Carmen Guzmán-Miralles

A novel one-dimensional oxalato-bridged copper(II) complex with 2,2′-bipyridine

Abstract The crystal structure of the compound {[Cu(ox)(bpy)]·2.5H2O}n 1 (ox=oxalate dianion, bpy=2,2′-bipyridine) consists of columnar stacks of neutral [Cu(ox)(bpy)] units linked by semicoordination Cu–O bonds. The magnetic properties show the occurrence of alternating ferro–antiferromagnetic interactions ( J AF =−2.1 cm −1 and J F =+0.2 cm −1 ).

Solid-state chemistry of nickel(II)-oxalate-amine systems. Synthesis, characterization and crystal structure of the bis(2,2′-bipyridine) (oxalato-O,O′)nickel(II) tetrahydrate

Abstract Purple single crystals of the mononuclear mixed-ligand complex [Ni(ox)(bipy)2]·4H2O, where ox is oxalate and bipy is 2,2′-bipyridine, were obtained by slow evaporation of a solution previously prepared by adding an ethanolic bipy solution to an aqueous solution of nickel(II) chloride hexahydrate and potassium oxalate monohydrate (molar ratio 1:2). The compound was characterized by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction. The crystal structure consists of neutral mono-nuclear [Ni(ox)(bipy)2] units and crystallization water molecules which are held together by an extensive three-dimensional network of OH…O and CH…O hydrogen bonds and face-to-face stacking interactions between the π-systems of the bipy aromatic rings. The nickel atom is coordinated by two oxygen atoms of a bidentate oxalate ligand and four nitrogen atoms belonging to two bipy in an octahedral cis arrangement. Thermal decomposition of the complex was studied by TG-DTA techniques in synthetic air and argon atmospheres.

Preparation, chemical characterization and structural studies of 3-aminopyridinium salts of dithiooxalate ligand complexes, [M(S2C2O2)2]2− (M = NiII, PdII or PtII

Abstract The synthesis conditions, solid-state characterization and crystal structures of three 3-aminopyridinium salts of planar inorganic dithiooxalato complexes, (HC 5 H 6 N 2 ) 2 [Ni(S 2 C 2 O 2 ) 2 ] ( 1 ), (HC 5 H 6 N 2 ) 2 [Pd(S 2 C 2 O 2 ) 2 ] ( 2 ) and (HC 5 H 6 N 2 ) 2 [Pt(S 2 C 2 O 2 ) 2 ] ( 3 ), are described. The compounds have been characterized by elemental analysis and thermal, spectroscopic and X-ray diffraction methods. These complexes show a high thermal stability and the surrounding atmosphere is an important factor which significantly influences the course of the thermal decompositions as well as the final products. The IR and UV—vis spectra confirm the presence of the 3-aminopyridinium cations and the complex anions. X-ray diffraction analyses show that the compounds are isostructural and crystallize in the monoclinic space group P 2 1 / n with two molecules in the unit cell. The crystal and molecular structure of 2 was determined by single-crystal X-ray diffraction. The crystal structure consists of mixed layers of quasi-planar complex [Pd(S 2 C 2 O 2 ] 2− anions and 3-aminopyridinium cations linked by strong NH ⋯ O hydrogen bonds and anion—cation π—π interactions.

Synthesis, structure and characterisation of [Ni(bipy)3][NaAl(ox)3]: (bipy = 2,2′-bipyridine, ox = oxalate)

The compound [Ni(bipy)3][NaAl(ox)3], where ox2– is the oxalate dianion and bipy is 2,2′-bipyridine, was obtained by mixing of K2[Ni(ox)2(H2O)2]·4H2O and [H2bipy]Cl2 in silica hydrogel at room temperature. The complex, which incorporates Na and Al from the silica gel, was characterised by Fourier-transform IR spectroscopy, energy-dispersive X-ray analysis, thermogravimetric techniques and single-crystal X-ray diffraction. It crystallises in the cubic system, space group P213, with a= 15.518(2)A, U= 3736.9(8)A3 and Z= 4. The crystal structure consists of a chiral, three-dimensional polymeric network of Al3+ and Na+ bridged by bis(bidentate oxalate) ligands, [NaAl(ox)3]n2n–, with the [Ni(bipy)3]2+ cations inserted in the anionic network cavities. The cations and anionic network are held together by means of electrostatic forces and weak C–H ⋯ O hydrogen bonds.

Studies on the thermal decomposition of dipotassium trans-diaquabis(oxalato-O,O′)nickelate(II) tetrahydrate

Abstract The thermal behaviour of the compound K 2 [Ni(C 2 O 4 ) 2 (H 2 O) 2 ]·4H 2 O has been studied by thermogravimetry and differential thermal analysis. Experiments were carried out in dynamic atmospheres of argon-oxygen and argon, respectively, over the temperature range 20–600°C. Thermoanalytical data show that the surrounding atmosphere significantly influences the dehydration process as well as the final products. In the oxidative atmosphere, the six water molecules are released during two almost overlapping endothermic steps, whereas in the inert atmosphere, the free water molecules and the coordinated ones are lost in separate stages. In both cases, dipotassium carbonate has been found as the final product, together with NiO in the oxidative environment and metallic nickel in the inert atmosphere.

Tetraphenylphosphonium 1,2-dithiooxalato-s,s′ complexes of nickel(II), palladium(II) and platinum(II). Synthesis, chemical characterization, spectroscopic and x-ray studies, and thermochemistry

Abstract Three salts of inorganic dithiooxalato complexes, (Ph4P)2[Ni(dto)2] (1), (Ph4P)2[Pd(dto)2] (2) and (Ph4P)2[Pt(dto)2] (3), where Ph4P+ is the tetraphenylphosphonium cation and dto2− is the 1,2-dithiooxalato-S,S′ ligand, were synthesized and characterized by elemental analysis, IR and UV-vis spectroscopies, thermal analysis (TG, DTG and DTA) and X-ray diffraction techniques. The IR and UV-vis spectra support the presence of the organic cation and the complex anions. The three compounds are isostructural and crystallize in the triclinic space group P 1 . The thermal analytical data show that the starting compounds and the surrounding atmosphere significantly influence the course of the decomposition reactions, as well as the final products. They were examined by elemental analysis and X-ray powder diffractometry. In an argon-oxygen atmosphere, a mixture of nickel(II, III) oxides and nickel(II) sulphide for 1, metallic palladium for 2 and platinum(0) for 3 were obtained, whereas under argon nickel sulphides, a mixture of Pd/PdS and metallic platinum were identified as the final products.

Structure of dipotassium trans-diaquabis(oxalato-O,O')nickelate(II)–water (1/4)

The crystal structure of the title compound was studied by single-crystal X-ray diffraction in order to determine the coordination geometry around the Ni II atom in the anionic complex. The crystal structure comprises centrosymmetric [Ni(C 2 O 4 ) 2 (H 2 O) 2 ] 2- complex anions, K + cations and free water molecules linked together through electrostatic interactions, K-O coordination, and an extensive network of hydrogen bonds of types O w -H...O and O w -H...O w

Thermal features and behaviour of protonated diethylenetriamme isopolyvanadates

Abstract Thermal decomposition of 3-aza-l,5-pentamethylenediammonium metavanadate(V), (H2C4H13N3)(VO3)2, and bis(diethylenetriammonium) decavanadate(V) tetrahydrate, (H3C4H13N3)2[V10O28] · 4H2O (hereafter abbreviated as DIENVA1 and DIENVA10, respectively) has been studied by thermogravimetry (TG and DTG) and differential thermal analysis (DTA) under argon-oxygen and argon atmospheres. Thermoanalytical data show that the decomposition processes are different for both compounds and the surrounding atmosphere influences the thermal processes as well as the final products. In argon-oxygen atmosphere, the compounds undergo decomposition during several endothermic and exothermic steps to give vanadium(V) oxide. In the oxidative thermal decomposition of DIENVA10, a mixture of mixed-valance vanadium oxides, V307 and V60i3, has been identified. The experiments in an inert atmosphere lead to vanadium(IV) and vanadium(III) oxides. The essential thermal features of the protonated diethyl-enetriamine isopolyvanadates are reviewed and discussed.

(μ-Oxalato-O1,O2:O1′,O2′)bis[aqua(diethyl­enetri­amine)nickel(II)] bis(hexafluorophosphate) dihydrate

The title compound, [Ni(2)(C(2)O(4))(C(4)H(13)N(3))(2)(H(2)O)(2)](PF(6))(2).2H(2)O, contains a dinuclear oxalato-bridged nickel(II) complex cation. The structure determination reveals the presence of a centrosymmetric binuclear complex where the oxalate ligand is coordinated in a bis-bidentate mode to the Ni atoms. The distorted octahedral environment of each Ni atom is completed by the three N atoms of the diethylenetriamine ligand in a fac arrangement and by one O atom from a water molecule. PF(6)(-) acts as counter-anion. A two-dimensional network of hydrogen bonds links the cations and anions and stabilizes the structure.

SYNTHESIS, CHEMICAL CHARACTERIZATION AND CRYSTAL STRUCTURE OF THE ANILINIUM BIS(1,2-DITHIOOXALATO-S,S')NICKELATE(II)

Abstract Purple single crystals of the complex (H3NC6H5)2[Ni(dto)2] (dto = S2C2022− = 1,2-dithiooxalato-S,S′) were grown in silica-hydrogel media. A microcrystalline powder of this compound was also obtained from an aqueous solution of anilinium hydrochloride and potassium bis(dithiooxalato)nickelate(II). The compound was characterized by elemental analysis, FT-IR spectroscopy and thermal techniques (TG/DTG and DTA). The crystal structure, determined by X-ray diffraction, consists of anilinium cations and [Ni(dto)2]2− anions, with a near perfect square-planar environment of sulfur atoms around the nickel atom. Crystal cohesion is assumed by electrostatic interactions, an extensive three-dimensional network of hydrogen bonds and weak face-to-face π-stacking interactions between the π-systems of the aromatic cations.