Search Results
Transition-metal complexes with hydrazides and hydrazones
7. Dioxomolybdenum(VI) complexes of salicylaldehydep-hydroxybenzoylhydrazone and their thermal stability
Several new complexes of dioxomolybdenum(VI) of the general formula [MoO2(L)S], whereL is the dianion of salicylaldehydep-hydroxybenzoylhydrazone andS denotes H2O, MeOH, py, PPh3, DMSO or DMF, were synthesized and characterized by elemental analysis, electronic UV-VIS and IR spectra, thermal analysis, molar conductivity and magnetic susceptibility measurements. Salicylaldehydep-hydroxybenzoylhydrazone participates in the coordination as a tridentate ligand with the ONO set of donor atoms. The complexes contain acis-MoO2 group and are of octahedral geometry. Complexes of the MoO2L type were also prepared by synthesis in CHCl3 solution and by isothermal heating of [MoO2(L)S] complexes. The MoO2L complex synthesized in CHCl3 solution has most probably a pentacoordinated structure while the complex obtained by isothermal heating of [MoO2(L)S] has a polymeric hexacoordinated structure.
Abstract
Thermal decomposition studies of 2,3,5-triphenyl tetrazolium halochromates have been carried out upto 1000°C at a linear heating rate of 10 deg·min−1. The complexes undergo two stage decomposition. First one corresponds to the redox decomposition of the complex along with the loss of a phenyl halide molecule and 3/2 mol of oxygen. While, the second step corresponds to the oxidation of the formazan type structure formed in the first step. The first step decomposition follows diffusion controlled reaction mechanism in a sphere governed by the equationg(α)=[1−(1−α)1/3]2. Activation energy and pre-exponential factors have been determined by Coats-Redfern model and Dixit-Ray model. Activation energy decreases as the electronegativity of the halide ion decreases.
Oxathioamidates (CSNR1 R 2COOKR 1=R 2=H (A),R 1=H andR 2=CH3 (B),R 1,=R 2=CH3 (C)) can act as O, S donors and form pentaatomic ring systems with divalent metals (M(II)=Mn, Fe, Co, Ni, Cu, Zn). Vibrational spectra and thermal analysis provide information on the amount and nature of associated water molecules. The dehydration of MA2(H2O)2 (M=Mn, Fe, Co, Ni) can be very well explained by the C.F.S.E. (crystal field stabilization energy) for weak field octahedral complexes. The complexes with ligand A and B decompose to form polymers by deprotonation on the thioamide group. The proposed structures are confirmed by the vibrational spectra. For ligand C no stable intermediates are formed during heating, degradation proceeds until metal sulphide remains.
Dithiomalonamide [H2A, CH2(CSNH2)2] and 2,2-dimethyldithiomalonamide [H2B, C(CH3)2(CSNH2)2] can act as bidentate ligands and form stable, cationic 1∶2 complexes with general formula M2(H2L)2X2 [M=Ni2+, Pd2+, Pt2+;X=C1, Br, I; H2L=H2A, H2B] in strong acidic medium. An elaborate thermal study is presented, based on results from elemental analyses and vibrational studies (IR and Raman spectroscopy). The H2A complexes start to decompose by releasing two HX molecules whereafter a stable intermediate M(HA)2 is formed. The H2B complexes degrade in a different way; the metal-sulphur bond is broken and the ligand is expelled as a whole. Influences of the metal ion and of the halogenide counterions are investigated.
Complexes of amic acids with polar aprotic solvents
IX. Interpolymer complexes of a polyamic acid with polybases
The polymer-polymer interactions of a polyamic acid (PAA) with polybases (polyvinylpyrrolidone, polyacrylonitrile and polyvinylpyridine) were studied by means of massspectrometric thermal analysis (MTA), TG, DTA and IR-spectroscopic methods in solution and in the solid state. The polybases were shown to substitute the solvent from its complex with PAA, forming H-bonds or salt-type polycomplexes with PAA. The MTA method proved to be very informative for the investigation of interpolymer interactions in the solid state.
The thermal properties of cyanatocopper complexes with pyridine, bipyridine and phenanthroline are described in this paper. It was found that the thermal stabilities of the complexes were found to increase in the order py≪bipy<phen ligands. The significantly higher thermal stability of the complexes with bipyridine and phenanthroline is caused by the presence of dimeric structural units in the crystal structure and intermolecular interactions of the cyanate and heterocyclic ligands.
Metal complexes with pyrazole-derived ligands
IV. Thermal decomposition of cobalt(II) complexes with 3(5)-anmo-4-acetyl-5(3)-methylpyrazole
The thermal decomposition of tetrahedral cobalt(II) complexes with 3(5)-amino-4-acetyl5(3)-methylpyrazole (HL) of the general formula [Co(HL)2X2] (X=Cl, Br, I, NCO, NCS) and octahedral [Co(HL)2(H2O)4](NO3)2 and [Co(HL)2−N(CN)2}2] complexes was investigated in air atmosphere in the interval from room temperature to 1000°C. Decomposition of the complexes occurred in several successive endothermic and exothermic processes, and the residue was in all cases CoO.
Pyridine-type complexes of transition metal halides
IV. Preparation and thermal studies on some new complexes of nickel(II)-halides formed with 2-, 3-, and 4-methyl-pyridines
Abstract
Formation of nitrogen ligated complexes of types NiL6X2, NiL4X2, NiL2X2 and NiL1X2 (whereL=pyridine, 2-, 3- and 4-methyl-pyridine andX=F, Cl, Br, I) have been studied by traditional preparative methods, i.e. from solutions and by solid-gas phase chemisorption. Quaternary mixed complexes were obtained by chemisorption from heated intermediates. The complexes thus formed were further analysed by simultaneous TG-DTG-DTA. Effects of the ligands on stoichiometry and thermal properties of the complexes are discussed.
Abstract
Copper complexes of some 1-phenyl-3-methyl-4-acyl-5-pyrazolones have been prepared. The complexes were characterized by elemental analyses and thermal analyses. It was shown that the melting points decrease linearly in increasing the molecular weight of the complexes.
Thermal decomposition of thorium(IV) complexes with benzenecarboxylic acids in air atmosphere
III. Thorium(IV) complexes with methylbenzoic and benzenedicarboxylic acids
Abstract
The conditions and products of thermal decomposition of thorium(IV) complexes with general formula Th(R-C6H4COO)4 (whereR=2-CH3, 3-CH3, 4-CH3), Th(OH)2(4-CH3C6H4COO)2. H2O and Th(OH)2(R-C6H4COO)2·nH2O (whereR=2-COO, 3-COO,n=2;R=4-COO,n=1) were studied. Anhydrous thorium(IV) complexes decompose in two steps. On heating, tetra(2-methylbenzoato)-thorium(IV) decomposes to yield ThO2 through the intermediate ThOCO3 whereas tetra(3-methylbenzoato)thorium(IV) and tetra(4-methylbenzoato)thorium(IV) decompose to ThO2 through oxocomplexes. Hydrated thorium(IV) complexes are dehydrated in one step and then anhydrous complexes decompose to ThO2. Di [1,2-(benzene)dicarboxylato]dihydroxythorium(IV) decomposes directly to ThO2, whereas the 1,3- and 1,4-isomers through the intermediate thorium(IV) oxocarbonates.
