S. S. Bhatt

Evaluation of optimum grafting parameters and the effect of ceric ion initiated grafting of methyl methacrylate on to jute fibre on the kinetics of thermal degradation and swelling behaviour

Abstract To effect useful changes in jute fibre, we graft copolymerized with methyl methacrylate (MMA) initiated by ceric ions and studied optimization of grafting parameters as a function of various reaction conditions. Jute and its graft copolymer thermally degrade in one and two stages, respectively, but follow the same degradation mechanism. The degradation mechanism and thermal kinetics were evaluated by applying seven kinetic degradation models. Both fibres decompose following the R-2 (PBR-cylindrical symmetry) kinetic equation. Initially, the thermal stability of the graft copolymer is better, as evident from higher energy of activation ( E act ) and higher initial decomposition temperature (IDT). Swelling ( P s) of graft copolymers increases as a function of grafting and at a particular graft level follows the order: DMF>H 2 0>iso-propanol.

Thermonanalytical investigations of monochlorobis (2,4-pentanedionato) vanadium(IV) aryloxides

The thermal decomposition of the complexes [Vcl (acac)2(OAr)] (where acac=2,4-pentanedionato anion; OAr=–OC6H4O-M-4, OC6H4OBut-4) has been studied using non-isothermal techniques (DTA and TG). The TGA indicate that the substitution of chlorine in VCl2(acac)2 with aryloxide ligands results in an increase in the initial temperature of decomposition (IDT) of the new complexes. The role of the substituent at the aryloxide ring on the thermal stability of the complexes is depicted and hence described. The ultimate decomposition product in all the complexes has been identified as V2O5. The kinetic and thermodynamic parameters namely, the energy of activation E, the frequency factor A, entropy of activation S and specific reaction rate constant kr etc. have been rationalized in relation to the bonding aspect of the aryloxide ligands.

4-METHOXYPHENOXO COMPLEXES OF MONOOXOVANADIUM(V) AND THEIR REACTIONS WITH CYANOANILINES AND CYANOPYRIDINES

Abstract The new 4-methoxyphenoxomonooxovanadium(V) complexes with the general formulae [VOCl3−x(OC6H4OMe-4)x] (where x = 1 → 3) have been conveniently synthesized in good yields using VOCl3 and the trimethylsilyl derivative of 4-methoxyphenol, Me3SiOC6H4OMe-4 as reactants in CCl4. The complexes were characterized by chemical analyses, conductively measurements, IR,1H NMR, electronic spectra and thermal studies. Coordination compounds of the parent complexes with cyanoanilines and cyanopyridines have been prepared and studied. Tentative stereochemistries are assigned in each case.

Synthesis and Reactions of Tetrakis(4-Methoxyphenoxo)titanium(IV)

Abstract The compound of the composition Ti(0C6H40Me-4)4 (I) has been isolated by reacting titanium tetra-chloride with 4-methoxy-phenol in 1:4 molar ratio in benzene and characterised on the basis of elemental analyses, conductance, molecular weights, IR and NMR spectral studies. Reactions of (I) with α -hydroxy-aldehydes and ketones and some nitrogenous bases such as 1,10-phenanthroline and 2,2-bipyridylhave also been investigated.

Synthesis and characterization of organotin(IV) 2,4-dinitrophenoxides

Complexes of the composition [R3Sn(DNP)] and [n‐Bu2SnCl2 − x(DNP)x] (R = Ph and Me; x = 1 and 2; DNP = anion of 2,4‐dinitrophenol) have been synthesized by the silver metathesis method, involving the reaction of Ph3SnCl, Me3SnCl and n‐Bu2SnCl2 with the silver salt of 2,4‐dinitrophenol in tetrahydrofuran at room temperature and were characterized by elemental analyses, conductivity measurements, IR, and 1H NMR studies. The IR spectral studies suggest a bidentate mode of coordination of phenol in these complexes. Double phenoxides of the type M2[R3Sn(DNP)3] (M = Na and K) have also been obtained by reacting the parent triorganotin(IV) phenoxides with alkali metal derivatives of the phenol in 1:2 molar ratio. Thermal investigations of these complexes depicted quite interesting behaviour, as the decomposition did not yield any residue, contrary to previous reports. The thermal behaviour of these complexes has shown their ability as high‐energy materials.

Synthesis, Characterization and Thermal Studies of Di- and Triphenyltin(IV) Complexes of p-Chloro- AND p-Nitrobenzohydroxamic Acids

Abstract Di- and triphenyltin(IV) complexes of the compositions Ph2SnC1n (XBHA)2-n and Ph3Sn(XBHA) (where n=O or 1, X=p-C1 or p-NO2 and BHA=anion of the hydroxamic acid, BH2A) have been synthesized by the reactions of Ph2SnC12 or Ph3SnC1 with the potassium salts of the respective p-chloro or p-nitrobenzo-hydroxamic acids in a MeOH/THF mixture. The complexes have been characterized by elemental analyses, molar conductance, molecular weight determinations and IR spectra. The results indicate that the ligand is bidentate, coordinating through the carbony1 and hydroxylamine oxygens. The reactions of Ph2SnC1(XBHA) with sodium derivatives of acetylacetone, dibenzoylmethane and salicylaldehyde (NaL) have led to the formation of mixed ligand complexes of the type Ph2Sn(XBHA). L Thermal decomposition of the complexes in an air stream yielded pure SnO2 at 700–800°C. Referee I: R. A. Geanangel Referee II: L. R. Sita

Thermal studies of some aryloxides of titanium(IV)

Thermal behaviour of aryloxides of titanium(IV) of composition TiCln(OAr)4−n (wheren=0→3 and OAr=OC6But-4, OC6H4OMe-4 and OC6H2-Bu2t-2,6−Me-4) has been studied by DTA and TG analysis. Multiple decomposition steps have been indicated by thermal weight losses which are both exothermic and endothermic as shown by DTA curves. Based upon the total % loss in weight; during entire decomposition titanium dioxide has been found to be the final residue in each case.

Synthesis, characterization, and acceptor behavior of dichlorotris(2-t-butylphenoxo)niobium(V)

The reaction of niobium pentachloride with three equivalents of 2-t-butylphenol in carbon tetrachloride afforded [NbCl2(OC6H4C(CH3)3-2)3]. The identity of the complex has been established by elemental analyses, molar conductance, molecular weight determination, IR, 1H, and 13C-NMR and UV-Vis spectral studies. Based upon these studies, a square–pyramidal geometry around niobium has been proposed. Thermal behavior of the complex has been studied by TGA and DTA. Acceptor behavior of [NbCl2(OC6H4C(CH3)3-2)3] toward Ph3P, Ph3As, Ph3PO, Ph3AsO, and an uncommon ligand arsenictrithiophenoxide As(SPh)3 allows the isolation of 1 : 1 addition compounds as shown by physicochemical, IR, and 1H-NMR spectral studies. The formation of [NbCl2(OC6H4C(CH3)3-2)3] · As(SPh)3 appears to be the first adduct of its class and suggests the suitability of As(SPh)3 as a ligand.

Synthesis and Characterization of para‐Nitrophenoxides of Zirconium(IV)

Abstract Compounds of the composition ZrCl3(OC6H4NO2‐p) and ZrCl2(OC6H4NO2‐p)2 have been synthesized from the reaction of ZrCl4 with equimolar and bimolar amounts of the trimethylsilyl derivative of p‐nitrophenol in benzene under reflux. Attempts to isolate the tetrakis derivative, Zr(OC6H4NO2‐p)4, even by heating the components in high‐boiling solvents were unsuccessful. Based upon analytical data, conductance, cryoscopic, IR and 1H NMR studies, dimeric structures with bridging through phenoxo groups have been proposed for these compounds. The thermal decomposition of these complexes is a combination of both exothermic and endothermic processes, as is inferred from TG/DT studies. Reactions of these compounds with nitrogen bases viz., pyridine, 1,10‐phenanthroline and 2,2′‐bipyridyl results in breakdown of the bridged structure and formation of simple addition compounds, which have been assigned octahedral structures.

PREPARATION, STRUCTURAL CHARACTERIZATION, AND PROPERTIES OF NIOBIUM PENTAARYLOXIDES, Nb(OAr)5

Reactions of niobium pentachloride with 4-t-butylphenol and 4-methoxyphenol in 1:5 molar ratios in CC14 have yielded pentaaryloxides of the composition Nb(OAr)5 and these have been characterized by chemical analyses, conductivity measurements, IR, 1H NMR, and UV-Vis studies. Double phenoxides of the composition M(I)[Nb(OAr)6] [M(I) = Na or K] have also been obtained by reacting alkali metal phenoxides with Nb(OAr)5 in equimolar ratios as evidenced from conductance composition curves. Further, the reactions of these double phenoxides with divalent cobalt and nickel chlorides form hetero-bimetallic compounds of the composition M(II)[Nb(OAr)6]2. The thermal behaviour of the compounds isolated in the present studies has also been discussed.