The reactions of [PtCl2(NCR)2] with telluroethers (ArAr'Te) in organic solvents have been investigated. The reactions in dichloromethane yield [PtCl2(TeArAr')2], while those in tetrahydrofuran (THF) give different products depending on the steric demands of the aryl groups on tellurium, the molarity of the reactants, and the reaction conditions. The reactions between [PtCl2(PhCN)2] and TeArAr' in 1:1 molar ratio at room temperature in THF yield several products, like [PtCl2(TeArAr')2] (Ar/Ar' = Ph/Ph, o-tol/Mes, Mes/Mes), [PtCl2(PhCN){NC(O)Ph[TeMes(o-tol)]}], and [PtCl2{NC(O)Ph(TeMes2)}2]. The reaction with TeMes2 in refluxing THF gave [PtCl2{NC(Ph)C4H7O}{NC(O)Ph(TeMes2)}] and [PtCl(TeMes2){Te(Mes)CH2C6H2Me2}], depending on the duration of heating. Reaction of [PtCl2(PhCN)2] with TeArMes afforded [PtCl2(TeArMes)2] (Ar = Ph, o-tol, and Mes), the formation of which decreased with increasing steric demand of the Ar group, together with [PtCl2{NC(O)Ph(TeArMes)}2]. The telluroether in the latter binds to nitrogen, and tellurium exists in the formal oxidation state of +4 (from XPS). The tellurium in these complexes exhibits secondary interactions with platinum (J((195)Pt-(125)Te) = 309-347 Hz) and with the carbonyl oxygen. These complexes slowly dissociate in solution to give [PtCl2(TeMesAr){NC(O)Ph(TeMesAr)}], finally leading to the formation of [PtCl2(TeMesAr)2]. Molecular structures of trans-[PtCl2(PhCN){NC(O)Ph[TeMes(o-tol)]}], trans-[PtCl2{NC(O)Ph(TeMes2)}2], trans-[PtCl2{NC(Ph)C4H7O}{NC(O)Ph(TeMes2)}], trans-[PtCl2{NC(O)Ph[TeMes(o-tol)]}2], trans-[PtCl2(TeMes2){NC(O)Ph(TeMes2)}], trans-[PtCl2{NC(O)Me(TeMes2)}2], and [PtCl(Te-o-tol){NC(O)Ph}2] have been unambiguously established by single-crystal X-ray diffraction analyses. Density functional theory calculations for some of the complexes were performed, and geometrical parameters are in good agreement with the values obtained from X-ray analyses.

Reactions of K2PtCl4 with TeRR' gave complexes of composition [PtCl2(TeRR')(2)] (R/R' = Ph-2(1a), o-tol(2) (1b), Mes2(1c), Ph/Mes (1d), o-tol/Mes (1e)). The complex [PtCl2(TeMes(2))(2)] in refluxing THF afforded a mononuclear cyclometalated complex [PtCl{(CH2C6H2Me2-4,6)TeMes}(TeMes(2))] (2). It tends to remain in equilibrium with a binuclear derivative [Pt(mu-Cl){(CH2C6H2Me2-4,6)TeMes}12 (3) in CDCl3 solution. The complexes Id and le did not undergo cyclometalation reaction under similar reaction conditions. The 2 on treatment with PPh3 gave [PtCl{(CH2C6H2Me2-4,6)TeMes}(PPh3)] (4). All the complexes have been, 3113, 125-re, characterized by elemental analysis and NMR (H-1, P-31, Te-125, Pt-195) spectroscopy. Anagostic interactions have been recognised for facilitation of cyclometalation reactions. The molecular structures of trans[PtCl2(TeMes)(2)] trans-[PtCl2(PhTeMes)(2)] (1d), trans-[PtCl2(o-tolTeMes)(2)] (le), [PtCl{(CH2C6H2Me2-4,6)TeMes}(TeMes(2))] (2) and [PtCl{(CH2C6H2Me2-4,6)TeMes}(PPh3)] (4) have been established unambiguously by single crystal X-ray diffraction analyses. (C) 2015 Elsevier B.V. All rights reserved.

Treatment of [PdCl2(PhCN)2] with diaryl telluride in 1 : 2 molar ratio gave mononuclear palladium complexes, trans-[PdCl2(TeR2)2] () (R = Mes () (Mes = 2,4,6-trimethylphenyl), Ph (), o-tol () (o-tol = ortho-tolyl)). Reaction of [PdCl2(TeMes2)2] with one equivalent of [PdCl2(PhCN)2] or Na2PdCl4 with TeRR' afforded chloro-bridged binuclear complexes, [Pd2(μ-Cl)2Cl2(TeRR')2] () (R/R' = Mes/Mes (); Mes/Ph (); Ph/Ph ()). A toluene-methanol solution of trans-[PdCl2(TeMes2)2] on refluxing for 30 minutes yielded a binuclear cyclopalladated complex, [Pd2(μ-Cl)2{CH2C6H2(4,6-Me2)TeMes)}2] (). When the refluxing was prolonged, a mononuclear complex cis-[PdCl2{MesTeCH2C6H2(4,6-Me2)TeMes}] () was isolated. Treatment of palladium acetate with TeMes2 afforded an acetato-bridged analogue of , [Pd2(μ-OAc)2{CH2C6H2(4,6-Me2)TeMes}2] () together with a very minor component, a tetranuclear complex, [Pd(μ-OAc)(μ-TeMes)]4 (). This reaction with unsymmetrical tellurides, MesTeR, also gave cyclopalladated complexes [Pd2(μ-OAc)2{CH2C6H2(4,6-Me2)TeR}2] (R = o-tol () and Ph ()) in which 2-methyl of the mesityl group of the telluride was exclusively metallated. The complex trans-[PdCl2(TeMes2)2] on refluxing in xylene gave palladium telluride, Pd7Te3. These complexes were characterized by elemental analyses, IR and NMR ((1)H, (13)C and (125)Te) spectroscopy. The molecular structures of trans-[PdCl2(TeMes2)2] (), [Pd2(μ-Cl)2Cl2(TeMes2)2]·2acetone (·2acetone), cis-[PdCl2{MesTeCH2C6H2(4,6-Me2)TeMes}] (), [Pd2(μ-OAc)2{CH2C6H2(4,6-Me2)TeMes)}2]·toluene (·toluene), [Pd2(μ-OAc)2{CH2C6H2(4,6-Me2)Tetol-o}2] () and [Pd(μ-OAc)(μ-TeMes)]4 () were established by single crystal X-ray diffraction analyses. The mononuclear complex was isolated in two polymorphic forms each with the trans configuration.

Organochalcogenolate-bridged cyclometalated palladium(II) complexes of the formulae, [Pd-2(mu-Epy)(2)(Me2NCH2C6H4-C,N)(2)] (2) (E = S (2a), Se (2b)), [Pd-2(mu-SAr)(mu-Cl)(Me2NCH2C6H4-C,N)(2)] (3) (Ar = Ph (3a), Mes (Mes = 2,4,6-Me3C6H2) (3b)) and [Pd-2(mu-SeAr)(2)(Me2NCH2C6H4-C,N)(2)] (4) (Ar = Ph (4a), Mes (4b)), have been synthesized by the reactions of [Pd-2(-Cl)(2)(Me2NCH2C6H4-C,N)(2)] with lead or sodium salts of the chalcogenolate ligand. These complexes have been characterized by elemental analysis, mass spectral data, and NMR (H-1 and Se-77{H-1}) spectroscopy. The molecular structure of 2, determined by single crystal X-ray diffraction analysis, revealed a Epy-bridged head-to-tail arrangement in which the eight-membered "(PdECN)(2") ring adopts a distorted twist boat conformation. The Pd center dot center dot center dot center dot Pd separation in 2a is within the van-der-Waals interaction but in 2b it is too large to support the presence of any metal-metal interaction. The thermal behavior of these complexes has been studied by thermogravimetric analysis.

The reaction of dimesityl selenide (Mes2Se) with either PdCl2(PhCN)2 in toluene or PdCl2 in toluene-acetonitrile yields a chloro-bridged binuclear palladium complex, [Pd2Cl2(μ-Cl)2(Mes2Se)2] (1), whereas with Na2PdCl4 in refluxing ethanol, a cyclometallated palladium complex, [Pd2(μ-Cl)2{MesSeC6H2(Me2)CH2}2] (2) is afforded. 2 can also be obtained when 1 is refluxed in ethanol. On treatment with Pb(Epy)2 in dichloromethane, 2 afforded the Epy-bridged binuclear complexes, [Pd2(μ-Epy)2{MesSeC6H2(Me2)CH2}2] (3; E = S (3a) or Se (3b)). Treatment of 2 with PPh3 yields a bridge-cleaved monomeric complex, [PdCl{MesSeC6H2(Me2)CH2}(PPh3)]. The molecular structures of 1-3 were established by X-ray diffraction analyses. All the complexes are dimeric, with the palladium atoms acquiring a distorted square planar configuration. There are intra-molecular C-H···Pd interactions (d(M-H): 2.75 Å and <C-H···Pd: 111.23°) in 1 which facilitate the activation of the C-H (sp(3)) bond leading to metallation. The optimized geometry of 1 obtained using the DFT(B3LYP) computational method identified a C-H···Pd contact distance of 2.78 Å. There are two independent molecules of 2 in the unit cell, which differ slightly in bond lengths, bond angles and torsion angles. The mechanism of formation of the dimeric species 2 is examined using DFT (B3LYP) computations.

Volatility of Cs from borosilicate glasses incorporated with different additives like ZnO, BaO, and CaO have been investigated as a function of heating temperatures (900°C, 950°C, and 1000°C) and time. According to the lower Cs volatility, the sequence of the incorporated oxides is arrived as ZnO < B2O3 < BaO < CaO. It is confirmed that the volatilization of Cs occurred predominantly through diffusion controlled process. From the temperature‐dependence volatility profiles of Cs, the activation energy and frequency factor was calculated and found to be in the range of 300–500 kJ/mol and 103–1012 cm2/s, lowest for ZnO and highest for CaO containing glasses. It was found that the frequency factor and not the activation energy were controlling the Cs loss. The observed variations in the activation energy and frequency factor have been explained by a unique model structure and possible interactions of Cs with different structural units formed due to incorporation of the different additives.

High cesium (Cs)‐bearing sodium borosilicate glasses incorporated with varying concentrations of TiO2 up to 10 mol% at the expense of B2O3 were prepared by the conventional melt quenching method. Physicochemical properties of the glasses studied include Cs volatilization losses, leaching, and glass transition temperatures. Structural aspects of the glasses were investigated using Fourier transform infrared, 11B MAS NMR, and UV‐visible optical absorption techniques. From the detailed investigations on these glasses, optimum concentration of TiO2 for minimum volatilization losses of Cs has been established. Structural studies revealed the role of TiO2 in the Cs volatilization as well as leaching characteristics of the glass. Based on our studies, it can be inferred that the glass sample with 5 mol% TiO2 content gives the optimum formulation with regard to the leaching and Cs volatilization losses. Results of the study are useful in the development of high Cs‐bearing glasses for their use as a gamma source for radiation technology application.

A sodium barium borosilicate glass matrix with a higher solubility of sulfate has been developed recently at Bhabha Atomic Research Centre for vitrification of sulfate bearing high‐level nuclear waste. We report here the studies carried out to understand the influence of sulfate ion on the three‐dimensional borosilicate network. Experiments were carried out with sodium barium borosilicate base glass samples loaded with varying amounts of SO42− (0–5 mol%). Phase separation studies on the samples revealed that as much as 3 mol% of SO42− can be loaded within the base glass without any phase separation, however, beyond this limit BaSO4 (barite) crystallizes within the matrix. Thermal analyses of the samples indicated a shift in glass transition temperature from 534° (0 mol% SO42−) to 495°C (3 mol% SO42−) and it remained more or less unaltered afterwards even with high SO42− loading. A similar observation of structure stabilization was obtained from 29Si MAS–NMR studies also, which showed that with 2 mol% of SO42− loading, the Q2:Q3 ratio changed from 59:41 (for samples with 0 mol% SO42− loading) to 62:38 and it remained almost the same afterwards even with higher SO42− loading. 11B MAS NMR patterns of the glass samples, however, remained unchanged with SO42− loading ([BO4]:[BO3]=38:62). Based on 29Si and 11B MAS NMR studies, the authors propose two different ways of interaction of SO42− ions with the borosilicate network: (i) the network modifying action of SO42− ions with ‐Si–O–Si‐ linkages, at low SO42− ion concentration (<2 mol%) and (ii) the preferential interaction of SO42− with the Ba2+ ions at high SO42− concentration (>2 mol%).