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Biguanide-amino acid complexes of the type Co(am)(Hbg)3+ 2, where am is the anion of glycine, sarcosine, L-alanine, L-valine, L-isoleucine, or L-proline, have been prepared and resolved. The absorption, circular dichroism (CD) and proton magnetic resonance spectra (for the alanine and valine complexes) are reported. For some salts of some of the complexes of optically active amino acids, one pure optical isomer could be obtained by slow crystallization from from the reaction solution. One optical isomer of the complexes containing optically active amino acids is present in the reaction mixture to a slightly greater extent than the other. The effects of hydroxide ion and heating on equilibration was studied. Assignments of absolute configurations were made from the CD spectra.

Through structural and circular dichroism spectral comparison, 1,1,1-tris(3′-aminopropylaminomethyl)-ethanecobalt(III), Co(spn)3+, has been determined to be a model for the oxyanion ion-pairs of Co(tn)3 3+. The CD spectral changes of δ-Co(spn)3+ in the presence of oxyanions in conjunction with previous investigations suggest that conformational changes of the six-membered rings cause the intensities of the Ea and A2 components of the octahedral T1 g band to change in a direction opposite to that observed when only asymmetric nitrogens are generated, either by oxyanion hydrogen bonding or by means of an alkyl cap. It appears that when both effects occur together it is the conformational change that dominates the CD spectral changes. In the absence of conformational change the asymmetric nitrogens cause the Ea component to decrease while the A2 component increases, as was found in previous studies. The nickel(II) and copper(II) complexes of spn are reported also.

Two new cobalt(III) complexes, [Co(acac)(bpy)2]2+ and [Co(acac)(phen)2]2+ (acac=acetylacetonate ion, bpy=2,2′-bipyridine and phen=1,10-phenanthroline) were prepared from the reaction of [Co(CO3)(bpy)2]+ and [Co(CO3)(phen)2]+, respectively, with acetylacetone, and converted to the partially resolved optically active forms using a SP-Sephadex ion-exchange column. [Co(acac)2(bpy)]+ was also resolved partially with a SP-Sephadex column. [Co(acac)2(phen)]+ was resolved with a combination of silver dibenzoyl-d-tartrate and dibenzoyl-d-tartaric acid. The circular dichroism (CD) spectra for these four complexes and for [Co(acac)2(en)]+ and [Co(acac)2(tn)]+ (en=ethylenediamine, tn=trimethylenediamine) were measured. A marked solvent effect was observed in the d-d transition region for the CD spectra of the [Co(acac)2L]+ complexes. The absolute configurations for all these complexes were assigned on the basis of their CD spectra.

Carbon-13 nuclear magnetic spectroscopy has been used to study a series of octahedral cobalt(III) complexes with various quinquedentate ligands and either NO− 2 or H2O coordinated in the sixth position. Measurements were made on eight nitro complexes and six aqua complexes. The quinquedentate ligands studied were ethylene-diamine-N,N′,N′-triacetate (ed3a), N-methylethylenediamine-N,N′,N′-triacetate (med3a), N-hydroxyethylethylenediamine-N′N′,N′-triacetate (hed3a), N-benzylethylenediamine-N′N′,N′-triacetate (bedea), 1,2 diamino-2-methylpropanetriacetate (dmp3a), and (R)-(-)-1,2-propanediaminetriacetate ((R)-pd3a). The identification of the trans-equatorial-isomer of [Co(ed3a)NO2]− has been confirmed using13C and proton magnetic resonance. Selective decoupling, off-resonance decoupling, and acid-catalyzed deuteration have been used to identify the resonances of specific carbons. Information about the stereochemistry of the complexes can be derived by comparing the chemical shifts in the 13C spectra.

One isomer of [Co(S-azet)3] (S-azet=S-azetidine-2-carboxylate ion) has been isolated and assigned the A-facial configuration from absorption and circular dichroism (CD) spectra. Both optical isomers of [Co(en)2S-azet]I2 were isolated and their absolute configurations assigned. Two isomers assigned as A (+)-β2-SS- and δ-(-)-β1-RR-[Co(trien)S-azet]I2 were isolated in the case of the triethylenetetraamine complex. The complexes are closely related to the corresponding S-proline complexes.

The preparation and characterization are described for the β1 and β2−-(RR and SS)- and the β2−(RS and SR)isomers for the glycine, (S and R)-alanine, and S-methionine complexes, and the β1− and β2−-(RR and SS) isomers for the S-proline complexes of the type β[Co(trien)aa]I2·H2O. The isomers differ in the orientation of the amino acid anion (aa) relative to the triethylenetetraamine (trien) ligand (β1 or β2) and the chelate ring conformations, which are designated by the absolute configurations of the coordinated secondary amine groups (R or S). The absolute configurations were assigned from the stereoselectivity of proline and spectral results. The circular dichroism (CD) spectra were used to relate configurations and conformations of the complexes, to examine the various contributions to the CD peak intensities and the addivity of these contributions.

Huckel molecular orbital calaulations have been carried out for N-methyl-salicylal-dimine N-salicylidene-aniline, and N-methoxy-benzylidene o -hydroxyaniline to aid in the interpretation of the spectra of a series of Schiff bases. The long wavelength bands of o -hydroxy aromatic Schiff bases were found to be in the order zwitter ion > cation ≅ anion > enol.

Silica gel, activated alumina, platinized asbestos, and partially reduced zinc oxide were found to have no effect on the rate of racemization of several complexes studied. Raney nickel caused the decomposition of [Co(en)3]Cl3. Activated carbon decomposed K3[Co(C2O4)3] and K3[Cr(C2O4)3]. It caused some conversion to the trans isomer of cis-[Co(en)2(NO2)2]Br3, in addition to accelerating the racemization of the complex. Using wood carbon activated at 700°C for 1 hr, the racemization of d -[Co(en)3]Cl3 was found to be essentially second order, first order in complex and first order in carbon. The activation energy for the racemization process was 17 kcal/mole. Although an electron exchange mechanism for the racemization on carbon cannot be ruled out, an intramolecular process is favoured.

The racemization of the [Co(en)3]3+ ion in the presence of activated carbon was found to be retarded by H2SO4, to a slightly lesser extent by Li2SO4 or MgSO4, and to a slight extent by Na2SO4. Salts containing the ClO4−, NO3− or NO2− ions accelerated the racemization. The racemization of the [Co(EDTA)]− ion in the presence of carbon was not greatly affected by added electrolytes. The racemization was slightly retarded by H2SO4, KNO3, and NaClO4 and slightly accelerated by alkali sulphates.

The absorption, circular dichroism, and magnetically induced circular dichroism spectra are reported for [Co(en)3]3+ and [Co(+)(pn)3]3+ in aqueous solution with and without various electrolytes. A method of interpretation of the MCD spectra with respect to the CD spectra is proposed. This interpretation suggests there is considerable trigonal splitting (∼1500cm−1) in solution, and refutes the possibility that the two bands in the Tlg(Oh) region originate from different conformational isomers in solution.

Circular dichroism spectra are reported for two isomers of [Co(+)-pn2(OH)2]3Co(ClO4)6. It is suggested that earlier assignments of the CD peaks in the region of absorption of the CoO6 chromophore be reversed. Assignments based upon intensities are without support where intensities are extraordinarily great, but the usual order of energy levels is expected. Absolute configurations are assigned based upon this interpretation of CD spectra.

The L-aspartato(iminodiacetato)cobaltate(III) complex ion has been prepared and separated into three optically active isomers by ion-exchange chromatography. These isomers were identified from their electronic absorption, circular dichroism and pmr spectra. Their spectra are compared to those of the three isomers of the bis(L-aspartato)-cobaltate(III) complex ion.

The relative stabilities of metal derivatives of 00′-dihydroxyazo dyes (terdentate groups) have been measured potentiometrically in dioxan-water (75: 25 by volume). The order of stability of the metal derivatives agrees with that already reported in the literature for monodentate and bidentate groups. The coordinating power of the diarylazo compounds for a given metal is proportional to the acid dissociation constants of the chelating agents. The one 0-hydroxy-0′-carboxyazo dye which has been studied forms less stable metal derivatives than the 00′-dihydroxyazo dyes and differs from them in coordinating with beryllium.

The three possible geometric isomers of bis(L-aspartato)-cobaltate(III) ion each give a twelve-line ABX pmr spectrum at 100 MHz. The parameters from analysis of the spectra have been used to calculate line positions and intensities which compare favorably with those observed. The conformation of the CH[sbnd]CH2 moiety in the flexible six-membered chelate ring is calculated from the vicinal coupling constants. The geometric configurations are assigned using the proton chemical shifts. The results are compared to those for N,N′-ethylenediamine-disuccinatocobaltate(III) ion.

The complexes [Co(en)2(dabp)]3 + and α-[Co(trien)(dabp)]3 + have been resolved. The β-trien complex was not sufficiently stable to permit resolution. Of the four possible stereoisomers of each complex, only two were isolated. The stereospecificity of these reactions was confirmed since R-dmdabp combined with cis-[Co(en)2Cl2]+ to form just one of the two possible configurational isomers. The CD spectra were examined to investigate the effect of ligand conformation on the rotatory strengths and to relate the absolute configurations to those of other tris-(diamine)cobalt(III) complexes.

The conditions for the activation of sugar carbon for the racemization of d -K[Co(EDTA)]. 2H 2 O have been investigated. The activity of the carbon increased with the number of activations and was greatest when the carbon was ignited in air and cooled in N 2 .

Carbon-13 nmr spectra are reported for s-facial, uns-facial, and meridonial isomers of [Co(dien)3]CI3 and [Co(dien)(IDA)] CI, and the s-fac and uns-fac isomers of K[Co(IDA)2]. The nmr peaks are assigned, the spectra clearly reflecting the symmetry of the individual isomers.