Tadashi Tokii

Bio: Tadashi Tokii is an academic researcher from Saga University. The author has contributed to research in topics: Copper & Crystal structure. The author has an hindex of 27, co-authored 226 publications receiving 2853 citations. Previous affiliations of Tadashi Tokii include Kwansei Gakuin University & Keio University.

1,3-Bis(salicylideneamino)-2-propanol as the ligand for manganese(III) ions

Abstract: Reaction of 1,3-bis(salicylideneamino)-2-propanol (H3L) with manganese(II) acetate tetrahydrate in the presence of ethylenediamine and sodium thiocyanate give a salen complex [Mn(salen)(NCS)] (H2salen = N,N′-disalicylideneethylenediamine), while that in the presence of water and triethylamine gives a binulear manganese(III) complex [Mn2(L)2(H2O)]·3CH3OH. Both complexes have been characterized by X-ray crystal structure analyses, electronic spectra, and magnetic susceptibilities.

Structural, magnetic and spectroscopic characterization of novel di-μ-carboxylato-bridged binuclear copper(II) complexes with 1,10-phenanthroline

Abstract: Bis(μ-carboxylato-O,O′)-diaquabis(1,10-phenanthroline)dicopper(II) dinitrate tetrahydrates, [Cu(RCOO)(phen)(H2O)]2(NO3)2·4H2O, where R=H, CH3, and (CH3)3C, were prepared and characterized by elemental analyses, electronic spectra, magnetic susceptibilities, and X-ray structure analysis. The magnetic susceptibility data conform to the usual dimer equation. The −2J values are 125 cm−1 for formate, 86 cm−1 for acetate, and 99 cm−1 for 2,2-dimethylpropanoate. The crystal structures of [Cu(HCOO)(phen)(H2O)]2(NO3)2·4H2O (1) and [Cu(CH3COO)(phen)(H2O)]2(NO3)2·4H2O (2) were determined by the single-crystal X-ray diffraction method. The crystallographic data are: Compound 1, monoclinic, I2⁄a, a=18.850(2), b=9.775(2), c=17.752(2) A, β=99.03(1)°, V=3230.4(8) A3, Z=4, R=0.055 for 2511 observed unique reflections; Compound 2, monoclinic, C2⁄c, a=18.563(4), b=14.272(5), c=14.126(3) A, β=106.72(2)°, V=3584(2) A3, Z=4, R=0.082 for 2092 reflections. The complexes consist of dimeric [Cu(RCOO)(phen)(H2O)]22+)] cations with ...

Synthesis, properties, and crystal structures of a series of dinuclear manganese(III) complexes with 1,5-bis(salicylideneamino)3-pentanol and various anions : formation of a tetranuclear manganese(III) complex

Abstract: μ-Alkoxo-bridged dinuclear and tetranuclear manganese(III) complexes with 1,5-bis(salicylideneamino)-3-pentanol (H3L), [Mn2(L)(CH3O)Cl2(CH3OH)2] (1), [Mn2(L)(CH3O)(CH3COO)(CH3OH)2]X (X = Br (2), I (3)), [Mn2(L)(CH3O)(CH3COO)(CH3OH)Y] (Y = NCS (4), N3 (5), ClO4 (6)), [Mn2(L)(CH3O)(NCO)2(H2O)2] (7), and [Mn4(L)2(O)2(CH3COO)2]·4H2O·2CH3OH (8) have been prepared and characterized by infrared and electronic spectra, magnetic susceptibilities, and cyclic voltammetry. The molecular structures of 1–5, 7, and 8 were determined by the single-crystal X-ray structure analyses. All the complexes except for 8 have a similar structure, where Cl−, CH3COO−, N3−, NCS−, CH3OH, or H2O is incorporated into the fifth or sixth coordination site on the Mn2(L)(CH3O) plane. The structure of 8, is a tetramer consisting of two Mn2(L)(O)(CH3COO) dimeric units held together through the oxo ions and the phenoxo-oxygen atoms of L. The spectral and magnetic properties were discussed in relation to the crystal structures.

The heck reaction as a sharpening stone of palladium catalysis.

Abstract: s, or keywords if they used Heck-type chemistry in their syntheses, because it became one of basic tools of organic preparations, a natural way to

Activation of c-h bonds by metal complexes

Abstract: ion. The oxidative addition mechanism was originally proposed22i because of the lack of a strong rate dependence on polar factors and on the acidity of the medium. Later, however, the electrophilic substitution mechanism also was proposed. Recently, the oxidative addition mechanism was confirmed by investigations into the decomposition and protonolysis of alkylplatinum complexes, which are the reverse of alkane activation. There are two routes which operate in the decomposition of the dimethylplatinum(IV) complex Cs2Pt(CH3)2Cl4. The first route leads to chloride-induced reductive elimination and produces methyl chloride and methane. The second route leads to the formation of ethane. There is strong kinetic evidence that the ethane is produced by the decomposition of an ethylhydridoplatinum(IV) complex formed from the initial dimethylplatinum(IV) complex. In D2O-DCl, the ethane which is formed contains several D atoms and has practically the same multiple exchange parameter and distribution as does an ethane which has undergone platinum(II)-catalyzed H-D exchange with D2O. Moreover, ethyl chloride is formed competitively with H-D exchange in the presence of platinum(IV). From the principle of microscopic reversibility it follows that the same ethylhydridoplatinum(IV) complex is the intermediate in the reaction of ethane with platinum(II). Important results were obtained by Labinger and Bercaw62c in the investigation of the protonolysis mechanism of several alkylplatinum(II) complexes at low temperatures. These reactions are important because they could model the microscopic reverse of C-H activation by platinum(II) complexes. Alkylhydridoplatinum(IV) complexes were observed as intermediates in certain cases, such as when the complex (tmeda)Pt(CH2Ph)Cl or (tmeda)PtMe2 (tmeda ) N,N,N′,N′-tetramethylenediamine) was treated with HCl in CD2Cl2 or CD3OD, respectively. In some cases H-D exchange took place between the methyl groups on platinum and the, CD3OD prior to methane loss. On the basis of the kinetic results, a common mechanism was proposed to operate in all the reactions: (1) protonation of Pt(II) to generate an alkylhydridoplatinum(IV) intermediate, (2) dissociation of solvent or chloride to generate a cationic, fivecoordinate platinum(IV) species, (3) reductive C-H bond formation, producing a platinum(II) alkane σ-complex, and (4) loss of the alkane either through an associative or dissociative substitution pathway. These results implicate the presence of both alkane σ-complexes and alkylhydridoplatinum(IV) complexes as intermediates in the Pt(II)-induced C-H activation reactions. Thus, the first step in the alkane activation reaction is formation of a σ-complex with the alkane, which then undergoes oxidative addition to produce an alkylhydrido complex. Reversible interconversion of these intermediates, together with reversible deprotonation of the alkylhydridoplatinum(IV) complexes, leads to multiple H-D exchange