Cr(III)-Tetraaza Macrocyclic Complexes Containing Auxiliary Ligands (Part IV); Synthesis and Characterization of Cr(III)-Acetylacetonato, -Malonato and -Oxalato Macrocyclic Complexes

Abstract

The reaction of cis-[Cr([14]-decane)(OH) 2 ] + ([14]-decane = rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-teraazacyclotetradecane) with auxiliary ligands {L a = acetylacetonate (acac), oxalate (ox) or malonate (mal)} leads to anew cis-[Cr([14]-decane)(acac)](ClO 4 ) 2 .(½)H 2 O (1), cis-[Cr([14]-decane)(ox)]ClO 4 .(½)H 2 O (2) or cis-[Cr[14]-decane)(mal)]ClO 4 .(1/4)H 2 O (3). These complexes have been characterized by a combination of elemental analysis, conductivity, IR and Vis spectroscopy, mass spectrometry, and X-ray crystallography. Analysis of the crystal structure of cis-[Cr([14]-decane)(acac)](ClO 4 ) 2 .(½)H 2 O reveals that central chromium(III) has a distorted octahedral coordination environment and two acetylacetonate-oxygen atoms are bonded to the chromium(III) ion in the cis positions. The angle N a x i a l -Cr-N a x i a l deviates by 11° from the ideal value of 180° for a perfect octahedron. The bond angle O-Cr-O between the chromium(III) ion and the two acetylacetonate-oxygen atoms is close to 90. The bond lengths of Cr-O between the chromium and the acetylacetonate-oxygen atoms are 1.950(3) and 1.954(2) A. They are shorter than those between chromium and nitrogen atoms of the macrocycle. The IR spectra of 1, 2 and 3 display bands at 1560 {ν(C=O)}, 1710 {ν a (OCO)} and 1660 cm - 1 {V a s (OCO)} attributed to the acac, ox and mal auxiliary ligands stretching vibrations, respectively.