The reactions of [Fe2(η-C5H5)2(CO)4−n(CNMe)n] (n = 0–4) complexes with halogens and mercury(II) salts

Halogens, X₂, and HgY₂ (X = Cl, Br, I; Y = X, F, NO₃, BF₄) cleave the metalmetal bonds in [Fe₂(η-C₅H₅)₂(CO)_4−n(CNMe)_n] complexes (n = 0–4). Typically, e.g., when n = 2, X₂ electrophiles give [Fe(η-C₅H₅)(CO)(CNMe)X] (a) and [Fe(η-C₅H₅)(CO)(CNMe)₂]X (b) in relative yields which depend on X, the reaction solvent and n, but HgY₂ give equimolar amounts of [Fe(η-C₅H₅)(CNMe)₂Y] (c and [Fe(η-C₅H₅)(CO)₂HgY] only. Hg(CN)₂ reacts more slowly than other HgY₂, and [Hg(PPh₃)₂I₂] does not react at all. It is suggested that the reactions which give rise to products of type (a), (b) or (c) are all two-electron oxidation which proceed by way of adducts containing μ-CA → X₂ or μ-CA → HgX₂ groups (Ca = CO or CNMe). One of these adducts has been isolated, namely [Fe₂(η-C₅H₅)₂(CNMe)₂{μ-CN(Me)HgCl₂}₂] · CHCl₃.     

Spectroscopic properties of [M(CN)5py]n− complexes [M  Fe(II), Co(III); py = pyridine]

The IR, electronic and NMR spectra of K₂[Co(CN)₅py]·H₂O and Na₃[fe(CN)₅py]·3H₂O, as well as the Mössbauer spectrum of the latter complex, are reported and discussed. In particular it is argued that the wavenumbers and intensities of the i.r.-active CN stretching vibrations and the NMR chemical shifts of the m- and p-but not o-protons suggest greater metal to ligand back π-bonding in the Fe(II) complex than in the Co(III) complex.     

New methods of preparation of hydroxy-closo-decaborates [B10H10 − n (OH) n ]2− (n = 1, 2)

New methods of preparation of hydroxy-closo-decaborates [B₁₀H_{10 ? n} (OH) _n ]^2? (n = 1, 2) that are based on the reaction of anions [B₁₀H_{10 ? n} (OAc) _n ]^2? and alkoxyethylidenoxonio-closo-decaborates [2-B₁₀H₉OC(OR)CH₃]^? with aqueous solution of hydrazine are proposed. The obtained compounds were characterized by IR, ESI/MS, and NMR (¹H, ¹¹B, ¹³C) spectroscopy.     

Hydrogen-bonded networks based on manganese(II), nickel(II), copper(II) and zinc(II) complexes of N,N′-dimethylurea

A project related to the crystal engineering of hydrogen-bonded coordination complexes has been initiatied and some of our first results are presented here. The compounds [Mn(DMU)₆](ClO₄)₂ (1), [Ni(DMU)₆](ClO₄)₂ (2), [Cu(OClO₃)₂(DMU)₄] (3) and [Zn(DMU)₆](ClO₄)₂ (4) have all been prepared from the reaction of N,N-dimethylurea (DMU) and the appropriate hydrated metal perchlorate salt. Crystal structure determinations of the four compounds demonstrate the existence of [M(DMU)₆]²⁺ cations and ClO₄ ^– counterions in (1), (2) and (4), whereas in (3) monodentate coordination of the perchlorate groups leads to molecules. The [M(DMU)₆]²⁺ cations and ClO₄ ^– anions self-assemble to form a hydrogen-bonded one-dimensional (1D) architecture in (1) and different 2D hydrogen-bonded networks in (2) and (4). The hydrogen bonding functionalities on the molecules of (3) create a 2D structure. The complexes were also characterised by room-temperature effective magnetic moments and i.r. studies. The data are discussed in terms of the nature of bonding and the known structures.     

Mechanochemical reactions of molybdenum and tungsten chalcohalides with (Bu4N)2[Zn(Dmit)2]. Crystal structure of (Bu4N)2[Mo3Se5.88S1.12(Dmit)3] · 1.15CH2Cl2

The mechanochemical reactions of cluster chalcohalides M₃Q₇X₄ (M = Mo, W; Q = S, Se, Te; X = Br, I) with (Bu₄N)₂[Zn(Dmit)₂] (Dmit is 1,3-dithia-2-thionedithiolate, C₃S₅ ^2?) are studied. It is shown that the reaction of Mo₃Se₇Br₄ with (Bu₄N)₂[Zn(Dmit)₂] followed by crystallization from CH₂Cl₂ results in the formation of a new compound of the composition (Bu₄N)₂[Mo₃Se_5.88S_1.12(Dmit)₃] · 1.15CH₂Cl₂ (I) characterized by IR spectroscopy, electrospray mass spectrometry, and X-ray structure analysis. Under similar conditions, W₃Q₇Br₄ and Mo₃Te₇I₄ form binuclear complexes [M₂O₂Q₂(Dmit)₂]^2? identified by electrospray mass spectrometry. Various types of nonvalent contacts Q…Q are observed in the crystal structure of compound I.     

Zinc(II) and copper(II) complexes of edampda2−: octahedral,trigonal bipyramidal and in between [edampda2−=N,N′-bis-(pyridylmethyl)ethylenediamine-N,N′-diacetate]

ZnII and CuII complexes of the ligand edampda2– [N,N-bis(pyridylmethyl)-ethylenediamine-N,N-diacetate] have been studied in solution by 1H n.m.r. and e.p.r. spectroscopies, respectively. [ZnII(edampda)] exists in solution in a major octahedral isomer (ca. 83%) in which the two carboxylate donors and two pyridylmethyl donors remain stereochemically rigid up to 333K at pD=6.0. The major octahedral complex has equivalent glycinato and pyridyl donors as shown by equivalent AB quartets for each type of chelate. By contrast, the [ZnII(edta)]2– analogue complex is known to have processes which rapidly equilibrate the coordinated carboxylates leading to coalesced, broad singlets instead of AB quartets down to 273K (freezing point of the sample). The minor [ZnII(edampda)] species has one pendant pyridylmethyl arm. The complex does not increase in abundance up to 333K via dissociation of the major species, suggesting that it possesses a different five-coordinate geometry (approximate trigonal bipyramid). The [CuII(edampda)] complex exhibits an e.p.r. spectrum that is intermediate between rhombic or tetragonal CuII complexes (near D4h) and the reversed-e.p.r. type of trigonal bipyramidal CuII complexes (ca. D3h). The single g value of 2.079 for gg>2.03 identifies the [CuII(edampda)] complex as distorted toward trigonal bipyramidal whereas its [CuII(edtaH2)(H2O)] analogue is known to be distorted toward square pyramidal. A binuclear CuI complex of edampda2– is formed only as a transient, and it rapidly disproportionates into [CuII(edampda)] and Cu metal. A mononuclear [CuI(edampda)]– complex persists for up to 8 h, but is oxidized within 3 min by O2 to the CuII complex. [CuII(edampda)] oxidizes to CuIII with a highly irreversible wave on glassy-carbon at +1.09V compared to the [NiII/III(edampda)] wave at +1.32V.     

Thermal decomposition kinetics of polymeric complexes of copper(II) and mercury(II) with N,N′-bis(dithiocarboxy)piperazine

The thermal decomposition behaviour of polymeric complexes of Cu(II) and Hg(II) with N,N-bis(dithiocarboxy)piperazine is investigated in air by thermogravimetric (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) techniques. The kinetic parameters (non-isothermal method) for their decomposition have been evaluated by graphical as well as by least-squares methods. The equations of Coats-Redfern, Freeman-Carroll and Horowitz-Metzger have been applied. The results indicate that the values ofE,A and S obtained by these three different methods agree well. It was also found that the decomposition of these metal chelates follow first-order kinetics.

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Zusammenfassung Mittels TG, DTG und DTA wurde das thermische Zersetzungsverhalten von Polymerkomplexen aus Cu(II) bzw. Hg(II) mit N,N-Bis(dithiocarboxy)piperazin an Luft untersucht. Für ihre Zersetzung (nichtisotherme Methode) wurden die kinetischen Parameter sowohl graphisch als auch durch Methoden mit den kleinsten Fehlerquadraten ermittelt. Dabei wurden die Gleichungen von Coats-Redfern, Freeman-Carroll und von Horowitz-Metzger angewendet. Alle drei Verfahren zeigen übereinstimmende Resultate fürE, A undS. Es wurde weiterhin gefunden, daß diese Metallchelate einer Reaktion erster Ordnung unterliegen.

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The authors are thankful to Prof. C. G. R. Nair, Head of the Department of Chemistry, University of Kerala and Dr. M. P. Kannan, Department of Chemistry, University of Calicut for some helpful discussions.     

Double Pseudo-Polymeric Gold(III)-Mercury(II) Complexes [Au(S2CNR2)2]nX [R2 = (CH2)6, (CH2)4O] Containing ([HgCl3]−)n, [HgCl4]2− and [Hg2Cl6]2− Anions: Chemisorption Synthesis,Principles of Supramolecular Self-Assembly,and Thermal Behavior

Russian Journal of General Chemistry - Novel pseudo-polymeric complexes of gold(III)-mercury(II) with cyclic alkylene dithiocarbamate ligands: ([Au{S2CN(CH2)6}2][HgCl3])n,...     

β-diketone complexes of manganese(II), cobalt(II), nickel(II) and palladium(II)

Summary The reactions of manganese(II), cobalt(II) and nickel(II) acetates (1 mole) with antipyrine-4-azo--ethylcyanoacetate (HL¹) and antipyrine-4-azo--acetylacetone (HL²) (1 mole) produce complexes of the M(L)₂ type. K₂PdCl₄ (1 mole) reacts with HL¹ and HL² (1 mole) to yield complexes of the general formula PdLCl, the ligands behaving as monobasic tridentates. The electronic spectral and magnetic data show the complexes to be high-spin octahedral, whereas the palladium(II) complexes are diamagnetic square planar. The complexes were characterized by elemental analyses, conductance measurements and i.r. and electronic spectra as well as magnetic susceptibility measurements and thermal (t.g.a. and d.t.a.) analysis.Nuclear Material Authority.     

Synthesis and crystal structure of new cobalt(II) and copper(II) complexes with deprotonated N -[2′-(4-methyl) pyrimidinyl]-2-nitrobenzenesulfonylurea

Cobalt(II) and copper(II) complexes with deprotonated N-[2′-(4-methyl)pyrimidinyl]-2-nitrobenzenesulfonylurea were synthesized and their structures were characterized by IR spectrum, elemental analysis and X-ray diffraction. The deprotonated sulfonylurea is a bidentate ligand to Co(II) or Cu(II) in octahedral geometry. In the packing diagrams of the complexes, C–H ··· O hydrogen bonds are observed. The UV and fluorescence spectra of the complexes are described, and the thermogravimetric analyses of the complexes were performed.     

Spectroscopic and structural properties of homonuclear Fe(II) polymeric compounds.—II. Thermal decomposition products of [Fe(pyrazine)2X2]n

The thermal decomposition of [Fe(pyz)₂X₂]_n (where pyz = pyrazine and X = Cl, Br or I) was investigated. For the chloride and bromide complexes the decomposition proceeds in two stages in which two pyrazine molecules dissociate successively, whereas in the iodide complex both pyrazine molecules dissociate in a single stage. Spectroscopic measurements (UV, Vis, Raman and Mössbauer spectra) indicate that intramolecular rearrangement resulting from dissociation of one pyrazine molecule leads to a change in coordination from FeN₄X₂ characteristic of initial compounds, [Fe(pyz)₂X₂]_n, to FeX₄N₂ characteristic of [Fe(pyz)X₂]_n which is accomplished through both pyrazine and halide bridges. Thus, polymers are being formed in which the (FeX₂)_n chains are being bridged by the pyrazine molecules. The magnetic moments of monopyrazine intermediate compounds are independent of temperature and low-temperature magnetic measurements do not indicate any magnetic ordering above 4.2 K.     

The reactions of [Fe2(η-Cp)2(CNAr)4] complexes with halogens and tin(II) halides

Summary [Fe₂(-Cp)₂(CNAr)₄] (2) (540-01, C₆H₄Me-2, C₆H₄Et-2, C₆H₃Me₂-2,4, C₆H₃Me₂-2,6, C₆H₃(Me)Et-2,6, C₆H₃Et₂-2,6 or C₆H₃ i-Pr₂-2,6) react with I₂ to give [Fe(-Cp)(CNAr)₂I], but with Br₂[Fe(-Cp) (CNAr)₃]⁺ salts are the only products; IBr gives a mixture of the two. With SnX₂ (X = F, Cl, Br or I) in refluxing n-butanol, (2) gives isolable [{Fe(-Cp)(CNAr)₂}₂SnX₂] only when the CNAr ligands have two ortho substituents, otherwise decomposition occurred. When X = F, [Fe(-Cp) (CNAr)₂SnF₃] was also obtained from this reaction. Attempts to prepare [Fe(-Cp)(CNAr)₂X] (X = Cl or Br) by reaction of (2) with HX in the presence of air gave rather unstable products which with SnX₂ formed [Fe(-C₅H₅)-(CNAr)₂SnX₃]. Similar compounds, [Fe(-Cp) (CNAr)₂ SnX₂I], were obtained from [Fe(-Cp)-(CNAr)₂I] and SnX₂ (X = Cl or Br but not I). All of these complexes are much less stable than their Fe(-Cp)(CO)₂ counterparts; all decompose in solution to [Fe(-Cp)(CNAr)₃]⁺ which then break down to unidentified species. X-ray diffraction studies show that in [Fe(-Cp)(CNC₆H₃-i-Pr₂-2,6)₂I] and [{Fe(-Cp)(CNC₆H₃Me₂-2,6)₂}₂SnBr₂] there is pseudo-octahedral coordination about Fe. In the latter there is also distorted tetrahedral coordination about Sn so that its structure is very similar to that of [{Fe(-Cp)(CO)₂}₂SnCl₂]. Spectroscopic studies show that in all complexes rotation of the aryl rings of the CNAr ligands cannot be slowed in solution, and that there is free rotation about all 540-02 bonds.     

New nickel dithiolene–diselenolene complexes obtained from 3,4-dichloro-1,2,5-thiadiazole: X-ray structure of (Bu4N)2[Ni(C2N2S2.2Se0.8)2]

The new (Bu₄N)₂[Ni(C₂N₂S_2.2Se_0.8)₂] (1) redox active nickel complex with a mixed S_0.6/Se_0.4 occupancy of thiolic sulfurs in the 1,2,5-thiadiazole-3,4-dithiolate (tdas) ligand has been prepared by reacting in situ NiCl₂·6H₂O with the products of the selenation reaction (grey selenium with NaBH₄ in EtOH) of 3,4-dichloro-1,2,5-thiadiazole (TDACl₂). Single crystal X-ray analysis of 1 shows that in the dianion, the central Ni-atom exhibits a square-planar geometry and that bond distances and angles are in agreement with those usually found in this class of complexes, except for the CC distance [1.428(5) Å] which is longer than those generally found in dianionic metal dithiolene or diselenolene complexes. The position at unusually low frequency (1311 cm⁻¹) of the CC stretching vibration in the Raman spectra agrees with structural results. A cyclic voltammetric study on 1 shows that the introduction of the selenium atom in the dithiolene core has the effect to make the dianion more easily to be oxidised than the corresponding tdas derivative. By chemical oxidation with I₂, Bu₄N[Ni(C₂N₂S_2.2Se_0.8)₂] (2) has been obtained. The existence of a monoanion as isolated species in solution and as dimers strongly antiferromagnetically coupled in the solid state is inferred from spectroscopic and EPR results.     

Copper(II) and palladium(II) complexes of N,N′-bis(2-hydroxyethyl)stilbenediamine

A new 1,2-diamine ligand, N,N-bis(2-hydroxyethyl)stilbenediamine (L), has been prepared by reduction of the condensation product of benzaldehyde with 2-aminoethanol with Al amalgam. Mononuclear complexes of the [CuL(H₂O)]X₂ type where X=Cl^– or AcO^– with Cu^II and PdLCl₂ with palladium(II) have been prepared and characterized by elemental analysis and i.r., u.v.–vis. or ¹H-n.m.r. spectroscopy.     

Synthesis and magnetic properties of copper(II)-MII-copper(II) trinuclear complexes with N,N′-bis(2-aminoethyl)oxamidocopper(II) [M = Co and Ni]

Summary Two novel trinuclear complexes were prepared, namely [Cu₂(oxae)₂(H₂O)₂M] (ClO₄)₂, [oxae = N,N-bis(2-aminoethyl) oxamido dianion; M = Co and Ni]. Based on elemental analyses, conductivity measurements and i.r. spectra, the complexes are proposed to have extended oxamidobridged structures. The magnetic susceptibility of [Cu₂-(oxae) ₂(H₂O)₂Co](ClO₄)₂ were measured over the 4–300 K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian, =–2J(₁·₂·₂·₃). The exchange integral, J, was found to be equal to –29.2 cm^–1, indicating an antiferromagnetic spin-exchange interaction between the adjacent metal ions.     

[Bu4N]2[Fe2(μ-S2O3)2(NO)4]: Synthesis,Structure, Redox Properties,and EPR Study

The [n-Bu₄N]₂[Fe₂(-S₂O₃)₂(NO)₄] complex was studied using X-ray diffraction analysis, cyclic voltammetry, and EPR spectroscopy, and its crystal structure was determined. The redox properties of the [Fe₂(-S₂O₃)₂(NO)₄]^2–anion in CH₃CN and CH₂Cl₂solutions were studied. An addition of excess reducer (sodium thiosulfate) to the thiosulfate complex was shown to produce an EPR signal with g= 2.03 typical of the mononuclear iron dinitrosyl complexes. The mechanism for [Fe₂(-S₂O₃)₂(NO)₄]^2–reduction was suggested.     

Theoretical analysis of spin crossover in iron(II) [2×2] molecular grids

We use quantum-chemical density functional theory calculations to elucidate the origin of spin-crossover pathways in two iron(II) [2×2] molecular grids with carbohydrazide-based bridging ligands. The complexes are characterized energetically and structurally in five available spin states. Special attention is paid to analysis of the structural distortion induced on each iron center by spin transition on any of its neighbors. The evolution of coordination polyhedra is monitored using the Continuous Shape Measures. It is demonstrated that a succession of spin transitions on different centers depends on the character of the induced distortion, either approaching or getting them away from a more regular low-spin geometry. These effects, resulting from the elasticity of bridging ligands, can be modulated by weak perturbations such as a change of the positions of the hydrogen atoms.     

Investigations on the redox behaviour of manganese in manganese(II)–saccharin and manganese(II)–saccharin–1,10-phenanthroline complexes

The redox behaviour of manganese system in Mn–Sac and Mn–Sac–Phen complexes were studied using cyclic voltammetry technique at glassy carbon electrode (GCE) in 0.1 M KCl electrolyte. The CV of Mn–Sac solution is more or less similar to that of uncoordinated Mn (in MnCl₂) accept slight difference in peak position and peak current. The presence of secondary ligand phenanthroline (in Mn–Sac–Phen complex) changes the CV of Mn system largely compared to those of uncoordinated Mn and Mn–Sac. The redox system is irreversible in Mn–Sac and quasi-reversible in Mn–Sac–Phen complex. The effect of concentration and pH on the redox behaviour of Mn system have been studied for both the complexes.     

Synthesis and structural features of copper(II) complexes of N,N,N′,N′-tetramethylethylenediamine with 2-chlorobenzoate1− and 2-hydroxybenzoate1−

Abstract

Two copper(II) coordination complexes, formulated as [Cu(tmen)(Clba)₂] (1) and [Cu(tmen)(Hsal)₂·H₂O] (2) (where tmen?=?N,N,N′,N′-tetramethyl ethylenediamine (C₆H₁₆N₂), Clba^1? = 2-chlorobenzoate (C₇H₄ClO₂^1?), and Hsal^1? (C₇H₅O₃^1? = monoanion of o-hydroxybenzoic acid (salicylic acid)), have been synthesized and characterized by elemental combustion analysis, spectroscopic techniques, thermal studies, and single crystal X-ray analyses. Complex 1 consists of two distinct monomeric units in which the coordination environment around the central copper(II) ion is a distorted octahedron with a CuN₂O₄ chromophore, constituted by a chelating tmen molecule, and two 2-chlorobenzoate^1? anions coordinated through their carboxylate-O atoms in an asymmetrical bidentate fashion. Complex 2 is also a monomer and consists of an CuN₂O₃ chromophore, in which tmen is coordinated to Cu(II) through its two N atoms in a chelating bidentate fashion, and an aqua-O and the two o-hydroxybenzoate^1? (HSal^1?) anions are coordinated through one of their carboxylate-O atoms in a monodentate mode, forming a square pyramidal structure. Hydrogen bonding interactions especially of O–H…O, N–H…O, and C–H…Cl types interweave monomeric units and stabilize the overall crystal structures in both complexes. Thermal analysis and antibacterial activities of 1 and 2 against various bacterial strains were also investigated.