The solid state and solution chemistry of dichlorobis(pyridine)cobalt(II)

The thermal decomposition of dichlorobisquinolinecobalt(II) was investigated. Kinetic analyses were performed on the dynamic and isothermal curves. The dynamic and d.s.c. studies revealed two simultaneously reactions while the isothermal reactions represented single processes. The scheme of thermal decomposition is:

Crystal Structure Analysis of Tetras[L-tris(ethylenediamine) cobalt(Ⅲ)] tris[hexacyanoruthenate(Ⅱ)]

1 INTRODUCTION The tris(ethylenediamine) cobalt (Ⅲ) complex in which there are L and D configurations is one of the very interest cations due to the chirality among research complexes and the characterization of reaction on the ion-pair charge-transfer transitions. It has been mentioned in a lot of examples on the chirality and the structure, such as [L-Co(en)3]- [?Co(edta)]2Cl?0H2O[1], [(+)DCo(en)3]Cl3稨2O[2], [(+)-Co(en)3?-)-Cr(en)3]Cl?.1H2O[3], [()-Co(en)3] (SCN)3[4], [(+)D…     

Kinetics of the thermal dehydration of trans-fluoroaquobis(ethylenediamine)chromium(III) tetracyanometallate(II) [metal(II) = Ni(II), Pd(II) and Pt(II)]

The solid phase thermal deaquation—anation of trans-[CrF(H₂O)(en)₂][M(CN)₄] (M = Ni, Pd, Pt; en = ethylenediamine) has been investigated by means of non-isothermal DSC and isothermal and non-isothermal TG measurements. The physical model for these reactions (nucleation, growth, diffusion or intermediates) has been found by comparison of the isothermal and non-isothermal TG data for all the principal g(α) expressions (0.2?α?0.8) and by the shape of the isothermal curves. The values found for activation energy are low (～ 130 kJ mol^?1 for the Ni compound, ～ 140 kJ mol^?1 for the Pd compound, and ～ 100 kJ mol^?1 for the Pt compound). These data permit the assignment of the deaquation—anation mechanism of the S_N1 type involving a square-base pyramid activated complex and elimination of water as Frenkel defects.     

Kinetics and mechanism of acid and base hydrolysis ofcis-chloro-(benzotriazole)bis(ethylenediamine)cobalt(III) andcis-chloro-(N-methylbenzotriazole)bis(ethylenediamine)cobalt(III) cations

Summary The kinetics of acid hydrolysis ofcis-[CoCl(btzH)(en)₂]²⁺ andcis-[CoCl(btzMe)(en)₂]²⁺ complexes (where btzH = benzotriazole, btzMe =N-methylbenzotriazole and en = ethylenediamine) have been investigated in HClO₄ at ionic strength 1 = 0.25 mol dm^–3 in the 30–40° range. In the 1.0 x 10^–1 to 1.0 X 10^–3 mol dm^–3 acid strength range, the rate of aquation of the [CoCl(btzH)(en)₂]²⁺ cation follows the relationship:-d ln[complex]/dt = k₁ + k₂K_NH[^H+]^–1, where k₁ and k₂ are aquation rate constants of the acid independent and acid dependent steps respectively, and K_NH is the acid dissociation constant of the coordinated benzotriazole.cis-[CoCl(btzMe)-(en)₂]²⁺ undergoes acid independent hydrolysis presumably due to the absence of a labile N-H proton. The base hydrolysis could be followed for thecis-[CoCl(btzMe)(en)₂]²⁺ complex only by measuring hydrolysis rates at 0°.     

Kinetics of aquation of cis-aquabromo-bis(ethylenediamine) complexes of cobalt(III) and chromium(III) in binary aqueous mixtures

Summary The kinetics of aquation of cis-[Co(en)₂(H₂O)Br]²⁺ and cis-[Cr(en)₂(H₂O)Br]²⁺ (en = ethylenediamine) were investigated in aqueous mixtures of MeOH, EtOH, i-PrOH and t-BuOH. The values of transfer functions corresponding to the transfer of reactants and activated complex from water to the solvent mixtures were evaluated from kinetic measurements and from solubilities of the complex salt. Analysis of the solvent effect confirmed a common I_d mechanism for the aquation of the Co^III and Cr^III complexes.     

Crystal Structure Analysis of Tetras[(-tris(ethylenediamine) cobalt(Ⅲ)] tris[hexacyanoruthenate(Ⅱ)]

The crystal of the title compound, [Co(en)3]4[Ru(CN)6]3(10H2O (en = ethylenediamine, C2H8N2), is formed from the octahedral cations of Co(en)33+ and anions of Ru(CN)64-. The Co atom is coordinated to six nitrogen atoms of ethylenediamines in a ( configuration and the Ru atom is also coordinated to six carbon atoms of cyanides. There is no bridging-cyanide between the metal ions in the structure. The crystal is of monoclinic, space group P21/c with a = 17.686(4), b = 14.496(4), c = 18.019(7) (A。）, β = 116.07(2), V = 4150(2) (A。）3, Z = 2, Mr = 1908.60, C42H116N42O10Co4Ru3, ((MoK() = 1.391 mm-1, Dc = 1.527 g/cm3, F(000) = 2084, R = 0.0520 and wR = 0.1070 for 5443 observed reflections (I > 2((I)).     

Kinetics and mechanism of hydrolysis ofcis-bis(ethylenediamine)imidazole(salicylato)cobalt(III) ion

Summary The kinetics of aquation and base hydrolysis reactions ofcis-[(en)₂Co(imH)O₂CC₆H₄OH-o-o]²⁺ (imH = imidazole) have been investigated in a medium of 1.0 M ionic strength, In the 0,1–1,0 M [H⁺] range (60–70°) aquation proceedsvia spontaneous and acid catalysed paths . In the 0,05–1.0 M [OH^–] range (30–40°), the complex exists predominantly as the bis-deprotonated species,cis-[(en)₂Co(im)O₂CC₆H₄O-o], and the pseudo-first-order rate constant fits the relationship k_obs = k_b + k_b° [OH^–] satisfactorily. The labilizing action of coordinated imidazolate anion(im^–) on the cobalt(III)-bound salicylate is 10³ times stronger than that of imidazole. The mechanism is essentially I_d in the aquation paths and SN₁cb (Co-O bond fission) in the alkali independent and dependent paths respectively.     

On the mechanism of cobalt(III) aminates pyrolysis

Pyrolysis of the complex (ato-N²)pentaammincobalt(III) perchlorate and the ligand 5-nitrotetrazole, and also of the initial complex aquapentaammincobalt(III) perchlorate was studied by the mass spectroscopy method. The leading oxidizer of ligands in the complexes is changed for the outer-sphere perchlorate ion at the pyrolysis temperature of ~250°C.     

Kinetics and mechanism of base hydrolysis oftrans-bis(Hmalonato)bis(ethylenediamine)cobalt(III) ion

Summary The kinetics of the first step of base hydrolysis oftrans-bis(Hmalonato)bis(ethylenediamine)cobalt(III) [malH^–=HO₂CCH₂CO ₂ ^– ] has been investigated in the 15–35° C range, I=0.3 mol dm^–3 (NaClO₄) and [OH^–]=0.015–0.29 mol dm^–3. The rate law is given by –d In[complex]_T/dt=k₁[OH^–] and at 30° C, k₁=8.5×10^–3 dm³ mol^–1s^–1, H=117.0±7.0 kJ mol^–1 and S=99.0±24.0 JK^–1mol^–1. The activation parameters data are consistent with the SN₁ cb mechanism.     

The solid state chemistry of dichlorobis(pyridine)manganese(II) and dichlorobis(pyridine)nickel(II)

Summary The thermal decompositions of [MnCl₂(py)₂] and [NiCl₂(py)₂] were investigated and the following dissociation reactions were observed: [MnCl₂(py)₂](s)MnCl₂(py)(s)+(py)(g) [MnCl₂(py)₂](s)MnCl₂(s)+2(py)(g) and [NiCl₂(py)₂](s)NiCl₂(py)(s)+(py)(g) [NiCl₂(py)₂](s)NiCl₂(s)+2(py)(g). Quantitative thermodynamic as well as kinetic data were obtained by performing dynamic and isothermal studies on the complexes. The DSC studies provided evidence for the existence of the additional intermediates [Ni₃Cl₆(py)₂] and [Mn₃Cl₆(py)₂], which could not be obtained from the dynamic and isothermal studies.     

Two polymorphs of tris(ethylenediamine)cobalt(III) tetrathioantimonate(V)

Details of the structures of two polymorphs of tris(ethylenediamine)cobalt(III) tetrathioantimonate(V), [Co(C₂H₈N₂)₃][SbS₄], are reported. The first polymorph crystallizes in the orthorhombic space group Pna2₁, whereas the second polymorph belongs to the tetragonal space group P4₂bc. Both structures contain octahedral [Co(en)₃]³⁺ cations (en is ethylenediamine) and tetrahedral [SbS₄]³⁻ anions, which are interconnected via various N—H...S hydrogen bonds to form two different types of three‐dimensional network.     

Synthesis,characterization, and mechanism of trans-dichlorido-bis-(ethylenediamine)cobalt(III) with L-cystine in the presence of chloride

Substitution reactions of trans-[CoCl₂(en)₂]Cl (where en?=?ethylenediamine) with L-cystine has been studied in 1.0?×?10^?1?mol?dm^?3 aqueous perchlorate at various temperatures (303–323?K) and pH (4.45–3.30) using UV-Vis spectrophotometer on various [Cl^?] from 0.05 to 0.01?mol?L^?1. The products have been characterized by their physico-chemical and spectroscopic data. Trans-[CoCl(en)₂(H₂O)]²⁺, from the hydrolysis of trans-[CoCl₂(en)₂]⁺ in the presence of Cl^?, formed a complex with L-cystine at all temperatures in 1?:?1 molar ratio. L-cystine is bidentate to Co(III) through Co–N and Co–S bonds. Product formation and reversible reaction rate constants have been evaluated. The rate constants for SN_i mechanism have been evaluated and activation parameters E _a, ΔH ^#, and ΔS ^# are determined.     

Kinetics and mechanism of an unique hydrolysis reaction of (hexafluoroacetylacetonato)bis(ethylenediamine)cobalt(III) in aqueous solution

Summary Addition of base to the title complex results in the rapid reversible formation of the hydrolysed species Co(en)₂-(hfac · OH)⁺ in which the coordinated hexafluoroacetylacetonato ligand contains a hydroxyl group on the carbonyl carbon atom. The kinetics of both the forward hydrolysis and reverse acidolysis reactions were followed spectrophotometrically using stopped-flow and T-jump techniques. The corresponding rate constants areca. 3×106 and 1×10⁸ M^–1s^–1, respectively, for various buffer systems at 25 °C and ionic strength 1.0 M. A combination of the kinetic and equilibrium data enables the estimation of the uncatalyzed (spontaneous) forward and reverse reaction components. The results are discussed with reference to similar data reported for the hydrolysis and reverse acidolysis reactions of the uncoordinated acetylacetonato ligand.     

Salt and medium effects in the aquation ofcis-amminebromobis(ethylenediamine)cobalt(III) ion

Summary The aquation kinetics ofcis-[Co(NH₃)Br(en)₂]²⁺ were studied in aqueous and mixed aqueous-nonaqueous solvents in the presence of KBr, KCl, LiCl, NaNO₃ and NaClO₄ as supporting electrolytes. It was found that the association between the complex ion and Cl^–, Br^– and NO ₃ ^– ions takes place. The association constants, K_IP, were evaluated from kinetic measurements. The kinetic parameters in the studied media are related to the influence of the cosolvents on the solvation spheres of the reactants and activated complex.     

Kinetics and mechanism of acid catalysed dissociation of some octahedral complexes of cobalt(III) and chromium(III)

Summary The kinetics of dissociation of glycinepentaamminecobalt(III) and tetraaquomonoacetylacetonatochrormium(III) ions in moderately strong perchloric acid media have been investigated spectrophotometrically. From the dependence of the rate on various acidity functions and the observed isokinetic and free energy relationships, both the complexes appear to react by an associative process involving interaction of the conjugate acid form of the substrate complex and H₃O⁺.