SYNTHESIS AND CHARACTERIZATION OF MU-CARBOXYLATO-O,O-MU-HYDROXO CHROMIUM(III) COMPLEXES CONTAINING AMINO-ACIDS, ACETATE AND NICOTINATE AS BRIDGING LIGANDS - CRYSTAL-STRUCTURE OF K2[CR(NTA)(OH)(ACETATE-O,O)CR(NTA)].4H2O

A series of μ-carboxylato-μ-hydroxo chromium(III) complexes containing amino acids, acetate and nicotinate as bridging ligands has been synthesized and characterized by 2H NMR and electronic absorption spectroscopy: [Cr(en)2(OH)(Hamino acid-O,O)Cr(en)2]5+ (en=ethylenediamine; Hamino acid-O,O=glycine (previously reported), alanine, serine and threonine); [Cr(en)2(OH)(acetate- O,O)Cr(en)2]4+ (previously reported); [Cr(nta)(OH)(acetate-O,O)Cr(nta)]2- (nta=nitrilotriacetate). The crystal structure of K2[Cr(nta)(OH)(acetate-O,O)Cr(nta)]·4H2O was determined. This complex crystallizes in the space group P1 of the triclinic crystal system with a=9.678(3), b=11.182(2), c=13.137(4) Å, α=97.57(2), β=102.26(2), γ=108.96(2)° and Z=2. Magnetic susceptibility data were also collected for this complex (80 to 280 K) and show a J/k value of -19.5 K. The 2H NMR spectra of these di- Cr(III) complexes, with deuterium labeled (2-carbon) bridging ligands, show isotropic shifts which are distinctly different from the shifts observed for the mononuclear Cr(III) complexes containing these ligands: amino acids, +72 to +81 ppm; acetate, +58 ppm (bis(en)) and +41 ppm (nta); nicotinic acid, +3.6 ppm. © 1990.