Synthesis of layered (2-D) V-based bimetallic oxalates from non-aqueous media that cannot be synthesized from aqueous media

The reaction of (NBu4)3[V(III)(ox)3] (1, ox = oxalate) and M(II) (M = Fe, Co, Ni, Cu) ions in MeCN, leads to the isolation of V-based coordination polymers of [N(n-Bu)4][Fe(II)V(II)I(ox)3].0.30[[N(n-Bu)4](BF4)] (2), [N(n-Bu)4][Co(II)V(III)(ox)3].0.75[[N(n-Bu)4](BF4)] (3), [N(n-Bu)4][Ni(II)V(III)(ox)3].0.20[[N(n-Bu)4](BF4)].0.20MeCN (4), and [N(n-Bu)4][Cu(II)V(III)(ox)2](BF4)2 (5) composition. Due to the lability of [V(III)(ox)3]3- to dissociate ox2-, these compounds cannot be prepared from aqueous media. 5 is best described as [N(n-Bu)4][V(III)Cu(II)(ox)2](BF4)2, and 2, 3, 4, and 5 are proposed to have a layered (2-D) motif for the MM(ox)x (x = 2, 3) extended framework. The [V(III)Cu(II)(ox)2] composition of 5 is reported for the first time for a bimetallic oxalate. 2 shows a weak antiferromagnetic interaction between Fe(II), S = 2 and V(III), S = 1 ions (theta = -9.4 K) within the 2-D layers. 3 and 5 do not magnetically order above 2 K. 4 magnetically order as ferromagnets below 2.55 K [taken as the onset of magnetization in chi'(T)], and has a glass transition temperature (chi'(max) at 1000 Hz) at 2.26 K.     

Light induced magnetic properties of spiropyrane tris(oxalato)chromate (III) single crystals

The effect of UV light on Weiss temperature and ESR spectra in 1-isopropyl-3, 3, 5′, 6′-tetramethylspiro[indolin-2,2′-[2H]pyrano[3,2-b]pyridinium] tris(oxalato)chromate (III) (Sp₃Cr(C₂O₄)₃) has been found. Additional line has been observed in the ESR spectra of irradiated samples in “strong” magnetic fields of ~15 kOe. The analysis of angular dependences of the ESR spectra allowed a contribution of Cr³⁺ ions to magnetic properties of Sp₃Cr(C₂O₄)₃ to be determined. The zero-field splitting parameters D=0.619 cm⁻¹, E=0.024 cm⁻¹ were derived from the experimental data. The parameters were typical for Cr³⁺ in the chromium oxalate. Weiss temperature changed sign from 25 to −25 K under UV irradiation. The value of Weiss temperature and its changing cannot be explained by exchange interaction, dipole-dipole interaction or the effect of crystal field. The existence of Weiss temperature is explained by the changes in amount and spin of paramagnetic particles. The change is due to thermoactivated redistribution of electrons between chromium ions and spiropyrane molecules. Light-induced transfer of electrons is also explaining the change in sign of Weiss temperature under UV irradiation.     

Synthesis and the thermal decomposition of iron(III) tris(oxalato) ferrate(III) tetrahydrate

The paper describes the synthesis and thermal decomposition of Fe[Fe(C₂O₄)₃]4H₂O in air. The compound is completely dehydrated at 170°C and some reduction in the inner sphere iron(III) occurs. At 290°C, a mixture of ferric oxide and ferrous oxalate is obtained. Beyond 420°C, the decomposition is complete and final residue is ferric oxide. A probable reaction mechanism is proposed.     

Synthesis, structural and magnetic studies of imidazolium bis(oxalato)cuprate(II)

Imidazoliumm bis(oxalato)cuprate(II) has been synthesized and its structure determined by X-ray crystallography. Variable temperature magnetic susceptibility measurements, as well as EPR and UV-vis spectroscopic studies, have been carried out. The results show that in the solid state the compound exists in a chain-like structure, with an asymmetric one-atom weak oxalate bridge joining adjacent Cu^II centres. Of the two oxygen atoms of each coordinated oxalate only one participates in bridging; thus, each oxalate ultimately achieves three-point coordination. Each of the imidazolium ions participates in two hydrogen through the N—H moieties. The compound exhibits a weak antiferromagnetic interaction (J = −0.40 cm⁻¹).EPR spectra reveal that the triplet state is appreciably populated at both room and liquid nitrogen temperatures.     

Synthesis, structure, and magnetic properties of the layered copper(II) oxide Na2Cu2TeO6

A new quaternary layered transition-metal oxide, Na2Cu2TeO6, has been synthesized under air using stoichiometric (with respect to the cationic elements) mixtures of Na2CO3, CuO, and TeO2. Na2Cu2TeO6 crystallizes in the monoclinic space group C2/m with a = 5.7059(6) A, b = 8.6751(9) A, c = 5.9380(6) A, beta = 113.740(2) degrees, V = 269.05(5) A3, and Z = 2, as determined by single-crystal X-ray diffraction. The structure is composed of infinity(2)[Cu2TeO6] layers with the Na atoms located in the octahedral voids between the layers. Na2Cu2TeO6 is a green nonmetallic compound, in agreement with the electronic structure calculation and electrical resistance measurement. The magnetic susceptibility shows Curie-Weiss behavior between 300 and 600 K with an effective moment of 1.85(2) muB/Cu(II) and theta(c) = -87(6) K. A broad maximum at 160 K is interpreted as arising from short-range one-dimensional antiferromagnetic correlations. With the aid of the technique of magnetic dimers, the short-range order was analyzed in terms of an alternating chain model, with the surprising result that the stronger intrachain coupling involves a super-superexchange pathway with a Cu-Cu separation of >5 A. The J2/J1 ratio within the alternating chain refined to 0.10(1), and the spin gap is estimated to be 127 K.     

Reactions of tris(oxalato)cobaltate(III) with two-electron reductants

The tris(oxalato)cobaltate(III) complex [Co(C(2)O(4))(3)](3-), E(o)(Co)(III/II)=+0.57 V) is readily reduced by the 2e(-) reagents, Sn(II) and Ge(II), in contrast to (NH(3))(5)CoCl(2+) and (NH(3))(5)CoBr(2+), which are unreactive toward these donors. Rates for the oxalato oxidant are only 10(-3)-10(-2) as great as those for vitamin B(12a)(aquacob(III)alamin, E(o)+0.35 V at pH 1), in accord with the suggestion that reductions of corrin-bound cobalt(III) by Sn(II) and Ge(II) occur predominantly through an additional path involving Co(i). Reductions of the oxalato complex by 2e(-) donors are taken to proceed by initial formation of odd-electron intermediates (e.g., Sn(III) and Ge(III)) which react rapidly with Co(III). Such a two-step sequence is in keeping with the observed behavior of the rare reductant, Ti(II), which is found to be oxidized by [Co(C(2)O(4))(3)](3-) more slowly than (independently prepared) Ti(III) under comparable conditions.     

New complexes of tris(2-aminoethanolato-O,N)cobalt(III) sulfates: Synthesis and structure

The reaction of [Co(Etm)₃] · 3H₂O (I) with sulfuric acid affords [Co(HEtm)₃]₂(SO₄)₃ · 4H₂O (II). The change in the synthesis procedure (the direction interaction of cobalt(II) sulfate with β-aminoethanol (HEtm)) makes it possible to isolate [Co(HEtm)₃](SO₄)(HSO₄) · H₂O (III) and {[Co(HEtm)₃][Co(Etm)₃]}₂(SO₄)₃ · 7.75H₂O (IV). The X-ray diffraction analyses of compounds II–IV show that all of them are of the ionic type. In compounds II and III, the ionic structure consists of the [Co(HEtm)₃]₃₊ cations and sulfate anions in a ratio of 2: 3 and 1: 2, respectively. The basic difference in compounds II and III is the different degrees of deprotonation of the acid residues. In complex II, two anions SO ₄ ^2? are doubly deprotonated. In complex III, of the four anions found in the independent part of the unit cell of the sulfate anion two anions are monodeprotonated. In structure IV, two crystallographically independent complexes [Co(HEtm)₃]³⁺ and [Co(Etm)₃] are joined into a dimer through the O-H?O hydrogen bonding.     

Synthesis and structural characterization of 2-D layered copper(II) styrylphosphonate coordination polymers

We report the synthesis, physicochemical characterization, and crystal structure of Cu-SP (SP?=?styrylphosphonic acid, H₂O₃PCH=CH₂(C₆H₅)), the first reported example of a metal derivative of SP. The starting SP acid was fully characterized by X-ray single-crystal diffractometry, elemental analysis (C and H), ³¹P-NMR, ¹³C-NMR, ¹H-NMR, HPLC, UV–vis, MS, TG, and FT-IR spectroscopy. The copper(II) derivative was synthesized and characterized by DTA-TG and FT-IR, and also its structure was determined from powder data. The crystal structure was refined by the Rietveld method. The crystal structure of Cu-SP shows a layered 2-D architecture, where the organic moieties are pointed toward the interlamellar space. The inorganic layers are composed of Cu²⁺ dimers, where the coordination geometry of Cu²⁺ can be described as distorted trigonal bipyramid. The three coplanar oxygens (O2, O3, and O3) have bond distances of 2.165(9), 1.982(9), and 2.103(11)?Å, respectively. The bond lengths for the apical oxygens (O1 and O2) are 1.908(13) and 1.996(11)?Å, respectively.     

Synthesis, morphology, structure, and magnetic characterization of layered cobalt hydroxyisocyanates

New layered pink cobalt hydroxyisocyanates have been prepared by controlled hydrolysis of aqueous solutions of CoCl2.6H2O. Co(OH)(1.4)(NCO) 0.6.0.6H 2O ( 1) is formed when urea is used as the hydrolysis agent and mannitol as the stabilizer, while Co(OH)(1.25)(NCO)(0.75).0.2H2O ( 2) is formed when the hydrolysis agent is changed to hexamethylenetetramine and NaOCN is added to the solution. IR spectroscopy of 1 and 2 indicates that the OCN (-) is N-bonded to Co (2+). The X-ray powder data for 1 could be indexed using an intergrowth model consisting of both rhombohedral ( R3 m (166); a = 3.2031(1) A, c = 23.6876(11) A, hydrotalcite-like, 3 R 1) and hexagonal ( P 63/ mmc (194); a = 3.2005(2) A, c = 15.8303(5) A, Manasseite-like, 2H1) polytypes. Rietveld refinement of the X-ray powder data was performed using a two polytype model and 30% random substitution of the OH (-) ions by OCN (-). Although it is less crystalline, the XRD data for 2 can be indexed using a rhombohedral-symmetry cell with unit cell parameters, a = 3.158 A and c = 21.57 A. Both 1 and 2 exhibit magnetically ordered ground states with a saturation magnetization of ca. 2.0 mu B. The magnetization data is consistent with 3D ferromagnetic ordering of edge-share octahedral-Co (2+) layers with effective spin S' = 1/2.     

Synthesis,structure, and reactions of tris(4-fluorophenyl)antimony dibromide

The interaction of tris(4-fluorophenyl)antimony with copper(II) bromide in acetone has afforded tris(4-fluorophenyl)antimony dibromide; recrystallization of the product from ethanol has yielded the (4-FC₆H₄)₃SbBr₂·[(4-FC₆H₄)₃SbBr]₂O adduct. [(4-FC₆H₄)₃SbCNS]₂O oxide has been prepared from tris(4-fluorophenyl)antimony dibromide and potassium thiocyanate in aqueous-acetone solution. Antimony atoms in the molecules of the prepared compounds exhibited the distorted trigonal bipyramid coordination with the electron-accepting ligands in the axial positions.     

Synthesis,crystal structure and magnetic properties of [Mn(LH)2(H2O)2] n with a two-dimensional layered structure and three-dimensional hydrogen bonding network

A new manganese polymer [Mn(LH)₂(H₂O)₂] _n (LH₂ = iminodiacetic acid) (1) has been prepared and structurally and magnetically characterized. The polymer has a two-dimensional (2D) layered structure with the unique Mn atom on an inversion center, surrounded by six oxygen atoms. In each layer, all iminodiacetic acid entities are coordinated to Mn atoms in a bridging/bidentate mode, thus linking the [Mn(LH)₂(H₂O)₂] monomeric units together to form a 2D layered polymer. Hydrogen bonding is responsible for an extended three-dimensional network. Analysis of variable-temperature magnetic susceptibility data (2–300) K shows that the polymer displays weak antiferromagnetic exchange interaction with a coupling constant, J = –0.28 cm^–1.     

Synthesis and structure of bis(monohaloacetates) of tris(5-bromo-2-methoxyphenyl)antimony

Tris(5-bromo-2-methoxyphenyl)antimony bis(monohaloacetates) [(5-Br)(2-MeO)C₆H₃]₃Sb[OC(O)CH₂X]₂, X = Cl (I), Br (II), I (III) have been synthesized by the reaction of tris(5-bromo-2-methoxyphenyl)antimony with chloro-, bromo-, and iodoacetic acids in the presence of hydrogen peroxide. According to X-ray analysis the antimony atom in I–III has a distorted trigonal-bipyramidal coordination.     

Synthesis, structure, and magnetic properties of two 1-D helical coordination polymeric Cu(II) complexes

Two helical coordination polymeric copper(II) complexes bearing amino acid Schiff bases HL or HL′, which are condensed from 2-hydroxy-1-naphthaldehyde with 2-aminobenzoic acid or l-valine, respectively, have been prepared and characterised by X-ray crystallography. In [CuL]_n (1) the copper(II) atoms are bridged by syn-anti carboxylate groups giving infinite 1-D right-handed helical chains which are further connected by weak C-H?Cu interactions to build a 2-D network. While in [CuL′]_n (2) the carboxylate group acts as a rare monatomic bridge to connect the adjacent copper(II) atoms leading to the formation of a left-handed helical chain. Magnetic susceptibility measurements indicate that 1 exhibits weak ferromagnetic interactions whereas an antiferromagnetic coupling is established for 2. The magnetic behavior can be satisfactorily explained on the basis of the structural data.     

Synthesis and structure of tris(4-fluorophenyl)antimony dicarboxylates

The interaction of tris(4-fluorophenyl)antimony with chloroacetic, 4-nitrophenylacetic, and benzoic acids in diethyl ether in the presence of tert-butyl hydroperoxide has yielded tris(4-fluorophenyl)antimony dicarboxylates, their Sb atoms bearing distorted trigonal bipyramid coordination with the carboxylate ligands in the axial positions. The intramolecular contacts between Sb atom and carbonyl O atom are formed in the molecules of the products. Their crystal packing is determined by weak intermolecular hydrogen bonds of the H···F and H···O=C types.     

Synthesis,spectroscopic characterization,and X-ray crystal structure of tris(trimethylsilyl)cyanurate

Tris(trimethylsilyl)cyanurate, C₁₂H₂₇N₃O₃Si₃ (1), has been synthesized and characterized by elemental analysis, IR, Raman, ¹³C and ²⁹Si NMR, and thermogravimetric methods. The molecular and crystal structure has been determined by single crystal X-ray diffraction. This compound crystallized in space group P6₃/m (176), Z = 2 with a = 11.017(2), b = 11.017(2), c = 9.676(3) Å; α = 90°, β = 90°, γ = 120°. The geometry of the molecule is compared with tris(trimethylsilyl)cyamelurate.