Yoshiharu Nakano

The first isolation of unsubstituted porphyrinogen and unsubstituted 21-oxaporphyrinogen by the ‘3+1’ approach from 2,5-bis(hydroxymethyl)pyrrole and tripyrrane derivatives

Abstract The treatment of 2,5-bis(hydroxymethyl)pyrrole or 2,5-bis(hydroxymethyl)furan with pyrrole in the presence of hydrochloric acid gave tripyrrane and 2,5-bis(2-pyrrolylmethyl)furan in 58–61% yield, which afforded the simplest porphyrinogen (hexahydroporphine) and 21-oxaporphyrinogen by the ‘3+1’ approach in 14 and 11% yields, respectively. 21-Oxaporphyrinogen has been shown to adopt a 1,2-alternated conformation in the solid state by X-ray crystallography.

Effect of the Introduction of Amide Oxygen into 1,10-Phenanthroline on the Extraction and Complexation of Trivalent Lanthanide in Acidic Condition

The extractability and complexation properties of lanthanides with N-alkyl-N-phenyl-1,10-phenanthroline-2-carboxamide were investigated. These ligands, which contain two aza-aromatic donors and an oxygen donor in a molecule, are newly developed extractants for actinides and lanthanides. N-Octyl-N-tolyl-1,10-phenanthroline-2-carboxamide exhibited high extractability of Eu3+ even under acidic conditions. In addition, strong complexation in acidic media was confirmed by spectroscopic titration experiments. Investigation of the complexation equilibrium revealed that the presence of an oxygen donor promotes ligand coordination with lanthanides over the competing protonation reaction in acidic solution.

Phenyl substitution reactions of 3-bromo-2,4-pentanedionato complexes

Phenyl substitution reactions of 3-bromo-2,4-pentanedionate metal (M=Cr and Co) complexes catalyzed by palladium (Suzuki coupling reaction) were carried out. Variously substituted products were identified by standard spectroscopic methods. In order to confirm the products, crystal structures of the several products were determined by the X-ray diffraction method.

New type of atropisomerism in metal complexes. Preparation and resolution of (3,4-diacetyl-2,5-hexanedionato)bis[(2,2',2"-triaminotriethylamine)cobalt(III)] ion.

A metal complex, (3,4-diacetyl-2,5-hexanedionato)bis[(2,2’,2’’triaminotriethylamine)cobalt(II1)] ion, was prepared and optically resolved. T h e optical resolution of the complex confirmed the expected novel twin structure and presented a new type of atropisomer in coordination chemistry. The optical absorption and circular dichroism a r e discussed in connection with the absorption spectrum of the related complex, (2,4-pentanedionato)(2,2’,2”-triaminotriethylamine)cobalt(III) ion, which corresponds to half of the above twin structure. Recently, several metal complexes having a new type of chiral source (restricted rotation) have been reported t h a t possess chirality different from those of traditional types which are confined mostly to the class of c e n t r o d i s ~ y m m e t r y . ~ Utsuno reported a propeller-like, fixed chiral conformation of pyridine rings in t h e trans-dichlorotetrakis(pyridine)cobalt(III) ion! We have reported t h e optical isomerism of a series of Co”’(tren) complexes of 3aryl-2,4-pentanedione, the chirality of which comes from restricted rotation of an ary l groups5 Figure 1 shows a typical example. In the present study, a new type of atropisomerism is reported. The twin complex [[Co(tren)l2taeI4+ (Figure 2) is the first example of an atropisomer in binuclear metal complexes.6 Although this complex may be only an extension of this series, since a different ligand is introduced into t h e [Co(acac)trenI2+ system instead of the aryl group in the above series, it is unique because it contains no unnecessary moiety and therefore shows genuine electronic transitions of t h e [Co(acac)trenI2+ chromophore. Thus, t h e title complex gives important information about the electronic s ta tes of [Co(acac)tren] 2+. Experimental Sect ion Instruments. Circular dichroism, IR, UV-visible, IH NMR, and ”C N M R spectra were measured with JASCO Model 5-500, Hitachi 295, Hitachi 200-10, Hitachi R-20, and JEOL JNM-FX60 spectrometers, respectively. Elemental analyses were carried out with a YANACO MT02 CHN-order. Preparations. (a) (2,4-Pentanedionato)(2,2’,2”-triaminotriethylamine)cobalt(III). A mixture of [Co(C03)tren]CI04.1 (5.5 g, 14 mmol)’ and 2 N hydrochloric acid solution (20 mL) was stirred for one-half hour. To this solution were added acetylacetone (4 mL) and 1 N sodium hydroxide solution (30 mL). The mixture was kept at 60-80 OC for 2 h under stirring. After the mixture cooled, potassium iodide (18.4 g, 0.1 1 mol) was added to give a red precipitate, yield 7.6 g (87%). A small amount of the complex was purified by means of cation-exchange chromatography using an SP-Sephadex column and 0.5 N sodium chloride solution as the eluent. After most of the sodium chloride was removed from the eluted solution of [Co(acac)trenI2+, excess sodium bromide was added to the resulting solution. The precipitate was recrystallized from water: IR 1520 and 1570 cm-’; IH N M R d 2.12, 2.20 (two kinds of methyl protons of the acetylacetonate ring), and 5.73 ’ Ibaraki University. * Okayama University. Previous address: Department of Chemistry, Faculty of Science, Nagoya University, Chikusa-ku, Nagoya 464, Japan. 0002-786318611508-7630

Ligand exchanging reactions of M(acac)3 (M=Cr or Co) in Lewis acidic conditions

01.50/0 (methine proton of the acetylacetonate ring). Anal. Calcd for C,,H2,N402CoBr2-3H20; C , 25.50; H, 6.03; N, 10.81. Found: C, 25.79; H, 6.28; N , 11.10. (b) (3,4-Diacetyl-2,5-hexanedionato)bis[(2,2’,2’’-triaminotriethylamine)cobalt(III)]. A reaction of [Co(CO3)trenl2+ (1 .O equiv) with H

The crystal structures of glycylglycine and glycine complexes of cis,cis-1,3,5-triaminocyclohexane–copper(II) as reaction intermediates of metal-promoted peptide hydrolysis

ae (0.5 equiv)8 similar to the preparation of [Co(acac)trenI2+ described above gave a solution of crude [ { C ~ ( t r e n ) ] ~ t a e ] ~ + . Sodium perchlorate (6-8 q u i v ) was added to the solution. The precipitate was filtered and recrystallized from water, yield 34%. The complex was often contaminated with brown impurities and therefore purified by means of ion-exchange chromatography. IR 1560 cm-I; IH N M R 6 2.10, 2.17 (CH3 of the acac ring), and 2.5-3.8 (CHI of the tren chain). Anal. Calcd for CzzH48C14C02N8020~2H20: C, 25.40; H, 5.40; N, 10.77. Found: C, 25.10; H, 5.10; N, 10.50. Optical Resolution of [{Co(tren)lZtae]4’. A previous communication reported the partial resolution of the complex by means of ion-exchange chromatography using a sodium D-tartrate solution as the eluent.6 A better result is obtained when the complex is recycled 7 times through an SP-Sephadex column (4.5 cm in diameter and 90 cm in length) using a 0.275 M solution of sodium D-tartratoantimonate(II1) as the eluent. Although the eluted fraction does not separate as two bands, we were able to obtain the enantiomeric isomers from the head and tail fractions which show a constant ratio of circular dichroism intensity to absorption coefficient. The head fractions show a negative sign at the lowest energy region (A€ = -0.57 at 18.42 X IO3 cm-I), and tail fractions show a positive sign (As = +0.55 at the same position). The concentration of the aqueous solution for the measurement of CD spectra was obtained from the calibration curve of the purified racemate. Results and Discussion Character izat ion of [Co(acac)trenI2+. T h e infrared spectrum of t h e complex showed two s t rong peaks a t 1520 a n d 1570 cm-I (1) The following abbreviations were used throughout this paper; tren for 2,2’,2”-triaminotriethylamine, acacH for acetylacetone, en for ethylenediamine, tae for tetraacetylethane. (2) This work was preliminarily communicated in this journal (ref 6) and represents a portion of Nakano Y. Doctoral Thesis, The University of Tsukuba. (3) Hawkins, C. J. Absolute Configuration of Metal Complexes; Wiley: New York, 1971. (4) Utsuno, S. J . Am. Chem. SOC. 1982, 104, 5846. (5) (a) Nakano, Y.; Sato, S . Inorg. Chem. 1982, 21, 1315. (b) Nakano, (6) Nakano, Y.; Yoshikawa, Y. J. Am. Chem. SOC. 1984, 106, 429. (7) Kimura, E.; Young, S.; Collman, J . P. Inorg. Chem. 1970, 9, 1183. (8) Charles, R. C. Organic Synthesis; Wiley: New York, 1963; Collect. Y. Bull. Chem. SOC. Jpn. 1982, 55, 1683.

COMPLETE CHROMATOGRAPHIC RESOLUTION OF AXIALLY CHIRAL β-DIKETONATE COMPLEXES ON CELLULOFINE C-200 [1]

Abstract Ligand exchanging reactions of tris(2,4-pentanedionato)M (M=Cr or Co) complexes with various bidentate under Lewis acidic conditions gave mixed metal complexes, bis(2,4-pentanedionato)ML (L=bidentate ligand) selectively. In the case of Cr(acac)3, intermediate cis-[Cr(acac)2(H2O)2]BF4 complex was isolated and the crystal structure of the intermediate complex was determined. Various mixed complexes of the type, [M(acac)2L] (M=Cr or Co, L=various bidentate ligands) could be prepared by means of one pot synthesis via the above intermediate. Among the reactions, the most interesting was that of ethoxymethylenemalonate. Isolated complexes were same type complexes from the reactions of chromium and cobalt complexes.

Photopromoted oxidative cyclization of an o -phenylene-bridged Schiff base via a manganese( III ) complex, leading to a fluorescent compound, 2-(2-hydroxyphenyl)benzimidazole

The glycylglycine and glycine complexes of cis,cis-1,3,5-triaminocyclohexane–copper(II), model reaction intermediates of peptide hydrolysis by CuII–triamine complexes, have been synthesized and characterized by X-ray crystallography.

A new type of atropisomeric cobalt(III) complex

Abstract New chromatography on Cellulofine C-200 (modified polysaccharide ion exchanger) completely resolved the atropisomers reported previously [2]. The present technique needs no optically active eluting agents, differing from conventional chromatography on SP-Sephadex. The chromatographed atropisomers, axially chiral β-diketonate cobalt(III)-tren complexes, are listed in the table in the text.

SYNTHESIS OF NEW CATIONIC SCHIFF BASE COMPLEXES OF COPPER(II) AND THEIR SELECTIVE BINDING WITH DNA

Visible light photolysis of [N,N′-o-phenylenebis-(salicylideneaminato)]diaquamanganese(III) resulted in the fluorescent compound 2-(2-hydroxyphenyl)benzimidazole by a one electron redox reaction between MnIII and the Schiff base ligand, followed by the base-hydrolysis of the oxidized Schiff base, and then the cyclization of the base-hydrolyzed product.