Several square-planar cobalt(III) complexes of bis(biuretato)-type were synthesized with new quadridentate ligands, alkylenebis(biuret)’s, where alkylene bridging group is (R,S)- or (R)-propylene, 1,1-dimethylethylene, cis-1,2-cyclohexylene, or tetramethylethylene. Faraday parameters for possible CT transitions in the complexes were expressed as functions of MO coefficients and energies. From the examination of the magnetic circular dichroism, the intense absorption band observed at ca. 20×103 cm−1 was assigned to ligand-to-metal charge-transfer transitions of ligand π(au of D2h) to metal dyz and dzx′, and the ground state was inferred to be one close to D4h symmetry. The band assignment was also consistent with the resonance Raman spectrum of potassium bis(biuretato)cobaltate(III). Absorption spectra of the complexes occasionally lost intensity with decrease of temperature. Origin of the thermochromism, which was found to be reversible, was also discussed.

Abstract Dithiocarbamato complexes, [Co(dtc)3−n(diamine)n]n+ (n=1 and 2 and dtc=dimethyldithiocarbamate) were newly prepared and characterized by means of their absorption, CD, and MCD spectra. (+)500CD-[Co(dtc)(en)2][Sb2(R,R-C4H2O6)2]·5H2O crystallized in the monoclinic space group of P21 with a=14.630(3), b=9.300(1), c=12.023(5) Å, β=110.78(3)°, V=1529.4(8) Å3, and Z=2. The refinement of 3346 reflections (Mo Kα radiation) led to R=0.073. The dtc complex had a Λ configuration. The Co–N bond trans to the dtc sulfur atom was longer by 0.026 A than the cis one. A novel oxidation derivative, [Co{(dimethylamino)thioxomethanesulfinato-O,S}(en)2]2+, was prepared and characterized by means of its XPS spectrum.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCoordination of cyclodextrin: synthesis and characterization of two diastereomers of (.alpha.- and .beta.-cyclodextrinato)bis(ethylenediamine)cobalt(III)(1+) and their related complexesKazuaki Yamanari, Motonori Nakamichi, and Yoichi ShimuraCite this: Inorg. Chem. 1989, 28, 2, 248–252Publication Date (Print):January 1, 1989Publication History Published online1 May 2002Published inissue 1 January 1989https://pubs.acs.org/doi/10.1021/ic00301a018https://doi.org/10.1021/ic00301a018research-articleACS PublicationsRequest reuse permissionsArticle Views131Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Abstract A series of mixed complexes [Co(pyt)3−n (diamine)n]n+ (n=0, 1, and 2; pyt=2-pyridinethiolate(1—) and diamine=ethylenediamine, (R)-propylenediamine, or 2,2′-bipyridine) have been prepared and characterized by means of their visible and ultraviolet absorption, circular dichroism, and magnetic circular dichroism spectra. In the [Co(pyt)3] or [Co(pyt)2(diamine)]+ complex, only one geometrical isomer, mer(S) or trans(S) respectively, has been obtained. The [Co(pyt)(en)2](ClO4)2 complex, which was spontaneously resolved, had an orthorhombic space group of P212121, with a=12.406(1), b=12.754(1), c=11.621(4) Å, V=1838.7(6) Å3, and Z=4. The refinement of 2276 reflections (Mo Kα radiation) led to R=0.049. The Co–N bond trans to the pyt sulfur atom was longer by 0.023(11) Å than the cis one. The novel oxidation product [Co(2-pyridinesulfenato-N,S)(en)2]2+ was photochemically converted into the N,O-chelated linkage-isomer [Co(2-pyridinesulfenato-N,O)(en)2]2+ in the solid state, accompanied by ring-expansion from a four- to a five-membered chelate ring.

Abstract Quantitative scale of a new parameter d has been proposed for the spectrochemical series of ligands in the mixed ligand complexes of d6 metals, which enables us to predict the positions of low energy d–d absorption bands of a d6 complex. Introduction of a new reduction parameter α has improved the prediction of the d–d bands of mixed cyano complexes of cobalt(III), mixed halogeno complexes of rhodium(III), iridium(III), and platinum(IV), and also several mixed carbonyl complexes of low-valent d6 metals.

AbstractFour kinds of conglomerates.

Abstract Alkali metal salts of two new telluratocobaltate(III) complexes, [Co(TeO6H4)3]3− and [Co4Te3O18(en)3]6−, have been prepared. The latter heteropoly type complex and the related periodate analogue [Co4I3O18(en)3]3− have been optically resolved.

Abstract Three geometrical isomers of [Co(NO2)2(NH3)2(en)]+ were newly prepared. Two cis(NO2) isomers (trans(NH3) and cis,cis) were clearly differentiated on the basis of the polarizabilities of the Raman bands due to Co–N(NH3 and en) stretching vibrations. The Raman polarization measurement was also applied successfully to the determination of the geometrical configurations of two [Co(CN)2(NH3)2(en)]+ isomers. The structural assignments were substantiated by optical resolution of the cis,cis isomers of [Coa2(NH3)2(en)]+ (a=NO2− and CN−).

Two diastereomers due to the chiral O-bonded sulfinate in Λ-[Co(NH2CH2CH2SO2-N,O)(en)2](ClO4)2 were separated and characterized by the visible-UV absorption, circular dichroism(CD), and 13C NMR spectra. The absolute configurations were determined by comparison of the CD spectra with that of the corresponding O-bonded Λ-R-seleninato complex. The racemization of the chiral sulfinato moiety proceeded at a relatively slow rate, which is responsible for the successful separation of the diastereomers.

Abstract The binary and ternary solubility phase diagrams for the system of Δ- and Λ-[Co(ox)(en)2]X (X=l-glutamate (l-Hglu−) and l-aspartate (l-Hasp−)) were determined in water. It was found that the former anion l-Hglu− behaves as an excellent resolving agent for [Co(ox)(en)2]+ but the latter anion l-Hasp− forms a pseudoracemate rac-[Co(ox)(en)2](l-Hasp).

Mixed-ligand [Pd(N)n(O)4–n]-type complexes constituting a long systematic series (n=0–4) were synthesized. Ammonia, ethylenediamine, rac-propylenediamine, trimethylenediamine, glycinate, β-alaninate, acetate, oxalate, and malonate were employed as ligands. Their magnetic circular dichroism (MCD) and electronic absorption spectra were discussed together with the CD spectra of the corresponding optically active complexes. The results strongly suggest that the dispersion of MCD observed in the spin-allowed d-d region is primarily a composite of B terms. Moreover, the MCD in the charge transfer region was found to be qualitatively additive with respect to contributions by the constituent ligands. From a detailed examination of the spin-allowed d-d absorption bands, it is noted that the substitution of an N,O-ligand for an N,N-ligand largely affects neither the band area nor band width whereas that of an O,O-ligand for an N,O-ligand does.

Several thiolato complexes of [Co(SNNS)(diamine)]+ type were prepared (diamine stands for en=1,2-ethanediamine, R-pn=(R)-1,2-propanediamine, and RR-chxn=(R,R)-1,2-cyclohexanediamine) and characterized from their visible–UV absorption, circular dichroism, and 13C NMR spectra, where SNNS denotes two kinds of open-chain quadridentate ligands, H2endet=3,6-dimethyl-3,6-diazaoctane-1,8-dithiol and R-H2pndet=(R)-3,4,6-trimethyl-3,6-diazaoctane-1,8-dithiol. Both the SNNS ligands gave the two geometrical isomers, cis-α(dark green) and cis-β(dark violet), whereas 3,7-dimethyl-3,7-diazanonane-1,9-dithiolate(2–) ligand gave no stable monomeric complex. Interestingly, stereoselective complex formation was found in Δ-cis-α-[Co(R-pndet)(en or RR-chxn)]+, Δ(SNRN)-cis-β-[Co(endet)(R-pn or RR-chxn)]+, and Δ(SNRN)-cis-β-[Co(R-pndet)(en or RR-chxn)]+, the Δ-cis-α configuration of the former complex being the novel one having the equatorially-oriented terminal chelate rings on the tertiary nitrogen atoms.

The magnetic circular dichroism (MCD) spectra of K2PtCl4 and K2PdCl4 have been carefully remeasured over the visible-near UV region. The examination of the electronic absorption and the MCD spectra together with their Gaussian analyses strongly suggests that the band of K2PtCl4 at 30.3×103 cm−1 contains both Γ5(1Eg) and Γ3(1B1g)←Γ1(1A1g) transitions, and the band of K2PdCl4 at 21.1×103 cm−1 all three spin-allowed d-d transitions. The separation of the Γ2(1A2g) and Γ5(1Eg) excited states is considerably large with K2PtCl4 as compared with K2PdCl4. The MCD for the high-intensity absorption bands in K2PtCl4 is different from that reported previously. On the basis of new MCD result, the bands at 43.3 and 46.6×103 cm−1 have been assigned to d-p transitions, a2u(pz)←a1g(dz2) and eg(dxz,yz), respectively.

A large number of mixed-ligand [Pd(N)n(O)4−n]-type complexes (n=1–4) which contain at least one optically active ligand were synthesized and isolated in a systematic manner. (S)-Propylenediamine, (2S)-N1,N1-diethyl-1,2-propanediamine, and (S)-amino carboxylates were employed as one ligand, which is optically active; ammonia, diamines, amino carboxylates, acetates, and dicarboxylates as the other ligand occupying the remaining coordination sites. Isomerism could be detected in the mixed complexes of an unsymmetrical diamine and an amino carboxylate and has been discussed on the basis of 13C NMR and CD spectra. Moreover, the influence of optically inactive ligands on the vicinal CD spectra has been examined, and also the additivity of vicinal CD contributions of two different optically active ligands has been demonstrated.

The electronic absorption and MCD spectra of [PdCl2L] (L=ethylenediamine(en), 1,3-propanediamine, N,N-dimethylethylenediamine, N,N′-dimethylethylenediamine, N,N-diethylethylenediamine, and N,N-dimethyl-1,3-propanediamine) and trans-[PdCl2(L)2] (L=EtNH2, Me2NH, Me3N, n-BuNH2, i-BuNH2, s-BuNH2, t-BuNH2, and rac-pea (pea=1-phenylethylamine)), and CD spectra of [PdCl2L] (L=(S)-1,2-propanediamine-(S-pn) and (2S)-N1,N1-diethyl-1,2-propanediamine) and trans-[PdCl2(S-pea)2] have been measured over the visible-near UV region, together with the corresponding spectra of [PtCl2L] (L=en and S-pn). The examination of the three kinds of spectra as well as their Gaussian analyses indicates that the splitting pattern of metal d orbitals for the cis type complexes is similar to that for [PdCl4]2−, and that as to the trans complexes the dx2−y2←dxz and dyz transitions split largely to give apparent two spin-allowed d-d bands characteristic of the trans complexes. The average energy of the dx2−y2←dxz and dyz transitions for the trans complexes is approximately equal to the energy of the dx2−y2←dxz,yz (D4h) ones for the cis complexes. The transition energies of dx2−y2←dxy and dx2 do not differ largely between both types of complexes. The assignments of high-intensity bands have also been made tentatively.

Several (diamine)(2,9-dimethyl-4,7-diazadecane-2,9-dithiolato)cobalt(III) complexes, [Co(SNNS)(diamine)]+ (diamine=1,2-ethanediamine and (R,R)-1,2-cyclohexanediamine), were prepared and characterized by the visible-UV absorption, circular dichroism(CD), and 13C NMR spectra. The above SNNS quadridentate ligand gave only the cis-β geometrical isomer, which was chromatographically separated into two diastereomers owing to the configurations of chiral nitrogen atoms. All the thiolato and the corresponding sulfinato complexes exhibited two CD bands of opposite signs in the Co(σ*)←S(σ) ligand-to-metal charge transfer band region. The sign pattern was found to be in connection with the absolute configurations of these complexes.

The H2O2 oxidation of [Co(N,N-dimethyldithiocarbamato-S,S′)(en)2]2+ and [Co(2-pyridinethiolato-S,N(en)2]2+ in acid media gave the novel complexes [Co (N,N-dimethylaminothioxomethanesulfinato-S,O)(en)2]2+ and [Co(2-pyridinesulfenato-S,N)(en)2]2+, respectively. The latter S,N-chelated isomer was photochemically converted into the O,N-chelated linkage-isomer [Co(2-pyridinesulfenato-O,N)(en)2]2+, accompanying ring-expansion from a four- to five-membered chelate ring. These complexes were characterized by the absorption, circular dichroism, and X-ray photoelectron spectra.