Allopurinol complexes with first row transition metal perchlorates

Summary Complexes of allopurinol (apH) with Fe^III and several 3d metal(II) (e.g. Fe, Co, Ni and Cu) perchlorates were prepared. The solid complexes isolated included two monomeric hexacoordinated adducts of the type [Fe(apH)₃-(OClO₃) (OH₂)₂]ClO₄ and [Fe(apH)₃(OClO₃)₂(OH₂)]ClO₄, involving N(8)-bound neutral apH ligands, and polymeric Co, Ni or Cu complexes containing both neutral apH and monoanionic ap^- ligands. The latter three complexes involved both N(8)-bound terminal apH and N(1), N(8)- or N(1), N(9)-bound bridging ap^- ligands, and were of the following types: [(apH)₂Cu(ap)] _n (ClO₄) _n , tetrahedral; [(apH)(H₂O)(OClO₃)Co(ap)] _n , pentacoordinated; and [(apH)₂(H₂O)(OClO₃)Ni(ap)] _n , hexacoordinated.Presented in part at the 203rd. American Chemical Society National Meeting; see Ref. 1.     

The hapticity of cyclooctatetraene in its first row mononuclear transition metal carbonyl complexes: Several examples of octahapto coordination

The two cyclooctatetraene metal carbonyls that have been synthesized are the tetrahapto derivative (η⁴-C₈H₈)Fe(CO)₃ and the hexahapto derivative (η⁶-C₈H₈)Cr(CO)₃ using the reactions of cyclooctatetraene with Fe(CO)₅ and with fac-(CH₃CN)₃Cr(CO)₃, respectively. Related C₈H₈M(CO)_n (M = Ti, V, Cr, Mn, Fe, Co, Ni; n = 4, 3, 2, 1) species have now been investigated by density functional theory in order to explore the scope of cyclooctatetraene metal carbonyl chemistry. In this connection, the existence of octahapto (η⁸-C₈H₈)M(CO)_n species is predicted as long as the central metal M does not exceed the 18-electron configuration by receiving eight electrons from the η⁸-C₈H₈ ring. Thus the lowest energy structures (η⁸-C₈H₈)Ti(CO)_n (n = 3, 2, 1), (η⁸-C₈H₈)M(CO)_n (M = V, Cr; n = 2, 1), and (η⁸-C₈H₈)Mn(CO) all have octahapto η⁸-C₈H₈ rings. An exception is (η⁶-C₈H₈)Fe(CO), with a hexahapto η⁶-C₈H₈ ring and thus only a 16-electron configuration for the iron atom. Hexahapto (η⁶-C₈H₈)M(CO)_n structures are predicted for the known (η⁶-C₈H₈)Cr(CO)₃ as well as the unknown (η⁶-C₈H₈)Ti(CO)₄, (η⁶-C₈H₈)V(CO)₃, (η⁶-C₈H₈)Mn(CO)₂, and (η⁶-C₈H₈)Fe(CO)₂ with 18, 18, 17, 17, and 18 electron configurations, respectively, for the central metal atoms. There are two types of tetrahapto C₈H₈M(CO)_n complexes. In the 1,2,3,4-tetrahapto (η⁴-C₈H₈)M(CO)_n complexes two adjacent CC double bonds, forming a 1,3-diene unit similar to butadiene, are bonded to the metal atom. In the 1,2,5,6-tetrahapto (η^2,2-C₈H₈)M(CO)₃ derivatives two non-adjacent CC double bonds of the C₈H₈ ring are bonded to the metal atom. The known (η⁴-C₈H₈)Fe(CO)₃ is a 1,2,3,4-tetrahapto complex. The unknown isomeric 1,2,5,6-tetrahapto complex (η^2,2-C₈H₈)Fe(CO)₃ is predicted to lie ∼15 kcal/mol above (η⁴-C₈H₈)Fe(CO)₃. The related 1,2,5,6-tetrahapto complexes (η^2,2-C₈H₈)Cr(CO)₄, (η^2,2-C₈H₈)Mn(CO)₄, [(η^2,2-C₈H₈)Mn(CO)₃]⁻, (η^2,2-C₈H₈)Co(CO)₂, and (η^2,2-C₈H₈)Ni(CO)₂ are all predicted to be low-energy structures.     

Urate complexes of dipositive first row transition metal ions

Summary The following complexes were prepared by reacting uric acid (uaH₂) with 3d metal(II) perchlorates in non-aqueous media: trans-[Mn(uaH)₂(OH₂)₄], octahedral, and [Co-(uaH)₂(OH₂)₂] tetrahedral, both involving O(8)-bound hydrogenurate; [Cu(ua)(OH₂)₃], tetrahedral, with the urate dianion binding via a ring nitrogen; and [Ni₂(uaH)₂-(uaH₂)(ClO₄)₂(H₂O)₃] formulated as a pentacoordinated linear polymetric species, involving bidentate bridging hydrogenurate, binding through O(8) and a ring nitrogen.Presented in part at the 4th Chemical Congress of North America (Ref. 1).     

Constitutional,configurational and conformational analysis of transition metal coordination complexes

Summary A computational approach to conformational analysis is applied to the study of transition metal coordination complexes. The method provides a means of rapidly exploring conformational space without any inherent reliance on energy calculations and is therefore applicable to a wide variety of systems. It has been incorporated into an algorithm which explores the constitutional, configurational and conformational degrees of freedom for a metal ion and a number of potential ligands. The program determines which of the possible coordination complex products could form stable conformations and can therefore be used to rationalise the products obtained from the mixture. The method is illustrated using two cases: the cobalt(III)-triethylenetetramine-glycine system and complexes of diindolopyridine derivatives.Abbreviations en ethylenediamine - trien triethylenetetramine - gly glycine - RMS root mean square - 3D three dimensional     

Toward accurate theoretical thermochemistry of first row transition metal complexes

The recently developed correlation consistent Composite Approach for transition metals (ccCA-TM) was utilized to compute the thermochemical properties for a collection of 225 inorganic molecules containing first row (3d) transition metals, ranging from the monohydrides to larger organometallics such as Sc(C(5)H(5))(3) and clusters such as (CrO(3))(3). Ostentatiously large deviations of ccCA-TM predictions stem mainly from aging and unreliable experimental data. For a subset of 70 molecules with reported experimental uncertainties less than or equal to 2.0 kcal mol(-1), regardless of the presence of moderate multireference character in some molecules, ccCA-TM achieves transition metal chemical accuracy of ±3.0 kcal mol(-1) as defined in our earlier work [J. Phys. Chem. A2007, 111, 11269-11277] by giving a mean absolute deviation of 2.90 kcal mol(-1) and a root-mean-square deviation of 3.91 kcal mol(-1). As subsets are constructed with decreasing upper limits of reported experimental uncertainties (5.0, 4.0, 3.0, 2.0, and 1.0 kcal mol(-1)), the ccCA-TM mean absolute deviations were observed to monotonically drop off from 4.35 to 2.37 kcal mol(-1). In contrast, such a trend is missing for DFT methods as exemplified by B3LYP and M06 with mean absolute deviations in the range 12.9-14.1 and 10.5-11.0 kcal mol(-1), respectively. Salient multireference character, as demonstrated by the T(1)/D(1) diagnostics and the weights (C(0)(2)) of leading electron configuration in the complete active self-consistent field wave function, was found in a significant amount of molecules, which can still be accurately described by the single reference ccCA-TM. The ccCA-TM algorithm has been demonstrated as an accurate, robust, and widely applicable model chemistry for 3d transition metal-containing species with versatile bonding features.     

Nicotinoyl hydrazide complexes of some first row transition metal ions

Summary Nicotinoyl hydrazide, L, complexes of the MLCl₂ · n EtOH type [M = manganese(II), iron(ll), cobalt(II), nickel(II) and copper(II); n = 0 or 1], WL₂) (NO₃)₂ [M = cobalt(II) and nickel(II)] and mixed metal complexes such as HgCo₂ L₂ Cl₆ and (NiL₂)HgI₄ have been prepared and their nature and structure studied by molar conductance, magnetic susceptibility, electronic, e.s.r. and i.r. spectral measurements. Octahedral structures have been proposed for all the complexes except MnLCl₂, CoLCl₂ and HgCo₂ L₂ C1₆ for which tetrahedral geometry is suggested.     

Energetics of the first and second coordination spheres of transition metal ions

For complexes of transition metals (manganese, iron, cobalt, nickel) with monodentate ligands, equilibrium metal-ligand distances and ligand bond energies in the first and second coordination spheres have been calculated by the CNDO method. Some effects of ligand bond energies in different coordination spheres are analyzed. These effects significantly differ between the first and second coordination spheres. In the first sphere, the ligand bond energy is mainly determined by the nature of the central ion and the type of donor atom of the ligand, but weakly depends on the structure of the ligand. Conversely, in the second coordination sphere, the ligand bond energy weakly depends on the nature of the central ion and the type of donor atom, but considerably depends on the structure of the ligands in the first coordination sphere. In the second coordination sphere, ligand binding is determined by ligand interactions with both the central ion and the ligands of the first sphere. In the general case, when strong specific interactions between ligands are absent, the energetics of the second sphere is determined by the size of the inner-spheric ligands, which may be considered to be a specific steric effect. V. I. Vernadskii Institute of Geochemistry and Analytical Chemistry. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 370–374, March–April, 1995. Translated from L. Smolina     

Functionalization of white phosphorus in the coordination sphere of transition metal complexes

This review highlights the stoichiometric functionalization of both white phosphorus and naked P_n fragments derived from the metal-mediated demolition of the P₄ tetrahedron. In a first section, the alkylation of P_n ligands is discussed giving specific examples such as: (i) the electrophilic alkylation of η³-P₃ or, μ,η³-P₃ ligands: (ii) the transfer of a methyl group from molybdenum to η⁵-P₅ ligands to yield a norbornadiene-like μ₃,η⁴:η¹:η¹-MeP₇ ligand; (iii) the formation of P-C or P-H bonds mediated by rhodium and iron complexes; (iv) the use of ammonium salts to transfer an alkyl to polyphosphido clusters. Different methods to functionalise white phosphorus or other P_n ligands, including the cyclization of acrolein with diphosphenes and the insertion of CO or carbenes across P-P, P-M bonds, and P-E bonds (E = S, Se), are illustrated in appropriate sections. Finally, the last part of the article, reports on the astounding coupling of alkynes and phosphalkynes with P_n ligands which is a versatile, not yet completely explored, method to form an unprecedented variety of carbon-phosphorus heterocycles.     

The preparation and thermal analysis studies on some first row transition metal complexes of 2-aminopyrimidine

Complexes of 2-aminopyrimidine with the chlorides, bromides and iodides of cobalt(II), zinc(II) and also with the chlorides and bromides of manganese(II), nickel(II) and copper(II) have been prepared. The chloride complex of iron(II) was also obtained. The stereochemical configurations of the complexes were deduced using spectral and magnetic properties. The decomposition of the complexes was studied by thermogravimetry and differential thermal analysis.

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Zusammenfassung Komplexe von 2-Aminopyrimidinen mit den Chloriden, Bromiden und Jodiden von Kobalt(II), Zink(II) und den Chloriden und Bromiden von Mangan(II), Nickel(II) und Kupfer(II) wurden hergestellt. Der Chloridkomplex von Eisen(II) wurde ebenfalls erhalten. Die stereochemischen Konfigurationen der Komplexe wurden aus spektralen und magnetischen Eigenschaften abgeleitet. Die Zersetzung der Komplexe wurde durch Thermogravimetrie und Differentialthermoanalyse untersucht.

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Résumé Les complexes de l'amino-2 pyrimidine avec les chlorures, bromures et iodures de cobalt(II), zinc(II) ainsi qu'avec les chlorures et bromures de manganèse(II), nickel(II) et cuivre(II) ont été préparés. Le complexe formé avec le chlorure de fer(II) a aussi été obtenu. Les configurations stéréochimiques des complexes ont été déduites des propriétés spectrales et magnétiques. La décomposition thermique des complexes a été étudiée par thermogravimétrie et analyse thermique différentielle.

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2- , (II) (II), (II), (II) (II). (II). . .

     

Electrostatic and covalent contributions in the coordination bonds of transition metal complexes

To develop a molecular mechanics force field for modeling complexes of transition metals and organic ligands, the electrostatic and covalent contributions in the coordination bonds were investigated using quantum mechanical density functional theory and model complexes of glyoxal diimine and the 2+ cations of the first row transition metals. The VDD and Hirshfeld charges are found to be closely correlated with the extent of the electron transfer between the ligands and the cations. Assuming the electrostatic contribution can be represented by the atomic partial charges, the covalent contributions in the coordination bonds are estimated to be in a range of 54-92% for the systems calculated. A simple force field was parametrized to validate the partial charge representation.     

Some first row transition metal complexes of nicotinamide and nicotinic acid

Some complexes of the chlorides and bromides of manganese(II), iron(II), cobalt(II), nickel(II) and copper(II) with nicotinamide and nicotinic acid have been prepared. These complexes have stoichiometryML ₂X₂ whereM is a metal ion,L is an organic ligand andX is a halide ion. Spectral and magnetic properties indicate that these compounds have octahedral polymeric structures. The decomposition of the complexes was studied by thermogravimetry and differential thermal analysis. In only one instance was a decomposition product of the formulaMLX₂ obtained. Its structure was also octahedral.

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Zusammenfassung Einige Komplexe der Chloride und Bromide von Mangan(II), Eisen(II), Cobalt(II), Nickel(II) und Kupfer(II) mit Nikotinamid und NikotinsÄure wurden hergestellt. Diese Komplexe sind von der StöchiometrieML ₂ X ₂ , wobeiM ein Metallion,L ein organischer Ligand undX ein Halogenidion ist. Die spektralen und magnetischen Eigenschaften deuten auf oktaedrische Polymerstrukturen dieser Komplexe hin. Die Zersetzung der Komplexe wurde durch Thermogravimetrie und Differentialthermoanalyse untersucht. In einem einzigen Falle wurde ein Zersetzungsprodukt der FormelMLX ₂ erhalten, dessen Struktur ebenfalls oktaedrisch war.

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Résumé Plusieurs complexes donnés par les chlorures et bromures de manganèse(II), fer(II), cobalt(II), nickel(II) et cuivre(II) avec le nicotinamide et l'acide nicotinique ont été préparés. Ces complexes répondent à la formule stchiométriqueML ₂X₂, oùM représente l'ion mé tallique,L un ligand organique etX un ion halogène. Les propriétés spectrales et magnétiques indiquent que ces composés ont une structure polymère octaédrique. La décomposition de ces complexes a été étudiée par thermogravimétrie et par analyse thermique différentielle. Dans un seul cas un produit de décomposition de formuleMLX₂ a été obtenu. Sa structure est également octaédrique.

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(II), (II), (II), (II) (II) . ML ₂ X ₂ , M — ,L — ,X — . , . . MLX ₂ , .

     

Acetone picolinoyl hydrazone complexes of some first row transition metal ions

Summary Acetone picolinoyl hydrazone (APH) complexes of the types M(APH)Cl₂nEtOH and M(APH-H)₂2EtOH (where M = manganese(II), iron(II), cobalt(II), nickel(II), or copper(II); n = 0 or 2) have been prepared and their nature and structures studied by molar conductance, molecular weight determination, thermal degradation, magnetic susceptibility, electronic and i.r. spectral measurements. Spin-free octahedral geometry has been proposed for all the complexes except Mn(APH)Cl₂ and Co(APH)Cl₂ for which tetrahedral geometry has been suggested.     

Gas-phase ion-molecule reactions of transition metal complexes: the effect of different coordination spheres on complex reactivity

Using a modified quadrupole ion trap mass spectrometer, a series of metal complex ions have been reacted with acetonitrile in the gas phase. Careful control of the coordination number and the type of coordinating functionality in diethylenetriamine-substituted ligands enable the effects of the coordination sphere on metal complex reactivity to be examined. The association reaction kinetics of acetonitrile with these pentacoordinate complexes are followed in order to obtain information about the starting complexes and the reaction dynamics. The kinetics and thermodynamics of acetonitrile addition to the metal complex ions are strongly affected by the chemical environment around the metal center such that significant differences in reactivity are observed for Co(II) and Cu(II) complexes with various coordination spheres. When thiophene, furan, or benzene moieties are present in the coordination sphere of the complex, addition of two acetonitrile molecules is readily observed. In contrast, ligands with better sigma donors react mainly to add one acetonitrile molecule. Among the ligands with good sigma donors, a clear trend in reactivity is observed in which complexes with nitrogen-containing ligands are the least reactive, sulfur-containing complexes are more reactive, and oxygen-containing complexes are the most reactive. In general, equilibrium and reaction rate constants seem to be consistent with the hard and soft acid and base (HSAB) principle. Interestingly, the presence of certain groups (e.g., pyridine and imidazole) in the coordination sphere clearly can change the acid character of the metal as seen by their effect on the binding properties of other functional groups in the same ligand. Finally, we conclude that because complexes with different coordination spheres react to noticeably different extents, ion-molecule (I-M) reactions may be potentially useful for obtaining coordination structure information for transition metal complexes.     

The synthesis and structural characterization of transition metal coordination complexes of coumarilic acid

The coumarilate (coum^?) complexes of Co^II(1), Ni^II(2) Cu^II(3) and Zn^II(4) were synthesized and characterized by elemental analysis, magnetic susceptibility, solid-state UV–Vis, FTIR spectra, thermoanalytical TG–DTG/DTA and single-crystal X-ray diffraction methods. It was found that all of the complex structures have 2 mol (coum^?) ligand bonded as monoanionic monodentate in the structures of 1 and 2 while they were coordinated to metal cations as monoanionic bidentate in the complexes 3 and 4. There was not any hydrate water in the metal complexes. The complexes of 1 and 2 have four moles of aqua ligand, and the other complexes have two moles. Thermal decomposition of each complex starts with dehydration, and then the decomposition of organic parts goes. The thermal dehydration of the complexes takes place in one (for the compounds of 2, 3, 4) or two (for the compound 1) steps. The decomposition mechanism and the thermal stability of the complexes under investigation were determined on the basis of their structures. Metal oxides were obtained as the final decomposition product.     

含有过渡金属配合物的层状钒氧化物的合成和性质（英文）

以钒酸铵为起始原料,在螯合配体存在下,利用水热合成法将其与二价第一行过渡金属阳离子在160℃反应得到了一个棕色块状化合物[Co(dien)_2]_2[V_6O_(17)]·3H_2O(1)(dien=二乙烯三胺),并用元素分析、红外光谱和X射线单晶衍射对之进行了定性分析.结果表明,化合物1属于单斜晶系,P2(1)/c空间群;其晶格参数为:a=1.613 4(4)nm,b=0.866 8(2)nm,c=1.398 1(4)nm;β=103.070(4)°;V=1.904 7(9)nm~3;ρ=2.016 g/cm~3;Z=2.化合物1是由钒氧层和[Co(dien)_2]~(2+)构成.这些钒氧层是由{VO}n螺旋链组成.     

Recent advancements in the anticancer potentials of first row transition metal complexes

The frequently severe effects of currently utilized platinum-based complexes have prompted researchers to develop less toxic transition metal based anticancer drugs. Transition metal complexes have recently gained considerable attention as promising anticancer agents due to their efficient drug design and fast optimisation. Some transition metal complexes displayed better anticancer activity than cis-platin. This led to the transition metal complexes for clinical application of chemotherapeutic drugs for cancer therapy. Cytotoxicity of the complexes has been evaluated on the basis of their IC₅₀ values. In this review, we have focussed on recent findings about the anticancer mechanism of action of first row transition metal complexes during the last ten years.     

Two new hybrid compounds assembled from Keggin-type polyoxometalates and transition metal coordination complexes

Two new hybrid compounds based on Keggin-type polyoxometalates: {[PMo₁₂O₄₀][Ni(Phen)₂(H₂O)]₂}·K·2OH⁻ (1) and [Cd₂(Phen)₄Cl₂][HPW₁₂O₄₀]·H₂O (2) (Phen=1,10-phenanthroline), have been prepared and characterized by IR, UV-vis, XPS, XRD and single crystal X-ray diffraction analyses. Compound 1 exhibits a 1-D chain structure constructed from Pseudo-Keggin polyoxometalate bi-supported transition metal coordination complexes linked by K⁺ ions. Compound 2 contains Pseudo-Keggin polyoxoanions [HPW₁₂O₄₀]²⁻ and novel metal-chloride-ligand coordination complexes [Cd₂(Phen)₄Cl₂]²⁺.     

Studies on transition metal murexide complexes

Iron, cobalt, nickel, copper, zinc, cadmium and mercury murexide complexes have been prepared and characterized. The thermal properties of these complexes are studied deeply by DTA technique where their thermal peaks are explained. The multi-stages thermal decomposition mechanism is proposed. The thermodynamic parameters of the decomposition steps are calculated. The entropy change values for all complexes are of the same magnitude and all transition states of the thermal reactions are more ordered than the reactants. The thermal reactions proceed in complicated mechanisms. The fractions appeared in the calculated orders of the thermal reactions confirmed that these reactions proceeded via complex mechanisms.     

Spectroscopy,structure, and electrochemistry of transition metal complexes having [M2N2OS2] coordination sphere

Binuclear transition metal complexes of bicompartmental SNONS donors were synthesized and characterized by various physico-chemical techniques. Two different precursors with chloromethyl/formyl functionality at the 2 and 6 positions of phenolate ring are used to construct the ligands. The quinoxaline scaffolds provide SN donors incorporated at the 2 and 6 positions. Copper and zinc complexes are square pyramidal, whereas nickel and cobalt complexes are octahedral. The influence of two metal centers in terms of cooperative effect on the electronic, magnetic, electrochemical, and structural properties was investigated.