>$L^2$</TEX> with the corresponding metal ion in acetonitrile. The cyanomethyl groups of <TEX>$[ML^2](ClO_4)_2readily$</TEX> react with water to <TEX>$yield[ML^3](ClO_4)_2$</TEX> containing pendant amide groups. The trans-octahedral complexes <TEX>$[ML^4](ClO_4)_2$</TEX>, in which two imidate ester groups are coordinated to the metal ion, can be also prepared by the reaction of <TEX>$[ML^2](ClO_4)_2with$</TEX> methanol under mild conditions. The hydrolysis and alcoholysis reactions of <TEX>$[ML^2](ClO_4)_2are$</TEX> promoted by the central metal ion, in spite of the fact that the cyanomethyl group is not involved in intramolecular coordination. The reactions are also promoted by a base such as triethylamine but are retarded by an <TEX>$acid(HClO_4).Interestingly$</TEX>, the imidate ester groups of <TEX>$[ML^4]^2$</TEX> are unusually resistant to hydrolysis even in 0.1 M <TEX>$HCIO_4$</TEX> or 0.1 M NaOH aqueous solution. Crystal structure of <TEX>$[NiL^4](ClO_4)_2shows$</TEX> that the Ni-N (pendant imidate ester group) bond is rlatively strong; the Ni-N bond distance is shorter then the Ni-N(tertiary) distance and is similar to the Ni-N (secondary) distance.