Synthesis, EPR spectrum and X-ray structure of tetra-n-butylammonium bis(benzene-1,2-dithiolato(2-)-κ2S,S′)platinate(I II)

The new salt, tetra-n-butylammonium bis(benzene-1,2-dithiolato(2-)-κ2S,S′)platinate(I II), [NBu4][Pt(C6H4S2) 2] (1), has been synthesized in ethanol/water, and fully characterized by single crystal X-ray structure determination. The central platinum in the complex ion [Pt(bdt)2]- is tetracoordinated by the S atoms of the bdt2- ligands (bdt2- is benzene-1,2-dithiolate) in a square-planar geometry. The well-resolved frozen solution EPR spectrum exhibits rhombic symmetry. The room temperature effective magnetic moment (μeff = 1.80 Bohr magneton) is in line with this spectrum and strongly supports the Pt(III) oxidation state in 1. This observation is in excellent agreement with previous results reported on closely related Ni(III), Pd(III) and Pt(III) species. © 2008 Elsevier Ltd. All rights reserved.Articl

Synthesis, crystal structure and thermal stability of the novel coordination polymer of general formula: {[(H₂O)Ba(<i>μ</i>-H₂O)Ba(OH₂)₄]@[(C₂O₄)₂Al(<i>μ</i>-OH)₂Al(C₂O₄)₂].H₂O}n^§

The novel coordination polymer of general formula {[(H2O)Ba(μ-H2O)Ba(OH2)4]@ [(C2O4)2Al(μ-OH)2Al(C2O4)2].H2O}n (1), has been synthesized in water and characterized by FTIR spectra, elemental and thermal analyses, and by full X-ray structure determination. Compound 1 crystallizes in an interesting nonmolecular coordination network where oxalato ligands μ-bridge neighboring Ba(II) and Al(III) centers. The asymmetric unit of 1 consists of one cationic tri-μ-oxygen-bridged pseudo-dimer - formally [(H2O)Ba1(μ-H2O)Ba2(OH2)4]4+ - one centrosymmetric anionic di-μ-hydroxido-bis[cis-bis(oxalato)aluminate] dimer - [(C2O4)2Al1(μ-OH) 2Al2(C2O4)2]4- - and one solvent water molecule. The Ba2+ ions in the cationic dimer are both ten-coordinate and 4.335(1) Å apart. The Al3+ ions in the anionic dimer each experience distorted octahedral coordination by six O atoms, being distant by 2.854 Å in average and centered at two independent lattice positions related by the P21/n space group symmetry. The anionic dimers are interconnected amongst themselves via O-H***O bridgings across the hydroxido groups into 1-D pillars that run parallel to [001]. These negatively charged pillars are tightly cross-linked via coordinate bonds of oxalato O atoms to the cationic Ba dimers. Coulombic interactions between the ionic motifs and extended 3-dimensional H-bonding involving solvent water molecules as well, concur to consolidate the bulk structure. Thermogravimetric analysis (TGA) shows that compound 1 is stable to heat up to 400 °C

Two isostructural oxalato-bridged dimetallic heptanuclear [Ba^II₃M^III₄] complexes (M = Cr; Fe) associated with 3-aminopyridinium cations: Synthesis, crystal structure and magnetic properties

Two heterometallic heptanuclear oxalato-bridged [Ba II 3M III 4] complexes, (Org-H) 6[Ba 3(H 2O) 5.1Cr 4(C 2O 4) 12]·5H 2O (1) and (Org-H) 6[Ba 3(H 2O) 5.3Fe 4(C 2O 4) 12]·5H 2O (2) (Org-H = C 5H 7N 2 +: 3-aminopyridinium cation), have been synthesized through an ion-exchange reaction strategy by combining {Ba 6(H 2O) 17[M III(C 2O 4) 3] 4}·7H 2O (M = Cr; Fe) with (C 5H 7N 2) 2C 2O 4 in a 1:3 M ratio. They have been characterized by elemental and thermal analyses, IR spectroscopy, single-crystal X-ray diffraction and variable temperature magnetic susceptibility measurements. The hybrid salts 1 and 2 are isostructural and they crystallize in the monoclinic space group C2/c. Their structures consist of [Ba 3(H 2O) 5M 4(C 2O 4) 12] 6− dimetallic heptanuclear units (M = Cr, Fe), six 3-aminopyridinium cations and five crystallization water molecules. The d-metal atom is located in a distorted (2 + 2 + 2) octahedral environment of six O atoms from three chelating oxalato(2−) ligands. In the crystal, intermolecular N[sbnd]H⋯O and O[sbnd]H⋯O hydrogen bonds link the anions and 3-aminopyridinium cations and lattice water molecules into a three-dimensional framework. In addition, π-π stacking interactions [centroid-centroid distances of 3.680 to 3.938 Å] between the pyridine rings contribute to the stabilization of the framework. The magnetic properties of the two salts have been investigated and they revealed weak antiferromagnetic coupling between d-metal atoms. </p

Tris(oxalato)chromate(III) hybrid salts templated by pyridinium and mixed pyridinium-ammonium cations: synthesis, structures and magnetism

By modifying the stoichiometric ratio of starting materials, two tris(oxalato)chromate(III) salts, (C7H11N2)3[Cr(C2O4)3] (1) and (C5H8N3)2(NH4)[Cr(C2O4)3]·2H2O (2) {(C7H11N2)+ = 2-amino-4,6-dimethylpyridinium, (C5H8N3)+ = 2,6-diaminopyridinium}, were synthesized and characterized by elemental and thermal analyses, single-crystal X-ray diffraction, IR and UV − Vis spectroscopies, EPR and SQUID measurements. Salt 1 exhibits a 3-D supramolecular framework based on [Cr(C2O4)3]3- and 2-amino-4,6-dimethylpyridinim cations, (C7H11N2)+, via N–H···O hydrogen bonds. Interestingly, π–π stacking interactions between pyridine rings contribute to the stabilization of the crystal packing. In contrast to salt 1, no π–π stacking interactions are observed in the mixed-cation salt 2 and its crystal packing is consolidated by N–H···O and O − H···O hydrogen bonds. EPR spectra of 1 and 2 are consistent with the oxidation state +3 of the chromium center in an octahedral environment. Temperature-dependence of the magnetic susceptibility data investigated from 2 to 300 K revealed the existence of zero-field splitting effects (ZFS) for Cr(III) ions in both compounds.</p