Dušan J. Radanović

Optical activity of cobalt(III), chromium(III) and rhodium(III) complexes with aminopolycarboxylate EDTA-type and related ligands

Article de synthese relatif aux complexes cites. Stereochimie, activite optique et configuration absolue. Complexes hexadentes, quinquadentis, complexes avec des coordinats de type edda lineaires

Coordination chemistry of hexadentate EDTA-type ligands with M(III) ions

Abstract In recent years, many edta-type ligands have been prepared and used to form hexadentate complexes with Co(III), Cr(III), and Rh(III). Absolute configurations have been determined by X-ray crystallography for representative complexes, substantiating assignments based on circular dichroism (CD) spectra. Within the first absorption band, the CD patterns for Co(III) complexes differ in energies of CD peaks relative to the absorption maximum, depending on the combinations of acetate and propionate arms. The overall pattern suggests that different combinations of three transitions usually appear. Some enlargement of chelate rings intended to relieve strain has been found to introduce other strain. Unexpected C-N bond cleavage for Cr(III) complexes of edta-type ligands with propionate arms led to the identification of conformational isomers.

Crystal structures of Na[M(1,3-PDTA)]·3H2O(M = Cr, Rh; 1,3-PDTA = 1,3-propanediaminetetraacetate), and the absolute configuration of the (-)D-Isomer of the Rh complex

Abstract In order to clarify the relation between the absolute configuration and circular dichroism, and to investigate the influence of the size of metal ion on the strain in chelate rings of M(1,3-PDTA) complexes (M = Co, Cr, Rh; 1,3-DPTA = 1,3-propanediaminetetraacetate), X-ray crystal structure analysis of Na[Cr(1,3-PDTA)]·3H2O and (-)DNa[Rh(1,3-PDTA)]·3H2O were performed. The crystals of the two compounds are isomorphous and belong to the orthorhombic system, space group P212121, Z = 4, with cell dimensions a = 16.514(5), b = 8.809(2), c = 11,429(3) A and a = 16.511(13), b = 8.836(13), c = 11.431(7) A for chromium and rhodium complex, respectively. The structures were determined on the basis of 1699 and 2928 diffractometer data points, and were refined by least squares methods to R 0.053 and 0.025 for chromium and rhodium complexes respectively. Crystal structures consist of the complex and of the sodium ions and molecules of water. In the complex anion, the metal ion is coordinated octahedrally by a sexidentate 1,3-PDTA ligand. The six membered 1,3-propanediamine chelate T ring in both compounds takes a twist-boat δ conformation. Two equatorially-disposed glycinate G rings have an envelope λ conformation and two out-of-plane R rings are relatively flat. The absolute configuration of the Rh complex is Λ. The absolute configuration of the Cr complex, a crystal selected by chance from the optically-inactive complex, is also Λ. The ring strains were determined and compared with those in related Co(III) complexes.

Crystal structures and absolute configurations of (+)589-Li[Co(edtp)]·3H2O and (+)589-Li[Cr(edtp)]·3H2O complexes of ethylenediamine-N,N,N′,N′-tetra-3-propionate ion and correlations with circular dichroism spectra

Abstract The complexes, (+)589-Li[M(edtp)]·3H2O (MCo or Cr; edtp  ethylenediamine-N,N,N′,N′-tetra-3-propionate ion) crystallize in the space group P21 of the monoclinic crystal system with Z=2. For MCo, a=8.824(2), b=11.910(3), c=8.7282(2) A, β=95.03(1)° and for MCr, a=8.705(1), b=11.940(2), c=9.033(1) A, β= 94.19(1)°. The absolute configuration is △(λλ) for each complex where λ designates the conformation of the axial β-alaninate rings. Significant sources of strain are found and discussed for both complexes. The distortion from octahedral coordination in these [M(edtp)]− complexes is greater for Co(III) than it is for Cr(III) which is unusual compared to other [M(edtp)]−- type complexes. The absolute configurations of the complexes are consistent with earlier reports of their circular dichroism spectra.

Simple synthetic method and structural characteristics of (1,3-propanediaminetetraacetato)cobalt(II) complexes: uniform crystal packing in a series of metal(II) complexes with 1,3-propanediaminetetraacetate ligand

Abstract Starting from Ba[Ba(1,3-pdta)]·2H2O three new hexadentate cobalt(II) complexes [MII(H2O)6][CoII(1,3-pdta)]·2H2O (MII=Ba (1), Co (2) and Mg (3)) (where 1,3-pdta represents the 1,3-propanediaminetetraacetate ion) have been prepared and characterized. Presented in this paper, the crystal structures of the complexes containing CoII and MgII counter cations are isomorphic, as are the other crystal structures of metal(II) complexes with 1,3-pdta ligand, so far reported in the literature. The complexes crystallize in the space group Pnna of the orthorhombic crystal system. The structural unit consists of discrete [CoII(1,3-pdta)]2− and [MII(H2O)6]2+ octahedra, and two water solvent molecules all of which lie on a twofold axis of symmetry. The complex cations and anions alternate in the crystal lattice each being octahedrally surrounded by the counter ions. Electronic absorption spectra of [CoII(1,3-pdta)]2− complexes are presented and discussed in terms of octahedral distortion in edta-type CoII complexes.

Synthesis and X-ray structural study of magnesium (1,3-propanediaminetetraacetato)cuprate(II) octahydrate, Mg[Cu(1,3-pdta)]·8H2O.: Stereochemistry of hexadentate copper(II)–edta-type complexes in relation to the structure of the ligand

Abstract The hexadentate complex Mg[Cu(1,3-pdta)]·8H2O (1) (where 1,3-pdta represents the 1,3-propanediaminetetraacetate ion) has been prepared and isolated and its structure established by X-ray crystallography. The structure converged to R=0.030 for 1537 observed reflections. The Cu(II) ion is surrounded by two nitrogen atoms and four oxygen atoms of the ligand, making a tetragonally elongated octahedron (T=0.868). The Mg cation is bonded octahedrally to six water molecules. Both complex ions utilize a two-fold symmetry axis that is present in the crystal. The conformations of the chelate rings were found to be envelope for the glycinates and skew-boat for the six-membered diamine (T) ring. Comparison of the structures of the hexadentate copper(II)–edta-type complexes shows an expected variation in their stereochemistry, depending on the structure of the ligand. Infrared (carboxylate region) and electronic absorption spectra are also given.

The favored trans(O6) geometry in hexadentate copper(II) complexes of 1,3-propanediamine-N,N′-diacetic-N,N′-di-3-propionic acid. Crystal structure of trans(O6)-Na2[Cu(1,3-pddadp)]·NaNO3·2H2O. Strain analysis and spectral assignments of complexes

The octahedral copper(II) complexes of 1,3-propanediamine- N,N′- diacetic- N,N′- di-3-propionic acid (H 4 1,3-pddadp) prepared in the region of pH 2 to 7 are hexadentates. Only one ( trans ( O 6 )) of the three geometrical isomers was found to dominate. The trans ( O 6 )-Na 2 [Cu(1,3-pddadp)]·NaNO 3 ·2H 2 O complex crystallizes in the space group P 2/ c of the monoclinic crystal system with a =9.231(2), b= 11.736(14), c =10.150(2) A, β =109.33(2)° and Z =2. The conformations of the chelate rings are found to be envelope for the glycinate and skew-boat for the β-alaninate and 1,3-propanediamine rings. The complex is a tetragonally elongated octahedron ( T ∼0.8) with C 2 molecular symmetry. IR (carboxylate region) and electronic absorption spectra are assigned and discussed in relation to the structure of complexes. For hexadentate Cu(II) edta-type complexes of known structures the strain analysis is also discussed.

Synthesis and characterization of hexadentate cobalt(III) complexes with novel edta-type ligands Part 2. Circular dichroism of the trans(O5O6) and trans(O6) isomers of a cobalt(III) complex of 1,3-propanediamine-N,N′-diacetic-N,N′-di-3-propionic acid

Abstract Cobalt(III) complexes with the hexadentate ligand, 1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate ion (1,3-pddadp) were prepared, chromatographically separated into two geometrical isomers with respect to the NO chelate ring size [trans(O5O6) and trans(O6)], and resolved. The 1H NMR, electronic absorption and circular dichroism (CD) spectra were used to characterize the complexes. The splitting of the T1g(Oh) band of the trans(O6-[Co(1,3-pddadp)]− complex indicates that the tetragonal field is enhanced, relative to the fields in other [Co(edta)]− -type complexes reported. The (+)546-trans(O5O6)-[Co(1,3-pddadp)]− and (+)546-trans(O6)-[Co(1,3- pddadp)]− complexes with a positive CD peak at lowest energy in the first spin-allowed d-d absorption band region are tentatively assigned the Λ absolute configuration. Preliminary results of a crystallographic study of the Ktrans(O6)-[Co(1,3-pddadp)]·3H2O confirm the assignments of geometrical isomers of the complexes.

Some hexadentate Ni(II)-edta-type complexes containing five-membered diamine rings. The molecular and crystal structure of the trans(O5) isomer of barium(ethylenediamine)-N,N′-diacetato-N,N′-di-3-propionato_)nicklate(II) hexahydrate, trans(O5)-Ba[Ni(eddadp)]·6H2O, and strain analysis of edta-type chelates in relation to their octahedral distortion

Abstract Two paramagnetic octahedral Ni(II)-edta-type complexes, Ba[Ni(eddadp)]·6H2O(1) (eddadp) = ethylenediamine-N,N′-diacetate- N,N′-di-propionate ion) and Ba(Ni(edtp)]· 3H2O(bd2) (edtp = ethylenediamine-tetra-3-propionate Ion) have been prepared and characterized. The ligands used, forming β-alaninate rings, are likely to function as inexandentate with a larger metal ions. Because of the strain in the equatorial plane, as expected, the trans(O5) configuration of complex 1 was found to dominate and this geometry was verified crystallographically. The crystal is monoclinic with the space group C2/c, a = 11.091(3), b = 13.526(4), c = 28.064 A , β = 93.56(2)° and Z = 8 . The IR (carboxylatesregion) and electronic absorption spectra of these complexes are reported. There is no added multiplicity found in the electronic spectra of complexes that generally are seen for octahedral or pseudooctahedral Ni(II) complexes. Spectra of these complexes are discussed in comparison with those of the trans(O5)-[Ni(SS-edds)]2− complex (SS-edds = SS-ethylenediamine-N,N′-disuccinate ion) of known structure. The magnetic measurements are also reported for the complexes studied. Structural parameters and strain analysis data of M-edta-type complexes are discussed in relation to their octahedral distortion.

CIRCULAR DICHROISM AND ELECTRONIC ABSORPTION OF RHODIUM(III) EDTA-TYPE COMPLEXES: Ethylenediamine-N,N′-diacetato-N,N′-di-3-propionatorhodate(III) and (S,S)-Ethylenediamine-N,N′-disuccinatorhodate(III) Ions

Abstract Electronic absorption and CD spectra are reported for the sexidentate complexes, trans(O5)-Rh(EDDDA)−, trans(O5 O6)-Rh(EDDDA)−, and trans(O5)-Rh(S,S-EDDS)− (EDDDA)=ethylenediamine-N,N′-di-3-propionate; S,S-EDDS=(S,S)-ethylenediamine-N,N′-disuccinate). Because of the sterospecific coordination of the S,S-EDDS ligand the absolute configuration of (+)D-trans(O5)-Rh(S,S-EDDS)− is known to be Λ. By comparison of their CD spectra to that of the (+)D isomer of trans(O5)-Rh(S,S-EDDS)−, the absolute configurations of the (−)DEDDDA complexes are assigned tentatively.