Structural and spectroscopic properties of potassium bis(glycylglycinato(2−)-O,N,N′)chromate(III) piperazine-2,5-dione

Co-ordination behaviour of N-carboxymethylpseudoephedrine: crystal structures of seven-co-ordinated cadmium(II) and fac-RS-octahedral copper(II) complexes

“…The geometry can be regarded as distorted pentagonal bipyramidal with one cpse ligand bonded to the metal ion in a similar arrangement to that of the copper() compound, with an oxygen from the carboxylate group in an apical position, Cd᎐O(6) 2.301(8) Å, and the nitrogen and the alkoxide oxygen in the equatorial plane, Cd᎐N(2) 2.448 (9) and Cd᎐O(7) 2.341(5) Å. The second cpse molecule is co-ordinated with all three atoms in the equatorial plane, an unusual co-ordination mode for this ligand, Cd᎐O(3) 2.368 (8), Cd᎐N(1) 2.398 (7) and Cd᎐O(4) 2.534(6) Å; these distances are similar to normal Cd᎐O and Cd᎐N bonds, 24-26 with exception of Cd᎐O(4) which is longer than expected, probably due to steric hindrance from the methyl group of the A ring of the other ligand, as can be appreciated from the small angle N(1)᎐Cd᎐O( 4) 67.7(3)Њ, which is substantially smaller than the corresponding one of complex 1, 79.5(2)Њ. The seventh position is occupied by a water mole-Table 3 Selected bond lengths (Å) and angles (Њ) with standard deviations in parentheses for compound 1 Cu᎐O( 7) Cu᎐O( 3) Cu᎐N( 1) O( 3)᎐C( 1) O( 4)᎐C( 4) N( 1)᎐C( 3) C( 1)᎐C( 2) C( 3)᎐C( 5) O( 4) ؒ ؒ ؒ O(5) * O( 4)᎐Cu᎐O( 7) O( 6)᎐Cu᎐O( 7) O( 4)᎐Cu᎐O( 6) N( 1)᎐Cu᎐N( 2) N( 1)᎐Cu᎐O( 4) N( 1)᎐Cu᎐O( 7) N( 2)᎐Cu᎐O( 4) N( 2)᎐Cu᎐O( 6) Cu᎐O( 6)᎐C( 13) Cu᎐O( 7)᎐C( 16) Cu᎐N( 2)᎐C( 14) Cu᎐N( 1)᎐C( 3) Cu᎐N( 1)᎐C( …”

“…Hydrogen atoms attached to carbon atoms were included at geometrically idealised positions and refined using a riding model with fixed isotropic U. For the two hydroxyl groups [O(4) and O (7)] and the water molecule [O(1)], hydrogen atoms could not be positioned from a Fourierdifference map and were omitted. The correct absolute configuration of the molecule was confirmed by refinement of a Rogers parameter: 23 η = 0.97 (6).…”

[Bis(3-aminopropyl)amine-N,N',N''][glycylglycinato(2–)-N,N',O]chromium(III) Perchlorate Monohydrate, [Cr(C4H6N2O3)(C6H17N3)]ClO4.H2O

“…EVvisible and infrared spectra can be used diagnostically to identify the geometric isomers of chromium(Ill) complexes with tridentate ligands (Subramaniam, 1989). It should be noted, however, that assignments based on spectroscopic investigations are not always conclusive (Steams & Armstrong, 1992).…”

“…The structure of the mer-[Cr(dpt)(Gly-Gly)] + cation, with the atom-numbering scheme, is shown in Fig The Cr--N(peptide) bond of 1.961 (5)A, is shorter than the average for a CrmN(amine) bond [2.107 (6) A] (Murdoch, Cooper, Hambley, Hunter & Freeman, 1986;Subramaniam, Garvey, Lee & Hoggard, 1988). This appears to indicate that the Cr--N(peptide) bond is stronger than those involving other N atoms.…”