Hexadentate rhodium(III) complexes of 1,3-propanediamine-N,N′-diacetic-N,N′-di-3-propionic acid.: Crystal structures of trans-(O5)-Na[Rh(1,3-pddadp)]-H2O and (+)589-trans-(O5O6)-Na[Rh(1,3-pddadp)]•3H2O and CD spectra correlation.: Octahedral distortion of [Rh(edta-type)]- complexes in relation to the structure of the ligand and geometry of the complex

Structural data are given for two earlier reported hexadentate Rh(III) complexes: trans-(O-5)-Na[Rh(1,3-pddadp)](H2O)-H-. (1) and trans-(O5O6)-Na[Rh(1,3-pddadp)](.)3H(2)O (2) (1,3-pddadp = 1,3-propanediamine-N,N'-diacetate-N,N'-di-3-propionate ion). Both complexes have been resolved. The absolute configuration around the Rh(III) ion for the (+)(589) optical isomer in the crystal 2 has been determined to be the Lambda (LambdaDeltaLambda). The complexes crystallize in monoclinic P2(1)/c (1) and orthorhombic P2(1)2(1)2(1) (2) space groups. Based on a low-temperature measurements (150 K), both crystal structures have been refined to a final R value of 0.029. The conformations of the glycinate rings in 2 are common (R relatively flat and G with a significant deviation) while the two R rings of 1 (in an envelope and twist conformations) show unusually large total deviation (of -6degreesav.). The six-membered beta-alaninate (R, G) and the diamine (T) rings adopt in both compounds distorted boat (twist-boat) conformations. Octahedral distortion of [Rh(edta-type)](-) chelates is discussed in relation to the structure of the ligand and the geometry of the complex. The CD spectra of the Lambda-(-)(589)-trans-(O-5)-Rh[(1,3-pddadp)](-) (1) and Lambda-(+)(589)-trans-(O5O6)-[Rh(1,3-pddadp)](-) (2) and the other Lambda-[Rh(edta-type)](-) complexes have been correlated and discussed. The lowest energy CD component is positive for the Lambda-isomers of 1 and 2, but negative for the other Lambda-[Rh(edta-type)](-) complexes that is forced to reverse the assignments of the CD peaks. (C) 2002 Elsevier Science B.V. All rights reserved.