Synthesis of a Di-N-cyanoethylated Tetraaza Macrocycle Containing Eight C-Methyl Groups and Its Nickel(II) Complex: Effects of the Methyl Groups on Their Properties

Abstract

A new di-N-cyanoethylated 14-membered tetraaza macrocycle 1,8-bis(2-cyanoethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane <TEX>$(L^2)$</TEX> and its nickel(II) complex <TEX>$[NiL^2(OAc)]^+$</TEX> have been prepared. The square-planar complex <TEX>$[NiL^2](C IO_4)_2$</TEX> can be prepared by addition of <TEX>$HClO_4$</TEX> to a hot aqueous solution of <TEX>$[NiL^2(OAc)]^+$</TEX> The Ni-N (tertiary amino group) bond distances <TEX>$(2.008{\AA})$</TEX> of <TEX>$[NiL^2](C IO_4)_2$</TEX> are relatively long, and the complex exhibits a d-d transition band at unusually long wavelength (ca. 515 nm). The complex <TEX>$[NiL^2](C IO_4)_2$</TEX> rapidly reacts with acetate ion or ethylenediamine (en) to produce <TEX>$[NiL^2(OAc)]^+$</TEX> or <TEX>[Ni(en)_3]^{2+}$</TEX>, respectively, and is readily decomposed in NaOH (0.01 M) solution. The chemical properties of <TEX>$[NiL^2]^{2+}$</TEX> as well as its synthetic procedure are quite different from those for other related 14-membered tetraaza macrocyclic complexes. Effects of the N-cyanoethyl and C-methyl groups on the properties of <TEX>$L^2$</TEX>.