Cr(III)-Tetraaza Macrocyclic Complexes Containing Auxiliary Ligands (Part II); Synthesis and Characterization of Cr(III)-Citrato Macrocyclic Complex

Abstract

The reaction of cis-[Cr([14]-decane)(OH<TEX>$_2)_2]^+$</TEX> ([14]-decane = rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-teraazacyclotetradecane) with auxiliary ligands {<TEX>$L_a$</TEX> = citrate(cit)} leads to a new dimeric complex cis-[{Cr([14]-decane)(<TEX>$\mu$</TEX>-cit)}<TEX>$_2](ClO_4)_2$</TEX>. This binuclear complex has been structurally 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)(<TEX>$\mu$</TEX>-cit)})(<TEX>$_2]^+$</TEX> reveals that each chromium has a distorted octahedral coordination environment and citrato ligands are monodentate to the two chromium atoms via the carboxyl groups. For dimeric complex the bridging geometry is as follows: Cr<TEX>$\ldots$</TEX>Cr = 7.361 <TEX>$\AA$</TEX>; Cr-O(average) = 1.958 (8) <TEX>$\AA$</TEX>; Cr-N range = 2.108 (9)-2.147(9) <TEX>$\AA$</TEX>; N(1)-Cr-N(3) (equatorial position) = 98.0(4)<TEX>$^{\circ}$</TEX>; N(2)-Cr-N(4) (axial position) = 166.4(4)<TEX>$^{\circ}$</TEX>; O(1)-Cr-N(2) = 98.1(4)<TEX>$^{\circ}$</TEX>; O(3)-Cr-N(4) = 96.6(3)<TEX>$^{\circ}$</TEX>; O(1)-Cr-O(3) = 90.4<TEX>$^{\circ}$</TEX>. The FAB mass spectrum of the dimeric complex displays peak due to the molecular ions cis-[{Cr([14]-decane)(<TEX>$\mu$</TEX>-cit)})(<TEX>$_2]^+$</TEX> at m/z 1053.