Ryokichi Tsuchiya

Thermal square planar-to-octahedral transformation of nickel(II) complexes containing butanediamines in a solid phase

Abstract Thermal reactions of the nickel(II) complexes, [Ni(m-bn or i-bn)2]X2 and [Ni(H2O)2(dl-bn)2]X2·n H2O, where m-bn, i-bn, and dl-bn are meso-2,3-butanediamine, 2-methyl-1,2-propanediamine, and dl-2,3-butanediamine, respectively, X is Cl−, Br−, I−, NO−3, or ClO−4, and n is 2 for bromide, and 0 for the others, were investigated in a solid phase before and after heating using thermal analyses (TG and DSC) and spectral and magnetic measurements. In the case of the chloride and bromide, the square planar bis(dl-bn) complexes obtained by dehydration of the respective diaqua complexes were transformed to the octahedral diacido bis(dl-bn) complexes upon further heating. The same structural transformation was observed in the thermal reactions of [Ni(m-bn)2](NO3)2 and [Ni(i-bn)2]Cl2. It was summarily recognized that such square planar-to-octahedral transformation was favored in the order dl-bn > i-bn > m-bn complexes in the respective halides, and it was a reversible thermochromism from yellow to blue. The changes in enthalpy of the reactions were endothermic and fell in the range of about 10–20 kJ mole−1. The possibility of such configurational change seems to be dependent mainly upon the ionic radius of the X anion, the orientation of two C-substituted methyl groups on butanediamines in the formation of the complexes, and the thermal stability of the complexes themselves.

Derivatographic studies on transition metal complexes: XIV. Thermal isomerization of trans-[CoBr2pn2](H5O2)Br2 in solid phase

Abstract Thermal isomerization of trans -[CoBr 2 pn 2 ](H 5 O 2 )Br 2 to the cis -form complex in the solid phase was studied by means of derivatographic and isothermal measurements. It was found that the rate constant of isomerization is larger than that of dehydration and dehydrobromination in the initial step of the reaction, different from the case of trans -[CoCl 2 pn 2 ](H 5 O 2 )Cl 2 . Another distinction was that anhydrous trans -[CoBr 2 pn 2 ]Br does not isomerize to the cis -form.

Derivatographic studies on transition metal complexes XV. Thermal isomerization of trans-[CrBr2pn2]Br.H2O in solid phase

Abstract The thermal trans -to- cis isomerization of [CrBr 2 pn 2 ]Br·H 2 O in a solid phase was studied by means of both derivatography and isothermal measurement. It was found that trans -[CrBr 2 pn 2 ]Br·H 2 O undergoes isomerization to the cis -complex by about 10% with complete dehydration followed by isomerization of the residual trans complex in the anhydrous state. It was characteristic of the complex, trans -[CrBr 2 pn 2 ]Br·H 2 O, that the thermal dehydration was remarkably rapid in comparison with that of the trans -[CoCl 2 pn 2 ](H 5 O 2 )Cl 2 and the isomerization of the cis complex occurred even in the anhydrous state though it did not in the corresponding cobalt(III) complex trans -[CoBr 2 pn 2 ](H 5 O 2 )Br 2 in an analogous state.

Phase transition and electrical properties of mono-, di-, tri- and tetraalkyl (or aryl) ammonium tetrahalogenocuprates(II)

Abstract The following four series of organoammonium tetrahalogenocuprates(II) were systematically prepared: (RNH 3 ) 2 CuX 4 , (R 2 NH 2 ) 2 CuX 4 , (R 3 NH) 2 CuX 4 and (R 4 N) 2 CuX 4 (where R = alkyl or aryl group; X = bromide or chloride ion). Their phase transitions and electrical properties were investigated by means of DTA, DSC, electrical conductivity measurements, and IR and UV spectrophotometries.

Thermal cis—trans isomerization of bis(diamine) cobalt(III) and chromium(III) complexes in a solid phase

Abstract Thermal cis—trans isomerization of the simple bis(diamine) complexes [MX 2 (aa or bb) 2 ]X · HX · n H 2 O and the mixed bis(diamine) complexes [MX 2 (aa)(bb)]X · HX · n H 2 O was investigated in a solid phase, where M = Co(III) or Cr(III) ion, X = Cl or Br, aa and bb are one of the diamines selected from ethylenediamine (en), d, l -1,2-propane-diamine (pn), d,l -2,3-butanediamine ( dl -bn), d,l -1,2-cyclohexanediamine (chxn), 1,3-propanediamine (ln) and d,l -2,4-pentanediamine (ptn), and n = 0–2. The information obtained may be summarized as follows. (1) The features of isomerization are considerably dependent upon the kind of metal ions, halide ions and diamines contained in the complexes. (2) Trans-cis isomerization was identified in the simple bis(diamine) complexes containing en, pn, dl -bn or chxn which can form five-membered chelate rings with metal ions, whereas cis-trans isomerization was detected in the simple bis(diamine) complexes containing tn or ptn which forms six-membered rings; all the mixed bis(diamine) complexes isomerize from trans to cis even when they have a combination of five- and six-membered chelate rings. (3) The cobalt(III) complexes isomerize in a temperature range of dehydration and/or dehydrohalogenation with activation energies of about 100 kJ mole −1 , whereas the chromium(III) complexes usually isomerize in the anhydrous state and the activation energies amount to as much as 150–190 kJ mole −1 . (4) “Aquation-anation” and “bond rupture” were proposed for the isomerization of the cobalt(III) and the chromium(III) complexes, respectively.

Derivatographic studies on transition metal complexes. XII. Thermal isomerization of trans-[CrBr2en2]Br·H2O and cis-[CrBr2tn2]Br·2 H2O in the solid phase☆☆☆

Abstract The thermal trans-to-cis isomerization of trans-[CrBr2en2]Br·H2O and cis-to-trans isomerization of cis-[CrBr2tn2]Br·2 H2O were studied by means of derivatographic and isothermal measurements. In both cases isomerization took place in anhydrous state after the complete dehydration. The activation energies for dehydration of the above two complexes were evaluated isothermally to be 61 and 38 kJ mole−1, respectively, and for their isomerization to be 420 and 275 kJ mole−1, respectively. These data were compared with those for the corresponding chloro complexes and the ease of isomerization between them was discussed.

Thermal reaction of five-coordinated nickel(ii) complexes containing N,N-BIS[2-(dimethylamino)ethyl]methylamine in the solid state

Abstract The following two types of 5-coordinated nickel(II) complexes of N,N -bis[2-dimethyl-amino)ethyl] methylamine (PMDN) were prepared; [NiX(NH 3 )pmdn]X· n H 2 O where X: Cl, Br or I; n : 0 or 1, and [Ni(A) 2 pmdn]X 2 where A: NH 3 or CH 3 CN; X: ClO 4 or BF 4 . In the solid-phase thermal reaction of [NiX(NH 3 )pmdn]X, the complexes evolved 1 mol of ammonia to undergo anation. On the other hand, the compounds [Ni(A) 2 pmdn]X 2 were found to evolve 1 mol of A to convert into square planar complexes.

Solid-phase thermal dehydrochlorination of tetrachlorocobaltates(II)

The following complexes of the type H2L[CoCl4] were prepared, where L is 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), 4,4′-dimethyl-2,2′-bipyridine (4,4′-dmbpy), 5,5′-dimethyl-2,2′-bipyridine (5,5′-dmbpy) or 4,4′,5,5′-tetramethyl-2,2′-bipyridine (tmbpy). The thermal dehydrochlorination of the complexes in the solid-phase was investigated under quasi-isothermal and -isobaric conditions (Q-conditions) and under dynamic conditions (D-conditions). (H2bpy)[CoCl4] and (H2phen)[CoCl4] evolved two moles of hydrogen chloride to convert first into the octahedral polymer α-[CoCl2(L)] and then the tetrahedral monomer β-[CoCl2(L)]. The other three complexes underwent dehydrochlorination to convert into the β-species without the formation of the α-species. The initiation temperatures of dehydrochlorination were 110°C for tmbpy, 115°C for 5,5′-dmbpy, 120°C for phen, and 130°C for bpy and 4,4′-dmbpy complexes. The kinetic parameters such as activation energy, frequency factor and activation entropy were estimated for the reactions.