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A (Mn4Ni4II)-Ni-III molecular square exhibiting slow magnetization relaxation has been prepared from the reaction of a Mn(4)(II)Mn(6)(III)Mn(2)(IV)cluster and a simple Ni-II source. Dalton Transactions

A convenient route has been developed for the formation of [(Ti3O)-O-IV(OMe)(6)(eta(5)-C5H5)(3)](I-3) (2) involving methanolysis (and possibly hydrolysis) of species derived from titanocene diiodide, [Ti-IV(eta(5)-C5H5)(2)I-2] (1), under aerobic conditions. Single-crystal X-ray crystallography reveals that the cation of 2 consists of three Ti-IV's in a triangular arrangement bridged by a central mu(3)-oxide; the latter lies 0.686 angstrom out of the Ti-3 plane. Each edge of the triangle is bridged by oxygen of eta(1) : mu-MeO-. Terminal ligation is provided by three methoxide and three cyclopentadienyl groups. All Ti-IV centers are five-coordinate in an extremely distorted geometry. IR and electronic data are discussed in terms of the known structure and coordination modes of O2-, MeO-, and eta(5)-C5H5-. A proposal for the mechanism of the unexpected formation of the triiodide (I-3(-)) counteranion that is present in the crystal structure of 2 is also provided. Journal of Coordination Chemistry

Two new complexes, [Zn(O(2)CPh)(2)(L)(2)] center dot 2MeOH (1 center dot 2MeOH) and [Ni(2)(O(2)CPh))(4)(L)(2)] center dot 2MeCN (2 center dot 2MeCN), have been synthesized and characterized by X-ray analysis in the course of an ongoing investigation of the M(II)/X(-)/L [M(II) = Co, Ni, Cu, Zn; X(-) = Cl(-), Br(-), I(-), NCS(-), NO(3)(-), N(3)(-), PhCO(2)(-); L = 1-methyl-4,5-diphenylimidazole] reaction system, aiming at understanding and assessing the relative strength and the way in which the intermolecular interactions control the supramolecular organization of these compounds. In the mononuclear complex 1 center dot 2MeOH, the benzoate ion acts as a monodentate ligand resulting in a distorted tetrahedral N(2)O(2) coordination environment. Complex 2 center dot 2MeCN exhibits a dinuclear paddle-wheel structure; each Ni(II) has a square pyramidal NiNO(4) chromophore with four benzoate oxygens in the basal plane and the pyridine-type nitrogen atom of one ligand L at the apex. The structure of 1 center dot 2MeOH is stabilized by intramolecular pi-pi interactions between aromatic rings of adjacent 4,5-diphenylimidazole moieties; it is a feature also evidenced in similar compounds of the type [MX(2)L(2)]. Bioinorg Chem Appl

The reactions of methyl 2-pyridyl ketone oxime, (py)C(Me)NOH, with MSO4 center dot xH(2)O (M = Zn, x = 7; M = Cd, x = 8/3), in the absence of an external base, have been investigated. The synthetic study has led to the two new complexes [Zn(SO(4)){(py)C(Me)NOH}(H(2)O)(3)] center dot H(2)O (1 center dot H(2)O) and [Zn(2)(SO(4))(2){(py)C(Me)NOH} (4)] center dot (py)C(Me)NOH [2 center dot (py)C(Me)NOH], and the coordination polymer [Cd(SO(4)){(py)C(Me)NOH} (H(2)O)](n) center dot [Cd(SO(4)){(py)C(Me)NOH}(H(2)O)(2)] n (3). In the three complexes the organic ligand chelates through its nitrogen atoms. The sulfate anion in 1 center dot H(2)O is monodentate; the complex molecule is the mer isomer considering the positions of the aqua ligands. The Zn(II) centers in 2 center dot (py)C(Me)NOH are bridged by two syn, anti eta(1): eta(1): mu(2) SO(4)(2-) ligands; each metal ion has the cis- cis-trans disposition of the coordinated sulfate oxygen, pyridyl nitrogen and oxime nitrogens, respectively. The molecular structure of 3 is unique consisting of two different linear and ladder - type chains. pi-pi stacking interactions and/or hydrogen bonds lead to the formation of interesting supramolecular architectures in the three complexes. The thermal decomposition of complex 3 has been studied. Characteristic vibrational (IR, Raman) bands are discussed in terms of the nature of bonding and the structures of the three complexes. (C) 2008 Elsevier B. V. All rights reserved. Inorganica Chimica Acta

The initial use of the picolinate (pic(-))/sulfate "blend" in metal chemistry has yielded two neutral coordination polymers. Complexes [Zn-2(SO4)(pic)(2)(H2O)(3)](n) (1) and [Cd-2(SO4)(pic)(2)(H2O)(3)](n) center dot nH(2)O (2 center dot nH(2)O) were prepared by the reaction of MSO4 center dot xH(2)O [M = Zn, x = 7; M = Cd, x = 8/3] with one equivalent of picolinic acid (picH) in aqueous solution in the absence of external base. The structures of both compounds have been determined by single-crystal X-ray crystallography. Complex I consists of helical chains which interact through hydrogen bonds and stacking interactions to form a 3D, 5-connected network. Complex 2 - nH(2)O consists of ribbons that are crosslinked by the sulfato ligands to give a 2D, 4-connected network. Hydrogen bonds and stacking interactions lead to the formation of a 3D supramolecular architecture. In both coordination complexes, the pic ligand adopts two different bridging coordination modes (2.111 and 2.201 in 1; 2.211 and 2.201 in 2 center dot nH(2)O), while the SO42- behaves as a bidentate bridging 2.1100 (Harris notation) ligand. The Zn(II) complex has 5- and 6-coordinate metal ions, whereas 6- and 7-coordinate Cd-11 atoms are present in 2 - nH(2)O. Characteristic vibrational (IR, Raman) bands are discussed in terms of the known structures, and the coordination modes of the pic(-) and SO42- ligands. The thermal decomposition of the Cd(11) compound has also been studied. (C) 2007 Elsevier Ltd. All rights reserved. Polyhedron

A systematic investigation of the CuCl2/Mebta (Mebta = 1-methylbenzotriazole) reaction system is described, involving the determination of the influence of the Cu-II:Mebta ratio, the nature of solvent and the presence of counterions on the identity of the reaction products. As a consequence, complexes [Cu2Cl4(Mebta)(4)] (1), [CuCl2(Mebta)(2)] (2), {[Cu2Cl4(Mebta)(2)]}(n) (3), [Cu4OCl6(Mebta)(4)] . 0.25H(2)O (4 . 0.25H(2)O) and [Cu2Cl2(Mebta)(6)](ClO4)(2) (5) have been isolated and structurally characterized by single-crystal X-ray studies. Mebta behaves as a monodentate ligand binding through N(3). I is a dinuclear complex, the structure of 2 consists of discrete monomeric units, and that of 3 is composed of linear, well-separated polymeric chains of Cu-II atoms. The molecules of 4 . 0.25H(2)O have a central mu(4)-oxide ion surrounded tetrahedrally by four Cu-II atoms. In the cations of 5 the two Cu-II centres are asymmetrically bridged by two chloro ligands, with three Mebta molecules completing five coordination at each metal. Complexes were characterized by spectroscopic (IR, far-IR, solution UV/Vis) and thermal decomposition (TG, DTG, and DTA) techniques. Variable-temperature magnetic susceptibility data for 1, 3 and 5 showed intramolecular (1, 5) and intrachain (3) ferromagnetic exchange interactions. Estimates of the J parameters, experimentally derived, were in close agreement with a new magneto-structural criterion developed by us, holding for bis(mu-chloro) copper(II) dimers. A comparison between the CuCl2/Mebta and CuBr2/Mebta systems is also presented. (C) 2004 Elsevier B.V. All rights reserved. Inorganica Chimica Acta

Angewandte Chemie-International Edition

Reaction of Cu(ClO4)(2). 6H(2)O with 1-methylbenzotriazole (Mebta) in EtOH yields [Cu(Mebta)(4)(H2O)] (ClO4)(2). 0.4EtOH in ca. 75% yield. The structure of this salt has been determined by single-crystal X-ray crystallography. Mebta behaves as a monodentate ligand binding through N(3). The metal coordination geometry is best described as distorted square pyramidal with the H2O ligand occupying the apical site. The complex was also characterized by molar conductivity, room-temperature effective magnetic moment and spectroscopic (i.r., far-i.r., u.v./vis, e.s.r.) studies. The data are discussed in terms of the nature of bonding and known structure. Comparison between the structural and spectroscopic properties of [Cu(Mebta)(4)(H2O)](ClO4)(2). 0.4EtOH and those of the (CuI)-I-I site of Cu-Zn superoxide dismutase shows that the former can be considered as a fairly good model for the latter. Transition Metal Chemistry

Cu(NO3)(2). 3H(2)O reacts with 1 equiv. of the tetradentate Schiff base N,N'-bis[1-(2-pyridyl)ethylidene]ethane-1,2-diamine (LA) in refluxing acetone to yield the [CuLA(ONO2)(H2O)](NO3) complex in ca. 80% yield. The structure of this salt has been determined by single-crystal X-ray crystallography. The copper is six-coordinated with the L-A ligand in the equatorial plane and weakly bonded aqua and nitrate ligands above and below this plane. The complex cation is hydrogen-bonded to the nitrate counter-ion. The complex was also characterized by elemental analyses, molar conductivity, room-temperature magnetic susceptibility and spectroscopic (i.r., far-i.r., u.v.-vis, e.s.r.) studies. The data are discussed in terms of the nature of bonding and the known structure. Transition Metal Chemistry

The 2:1 reaction between Zn(O(2)CMe)(2). 2H(2)O and 1-Meim in refluxing MeCN gives [Zn(7)O(2)(O(2)CMe)(10)(1-Meim)(2)] 1 which comprises two vertex-sharing tetranuclear Zn(4)(mu(4)-O)(eta(1): eta(1) :mu(2)-O(2)CMe)(5)(1-Meim) units; solid-state (13)C and (15)N NMR spectra reveal structural details of the complex. Chemical Communications

The reactions of ZnX(2) and CdX(2) (X = Cl, Br, I) with the biheteroaromatic ligand 2-(2'-pyridyl)quinoxaline (L) were studied in ethanolic solutions. The new complexes [ZnX(2)L] (X = Cl, Br, I), [CdI(2)L] and [Cd(2)X(4)L(2)] were isolated and characterized by elemental analyses, conductivity measurements, X-ray powder patterns, thermal methods (TG/DTG, DTA) and spectroscopic (IR, far-IR, Raman, H-1 NMR) studies. The X-ray crystal structure of [ZnCl(2)L] . 0.5MeOH shows a distorted tetrahedral geometry around the zinc(II) atom. The ligand L acts as a bidentate chelate with the ligated atoms being the pyridine nitrogen and one of the quinoxaline nitrogens. A monomeric pseudo-tetrahedral structure is also assigned for [ZnBr2] and [MI(2)L] (M = Zn, Cd). Dimeric structures are proposed for the chloro and bromo cadmium(II) compounds, in which the two metal centres are bridged by two halo ligands, with a terminal halide and a chelating molecule of L completing five-coordination at each metal. All data are discussed in terms of the nature of bonding and known and assigned structures. A complex with the empirical formula Cd(2)Cl(4)L was isolated during the thermal decomposition of [Cd(2)Cl(4)L(2)]; the vibrational study of this thermally stable intermediate shows that L acts as a tridentate bridging ligand. The crystal structure of [Hg(2)Br(4)L(2)], which was not available when the results of the HgX(2)/L chemistry had been published, is also described. Polyhedron

The mercury(II) complexes [Hg(2)X(4)L(2)] (X=Cl,Br) and [HgI(2)L], where L is 2-(2'-pyridyl)quinoxaline, have been prepared and studied by; a combination of conductivity measurements and FT-IR and far-IR, Raman and H-1 NMR spectroscopy. The structures of the free ligand L and [Hg(2)Cl(4)L(2)] have been determined from three-dimensional X-ray data collected by counter methods. Compound L crystallizes in space group P2(1)/c with a=4.163(2), b=16.953(4), c=14.509(3) Angstrom, beta=94.79(2)degrees and Z=4. The complex [Hg(2)Cl(4)L(2)] crystallizes in space group P2(1)/n with a=7.627(3), b=15.617(4), c=11.099(4), beta=92.03(3)degrees and Z=2. In free L, the pyridine nitrogen and the nearest quinoxaline nitrogen are located on the opposite side of the carbon-carbon bond which connects the two rings; the reverse conformation has been observed on complexation. The structure of [Hg(2)Cl(4)L(2)] consists of two Hg(II) centres bridged by two chloro ligands, with a terminal chloride and a chelating molecule of L completing five-coordination at each metal. The geometry at mercury is a distorted trigonal bipyramid with the bridging chlorides occupying apical and equatorial sites of each Hg(II) atom. The bromo compound is isostructural with [Hg(2)Cl(4)L(2)], while a monomeric pseudotetrahedral structure is assigned for the iodo complex in the solid state. Inorganica Chimica Acta

Treatment of Fe(NO3)(3).9H(2)O with 1-methylbenzotriazole in EtOH-CH(OEt)(3) gave the unique, oxo-bridged complex [Fe2O(NO3)(4)(C7H7N3)(4)]; crystal structure and Mossbauer studies showed that the molecule has both bidentate and monodentate nitrates and possesses an S = 0 ground state, respectively. Journal of the Chemical Society-Dalton Transactions

The synthesis and study of a number of new iron(III) complexes of the ligands 3-hydroxy-2(1H)-pyridinone (3,2-opoH), 2,3-dihydroxybenzoic acid (2,3-dhbH3) and 3,4-dihydroxybenzoic acid (3,4-dhbH3) are described. These complexes have the formulae [Fe(3,2-OPO)2Cl]-Pr(n)OH, K[Fe(2,3-dhbH)2(H2O)2], [Fe(2,3-dhb)(H2O)2], K[Fe-(3,4-dhbH)2(H2O)2], [Fe(3,4-dhb)(H2O)2] and K6[Fe(3,4-dhb)3].3H2O. The complexes were characterized by elemental analyses. X-ray powder patterns, t.g.a./d.t.g. techniques, magnetic susceptibilities and spectroscopic (u.v.-vis., i.r. and variable-temperature Fe-57-Mossbauer) studies. Monomeric octahedral structures are assigned for the 1:2 2,3-dhbH-2- CoMplex and the 1:3 3,4-dhb3-compound. Dinuclear and/or oligonuclear structures are tentatively proposed for the remaining complexes in the solid state. In [FeL(H2O)2] (L3- = 2,3-dhb3- or 3,4-dhb3-), iron(III) appears to be 5-coordinate. Both oxygens of 3,2-opo- participate in coordination, while the dihydroxybenzoato ligands exhibit various coordination modes, depending mainly on the positions of the hydroxy groups, their anionic charge and the ligand:metal molar ratio used. Transition Metal Chemistry

By using the ''complexes as ligands'' synthetic strategy and the unique [Pd(LH)2] and [Pt(LH)2] precursors, the novel heterobimetallic polymeric compounds [MPdL2]n and [CuPtL2]n (M = Co, Ni, Cu, Zn, Pt; L2- = the dianion of N,N'-dimethylmonothiooxamide) have been prepared. The vibrational analysis of the complexes is given using various isotopic substitutions. The polymers consist of alternate planar PdO2S2 (or PtO2S2) and tetrahedrally-distorted planar MN4 structural units. Spectroscopy Letters

The reaction of the unexpectedly formed ligand 2-(2'-pyridyl)quinoxaline (L) With CuCl2 in ethanol, followed by recrystallization from methanol, yields the dinuclear copper (II) complex [Cu2Cl4L2]. The crystal structure of this compound shows a bidentate chelating behaviour of L and different (terminal, asymmetric bridging) chloride coordination modes. Some properties of the dimer are also described. Polyhedron

The complexes (MLCl2] (M=Co, Ni, Cu, Zn), where L is the new ligand 2-(2'-pyridyl)quinoxaline derived unexpectedly from 2-acetylpyridine and 1,2-phenylenediamine, were isolated. The ligand and its complexes have been characterized by a variety of physical and spectroscopic techniques. L behaves as a bidentate chelating ligand in the monomeric pseudotetrahedral Zn(II) compound; all three nitrogen atoms of L are involved in coordination in the polymeric Co(II), Ni(II) and Cu(II) complexes giving five-coordinate (Co(II)) or six-coordinate (Ni(II), Cu(II)) structures. Inorganica Chimica Acta

Transition metal(II) chloro complexes of the new Schiff base ligand 1,2-bis(2'-pyridylmethyleneimino)benzene (L), derived from 2-pyridinecarboxaldehyde and 1,2-phenylenediamine, were prepared. Compounds of [MnLCl2].H2O, [CoLCl2].2H2O, [NiLCl2] and [Zn3L2Cl4]Cl2 were prepared. Details are given of the formation of the complex [Cu(L.EtOH)Cl2], in which one molecule of EtOH adds across only one of the Schiff base C=N groups to give the coordinated ligand L.EtOH. The rationalization of this type of reaction by considering the steric requirements of the ligand is given. The complexes were characterized by elemental analyses, conductivity measurements, thermal techniques, mass spectra, magnetic susceptibilities and spectroscopic (i.r., ligand field, e.s.r., H-1 n.m.r.) studies. The nitrogen donor atoms of the tetradentate ligands L and L.EtOH are assumed to adopt an essentially planar arrangement about manganese(II), cobalt(II), nickel(II) and copper(II), with the remaining axial coordination sites occupied by chloro ligands to yield high-spin octahedral molecules. A trinuclear structure, based on tetrahedrally coordinated metal ions, is proposed for the zinc(II) complex. Transition Metal Chemistry

An inorganic model approach to the corrosion inhibition of metals by benzotriazoles has been initiated. The preparation and characterization of monomeric cobalt(II) complexes of the types [CoX2(Mebta)2] (X = Cl, Br, NCS, NO3), (MebtaH)[CoCl3(Mebta)], (MebtaH)2[CoCl4], [Co(NCS)2(Mebta)4], [Co(NCS)2(MeOH)2(Mebta)2] and [Co(NO3)2 L2(Mebta)2] (L = H2O, MeOH), where Mebta = 1-methylbenzotriazole, are described. Four representative complexes have been structurally characterized by single-crystal X-ray diffraction studies; [CoCl2(Mebta)2] (1), trans-[Co(NCS)2(Mebta)4] (5), trans-[Co(NCS)2 (MeOH)2(Mebta)2] (6) and cis-[Co(NO3)2(Mebta)2] (8). Mebta acts as a monodentate ligand binding through N(3). The geometry about cobalt in 1 is tetrahedral, while complexes 5, 6 and 8 have octahedral stereochemistries. The new complexes were also characterized by elemental and thermogravimetric analyses, conductivity measurements, variable-temperature magnetochemistry and spectroscopic (IR, ligand field, low-temperature ESR) methods. The data are discussed in terms of the nature of bonding and known structures. Polyhedron

Synthetic procedures are described that allow access to anilinium salts containing the complex anions [Hg2Cl6]2-, [Hg2Cl4X2]2- (X = Br, I), [CdHgI6]2-, [CdHgI4Br2]2- and [CdHgBr4I2]2-. Isolated dimeric structures are proposed for the new complexes in the solid state, using X-ray powder patterns, Far-IR and Raman spectra. The spectral detail is greatly enhanced in measurements at low temperature (approximately 100 K). Zeitschrift Fur Naturforschung Section B-a Journal of Chemical Sciences

The synthesis of the Ni(II), Pd(II) and Cu(II) complexes of N,N'-bis(aminoalkyl)oxamides (LH2) is described and structures are proposed on the basis of their physical and spectroscopic properties. With Ni(II) and Pd(II) only one complex is formed with general formula NiL or PdL, characterised by coordination through two deprotonated amide N-atoms and two terminal NH2 groups. With Cu(II) it proved possible to obtain three structurally different compounds, depending on the pH, with general formulae Cu(LH2)X2, Cu2(L)X2 and CuL in which X = Cl, Br or NO3. The structure of [Cu2(C8O2N4H16](NO3)2 was solved by means of x-ray diffraction; Mr = 451.33, monoclinic, space group P2(1)/n, a = 9.503(4), b = 7.614(1), c = 10.407(3) angstrom, beta = 98.43(3)-degrees, V = 744.3(7) angstrom 3, Z = 2, Dx = 1.202 g cm-3, mu = 1.33 cm-1, lambda-(MoK-alpha) = 0.71073 angstrom, F(000) = 520, room temperature, R = 0.043, wR = 0.047 for 1080 observed [I greater-than-or-equal-to 3-sigma(I)] not systematically absent reflections out of 1423 measurements and 137 variables. The compound has a conformational chair/boat disorder with 82% in the more stable chair form. Transition Metal Chemistry

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