Cr(III)-Tetraaza Macrocyclic Complexes Containing Auxiliary Ligands (Part I); Synthesis and Characterization of Cr(III)-Benzoato and Chlorobenzoato Macrocyclic Complexes

Abstract

The reaction of <TEX>$cis-[Cr([14]-decane)(OH_2)_2]^+$</TEX> ([14]-decane = rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-teraazacyclotetradecane) with auxiliary ligands {<TEX>$L_a$</TEX> = benzoate(bz) or chlorobenzoate(cbz)} leads to a new compound <TEX>$[Cr([14]-decane)(bz)_2]ClO_4$</TEX> or <TEX>$[Cr([14]-decane)(cbz)_2]ClO_4$</TEX>. These complexes have been characterized by a combination of elemental analysis, conductivity, IR and Vis spectroscopy, mass spectrometry, and X-ray crystallography. The crystal structure of <TEX>$[Cr([14]-decane)(cbz)_2]^+$</TEX> was determined. The complex shows a distorted octahedral coordination environment with the macrocycle adopting a folded cis-V conformation. The angle <TEX>$N_{axial}-Cr-N_{axial}$</TEX> deviates by <TEX>$14.5^{\circ}$</TEX> from the ideal value of <TEX>$180^{\circ}$</TEX>for a perfect octahedron. The bond angle cis-O-Cr-O between the Cr(III) ion and the two carboxylate oxygen atoms of the monodentate p-chlorobenzoate ligands is close to 90<TEX>$^{\circ}$</TEX>. The FAB mass spectra of the <TEX>$cis-[Cr([14]-decane)(La)_2]ClO_4$</TEX> display peaks due to the molecular ions <TEX>$[Cr([14]-decane)(bz)_2-H]^\;,\;[Cr([14]-decane)(cbz)_2-2H]^$</TEX> at m/z 578, 646, respectively.