Cobalt, tris complexes conformation

Cobalt, tris(l,2-propanediamine)-complexes structure, 1, 25 conformation, 1,25 nomenclature, 1, 129 stereonotation, 1,129... 

The absorption spectrum of the Field-Durrant solution with potassium bicarbonate is characteristic of the cobalt(III) complex there are two d—d absorption bands and one charge-transfer (CT) band, and the pattern of the spectrum is similar to that of the familiar tris(oxalato)cobaltate(III) anion except for some bathochromic shifts of the carbonate complex. Regarding the d—d bands, conformity to Beer s law is confirmed with ca. 10 10 mol/dm solutions using 1-cm absorption cell. Data on the solution spectrum with the values of the parameters A and B are given in Table 2.1... 

The two cobalt(III) hexaamines with relatively short metal-donor distances considered here are [Co(7ra s-diammac)]3+ trans-diammac is trans-1,4,8,11 -tetraazacy-clotetradecane-6,13-diamine, see Fig. 17.11.1) and [Co(trap)2]3+ (trap is 1,2,3-tri-aminopropane, see Fig. 17.11.2). There are three conformers of [Co(taa s-di-ammac)]3+ (35, 51,15 where 5 and 1 refer to the conformation of the five-mem-bered chelate rings in the complex - see also Section 17.3). The A<5-conformer is the most stable form and has been characterized by an X-ray diffraction study. 15-[Co(fra .v-diammac)]3+ has very short Co-N bonds (1.937A (four equatorial bonds), 1.946 A (two axial bonds)), and the experimentally determined high ligand field and the strongly negative redox potential confirm that these structural features are conserved in solution190 231,2811. 

Freedman TB, Cao XL, Young DA et al (2002) Density functional theory calculations of vibrational circular dichroism in transition metal complexes Identification of solution conformations and mode of chloride ion association for (+)-tris(ethylenediaminato)cobalt (III). J Phys Chem A 106 3560-3565... 

Stepwise methylation of apical amino substituents in cobalt(III) sarcophaginate make it possible to obtained a tris-N-methylated complex with conformational inversions in the ethylenediamine moieties from mainly a ZeZ -conformation in [Co(diAMsar)] + cation to an 063 conformation in [Co(diMe3AMHsar)]3+ sarcophaginate both in the solid state and in solution [116]. 

The twist boat form is chiral and there are two enantiomeric conformations. The chirality can be defined in the same way as a cobalt-ethylenediamine ring and designated as S and X. The third form, a boat form cannot be accommodated to form a tris(bidentate) complex and, in fact, such a structure has not yet been reported. Niketii and Woldbye showed that there exist 16 possible conformers of the [M(tn),] system for each of the absolute configurations A and A, in which they adopt the three stable configurations chair andS- and X-skew boat forms (32). 

For the tris[( )-propylenediamine]cobalt(III) ion, there are 24 possible isomers (Table 3.1, where symbols A and A refer to the absolute configurations of the complex ion, lei and ob to the conformations of the chelate ring, and fac and mer to the isomerism with respect to the methyl groups of the chelated pn molecules). Dwyer et al. studied this system by column chromatography with cellulose powder and paper chromatography (see Section 3.4). MacDermott separated the fac isomer... 

In 1959 Corey and Bailar d t with stereo specific effects in complex ions. The results of the conformational analysis for the [Co(en)3] ion showed that one conformational form of a chelated en, /e/ , is more stable than the other, ob , by ca. 0.6 kcal/mol. For the tris(propylenediamine)cobalt(III) ion, the three most stable pn chelate rings are suggested to have equatorial conformation with... 

It has been established by X-ray analysis that in potassium (-b)58 -tris-(l,10-phenanthroline)nickel(ii) (—)5g,-trisoxalatocobaltate(m) dihydrate both complex ions have the A configuration. The mean Co-O distance is 1.93 A. The complex anion in sodium (- -)s4,-bismaIonatoethylenediamine-cobaltate(iii) has the A configuration the six-membered malonato chelate rings adopt boat conformations. ... 

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