An alternating copper(II) chain with bridging oxamidato and nitrito ligands: crystal structure and magnetic properties of [Cu(NO2)(2)CuL](n) (L = N,N'-bis(2-methyl-2-aminopropyl) oxamide)

The reaction of the monomeric cis-oxamido copper complex CuL (L standing fo r N,N'-bis(2-methyl-2-aminopropyl) oxamide) with copper and nitrite ions yi elds a chain compound [Cu(NO2)(2)CuL](n) resulting from the trans isomeriza tion of the oxamide ligand. Within each chain, the Cu(II) ions are alternat ely bridged by one dideprotonated ligand (L)(2-) and two (NO2)(-) ions. In addition, there may be an interaction between each copper ion and a second nitrite oxygen. So, each NO, group acts simultaneously as a mu-1,1 bridging ligand and as a chelating ligand via two oxygen atoms. The structural data support a distorted 4 + 2 coordination mode for the copper ions. Analysis of the thermal variation of the magnetic susceptibility shows that the exch ange interaction supported by the oxamidato bridge is antiferromagnetic and two orders of magnitude larger than the interaction occurring via the NO2 groups, the sign of which is also antiferromagnetic. (C) 1999 Elsevier Scie nce S.A. All rights reserved.