Synthesis and characterization of some metal complexes of cystine: [Mn(C6H10N2O4S2)]; where MII = Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II)

Cystine forms metal complexes of general formula [M^II(C₆H₁₀N₂O₄S₂)]; where M^II = Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) in the aqueous medium. Before reacting with metal salts the ligand solution was neutralized by NaHCO₃ solution. The complexes were formulated by comparing the C, H, N, S and metal analysis data. The prepared complexes were characterized by different physicochemical methods. The UV-vis, FTIR spectral analysis, magnetic susceptibility of these complexes are discussed. Cyclic voltammetric studies of some of the complexes are also reported.     

Charge Transfer Salts of BO with Paramagnetic Isothiocyanato Complex Anions: (BO)[M(isoq)2(NCS)4]; M=Cr or Fe, isoq=isoquinoline and BO=Bis(ethylenedioxo)tetrathiafulvalene

The preparation, X-ray structures and magnetic properties of two isostructural new charge transfer salts: (BO)[M(isoq)₂(NCS)₄]; M=Cr^III(1), Fe^III(2) and isoq=isoquinoline are reported. Their structure consists of alternate organic and inorganic layers, each layer being formed by mixed columns of BO radical cations and paramagnetic metal complex anions. There are short intermolecular contacts between donor and anion (S2_anion· · ·S4_BO<3.5 Å) and between adjacent BO molecules (O· · · O1<3.2 Å). The two compounds are insulators. ESR measurements show single signal without separating the donor and anion spins. The magnetic measurements obey the Curie-Weiss law and revealed dominant antiferromagnetic interactions between anion spin and donor spin, but long-range magnetic ordering did not occur down to 2 K. This is directly related to structural reasons which were deduced from a comparison of the title compounds with other 1:1 salts containing same anion complexes and different donors.     

Butylene linked palladium N-heterocyclic carbene complexes: Synthesis and catalytic properties

New bis(NHC)-Pd complexes were synthesized and characterized by elemental analysis, ¹H NMR, ¹³C NMR, and IR spectroscopy. The reaction of Pd(OAc)₂ and bis(benzimidazolium) salts in DMSO gave the monomeric palladium complex in which the N-heterocyclic carbene was bound to the metal centre. The crystal and molecular structure of the cis-dibromo{1,1′-di[2,3,4,5,6-pentamethylbenzyl]-3,3′-butylenedibenzimidazol-2,2′-diylidene}-palladium(II) complex was determined by single-crystal X-ray diffraction. The activity of the Pd(II) complexes in the direct arylation of benzothiazole with arylbromides was investigated. A preliminary catalytic study showed that these bis(NHC)-Pd complexes were highly active in the direct arylation of benzothiazole with arylbromides.     

Metal diphosphonates with double-layer and pillared layered structures based on N-cyclohexylaminomethanediphosphonate

Based on N-cyclohexylaminomethanediphosphonic acid (cmdpH₄), four new metal diphosphonate compounds with formula M₃(cmdpH)₂(H₂O)₂ [M=Zn(1), Co(2)] and M₂(cmdpH₂)₂(4,4′-bipy)_0.5(H₂O) [M=Co(3), Mn(4)] have been obtained and structurally determined. Compounds 1 and 2 are isostructural. Within the structure, the M(2)O₆ octahedra are each corner-shared with four PO₃C tetrahedra to form a single layer containing 3- and 7-member rings. Neighboring single layers are pillared by M(1)O₄ tetrahedra, resulting in a novel double-layer structure. The organic moieties of cmdpH³⁻ are grafted on the two sides of the double layer. Compounds 3 and 4 are also isostructural, displaying a pillared layered structure. Within the inorganic layer, the M(1)O₅ tetragonal pyramids and M(2)NO₅ octahedra are each linked by PO₃C tetrahedra through corner-sharing, forming a layer in the ab plane which contains 3- and 10-member rings. These layers are pillared by 4,4′-bipyridine via coordination with the M(2) atoms from the adjacent layers, leading to a three-dimensional open framework structure with channels generated along the a-axis. The organic groups of cmdpH₂²⁻ locate within the channels. Magnetic studies show that antiferromagnetic interactions are dominant in compounds 2-4. Field dependent magnetization reveals a spin flop behavior for 2.     

Electrical conduction of bis(1,2-diondioximato)metals(II) and their partially oxidized complexes at high pressures

The resistivity of one-dimensional d⁸-metal complexes with various kinds of 1,2-diondioxime(dimethylglyoxime, nioxime, and diphenylglyoxime) ligands has been measured at high pressures. The resistivity of M(dmg)₂ and M(niox)₂ decreased with increasing pressure. The resistivity of M(dmg)₂ is much lower than that of M(niox)₂ at high pressure, though M-M distances and optical energy gaps in both salts are almost the same at atmospheric pressure. An anomalous low resistivity has been observed in Pt(dmg)₂ at about 40 kbar. The electrical resistivity of M(niox)₂ and M(dmg)₂, oxidized by oxidizing agents, decreased with increasing pressure. The resistivity of partially oxidized Pt complexes is significantly higher than that of the parent compounds at high pressure. On the contrary, partially oxidized Ni and Pd complexes are more conductive than unoxidized compounds at high pressures. The electrocal resistivity of unoxidized and partially oxidized Pt complexes increased with increasing pressure at higher pressures. The resistivity minimum at high pressure has been observed only in Pt complexes. The infrared spectra of the d⁸-metal complexes and their partially oxidized complexes have been investigated. The frequency of the CN stretching vibration in M(dmg)₂ and M(niox)₂ salts increases in the order Ni > Pd > Pt; on the other hand, the frequency of M(niox)₂X_n increases in the order Ni < Pd < Pt. The frequency of the CN stretching vibration is closely related to the effect of metal-ligand π1 back bonding in d⁸-metal complexes. Some anomalies in the resistance-pressure curve have been found in Ni(dpg)₂, Ni(dpg)₂I, Ni(dpg)₂I_0.5, and Ni(dpg)₂I_0.14. The anomalies are explained by new pressure-induced phase transitions.     

[H2en]2{La2M(SO4)6(H2O)2} (M=Co, Ni): First organically templated 3d-4f mixed metal sulfates

The first organically templated 3d-4f mixed metal sulfates, [H₂en]₂{La₂M(SO₄)₆(H₂O)₂} (M=Co 1, Ni 2) have been synthesized and structurally determined from non-merohedrally twinned crystals. The two compounds are isostructural and their structures feature a three-dimensional anionic network formed by the lanthanum(III) and nickel(II) ions bridged by sulfate anions. The La(III) ions in both compounds are 10-coordinated by four sulfate anions in bidentate chelating fashion, and two sulfate anions in a unidentate fashion. The transition metal(II) ion is octahedrally coordinated by six oxygens from four sulfate anions and two aqua ligands. The doubly protonated enthylenediamine cations are located at the tunnels formed by 8-membered rings (four La and four sulfate anions).     

Formation of [CoCl4(H2O)2] complex in CoCl2·MgCl2·8H2O double salt: structural and energetic properties of [MCl4(H2O)2] and [M(H2O)6] (M=Mg, Co)

The crystal structure of the double salt CoCl₂·MgCl₂·8H₂O has been determined by the X-ray diffraction method. It crystallizes in the space group with a=6.0976(9), b=6.308(1), c=8.579(3) Å, α=81.99(2)°, β=88.40°, γ=84.61(1)°, Z=1, and R=0.027. The crystal consists of two kinds of well separated octahedra, [CoCl₄(H₂O)₂]²⁻ and [Mg(H₂O)₆]²⁺. The former is unique as aquachloro complexes of Co²⁺. In order to elucidate the reason prepared as such unique complexes in the double salts, formation energies for [MCl₄(H₂O)₂]²⁻ and [M(H₂O)₆]²⁺ (M=Co, Mg) have been calculated by using the density functional methods, and it has been revealed that the formation energies of the first coordination sphere for the metal ions and the Cl⁻?H₂O hydrogen bond networks around [CoCl₄(H₂O)₂]²⁻ play a decisive role in forming [CoCl₄(H₂O)₂]²⁻ with the regular octahedral geometry in the double salt.     

Phenylimido Complexes of Technetium and Rhenium with Maleonitriledithiolate

[Tc(NPh)Cl₃(PPh₃)₂] or [Re(NPh)Cl₃(PPh₃)₂] react with two equivalents of Na₂mnt (mnt^2– = 1,2‐dicyanoethene‐1,2‐dithiolate) with formation of anionic complexes of the composition [M(NPh)(mnt)₂]^–. The products can be isolated as large red blocks of their AsPh₄⁺ salts. The complex anions contain square‐pyramidal coordinated metal atoms with the phenylimido ligands in apical positions. The M–N–C bonds are almost linear. A similar phenylimido complex with an additional amino group was synthesized from [Re(NC₆H₄‐4‐NH₂)Cl₃(PPh₃)₂]. The presence of such substituents may allow coupling of the metal complexes to biomolecules such as peptides, proteins, or sugars, provided the M=N bonds are sufficiently stable against hydrolysis.     

The stereochemistry of Tutton's salts X2[M(H2O)6](YO4)2

Neutron structure determinations have been made of Tutton's salts, X₂[M(H₂O)₆] (YO₄)₂, where Y = Se, X = K⁺, M = Cu²⁺; Y = S, X = K⁺, M = Ni²⁺, Cu²⁺, Zn²⁺; X = Rb⁺, Cs⁺, M = Cu²⁺. This work has shown that there are extensive hydrogen networks with almost linear hydrogen bonds from [M(H₂O)₆]²⁺ to (YO₄)^2?. The (H … O) distance increases in the Cu²⁺ series for X = K⁺ to Cs⁺ but there is no difference for the potassium copper salts when Y = Se or S. Three different distorted [M(H₂O)₆]²⁺ octahedra were found in the series (orthorhombic, tetragonal with two long and four short, or four long and two short bonds). The interatomic distances from X⁺ to the neighboring O in a distorted XO₈⁺ dodecahedron increases with increased cation size, implying that the X⁺ polyhedron is maintaining its shape.     

Metal coordination architectures of N-acyl-salicylhydrazides: The effect of metal ions and steric repulsion of ligands to their structures of polynuclear metal complexes

Three polynuclear transition metal complexes [Mn₈(DMF)₈(L1)₈] · 4DMF (1), [Mn₆(DMF)₆(L2)₆] · [Mn₆(DMF)₄(H₂O)₂(L2)₆] · 2DMF (2), [Cu₃(L3)₂(py)₂] (3) of the pentadentate ligands N-acyl-salicylhydrazides were synthesized and characterized, their crystal structures were investigated. The oxidation state and properties of the central metal ions are important in crystal structure formation, trivalent Mn(III) ion which easily form stable octahedral coordination metallamacrocycle complexes, metallacrowns 1 and 2 were obtained; while bivalent Cu(II) ion is easier to form square planar, trinuclear complexes 3 was obtained. The steric effect of the N-acyl side chains also plays an important role in the structures of these polynuclear complexes. The magnetic property of 1 was also investigated.     

[M(NH3)5Cl]WO4 (M = Cr, Rh): Synthesis, crystal structure, thermal properties

By single crystal X-ray diffraction the crystal structure of a series of [M(NH₃)₅Cl]WO₄ (M = Cr, Rh) complex salts is determined. The features of thermal expansion of the single crystal of [Cr(NH₃)₅Cl]WO₄ are studied by low- and high-temperature X-ray diffractometry in the temperature range from ?173°C to +127°C. It is shown that with an increase in the temperature, W-O distances and ∠O-W-O bond angles equalize and the average W-O distances decrease by 0.012 Å. The thermal properties of the salts in different gaseous atmospheres are examined and the phase composition of the obtained products is studied.     

Synthesis, structure and physical properties of Ru ferrites: BaMRu5O11 (M=Li and Cu) and BaM′2Ru4O11 (M′=Mn, Fe and Co)

The synthesis, structure, and physical properties of five R-type Ru ferrites with chemical formula BaMRu₅O₁₁ (M=Li and Cu) and BaM′₂Ru₄O₁₁ (M′=Mn, Fe and Co) are reported. All the ferrites crystallize in space group P6₃/mmc and consist of layers of edge sharing octahedra interconnected by pairs of face sharing octahedra and isolated trigonal bipyramids. For M=Li and Cu, the ferrites are paramagnetic metals with the M atoms found on the trigonal bipyramid sites exclusively. For M′=Mn, Fe and Co, the ferrites are soft ferromagnetic metals. For M′=Mn, the Mn atoms are mixed randomly with Ru atoms on different sites. The magnetic structure for BaMn₂Ru₄O₁₁ is reported.     

Reaction of ZnCl2 and HgCl2 metal salts with a bidentate Schiff base ligand in methanol solution, X-ray crystal structure, and theoretical studies

From the reaction of ZnCl₂ and HgCl₂ metal salts with (E)-4-chloro-N-(pyridine-2-ylmethylene)benzeneamine (L) in methanol solution, two binuclear Schiff base complexes were prepared. Both complexes were characterized by elemental analysis, UV–Vis, and IR spectrophotometry. X-ray crystal structure analysis showed that metal ion in the resulting centrosymmetric dinuclear ML₂Cl₄ complexes is in a distorted trigonal bipyramidal and a distorted square pyramidal coordination environment in the case of Zn(II) and Hg(II) metal ions, respectively. Three types of reaction between MCl₂ salts and ligand L producing three different types of products—ML₂ ²⁺, MLCl₂, and M₂L₂Cl₄—were simulated in both the gas phase and solution. The gas phase calculations at DFT (B3LYP) level of theory using SDD, CEP-121G, and LanL2DZ basis sets showed that the binuclear M₂L₂Cl₄ complexes are more stable than corresponding mononuclear MLCl₂ complexes. Furthermore, both the gas phase and solution studies showed that the formation of M₂L₂Cl₄ complexes from the metal cations, chloride anion, and ligand molecule is energetically more favored than that of MLCl₂ and ML₂ ²⁺ complexes.     

Magnetoresistance Study on TPP[M(Pc)(CN)2]2 (M=Fe, Co, Fe0.30Co0.70) Salts

The magnetoresistance study on TPP[M(Pc)(CN)₂]₂ (M=Fe, Co, Fe_0.30Co_0.70) salts is reported. These three salts have similar columnar structures, nevertheless exhibit different electrical behaviors. TPP[Fe(Pc)(CN)₂]₂ exhibits anisotropic giant negative magnetoresistance, while TPP[Co(Pc)(CN)₂] exhibits large positive magnetoresistance. The alloyed compound, TPP[Fe_0.30Co_0.70 (Pc)(CN)₂]₂, also exhibits anisotropic negative magnetoresistance, although the decrease in the resistivity under the magnetic field is less than that of TPP[Fe(Pc)(CN)₂]₂. The g-tensor anisotropy in the [Fe(Pc)(CN)₂] unit qualitatively explains the field-orientation dependence of the negative magnetoresistance. Magnetic fluctuation associated with a weak-ferromagnetic transition is suggested as a possible origin of the giant negative magnetoresistance.     

Palladium(0) and platinum(0) complexes of p,p′-diisopropyldibenzylideneacetone and their NMR spectra

The zerovalent diisopropyldibenzylideneacetone (dipdba, p-i-PrC₆H₄CHCHCOCHCH-p-i-PrC₆H₄) complexes M₂(dipdba)₃ (III, M = Pd; IV, M = Pt) have been prepared and their NMR spectra studied in solution. The ¹H and ¹³C NMR spectra of III and IV show complex patterns which are consistent with the complexes having very asymmetric structures in solution. The metal atoms are π-bonded to the olefins and the frameworks are stereochemically rigid over the temperature range ?90°C to +60°C on the NMR time scale. The ¹H spectra show the aryl groups to be rotating at +25°C but to be frozen out on the NMR time scale at low temperatures.     

Homo‐ and Heteronuclear Compounds with a Symmetrical Bis‐hydrazone Ligand: Synthesis,Structural Studies,and Luminescent Properties

Nine new coordination compounds have been synthesized by the reaction of salts of bivalent metal ions (a=Zn^II, b=Cu^II, c=Ni^II, d=Co^II) with the bis(benzoylhydrazone) derivative of 4,6‐diacetylresorcinol (H₄L). Three kinds of complexes have been obtained: homodinuclear compounds [M₂(H₂L)₂]?nH₂O ( 1 a , 1 b , 1 c , and 1 d ), homotetranuclear compounds [M₄(L)₂]?n(solv) ( 2 a and 2 c ), and heterotetranuclear compounds [Zn₂M₂(L)₂]?n(solv) ( 2 ab , 2 ac , and 2 ad ). The structures of the free ligand H₄L?2 DMSO and its complexes [Zn₂(H₂L)₂(DMSO)₂] ( 1 a* ), [Zn₄(L)₂(DMSO)₆] ( 2 a* ), and [Zn_0.45Cu_3.55(L)₂(DMSO)₆]?2 DMSO ( 2 ab* ) were elucidated by single‐crystal X‐ray diffraction. The ligand shows luminescence properties and its fluorimetric behavior towards M^II metals (M=Zn, Cu, Ni and Co) has been studied. Furthermore, the solid‐state luminescence properties of the ligand and compounds have been determined at room temperature. ¹H NMR spectroscopic monitoring of the reaction of H₄L with Zn^II showed the deprotonation sequence of the OH/NH groups upon metal coordination. Heteronuclear reactions have also been monitored by using ESI‐MS and spectrofluorimetric techniques.     

Complexing behaviour of aromatic thioamides (ArCSNHCOR). Transition metal complexes of N-carboethoxy-4-chlorobenzene- and N-carboethoxy-4-bromobenzene thioamide ligands

N-Carboethoxy-4-chlorobenzene thioamide (Hcct or HL) and N-carboethoxy-4-bromobenzene thioamide (Hcbt or HL) react with bivalent (Ni, Co, Cu, Ru, Pd and Pt), trivalent (Ru and Rh) and tetravalent (Pt) transition metal ions to give [M^II(L)₂], [Ru^III(L)₃], [Rh^III(L)(HL)Cl₂] and [Pt(L)₂Cl₂] complexes, respectively. In the presence of pyridine, Co^II and Ni^II salts react with the ligands (HL) to give [M^II(L)₂Py] (M = Co and Ni) complexes. Soft metal ions abstract sulphur from the ligands to yield the corresponding sulphide, together with oxygenated forms of the ligands. All the metal complexes have been characterised by chemical analyses, conductivity, spectroscopic and magnetic measurements.     

Titanium-based mixed oxides from a series of titanium(IV) citrate complexes

The isostructural hexaaquatransition-metal/titanium citrate complexes (NH₄)₂[M(H₂O)₆][Ti(H₂cit)₃]₂·6H₂O [M(II)=Mn 1, Fe 2, Co 3, Ni 4, Cu 5, and Zn 6] (H₄cit=citric acid), which were synthesized by reacting titanium(IV) citrate with divalent metal salts in the 1.0-3.5 pH range, adopt hydrogen-bonded chain motifs. The crystal structures feature three bidentate citrate anions that chelate to the titanium atom through their negatively charged α-alkoxy and α-carboxy oxygen atoms; the chelation is consistent with the large downfield shifts of ¹³C NMR for carbon atoms for complex 6. The thermal decomposition of the complexes furnishes mixed metal oxides. The main-group magnesium analog when heated at 600 °C yielded MgTi₂O₅ that is of the pseudobrookite type; the particle size is approximately 30 nm.     

Synthesis,structures and magnetic properties of nickel bis (dithiolene) complexes with [Fe(qsal)2]+

Two new compounds containing the possible Fe(III) spin-crossover cation, [Fe(qsal)₂]⁺ (qsalH = N-(8-quinolyl)salicylaldimine), and nickel bis(dithiolene) anions have been synthesized. Both are 1 : 1 salts [Fe(qsal)₂][Ni(dddt)₂] · CH₃CN · CH₃OH (1) and [Fe(qsal)₂][Ni(pddt)₂] (2) (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate; pddt = 6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate). They have been characterized by X-ray crystal structure determination, elemental analysis, UV-Vis spectra and magnetic susceptibility measurements. The UV–Vis spectra are dominated by [Ni(L)₂]^? (1, L = dddt; 2, L = pddt). Magnetic studies show antiferromagnetic interaction in 1 from intermolecular S···S contacts and π–π stacking interactions, while the antiferromagnetic interaction in 2 is very weak.