An alternating copper(II) chain with bridging oxamidato and nitrito ligands: crystal structure and magnetic properties of [Cu(NO 2) 2CuL] n (L= N, N′-bis(2-methyl-2-aminopropyl) oxamide)

Abstract

The reaction of the monomeric cis-oxamido copper complex CuL (L standing for N, N′-bis(2-methyl-2-aminopropyl) oxamide) with copper and nitrite ions yields a chain compound [Cu(NO 2) 2CuL] n resulting from the trans isomerization of the oxamide ligand. Within each chain, the Cu(II) ions are alternately bridged by one dideprotonated ligand (L) 2− and two (NO 2) − ions. In addition, there may be an interaction between each copper ion and a second nitrite oxygen. So, each NO 2 group acts simultaneously as a μ-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 exchange interaction supported by the oxamidato bridge is antiferromagnetic and two orders of magnitude larger than the interaction occurring via the NO 2 groups, the sign of which is also antiferromagnetic.