Studies on Mixed Chelates. XX. Mono- and Binuclear Nickel(II) and Copper(II) Complexes with N,N,N′,N″,N″′,N″′-Hexamethyltriethylenetetramine and β-Diketonates

Nine mixed chelates of Ni(II) and Cu(II) with N,N,N′,N″,N″′,N″′-hexamethyltriethylenetetramine (hmtt) and β-diketonate (dike) ligands were prepared and characterized. Except for [Ni(dipm)(hmtt)]ClO4 (dipm = dipivaloylmethanate), all of them were found to be binuclear chelates: (i) [M2(dike)4(hmtt)] (M = Ni, dike = dipm,acac(acetylacetonate), tfac, or hfac(tri- or hexafluoroacetylacetonate); M = Cu, dike = hfac), (ii) [Ni2(NO3)2(dike)2(hmtt)] (dike = dipm, acac), and (iii) [Cu2(acac)2(hmtt)](ClO4)2. Although they are similar to their mononuclear analogues containing N,N,N′,N′-tetramethylethylenediamine (tmen), a number of characteristic differences exist. Though the Ni(II) chelates are only slightly solvatochromic, the Cu(II) chelates are strongly so.