Structural characterization of the trans -equatorial isomer of (aqua)(ethylenediamine- N , N , N ′-tripropionato)chromium(III) trihydrate,[Cr(edtrp)(H2O)] · 3H2O

The structure of trans-equatorial [Cr(edtrp)(H2O)] · 3H2O (edtrp3− is the anion of ethylenediamine-N,N,N′-tripropionic acid) was determined by single crystal X-ray diffraction. The chromium(III) ion is surrounded octahedrally by the two nitrogen and three oxygen atoms of the quinquedentate edtrp3−, forming a five-membered diamine ring and the three six-membered β-propionato chelate rings. The remaining coordination position is occupied by the H2O ligand. The crystal structure conformation is compared to the result of recent molecular mechanics analysis. The ring strain of R and G chelate rings was found to be in agreement with the previously proposed mechanisms for the C—N bond cleavage and recombinatio

Structural analysis of conformational flexibility in (aqua)(propanediamine-<b><i>N</i></b>,<b><i>N</i></b> '-diacetato-<b><i>N</i></b>-propionato)chromium(III) dihydrate. Crystal structure of <b><i>cis</i></b>-polar, <b><i>trans</i></b>(H₂O,O⁵)-[Cr(1,3-pddap)(H₂O)]<b>·</b>2H₂O

The quinquedentate complex trans(H₂O,O⁵)-[Cr(1,3-pddap)(H₂O)] · 2H₂O (where 1,3-pddap is the 1,3-propanediamine-N,N '-diacetate-N-3-propionate ion) was prepared and its structure established by X-ray diffraction method. It crystallizes in the orthorhombic space group Pna2₁, a = 17.290(2), b = 10.821(2), c = 7.872(1) Å, Z = 4. The metal atom is surrounded octahedrally with two nitrogen and three oxygen donors of (1,3-pddap)³⁻, forming two six-membered and two five-membered metal chelate rings, and with one water molecule occupying the trans position with respect to the oxygen of the axial glycinate ring. Conformational analysis of the five geometrical isomers of [Cr(1,3-pddap)(H₂O)], performed with the Consistent Force Field (CFF) program and recently developed edta force field, revealed that the global minimum is indeed the trans(H₂O,O⁵) isomer with the geometry in a very good agreement with the crystallographic structure. General patterns for the conformational preferences of edta-type complexes of trivalent first-row transition metals are exposed and discussed

Crystal structure of fac-trichlorido[tris(pyridin-2-yl-N)amine]chromium(III)

In the neutral complex molecule of the title compound, fac-[CrCl3(tpa)] [tpa is tris(pyridin-2-yl)amine; C15H12N4], the CrIII ion is bonded to three N atoms that are constrained to a facial arrangement by the tpa ligand and by three chloride ligands, leading to a distorted octahedral coordination sphere. The average Cr—N and Cr—Cl bond lengths are 2.086 (5) and 2.296 (4) Å, respectively. The complex molecule is located on a mirror plane. In the crystal, a combination of C—H...N and C—H...Cl hydrogen-bonding interactions connect the molecules into a three-dimensional network