Physical and Structural Characterization of Ce(IV) β-Diketonate Complexes: Evidence for Geometrical Isomers in the Solid-State

The Ce(IV) β-diketonate complexes CeL ₄ [where L is txhd (2,2,6-trimethyl-3,5-heptanedionate) 1; tmod (2,2,7-trimethyl-3,5-octanedionate) 2; tmhd (2,2,6,6-tetramethyl-3,5-heptanedionate) 3] were prepared by the interaction of the sodium salt of the diketonate with cerium(III) nitrate hexahydrate in aqueous ethanol solution. Differential scanning calorimetry and thermogravimetric analysis showed that 1 has a significantly lower sublimation temperature, but higher decomposition temperature than 3. The solid-state structures of the three complexes were determined via single crystal x-ray diffraction methods. Complex 2, which does not sublime, had significantly closer intermolecular contacts than those found for 1 and 3.     

Mixed-Ligand Metal Succinate Complexes with 1,10-Phenanthroline and Ethylenediamine: Synthesis,Characterization, Spectroscopic and Thermal Studies. Crystal Structure of Succinatocobalt(II) Complex with Phenanthroline

The novel mixed-ligand metal succinate (suc) complexes with 1,10-phenanthroline (phen) and ethylenediamine (en) have been synthesized and characterized by elemental analyses, magnetic moments, UV-VIS and IR spectra. Thermal reactivity of the complexes was studied in air using DTA and TG, and decomposition of the complexes resulted in the formation of corresponding metal oxides. The crystal structure of the [Co(suc)(H₂O)(phen)₂]·1.5H_CO·C₄H₁₀O complex was determined by x-ray diffraction. The Co(II) complex crystallizes as a monobutanol solvate. In the complex, the cobalt ion lies on an inversion center and displays a distorted octahedral coordination with one aqua, one suc and two phen ligands. The suc ligand acts as a monodentate ligand through one of the negatively charged O atoms, while phen behaves as N-donor bidentate ligand. The crystal also contains disordered lattice water molecules and the structure is stabilized by extensive hydrogen bonding to form a three-dimensional infinite network.     

Ruthenium carbonyl derivatives of N-salicylidene-2-hydroxyaniline

The ruthenium tricarbonyl derivative [Ru(CO)₃(sha)] (1), was synthesized from reaction of [Ru₃(CO)₁₂] with N-salicylidene-2-hydroxyaniline (shaH₂) Schiff base. The corresponding reactions of the ruthenium cluster with shaH₂ in presence of a secondary ligand L,L?=?pyridine and triphenyl phosphine resulted in the formation of the dicarbonyl derivatives [Ru(CO)₂(shaH₂)(L)] (2, 3). In the presence of L?=?2-aminobenzimidazole or thiourea, two complexes [Ru(CO)₂(sha)(L)] (4, 5) were formed and the shaH₂ ligand bonded to ruthenium oxidatively. The bipyridine(bpy) derivative had the molecular formula [Ru(CO)₂(shaH)(bpy)] (6), with shaH coordinated bidentate. All complexes were characterized by elemental analysis and mass, IR, ¹H NMR and UV–Vis spectroscopy. The spectroscopic studies of these complexes revealed several structural arrangements and different tautomeric forms.     

Syntheses,crystal structures,and electrochemical characterizations of two octahedral iron(III) complexes with Schiff base of pyridoxal and aminoguanidine

This article presents the synthesis, physico-chemical, in particular voltammetric, characteristics of two iron(III) complexes with pyridoxal aminoguanidine (PLAG), [Fe(PLAG)Cl₂(H₂O)]Cl (1) and [Fe(PLAG)₂](NO₃)₃ (2). As expected, the zwitterion of the chelate ligand is coordinated tridentate through oxygen of phenol and nitrogen atoms of azomethine and imino groups of the aminoguanidine fragment. In both complexes, Fe(III) is distorted octahedral. [Fe(PLAG)₂](NO₃)₃ (2) is the first bis(ligand) complex with this ligand. Cyclic voltammetric characteristics of the ligand and complexes were studied in DMF in the presence of TBAP or LiCl as supporting electrolytes. The complexes are unstable in this solvent, especially in the presence of an excess of chloride, thus forming several reducible species whose stabilities and behaviors were characterized.     

Binary and Ternary Complexes Involved in the Systems Methioninehydroxamic Acid - Glycylglycine - Ni(II) or Cu(II) Ions

The formation constants of binary and ternary complexes involved in the systems methioninehydroxamic acid (MX), glycylglycine (GG) and Cu(II) or Ni(II) were determined by pH-metric titration in aqueous solution at an ionic strength (I)= 0.15 M NaCl) and T = 25°C. Ternary species of the type (MX : GG : Ni(II) or Cu(II) : H) = (1 : 1 : 1 : r), (2 : 1 : 1 : r) and (1 : 2 : 1 : r) exist in the pH range ～3 to ～10. Differential pulse polarography (DPP) was used to follow complex formation and to study the reduction properties of these metal ions in the presence of MX, and GG. The metal oxidation states were more stabilized in the ternary systems than in the binary systems except for a few Ni(II) systems. Spectral studies in the UV-Vis-nIR were used to monitor the presence of ternary species in the Ni(II) and Cu(II) systems. In addition, EPR studies were also used to record the magnetic properties of the binary and ternary species in the Cu(II) systems.     

Syntheses,Structures and Characterization of Cobalt(II) and Cobalt(III) Complexes with N-Benzylated Polyamines and a Terminal Azido Ligand

Mononuclear cobalt(II) and cobalt(III) complexes, [Co(trenb)(N₃)]Cl (1) and [Co(dienb)(N₃)₂(OAc)] (2) (trenb = tris[2-(benzylamino)ethyl]amine, dienb = 1,9-diphenyl-2,5,8-triazanonane) were synthesized and characterized by elemental analyses, IR and electronic spectra. Their crystal structures were also determined by X-ray diffraction analyses. In Complex 1, cobalt(II) is five-coordinate trigonal bipyramidal with one azido nitrogen atom and four nitrogen donors of the tripodal ligand; the chloride interacts weakly with one of the secondary amino groups of trenb via a hydrogen bond. In Complex 2, cobalt(III) is in a distorted octahedral coordination environment, consisting of three nitrogen atoms of the amine ligand, two azide nitrogen atoms and an oxygen atom of the acetate ion; a six-membered ring involving the hydrogen bond may stabilize the complex, which maintains its solid geometry in DMF as indicated by the electronic spectrum.     

Hg(II), Tl(III), Cu(I), and Pd(II) Complexes with 2,2'-Diphenyl-4,4'-Bithiazole (DPBTZ), Syntheses and X-Ray Crystal Structure of [Hg(DPBTZ)(SCN)2]

Reaction of the ligand 2,2′-diphenyl-4,4′-bithiazole (DPBTZ) with Hg(SCN)₂, Tl(NO₃)₃, CuCl, and PdCl₂ gives complexes with stoichiometry [Hg(DPBTZ)(SCN)₂], [Tl(DPBTZ)(NO₃)₃], [Cu(DPBTZ)(H₂O)Cl]_, and [Pd(DPBTZ)Cl₂]. The new complexes were characterized by elemental analyses and infrared spectroscopy. The crystal structure of [Hg(DPBTZ)(SCN)₂] determined by X-ray crystallography. The Hg atom in the title monomeric complex, (2,2′-diphenyl-4,4′-bithiazole)mercury(II)bisthiocyanate, [Hg(C₁₈H₁₂N₂S₂)(SCN)₂], is four-coordinate having an irregular tetrahedral geometry composed of two S atoms of thiocyanate ions [Hg-S 2.4025(15) and 2.4073(15) Å] and two N atoms of 2,2′-diphenyl-4,4′-bithiazole ligand [Hg-N 2.411(4) and 2.459(4) Å]. The bond angle S(3)-Hg(1)-S(4) of 147.46(5)° has the greatest derivation from ideal tetrahedral geometry. Intermolecular interaction between Hg(1) and two S atoms of two neighboring molecules, 3.9318(15) and 3.9640(18) Å, make the Hg(1) distort from a tetrahedron to a disordered octahedron. The attempts for preparation complexes of Tl(I), Pb(II), Bi(III), Cd(II) ions with 2,2′-diphenyl-4,4′-bithiazole ligand were not successful and also the attempts for preparation complexes of 4,4′,5,5′-tetraphenyl-2,2′-bithizole ligand with Cu(II), Ni(II), Co(II), Co(III), Mn(II), Mn(III), Fe(II), Fe(III), Cr(III), Zn(II), Tl(III), Pb(II), Hg(II), Cu(I), Pd(II) were not successful. This point can be regarded as the initial electron withdrawing of phenyl rings and also their spatial steric effects.     

Syntheses and Crystal Structures of Two One-Dimensional Chain Copper Benzoylacetone Complexes Bridged Through Azobispyridine Ligands

Two copper complexes [Cu(bzac)₂(4,4′-azpy)]·H₂O (1) and [Cu(bzac)₂(3,3′-azpy)] (2) (bzac = benzoylacetone, 4,4′-azpy = 4,4′-azobispyridine, 3,3′-azpy = 3,3′-azobispyridine) have been synthesized and characterized. The crystal structures were determined by X-ray diffraction analysis. In crystals of Complexes 1 and 2, the copper atoms have distorted octahedral symmetry. The two compounds possess very similar one-dimensional linear chains linked through the rod-like 4,4′-azpy or 3,3′-azpy ligands.