Reactions of (Hydroxo)aluminium(III)tetra(4-chloro)phthalocyanine in Sulfuric Acid

Spectrophotometric and quantum-chemical data showed that (hydroxo)aluminium(III)tetra(4-chloro)phthalocyanine forms one protonated form (trans-dication) in aqueous concentrated H₂SO₄. The kinetics of the protonated complex dissociation across the Al–N bonds is studied. The effect of the halogen substitution in the aluminium phthalocyanine macrocycle on its basicity and stability is discussed.     

Reactions of Nitro and Halonitro Derivatives of Aluminum(III) and Copper(II) Phthalocyanines with Concentrated Sulfuric Acid

Transformations of the complexes CuPc(4-NO₂)₄, CuPc(4-Br)₄(5-NO₂)₄, (OH)AlRs(4-NO₂)₄, and (OH)AlPc(4-Cl)₄(5-NO₂)₄ in concentrated sulfuric acid were studied by spectrophotometry. One protonated form of CuPc(4-Br)₄(5-NO₂)₄ and (OH)AlPc(4-NO₂)₄ and two protonated forms of CuPc(4-NO₂)₄ and (OH)AlPc(4-Cl)₄(5-NO₂)₄ were detected experimentally and also by ZINDO1 calculations. Step protonation constants of CuPc(4-NO₂)₄ and (OH)AlPc(4-Cl)₄(5-NO₂)₄ were determined by quantum-chemical calculations and acid-base titration; these complexes can be regarded as weak bases with respect to H₂SO₄. The kinetics of dissociation of the complexes at the MÄN bonds were studied. The rate of dissociation of the Cu(II) complexes and (OH)AlPc(4-NO₂)₄ is proportional to [MPc(R) _n ] and [H₃O⁺]². The rate of dissociation of (OH)AlPc(4-Cl)₄(5-NO₂)₄ showed a weak extremal dependence on the composition of the medium, which was explained by change of its structure in 17.0 M H₂SO₄. The electronic effect of substituents on the reaction center was considered with account taken of a complex mechanism of activation and fine details of the molecular structure of macrocyclic complexes.     

Structure and properties of tetrakis[3(4)-chlorophthalocyaninato]copper(II) protonated forms in the isolated state and in the sulfuric acid solutions

Results of the quantum-chemical PM3 and experimental spectrophotometric studies of the stepwise protonation of tetrakis[3(4)-chlorophthalocyaninato]copper(II) are presented. The number, structure, and energy characteristics of consecutively protonated isolated molecules of the substituted complexes have been determined; the stability and electron absorption spectra of the complexes protonated forms in concentrated sulfuric acid solution have been studied. The special effect of substitution with halogen on the electronic structure of the exocyclic nitrogen atoms of (phthalocyaninato)copper(II) has been examined.     

Effect of Inter‐Porphyrin Distance on Spin‐State in Diiron(III) μ‐Hydroxo Bisporphyrins

The synthesis, structure, and properties of bischloro, μ‐oxo, and a family of μ‐hydroxo complexes (with BF₄^?, SbF₆^?, and PF₆^? counteranions) of diethylpyrrole‐bridged diiron(III) bisporphyrins are reported. Spectroscopic characterization has revealed that the iron centers of the bischloro and μ‐oxo complexes are in the high‐spin state (S=⁵/₂). However, the two iron centers in the diiron(III) μ‐hydroxo complexes are equivalent with high spin (S=⁵/₂) in the solid state and an intermediate‐spin state (S=³/₂) in solution. The molecules have been compared with previously known diiron(III) μ‐hydroxo complexes of ethane‐bridged bisporphyrin, in which two different spin states of iron were stabilized under the influence of counteranions. The dimanganese(III) analogues were also synthesized and spectroscopically characterized. A comparison of the X‐ray structural parameters between diethylpyrrole and ethane‐bridged μ‐hydroxo bisporphyrins suggest an increased separation, and hence, less interactions between the two heme units of the former. As a result, unlike the ethane‐bridged μ‐hydroxo complex, both iron centers become equivalent in the diethylpyrrole‐bridged complex and their spin state remains unresponsive to the change in counteranion. The iron(III) centers of the diethylpyrrole‐bridged diiron(III) μ‐oxo bisporphyrin undergo very strong antiferromagnetic interactions (J=?137.7 cm^?1), although the coupling constant is reduced to only a weak value in the μ‐hydroxo complexes (J=?42.2, ?44.1, and ?42.4 cm^?1 for the BF₄, SbF₆, and PF₆ complexes, respectively).     

Structure of tetrakis(pyridinioacetate) neodymium(III) tetrahydrate perchlorate

The structure of tetrakis(pyridinioacetate) neodymium(III) tetrahydrate perchlorate, [Nd(pyBET)₄ · 4H₂O](ClO₄)₃, is reported. The neodymium atom is eight-coordinate dodecahedrally distorted polyhedron. The molecule consists of discrete [Nd(pyBET)₄ · 4H₂O]³⁺ cation and perchlorate anions held by ionic electrostatic force.     

Comparative electrooxidation of nitrite by electrodeposited Co(II), Fe(II) and Mn(III) tetrakis (benzylmercapto) and tetrakis (dodecylmercapto) phthalocyanines on gold electrodes

This work reports on the electrooxidation of nitrite using Co(II), Fe(II) and Mn(III) tetrakis (benzylmercapto) and tetrakis (dodecylmercapto) phthalocyanines electrodeposited onto a gold electrode. Good catalytic activity (in terms of lowering overpotential) was obtained for these molecules when compared to previously reported MPc catalysts. The catalytic current was found to vary linearly with nitrite concentration in the range employed in this work (0.1-1 mM) and high sensitivities ranging from 6.9 to 9.9 μA mM⁻¹ were observed for all the modified electrodes.     

2:2 Fe(III):ligand and "adamantane core" 4:2 Fe(III):ligand (hydr)oxo complexes of an acyclic ditopic ligand

A bis-hydroxo-bridged diiron(III) complex and a bis-mu-oxo-bis-mu-hydroxo-bridged tetrairon(III) complex are isolated from the reaction of 2,6-bis((N,N'-bis-(2-picolyl)amino)methyl)-4-tert-butylphenol (Hbpbp) with iron perchlorate in acidic and neutral solutions respectively. The X-ray structure of the dinuclear complex [{(Hbpbp)Fe([mu-OH)}(2)](ClO(4))(4).2C(3)H(6)O (1.2C3H6O) shows that only one of the metal-binding cavities of each ligand is occupied by an iron(III) atom and two [Fe(Hbpbp)]3+ units are linked together by two hydroxo bridging groups to form a [Fe(III)-(mu-OH)](2) rhomb structure with Fe...Fe = 3.109(1)A. The non-coordinated tertiary amine of Hbpbp is protonated. Magnetic susceptibility measurements show a well-behaved weak antiferromagnetic coupling between the two Fe(III) atoms, J= -8 cm(-1). The tetranuclear complex [(bpbp)(2)Fe(4)(mu-O)(2)(mu-OH)(2)](ClO(4))(4)(2) was isolated as two different solvates .4CH(3)OH and .6H(2)O with markedly different crystal morphologies at pH ca. 6. Complex .4CH(3)OH forms red cubic crystals and .6H(2)O forms green crystalline platelets. The Fe(4)O(6) core of shows an adamantane-like structure: The six bridging oxygen atoms are provided by the two phenolato groups of the two bpbp(-) ligands, two bridging oxo groups and two bridging hydroxo groups. The hydroxo and oxo ligands could be distinguished on the basis of Fe-O bond lengths of the two different octahedral iron sites: Fe-mu-OH, 1.953(5), 2.013(5)A and Fe-mu-O, 1.803(5), 1.802(5)A. The difference in ligand environment is too small for allowing Mossbauer spectroscopy to distinguish between the two crystallographically independent Fe sites. The best fit to the magnetic susceptibility of .4CH(3)OH was achieved by using three coupling constants J(Fe-OPh-Fe)= 2.6 cm(-1), J(Fe-OH-Fe)=-0.9 cm(-1), J(Fe-O-Fe)=-101 cm(-1) and iron(III) single ion ZFS (|D|= 0.15 cm(-1)).     

Two tetrakis(benzoylacetonato)lanthanide species: synthesis,characterization and structures of tetrakis(benzoylacetonato)cerium(IV) and triethylammonium tetrakis(benzoylacetonato)lanthanate(III) tetrahydrate

Tetrakis(benzoylacetonato)cerium(IV), [Ce(bzac)₄] and triethylammonium tetrakis(benzoylacetonato)lanthanate(III) tetrahydrate, [Et₃NH][La(bzac)₄] · 4H₂O were prepared and characterized by TG and DCS measurements, IR spectroscopy, and X-ray structure analysis. The coordination polyhedron of cerium is a trigonal dodecahedron, while that of lanthanum is a distorted square antiprism. Thermal and spectroscopic measurements indicate that bonding of the ligand to metal is stronger in [Ce(bzac)₄] than in [La(bzac)₄]^?.     

Monomeric iron(II) hydroxo and iron(III) dihydroxo complexes stabilized by intermolecular hydrogen bonding

Using the multidentate ligand bis(N-methylimidazol-2-yl)-3-methylthiopropanol (L), the mononuclear iron(II) hydroxo and iron(III) dihydroxo complexes [Fe(II)(L)2(OH)](BF4) (1) and [Fe(III)(L)2(OH)2](BF4) (2) have been synthesized and characterized by X-ray diffraction and spectroscopic methods. The X-ray data suggest that the remarkable stability of the Fe-OH bond(s) in both compounds results from intermolecular hydrogen-bonding interactions between the hydroxo ligand(s) and the tertiary hydroxyl of the L ligands, which prevent further intermolecular reactions.     

Syntheses and structural analyses of nine-coordinate protonated (Py)2[GdIII(HNta)(Nta)(H2O)] · 5H2O and eight-coordinate (NH4)3[HoIII(Nta)2] complexes

The syntheses and structural determination of Gd(III) and Ho(III) complexes with nitrilotriacetic acids (Nta) were reported in this paper. Their structures and compositions were determined and characterized by single-crystal X-ray structure analyses, elemental analyses, and IR spectra. The first protonated Nta complex was found. Structural analyses indicate that the structure greatly changes, while an alternative Nta ligand was protonated in the ((Py)₂[Gd^III(HNta)(Nta)(H₂O)] · 5H₂O complex and the(NH₄)₃[Ho^III(Nta)₂] complex crystallized as a centrosymmetric structure. By contrast, it is further confirmed that the coordination number and coordinate structure of all trivalent rare-earth metal complexes with aminopolycarboxylic acids mainly depend on the ionic radii and electronic configuration of the central metal ions and their countercations.     

Synthesis of bifunctional tetrakis(trimethylsilyl)silane derivatives

Bifunctional derivatives (XMe₂Si)₂Si(SiMe₃)₂ (X = H, Cl, or OH) were synthesized for the first time by the reaction of tetrakis(trimethylsilyl)silane with SbCl₅. The molecular and crystal structure of bis(hydroxydimethylsilyl)bis(trimethylsilyl)silane was established by X-ray diffraction. The fragmentation of the resulting compounds under electron impact was studied by mass spectrometry. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 461–466, March, 2006.     

Crystal Structure of a New Triply‐Bridged Cobalt(III) Dimer with 2, 2′‐Dipyridylamine (dipyam), [Co2(μ‐OH)2(μ‐OAc)(OAc)2(dipyam)2]AcO·EtOH

The structure of [Co₂(μ‐OH)₂(μ‐OAc)(OAc)₂(dipyam)₂]AcO · EtOH ( 1 ) has been determined by single‐crystal X‐ray analysis. The cationic complex may be described as a “di(μ‐hydroxo)(μ‐acetato)dicobalt(III)” core with chelating 2, 2′‐dipyridylamine and monodentate acetate ligands. The coordination polyhedron around each cobalt atom is a distorted octahedral. The dimers are linked in the crystal by N‐H···O_{ionic AcO} and C‐H···O_{monodentate AcO} hydrogen bonds. Spectroscopic data are also presented.     

Ligand substitution kinetics of the iron(III) hydroxo dimer with simple inorganic ligands

The kinetics and mechanisms of ligand substitution reactions of the iron(III) hydroxo dimer, Fe(2)(mu-OH)(2)(H(2)O)(8)(4+), with various inorganic ligands were studied by the stopped-flow method at 10.0 or 25.0 C in 1.0 M NaClO(4). The transient formation of the following di- and tetranuclear complexes was confirmed: Fe(2)(OH)SO(4)(3+), Fe(2)(OH)H(2)PO(2)(4+), Fe(2)(OH)HPO(3)(3+), Fe(2)(OH)SeO(3)(3+), and Fe(4)(AsO(4))(OH)(2)(7+). The catalytic effect of arsenic(III) on the hydrolytic reaction of iron(III) was also attributed to the formation of a dinuclear complex at very low concentration levels. Fast formation and subsequent dissociation of the multinuclear species into the corresponding mononuclear complexes (FeL) proceed via parallel reaction paths which, in general, show composite pH dependencies. The appropriate rate laws were established. The reactions of the different ligands occur at very similar rates, though the uninegatively charged singly deprotonated form reacts about 1 order of magnitude faster than the neutral form of the same ligand. The results can conveniently be interpreted in terms of a dissociative interchange mechanism which postulates the formation of an intermediate complex in which the ligand is coordinated to only one Fe(III) center of the hydroxo dimer. In a subsequent fast step, the ligand forms a bridge between the two metal ions by replacing one of the OH groups. The dissociation of the dinuclear complex into FeL most likely proceeds via the same intermediate.     

Synthesis and crystal structures of supramolecular compounds of polynuclear aluminum(III) aqua hydroxo complexes with cucurbit[6]uril

Supramolecular compounds of the di-, trideca-, and triacontanuclear aluminum aqua hydroxo complexes, viz., [Al₂(OH)₂(H₂O)₈]⁴⁺, [Al₁₂(AlO₄)(OH)₂₄(H₂O)₁₂]⁷⁺, and [Al₃₀O₈(OH)₅₆(H₂O)₂₆]¹⁸⁺, respectively, with the organic macrocyclic cavitand cucurbit[6]uril (C₃₆H₃₆N₂₄O₁₂) were prepared by evaporation of aqueous solutions of aluminum nitrate and cucurbit[6]uril after the addition of pyridine, ammonia, KOH, or NaOH at pH 3.1–3.8. X-ray diffraction study demonstrated that the aqua hydroxo complexes are linked to the macrocycle through hydrogen bonds between the hydroxo and aqua ligands of the polycations and the portal oxygen atoms of cucurbit[6]uril. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 261—268, February, 2006.     

Structure of the hydrated, hydrolysed and solvated zirconium(IV) and hafnium(IV) ions in water and aprotic oxygen donor solvents. A crystallographic, EXAFS spectroscopic and large angle X-ray scattering study

The tetrameric hydrolysis products of zirconium(IV) and hafnium(IV), the zirconyl(IV) and hafnyl(IV) ions, [M(4)(OH)(8)(OH(2))(16)(8+)], often labelled MO(2+).5H(2)O, are in principle the only zirconium(IV) and hafnium(IV) species present in aqueous solution without stabilising ligands and pH larger than zero. These complexes are furthermore kinetically very stable and do not become protonated even after refluxing in concentrated acid for at least a week. The structures of these complexes have been determined in both solid state and aqueous solution by means of crystallography, EXAFS and large angle X-ray scattering (LAXS). Each metal ion in the [M(4)(OH)(8)(OH(2))(16)](8+) complex binds four hydroxide ions in double hydroxo bridges, and four water molecules terminally. The M-O bond distance to the hydroxide ions are markedly shorter, ca. 0.12 A, than to the water molecules. The hydrated zirconium(IV) and hafnium(IV) ions only exist in extremely acidic aqueous solution due to their very strong tendency to hydrolyse. The structure of the hydrated zirconium(IV) and hafnium(IV) ions has been determined in concentrated aqueous perchloric acid by means of EXAFS, with both ions being eight-coordinated, most probably in square antiprismatic fashion, with mean Zr-O and Hf-O bond distances of 2.187(3) and 2.160(12) A, respectively. The dimethyl sulfoxide solvated zirconium(IV) and hafnium(IV) ions are square antiprismatic in both solid state and solution, with mean Zr-O and Hf-O bond distances of 2.193(1) and 2.181(6) A, respectively, in the solid state. Hafnium(IV) chloride does not dissociate in N,N'-dimethylpropyleneurea, dmpu, a solvent with good solvating properties but with a somewhat lower permittivity (epsilon= 36.1) than dimethyl sulfoxide (epsilon= 46.4), and an octahedral HfCl(4)(dmpu)(2) complex is formed.     

Specific feature of synthesis and technological scheme for manufacture of nonstoichiometric hydroxo chromium(III) formates

Specific features of the hydrothermal interaction between chromium(VI) oxide and formic acid to give water-soluble nonstoichiometric hydroxo chromium(III) formates with compositions from the range Cr(OH)_0.66(HCOO)_2.34-Cr(OH)_1.55(HCOO)_1.45 were studied. These compounds can be used in formulations for chromium-plating electrolytes and tanning agents.     

Synthesis,Structure and Magnetic Property of an “Adamantane” Type Tetranuclear Iron(III) Complex

A new tetranuclear complex [Fe₄ L ₂(μ‐O)₂(μ‐>OH)₂](ClO₄)₄·H₂O ( 1 ), (H L = N,N,N′,N′‐tetrakis‐[(2‐pyridyl)methyl]‐2‐hydroxypropane‐1,3‐diamine) has been synthesized and its crystal structure and magnetic properties are shown. X‐ray crystallography reveals that complex 1 contains a quadruply‐charged, tetranuclear iron(III) cation and four perchlorate anions. In 1 , the Fe₄O₆ core is composed of a tetrahedron of iron atoms bridged by six oxygen atoms (two oxo, two hydroxo, and two alkoxo groups from L ). This results in an adamantane‐type geometry with the iron atoms occupying the bridgehead positions. Susceptibility data of 1 indicate strong intramolecular antiferromagnetic coupling of high‐spin Fe^III atoms.     

A square‐planar hydrated cationic tetrakis(methimazole)gold(III) complex

The cationic pseudo‐square‐planar complex tetrakis(1‐methyl‐2,3‐dihydro‐1H‐imidazole‐2‐thione‐κS)gold(III) trichloride sesquihydrate, [Au(C₄H₆N₂S)₄]Cl₃·1.5H₂O, was isolated as dark‐red crystals from the reaction of chloroauric acid trihydrate (HAuCl₄·3H₂O) with four equivalents of methimazole in methanol. The Au^III atoms reside at the corners of the unit cell on an inversion center and are bound by the S atoms of four methimazole ligands in a planar arrangement, with S—Au—S bond angles of approximately 90°.     

Features of the Formation of the [(O)VIV(C2O4)(Phen)(H2O)] Complex in the Malic Acid Oxidation Process

Complex [(O)V^IV(C₂O₄)(Phen)(H₂O)] was obtained on the basis of V₂O₅ and malic acid in the presence of concentrated HNO₃ and phenanthroline. Its structure was determined by the X-ray structural analysis; its magnetic susceptibility was measured. The role of the \(\rm{VO}^+_2\) and VO²⁺ cations in the oxidation and complex-formation processes was considered. A method for the conversion of malic acid to oxalate anions through the formation of oxaloacetic acid and the intermediate products of its decarboxylation reactions was proposed. It was shown by the DFT M06/6-31G(d,p) method that the transition state energy decreases in the way of the HOC(O)C(0)CH₂-COOH bond breakage during decarboxylation compared with the free acid in the intermediate of its anion with VO²⁺.